GB2108256A - Vehicle lamp - Google Patents

Abstract

A vehicle lamp assembly 11 for a combined head lamp 12 and turn- indicator lamp 13 comprises bulbs 17 and 18 for the head lamp and turn- indicator lamp respectively. An uncoloured transparent lens 21 covers both bulbs. An amber coloured filter 22 is located between the lens and the turn- indicator bulb 18 so that when the bulb 18 is lit it shows amber. The outside of the filter 22 is metallised to form a reflective surface which does not prevent light from the bulb emerging through the filter from outside the lamp so that the colour of the filter cannot be seen when the lamp bulb 18 is not lit. The interior of the lamp assembly thus appears a generally uniform colour when the lamp is unlit giving a pleasing visual appearance to the lamp assembly. <IMAGE>

Description

SPECIFICATION Vehicle lamp The present invention relates to improvements in vehicle lamps.

In modern vehicle design it is common to combine lamps serving different purposes into a single unit or cluster. For example, at the front of a vehicle the turn-indicator lamp may be incorporated into the unit which houses the vehicle head and side lamps, and at the rear of a vehicle the tail lamp, the rear stop lamp, the rear turn-indicator lamps, the rear fog lamp and the reversing lamp may be combined into a single unit or cluster.

The lamps serving the various functions must show different colours when lit in order to comply with Government regulations.

For example the turn-indicator lamp must show amber whereas other lamps at the front of the vehicle must show white. Car designers have however indicated a need for aesthetic reasons for lamps that are housed in a single unit or coloured lamps situated adjacent to uncoloured lamps to appear the same colour when unlit. Various attempts have been made to meet that requirement while at the same time satisfying the colour and photometric requirements of Government regulations. In one example, a combined headlamp andfrontturn- indicator lamp has a clear lens covering both lamps.

Between the turn indicator lamp and the clear lens is an amber filter and between the filter and the lens is a mask which prevents the filter being seen directly through the lens when unlit but which has angled slits which, when the lamp is lit, allow light from the lamp bulb passing through the filter to strike the parabolic reflector behind the bulb and thus be reflected out through the clear lens. Such an arrangement adds substantially to the cost of the unit and is not entirely satisfactory in that the colour of some areas of the filter can still be seen reflected in the parabolic reflector when the lamp is unlit.

According to the present invention a vehicle lamp assembly comprises a lamp bulb mounted in a housing, a lens covering the housing, a colour filter interposed between the lens and the lamp bulb and a reflective surface between the lens and the colour filter arranged to reflect light falling on it from the lens but to transmit light from the filter. With this arrangement, when the lamp is unlit, the colour of the filter cannot be seen from outside the lamp but when the lamp bulb is lit the light passing through the filter is transmited by the reflective surface.

Conveniently the reflective surface is provided on the outer surface of the filter and is formed by half-silvering or metallising the surface of the filter.

The filter may be in the form of a cup which fits around the lamp bulb. With this arrangement the edge of the cup may contact a parabolic reflector behind the lamp bulb. Alternatively the filter may extend across the entire width of the parabolic reflector.

Where it is desired to provide a vehicle lamp assembly in which two lamps are required to show different colours, for example white and amber, two lamp bulbs are located in the housing and the colour filter is located between only one of the lamps and the lens.

Usually the lens will be uncoloured, but in suitable applications, such as a rear lamp and turn indicator lamp cluster, a coloured lens may be used provided that the colour of the lens is such as to allow light of the desired colour from the filtered and unfiltered lamps to emerge.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings of which : Figure 1 shows a horizontal cross-section through a first lamp assembly in accordance with the invention; Figure2 shows diagrammatically how the filter of the assembly of Figure 1 is formed; Figure 3 shows a horizontal cross-section through a second lamp assembly in accordance with the invention; and Figure 4 shows a horizontal cross-section through a third lamp assembly in accordance with the invention.

Referring to Figure 1, a lamp assembly 11 for a combined head lamp 12 and turn-indicator lamp 13 comprises a moulded, pressed or cast housing 14.

The rear wall of the housing is provided with bulb holders 15 and 16 which receive the bulbs 17 and 18 for the headlamp 12 and turn indicator lamp 13.

Around each bulb holder 15, 16 the rear wall is shaped and metallised to form a parabolic reflector 19,20.

An uncoloured clear transparent lens 21 covers the front of the housing 14. The lens may be formed as a single continuous piece covering both the headlamp and turn indicator lamp or, as shown in the drawings, as separate pieces covering each lamp.

An amber colour filter 22 is located between the lens and the turn-indicator lamp bulb 18. The colour filter 22 is cup-shaped with a frusto-conial side wall.

The rear edge of the cup-shaped filter abuts the parabolic reflector 19 so that the lamp bulb 18 is totally enclosed. The outer surface 23 of the filter 22 is metallised by vacuum deposition so that it reflects light coming from the lens 21 as indicated by the arrow A but transmits light from the bulb 18 via the filter 22. The reflective surface 23 of the filter prevents the colour of the filter being seen when the lamp bulb 18 is unlit so that the entire lamp assembly appears the same colour, but allows the coloured light from the filter to emerge when the bulb 18 is lit.

