EP0451039B1 - Intermediate lens for rear lamps and method of fabrication - Google Patents

Description

The present invention relates generally to signaling lights, in particular for motor vehicles, and relates more particularly to a new intermediate screen for signaling lights and a new method for the manufacture thereof.

Some signal lights known in the art include a filament lamp, an intermediate screen, and a globe or closing light. A mirror can be provided if necessary to recover as much as possible the flux emitted by the lamp in the direction opposite to the screen and to the indicator.

Traditionally, the purpose of the intermediate screen is to straighten the light rays received from the lamp and, where appropriate, from the mirror in order to bring the beam formed to comply with a given photometry. This must be done in such a way that the fire observed from the outside looks as uniform as possible in terms of brightness.

Thus it is known to provide on the interior surface and / or on the exterior surface of the intermediate screen streaks, preferably concentric, the respective profiles of which are calculated so as to provide a deflection, by total refraction or reflection, which is perfectly suited to the orientation of the light rays received from the lamp and, where appropriate, from the reflector. Document US-A-4,823,246 teaches such an intermediate screen.

It is therefore understood that the production of matrices intended for the manufacture of such intermediate screens (generally made of molded plastic, transparent or colored), is extremely tedious, long and costly. More precisely, it is necessary, for each streak or limited group of streaks, to adjust the angle of attack of the tool as a function of the prism angles which it is desired to give to the streak.

In addition, in order to be able to engrave the faces of ridges as far as the bottom of deep ridges, it is necessary to provide an extremely narrow, and therefore fragile, tool.

The present invention aims to overcome these drawbacks of the prior art and to propose an intermediate screen which is much easier and economical to produce, while giving satisfactory results from an optical point of view.

To this end, the invention relates to a first aspect, an intermediate screen as defined in claim 1.

Thanks to the invention, as will be seen, all the streaks of the sub-assembly or sub-assemblies can be produced by etching a mold using a single cutting tool with two cutting edges of well-defined mutual inclination cuts. , or with a very limited number of such tools.

Preferred, but not limiting, aspects of the intermediate screen according to the invention are set out in subclaims 2 to 6.

According to a second aspect, the invention relates to a manufacturing method by machining a half-mold for the production by molding of an intermediate screen for example as defined above, having the characteristics of claim 7.

Finally, according to a third aspect, the invention relates to a method of manufacturing by machining a half-mold for the production by molding of a screen. plate-shaped intermediate, for example of the type defined above, having the features of claim 8.

• la figure 1 est une vue d'ensemble schématique, en coupe horizontale, d'un feu de signalisation incorporant un écran intermédiaire,
• la figure 2 est une vue en élévation schématique de l'écran intermédiaire,
• la figure 3 est une vue en coupe horizontale de l'écran de la figure 2,
• la figure 4 représente plusieurs détails, à échelle agrandie, de l'écran de la figure 3,
• la figure 5 représente un autre détail à échelle agrandie de l'écran de la figure 3, et
• la figure 6 est une vue schématique en perspective illustrant un premier procédé de réalisation d'un demimoule pour un écran intermédiaire selon l'invention,

   On indiquera tout d'abord que, d'une figure à l'autre, des éléments ou parties identiques ou similaires sont désignés par les mêmes références.Other aspects, aims and advantages of the present invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of nonlimiting example and made with reference to the accompanying drawing, on which :

• FIG. 1 is a schematic overview, in horizontal section, of a signaling light incorporating an intermediate screen,
• FIG. 2 is a schematic elevation view of the intermediate screen,
• FIG. 3 is a view in horizontal section of the screen in FIG. 2,
• FIG. 4 represents several details, on an enlarged scale, of the screen of FIG. 3,
• FIG. 5 represents another detail on an enlarged scale of the screen of FIG. 3, and
• FIG. 6 is a schematic perspective view illustrating a first method of producing a half-mold for an intermediate screen according to the invention,

First of all, it will be indicated that, from one figure to another, identical or similar elements or parts are designated by the same references.

Referring firstly to Figure 1, there is shown a motor vehicle signaling light, which comprises a lamp 10, a reflector 20, an intermediate screen 30 and a globe or closing light 40. The reflector is conventionally charged to recover the luminous flux emitted towards the bottom of the fire. The purpose of the intermediate screen is to straighten the rays received directly from the lamp so that they participate in the formation of the beam, its design being such that the rays reflected by the reflector 20, after passing through said screen, also continue to participate to the beam, i.e. are not excessively deflected laterally. Conventionally, the intermediate screen 30 comprises a series of concentric streaks, all centered on a reference center C which is the normal projection of the source on the screen, and preferably of small width (of the order of the fraction of millimeter or millimeter). We note indeed with streaks of greater width the visible presence on the lit fire of alternately dark and bright concentric circles, which is not desirable in particular on the aesthetic level.

