Patent Application
20060071606
The present invention concerns an indirectly heated electrode for gas discharge tube, a gas discharge tube using this indirectly heated electrode for gas discharge tube, and a lighting device for the gas discharge tube using the abovementioned indirectly heated electrode for gas discharge tube.
A known example of the abovementioned indirectly heated electrode for gas discharge tube is that which is disclosed in Japanese Examined Patent Publication No. 62-56628 (U.S. Pat. No. 4,441,048). The indirectly heated electrode for gas discharge tube (indirectly heated cathode for gas discharge tube) that is disclosed in Japanese Examined Patent Publication No. 62-56628 has an arrangement wherein a double coil is wound a plurality of turns around and fixed closely to the outer wall of a cylinder of good thermal conductivity, a uniform cathode surface is formed by applying a paste-form cathode material in the space inside the primary coil and between the secondary coil of the double coil, and providing a heater inside the cylinder.
An object of the present invention is to provide an indirectly heated electrode for gas discharge tube, which is elongated in the service life of the electrode and enables a stable discharge to be obtained, a gas discharge tube using this indirectly heated electrode for gas discharge tube, and a lighting device using the gas discharge tube that uses the abovementioned indirectly heated electrode for gas discharge tube.
Using the discharge surface potential as an experimental factor, the present inventor made comparisons with prior-art indirectly heated electrodes (indirectly heated cathodes), mainly in regard to the cathode fall voltage (box potential), and as a result of research, made the following new findings.
The terms, “equipotential surface,” “equipotential interface,” and “box potential,” and the modes of discharge, which are used below, shall be defined as follows. An “equipotential surface” shall be defined as a state in which a discharge surface that is in an equipotential state in terms of electric potential is formed. An “equipotential interface” shall be defined as a structure with which a metal oxide is contact coated, as a material likely to emit electrons, onto an equipotential surface and put in contact with a gas. “Box potential” shall be defined as the potential that is generated between a cathode and a terminal that is in the vicinity of the cathode but is electrically insulated from the cathode during discharge. This value is approximately the cathode fall voltage, which is a term among generally used terms for discharge properties. An “ionic current” shall be defined as a current generated by ionized gas resulting from the ionization of the gas molecules in a gas discharge tube due to collision of the gas molecules with electrons. “Thermionic emission” refers to an electron emission phenomenon, that is, an emission of electrons into space that occurs when the temperature of a metal is raised and the thermal kinetic energy increases beyond the electron energy barrier (work function) of the metal, and here, this term refers to an emission of electrons from a metal oxide that is a chemically unstable material likely to emit electrons. “Secondary electron emission” refers to an electron emission phenomenon, that is, an emission of electrons into space from a cathode when an ionized gas collides with the cathode.
A comparison of the box potentials before and after the attaining of an equipotential state in DC operation shows that these box potentials differ significantly as shown in
Id=Ii+Ie=Ii(1+y)+Ith (1)
Ie=Ith+γIi (2)
Vc={Vo+(1−Ith/Id)}/{α(y+Ith/Id)} (3)
Equations related to the Schottky effect:
Ie=Ith exp{(e/kT)sqr(eE/4πεσ) (4)
Ith=SATˆ2*exp(−eφ/kT) (5)
Ise=Ith[exp[(e/kT)sqr(eE/4πεσ)−1] (6)
In the above, Ii: ion current
Ie: emission current
Ith: thermionic current
Ise: secondary electron current
Id: discharge current
Vc: cathode fall voltage
γ: factor (gain) related to secondary electron emission
α, Vo: parameters
S: surface area of electrode
A: constant determined by the material
T: cathode temperature
e: negative charge of an electron
φ: work function
k: Boltzmann's constant
εo: dielectric constant of vacuum
E: electric field strength at cathode fall part
The ion current (corresponding to Ii) and the emission current (electrons: corresponding to Ie) in a gas discharge tube shall now be considered. In comparison to an electron with a static weight of 9.109×10−31 kg, even hydrogen, which is the lightest element, is considerably heavier with amass of 1.675×10−27 kg. Furthermore, whereas ionized gas is drawn towards and collides with the cathode, an electron is detached from the cathode. The impact force of ionized gas thus exceeds the impact force of an electron and the damage that ionized gas applies to the cathode is greater than the damage due to an electron. The detrimental effect that an ion current has on the cathode can be understood from the above. Meanwhile, from the standpoint of light emission and discharge phenomenon of a gas discharge tube, the ionized gas contributes as a light emitting material and also provides the effect of drawing out more discharge current into space-in accordance to the ion current in comparison to vacuum. With a gas discharge tube, it is important in terms of service life characteristics and stability to minimize the effects on the cathode while taking into consideration the merits and demerits of the ion current.
The box potential approximates the cathode fall voltage, indicates the excitation and ionization states of the gas in relative manner, and serves as a guideline for the amount of ionized gas generated. A lower box potential indicates a lower amount of ionized gas generated.
It was mentioned above that, in gas discharge, there are the three discharge modes of ion current, thermionic emission, and secondary electron emission. Thermionic emission is caused by the heating of barium or other metal oxide as a material likely to emit electrons. Thermionic emission serves the role of causing gas ionization at the beginning of discharge and thereby initiating discharge. In the case of gas discharge, after the initiation of discharge, ionized gas begins to collide in a manner such that it becomes drawn towards the thermions that are emitted from the metal oxide that is the material likely to emit electrons. As a result of the collision of the ionized gas in this process, secondary electron emission occurs mainly from the interface between an electric conductor and the metal oxide that is the material likely to emit electrons. In the case of gas discharge, the discharge current density per unit area becomes several dozen to several hundred times that of vacuum discharge and a large part of the total discharge current is formed by secondary electron emission.
With regard to the supply of secondary electrons, the electrical resistivity of the metal oxide that is the material likely to emit electrons is considerably greater than that of the electrical conductor, the amount supplied by just the metal oxide that is the material likely to emit electrons is limited, and much of the secondary electrons supplied are supplied via the electrical conductor and emitted from the interface between the metal oxide that is the material likely to emit electrons. With regard to how the electrons that become the basis of secondary electrons are supplied to the electrical conductor, these may be supplied directly from an external circuit or may be supplied via the surface of contact with the metal oxide that is the material likely to emit electrons. Though thermionic emission from the metal oxide that is the material likely to emit electrons that does not form an interface with the electrical conductor also occurs, as mentioned above, in regard to the supply of secondary electrons, there is a limit to the supply from just the metal oxide that is the material likely to emit electrons, and in gas discharge, the absolute amount taken up by the discharge current from just the metal oxide that is the material likely to emit electrons is extremely low. To summarize the above, the location in the cathode at which electron emission mainly occurs during gas discharge is the interface of electrical conductor and the metal oxide that is the material likely to emit electrons.
A model of an equipotential interface model shall now be described with reference to
Besides the heater application voltage (Vf), that is, the amount of forced heating of the cathode, the amount of so-called self-heating, which occurs when the ionized gas collides with the cathode, is also a component factor of the cathode temperature, and the cathode temperature is determined by the total of these heating amounts. In a region in which the amount of heat loss from the cathode is high, the thermion generation amount is low, the ion current becomes dominant in a compensating manner, and the cathode fall voltage becomes greater than or equal to the ionization voltage, thereby accelerating the generation of ionized gas. If in this region, the electric potential distribution of the cathode surface is non-uniform, localized discharge (skewing of the discharge position) due to concentrating of the ion current and secondary electron current occurs readily, leading to large damage of the cathode surface due to ionized gas impact and tending to cause the cathode material (metal oxide that is the material likely to emit electrons) to undergo removal (sputtering) and stabilization (mineralization) by oxidation with the reduced metal.
On the other hand, in the region at the left side of
An important component factor of the present model is the discharge area. This can be regarded as equivalent to the electrode surface area (S) in the relationship equations. As mentioned above, in gas discharge, electron emission from the interface of the electrical conductor and the metal oxide that is the material likely to emit electrons constitutes the main part of the discharge. In addition, the discharge area differs not only according to the uniformity of temperature but also according to whether or not the potential is uniform (equipotential). That is, the discharge area is proportional to the area of the equipotential surface or the length of the equipotential surface part, and as the equipotential surface becomes wider or longer, the electrode surface (S: discharge area) increases, the proportion of thermionic current (Ith) increases in accordance to the above Equation (5), the amount of ion current decreases in accordance to the above Equation (1), the ion current and the secondary electron current become dispersed across the equipotential surface, the distribution of regions of the model of
It can be understood from the above that with gas discharge, by decreasing the amount of ion current in comparison to a conventional cathode that is not put in an equipotential state, the impact of ionized gas per unit discharge area can be relaxed, and as a result, the load on the cathode is lightened, the lowering of the thermion emission ability is lessened, and the service life characteristics are improved, and in accompaniment, the movement of the discharge position is lessened and the stability is improved.
