Abstract:
A latch for an appliance or the like provides a floating bolt assembly spring biasing a door against a sealing gasket in different positions depending on gasket compliance. A lock provides a stop that may adjustably bridge a distance between the latch frame and the floating bolt assembly as the gasket ages thereby providing positive locking of the door over the life of the appliance.

Description:
RELATED APPLICATIONS 
     The present application is based on International Application Number PCT/US2008/064506 filed May 22, 2008, and claims priority from U.S. Provisional Application No. 60/939,958 filed May 24, 2007, the disclosures of which are hereby incorporated by reference herein in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Background of the Invention 
     The present invention relates to a latching mechanism for doors on household appliances and particularly to locking latching mechanisms that accommodate changes in the compression of a door gasket. 
     Appliances such as dishwashers and front-loading washing machines may have an access door with a gasket that must be compressed to seal water within a washing chamber. Small area, highly compliant gaskets may be sealed by pressure from the user during the closing of the door. The gasket may then be held in a compressed state by a latch mechanism. 
     Gaskets that require more force may be compressed by a latch mechanism having a lever operated by the user to engage a catch and draw the catch inward with a lever advantage to compress the gasket and hold the door shut. 
     A closing lever may be avoided in latch mechanisms that provide an “over-center” spring mechanism. During initial stages of closing of the door, closing force on the door is used to energize a spring. When the door closes past the over-center point, the spring releases its energy in a manner to pull the door fully closed. An example of an over-center spring mechanism is described in U.S. Pat. No. 4,497,513 to Sasaki. 
     A variation on the over-center spring mechanism stores energy in a spring as the door is opened and holds that energy until the door is closed again. An over-center design is still employed and therefore a slight compression of the spring is required when the door is closed to release the energy. A latch of this kind is disclosed in U.S. Pat. No. 2,833,578 to Burke. 
     U.S. Pat. No. 6,290,270 to Spiessl shows a variation on Burke in which the latch spring is compressed when the door is opened and this energy is released when the door is closed, assisting the user in compressing the door gasket. In this design, the latching mechanism “floats” on a spring-loaded lever to accommodate aging of the gasket. As the gasket ages and compresses more, the latching mechanism moves further “inboard” on the spring-loaded lever to ensure complete closure. 
     U.S. Pat. Application No. 2005/0194795 to Hapke, assigned to the assignee of the present invention and hereby incorporated by reference, teaches an improvement on the Spiessl design that employees a sliding carriage in lieu of the lever. The carriage allows the spring force to be more evenly distributed permitting increased use of molded thermoplastic rather than metallic components. 
     Modern appliances may require locking of the appliance door during certain stages of the washing cycle, for example, when it is likely that opening the door would release water or present a hazard to the user. The Hapke application teaches implementing a lock in an appliance latch by using a stop connected to a bi-directional solenoid. The bi-directional solenoid has one coil for moving a stop to block opening of the latch and a second opposed coil for retracting the stop to release the latch. The Hapke and Spiessl latches release by movement of the floating latch mechanism “outboard” toward the door. Thus, the latch may be locked simply by blocking this movement with a stop positioned between the floating latch mechanism and a fixed frame member. 
     In the “floating” latch designs described above, where the latch mechanism moves as the gasket ages, a locking stop must be positioned so that it will engage and thus block the latch mechanism when the gasket is new and the latch mechanism floats in an extreme “outboard” position. As the gasket ages, this stop location allows a slight opening of the door that could permit water leakage around the aged gasket. 
     SUMMARY OF THE INVENTION 
     The present invention provides a stop mechanism that automatically accommodates inboard movement in “floating” latch mechanisms as the gasket ages by variably bridging different axial separations between the latch frame and the floating carriage. In a preferred embodiment this stop is wedge-shaped so that lateral motion can bridge any given axial separation distance. 
     In another embodiment, the present invention provides an improved hook cam designed for such floating latch mechanisms. The hook cam must be rotated to release the latch against a frictional contact between the hook cam and a stationary pin. In this embodiment, the hook cam provides an actuation lever having an extended lever arm that reduces the force needed to rotate the hook cam. A slider element allows the extended lever arm to be actuated by the latch strike, the latter which must be close to the center of the hook cam in order to engage with the hook. 
     The present invention further provides an actuator for a locking stop that employs a single acting solenoid to both lock and unlock the latch without consuming power when the latch resides in either the locked or unlocked state. 
