LIGHTING DEVICE WITH A SIGNALING FUNCTION IN A SHEET OF LIGHT CROSSED BY A LIGHTING BEAM

Abstract

LIGHTING DEVICE WITH A SIGNALING FUNCTION IN A SHEET OF LIGHT CROSSED by a LIGHTING BEAM The invention relates to a lighting device (2) comprising a lighting module (6); and a light signaling module (8) disposed in front of the lighting module (6), and comprising an optical part (10) made of transparent or translucent material extending transversely to the optical axis (12); in which the optical part (10) comprises at least one light guide (10.4.1, 10.4.2, 10.4.3) comprising successively, a first portion of circular cross-section with, on a rear face, light-reflecting patterns towards a front face, a second portion of rectangular cross-section without light-reflecting patterns, arranged opposite the lighting module (6), and a third portion of circular cross-section with, on a rear face, light-reflecting patterns towards a front face, the light being able to propagate from the first portion to the second portion and then to the third portion. (Figure to be published with the abbreviation: Figure 2).

Description

Title of the invention: LIGHTING DEVICE WITH A LINE SIGNALING FUNCTION CROSSED BY A LIGHTING BEAM Technical field

[0001] The invention relates to the technical field of light signaling and lighting, in particular for motor vehicles. Prior art

[0002] It is known to provide in a motor vehicle headlight, a light signaling module providing functions such as a daytime running light function, more commonly designated by the acronym DRL (meaning in English "Daytime Running Light") and / or a direction indication function, more commonly designated "turn signal". It is known to provide such a light signaling module in the form of a sheet light guide or with a generally circular section with, on a rear face, patterns for returning light towards a front face of the light guide. This type of light signaling module in the form of a light guide is then arranged next to a lighting module, possibly on either side laterally and / or below the lighting module in question, in order to bypass the lighting module and avoid any interference with the lighting light beam that it produces.However, it is generally desirable for this light signaling module to extend laterally on either side of the lighting module. Such a configuration then requires the provision of two separate light guides, with separate light sources. Such a construction increases manufacturing and assembly costs. Statement of the invention

[0003] The invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More particularly, the invention aims to propose a lighting device which integrates at least one light signaling function on either side of a lighting function and which is more economical.

[0004] The subject of the invention is a lighting device comprising a lighting module configured to produce a light beam along an optical axis; and a light signaling module arranged at the front, along the optical axis, of the lighting module, and comprising an optic made of transparent or translucent material capable of transmitting light and extending transversely to said optical axis; in which the optical part comprises at least one light guide comprising successively, a first portion of circular cross-section with a front face and a side face rear provided with light-reflecting patterns towards said front face, a second portion of rectangular cross-section without light-reflecting patterns, arranged opposite the lighting module, and a third portion of circular cross-section with a front face and a rear face provided with light-reflecting patterns towards said front face.

[0005] According to an advantageous embodiment of the invention, the light signaling module comprises one or more light sources optically coupled to the first portion of each light guide, said light signaling module being free of a light source directly coupled to the third portion of each light guide.

[0006] The optical part is configured such that light from the light source(s) coupled to the first portion of each light guide propagates from the first portion to the second portion and then to the third portion of said light guide.

[0007] The second portion of the light guide comprises a front face and a rear face parallel to the front face.

[0008] According to an advantageous embodiment of the invention, the optical part comprises at least two superimposed light guides.

[0009] According to an advantageous embodiment of the invention, the first portions, respectively the third portions of the superimposed light guides are connected to each other by a rib.

[0010] According to an advantageous embodiment of the invention, the second portions of the superimposed light guides are connected to each other.

[0011] According to an advantageous embodiment of the invention, the first portion and the third portion of each of the superimposed light guides have a diameter D and the at least one rib has a thickness e such that 0.2D <e<0.3D.

[0012] According to an advantageous embodiment of the invention, the first portion and the third portion of each of the superimposed light guides have a diameter D, and the rectangular cross-section of the second portion of each light guide has a thickness E such that 0.9D <E<l.LD.

[0013] According to an advantageous embodiment of the invention, the lighting device further comprises a cover arranged at the front of the optical part and having openings facing zones of the first and third portions of the superimposed light guides.

