Abstract:
A lock system for an appliance providing multiple detection switches for lid closure and lid locking encodes the switch states as different voltages on a single signal line to reduce wiring harness costs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application 61/753,476 filed Jan. 17, 2013 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 lock assembly providing a reduced wiring. 
       BACKGROUND OF THE INVENTION 
       [0003]    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 either during the spin or agitate cycle. 
         [0004]    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 or an electrical motor may be used for the locking mechanism to permit rapid access to the clothes when the spin basket has stopped. The electrical motor or a bi-stable solenoid may receive a first polarity pulse of electricity to lock the lid and a second polarity pulse of electricity to unlock the lid, thereby saving electrical power in the steady-state. 
         [0005]    In order to prevent defeat of the lock, it is known to put a lid switch in series with the electrical actuator 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 strike. The lock switch is then placed in series with the washing machine motor or tied to the washing machine controller 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. 
         [0006]    More recently, improved prevention of lock tampering has been provided by providing separate switches that detect both a locked state and an unlocked state of the lock. The separate switches provide the ability to detect a jamming of the lock mechanism preventing full movement of the lock mechanism between locked and unlocked states, such as may also indicate tampering or damage to the lock. 
         [0007]    These additional switches require separate independent electrical conductors leading between the lock mechanism and the appliance control increasing the cost of the wiring harness and the complexity of manufacturing. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention significantly decreases the cost of wiring needed to connect a multi-switch appliance lock to an appliance controller by encoding the multiple states of these physically separate switches into distinct electrical levels that may be conveyed over a single wire. This signal may be decoded at the appliance controller by an analog-to-digital converter. 
         [0009]    Specifically, in one embodiment, the invention provides a door lock for a door of an appliance and a door locking element movable between an unlock position and lock position to lock the door. A door position switch is positioned to sense a closure of the door and a lock sensing switch is positioned to sense the door locking element being in the lock position. A first and second resistor each having different unique values are each attached to a corresponding one of the door position switch and the lock sensing switch so that corresponding switches control current through the corresponding attached resistors, the first, and second resistor communicating with a signal wire to provide a unique current through a signal wire as a function of the states of the door position switch and the lock sensing switch. 
         [0010]    It is thus a feature of at least one embodiment of the invention to accurately convey the state of door closure and door locking switches through a single wire as different currents or voltages. 
         [0011]    The door lock may further include an unlock sensing switch having a state indicating that the door locking element is in the unlock position and a third resistor having a different unique value from the first and second resistors, the third resistor attached to the unlock sensing switch which controls current through the third resistor. The first, second, and third resistors may communicate with the signal wire to provide a unique current through the signal wire as a function of the states of the door position switch, the lock sensing switch and the unlock sensing switch. 
         [0012]    It is thus a feature of at least one embodiment of the invention to permit redundant switch signals without unduly increasing wiring harness cost. 
         [0013]    The door lock may further include an electrical actuator that retains its state without power communicating with the door locking element to receive electrical power over an actuation wire to move the door locking element between the unlock and lock position. In one embodiment, the actuation element may be a bi-stable electrical solenoid or electrical motor. 
         [0014]    It is thus a feature of at least one embodiment of the invention to provide necessary lock and unlock confirmation signals permitting energy-efficient actuators to be used in the door lock. 
         [0015]    The first, second, and third resistors may be each connected in series, respectively, with one of the door position switch, the lock sensing switch and the unlock sensing switch, and wherein the series-connected resistors and switches are connected jointly in parallel to the signal wire. Alternatively, each of the first second and third resistors may be connected in parallel, respectively, with one of the door position switch, the lock sensing switch, and the unlock sensing switch, and the parallel connected resistors and switches may be connected jointly in series to the signal wire. 
         [0016]    It is thus a feature of at least one embodiment of the invention to provide for flexible interconnection of the independent switches for encoding a combination signal on the signal wire. 
         [0017]    The door lock may further include a sensing resistor receiving current from the signal wire to generate a voltage proportional to that current. 
         [0018]    It is thus a feature of at least one embodiment of the invention to provide an output voltage that may be decoded into switch states. 
         [0019]    The sensing resistor may be in the housing. 
         [0020]    It is thus a feature of at least one embodiment of the invention to minimize the effect of harness resistance by converting current flow into a voltage within the housing and communicating the voltage over the harness to a high resistance input. 
         [0021]    The first, second, and third resistors may each be greater than or equal to twice the resistance value of the next lowest resistance of the first, second and third resistors. 
         [0022]    It is thus a feature of at least one embodiment of the invention to approximate a binary encoding system providing good noise immunity between encoded states. 
         [0023]    Each of the resistor values may be less than 1000 ohms. 
         [0024]    It is thus a feature of at least one embodiment of the invention to provide a low impedance resistor divider to be better immune from electrical interference. 
         [0025]    Each of the door position switch, lock sensing switch and unlock sensing switch maybe independently mechanically operable. 
         [0026]    It is thus a feature of at least one embodiment of the invention to encode switches that may assume a large number of combinational states. 
         [0027]    Each of the door sensing switch, the lock sensing switch and the unlock sensing switch may be a single pole, single throw switches that close when the door is closed, the lock is in the lock position and the lock is in the unlock position, respectively. 
         [0028]    It is thus a feature of at least one embodiment of the invention to employ switches whose failure in an open state would promote safe operation of the appliance. 
         [0029]    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 DRAWINGS 
         [0030]      FIG. 1  is a simplified diagram of a locking latch of the present invention for a washing machine or the like showing an arrangement of a lid position sensor, lock and unlock switches and an electrical actuator moving a bolt to engage with a striker on the lid whose positions they be sensed over a single conductor (referenced to a voltage level); 
           [0031]      FIG. 2  is a schematic representation of a first embodiment of an encoding circuit for encoding switch states into voltage levels; 
           [0032]      FIG. 3  is a figure similar to that of  FIG. 2  of an alternative embodiment showing both switches and a current sensing of the encoded switch states; 
           [0033]      FIG. 4  is a figure similar to that of  FIG. 2  showing an alternative wiring system; and 
           [0034]      FIG. 5  is a schematic representation of an embodiment of the invention in which an electrical actuator such as a motor may be controlled over the same wire as that used to sense switch positions. 
       