     Specifically then, the invention may provide a locking appliance latch for receiving a strike to hold a gasketed door closed. The latch includes a latch frame attached to the appliance supporting a carriage spring-biased in a door closing direction. A bolt (for example, a rotating hook) held by the carriage may releasably engage a strike (for example, a U-shaped loop) to pull the door against the gasket. A stop may be moved to a lock position to bridge a separation distance between the carriage and latch frame for a range of distances between the carriage and the latch frame. An electric actuator moves the stop between the lock position and an unlocked position removed from bridging the carriage and latch frame. 
     It is thus an object of at least one embodiment of the invention to provide a stop for a floating latch design that prevents leakage as a gasket ages when the locked door is pulled. 
     The stop may be a wedge laterally movable in a direction perpendicular to an axial separation between the carriage and latch frame to bridge the distance between the carriage and latch frame for the range of axial distances. 
     It is thus an object of at least one embodiment of the invention to provide a simple adjustment mechanism that employs lateral movement to change an effective axial stop width. 
     The wedge may include a set of teeth engaging corresponding teeth on an opposed a wedge on the carriage. 
     It is thus an object of at least one embodiment of the invention to eliminate the need for high contact forces between the wedges as would be required if one were to rely on frictional resistance to sliding. 
     The teeth may have lateral faces. 
     It is thus an object of at least one embodiment of the invention to permit substantially zero force engagement and disengagement between the stop and carriage. 
     The lateral motion may be provided by rotary motion of a stop support. 
     It is thus an object of at least one embodiment of the invention to provide an extremely compact stop system. 
     The stop may provide multiple wedges rotatable about a common center to laterally engage corresponding wedges on the carriage to bridge the axial separation between the carriage and latch frame for the range of axial separations. 
     It is thus an object of at least one embodiment of the invention to permit the present device to be manufactured of moldable thermoplastic material by distributing the stop forces among multiple stops. 
     The spring biasing may be provided by a single helical spring surrounding the bolt and strike when the bolt and strike are engaged. 
     It is thus an object of at least one embodiment of the invention to provide a spring distributed over a broad area and thus suitable for use with thermoplastic components. 
     The stop may attach to the carriage when in the locked position to move with the carriage, without further lateral engaging motion away from abutment with the latch frame when the carriage moves in the door opening direction. 
     It is thus an object of at least one embodiment of the invention to prevent increasing the bridging separation provided by the stop (and the forces necessary to release the stop) if the door is pressed inward when the door is in a locked condition. 
     The invention may provide a guide track returning the stop to abutment with the latch frame when the stop is moved to the unlocked position. 
     It is thus an object of at least one embodiment of the invention to ensure disengagement of the stop in the unlocked condition. 
     The carriage and the stop may be constructed of moldable thermoplastic. 
     It is thus an object of at least one embodiment of the invention to produce a design suitable for use with thermoplastic materials subject to cold flow and strength limits. 
     In one embodiment, the invention may provide the appliance latch with a floating carriage supported by a latch frame and spring biased in a door closing direction. A bolt held by the carriage may releasably engage a strike to pull a door against a gasket under the spring biasing of the carriage. The bolt may provide a rotating hook having: (a) a hook portion for engaging the strike; (b) a constant radius portion abutting a stop fixed to the latch frame before the hook portion engages the strike to hold the carriage against its spring biasing with a biasing spring under compression; (c) an actuation arm rotating the bolt through force applied at a first point on the actuation by closing of the door, the first point on the actuation arm being outside of a second point of contact between the strike and the latch measured from a pivot point of the bolt. 
     It is thus an object of at least one embodiment of the invention to reduce the force necessary to close the door. 
     The latch may include a sliding element contacting the strike at a first point and contacting the actuation arm at a second point. 
     It is thus an object of at least one embodiment of the invention to allow the rotating force to be applied by the strike itself, even though the strike must be close to the hook cam to be engaged by the hook cam. 
     The bolt may be a moldable thermoplastic. 
     It is thus an object of at least one embodiment of the invention to provide a mechanism of reducing closure forces suitable for use with thermoplastic components. 
     In one embodiment, the invention may provide a locking appliance latch having a bolt assembly to engage a strike by moving from a first position to a second position and to release the strike by moving from the second position to the first position. A stop is provided that may move to a locked position to block movement of the bolt assembly from the second position to the first position, thereby to lock the latch, and which may further move to an unlocked position allowing movement of the bolt assembly from the second position to the first position, thereby to unlock the latch. 