[0014] According to an advantageous embodiment of the invention, the optical part comprises an additional light guide superimposed on said at least one light guide and comprising a circular cross-section over its entire length. In particular, the additional light guide extends along the first, second and third portions of at least one of the light guides taken from among said at least one light guide. Preferably, the additional light guide is connected to the first, second and third portions of at least one light guide taken from among said at least one light guide by a rib.

[0015] According to an advantageous embodiment of the invention, for each of said at least one light guide of the optical part, the first portion connects directly with a lateral light entry face of the rectangular cross-section of the second portion.

[0016] According to an advantageous embodiment of the invention, for each of said at least one light guide of the optical part, the rectangular cross-section of the second portion comprises a lateral face for exiting light towards the third portion, said lateral face for exiting light being beveled.

[0017] According to an advantageous embodiment of the invention, the light exit lateral face matches the circular cross-sections of the third portion of the at least two superimposed light guides of the third portion of the optical part and connects with the rib(s) between said at least two superimposed light guides.

[0018] The light entry lateral face is advantageously flat or between two planes separated from each other by 5 mm, preferably 3 mm, or less.

[0019] The measures of the invention are advantageous in that they make it possible to arrange a light guide in front of a lighting module without disturbing the light beam of said lighting module and while only supplying said guide with light from one side. In other words, the measures of the invention make it possible to provide a light guide with an intermediate portion, formed by the second portion, which is neutral, that is to say which is capable of being arranged in front of a lighting module so as to be crossed by the light beam without disturbing said beam, while ensuring transmission of light along this portion between the first portion and the third portion, without emitting light, when light is guided in the light guide. Brief description of the drawings

[0020] [Fig. 1] is a front view of a light device according to the invention;

[0021] [Fig.2] is a front view of the interior of the light device of [Fig.l], namely a lighting module, a light signaling module arranged in front of the lighting module and a cover arranged in front of the light signaling module;

[0022] [Fig.3] is a front view of the light signaling module of the light device of Figures 1 and 2;

[0023] [Fig.4] is a sectional view IV-IV of the light signaling module of [Fig.3];

[0024] [Fig.5] is a sectional view IV of the light signaling module of [Fig.3];

[0025] [Fig.6] is a top view of the light signaling module of [Fig.3]. Detailed description

[0026] In the following description, the concepts of relative position such as "at the front" and "at the rear" are to be understood along the direction of the optical axis of the lighting device in the main propagation direction of the light along this optical axis. The concepts such as "next to", "to the left" and "to the right" are to be understood along a horizontal direction and transverse to the optical axis when the lighting device is in the normal operating position, as illustrated in Figures 1 to 4.

[0027] [Fig. 1] is a front and perspective view of a lighting device 2 for a motor vehicle, according to the invention. The lighting device 2 comprises a glass 4 made of transparent or translucent material covering lighting and light signaling modules, not visible in [Fig.l].

[0028] [Fig. 2] is a front and perspective view of the lighting device 2 of [Fig. 1], however without the glass 4. A lighting module 6, a light signaling module 8 arranged at the front of the lighting module 6, and a cover 14 arranged at the front of the light signaling module 8 can be seen.

[0029] The lighting module 6 is configured to produce a lighting beam along an optical axis 12, such as for example a regulatory lighting beam with an upper horizontal cut-off, commonly referred to as “code” or “low-beam” and / or a regulatory lighting beam without an upper horizontal cut-off, commonly referred to as “high-beam”. Such a lighting module is known per se and does not require further description.

[0030] The light signaling module 8 comprises an optical part 10 made of transparent or translucent material and in the form of a sheet, capable of guiding light, and one or more light sources 16. As visible in [Fig. 3], the optical part 10 comprises a plurality of light guides 10.4.1, 10.4.2, 10.4.3. The light sources 16 are configured to illuminate a light entry face of each of the light guides 10.4.1, 10.4.2, 10.4.3. In the example illustrated, the entry face of the light guides 10.4.1, 10.4.2, 10.4.3 is located at a rear end of the optical part 10.

[0031] It can be observed that the optical part 10 in a sheet has a horizontal L-shaped profile with a branch transverse to the optical axis 12 and located at the front of the lighting module 6, and a longitudinal branch generally parallel to the optical axis 12 or inclined by less than 30° relative to the optical axis 12. The light entry face of the light guides 10.4.1, 10.4.2, 10.4.3 is in this case located at one end rear of the longitudinal branch.

