WO2002056336A2

WO2002056336A2 - Stabilized heat shield for halogen lamp

Info

Publication number: WO2002056336A2
Application number: PCT/US2001/050884
Authority: WO
Inventors: Yutao Zhou; Rajasingh Schwartz Isreal; Tianji Zhao; Sharon Hermannoff
Original assignee: General Electric Company
Priority date: 2000-11-16
Filing date: 2001-11-09
Publication date: 2002-07-18
Also published as: WO2002056336A3

Abstract

A heat shield (180) for a lamp (110) is welded or otherwise rigidly attached to a rigid support lead (162). The support lead supports an envelope (136) containing a fill of a halide material and is electrically connected to a filament (132) disposed within the envelope. The support lead has a dog-leg configuration, which allows the heat shield to be attached to and supported by an intermediate portion (168) of the dog-leg. This attachment maintains the position of the heat shield for optimum reflection of heat and prevents rattling of the heat shield when the lamp is turned over.

Description

STABILIZED HEAT SHIELD FOR HALOGEN LAMP

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to the lamp arts. More particularly, it relates to a stablized heat shield for use in parabolic aluminized reflector (PAR) lamps and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to reflective lamps employing a variety of light sources.

Discussion of the Art

Parabolic aluminized reflector lamps are widely used in spotlighting, such as in headlamps, domestic fixtures, recessed lighting fixtures, and a variety of other applications. Such lamps commonly employ a tungsten-halogen tube as a light source, which is mounted within the internal reflector cavity, approximately at its focal point. During operation, the lamp tends to generate heat so that the interior of the lamp often reaches temperatures of about 300°C. Such temperatures can be deleterious to the end seal of the tungsten halogen tube of the lamp.

To keep the heat away from the base, a heat shield may be mounted adjacent the light source, which reflects the heat away from the one end of the tungsten halogen tube. A central aperture in the heat shield allows the shield to fit around a tubular portion of the light source and rest on the wider, bulbous portion. The heat shield thus has a certain degree of flexibility of movement and may align itself poorly with the light source, resulting in uneven reflection of light and unstable distribution. Additionally, the heat shield may rattle during transport, hitting the glass envelope of the tungsten halogen tube and the adjacent supporting lead, which causes noise when the consumer shakes the lamp. Purchasers who are accustomed to rejecting lamps which rattle, as indicative of a filament failure, may tend to assume that the lamp has failed. The present invention provides a new and improved lamp and method of use with a stabilized heat shield, which overcomes the above-referenced problems and others.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment of the present invention, a light source is provided. The light source includes a lamp envelope. An energizable element is disposed within the envelope. Leads electrically connect the energizable element with a source of power. A heat shield is attached to one of the leads.

In another exemplary embodiment of the present invention, a method of forming a light source is provided. The method includes providing an envelope containing an energizable element and electrically connecting a support lead with the energizable element, the support lead supporting the envelope. The method further includes attaching a heat shield to the lead, energizing the light source, and reflecting heat with the heat shield.

One advantage of the present invention is that it enables a heat shield to be accurately positioned within a lamp.

Another advantage of the present invention is that the heat shield is retained in position, reducing rattling of the heat shield during transport and potential damage to other elements of the lamp. Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a schematic cross-sectional view of an arc tube and heat shield of a prior art lamp;

FIGURE 2 is a side-sectional view of a lamp, according to the present invention;

FIGURE 3 is an enlarged side-sectional view of the light source of FIGURE 2, according to a first embodiment; FIGURE 4 is an enlarged side-sectional view of the light source of FIGURE 2, ^" according to a second embodiment;

FIGURE 5 is an enlarged perspective view of the heat shield of FIGURE 2 positioned around a lamp envelope (shown in phantom).

DETAILED DESCRIPTION OF THE INVENTION With reference to FIGURE 1 , a prior art lamp is shown. The lamp includes a light source 10, comprising an envelope 12 which encloses a filament 14. A heat shield 16 is mounted around the envelope, adjacent the filament. The heat shield 16 has a first hole 18 for receiving a tubular portion 20 of the envelope and a second hole 22, which receives a supporting lead 24. The heat shield is free to move vertically between the bulbous portion of the envelope and a kinked or dog-leg portion 26 of the supporting lead 24, as the lamp is turned over.