     The stop may be driven by an actuator assembly moving the stop between the locked and unlocked position. The actuator assembly may include an electrical solenoid, energizable to provide an actuation force in only a single direction, attached to a bi-stable mechanical linkage positioned between the electrical solenoid and the stop. The bi-stable mechanical linkage operates to move the stop to the locked position with an initial actuation force/release and to move the stop to the unlocked position with a subsequent actuation force/release. 
     It is thus an object of at least one embodiment of the invention to permit a single solenoid to provide both unlocked and locked states of the stop without requiring power consumption in those states after the state transition is complete. 
     The bi-stable mechanical linkage may be a cardioid track traversed by a follower where one of the track and follower is fixed with respect to the latch frame. 
     It is thus an object of at least one embodiment of the invention to provide a compact mechanism that may be integrally molded into the components without substantially increasing the parts count. 
     The follower may be a ball held in a second track perpendicular to the actuation direction. 
     It is thus an object of at least one embodiment of the invention to provide a simple follower mechanism that may float within the tracks. 
     The invention may further include a spring biasing the solenoid in a direction opposed to the actuation force, and the bi-stable mechanism may control a spring biasing of the stop allowing the stop to be mechanically decoupled from the bi-stable mechanism. 
     It is thus an object of at least one embodiment of the invention to provide movement of the stop that may change depending on the separation between the floating carriage and the latch frame. 
     The bi-stable mechanism may be further coupled to a switch contact. 
     It is thus another object of at least one embodiment of the invention to provide an electrical indication of the state of the latch as locked or unlocked. 
     The solenoid may provide an extension of an operator with energizing of the solenoid. 
     It is thus an object of at least one embodiment of the invention to use a push type solenoid to eliminate interference with electrical contacts indicating the state of the switch. 
     These particular features and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a simplified perspective view of an appliance suitable for use with the present invention showing the appliance door and one possible location of the latch elements; 
         FIG. 2  is side elevational cross-section through a latch of the present invention showing a floating carriage forming part of the latch as positioned before receiving a strike to hold the door shut; 
         FIG. 3  is a figure similar to that of  FIG. 2  showing the configuration of the floating carriage after receiving the strike and holding the door closed; 
         FIG. 4  is an exploded perspective view of the floating carriage as biased by a helical spring that may surround the strike; 
         FIG. 5  is a plan view of the floating carriage in partial cut away to show inter-engaging ramps of a lock mechanism; 
         FIGS. 6   a - 6   c  are simplified representations of the ramps of  FIG. 5  for two states of gasket aging and under compression of the door after locking, respectively; 
         FIG. 7  is a front elevational view of the floating carriage positioned above a stop support next to an actuating mechanism implementing the lock of  FIG. 5 ; and 
         FIGS. 8   a - 8   d  are transparent views through a bi-stable element of the actuating mechanism shown in four stages of actuation depicted next to representations of the actuating solenoid and its operator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , an appliance  10  such as a washing machine may have a cabinet  12  opening along a front face to provide access to dishes within the interior of the cabinet  12 . The front face may include a gasket  14  that is compressed with closure of a door  16  sized to cover the front face of the cabinet  12  to prevent access to its interior during operation and to prevent leakage of water during the wash cycle. 
     The door  16  may be hinged, for example, at a side edge and the opposite side edge held closed by means of a latch  18  held in the cabinet  12  and receiving a strike  15  attached to the door and extending toward the front face of the cabinet  12 . It will be understood generally that the positions of the strike  15  and latch  18  may be reversed. 
     Referring now to  FIGS. 1 and 2 , the latch  18  may include a floating carriage  22 , preferably molded of thermoplastic, and movable along an axis  24  along a direction of opening of the door  16  under the restraint of guide surfaces (not shown). The floating carriage  22  supports a hook cam  30  at its center, the hook cam  30  rotating about a pivot axis  33  generally perpendicular to the door-opening axis  24 . The hook cam  30  may be molded of a self-lubricating thermoplastic. 
     Referring momentarily also to  FIG. 4 , the floating carriage  22  may be biased by a helical spring  26  applying a force on the floating carriage  22  directed generally inboard  28 . The helical spring  26  may have sufficient diameter to fully surround the strike  15  and the hook cam  30  and may fit partially within a receiving circular slot  54  cut in the periphery of the floating carriage  22 . 
     Referring now to  FIG. 2 , the hook cam  30  may include a hook portion  32 , a constant radius portion  36 , and an actuation arm  38 . Before the strike  15  is received by the hook cam  30 , the constant radius portion  36  abuts a stop  40  affixed to a latch frame  41  and generally fixed with respect to the cabinet  12 . This abutment prevents inboard motion of the floating carriage  22 . 
