Abstract:
A latch for a washing machine or other appliance provides two interengaging elements on a lid and housing each having a magnet oriented for mutual repulsion. Proper repulsion of the magnets is necessary to signal that the lid is properly closed such as may be used to determine if the appliance may be locked and safely operated, for example, in a clothes spinning mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on International Application No. PCT/US2011/026199 filed Feb. 25, 2011 and claims the benefit of U.S. provisional application 61/309,208 filed Mar. 1, 2010. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to home appliances such as clothes washing machines and the like and in particular, to a lid locking mechanism that is highly resistant to tampering. 
     BACKGROUND OF THE INVENTION 
     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 lid in the closed position. 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. 
     In order to prevent tampering with the lock mechanism, for example, by holding the lid open when the lock is actuated, it is known to provide for lid closure sensing to ensure that the lid is in a proper position before the lock mechanism is engaged. Conventional mechanical lid closure switches can often be defeated by wedging the switch open for example with the end of a pencil or the like. U.S. Pat. No 7,251,961, assigned to the assignee of the present invention and hereby incorporated by reference, describes a lid sensor using a magnet and electrical reed switch to detect lid closure. The use of a magnetic actuator reduces the possibility of casual tampering. 
     SUMMARY OF THE INVENTION 
     The present invention provides a magnetic anti-tamper feature with even greater resistance to tampering by employing a mechanism that requires a particular polarity of magnetic field and a magnet strength and proximity that is not easily duplicated. 
     Specifically, the present invention provides an appliance latch having a bolt and a corresponding latch for receiving the bolt, the bolt and latch positionable on an appliance door and appliance frame. A first magnet is positioned on the bolt and a second magnet is positioned on a movable element within the latch to be moved in response to proximity of the first magnet when the bolt is received by the latch. An electric switch actuatable with movement of the movable element, provides a switch signal indicating proper engagement of the bolt and latch for locking. A lock element holds the bolt engaged with the latch when the bolt is properly engaged with the latch and a lock signal has been received by the lock element allowing release of the bolt from engagement with the latch when a release signal has been received by the lock element. 
     It is thus a feature of at least one embodiment of the invention to prevent defeat of a lid locking system, intended to protect the consumer from injury, by providing a sophisticated interlock system requiring multiple correctly positioned magnets. 
     The polarity of the first and second magnet may be such as to repel the movable element from the bolt when the bolt is properly engaged within the latch. 
     It is thus a feature of at least one embodiment of the invention to prevent defeat of the present system by materials that exhibit magnetic attraction such as steel. 
     The movable element may actuate a switch controlling the lock switch signal. 
     It is thus a feature of at least one embodiment of the invention to provide a signal to an appliance controller affirming proper closure of the lid for locking, such as may be used to trigger a locking action and to confirm proper locking of the lid. 
     The lock element may include a trap moved from a first bolt-releasing position to a second, bolt-retaining position by the engagement of the bolt with the latch, and a blocking element receivable by the trap when the trap is in the second, bolt-retaining position to block movement of the trap to the first of both releasing positions. An electric actuator communicating with the blocking element may move the blocking element into receipt by the trap when the lock signal has been received by the lock element and remove the blocking element from receipt by the trap when the release signal has been received by the lock element. 
     It is thus a feature of at least one embodiment of the invention to provide a latch in which a lid switch signal based on the position of the bolt also indicates that the bolt may be locked in position by an electric actuator. 
     The electric actuator may be a solenoid and bistable mechanism moving the blocking element between receipt by the trap and removal from the trap with successive energizing of the solenoid and wherein the lock signal is a first energizing and the unlock signal is a second energizing of the solenoid. 
     It is thus a feature of at least one embodiment of the invention to provide a locking system with reduced energy consumption and which is not defeated by momentary power loss. 
     The trap may be a sliding member and the movable element holding the second magnet may be slidably held by the trap. 
     It is thus a feature of at least one embodiment of the invention to provide a compact assembly that ensures good proximity of the movable element and magnet to the bolt being received by the trap. 
     The bolt may be received in the latch along an axis and may travel perpendicularly to the axis as it is received within the latch. The bolt may include a spring urging the bolt in a first direction perpendicular to the axis. The first direction may be the same as a direction of movement of the trap toward the bolt retaining position. 
     It is thus a feature of at least one embodiment of the invention to employ the bolt and a spring to position the trap for retaining and holding the bolt. 
     The bolt may be mounted for travel perpendicular to the axis and a cam surface of the latch may move the bolt to push the trap toward the bolt retaining position. 
     It is thus a feature of at least one embodiment of the invention to position the trap via a cam surface acting on the bolt 
     The engagement of the bolt with the trap may activate a switch indicating closing of the lid. 
