Abstract:
The present invention relates to a light device projecting a light beam along a principal lighting axis, by means of at least one light source, the light device also comprising at least one reflector, a frame and a shield. The shield is able to move in rotation about an axis of rotation and has an “active” edge composed of a set of distinct portions, at least part of one of the portions of the said portions taking part in the production of at least two different cutoffs of the light beam emitted by the said light source.

Description:
FIELD OF THE INVENTION 
   The object of the present invention is a multifunction light device, in particular of the elliptical type. In this type of light, a light concentration spot is generated by a light source disposed in a reflector. Typically the light source is disposed at the first focus of a reflector in the form of an ellipsoid, the said spot forming at the second focus of the reflector. The light concentration spot is then projected onto the road by a conversion lens, for example a lens of the planar-convex type. 
   BACKGROUND OF THE INVENTION 
   The aim of the invention is essentially to propose a solution for obtaining, from a relatively simple light device of the elliptical type, various light beams corresponding to various cutoff lines satisfying various standards and/or regulations, in particular without having recourse to a multitude of shields. 
   The field of the invention is, in general terms, that of lighting devices of the motor vehicle light type. In this field, various types of light device are known, amongst which there are essentially:
         side lights, with low intensity and range;   passing, or dipped-beam, lights, with greater intensity and range on the road of around 70 metres, which are used essentially at night and where the distribution of the light beam is such that it makes it possible not to dazzle the driver of a passing vehicle;   long-range headlights, and auxiliary lights of the long range type, where the area of vision on the road is around 200 metres, and which must be switched off when passing another vehicle in order not to dazzle its driver;   fog lights.       

   In addition, a type of improved light is known, referred to as dual-function lights, which combine the functions of dipped lights and long-range lights: for this purpose, it is possible for example to dispose inside the dual-function light a removable shield consisting for example of a metallic plate, able to move on demand from a first position in which it does not obscure the light beam produced by the light source of the light, the range of the light then corresponding to that of main-beam lights, and a second position in which it obscures part of the light beam produced by the light source of the light, the range of the light then being limited to that of dipped lights. The light must, in the second position, generate a beam with a regulatory cutoff corresponding to a dipped beam, the form of the cutoff being given by the form of the shield intercepting part of the light beam. This type of design is principally used in light devices of the elliptical type. 
   However, the conventional light devices which have just been mentioned, more particularly those which are used as dipped lights, produce light beams which are open to improvement when these light devices are used in certain conditions. 
   Thus, when a vehicle is on a motorway, it is judicious to concentrate the light flux of the dipped light at the optical axis of the light device, in order to make the beam produced carry a little further. On the contrary, when a vehicle is travelling in town, it is not necessary to make the light beam carry as far as on clear roads. 
   Thus, in addition to the conventional main light functions, in particular dipped and main beam, various improvements have progressively appeared. Thus elaborate functions or advanced functions have been seen to develop which slightly modify the positioning of the cutoff of the light beam produced, amongst which there are in particular:
         a function known as Town Light in English, standing for town beam. This function provides a slight reduction in the range of the light device, possibly by providing a broadening of the beam of the dipped beam type;   a function known as Motorway Light in English, standing for motorway light. This function provides an increase in the range of a dipped light.       

   In addition, it must be recalled that, for countries where the traffic travels on the right, the cutoff line of a beam of the dipped type is symmetrical, with respect to a vertical central axis, with that observed in countries where the traffic travels on the left.  FIG. 1  depicts, by way of example and schematically, four projections on a planar surface of the various light beams that have just been mentioned. The planar projection surface is disposed facing the light device in question, perpendicular to its optical axis. The darkened part of these projections corresponds to an absence of light in this part, the part left white corresponding to a normal illumination by means of the light device in question. Thus there have been shown a first cutoff  101 , corresponding to a dipped beam in traffic on the right, a second cutoff  102  corresponding to a motorway beam in traffic on the right, a third cutoff  103  corresponding to a town beam or fog light, a fourth cutoff  104  corresponding to a dipped beam in traffic on the left, a fifth cutoff  105  corresponding to a motorway beam in traffic on the left and a sixth cutoff  106  corresponding to a main beam. 