     The actuation arm  38  of the hook cam  30  is held by a slider  44  sliding along axis  24  as retained by the floating carriage  22  where it contacts the slider  44  at contact point  46 . A front surface of the slider  44  extends radially inward from the outer periphery of the floating carriage  22  to a point closer to the pivot point  33  where it may contact the strike  15  at a contact point  48  closer to the pivot point  33  than is the contact point  46 . Thus, the slider  44  allows the force of the strike  15  to be applied along a relatively greater lever arm distance  50  of the actuation arm  38  (between point  46  and pivot point  33 ) than the lever arm distance  52  provided by direct contact between the strike  15  and the hook cam  30  (between point  48  and pivot point  33 ). Note that the strike  15  must remain relatively close to the pivot point  33  so as to be engaged by the hook portion  32  as will now be described. 
     Referring to  FIG. 3 , as the strike  15  moves inward, it presses the slider  44  inboard which presses on the actuation arm  38  rotating the hook cam  30  in a counterclockwise manner so that hook portion  32  engages the strike  15  capturing it. This rotation causes the constant radius portion  36  of the hook cam  30  to move beyond the stop  40  allowing the floating carriage  22  to move inboard under the influence of the helical spring  26 . It will be understood that the released energy from the helical spring  26  provides a compression of the door against the gasket (as shown in  FIG. 1 ) and also allows greater amounts of inboard movement of the floating carriage  22  as the gasket ages. 
     The present invention incorporates by reference the disclosure of U.S. patent application 2005/0194795 to Kenyon A. Hapke et al., filed Sep. 8, 2005 and entitled: “Appliance Latch Having a Rotating Latch Hook Mounted on a Linear Slide” which describes an analogous locking system. 
     Referring now to  FIGS. 3 and 5 , it will be understood that the latch  18  may be locked by preventing motion outboard  56  by the floating carriage  22  sufficient to allow the hook cam  30  to move beyond the stop  40  thereby allowing clockwise rotational of the hook cam  30  to release the strike  15 . In a preferred embodiment of the present invention, this blocking is accomplished by two mechanisms, first, a series of ramps  60  extending outboard from an underside of the floating carriage  22  and arranged generally at a constant radius about the center  72  of the floating carriage  22  as shown in  FIG. 7 . A face of each ramp  60  is sloped with respect to axis  24  and may have a set of teeth  62  having lateral faces  64  (perpendicular to axis  24 ) joined by oblique faces  66 . These teeth  62  match corresponding teeth  62 ′ on a series of corresponding stop ramps  68  attached to a stop support  70  and extending inboard  28 . Rotation  74  (shown in  FIG. 7 ) of the stop support  70  along a face of the frame  41  about the center  72  provides lateral motion that allows engagement or disengagement of the teeth  62 ,  62 ′ for the multiple ramps  68  and  60 . The stop support  70  and stop ramps  68  may be molded of thermoplastic material. 
     The second mechanism is a pre-stop  61  extending inboard from the stop support  70  and moving with rotation of the stop support  70  out of alignment with notches  63  on a lip of the floating carriage  22  to block its outboard motion. The pre-stop  61  positively locks the latch  18  but does not provide the gasket compensation provided by the ramps  60  and  62  as will now be described. 
     Referring now to  FIGS. 1 and 6   a , when the gasket  14  is new, ramps  60  engage ramps  68  with substantial overlap  76  because of the relatively outboard position of ramps  60  caused by the new gasket. In contrast, as shown in  FIG. 6   b  as the gasket  14  ages, the overlap  76  decreases caused by shrinkage or reduced elasticity of the gasket  14 . In either case, however, the overlap is sufficient to fully engage multiple of the teeth  62 ,  62 ′ preventing further outward motion of the door  16  once the latch has been locked thus eliminating the possibility of leakage if the door is inadvertently pulled. 
     Referring now to  FIGS. 1 and 6   c , in the event that the door  16  is pushed inboard after the stop ramps  68  are engaged with the ramps  60 , teeth  62 ,  62 ′ ensure that the ramp  68  is pulled along with ramps  60  causing stop support  70  to be pulled away from the frame  41  accommodating this movement, and increased compression of the gasket  14  without allowing additional lateral motion of the stop support  70  or a decreasing of the overlap  76 . In this way, increased forces between ramps  68  and  60  are avoided when the inboard force on the door  16  is released and stop support  70  abuts frame  41  again. Such increased force could prevent disengagement of the stop ramps  68  by the actuating mechanism as will be described below. 