    
    
       [0035]    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 
       [0036]    Referring now to  FIG. 1 , a prior art locking latch  10  may work with an appliance  12 . A front loading washing machine is shown having a door  14  that may open and close to selectively expose an internal spin basket  16  operated by a motor  18 . The invention also contemplates use in a top loading washing machine. 
         [0037]    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 or a reed relay) indicating that the door is closed. The door switch  24  in this case may 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. 
         [0038]    When the door  14  is closed, an electrical signal may be provided to an actuator  26 , such as a bi-stable solenoid or permanent magnet DC motor, 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. 
         [0039]    The mechanical element attached to the bolt  28  may also activate a home switch  31  when the door is unlocked. The home switch  31  is configured to be electrically open when the door is locked and electrically closed when the door  14  is unlocked. Generally, but not always, the state of the lock switch  30  and the home switch  31  will be opposite. 
         [0040]    Each of the switches  24 ,  30 , and  31 , may be single pole, single throw switches connected in series to one of a set of corresponding resistors  32 ,  34  and  36  unique to each of the switches  24 ,  30 , and  31 . The series connected switches ( 24 ,  30 , and  31 ) and resistors ( 32 ,  34 , and  36 ) may be joined together in parallel to a node  39 . A sensing resistor  47  may have one end connected to the node  39  and the other end connected to a reference voltage to provide a voltage divider encoding network  38 . A driving voltage  40  may be applied to one side of the encoding network  38  through a power conductor  82  and the node  39  may be connected to a single signal line  42  to input to analog to digital converter  52  of a microcontroller  44  within the appliance  12 . 
         [0041]    Each of the switches  24 ,  30 ,  31  and resistors  32 ,  34 ,  36 , and  47  together with the actuator  26  may be held in a housing  43  to provide an integrated locking mechanism. 
         [0042]    Generally the microcontroller  44  will include a computer processor  46  communicating with a memory  48  holding a program in non-transient form for controlling general appliance functions including motor  18  and appliance displays based on signals received from appliance control knobs well known in the art. In this regard, the microcontroller  44  may include general input and output circuits  50  communicating with other elements of the appliance  12  and in particular an input to an analog-to-digital converter  52  receiving signal line  42 . Generally, the program executed by the microcontroller  44  will suspend operation of the appliance  12  when the door  14  is open, and will provide for a locking of the door  14  during certain cycles of appliance operation and suspend operation of the appliance  12  if locking is not detected. Detection of tampering as will be discussed below may also cause the suspension of operation of the appliance  12 . Such tampering may be indicated, for example, if no locking signal of switch  30  is detected after the actuator  26  has been energized. 
         [0043]    Referring now also to  FIG. 2 , in one embodiment, the resistors  32 ,  34 , and  36  stand in an approximately binary sequence. Thus, for example, resistor  32  may be 100 ohms, resistor  34  200 ohms and resistor  36  500 ohms. It will be appreciated in this example that the exact binary values are not required and that these resistances may be adjusted so long as they remain approximately in this proportion and/or conform to standard resistance values. 
         [0044]    As noted above, in one possible mode of operation, the encoding network  38  may be placed in series with a voltage source  45  (either AC or preferably DC) and a sensing resistor  47 , the latter forming a voltage divider together with the effective total resistance of the encoding network  38 . As different of the switches  24 ,  30 , and  31  are opened and closed, the voltage at a node point  49  between the sensing resistor  47  and the encoding network  38 , communicating with analog-to-digital converter  52 , will vary uniquely depending on the combination of switch closures. 
         [0045]    The following table shows the encoding of this embodiment: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                 lid 
                 lock 
                 home 
                 Effective resistance 
               
