Abstract:
A locking latch for an appliance provides an improved three-wire interface that reduces the chance of malfunction if the door is forcibly opened when it is in the lock state and a bi-stabile actuator is used. In one embodiment, the door switch is positioned to disengage the major load of the washing machine when the doors open, regardless of the lock or unlock state.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a National Phase of International Application Number PCT/US2010/048250 filed Sep. 9, 2010, and claims the benefits of United States Provisional Application Serial No. 61/241,285, filed Sep. 10, 2009. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to clothes washing machines and the like and specifically to a lock assembly for preventing access to the spin basket of such a washer during the spin cycle. 
     BACKGROUND OF THE INVENTION 
     During the spin cycle of a washing machine, water is removed from wet clothes centrifugally by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user, the user must be prevented from having access to the spin basket while the spin basket is in motion. 
     One way of protecting the user from access to the rotating spin basket uses an electrically locking latch for the washing machine lid. The latch holds and locks the lid in a closed position for the duration of the spin cycle and for a period after the spin cycle necessary for the spin basket to coast to a stop. This locking latch may be operated by a thermoelectric element such as a bimetallic strip or wax motor. Preferably, however, a fast acting solenoid may be used for the locking mechanism to permit rapid access to the clothes when the spin basket has stopped. Often, to save electrical power, a solenoid may be a bi-stable solenoid receiving a first pulse of electricity to lock the lid and a second pulse of electricity to unlock the lid. 
     In order to prevent defeat of the lock, it is known to put a lid switch in series with the bi-stable solenoid to prevent the locking action when the lid is open. This lid switch may be accompanied with a “lock switch” indicating that the bolt of the lock is engaged with a door striker. The lock switch is then placed in series with the washing machine motor to prevent activation of the spin cycle when the lid is not properly locked. Together the lid closure switch and the lid lock switch provide some assurance that the lid is properly closed and locked before power is applied to the washing machine mechanism. 
     SUMMARY OF THE INVENTION 
     The present inventors have recognized that in some situations where a lid lock employs a bi-stabile solenoid or similar mechanism and when the lid is forced open, the washing machine may remain activated. This situation will be discussed in more detail below. The present invention provides a system to disable the washing machine motor in such circumstances while still employing a simple three-wire interface. 
     Specifically, the present invention provides a door lock for a door of an appliance having a housing attachable to the appliance near the door, providing three connection conductors for attaching the door lock to other electrical components of the appliance including a first connection conductor connected to an appliance motor and a second connection conductor connected to a power source. The housing holds a door position detector positioned to respond to the closure of the door when the housing is mounted to the appliance, a bi-stable electrical actuator for actuating a door locking element of a latch retaining the door when the housing is mounted to the appliance, and a lock sensing switch which responds to a positioning of the door locking element, the lock sensing switch connected to the first connection conductor. The door position element blocks power to the motive element of the appliance through the first connection conductor when the door is open. 
     It is thus a feature of at least one embodiment of the invention to provide a lock system that may use a bi-stable actuator and still disable the appliance if the door is forcibly opened. Because the door position element blocks power to the motive element of the appliance regardless of the state of the bi-stable actuator, the problem of the bi-stable actuator being disconnected when the door is opened (and thus being unable to affect the lock sensing switch) is avoided. 
     The lock sensing switch may be connected between the first connection conductor and a common point. The door position detector is a switch open when the door is open and connected between the second connection conductor and the common point and the bi-stable electrical actuator is connected between a third connection conductor and the common point. 
     It is thus a feature of at least one embodiment of the invention to provide direct electrical control of the appliance by the door position detector regardless of the state of the bi-stabile actuator and the lock sensing switch. 
     Power may flow through the motive element by passing through the first and second connection conductors. 
     It is thus a feature of at least one embodiment of the invention to provide a system compatible with a cost-effective three-wire interface. 
     The appliance may be a washing machine and the motor may drive rotation of a spin basket of the washing machine accessible through the door. 
     It is thus a feature of at least one embodiment of the invention to provide an enhanced resistance to vandalism that might compromise the safety of high-speed spin cycle washing machines. 
     In one embodiment, the lock sensing switch may be connected between the first connection conductor and a common point, the second connection conductor may connect to the common point and the bi-stable electrical actuator may be connected between a third connection conductor and the common point, and the door position detector may be a mechanical element preventing closure of the lock sensing switch when the door is open. 