   It is therefore sought to propose light devices which are capable of modifying the cutoff of the light beam that they produce, so as to be able to propose alternatively in particular the six beams shown in  FIG. 1 . 
   To this end various solutions have been proposed in the prior art. 
   A first solution, described in the document U.S. Pat. No. 5,673,990, consists of a light device provided with a movable screen for in particular vertical sliding in order to form on demand a beam with a particular cutoff. 
   A second solution, described in the European patent application EP 1 197 387, describes the use, in each light device of the dipped beam type, of a plate, approximately square in shape, in rotation on itself, the axis of rotation being inclined with respect to a main lighting axis. Each side of the plate makes it possible to obtain a light beam corresponding to a particular cutoff when the side in question is brought, by rotation of the plate, facing the light source of the light device in question. 
   However, with these two solutions, the changes in position of the screens or movable plates in order to pass from a first beam having a first cutoff to a second beam having a second cutoff take place by means of awkward transition phases with a modification disturbing the light distribution below the cutoff line. Moreover, the first solution requires a particularly complex and high-precision mechanism. 
   One object of the invention is to respond to all the problems that have just been mentioned. To this end, in the invention, it is proposed to use a shield rotationally moving about a substantially vertical axis, or one inclined with respect to the vertical. Part of the shield terminates in a so-called “active” edge (that is to say the edge which will determine the light/dark limit of the light beam emerging from the light), the shape of which defines the cutoff of the beam of the light device in which the shield is disposed. It is a case generally of the top edge of the shield, “top” having to be understood in the light of the shield mounted in the light in the operating position in the vehicle. In order to be able to offer a large number of distinct cutoffs by means of the same shield moving in rotation, it is proposed, in the invention, that certain sectors of the “active” top part of the shield make their contribution in the production of several cutoffs. 
   To this end, in the invention, a clever succession of shapes is proposed, defining the active or top edge terminating the shield, so that at least part of one of these shapes can be used in the production of at least two beams, having different cutoffs, preferably corresponding to two consecutive positions of the shield considering the rotation movement of the shield about the vertical axis. 
   SUMMARY OF THE INVENTION 
   The invention therefore essentially concerns a light device projecting a light beam along a principal illumination axis by means of at least one light source, the light device also in particular comprising a reflector, a frame and a shield, such that the shield is able to move in rotation about an axis of rotation (in particular a single axis of rotation). In addition, the shield has an active (top) edge composed of a set of distinct portions, at least part of one of the portions of the set of portions acting in the production of at least two different cutoffs of the diffused light beam. Preferably, the axis of rotation of the movable shield is unique. Light device should be taken to mean a set of components able to generate a light beam and intended to be integrated in a lighting device of the motor vehicle light type. 
   The light device according to the invention can also have, apart from the characteristics stated in the previous paragraph, one or more of the following secondary characteristics:
         the two different cutoffs correspond to a first light beam and to a second light beam, a transition from the first light beam to the second light beam being obtained by rotation of the shield in order to make it pass from a first position to a second position, the first position and the second position being consecutive positions amongst a set of previously determined positions of the shield;   the shield is able to define, according to its relative position with respect to the frame, at least one of the beams amongst the following group:
           dipped beam for driving on the right;   motorway beam for driving on the right;   town or fog beam;   motorway beam for driving on the left;   dipped beam for driving on the left;   main beam;   
           the top edge of the shield has successively a first substantially planar area situated at a first level, a second substantially planar area situated at a second level higher than the first level, and a third substantially planar area situated at the first level;   the “active” edge of the shield has at least two substantially planar areas situated at a first level disposed between at least one substantially planar area disposed at a second level, lower or higher than the first level;   the “active” edge of the shield has at least one substantially planar area situated at a first level, at least one substantially planar area situated at a second level, and at least one substantially planar area situated at a third level;   the “active” edge of the shield has at least four substantially planar areas disposed so that two successive areas are at different levels and connected to each other by at least one oblique transition area;   the “active” edge of the shield has successively a first substantially planar area situated at a first level, a second substantially planar area situated at a second level lower than the first level, a third substantially planar area situated at a third intermediate level, a fourth substantially planar area situated at the second level and a fifth substantially planar area situated at the first level;   the transition between two successive substantially planar areas having different levels is provided by an oblique area of the top edge of the shield;   the “active” edge of the shield has for example symmetry with respect to a plane passing through the axis of rotation of the shield;   a transition between the first planar area and the second planar area, and/or between the second planar area and the third planar area, is provided by a substantially oblique area of the active or top edge of the shield;   the axis of rotation is substantially vertical; however it may also be (slightly) oblique with respect to the vertical;   the light device comprises a fixed screen rigidly fixed to the frame;   the fixed screen is able to cooperate with the shield in order to produce a previously determined light beam of the light device;   the light device comprises a stepping motor for driving the shield in rotation about its axis of rotation;   the top or active edge of the shield is supported by a first lug and a second lug both inclined with respect to the axis of rotation, the first lug and the second lug joining at a ring centred on the axis of rotation. Any other mechanical means of holding the active edge of the shield is possible.       