     It is thus a feature of at least one embodiment of the invention to eliminate the need for a separate lid switch operator. 
     Motion of the bolt to disengage from the latch when the blocking element is received by the trap may cause an abutting of the blocking element against a frangible portion of the trap which when broken prevents activation of the locking switch. 
     It is thus a feature of at least one embodiment of the invention to detect damage to the latch by forcible opening that might prevent future locking. 
     The frangible portion of the trap may support a spring element away from an opening into which the blocking element may be received such that removal of the frangible element causes the spring element to occlude the opening. 
     It is thus a feature of at least one embodiment of the invention to provide a simple method of signaling damaged by defeating the blocking element and thus deactivating the lock signal. 
     The appliance may be a washing machine having a spin basket operated by a motor and further including an appliance control receiving a signal generated at least in part from the locking switch to block power from the motor when proper engagement of the bolt and latch is not indicated by the locking switch. 
     It is thus a feature of at least one embodiment of the invention to provide an improved latch for washing machines. 
     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 FIGURES 
         FIG. 1  is a perspective view and inset detail of a top loading washing machine suitable for use with the present invention showing a strike aperture positioned near the front of an upwardly opening lid and showing a downwardly extending bolt for engaging a strike when the lid is closed; 
         FIG. 2  is a fragmentary cross-section along line  2 - 2  of  FIG. 1  showing a floating mounting of the bolt allowing close tolerance interaction between the bolt and strike to move a trap element to a retaining and locking position; 
         FIG. 3  is a top plan cross-sectional view of a trap engaging the bolt when the bolt is received by the strike and showing the position of magnets within the bolt and held by an anti-tamper slider within the trap, the former movable within the trap under the influence of magnetic repulsion; 
         FIG. 4  is a perspective view showing the orientation of the magnets in the bolt and anti-tamper slider providing improved accommodation of positioning errors; 
         FIG. 5  is a simplified perspective view of the trap engaging the bolt showing the positioning of the anti-tamper slider and a breakaway aperture at the front of the trap and showing a bi-stable actuator above the trap for controlling a blocking element descending to block movement of the trap; 
         FIGS. 6   a  and  6   b  are cross-sectional views taken along line  6 - 6  showing engagement of a blocking element within the aperture of the trap and showing a blocking of that engagement when aperture integrity has been compromised through forcing open of the latch; 
         FIG. 7   a  is a top plan view of the bi-stable actuator of  FIG. 5  in a first state removing the blocking element from engagement with the trap; 
         FIG. 7   b  is a figure similar to that of  FIG. 7   a  showing the bi-stable actuator in a second state engaging the blocking element with the trap to prevent the movement of the trap; 
         FIG. 8  is a view similar to that of  FIGS. 7   a  and  7   b , with the blocking element and supporting lock switch removed for clarity, showing actuation of the solenoid during movement between the states of  FIGS. 7 and 8  such as frees an antivibration tooth for clearance of the solenoid plunger; 
         FIG. 9  is a side elevational view of the blocking element and lock switch of  FIGS. 5 ,  7   a  and  7   b;    
         FIG. 10  is a schematic diagram of the interconnection of the solenoid, lock switch and lid switch; 
         FIG. 11  is a cross-section through a strain relief that may be used in the present invention providing a clamping of electrical wires while redirecting them to a 90° bend; and 
         FIG. 12  is a fragmentary, perspective view of the strain relief of  FIG. 11  in exploded form. 
     
    
    
     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 EMBODIMENT 
     Referring now to  FIG. 1 , a top loading washing machine  10  suitable for use with the present invention includes a lid  12  opening upward about a horizontal lid hinge axis  14 . The lid hinge axis  14  is positioned near the top rear edge of the washing machine  10  so that a rear edge  16  of the lid  12  may raise and lower to expose and cover an opening  20  through which clothing may be inserted into the spin basket. 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 from the following description with an appropriate adjustment of the orientation. 
     A horizontal surface of the top  22  of the washing machine  10 , at the periphery of the opening  20 , may support a strike aperture  24  form in a housing  21  of a latch  25  fastened to the underside of the top  22 . The strike aperture  24  opens upward to receive a downwardly extending bolt  26  attached to an underside of the lid  12 . Both the strike aperture  24  and the bolt  26  are offset parallel to the axis  14  and offset from a center of the front edge  16  so as to minimize interference with loading and unloading the washing machine  10 . 
