Patent Publication Number: US-9837225-B2

Title: Electrical pushbutton snap switch

Description:
RELATED APPLICATIONS 
     This application claims priority to European Patent Application No. 14196882.6, filed Dec. 9, 2014, the contents of which are incorporated herein by reference in its entirety. 
     BACKGROUND 
     This disclosure relates to an electrical switch and particularly to an electrical snap switch. 
     Existing snap switch designs generally include a conductive unit that is fixed with respect to the housing and that includes fixed contacts. For example, U.S. Pat. No. 7,205,496 discloses a switch, which includes a spring that is a helicoidally wounded traction spring and in which the pushbutton driving portion acts on the middle section of the spring. 
     An attempt to improve the working of such a snap switch is disclosed in U.S. Pat. No. 6,255,611. According to such an arrangement, when an external force is applied to the pushbutton, a jointed end of the driving portion of the pushbutton and the elastic spring is forced to move downwards until it passes a critical line, at which point the swaying element is coupled with another conductive fixed contact to supply power or electrical signals. However, the changeover speed remains insufficient and no solution is provided for a “double” or “twin” design for selectively establishing simultaneously two first conductive ways. This design is also generating significant impact or noises between the fixed and movable contacts, such noises are often not acceptable, for instance, when the switch is located in the interior of a vehicle. 
     Other improvements, such as U.S. Patent Application Publication No. 2013/0068600 and European Patent Application No. EP2151839, disclose swaying conductive element that has sliding movable contacts moving in a vertical plane. 
     The drawbacks in all the above mentioned designs are that the number of components is important, and that the design of the swaying conductive element or body is very complex and does not permit any variations in the design, especially concerning the number of switching conductive ways to be established or interrupted. 
     This document describes methods and devices that are directed to solving at least some of the issues described above. 
     SUMMARY 
     In an embodiment, an electrical snap switch includes a housing that has a receiving portion, a pushbutton having a lower portion disposed in the housing and an upper portion extending out of the housing. The pushbutton includes an actuating portion laterally extending from the lower portion of the pushbutton. The pushbutton is arranged such that it moves vertically relative to the housing when an external force is applied to the pushbutton. In one embodiment, the switch also includes at least a pair of associated contact elements placed in the receiving portion. The pair of associated contact elements includes: a fixed contact element placed in the receiving portion, and a movable contact element facing the fixed contact element and configured to come into contact with the fixed contact element for establishing a conductive path between the movable contact element and the fixed contact element. The switch also includes a snap-action switching device placed in the housing. The switching device includes a tilting driving member pivotally mounted at a pivotal end to the housing around a horizontal axis, whereas the pivoting axis is fixed with respect to the housing. The switching device also includes a traction spring extending longitudinally and having one end hooking to the driving member distal to the pivotal end, and configured to pivot the driving member between an upper position and a lower position by the actuating portion of the pushbutton when the pushbutton moves vertically relative to the housing. In one embodiment, the movable contact element is a movable portion of an elastically deformable conductive blade supported by the housing. The driving member includes a cam configured to cooperate with a cam follower portion of the blade to deform or relax the blade transversely to cause the movable contact element to come into contact or release from contact with the fixed contact element, therefore to realize switching. 
     In another embodiment, additional pairs of contact elements can be provided, and the driving member can have additional cams configured to cooperate with additional blades to realize switching at multiple contact points. In another embodiment, dampening abutment devices can be used at upper or lower positions when the driving member moves pivotally. The dampening devices can be individual dampening blocks or integrated into one piece that fits between the housing and housing upper cover. 
     The traction spring inside the snap on switching device can be configured to move the driving member in various ways. For example, the traction spring can be hooked between a pivotal point about which the driving member pivotally moves and a hook point on the pushbutton. In another embodiment, the traction spring can be hooked between the pivotal point and the interior side of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view which illustrates an embodiment of a bistable snap switch according to one embodiment. 
         FIG. 2  shows some of the components of  FIG. 1  in an exploded view. 
         FIG. 3  is a top view of the lower part of the housing of the snap switch and inside components according to one embodiment. 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3  showing the components in their upper position. 
         FIG. 5  is a top view of the lower part of the housing of the snap switch without the inside components. 
         FIG. 6  is a half perspective view of the lower part of the housing of  FIG. 2 . 