The effectiveness of an equipotential surface for a gas discharge tube shall now be discussed. As mentioned above, with vacuum discharge, the mode of discharge can be expressed by just thermionic emission, and vacuum discharge thus differs in the mode of discharge from gas discharge. The discharge area in vacuum discharge can said to be determined by the surface area formed by the metal oxide that is the material likely to emit electrons at the thermionic emission surface. The discharge area components in a gas discharge tube having the discharge modes of ion current and secondary electron emission in addition to thermionic emission thus differs from the discharge area components in vacuum discharge, and since with a cathode in gas discharge, the location at which electron emission principally occurs is the interface of the electrical conductor and the metal oxide that is the material likely to emit electrons, it was found that an equipotential surface, which is formed of the electrical conductor and is substantially equalized in potential, is effective as a discharge surface in gas discharge.
Furthermore, by making the material, to be used as the means for forming an equipotential surface, have a mesh structure, a wire structure, or a plate-and-filament structure, such as a ribbon structure or a foil structure, the amount of heat loss can be restrained while restraining as much as possible the increase of the surface area that is to be the heat radiating surface and the volume that is to be the heat transfer part. By increasing the parts of contact of the metal oxide and the equipotential surface, as a result, the discharge area is increased. From the above, it was found that by making the material, to be used as the means for forming an equipotential surface, have a mesh structure, a wire structure, or a plate-and-filament structure, the effect of the equipotential surface can be increased.
In a conventional case where the potential distribution of the cathode surface is non-uniform, since the heat generation amount is non-uniform accordingly, the density of thermion generation is also non-uniform and localized discharge (skewing of the discharge position) occurs due to the concentrating of ion current and secondary electron current. Localized discharge causes the cathode material (metal oxide that is the material likely to emit electrons) to undergo removal (sputtering) and stabilization (mineralization) by oxidation with the reduced metal, that is, causes degradation of the thermionic emission ability and movement of the discharge position to another position with better thermionic emission characteristics. By thus repeating localized degradation of thermionic emission, the cathode surface becomes degraded. The abovementioned movement of the discharge position also causes the discharge itself to become unstable.
Based on the above research results, the present invention provides, in an indirectly heated electrode for gas discharge tube, to be used in a gas discharge tube in which gas is sealed in an airtight manner, the indirectly heated electrode for gas discharge tube comprising: a heater, having an electrical insulating layer formed on a surface thereof; an electron emitting part, emitting electrons upon receiving heat from the heater; and an electrical conductor, disposed at the surface most part of the electron emitting part and having a predetermined length.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electron emitting part by the electrical conductor and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The occurrence of localized discharge can thus be restrained and long service life of the indirectly heated electrode for gas discharge tube can be realized. Since the movement of the discharge position is also restrained, stable discharge can be obtained over a long period of time. Also due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
Also, the electron emitting part preferably comprises: a metal oxide as a material likely to emit electrons; and a coil member, which holds the metal oxide; and the electrical conductor is preferably put in contact with the metal oxide and in contact with a plurality of coil portions of the coil member along the length direction of the coil member. In this case, the potential of the discharge surface that is made up of a plurality of discharge points or discharge lines by the electrical conductor is made substantially uniform. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and the movement of the discharge position can be restrained as well. As a result, long service life and stable discharge of an indirectly heated electrode for gas discharge tube can be realized by a simple arrangement in which an electrical conductor is disposed so as to be in contact with a metal oxide.
Also, the coil member is preferably a multiple coil arranged by winding a coil in coil form. In this case, the metal oxide that is the material likely to emit electrons is held in a manner where it is sandwiched between the pitches (spacings), which are the gaps between the wire material that forms the coil. Since the distance between pitches is small and gap-like, the falling off the metal oxide due to vibration can be restrained. Also, since a plurality of pitches of gap-like structure exist, a large amount of metal oxide can be held, providing the effect of replenishing the metal oxide loss that accompanies the degradation with time during discharge.
Also, the coil member is preferably a multiple coil, arranged by winding a coil having a mandrel in coil form. In this case, the metal oxide that is the material likely to emit electrons is held in a manner where it is sandwiched between the pitches (spacings), which are the gaps between the wire material that forms the coil. Since the distance between pitches is small and gap-like, the falling off the metal oxide due to vibration can be restrained. Also, since a plurality of pitches of gap-like structure exist, a large amount of metal oxide can be held, providing the effect of replenishing the metal oxide loss that accompanies the degradation with time during discharge. Furthermore, since a mandrel is provided, deformation of the multiple coil during processing can be restrained.
Also, the electrical conductor is preferably a high-melting-point metal that has been formed to a mesh. By making the electrical conductor a high-melting-point metal that has been made formed to a mesh, an electrical conductor, which can restrain the degradation of the thermionic emission ability and the movement of the discharge position, can be realized at low cost and in a simpler manner. Since the electrical conductor in this case is a rigid body, it is easy to process and can be put in close contact with the metal oxide. The locations at which the high-melting-point metal contacts the metal oxide can readily made large in number as well.
Also, the electrical conductor is preferably a high-melting-point metal that has been formed to a wire or a plate. By making the electrical conductor a high-melting-point metal that has been formed to a wire or a plate, an electrical conductor, which can restrain the degradation of the thermionic emission ability and the movement of the discharge position, can be realized at low cost and in a simpler manner. Since the electrical conductor in this case is a rigid body, it is easy to process and can be put in close contact with the metal oxide. With the present Specification, “plate” shall refer inclusively to such shapes as a ribbon shape, foil shape, etc.
Also, the metal oxide is preferably an oxide of a single metal among barium (Ba), strontium (Sr), and calcium (Ca) or a mixture of oxides of these metals or contains an oxide of a rare earth metal. By the metal oxide being an oxide of a single metal among barium, strontium, and calcium or a mixture of oxides of these metals or containing an oxide of a rare earth metal, the work function of the electron emitting part can be made small effectively and the emission of thermions can thus be facilitated.
It is also preferable to have in addition a tubular base metal and for the heater to be disposed at the inner side of the base metal and the electron emitting part to be disposed at the outer side of the base metal. In this case, the heat of the heater can be transferred definitely to the electron emitting part in the active state. Though a cylindrical shape is generally used as the shape of the base metal, the shape may also be an arcuate shape with a notched part.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal, and wherein the metal oxide is set to a ground potential.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the indirectly heated electrode for gas discharge tube can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal, and wherein the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the indirectly heated electrode for gas discharge tube can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal, and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the indirectly heated electrode for gas discharge tube can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal and the coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, having a mandrel and wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the coil member, and wherein the metal oxide is set to a ground potential.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and the surface part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Since a mandrel is provided, deformation of the coil member during processing can be restrained. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, having a mandrel and wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the coil member; and where in the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and the surface part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Since a mandrel is provided, deformation of the coil member during processing can be restrained. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, having a mandrel and wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the coil member; and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and the surf ace part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stabled is charge over a long period of time can be realized. Since a mandrel is provided, deformation of the coil member during processing can be restrained. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, having a mandrel and wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the coil member; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and the surface part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Since a mandrel is provided, deformation of the coil member during processing can be restrained. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a coil member, having a mandrel and wound in coil form; a heater, disposed at the inner side of the coil member and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the coil member; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal and the coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and the surface part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Since a mandrel is provided, deformation of the coil member during processing can be restrained. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
It is favorable for the coil member to be a single coil. It is also favorable for the coil member to be a multiple coil arranged by winding a coil in coil form. In particular, in a case where the coil member is a multiple coil, the metal oxide that is the material likely to emit electrons is held in a manner where it is sandwiched between the pitches (spacings), which are the gaps between the wire material that forms the coil. Since the distance between pitches is small and gap-like, the falling off the metal oxide due to vibration can be restrained. Also, since a plurality of pitches of gap-like structure exist, a large amount of metal oxide can be held, providing the effect of replenishing the metal oxide loss that accompanies the degradation with time during discharge.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and the surface part of the coil member, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a coil member, wound in coil form around the outer side of the base metal; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the metal oxide is set to a ground potential.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, by the base metal, the heat of the heater can be transferred without fail to the metal oxide in the active state. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a coil member, wound in coil form around the outer side of the base metal; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, by the base metal, the heat of the heater can be transferred without fail to the metal oxide in the active state. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a coil member, wound in coil form around the outer side of the base metal; a high-melting-point metal, formed to a mesh and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, by the base metal, the heat of the heater can be transferred without fail to the metal oxide in the active state. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a coil member, wound in coil form around the outer side of the base metal; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the coil member is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the coil member is grounded, thermions, secondary electrons, etc. are supplied via this coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, by the base metal, the heat of the heater can be transferred without fail to the metal oxide in the active state. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a coil member, wound in coil form around the outer side of the base metal; a high-melting-point metal, formed to a wire or a plate and disposed along the length direction of the coil member at the outer side of the coil member; and a metal oxide, serving as a material likely to emit electrons and held by the coil member so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is in electrical contact with the coil member at a plurality of locations and the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since the high-melting-point metal is grounded, thermions, secondary electrons, etc. are supplied via this high-melting-point metal and the coil member. Also, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a wire or a plate and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stabled is charge over a long period of time can be realized. Also, by the base metal, the heat of the heater can be transferred without fail to the metal oxide in the active state. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a heater, having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed along the length direction of the heater at the outer side of the heater; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a heater, having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh, extended in the length direction in a waving manner, and disposed along the length direction of the heater at the outer side of the heater; a conductive wire, having a shape that spans a depressed part at one side of the high-melting-point metal in one direction along the width direction of the high-melting-point metal and spans a depressed part at the other side of the high-melting-point metal in the reverse direction along the width direction of the high-melting-point metal; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to a mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The conductive wire preferably comprises a mandrel and a filament wound around the outer circumference of the mandrel. In this case, since the conductive wire has a mandrel, the deformation of the conductive wire during processing can be restrained.
