Abstract:
A plunger switch assembly and method of operation comprises a housing having an interior cavity for locating electronic components, a contact support movably located within the interior cavity. The contact support holds and moves at least one electrical contact that engages a corresponding contact located on a printed circuit board. The plunger switch assembly further includes an actuating member for moving the contact support and at least one electrical contact within the interior cavity of the housing, a carriage cover located over the housing for guiding the actuating member, and an active sealing arrangement for preventing debris from entering the housing.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The following application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/820,424 filed May 7, 2013 entitled PLUNGER SWITCH AND METHOD OF OPERATING SAME. The above-identified application is incorporated herein by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to electrical switches, and more particularly to a plunger switch assembly and method of operation. The plunger switch assembly includes an active sealing arrangement that prevents contamination to internal components. 
     BACKGROUND 
     Electrical switches using push button or plunger type switch actuators have many applications including use in automobile car doors, ignition circuits, power take-offs for lawn mowers and garden tractors, refrigerator doors, home appliances, and the like. These push buttons may be normally open, normally closed or a combination of the two. 
     It is possible to construct switches having more than two terminals, which combine the features of normally open and normally closed switches. For example, a “double-pole double-throw” switch behaves as a normally open switch and a normally closed switch in parallel operated by a single plunger. When the plunger is in a normal position, a pair of normally closed terminals is bridged and a pair of normally open terminals is isolated. Alternatively, when the plunger is moved to an actuated position, the normally open terminals are bridged and the normally closed terminals are isolated. A “single-pole double-throw” switch behaves like a double-pole double-throw switch in which one of the normally open terminals is coupled to one of the normally closed terminals. When the plunger is in the normal position, a common terminal is bridged with a normally closed terminal while a normally open terminal is isolated. Alternatively, when the plunger is in the actuated position, the common terminal is bridged with the normally open terminal while the normally closed terminal is isolated. Such switches can then be configured to communicate on a LIN or CAN bus. 
     Typically located within a housing supporting electrical switch are electrical components such as contacts, printed circuit boards, etc. that are adverse to contamination, such as water or debris. It is not uncommon for such electrical switches to be exposed to such harsh environments, especially those switches used on garden tractors. 
     Further discussion relating to the different switch constructions can be found in U.S. Pat. No. 5,528,007 entitled PLUNGER SWITCH AND METHOD OF MANUFACTURE that issued on Jun. 18, 1996 and assigned to the assignee of the present disclosure. U.S. Pat. No. 5,528,007 is incorporated herein by reference in its entirety. 
     SUMMARY 
     One example embodiment of the present disclosure includes a plunger switch assembly and method of operation comprising a housing having an interior cavity for locating electronic components, a contact support movably located within the interior cavity. The contact support holds and moves at least one electrical contact that engages a corresponding contact located on a printed circuit board. The plunger switch assembly further includes an actuating knob for moving the contact support and at least one electrical contact within the interior cavity of the housing, a carriage cover located over the housing for guiding the actuating knob, and an active sealing arrangement for preventing debris from entering the housing. 
     Another example embodiment of the present disclosure includes a switch assembly comprising a housing having an interior cavity for locating electronic components, a contact support movably located within the interior cavity. The contact support holds and moves at least one electrical contact that selectively electrically communicates with a corresponding region on a printed circuit board. The printed circuit board is fixedly located in a base of the housing. The switch assembly also includes an actuating knob for moving the contact support and the at least one contact within the interior cavity of the housing such that the moving results in selective communication with the printed circuit board. A carriage cover is located over the housing for guiding the actuating knob, and a thermoplastic active sealing arrangement is provided for preventing debris from entering the housing. The active sealing arrangement comprises a bellows that expands and contracts as the actuating knob is moved from a first position to a second position. 
