GB2105025A - Vehicle lamp assemblies - Google Patents

Abstract

A vehicle lamp assembly consists of a light source 14 in a parabolic reflector 10 arranged to direct light on to a composite element 16. The composite element 16, has outer and inner component 18 and 20 separated by a zig zag like airgap, having alternate sections pointing to which are horizontal and 24 which extend at an angle such that downwardly directed light from outside the lamp suffers total internal reflection at such airgap. The horizontal sections of the airgap are filled by baffle 22 which also act as spacers to maintain the required separation of the two components 18 and 20. The composite element 16 reduces the risk of the lamp appearing illuminated when it is not. <IMAGE>

Description

SPECIFICATION Vehicle lamp assembly This invention relates to vehicle lamp assemblies of the type in which the colour of the light to be produced by the lamp cannot readily be perceived when the lamp is not illuminated. This reduces the risk that, in bright sunlight for example, the lamp assembly may appear to be illuminated, when in fact it is not.

According to the invention, a vehicle lamp assembly comprises a light source, a lighttransmitting cover element and a lighttransmitting intermediate element disposed between the source and the cover element, wherein the surface of the cover element facing the intermediate element comprises corrugations extending transversely across the lamp and formed of intersecting plane surface elements, each of which extends transversely across the cover, alternate surface elements forming a first set each of which is inclined at an acute angle to the tangent to adjacent corrugations, and the other surface elements forming a second set, and the surface of the intermediate element facing the cover comprises complimentary corrugations formed of first and second sets of surface elements interleaved with the corrugations and the cover, the first set of surface elements of the intermediate member being parallel to and spaced from respective surface elements of the first set of surface elements of the cover by a medium of reflective index less than that of the cover and than that of the intermediate member and the second set of surface elements of the cover and intermediate element being so arranged that the light incident from within the cover and the intermediate element respectively is absorbed.

Preferably, the light source is arranged to direct collimated light on to the intermediate element. For this purpose, the light source may include a Fresnel system, a parabolic reflector or both.

In use, the lamp assembly is mounted with the first sets of surface elements sloping downwardly and inwardly. Consequently, a horizontal beam of light is transmitted across the first sets of surface elements but a downwardly directed beam of light, at above a predetermined angle of incidence, from outside the lamp or such an upwardly directed beam from inside is subject to total internal reflection at the surface elements of the first set, with the result that it is directed on to the surface elements of the second set, where it is absorbed.The result is that if either the intermediate element is made of a coloured material or a separate colour filter is provided between the intermediate element and the light source, only light which is incident on the cover or the intermediate element at an angle such as not to suffer total internal reflection is capable of enabling the colour of the lamp to be perceived from outside.

In one form of the invention, opaque inserts e.g. of metal or plastics, are located between the two second sets of surfaces, the various inserts may serve as spacers holding the cover and the intermediate element apart to maintain the required air gap. Lenses may be formed on the inner surface of the intermdiate member to deflect light from the source away from the baffles and at the same time, give the emerging light the required divergence.

Alternatively, a separate diffusing element may be disposed outside the cover or the cover itself may be arranged to serve as a diffuser.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional view of a vehicle lamp assembly in accordance with the invention; and Figure 2 is a schematic cross sectional view of an enlarged scale of part of the lens assembly of the lamp shown in Fig. 1.

Referring to the drawings, the lamp assembly shown therein, which is a vehicle lamp assembly, comprises a parabolic reflector Referring to the drawings, the lamp assembly shown therein, which is a vehicle signalling lamp assembly, comprises a parabolic reflector 10 in which a light bulb 12 is mounted so that the filament 1 4 thereof is at the focus of the refelctor 1 0. A compound lens assembly 1 6 overlies the reflector 1 0.

The lens assembly 1 6 comprises an outer component 1 8 which is coloured in accordance with the appearance which the lamp assembly is to present when the bulb 1 2 is not illuminated and an inner component 20 which is coloured so that in combination with the outer component, the lamp assembly emits light of a colour suitable for the function to be performed, e.g. amber for a direction indicator lamp assembly, red for a brake lamp assembly. In many circumstances it will be convenint for the outer component 1 6 to be a neutral grey colour, in which case the inner component 1 8 will be of the actual colour required for the emitted light.