[0032] The cover 14 has a horizontal U-shaped profile with a central part 14.1 transverse to the optical axis 12 and located at the front of the lighting module 6 and directly at the front of the transverse branch of the optical part 10, and two longitudinal lateral branches 14.2 and 14.3 located on either side of the central part 14.1, and generally parallel to the optical axis 12 or inclined by less than 30° relative to the optical axis 12. The transverse branch 14.3 on the right in [Fig.2] extends directly along and outside the longitudinal branch of the optical part 10.

[0033] The cover 14 comprises on the central part 14.1 openings 14.4, in this case generally rectangular and horizontal, through which the light beams of the lighting module 6 and of the light signaling module 8 can pass. The cover 14 thus essentially forms a wall in the form of a generally opaque sheet, matching the optical part 10 and provided with openings 14.4 allowing the light beams to pass.

[0034] [Fig. 3] illustrates in front view the optical part 10 of the light signaling module 8 of the lighting device of figures 1 and 2.

[0035] As previously described, the optical part 10 in a sheet comprises a plurality of light guides 10.4.1, 10.4.2, 10.4.3. In the example illustrated, the optical part 10 comprises three light guides 10.4.1, 10.4.2, 10.4.3, it being understood that this example is not limiting and that the optical part 10 could comprise any other number of light guides.

[0036] Each of these light guides 10.4.1, 10.4.2, 10.4.3 essentially comprises three portions, namely successively a first portion 10.1 of circular cross-section with, on a rear face, light-reflecting patterns 10.4.6 towards a front face, a second portion 10.2 of rectangular cross-section without light-reflecting patterns, arranged opposite the lighting module 6 (as visible in [Fig.2]), and a third portion 10.3 of circular cross-section with, on a rear face, light-reflecting patterns 10.4.6 towards a front face.

[0037] In each of the light guides 10.4.1, 10.4.2, 10.4.3, the light is able to propagate from the first portion 10.1 to the second portion 10.2 and then to the third portion 10.3. It is therefore understood that the free end of the first portion 10.1 of the light guides 10.4.1, 10.4.2, 10.4.3 corresponds to the light entry face of the light guides 10.4.1, 10.4.2, 10.4.3. In other words, in each of the light guides 10.4.1, 10.4.2, 10.4.3, the light can propagate from the light input of the light guide 10.4.1, 10.4.2, 10.4.3 on the first portion 10.1, along said first portion 10.1 to the second portion 10.2, while producing a signaling light beam transversely to the light guide 10.4.1, 10.4.2, 10.4.3 thanks to the light return patterns 10.4.6. Then, the light can propagate along the second portion 10.2 and up to the third portion 10.3, without producing a signaling light beam since the second portion 10.2 is devoid of light-reflecting patterns. The light is then guided by total internal reflections in the second portion. Finally, the light can propagate along the third portion 10.3 while producing a signaling light beam transversely to the light guide 10.4.1, 10.4.2, 10.4.3 thanks to the light-reflecting patterns 10.4.6.

[0038] The circular shape or each of the circular shapes of the cross sections of the first and third portions 10.1 and 10.3 extends so as to form a profile capable of conducting the light by successive reflections on the diopter formed between the transparent or translucent material of said profile and the ambient air, and of causing a portion of it to exit by the presence on the rear face of light-reflecting patterns 10.4.6 towards the front face. This principle of light transmission with a progressive exit of a portion of the light is well known in itself and does not require further detail.

[0039] It will be noted that openings 14.4 of the cover 14 ([Fig.2]) are arranged opposite the first and third portions 10.1, 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3. In addition, the cover comprises openings 14.4 arranged opposite the second portion 10.2 of the light guides 10.4.1, 10.4.2, 10.4.3, and more particularly opposite an output face of the lighting module 6 through which the lighting beam is emitted. Alternatively, the cover could comprise only a single opening arranged opposite the lighting module 6.

[0040] The light guides 10.4.1, 10.4.2, 10.4.3 are superimposed, that is to say that the light guides 10.4.1, 10.4.2, 10.4.3 are arranged one above the other. The first, second and third portions of each of the light guides 10.4.1, 10.4.2, 10.4.3 are also superimposed. The first portions 10.1 of the light guides 10.4.1, 10.4.2, 10.4.3 are connected to each other by a rib 10.5. Furthermore, the second portions 10.2 of the light guides 10.4.1, 10.4.2, 10.4.3 are connected to each other. The second portions 10.2 thus form a block of constant thickness E and whose front and rear faces are flat and parallel.

