Indicating display for a motor vehicle, in particular a raised stop light unit

The present invention relates in general terms to indicating displays for motor vehicles, and more particularly to an indicating display which is equipped with a plurality of light sources which are aligned with each other, and all of which take part in a common indicating function.

An indicating display of the above general type, known in the current state of the art, comprises for example a plurality of light emitting diodes. This may for example consist of a raised stop lamp for fitting in a rear window or in a rearwardly facing part of a motor vehicle.

In order that such a display shall satisfy the photometric requirements imposed by current regulations, it includes, arranged in line with the light emitting diodes, an intermediate screen which is provided with Fresnel lenses, each of which is associated with a corresponding one of the diodes in order to concentrate the light in the axis of the vehicle, and a lens which receives light from the intermediate screen and which is provided with contoured elements for the horizontal and vertical distribution of the light. One drawback of this known solution lies in the fact that, because of the presence of the light sources, the intermediate screen and the lens, arranged one after another in a straight path, the indicating light unit has a substantial length in the direction of the optical axis.

This disadvantage is even more inconvenient in the case of raised stop lights which are fitted within the cabin of the vehicle. For a unit fitted in such a position, it is desirable that its size should be as small as possible.

A main object of the present invention is therefore to provide an indicating display having a shortened axial length.

According to the invention, an indicating display for a motor vehicle, of the type comprising a plurality of light sources aligned with each other, optical means for concentrating the light flux emitted by the sources into a general emission direction, and a lens which is provided with optical means for diffusing the light, is characterised in that the optical concentrating means consist of a mirror having a parabolic cross section delimited by two planes, both of which lie on the same side of its optical axis, and which extend in line with the lens, and in that the light sources are offset vertically with respect to the lens.

According to a preferred feature of the invention, the mirror is defined by a part of the housing.

Preferably, the light sources are situated substantially below the lens, in a cavity which is delimited by portions of the housing which extend the latter downwardly.

According to another preferred feature of the invention, the mirror consists of a plurality of portions of paraboloids of revolution, the foci of which lie substantially on the corresponding respective light sources.

Preferably, the light sources are light emitting diodes.

According to a further preferred feature of the invention, the housing includes two extensions having unequal lengths and extending from the upper and lower edges of the lens, the said extensions receiving at their free end a smooth transparent inclined cover plate.

Preferably, the light sources are oriented generally in a direction opposed to the exit direction of the light from the indicating display.

Further features, objects and advantages of the present invention will appear more clearly on a reading of the following detailed description of a preferred embodiment of the invention, which is given by way of example and with reference to the accompanying drawings.

FIG. 1 is an elevation in cross section of a raised stop light of the prior art, for the rear window of a motor vehicle.

FIG. 2 is an elevation in vertical axial cross section of an indicating display in accordance with the present invention.

Before reference is made to FIG. 2 showing the preferred embodiment of the invention, reference is briefly made to the prior art indicating display, in the form of a raised stop light, which is shown in FIG. 1 . This includes a row of light emitting diodes D. In front of the light emitting diodes D, an intermediate screen F, having Fresnel lenses each of which is associated with a respective one of the diodes D, is mounted within the housing of the raised stop light unit. The purpose of the intermediate screen F is to concentrate the light along the axis of the vehicle. In front of the screen F, is a lens V which includes elements for the horizontal and vertical distribution of the light. The unit shown in FIG. 1 is an example of the units described above under the heading “Background of the Invention”.

Reference is now made to FIG. 2, which shows an indicating display which in this example is a raised stop lamp adapted to be fitted in an opening in the bodywork of the motor vehicle, so as to be visible from behind the vehicle.

The raised stop lamp unit shown in FIG. 2 comprises: a housing generally indicated by the reference numeral 10 ; a printed circuit 20 which is mounted within the housing, and which supports a set of light emitting diodes 30 ; a lens 40 ; and a transparent external cover plate 50 .