Each stripe has a V-shaped profile and can be defined on the one hand by its width L, and on the other hand by the angles α, β of its two faces of rectilinear and inclined profile, that is to say conical.

The indicator 40 preferably comprises, on its inner surface, a series of balls or the like intended to homogenize the light beam obtained.

We will now describe in more detail, with reference to Figures 2 to 5, an intermediate screen 30 according to a preferred embodiment of the invention. In the present example, the screen 30 has three areas distinct denoted Z1, Z2 and Z3, separated by vertical transitions T12 and T23.

The lateral zones Z1 and Z3 each comprise, on the inner surface of the plate P constituting the screen 30, a series of concentric grooves. The streaks S1 of the zone Z1 are in the present example all identical, that is to say that the associated parameters L1, α1 and β1 are the same regardless of the streak S1. Likewise, the streaks S3 of the zone Z3 all have the same parameters L3, α3 and β3.

According to an essential aspect of the invention, at least one area of the screen, here the central area Z2, has ridges which can be characterized by the fact that their angles α2 and β2 vary from one streak to another, however, the sum α2 + β2 remains constant.

In this case, the zone Z2 is subdivided into two subzones Z2 ′ and Z2˝, respectively interior and exterior, the transition between the two subzones taking place along a circular line L2 which is located at the transition between two adjacent streaks.

Zone Z2 ′ has streaks S2 ′ whose opening angle (sum of angles α2 ′ and β2 ′) is equal to a first value Θ2 ′, while zone Z2˝ has streaks S2˝ whose angle aperture Θ2˝ = α2˝ + β2˝ is equal to a second value, different from the first value Θ2 ′ and in this case lower.

There is shown in detail in Figure 5 a radial section of a part of the subzone Z2 ''. We can observe that the angles α2˝ and β2˝ vary according to a monotonous progression from one streak to another, the angle α2 '' decreasing as we move away from the reference point C while the angle β2 '' increases. But throughout this sub-area, the sum α2 '' + β2 '' remains constant.

The behavior of the streaks S2 ′ of the zone Z2 ′ is similar, only the opening angle Θ2 ′ being different, as well as possibly the width L2 ′ of the streaks.

Of course, although in the example illustrated, only the central zone Z2 of the screen has streaks of variable profile, the other zones of the screen could also include such streaks.

The foregoing description has been made with reference to circular and concentric ridges. But it is understood that the invention also applies to juxtaposed streaks constituted in practice by a single streak developed in a spiral (it will be noted here that, although we find ourselves in this case in the presence of a single streak , we will continue to speak of a plurality of streaks side by side, for the sake of simplification).

In the case of spiral streaks, the angles α and β which characterize each streak can vary either continuously and progressively as one moves along the streak, or by jumps, for example by angular steps of 360 °. We understand that we then obtain the same result as with concentric streaks, namely that from one streak to another, the characteristic angles α and β have varied, with here again the characteristic α + β = constant which that is the streak of the same subset.

A notable advantage of the present invention lies in that, for the production by machining of a model or of a half-mold which will make it possible to produce screens in large series, the ridges (for example S2˝) can be produced at using a single cutting tool, having two cutting edges inclined with respect to each other by the angle Θ2˝, the inclination of which is simply modified when changing from the engraving of a streak to the engraving of the next streak.

This process is illustrated diagrammatically in FIG. 6. Conventionally, each streak is produced by rotating the model M around an axis A perpendicular to the plane of the screen to be produced and passing by its reference center C, while the cutting tool OC is kept fixed. To make the next impression (assumed to be further from the center C), simply lift the tool and move it away from point C by the appropriate distance equal to the pitch of the streaks.

According to the invention, the mold is produced according to the above process, but also by modifying the inclination of the cutting tool OC when moving on to the production of the next impression. Thus it can be observed in FIG. 6 that, for the production of the imprint Sa, the cutting tool OC (indicated in dashed lines) is inclined, in the radial plane passing through C, relative to the normal at the surface, by a certain angle Ωa adapted to the angles αa and βb sought; for the realization of the following streak, the inclination of the cutting tool is modified to become Ωb, adapted to the new angles αb and βc sought.

Thus, the method of making the mold is not substantially complicated compared to the techniques conventionally used, only an appropriate angular offset of the cutting tool being to be carried out in addition to its linear offset in the radial direction when passing a streak. to the other.

Depending on the size and opening angle of the streaks, and depending on the nature of the material, each streak can be produced either in one machining pass or in several passes. In both cases, the advantage remains of not having to make a tool change.

