Abstract:
A door locking mechanism for an appliance provides a bolt that may be moved by an actuator between an extended and retracted position. A bolt stop mechanism blocks movement of the bolt in retraction at one of two positions, depending on how the bolt was extended before the retraction. In this way the bolt automatically retracts when the door is not present because this causes extra extension of the bolt and an over-travel position need not be directly sensed reducing controller complexity or wiring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application 61/711,418 filed Oct. 9, 2012 and hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to clothes washing machines and the like and specifically to a door locking mechanism. 
       BACKGROUND OF THE INVENTION 
       [0003]    The spin cycle of a washing machine removes water centrifugally from wet clothes by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user during the spin cycle, it is known to use an electronically actuated lock for holding the washing machine door in the closed position. 
         [0004]    U.S. Pat. Nos. 6,363,755; 5,823,017; and 5,520,424, assigned to the present assignee and hereby incorporated by reference, describe several locking mechanisms. Desirably, the locking mechanism minimizes projecting parts on the washing machine door which might snag clothing or reduce access to the spin basket, and is simply integrated into the washing machine housing. 
         [0005]    A signal indicating the state of the washing machine door as opened or closed may be used to ensure the door is closed before the lock bolt is engaged. Such a signal may be provided by a switch communicating with the washing machine door. Ideally such a switch could not be easily defeated, would operate reliably when used with other washing machine components with normal manufacturing tolerances, and would be resistant to contamination by water and dirt. 
         [0006]    U.S. Pat. No. 7,493,783, hereby incorporated by reference, describes a door lock that can sense whether the door is closed by distinguishing between an “over-travel” position of the bolt that can occur when the bolt is extended and the door is up and so does not block the extension of the bolt, and an “engagement” position of the bolt that occurs when the door is down and the bolt is received by the door blocking overextension of the bolt. An appliance controller, by distinguishing between three electrical signals indicating, respectively, the unlock position, the over-travel position, and the lock position, can determine that the door is properly locked with the bolt engaging the door. 
         [0007]    Many existing controllers do not have the capability to accommodate additional signals and respond to those signals by retracting the lock. Alternatively, it may be desirable to avoid the extra wiring necessary to communicate an over-travel position to the appliance controller. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides an improved bolt actuator that can eliminate the need to sense and react to the over-travel position thereby allowing it to be used in conventional washing machine control systems without the need for extra wiring to communicate an over-travel signal. Under a proper sequence of bolt movements to lock the door, the bolt will rest at a lock position only when the door is closed and otherwise will rest at the unlock position. In this way, conventional control signals may be accommodated. In addition, the use of only two signals may reduce wiring between the controller and the lock. 
         [0009]    Specifically then, the present invention provides an electric lock for a household appliance having a door that may be locked when the door is in a closed position by receipt of a bolt extending from an appliance frame to be received by the door in the closed position. The electric lock includes a lock housing fixable to the appliance frame and a bolt attached to be movable with respect to the housing to extend outward to a lock position when the door is closed and to retract inward to an unlock position when the door is closed allowing the door to move the open position. An actuator system communicates with the bolt to alternately urge the bolt toward the lock position and the unlock position based on at least one signal received from an external appliance control. A bolt stop mechanism communicates with the bolt to block movement of the bolt against retraction at one of the lock and unlock positions depending on and immediately preceding the extension of the bolt. 
         [0010]    It is thus a feature of at least one embodiment of the invention to provide a door-sensing lock that automatically retracts the bolt when the door is not closed. In this way additional signals and/or additional control logic is not required of the appliance controller. 
         [0011]    The bolt may extend to an over-travel position when the door is not in the closed position and to the lock position having less extension than the over-travel position when the door is in the closed position and the bolt stop mechanism may block movement of the bolt in retraction at one of the lock and unlock positions depending on whether the bolt moved to the locked or over-travel position in the immediately preceding extension of the bolt. 
         [0012]    It is thus a feature of at least one embodiment of the invention to sense the position of the door without the need for additional sensors by using bolt extension distance. 
         [0013]    The bolt stop mechanism may block movement of the bolt in retraction at the lock position when the door blocks a previous travel of the bolt in extension and the bolt stop mechanism blocks movement of the bolt at the unlock position when the door does not block a previous travel of the bolt in extension. 
         [0014]    It is thus a feature of at least one embodiment of the invention to allow a locking position of the bolt only when the door is closed and otherwise to automatically retract the bolt. 
         [0015]    The lock may further include contacts providing an electrical signal uniquely identifying that the bolt is in the lock position. 
         [0016]    It is thus a feature of at least one embodiment of the invention to provide a traditional “lock” signal used by most controllers to control operation of the appliance. 
         [0017]    The contacts may provide only an electrical signal uniquely identifying that the bolt is in the lock position and not distinguishing whether the bolt is in an over-travel position or unlock position. 