The housing 10 comprises a first part 11 which is closed by the lens 40 and which encloses the printed circuit 20 and the light emitting diodes 30 . This part 11 has two oblique base walls 11 a and 11 b , which define a right angle between them. The part 11 also includes a posterior wall 11 c , together with a further wall 11 d . The posterior wall 11 c is essentially vertical, and extends the oblique base wall 11 b upwards.

The internal surface of the wall 11 d consists of a plurality of portions in the form of a paraboloids of revolution, the foci of which are spaced apart at regular intervals on a line which lies at a level lower than the wall 11 d . In this example, this line lies at approximately the same height as the other end of the oblique base wall 11 a , this level intersecting the middle of the posterior wall 11 c . At least the wall 11 d of the housing part 11 a is provided with an internal reflective coating, which is formed for example by vacumetallisation.

The part 11 of the housing also has another wall 11 e which extends forwards (i.e. towards the right in FIG. 2) from the upper end of the wall 11 d , and a further wall 11 f which extends rearwardly from the upper end of the wall 11 e.

The lens 40 is formed on its inner face with balls, toroids or spheres 41 for diffusing the light. It is mounted generally vertically in the aperture which is defined between the front end of the wall 11 e and the rear end of the wall 11 f , and is secured in position by adhesive bonding or ultrasonic welding, for example.

The printed circuit 20 is mounted in the cavity defined by the housing part 11 . The printed circuit is of elongate form and follows the line of the foci of the parabolic reflective portions, or mirrors, that constitute the housing wall 11 d . The printed circuit 20 is oriented obliquely, essentially parallel with the base wall 11 a , in a plane which defines an angle α with the general direction of emission of light by the stop lamp unit, this direction being generally horizontal.

The light emitting diodes 30 are of any suitable standard kind, and they are soldered on the printed circuit 20 . Each light emitting diode emits light at the level of the focus of one of the respective parabolic mirrors of the wall 11 d , mainly towards the said mirror. In this way, a substantial proportion of the light emitted by the light emitting diodes 30 is directed towards their respective mirrors 11 d . These mirrors concentrate the light through the lens 40 , which provides the diffusion which is necessary in order to satisfy the regulation photometric grid.

The various parameters which play a part in the design of the mirror, namely its upper and lower overall dimensions, and, most particularly, the focal length of each parabolic portion, are defined in particular by the available depth and by the distance between each light source and the next.

It will be observed here that the light emitting diodes 30 lie substantially below the lens 40 , and that the limiting planes P 1 and P 2 of the housing portion which defines the mirror 11 d , both lie above the line which passes through the light emitting diodes 30 . It will also be observed that the diodes 30 are oriented in a direction which is generally opposed to the exit direction of the light.

The housing 10 of the stop light unit also includes a second part 12 which defines a visor that provides the transition with an inclined opening in the bodywork of the vehicle (not shown), and which also provides the necessary optical seal. The housing part 12 has a first wall 12 a which is generally horizontal and which extends the wall 11 f of the first housing part 11 outwardly, together with a second wall 12 b which is substantially shorter than the wall 12 a . The second wall 12 b also extends outwardly, in this case from the wall 11 e of the housing part 11 . The protective transparent cover plate 50 is fitted between the free edges of the two walls 12 a and 12 b.

By virtue of the use of mirrors of the parabolic type which form part of the housing of the unit, and by virtue also of the disposition of the light emitting diodes 30 , the resulting stop light unit is extremely compact in length, without its selling cost being increased by any significant amount.

Although a mirror has been described above which consists of a plurality of portions of paraboloids of revolution, it will of course be understood that other embodiments could be envisaged for the mirror. In particular, it may consist of a parabolic cylinder, the focal line of which passes through the various light sources, or through surfaces which have a profile that may for example be defined mathematically, being such as to provide all the required light distribution upstream of the lens 40 .

In another embodiment, the invention may be applied to a raised stop light for an inclined rear window.