Patent Publication Number: US-11031196-B2

Title: Electric switch of the normally open type

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent document claims priority to and is a Continuation In Part of U.S. patent application Ser. No. 16/733,303 filed on Jan. 3, 2020, now U.S. Pat. No. 10,892,120, which in turn claims priority under 35 U.S.C. § 119(1) to France Patent Application Number 1900062, filed on Jan. 4, 2019. 
    
    
     BACKGROUND 
     This disclosure relates to an electric switch of the normally open type. In particular, this disclosure relates to an electric switch that may be used for medical applications, such as a switch that can to detect with accuracy and reliability a number of doses of medicine. 
     To accurately and reliably detect dosage activity, an electric switch must have different characteristics and performance qualities including very small dimensions, a very large overtravel, very low dimensional tolerances relating to the position of the point of electrical contact, a low actuation force, and a high actuation frequency. Suitable switches are not presently available in the prior art. 
     For example, according to a design known in particular from Japan Patent Application Publication Numbers JPH05211021A (titled Push Switch, published Aug. 20, 1993) and JPH1050174 (titled U-Shaped Contact Spring Piece for Switch, published Feb. 20, 1998), the switch includes a pivoting actuator that supports a moveable contact blade, two free contact branches of which make electrical contact with fixed conductor tracks when the actuator is in active angular position. In such a design, the shape of the moveable contact blade and its installation in the actuator induce significant position tolerances of the free contact ends of the contact branches after installation and assembly. In addition, the design makes very large series production difficult. 
     A normally closed switch is also known from U.S. Pat. No. 4,686,336 to Sorenson, comprising a casing which defines an inner cavity; a push button which is moveably installed with respect to the casing; a fixed contact blade; a moveable contact blade which comprises a first part which is rigidly fixed in the casing and a second part which extends from the first part in a cantilever arrangement, in which, when a distal end of the second part of the moveable blade is in contact with the fixed blade, the moveable blade closes an electrical circuit; and at least one positive stop which cooperates with the fixed blade; in which switch, when a force is applied to the push button, the distal end of the second part of the moveable blade bends and moves in a first direction, then breaks the contact with the fixed blade, thus opening the electrical circuit; and in which, when the force is released, the distal end of the second part of the moveable blade moves in a second direction opposite the first direction, and comes into contact with the fixed blade, thus closing the circuit; and in which one or more of the positive stops applies/apply pressure and opposes/oppose the movement of the fixed blade in the second direction and thus maintains/maintain a predetermined position of the fixed terminal, but does/do not interfere with the moveable blade or does not/do not block it. 
     Similar designs of electrical switches with two blades, which are of the normally closed type, including one rigid fixed, or symmetrically of the normally closed type are also known from U.S. Patent Application Publication Number 2004/0154907 (Blossfeld et al.). 
     An electric switch is also known from U.S. Pat. No. 5,334,034 (Reichardt et al.) of the normally open type. 
     To address shortcomings of the prior art such as those described above, this document proposes an electric switch of this type which at the same time allows a low tolerance for the value of the closing travel of the switch, and a significant overtravel on actuation, while keeping the electrical circuit closed. 
     SUMMARY 
     In various aspects, this document discloses an electric switch of the normally open type. The switch includes: (i) a body made of insulating material; (ii) an actuator which is moveably installed with respect to the body between (a) a high rest position in which the actuator abuts against a facing portion of the body, and (b) a low active contact position. The switch also includes a first contact blade supported by the body which is elastically deformable when action of the actuator between: (a) a high rest position in which the first contact blade elastically abuts upwards against a facing portion of the actuator, the actuator being elastically returned to its high rest position by the first contact blade, and (b) a low active contact position. The switch also includes a second contact blade supported by the body which is elastically deformable downwards from a rest position in which it elastically abuts upwards directly against a facing portion of the body, or indirectly with interposition of a part of the actuator. In the switch, a first contact section belonging to the first contact blade extends above a second contact section belonging to the second contact blade. The first and second contact sections are superposed and are vertically distanced from each other when the actuator is in its high rest position, and are in mutual electrical contact when the actuator is in its low active contact position so as to establish an electrical switching path. The first and the second contact sections are arranged in parallel and in opposite directions. The second contact section includes a central opening which is able to accommodate the first contact section. 
