Abstract:
A lock for a washing machine or the like provides fast actuation through a solenoid driven bolt that remains stably in the locked position after power is no longer applied to the solenoid. The possibility of power failure preventing subsequent access to the washing machine is avoided through the use of a slower actuation time, thermal actuator storing sufficient energy to unlock the bolt after a time delay when power is lost.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 60/925,597, filed Apr. 20, 2007, the disclosure of which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     BACKGROUND OF THE INVENTION 
     The present invention relates to latching mechanisms for the doors of appliances such as clothes washing machines and, in particular, to an electrically actuated lock for such latching mechanisms. 
     Appliances, such as clothes washing machines and dishwashers, may operate automatically through one or more cycles under the control of a timer. During cycles when the consumer might be exposed to spraying water or hazardous moving parts, the door to the appliance may be locked by an electrical signal from the timer. The locking mechanism may, for example, insert a blocking member into a portion of the door latch to prevent the latch from opening, or the locking mechanism may insert a bolt directly between the appliance frame and door. 
     One method of actuating the locking mechanism is to use a thermal actuator, for example, a wax motor or bi-metallic strip. Such thermal actuators have the disadvantage of requiring a heating or cooling of a material. This heating or cooling process typically takes some time, preventing rapid locking or unlocking of the locking mechanism. 
     An alternative method of actuating the locking mechanism is to use an electrical solenoid having a ferromagnetic armature that moves through a conductive coil when electrical power is applied to the coil to form an electromagnet. Electrical solenoids provide for rapid actuation but at a cost of increased size and expense, particularly if the coil windings, the latter of which normally must be rated for continuous duty to maintain the locking mechanism in its locked or unlocked state. The use of continuous duty solenoids in locks can also create a problem in the event of a electrical power loss, caused either by an electrical outage, or the appliance being unplugged, where the end user will have access to the inside of the washer while the drum is still spinning. The disadvantages inherent in the use of a continuous duty solenoid can be overcome through the use of an electromagnetically pulsed bi-stable solenoid. A bi-stable solenoid may include a magnetized armature movable in different directions by different polarities of current through a single solenoid coil, a pair of back to back independent solenoid coils passing a ferromagnetic armature between them when one or the other is energized, or a single solenoid activating a mechanism that cycles between two states with each activation. The bi-stable solenoid may be coupled with an over-center spring or the like to hold the armature in its last position when no power is applied or during a power loss. 
     Such bi-stable solenoids provide rapid actuation and overcome the power dissipation problems inherent with continuous duty solenoids. When used in a locking application, however, they have an important shortcoming. In the event of a loss of electrical power, the door latch may be locked indefinitely because no power is available to move the bi-stable solenoid to its unlocked state. This is an important problem in commercial laundry establishments where, in the event of power failure, customers will not be able to collect their clothes and yet may be reluctant to leave their clothes unattended. 
     U.S. Pat. No. 6,363,755 to Hapke et al issued Apr. 2, 2002 and entitled “Timed Release Washing Machine Lid Lock” describes a circuit that holds energy in a capacitor to be used to unlock a bi-stable lock mechanism at the end of a spin cycle even if power has been lost. This approach, while extremely flexible, requires an additional electrical circuit and a capacitor sized to store sufficient energy, which can be expensive. 
     U.S. Pat. No. 5,572,869 to Schantz et al issued Nov. 12, 1996 and entitled “Actuator Assembly for use in Appliances” describes a “wax motor” that uses an internal heating element to generate a force and displacement. This device stores energy within a compression spring that can be used to deliver a secondary force and displacement (in the opposite direction) after electrical power is removed and upon cooling of the heating element (which occurs after some time delay). 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides latching mechanism that employs a bi-stable solenoid for rapid locking and unlocking of an appliance door while storing energy to unlock the appliance door in the event of power failure in a separate thermal actuator. The thermal actuator may have improved costs and power consumption qualities over a continuous duty solenoid. 
