Abstract:
The invention proposes a switch ( 10 ) comprising a casing ( 12 ) which carries a pair of fixed contact elements ( 48 ), a contact bar ( 96 ) which is movable between a rear closure position and a front opening position, and a member ( 60 ) for actuation of the movable contact bar ( 96 ) which is mounted so as to slide between a rear rest position and a front triggering position, the movable contact bar ( 96 ) and the actuation member ( 60 ) constituting a movable assembly, and the switch ( 10 ) comprising a return spring ( 108 ) which co-operates with the movable contact bar ( 96 ) so as to urge it towards its rear closure position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This is a Continuation-In-Part of PCT/EP2005/051407 filed 29 Mar. 2005, which designated the US, and which claimed priority from French patent application No. 04/03780 filed 9 Apr. 2004. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an electrical switch. 
   The invention relates more particularly to an electrical switch of the normally closed type comprising:
         a casing which carries a pair of fixed contact elements each of which comprises a contact head which delimits a front transverse fixed contact surface and which is arranged inside the casing in such a way that the two fixed contact surfaces are longitudinally aligned:   a contact bar, forming a movable contact, which runs transversely opposite the two fixed contact surfaces and which is mounted movably, according to a horizontal longitudinal direction, between:       

   at least one rear closure position in which a rear contact surface of the contact bar is in contact bearing on the said fixed contact surfaces so as to establish an electrical link between the two fixed contact elements of the switch; 
   and a front opening position in which the said rear contact surface is offset longitudinally towards the front in such a way as to interrupt the said electrical link;
         and a member for actuation of the movable contact bar which is mounted so as to slide longitudinally in the casing between:       

   at least one rear rest position in which it is in abutment against a portion of the casing and in which the movable contact bar is in its rear closure position; 
   and a front triggering position in which the movable contact bar is in its front opening position; 
   the moveable contact bar and the actuation member constituting a movable assembly, and the switch comprising a return spring which co-operates with the movable contact bar so as to urge it towards its rear closure position. 
   A switch of this type is known from document DE-A-3,138,379. 
   In addition, it allows no modularity in the switch design, especially as regards the use of various light sources and/or the electrical connection and supply circuits for the light sources. 
   SUMMARY OF THE INVENTION 
   In order to afford it great stability of contact in the normally closed position, the switch according to the present invention is characterized in that the movable contact bar is mounted rocking on the actuation member about an upper transverse axis, the actuation member comprises a front face for driving the movable contact bar towards which the bar is returned by the spring, and the said front drive face is offset longitudinally towards the rear with respect to the contact bar when the bar is in its rear closure position and when the actuation member is in its rear rest position. 
   According to other characteristics of the invention:
         the said front drive face is able to co-operate with a portion of the rear contact surface of the movable contact bar;   the said portion of the rear contact surface of the movable contact bar is situated between two transverse end portions each of which bears on an associated fixed contact surface when the bar is in its rear closure position;   the said rear contact surface is a surface in the form of an arc of a convex cylinder of transverse axis, and the said front fixed contact surfaces are vertical plane surfaces;   the actuation member comprises a horizontal central finger for guiding the return spring which runs towards the front through a corresponding notch of the movable contact bar, and the return spring is a spiral compression spring through which the guiding finger passes, the front longitudinal end of which bears on a wall of the casing, and the rear longitudinal end of which bears on a front face portion of the movable bar;   the actuation member is able to occupy a so-called overtravel position which is offset longitudinally towards the front with respect to its front triggering position;   the switch exhibits a general symmetry of design with respect to a vertical and longitudinal mid plane.       

   Other characteristics and advantages of the invention will become apparent on reading the detailed description of a preferred embodiment of the invention for the understanding of which reference may be made to the appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front three-quarter perspective top view of a switch embodied in accordance with the teachings of the invention; 
       FIG. 2  is an exploded perspective view, similar to that of  FIG. 1 , which illustrates the various components of the switch; 
       FIG. 3  is an end view along the arrow F 3  of  FIG. 1 ; 
       FIG. 4  is a plan view of the switch of  FIG. 3 , without its upper lid; 
       FIGS. 5 to 7  are sectional views along the lines  5 — 5  and  7 — 7  of  FIG. 3  in which the member is illustrated in the rear rest position and the movable contact bar is illustrated in its rear closure position; 
       FIG. 8  is a view similar to that of  FIG. 7  in which the member is illustrated in the front triggering position; 
       FIG. 9  is a view similar to that of  FIG. 7  in which the member is illustrated in its overtravel position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the description which follows, in order to facilitate the comprehension thereof and of the claims, the terms horizontal, vertical, upper, lower, longitudinal and transverse will be adopted with reference to the trihedrons L, V, T indicated in the figures. 
   The front, rear orientation would also be used according to the left, right orientation of  FIGS. 5 to 9 . 