     Optionally, the central opening of the switch may be delimited by a transversal contact edge which cooperates with the first contact section when the first contact blade is in its active low contact position. The first contact section may include a longitudinal rib which is formed to protrude downwards with respect to the plane of the underside of the first section and which is able to cooperate with said transversal contact edge of the central opening, and the transversal contact edge may include a transverse contact bend for cooperating with convexity of the longitudinal rib. 
     In some embodiments, a transversely central portion of the contact edge is extended by a bent contact tab that extends longitudinally forwards and downwards, and the bent contact tab and an adjacent portion of the second contact section may be shaped as a horizontal and transverse bend with its convexity pointing towards the convexity of the longitudinal rib. 
     In some embodiments, the contact tab may be generally planar and may be positioned at an angle of approximately forty five degrees to the plane of a substantially planar and horizontal adjacent portion of the second contact section. 
     Optionally, each contact blade may include a section for fastening the contact blade to the body, the section being extended by a contact section which, at rest, extends essentially horizontally. Also, each contact section may extend longitudinally and may be able to pivot around an essentially horizontal transversal axis. 
     Optionally, the actuator may include an active lower part which cooperates with the first contact blade and which is situated vertically in way of the first and second contact sections. The central opening may be delimited by a transversal contact edge which cooperates with the first contact section when the first contact blade is in its active low contact position. When the second contact blade is in its rest position, the active lower part of the actuator may be situated longitudinally substantially in way of the transversal contact edge, and the second contact section may abut against a facing portion of the body in a zone which is situated longitudinally substantially in way of the transversal contact edge. 
     Optionally, the actuator may include a tilter installed to pivot with respect to the body around a horizontal axis. 
     Optionally, the actuator may include a push button installed to slide vertically with respect to the body. 
     Optionally, the actuator may include an active lower part which cooperates with the first contact blade and which is situated vertically in way of the first and second contact sections, and the body may include include a top cover forming a casing in which the two contact sections and the lower active part of the actuator are accommodated, and a bottom base plate on which the top cover is fastened. The actuator also may include an upper actuation part which protrudes out of the top cover. The lower active part of the actuator may be a transversal bulge delimited by a convex cylindrical outer surface whose axis is parallel to the axis of rotation of the actuation tilter. 
     Optionally, the actuator may include an active lower part which cooperates with the first contact blade and which is situated vertically in way of the first and second contact sections, and the lower active part of the actuator may cooperate with the first contact section belonging to the first contact blade. 
     Optionally, at least the cooperating convex surface portions of the longitudinal rib and of the transverse contact bend may be provided with a layer of gold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention will emerge on reading the detailed description that will follow, for the understanding of which, reference will be made to the attached drawings, in which: 
         FIG. 1  is a perspective view which illustrates an embodiment of an electric switch on which the actuator is shown in the high rest position. 
         FIG. 2  is a view of the embodiment of  FIG. 1 , on which the actuator is shown in the maximum active low position. 
         FIG. 3  is a view of the embodiment of  FIG. 2 , on which the switch is shown without its top cover forming a casing. 
         FIG. 4  is an exploded perspective view of the components of the electric switch of  FIG. 1 . 
         FIG. 5  is an underside view of the electric switch of  FIG. 1  which is illustrated without its bottom base plate. 
         FIG. 6  is a perspective view of the two contact blades of the electric switch of  FIG. 1 . 
         FIG. 7  is a half perspective view of the electric switch of  FIG. 1  which is illustrated in section through the median vertical and longitudinal plane of  FIG. 5 . 
