The invention relates to a lamp as well as a manufacturing method therefor. Particularly, it relates to flash lamps.
A flash lamp according to the preamble of the independent claims is known from DE 102 57 477.4.
Here, the opening of a glass tube is sealed by melted-on aluminum. This may be carried out on both sides in the same way. In order to obtain favorable ignition characteristics of the flashtube, specifically formed auxiliary bodies made of specific materials are melted inside the flash lamp into the sealing aluminum. The auxiliary bodies are made of, or provided with, materials which easily emit electrons so as to be able to readily provide the electrons necessary for sparking.
In order to obtain favorable ignition characteristics substantial attention was put on the material selection for the auxiliary bodies because this may improve the ignition quality of the above-described flash lamps. In fact, good ignition of the flash lamps can be achieved by means of this technology. The separate auxiliary body was provided because it was not possible to directly provide the aluminum melted on for sealing the tube opening at the inner surface thereof with the desired material properties. Accordingly, it was necessary to insert a correspondingly made auxiliary body into the tube interior and to melt it onto the sealing aluminum to also bring it into electrical contact.
The known structure has the drawback that its manufacture is cumbersome and therefore expensive. First, the auxiliary body has to be produced, next it has to be inserted into the tube interior and then brought into contact in a suitable manner. Moreover, as an auxiliary body is provided in addition to the seal, the dimensions of the flash lamp are comparatively long as the flash length (gap between the electrodes) in the axial direction is lengthened by the axial extension of the two seals and that of the auxiliary body.
Both drawbacks—laborious and thus expensive manufacturing method and comparatively large design—comply less and less with modern requirements. On the one hand, more and more disposable cameras (i.e., which serve for exposing a single film) are also equipped with flash lamps. These must be especially cheap. Moreover, an increasing number of mobile electronic devices, such as palms, mobile phones, PDAs, are equipped with cameras which themselves require a flashlight. In this case, in particular the dimension is a critical value.
It is the object of the invention to provide a flash lamp and a manufacturing method therefor which permit the assembly of a compact and easily ignitable lamp of long durability in a simple manufacturing process.
This object is achieved by means of the features of the independent claims. The dependent claims are directed to preferred embodiments of the invention.
A lamp comprises a preferably tubular container consisting of at least partly transparent material, such as glass, in particular quartz glass or hard glass, with at least a first opening sealed by a metallic, preferably aluminum-containing first seal. The surface of the first seal facing the interior of the container includes a convex portion, in particular a dome arching towards the interior of the container. The angle between the inner wall of the container and the surface of the seal may be acute, particularly <90°, preferably <45°.
The connection of the first seal to the container and the container wall, respectively, can be achieved by melting the first seal onto the container surface.
A lamp, particularly a flash lamp, may include a preferably tubular container consisting of an at least partly transparent material, preferably glass, quartz glass or hard glass, which has a first opening sealed with a first seal that may be metallic and preferably contains aluminum. Inside the container there may be a material which easily emits electrons. The material may include barium and/or caesium. It may be caesium iodide.
Cameras and in particular portable telecommunications devices equipped with cameras may include the above-described flash lamps.
According to the invention the metal sealing the container opening has an electrical function as a cathode and a mechanical function as a seal. It has surprisingly been found that the comparatively low-melting aluminum is yet suitable as an electrode material. Due to its low vapor pressure, its low tendency to sputter and its good thermal conductivity it does not lead to any blackening of the inner wall of the lamp when it is used as an electrode material.
In the following, separate embodiments are described with reference to the drawings, wherein:
The lamp comprises an container which in the embodiment of
The first seal includes aluminum or an aluminum alloy. Due to their material characteristics with respect to durability, connectibility with the surrounding glass and electric values, aluminum and aluminum alloys are very suitable materials. The seal does not include auxiliary bodies, at least not of the kind which would have an electrical function as an interior anode or cathode. The surface of the first seal 11 facing the interior 17 of the container may directly be the material of which the first seal 11 is made. Its material composition may be comparatively homogeneous across the whole volume, which, however, does not exclude the provision of coating layers. It is preferred for the first seal not to include any auxiliary body. It will then have a comparatively homogeneous structure. However, a contact may for example be cast onto or into the outside.