     It is thus a feature of at least one embodiment of the invention to provide the benefits of enhanced resistance to forcible opening of the appliance door with a single electrical switch. 
     The lock sensing switch may communicate with the bi-stable electrical actuator by means of a mechanical operator and wherein the door position detector, when the door is open, blocks movement of the mechanical operator directed to close the lock sensing switch. 
     It is thus a feature of at least one embodiment of the invention to provide a simple mechanism for mechanical interlock of the door sensor and lock switch. 
     The door position detector and the mechanical operator may communicate by means of a cam surface and cam follower wherein motion of the door position along a first axis may control motion of the mechanical operator along a second perpendicular axis. 
     It is thus a feature of at least one embodiment of the invention to provide a compact mechanical apparatus that may sense both door movement and lock movement when these two movements are not aligned. 
     The bi-stable electrical actuator moves between a first and second state with successive electrical pulses and remains in either the first or second state when power is not applied, and wherein the door is locked in the first state. 
     It is thus a feature of a least one embodiment of the invention to provide a system that may use energy-efficient bi-stabile actuators that will hold a lock or unlock position without the application of electrical power. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified diagram of a prior art locking latch for a front loading washing machine or the like showing an interconnection of a lid position sensor, lock switch and electrical actuator moving a bolt to engage with a striker on the lid; 
         FIG. 2  is a schematic representation of an alternative interconnection of the components of  FIG. 1  in a first embodiment according to the present invention in which the lid sensor is a switch placed in series with connection of the lock switch with respect to power flow to the motor; 
         FIG. 3  is a figure similar to that of  FIG. 2  of an alternative embodiment in which the actuator and lid switch are placed in parallel; 
         FIG. 4  is a figure similar to that of  FIGS. 2 and 3  eliminating the lid switch and using instead a mechanical intermediary between the actuator and the lock switch; 
         FIG. 5  is a simplified schematic diagram showing the principle of operation of the mechanical intermediary, with portions of the mechanical intermediary rotated into the plane of the figure for clarity and showing the latch in a first state with the door closed but unlocked; 
         FIG. 6  is a figure similar to that of  FIG. 5  showing a second state with the door closed and the actuator activated to lock the door; 
         FIG. 7  is a figure similar to that of  FIGS. 5 and 6  in a third state with the actuator activated to lock the door while the door is open; 
         FIG. 8  is a front elevational view of an implementation of the latch of the present invention shown in a state with the door open corresponding generally to  FIG. 7 ; 
         FIG. 9  is a figure similar to that of  FIG. 8  showing a state when the door is in the closed position and the actuator activated to lock the door corresponding generally to  FIG. 6 ; 
         FIG. 10  is a simplified diagram similar to that of  FIG. 5  for a second embodiment in which the lid detector is mechanically independent from the lock switch; 
         FIG. 11  is a figure similar to that of  FIG. 6  for the embodiment of  FIG. 10 ; 
         FIG. 12  is a figure similar to that of  FIG. 7  for the embodiment of  FIG. 10 ; 
         FIG. 13  is a front elevational view similar to that of  FIG. 8  for the embodiment of  FIG. 10 ; and 
         FIG. 14  is a figure similar to that of  FIG. 13  similar to that of  FIG. 9  for the embodiment of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a prior art locking latch  10  may work with an appliance  12  such as a front loading washing machine having a door  14  that may open and close to selectively expose an internal spin basket  16  operated by a motor  18 . 
     The door  14  may hinge at one edge and at an opposed edge hold a striker  20  having a loop portion  22  that may pass into the housing of the appliance  12  to be received by the locking latch  10  held therein. The loop portion  22  of the striker  20 , when the door  14  is closed, may activate a door position detector, being in this case an electrical door switch  24  (for example, a single pole single throw switch) indicating that the door is closed. The door switch  24  in this case will be a normally open switch that is open when the door  14  is open and closed when the door  14  is closed. Other indirect mechanisms for detecting door closure may also be used. 
     When the door  14  is closed, an electrical signal may be provided to an actuator  26 , such as a bi-stable solenoid, to drive a bolt  28  through the loop portion  22  to lock the door  14  against opening. A mechanical element attached to the bolt  28  may also activate a lock switch  30  when the door is so locked. The lock switch  30  is configured to be electrically open when the door  14  is unlocked and electrically closed when the door  14  is locked. 
