US3781582A - Triple purpose heat shield,light collector and mount support for a tungsten-halogen projection lamp - Google Patents

Abstract

A multi-purpose member used in combination with a tungstenhalogen projection lamp, whereby the multi-purpose member reflects radiation back onto the filament of the projection lamp. The multi-purpose member also serves as a heat shield, a light shield, and a positioning and supporting means for the filament. This combination provides the accomplishment of the several functions at a lower cost than if the functions were provided separately, and also improves the efficiency of the lamp.

Description

United States Patent 1191. De Caro 1 Dec. 25, 1973 1 d TRIPLE PURPOSE HEAT SHIELD, LIGHT COLLECTOR AND MOUNT SUPPORT FOR A TUNGSTEN-HALOGEN PROJECTION LAMP [75] Inventor: Aristide R. De Caro, Edison, NJ.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

221 Filed: June2l, 1972 211 Appl. No.: 265,024

[52] US. Cl 313/37, 3l3/40,.313/113, 313/115, 313/222, 313/271, 313/272,

[51] Int. Cl. IIOlj 61/10, I-IOij 1/92, HOlj 19/46 [58] Field of Search 313/37, 40, 271, 313/273, 115, 272, 331, 222, 315, 316,113

[56] References Cited UNITED STATES PATENTS 3,330,984 7/1967 Smith 313/272 X 2,400,081 5/1946 Eitel ct a1. 313/40 Primary Examiner-Paul A. Sacher Attorney-A. T. Stratton et a1.

[57] ABSTRACT A multi-purpose member used in combination with a tungsten-halogen projection lamp, whereby the multipurpose member reflects radiation back onto the filament of the projection lamp. The multi-purpose member also serves as a heat shield, a light shield, and a positioning and supporting means for the filament.

' This combination provides the accomplishment of the 'several functions at a lower cost than if the functions were provided separately, and also improves the efficiency of the lamp.

5 Claims, 3 Drawing Figures TRIPLE PURPOSE HEAT SHIELD, LIGHT COLLECTOR AND MOUNT SUPPORT FOR A TUNGSTEN-HALOGEN PROJECTION LAMP BACKGROUND OF THE INVENTION The tungsten-halogen incandescible projection lamp is'now well known in the art. Many such lamps use'light shields on the dome of the lamp to minimize stray light which might otherwise emit from the projector. One arrangement for providing such light shielding is provided for by covering a portion of the exterior of the envelope with a light absorbing material. One such arrangement is described in Canadian Pat. No. 881,081, issued Sept. 14, I971, now U.S. Pat. No. 3,667,652 to Noteltiers et al.

Other projection lamps have used a heat shield to prevent; overheating of parts outside of the bulb. External ceramic caps have been used, for example, to prevent overheating of projector parts adjacent to the lamp.

Projector lamps have also used reflectors to reflect radiation emitting from the filament. The primary purpose of such reflectors, however, has generally been to reflect light out of the lamp in the desired direction, rather than reflecting radiation back to the filament. In U.S. Pat. No. 3,082,345, issued Mar. 19, 1963, to A. A. Bottone, it was noted that the reflector increased the filament temperature, but the primary purpose of the reflector was still to focus the light output into the lens system of the projector.

Top supports have also been used in projection lamps to provide additional support for the stem (the stem is the general filament support structure and includes the lead-in wires, the bridges and the filament support wires), and more precisely orient the filament. One such arrangement is provided in U.S. Pat. No. 3,496,403, issued Feb. 17, 1970 to J. J. Palermo et al.

SUMMARY OF THE INVENTION The present invention provides a single member which serves to intercept radiation from the filament both to reflect filamentgenerated radiation back toward the filament to augment filament operational efficiency, and to minimize any light and heat emission through thedome of the lamp. This multi-purpose metallic member is rigidly mounted between the dome and the stern and has a periphery of such a shape as to provide a close fit of the member into the generally tubular envelope. The configuration of the member together with the rigid mounting of the member restricts movement of the stem relative to the envelope and thereby positions and supports the filament. Preferably, the metal of this metallic member istungsten or molybdenum.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be obtained from the exemplary embodiments shown in the having a peripheral shape as would be used with a flattened tubular envelope projection lamp; and

FIG. 3 is a front elevational view of a projection lamp incorporating a shaped, rather than a flat, multipurpose member.

DESCRIPTION OF THE PREFERRED EMBODIMENT idly mounted on the stem 18 intermediate the filament 16 and the envelope dome 22 and generally transverse to the elongated dimension of the envelope the radiation-reflecting member 20 serves as a heat shield, light shield, reflector to reflect radiation back toward the filament l6, and supplemental supporting and positioning means for the incandescible filament 16.

The term internal cross-section, as used herein, means the cross-section of the volume within the envelope, when sectioned transverse to the elongated dimension of the envelope. This would be a horizontal cross-section of the envelope, bounded by the internal surface of the envelope, if the lamp was in a base-down position.

