Abstract:
A switch suitable for use in contaminated environments provides for internal support of the operator allowing an oversized opening in the housing of the switch through which the operator extends. In this way contamination on the outer surface of the operator may be accommodated without a jamming of the operator in the retracted position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on U.S. provisional application 61/655,727 filed Jun. 5, 2012 and hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an electrical switch having a pushbutton operator that is resistant to contamination that would cause sticking of the pushbutton in an activated position. 
     BACKGROUND OF THE INVENTION 
     Modern appliances such as frontloading washing machines or dryers may provide for lid or door switches detecting when the appliance lid or door is open. These lid switches turn off the appliance to allow the user unhampered access to the clothing in the machine and to protect the consumer from machinery moving inside the appliance. Such switches may provide a button or “switch operator” extending from the housing of the appliance to be activated by closing of the door, the latter which presses the button inward into the housing. 
     The switch operator may slide within a sleeve that provides for mechanical support to the switch operator guiding it in axial translation when the switch operator is pressed by the door. The sleeve may conform closely to an outer surface of the switch operator both to prevent the ingress of contaminants into the housing and to prevent camming or jamming of the switch operator as it is pressed inward by the door. The sleeve may be stationary with respect to the housing and therefore sealed to the housing. 
     Contaminants such as water, bleach, fabric softener and detergent that are blocked by the close fit between the sleeve and the switch operator may nevertheless accumulate and dry on the outer surface of the switch operator that protrudes from the housing when the door is open. Such contaminants can cause the switch operator to jam within the sleeve when it is retracted therein potentially allowing operation of the appliance even when the door is open. 
     SUMMARY OF THE INVENTION 
     The present invention provides a pushbutton switch operator assembly that better resists contamination in the laundry environment or the like by providing a support for the switch operator that is removed from the opening through which the switch operator extends. In this way, the opening through which the switch operator expands may be enlarged so that contamination building up on the switch operator does not interfere with the switch operator movement. Contamination entering through this opening may be diverted in a safe drain passage out of the housing of the switch and/or may be blocked when the switch is fully extended by a rearward collar on the switch operator. 
     Specifically, then, the present invention provides, in one embodiment, an electrical switch having: a housing providing an opening therein, electrical contacts held within the housing, and a switch operator shaft communicating with the electrical contacts for opening and closing the electrical contacts. The switch operator is supported by a support structure positioned within the housing allowing the switch operator to move along an axis to project through the opening in the housing in an extended state and to retract at least in part into the housing in a retracted state. The support structure is removed from the opening, the latter of which provides substantially no support of the switch operator shaft. The switch operator shaft has a first radial extent about the axis smaller than the opening in the housing so that there is substantially no contact between the switch operator shaft and the opening in the housing when the switch operator shaft is in a retracted position. 
     It is thus a feature of at least one embodiment of the invention to provide a switch with an operator that is more resistant to contamination of the outer operator surface. By moving the support structure away from this outer surface, interference between the outer surface and a supporting escutcheon opening is reduced. 
     The housing may include a drain port for conducting liquid carried from outside the housing along the switch operator shaft into the housing out of the housing along the drainage path removed from the contacts. 
     It is thus a feature of at least one embodiment of the invention to accommodate some ingress of contamination when the switch operator is fully retracted. 
     The electrical contacts may communicate with the switch operator by means of a lever having a first cam surface interacting with the switch operator to pivot the lever with axial movement of the switch operator and wherein the lever extends in a direction substantially perpendicular to the axis and the drainage path. 
     It is thus a feature of at least one embodiment of the invention to offset the electrical components of the switch outside of the natural drainage of contamination of the switch operator. 
     The switch operator shaft may include an axial bore and the support structure may be a pillar extending along the axis and fitting slidably within the axial bore. 
     It is thus a feature of at least one embodiment of the invention to shield the support structure within the switch operator to better resist contamination. 
     The pillar may include a central bore receiving a helical compression spring extending between a bottom of the central bore of the pillar and a top of the axial bore of the switch operator shaft to urge the switch operator shaft toward the extended state. 
     It is thus a feature of at least one embodiment of the invention to provide a spring-biasing of the switch operator that is both resistant to contamination and centered along an axis of movement of the switch operator to reduce camming. 
     The invention may include a key element on the switch operator shaft for resisting rotation of the switch operator shaft about the axis during movement between the extended and retracted state. 
     It is thus a feature of at least one embodiment of the invention to allow reliable intercommunication between the switch operator and the contacts such as may otherwise be disturbed by rotation of the switch operator. 
