This application claims priority from Japanese Patent Application Serial No. 2007-295034 filed Nov. 14, 2008, the contents of which are incorporated herein by reference in its entirety.
Described herein are a fused joint structure in an electric supply structure of a lamp tube, and a forming method thereof.
Conventionally, in a halogen lamp for business machine, a mercury lamp for a liquid crystal projector light source, or a metal halide lamp for general lighting, etc., an internal lead and an external lead are joined together through a metallic foil in a sealing portion, so as to secure airtightness of a light emission space in the lamp tube. When such internal and external leads were conventionally joined to the metallic foil, for example, a joint portion of the metallic foil and the internal lead of the halogen lamp for business machine, which is currently sealed by pinch sealing, or a joint portion of the metallic foil and the internal lead of a mercury lamp for a projector light source, which is currently sealed by shrink-sealing, was joined by a resistor welding.
However, in such a resistor welding process, the welding conditions change due to changes of a welding electrode rod with passage of time, so that the welding quality is not stabilized, whereby there is a problem of peeling due to insufficient adhesive strength or a problem of generation of holes in the metallic foil at time of the welding. Furthermore, in the resistance welding process, application of pressure is necessary at the time of welding in order to obtain the welding strength, so that there is a possibility that deformation and creasing of detailed parts, such as the electrode or the lead rod may occur by the pressurization.
Japanese Laid Open Patent No. 2004-363014 teaches a tungsten electrode and a molybdenum foil are joined by a laser welding using a YAG laser in manufacture of a high-pressure discharge lamp, instead of the resistance welding. Also, refer to Japanese Laid Open Patent No. 2003-257373.
However, when the inventors actually welded a lead rod and a metallic foil of the lamp electrode by a YAG laser, as shown in
In view of the above problems of the prior art, it is an object of the present invention to propose a fused joint structure in a lamp tube and a forming method therefore, in which it is possible to acquire the stable and high strength of welding and it is possible to realize reduction of deformation, insufficient welding strength, and a problem of generation of holes due to the welding.
In view of the above problems, the present fused joint structure comprises a metallic foil, a conductive member made of high melting point metal, wherein a concave portion is formed in the metallic foil and the conductive member on an area where the metallic foil is put on a surface of the conductive member, and wherein a circumferential edge of the concave portion is covered with the conductive member.
In another aspect thereof, the conductive member may be made of tungsten or molybdenum, and the metallic foil may be made of molybdenum.
In still another aspect thereof, the fused joint structure is formed in a method in which laser light whose energy is 40 MW/cm2 or more, is irradiated on the area where the metallic foil is put on a surface of the conductive member, so as to joint the conductive member and the metallic foil.
In the fused joint structure in the lamp tube according to the present invention, it is possible to acquire the stable and high strength of welding (portion) and it is possible to realize reduction of deformation, insufficient welding strength, and generation of holes due to the welding. Furthermore, in the forming method of the fused joint structure in the lamp tube according to the present invention, it is possible to offer a fused joint structure having a stable and high welding strength.
Other features and advantages of the present fused joint structure in a lamp tube, and the present forming method therefor will be apparent from the ensuing description, taken in conjunction with the accompanying drawings, in which:
A description will now be given, referring to embodiments of the present fused joint structure in a lamp tube, and the present manufacture method therefor. While the claims are not limited to such embodiments, an appreciation of various aspects of the present flash lamp emitting device is best gained through a discussion of various examples thereof.
A lamp tube in which a fused joint structure according to the present invention is provided is, for example, a halogen lamp such as an incandescence lamp and a discharge lamp. In addition, in the present invention, a “conductive member” will refer to an internal lead rod and an external lead rod in case of a halogen lamp. In case of a discharge lamp using one metallic foil sealing, it refers to an electrode rod and an external lead rod. In case of a discharge lamp using two or more metallic foil sealing, and it refers to a disk-like member connected to an electrode rod to which two or more metallic foils are welded and a disk-like member connected to an external lead.
