Method of manufacturing vaporized metal discharge lamp and apparatus therefor

Abstract: A method of manufacturing a vaporized metal discharge lamp includes the steps of attaching a metal halide to the tip of a metal rod through vapor deposition or sputtering; inserting the rod into a light emission envelope of the lamp; and transferring the metal halide attached to the metal rod tip to the inside of the envelope through high frequency induction heating.

Description: The present invention relates to a method of manufacturing a vaporized metal discharge lamp according to the first part of claim 1. Such a method is known from CH-A-119 065. More particularly the present invention relates to a vaporized metal discharge lamp of the type that mercury, inert gas and metal halides are filled in the transparent light emission envelope mounted with electrodes, and more particularly to a method of filling metal halides in the envelope. Generally, metals such as thallium, natrium, indium and the like are filled in the form of metal halides in the light emission envelope of a high pressure mercury discharge lamp, to improve light emission efficiency, color rendition and the like. However, of the metal halides, there is a substance which has a high moisture absorption, such as indium iodide so that it can not be exposed to atmospheric air. Thus, the method of manufacturing a vaporized metal discharge lamp has been made complicated. According to a most common manufacturing method, granular metal halides previously dehydrated and weighted are first filled in a light emission envelope within a dry box under an inert gas atmosphere. Next, the light emission envelope is air tightly sealed from external atmospheric air by proper means and coupled to an air exhaust device to exhaust air within the light emission envelope. Thereafter a series of processes including mercury dropping, inert gas introducing, and sealing are carried out, thus resulting in a complicated manufacturing procedure. In Japanese Patent Publications JP-A-40-19548, JP-A-43-17787, JP-A-46-19390 and etc., there has been proposed a manufacturing method whereby a metal halide pool is formed at the air exhaust pipe or at the sealing member, the metal halide is heated while exhausting air via the air exhaust pipe to dehydrate it and vaporize it so as to make it easy to be moved. Then, such metal halide is introduced into the light emission envelope previously cooled, and is concentrated within the envelope. Further, in Japanese Patent Publication JP-A-54-14874, a manufacturing method has been proposed whereby a metal halide dropping device is mounted in the air exhaust system to drop it into the light emission envelope. In spite of the complicated and inefficient conventional method described first in the above, it is still difficult to completely remove water, oxygen and the like adsorped on the surfaces of jigs and the like within the dry box, and of jigs and the like for maintaining air tightness of the light emission envelope. These substances are adsorped by the metal halide, resulting in the disadvantages such as an extraordinary high discharge start voltage, early blackening of the envelope, inactivation of the lamp. These disadvantages are not eliminated up to date. According to the manufacturing method disclosed in Japanese Patent Publications Nos.40-19548, 43-17787, and 46-19390, the metal halide does not contact the atmospheric air so that the conventional disadvantages such as an extraordinary high discharge voltage, early blackening of the envelope, inactivation of the lamp have been eliminated. However, it has been found that there arises a new problem that it is very difficult to fill reliably a predetermined amount of metal halide in the light emission envelope. In particular, even if a metal halide precisely weighted is placed in the metal halide pool, the vapor of heated metal halide will be concentrated, during transfer thereof, at the low temperature areas not only within the light emission envelope but also within an introduction pipe, air exhaust pipe and the like. Thus, all the metal halide previously weighted cannot be concentrated within the light emission envelope. The fluctuation of filling amount becomes more conspicuous as the light emission envelope becomes smaller. The fluctuation of filling amount of metal halide directly influences the discharge characteristic of the lamp so that this manufacturing method leaves a significant problem. The manufacturing method proposed in Japanese Patent Publication No.54-14874 also has a disadvantage which cannot be overlooked. In particular, first, as the discharge lamp becomes smaller, the filling amount of a metal halide also becomes less so that the size of the metal halide becomes not easy to