OVERMOULDING AN OPTICAL ELEMENT ON A THERMOPLASTIC FRAME

Abstract

An optical assembly of a light-emitting module, especially of a lighting and/or signalling module, for a motor vehicle, including an optical element, a frame; the optical element being overmoulded on the frame, the frame being shaped so as to make a mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

Claims

1: Optical assembly of a light-emitting module, especially of a lighting and/or signalling module, for a motor vehicle, comprising: an optical element; a frame; said optical element being overmoulded on the frame, said frame being shaped so as to make a mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

2: Assembly according to claim 1, wherein at least one contact surface of the frame with the optical element comprises at least one hole, wherein the hole makes the mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

3: Assembly according to claim 2, wherein said at least one hole comprises a through-hole so that, following the overmoulding, the optical element partially surrounds the frame.

4: Assembly according to claim 1, wherein the frame comprises a central hole arranged so as to enable light to pass through the optical element.

5: Assembly according to claim 4, wherein the frame comprises at least eight holes distributed substantially uniformly around the central hole.

6: Assembly according to claim 5, wherein the frame comprises at least sixteen holes distributed substantially uniformly around the central hole.

7: Assembly according to claim 6, wherein the frame comprises at least twenty holes distributed substantially uniformly around the central hole.

8: Assembly according to claim 1, wherein at least one contact surface of the frame with the optical element comprises at least one asperity, wherein the asperity makes the mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

9: Assembly according to claim 1, wherein said frame is made of a thermoplastic material and the optical element is made of silicone.

10: Assembly according to claim 1, wherein said frame is further connected to a second optical element, so as to carry out an optical function by arranging the second optical element relative to the optical element.

11: Process for manufacturing an optical assembly of a light-emitting module, especially of a lighting and/or signalling module, for a motor vehicle, wherein the process comprises the steps of: producing a frame; overmoulding an optical element on said frame; said frame being produced so as to make a mechanical attachment between the frame and the optical element during the step of overmoulding the optical element on the frame.

12: Process according to claim 11, wherein the production of the frame comprises the drilling of at least one hole, wherein the hole makes the mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

13: Process according to claim 12, wherein said at least one hole comprises a through-hole so that, following the overmoulding, the optical element partially surrounds the frame.

14: Process according to claim 11, wherein the production of the frame is carried out using a thermoplastic material and the overmoulding of said optical element on said frame is carried out using silicone.

15: Process according to claim 11, further comprising a step of connecting a second optical element to said frame, so as to carry out an optical function by arranging the second optical element relative to the optical element.

16: Assembly according to claim 2, wherein the frame comprises a central hole arranged so as to enable light to pass through the optical element.

17: Assembly according to claim 2, wherein the frame comprises at least eight holes distributed substantially uniformly around the central hole.

18: Assembly according to claim 2, wherein at least one contact surface of the frame with the optical element comprises at least one asperity, wherein the asperity makes the mechanical attachment between the frame and the optical element following the overmoulding of the optical element on the frame.

19: Assembly according to claim 2, wherein said frame is made of a thermoplastic material and the optical element is made of silicone.

20: Assembly according to claim 2, wherein said frame is further connected to a second optical element, so as to carry out an optical function by arranging the second optical element relative to the optical element.

Description

[0066] Other features and advantages of the invention will become apparent on examining the detailed description below, and the appended drawings in which:

[0067] FIG. 1 illustrates an assembly, according to one embodiment of the invention;

[0068] FIG. 2 represents a cross-sectional view of an assembly, according to one embodiment of the invention;

[0069] FIG. 3 represents a cross-sectional view of an assembly, according to one embodiment of the invention;

[0070] FIGS. 4A, 4B and 4C represent several cross-sectional views, according to various embodiments of the invention;

[0071] FIGS. 5A, 5B and 5C represent several different embodiments of the invention;

[0072] FIG. 6 is a diagram illustrating the steps of a process according to one embodiment of the invention.

[0073] FIG. 1 represents an assembly 100 comprising an optical element 102 and a frame 101 acting as support for the optical element 102. The optical element 102 is preferably made of silicone and may for example be a lens. No limitation is attached to the optical function fulfilled by the optical element 102. The optical element 102 is overmoulded on the frame 101 so as to form a single part: the assembly 100.

[0074] Advantageously, the frame 101 may be provided with a central hole around which the optical element 102 is overmoulded in order to allow incident light to pass through the optical element 102. The frame may have fastening supports 103 that make it possible to integrate the assembly 100 in a light-emitting module, for example a lighting and/or signalling module for a motor vehicle. The shape and the positioning of the fastening supports 103 in FIG. 1 are only one example of the fastening of the assembly 100.

[0075] The shape of the frame 101 according to the invention enables the assembling with the optical element 102. Indeed, it will be seen hereinbelow that the design of the frame 101 has an influence on the fastening of the optical element 102 following the overmoulding of the optical element 102 on the frame 101.