         FIG. 7  is an enlarged perspective view of the fixed and movable contact elements in association with the driving member in its upper position. 
         FIG. 8  is a cross section view taken along the vertical plane  8 - 8  of  FIG. 7 . 
         FIGS. 9( a ) and 9( b )  (hereinafter “ FIG. 9 ”) are longitudinal end views along the arrow F 9  of  FIG. 7 , showing the fixed and movable contact elements. 
         FIG. 10  is a cross-sectional view taken along line  4 - 4  of  FIG. 3  showing the components in their lower position. 
         FIG. 11  is a view analogous to the view of  FIG. 7  showing the driving member in its lower position. 
         FIG. 12  is bottom view of the upper cover part of the housing according to one embodiment. 
         FIGS. 13 and 14  are simplified schematic views similar to the views of  FIGS. 7 and 11  showing another example of a snap switch according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     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” means “including, but not limited to.” 
     In the description that follows, identical, similar or analogous components are designated by the same reference numbers. 
     As a non-limiting example, to assist in understanding the description and the claims, the terms vertical, horizontal, bottom, top, up, down, transversal, longitudinal, and so on will be adopted with reference to the L, V, T trihedron indicated in the figures, and without any reference to the gravity. 
     In the illustrated embodiment, the design of the whole switch is symmetrical with respect to the vertical median plane VMP corresponding to line  4 - 4  of  FIG. 3 . 
     With reference to  FIG. 1 , in one embodiment, a snap switch  10  may include a housing  12 , of rectangular parallelepipedic shape, and the housing may include a housing upper cover part  16  and a housing lower part or half  14 —defining a receiving portion—made of moulded plastics and which might be ultrasonic welded after mounting and assembly. 
     The switch  10  may further comprise a vertically extending and displaceable pushbutton  18  having a free upper end  20  for receiving an actuation force. The main vertical upper stem  22  ( FIG. 2 ) of the pushbutton  18  extends through a hole  24  of the housing upper cover part  16  in combination with a sealing boot  26 . 
     With reference to  FIG. 2 , the pushbutton  18  is, in a non-limiting manner, a plastic moulded part comprising a lower actuating portion  28 , which is an extension of the main vertical stem  22  and which is arranged and extends inside the housing  12 . The lower actuating portion  28  comprises a pair of vertically and transversely extending lateral guiding wings  30 , which are received in mating and complementary pairs of vertical grooves  32  ( FIG. 12 ), which are arranged in the upper cover part  16  of the housing  12 . The pushbutton is thus guided vertically with respect to the housing  12  along a vertical actuation axis A 1 . 
     The switch  10  may further comprise a return spring  36  disposed vertically between the lower part  14  of the housing  12  and the lower actuating portion  28  of the pushbutton  18 . The return spring  36  is a vertically and helicoidally wounded spring, which is received in a pit  40  of the lower part  14  and has its upper end acting on an internal horizontal face  42  of the actuating portion  28  ( FIG. 4 ). 
     With reference to  FIG. 4 , the return spring  36  is mounted so as to be vertically compressed in such a way that, when an external force that is applied downwardly to the free upper end  20  of the pushbutton is removed, the pushbutton is returned back to its upper rest position by the return spring  36 . This upper rest position is defined by the cooperation of an upper face  34  of the actuating portion  28  with a lower facing face  31  of the upper cover part  16 . Starting from this upper position, and by compressing the return spring  36 , the pushbutton  18  can be pushed downwardly towards its extreme lower position, which is defined by the cooperation of a lower face  33  of the actuating portion  28  together with a facing portion  35  of the lower housing part  14 . 
     The lower actuating portion  28  comprises a vertically open slit  44 . The slit  44  is delimited longitudinally by a transversal stem shaped portion  46  for constituting, in this example, a spring hooking portion. The pushbutton  18  is longitudinally arranged at one end of the housing  12  and the actuating portion  28  extends longitudinally towards the other opposite end of the housing  12 , having its portion  46  oriented longitudinally towards said other opposite end. 
