Patent Publication Number: US-8115131-B2

Title: Electrical pushbutton snap switch

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of European Patent Application No. 0816139.1 filed Aug. 4, 2008. 
     BACKGROUND 
     The present invention relates to an electrical switch, also known as a snap switch. Such an electrical snap switch is designed for selectively establishing either a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. Typical electrical snap switches may include a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established. The electrical snap switch may further include a conductive unit which is fixed with respect to the housing and which includes first, second, and third conductive fixed contacts. The electrical snap switch may include a switching unit comprising a conductive swaying element, a first end of the conductive swaying element being pivotally engaged with the first conductive element, and the second end of the conductive swaying element being arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to the housing and a second end secured to the swaying element such that when the pushbutton is in the first pushbutton position, the spring is in a first spring position and the spring causes the swaying element to electrically connect the first and second conductive fixed contacts, and when the pushbutton is moved to the second pushbutton position, the spring is moved to a second spring position and the spring causes the swaying element to also move to electrically connect the first and third conductive fixed contacts, 
     An example of such a switch is disclosed in U.S. Pat. No. 7,205,496, the contents of which are hereby incorporated by reference, in which the spring is a helicoidally wounded traction spring and in which the pushbutton driving portion acts on the middle section of the spring. Due to this arrangement, an abrupt changeover of the switching unit occurs but it is not possible to obtain a quick changeover and, furthermore, the elastic behaviour of the spring is affected by its cooperation with the driving portion and the changeover point, or instant, varies and the switch is therefore not reliable. The same drawbacks are also inherent to the design disclosed in U.S. Pat. No. 4,636,597. 
     An attempt to improve the working of such a snap switch is illustrated in U.S. Pat. No. 6,255,611 in which the switching unit is bistable between first and second positions of the swaying element, in which the switch comprises a return spring which is disposed between the housing and the pushbutton, in which, when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring, and in which the traction spring has a first end connected to the driving portion of the pushbutton and a second end secured to the swaying element, so that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position, and when the pushbutton is moved to the second pushbutton position, the first end of the spring is moved to a second spring position. 
     According to such an arrangement, when an external force is applied to the pushbutton, the 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, each one between a first conductive fixed contact and a second conductive fixed contact. Similarly, there is no design that simultaneously provides two second conductive ways, each one between the first conductive fixed contact and a third conductive fixed contact. 
     SUMMARY 
     The invention described in this document is not limited to the particular systems, methodologies or protocols described, as these may vary. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present disclosure. 
     It should be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used herein, the term “comprising” means including, but not limited to.” 
     In one general respect, the embodiments disclose a switch for selectively establishing a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. The switch includes a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established. The switch also includes a conductive unit which is fixed with respect to the housing and which includes the first, second, and third conductive fixed contacts; and a switching unit. The switching unit includes a conductive swaying element, wherein a first end of the conductive swaying element is pivotally engaged with the first conductive fixed contact, and a second end of the conductive swaying element is arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to a driving portion of the pushbutton and a second end secured to the swaying element. The switch is configured such that when the pushbutton is in the first pushbutton active position, the first end of the traction spring is in a first spring position and the traction spring causes the swaying element to electrically connect the first and second conductive fixed contacts, and when the pushbutton is moved to the second active pushbutton position, the first end of the traction spring is moved to a second spring position and the traction spring causes the swaying element to move to electrically connect the first and third conductive fixed contacts. The switch is further configured such that the switching unit is bistable between the first and second positions of the swaying element, the switch comprises a return spring which is disposed between the housing and the pushbutton, and when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring. 