With reference now to FIGURE 2, a lamp 110 according to the present invention is shown. The lamp 110 includes a reflector housing 112, formed from pressed glass, plastic, or other suitable material, which defines an internal cavity 114. The housing includes a concave, preferably parabolic, reflector portion 116 and a neck portion 118 having a longitudinally extending conical configuration as shown. The neck portion 118 can be secured to an externally threaded metal shell or cap 120 of a base portion 122 of the lamp in a conventional manner, such as by press fitting. An interior parabolic surface 126 of the reflector housing is coated with a layer 128 of a reflective material, such as aluminum, silver, or a dichroic type material. While the lamp is described with particular reference to a PAR-type reflector, other reflector housings are also contemplated, including spherical, elliptical or other housing shapes. A light-transmissive lens 129 closes an upper open end of the reflector.

A light source 130, such as a tungsten-halogen light source is disposed within the internal cavity 114, with its major dimension along the axis x of the lamp. A representative tungsten-halogen light source 130 includes an energizable element 132, such as an axially aligned tungsten coil filament, which is hermetically sealed within an elongated envelope 136 formed from aluminosilicate glass or other light-transmissive material. The lamp envelope 136 encloses a gaseous fill, which contains at least one rare gas, such as ^"krypton, and a vaporizable halogen substance, such as an alkyl halide compound (e.g., methyl bromide). While the invention is described with respect to a halogen lamp, it should be appreciated that other light sources may alternatively be employed, such as ceramic metal halide arc tubes, and the like. The term "energizable element," as used herein, thus encompasses filaments and also other energizable materials which generate light on application of an electric current, such as the metal halide fill in the gap between the electrodes of a ceramic metal halide arc tube. With reference also to FIGURES 3 and 4, the envelope 116 includes upper and lower tubular portions 138, 140, which are generally cylindrical in shape. These taper outwardly to a wider, central bulbous portion 142, which may be elliptical, spherical, or the like. The center of the tungsten coil 132 resides approximately at the focal point of the reflector, within the bulbous portion 142 of the envelope. The terms "upper" and "lower" and similar terms are used herein with respect to the lamp as shown in FIGURE 2. It should be appreciated that in use, the lamp may be inverted from the position shown in FIGURE 2, with the base 122 screwed into a ceiling fixture, or the like.

The filament coil 132 is physically suspended within the lamp envelope by a composite assembly 148 of lead wire electrical conductors. Specifically, first and second lead-in wires 150, 152 are press-fit into respective ends of the tubular portions 138, 140 of the envelope, respectively, and are connected via molybdenum foil connectors 154, 156 to second wires 158, 160, which join the coil 132 at upper and lower ends thereof. The leads are formed from electrically conductive metal, such as molybdenum, or other suitable material.

The upper lead-in wire 150 is externally connected to a support lead 162, which provides a rigid support for the envelope. The support lead 162 is formed from stainless steel or other suitable material and is electrically connected with the cap 120. The support lead has a dog-leg configuration. Specifically, as shown in FIGURE 3, the support lead includes a first, horizontal leg 164, connected with the upper lead in wire, which is oriented perpendicular to the major dimension of the envelope. A second leg 166 extends vertically from the other end of the horizontal leg 164, generally parallel to the upper tubular portion 138 to just below the bulbous portion 142. A third, horizontal leg 168 carries the support lead inwardly, towards the lower ^"tubular portion of the envelope. A final vertical leg 170 extends generally parallel with the lower tubular portion into the base of the lamp, where it is rigidly fixed to the neck portion of the reflector by adhesive joinder with a suitable epoxy cement 171. The second horizontal leg 168 thus spaces the two vertical legs 166, 170 and lies generally perpendicular to these to create a shelf. A wire connector 172 electrically connects the support lead 162 with the cap. Another wire connector 174 connects the lower lead-in wire 152 with an electrically separate portion of the cap. With reference also to FIGURE 5, a heat shield 180, generally in the form of a disc, is interposed between the bulbous filament-containing portion 142 of the envelope and the neck 118 of the reflector. The heat shield reflects and/or absorbs heat generated by the light source 130, thereby reducing the amount of heat which reaches the base 122 of the lamp. As shown in FIGURE 2, the heat shield is aligned generally perpendicularly to the axis x of the lamp.

While a circular heat shield is preferred, the heat shield may also be in the shape of a square or of other suitable shape. The heat shield is preferably of sufficient diameter to shield the neck portion 118 of the reflector. The heat shield of FIGURE 2 is of approximately the same diameter as the neck of the reflector, although a wider or narrower diameter heat shield could alternatively be used. The heat shield may be formed from stainless steel or other suitable, relatively rigid material, which is able to withstand the temperatures experienced during operation of the lamp without undue deformation.