     With reference to  FIG. 7 , the snap switch  10  comprises a conductive unit  50  that includes several conductive fixed contacts belonging to metallic fixed conductive pins made of a cut metal sheet. In one embodiment, the conductive unit comprises a pair of first conductive fixed contacts  56 , each one comprising a first fixed upper contact zone  57 , arranged inside the housing  12 , in the form of a vertical and longitudinal contact plate. The two first upper contact plates  57  are transversely aligned in a vertical plane P 1  ( FIG. 3 ). 
     In one embodiment, the conductive unit comprises a pair of second conductive fixed contacts  54 , each comprising a second fixed upper contact zone  55 , arranged inside the housing  12 , in the form of a vertical and longitudinal contact plate. The two second upper contact planes  55  are transversely aligned in a vertical plane P 2  ( FIG. 3 ). 
     In one embodiment, the conductive unit comprises a pair of third conductive fixed contacts  52 , each comprising a fixed third upper contact zone  53 , arranged inside the housing  12 , in the form of a vertical and longitudinal contact plate. The two third upper contact plates  53  are transversely aligned in a vertical plane P 3  ( FIG. 3 ), which is arranged longitudinally close to the pushbutton switch  18 , between the axis A 1  and the transversal stem shaped portion  46 . 
     Each contacting plate,  53 ,  55  or  57  defines a fixed contact face  58 ,  60  and  62  respectively which is oriented inwardly. As it can be seen at  FIGS. 3, 5 and 9   a - 9   b , on each lateral side, the fixed contact faces  60  and  62  extend substantially in the same vertical and longitudinal plane. Each fixed contact face  58  is slightly inwardly offset with respect to the common plane in which extend the faces  60  and  62  (see  FIGS. 9 a -9 b   ). 
     The lower part  14  of the housing  12  is a plastic piece over moulded on the fixed contacts  50  and each fixed contact comprises a tail extending vertically outwardly for the electrical connection of the fixed contacts and of the snap switch  10 , in a known manner, for instance on the upper face of a printed circuit board. 
     In one embodiment, with reference to  FIGS. 7 and 4 , each one of the first or second fixed contact zones  57 / 62  or  55 / 60  is associated with a first movable contact  64  and a second movable contact  66 , respectively. The first and second movable contacts are arranged transversely facing the associated fixed contact zone. 
     With reference to  FIGS. 9 a -9 b   , the first movable contact  64  is a movable portion, in the form of a fork, of a first elastically deformable conductive blade  68  that is supported by the lower part  14  of the housing  12 . The second movable contact  66  is a movable portion, in the form of a fork, of a second elastically deformable conductive blade  70  that is supported by the lower part  14  of the housing  12 . Each deformable contact blade  68 ,  70  is the form of a cut and bent sheet of conductive metal having a general shape of a hairpin. 
     With reference to  FIG. 7 , each deformable contact blade  68 ,  70  comprises two vertically oriented and globally parallel branches, each having a fixed branch  68 F,  70 F and an active branch  68 A,  70 A, both branches being connected by a 180° upper bent portion  72 ,  74  extending between the adjacent upper ends of the two branches  68 F/ 68 A and  70 F/ 70 A, respectively. Further, each fixed branch  68 F,  70 F extends vertically upwardly and has a lower end  76 ,  78  attached to the housing lower part  14 . Each lower end  76 ,  78  of the fixed branch  68 F,  70 F is vertically inserted (forced fit) and fixed in a receiving portion of the lower part  14  of the housing  12 . In a non-limiting manner, on each side, the lower ends  76 ,  78  of two adjacent fixed branches  68 F,  70 F are connected together by a longitudinal and vertical band  89 . 
     With reference to  FIGS. 9 a -9 b   , each active branch  80 ,  82  extends downwardly and comprises an upper bent portion having its convexity transversely and inwardly oriented to constitute a cam follower portion, and a lower bent free end portion  64 ,  66  having its convexity transversely and outwardly oriented to constitute the movable contact portion. 
     In one embodiment, when the deformable contact blades  68 ,  70  are in a free state, i.e. when they are not elastically deformed, there is a play or gap “j” between a movable contact portion  64 ,  66  and its associated and facing face  62 ,  60  of the corresponding fixed contact plate  57 ,  55 . 
     As it will be explained with reference to  FIG. 7 , each blade  68 ,  70  is deformable, under a transversal and horizontal pressure acting on the cam portion  80 ,  82 , starting from its free non-active state towards a deformed and active state, in which the movable contact portion  64 ,  66  is in electrically conductive contact with a facing and associated fixed contact face  62 ,  60 . 