[0041] In [Fig. 3], it can be seen that the light guides 10.4.1, 10.4.2, 10.4.3, and in particular the first and third portions 10.1, 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3 extend essentially horizontally, it being understood, however, that the light guide(s) may have non-rectilinear profiles and / or profiles inclined relative to the horizontal. It can be seen that some of the light guides, in this case the light guides 10.4.2, 10.4.3, form a downward projection in their first portion 10.1.

[0042] By portion of circular cross-section, it is understood that the section of the portion is not necessarily formed by a geometrically perfect circle, but that the section may present a certain ovality or, more generally, a certain irregularity compared to a geometric circle, provided that it is a closed contour with a general appearance of a circle.

[0043] The second portion 10.2 has a rectangular cross-section, namely with a rear face and a front face both flat and parallel, the rear face being free of patterns capable of returning the light towards the front face. Thus, the second portion 10.2 exclusively allows the transmission of the light coming from the first portion 10.1, towards the third portion 10.3 without emitting a light beam, in particular towards the front of the optical part 10.

[0044] The two flat and parallel front and rear faces of the second portion 10.2 are advantageous in that they avoid any deformation of the light beam emitted by the lighting module 6 ([Fig.2]) passing through them. For the light rays perpendicular to the rear face of the second portion 10.2, it is understood that these will not undergo any deviation when passing through the diopter formed by the rear face. Similarly, they will not undergo any deviation when passing through the diopter formed by the front face. For the rays having an angle of incidence, in principle small, with the entry diopter, they will undergo a refraction which will be compensated by opposite refraction when passing through the exit diopter.

[0045] Still in [Fig.3], it can be observed that the first and third portions 10.1, 10.3 of the light guides 10.4.1, 10.4.2 and 10.4.3 connect with the rectangular section of the second portion 10.2 of the optical part.

[0046] The optical part 10 also comprises an additional light guide 10.4.4 superimposed on the light guides 10.4.1, 10.4.2, 10.4.3. It is understood that this additional light guide 10.4.4 is optional.

[0047] Just like the light guides 10.4.1, 10.4.2, 10.4.3, the additional light guide 10.4.4 makes it possible to participate in the formation of a signaling function. It can be observed that the additional light guide 10.4.4 extends along the entire length of light guides 10.4.1, 10.4.2, 10.4.3, and in particular along the first, second and third portions 10.1, 10.2, 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3. It is located below the light guide 10.4.3. It is connected to the first, second and third portions 10.1, 10.2, 10.3 of the light guide 10.4.3 by a rib 10.5.

[0048] This additional light guide 10.4.4 has a circular cross-section along its entire length. Advantageously, this circular cross-section can be constant along the entire length of the additional light guide 10.4.4. In particular,

[0049] The additional light guide 10.4.4 comprises a front face and a rear face provided with light return patterns 10.4.6 towards the front face along its entire length. A light source 16 is arranged at a first end located on the side of the first portions 10.1 of the light guides 10.4.1, 10.4.2, 10.4.3. The light guide additional light guide 10.4.4 allows the light from the light source 16 to be guided from its first end to its second end, opposite the first end. The additional light guide 10.4.4 therefore allows light to be emitted along its entire length.

[0050] [Fig.4] is a sectional view IV-IV of the third portions 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3 of [Fig.3]. It shows the circular cross-sections of the third portion 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3 and the circular cross-section of the additional light guide 10.4.4, with on their rear face the light return patterns 10.4.6 towards their opposite front face, mentioned previously.

[0051] It is also possible to observe the ribs 10.5 connecting together the circular cross-sections of the third portions 10.3. Each of the ribs 10.5 has a thickness e less than the diameter or average diameter D of the circular cross-sections of the third portion 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3, and preferably less than the diameter or average diameter D of the circular section of the additional light guide 10.4.4. Advantageously 0.2D <e<0.3D, de manière, d’une part, à limiter les transmissions parasites de lumière entre les troisièmes portions de section circulaire et entre les troisièmes portions de section circulaire et le guide de lumière additionnel 10.4.4, et, d’autre part, à assurer une rigidité mécanique suffisante à la pièce optique 10 et à faciliter sa fabrication par injection plastique. Des variations d’épaisseurs importantes sont en effet susceptibles de présenter des difficultés d’injection de matière plastique.It should be noted that the representation of [Fig.4] and the characteristics associated therewith also apply to a cross-section of the first portion 10.1 of the optical part 10 ([Fig.3]), and in particular, the dimensional characteristics described in relation to the third portions 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3 apply mutatis mutandis to the first portions 10.1 of the light guides 10.4.1, 10.4.2, 10.4.3.