     Yet another example embodiment of the present disclosure includes a method of assembling a switch assembly, the method comprises the steps of providing a housing having an interior cavity for locating electronic components and locating a movable contact support within the interior cavity. The contact support holds and moves at least one electrical contact that engages a corresponding contact located on a printed circuit board. The method also includes the step of providing an actuating knob for moving the contact support and at least one contact within the interior cavity of the housing, and locating a carriage cover over a portion of the housing for guiding the actuating knob. The method also includes the step of providing an active sealing arrangement for preventing debris from entering the housing. 
     In another example embodiment of the present disclosure, a switch assembly comprises a housing having an interior cavity for locating electronic components and a knob moveably located between positions within the housing such that when the knob changes positions, the desired state changes in the switch assembly. The switch assembly also comprises an active sealing arrangement fixedly attached to the knob, the active sealing arrangement includes a moveable bellows such that movement of the knob relative to the housing results in corresponding movement in the bellows of the active sealing arrangement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the present disclosure will become apparent to one skilled in the art to which the present disclosure relates upon consideration of the following description of the disclosure with reference to the accompanying drawings, wherein like reference numerals refer to like parts unless described otherwise throughout the drawings and in which: 
         FIG. 1  is an upper perspective view of a plunger switch assembly constructed in accordance with one example embodiment of the present disclosure; 
         FIG. 2  is a front elevation view of  FIG. 1 ; 
         FIG. 3  is a side elevation view of  FIG. 1 ; 
         FIG. 4  is a top plan view of  FIG. 1 ; 
         FIG. 5  is a bottom plan view of  FIG. 1 ; 
         FIG. 6  is a front sectional elevation view of  FIG. 1  about section lines  6 - 6  illustrated in  FIG. 4 ; 
         FIG. 7  is a side sectional elevation view of  FIG. 1  about section lines  7 - 7  illustrated in  FIG. 4   
         FIG. 8  is an exploded assembly view of  FIG. 1 ; 
         FIG. 9  is a sectional perspective view of  FIG. 6 , illustrating the plunger switch assembly in a first actuation position; 
         FIG. 10  is a sectional perspective view of  FIG. 6 , illustrating the plunger switch assembly in a second actuation position; 
         FIG. 11  is a sectional perspective view of  FIG. 6 , illustrating the plunger switch assembly in a third actuation position; 
         FIG. 12  is a upper perspective view of an active sealing arrangement constructed in accordance with one example embodiment of the present disclosure; 
         FIG. 13  is a lower perspective view of  FIG. 12 ; 
         FIG. 14  is an top plan view of  FIG. 12 ; 
         FIG. 15  is a side elevation view of  FIG. 12 ; 
         FIG. 16  is a bottom plan view of  FIG. 12 ; 
         FIG. 17  is an elevation view of the  FIG. 12  in which the bellows member is elongated to a extended or third position; and 
         FIG. 18  is an elevation view of  FIG. 12  in which the bellows member is relaxed to an in situ or first position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures generally wherein like numbered features shown therein refer to like elements throughout unless otherwise noted. The present disclosure relates to electrical switches, and more particularly to a plunger switch assembly and method of operation. The plunger switch assembly includes an active sealing arrangement that prevents contamination to internal components. In one example embodiment, the switch assembly includes an integrally connected printed circuit board that is configured to support multiple electronic/electrical system architecture, and/or to display operation status with one or more LED&#39;s. In another example embodiment, the switch assembly comprises light pipes that allow for the passing of illumination from the circuit board to alert the operator of the operating state. 
       FIG. 1  illustrates a perspective view of a plunger switch assembly  10  constructed in accordance with one example embodiment of the present disclosure. The switch assembly  10  as would be appreciated by one of ordinary skill in the art operates in both a normally open “NO” or normally closed “NC”, single-pole double-throw, and double-pole double-throw configurations, based on the construction of the contact combinations with respective terminals, as further discussed below and in U.S. Pat. Nos. 5,528,007 and 5,221,816, which are incorporated herein by reference in their entireties. Such switches can then be configured to communicate on a LIN or CAN bus. 