         FIG. 8  is a view similar to that of  FIG. 7  on which the actuator is shown in active low position. 
         FIG. 9  is a front view of the electric switch of  FIG. 7 . 
         FIG. 10  is a sectional view of the electric switch of  FIG. 1  along the line A 3 -A 3  of  FIG. 5 . 
         FIG. 11  is a sectional view through the median vertical and longitudinal plane of  FIG. 5  of the two contact blades illustrated on  FIG. 6 . 
         FIG. 12  is a view similar to that of  FIG. 11  on which the two contact blades are shown in the position they occupy when the actuator is in its maximum active low position illustrated on  FIGS. 3 and 8 . 
         FIG. 13  is a perspective view similar to that of  FIG. 6  which illustrates a variant of the design of the first and the second contact sections belonging to the first contact blade and to the second contact blade respectively. 
         FIG. 14  is a sectional view through a median vertical and longitudinal plane of the first and second contact blades illustrated on  FIG. 13 . 
         FIG. 15  is an underside view of the first and second contact blades illustrated on  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     For the description of the invention and understanding the claims, the vertical, longitudinal and transversal orientations V, L, T indicated on the figures, whose longitudinal L and transversal T axes extend in a horizontal plane, will be adopted as non-limitative and without limitative reference to earth gravity. 
     By convention, the longitudinal axis L is oriented from the back to the front. 
     In the description that will follow, identical, similar or analogous elements will be designated by the same reference numbers. 
     In the description that will follow, each electric switch has a general symmetry of design with respect to the median vertical and longitudinal plane. 
     As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used in this document, the term “comprising” (or “comprises”) means “including (or includes), but not limited to.” When used in this document, the term “exemplary” is intended to mean “by way of example” and is not intended to indicate that a particular exemplary item is preferred or required. 
     In this document, the term “connected”, when referring to two physical structures, means that the two physical structures touch each other. Devices that are connected may be secured to each other, or they may simply touch each other and not be secured. 
     In this document, the term “operably connected”, when referring to two physical structures, means operation (i.e., movement) of one structure will cause the other structure to responsively move. Operably connected structures may be physically connected to each other, or they may be indirectly connected via one or more intermediate structures. 
     When used in this document, relative terms of position such as “up” and “down”, “upper” and “lower”, and “upward” and “downward” are not intended to have absolute orientations but are instead intended to describe relative positions of various components with respect to each other. For example, a first component may be an “upper” component and a second component may be a “lower” component when a device of which the components are a part is oriented in a first direction. The relative orientations of the components may be reversed, or the components may be on the same plane, if the orientation of the structure that contains the components is changed. The claims are intended to include all orientations of a device containing such components. 
     The electric switch  100  includes, arranged vertically from top to bottom, a top cover  110 , an actuator  50 , a first contact blade  70 , a second contact blade  90 , and a bottom base plate  30 . 
     The top cover  110  and the bottom base plate  30  form the body of the electric switch  100 . 
     The top cover  110  is a moulded piece of insulating plastic material which here is in the shape of a rectangular parallelepiped casing whose underside  111  is open and which includes a horizontal top wall  112 , two opposite longitudinal side walls  113  and two opposite transversal side walls  114  which delimit an inner housing  115 . 
     The inner side  116  of each longitudinal side wall  113  includes, at its top part, a central portion  117  in extra thickness which is longitudinally centred and which is delimited by a bottom horizontal edge  118 . 
     Each portion  117  also includes, close to its rear longitudinal end, a semi-cylindrical housing  119  which is vertically open downwards. 
     The top wall  112  is delimited by a horizontal top side  20  and by a horizontal underside  21 . 
     The top wall  112  includes a central opening  22  of rectangular contour. 
     At each opposite transversal end of each transversal side wall  114 , the top cover  110  includes a vertical slot  23  for transversal orientation which is vertically open downwards, the slots  23  thus being transversally aligned in pairs. 
