GB2070222A - Lamp unit for a vehicle - Google Patents

Abstract

A lamp unit for a vehicle, particularly an indicator light, comprises a paraboloidal reflector 1 with a bulb 3 whose filament 4 is at the focus F of the reflector 1. The bulb 3 is surrounded by a coloured transparent cover 11 which has an opaque mask 13 on its outer surface, the mask 13 having transparent zones 15, 16 arranged to allow light from the bulb 3 to pass. The transparent zones 15, 16 are such that more light is allowed to pass downwards than upwards. The lamp has a transparent front glass 7 the upper part of which diffuses light to a greater extent than the lower part. This arrangement minimises the risk of phantom signals. In a modification the opaque mask is a separate member spaced from the cover. <IMAGE>

Description

SPECIFICATION Lamp unit for a vehicle The present invention relates to a lamp unit for example for signalling in motor vehicle, i.e. the lights situated at the front and the rear of a vehicle for indicating, by the emission of a light of conventional colour, the imminence of a change in direction, braking, breakdown, or simply the presence of the vehicle.

In a known arrangement, such lamps have a light source, generally consisting of the filament of an incandescent bulb, arranged substantially at the focus of a substantially parabolic reflector closed by a front glass. This glass is colourless, and the conventional colour of the signal emitted by the lamp when its filament is supplied with electricity is obtained by means of a coloured transparent cover surrounding the light source.

The separation of the front glass of the lamp and the means for colouring the signal has the advantage of giving adjacent lights at the front or the rear of a vehicle the same external appearance, namely that of the front glass, when they are not in use. In contrast the direct colouring of the front glass of each lamp leads to different colours being adjacent one another since the conventional colours attributed to the different functions referred to above are often different. These do not always match the colour of the bodywork of the vehicle.

However, these lamps have a disadvantage in that sometimes when they receive from outside a light of strong intensity, either natural or artificial, they appear to be switched on when they are off and thus give erroneous and sometimes dangerous information.

In fact it appears that a bright light, especially if it is directional such as sunlight or the light emitted by another vehicle's headlight, can penetrate to the interior of the lamp through its transparent glass, be reflected once on the reflector which concentrates it at the focus. This light then passes through the coloured cover, is reflected a second time after having again passed through the coloured cover, and leaves the lamp through the front glass after having taken on the colour of the cover. This phenomenon is known as "phantom light".

It is an object of the present invention to provide a lamp in which the phantom light is minimised. It is a further object to attain this effect with the minimum of hindrance to the passage towards the reflector of the beam emitted by the light source of the lamp itself when the lamp is in use.

According to the present invention there is provided a lamp unit for a vehicle, comprising a reflector, a light source substantially at the focus of the reflector, a coloured transparent cover surrounding the light source, masking means at least partially surrounding the cover between the cover and the reflector, the masking means having relatively more transparent zones and relatively more opaque zones arranged to transmit more light from the light source towards the lower part of the reflector than towards the upper part, and a transparent front glass whose upper part is adapted to diffuse light to a greater extent that its lower part.

Thus, modifications are provided firstly to the front glass of the lamp in order to orientate rays from outside which thus limit the portion of these rays which is reflected towards the focus of the reflector, and secondly to the interior of the lamp in order to impede the passage of these rays between their two potential reflection zones on the reflector, that is to say in order to try to ensure that a ray reflected a first tiruPe on the reflector in the direction of the focus cannot be reflected there again after having passed through the coloured cover and so to leave the lamp.

This combination may provide a suitable way of reconciling the two objectives which are at odds consisting on the one hand of eliminating the phantom light phenomenon, implying impeding the progress of a ray from the outside to the interior of the lamp, and on the other hand trying to optimise the use of the ray emitted by the source when it is in use.

The masking means can allow light which reaches it in the geometrically determined more transparent zones to pass towards the cover. However, due to the geometric properties of the reflector, whose shape is preferably generally paraboloidal, this radiation tends to leave the masking means in geometrically determined zones where it can be intercepted.

Thus, preferably, the masking means is provided alternately with relatively opaque zones and relatively transparent zones arranged relative to the focus so as to intercept any radiation which may have penetrated to the cover as it is leaving.

The invention may be carried into practice in various ways and some embodiments will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view, partially cut away, of an indicator lamp according to the invention; Figure 2 is a vertical section through the lamp of Fig. 1 on a plane including the axis of the lamp; Figure 3 is a vertical section through a second embodiment, with some parts omitted, on a plane including the axis of the lamp.

The lamp illustrated in Figs. 1 and 2 comprises a paraboloidal reflector 1 having a focus F, and having a surface of revolution about the axis 2 of the lamp, which axis is approximately horizontal in use.

The reflector 1 is formed with a hole at the apex of the paraboloid through which the base 9 of the lamp 3 extends. The filament 4 of the lamp 3 is located substantially at the focus F of the paraboloid.