               
                   
                 switch 
                 switch 
                 switch 
                 of encoding network 
               
               
                   
                 24 
                 30 
                 31 
                 resistors 32, 34, 36 
               
               
                   
                   
               
             
             
               
                   
                 Open 
                 Open 
                 Closed 
                 500 ohms 
               
               
                   
                 Closed 
                 Open 
                 Closed 
                  83 ohms 
               
               
                   
                 Closed 
                 Closed 
                 Open 
                 166 ohms 
               
               
                   
                   
               
             
          
         
       
     
         [0046]    It will be appreciated that the above table shows only legitimate states of the switches  24 ,  30 , and  31  (each state representing one row) but that unique resistance values may also be provided for additional illegal states (for example, where the lock switch  30  and home switch  31  have the same state or where the lock switch  30  is locked while the lid is open). By detecting these illegal states, the present system can detect a variety of malfunctions. Each state provides a distinct and separate resistance but it will be appreciated that the difference in resistance between successive states need not be uniform and, in cases where some illegal states will not be sensed, a unique resistance is not necessary for each possible illegal state. 
         [0047]    It will be understood that the variation of the effective resistance of the encoding network  38  will produce a corresponding change in the voltage at the node point  49  based on standard voltage divider equations and be dependent on the value of sensing resistor  47 . 
         [0048]    In this regard, the present invention allows the elimination of two wires associated with two of the switches  24 ,  30 , and  31  and possibly four wires if one considers the separate return wires. Generally three wires will be required including the signal line  42 , a ground connection  53  and an actuator wire  51  communicating with actuator  26 . The ground connection  53  may be shared between the sensing switches  24 ,  30 , and  31  and the actuator  26 . 
         [0049]    Referring now to  FIG. 3 , it will be appreciated that the invention may also be used with two switches  24  and  30  only, for example, in cases where the extra switch  31  is not desired. Further, it will be appreciated that the voltage divider formed by sensing resistor  47  in  FIG. 2  may alternatively be replaced with a current sensor measuring the current through the encoding network  38  in the manner of a current loop detector. In this latter embodiment, sensing resistor  47  can be removed. 
         [0050]    Referring now to  FIG. 4 , it will be appreciated that the parallel wiring shown in  FIG. 2  may be substituted with the serial wiring system. In this case switch  24  is wired in parallel with resistor  32 , switch  30  is wired in parallel with resistor  34 , and switch  31  is wired in parallel with resistor  32 . The parallel connections of each switching resistor are then connected in series with sensing resistor  47  across voltage source  45 . In this case the following encoding is provided: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                 lid 
                 lock 
                 home 
                 Effective resistance 
               
               
                   
                 switch 
                 switch 
                 switch 
                 of encoding resistors 
               
               
                   
                 24 
                 30 
                 31 
                 32, 34, 36 
               
               
                   
                   
               
             
             
               
                   
                 Open 
                 Open 
                 Closed 
                 300 ohms 
               
               
                   