     In another general respect, the embodiments disclose a switch for selectively establishing simultaneously two first conductive ways, each one between a first conductive fixed contact and a second conductive fixed contact or simultaneously two second conductive ways, each one between the first conductive fixed contact and a third conductive fixed contact. The switch includes a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive ways are established and a second pushbutton active position in which the second conductive ways are established. The switch also includes a conductive unit which is fixed with respect to the housing and which includes the first, second, and third conductive fixed contacts and a switching unit. The switching unit includes a pair of conductive swaying elements, a first end of each conductive swaying element being pivotally engaged with a first associated conductive fixed contact, and the second end of each conductive swaying element being positioned to selectively electrically connect the first associated conductive fixed contact to either a second associated conductive fixed contact or a third associated conductive fixed contact, and a traction spring having a first end operatively connected to the driving portion of the pushbutton and a second end secured to the swaying elements. The switch is configured such that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position and the traction spring causes the swaying elements to electrically connect the first and second associated conductive fixed contacts, and when the pushbutton is moved to the second pushbutton position, the first end of the traction spring is moved to a second spring position and the traction spring causes the swaying elements to also move to electrically connect the first and third associated conductive fixed contacts. The switch is further configured such that the switching unit is bistable between the first and second positions of the swaying element, the switch comprises a return spring which is disposed between the housing and the pushbutton, and when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Other characteristics and advantages of the invention will become apparent from reading the following detailed description, for an understanding of which reference should be made to the appended drawings in which: 
         FIG. 1  is a top perspective view which illustrates various embodiments of an embodiment of a bistable snap switch according to principles of the present invention; 
         FIG. 2  is a perspective view similar to  FIG. 1  showing various components in an exploded view; 
         FIG. 3  is an enlarged view of the lower part of  FIG. 2 ; 
         FIG. 4  is a top view the various components illustrated in of  FIG. 3 ; 
         FIG. 5A  is a cross-sectional view taken along line  5 - 5  of  FIG. 4  showing various components in their first position; 
         FIG. 5B  is a cross-sectional view taken along line  5 - 5  of  FIG. 4  showing various components in their first position; 
         FIG. 6  is a lateral view of some of the main components of the conductive and switching units of the snap switch of  FIGS. 1 and 2 ; 
         FIG. 7  is a top perspective view of various components of  FIG. 6 , some being illustrated in a partially exploded position; 
         FIG. 8  is a top perspective view of a lower half of the snap switch housing; 
         FIG. 9  is a bottom perspective view of a upper half of the snap switch housing. 
     
    
    
     DETAILED DESCRIPTION OF THE FIGURES 
     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 an electrical switch may be symmetrical with respect to the vertical median plane VMP corresponding to exemplary line  5 - 5  of  FIG. 4 . 
       FIG. 1  shows a snap switch  10 . The snap switch  10  may include a housing  12 , of rectangular parallelepipedic shape. The housing  12  may be made of a housing upper part or half  16  and a housing lower part or half  14 , each of which may be made of moulded plastics and ultrasonic welded to each other after mounting and assembly. 
     As shown in  FIG. 2 , the switch  10  may also comprise a vertically extending and displaceable pushbutton  18  having a free upper end  20  for receiving an actuation force. A main vertical upper stem  22  of the pushbutton  18  may extend through a hole  24  of the housing upper part  14  in combination with a sealing boot  26 . The pushbutton  18  may be a plastic moulded part comprising a lower driving portion  28  which is an extension of the main vertical stem  22  and which is arranged and extends inside the housing  12 . The lower driving portion  28  may comprises a pair of vertically and transversely extending lateral guiding wings  30  which are received in mating and complementary pairs of vertical grooves  32  and  34  which may be arranged in the two halves  14  and  16  of the housing  10  (as shown in  FIGS. 8 and 9 ). 
     As illustrated in  FIGS. 5A and 5B , the switch  10  may further comprise a return spring  36  disposed vertically between the lower part  14  of the housing  12  and the lower driving portion  28  of the pushbutton  18 . The return spring  36  may be a vertically and helicoidally wounded spring which is received in a pit  40  of the lower part  14 . The return spring may be positioned such that its upper end may act on a lower vertically extending finger  42  of the driving portion  28 . 
     The return spring  36  may be mounted so as to be vertically compressed in such a way that, when an external force 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 may be defined by the position of upper edges  31  of the wings  30  with the upper bottoms  35  of the grooves  34 . 
     Starting from this upper position (and by compressing the return spring  36 ), the pushbutton  18  may be pushed downwardly towards its extreme lower position as is defined by the position of lower edges of the wings  30  with the lower bottoms of the grooves  34 . 