A first embodiment according to the present invention will be described referring to
Formation of the fused joint structure according to the embodiment is set forth below. The electrode rod 5, and the metallic foil 6 which is conductive member, are put one on top of another, and laser light from a fiber laser apparatus whose energy density is set to 40 MW/cm2, is irradiated from a side of the metallic foil 6. Specifically, when the molybdenum (Mo) foil and the tungsten (W) rod are welded to each other, under conditions in which, in the fiber laser apparatus, the diameter of the laser light is reduced to about 20 μm (micrometers), the energy density is 40 MW/cm2, for example, 60 MW/cm2, and a laser output thereof is 200 W, the laser light is irradiated thereto at a distance of 100 mm from the side of the molybdenum (Mo) foil, for 2.5 msec. Here, the molybdenum (Mo) foil is shaped in a gutter like shape by bending the molybdenum foil with a 0.7 mm width, in accordance with the shape of the tungsten rod so as to have a 0.5 mm width and a 20 μm (micrometers) thickness. The diameter of tungsten (W) rod is 0.4 mm. As mentioned above, irradiated laser light penetrates the molybdenum (Mo) foil which is the upper material of the put-together materials, and the tungsten (W) which is the lower material is blown off so that some of the tungsten (W) which is blown off sublimates. However, the surface viscosity of some of the tungsten (W) which has been blown off, decreases, thereby flowing onto the molybdenum (Mo) foil around the blown off portion, whereby the molybdenum (Mo) foil is sandwiched in shape of the circumference edge between the tungsten (W) which flows onto the molybdenum and the tungsten (W) rod which is the lower material. Thus, in the welding structure, the tungsten (W) rod is blown off so that a concave portion is formed as shown in
A second embodiment according to the present invention will be described below referring to
Next, the fused joint structure according to the embodiment is formed as set forth below. The metal disk 18 formed integrally with the electrode rod 15 as a conductive member, and the metallic foil 16 are put together, and laser light emitted from the metallic foil 16 side of a fiber laser apparatus in which the energy density is 40 MW/cm2 is irradiated thereto. Specifically, when the molybdenum (Mo) foil and the molybdenum (Mo) disk are welded with each other, under condition where in the fiber laser apparatus, the diameter of the laser light is reduced to about 20 μm (micrometers), the energy density is 40 MW/cm2 or more, for example, 60 MW/cm2, and a laser output thereof is 200 W, the laser light whose output is 200 W is irradiated thereto at a distance of 100 mm from the side of the molybdenum (Mo) foil, for tens of microseconds, while the molybdenum (Mo) foil and the molybdenum (Mo) disc are brought into close contact with each other by a jig etc. The molybdenum (Mo) foil is 8-12 mm in width and 40 μm (micrometers) in thickness, the molybdenum (Mo) disk is 17 mm in diameter. The molybdenum (Mo) foil with 40 μm thickness which is the upper material, and the molybdenum (Mo) disc with the 17 mm diameter and 0.5 mm thickness are put together, and then when 200 W output fiber laser in which the diameter of a beam is narrowed down to 20 μm or less, is irradiated from above the molybdenum (Mo) foil, the molybdenum (Mo) which is the upper material, is sandwiched by the lower material and the molybdenum which has been blown off from the molybdenum (Mo) disk which is the lower material, so that the same welding structure as shown in
A third embodiment according to the present invention will be given below, referring to
Next, ten (10) fused joint structures were prepared by conventional resistance welding, that is, welding in which YAG laser is used as described in Japanese Laid Open Patent No. 2004-363014, and also ten (10) fused joint structures were prepared by welding according to the present invention which fiber laser is used.
The preceding description has been presented only to illustrate and describe exemplary embodiments of the present fused joint structure in a lamp tube, and the present forming method thereof according to the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope.
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Number | Date | Country | |
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20090121635 A1 | May 2009 | US |