Lighting Device for a Signal Light for a Motor Vehicle, Promoting Increased Light Propagation in a Light Guide

Abstract

The invention relates to a lighting device for a signal light of a motor vehicle, generating increased light propagation in a light guide. To this end, the lighting device comprises a light guide defined by a front face, a light source illuminating a first end of the light guide, and a first mask which is positioned in front of the light source and a part of the front face of the light guide, such that the first mask hides the light source from an observer looking at the front face of the light guide. Advantageously, the front face of the light guide, facing the first mask, is at least partially covered by a separating layer reflecting the light emitted by the light source.

Claims

1. A lighting device comprising a light guide delimited by a front face, a light source lighting a first end of the light guide as well as a first mask positioned in front of the light source and a part of the front face of the light guide, so that the first mask hides the light source to an observer looking at the front face of the light guide, the front face of the light guide, opposite the first mask, being at least partially covered by a interlayer reflecting the light emitted by the light source, wherein the interlayer is set back from the end of the first mask that covers the front face of the light guide.

2. The lighting device as set forth in claim 1, wherein the interlayer extends continuously along the front face, in a direction of propagation of the light emitted by the light source in the light guide, between the first end of the light guide hidden behind the first mask and an end of the first mask hiding a part of said front face.

3. The lighting device as set forth in claim 1, wherein the interlayer covers between 10% and 100% of the front face of the light guide hidden behind the first mask.

4. The lighting device as set forth in claim 1, wherein the interlayer covers the end of the front face of the light guide hidden behind the first mask.

5. The lighting device as set forth in claim 4, wherein the end of the first mask is curved towards the front face of the light guide, so as to fully hide the interlayer to an observer.

6. The lighting device as set forth in claim 1, wherein the thickness of the interlayer is lower than 5 mm, preferably lower than 1 mm.

7. The lighting device as set forth in claim 1, wherein the interlayer is in contact with the first mask.

8. The lighting device as set forth in claim 1, wherein the light guide comprises diffractors that act to diffract the light propagating in the light guide.

9. The lighting device as set forth in claim 8, wherein the first mask covers one or several diffractors.

10. (canceled)

11. The lighting device as set forth in claim 1, wherein the light guide includes, at a second end, a groove receiving a second mask so that the latter flushes with the front face of the light guide.

12. A signalling light for a motor vehicle comprising a lighting device as set forth in claim 1.

13. The signalling light as set forth in claim 12, wherein the light guide forms an intermediate screen or an outer screen of the signalling light.

14. (canceled)

15. A method for manufacturing a lighting device as set forth in claim 1, implementing a step of overmoulding the interlayer arranged on a part of the front face of the light guide, so as to form the first mask.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be better understood, thanks to the following description, which relates to preferred embodiments, given by way of non-limitative examples, and explained with reference to the appended schematic drawings, in which:

[0033] FIG. 1 is a schematic longitudinal cross-sectional view of a lighting device according to the state of the art;

[0034] FIG. 2 is a schematic longitudinal cross-sectional view of a first embodiment of a lighting device according to the invention;

[0035] FIG. 3 is a schematic longitudinal cross-sectional view of a second embodiment of a lighting device according to the invention;

[0036] FIG. 4 is a schematic longitudinal cross-sectional view of a third embodiment of a lighting device according to the invention;

[0037] FIG. 5 is a schematic longitudinal cross-sectional view of a fourth embodiment of a lighting device according to the invention;

[0038] FIG. 6 is a schematic longitudinal cross-sectional view of a fifth embodiment of a lighting device according to the invention;

[0039] FIG. 7 is a schematic longitudinal cross-sectional view of a sixth embodiment of a lighting device according to the invention;

[0040] FIG. 8 is a schematic longitudinal cross-sectional view of a signalling light comprising a lighting device according to FIG. 7; and

[0041] FIG. 9 is a front view of the front face of a signalling light according to FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

[0042] As a reminder, the invention proposes a lighting device for a motor vehicle signalling light, comprising a light guide lighted substantially homogeneously along the guide, while favouring the propagation of a greater quantity of light in the guide.

[0043] According to a first embodiment illustrated in FIG. 2, a lighting device 2A according to the invention is distinct from the lighting device 1 described hereinabove in that the light guide 4 is substantially convex at its front face 6 and in that it comprises an interlayer 22 interposed between the front face 6 and the first mask 20. It is to be noted that the identical elements between these two lighting devices 1 and 2A are indexed by the same numerical references.

[0044] More precisely, the interlayer 22 is in contact with the front face 6 of the light guide and the first mask 20. The interlayer 22 is at least partially reflective, preferably totally reflective, to the light beam 16 emitted by the light-emitting diode 18. Hence, advantageously, a greater quantity of light emitted by the light-emitting diode 18 propagates in the light guide 4. That way, the light guide 4 is perceived as brighter by an observer looking at the front face 6 of the light guide, in comparison with the light guide 1 described hereinabove.