When the first seal is produced (attachment to the tube), it is ensured that in the end the interior surface of the first seal 11 is not oxidized. This may comprise removing any previously generated oxide layers and/or subsequent working in an inert or evacuated environment.
The first seal 11 may be formed inside without an auxiliary body. The surface of the first seal 11 facing the interior 17 of the container is convex in at least some parts and may be dome-shaped, as shown in
The connection of the first seal 11 to the glass tube is vacuum-tight and gastight, respectively. Neither does ambient air from outside enter into inside the glass tube nor does the gas filling of the tube in turn pass from inside to the outside during the life-time of the flash lamp. The gastight connection between the first seal 11 and the glass tube 10 can be made at the inner wall 16 of the glass tube 10. However, the connection between the first seal 11 and the face 15 of the glass tube may also be gastight if and as far as this face 15 is covered by the first seal 11.
The outside surface of the first seal 11 may level with the face 15 of the tube 10. It may also arch convexly to the outside or concavely to the inside. The first seal 11 may completely or partly cover the face 15. On the left,
Reference numeral 18 denotes the spot of the first seal 11 extending farthermost into the tube, i.e. which is closest to the other, opposite electrode. In any way, it is preferred that this portion 18 be convex. The first seal 11 is electrically conductive and forms a first electrode of the lamp. The second seal 12 may be conductive and form the second electrode of the lamp. The foremost portion 18 does not abut the inner wall 16 of the glass tube 10. Rather, it is spaced apart therefrom, preferably by at least 10% of the inner diameter di of the tube.
The invention as described by means of the embodiment of
The outside surface of the first seal 11 can be shaped in such a way that it is solderable. For example, the shaping may comprise a coating 32 which completely or partly covers the outside surface of the first seal 11. The coating consists of a different material or alloy than the material of the first seal 11.
In the case of a constant circular cross-section, the outer diameter da is preferably <20 mm, more preferably <10 mm, more preferably <5 mm and more preferably <3 mm. The inner diameter di is preferably <18 mm, preferably <8 mm, more preferably <3 mm, more preferably <2 mm. The flash length 1a (gap between the electrodes of the lamp, more concretely between the foremost portions 18 of the seals) is preferably <15 mm, more preferably <6 mm, more preferably <3 mm, more preferably <2 mm.
The material of the first seal contains aluminum. It may be a specific aluminum alloy. The aluminum or its alloy does not include elements which vaporize easily. Pure aluminum (weight proportion in particular >98%, preferably >99.9%) may also be used.
The interior 17 of the lamp contains an inert gas, preferably xenon, at a predetermined filling pressure. It is preferred for the interior 17 of the lamp to also contain a material which easily emits electrons. The material may include pure caesium and/or barium or compounds of these elements. It may include caesium iodide. At room temperature, the material is present as gas or vapor. Liquid droplets may also be present.
As far as it is stated that the first seal does not include an auxiliary body this may be understood implicitly or to the effect that it does not include an auxiliary body with an electrical function, in particular as an inside cathode and anode, respectively, of the flash lamp. However, auxiliary bodies with a different function, for example, for forming a volume at the seal, may be provided, such as a molded-in body consisting, for example, of glass, which seals at least a part of the volume of the opening and is at least partly surrounded by the aluminum-containing material.
Preferably at least 20%, more preferably at least 40%, of the surface of the first seal located inside the container are convexly shaped.
Starting from the face 15 of the tube, the depth of penetration t of the first seal 11 into the interior of the tube is preferably smaller than twice the inner diameter di of the tube.