     Specifically, the present invention provides a door locking assembly for use in an appliance receiving electrical power from a power line and having a door that may be opened to provide access to a wash chamber. The door locking assembly includes a bi-stable electromagnetic locking mechanism which, in a locked state, holds the door closed until an electrical unlock signal is received and, in an unlocked state, allows the door to be freely opened until an electrical lock signal is received. The electromagnetic locking mechanism is capable of remaining stably in the locked state or unlocked state absent application of the electrical unlock signal or the electrical lock signal. A thermal actuator communicates with the bi-stable electromagnetic locking mechanism to: (1) store energy while the power line provides electrical power, (2) use the stored energy to unlock the bi-stable electromagnetic locking mechanism when the bi-stable electromagnetic locking mechanism is in a locked state and power is lost at the power line, and (3) provide a time delay period, to allow the appliance to come to a standstill, before the thermal actuator cools to a point where an unlock status is initiated. 
     Thus it is an object of one embodiment of the invention to provide the high-speed and low power consumption of a bi-stable actuator while preventing a lockout in the event of power failure. 
     The thermal actuator may store energy only while the power line provides electrical power and a separate activation signal related to the electrical lock signal is received from a cycle timer. 
     It is thus an object of one embodiment of the invention to minimize energy dissipation in the thermal actuation element until lockout protection is required. 
     The thermal actuator may store energy before the electrical lock signal has been received. 
     Thus it is an object of one embodiment of the invention to eliminate the possibility of lockout when the thermal actuator is not fully heated and thus is not capable of providing an unlocking. 
     The stored energy may be held in a spring flexed by thermal expansion of a material heated by electrical power terminating with loss of power from the power line and released after a predictable cool down period. 
     It is thus an object of one embodiment of the invention to monitor a power line power by the seating of a material with power line power. 
     The thermal actuator may be a wax motor. 
     It is thus an object of one embodiment of the invention to provide a low-cost, high force, and robust thermal actuator. 
     The wax motor may receive a voltage from the power line. 
     It is thus an object of one embodiment of the invention to eliminate the need for intermediate power conditioning circuits. 
     The thermal actuator may communicate with the bi-stable electromagnetic locking mechanism through a coupling providing engagement between the thermal actuator and the bi-stable electromagnetic locking mechanism during cooling of the thermal actuator when the electromagnetic locking mechanism is locked, and providing disengagement between the thermal actuator and the bi-stable electromagnetic locking mechanism at other times. 
     It is thus an object of one embodiment of the invention to provide unencumbered movement of the electromagnetic locking mechanism when power failure initiated unlocking is not required. 
     The coupling may provide a tooth and socket engaging each other when the thermal actuator has substantially fully stored energy and disengaging when the thermal actuator has substantially fully exhausted stored energy. 
     It is thus an object of one embodiment of the invention to provide a simple mechanical coupling mechanism. 
     The door locking assembly may further include an operator manually accessible from the outside of the door locking assembly and communicating with the bi-stable electromagnetic locking mechanism to move the bi-stable electromagnetic locking mechanism to an unlocked state when the operator is manually operated. 
     It is thus an object of one embodiment of the invention to provide for a manual override in the event of power failure or before connection of power. 
     The bi-stable electromagnetic locking mechanism may be a sliding bolt driven by a bi-stable solenoid. The bi-stable solenoid may comprise two electrically independent solenoid coils arranged in opposition about a common armature. 
     It is thus an object of one embodiment of the invention to employ a high-speed solenoid actuator made cost-effective by its ability to be used in a non-continuous mode. 
     The bi-stable electromagnetic locking mechanism includes a bi-stable bolt engaging a latch. 
     It is thus an object of one embodiment of the invention to permit an integrated latch lock assembly for improved manufacturing. 