     The various elements of the actuator  26 , the lock switch  30 , and the door switch  24  may be connected in a “three wire” configuration. This three-wire configuration provides three connection conductors  32   a ,  32   b , and  32   c  joined at a common junction  34 . The connection conductors  32  may be leads or terminals of types well known in the art allowing the lock switch  30  to be connected to other components of the appliance  12 . 
     One end of connection conductor  32   a  connects to the lock switch  30  which then connects to the common junction  34 . This connection conductor  32   a  provides a connection between the motor  18  and a common voltage point of connection conductor  32   b  when lock switch  30  is closed so that power is applied to the motor  18 . Common junction  34  is connected directly to connection conductor  32   b . The third connection conductor  32   c  connects to the common junction  34  through the series connected combination of the actuator  26  and the door switch  24  so that the actuator  26  may receive power as connected to the common voltage point of connection conductor  32   b  only when the door switch  24  is closed and the appropriate pulses are applied to connection conductor  32   c.    
     It will be understood in this context, that the common voltage point of connection conductor  32   b  does not denote a particular polarity (for example line or ground) but is simply a connection that completes a power circuit. This three-wire circuit is described generally in US patent application 2008/0106105 filed Nov. 30, 2005 and hereby incorporated by reference. 
     As will be appreciated from this description, with this connection of the elements, the lock switch  30  cannot be closed by the actuator  26  unless the door switch  24  is closed and thus the door  14  is closed. This keeps the bolt  28  from engaging when the door  14  is open. Note, however, that if the door  14  is forcibly opened while the bolt  28  is in the lock state, for example, by breaking the end of bolt  28  or the loop portion  22  (without proper retraction of the bolt  28 ), the motor  18  may continue to operate exposing the user to the rotating spin basket  16  despite the opening of the door switch  24 . This is because the actuator  26  is bi-stable and therefore opening of the door switch  24  to remove power from the actuator  26  does not retract the actuator  26 . Further, in this case, the door switch  24  would open preventing the actuator  26  from receiving a disengaging pulse such as would retract the bolt  28  and release the lock switch  30  to turn off the motor  18 . That is, monitoring of the functional door switch  24  to send signals to open the lock switch  30  to turn off the motor would be of no avail. 
     Referring now to  FIG. 2 , the present invention modifies the circuit of  FIG. 1 , in a first embodiment, by relocating the door switch  24  to the branch of the circuit from the common junction  34  to the connection conductor  32   b  so that connection conductor  32   c  contains only the actuator  26 . As before, connection conductor  32   b  connects to the common voltage point and connection conductor  32   a  connects through the lock switch  30  to the common junction  34 . This configuration allows the door switch  24  to control current flowing in both of connection conductors  32   c  and  32   a  so that when the door  14  opens, in the scenario described above, power will be interrupted at the motor  18  through the agency of the opening of the door switch  24 . This approach requires that the current carrying capacity of the door switch  24  be sufficient to interrupt the current required by the motor  18 . 
     Referring now to  FIG. 3 , in an alternative embodiment, the door switch  24 ′ is moved from being in series with the actuator  26  on a branch of the circuit leading to connection conductors  32   c , per  FIG. 1 , to being in parallel with actuator  26  on a branch extending between the common junction  34  and connection conductors  32   c . In addition, the door switch  24 ′ is changed to be a normally closed switch that is closed when the door  14  is open and open when the door  14  is closed. Connection conductor  32   b  connects directly to the common junction  34  and connection conductor  32   a  connects through lock switch  30  to the common junction  34 . It will be understood, then, that when the door  14  is open, door switch  24 ′ shorts the actuator  26  preventing it from being actuated. Nevertheless, this configuration allows an appliance controller (for example a microcontroller, not shown) to monitor whether the door is opened or closed at all times by monitoring the impedance between connection conductor  32   c  and connection conductor  32   b . A high impedance means that the door  14  is closed while a low impedance means that the door  14  is opened. The appliance controller may then break the power to connection conductor  32   c  to open lock switch  30  and thus to cut power to the motor  18 . 