[0045] By way of non-limitative example, the interlayer 22 is made from aluminium. The interlayer 22 extends from the first end 12 of the light guide 4, hidden by the first mask 20, up to an end 24 of the first mask hiding a part of the front face 6 of the light guide 4. In other words, the interlayer 22 extends over 100% or all the length L of the first mask 20 that hides the front face 6 of the light guide 4.

[0046] Preferably, the interlayer 22 is the thinnest possible in order to optimize the total thickness of the lighting device 2A. Of course, the interlayer is also thick enough to reflect most of the light beams 16 propagating in the light guide 4. For example, as a function of the nature of the interlayer, the thickness thereof is comprised between 0.1 mm and 2 mm, preferably of the order of 1 mm.

[0047] According to the present example, the light guide 4 comprises an inflexion point so as to form a three-dimensional wall whose thickness, defined as the distance separating its front face 6 from its rear face 8, is comprised between 1 mm and 50 mm, preferably of the order of 25 mm. Of course, according to other embodiments not shown, the light guide may be concave and/or convex.

[0048] The light guide 4 is transparent in order to allow the propagation of the light beams 16 along said guide. Preferably, the measured HAZE value at the front face of the light guide is comprised between 60% and 98%, preferably higher than 70%. By way of non-limitative example, the light guide 4 is formed from a poly(methyl methacrylate) (PMMA) and/or a polycarbonate (PC).

[0049] The first mask 20 is also made from one of the materials mentioned hereinabove and processed so as to be opaque to the light beams 16. In practice, the light guide 4 may have a length, defined along the axis (AA), of about 200 mm to 300 mm when lighted by a light-emitting diode at its first end 12, and even up to 600 mm when another light-emitting diode lights its second end 14 (not shown in the Figures).

[0050] FIG. 3 now illustrates a second embodiment of a lighting device 2B according to the invention. This embodiment is distinct from the example described hereinabove in that the interlayer 22 is set back from the end 24 of the first mask 20, so that it is difficult for an observer facing the front face 6 to observe the interlayer 22. Preferably, the end 24 of the first mask 20 protrudes from the interlayer film 22 by a length adapted to reduce the impression of hot point observable at the edge of the interlayer 22. By hot spot, it is meant herein an area of the light guide 4 that is locally more lighted at its front face 6 by the light source 18. According to the present example, the end 24 of the first mask protrudes from the interlayer by a length comprised between 5 mm and 15 mm, preferably of the order of 10 mm. Of course, this value is liable to change as a function of the thickness of the interlayer and of the power of the light source.

[0051] FIG. 4 illustrates a third embodiment of a lighting device 2C according to the invention. This embodiment is distinct from the example described hereinabove in that the end 24 of the first mask 20 covers a part of the front face 6 of the light guide 4, so as to fully hide the interlayer 22 to an observer facing the front face 6. Preferably, the end 24 is in direct contact with the front face 6 of the light guide 4, so that the first mask 20 and the light guide form a housing protecting the interlayer film 22, in particular from humidity and dust. According to a preferred embodiment, the end 24 of the first mask 20 extends over a length comprised between 5 mm and 6 mm on the front face 6, in order to reduce the hot spot impression described hereinabove.

[0052] FIG. 5 illustrates a fourth embodiment of a lighting device 2D according to the invention. This fourth example is distinct from the previous example in that the light guide 4 includes a groove opening both into a part of the lateral face 10 delimiting its second end 14 and into a part of its front face 6. The groove receives a second mask 21 flushing with the front face 6. Like the first mask 20, the presence of the second mask 21 aims to attenuate the hot spot feeling at the end of the light guide. Preferably, this second mask is moulded into said groove. Preferably, the first and the second mask are moulded at the same time on the light guide 4.

[0053] FIG. 6 illustrates a fifth embodiment of a lighting device 2E according to the invention, in which the light guide 4 includes conical cavities 26 at its rear face 8. Each cavity 26 acts to scatter a part of the light beams 16 propagating between the first end 12 and the second end 14 of the light guide 4, in order to uniformize the light output of the light guide for an observer and to also eliminate the scattering irregularities.

[0054] Preferably, a few cavities 26 are provided opposite the first mask 20 in order to preserve an optimum propagation of the light beams 16 in the light guide 4 at the first mask 20, while allowing an observer to better perceive the light beyond the first mask when he/she inclines his/her viewing angle to observe behind said mask. Preferably, the smallest distance separating a cavity 26 from the first end 12 of the light guide is comprised between 5 mm and 20 mm, preferably of the order of 10 mm. Of course, like the first mask 20, the second mask 21 may also cover a few cavities 26 for the same reasons.