     The outer side  24  of each longitudinal side wall  113  includes a recess  25  fitted with a central locking tab  26  in relief. 
     The bottom base plate  30  is a moulded part of insulating plastic material, generally rectangular in shape which is vertically delimited by a horizontal top side  31  and a horizontal underside  32 , and laterally by two longitudinal vertical edges  33  and two transversal vertical edges  34 . 
     Each longitudinal edge  33  includes a sill  35  above which a hoop or lug  36  extends vertically, each of which cooperates with an associated locking tab  26  to ensure assembly of the two components  110  and  30  of the body of the electric switch  100 . 
     Close to each transversal edge  34 , the bottom base plate  30  includes a block  37 , generally rectangular parallelepiped in shape, which extends vertically upwards above the top side  31  and which is delimited by an outer vertical transversal side  38 . 
     The block  37  includes two longitudinal extensions  39 , each of which supports a vertical post  40  delimited by a top horizontal facet  41 . 
     As can be seen in particular on  FIGS. 9 and 10 , with the top cover  110  in assembled position on the bottom base plate  30 , the top end of each vertical post  40  is accommodated in an associated housing  19 . 
     Below its underside  32 , the base plate  30  includes two pieces  42  and  43  for positioning and fool proofing the positioning of the electric switch  100 , for example on a printed circuit board (not illustrated). 
     The actuator  50  is a moulded piece of insulating plastic material. 
     In the different embodiments illustrated on the figures, the actuator  50  is a tilter or tipper which is installed, at its rear end, to pivot with respect to the top cover  110  around a transversal and horizontal axis A 1 . 
     To that effect, the rear longitudinal part of the actuator  50  is configured as a shaft  51  which is terminated at each end by a cylindrical pin  52 . 
     Each pin  52  is dimensioned such that it is accommodated with slight play in an associated semi-cylindrical housing  19  so as to be able to pivot there in both directions around the axis of rotation A 1 . 
     Each pin  52  is inserted vertically from bottom to top in the associated housing  19  and, with the top cover  110  in assembled position on the bottom base plate  30 , the pin is held by the top facet  41  in its associated housing  19  facing the vertical post  40 , (see  FIG. 10 ). 
     The main front part of the actuator  50  is in the shape of a rectangular parallelepiped block  53  which is vertically delimited by a flat top side  54  and by a parallel flat underside  55 . 
     Above its flat top side  54 , the block  53  includes a central protruding slab  56 , also rectangular parallelepiped in shape, which is transversally centred. 
     As can be seen in particular on  FIGS. 1 and 9 , the central slab  56  is dimensioned such that it can be accommodated, with slight play, in the central opening  22  of rectangular contour of the top wall  112 . 
     This is the case in particular when the actuator is in its high rest position illustrated on  FIGS. 1, 7 and 9  in which the side portions  57  of the top side  54  of the block  53  vertically abut upwards against facing portions of the horizontal underside  21  of the top wall  112  of the top cover  10 . 
     In this rest position, the actuator  50  thus extends essentially horizontally forwards from the rear shaft  51 . 
     Above its horizontal top side  58 , the central slab  56  supports a top finger  59  which comprises the top part of the actuator  50 , making it possible to act on the latter for the purpose of causing it to pivot around its axis of rotation A 1 , clockwise in consideration of  FIG. 9 . 
     With the actuator  50  in the top rest position, the top actuation finger  59  extends essentially vertically upwards above the horizontal top side  20  of the top wall  112 . 
     As can be seen in particular on  FIGS. 2 and 8 , the actuator is able to pivot to a maximum “low” angular position in which the top finger  59  is fully retracted downwards such that its top free end edge  60  is flush with the plane of the top side  20  of the top wall  112 . 
     At its front longitudinal end, the flat underside  55  of the block  53  includes a semi-cylindrical bulge  61  which extends over the entire transversal width of the block  53 . 