The first seal can be melted on the container wall—as schematically shown in FIG. 10—as a method for manufacturing the seal and the lamp, respectively, in a way that the liquid or doughy material 112 of the seal is pressed against the capillary resistance and possibly against the material resistance from a supplied external device 110 into the opening of the container 10 to be sealed where it cools and solidifies. When it is pressed inside, the material at first only passes to the face of the tube 10 (dashed surface 114) while lying inside the device 110 (dashed surface 113), then begins to extend into the tube 10 (dashed surface 113) and finally assumes the ultimate position (surface 113) in which it solidifies. The symbol 111 denotes heating means. Controlled pressing means which effect that the material is pressed inside are not shown. An optical sensor may be provided for the control feedback.
Comparatively pure aluminum can be processed in a temperature range of above 660° C. and preferably below 700° C. It may also be processed in a temperature range below 660° C. and preferably above 640° C. When it is still in a warm state exchange processes (diffusion) after the pressing-in take place between the seal material and the material of the container wall which result in an intimate and durable vacuum-tight connection.
Depending on the temperature of the pressed-in material the process may include features of impact extrusion, i.e. wherein more or less doughy material is pressed into the opening with the required pressure.
As an alternative, the method may provide the formation of a preshaped solid formed body which is positioned in the opening to be sealed and, if needed, is subsequently heated together with the material of the container until is softens (doughiness) or melts to a degree that it melts onto the wall.
In all above-mentioned method options the container material may be preheated at least in the area of the opening to be sealed, particularly up to a temperature of over 100° C., preferably over 200° C. Method processes may take place in an inert atmosphere or in a vacuum. After the material has been melted on, it is possible to control the course of the cooling, for example via adjusting the ambient temperature, heat supply, cooling or the like. These parameters may also change with time.
In all previous embodiments, the metal seal assumed an electrical function (in particular contacting from the inside of the lamp to the outside of the lamp, formation of electrodes, arranging the ignition and burning characteristics) as well as a mechanical function (gastight, preferably vacuum-tight seal of an opening). In the embodiments described below with reference to
a shows the preparative step during the manufacture of the lamp and in particular the sealing of one end of the lamp. Reference numeral 81 denotes a metal pin which contributes to the electric contacting from the outside to the inside of the lamp. It is preferred that it includes a refractory material (melting point >1000° C.), such as molybdenum and/or tungsten and/or Kovar. This pin 81 is provided in advance with a collar 82 made of glass by melting it for example vacuum-tightly onto the pin 81, the outer diameter of which is slightly smaller than the inner diameter of the tube 10. Moreover, a body 83 consisting of a metal material, in particular including or consisting of aluminum, is loosely placed into the interior of the lamp. The body 83 may be an annular body which is pulled over the inner end of the pin 81. The outer dimensions of the body 83 are also smaller than the inner dimensions of the tube 10.
As shown in
b shows the final state: The body 85, the shape of which has been changed (due to melting and resolidification) adjoins the pin 81 on the one hand and the inner wall of the tube 10 on the other hand. The pin 81 penetrates the body 85 and its inner end forms the innermost portion 18. The symbol 84 denotes the material which corresponds to the preglassification 82 and is intimately amalgamated with the inner wall of the tube 10. The pin 81 has an end protruding outside which is used for the outer contacting of the lamp.
Thus, with its electric properties the inner aluminum body 85 may contribute to the improvement of the discharge characteristics and ignition characteristics of the tube. In particular, it has surprisingly been found that aluminum is generally well suited as an electrode material. It has a low tendency to sputter and a low vapor pressure and, contrary to the usual expectations, will thus not contribute to blackening the inner wall of the tube even after repeated discharges despite its comparatively low melting point. This especially applies if comparatively pure aluminum is used (also in the embodiments described before), that is, aluminum of a purity of >99 wt. %, preferably >99.9 wt. %, more preferably >99.97 wt. %.
a and 9b qualitatively show the same Figures as
In the final state (
In the embodiment of
The features of the various embodiments described in the specification may be combined as far as they are no technical alternatives which exclude each other.
Number | Date | Country | Kind |
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10 2005 022 376.1 | May 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP06/03758 | 4/24/2006 | WO | 00 | 7/14/2008 |