Patent Abstract:
A circuit is provided. The circuit includes a processor programmed to prevent overfilling of a cabinet with a fluid and a backup circuit having fixed logic. The backup circuit is electrically coupled to the processor to redundantly prevent overfilling the cabinet with the fluid.

Full Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to washing machines, and more particularly, to methods and apparatus for controlling wash temperatures. 
   Washing machines typically include a cabinet that houses an outer tub for containing wash and rinse water, a perforated clothes basket within the tub, and an agitator within the basket. A drive and motor assembly is mounted underneath the stationary outer tub to rotate the basket and the agitator relative to one another, and a pump assembly pumps water from the tub to a drain to execute a wash cycle. 
   At least some known washing machines provide that an operator can select from three wash temperatures. Such machines have valve systems including hot and cold water valves. For a hot wash operation, for example, the hot water valve is turned on, i.e., opened, and for a cold wash operation, the cold valve is opened. For a warm wash, both the hot valve and cold valve are opened. The flow rates of water through the valves is selected so that the desired warm temperature is achieved using hot and cold water. 
   The use of a pressure sensor to measure water level allows for more accurate control of multiple water levels compared to the use of a pressure switch. Unfortunately, this provides an opportunity for a single point error in the microprocessor hardware, or software to generate an over fill condition. At least one known system externally monitors the pressure sensor signal and generates a signal that opens a relay that breaks the line voltage to the water valve. The use of a relay adds a cost to the circuit. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a circuit is provided. The circuit includes a processor programmed to prevent overfilling of a cabinet with a fluid, and a backup circuit having fixed logic. The backup circuit is electrically coupled to the processor to redundantly prevent overfilling the cabinet with the fluid. 
   In another aspect, a washer overfill protection system is provided. The washer overfill protection system includes a pressure sensor configured to generate a variable frequency signal that is proportional to the fluid level of the washer, a converter electrically coupled to the pressure sensor, the converter is configured to generate an voltage that is proportional to the frequency of the output of the pressure sensor, and a microprocessor electrically coupled to the converter. The microprocessor is configured to calculate the fluid level from the voltage of the converter, and the microprocessor is electrically coupled to a fluid valve. The washer overfill protection system further includes a backup circuit having fixed logic. The backup circuit is electrically coupled to the converter and the fluid valve. The backup circuit is configured to at least one of turn on the fluid valve and turn off the fluid valve when the microprocessor fails. 
   In a further aspect, a washing machine is provided. The washing machine includes a cabinet, a tub and basket mounted within the cabinet, a cold water valve for controlling flow of cold water to the tub, a hot water valve for controlling flow of hot water to the tub, and a circuit coupled to at least one of the hot water valve and the cold water valve to control opening and closing of the hot and cold water valves. The circuit includes a processor programmed to prevent overfilling of the cabinet and a backup circuit having fixed logic. The backup circuit is electrically coupled to the processor to redundantly prevent overfilling the cabinet. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective cutaway view of an exemplary washing machine. 
       FIG. 2  is front elevational schematic view of the washing machine shown in  FIG. 1 . 
       FIG. 3  is a schematic block diagram of a control system for the washing machine shown in  FIGS. 1 and 2 . 
       FIG. 4  is a schematic diagram of a over fill protection circuit for the washing machine shown in  FIGS. 1 and 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a perspective view partially broken away of an exemplary washing machine  50  including a cabinet  52  and a cover  54 . A backsplash  56  extends from cover  54 , and a control panel  58  including a plurality of input selectors  60  is coupled to backsplash  56 . Control panel  58  and input selectors  60  collectively form a user interface input for operator selection of machine cycles and features, and in one embodiment a display  61  indicates selected features, a countdown timer, and other items of interest to machine users. A lid  62  is mounted to cover  54  and is rotatable about a hinge (not shown) between an open position (not shown) facilitating access to a wash tub  64  located within cabinet  52 , and a closed position (shown in  FIG. 1 ) forming a substantially sealed enclosure over wash tub  64 . As illustrated in  FIG. 1 , machine  50  is a vertical axis washing machine. 
   Tub  64  includes a bottom wall  66  and a sidewall  68 , and a basket  70  is rotatably mounted within wash tub  64 . A pump assembly  72  is located beneath tub  64  and basket  70  for gravity assisted flow when draining tub  64 . Pump assembly  72  includes a pump  74  and a motor  76 . A pump inlet hose  80  extends from a wash tub outlet  82  in tub bottom wall  66  to a pump inlet  84 , and a pump outlet hose  86  extends from a pump outlet  88  to an appliance washing machine water outlet  90  and ultimately to a building plumbing system discharge line (not shown) in flow communication with outlet  90 . 