     One application of the switch assembly  10  includes a power take-off for a lawn mower indirectly through an electronic control unit or directly, controlling the transfer of power from an engine output shaft to an accessory such as the lawn mower blades. In an alternative example embodiment, the switch assembly  10  includes in addition to normally open (NO) and normally closed (NC) positions, momentary or intermediate positions containing, both, neither, or one of the above positions for one or more terminals. 
       FIGS. 2-8  are further illustrative views of the plunger switch assembly  10  in accordance with the example embodiment of  FIG. 1 . The plunger switch assembly as best seen in the exploded view of  FIG. 8  comprises an actuation member or knob  12 , carriage  14 , active sealing arrangement  16 , housing  18 , actuator assembly  20 , printed circuit board  22 , contact bridge  24 , and base  26 . In the illustrated example embodiment, the knob  12 , carriage  14 , housing  18 , guide  24 , base  26 , and a portion of the actuator assembly  20  are made from molded plastic. It should be appreciated that other materials could be used instead of plastic of similar strength without departing from the spirit and scope of the present disclosure. 
     In one example embodiment, the plunger switch assembly  10  is constructed to be positioned or located within a dash panel of lawn tractor. The housing  18  includes wing-clips  19  that expand and contract when the switch is positioned within a dash panel opening, such that the wings compress as they pass through the opening, projecting outward once travel beyond the opening occurs. The dash panel then resides in a gap  21  between the carriage and wings  19  as illustrated in  FIG. 2 . 
     The housing  18  includes an interior cavity  23 . The interior cavity supports electronic components  25  that includes the PCB  22  and its associated wipers and contact terminals. 
     The first and second biasing members  28 , and  30 , are in the example embodiment metal coil springs forming a portion of the actuator assembly  20 . The biasing members  28 ,  30  are symmetrically supported within the actuator assembly  20  by a contact support  34 . The contact support  34  translates within the housing  18  when the knob  12  is actuated between various positions. In the illustrated example embodiment, the contact support  34  is made of plastic and is held in a natural or in situ position by the biasing members  28  and  30 , as illustrated in  FIGS. 6, 7, and 9 . 
     Secured to the contact support  34  is the contact bridge  24  having one or more contacts or leads  40 . The contact bridge  24  is translated with the contact support  34  as the knob  12  is moved between different positions, as illustrated in  FIGS. 9-11 . As the contact support  34  and contact bridge  24  are translated to different positions, a plurality of similar or different length and spaced contacts or wipers  40  secured to the contact support by fastener  32  and are equally moved between the different positions and engage or wipe harness terminals or leads  38  fused to the PCB  22 . 
     In one example embodiment, the contacts  36  on the PCB  22  are in communication with terminals  38  and fix the PCB to the base  26  through corresponding openings as illustrated in  FIG. 8 . The leads  40 , contacts  36 , and terminals  38  are arranged to provide pre-determined electrical continuity in a plurality of switch positions ( FIGS. 9-11 ), i.e. multiple poles/or throws. Stated another way, as the spaced contacts  40  move between the different positions of  FIGS. 9-11 , different harness terminals  38  are opened and/or closed in the switch  10 , dependent on the construct of the PCB  22  and the connections to a wiring harness (not shown), as would be appreciated by those of ordinary skill in the art. 
     In one example embodiment, the PCB  22  can be unpopulated such that the switch  10  provides contact closure, or can be populated to provide an electronic interface, such as open collector input, local interconnect network (LIN), or controller area network (CAN) bus, and the like. The PCB  22  in yet another example embodiment supports a light emitting diode (LED) to provide an indication for switch position or machine state. In the illustrated example embodiment, the LED emits light through any combination of light pipes  52 ,  54 , that are fixedly positioned within the active sealing arrangement  16 . In one example embodiment, the light pipes  52 ,  54  are cylindrical translucent plastic rods. 