The present invention provides an indirectly heated electrode for gas discharge tube comprising: a base metal, formed to a tubular form; a heater, disposed at the inner side of the base metal and having an electrical insulating layer formed on a surface thereof; a high-melting-point metal, formed to a mesh and disposed on the surface of the base metal along the length direction of the heater; and a metal oxide, serving as a material likely to emit electrons and disposed so as to be in contact with the high-melting-point metal; and wherein the high-melting-point metal is grounded.
In the indirectly heated electrode for gas discharge tube of the present invention, since an equipotential surface is effectively formed at the electrode surface by the high-melting-point metal that is formed to mesh and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of the metal oxide and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained and long service life of the electrode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the high-melting-point metal is a rigid body, it is easy to process and can be put in close contact with the metal oxide. Also, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art, thus enabling the provision of an indirectly heated electrode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and enabling realization of pulse operation and large current operation.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube comprising: a sealed container, having a fluorescent film formed on the inner surface thereof; and wherein the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention is sealed in an airtight manner along with a rare gas in the sealed container.
In the present invention, since the gas discharge tube using an indirectly heated electrode for gas discharge tube of the present invention has the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention sealed in an airtight manner therein, a gas discharge tube of long service life and stable operation can be realized.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube comprising: a sealed container, having a fluorescent film formed on the inner surface thereof; and wherein the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention is sealed in an airtight manner along with a rare gas and mercury in said container.
In the present invention, since the gas discharge tube using an indirectly heated electrode for gas discharge tube of the present invention has the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention sealed in an airtight manner therein, a gas discharge tube of long service life and stable operation can be realized.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube, wherein the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention is sealed in an airtight manner along with a rare gas in a container.
In the present invention, since the gas discharge tube using an indirectly heated electrode for gas discharge tube of the present invention has the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention sealed in an airtight manner therein, a gas discharge tube of long service life and stable operation can be realized.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube, wherein the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention is sealed in an airtight manner along with a rare gas and mercury in a container.
In the present invention, since the gas discharge tube using an indirectly heated electrode for gas discharge tube of the present invention has the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention sealed in an airtight manner therein, a gas discharge tube of long service life and stable operation can be realized.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube, wherein a pair of the indirectly heated electrodes for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention are sealed in an airtight manner along with a rare gas in a translucency container while being set apart by a predetermined gap.
In the present invention, since the gas discharge tube using an indirectly heated electrode for gas discharge tube has a pair of the indirectly heated electrodes for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention sealed in an airtight manner while being set apart by a predetermined gap, a gas discharge tube of long service life and stable operation can be realized. In particular, an arrangement suitable for a gas discharge tube, with which a negative glow discharge due to AC discharge across a pair of electrodes is to be mainly performed, is provided.
The present invention provides a gas discharge tube using an indirectly heated electrode for gas discharge tube comprising: the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention; an anode, receiving electrons emitted from the indirectly heated electrode for gas discharge tube; a focusing electrode, disposed between the indirectly heated electrode for gas discharge tube and the anode and converging the thermions; and an electrically-insulating, discharge shielding part, housing the anode; and wherein the indirectly heated electrode for gas discharge tube, the anode, the focusing electrode and the discharge shielding part are equipped inside a sealed container in which a gas is sealed.
In the present invention, since the present invention's gas discharge tube using an indirectly heated electrode for gas discharge tube uses the indirectly heated electrode for gas discharge tube as set forth in any of the first to twenty ninth Claims of the invention, a gas discharge tube of long service life and stable operation can be realized.
The present inventors also found anew as a result of research that the gas discharge tube using an indirectly heated electrode for gas discharge tube of the thirty fifth Claim can be driven under the relationships expressed by the following equations (7) and (8):
If0=Ip (7)
Vf1=0 (8)
In the above, If0: initial current supplied to the heater in the starting state
Ip: discharge current
Vf1: voltage applied to the heater during operation.
Based on the above research results, the present invention provides in a gas discharge tube lighting device using an indirectly heated electrode for gas discharge tube, which is installed in and connected to the indirectly heated electrode for gas discharge tube, the anode, and the focusing electrode in the gas discharge tube using an indirectly heated electrode for gas discharge tube of the thirty fifth Claim, a gas discharge tube lighting device using an indirectly heated electrode for gas discharge tube comprising: a power supply, connected between the indirectly heated electrode for gas discharge tube and the anode; an auxiliary lighting circuit unit, connected between the anode and the focusing electrode and generating a trigger discharge across the indirectly heated electrode for gas discharge tube and the focusing electrode; and a make-and-break switching circuit unit, connected between the indirectly heated electrode for gas discharge tube and the anode and supplying electricity to the heater for a predetermined period and then cutting off the supply of electricity to the heater after the elapse of the predetermined period.
In the present invention, lighting device for a gas discharge tube using an indirectly heated electrode for gas discharge tube, a lighting device for lighting the thirty fifth Claim's gas discharge tube using an indirectly heated electrode for gas discharge tube can be realized. Also, a single power supply can be used as the power supply for the pre-heating of the indirectly heated electrode for gas discharge tube, the starting of trigger discharge (discharge due to initial gas ionization), and the main discharge, making unnecessary a separate power supply for the pre-heating of the indirectly heated electrode for gas discharge tube (for the heater) and thereby enabling significant reduction of the number of parts and simplification of arrangement.
The auxiliary lighting circuit unit preferably includes a capacitor that is installed and serially connected between the anode and the focusing electrode. By the auxiliary lighting circuit unit including a capacitor that is installed and serially connected between the anode and the focusing electrode, the auxiliary lighting circuit unit can be realized in a simple and low-cost manner.
The auxiliary lighting circuit unit preferably furthermore includes a fixed resistor that is connected in parallel to the capacitor. By the auxiliary lighting circuit unit furthermore including a fixed resistor that is connected in parallel to the capacitor, the gas discharge tube lighting property can be improved.
It is also preferable that a fixed resistor for current detection, which is serially connected and installed between the anode and the power supply, be equipped furthermore. By furthermore equipping a fixed resistor for current detection, which is serially connected and installed between the anode and the power supply, the voltage can be lowered during operation and the consumption power of the gas discharge tube can thereby be reduced.
Preferred embodiments of the present invention's indirectly heated electrode for gas discharge tube, gas discharge tube using the abovementioned indirectly heated electrode, and lighting device for the abovementioned gas discharge tube shall now be described in detail with reference to the drawings. In the following description, the same symbol shall be used for the same elements or elements with the same functions and redundant description shall be omitted.
As shown in
Double coil 2 is a multiple coil arranged from a coil that is wound in coil form, and a tungsten element wire of 0.091 mm diameter is formed into a primary coil with a diameter of 0.25 mm and a pitch of 0.146 mm and this primary coil is formed into a double coil with a diameter of 1.7 mm and a pitch of 0.6 mm. Heater 1 is inserted into and disposed at the inner side of double coil 2. As a holding means (coil member), a triple coil or a single coil, etc. may be used in place of double coil 2. Also, a mesh member may be used in place of a coil member. By using such a coil or mesh member, the holding member that holds metal oxide 10, which is the material likely to emit electrons, can be reduced in heat radiating area.
Mesh member 3 is a conductive rigid body (metal conductor) formed of a single, high-melting-point metal (with a melting point of at least 1000° C.) selected from among groups IIIa to VIIa, VIII, and Ib of the periodic table or, more specifically, from among tungsten, tantalum, molybdenum, rhenium, niobium, osmium, iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, rare earth metals, etc. or an alloy of these metals. With the present embodiment, a mesh member made by weaving tungsten element wires of 0.03 mm diameter into mesh form is used. The mesh size of mesh member 3 is set to 80 mesh. Mesh member 3 has a predetermined length and is disposed across the length direction of double coil 2 at the outer side of double coil 2 so as to be substantially orthogonal to the discharge direction. This mesh member 3 is disposed at the surface most part of the electron emitting part that includes double coil 2 and metal oxide 10, which is the material likely to emit electrons.
Double coil 2 and mesh member 3 are connected via a lead rod 7 to the ground terminal of heater 1 and is thereby grounded (set to GND). Metal oxide 10, which is the material likely to emit electrons, is thereby set to the ground potential.
In
An example of a process for manufacturing indirectly heated cathode for gas discharge tube C1 (for positioning heater 1 and mesh member 3 with respect to double coil 2) shall now be described based on
First as shown in
Next as shown in
Also, in place of using wire member 6, made of nickel, a plate member 8, made of molybdenum, may be used as shown in
Returning now to
As metal oxide 10, a single oxide of a metal selected from among barium (Ba), strontium (Sr), and calcium (Ca), or a mixture of such oxides, or an oxide, with which the principle component is a single oxide of a metal selected from among barium (Ba), strontium (Sr), and calcium (Ca) or a mixture of such oxides and a sub-component is an oxide of a metal selected among rare earth metals including lanthanum (metals of group IIIa of the periodic table), is used. Each of barium, strontium, and calcium is low in work function, can emit thermions readily, and enable the thermion supply amount to be increased. Also, in a case where a rare earth metal (metal of group IIIa of the periodic table) is added as a sub-component, the thermion supply amount can be increased further and the sputter resistance can be improved as well.