   “Level” means the relative height of the area in question, the shield in the position of use as depicted in the figures.
         the shield is duplicated at least partially, so as to have at least locally two “active” edges mutually offset with respect to the optical axis. This duplication makes it possible in fact to best correct any problems of iridescence, chromatic aberrations at the cutoff.       

   In this case, the shield is preferably duplicated so as to have two “active” edges in the active portion or portions in the dipped beam position close to the optical axis. On the other hand, it is possible to have only one active edge for the other functions, particularly in the active areas of the shield close to the optical axis and involved in obtaining a beam of the motorway type. This is because, for a beam of the motorway type, the cutoff is projected further than in the case of a beam of the passing/dipped type and consequently the problems of chromatics close to the cutoff are less or not at all perceptible. 
   Another object of the invention is a motor vehicle equipped with such a light device. 
   The invention and its various applications will be better understood from a reading of the following description and an examination of the figures which accompany it. The latter are presented only by way of indication: they are schematic and are in no way limiting of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     in  FIG. 1 , already described, a schematic representation of the various light beam cutoffs which can be obtained by virtue of the light device according to the invention; 
     in  FIG. 2 , a view in section along a vertical longitudinal plane of an example embodiment of a light device according to the invention; 
     in  FIG. 3 , a view in section along a horizontal longitudinal plane of the light device of  FIG. 2 ; 
     in  FIG. 4 , a front view of a first example embodiment of a shield acting in the light device according to the invention; 
     in  FIG. 5 , a perspective view of the shield of  FIG. 4 ; 
     in  FIG. 6 , a schematic representation of the shield of  FIGS. 4 and 5  mounted on a motor driving it in rotation; 
     in  FIG. 7 , a detailed representation of the form of a top edge of the shield of  FIGS. 4 to 6 ; 
     in  FIG. 8 , a perspective view of an example embodiment of the light device according to the invention; 
     in  FIGS. 9   a - 9   b , a schematic representation of the shield according to the invention in accordance with a second example. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The elements appearing in different figures keep the same references. 
   The first example depicted, in different views and, according to the figure, in greater or lesser detail, shows a light device  2  according to the invention; it comprises a light source  9  producing a light beam, a reflector  4 , part of which provides a concentration of light in the vicinity of the screen, for example in the form essentially of an ellipsoid. The horizontal longitudinal axis  6  forms a principal lighting direction, or optical axis, of the light. The light comprises a lamp holder  8  fixed to the reflector  4  at the rear part thereof, a lens holder  10  fixed at the front part of the reflector, and a lens  12  fixed at the front part of the lens holder  12 , a focal plane of the lens passing in the vicinity of a second focus of the reflector. The lamp holder  8 , the reflector  4 , the lens holder  10  and the lens  12  follow each other along the axis  6 . The reflector  4  and the lens holder  10  constitute a frame of the light device  2 , which may also comprise a housing enclosing all the elements that have just been mentioned. 