     The transversal bulge  61  is delimited by a convex cylindrical outer surface  62  whose axis A 2  is parallel to the axis of rotation A 1  of the actuator  50 . 
     So as to establish, or not, an electrical switching path, the electric switch  100  includes a first top contact blade  70  and a second bottom contact blade  90 . 
     Each of the two contact blades is made of conducting material, for example of snipped and folded sheet metal. 
     The first contact blade  70  includes a first section  71  for fastening the first contact blade  70  to the body of the electric switch  100 , the blade being extended by a first contact section  72  which, at rest, extends essentially horizontally. 
     The first fastener section  71  is in the shape of a fastener branch  73  of vertical and transversal orientation, each end of which is configured as a fastener plate  74 , each of which is inserted vertically to be accommodated in an associated slot  23  adjacent to the rear transversal side wall  114  of the top cover  110 . 
     Centrally, the fastener branch  73  is extended by a vertical connection branch  75 . 
     The first contact section  72  extends longitudinally cantilevered forwards from the top end of the connection branch  75 . It is connected to it by a substantially right angled bend  76 . 
     The first contact section  72  of the first contact blade  70  is vertically delimited by a flat top side  77 , by a flat contact underside  78 , and by a forward free end transversal edge  79 . 
     The first contact section  72  is also delimited by two opposite longitudinal edges  80 . 
     As can be seen in particular by comparing  FIGS. 11 and 12 , or  7  and  8 , the first contact blade  70  is able to deform elastically in the form of pivoting of the first contact section  72  at the connection bend  76 , from a high rest position ( FIGS. 7 and 11 ) to a low active contact position ( FIGS. 8 and 12 ) around an essentially transversal and horizontal axis. 
     At its inner edge, the fastener branch  73  is extended horizontally rearwards by a horizontal plate  81  for electrical connection of the first contact blade  70 . 
     With the first contact blade  70  inserted and installed in the top cover  10 , the first contact section  72  elastically abuts upwards, through its top side  77 , against a generatrix of the convex cylindrical side  62  of the transversal bulge  61  of the actuator  50 . 
     The second contact blade  90  includes a second section  91  for fastening the second contact blade  90  to the body of the electric switch  100 , the blade being extended by a second contact section  92  which, at rest, extends essentially horizontally. 
     The second fastener section  91  is in the shape of a fastener branch  93  of vertical and transversal orientation, each end of which is configured as a fastener plate  94 , each of which is vertically inserted to be accommodated in a slot  23  adjacent to the front transversal side wall  114  of the top cover  110 . 
     Centrally, the fastener branch  93  is extended by a vertical connection branch  95 . 
     The second contact section  92  extends longitudinally cantilevered rearwards from the top end of the connection branch  95 . It is connected to it by a substantially right angled bend  96 . 
     The second contact section  92  of the second contact blade  90  is vertically delimited by a flat top side  97 , by a flat underside  98 , and by a rear free end transversal edge. 
     The second contact section  92  is also delimited by two opposite longitudinal edges  99 . 
     As can be seen in particular by comparing  FIGS. 11 and 12 , or  7  and  8 , the second contact blade  90  is able to deform elastically in the form of pivoting of the second contact section  92  at the connection bend  96 , around an essentially transversal and horizontal axis. 
     At its lower edge, the fastener branch  93  is extended horizontally forwards by a horizontal plate  101  for electrical connection of the second contact blade  90 . 
     The transversal width LT of the second contact section  92  which separates its two opposite longitudinal edges  99  is such that, in inserted and installed position in the top cover  110 , it elastically abuts upwards, through its top side  97 , on the two opposite sides, against the facing bottom edges  118  of the portions  117  in extra thickness. 
     As can also be seen on  FIGS. 5 to 7 and 9 and 11 , the two contact sections  72  and  92  are essentially arranged head to tail and vertically one above the other. 
     The second contact section  92  includes a central opening  102  which is able to accommodate the first contact section  72 . 