     Referring now to  FIG. 2 , the bolt  26  may include a downwardly extending arm  28  terminating in a hook portion  30  extending leftward from the arm  28 , as shown in  FIG. 2 , generally toward a user of the washing machine  10 . The upper end of the arm  28  may be mounted to the lid  12  to pivot left and right as indicated by arrows  32  with respect to the lid  12  under restoring spring forces indicated schematically by springs  34 . In this way, the left and right surfaces of the hook portion  30  may translate as may be necessary to accommodate positional tolerances in the manufacture of the washing machine  10  and wear of the washing machine  10  and to provide movement of a trap to be described. 
     As the lid is closed, the hook portion  30  moves toward the strike aperture  24  and is guided rightward by a right facing first sloping edge  36  of an aperture bezel  38  defining the strike aperture  24 . The aperture bezel moves the hook portion  30  to position  29   b  with a left edge of the bolt  26  aligned at first position  31  with the right edge of an un-retracted trap  40  (shown in a retracted position in  FIG. 2 ). The bolt  26  is then urged left by a left facing second sloping edge  42  so as to push the trap  40  leftward against a restoring spring (not shown in  FIG. 2 ) so that a left edge of an opening in the trap  40  is moved to position  31 ′ as hook portion  30  passes to position  29   c.    
     A following surface  33  of the trap  40 , when the trap is retracted with the bolt  26  in position  29   c,  prevents rightward movement of the hook portion  30  trapping it beneath a ledge on the underside of the sloping edge  36 . This serpentine path defined by sloping edges  36  and  42  ensures that the left edge of the bolt  26  abuts the left edge  41  of the trap  40  in close proximity despite tolerance variations between the lid  12  and the top  22  and allows the bolt  26  to move the trap  40  to the retracted position needed for locking as will be described. 
     Referring now to  FIG. 3 , the trap  40  may hold within it an anti-tamper slider  44  movable independently of the trap  40  in a left-right direction  47  within a range dictated by stop surfaces  43 . The hook portion  30  of the bolt  26  may contain an embedded magnet  46  having an orientation to oppose and repel a corresponding magnet  48  in a right end of the anti-tamper slider  44  proximate to the left edge  41  of the opening of the sliding trap  40 . The force of magnetic repulsion as the bolt  26  slides into the left edge  41  moves the anti-tamper slider  44  left to close a contact set  50  mounted on a stationary point with respect to the sliding of the trap  40  and used to indicate the presence of the bolt  26  at position  29   c  and hence closure of the lid  12 . The anti-tamper slider  44  thereby distinguishes the bolt  26  from a tool that may be used to tamper with the trap  40  even if the tool is ferromagnetic. 
     The anti-tamper slider is biased rightward by the contact set  50  and moves independently of motion of the trap  40  throughout most of the range of travel of the trap  40 . The stop surfaces  43  ensure some movement of the anti-tamper slider  44  with movement of the trap  40  that prevents it from sticking, but this movement is insufficient to activate a contact set  50 . 
     Referring now to  FIG. 4 , the magnets  46  and  48  may be rectangular prisms having their greatest dimension extending relative to each other at a perpendicular angle to provide improved immunity against slight misalignment of the magnets in a lateral direction (parallel to the hinge axis) and up and down along the direction of engagement of the bolt  26 . Generally, a strong and concentrated magnetic field of the correct polarity is necessary to activate the anti-tamper contact set  50  which prevents operation of the washing machine if the bolt  26  is not in its correct position  29   c.    
     Referring now to  FIG. 5 , the sliding trap  40  is normally biased rightward by a biasing spring showed schematically as spring  52  to receive hook portion  30  when hook portion  30  is moved into position  29   b  shown in  FIG. 2  then to hold the hook portion  30  against upward motion. The trap  40  includes an aperture  63  at its left edge. When the trap  40  is retracted leftward, capturing the hook portion  30 , the aperture  63  aligns with a blocking element  54  which may descend into the aperture  63  from an actuator mechanism  55  positioned above the trap  40 . In this configuration, rightward movement of the trap  40  is stopped by interference between a left surface of the blocking element  54  abutting a blockade surface  53  forming a left wall of the aperture  63 . Thus, the trap  40  acts as a trap to hold the bolt  26  in position when the blocking element  54  acts as a blocking element to the trap  40 . 
     Referring now to  FIGS. 5 ,  6   a  and  9 , the blocking element  54  may be moved downward under the influence of a flexible leaf spring  56 . The flexible leaf spring  56  holding one of a pair of contacts of a lock switch  57  indicating proper locking of the latch  25  when the blocking element  54  is lowered and the contacts connect closing the lock switch  57 . At this time, the blocking element  54  may only be disengaged by action of a bistable solenoid mechanism  60  (shown schematically in  FIG. 5  and described below) providing a wedge element  58  that may lift the leaf spring  56  to raise the blocking element  54  by contacting a sloped portion  59  of the leaf spring  56 . 