                 Closed 
                 Open 
                 Closed 
                 200 ohms 
               
               
                   
                 Closed 
                 Closed 
                 Open 
                 500 ohms 
               
               
                   
                   
               
             
          
         
       
     
         [0051]    Referring now to  FIG. 5 , the same conductor of the signal line  42  used to sense the position or state of switches  24 ,  30 , and  31  in the encoding network  38 , may also be used to control the actuator  26  used to lock and unlock the appliance door. For this purpose, the actuator  26  is connected in parallel across the series combination of switch  24  and resistor  32 , switch  30  and resistor  34 ; and switch  31  and resistor  36 . In this example, the actuator  26  will have a resistance of approximately  40  ohms. 
         [0052]    A more complex control circuit  60  may be employed with the encoding network  38  and parallel connected actuator  26 . Signal line  42 , in this case, will not lead directly to the analog to digital converter  52  of microcontroller  44  but will be received at a pole  62  of a first electrical relay  64 , the first pole  62  switchable between a first and second throw  66  and  67  according to a control line  68  actuating a coil as shown or other control elements of a solid-state relay. Control line  68  may be received by a digital output  70  of the microcontroller  44  possibly with buffering circuitry (not shown). 
         [0053]    Throw  66  connects to the A/D converter  52  and sensing resistor  47  as described above. Throw  66  connects to pole  72  of a second relay  74  having first and second throws  76  and  78  that connect, respectively, to a positive actuator drive voltage (for example 13 volts) and to ground. The switching of relay  74  is according to control signal  80  also received by a digital output  70  of the microcontroller  44 . 
         [0054]    The power conductor  82  of the encoder network  38 , as is attached to the common junction of one terminal of switches  24 ,  30 ,  31 , and actuator  26  (opposite the connection of signal line  42 ) may be received by a pole  84  of a third relay  86 . This relay  86  provides a first throw  88  connected to the motor drive voltage and a second throw  90  connected to the first pole  92  of a fourth relay  94 . A first throw  96  of relay  94  connects to a measurement voltage (e.g. five volts) and a second poll  98  of relay  94  connects to ground. Relay  86  may be controlled by signal line  100  and relay  94  may be controlled by signal line  102  both of which also connect a digital output  70 . 
         [0055]    It will be understood from this description that by proper control of relay  64 ,  86  and  94  by the microcontroller  44 , that the measurement voltage may be applied to power conductor  82  and the resulting current conducted to the sensing resistor  47  and A/D converter  52  of microcontroller  44 . The measurement voltage is selected to be insufficient to drive the actuator  26  thereby providing interrogation without actuation. In this case the state of the switches may be determined according the following Table III. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE III 
               
               
                   
               
               
                   
                   
                   
                 Effective resistance 
                 voltage at A/D 
               
               
                 lid 
                 lock 
                 home 
                 of encoding network 
                 converter with 
               
               
                 switch 
                 switch 
                 switch 
                 resistors 32, 34, 
                 100 ohm sensing 
               
               
                 24 
                 30 
                 31 
                 36 and motor 
                 resistor 47 
               
               
                   
               
             
             
               
                 Open 
                 Open 
                 Closed 
                 37 ohms 
                 3.65 v 
               
               
                 Closed 
                 Open 
                 Closed 
                 26 ohms 
                 3.97 
               
               
                 Closed 
                 Closed 
                 Open 
                 24 ohms 
                 4.03 
               
               
                   
               
             
          
         
       
     
         [0056]    Alternatively, the state of relay  64  may be changed so that signal line  42  connects with pole  72  of relay  74 . In this mode, it will be appreciated that control of relays  74 ,  86  and  94  may be performed to apply actuation voltage in either of two polarities across the electrical actuator  26 . Sufficient current can be provided in this states to drive the actuator  26  regardless of the states of switches  24 ,  30  and  31  such as may shunt the actuator  26  with the resistances  32 ,  34  and  36 . 
         [0057]    In this way a single conductor of the signal line  42  (augmented by a separate power conductor  82 ) can provide not only a reading of the state of the locking latch  10  but may also power the latch to lock or unlock it depending on that state reading. 
         [0058]    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. 
         [0059]    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 “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. 
         [0060]    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. 
         [0061]    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. 
         [0062]    Various features of the invention are set forth in the following claims.