   The switch  10  illustrated in the figures is an electric switch of the normally closed type which exhibits a symmetry of design and embodiment with respect to a vertical mid plane of longitudinal orientation PVM. 
   It comprises a main body or casing  12  of right-angled parallelepipedal general shape delimited by two opposite vertical lateral walls  14 , a front transverse vertical wall  16 , a rear transverse vertical wall  18  which comprises a centred rectangular vertical window  20  which emerges into its free upper edge  22 , and by a horizontal bottom wall  24 . 
   The open upper face  26  of the casing  12  is closed by complementary upper lid  28  in the form of a horizontal plate whose rear transverse edge  30  comprises a polarization lug  32  which, in the lid mounted position and as may be seen for example in  FIG. 1 , is received in the upper part of the window  20 . 
   The walls  14 ,  16 ,  18 , the bottom  24  and the upper lid  28  delimit an internal cavity  34  in which various components of the switch  10  are arranged. 
   The casing is embodied by moulding from insulating plastic and it extends, vertically to the rear, beyond the lower face  36  of the bottom  24 , via a block  38  narrower in the longitudinal direction, and which comprises two emergent vertical slots  40 . 
   The switch  10  comprises two fixed contact elements  42  made of an electrically conducting material each of which is embodied by blanking from a vertical plate of transverse orientation. 
   Each fixed contact element  42  comprises a lower rod  44  which is received through an associated slot  40  and which projects vertically downwards beyond the lower face  39  of the lower block  38  so as to constitute an electrical connection terminal of the switch, for example for connection with a printed circuit board, not represented. 
   Each fixed contact element  42  comprises an upper contact head  48  which is arranged inside the internal cavity  34  of the casing  12  and in which it is positioned with accuracy and immobilized in position. 
   Each contact head  48  comprises, in its transversely interior vertical edge  50 , an aperture  52  corresponding to the window  20 , while its transversely exterior vertical edge  54  is received in a groove  56  of the interior face  15  of the associated lateral wall  14 . 
   The front face  58  of each contact head  48  constitutes a fixed contact surface and the two surfaces  58  are substantially co-planar and of transverse vertical orientation. 
   The switch  10  comprises an actuation member or actuator  60  which comprises a front body  66  arranged inside the internal cavity  34  and a rear operating pusher or button  62 . 
   The pusher  62  is of rectangular cross section complementary to the window  20  through which it projects longitudinally towards the rear in such a way that at least its rear transverse face  64  is permanently situated outside the casing  12  so as to allow actuation by acting on said face, from the rear to the front in the direction indicated by the arrow F 3 . 
   The pusher  62  is embodied in one piece by moulding from an insulating plastic together with the front body  66 . 
   The front body  66  comprises a sturdy rear central part  68  whose rear face  70  bears against opposite portions of the interior face of the rear wall  18  when the actuation member  60  is in its rear rest position illustrated in  FIGS. 3 to 7 . 
   This central part  68  comprises two opposite vertical and transverse wings  72  of smaller longitudinal thickness than the central part  68  and each of which comprises a front transverse face  74  of vertical orientation which constitutes a part of the front face of the actuator for driving the movable contact element of the switch which will be described hereinbelow. 
   Between the two wings  72 , the central part comprises a central horizontal finger  76  which runs longitudinally towards the front and, underneath the finger  76 , a longitudinal central lower branch  78  for guiding and positioning the front body  66  which slides on the upper face  25  of the bottom wall  24 . 
   To supplement the guiding by longitudinal sliding of the body  66  in the cavity  34 , the former comprises on the one hand an upper horizontal partition or roof  82  whose horizontal upper face  84  slides along the lower face  29  of the lid  28  and, on the other hand, two opposite upper lateral branches  86  which run horizontally towards the front and each of which comprises an exterior vertical lateral face  88  which slides along the internal face  15  of the corresponding lateral wall  14  of the casing  12 . 
   Thus, the front body  66  is perfectly guided by longitudinal sliding in the internal cavity  34 . 
   Finally, the front body comprises two housings  92  forming bearings of common horizontal and transverse axis A. 
   Each bearing  92  is arranged projecting along the internal vertical lateral face  90  of a lateral branch  86  and under the roof  82 . 
   Each bearing  92  is semi-cylindrical and it is open longitudinally towards the front. 
   The movable contact element  94  of the switch  10  is embodied in the form of a rocker made of a conducting material which is embodied by blanking, forming and blowing from a thick plate. 
   The rocker  94  comprises a lower movable contact bar  96  and an upper articulation part  98  for its rockable mounting on the front body  66  of the actuator  60 , about the axis A. 
   The lower movable contact bar  96  runs horizontally and transversely inside the cavity  34 . 
