GB2074303A - Lamp Fitting, Particularly a Miner's Cap Lamp - Google Patents

Abstract

A miner's cap lamp has a reflector (11) with an outer annular zone (14) of parabolic cross-section on the lamp bulb as focus for producing a bright central disc of illumination, and an inner reflective zone (13) for producing a larger area of duller illumination. <IMAGE>

Description

SPECIFICATION Lamp Fitting This invention relates to a lamp fitting.

According to the present invention, a lamp fitting comprises a reflector with two annular zones of different curvature, the outer of which produces a central disc of high illumination.

The other zone can provide a larger less brightly illuminated area. That is a requirement for a miner's cap lamp in some mines, and a typical specification is a pattern at a few feet from the lamp in which the central brighter disc is 20 centimetres in diameter, while the outer less brilliant annulus is 40 centimetres in diameter.

The outer zone is preferably of parabolic crosssection, with the lamp filament at or near the focus to produce the central disc equal in diameter to, or a little larger than the reflector.

In the past, light has tended to spread from the front of the bulb in a rather haphazard manner.

The present invention enables a bright central disc of illumination to be achieved, while the surrounding less brightly lit area is of controlled size and brightness because it is derived principally from a zone of the reflector rather than just from the front of the lamp.

The outer annular zone could be more reflective than the inner annular zone and the two zones could join each other to form a cusp in cross-section.

Conveniently, the reflector is a plastics moulding with a silvered or aluminised surface.

One way of making one zone more reflective than the other is to coat one zone with silver, and the other with aluminium, but an alternative method is to coat the whole of the reflector surface with silver and then apply an aluminium paint over the less reflective zone. Again, one zone can be moulded to be rougher than the other and then when they are both sprayed with an aluminium spray, the rough zone will not be as reflective as the smoother zone.

The invention may be carried into practice in various ways, and one embodiment will now be described by way of example, in which the single figure is a cross-section through a miner's cap lamp.

The lamp has a reflector in the form of a plastics moulding 11 which is symmetrical about a polar axis 12, and has two annular zones, namely a central zone 13, and a surrounding annular zone 14. The central zone 13 is apertured at 1 5 for a fitting 16 for a bulb with a filament at 1 7 on the axis 12. The bulb will be powered from a battery held on a casing on the miner's belt while the reflector and bulb are in a casing 20 mounted on his helmet.

The outer zone 14 is a paraboloid with a focus close to the filament of the bulb 1 7, and produces a bright circle of light about 20 cms in diameter at three or four feet from the lamp; as shown by the line with double arrow-heads.

The inner zone 13 is of such curvature in relation to the position of the filament 1 7 that it produces a large dimly lit area as indicated by the lines with single arrow-heads. It may be of nonparabolic or irregularly curved cross-section.

There is a circle 18 where the zones 13 and 14 join.

The drawing makes it clear that light from the bulb 1 7 reflected from the inner zone 13 is reflected outwardly of light reflected from the outer zone 14, as indicated by the respective lines of light 21 and 22. A 4 watt bulb can produce by way of the outer zone 14 a central disc of alumination of 20 cms diameter say, 2 metres away from the lamp with an intensity of 350 lux, whereas the inner or central zone 13 produces a surrounding annular ring of illumination at perhaps 50 lux with a diameter of about 40 cms.

The central disc will tend to be brighter than the surrounding ring particularly if the zone 14 is of greater area than the zone 13. In any case the outer zone 14 can be made more highly reflective than the inner zone 13, so that the central disc is brighter than the surrounding annular partly illuminated region. That could be achieved by moulding the inner surface of zone 13 to be rougher than that of zone 14, and then applying an aluminium paint on both zones of operation.

Claims

1. A lamp fitting comprising a reflector with two annular zones of different curvature, the outer of which produces a central disc of high illumination from a lamp when mounted in the reflector.

2. A fitting as claimed in Claim 1 in which the outer zone is of parabolic cross-section.

3. A fitting as claimed in Claim 2 including means for mounting a bulb with its filament at or near the focus of the parabola.

4. A fitting as claimed in any of the preceding claims in which the inner reflector zone is of such a curvature in relation to the position of the bulb filament that the inner zone produces a relatively large disc of relatively low illumination.

5. A fitting as claimed in any of the preceding claims in which the outer zone is more reflective than the inner zone.

6. A fitting as claimed in any of the preceding claims in which the reflector is a plastics moulding with a silvered or aluminised surface.