The embodiment shown is a corner light 7 which is intended to be alongside another lamp 6, and which may be at the front or the rear of the vehcle. The periphery 5 of the reflector 1 has a complex contour since it is connected on the one hand to the periphery of a transparent front glass 8, closing the reflector about the bulb 3, towards the side of the vehicle and towards the top and the bottom, and on the other hand it is connected to the adjacent light 6 through a vertical partition 10 which is opaque.

The front glass 8 is colourless, as is the bulb 3 which emits a white light when its filament 4 is supplied with electricity, and it is a coloured transparent cover 11 which gives the colour conventionally attributed to the function of the lamp. The cover 11 surrounds the part of the bulb 3 situated inside the reflector 1 and is connected to the reflector 1 at the level of the base 9 of the bulb through a collar 12.

A mask 1 3 is provided around the coloured cover 11. The mask 1 3 is partially impermeable to light travelling from outisde the cover 11 towards its interior i.e., light from the reflector 1 or from the front glass 8, must also be partially permeable to light emitted from the filament 4 when it is supplied with electricity so as to permit the lamp to function. In the embodiment shown in Figs. 1 and 2, the mask 1 3 is produced by direct deposition of metal onto the outside surface of the cover 11 by a vacuum metal plating process.

The plating is carried out so that parts of the cover are plated while other parts are not.

Thus, some zones 14 of the cover 11 are rendered totally impermeable to light and reflective towards the exterior, while other zones such as 1 5 and 1 6 are not plated and so preserve the initial transparency of the cover 11. The metal plated zones 14 of the cover prevent rays reaching the interior of the cover from both the front glass 8, and from the reflector 1, and tend on the contrary to reflect these rays directly towards the front glass 8 or indirectly towards the latter by reflection on the reflector 1. The zones which are not metal plated only allow a small part of this light to penetrate to the interior of the cover 11 but are arranged so as to prevent these rays as far as possible from leaving.

The opaque zones 1 4 are arranged symmetrically with reference to the focus F so as to be opposite the zones 1 5 or 1 6 which are not metal plated. Thus a ray which enters the lamp through the front glass 8, and which is reflected by the reflector 1 towards the focus F, can enter the coloured cover 11 via a zone 1 5 or 16, after passing through the focus F, however, it will encounter a zone 14 which prevents it from leaving the cover 11 but refledts it, greatly attenuated, back to the interior from which it can only leave in a barely visible form.A ray striking the mask 1 3 at a zone 14 after reflection on the reflector 1 will be reflected again towards this reflector, without passing through the coloured cover 11, and so leaves the lamp without having been coloured.

The metal plated zones 14 and the non metal plated zones 1 5 and 1 6 are arranged to co-operate with a particular design of the glass 8 so as to exploit to the maximum the light emitted by the filament of the bulb when' the latter is supplied with electricity.The zones 1 5 which are not metal plated take the form of three slots made in the coating 14 on - the upper part of the mask 1 3. These three slots form circumferential rings about the axis 2 an have an angular developement of a little less than 180 . Their individual widths, measured parallel to the axis 2, and the sum of their individual widths are small relative to the corresponding overall dimension of the mask 13, and are thus less than the corresponding cumulative dimension of the opaque zones 14 on the upper part of the cover. The transparent zones are arranged close to the collar 12, and so to the reflector 1. The mask 1 3 has an opaque zone in the form of a cap facing the glass 8.

The transparent zone 1 6 is a single zone situated in the lower part of the mask 13, and its area is greater than the cumulative area of the slots 1 5. It has a shape corresponding to a plane trapezoidal development, the large base of the trapezium being adjacent the collar 12, and having an angular development a little less than 180".

The glass 8 has a different structure respectively in its upper half and its lower half. The upper half has on its interior surface a series of near hemispherical reliefs 1 7 which are strongly diffusing. The lower half has on its interior surface a series of curved reliefs 1 8 which are less strongly diffusing. Thus, natural light coming from the sky and striking the upper part of the glass 8 obliquely is largely deflected and little is reflected on the reflector 1. The small portion of this light which strikes the mask 1 3 after refelction on the reflector 1 is for the most part reflected towards the front glass 8, that is to say towards the exterior by the opaque reflecting zones 14. Only a tiny portion of the light penetrates to the interior of the coloured cover 11 through the transparent zones 1 5 and even less leaves there, thus having no marked influence on the external appearance of the lamp. Conversely, when the filament 4 of the bulb 3 is supplied with electricity, the rays which pass through the zones 1 5 are reflected by the reflector 1 onto the upper part of the glass 8, the reliefs 1 7 give width to the beam leaving the lamp.