     Referring again to  FIG. 5 , the blockade surface  53  may be formed by a thin member that can break away as shown in  FIG. 6   b  if the lock is forcibly opened by pressing rightward on the trap  40  when the blocking element  54  has descended, such as may occur from a forcible extraction of the bolt  26 . When the blockade surface  53  is broken away, a leaf spring  71  positioned on the under surface of the trap  40  is free to move upward and carries with it the blocking element  54 , opening contacts on the lock switch throughout the range of travel of the trap  40 . 
     Referring now to  FIGS. 9 ,  7   a  and  7   b , the bi-stable mechanism may include an electrical solenoid  62  having a plunger  64  pulled into the solenoid when the solenoid is actuated. The plunger  64  may be surrounded by a helical compression spring  66  that extends the plunger  64  from the solenoid  62  when the solenoid  62  is not actuated. A distal end of the plunger  64  may connect to a pivoting hook  67  guided into alignment with an axis of the plunger  64  when the plunger is fully extended by means of an angled track  68  sloping to an apex spaced from the solenoid  62  and aligned with an axis of the plunger  64 . 
     When the solenoid  62  is actuated, the hook  67  is drawn inward and contacts a serrated front surface of a rocking element  70  so that successive energizing of the solenoid  62  releasing and then pulling in the plunger  64  causes the rocking element  70  to rock between extremes depicted in  FIGS. 7   a  and  7   b . A serrated surface of the rocking element  70  guides the hook  67  to pull on opposite sides of the rocking element  70  as it moved from the resting position at the apex of the track  68 , causing this bi-stable motion. 
     The rotated extreme, shown in  FIG. 7   b  in a fully clockwise direction, normally provides a locked state for the trap  40 , while the rotated extreme of  FIG. 7   a  in a fully counterclockwise direction normally provides an unlocked state of the trap  40 . 
     Referring again to  FIG. 9 , the unlocked state is associated with the wedge element  58  being positioned beneath a sloped portion  59  of the leaf spring  56  to raise the blocking element  54  from engagement with the aperture of the trap  40  (shown in  FIG. 5 ). In contrast, the locked state is associated with the wedge element  58  being removed from the sloped portion  59  of the leaf spring  56  allowing the blocking element  54  to descend into the aperture of the trap  40 . 
     Referring now to  FIGS. 7   a ,  7   b , and  8 , the rocking element  70  may have an anti-vibration tooth  72  extending leftward therefrom to abut an end of the plunger  64  when the solenoid  62  is not being energized and yet is fully extended by helical springs  66 . The anti-vibration tooth  72 , which is positioned abutting opposite sides of the extended plunger  64  for the unlocked state of  FIG. 7   a  and the locked state of  FIG. 7   b , prevents rotation of the rocking element  70  from vibration alone so long as the solenoid plunger  64  is fully extended. When the solenoid  62  is actuated, however, as shown in  FIG. 8 , a pulling in of the solenoid plunger  64  allows the anti-vibration tooth  72  to slip past the end of the plunger  64  and rotation of the rocking element  70  to occur. 
     Referring now to  FIG. 10 , the latch  25  may provide for four conductors  76  that may be connected, for example, by releasable connectors or the like to a cycle timer or other control apparatus on the washing machine  10 . One of these conductors  76  provides connection for a common source of voltage that connects to one side of the contact set  50  providing a lid switch whose other side connects to a conductor  76  providing the lid switch signal. The common conductor may also connect to one side of the lock switch  57 , the other side of which provides a lock switch signal on conductor  76 . Finally, the common conductor may also connect to one side of the solenoid  62 , the other side providing a conductor for receiving a lock signal, and a release signal being successive electrical current flows. 
     Referring now to  FIGS. 11 and 12 , the present invention may also provide a wiring harness  80  exiting a housing holding the above-described mechanism. The wires may be contained inside a so-called split loom tube  82  having a bellows-shaped outer surface. A two-part bushing  84  may provide for a first and second portion  86   a  and  86   b  that snap together to engage the troughs of the split loom tube  82  with correspondingly spaced teeth  88 . The second portion  86   b  provides an upwardly extending finger  90  and the first portion provides a downwardly extending finger  91  which bend the internally contained wiring  92  into a serpentine path as the portions  86   a  and  86   b  are brought together. The path exits upward through a bushing  94  at approximately 90° to the axis of the split loom tube  82 . In this way a strain relief can be obtained that also provides for a bending of the wires for a 90° entry 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “left”, “right”, “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     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.