be dropped. In addition, it has been found that even if the metal halide is made dropped by all means, it collides with or attaches to the wall of the light emission envelope while dropping into the envelope so that the amount of the metal halide reaching the inside of the envelope reduces and also fluctuates to large extent. Therefore, a discharge lamp manufactured by this method has a fluctuation of the filling amount of the metal halide so that the fluctuation of the discharge characteristic cannot be avoided, similar to the discharge lamp manufactured by the former methods. Further, according to the above methods heretofore proposed, it is necessary to weight the metal halide for each discharge lamp beforehand. This weighting work is also required to be carried out within the dry box and is very inefficient. Furthermore, since several types of metal halides are mixed and used in general, not only the number of weighting operations becomes large, but also the amount of each metal halide becomes very small. A precise weighting work for such a minute amount has been required. However, in practice, both the work efficiency and weighting precision are impossible to be realized at the same time. It is an object of the present invention to provide a method of and an apparatus for manufacturing a vaporized metal discharge lamp capable of solving all the prior art problems described above. According to an aspect of this invention, a metal halide is vapor deposited or sputtered on the tip of a metal rod and thereafter, the rod is inserted into the light emission envelope and heated through high frequency induction to move the metal halide having been attached to the tip of the metal rod to the inside of the envelope. According to a further aspect of this invention, the steps of attaching a metal halide to the tip of a rod and of inserting the rod into the light emission envelope are continuously carried out within a same container. Brief Description of the Drawings These and other features and advantages of the present invention will be described in more detail in the following, by way of example, reference being made to the accompanying drawings, in which Fig.1 is is a perspective view of the apparatus used with the manufacturing method of this invention; Fig.2 illustrates the vapor deposition of a metal halide onto the tip of a metal rod; and Fig.3 illustrates the transfer of the metal halide into the light emission envelope. Detailed Description of the Preferred Embodiment An embodiment of this invention will be described in detail with reference to the accompanying drawings. Referring to the figures showing an embodiment of this invention, a dry box 3 is coupled to an apparatus main body 1 with air tight means 5 interposed therebetween. After introducing inert gas such as nitrogen into the inside of the dry box 3 and releasing the air tight means 5, it becomes possible to feed a metal halide 11 within a vapor deposition source container 9 to the apparatus main body 1 without contact with the atmospheric air. The vapor deposition source container 9 can be heated with a heater (not shown) or the like and is movable in the direction indicated by an arrow between the apparatus main body 1 and the dry box 3. A metal rod 13 mounted within the apparatus main body 1 is movable in the direction indicated by another arrow. The apparatus main body 1 is coupled to pipes 15 and 15′ for exhausting gas and air respectively, which pipes are connected to gas and air exhaust pumps (not shown). The apparatus main body 1 is also provided with a head 19 for mounting a light emission envelope 21 thereto by means of a gate valve 17. Before the vapor deposition source container 9 is inserted into the apparatus main body 1, the gate valve 17 of the apparatus main body is closed and the air exhaust pipe 15 is coupled to the air exhaust pump to exhaust air within the apparatus main body. In addition, gas and air within the light emission envelope 21 are exhausted through the air exhaust pipe 15′. Next, the vapor deposition source container 9 is moved to the inside of the apparatus main body 1 by releasing the air tight means 5 and thereafter, the metal rod 13 is moved downward to maite a metal halide 11b to be vapor deposited onto the tip 13a of the metal rod 13 as shown in Fig.2. As the metal halide 11b is heated with a heating device (not shown), it is transformed into vapor 11a and concentrated on the rod tip 13a to form a film 11b of metal halide. The amount of metal halide deposited can be controlled precisely in accordance with the heating temperature and time. The control of the vapor deposition time may be carried out by mounting a shutter (not shown) at the hole of a lid of the vapor deposition source container 9, and by adjusting