Patent Grant
7775847
This application claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2006-249597 filed on Sep. 14, 2006, which is hereby incorporated in its entirety by reference.
1. Technical Field
The presently disclosed subject matter relates to a method for manufacturing a hot cathode fluorescent lamp.
2. Description of the Related Art
Hot cathode fluorescent lamps have a filament coated with an emissive material (being a so-called “emitter”) in the form of carbonate. If such a filament is supplied with a current while under vacuum, heat energy is generated at the filament, thereby changing the emitter that is in the form of carbonate into the corresponding metal oxide (being activated) to exhibit an electron emission characteristic.
One conventional exemplary configuration of such a hot cathode fluorescent lamp is shown in
Such a conventional hot cathode fluorescent lamp should have an insulating coating on the lead wires 51 that extend from the flare stem 52 to the vicinity of the filament coil 50. This insulating coating can restrict the injection of electrons into the lead wires 51 located at a position which is opposite to the discharge passage. This restriction can reduce the electrode fall voltage and can suppress the voltage drop. In addition to this, it is possible to improve its luminous efficiency.
In some other hot cathode fluorescent lamps, the same effects can be given by using a bead stem instead of such a flare stem 52 (see, for example, Japanese Patent Application Laid-Open No. Hei 06-349448).
In the hot cathode fluorescent lamp configured as described above, the flare stem 52 seals the lead wires 51 and the exhaust pipe 53 therein. The lead wires are disposed substantially parallel with each other in the longitudinal direction of the glass bulb 55. It should be noted that the exhaust pipe 53 extends from the inside of the glass bulb 55 to the outside of the glass bulb 55. In addition to this, the lead wires 51 are connected to the filament coil 50 disposed in the end region of the glass bulb 55 and extend to the outside of the glass bulb 55.
In this instance, if the outer diameter of the glass bulb 55 is 7 mmφ, the outer diameter of the exhaust pipe 53 should be 2 mmφ (i.e., a very thin pipe), which is the minimum limit for fabrication, due to the positional relationship between the lead wires 51 and the exhaust pipe 53. Since the flare stem 52 must be formed by flame processing, it is difficult to use a larger-sized flare stem to ensure the dimensional accuracy. Therefore, the miniaturization of such a flare stem is limited. Accordingly, if the flare stem 52 is used for the mount 54, the outer diameter of the glass bulb 55, to which the flare stem 52 is to be attached, must be approximately 7 mmφ or greater. In other words, if a fluorescent lamp employs a glass bulb 55 with the diameter of less than approximately 7 mmφ, such a fluorescent lamp cannot employ a mount using the flare stem 52.
On the other hand, if a bead stem is used for the mount 54, one side of the glass bulb where the mount is located is utilized as an exhaust pipe section. In this instance, the lead wires are connected to the filament coil at respective ends and are positioned within the exhaust pipe section at respective other ends. In other words, the lead wires are positioned within the vacuum system to be in vacuum.
After the inside of the glass bulb is evacuated, the filament coil supported within the glass bulb is supplied with a current to activate the emitter coated on the filament coil. In order to connect the lead wires located inside the glass bulb with an external power source line, a clamp section to connect them should be provided inside the exhaust pipe. Accordingly, the clamp section should have an air discharge function as well as a chucking function for supplying a current. In order to achieve both of these functions, the clamp section is required to have an accurate and complex structure for keeping airtightness.
Furthermore, suppose that the lead wires are connected to the filament coil at respective ends and protrude from the end of the exhaust pipe section of the vacuum system at respective other ends. In this case, if the outer diameter of the exhaust pipe section (glass bulb) is less than approximately 7 mmφ, the outer diameter of the lead wires should be 0.3 mmφ or less, which is very thin in this type of lead wire. Accordingly, if the lead wires extend over a long distance, the wires may sag and/or bend undesirably, resulting in possible contact with each other or other problems.
Furthermore, if the diameter of the glass bulb is made smaller, the filament coil would be closer to the inner wall of the glass bulb. In this case, only with the bead stem, it is difficult to secure a certain gap between the filament coil and the inner wall of the glass bulb with high accuracy. In an extreme case, it would be conceivable that the filament coil is brought into contact with the inner wall of the glass bulb. If the filament coil comes into contact with the inner wall of the glass bulb, the heat generated at the filament coil may transfer to the glass bulb, resulting in a deterioration of the stable activation of the emitter. This may lead to unstable luminous intensity at the time of turning on. Furthermore, this may undesirably affect the product life characteristics of the hot cathode fluorescent lamp itself.
The presently disclosed subject matter has been developed in view of the foregoing features, problems, and characteristics associated with conventional technologies. A method for manufacturing a hot cathode fluorescent lamp is disclosed which attempts to ensure the stable initial luminous intensity and provide improved product life characteristics even if the hot cathode fluorescent lamp employs a glass tube with a smaller outer diameter. The presently disclosed subject matter also relates to a method for manufacturing a hot cathode fluorescent lamp with good productivity and with good reproduction stability.