     In the non-limiting example illustrated in the drawings, the two adjacent deformable blades  68  and  70  have a common output in the form of the band  89 , which is also the lower connecting part for a permanently fixed contacting third blade  71 . Each third blade  71  is shaped as the deformable active blades  68  and  70 , but it is configured to have its lower free end portion  67  permanently in electrical contact with the contact face of the third contact plate  53 . Consequently, the deformable blades  68  and  70  are electrically connected to the fixed contact  52 . 
     When the first movable contact portion  64  is deformed and is in its active state for establishing a first conductive way, the contact  56  is electrically connected to the contact  52 . When the second movable contact portion  66  is deformed and is in its active state for establishing a second conductive way, the contact  54  is electrically connected to the contact  52 . 
     Returning to  FIG. 4 , the control of the change of state of the movable contact portions  64  and  66  is further explained. In one embodiment, the snap switch  10  comprises a snap-action switching device comprising a tilting, or rocking or swaying driving member  84  which is pivotally mounted with respect to the housing  12  around a horizontal axis A 2 , and a traction spring  86 . In one embodiment, the traction spring  86  is a helicoidally wounded traction spring. The driving member  84  is a non-conductive plastic moulded component in the form of a longitudinal yoke delimiting an internal longitudinal funnel  88  for receiving the traction spring  86 . The driving member  84  is delimited by two opposed lateral longitudinal and vertical driving faces  90  ( FIG. 11 ). 
     With reference to  FIG. 3 , at its longitudinal end proximal to the actuating portion  28  of the pushbutton  18 , the driving element  84  comprises two aligned convex fulcrum portions  92 , which extend transversely. Each fulcrum portion  92  is received in a complementary concave portion formed in the housing  12  for pivotally mounting the driving member  84  with respect to the housing  12  around a horizontal and transversal axis A 2 . 
     Returning to  FIG. 4 , the driving member  84  comprises a transverse stem shaped transverse portion  94  for hooking one end of the traction spring  86 . The traction spring  86  has a first end  85  operatively connected to the portion  46  of the actuating portion  28  of the pushbutton, and a second opposed end  87  hooked to the portion  94  of the driving member  84 . 
     In one embodiment, with further reference to  FIG. 4 , under the action of the traction spring  86  and of the return spring  36 , the driving unit  84  and the pushbutton  18  can be in their “upper” rest positions. This upper position is defined by the cooperation between an upper face portion  96  of the driving member with an internal facing portion  98  of the upper cover part  16 . 
     When the user pushes downwardly on the stem  22  of the pushbutton, the actuating portion  28  of the pushbutton  18  acts, by means of the portion  46 , on the first end  85  of the traction spring  86  to provoke the pivoting of the driving member  84 , around the fixed horizontal axis A 2 , towards its second “lower” position illustrated at  FIG. 10 . This lower position is defined by the cooperation between a lower face portion  100  of the driving member  84  with an internal facing portion  102  of the lower part  14  of the housing  12 . 
     With reference to  FIG. 11 , for selectively acting on the deformable blades  68  and  70 , each lateral driving face  90  comprises two adjacent protruding driving cams, i.e. a first cam C 1  and a second cam C 2 . 
     Turning to  FIG. 7 , the first cam C 1  is dimensioned and designed for cooperating with the cam follower portion  80  of the first deformable blade  68 . When the driving member  84  is in its upper position (in which the first end of the traction spring is in an upper spring position), the first cam C 1  is permanently acting on the associated first cam follower portion  80  and the first conductive path is established. When the driving member  84  is in its lower position (in which the first end of the traction spring is in a lower spring position), the first cam C 1  is no longer acting on the first cam follower portion  80  and the first conductive path is no longer established. 
     The second cam C 2  is dimensioned and designed for cooperating with the second cam follower portion  82  of the second deformable blade  70 . When the driving member  84  is in its upper position, the second cam C 2  is not acting on the second cam follower portion  82  and the second conductive way is not established. When the driving member  84  is in its lower position, the second cam C 2  is permanently acting on the associated second cam follower portion  82  and the second conductive path is established. 