     The lower driving portion  28  comprises an open V-shaped slit  44 . As shown in  FIGS. 5A and 5B , the slit  44  may be delimited by a first upper driving inner wall  46  and a second lower opposite driving inner wall  48 . The pushbutton  18  may be longitudinally positioned at one end of the housing  10  and the V-shaped slit  44  may longitudinally converge towards the other opposite end of the housing  10 . Each wall  46  and  48  may plane and terminate in an inclined small plane face  47 ,  49 , both of which may be positioned horizontal and parallel with respect to the other. 
     As shown in  FIGS. 5A ,  5 B and  6 , the snap switch  10  may include a conductive unit made of several conductive fixed contacts belonging to metallic fixed conductive pins made of a cut metal sheet. The conductive unit may include a pair of first conductive fixed contacts  52 . The two first contacts  52  may be a pair of vertical conductive pins, each one comprising a fixed contact zone  53  in the form of a V-shaped groove. The two first contacts  52  may align transversely in a vertical plane which is substantially a middle plane arranged longitudinally between the pushbutton switch  18  and the other associated fixed contacts. 
     The conductive unit may also include a pair of second conductive fixed upper contacts  54 . The two second contacts  54  may be a pair of vertical conductive pins, each pin having an upper horizontally bent portion  56  and a lower face thereof constituting a fixed contact zone  57 . The two second contacts  54  may align transversely in a vertical plane which is arranged longitudinally substantially at the longitudinal end of the housing  10  opposed to the pushbutton switch  18 . 
     The conductive unit may further include a pair of third conductive fixed lower contacts  58 . The two third contacts may be a pair of vertical conductive pins, each pin having an upper horizontally bent portion  60  and an upper face thereof constituting a fixed contact zone  61 . The two third contacts  58  may align transversely in a vertical plane which is arranged longitudinally substantially at the longitudinal end of the housing  10  opposed to the pushbutton switch  18 . 
     All four bent portions  56  and  60  may align in the same transversal plane such that they form two pairs of fixed facing contact zones  57 ,  61  defining a vertical space there between. An imaginary horizontal plane passing through the centre of the grooves  53  may pass substantially in the middle of the vertical space between the pairs of fixed facing contact zones  57 ,  61  as shown in  FIGS. 5A and 5B . 
     As illustrated in  FIG. 7 , the snap switch  10  may further includes a switching unit  62 . The switching unit  62  may be made of a pair of twin mobile contact conductive blades  64  manufactured from a cut metal sheet. Each blade  64  may constitute a swaying element and may be configured to move between the second  54  and third  58  fixed contacts. Similarly, each mobile contact blade  64  may extend longitudinally between the first fixed contacts  52  at one end, and the other fixed contacts  54  and  58  at the other end. 
     As shown in  FIG. 7 , each mobile contact blade  64  may have a first end  66  slightly bent downwardly with respect to the general plane of the blade, and a transverse edge  67  thereof may be pivotally received in a corresponding groove of an associated first fixed contact. Each mobile contact blade  64  may also have a second end  68  in formed, for example, as a fork which is positioned between the facing opposite conductive zones  57  and  61  such that the contact blade may selectively electrically connect the first conductive fixed contacts  52  to either the second  54  or the third  58  conductive fixed contacts, depending on the position of the mobile contact blade  64 . 
     As shown in  FIGS. 1 ,  2  and  3 , each of the conductive pins  52 ,  54 ,  58  may be inserted (e.g., by forced fitting) and positioned in the lower portion  14  of the housing. Similarly, each of the conductive pins  52 ,  54 ,  58  may extend outwardly through corresponding holes vertically beyond the lower face  17  in order to constitute connecting pins of the switch  10  for connection of the latter on a printed circuit board (not shown). These terminals may be sealed with some epoxy resin depending upon the application of the switch  10 . 
     As shown in  FIGS. 5A ,  5 B,  6  and  7 , the switch  10  may include a transmitting element  70  which may be a plastic component overmoulded on the metallic swaying contact blades  64 . The transmitting element  70  may function as a single and common spring force transmitting element. 