     The key element may be a radially extending finger fitting within a channel parallel to the axis and fixed with respect to the housing. In one example, the key element may extend radially outward and the channel is outside of the switch operator shaft. 
     It is thus a feature of at least one embodiment of the invention to provide a simple method of preventing rotation of the switch operator that may employ an arbitrarily long lever to be removed from contamination or the need for close tolerances. 
     Alternatively the key element may radially extend inward and the channel is a portion of the pillar. 
     It is thus a feature of at least one embodiment of the invention to provide a key element that is largely shielded from the possibility of contamination 
     The electrical switch may include a shaft collar extending radially about the axis from a rear end of the switch operator shaft and having a radial extent larger than the radial extent of the switch operator shaft and substantially equal to the opening in the housing to obstruct the opening in the housing when the switch operator shaft is in the extended state. 
     It is thus a feature of at least one embodiment of the invention to provide a mechanism for blocking ingress of contamination, for example when the washing machine or dryer door is open and the switch is most subject to contamination, and to provide a trip ledge for truncating inflow of contamination along the switch operator held by capillary attraction. 
     The electrical contacts may be closed when the switch operator is in the retracted state. 
     It is thus a feature of at least one embodiment of the invention to provide for an open state of at least one pair of contacts (for example that may control the activation of internal machinery) when the switch operator is in the extended state most susceptible to jamming. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a front-loading washing machine suitable for use with the present invention showing an enlarged detail of a switch operator extending from a housing of the appliance; 
         FIG. 2  is an exploded diagram of the switch operator as supported by an internal pillar and biased by a helical compression spring showing a rearward flaring of the switch operator to provide sealing, and a drip ring and sideably extending tabs that stabilize the switch operator against rotation, limit outward travel of the switch operator and activate an internal switch mechanism; 
         FIG. 3 a    is a cross-section taken along line  3 - 3  of  FIG. 1  showing the switch operator in an extended position when an appliance door is open; 
         FIG. 3 b    is a figure similar to that of  3   a  showing the switch operator in a retracted position when the appliance door is closed; 
         FIG. 4  is a figure similar to  FIG. 2  showing an internal slot stabilizing the switch against rotation; 
         FIG. 5  is a perspective view of a switch that may incorporate the switch operator of the present invention extending therefrom for actuation of the switch and having electrical conductors for connecting the switch to other elements such as a motor of an appliance; and 
         FIG. 6  is an elevational cross-section along line  2 - 2  in  FIG. 1  showing a mechanical linkage between the switch operator and an over-center spring mechanism for moving a center contact between two outer flanking contacts each connected to different of the conductors of  FIG. 2 , where the lower flanking contact is mounted to be substantially stationary and the upper flanking contact is mounted on a flexible support arm, the switch being shown in a first “safe” state with the switch operator released. 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , an appliance  10 , for example a front-loading washing machine, may provide for a housing  12  having an opening  14  in a front wall  13  for providing a user access to a washing volume  15  of a type well known in the art. The opening  14  may be coverable by a door  16  that may seal against the opening  14  to block the flow of water therethrough. While a washing machine is shown in the following example, the invention may also be used in other appliances subject to contamination including dryers, these appliances referred to herein, generally, as laundry machines. 
     The door  16  may hinge, for example, about a vertical axis at one edge of the door  16  to a side of the opening  14  so that the opposite edge of the door  16  may swing inwards covering the opening  14  and pressing inward on a switch operator  18  protruding from that opposite edge. The pressing inward of the switch operator  18  provides an electrical signal to a control system of the appliance  10  indicating closure of the door  16  and normally allowing activation of internal mechanisms such as a spin basket/agitator, water valves and the like. 
     In one embodiment, the switch operator  18  may present a button providing a substantially cylindrical outer surface axially aligned with the horizontal axis  20  and movable along the horizontal axis  20  generally perpendicular to a front face of the appliance. 
     The switch operator  18  may extend through a front faceplate  22  being an integral or connectable part of the switch  48  associated with the switch operator  18 , for example, providing an escutcheon that seals against the housing  12 . An opening  24  in the faceplate  22  through which the switch operator  18  extends is sized to be larger than the radius circumscribing the extending portion of the switch operator  18  (being the radius of the cylinder of the switch operator  18  when it is cylindrical). This opening  24  is nevertheless filled when the switch operator  18  is fully extended (as shown in  FIG. 1 ) by a collar  26  extending radially outward near a rear edge of the switch operator  18  (closest to the housing  12 ) and integrally formed with the remainder of the switch operator  18 , for example, as a thermoplastic injection molded part. This collar  26  may be circular or other shape conforming to the opening  24 . Alternatively, the collar  26  may be a rearward flaring on the switch operator  18 . 