One aspect of the presently disclosed subject matter is a method for manufacturing a hot cathode fluorescent lamp. The hot cathode fluorescent lamp can include a glass tube that has an inner wall which is uniformly coated with a phosphor, glass beads for sealing respective ends of the glass tube, mercury and a rare gas which are sealed within the glass tube, lead wires which are sealed within the respective glass beads and penetrate the respective glass beads, and filaments which are provided at respective ends of the glass tube within the glass tube and which are connected to respective lead wires. The method can include: preparing the glass tube, the inner wall of which is uniformly coated with a phosphor, and two mounts, each of the mounts sealing a pair of the lead wires, ends of the lead wires of one of the mounts each having a bent portion bent outwardly with respect to an axial direction of the glass tube, the other ends of the lead wires supporting and connecting to the filament, the filament being coated with an emissive material; inserting one of the mounts while the filament is directed toward the glass tube till the bent portions of the lead wires abut against an opening end of the glass tube so as to dispose the filament in the vicinity of the one end of the glass tube; forming a vacuum system using an inner space communicating with the glass tube and an exhaust pipe by welding the opening end of the glass tube and an opening end of the exhaust pipe made of a glass material while the bent portions are sandwiched between the opening ends of the glass tube and the exhaust pipe, inserting the other mount while the filament is directed toward the glass tube and disposing the other mount at an appropriate position near the other opening end of the glass tube, and welding the glass tube and the glass bead of the other mount at a predetermined position; activating the emissive material on the filament by evacuating the vacuum system and applying a voltage to the bent portions of the lead wires protruding from the welding portion between the glass tube and the exhaust pipe toward outside of the vacuum system; after activating the emissive material on the filament, supplying mercury and a rare gas into the vacuum system, and sealing the glass tube and the glass bead of the one mount; and removing unnecessary portions of the glass tube, the exhaust pipe and the lead wires.
In an exemplary configuration, the inner diameter of the exhaust pipe can be equal to or greater than the inner diameter of the glass pipe.
In accordance with an aspect of the method for manufacturing a hot cathode fluorescent lamp of the presently disclosed subject matter, the vacuum system can be formed by the inner space of the glass tube and that of the exhaust pipe. One end of the lead wire can be connected to the filament, and the other end thereof can be configured to protrude from the vacuum system toward the outside of the vacuum system. Accordingly, the clamping-connection to the lead wires with the external power source line can be achieved outside the vacuum system so that a voltage can be applied between the ends of the lead wires and the emitter on the filament can be activated by heat generated by energizing the filament.
Accordingly, it is not necessary for the clamp section to have an air discharge function. This can eliminate any complex chucking function for supplying a current.
In manufacturing a conventional hot cathode fluorescent lamp using bead stems, the positioning of the bead stems within the glass tube is sometimes unstable. In some cases, the filament supported by and connected to the lead wires which are sealed in the bead stem may tilt to deteriorate the positional accuracy of the filament, resulting in possible contact with the inner wall of the glass tube.
On the contrary, in accordance with an aspect of the disclosed method for manufacturing a hot cathode fluorescent lamp, the glass tube and the exhaust pipe are integrally welded with the lead wires being sandwiched therebetween. Accordingly, the bead stem sealing the lead wires can be fixed in position within the glass tube by means of the sandwiched lead wires. Consequently, the filament supported by and connected to the lead wires which are sealed in the bead stem can be kept at a predetermined position within the glass tube with high positional accuracy.
This can prevent any contact of the filament coil with the inner wall of glass tube, thereby ensuring or at least making more likely the stable activation of the emitter as well as stable initial luminous intensity. Further to this, the product life characteristics of the hot cathode fluorescent lamp itself as well as the reproducibility of production can be improved.
In accordance with an aspect of the presently disclosed subject matter, the inner diameter of the exhaust pipe may be equal to or greater than the inner diameter of the glass tube. By doing so, it is possible to increase an exhaust rate from the vacuum system, thereby improving the production efficiency.
Furthermore, since the mount in accordance with the presently disclosed subject matter does not necessarily employ flare stems, very thin hot cathode fluorescent lamps with the inner diameter of, for example, 7 mmφ or smaller can be manufactured.
In accordance with another aspect of the disclosed subject matter, a method for manufacturing a fluorescent lamp can include providing a first tube having a longitudinal axis and a first cross-sectional diameter, a second tube having a second cross-sectional diameter, and a mount structure separate from the second tube, the mount structure including a bead, a filament, and lead wires. The method can include placing the mount structure in a first end portion of the first tube, placing the second tube adjacent the first tube and mount structure to locate the lead wires between the first tube and the second tube, heating the first tube and the second tube to seal the lead wires between at least a portion of the first tube and a portion of the second tube, exhausting the first tube during or subsequent to heating the first tube and the second tube, and sealing the first end portion of the first tube.
These and other characteristics, features, and advantages of the disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein:
a)-(h) include process diagrams (a) through (h) showing a method for manufacturing a hot cathode fluorescent lamp in accordance with principles of the presently disclosed subject matter;
A description will now be given of exemplary embodiments in accordance with the presently disclosed subject matter in detail with reference to
a)-(h) show a method for manufacturing a hot cathode fluorescent lamp in accordance with the presently disclosed subject matter. Hereinafter, the manufacturing processes will be described in detail.