As the cathode material, metal oxide 10 is coated in the form of a metal carbonate (for example, barium carbonate, strontium carbonate, calcium carbonate, etc.) and obtained by vacuum thermal decomposition of the coated metal carbonate. If vacuum thermal decomposition is to be performed by passage of electricity through the heater, AC thermal decomposition is preferred over DC thermal decomposition. In the final stage, the metal oxide 10 that is thus obtained becomes the material likely to emit electrons. The metal carbonate that is to be the cathode material is coated from the mesh member 3 side in the condition where heater 1 is positioned at the inner side of double coil 2 and mesh member 3 is positioned at the outer side of double coil 2 as shown in
Also, a metal carbonate may be coated as the cathode material onto double coil 2 (mesh member 3) in the condition in which heater 1 is not positioned at the inner side of double coil 2 and heater 1 may be inserted after the coating of the metal carbonate. If there are pores in the electrical insulating layer 4 formed on heater 1 and the metal carbonate is coated with heater 1 being positioned, the coated metal carbonate may enter inside the pores and cause short-circuiting of heater 1 with the metal oxide 10 that is obtained from the metal carbonate. The above-described insertion and positioning of heater 1 after the coating of the metal carbonate is performed to avoid such a situation.
As shown in
Though besides the abovementioned metal oxides, the use of a metal boride, such lanthanum boride, a metal carbide, a metal nitride, etc. as the thermion supply source may be considered, metal borides, metal carbides, metal nitrides are poor in performance as a thermion supply source that can serve as a hot cathode for gas discharge tube and there is no meaning in adding such compounds as a principle component or a sub-component. However, such compounds may be used at peripheral parts of the cathode for effects besides the effect as a thermion supply source, such as for improving the insulation effect in order to restrain the amount of heat dissipation to parts besides the discharge part.
Also, though indirectly heated cathode for gas discharge tube Cl may be arranged by setting the double coil 2, which holds metal oxide 10 in advance, to be in contact with mesh member 3, so as to set up a condition wherein mesh member 3 contacts metal oxide 10 definitely, it is preferable to coat a metal carbonate as a cathode material in the condition where mesh member 3 has been positioned at the outer side of double coil 2 and to then convert the metal carbonate to metal oxide 10 as described above.
Here, if the line (longitudinal line) resistance in one direction of mesh member 3 is R1h and the line (transverse line) resistance in the other direction is R1s, the relationships of resistance values R1A, R1B, and R1C with respect to the ground (GND) of three predetermined points (designated as point 1A, point 1B, and point 1C, starting from the point closer to the ground (GND) that is the electron supply source) of mesh member 3 will be as follows:
R1A=1/(R1h+2×(R1h+R1s)) (9)
R1A<R1B<R1C (10)
and the discharge will occur in a continuous manner from the vicinity of the part including metal oxide 10 on mesh member 3. Though the discharge current amount will differ according to the work function of each location, suppose that:
I1A>I1B>I1C (11)
As a result, the potential difference among point 1A, point 1B, and point 1C will then be small and proportional to the mesh number and at an approximate level, the potential difference will be small enough to be virtually negligible. Furthermore, a part of the discharge current will not enter mesh member 3 directly from the ground (GND) but will be supplied via metal oxide 10, and this current that is supplied via metal oxide 10 becomes a base for a discharge distribution that is a wide, gradual, continuous, single-peak distribution. This distribution also approximates the temperature distribution of the surface of metal oxide 10.
Since with indirectly heated cathode for gas discharge tube C1 of the first embodiment, mesh member 3 is put in contact with metal oxide 10 as described above, mesh member 3 effectively forms an equipotential surface at the discharge surface (surface of metal oxide 10 and surface of mesh member 3) of indirectly heated cathode for gas discharge tube C1. That is, mesh member 3 is arranged from a plurality of electrical wiring (conductive paths) and does not restrict the flow of current to a single direction. The electrical resistances across ends of the surface of mesh member 3 are thus considerably small, the surface of mesh member 3 is thus put in a substantially equipotential state, and the potential of the discharge surface that is made up of a plurality of discharge points or discharge lines will be substantially uniform. In other words, by mesh member 3, a plurality of electrical circuits, with which discharge currents can flow in directions parallel to the discharge surface, are formed on the discharge surface, that is, a plurality of paths (equipotential circuits) for emission electrons (emissions) are formed.
With indirectly heated cathode for gas discharge tube C1, since an equipotential surface is thus formed effectively by mesh member 3 in contact with metal oxide 10 and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission a mount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened. The sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, can thus be restrained, that is, the degradation of the thermionic emission ability can be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized. Also, since the discharge area is increased, the operation voltage and the generated heat amount of indirectly heated cathode for gas discharge tube C1 can be reduced.
Also, with indirectly heated cathode for gas discharge tube C1, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also since mesh member 3 is used as the electrical conductor, an electrical conductor of an arrangement, which can restrain the degradation of the thermionic emission ability and the movement of the discharge position, can be realized at low cost and in a simpler manner. Also, since mesh member 3 (electrical conductor) is a rigid body, it is easy to process and can be put in close contact with metal oxide 10. Furthermore, the locations at which mesh member 3 contacts metal oxide 10 can be made numerous readily.
With indirectly heated cathode for gas discharge tube C1 of the first embodiment, since heater 1 is used as a core at the outer side of which double coil 2, which holds metal oxide 10, is positioned in a surrounding manner, and mesh member 3 is positioned so as to be in contact with the surface part of metal oxide 10 that is held by double coil 2, the vibration restraining effect of double coil 2 is put to work and the falling off of metal oxide 10 can be prevented thereby. Also, since a large amount of metal oxide 10 will be held between the pitches of double coil 2, the effect of replenishing the metal oxide loss that accompanies the degradation with time during discharge is provided.
As the mesh size of mesh member 3 becomes smaller, the exposed area of metal oxide 10 decreases and thus the sputter resistance of metal oxide 10 improves. However, theoretically, a certain size by which excited or ionized gas that collide with metal oxide 10 will pass through will be necessary in order to cause secondary electron emission. Also, by making the mesh size small, since the area of the equipotential surface is increased, the discharge area can be increased further.
An experiment was conducted to confirm the long service life effect that is obtained by forming an equipotential surface by means of an electrical conductor in the present invention's indirectly heated electrode for gas discharge tube. The results are shown in
As can be understood from
A modification example of the first embodiment shall now be described with reference to
As shown in
Double coil 41, like double coil 2 of the first embodiment, is a multiple coil arranged from a coil wound in coil form and has a mandrel 42. Heater 1 is disposed at the inner side of double coil 41. Mesh member 3 is disposed between heater 1 and double coil 41 and so as to be substantially orthogonal to the discharge direction along the length direction of double coil 41 (heater 1). As shown in
With this modification example, since double coil 41 has mandrel 42, the additional effect that the deformation of double coil 41 during processing can be restrained is provided.
As shown in
Wire member 21, which is formed in wire form, is, like mesh member 3, a conductive rigid body (metal conductor) formed of a single, high-melting-point metal (with a melting point of at least 1000° C.) selected from among groups IIIa to VIIa, VIII, and Ib of the periodic table or, more specifically, from among tungsten, tantalum, molybdenum, rhenium, niobium, osmium, iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, rare earth metals, etc. or an alloy of these metals. With the present embodiment, a wire member made of tungsten is used. The diameter of wire member 21 is set to approximately 0.1 mm. Wire member 21 has a predetermined length and is disposed across the length direction of double coil 2 at the outer side of double coil 2 so as to be substantially orthogonal to the discharge direction. As shown in
Wire member 21 is grounded by being connected to the ground terminal of heater 1. The number of wire member 21 is not limited to one and a plurality of two or more may be provided. Also, welding may be performed at the respective points of contact of wire member 21 with double coil 2.
Wire member 21 is grounded (set to GND) by being connected via lead rod 7 to the ground terminal of heater 1. Double coil 2 is thereby grounded and metal oxide 10, which is the material likely to emit electrons, is thereby set to the ground potential.