[0076] The frame 101 acting as support for the optical element 102 may be moulded, for example in the case where the frame 101 is made of thermoplastic material. However, no limitation is attached to the way in which the frame is produced.

[0077] The design of a mould for the frame 101 having the geometry and the features described below and enabling the fastening of the optical element 102 following the overmoulding step, may be created beforehand. The frame 101 may also be a metal part, produced for example by machining.

[0078] FIG. 1 more particularly represents a view in a plane perpendicular to light rays that reach the optical element 102, of the assembly 100 comprising the frame 101 and the optical element 102.

[0079] FIG. 2 represents a cross-sectional view of the assembly 100 comprising a frame 101 and an optical element 102, according to one embodiment of the invention. More particularly, FIG. 2 represents a cross-sectional view resulting from a three-dimensional representation of the assembly 100 along a plane perpendicular to the plane of FIG. 1. In FIG. 2 it is seen that the optical element 102 completely surrounds the frame at the locations 103. The locations 103 correspond to through-holes in the frame 101. Indeed, during the overmoulding of the optical element 102 on the frame 101, the overmoulded optical element 102 comes to completely surround the frame 101 at the locations 103. The purpose of this is to strengthen the mechanical adhesion between the frame 101 and the optical element 102, and to prevent the optical element 102 from becoming detached from the frame 101. The way in which the optical element 102 comes to surround the frame 101 at the two locations 103 is identical. However, nothing decrees that the design of the frame has two identical through-holes. The elements 103 from FIG. 2 can be considered as mechanical attachment within the meaning of the invention.

[0080] It is seen in FIG. 2 that there is no visible fastening between the optical element 102 and the frame 101, the assembly 100 indeed forms one single part.

[0081] FIG. 3 represents a cross-sectional view of an assembly 300, according to one embodiment of the invention. The assembly 300 comprises an optical element 303 and a frame 301 acting as support therefor. The elements 302 and 304 from FIG. 3 represent two types of mechanical attachments produced according to a different arrangement. Indeed, in the same way as in FIG. 2, the mechanical attachment 302 consists in completely surrounding the frame 301 with the optical element 303, which corresponds to a through-hole.

[0082] The mechanical attachment 304 is different from the mechanical attachment 302. Indeed, for the mechanical attachment 304, the frame 301 is shaped so that the optical element 303 penetrates the frame 301 according to the geometry illustrated in FIG. 3. Consequently, the shape of the frame 301 is produced beforehand so as to enable such a mechanical attachment and thus to provide the optical element 303 with the space required within the frame 301 in order to be inserted therein. In the example from FIG. 3, the mechanical attachments differ within the assembly. Each of these mechanical attachments fulfils a different function. The mechanical attachments 302 and 304 may each prevent a different movement and thus maintain the contact and limit the mechanical clearance between the optical element 303 and the frame 301 so as to form a single part: the assembly 300.

[0083] Several parameters are taken into account for the geometry and the positioning of the mechanical attachments, such as the temperature for example. Indeed, for an optical element made of silicone, the thermal expansion coefficient is high. A frame made of thermoplastic material is also influenced by temperature variations. The temperature variation deforms both the frame and the optical element. It is consequently preferable to take this factor into account in order to avoid the thermal deformation of the optical element and also of the frame acting as support therefor. For example, in the case of integrating such an assembly within a motor vehicle projection device, the temperatures may be subjected to variations from 40 C. to +120 C.

[0084] Furthermore, in the case of a frame made of thermoplastic material and of an optical element made of silicone or different thermoplastic material, there is a low chemical adhesion between the two elements. It is therefore advantageous to impose a certain geometry on the frame acting as support for the optical element in order to produce mechanical attachments that prevent any unexpected movement, as is provided for by the present invention.

[0085] FIGS. 4A to 4C illustrate mechanical attachments between optical element and frame according to embodiments of the invention. Only the mechanical attachment is represented each time, and it will be understood that only a portion of the assembly according to the invention is thus represented.

[0086] FIG. 4A represents a cross-sectional view of a mechanical attachment according to one embodiment of the invention. The assembly 400 comprises a frame 402 and an optical element 401. A mechanical attachment 403 enabling contact to be maintained between the optical element 401 and the frame 402 is also seen. This mechanical attachment 403 is produced using a through-hole having a constant cross section within the frame 402, it being possible for the optical element 401 to thus pass completely through the frame 402.

[0087] In FIG. 4A it is observed that the mechanical attachment 403 differs from the mechanical attachments represented in the previous figures. Varying the geometry and the features of the frame 402 allows multiple possibilities regarding the design of the optical element and also the design of the mechanical attachments. Indeed, during the overmoulding, the optical element 401 adopts the geometry of the frame 402.