[0052] [Fig. 5] is a sectional view VV of the second portion 10.2 of the light guides 10.4.1, 10.4.2, 10.4.3 of [Fig. 3]. It shows the rectangular cross-section 10.4.5 of the light guides 10.4.1, 10.4.2, 10.4.3, and more particularly, it shows the section of the block formed by all the second portions 10.2 connected together. In the section, the rear face 10.4.5.1 and the front face 10.4.5.2 can be seen. As mentioned previously, these two faces are advantageously flat and parallel.

[0053] In the example illustrated, the rectangular cross-section 10.4.5 has a thickness E which is comparable, preferably identical, to the diameter or average diameter D of the circular cross-sections of the first and third portions 10.1, 10.3 of the light guides 10.4.1, 10.4.2 and 10.4.3, as well as of the cross-section circular of the additional light guide 10.4.4 present in this case below the rectangular cross-section 10.4.5. Advantageously, 0.9D <E<l.LD. On peut également observer la nervure 10.5 reliant la section transversale rectangulaire 10.4.5, et en particulier la section transversale rectangulaire 10.4.5 de la deuxième portion 10.2 du guide de lumière 10.4.3 au guide de lumière additionnel 10.4.4 adjacent. Similairement aux nervures 10.5 de la [Fig.4], elle présente une épaisseur e inférieure à l’épaisseur E de la section transversale rectangulaire 10.4.5, avec avantageusement 0.2-E<e<0.3-E.

[0054] [Fig. 6] is a top view of the optical part 10 in the form of a sheet of figures 2, 3, 4 and 5.

[0055] The top view of [Fig. 6] is truncated in that the first portion 10.1 is only partially shown. The view in question shows the connections between the circular cross-sections of the first and third portions 10.1, 10.3 of the light guides 10.4.1, 10.4.2 and 10.4.3, and the rectangular cross-section 10.4.5 of the second portion 10.2 of the light guides 10.4.1, 10.4.2, 10.4.3. Since the view is from above, only the first light guide 10.4.1 from the top is visible, it being understood, however, that what is visible and will be described also applies to the other light guides 10.4.2 and 10.4.3.

[0056] It can be observed that the circular cross-section of the first portion 10.1 of the light guide 10.4.1 connects directly to a lateral face 10.4.5.3 of the rectangular cross-section 10.4.5 of the second portion 10.2 of the light guide 10.4.1. This lateral face 10.4.5.3 then forms a light entry face for the second portion 10.2. It can be planar or have a geometry close to a plane. Indeed, as the light propagates by successive reflections, by total reflection, on the diopter formed by the external surface of the first portion 10.1 of the light guide 10.4.1, when the light arrives at the entry face 10.4.5.3 of the second portion 10.2, it can continue to propagate in the second portion 10.2 of the light guide 10.4.1, in the direction of the third portion 10.3 of the light guide 10.4.1 by successive reflections essentially on the rear face 10.4.5.1 and the front face 10.4.5.2 and incidentally on the upper and lower faces (not referenced) of the second portion 10.2. .

[0057] It can be observed that the lateral exit face 10.4.5.4 of the rectangular cross-section 10.4.5 of the second portion 10.2, opposite the lateral light entry face 10.4.5.3, ensures the connection between the second portion 10.2 and the third portion 10.3 of the light guide 10.4.1. It can be observed that this lateral light exit face 10.4.5.4 is profiled, in a bevel, to ensure progressive guidance of the light towards the third portion 10.3 of the light guide 10.4.1. More particularly, this lateral light exit face 10.4.5.4 has a cross-section longitudinal bevel between the circular cross-sections of the third portions 10.3 of the superimposed light guides, with a width ranging from the thickness E of the rectangular cross-section 10.4.5 to the thickness e of the rib 10.5. The light exit lateral face 10.4.5.4 thus forms a connecting bevel between the thicknesses E and e, this bevel matching the circular cross-sections of the third portion 10.3 of the light guides 10.4.1, 10.4.2, 10.4.3, as can be seen in [Fig.3]. This connecting bevel makes it possible to promote the guidance of the light emerging from the rectangular cross-section 10.4.5 between the circular cross-sections of the light guides 10.4.1, 10.4.2, 10.4.3, towards said circular cross-sections.