In the process shown in
In the mount 2a, the other ends of the pair of lead wires (at the opposite end to the filament 6 side) have respective bent portions 7 which are bent outwardly in opposite respective directions. It should be appreciated that the bent portions 7 are not necessary to be bent in exactly opposite respective directions as shown in the drawing. In other words, the bent portions 7 may be bent in any direction as long as a certain insulating distance between the lead wires with respect to the axial direction of the glass tube can be secured (for example, in a normal direction, in a radial direction, or the like).
In the process shown in
In the process shown in
Accordingly, the bent portions 3a are sealed in the welding portion 13 of the opening end 9 of the glass tube 1 and the opening end 11 of the exhaust pipe 10. At the same time, the inner space of the glass tube 1 and the inner space of the exhaust pipe 10 communicate with each other and this state can be kept.
In the presently disclosed subject matter, when the inner diameter of the glass tube 1 is D1 and the inner diameter of the exhaust pipe 10 is D2, the relationship between the inner diameter of the glass tube 1 and the inner diameter of the exhaust pipe 10 may be D1>D2. However, in other modes of the presently disclosed subject matter, it is possible to hold D1=D2 as shown in
In the process shown in
In the process shown in
In the process shown in
In the process shown in
In the process shown in
Therefore, the complete hot cathode fluorescent lamp is constituted by a glass tube that can have an inner wall which is uniformly coated with a phosphor and which is sealed with the respective glass beads at both ends thereof. Mercury and a rear gas can be sealed within the glass tube. Filaments can be located at respective ends of the inner space of the glass tube, and the lead wires can be connected to the respective filaments through respective glass beads.
As described above, in accordance with a method for manufacturing a hot cathode fluorescent lamp, even if a hot cathode fluorescent lamp with a glass tube of thin diameter (for example, the inner diameter of less than 7 mmφ) which does not include flare stems is conventionally manufactured, the ends of the lead wires, which support and are connected to the respective filaments at ends thereof, can protrude from the vacuum system to the outside of the vacuum system. The vacuum system can be constituted by the inner space of the glass tube and the inner space of the exhausted pipe communicating with each other. The ends of the lead wires of the mount can be clamp-connected to the power source lines outside the vacuum system and a voltage can be applied thereto, thereby energizing the filaments to activate the emitter on the filaments by generated heat.
Accordingly, it is not necessary for a clamp section to have an air discharge function. This can eliminate complex chucking functions in which a current is supplied.
In manufacturing a conventional hot cathode fluorescent lamp using bead stems, the positioning of the bead stems within the glass tube is unstable. In some cases, the filament supported by and connected to the lead wires which are sealed in the bead stem may tilt, resulting in possible contact with the inner wall of the glass tube.
On the contrary, in accordance with an aspect of a method for manufacturing a hot cathode fluorescent lamp according to the presently disclosed subject matter, the glass tube and the exhaust pipe can be integrally welded with the lead wires sandwiched therebetween. Accordingly, the bead stem sealing the lead wires can be fixed in position within the glass tube by means of the sandwiched lead wires. Consequently, the filament supported by and connected to the lead wires which are sealed in the bead stem can be kept at a predetermined position within the glass tube with high positional accuracy.
The above-described structure can prevent contact of the filament coil to the inner wall of glass tube, thereby ensuring or facilitating stable activation of the emitter as well as stable initial luminous intensity. In addition to this, the product life characteristics of the hot cathode fluorescent lamp itself as well as the reproducibility of production can be improved.
Furthermore, the inner diameter of the exhaust pipe forming the vacuum system may be equal to or greater than the inner diameter of the glass tube. By doing so, it is possible to increase exhaust rate from the vacuum system, thereby improving the production efficiency.
Furthermore, since the above-described mount does not employ a flare stem, and therefore very thin hot cathode fluorescent lamps with the inner diameter of, for example, 7 mmφ or smaller can be manufactured.
It should be understood that various modifications and changes from the above described embodiments are contemplated and would fall within the scope of the presently disclosed subject matter. For example, the term glass can be considered to refer to any of the known materials used for manufacturing light bulb housing structures, including pure quartz materials, and other silica based and ceramic glasses and mixtures. Glass beads can be formed in various shapes and sizes and still fall within the spirit and scope of the presently disclosed subject matter. Likewise, the shape and size of the glass tube 1 can also be varied to include bent tubes, square cross-section tubes, polygonal cross-section tubes, oval cross-section tubes, non-symmetrical cross-section tubes, etc.
While there has been described what are at present considered to be exemplary embodiments of the presently disclosed subject matter, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover such modifications as fall within the true spirit and scope of the presently disclosed subject matter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-249597 | Sep 2006 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4272702 | Teshima et al. | Jun 1981 | A |
| 6890235 | Lee | May 2005 | B2 |
| 6988923 | Kobayashi et al. | Jan 2006 | B2 |
| Number | Date | Country |
|---|---|---|
| 6-349448 | Dec 1994 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080070467 A1 | Mar 2008 | US |