     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 DRAWINGS 
         FIG. 1  is a simplified perspective view of a front-loading washing machine suitable for use with the present invention; 
         FIG. 2  is a perspective view of the door locking assembly of the present invention as may be incorporated into the housing of the washing machine of  FIG. 1 , also showing a latch tongue as attached to the door of the washing machine of  FIG. 1  and received by the door locking assembly; 
         FIG. 3  is a simplified elevational view of the principal elements of the door locking assembly of  FIG. 2  in an unlocked state; 
         FIG. 4  is a figure similar to that of  FIG. 3  showing the door locking assembly in a locked state as driven by a bi-stable solenoid; 
         FIG. 5  is a figure similar to that of  FIGS. 3 and 4  showing a thermal actuator engaging an unlocking mechanism when the thermal actuator is fully heated; 
         FIG. 6  is a figure similar to that of  FIGS. 3-5  showing retraction of the thermal actuator upon power loss and cooling to unlock the door locking assembly; 
         FIG. 7  is a detailed view of the thermal actuator of  FIGS. 3-5  at an initial stage of heating before it is fully heated; 
         FIG. 8  is a figure similar to that of  FIG. 7  showing the thermal actuator fully heated and engaging the unlocking mechanism; 
         FIG. 9  is a figure similar to that of  FIGS. 7-8  showing the thermal actuator in an initial stage of cooling after being fully heated and pulling back on the unlocking mechanism; 
         FIG. 10  is a figure similar to that of  FIGS. 7-9  showing the thermal actuator fully cooled after full heating causing the disengagement of the unlocking mechanism by a stationary wedge; and 
         FIG. 11  is an electrical timing diagram showing various control signals that may be received by the locking assembly of the above figures. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a front loading washing machine  10  may provide a cabinet  11 , having at its front surface a door  12 , the latter opening about a hinge  14  between an open and closed position to provide access to a washing chamber  15 . The door  12  may be retained in the closed position (as shown) by a door locking assembly  16  having components within the cabinet  11  and attached to a rear face of the door  12 . 
     Referring now also to  FIG. 2 , the door locking assembly  16  may provide a housing  18  with an opening  25 , a similar opening in the front surface of the cabinet  11  to receive a latch tongue  22  attached to the rear side of the door  12 . The latch tongue  22  is releasably held by a latching assembly  24  within the housing  18 . A latching assembly  24  suitable for this purpose is described in co-pending U.S. application Ser. No. 11/071,910 entitled: “Appliance Latch Having a Rotating Latch Hook Mounted on a Linear Slide” and U.S. patent application Ser. No. 11/684,287 entitled: “Low Power Consumption Lock for Appliance Lock”, both assigned to the assignee of the present invention and hereby incorporated by reference. 
     Referring still to  FIG. 2 , the door locking assembly  16  may provide for connector elements  26  communicating with wiring harness  28  exchanging signals with a cycle timer assembly  30 , the latter communicating with a power line  31  providing power, for example 110 VAC, powering the cycle timer assembly  30 . The cycle timer assembly  30  may receive signals from the door locking assembly  16  and provide signals to the door locking assembly  16  both in the form of 110 VAC, and 12 VDC, as will be described further below. 
     Referring now to  FIGS. 1 and 3 , the door locking assembly  16  may provide for a locking bolt  32  that may slide along axis  34  under the influence of a bi-stable actuator  36 . When the locking bolt  32  is in the upward position (as depicted) it is removed from the latching assembly  24  allowing the latching assembly  24  (and thus the door  12 ) to open and close normally under the control of a user of the washing machine  10 . When the locking bolt  32  is in the downward position, it blocks the latching assembly  24  preventing the door  12  from opening. 
     The bi-stable actuator  36  may provide for two solenoid coils  38   a  and  38   b  arranged along the axis  34  and having an internal armature  40  that may be passed between them depending on which solenoid coil  38   a  or  38   b  is activated. The armature  40  is pulled into coil  38   a  upon receipt of a 110 VAC unlock signal at terminals  42  of the coil  38   a  from the cycle timer assembly  30 . This flexes an over-center spring  44  stably holding the bolt  32  in the upward position even when power is removed from coil  38   a . The bolt  32  is normally in this position before the washing machine  10  is started and after the washing machine  10  ends its cycles. Alternatively, the bi-stable actuator  36  may be a single solenoid coil (not shown) operating in either of two polarities with a permanent magnet internal armature. 
     Referring now to  FIG. 4 , a locking signal may be received by solenoid coil  38   b  from the cycle timer assembly  30  pulling the armatures  40  and bolt  32  downward (as depicted) causing the over-center spring  44  to snap downward holding the bolt  32  in that position even after removal of power of the unlocking signal in the coil  38   b . As noted above, in this position the bolt  32  interferes with the latching assembly  24  preventing the door  12  from being opened by the user. 
     When the bolt  32  is in the locked position, an upwardly extending pin  46  on the bolt  32  moves proximate to a right end (as depicted) of an unlocking lever  48  pivoting about a pivot point  50  and held in an extreme clockwise position against the stop  52  by spring  54 . A left end of the unlocking lever  48  opposite pivot point  50  with respect to the right end of the unlocking lever  48  is pivotally attached to an unlocking linkage  56  extending downward along axis  34 . The unlocking linkage  56  is branched to provide a first branch extending outside of the housing  18  to a manual operator  58  that may be grasped by a person. 