   The light device  2  comprises a screen  14 , rigidly fixed to the frame. The screen  14  has a curved shape, with a substantially cylindrical cross-section with a vertical generatrix and a centre of curvature situated towards the front of the light. The screen  14  extends vertically over a low height and horizontally over approximately the entire width of the reflector  4 . It has a horizontal top end extending, on each side of the axis  6 , at 0.5% below the axis  6 , with reference to the focus of the lens  2 . At the axis  6 , the top end of the screen  14  has a recess  17 , visible in  FIG. 3 , approximately one centimeter deep, and over a portion of the top end corresponding to an angle of approximately 30°, the top end describing a shape that can be assimilated to an arc and a circle. The screen is fixed by two lateral lugs  15  gripped between the edges of the reflector  4  and lamp holder  8 . It prevents any risk of dazzling of a driver passed during the movement of a movable shield  16  about a substantially vertical axis of rotation  18 . The shield  16  is, during its rotation, caused to pass in front of the recess  17 , and to fill it in in the majority of positions, which will be detailed below, that can be adopted by the shield  16 . 
   The shield  16  comprises, in the example described, a ring  22  forming a base of the shield  16 , centred on the axis of rotation  18  and having a central opening  20 ; a first lug  24  and a second lug  26 , fixed to the ring  22 , move away from a base plane defined by the ring, for example at an angle of between 40° and 50° with respect to this base plane. The two lugs  24  and  26  are joined at a first end at the ring  22  and at a second end by means of a support element  28 , approximately contained in a plane defined by the two lugs  24  and  26 . The latter therefore leave an empty space  30  between them. Their separation is for example between 60° and 70°; in a particular example, it is 66°. 
   The support element  28  is extended by a top part  32 , curved, and substantially vertical, or having, as shown in  FIG. 1 , an angle of between 5° and 10° with respect to the axis  18 . The top part is curved in order to be able to move in rotation along the screen  14 . The top part  32  terminates, at its free end, in a top edge  34 , the shape of which defines the curvature, and therefore the nature of the light beam, obtained by means of the light device in question. 
   The shape of the top edge  34  is more particularly detailed in  FIG. 7 . In this example, the top edge  34  consists of a first portion  36 , situated on the left hand part of the top edge  34 , and a second portion  37  situated on the right hand part of the top edge  34 . 
   The first portion  36  and second portion  37  do not overlap but follow each other directly on the top edge  34 . The first portion  36  has, starting from the left hand end of the top edge  34 , successively a first planar area  38  situated at a first level, and a second planar area  40  situated at a second level higher than the first level, a first oblique area  42  providing the transition between the first planar area  38  and the second planar area  40 . The second portion  37  has, starting from the right hand end of the top edge  34 , successively a first planar area  44  situated at the first level and, in line with the second planar area  40  of this first portion  36 , a second planar area  46  situated at the second level, a second oblique area  48  providing the transition between the first planar area  44  and the second planar area  46 . 
   Each of the portions  36  and  37  describes a first measuring curve with an angle of approximately 30° considering that the top edge describes a shape that can be assimilated to an arc of a circle. Thus, when one of the portions is brought, by rotation about the axis  18 , opposite the recess  17 , it creates a cutoff line which is peculiar to it. 
   In the example shown, if there is adopted as the central position of the shield a position in which the junction point between the area  40  and the area  47  is placed opposite a central position of the recess  17 , it is possible to obtain the following different light beams:
         central position: flat cutoff beam  103 , the dimension of the areas  40  and  46  being sufficient to fill in in length the entire recess  17 ;   rotation of 13.5° approximately about the axis  18 : motorway beam in right hand traffic  102 , a small part of the area  40  and a large part of the portion  37  filling in in length the entire recess  17 ;   rotation of 15° approximately about the axis  18 : beam for traffic on the right  101 , the portion  37  filling in in length the entire recess  17 ;   rotation of −13.5° approximately about the axis  18 : motorway beam for traffic on the left  105 , a small part of the area  46  and a large part of the portion  36  filling in in length the entire recess  17 ;   rotation of −15° approximately about the axis  18 : beam for traffic on the left  104 , the portion  36  filling in in length the entire recess  17 ;   rotation greater than approximately 30°, or less than approximately 30° about the axis  18 : main beam; it is noted that, in the example according to the invention, there are therefore two distinct positions of the shield  16  for obtaining a main beam; the latter is therefore directly accessible, without passing through intermediate steps corresponding to other beams, whether the shield be positioned in a traffic on the left or traffic on the right configuration.       