     In one example, the transmitting element  70  may be formed as a reversed U-shaped stirrup wherein each lower end  72  of a lateral transverse branch is overmoulded on a corresponding facing portion of the associated blade  64  which is positioned close to its first end  66 . The stirrup  70  may also include a central and substantially horizontal branch  74  which extends longitudinally towards the second free ends  68  of the blades  64 . The free end  76  of the central branch  74  may terminate in a hook  78 . 
     As shown in  FIG. 7 , as a result of the pivotal arrangement of the switching unit  62 , with respect to the fixed contacts  52  and around the horizontal and transverse axis A-A, between the two upper and lower positions of the switching unit, the snap switch  10  may permit selective and simultaneous establishing of two first conductive ways, each one between a first conductive fixed contact  52  and a second conductive fixed contact  54  when the mobile switching unit  62  is in the position illustrated in  FIGS. 5A and 5B , i.e. when the pushbutton is in the first upper active position. The switching unit  62  may also permit selective and simultaneous establishment of two second conductive ways, each one between a first conductive fixed contact  52  and a third conductive fixed contact  58  when the pushbutton is in the second lower active position. 
     The switching unit may be bistable between the first upper position and second lower positions. In this example, the switch may comprise a traction spring  80  having a first end  82  operatively connected to the driving portion  28  of the pushbutton via, for example, a tilting lever, and a second end  84  secured to the mobile contacts by means of the force transmitting element  70 . The traction spring  80  may be a helicoidally wounded spring having its second end  84  hooked in a hook  78  of a branch  74  of the force transmitting element. The first end  82  of the traction spring  80  may be connected to the pushbutton  18  by means of a tilting lever  86  which is pivotally mounted with respect to the housing  12 . 
     The tilting lever  86  may be formed as a metal plate pivotally mounted around a transverse and horizontal axis B-B parallel to the plane of the plate  86 . The tilting lever  86  may generally be in the form of a T having two first parallel and lateral branches  88 , each one having a transverse free edge  89 . Each free edge  89  may be pivotally received in a corresponding groove of an associated fixed structural bracket element  90 . 
     The structural bracket  90  may be a metallic cut element inserted (e.g., via forced fitting) in the lower part  16  of housing  12 , but which has no conductive or electrical contact function. The tilting lever  86  may also comprise a second central longitudinally extending central branch  94  which constitutes the second end of the lever  86  which is received freely with play in the slit  44 . The tilting lever  86  may also comprises a central hole  96  in which the first end  82  of the traction spring  80  is hooked, the hole  96  being positioned at a point which is positioned between the first  88 - 89  and second  94  ends of the tilting lever  86 . 
     Due to the various geometrical parameters and dimensions, and under the action of the traction spring  80  and of the return spring  36 , the bistable switching unit  62 , the lever  86  and the pushbutton  18  may all normally be in their “upper” rest positions as illustrated in  FIGS. 1  to  5 B. When the users pushes downwardly on the stem  22  of the pushbutton, the driving portion  28  of the pushbutton  18  may act, by means of the upper inner wall  46 , on the second end  94  to pivot the lever  86  from its upper first lever position in which the first end  82  of the spring  80  is in its first stable “upper” spring position, to its second stable “lower” lever position in which the first end  82  of the spring  80  is in its lower second position. 
     This change of position may provoke the switching, i.e. the simultaneous interruption of the two first conductive ways between the fixed contacts  52  and  54 , and the subsequent simultaneous establishment of the two second conductive ways between the fixed contacts  52  and  58 . It may also provoke the compression of the return spring  36 . When the users releases any actuation effort on the stem  22 , the previously compressed return spring  36  may act upwardly on the pushbutton  18  to push it vertically and upwardly. The driving portion  28  of the pushbutton  18  may similarly act, by means of the lower inner wall  48  of the slit  44 , on the second end  94  to pivot the lever from its the second stable “lower” lever position in which the first end  82  of the spring  80  is in its lower second position, to its upper first lever position in which the first end  82  of the spring  80  is in its first stable “upper” spring position. 
     The described embodiment herein comprises a “double” or “twin” arrangement of two switches. However, the invention also applies to a “single” or “unique” switch for selectively establishing a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. This switch is primarily used in the automotive industry for actuation of an electronic parking brake. However, this switch may be also used in many applications including automotive air-bag systems as a system shut off switch. This switch may also 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.