[0055] FIG. 7 illustrates a sixth embodiment of a lighting device 2F according to the invention. This new embodiment is distinct from the fifth one in that the lighting device 2F now includes a plate 28 covered with a reflective layer. The reflective layer is placed opposite the rear face 8 of the light guide 4. More precisely, the reflective layer reflects the light scattered by the light guide 4, towards the front face 6 thereof. By way of non-limitative example, the reflective layer covering the plate 28 may be of same nature as the interlayer 22, i.e. with a smooth and metallized surface. This advantageously allows giving a dynamic effect to the cavities 26, by creating as an optical effect for an observer of the front face 6 of the light guide 4 that the cavities 26 move when the observer changes his/her angle of observation of said front face 6. Conversely, the reflective layer covering the plate 28 may have a grained surface, in order to uniformize the light reflecting on it and hence to accentuate the impression of a homogeneous light strip emitted by the light guide 4.

[0056] According to a variant embodiment, the light guide 4 is colourless and the reflective layer covering the plate 28 is bright to favour the reflection of a greater quantity of light. According to a preferred embodiment, the reflective layer has a colour similar to that of the body of a motor vehicle provided with a lighting device according to the invention. Hence, in the absence of emission of a light signal by the light source, the light guide allows the outer light to reflect on the reflective layer to give an impression of homogeneity of the body. This embodiment hence offers a more aesthetic integration of the lighting device on the body.

[0057] According to another variant embodiment of the invention, not shown, the light source is controlled by a lighting device allowing progressively varying the intensity and/or the colour of the light emitted by said source, so as to create an effect of progressive lighting of the light guide 4.

[0058] The lighting devices described hereinabove are preferably intended to equip a signalling light or a side light for a motor vehicle, for example an additional element of the signalling and/or positioning light. By way of example, the sixth embodiment described hereinabove may be integrated in an optical case 32 to form a signalling light 3 illustrated in FIGS. 8 and 9. Advantageously, the light guide 4 forms an outer screen of the signalling light 3. The light guide then simultaneously ensures the two following functions: protecting the components present in the optical case 32 and displaying a light signal at the light guide, for warning an observer about the position and/or of the change of direction of a motor vehicle provided with a signalling light according to the invention. It is therefore no longer necessary to use a specific protective screen, which advantageously allows doing without such a screen and reducing the depth and the weight of the signalling light. By way of example, the depth of a signalling light according to the invention may hence be equal to or lower than 50 mm or than 15 mm, preferably equal to or lower than 9 mm. A shallow signalling light as proposed by the invention allows a better adaptability on a wider variety of bodies due to its lower bulk. According to another advantage, the first mask 20 and the second mask 21 form a frame as illustrated in FIG. 9, preferably overmoulded on the front face 6 of the light guide, so as to delimit a window whose contours may be of varied shapes in order to personalize the light strip emitted by the lighting device according to the invention.

[0059] As mentioned hereinabove, the invention also relates to a method for manufacturing a lighting device as described hereinabove. According to a non-limitative example, the manufacturing method implements a first step of moulding the light guide 4, in a mould designed for that purpose, by a technique of hot injection of plastic material. The plastic material used is, for example, poly(methyl methacrylate) (PMMA) and/or a polycarbonate (PC). As illustrated in FIG. 4, the light guide is delimited at its larger faces by a front face 6 opposite to a rear face 8. According to the present example, the surface delimited by the front face 6 is comprised between a few cm.sup.2 and a few m.sup.2. The thickness of the light guide 4 is comprised in the ranges of values mentioned hereinabove. The light guide 4 is manufactured so as to form a three-dimensional wall, able to serve as an outer screen for an optical case.

[0060] Then, during a second step, an interlayer 22 as described hereinabove is applied against a part of the front face 6 of the light guide 4, located at the first end 12 thereof. This second step is performed after the light guide 4 has been cooled down enough, so that the temperature of its front face 6 is lower than 80 C., preferably lower than 60 C. The risks of deformation or degradation of the interlayer are hence limited. The thickness of the interlayer 22 is comprised in the range of values mentioned hereinabove.

[0061] During a third and last step, the interlayer 22 is overmoulded to form the first mask 20 according to the invention, by injection of a plastic material compatible with that used to form the light guide 4. By compatible, it is meant the use of a plastic material forming an adherent and seal layer on the light guide. More precisely, the plastic material is spread against the interlayer 22 and a part of the front face 6 of the light guide 4 as illustrated by FIG. 4, so as to encapsulate the interlayer 22 between the light guide 4 and the first mask 20.

[0062] Hence, advantageously, the interlayer 22 is protected from the outer environment. The lighting device 2C may then be used as an outer screen for a motor vehicle signalling light. The signalling light then has a far lower thickness with respect to the state of the art, because it is no longer required to place a specific protective screen in front of the lighting device to protect it from the outer environment.

[0063] The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.