     It should be appreciated by those skilled in the art that the plunger switch assembly  10  in one example embodiment has a plurality of momentary and non-momentary positions. For momentary positions, cantilever supports  56  keep the switch  10  in the non-momentary position or second position, as illustrated in  FIG. 10 . The second or non-momentary position is located between a down or first position shown by arrow A in  FIG. 9  and an up or third position illustrated by arrow A in  FIG. 11 . During movement of the switch assembly  10  between first and third positions, moving components  60  are translated comprising the knob  12 , bellows  50 , actuator assembly  20 , contact bridge  24 , contacts  40 , and fastener  32 . 
     In the non-momentary position, the cantilever supports  56  are supported by biasing members  28 ,  30 , to limit vibration/bounce until an external force is applied (by a user translating the knob  12  in either the first or third directions), which results in a deflection of the supports  56 . The moving components  60  and particularly the cantilever supports  56  are returned to the non-momentary or second position upon removal of the external force. 
     Thus, as the moving components  60  are translated between the first and second positions, the desired state of the switch  10  is changed, i.e. from open, closed etc. The construct of the switch assembly  10 , and particularly the biasing members  28 ,  30  and their arrangement and support of the leads  40  that engage the PCB  22 , minimizes vibration to the switch and advantageously adds to a longer life cycle of the electrical components associated with the PCB. Such construction also limits oscillation and unintended actuation of the switch  10 . 
     As the bridge contact  24  moves, the leads  40  engage and/or disengage traces  36  on the PCB  22  that is fixed in the base  26 . The traces  36  are in communication with terminals  38  that are electrically coupled to a wiring harness (not shown) as the knob  12  moves between the positions of  FIGS. 9-11 . The contact bridge  24  is connected by the fastener  32  to a threaded connection or tapped opening in the bottom of a post  42  molded into the knob  12 . The fastener  32  passes through the bridge contact  24 , contact support  34 , and an aperture  44  located in a bottom portion  46  and extending opposite to an upper portion  48  of a bellows  50 . 
     In an alternative example embodiment, the aperture  44  stretches to surround and fixedly attached to the post  42  in a compression fit of the bellows  50  about the post. Thus, in such an example embodiment, the need for the fastener  32  for attaching the bellows  50  to the post  42  is avoided. 
     Biasing members  28  are retained by spaced cantilever supports  56  and upper and lower rods  62  molded within the housing  18  and base  26 . While biasing members  30  are supported by sleeves  64  projecting from the base  26  and surround cantilever supports  56 . 
     Conventional plunger switches are prone to ingestion of water and debris. This presents problems when the wetting current is below one (1) amp (A), as second-generation plungers switches are being designed to operate with lower power requirements. At wetting currents below one (1) amp (A), break through contact with the presence of debris typically increases failure rates in conventional switches. Thus, the need for better sealing constructions in second-generation plunger switches to resist the infiltration of debris and water. 
     As such, the plunger switch assembly  10  provides environmental sealing capability through the active sealing arrangement  16  to keep the electrical components, including the PCB  22  and contacts  36  advantageously free from water and debris for low amperage (one (1) amp (A)) applications of the present disclosure. In particular, the design of the active sealing arrangement  16  is constructed to keep the electrical components within the housing  18  environmentally sealed by being expandable and adaptable to interface with low current applications, such as CAN or LIN bus systems. 
     In the example embodiment of  FIGS. 12-18 , the active sealing arrangement  16  includes a substantially planar member  66  having upper and lower planer sides  68 ,  70 , respectively. Supported substantially symmetrically within the planar member  66  is the bellows  50  that extends from the upper side  68  through the planer member and out the lower side  70 . In the illustrated example embodiment, the active sealing arrangement  16  that comprises bellows  50  are made from a polymer such as a thermoplastic elastomer (TPE) or thermoset material, an elastomeric material such as silicone rubber, natural rubber, or other sealing material having similar flexibility and sealing properties. 