An example of a process for manufacturing indirectly heated cathode for gas discharge tube C2 (positioning heater 1 and wire member 21 with respect to double coil 2) shall now be described based on
First as shown in
Thereafter, heater 1 is inserted into the inner side of double coil 2, and as shown in
An example of a process for manufacturing indirectly heated cathode for gas discharge tube C2 (positioning heater 1 and wire member 21 with respect to double coil 2) shall now be described based on
First as shown in
Double coil 2 is then passed through the bent tungsten wire 22 and then the end parts of tungsten wire 22 are welded to lead rod 7. Thereafter, heater 1 is inserted into the inner side of double coil 2 and, as shown in
An example of a process for manufacturing indirectly heated cathode for gas discharge tube C2 (positioning heater 1 and wire member 21 with respect to double coil 2) shall now be described based on
First as shown in
Double coil 2 is then passed through the bent tungsten wire 22 and then the bent parts 22b of tungsten wire 22 are welded to lead rod 7. Thereafter, heater 1 is inserted into the inner side of double coil 2 and, as shown in
Returning now to
As a further example of a process for manufacturing indirectly heated cathode for gas discharge tube C2, the process described using
As described above, with indirectly heated cathode for gas discharge tube C2 of the second embodiment, since wire member 21 is put in contact with metal oxide 10, an equipotential surface is formed effectively by wire member 21 by wire member 21 being in electrical contact with double coil 2 at a plurality of locations, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C2, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also since wire member 21 is used as the electrical conductor, an electrical conductor of an arrangement, which can restrain the degradation of the thermionic emission ability and the movement of the discharge position, can be realized at low cost and in a simpler manner. Also, since wire member 21 (electrical conductor) is a rigid body, it is easy to process and can be put in close contact with metal oxide 10.
As modification examples of indirectly heated cathode for gas discharge tube C2 of the second embodiment, a single wire member 21 may be disposed along the length direction of double coil 2 while being wound a plurality of times around double coil 2 as shown in
Also as modification examples of indirectly heated cathode for gas discharge tube C2 of the second embodiment, a single wire member 21 may be disposed along the length direction of double coil 2 while being bent a plurality of times in a meandering manner at the outer side of double coil 2 as shown in FIGS. 18 to 20B. In
As further modification examples of indirectly heated cathode for gas discharge tube C2 of the second embodiment, a single wire member 21 may be wound a plurality of times over the entire periphery of double coil 2 as shown in FIGS. 21 to 23B. In
As yet a further modification example of indirectly heated cathode for gas discharge tube C2 of the second embodiment, an arrangement may be considered wherein a tungsten wire 22 is bent into hairpin form, a part at one side of the single tungsten wire 22 (corresponding to wire member 21) that has been bent into hairpin form is passed through the inner side of double coil 2, and, with double coil 2 being sandwiched by the part at one side of wire 22 and a part at the other side of wire 22, the end parts of wire 22 are welded to lead rod 7 as shown in
Though illustrations of metal oxide 10 and electrical insulating layer 4 are omitted for the sake of description in
A modification example of the second embodiment shall now be described based on
As shown in
Double coil 41, like double coil 2 of the second embodiment, is a multiple coil arranged from a coil wound in coil form and has a mandrel 42. Heater 1 is disposed at the inner side of double coil 41. Wire member 21 is disposed at the outer side of double coil 41 so as to be substantially orthogonal to the discharge direction along the length direction of double coil 41 (heater 1). As shown in
With this modification example, since double coil 41 has mandrel 42, the additional effect that the deformation of double coil 41 during processing can be restrained is provided.
A modification example of the second embodiment shall now be described based on
As shown in
Single coil 44 is a coil member arranged from a coil wound in the form of a single coil and is formed of a tungsten element wire. Heater 1 is disposed at the inner side of single coil 44. Wire member 21 is disposed at the outer side of single coil 44 so as to be substantially orthogonal to the discharge direction along the length direction of single coil 44 (heater 1). As shown in
As shown in
Base metal 31 is formed to a tubular form and is conductive. Base metal 31 is formed for example of molybdenum, etc. Heater 1 is inserted into and disposed at the inner side of this base metal 31. Double coil 2 is wound a plurality of times around and fixed to the outer surface of base metal 31. Mesh member 3 is positioned substantially orthogonal to the discharge direction. Base metal 31 and mesh member 3 are put in a grounded state by being connected to lead rod 7 and double coil 2 is grounded via base metal 31. Metal oxide 10, which is the material likely to emit electrons, is thereby set to the ground potential. Base metal 31 also functions as a barrier between metal oxide 10, which is the material likely to emit electrons, and electrical insulating layer 4, which is formed on heater 1.
As base metal 31, a high-melting-point metal with a melting point that is higher than the cathode temperature during operation may be used. Also, in place of using double coil 2, a double coil 41 having a mandrel or a single coil may be used. Also, though a tubular member of cylindrical shape is generally used as base metal 31, a tubular member having an arcuate shape with a notch (an open shape) may be used instead.
Metal oxide 10 is held by double coil 2 and is put in contact with mesh member 3. Metal oxide 10 and mesh member 3 are exposed to the outer side of indirectly heated cathode for gas discharge tube C4 so that the surface of metal oxide 10 and the surface of mesh member 3 make up a discharge surface and the surface part of metal oxide 10 is put in contact with mesh member 3. Metal oxide 10 is disposed in the same manner as in the first embodiment. In
As described above, with indirectly heated cathode for gas discharge tube C4 of the third embodiment, since mesh member 3 is put in contact with metal oxide 10, an equipotential surface is formed effectively by mesh member 3 in contact with metal oxide 10, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C4, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also, base metal 31 is provided and can act as a heat conductor for aiding thermal decomposition when a metal carbonate is converted (thermally decomposed) to metal oxide 10 as a thermion supply source. Also, metal oxide 10 and heater 1 can be separated definitely. Furthermore, the reducing ability possessed by base metal 31 can be put to use to reduce metal oxide 10 and produce the free metal element during operation to improve the electron emission ability. Furthermore, the heat from heater 1 can be transferred to metal oxide 10 definitely in the active state.
A modification example of the third embodiment shall now be described based on
As shown in
Double coil 41, like double coil 2 of the third embodiment, is a multiple coil arranged from a coil wound in coil form and has a mandrel 42. Heater 1 is disposed at the inner side of double coil 41. Mesh member 3 is disposed between heater 1 and double coil 41 so as to be substantially orthogonal to the discharge direction along the length direction of double coil 41 (heater 1). As shown in
With this modification example, since double coil 41 has mandrel 42, the additional effect that the deformation of double coil 41 during processing can be restrained is provided.
As shown in
Wire member 21, which is formed to a wire form, is arranged by bending a single wire member a plurality of times in a meandering manner at the outer side of double coil 2 and disposing the wire member so as to be substantially orthogonal to the discharge direction along the length direction of double coil 2. As shown in
Wire member 21 may be disposed in the same manner as in the above-described second embodiment or modification examples thereof and is not limited in number to one but may be provided in plurality of two or more. Also, in place of using double coil 2, a double coil 41, having a mandrel 42 such as that shown in
In
As described above, with indirectly heated cathode for gas discharge tube C5 of the fourth embodiment, since wire member 21 is disposed in contact with metal oxide 10, an equipotential surface is formed effectively by wire member 21 being in electrical contact with double coil 2 at a plurality of locations, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C5, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also base metal 31 is provided and can act as a heat conductor for aiding thermal decomposition when a metal carbonate is converted (thermally decomposed) to metal oxide 10 as a thermion supply source. Also, metal oxide 10 and heater 1 can be separated definitely. Furthermore, the reducing ability possessed by base metal 31 can be put to use to reduce the metal oxide 10 and produce the free metal element during operation to improve the electron emission ability. Furthermore, the heat from heater 1 can be transferred to metal oxide 10 definitely in the active state.
An example of a process for manufacturing indirectly heated cathode for gas discharge tube C5 (positioning double coil 2 and wire member 21 with respect to base metal 31) in a case where there is a single wire member 21 shall now be described based on
As shown in
As shown in
Indirectly heated cathode for gas discharge tube C9 is manufactured by adhering mesh member 3 (in the grounded state) to the outer side of heater 1, coating a metal carbonate from the mesh member 3 side, and converting this metal carbonate to metal oxide 10. It is sufficient that heater 1 have an arrangement wherein an electrical insulating layer 4 is formed at the part to which mesh member 3 is adhered in order to prevent short-circuiting with mesh member 3, and the entire surface of the tungsten filament coil does not necessary have to be coated with an electrical insulating material. Mesh member 3 is disposed substantially orthogonal to the discharge direction, that is, along the length direction of heater 1.
As described above, with indirectly heated cathode for gas discharge tube C9 of the fifth embodiment, since mesh member 3 is put in contact with metal oxide 10, an equipotential surface is formed effectively by mesh member 3 in contact with metal oxide 10, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C9, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Mesh member 3 may be folded or laminated and thereby be made thick to increase the amount of metal oxide 10 held and improve the holding performance.
As shown in
Conductive wire 45 comprises a mandrel (core wire) 46 and a filament (for example, a tungsten element wire) 47, which is wound around the outer periphery of mandrel 46, and has the same arrangement as double coil 41. Conductive wire 45 has a shape that spans a depressed part at one side of mesh member 3 in one direction along the width direction of mesh member 3 and spans a depressed part at the other side of mesh member 3 in the reverse direction along the width direction of mesh member 3.
As described above, with indirectly heated cathode for gas discharge tube C11 of the sixth embodiment, since mesh member 3 is put in contact with metal oxide 10, an equipotential surface is formed effectively by mesh member 3 in contact with metal oxide 10, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C11, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also, with indirectly heated cathode for gas discharge tube C11, since conductive wire 45 has mandrel 46, the additional effect that the deformation of conductive wire 45 during processing can be restrained is provided.
As shown in
Indirectly heated cathode for gas discharge tube C10 is manufactured by fixing mesh member 3, in the grounded state, to the outer side of base metal 31, coating a metal carbonate from the mesh member 3 side, and converting this metal carbonate to metal oxide 10.