We will now describe, still with reference to FIG. 6, a variant of the method of manufacturing a mold according to the invention. In this variant, each streak zone is produced using a single streak developed in a spiral. In this case, the streak is produced without having to lift the cutting tool to pass from one streak to another, but by radially moving said tool in a linear relationship in function of the absolute angle of rotation of the mold around point C. In this case, this rectilinear radial displacement of the tool is combined with a pivoting of the latter around a beam essentially perpendicular to the radial plane perpendicular to the surface of the mold and passing in the vicinity of the tool and the reference center C. In this case, the angle of inclination of the tool OC progressively changes from the value Ωa to the value Ωb when the mold rotates by 360 °.

In a particular embodiment of the invention, all the ridges of the intermediate screen 30 have the same width. They can of course have different widths.

Of course, the present invention is in no way limited to the embodiment described above and shown in the drawings, but those skilled in the art will be able to make numerous variants or modifications to the scope of the claims.

In particular, he will be able to use the teachings of the present invention to produce intermediate screens of entirely arbitrary types, comprising zones of ridges in any number and in any arrangement, one or more of which will be provided with ridges with constant opening and inclinations varying from one streak to another. The values of the various streak parameters entering into the design of the screen are determined essentially according to the nature and the arrangement of the source and the reflector and the type of light signal to be formed, and can vary to a very large extent. .

Furthermore, it is of course possible to envisage using a common intermediate screen for a set of signaling lights arranged side by side. It is also possible, thanks in particular to the performance of current digital machine tools, to implement the present invention in non-intermediate screens. flat and may have strongly curved parts, especially in the corner regions of the rear light units.

Finally, the ridges produced in accordance with the present invention may have a profile other than circular or spiral, for example by virtue of a controlled radial displacement of the cutting tool during the rotation of the mold being engraved.

Claims (9)

1. An intermediate screen (30) for a signal light, of the type constituted by a plate (P) for passing light, including a set of light-deflecting grooves (S) on at least one of its faces, the grooves being essentially concentric and each being defined by two faces of essentially rectilinear profiles and of given angles of inclination (α,β) relative to a normal to the plate, characterized in that, for at least one subset of adjacent grooves (S2', S2''), the angles of inclination (α2', β2'; α2'', β2'') of the faces defining each groove vary from one groove to another and are such that the sum of said angles (ϑ2'; ϑ2'') is constant.
2. A screen according to claim 1, characterized in that it includes two lateral zones (Z1, Z3) having grooves whose faces have angles of inclination (α1, β1 ; α3, β3) remain essentially constant from one groove to the other.
3. A screen according to claim 2, characterized in that it includes a central zone (Z2) having a first sub-zone (Z2') of grooves having varying angles of inclination of their faces, with a sum that is equal to a first predetermined value, and a second sub-zone (Z2'') of grooves having varying angles of inclination of their faces, with a sum that is equal to a second predetermined value.
4. A screen according to claim 3, characterized in that the two sub-zones (Z2', Z2'') of the central zone are separated from each other by a transition line (L2) which is essentially circular and concentric with the grooves.
5. A screen according to any one of claims 3 and 4, characterized in that the lateral zones and the central zone are separated by transitions (T12, T23) that are essentially straight and vertical.
6. A screen according to any one of claims 1 to 5, characterized in that grooves are provided on both faces of the plate (P).
7. A method of machining a half-mold (M) for molding a plate-shaped intermediate screen in the form of a plate according for instance to any one of the preceding claims, wherein, in order to make at least one group of mold prints corresponding to a sub-set of the grooves of the screen,

   (a) an essentially circular first groove is made, in one or several passes, by means of a cutting tool (OC) having two cutting edges at a determined angle relative to each other, by rotating the half-mold about a reference center (C), characterized in that

   (b) the cutting tool is caused to pivot through a determined angle (Ωb-Ωa) in a plane extending at the vicinity of the cutting tool and through said axis of rotation, and

   (c) steps (a) and (b) are repeated to make all of the grooves of the group one after another.
8. A method of machining a half-mold (M) for molding a plate-shaped intermediate screen according for instance to any one of claims 1 to 6, wherein, in order to make at least one group of mold prints correspnding to a sub-set of the grooves of the screen, a single spiral groove is made by means of a cutting tool (OC) having two cutting edges at a determined angle to each other in one or several passes by rotating the piece about a reference center, characterized in that said rotation is combined to a continuous linear displacement of the cutting tool radially relative to the reference center, and further combined to a variation of inclination of the tool in a plane passing at the vicinity of said tool and said reference center.
9. A signal light, in particular for a motor vehicle, characterized in that it includes a light source (10), a closure glass (40) and an intermediate screen (30) according to any one of claims 1 to 6

Images