the amount of opening/closing the shutter. Two vapor deposition source containers 9 are shown in Fig.1 by way of example. However, the number of containers 9 is set as desired to allow the necessary types of metal halides to be vapor deposited sequentially on the tip 13a of the metal rod. The steps of vapor depositing the metal halide 11 to the tip 13a of the metal rod may be carried out at the same time as the step of exhausting gas and air within the light emission envelope 21, or may be carried out in the reversed order. Next, the vapor deposition container 9 is moved to the original position and the gate valve 17 is opened to insert the metal rod 13 into the inside of the light emission envelope 21 as shown in Fig.3. Then, the rod 13 is heated with a high frequency induction coil 25 to again vapor deposit the entire amount of the metal halide 11b having been vapor deposited on the metal rod tip 13a, onto the inside of the envelope to form a film 11c of metal halide thereat. By adjusting the temperature of the vapor deposition source container and the pressure of atmosphere in accordance with the type of metal halide, it becomes possible to exhaust gas and water contained in the metal halide. By adjusting particularly the condition for vapor depositing metal halide and the condition for exhausting gas and water, it becomes possible to control the amount of vapor deposition and exhaust gas and air at the optimum conditions. Further, attachment of the metal halide 11 to the metal rod 13 is not limited only by means of vapor deposition, but sputtering and other methods are also possible with a modification of the structure of the container being given. According to the present invention, all the processes of exhausting gas and water contained in the metal halide, weighting the metal halide, and feeding it into the light emission envelope can be carried out continuously within the sealed container shielded from external air, without leaving a chance of contacting with impurity gas and moisture. Further, since jigs do not contact external air, it is possible to avoid secondary contact of the metal halide with external air. As a result, the conventional disadvantages including extraordinary high discharge start voltage, blackening of the envelope wall, and inactivation of the lamp can be eliminated. Furthermore, in manufacturing a small size discharge lamp which uses a small amount of metal halide to be filled in the envelope, the amount of deposition onto the metal rod can be precisely controlled by maintaining constant the work conditions such as temperature, pressure and the like. Thus, the fluctuation to be caused by the fluctuation of the filling amount can be eliminated. Still further, the processes of exhausting air within the envelope, weighting the metal halide, and feeding it to the inside of the envelope can be carried out continuously, thereby realizing a very efficient method of manufacturing a vaporized metal discharge lamp.

Claims: A method of manufacturing a vaporized metal discharge lamp comprising the steps of: attaching a vaporizable material to a metal rod (13); inserting said rod (13) into a light emission envelope (21) of said lamp; and transferring said vaporizable material attached to said metal rod to the inside of said envelope (21) through high frequency induction heating, characterized in that a metal halide is attached to the tip of said metal rod through vapor deposition or sputtering and in that said step of attaching the metal halide to said metal rod tip and said step of inserting said rod (13) into the inside of said envelope (21) are carried out continuously within a same container (1). Apparatus for carrying out the method of claim 1 comprising a dry box (3) coupled to an apparatus main body (1) with air tight means (5) interposed therebetween, a heatable vapor deposition source container (9) being movable between the dry box (3) and the main body (1), which is coupled by pipes (15, 15') to gas and air exhaust means and is provided with a head (19) for mounting a light emission envelope (21) of a lamp thereto by means of a gate valve (17), a holder for a metal rod (13) being movable within the main body (1) towards the head (19) substantially perpendicular to the direction of movement of the vapor deposition source container (9), and a high frequency heating device (25) for heating the light emission envelope (21). Apparatus as set forth in claim 2, wherein a shutter is mounted at a hole of a lid of the vapor deposition source container (9).

Inventors: OMORI SHINYA, OSE AKIRA, TSURUMARU AKIHIKO, OMORI, SHINYA, OSE, AKIRA, TSURUMARU, AKIHIKO
Applicants: STANLEY ELECTRIC CO LTD, STANLEY ELECTRIC CO., LTD.
Application year: 1988
Main classification: H01J9
IPC codes: H01J9