Improved spotlight arrangement

Abstract: A spotlight comprises a light source (14) mounted within an enclosure (11) fitted with a light-transmissive cover (28) which is formed with a central opening (29) above the light source. A clearance space between the light source and the cover allows light from light source (14) to spill over into the enclosure and thereby illuminate the cover from behind. Another enclosure (12) containing control gear (17) for the light source is thermally insulated from enclosure (11) by an air gap (21).

Description: The invention relates to an improved spotlight arrangement. The PAR 38 lamp marketed by the Applicant company, is a sealed beam incandescent light source provided with a parabolic reflector which is usually aluminised. Three types of reflector lamps are in general use providing a narrow, medium or wide beam. Although the PAR 38 can be used as a floodlight its primary use is as a spotlight, in which case the light source is fitted with a borosilicate glass stippled cover over the front face. The PAR 38 lamp is supplied in the range 100 - 150W and there are many in use. If a PAR 38 lamp fails and needs to be replaced then it is necessary to replace the complete lamp. US patent number 4,207,607 discloses an alternative to the PAR lamp, exhibiting a complex rotatably secured transmitting member which enables the reflected radiation energy to be adjusted or altered. The lamp can be utilised in either the spotlight or the floodlight configuration. However, once again should this lamp fail, the complete lamp needs to be replaced. Another lamp which is successfully marketed is the low voltage spotlight sold under the trade mark Lightstream. This is a tungsten halogen incandescent filament lamp fitted integrally within a facetted mirror reflector. Because of the greater efficiency of the tungsten halogen lamp it is found that, as far as light output is concerned, a 50W Lightstream lamp could be readily substituted for the 100 - 150W PAR 38 lamp in existing fittings. Moreover since there are many PAR 38 lamps in use, if a spotlight simulating the PAR 38 could be provided there would be a large retrofit market for such lamps. An object of this invention is to integrate a tungsten halogen incandescent lamp within the housing of a PAR 38 or similar type of incandescent lamp to be an effective replacement therefor. In its broadest aspect the invention provides a spotlight comprising an enclosure; a light-transmissive cover for said enclosure, and a light source comprising an incandescent filament lamp within a mirror reflector having a rim; characterised in that the cover has a central opening; said light source is mounted within the enclosure and generally aligned with the central opening; the rim of the light source being close to the edge of the central opening, the arrangement being such that some of the light passes from the light source into the enclosure below the cover and thereby illuminates the cover from behind. The invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 is perspective end view on the front of a spotlight in accordance with the invention, Figure 2 is a part sectional elevation of a spotlight in accordance with the invention, Figure 3 is a perspective end view on the rear of a spotlight in accordance with the invention. In figure 1 reference numeral 10 indicates a spotlight generally in accordance with the present invention comprising a first enclosure member 11 and a second enclosure member 12 which terminates in an Edison screw terminal 13. As best seen in Figure 2, first enclosure 11 houses a light source 14, in the form of a tungsten halogen incandescent filament lamp 15 integral with a facetted mirror reflector 16, this light source being marketed by Applicant company under the trade mark Lightstream. Also as shown in Figure 2, second enclosure 12 houses control gear (electronic) represented diagrammatically by dotted lines 17 which is required to run light source 15. The control gear 17 is surrounded by potting compound for cooling. In order to keep heat generated by the tungsten halogen lamp 15 away from control gear 17, enclosure 11 with aluminised reflector surface 20, is formed free of any openings so that heat will not flow rearwardly. Moreover, in order to minimise heat transfer between the first and second enclosures 11, 12 respectively an air gap 21 is formed between them. As an additional aid to this end control wire 22 connecting lamp 15 with control gear 17 is formed with a loop 23 which is placed within air gap 21. By this means it is found that a temperature differential of approximately 80 centigrade degrees can be maintained between bottom 24 of first enclosure 11 and top 25 of second enclosure 12. Structural connection between the first and second enclosures 11,12 is made by hollow leg members 26 attached to second enclosure 12 and by pin members 27 as best seen in Figure 2. This arrangement also tends to reduce heat transfer from the light source pinch 19 to the heat sensitive control gear 17. A cover member 28 of light transmitting polycarbonate material snap fits to reflector 20 to complete enclosure 11. Cover 28 has a stippled surface which forms a light reflecting surface and compliments the facetted surface of reflector 16 as best seen in Figure 1. Cover 28 has clearance opening 29 through which reflector lamp 14 may be inserted into its holder 30 within enclosure 11. During operation of the reflector lamp 14 light, of course, projects through opening 29, however when viewed end-on as in Figure 1, it is found that light unexpectedly appears to come also from the unlit portion 31 of cover 28 as well as the lit portion formed by opening 29. This means that the spotlight effect provided by the simulated PAR 38 substantially is the same as that provided by a true PAR 38. Because reflector lamp 14 is stepped back slightly from the cover 28 it is believed stray light beams penetrate the clearance space between cover 28 and the rim of reflector 16 and spill into the remainder of enclosure 11 not occupied by reflector lamp 14. It will be appreciated that with a simulated PAR 38 only the light source 14 needs to be replaced and housings 11 and 12 need not be replaced. A typical embodiment of the present invention would utilise a 50 Watt Lightstream lamp with a 50 mm reflector but wattages range from 20 to 70 with two sizes of reflector available, namely 35 mm and 50 mm. Any combination of these could be used in the present invention. The overall diameter of the cover member is 120 mm on a 137.5 mm radius, with a 52 mm diameter opening. The overall length of the simulated PAR 38 is 136 mm and the length of the air gap between the first and second enclosing is 10mm. The Lightstream lamp is stepped back approximately 2mm from the inside of the cover.

Claims: A spotlight (10) comprising an enclosure; a light-transmissive cover (28) for said enclosure, and a light source (14) comprising an incandescent filament lamp (15) within a mirror reflector (16) having a rim; characterised in that the cover (28) has a central opening (29); said light source (14) is mounted within the enclosure and generally aligned with the central opening; the rim of the light source being close to the edge of the central opening, the arrangement being such that some of the light passes from the light source into the enclosure below the cover and thereby illuminates the cover from behind. A spotlight according to Claim 1 wherein said enclosure has a light-reflective interior surface (20) at least at the rear thereof. A spotlight according to Claims 1 or 2 including a further enclosure containing electrical control gear (17) for the light source, said enclosures being insulated thermally from one another by an air gap. A spotlight according to Claim 3 wherein said enclosures are interconnected structurally by a plurality of leg members (26). A spotlight according to Claim 3 or Claim 4 wherein said light source and said electrical control gear are interconnected electrically by a lead wire (22) which has a looped configuration (23).

Inventors: PAVELIN ERNEST JAMES, PAVELIN, ERNEST JAMES
Applicants: EMI PLC THORN, THORN EMI PLC
Application year: 1987
Main classification: F21M1
IPC codes: F21V15, F21V23, F21S2, F21V19