The poorly diffusing structure of the lower part of the glass 8 has the effect that light from the sky is not reflected twice by the reflector 1 and do not leave the lamp via the glass 8 in the directions of observation, consequently, they do not affect the colourless appearance of the lamp. When the filament 4 of the bulb 3 is supplied with electricity, the more poorly diffusing lower part of the glass 8 has the effect of intensifying the light along the lamp axis, using the major part of the light emitted passing through the zone 1 6.

The number distribution and the shape of the transparent zones 1 5 and 1 6 on the upper part and the lower part of the cover 11 can be modified, though preferably the greater part of the light coming from the sky is stopped on at least one of these two parts of the cover 11.

Instead of being formed from alternating metal plated and non metal plated zones, the mask 1 3 can be produced by metal plating of the cover 11 in a modulated manner, the object being that the cover should be reflective over the whole of its surface which faces towards the reflector 1 and the glass 8, but has zones which are permeable to light travelling in a direction from the filament 3 towards the reflector 1. These permeable zones may correspond to the zones 1 5 and 1 6 of the example illustrated in Figs. 1 and 2, but there may also be permeable zones facing directly towards the glass 8 if appropriate.Thus, the same mask may combine metal plated surfaces, semi-plated surfaces and non-metal plated surfaces to give a modulated transparency to the light from the bulb to provide optimum opacity as regards external light, but with a distribution of the transparent or more transparent zones and the opaque or more opaque zones analogous to that described above.

Fig. 3 shows an embodiment in which the metal plated mask 1 3 is replaced by a separate mask 23. Reference numerals 1 9 to 22 designate the elements designated in Figs. 1 and 2 respectivey by the reference numerals 1, 2, 3 and 9.

This mask 23 is attached to the reflector 1 9 outside the coloured cover 26 and faces towards the colourless transparent front glass (not shown). Towards its top the mask 23 has slots 24 in positions similar to those of the slots 1 5 in Figs. 1 and 2 and towards its bottom, it has slots 25 which, although different from the single continuous zone 1 6 of the cover 1 3 shown in Figs. 1 and 2, are located in a similar position. The slots 25 represent a greater surface area than that of the upper slots 24.

In order to avoid excessive heating of the coloured cover 26 inside the mask 23 they are separated by a space 27, permitting air to circulate between the slots 24 and 25 over the surface of the cover 26. The coloured cover 26 can itself have apertures in order to permit ventilation of the bulb 21. These apertures are arranged in such a way that the white light emitted by the bulb 21 cannot reach the exterior of the mask 23 and are for example situated opposite an opaque region of the mask. The cover 11 of the embodiment shown in Figs. 1 and 2, could also have such apertures arranged in the form of deflectors allowing the light emitted by the bulb 21 to pass through the coloured portion before reaching the outside.

If required, the external surface of the mask may have, at last partially, colouring analogous to that of elements outside and/or adjacent to the lamp. These elements may be part of the bodywork or may be coloured elements attached to the bodywork, for example catadioptric reflectors. Thus external light entering the lamp light is coloured when it is reflected on the mask and leaves the lamp giving an impression of colour in harmony with that of the neighbouring zone. In this way the external surface of the mask can be given for example a pink colour in order to harmonise the external appearance of the lamp when it is not in use with the red colour of adjacent catadioptric reflectors.

Claims (9)

1. A lamp unit for a vehicle comprising a reflector, a light source substantially at the focus of the reflector, a coloured transparent cover surrounding the light source, masking means at least partially surrounding the cover between the cover and the reflector, the masking means having relatively more transparent .zones and relatively more opaque zones arranged to transmit more light from the light source towards the lower part of the reflector than towards the upper part, and a transparent front glass whose upper part is adapted to diffuse light to a greater extent that its lower part.

2. A lamp unit as claimed in Claim 1, in which a relatively more opaque zone is lo cated opposite a relatively more transparent zone symmetrically with respect to the reflector focus.

3. A lamp unit as claimed in Claim 1 or Claim 2 in which the masking means is reflective towards the exterior of the unit.

4. A lamp unit as claimed in any of Claims 1 to 3, in which the masking means comprises a metal layer on the outer surface of the cover.

5. A lamp unit as claimed in any of Claims 1 to 3, in which the masking means comprises a partially opaque shell arranged around the cover.

6. A lamp unit as claimed in Claim 5, in which the shell is spaced from the cover.

7. A lamp unit as claimed in any of Claims 4 to 6, in which the masking means is of varying transparency, thereby having zones which are respectively more transparent and more opaque.

8. A lamp unit as claimed in any of Claims 4 to 6, in which the masking means is generally opaque with breaks defining the transparent zones.

9. A lamp unit for an indicator light on a vehicle constructed and arranged substantially as herein specifically described with reference to and as shown in Figs. 1 and 2 or Fig. 3 of the accompanying drawings.