As described above, with indirectly heated cathode for gas discharge tube C10 of the seventh embodiment, since mesh member 3 is put in contact with metal oxide 10, an equipotential surface is formed effectively by mesh member 3 in contact with metal oxide 10, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of the cathode can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated cathode for gas discharge tube C10, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated cathode for gas discharge tube of large discharge current with substantially the same shape as that of the prior art and the realization of pulse operation and large current operation.
Also, with indirectly heated cathode for gas discharge tube C10, since mesh member 3 is folded and laminated, the amount of metal oxide 10 held can be increased and the holding performance can be improved.
Next, a gas discharge tube of an eighth embodiment, which uses any of the indirectly heated cathodes for gas discharge tube C1 to C11 of the above-described arrangements, shall be described based on
A gas discharge tube DT1 has a tubular bulb 51 as a sealed container, and a fluorescent film 52 is formed on the inner surface of this tubular bulb 51. Indirectly heated cathodes for gas discharge tube C1 are sealed in an airtight manner at both ends of the interior of tubular bulb 51 in a state where the equipotential surfaces, that is, electrical conductors 3 face each other. By making the equipotential surfaces face each other, the operation of gas discharge tube DT1 is made more stable. Argon or other rare gas, or argon or other rare gas and mercury is or are sealed in the interior of tubular bulb 51.
As a lighting circuit for gas discharge tube DT1, a known, starter (preheating starting) type lighting circuit, having a glow tube 53, a ballast 54, and AC power supply 55 as shown in
Thus with gas discharge tube DT1 of the eighth embodiment, by use of any of indirectly heated cathodes for gas discharge tube C1 to C11, a gas discharge tube (rare gas fluorescent lamp or mercury fluorescent lamp) of long service life and stable operation can be realized.
Though when an AC power supply is used as the power supply, the indirectly heated cathode for gas discharge tube C1 to C11 will undergo a cathode cycle and an anode cycle repeatedly, in the cathode cycle, sputtering of metal oxide 10 due to excessive ion current flow can be prevented by the increase of the discharge area. Also in the anode cycle, mesh member 3 serves the role of an electron focusing part and since the electron receiving area is large, excessive temperature rise can be prevented and vaporization of metal oxide 10 can be restrained.
With the present invention's gas discharge tube, a test was conducted to confirm the long service life and stable operation effects that are provided by the use of any of the indirectly heated cathodes for gas discharge tube C1 to C11 of the above-described arrangements. The results are shown in
With each indirectly heated cathode for gas discharge tube C2, a filament coil, formed by doubly winding a tungsten element wire of 0.55 diameter, was used for the heater. The double coil was made by winding a tungsten element wire of 0.091 mm diameter around a molybdenum mandrel (0.25 mm diameter) at a pitch of 0.15 mm to prepare a primary coil and winding this primary coil six times at a diameter of 1.7mm and a pitch of 0.51 mm. A tungsten element wire of 0.10 mm diameter was used as the wire member and this was formed to a hairpin shape with a gap of approximately 1 mm.
As can be understood from
Also, to make use of the characteristic of the dispersion of discharge, the present invention's indirectly heated cathode for gas discharge tube may be employed in a lamp with one outer electrode, which has an electrode 58 at the exterior of a container 57, has any of indirectly heated cathodes for gas discharge tube C1 to C11 disposed inside container 57, has a rare gas sealed inside container 57, and is driven using a high-frequency power supply 59 as shown in
This type of lamp is an excimer lamp, which is an excimer light emitting lamp. For emission of excimer light using xenon gas as the sealed gas, the gas pressure is set in the range of 2000 Pa (10 Torr) to 100000 Pa (1 atm) and preferably in the range of 10000 Pa (75 Torr) to 50000 Pa (375 Torr).
In a case where a double coil having a mandrel is used as the coil member and an AC power supply is used as the power supply, the discharge is maintained by the balance of the heat amount on the surface of the mandrel. Due to the discharge on the surface of the mandrel, the amount of heat generated on the surface of the electrode is proportional to the discharge current (Id, unit: ampere) Also, as the cross-sectional area (Sm, unit: mm square) of the mandrel increases, the surface area increases and thus the amount of heat loss increases. From the above, the electrode surface temperature (Tc) is in the following relationship:
Tc∝Id/Sm (12)
If the electrode surface temperature is lower than the allowable range, it will be inadequate in terms of the cathode operating temperature. Thus in order to sustain the discharge, the temperature is raised locally to supply thermions, thus causing concentration of discharge. The resulting localized overheating enhances the sputter phenomenon of the material likely to emit electrons and accelerates the degradation of the electrode. On the other hand, if the electrode surface temperature is higher than the allowable range, the entire electrode surface is put in an overheated state, thereby enhancing vaporization of the material likely to emit electrons and accelerating the degradation of the electrode.
Upon conducting experiments with indirectly heated electrodes for gas discharge tube of the arrangement shown in
3<Id/Sm<16 (13)
Also, the present inventors found the following range to be even more preferable:
4<Id/Sm<10 (14)
In the experiments, tungsten element wires of 0.05 mm to 0.20 mm were used as wire members 21 and these tungsten element wires were formed into hairpin forms with gaps of 0.5 mm to 2 mm.
Next, a gas discharge tube of an in th embodiment, which uses any of the indirectly heated cathodes for gas discharge tube C1 to C11 of the above-described arrangements, shall be described based on
The gas discharge tube shown in
With each indirectly heated cathode for gas discharge tube C2, a filament coil, formed by doubly winding a tungsten element wire, was used for heater 1. The double coil was made by winding a tungsten element wire of 0.091 mm diameter around a molybdenum mandrel (0.25 mm diameter) at a pitch of 0.218 mm to prepare a primary coil of 0.433 mm of outer circumferential diameter and winding this primary coil six times at a diameter of 1.7 mm and a pitch of 0.51 mm. A tungsten element wire of 0.10 mm diameter was used as wire member 21.
For the sealed gas, mercury was added to argon at a pressure of 470 Pa. The gap between indirectly heated cathodes for gas discharge tube C2 is preferably set to 10 mm or less so that the discharge voltage will be 20 V or less. A plurality of pairs of indirectly heated cathodes for gas discharge tube C2 may be disposed inside spherical bulb 301. In consideration of the light emission efficiency in a case where there is a fluorescent material, the inner diameter of spherical bulb 301 is preferably in the range of 20 mm to 60 mm.
As a lighting circuit, as shown in
Thus with the gas discharge tube of the ninth embodiment, by use of any of indirectly heated cathodes for gas discharge tube C1 to C11, a gas discharge tube (rare gas fluorescent lamp or mercury fluorescent lamp) of long service life and stable operation can be realized. In particular, an arrangement suitable for a gas discharge tube, with which a negative glow discharge due to AC discharge across a pair of electrodes is to be mainly performed, can be provided.
With each of the gas discharge tubes of the eighth and ninth embodiments, in the case of AC operation, each of the pair of electrodes (indirectly heated cathodes for gas discharge tube C1 to C11) alternatingly serves, as the main functions, the role of a cathode that emits electrons and an anode into which electrons flow. When functioning as an anode, a large amount of heat is generated at an electrode due to the voltage drop that occurs when the electrons flow in. By using the heat amount, which is generated when an electrode functions as the anode, as the heat amount necessary for thermionic emission when the electrode functions as the cathode, stable, sustained discharge can be realized without the supply of heat from heater 1 or with a lower supply of heat in comparison to DC operation during sustained discharge of the gas discharge tube.
Next, a gas discharge tube of a tenth embodiment, which uses any of the indirectly heated cathodes for gas discharge tube C1 to C11 of the above-described arrangements, shall be described based on FIGS. 48 to 50.
A deuterium gas discharge tube DT2 has a glass outer container 61. As shown in
As shown in
Also as shown in
As shown in
As shown in
As shown in
The respective electrodes inside light emitting part 62, which is assembled in the above-described manner, are positioned as shown in
The operation of deuterium gas discharge tube DT2 shall now be described with reference to
Thus with deuterium gas discharge tube DT2 of the tenth embodiment, a deuterium gas discharge tube of long service life and stable operation can be realized by the use of any of indirectly heated cathodes for gas discharge tube C1 to C11.
An eleventh embodiment's lighting device for gas discharge tube shall now be described based on
A lighting device 101 comprises a constant current power supply 103, connected as a power supply between indirectly heated cathode for gas discharge tube C1 and anode 74 of deuterium gas discharge tube DT2, an auxiliary lighting circuit unit 111, connected between anode 74 and focusing electrode 76 in order to generate a trigger discharge across indirectly heated cathode for gas discharge tube C1 and focusing electrode 76, a make-and-break switching circuit unit 121, connected between indirectly heated cathode for gas discharge tube C1 and anode 74 and supplying electricity to a heater 1 for a predetermined period and then cutting off the supply of electricity to heater 1 after the elapse of the predetermined period, and a fixed resistor 131 for current detection, serially connected and installed between anode 74 and constant current power supply 103.
Constant current power supply 103 supplies a DC open voltage of approximately 160 V and a steady-state current of approximately 300 mA. A negative resistance 105 and a diode 107 for discharge stabilization are connected serially to this constant current power supply 103. Negative resistance 105 is set to approximately 50 to 150Ω.