7. A lamp having a fitting as claimed in any of the preceding claims.

8. A lamp constructed and arranged substantially as herein specifically described with reference to the accompanying drawing.

9. A lamp as claimed in either of Claims 7 or 8 adapted to be mounted on a cap.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Lamp Fitting This invention relates to a lamp fitting. According to the present invention, a lamp fitting comprises a reflector with two annular zones of different curvature, the outer of which produces a central disc of high illumination. The other zone can provide a larger less brightly illuminated area. That is a requirement for a miner's cap lamp in some mines, and a typical specification is a pattern at a few feet from the lamp in which the central brighter disc is 20 centimetres in diameter, while the outer less brilliant annulus is 40 centimetres in diameter. The outer zone is preferably of parabolic crosssection, with the lamp filament at or near the focus to produce the central disc equal in diameter to, or a little larger than the reflector. In the past, light has tended to spread from the front of the bulb in a rather haphazard manner. The present invention enables a bright central disc of illumination to be achieved, while the surrounding less brightly lit area is of controlled size and brightness because it is derived principally from a zone of the reflector rather than just from the front of the lamp. The outer annular zone could be more reflective than the inner annular zone and the two zones could join each other to form a cusp in cross-section. Conveniently, the reflector is a plastics moulding with a silvered or aluminised surface. One way of making one zone more reflective than the other is to coat one zone with silver, and the other with aluminium, but an alternative method is to coat the whole of the reflector surface with silver and then apply an aluminium paint over the less reflective zone. Again, one zone can be moulded to be rougher than the other and then when they are both sprayed with an aluminium spray, the rough zone will not be as reflective as the smoother zone. The invention may be carried into practice in various ways, and one embodiment will now be described by way of example, in which the single figure is a cross-section through a miner's cap lamp. The lamp has a reflector in the form of a plastics moulding 11 which is symmetrical about a polar axis 12, and has two annular zones, namely a central zone 13, and a surrounding annular zone 14. The central zone 13 is apertured at 1 5 for a fitting 16 for a bulb with a filament at 1 7 on the axis 12. The bulb will be powered from a battery held on a casing on the miner's belt while the reflector and bulb are in a casing 20 mounted on his helmet. The outer zone 14 is a paraboloid with a focus close to the filament of the bulb 1 7, and produces a bright circle of light about 20 cms in diameter at three or four feet from the lamp; as shown by the line with double arrow-heads. The inner zone 13 is of such curvature in relation to the position of the filament 1 7 that it produces a large dimly lit area as indicated by the lines with single arrow-heads. It may be of nonparabolic or irregularly curved cross-section. There is a circle 18 where the zones 13 and 14 join. The drawing makes it clear that light from the bulb 1 7 reflected from the inner zone 13 is reflected outwardly of light reflected from the outer zone 14, as indicated by the respective lines of light 21 and 22. A 4 watt bulb can produce by way of the outer zone 14 a central disc of alumination of 20 cms diameter say, 2 metres away from the lamp with an intensity of 350 lux, whereas the inner or central zone 13 produces a surrounding annular ring of illumination at perhaps 50 lux with a diameter of about 40 cms. The central disc will tend to be brighter than the surrounding ring particularly if the zone 14 is of greater area than the zone 13. In any case the outer zone 14 can be made more highly reflective than the inner zone 13, so that the central disc is brighter than the surrounding annular partly illuminated region. That could be achieved by moulding the inner surface of zone 13 to be rougher than that of zone 14, and then applying an aluminium paint on both zones of operation. Claims

1. A lamp fitting comprising a reflector with two annular zones of different curvature, the outer of which produces a central disc of high illumination from a lamp when mounted in the reflector.

2. A fitting as claimed in Claim 1 in which the outer zone is of parabolic cross-section.

3. A fitting as claimed in Claim 2 including means for mounting a bulb with its filament at or near the focus of the parabola.

4. A fitting as claimed in any of the preceding claims in which the inner reflector zone is of such a curvature in relation to the position of the bulb filament that the inner zone produces a relatively large disc of relatively low illumination.

5. A fitting as claimed in any of the preceding claims in which the outer zone is more reflective than the inner zone.

6. A fitting as claimed in any of the preceding claims in which the reflector is a plastics moulding with a silvered or aluminised surface.

7. A lamp having a fitting as claimed in any of the preceding claims.

8. A lamp constructed and arranged substantially as herein specifically described with reference to the accompanying drawing.

9. A lamp as claimed in either of Claims 7 or 8 adapted to be mounted on a cap.