     The central opening  102  is longitudinally delimited rearwards by a transversal contact edge  104 , and transversally by two longitudinal and opposite inner edges  106 . 
     The contact edge  104  is able to cooperate with the first contact section  72  when the second contact blade  90  reaches its active contact low position. 
     The inside transversal width of the opening  102  which separates its two opposite inner edges  106  is greater than the transversal width of the first contact section  72 . 
     In rest position, and as can be seen in particular on  FIG. 9 , the dimensioning and installation of the first contact blade  70  are such that its first contact section  72  elastically stresses the actuator  50  by acting on the bulge  61 , essentially vertically upwards. 
     The actuator  50  is thus elastically returned to its “high” angular rest position in which it vertically abuts upwards against the underside  21  of the top wall  112 . 
     In this position, the side portions  57  of the top side  54  of the actuator  50  vertically abut upwards against the facing portions of the underside  21 . 
     The first contact blade  70  thus acts as a spring for returning the actuator  50  to its rest position. 
     The geometric position of the first contact section  72  with respect to the top cover  110 , and in particular its vertical elevation, is defined indirectly through the actuator  50  whose vertical elevation of the bulge  61  is defined in turn with respect to the top cover  110 . 
     In rest position, and as can be seen in particular on  FIG. 9 , the dimensioning and installation of the second contact blade  90  are such that its second contact section  92  elastically abuts under load against the bottom edges  118  of the portions  117  in extra thickness of the top cover  110 . 
     As can be seen in particular on  FIG. 9 , the second contact section abuts against the bottom edges  118  in a longitudinal zone which is situated substantially in way of the transversal contact edge and to the bottom active part  61 ,  62  of the actuator. 
     The geometric position of the second contact section  92  with respect to the top cover  110 , and in particular its vertical elevation, is defined here directly with respect to the top cover  110 . 
     In rest position, the design according to the invention thus makes it possible with very great accuracy to guarantee the relative vertical position of the first contact section  72  above the second contact section  92  with a perfectly controlled elevation or air gap “e” which only depends on the dimensions of the top cover  110  and the actuator  50  which are pieces of plastic material obtained by moulding. 
     The generatrix of the convex outer surface  62  of the bulge  61  abutting on the top side  77  of the first contact section  72  is substantially vertically aligned with the future line of electrical contact between the two contact sections  72  and  92 . 
     The design and embodiment of the contact blades  70  and  90  and potential dimensional and shape variations thereof have virtually no influence on this relative positioning. 
     Actuation takes place by acting on the top finger  59  so as to cause the actuator to pivot around the axis A 1 , in a clockwise direction in consideration of  FIG. 9 , for the purpose of bringing it to its low active contact position. 
     During this actuation travel, the bulge  61  acts on the top side  77  of the first contact section  70  so as to cause it to pivot clockwise essentially at the bend  76 . 
     The first contact section  72  is almost rigid and it pivots until a portion of its contact underside  78  makes electrical contact with the transversal contact edge  104  of the opening  102 . 
     During this first part of the actuation travel, the second contact section  92  is fixed with respect to the first contact section  72 . The travel until electrical contact has been established is thus constant and precise. 
     As soon as contact is made, the second contact section  92  starts to pivot around the bend  96  in an anticlockwise direction while ensuring high electrical contact pressure. 
     According to a variant, not illustrated in  FIGS. 1 to 12 , the first contact section  78  includes a longitudinal rib which is formed to protrude downwards with respect to the plane of the underside  78 . Contact is thus made between the longitudinal summit of the rib and the transversal contact edge  104  by virtue of an almost punctual contact. This design of the first contact section  72  makes it possible further to increase the accuracy of the value of the actuation travel until electrical contact is established. 
     After electrical contact has been established, the angular actuation travel of the actuator  50  can be continued by thus allowing a significant overtravel. 
     This is due to the design according to which the first contact section  72  is then accommodated in the opening  102  (see  FIGS. 3, 8 and 12  in particular). 