     Referring now to  FIG. 2 , a rear edge of the switch operator  18  behind the radially extending collar  26  may include side tabs  30   a  and  30   b  extending from the switch operator perpendicularly to the axis  20  on either side of the axis  20 . The tab  30   a  may engage with a cam surface  34  to move a rocker arm  36  about a fulcrum  38  when the switch operator  18  is pressed inward. The rocker arm  36  communicates with electrical contacts  39  of a type known in the art to provide a switching of electrical current through switch leads  40 . More specifically, at least two contacts  39  of the switch  48  may contact when the switch operator  18  is fully depressed, for example, to allow current flow to an appliance motor (not shown) when the door  16  is closed. Conversely, the two contacts  39  may be separated when the switch operator  18  is fully extended to break current flow to the appliance motor. 
     The remaining and opposite tab  30   b  may be received by a guide slot  44 , for example, formed in a housing  46  of the switch  48 . Engagement between the tabs  30   b  and guide slot  44  over the full extension range of the switch operator  18  helps prevent rotation of the switch operator  18  and ensures proper alignment of the tab  30   a  and the cam surface  34 . The tabs  30   a  and  30   b  may also limit the outward travel of the switch operator  18  by extending beyond the collar  26  to abut a rear surface of opening  24  as the switch operator  18  moves outward. 
     A guide pillar  50  may extend forward along axis  20  from a portion of the housing  46  adjacent to the guide slot  44  and have an outer diameter that may fit within an axial bore  52  formed coaxially within the switch operator  18  and opening rearwardly therefrom. The interface between the pillar  50  and the bore  52  provides the axial guidance of the switch operator  18  when it is extended and retracted that would otherwise be provided by a tightly fitting outer sleeve not employed in the present invention. The pillar  50  may itself include an internal coaxial bore  54  that may receive a helical compression spring  56  fitting between the bottom of the bore  54  at one end and a top of the bore  52  in the switch operator  18  on the other end. The helical compression spring  56  operates to bias the switch operator  18  to its fully extended outward position in the absence of pressure by the door  16 . 
     Referring now to  FIG. 3 a   , when the switch operator  18  is in its outermost position (limited by the tabs  30   a  and  30   b  not shown in  FIG. 3 a   ) the collar  26  substantially fills the diameter  68  of the opening  24  to prevent contamination  60  outside of the appliance  10  from passing into the inner volume  62  of the switch  48  or inside the appliance  10 . 
     Nevertheless contamination  60 , for example bleach or other cleaning products described above, can contact the outer surface of the extended switch operator  18  and may harden in the form of crystals or the like as surface contamination  64  which increases the effective diameter  70  of the switch operator  18  beyond the actual diameter  72  of the switch operator  18 . This increase in effective diameter  70  would normally cause jamming of the switch operator  18  against an outer supporting sleeve but in the present invention the effective diameter  70  will remain below the diameter  68  of the opening  24  during typical use. Contamination  60  which drips off of the switch operator  18 , when the switch operator  18  is fully extended, will be guided by the lower portion of the collar  26  and the inter-fitting faceplate  22  to remain outside of the housing  12 . The switch operator  18  is held, when the door  16  is open, in this fully extended position by the extension of the helical spring  56 . 
     Referring now to  FIG. 3 b   , when the switch operator  18  is pressed inward by the door  16 , the surface contamination  64  may pass easily through the opening  24  as the collar  26  moves back and the spring  56  is compressed. Contamination  60  on the switch operator  18  or otherwise introduced through the opening  24  at this point in time may wick along the under surface of the switch operator  18  but will be prevented from entering the low clearance space between the pillar  50  and the inner bore of the switch operator  18  by the action of the collar  26  which forms a drip ring conducting any such liquid to a lower point  66  away from this interface and along a drain path  67  leading out of the housing  46 . 
     Referring momentarily to  FIGS. 1 and 6 , symmetric drain paths  67  and  67 ′ are placed on opposite sides of the housing  46  to allow the housing  46  to be mounted to the appliance  10  in either of two orientations so that one of the drain paths  67 ,  67 ′ is directed downward. 