   It is found that, by virtue of the clever succession of the areas  38 ,  40 ,  44  and  46 , up to six distinct beams are obtained by virtue of the shield  16 , which is also of small size, and whose movement takes place simply about the single axis of rotation  18 . As could be understood in the enumeration of the various possible positions of the shield, certain areas, and even certain parts of the areas constituting the portions  36  and  37 , take part in the achievement of several cutoffs, and therefore in the production of several light beams. 
   In one example embodiment, the shield  16  is driven in rotation by an actuator, for example a motor of the stepping motor type  50  visible in  FIG. 6 , comprising for example 96 steps. The motor can be disposed inside the light device, or under the lens holder  10 . It is held by means of a fixing system involving for example a nut  52 . Its functioning is managed by a microcontroller, in which particular positions of the shield  16  have been stored in advance, in particular the six positions that have just been described. The positioning of the shield  16  in one of the previously stored memories can be controlled by the driver from the vehicle dashboard. 
     FIGS. 9   a - 9   b  correspond to a second embodiment of a shield according to the invention, in front view and side view. 
   As depicted in  FIG. 9   a , this shield has an active edge profile composed of two planar areas  60 ,  60 ′ at an upper level end  2 , disposed between two planar areas  61 ,  61 ′ disposed at an intermediate level n 1 , themselves disposed on each side of a planar area  62  disposed at a lower level n 0 . In addition, two successive planar areas are connected to each other by an oblique area, as in the first example: the areas  63 ,  63 ′ between each area  60 ,  60 ′ and  61 ,  61 ′ and the areas  64 ,  64 ′ between the areas  61 ,  61 ′ and the area  62 . 
   By adopting as the central position of this shield a position in which the edge  62  is placed opposite a central position of the recess  17 , it is possible to obtain with this shield the following various light beams:
         rotation by approximately 10° to the right about the axis  18 : motorway beam in right hand traffic  102 , a small part of the area  62  and a large part of the portions  61  and  60  filling in in length the entire recess  17 ;   rotation by approximately 21° to the left about the axis  18 : right hand traffic  101 , the portions  62 ,  61 ′ and  60 ′ filling in in length the entire recess  17 ;   rotation by approximately 20° to the left about the axis  18 : motorway beam in left hand traffic  105 , a small part of the area  62  and a large part of the portions  61 ′ and  60 ′ filling in in length the entire recess  17 ;   rotation by approximately 21° to the right about the axis  18 : beam for traffic on the left  104 , and the portions  62 ,  61  and  60  filling in in length the entire recess  17 ;   rotation by more than approximately 72° towards the left, or less than approximately 72° towards the right about the axis  18 : main beam.       

   This shield is in particular advantageous in the “motorway” position, making it possible to reduce any risk of dazzling of the driver coming in the opposite direction. 
     FIG. 9   b  makes it possible to distinguish another particularity of the shield according to the second example: the shield  16  has locally not one active edge  34  but two,  34  and  34 ′, offset with respect to the optical axis  18  and having identical profiles. These are more particularly the areas  60 ,  61 ,  63 ,  60 ′,  61 ′,  63 ′ which are duplicated, whilst the areas  64 ,  64 ′ and  62  are not duplicated. In concrete terms, the edge  34 ′ in the non-duplicated areas has an edge at a sufficiently low level to become inactive optically whilst ensuring the mechanical continuity of the edge  34 ′. It can be seen that the active edge  34  is placed after the duplicated edge  34 ′ relative to the direction of the light coming from the source associated with the reflector. The choice of duplicating the shield reduces any problems of iridescence at the cutoff. The choice of duplicating only certain portions of the shield stems from the observation that it is particularly for beams of the dipped/passing type that any phenomena of chromatic aberrations are more of a nuisance, since the cutoff is projected at a relatively short distance from the vehicle. However, the situation is different with a beam of the motorway type, where the cutoff is projected further, and any iridescence is less perceptible. Thus only the areas close to the optical axis are duplicated (where the light flux is the greatest) and in the active areas of the shield used for dipped beam. It would also be possible to choose to duplicate the entire shield. 
   The invention thus makes it possible to adapt a shield according to the number and form of the cutoffs required, whilst keeping efficacy, compactness and ease of passing from one cutoff to another, without visual nuisance either for the driver or for the driver of the car arriving in the opposite direction on a road.