     Referring now to  FIG. 4 , in a third alternative embodiment, the door switch  24  is eliminated and the actuator  26  is allowed to control the lock switch  30  only through mechanical intermediary  43  having operator  42  mechanically moving by the closure of the door  14 , the mechanical intermediary  43  operating so that the actuator  26  may close the lock switch  30  only when the door  14  is closed. The operator  42  thus provides a door position detector in a mechanical form. The mechanical operator  42  may be spring biased outward by a spring (omitted for clarity) to be pushed against the biasing by the closing door  14 . 
     Referring now to  FIG. 5 , the operation of a mechanical intermediary  43  of  FIG. 4  may be understood by a simplified diagram in which the operator  42  moves rightward (as depicted) when the door  14  is closed and leftward when the door  14  is open. In this example, the actuator  26  may rotate a stop support  70  from the position shown in  FIG. 5  to a counterclockwise position shown in  FIGS. 6 and 7  to effect a locking of the latch. Structure suitable for this purpose is described below and in detail in a pending US application 2010/0052338 entitled “Gasket-Compensating Latch Mechanism” and the pending US application 20050194795 entitled: “Appliance Latch Having a Rotating Latch Hook Mounted on a Linear Slide”, the specifications of which are hereby incorporated in their entirety by reference. 
     When the stop support  70  is in its unlock position as shown in  FIG. 5  and the door  14  is closed, as depicted, contacting the operator  42 , a cam surface  95  on the stop support  70  presses upward on the blocking lever assembly providing the mechanical intermediary  43  causing a free end of the lever assembly to hold electrical contacts  92  apart, the electrical contacts providing the lock switch  30 . As depicted, the upper contact  92  contacting the lever of mechanical intermediary  43  is movable on a leaf spring which presses downward on the mechanical intermediary  43  and the lower contact  92  is fixed. 
     As shown in  FIG. 6 , when the bi-stable actuator  26  causes counterclockwise rotation of the stop support  70  to lock the latch, the cam surface  95  is moved away from engagement with the lever assembly of the mechanical intermediary  43  allowing the latter to drop in a clockwise rotation about pivot point  41  so that the free end of the lever of the mechanical intermediary  43  no longer separates contacts  92  permitting closure of the lock switch  30 . 
     As shown in  FIG. 7 , if the door  14  is open however, moving the door  14  away from the operator, the operator  42  moves leftward (under the influence of a spring not shown) and an engaging surface  46  of the operator  42  contacts a corresponding engaging surface  48  on the lever of mechanical intermediary  43  to prevent rotation of the lever of mechanical intermediary  43  in a clockwise direction so that its free end may not move downward to allow closure of the contacts  92  regardless of position of the stop support  70 . Thus, the actuator  26  may only close the contacts  92  when the door  14  is closed. 
     Referring now to  FIGS. 8 and 9 , for reasons of mechanical compactness, in one embodiment of the invention, the operator  42  may be rotated 90° to move linearly not left and right as depicted in  FIGS. 5-7  but in and out of the plane of the paper in  FIGS. 8 and 9 . In order to provide for the necessary mechanical interaction, the engaging surface  48  is formed as a ramp having a radial component about pivot point  41  which may be engaged to cause a counterclockwise rotation of the mechanical intermediary  43  about pivot point  41  when the engaging surface  46  moves downward (into the plane of the paper) as shown in  FIG. 8  when the door  14  is open, separating contacts  92 . Conversely, when the door  14  is closed, engaging surface  46  may move upward (out of the plane of the paper) as shown in  FIG. 9  allowing a clockwise rotation about pivot point  41  and a closure of contacts  92  if cam surface  95  is not engaged. 
     Referring now to  FIGS. 10-12 , in an alternative embodiment, the circuit of  FIG. 2  may be implemented by a variation on the configurations of  FIGS. 5-7  where the lever of mechanical intermediary  43  no longer mechanically communicates with the operator  42  but operates independently with rotation of the stop support  70  and engagement with cam surface  95  to open contacts  92  (as described above). 
     The contacts  92  are unaffected by movement of the mechanical operator  42 . One side of the contacts  92  may be connected to connection conductor  32   a  and the other side connected to a junction plate  100  (providing a common junction  34  described above) which connects to one lead of actuator  26  whose other lead provides connection conductor  32   c . When the stop support  70  is in its unlock position, as shown in  FIG. 10 , the contacts  92  will be open and when the stop support  70  is in its lock position, as shown in  FIGS. 11 and 12 , the contacts  92  are closed. 