Claims

Claims

1. Lighting device (2) comprising: - a lighting module (6) configured to produce a light beam along an optical axis (12); and - a light signaling module (8) arranged at the front, along the optical axis (12), of the lighting module (6), and comprising an optical part (10) made of transparent or translucent material capable of guiding light and extending transversely to said optical axis (12); characterized in that said optical part (10) comprises at least one light guide (10.4.1, 10.4.2, 10.4.3) comprising successively, a first portion (10.1) of circular cross-section with a front face and a rear face provided with light-reflecting patterns (10.4.6) towards the front face, a second portion (10.2) of rectangular cross-section (10.4.5) without light-reflecting patterns, arranged opposite the lighting module (6), and a third portion (10.3) of circular cross-section with a front face and a rear face provided with light-reflecting patterns (10.4.6) towards the front face.

2. Lighting device (2) according to claim 1, wherein the light signaling module (8) comprises one or more light sources (16) optically coupled to the first portion (10.1) of each light guide (10.4.1, 10.4.2, 10.4.3), said light signaling module (8) being free of light source directly coupled to the third portion (10.3) of each light guide (10.4.1, 10.4.2, 10.4.3).

3. Lighting device (2) according to one of claims 1 and 2, in which the optical part (10) comprises at least two superimposed light guides (10.4.1, 10.4.2, 10.4.3).

4. Lighting device (2) according to claim 3, wherein the first portions (10.1), respectively the third portions (10.3) of the superimposed light guides are connected to each other by a rib (10.5).

5. Lighting device (2) according to one of claims 3 or 4, wherein the second portions (10.2) of the superimposed light guides (10.4.1, 10.4.2, 10.4.3) are connected to each other.

6. Lighting device (2) according to one of claims 3 to 5, wherein the first portion (10.1) and the third portion (10.3) of each superimposed light guides (10.4.1, 10.4.2, 10.4.3) have a diameter D and the at least one rib (10.5) has a thickness e such that 0.2D <e<0.3D.

7. Lighting device (2) according to one of claims 3 to 6, in which the first portion (10.1) and the third portion (10.3) of each of the superimposed light guides (10.4.1, 10.4.2, 10.4.3,) has a diameter D and the rectangular cross-section (10.4.5) of the second portion (10.2) of each light guide (10) has a thickness E such that 0.9D <E<1.1D.

8. Lighting device (2) according to one of claims 3 to 7, further comprising: - a cover (14) arranged at the front of the optical part (10) and having openings (14.4) facing zones of the first and third portions (10.1, 10.3) of the superimposed light guides (10.4.1, 10.4.2, 10.4.3).

9. Lighting device (2) according to one of claims 1 to 8, in which the optical part (10) comprises an additional light guide (10.4.4) superimposed on said at least one light guide (10.4.1, 10.4.2, 10.4.3) and comprising a circular cross-section over its entire length.

10. Lighting device (2) according to one of claims 1 to 9, wherein for each of said at least one light guide (10.4.1, 10.4.2, 10.4.3) of the optical part (10), the first portion (10.1) connects directly with a light entry lateral face (10.4.5.3) of the rectangular cross-section (10.4.5) of the second portion (10.2).

11. Lighting device (2) according to one of claims 1 to 10, wherein, for each of said at least one light guide (10.4.1, 10.4.2, 10.4.3) of the optical part (10), the rectangular cross-section (10.4.5) of the second portion (10.2) comprises a light exit lateral face (10.4.5.4) towards the third portion (10.3), said light exit lateral face (10.4.5.4) being bevelled.

12. A lighting device (2) according to claim 11 when dependent on claim 4, wherein the light exit side face (10.4.5.4) matches the circular cross-sections of the third portion of the at least two superimposed light guides (10.4.1, 10.4.2, 10.4.3) and connects with the rib(s) (10.5) between said at least two superimposed light guides (10.4.1, 10.4.2, 10.4.3).

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