     A guide track  39  returns the stop support  70  to abutment with the frame  41  after this inboard force when the stop is rotated to an unlocked position. 
     Referring now to  FIG. 7 , rotation of the stop support  70  about center  72  is provided by means of a single acting push solenoid  80  having an operator  81  moving a bi-stable mechanism  82  along actuation axis  84 . As is understood in the art, the push solenoid  80  when energized extends its operator  81  and when de-energized provides no force on the operator  81  allowing it to remain where it is or be pulled back by a spring bias or gravity 
     The bi-stable mechanism  82  provides an upwardly extending peg  86  that may abut an ear  88  (also shown in  FIG. 5 ) attached to the stop support  70 , pushing the stop support  70  in a clockwise direction when the bi-stable mechanism  82  moves upward along axis  84  with extension of operator  81 . This clockwise motion is such as to disengage ramps  60  from stop ramps  68  with positive abutment of the peg  86  and ear  88 . 
     On the other hand, the peg  86  may pull away from the ear  88  when the operator  81  retracts allowing the amount of rotation of the stop support  70  to vary as defined by engagement of the ramps  60  and  68  and the axial separation of the floating carriage  22  from the frame  41 . A retraction spring  90  is attached to the ear  88  at attachment point  93  to provide a counterclockwise rotational bias to the stop support  70 . 
     The bi-stable mechanism  82  may communicate directly with electrical contacts  92  that provide an indication of the state of lock or unlock of the latch  18 . In a preferred embodiment, however, electrical contacts  92  are activated by a cam surface  95  extending radially from the stop support  70  to rotate therewith. The cam surface  95  activates a cam follower  98  activating the electrical contacts  92  allowing them to close when the latch  18  is locked. 
     Generally, the bi-stable mechanism  82  moves between an upward position (as shown in  FIG. 7 ) disengaging the ramps  60  and  68  and a lowered position allowing engagement of the ramps  60  and  68  for every two cycles of energizing and de-energizing push solenoid  80 . When push solenoid  80  is not energized, the bi-stable mechanism  82  remains in its last position (up or down) without the need for continued application of power to a coil of the push solenoid  80 . 
     Referring now to  FIG. 8   a , bi-stable mechanism  82  provides a linear slot  100  on its undersurface (shown in phantom in  FIG. 8   a ) holding a steel ball  102  that may move left and right within the linear slot  100 . The steel ball  102  is also partially held within a cardioid track  104  formed by an upper face of the frame  41  abutting the undersurface of the bi-stable mechanism  82 . As shown in  FIG. 8   a , when solenoid  80  is de-energized with operator  81  extended, the ball  102  may rest between the two shoulders of the cardioid of cardioid track  104  trapped by the downward force of the spring  90  (shown in  FIG. 7 ) and holding the bi-stable mechanism  82  in its upward state disengaging ramps  60  and  68  (shown in  FIG. 5 ). No power needs to be applied to the coil of solenoid  80  to stably retain this state. It will be understood that the positions of the linear slot  100  and cardioid track  104  may be reversed with the cardioid track  104  on the undersurface instead of the linear slot  100 . 
     Referring now to  FIG. 8   b , when push solenoid  80  is next activated further extending operator  81 , the ball  102  is forced upward into the left shoulder of the cardioid and moved slightly leftward from its previous position. 
     When the push solenoid  80  is deactivated the ball  102  may fall under vertical gravitational attraction and the influence of the track  100  along a left side of the cardioid track  104 , allowing the bi-stable mechanism  82  to drop downward and allowing the ramps  60  and  68  to engage. In this lower state, again, no power need be applied to the push solenoid  80 . 
     Referring now to  FIG. 8   d , when the push solenoid  80  is energized for a second time, operator  81  extends upward allowing the ball  102  to pass up the right side of the cardioid track  104 . When power is released from the push solenoid  80 , the ball  102  will drop into its position shown in  FIG. 8   a  and the cycle will be complete and repeatable. Thus, a single push solenoid  80  may provide for two states of lock and unlock without requiring power when those states have been attained. 
     It will be understood that elements of these particular embodiments may be mixed and matched. Thus, for example, the adjustable stop system of  FIGS. 5 and 6   a - 6   c  (embodiment A) may be used with or without the increased lever provided by the actuation arm on the hook cam of  FIGS. 2 and 3  (embodiment B) and the bi-stable actuator of  FIGS. 7 ,  8   a - 8   d  (embodiment C), each of which may also be used alone or in combination with the other embodiments. 
     Further, 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 is also 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.