The radiationreflecting member 20 can be fabricated from any metal or metals which withstand the halogen atmosphere and the approximately 600C maximum temperature of the reflective metallic member, for example, a platinum-plated radiation-reflecting member 20 can be used, but radiation-reflecting members of a single metal and especially of either tungsten or molybdenum are preferred.

FIG. 2 shows the bottom view of a flat radiationreflecting member 20 which has a periphery shaped for use in an oval envelope, and a polished finish 24 to increase the reflection of radiation back towards the filament 16. While the flat configuration ofradiationreflecting member 20 provides slightly lower efficiency than configurations which focus the reflected radiation back onto the filament 16, the flat configuration provides for ease of fabrication. When the stem 18 is tung-' sten and the radiation-reflecting member 20 is fabricated from tungsten, the radiation-reflecting member 20 can conveniently be welded to the stem 18.

FIG. 3 is a front elevational view of a tungstenhalogen projection lamp incorporating a radiationreflecting member 20 of formed configuration, with its concave side toward the filament to focus the reflected radiation upon the filament. When the envelope 12 has a tubular internal cross-section, the radiation-reflecting member 20 can be a spherical section positioned so as to have the center of the sphere of which it is a section positioned within the incandescible filament 16. A radiation-reflecting member 20 formed in an elliptical section can also be used.

It is convenient to make the radiation-reflecting member 20 from relatively thin sheet in either the flat or the formed configuration. Tungsten sheet of 0.003 inch thickness, for example, has proven satisfactory.

The radiation-reflecting member 20 can be used with many configurations of tungsten halogen projection lamps, including configurations in which conventional reflectors are used. Such a configuration would have dual reflectors, the radiation-reflecting member 20 of 5 this invention and a conventional reflector which con centrates light into the condensing lens of the projector, such as described in the aforementioned US. Pat. No. 3,082,345.

I claim as my invention:

1. In combination with a tungsten-halogen projection lamp of the type having an elongated envelope of predetermined configuration of internal cross-section and terminating in an envelope dome at one end and a base at the other end, and a stem extending generally longitudinally into said envelope and supporting an incandescible filament, the improvement which comprises:

a metallic radiation-reflecting member having a periphery similar in configuration but slightly smaller than the configuration of the internal cross-section of said envelope, said radiation-reflecting member rigidly mounted on said stem intermediate said filament and said envelope dome and generally transverse to the elongated dimension of said envelope, said radiation-reflecting member intercepting radiations from said filament both to minimize any light and heat emission through said dome of said lamp and to reflect filament-generated radiations back toward said filament, the configuration of said radiation-reflecting member together with said rigid mounting of said radiation-reflecting member on said stem restricting movement of said stem relative to said envelope, whereby said radiationreflecting member serves the multiple functions of heat shield, light shield and radiation-reflector to augment operational efficiency, as well as serving as supporting and positioning means for said filament.

2. The combination of claim 1, wherein the metal of said radiation-reflecting member is tungsten.

3. The combination of claim 2, wherein said metal of said radiation-reflecting member is tungsten and a polished finish is provided on said radiation-reflecting member to increase the reflection of radiation back towards said filament.

4. The combination of claim 3, wherein said radiation-reflecting member is formed to focus said reflected radiation upon said filament.

5. The combination of claim 1, wherein the metal of said radiation reflecting member is molybdenum.

Claims (5)

1. In combination with a tungsten-halogen projection lamp of the type having an elongated envelope of predetermined configuration of internal cross-section and termInating in an envelope dome at one end and a base at the other end, and a stem extending generally longitudinally into said envelope and supporting an incandescible filament, the improvement which comprises: a metallic radiation-reflecting member having a periphery similar in configuration but slightly smaller than the configuration of the internal cross-section of said envelope, said radiation-reflecting member rigidly mounted on said stem intermediate said filament and said envelope dome and generally transverse to the elongated dimension of said envelope, said radiation-reflecting member intercepting radiations from said filament both to minimize any light and heat emission through said dome of said lamp and to reflect filament-generated radiations back toward said filament, the configuration of said radiation-reflecting member together with said rigid mounting of said radiation-reflecting member on said stem restricting movement of said stem relative to said envelope, whereby said radiation-reflecting member serves the multiple functions of heat shield, light shield and radiation-reflector to augment operational efficiency, as well as serving as supporting and positioning means for said filament.

2. The combination of claim 1, wherein the metal of said radiation-reflecting member is tungsten.

3. The combination of claim 2, wherein said metal of said radiation-reflecting member is tungsten and a polished finish is provided on said radiation-reflecting member to increase the reflection of radiation back towards said filament.

4. The combination of claim 3, wherein said radiation-reflecting member is formed to focus said reflected radiation upon said filament.

5. The combination of claim 1, wherein the metal of said radiation reflecting member is molybdenum.

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