The heat shield has a centrally positioned aperture 182, which is sized to receive the tubular portion 140 of the envelope therethrough but which is preferably too small to slide over the bulbous portion 142. As shown in

FIGURE 5, the aperture may be fitted with resiliently flexible tabs 184 (for and shown in FIGURE 5), which flex as the heat shield is fitted over the tubular portion and grip the tubular portion when in place. A second, smaller aperture 186 in the heat shield is positioned off-center and receives the supporting lead 162 therethrough. As shown in FIGURES 2 and 3, the heat shield is on top of the horizontal leg of the supporting lead, with the smaller aperture receiving the vertical leg 166 therethrough. In an alternate embodiment, shown in FIGURE 4, the heat shield is on the other, lower side of the horizontal leg, with the smaller aperture receiving the vertical leg 170 therethrough. Such an arrangement may be preferable in lamps which are ^"primarily to be used in recessed or other ceiling-mounted fixtures, where the base portion 122 of the lamp is uppermost. The heat shield 180 is the same as in FIGURES 2 and 3; however, it will be appreciated that the aperture for the supporting lead is positioned slightly closer to the central aperture to accommodate the supporting lead.

To inhibit movement of the heat shield, the heat shield is joined to the support lead, so that the heat shield is no longer free to move relative to the support lead. In a preferred embodiment, a surface 190, (192 in FIGURE 4) of the heat shield adjacent the horizontal leg 168 is welded, cemented or otherwise attached to the horizontal leg (the lower surface 190 in the case of the embodiment of FIGURES 2 and 3, the upper surface 192 of the heat shield in the case of the embodiment of FIGURE 4). In a preferred embodiment, the attachment is achieved by spot welding the stainless steel heat shield to the stainless steel support lead. Alternatively, an adhesive, such as a heat resistant cement, may be used to attach the two components.

The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the proceeding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A light source 110 comprising: a lamp envelope 136;

an energizable element 132 disposed within the envelope;

leads 150, 152, 162 which electrically connect the energizable element with a source of power; and

a heat shield 180 attached to one of the leads 162.

2. The light source of claim 1 , wherein a pair of lead wires 158, 160 are connected to opposite ends of the energizable element for energizing the energizable element.

3. The light source of claim 1 , wherein the energizable element 132 comprises a filament.

4. The light source of claim 1 , wherein the lead 162 is positioned outside the envelope.

5. The light source of claim 1 , wherein the lead is formed from a rigid material to support the envelope.

6. The light source of claim 5, wherein the lead is formed from stainless steel.

7. The light source of claim 1 , wherein the lead comprises a central member 168 disposed between two substantially parallel members 166, 170.

8. The light source of claim 7, wherein the central member has an upper surface and a lower surface.

9. The light source of claim 8, wherein the heat shield is attached to the upper surface of the central member of the lead.

10. The light source of claim 8, wherein the heat shield is attached to the lower surface of the central member of the lead.

11. The light source of claim 1 , wherein the heat shield includes an aperture 182 located substantially in the center thereof, which receives a portion 140 of the envelope therethrough.

12. The light source of claim 11 , wherein the heat shield includes a second aperture 186 located off center of the circular aperture, which receives the lead 162 therethrough.

13. The light source of claim 1 , further including; a reflector housing 112; and

a base 122 connected with a neck portion 118 of the reflector housing, the heat shield inhibiting heat emitted from the envelope from entering the base during operation of the light source.

14. A method of forming a light source 110 comprising: providing an envelope 136 containing an energizable element 132; electrically connecting a support lead 162 with the energizable element, the support lead supporting the envelope; attaching a heat shield 180 to the lead; energizing the light source; and reflecting heat with the heat shield.

15. The method of claim 14, further comprising:

connecting a pair of lead wires 150, 152 to opposite ends of the energizable element for energizing the energizable element, one of the lead wires being connected to the support wire.

16. The method of claim 14, wherein the step of attaching the heat shield to the lead includes:

welding a surface of the heat shield to the lead 162.

17. The method of claim 16, wherein the step of attaching the heat shield to the lead includes: attaching a surface 190, 192 of the heat shield to a leg 168 of the lead 162 which spaces two generally parallel legs 166, 170 of the lead.