     Referring now to  FIG. 4 , in an alternative embodiment or in conjunction with the embodiment of  FIG. 2 , the pillar  50  may have a side slot  74  running along axis  20  to give the pillar  50  a C-shaped cross-section. An internal tooth  76  within the bore  52  of the switch operator  18  may slide along the slot  74  to prevent rotation of the switch operator  18  with axial movement of the switch operator  18  in the same manner as the guide slot  44  while allowing elimination of the guide slot  44 . 
     It will be appreciated that any contamination that collects between the collar  26  and the opening  24 , for example, when the switch operator is fully extended as shown in  FIG. 3 a   , will be broken by movement of the switch operator  18  inward by closing of the door  16  or otherwise will prevent the appliance motor from being activated thus holding the appliance  10  in a safe state. 
     Referring now to  FIG. 5 , the housing  46  of the electrical switch  48  may be constructed of an insulating thermoplastic material molded to include the opening  24  through which the pushbutton switch operator  18  extends. Conductive leads  40  may extend through other openings in the housing  46  to communicate with external electrical circuits, for example motors or actuators of a household appliance (not shown). 
     Referring now to  FIG. 6 , the electrical switch  48  may contain an upper contact  118 , a center contact  120 , and a lower contact  122  arranged to provide a single pole, double throw electrical switch with the upper contact  118  and lower contact  122  generally flanking the center contact  120 . The center contact  120  may move between the upper contact  118  and lower contact  120  to selectively and alternatively connect to only one of the upper contact  118  and lower contact  122 . 
     The center contact  120  may be supported on a relatively rigid conductive lever  124  attached at a knife edge pivot point  126  to a conductive support bracket  128 , the latter communicating with one of the conductive leads  40  and pivot point  126  allowing electrical conduction from the conductive lever  124  to the conductive lead  40 . By pivoting the lever  124  around the pivot point  126 , the lever  124  may be moved upward and downward so that the center contact  120  alternately connects electrically to upper contact  118  and lower contact  122 . 
     A helical over-center spring  130  attaches to a center portion of the lever  124  and extends away from the center contact  120  to a support post  132  on the housing  46  to provide a force on the lever  124  tending to engage the lever  124  and support bracket  128  at the pivot point  126 . 
     The switch operator  18 , when pressed inward (into the page as depicted in  FIG. 6 ), presses against a cam surface  34  attached at one end of a rocker arm  36  to rotate the rocker arm  36  counterclockwise about a center-positioned fulcrum  38  held on a fulcrum block  127 . An opposite end of the rocker arm  36  provides an upwardly extending finger  140  which deflects a center region of the helical over-center spring  130  upward to change its line of action  142  with respect to the fulcrum  38 . The line of action  142  represents a force vector asserted on the lever  124  by the helical over-center spring  130 . When the line of action  42  is above the pivot point  126 , the lever  124  will snap rapidly upward and when the line of action  42  is below the pivot point  126 , lever  124  will snap rapidly downward. 
     Referring still to  FIG. 6 , the upper contact  118  and lower contact  122  are each generally supported on a cantilevered conductive metal strip to one of the conductive leads  40 . Specifically, the upper contact  118  is supported on a lower distal end of flexible metal lever  146  and the lower contact  122  is supported on an upper distal end of a substantially rigid conductive metal strip  144 . Generally the strip  144  and lever  146  extend from their respective contacts  118  and  122  in the opposite direction as the lever  124 . 
     When the switch operator  18  is released and the rocker arm  36  rotates to its full clockwise position, the line of action  142  of the helical over-center spring  130  moves below the pivot point  126  and a lower surface of the center contact  120  contacts an upper surface of the lower contact  122  at a first position as pulled together by a torsional vector component of the force along the line of action  142  of the over-center spring  130 , the force pulling downward on lever  124 . An upper surface of contact  120  is separated from a lower surface of the upper contact  118  so that a circuit is “made” between contacts  121  and  122  and “broken” between contacts  121  and  118 . 
     When the switch operator  18  is compressed, the rocker arm  36  rotates to a full counterclockwise position pressing upward on the helical over-center spring  130  to move the line of action  142  above the pivot point  126  pulling upward on lever  124  so that an upper surface of contact  122  contacts the lower surface of contact  118  at a second position. Under the force of contact  122 , flexible lever  146  is moved upward allowing the lever  146  to straighten as it rotates to break any microscopic welds. 
     Various of the components of the switch  48  as described above are the subject of co-pending application publication number 2013/0015049 published Jan. 17, 2013 and hereby incorporated in its entirety by reference. 
     Various features of the invention are set forth in the following claims. It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.