   In cross section through a longitudinal vertical plane, it exhibits a globally bowed profile in the form of a cylindrical arc and it is thus delimited by a convex inwardly curved rear face which constitutes the rear contact surface  100  of the movable bar  96  which is able to co-operate with the fixed contact surfaces  58 . The central part of the contact bar  96  comprises a notch  102  which is open towards the bottom for the passage of the horizontal central finger  76 . 
   The upper articulation part  98  of the rocker  94  comprises two opposite co-axial lateral journals  104  each of which is received rotatably in a semi-cylindrical bearing  92 . 
   The switch  10  finally comprises a spiral compression spring  108  through the rear part of which the finger  76  for guiding the spring passes longitudinally. The spring is mounted compressed longitudinally between the front concave bent face  97  of the contact bar  96  against which it bears via its rear end turn  114  and an opposing portion of the internal face  17  of the front transverse wall  16  against which it bears via its front end turn  112 . 
   The guidance of the return spring  108  is moreover ensured by a lower stud  116  of the cover  28  and by two internal lateral studs  118  of the casing  12 . 
   When the rocker  94  is mounted on the front body  66 , it constitutes together with the latter an assembly that is longitudinally movable in the internal cavity  34 . 
   For this purpose, the return spring  108  forces the journals  104  into the depths of the bearings  92  permanently. 
   In the rear rest position, and as may be seen in  FIGS. 5 to 7 , the dimensions and the arrangement of the various components are such that the front faces  74  for driving the actuation member  60 ,  66  which are substantially co-planar, are situated longitudinally towards the rear set back from the front fixed contact faces  58 . 
   Consequently, the rear face  100  bears longitudinally, via its opposite transverse end spans or portions, on the fixed contact faces  58  with a high contact pressure due to the action of the return spring  108 . 
   In this position, the electrical link between the two fixed contact elements  42  is closed by the contact bar  96  and the switch  10  is thus of the so-called normally closed type NF at rest, that is to say when no action is exerted on the push button  62 . 
   In this rest position of the actuator  60  and closure position (of the link) of the movable contact bar  96 , the rocker  94  is in an angular position, about its axis A, in which the rear face  99  of its upper articulation part  98  forms an acute angle alpha with respect to the vertical which, in the example illustrated in  FIG. 7 , is around 16°30′. 
   From this position, by exerting an actuation force along the arrow F 3  on the rear face  64  of the push button  62 , the front body  66  moves longitudinally towards the front against the force exerted by the return spring  108 . 
   During this actuation travel, the journals remain supported in the bearings and the upper part  98  moves with the front body  66 , while the rocker  94  rocks progressively in the anti-clockwise direction so as to reach the position illustrated in  FIG. 8 . 
   In this so-called triggering position of the switch  10 , the front actuation faces  74  have reached the opposing portions of the convex rear face  100  of the movable contact bar  96  so that they are henceforth mutually supported. 
   On completion of this actuation travel, or triggering travel (very short of the order of 0.4 mm) the angle alpha is of the order of 26°. This angle is henceforth a maximum since the rocker  94  can no longer pivot further with respect to the front body  66 . 
   Between the rear rest position and the position of triggering of the switch, the movable contact  94  rubs on the two contact heads  48  during the rocking thereof. This rubbing of the moveable contact  94  ensures self-cleaning of the contact surfaces. 
   Once the forward travel continues, the rear transverse contact face  100  of the movable contact bar  96  leaves the front fixed contact surfaces  58  of the heads  48 , interrupting the electrical link between the contact elements  42 . The bar thus occupies its front position, so-called opening position (of the electrical link). 
   As may be seen by comparing  FIGS. 8 and 9 , it is possible to apply to the push button  62 , and hence to the actuation member  60 , an overtravel of actuation according to the arrow F 3  which here is a maximum of 1.6 mm, i.e. a maximum total travel of the button of the order of 2 mm. This position is determined in particular by the coming into abutment of the front free ends  87  of the upper lateral branches  86  against the opposing portions of the internal face  17  of the front transverse wall  16 . 
   When the user relaxes his action on the push button  62 , and under the action of the return spring  108  which acts permanently on the contact bar  96  and hence on the front body  66  of the actuator  60 , the movable assembly  60 – 94  recoils rearwards, passing again through the position illustrated in  FIG. 8  in which the electrical link is again established by the coming into contact of the movable contact bar  96 – 100  with the front fixed contact surfaces  58 . 
   Thereafter, the bar  96  no longer moves longitudinally towards the rear and it is the rocker  94  which rocks in the clockwise direction to compensate for the end of travel of the actuator  60 – 66  until its rear rest position illustrated in  FIG. 7 . 
   By virtue of the design according to the invention, one ensures very good contact pressure of the movable contact bar  96  on the fixed contacts  48 – 58  and very good stability of the contact until the opening of the electrical link.