     Mechanical operator  42  contacts the door  14  to open or close a second set of contacts  102  that are independent of contacts  92 . This set of contacts  102  has one contact tied to the junction plate  100  and the other connected to connection conductor  32   b . As in the embodiment of  FIGS. 5-7 , the operator  42  may be biased by a spring  104  that tends to push the mechanical operator  42  outward so that closure of the door  14  presses the mechanical operator  42  inward against the biasing of the spring to close the contacts  102 . This spring  104  may be implemented by a leaf spring supporting one of the contacts  102 . Thus, when the door  14  is closed, as shown in  FIGS. 10 and 11 , the contacts  102  are closed and when the door is open, the contacts  102  are open. 
     Referring now to  FIG. 13 , the mechanism of  FIGS. 10-12  may be implemented, again, for reasons of mechanical compactness, by rotating a portion of operator  42  by ninety degrees to move linearly not left and right as depicted in  FIGS. 10-12  but in and out of the plane of the paper of  FIGS. 13 and 14 . In this case operator  42  is implemented as two components: translating operator  42   a  which moves in and out of the plane of the paper in a manner similar to that described in  FIGS. 8 and 9 , and pivoting operator  42   b  which moves left and right to activate contacts  102  by separating the leaf springs on which they are supported. This conversion of motion of translating operator  42   a  into and out of the plane of the paper to the left and right motion of pivoting operator  42   b  is accomplished by the cam surface formed between ramp  106  formed on pivoting operator  42   b  and engaging surface  108  attached to translating operator  42   a . The ramp  106  has a radial component with respect to a center of rotation  110  of the pivoting operator  42   b  so that motion of the engaging surface  108  against the ramp  106  provides a mechanical coupling causing rotational left and right motion of operator  42   b  about center of rotation  110  with in and out motion of operator  42   a . Thus, as shown in  FIG. 13 , when the door  14  is open, translating operator  42   a  and engaging surface  108  move downward (into the plane of the paper) pressing against ramp  106  causing a counterclockwise pivoting of pivoting operator  42   b  about center of rotation  110  to rotate leftward about an axis generally aligned with the linear motion of translating operator  42   a  to open contacts  102 . Conversely, as shown in  FIG. 14 , when the door  14  is closed, when translating operator  42   a  and engaging surface  108  move upward (out of the plane of the paper), they release ramp  106  causing a clockwise pivoting of pivoting operator  42   b  in response to spring forces applied on operator  42   b  by the flexed leaf spring holding a movable one of contacts  102 , allowing those contacts  102  to close. In this way the elements of circuit shown in  FIG. 2  may be implemented. 
     In the above described embodiments, the stop support  70  may be a type as described in US patent application 2010/0052338 (the &#39;338 application) cited above, where the stop support  70  (labeled stop support  70  in the &#39;338 application) supports a cam surface  95  (labeled as cam surface  95  in the &#39;338 application) that may be moved by means of an actuator  26  (labeled as solenoid  80  in the &#39;338 application). In this case, the bolt  28  is provided by the intra-engagement of a pair of ramps (labeled as ramps  60  and  68  in the &#39;338 application) which may prevent opening of the latch when the bolt  28  engages the stop support  70  and whose engagement is indicated by the rotated position of stop support  70 . The present invention may thus include these elements and the associated elements in these applications that provide for: gasket adjusting features (ramps  60  in the &#39;338 application), bi-stability of a single acting solenoid (cardioids track  104  and associated components in the &#39;338 application), and storage of energy in a spring when the doors opened, that helps close the door when the door is closed (spring  26  in the &#39;338 application). In the mechanism of the cardioids track  104 , the steel ball  102  and slot  100  may be replaced by the tip of the spring form wire having its other end attached to the bi-stable mechanism  82 . 
     It will be understood that the present invention is applicable to a variety of different appliance types and that the motor  18  may be represented in such appliances by other electrical or mechanical elements that must be de-energized upon opening of the door for the safety of the user. It will be further understood that the present invention is equally applicable to top-load and front-load type washing machines and that the terms ‘lid’ and ‘door’ should be considered interchangeable in this regard. 
     Variations and modifications of the foregoing are within the scope of the present invention. It is 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. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.