[0088] FIG. 4B represents a cross-sectional view of a mechanical attachment 413 according to one embodiment of the invention. The assembly 410 comprises a frame 412 and an optical element 411. The mechanical attachment 413 enables contact to be maintained between the optical element 411 and the frame 412. The mechanical attachment 413 corresponds to a hole having a non-constant cross section. The hole represented in FIG. 4B is a blind hole, but the invention also makes provision for the use of a through-hole having a non-constant cross section. The cross section of the hole within the frame 412 is increasing, in the shape of a T. The contact surfaces between the optical element and the frame differ from the previous figures.

[0089] It is possible to design, on computer-aided design software, the contact surfaces between an optical element and a frame acting as support therefor in order to characterize this set as an assembly. Indeed, once the contact surfaces and also the contours of the optical element and of the frame are drawn in the plan, it is possible, by extrusion, to obtain a model representing the assembly in three dimensions. This model of the three-dimensional assembly may then be used for the manufacture.

[0090] FIG. 4C represents a cross-sectional view of mechanical attachments 423 and 424 according to one embodiment of the invention. The assembly 420 comprises a frame 422 and an optical element 421. The mechanical attachment 423 corresponds to a hole having a non-constant cross section within the frame 422. The hole corresponding to the mechanical attachment 423 is a blind hole in FIG. 4C, but the invention also makes provision for the use of a through-hole having a non-constant cross section. More specifically, the mechanical attachment 423 corresponds to a hole, the cross section of which is increasing with a linear profile.

[0091] The mechanical attachment 424 corresponds to a hole having a non-constant cross section within the frame 422. The hole corresponding to the mechanical attachment 424 is a blind hole in FIG. 4C, but the invention also makes provision for the use of a through-hole having a non-constant cross section. The cross section of the hole corresponding to the mechanical attachment 424 does not have an exactly linear profile. The cross section starts with a parabolic profile followed by a linear profile.

[0092] Thus, depending on the application, on the type of material used and on the imposed stresses, the present invention enables a high degree of precision regarding the type and the number of mechanical attachments for the design of the frame.

[0093] FIG. 5A represents an embodiment of an assembly according to the invention. More specifically, FIG. 5A represents a frame 500 acting as support for the overmoulding of an optical element, not represented in the figure. The frame 500 comprises a central hole 501 enabling incident light to pass through the optical element when the latter is overmoulded on the frame 500. The frame 500 may comprise at least eight holes 502, in particular eight holes, uniformly distributed around the central hole 501 and enabling the optical element to be held once overmoulded on the frame. The holes 502 may be of substantially identical sizes and may be positioned on tabs belonging to the frame 500. The holes 502 are made on the frame 500 prior to the step of overmoulding the optical element on the frame 500.

[0094] FIG. 5B represents an embodiment of an assembly according to the invention. More specifically, FIG. 5B represents a frame 510 acting as support for the overmoulding of an optical element, not represented in the figure. The frame 510 comprises a central hole 511 enabling incident light to pass through the optical element when the latter is overmoulded on the frame 510. The frame 510 may comprise at least sixteen holes, in particular sixteen holes, uniformly distributed around the central hole 511 and enabling the optical element to be held once overmoulded on the frame. The holes 512 may be of substantially identical sizes and may be positioned on tabs belonging to the frame 510. Increasing the number of holes within the frame makes it possible to increase the mechanical adhesion between the frame and the optical element once the latter is overmoulded on the frame.

[0095] FIG. 5C represents an embodiment of an assembly according to the invention. More specifically, FIG. 5C represents a frame 520 acting as support for the overmoulding of an optical element, not represented in the figure. The frame 520 comprises a central hole 521 enabling incident light to pass through the optical element when the latter is overmoulded on the frame 520. The frame 520 may comprise at least twenty holes, in particular twenty holes 521 uniformly distributed around the central hole 521 and enabling the optical element to be held once overmoulded on the frame. The holes 522 may not all be of substantially identical sizes. Indeed, sixteen holes 522 may be of substantially identical sizes, similarly to FIG. 5B and four additional holes 522 of smaller sizes are inserted on tabs that are also of smaller size.

[0096] FIG. 6 represents a diagram illustrating the steps of a process according to one embodiment of the invention. More specifically, FIG. 6 comprises two steps 601 and 602 of a process for manufacturing an assembly of an optical element, preferably made of silicone with a frame acting as support therefor. The first step 601 (FAB_SUP) corresponds to the manufacture of the frame. The frame may also be considered to be a support. The frame may be manufactured by moulding in the case of a frame made of thermoplastic material. The frame may also be a metal element and therefore be manufactured by machining. The step 602 (MOL_ELT) corresponds to a step of overmoulding the optical element on the frame. The objective of this step is to form, from two separate parts which are the optical element and the frame, a single part: the assembly. Irrespective of the process for manufacturing the frame during step 601, the frame is shaped so as to make a mechanical attachment between the frame and the optical element during the overmoulding of the optical element on the frame. The frame is therefore designed with a particular geometry so as to provide the mechanical attachments for the optical element as a function of the application of said assembly.

[0097] Of course, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that a person skilled in the art could envisage within the context of the present invention and especially all combinations of the various embodiments described above.