     The active sealing arrangement  16  provides a seal between two halves of the housing  18  plunger switch assembly  10 . In particular, the active sealing arrangement  16  seals in addition to the connection between the housing  18  and the carriage  14 , it actively seals the connection between the plunger knob  12  and the contact carrier or support  34 . During assembly, the active sealing arrangement  16  is sandwiched between a top surface  72  on the housing  18  and an inner surface  74  of the carriage  14 . The lower planar surface  70  engages the top surface  72  and the upper planar surface  68  contacts the inner surface  74 . Bellows  50  of the active sealing arrangement  16  partially passes through an opening  76  found in the top surface  72  of the housing  18 . Light pipes  52 ,  54  orient the seal  16  and project through corresponding receiving holes  78 ,  80  in the top surface  72  and receiving holes  82 ,  84  in passing through the carriage  14 . 
     The bellows  50  is adaptive and expandable because it changes shape based on the position of the moving components  60  and the location of the knob  12 , as illustrated in  FIGS. 9-11 . In  FIG. 13 , the construct of the bellows  50  demonstrates that its end  90  (shown in phantom originally as a coned shaped bellows) is rolled inward in the direction of arrows R through the central aperture  44  until being positioned at a location beneath the planar member  66 , forming rolling end  92 . The planar member  66  includes a clearance opening  94  that allows the bellows  50  to pass back and forth through the planar member without interference. 
     Located at the bottom portion  46  of the bellows  50  and within the central aperture  44  is an annular flange  96 . The annular flange  96  is pinched between a bottom  98  of the post  42  and a plate  100  supporting the cantilever members  56  of the contact support  34 . In one example embodiment, the active sealing arrangement  16  that includes bellows  50  and light pipes  52 ,  54  is molded as a single unitary member. In an alternative example embodiment, the bellows  50  and light pipes  52 ,  54  are separately molded and secured into the planar member  66 . 
     The active sealing arrangement  16  construction and method of operation as discussed below, advantageously in addition to providing enhanced sealing protection from contaminates, reduces the activation force required to operate the plunger switch assembly  10  when compared to a traditional seal such as an o-ring. This is because the active sealing arrangement  16  advantageously moves with the post  42 , knob  12 , and moving components  60  instead of having a friction engagement required by an o-ring sealing connection. 
     During operation, the active sealing arrangement  16  is active because it both expands and contracts in the same direction but opposite the planar member  66 . That is, if the plunger switch assembly  10  (and moving components) is being actuated to the first position (downward as shown by arrow A in  FIG. 9 ), the bellows  50  is expanded (downwardly) below the planar member  66  and contracted (downwardly) above the planar member as illustrated by arrows L 1  and U 1 , respectively in  FIG. 17 . Alternatively, if the plunger switch assembly  10  is being actuated to the third position (upward as shown by arrow A in  FIG. 11 ), the bellows  50  is contracted (upwardly) below the planar member  66  and expanded (upwardly) above the planar member as illustrated by arrows L 3  and U 3 , respectively in  FIG. 18 . As can be seen in  FIGS. 9-11 , the active sealing arrangement  16  rolls inside the central aperture  44  during a downward motion and outside the central aperture during an upward motion of the moving components  60 . 
     In one example embodiment, the bellows  50  and its active movement is fixed within the planar member  66 . That is, the bellows as it moves from various positions shown in  FIGS. 9-11 and 17-18 , its outer diameter remains stationary at the planar member  66 . 
     As used herein, terms of orientation and/or direction such as upward, downward, forward, rearward, upper, lower, inward, outward, inwardly, outwardly, horizontal, horizontally, vertical, vertically, distal, proximal, axially, radially, etc., are provided for convenience purposes and relate generally to the orientation shown in the Figures and/or discussed in the Detailed Description. Such orientation/direction terms are not intended to limit the scope of the present disclosure, this application and the invention or inventions described therein, or the claims appended hereto. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.