         [0018]    It is thus a feature of at least one embodiment of the invention to reduce the cost of the wiring harness between the lock and the controller by simplifying the signals that need to be communicated therebetween. 
         [0019]    Alternatively, the contacts provide a second electrical signal uniquely identifying that the bolt is in the unlock position. 
         [0020]    It is thus a feature of at least one embodiment of the invention to provide a flexible design that can provide for additional unlock confirmation together with automatic bolt retraction. 
         [0021]    The bolt stop mechanism may be a track and track-follower together providing bi-stability with successive cycles of extension and retraction when the bolt is blocked by the door and providing monostability with successive cycles of extension and retraction when the bolt is not blocked by the door. 
         [0022]    It is thus a feature of at least one embodiment of the invention to provide a simple mechanical element that implements the necessary logic of automatically retracting the bolt if the door is not in position. 
         [0023]    The follower is a tip of a flexible spring. 
         [0024]    It is thus a feature of at least one embodiment of the invention to provide a mechanism that does not require particular orientation for proper operation of the bi-stable mechanism. 
         [0025]    The track may be on the bolt. 
         [0026]    It is thus a feature of at least one embodiment of the invention to take advantage of the extent of the bolt by incorporating a portion of the mechanism into the bolt itself. 
         [0027]    The actuator system may include an electric motor. 
         [0028]    It is thus a feature of at least one embodiment of the invention to provide a rapid low noise actuation compatible with the bi stable mechanism. 
         [0029]    The motor may be a DC permanent magnet motor. 
         [0030]    It is thus a feature of at least one embodiment of the invention to provide a simple method of providing the two directions of actuation required of the bolt stop mechanism, for example, by reversing the polarity to the motor. 
         [0031]    The motor may communicate with the bolt by a pinion gear on a shaft of the motor engaging a rack on the bolt. 
         [0032]    It is thus a feature of at least one embodiment of the invention to provide a motor with the linear conversion mechanism providing sufficient mechanical advantage to prevent motor cogging. 
         [0033]    The electric lock may further include a door sensor sensing whether the door is in the closed position independent of the bolt position. 
         [0034]    It is thus a feature of at least one embodiment of the invention to permit the detection of door position during periods when the lock is not to be actuated, for example, to control the filling cycle in response to the door being open. 
         [0035]    These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 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 
         [0036]      FIG. 1  is a perspective view of a top loading washing machine suitable for use with the present invention showing a strike opening on a side of the opened door of the washing machine and a bolt for engaging the same when the door is closed; 
           [0037]      FIG. 2  is a fragmentary cutaway of the portion of the door and washing machine near the bolt of  FIG. 1  showing support of a locking mechanism beneath a door well; 
           [0038]      FIG. 3  is a simplified top plan view of the bolt of  FIG. 2  extending through a wall of the door well to engage a strike of the door and illustrating an unlock position, lock position, and over-travel position of the bolt and further showing corresponding states of an electrical switch connected to the bolt providing unique indications of whether the bolt is in any of the three positions of unlock, lock, and over-travel; 
           [0039]      FIG. 4  is a perspective view viewing an underside of the bolt showing an electric motor and rack and pinion mechanism for extending and retracting the bolt and showing a cardioid track and wire-follower controlling a resting position of the bolt depending on a presence or absence of the door and showing the electrical switch communicating with the bolt for detecting bolt position; 
           [0040]      FIG. 5  is a fragmentary top view of the electrical switch of  FIG. 4 ; 
           [0041]      FIGS. 6   a - 6   f  are depictions of the cardioid track of the bolt of  FIG. 4  in various positions together providing a diagram of movement of the cardioid track with respect to the wire-follower for two conditions where the door is present or absent and showing states of sensor switches during those movements; and 
           [0042]      FIG. 7  is a detailed perspective view of the ramps and levels of the cardioid track of  FIG. 5  promoting a bi-stable operation. 
       
    
    
       [0043]    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 
       [0044]    Referring now to  FIG. 1 , a top loading washing machine  10  suitable for use with the present invention provides a housing  11  supporting a door  12  opening upward about a horizontal door hinge axis  14 . The door hinge axis  14  is positioned near the top rear edge of the housing  11  of the washing machine  10  so that a front edge  16  of the door  12  may raise and lower to expose and cover an opening  20  in the housing  11  through which clothing may be inserted into a spin basket (not shown). A front-loading washing machine (not shown) is also suitable for use with the present invention as will be apparent to those of ordinary skill in the art. 