The boundary between the two components 1 8 and 20 of the lens assembly 1 6 is of generally zig-zag formation, the inner surface of the outer component 1 8 comprising alternate horizontal parts 22 and downwardly, inwardly inclined parts 24, while the outer surface of the inner component 20 comprises complementary horizontal surfaces 26 and inclined surfaces 28. Thus the confronting surfaces of the two elements 1 8 and 20 consist of respective series of horizontally oriented triangular prisms with prisms of the outer component 1 8 inverted relative to those of the inner component 20, so that the two compo nents 18 and 20 fit together with a narrow parallel-sided gap between their inclined faces 24 and 28.Opaque baffle elements 30 between the surfaces 22, both prevent transmission of light through such surfaces and also serve as spacers to maintain the air gap between the surfaces 24 at the required value.

The- inclination of the inclined surfaces 24 is such that a light ray such as the ray 32 entering the outer component 1 8 at an angle to the horizontal greater than a predetermind value (typically of the order of 30 ), suffers total internal reflection at the inclined surface 24 of the outer component 1 6 with the result that it is directed either on to the adjacent opaque baffle 30 (as shown) or back out through the front of the lens 16. Since such a light ray does not reach the coloured inner lens component 20, its appearance is not affected by the colour of the inner element 20.Light which is incident on the lamp assembly from outside at an angle sufficiently close to the horizontal to avoid total internal reflection at the inclined surface 24, would be incident on the reflector 10, yielding an uncollimated upwardly directed light ray such as the ray 34. As shown, this ray 34 is totally internally reflected at the inclined surface 28 of the inner component 20 with the result that it is either directed on to one of the baffles 30 as shown, or reflected back into the lamp.

On the other hand, collimated light from inside the lamp, such as would be produced by the parabolic reflector 10 from the bulb 12, e.g. the beam comprising rays 36, is able to pass freely across the air gap between the inner and outer lens components 20 and 1 8 and these emerge from the front of the lamp assembly with the colour imparted by the inner component 20.

In Fig. 2, the inner surface of the inner component 20 is illustrated as having a series of lenses 30 formed thereon. These lenses serve to impart the required divergence to the collimated light as it emerges from the lamp assembly and also tend to deflect collimated light away from the edges of the baffles 22.

As an alternative such lenses may be formed on the outside of the outer element 1 8 and/ or the required diffusion may be provided by a separate diffuser element outside the outer element 18, the area obstructed by the edges of the baffles 30 being so small that the proportion of light lost in these circumstances is acceptable.

Claims (4)

1. A vehicle lamp assembly comprising a light source, a light-transmitting cover element and a light-transmitting intermediate element disposed between the source and the cover element, wherein, the surface of the cover element facing the intermediate element comprises corrugations extending transversely across the lamp and formed of intersecting plane surface elements, each of which extends transversely across the cover, alternate surface elements forming a first set each of which is inclined at an acute angle to the tangent to adjacent corrugations, and other surface elements forming a second set, and the surface of the intermediate element facing the cover comprises complementary corrugations formed of first and second sets of surface elements interleaved with the corrugations and the cover, the first set of surface elements of the intermediate member being parallel to and spaced from respective surface elements of the cover by a medium of reflective index less than that of the and than that of the intermediate member and the second set of surface elements of the cover and of the intermediate element being so arranged that light incident from within the cover and the intermediate element respectively is absorbed.

2. A vehicle lamp assembly according to claim 1, wherein a respective insert of rigid opaque material is disposed between each second surface of the cover and corresponding surface of the intermediate element, said insert serving both to absorb light incident on said second surfaces and to maintain the required spacing between the cover and the intermediate element.

3. A vehicle lamp assembly according to claim 1 or 2, wherein the light source is arranged to direct collimated light on the intermediate element.

4. A vehicle lamp assembly substantially as herein before described with reference to the accompanying drawings.