     This additional part of the actuation travel down to its maximum low position takes place contrary to the initial elastic preloading force of the second contact section  92 . 
     During this second part of the actuation travel, the line of contact between the transversal contact edge  104  and the underside  78  of the first contact section  72  moves slightly longitudinally forwards towards the free end edge  79 , thus ensuring a “self-cleaning” effect of the electrical contact zone. 
     The maximum actuation travel illustrated on  FIGS. 3, 8 and 12  corresponds here to full retraction of the top finger  59  of the actuator  50  into the top cover  110  with its top free end edge  60  flush with the plane of the top side  20  of the top wall  112 . 
     As an example, the dimensions—length, width and height—of the body of the electric switch  100  are 4.4 mm, 2.8 mm and 2.1 mm respectively with an actuation force less than or equal to 0.50 Newton (50 grams). 
     The design according to the invention, and in particular that of this first embodiment, is not limited to a pivoting actuator or tilter acting directly on the first contact section. 
     As a variant, the actuator can be a push button which is installed vertically moveable with respect to the top cover, with respect to which it is for example guided to blade. 
     In such a design, the actuation point of a bottom end of the push button acting on the top side of the first contact section only moves vertically. 
     It is possible to act directly on a top end of such a push button, or indirectly by means of a lever which is installed articulated on the top cover around an essentially horizontal axis which can have any orientation with respect to the transversal direction T. 
       FIGS. 13 to 15  illustrate a variant of the first contact blade  70  and of the second contact blade  90  that have been described in relation with the first embodiment illustrated in  FIGS. 1 to 12 . 
     The first contact section  78  includes a longitudinal rib  200  which is formed to protrude downwards with respect to the plane of the underside  78  of the first contact section  72 . 
     The convexity  202  of the rounded longitudinal rib  200  has its convexity  202  pointing downwards. 
     The longitudinal rib  200  is transversely centered between the two opposite longitudinal edges  80  of the first contact section  78 . The longitudinal rib extends over the second contact section  92  of the second contact blade  90  which, at rest, extends essentially horizontally partly over the central opening  102  which is able to accommodate the first contact section  72 , and that is longitudinally delimited rearwards by a transversal contact edge  104 . 
     When the second contact blade  90  reaches its active contact low position, the contact edge  104  is able to cooperate with the longitudinal convex summit edge  202  of the longitudinal rib  200  by virtue of an almost punctual contact. 
     To this end, the transversely central portion of the contact edge  104  is extended by a bent contact tab  204  that extends longitudinally forwards and downwards. 
     The contact tab  204  is generally plane and is at an angle of approximately forty five degrees to the plane of the substantially plane and horizontal adjacent portion  206  of the second contact section  92 . 
     The connection area between the contact tab  204  and the adjacent portion  206  of the second contact section  92  is shaped as a horizontal and transverse bend  208  with its convexity pointing upwards. 
     The design, dimensioning and relative positioning according to the invention of the longitudinal rib  200  and the transversal bend  208  are such that, all along the actuation travel, the contact between these two lines of contact is a point of contact. 
     This point of contact between the longitudinal rib  200  and the transverse bend  208  moves slightly longitudinally forwards towards the free end edge  79 , thus ensuring a “self-cleaning” effect of the electrical contact zone. 
     According to an embodiment and with a view to improving the quality of the electrical contact, at least the cooperating convex surface portions of the rib  200  and of the bend  208  are provided with a layer of gold. 
     The variant illustrated at  FIGS. 13 to 15  provides an optimization of the design permitting to obtain a very smooth signal transition upon establishment of the contact over a very wide operating range. 
     The operation of the switch is thus possible between 1 Hz and 400 Hz, at all activation heights of the product and the signal switching is effected within about 1 ms. 
     The features and functions described above, as well as alternatives, may be combined into many other different systems or applications. Various alternatives, modifications, variations or improvements may be made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.