         [0045]    The washing machine  10  may include user controls  15 , for example, controlling a cycle operation of the washing machine  10  as communicated with a controller  19 , for example, a microprocessor or the like executing a stored program. The controller  19  may control appliance actuators  21 , for example a spin basket motor, water valves, and the like, which implement the appliance washing functions. The controller  19  may further communicate with an electric lock  23  attached to the housing  11  and serving to lock the door  12  in the closed position under the control of the controller  19  and which may include a door position sensor as will be discussed. 
         [0046]    Referring now to  FIG. 2 , when the door  12  is in the closed position, it may sit within a door well  18  having vertical walls  32  surrounding vertical walls  22  of the door  12  and having a horizontal ledge  17  on which the lower surface of the door  12  may rest. A vertical wall  22  of the door  12  near a front edge  16  of the door  12  provides a strike plate  24  having a bolt hole  26 . 
         [0047]    Referring also to  FIG. 3 , the bolt hole  26  is sized to receive a leading edge  28  of a lateral extension  40  of a bolt  30  passing horizontally along an axis  62  from a housing  25  of the electric lock  23 . The bolt  30  extends from the housing  25  through a vertical wall  32  of the door well  18  opposite the strike plate  24  when the door  12  is closed. When the leading edge  28  of the bolt  30  is engaged in the bolt hole  26 , the door  12  may not be raised vertically as indicated by arrow  36  as a result of the lower edge of the bolt hole  26  interfering with a lower face of the leading edge  28 . 
         [0048]    The leading edge  28  of the bolt  30  may be blocked from further extension by a stop  34  behind the bolt hole  26  when the door  12  is closed. When the door  12  is open, however, the leading edge  28  no longer blocked by the stop  34  may move to an over-extension position as will be described. 
         [0049]    Referring now to  FIGS. 3 ,  4  and  5 , as will be discussed in detail below, the bolt  30  communicates via a side arm  46  (shown schematically in  FIG. 3 ) with a contact set  52 . The contact set  52  provides a two-throw switch in which a pole  54  (attached to the side arm  46 ) interconnects between respective terminals  56   a ,  56   b , and  56   c  fashioned on the upper surface of the printed circuit board  57  fixed with respect to the housing  25 . 
         [0050]    Terminals  56   a  and  56   b  are joined by the conductive pole  54  in a lock position (B) in which the leading edge  28  engages the bolt hole  26  abutting the stop  34  but disconnects between terminals  56   a  and  56   b  and interconnects between respective terminals  56   c  and  56   b  in the unlock position (A) when the leading edge  28  is removed from the bolt hole  26 . In an over-travel position (C) where the leading edge extends beyond the lock position not stopped by the stop  34  when the door  12  is open, the pole  54  connects only to terminal  56   a  Accordingly, the unlock position can be uniquely identified, but the lock position and the over-travel position cannot be positively distinguished by means of signals conveyed over separate conductors  59  attached to terminals  56   a  and  56   c  (and a common conductor attached to terminal  56   b ) conveying two signals of lock signal  96  and unlock/over-travel signal  91 . 
         [0051]    Referring now to  FIG. 4 , the bolt  30  may be driven along axis  62  by means of a rack gear  64  position on a lower surface of the bolt  30  driven by a pinion gear  66  turned by a DC permanent magnet motor  68  attached to the housing  25 . The arm  46  communicating between the bolt  30  and the contact set  52  may extend from a lower surface of the bolt  30  and pass in cantilevered fashion under a pole support element  70 , the latter of which passes upward through a slot  50  in the printed circuit board  57  to join with the pole  54  of the contact set  52  described above. 
         [0052]    A cardioid track  72  may be provided by means of a groove on the under surface of the bolt  30  to the side of the rack gear  64 . An upwardly extending pin  74  being part of a wire form  75  may flex laterally generally perpendicular to axis  62  but may be relatively inflexible along axis  62  with respect to the housing  25 . The pin  74  may fit in the groove of the cardioid track  72  to constrain motion of the bolt  30  with respect to the housing  25  as driven by the motor  68  as will be described below. 
         [0053]    When the motion of the bolt  30  is constrained by the pin  74  (or by stop  34  in the door shown in  FIG. 3 ) the motor  68  may simply stall for a short period of time and is current limited (for example, by internal resistance) to allow the stall condition to be accommodated. In this way the motor  68  may be driven in an “open-loop fashion” by an appliance controller (not shown). 
         [0054]    An upper surface of the printed circuit card may hold a reed switch  61  for detecting a change in a magnetic field caused by closure of the door  12  as described in U.S. Pat. No. 7,493,783 issued Feb. 24, 2009, assigned to the assignee of the present invention, and hereby incorporated by reference. In this way the reed switch  61  provides a separate door closure signal indicating the state of the door  12  as opened or closed. 