Auxiliary lighting circuit unit 111 includes a fixed resistor 113, which is serially connected and installed between anode 74 and focusing electrode 76, and a capacitor 115, which is connected in parallel to this fixed resistor 113. Make-and-break switching circuit unit 121 includes a glow tube 123. A switch, which is opened after operation (lighting) of deuterium gas discharge tube DT2 may be provided between auxiliary lighting circuit unit 111 and focusing electrode 76. Also, in place of a glow starter system using glow tube 123, an electronic starting system using a semiconductor element with a timer function or a mechanical (contact) switch, which may or may not have a timer function, may be used.
The operation of lighting device 101 shall now be described based on
Though not illustrated in
When these preparations for trigger discharge have been made, the glow discharge at glow tube 123 stops and by the separation of the electrodes of glow tube 123, a potential of approximately 130V is generated at focusing electrode 76 from constant current power supply 103 and via the parallel-connected capacitor 115 and fixed resistor 113, and a trigger discharge is generated across indirectly heated cathode for gas discharge tube C1 and focusing electrode 76 (period A2 in
By thus causing a trigger discharge to occur, an arc discharge is made to occur across indirectly heated cathode for gas discharge tube C1 and anode 74, and based on the current of approximately 300 mA that is supplied across indirectly heated cathode for gas discharge tube C1 and anode 74 from constant current power supply 103, arc discharge is sustained in a stable manner until the main power switch is turned OFF (period A3 in
Since deuterium gas discharge tube DT2 using any of indirectly heated cathodes for gas discharge tube C1 to C3 can be driven in accordance to the relationship expressed by equations (7) and (8) given above, with lighting device 101 of the eleventh embodiment, a lighting device for lighting deuterium gas discharge tube DT2 using any of indirectly heated cathodes for gas discharge tube C1 to C3 can be realized. Also, since a single constant current power supply 103 can be used for the preheating of any of indirectly heated cathodes for gas discharge tube C1 to C3, for the starting of the trigger discharge (discharge by initial gas ionization), and for the main discharge, a power supply for preheating (heater) of any of indirectly heated cathodes for gas discharge tube C1 to C3 is made unnecessary in particular, thus enabling significant reduction of the number of parts and simplification of arrangement.
Also, with lighting device 101, since make-and-break switching circuit unit 121 includes a glow tube 123, make-and-break switching circuit unit 121 can be realized simply and at low cost. Furthermore, since auxiliary lighting circuit unit 111 includes a capacitor 115, auxiliary lighting circuit unit 111 can be realized simply and at low cost. Also, since auxiliary lighting circuit unit 111 includes a fixed resistor 113, the lighting property of deuterium gas discharge tube DT2 can be improved.
Also, with lighting device 101, since a fixed resistor 131 for current detection is provided, the voltage during operation of deuterium gas discharge tube DT2 can be lowered and the consumption power of deuterium gas discharge tube DT2 can thus be lowered.
A twelfth embodiment's lighting device for gas discharge tube shall now be described based on
A lighting device 201 is a general lighting device for a deuterium gas discharge tube and, though details shall be omitted, has a cathode heating voltage source 211, connected to indirectly heated cathode for gas discharge tube C4, and has, as a discharge starting circuit between anode 74 and indirectly heated cathode for gas discharge tube C4, a trigger switch 221, a fixed resistor 223, and a capacitor 225, which are connected successively and serially, and a discharge starting voltage source 227, which is connected in parallel to these parts.
With lighting device 201 of the twelfth embodiment, during the lighting of the deuterium gas discharge tube, the operation voltage of either of indirectly heated cathodes for gas discharge tube C4 and C5 can be lowered to lower the amount of heat generated by either of indirectly heated cathodes for gas discharge tube C4 and C5.
In a case where lighting device 201 is to be used as a lighting device for a deuterium gas discharge tube using any of indirectly heated cathodes for gas discharge tube C1 to C3, it is preferable to serially connect a make-and-break switch to cathode heating voltage source 211 and to open this make-and-break switch during operation of the deuterium gas discharge tube in accordance to the relationships of equations (7) and (8) given above.
Though in the first to seventh embodiments, a mesh member 3 or a wire member 21 is used as the electrical conductor, the electrical conductor is not limited thereto, and a rigid body, which is conductive and has a melting point that is higher than the operating temperature of the cathode, for example, a high-melting-point metal formed to a plate shape (including a ribbon-like or foil-like shape) may be used instead, and a porous metal of low thickness, carbon fibers, etc. may also be used in place of a high-melting-point metal. Also for improvement of the sputter resistance and improvement of the discharge performance of metal oxide 10, a nitride or carbide of tantalum, titanium, niobium, etc. may be attached to the surface of metal oxide 10, mesh member 3, wire member 21, or base metal 31.
As a further modification example of any of the first to seventh embodiments, a plurality of double coils 2 may be provided and a mesh member 3 or a wire member 21 may be disposed across these double coils 2 as shown in
Also, though with the first to seventh embodiments, the surface of mesh member 3 or the surface of wire member 21 is exposed, there is no need for these surfaces to be exposed, and as long as mesh member 3 or wire member 21 is in contact with metal oxide 10, the surface of mesh member 3 or the surface of wire member 21 may be covered by metal oxide 10.
Also, though with the tenth embodiment, the present invention was applied to a side-on type deuterium gas discharge tube, the present invention is not limited thereto and may be applied to a head-on type deuterium gas discharge tube with which light is taken out from a top part of the tube.
A gas discharge tube of a thirteenth embodiment shall now be described based on
As shown in
Though the excimer light emission efficiency varies according to the discharge distance and the discharge sustaining voltage that arises in association with the discharge, the factor that affects the light emission efficiency the most is the sealed gas pressure. Xenon, having a light emission region at 172 nm, is most practical in terms of use, and xenon gas may be used upon being mixed with an other rare gas, such as krypton, neon, etc. Here, as the pressure of the xenon gas that is sealed for practical purposes, a pressure in the range of 2 kPa to 100 kPa may be used in accordance to the discharge distance and other discharge conditions. A xenon gas pressure range of 10 kPa to 50 kPa is favorable for use in that the excimer light emission efficiency peaks within this range.
Outer electrode 411 is formed as a conductive rigid body (metal conductor) of, for example, nickel, stainless steel, etc. With the present embodiment, a nickel element wire of approximately 0.1 mm diameter is woven into mesh form to arrange outer electrode 411. The mesh size of outer electrode 411 is set to approximately 5 to 20 mesh. As shown in
As shown in
Heater 1 comprises a filament coil, with which a tungsten element wire of 0.03 to 0.1 mm diameter, that is for example, a tungsten element wire of 0.07 mm diameter is wound in double, and an electrical insulating material (for example, alumina, zirconia, magnesia, silica, etc.) is coated by electrodeposition, etc. and formed as electrical insulating layer 4 on the surface of this tungsten filament coil. One end part 1a of heater 1 is electrically connected to one lead-in wire 403 among the pair of lead-in wires 403 and 405. The other end part 1b of heater 1 is electrically connected to the other lead-in wire 405 among the pair of lead-in wires 403 and 405.
Electron emitting part 425 emits electrons upon receiving the heat from heater 1 and has a double coil 41 and a metal oxide 10 as a material likely to emit electrons. Double coil 41 is a multiple coil arranged from a coil that is wound in coil form, and a tungsten element wire of 0.091 mm diameter is formed into a primary coil with a diameter of 0.25 mm and a pitch of 0.146 mm and this primary coil is formed into a double coil with a diameter of 1.7 mm and a pitch of 0.6 mm. Heater 1 is inserted into and disposed at the inner side of double coil 41.
Double coil 41 has a mandrel 42. Here, the mandrel is a core wire that serves the role of a mold that determines the winding diameter in the process of preparing the filament coil.
Each wire member 21 is a conductive rigid body (metal conductor) formed of a single, high-melting-point metal (with a melting point of at least 1000° C.) selected from among groups IIIa to VIIa, VIII, and Ib of the periodic table or, more specifically, from among tungsten, tantalum, molybdenum, rhenium, niobium, osmium, iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, rare earth metals, etc. or an alloy of these metals. With the present embodiment, wire members made of tungsten are used. The diameter of each wire member 21 is set to approximately 0.1 mm. Each wire member 21 is disposed across the length direction of double coil 41 at the outer side of double coil 41 so as to be substantially orthogonal to the discharge direction, and double coil 41 and wire member 21 are electrically connected. Though in the present embodiment, the number of wire members 21 is set to two, the number is not limited thereto and may be one or three or more. As with one end part 1a of heater 1, wire member 21 is electrically connected to lead-in wire 403.
Metal oxide 10 is held by double coil 41 and is put in contact with wire member 21. Metal oxide 10 and wire member 21 are exposed to the outer side of indirectly heated electrode C2 so that the surface of metal oxide 10 and the surface of wire member 21 make up a discharge surface and the surface part of metal oxide 10 is put in contact with wire member 21.