     When the user pushes downwardly on the stem  22  of the pushbutton, the actuating portion  28  of the pushbutton  18  acts to pivot the driving member  84  from its upper position to its lower active position. Such pivoting of the driving member from its upper active position towards its lower active position provokes a simultaneous change of the state of the first conductive path (passing from an “ON” status to an “OFF” status) and of the second conductive path (passing from an “OFF” status to an “ON” status). This change of position provokes the switching, i.e. the simultaneous interruption of the two first conductive paths—between the fixed contacts  52  and  56 , and the subsequent simultaneous establishment of the two second conductive paths between the fixed contacts  52  and  54 . It also provokes the compression of the return spring  36 . 
     When the user releases its actuation effort on the stem  22 , the previously compressed return spring  36  acts upwardly on the pushbutton  18  to push it vertically and upwardly. The actuating portion  28  of the pushbutton  18  acts to pivot the driving member  84  from its lower to its upper position. Depending on the upper or lower position of the driving member  84 , each cam may or may not cooperate with an associated cam follower portion of an associated elastically deformable blade to deform, or to relax, said blade for establishing or interrupting the associated conductive path. 
     The embodiments described above use a “caming” driving member to enable over travel of actuation. Manufacturing costs can also be reduced. In one embodiment, various fixed and movable contact elements can be fixed to and supported by the plastic moulded housing. Alternatively or additionally, the driving member can also be plastic moulded. Further, the tilting or swaying member does not comprise any metallic current conductive portion or element. Durability problem can also be solved because no sliding contacts are used. 
     As would be appreciated to a person ordinarily skilled in the art, the various embodiments disclosed in this document permit any variations in the arrangement of the establishment and interruption of conductive paths, such as in different position and in different number. These embodiments also permit use in and variations adapted for different applications. For example, the disclosed switch can be used in the automotive industry for actuation of an electronic parking brake. This switch may also be used in many applications including automotive air-bag systems as the system shut off switch. This switch can be used in any electronics application which, for instance, requires a double pole double throw circuit particularly if fast switching of both poles is desired. 
     In one embodiment, with reference to  FIGS. 13 and 14 , the return spring  36  can be optional, and instead, the actuating portion  28  is acting directly on the body of the traction spring  86 , which has thus double function acting on the pushbutton  18  and on the driving member  84 . The end  85  of the traction spring  86  can be hooked on the housing. 
     In one embodiment, the switch comprises an integrated damping device in order to reduce the noise generated by the driving member  84  when it reaches its upper position or its lower position, and the impacts on the facing part or portion of the housing. With further reference to  FIGS. 13 and 14 , the damping device comprise two elastic dampening abutment blocks  104 U and  104 L, respectively, for defining the upper and the lower position of the driving member  84 . This permits to have the two dampening blocks on the same side of the driving member and thus to integrate the two abutment dampening blocks in a common “dampening” component. 
     By way of example, the two blocks, together with the sealing boot  26  can be integrated in a one piece dampening, and sealing component  106  can be made of silicon or rubber or elastomer in the shape of a horizontal sealing sheet  108  and extending on all the area of the cover  16 , so that it is vertically interposed between the upper edge of the lower housing part  14  and the under face of the cover part  16 . Beyond the transverse portion  94  for hooking the end  87  of the traction spring  86 , the driving member  84  includes an extension  108 , which cooperates with the block  104 U when the driving member is in its upper position. Further, the driving member includes an extension  100 , which cooperates with the block  104 L when the driving member is in its lower position. 
     Alternatively and/or additionally, it is also possible to integrate the dampening abutment blocks  104 U and  104 L directly with the body of driving member  84 , for example in the zones  96  and  100  of the driving member  84 . Since the above disclosed embodiments of conductive paths and the arrangements of the contacts permit over travel without affecting the operation, it is possible to determine the two positions of the driving member  84  by means of non-rigid abutments such as the dampening abutment blocks  104 U and  104 L. 
     As will be appreciated by any person ordinarily skilled in the art, the arrangement of the above disclosed dampening device is not limited to a snap switch having aforementioned contacts arrangement. The dampening device may apply to any snap switch of the type comprising a housing and a driving member defining abutment zones that are configured to cooperate with associated abutment zones of the housing. 
     The above-disclosed features and functions, as well as alternatives, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated 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.