         [0055]    Referring now to  FIG. 6   a , with the bolt  30  in the unlock position fully withdrawn from the door  12 , the pin  74  will be in a unlock zone  76  at one extreme end of an axial track  77  of the multi-path cardioid track  72  near the leading edge  28  of the bolt  30 . In this position, the pin  74  will block further retraction of the bolt  30 . 
         [0056]    When the door  12  is closed and the motor  68  is reversed by means of a positive polarity pulse  80  of motor current  82  from the appliance controller  19 , the bolt  30  will extend to hit stop  34  (shown in  FIG. 3 ) and the pin  74  will move to a lock zone  78  adjacent to a branching cross-track  83  of the cardioid track  72  as indicated by arrow  84 . As noted, further motion of the bolt  30  is blocked by an abutment of the bolt  30  with the stop  34 . Referring also to  FIG. 7 , when the pin  74  is adjacent to the branching cross-track  83  it will pass and drop down (with respect to the bolt  30 ) over a ledge  81  in the cardioid track  72  urged by a spring bias of the wire form  75 . 
         [0057]    Referring to  FIGS. 6   b  and  7 , a reverse polarity pulse  86  of motor current  82  provided by a central controller  19  will then cause the pin  74  to move into the cross-track  83  as guided by the ledge  81 . There, the pin  74  is captured by an apical notch  85 , as indicated by arrow  87 , preventing further retraction of the bolt  30  and maintaining engagement between the bolt  30  and the bolt hole  26  of the door  12 . In arriving at the apical notch  85 , the pin  74  drops over a ledge  88  blocking its regression along cross-track  83 . 
         [0058]    Referring momentarily also to  FIG. 3 , when the pin  74  is thought to be within the lock zone  78 , the contact set  52  may provide a unlock signal  96  indicating that the lock is in the unlock zone  76 . For reasons of tolerances, the absence of the unlock signal  96  is used to confirm the correct location of the pin  74  in the area of the lock zone  78   
         [0059]    Referring to  FIGS. 6   c  and  7 , the appliance controller  19  in a final step of locking the door  12  may then provide another positive polarity pulse  90  to the motor  68  which moves the pin  74  as indicated by arrow  92  to a position within a second axial track  94  generally parallel to axial track  77  but displaced to the side thereof. In arriving at the second axial track  94 , the pin drops over a ledge  93  preventing retraction into the cross-track  83 . This new position is still adjacent to the cross-track  83  with further extension of the bolt  30  blocked by the stop  34  shown in  FIG. 3 . This position provides a locking with full engagement of the bolt  30  with the bolt hole  26  despite possible variations in the separation of the door  12  from the wall  32  caused by manufacturing tolerances. This final positive polarity pulse  90  may be provided only when there has been confirmation that the door is in place by a checking that there is no continuity through interconnection of terminals  56   b  and  56   c , that is, no unlock signal  96 . Referring to  FIGS. 6   d  and  7 , when it is desired to unlock the door  12 , another reverse polarity pulse  98  may be applied to the motor  68 , this current  82  causing the pin  74  to move along the axial track  94  as indicated by arrow  100  back to the unlock zone  76 . 
         [0060]    Referring now to  FIG. 6   e  and considering the case where the door  12  is open and the stop  34  displaced from interaction with the bolt  30  (counter to that as shown in  FIG. 3 ), the positive pulse  80  may be applied to the motor  68  when the bolt  30  is in the full unlock position with the pin  74  in unlock zone  76 . As with the case of  FIG. 6   a , this pulse  80  will cause the pin  74  to move along the axial track  77 , but in this case past the cross-track  83  to an over-travel zone  102  at an opposite end of axial track  77  as indicated by arrow  104 . In reaching this over-travel zone  102 , the pin must drop over a ledge  101  even with a bypass track  106 . The subsequent reverse polarity pulse  86  will then cause the pin  74  to pass along bypass track  106  guided by ledge  104  from axial track  77  to axial track  94  to pass all the way back to the unlock zone  76  as indicated by arrow  108  bypassing the lock zone  78 . 
         [0061]    Unlike the situation described with respect to  FIG. 6   b , at the conclusion of this negative pulse  86 , the pin  74  will not be in the lock zone  78  but rather at the unlock zone  76  and accordingly there will be a signal on unlock signal line  96  at the conclusion of these motions clearly discriminating from the case of  FIG. 6   b  and indicating that the door  12  is not in the closed position. This determination will cause the motor controller to eliminate subsequent pulses  90  and  98  and may be used to prevent a starting of an appliance motor such as a washtub motor or the like. The retraction of the bolt to the unlock zone  76  brings it out of interference with the door should the door  12  be subsequently closed. 
         [0062]    As will be understood from the above discussion, the controller  19  may investigate the contact set  52  after the pulses  80  and  86  to determine whether the appliance should be activated as properly locked without the need for additional analysis or retraction of the bolt  30 . 
         [0063]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. 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.