As metal oxide 10, a single oxide of a metal selected from among barium (Ba), strontium (Sr), and calcium (Ca), or a mixture of such oxides, or an oxide, with which the principle component is a single oxide of a metal selected from among barium (Ba), strontium (Sr), and calcium (Ca) or a mixture of such oxides and a sub-component is an oxide of a metal selected among rare earth metals including lanthanum (metals of group IIIa of the periodic table), is used. Each of barium, strontium, and calcium is low in work function, can emit thermions readily, and enable the thermion supply amount to be increased. Also, in a case where a rare earth metal (metal of group IIIa of the periodic table) is added as a sub-component, the thermion supply amount can be increased further and the sputter resistance can be improved as well.
As the electrode material, metal oxide 10 is coated in the form of a metal carbonate (for example, barium carbonate, strontium carbonate, calcium carbonate, etc.) and obtained by vacuum thermal decomposition of the coated metal carbonate. In the final stage, the metal oxide 10 that is thus obtained becomes the material likely to emit electrons. The metal carbonate that is to be the electrode material is coated from the wire member 21 side in the condition where heater 1 is positioned at the inner side of double coil 41 and wire member 21 is positioned at the outer side of double coil 41.
Referring again to
With gas discharge tube DT3 of the above-described arrangement, when indirectly heated electrode C2 is preheated and a high-frequency voltage is applied across outer electrode 411 and indirectly heated electrode C2, electron emitting part 425 (metal oxide 10) receives the heat from heater 1 and emits electrons, and a dielectric barrier discharge is thus generated. By the generation of this dielectric barrier discharge, excimer molecules of xenon gas are formed. Excimer light (vacuum ultraviolet light) is then emitted by the formed excimer molecules of xenon. If a fluorescent material is coated onto the inner surface of glass bulb 401, the coated fluorescent material is excited by the excimer light and emits visible light.
Thus with gas discharge tube DT3 of the thirteenth embodiment, since indirectly heated electrode C2 is used as the inner electrode, the potential (acceleration voltage) necessary for emission of discharge electrons from indirectly heated electrode C2 can be kept low and the emission efficiency of gas discharge tube DT3 can be made high.
Also since indirectly heated electrode C2 is used as the inner electrode, a high discharge current can be taken out from the inner electrode (indirectly heated electrode C2). The discharge current amount per unit area of outer electrode 411 is thus increased and the amount of xenon excimer molecules that are produced is increased. As a result, the optical output of gas discharge tube DT3 can be made high.
With indirectly heated electrode C2 of the thirteenth embodiment, since wire member 21 is disposed in contact with metal oxide 10, an equipotential surface is formed effectively by wire member 21, and thermionic emission thus occurs over a wide region of the equipotential surface that is formed, the discharge area is increased, the electron emission amount per unit area (electron emission density) is increased, and the load placed on the discharge position is lightened, thereby enabling the sputtering of metal oxide 10 and stabilization (mineralization) due to oxidation with the reduced metal, which are degradation factors, to be restrained, that is, the degradation of the thermionic emission ability to be restrained. As a result, the occurrence of localized discharge can be restrained and long service life of indirectly heated electrode C2 can be realized. Since the movement of the discharge position is also restrained, stable discharge over a long period of time can be realized.
Also, with indirectly heated electrode C2 of the thirteenth embodiment, due to the increase of the discharge area, even if the current density is slightly increased and the load is somewhat increased, that is, even if the discharge current is increased, the damage can be made less than that of the prior art. This enables the provision of an indirectly heated electrode of large discharge current with substantially the same shape as that of the prior art.
Also since wire member 21 is used as the electrical conductor in indirectly heated electrode C2 of the thirteenth embodiment, an electrical conductor of an arrangement, which can restrain the degradation of the thermionic emission ability and the movement of the discharge position, can be realized at low cost and in a simpler manner. Also, since wire member 21 (electrical conductor) is a rigid body, it is easy to process and can be put in close contact with metal oxide 10.
Also with indirectly heated electrode C2 of the thirteenth embodiment, since heater 1 is used as a core at the outer side of which double coil 41, which holds metal oxide 10, is positioned in a surrounding manner and wire member 21 is positioned so as to be in contact with the surface part of metal oxide 10 that is held by double coil 41, the vibration restraining effect of double coil 41 is put to work and the falling off of metal oxide 10 is thereby prevented. Also, since a large amount of metal oxide 10 will be held between the pitches of double coil 41, the effect of replenishing the metal oxide loss that accompanies the degradation with time during discharge is provided.
Also with indirectly heated electrode C2 of the thirteenth embodiment, since double coil 41 has mandrel 42, the deformation of double coil 41 during processing can be restrained. Furthermore, since double coil 41 has mandrel 42, double coil 41 is made high in heat capacity and improved in heat resistance.
A gas discharge tube DT4 of a fourteenth embodiment shall now be described based on
As with the thirteenth embodiment, a gas discharge tube DT4 is equipped with a glass bulb 401, lead-in wires 403 and 405, an outer electrode 411, and an indirectly heated electrode C2. However, as shown in
As shown in
As shown in
With gas discharge tube DT4 of the above-described arrangement, when indirectly heated electrode C2 is preheated and a rectangular wave voltage is applied across outer electrode 411 and indirectly heated electrode C2, electron emitting part 425 (metal oxide 10) receives the heat from heater 1 and emits electrons, and a dielectric barrier discharge is thus generated. Excimer molecules of xenon gas are formed by this dielectric barrier discharge and excimer light is thereby emitted.
As with gas discharge tube DT3 of thirteenth embodiment, since indirectly heated electrode C2 is used as the inner electrode in gas discharge tube DT4 of the fourteenth embodiment, the potential (acceleration voltage) necessary for emission of discharge electrons from indirectly heated electrode C2 can be kept low and the emission efficiency of gas discharge tube DT4 can be made high.
Also since indirectly heated electrode C2 is used as the inner electrode, a high discharge current can be taken out from the inner electrode (indirectly heated electrode C2). The discharge current amount per unit area of outer electrode 41 is thus increased and the amount of xenon excimer molecules that are produced is increased. As a result, the optical output of gas discharge tube DT4 can be made high.
Also, with gas discharge tube DT4 of the fourteenth embodiment, since excimer light is reflected by light reflecting member 451 and is emitted from a part at which light reflecting member 451 is not provided, a large optical output can be obtained at a compact size in comparison to a gas discharge tube of an arrangement with which light is emitted substantially uniformly from the entire circumference of the outer surface of a glass bulb 401 (for example, gas discharge tube DT3 of the thirteenth embodiment).
A gas discharge tube DT5 of a fifteenth embodiment shall now be described based on
As with the thirteenth and fourteenth embodiments, a gas discharge tube DT5 is equipped with a glass bulb 410, lead-in wires 403 and 405, outer electrode 411, and indirectly heated electrode C2. As shown in
As shown in
As with gas discharge tube DT3 of thirteenth embodiment and gas discharge tube DT4 of the fourteenth embodiment, since indirectly heated electrode C2 is used as the inner electrode in gas discharge tube DT5 of the fifteenth embodiment, the potential (acceleration voltage) necessary for emission of discharge electrons from indirectly heated electrode C2 can be kept low and the emission efficiency of gas discharge tube DT5 can be made high.
Also since indirectly heated electrode C2 is used as the inner electrode, a high discharge current can be taken out from the inner electrode (indirectly heated electrode C2). The discharge current amount per unit area of outer electrode 41 is thus increased and the amount of xenon excimer molecules that are produced is increased. As a result, the optical output of gas discharge tube DT5 can be made high.
Also, as with gas discharge tube DT4 of the fourteenth embodiment, since excimer light is reflected by light reflecting member 451 and is emitted from a part at which light reflecting member 451 is not provided with gas discharge tube DT5 of the fifteenth embodiment, a large optical output can be obtained at compact size in comparison to a gas discharge tube of an arrangement with which light is emitted substantially uniformly from the entire circumference of the outer surface of a glass bulb 401 (for example, gas discharge tube DT3 of the thirteenth embodiment).
Though with the thirteenth to fifteenth embodiments described above, examples of use of indirectly heated cathode for gas discharge tube C2 of the second embodiment as the indirectly heated cathode for gas discharge tube were described, any of indirectly heated cathodes for gas discharge tube C1 and C4 to C11 may be used in place of indirectly heated cathode for gas discharge tube C2. Also, besides xenon gas, a single gas of krypton (Kr), argon (Ar), or neon (Ne) or a mixed gas, etc. may be used as the gas with which excimer molecules are formed by dielectric barrier discharge.
This invention's indirectly heated cathode for gas discharge tube, gas discharge tube using this cathode, and lighting device for the gas discharge tube may be used in rare gas lamps, rare gas fluorescent lamps, mercury lamps, mercury fluorescent lamps, deuterium lamps, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2000-379360 | Dec 2000 | JP | national |
| P2001-238226 | Aug 2001 | JP | national |
| P2001-238207 | Aug 2001 | JP | national |
This is a continuation application of copending application Ser. No. 10/450,110, having a § 371 date of Jun. 11, 2003, which is a national stage ailing based on PCT International Application No. PCT/JP01/10940, filed on Dec. 13, 2001. The copending application No. Ser. 10/450,110 is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10450110 | Jun 2003 | US |
| Child | 11222934 | Sep 2005 | US |