     As shown in  FIG. 6 , when the manual operator  58  is pulled, it rotates unlocking lever  48  in a counterclockwise direction pushing upward on pin  46  causing an axial retraction of the bolt  32  away from the latching assembly  24 . Typically, the bolt  32  will rise further than the unlocking lever  48  under the influence of the over-center spring  44 . The manual operator  58  thus allows a service person to unlock the washing machine  10  particularly before it has been attached to the power line  31 . Pin  46 , spring  54 , unlocking lever  48  and unlocking linkage  56  together comprise an unlocking mechanism. 
     Referring now to  FIG. 5 , a wax motor  59  may receive line power from the cycle timer assembly  30  to heat internally contained wax whose expansion causes the extension of an operator  60  upward (as depicted) toward an angled tooth  62  attached to a second branch of the unlocking linkage  56 . As is well understood in the art, the expansion of the wax pushes the operator  60  outward against the force of a contained spring that is increasingly flexed during that expansion. 
     Referring now to  FIG. 7 , as operator  60  begins to rise (representing a state of partial heating of the wax motor  59 ) a bottom surface of the angled tooth  62  is pushed leftward (as depicted) by an upper surface of the operator  60 . 
     Referring to  FIG. 8 , with increased extension of the operator  60  (representing a full heating of the wax motor  59 ) an inner edge of the angled tooth  62  moves over a slot  64  cut radially in the upper end of the operator  60  so that the right edge of the angled tooth  62  engages the slot  64 . Note that over travel of the operator  60  upward may cause disengagement of the angled tooth  62 , but that the angled tooth  62  will reengage with the slot  64  when the operator  60  retracts. 
     When power is removed from the wax motor  59 , as shown in  FIG. 9 , the operator  60  moves downward driven by the inner spring of the wax motor  59  (not shown) and the contraction of the contained wax. As the operator  60  moves downward, it pulls with it the angled tooth  62  and the unlocking linkage  56  raising the bolt  32  as shown in  FIG. 6  in a manner similar to that done by the manual operator  58 . 
     Referring now to  FIGS. 6 and 10 , upon complete cooling of the wax motor  59 , the operator  60  retracts sufficiently far to pull the angled tooth  62  against a wedge stop  70  causing the angled tooth  62  to swing leftward disengaging it from the slot  64  and allowing the angled tooth  62  and the unlocking linkage  56  to move upward under the influence of spring  54  returning to a state approximating that of  FIG. 3 . 
     It will be noted that the wax motor  59  remains generally disengaged from the bolt  32  and the unlocking linkage  56  until the operator  60  of the wax motor  59  is fully extended and then retains connection until the operator  60  is fully withdrawn. This and the abutting connection between pin  46  and unlocking lever  48  allows free movement of the bolt  32  during all but a power failure situation. 
     Referring now to  FIGS. 2 ,  3  and  11 , the cycle timer assembly  30  at time  80 , upon the start of the washing machine  10 , may provide 110 VAC activation signal to the wax motor  59  causing its operator  60  to move upward as shown by trajectory  82 . The heating process produces a time delay before the operator  60  is fully extended, yet this upward extension does not interfere with the operation of the bolt  32  but prepares the locking assembly  16  to react to power loss even before the door  12  is locked by a locking pulse  86  applied to coil  38   b  as described above. 
     Alternatively the cycle timer assembly  30  may wait until a time  84  to provide an activation signal to the wax motor  59 , ideally slightly before but possibly completely aligned with the lock on locking pulse  86  to produce trajectory  82 ′. In this way, power consumption by the wax motor  59  is reduced. The activation signal  88  can remain on continuously but preferably is turned off upon application of unlocking pulse  90  to coil  38   a  by the cycle timer assembly  30 . 
     The present invention contemplates that a power failure may occur at time  92  before the application of the unlocking pulse  90 . In this case, the activation signal  88  (and other signals from the cycle timer assembly  30 ) derived from the power line  31  cease and the operator  60  of the wax motor  59  retracts unlocking the washing machine  10  after first delay at time  94 . 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to 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.