The arrangement for metallising the filter is shown in Figure 2. The process is conducted under extreme vacuum conditions and the metal to be deposited is vaporised by electrically heating it to above its melting point. The components to be metallised are positioned radially around the heating elements with the surfaces requiring metal deposition facing the elements. During the vaporising process the metal radiates outwards and dependent on the amount of metal available will evenly coat all objects in its path with a layer 2 to 3 microns thick.

The filter has the frusto-conical shape so as to provide two distinct areas for metallising. The flat top wall 24 of the filer, before metallising is finished with a matt texture whereas the frusto-conical side wall 23 is finished with a high degree of polish. The matt surface increases the scattering of light falling on it and thus tends to make the filter look less prominent when seen through the lens. The polished side wall causes the minimum of interference with light passing through the filter.

In the metallising process the flat top surface 24 is plated at right angles to the path of the metal vapour and consequently is coated to the full 2-3 microns depth.

The frusto-conical wall 23, being oblique to the path of the metal vapour, receives a thinner coating than the top wall since the metal vapour projected through the notional annulus of radial width A is distributed over a layer surface area. The thickness of the coating on the wall 23 is given as T x A/(A2 + C2)2 where T is the thickness of the coating on the top wall and A and C are the dimensions indicated in the drawings. The depth of the metallised coating on the surface of the wall 25 is therefore reduced to 0.5 to 1.5 microns which is a sufficient depth to reflect exterior light and thus hide the underlying colour of the filter 22, and yet permit up to 85% of the light radiated from the filament of the bulb 18 to pass through as coloured light and thus perform the photometric function of the lamp.

The 2-3 micron coating on the top wall 24 is too thick to allow transmission of light from the filter but the side wall 25 permits sufficient light to pass to meet the photometric requirements for the lamp.

Ideally the thickness of the coating should be the same for the top and side walls 24 and 23 so that both walls transmit light from the filter. This may be achieved by placing a mask over the top wall to prevent the deposition of metal for part of the time while metal is being deposited.

When the lamp assembly 11 is in use and the lamp bulb 18 is lit, the light falling on the parabolic reflector 19, which is also exposed to the metalling process, is reflected forwards onto the lens 21. Some of the light will pass through the filter 22 before striking the reflector, the rest will pass through it after striking the refelector. The light falling on the lens 21 is then redirected by prismatic elements (not shown) to give the desired photometric pattern of light distribution required for the lamp.

When the lamp is unlit, the metallised filter 22 and the metallised parabolic reflector 19 blend to give a matching appearance which blend with one another and with the adjacent headlamp 12 when it too is unlit.

Figure 3 shows an alternative embodiment in which the colour filter 22a is placed close to the lens and has a similar contour to the lens 21. It extends so as to completely cover the parabolic reflector 19 so that all light reflected from the reflector passes through the filter after reflection. The surface of the filter is coated to a thickness of 0.5 to 1.5 microns to mask the underlying colour of the filter by totally reflecting all exterior light, whilst allowing light from the lamp bulb 18to pass through it. In all other respects the embodiment of Figure 3 is the same as that of Figure 1.

The matching of the appearance oftheturn- indicator lamp of Figure 3 with the head lamp may not be good because of the proximity of the reflective surface 23 of the filter 22A to the lens giving a different appearance of depth. To meet this problem the lamp assembly may be modified as shown in Figure 4. In this arrangement the filter 22B is shaped to follow the contour of the rear of the housing with a projecting portion 30 to go round the lamp bulb 18. In other respects the embodiment of Figure 4 is the same as that of Figure 3.

Claims (10)

1. A vehicle lamp assembly comprises a lamp bulb mounted in a housing, a lens covering the housing, a colour filter interposed between the lens and lamp bulb and a reflective surface between the lens and the colour filter arranged to reflect light falling on it from the lens but to transmit light from the filter.

2. Avehicle lamp assembly according to claim 1 in which the reflective surface is provided on the outer surface of the filter.

3. A vehicle lamp assembly according to claim 2 in which the refictiveLsurface is provided by metallising the outer surface of the filter.

4. A vehicle lamp assembly according to claim 1, 2 or 3 in which the filter is cup-shaped and fits over the lamp bulb.

5. A vehicle lamp assembly according to claim 4 in which the edge of the cup abuts the parabolic reflector behind the lamp bulb.

6. A vehicle lamp assembly according to any of claims 1 to 3 in which the filter extends across the entire width of the parabolic reflector behind the lamp.

7. A vehicle lamp assembly in which the filter has a cup shaped projection which fits over the lamp, the remainder of the filter lying close to the parabolic reflector.

8. A lamp assembly according to any of the preceding claims including two lamps which are required to show different colours when lit, two lamp bulbs being located in the housing, the lens covering both bulbs and the filter being located between only one of the bulbs and the lens.

9. A lamp assembly according to any of the preceding claims in which the lens is of uncoloured material.

10. A lamp assembly substantially as hereinbefore described with reference to Figures 1 and 2, or Figure 3 or Figure 4 of the accompanying drawings.