     FIG. 2  is a front elevational schematic view of washing machine  50  including wash basket  70  movably disposed and rotatably mounted in wash tub  64  in a spaced apart relationship from tub side wall  64  and tub bottom  66 . Basket  70  includes a plurality of perforations therein to facilitate fluid communication between an interior of basket  70  and wash tub  64 . 
   A hot liquid valve  102  and a cold liquid valve  104  deliver fluid, such as water, to basket  70  and wash tub  64  through a respective hot liquid hose  106  and a cold liquid hose  108 . Liquid valves  102 ,  104  and liquid hoses  106 ,  108  together form a liquid supply connection for washing machine  50  and, when connected to a building plumbing system (not shown), provide a fresh water supply for use in washing machine  50 . Liquid valves  102 ,  104  and liquid hoses  106 ,  108  are connected to a basket inlet tube  110 , and fluid is dispersed from inlet tube  110  through a known nozzle assembly  112  having a number of openings therein to direct washing liquid into basket  70  at a given trajectory and velocity. A known dispenser (not shown in  FIG. 2 ), may also be provided to produce a wash solution by mixing fresh water with a known detergent or other composition for cleansing of articles in basket  70 . 
   In an alternative embodiment, a known spray fill conduit  114  (shown in phantom in  FIG. 2 ) may be employed in lieu of nozzle assembly  112 . Along the length of the spray fill conduit  114  are a plurality of openings arranged in a predetermined pattern to direct incoming streams of water in a downward tangential manner towards articles in basket  70 . The openings in spray fill conduit  114  are located a predetermined distance apart from one another to produce an overlapping coverage of liquid streams into basket  70 . Articles in basket  70  may therefore be uniformly wetted even when basket  70  is maintained in a stationary position. 
   A known agitation element  116 , such as a vane agitator, impeller, auger, or oscillatory basket mechanism, or some combination thereof is disposed in basket  70  to impart an oscillatory motion to articles and liquid in basket  70 . In different embodiments, agitation element  116  may be a single action element (i.e., oscillatory only), double action (oscillatory movement at one end, single direction rotation at the other end) or triple action (oscillatory movement plus single direction rotation at one end, singe direction rotation at the other end). As illustrated in  FIG. 2 , agitation element  116  is oriented to rotate about a vertical axis  118 . 
   Basket  70  and agitator  116  are driven by motor  120  through a transmission and clutch system  122 . A transmission belt  124  is coupled to respective pulleys of a motor output shaft  126  and a transmission input shaft  128 . Thus, as motor output shaft  126  is rotated, transmission input shaft  128  is also rotated. Clutch system  122  facilitates driving engagement of basket  70  and agitation element  116  for rotatable movement within wash tub  64 , and clutch system  122  facilitates relative rotation of basket  70  and agitation element  116  for selected portions of wash cycles. Motor  120 , transmission and clutch system  122  and belt  124  collectively are referred herein as a machine drive system. 
   Washing machine  50  also includes a brake assembly (not shown) selectively applied or released for respectively maintaining basket  70  in a stationary position within tub  64  or for allowing basket  70  to spin within tub  64 . Pump assembly  72  is selectively activated, in the example embodiment, to remove liquid from basket  70  and tub  64  through drain outlet  90  and a drain valve  130  during appropriate points in washing cycles as machine  50  is used. In an exemplary embodiment, machine  50  also includes a reservoir  132 , a tube  134  and a pressure sensor  136 . As fluid levels rise in wash tub  64 , air is trapped in reservoir  132  creating a pressure in tube  134  that pressure sensor  136  monitors. Liquid levels, and more specifically, changes in liquid levels in wash tub  64  may therefore be sensed, for example, to indicate laundry loads and to facilitate associated control decisions. In further and alternative embodiments, load size and cycle effectiveness may be determined or evaluated using other known indicia, such as motor spin, torque, load weight, motor current, and voltage or current phase shifts. 
   Operation of machine  50  is controlled by a controller  138  which is operatively coupled to the user interface input located on washing machine backsplash  56  (shown in  FIG. 1 ) for user manipulation to select washing machine cycles and features. In response to user manipulation of the user interface input, controller  138  operates the various components of machine  50  to execute selected machine cycles and features. 
   In an illustrative embodiment, clothes are loaded into basket  70 , and washing operation is initiated through operator manipulation of control input selectors  60  (shown in  FIG. 1 ). Tub  64  is filled with water and mixed with detergent to form a wash fluid, and basket  70  is agitated with agitation element  116  for cleansing of clothes in basket  70 . That is, agitation element is moved back and forth in an oscillatory back and forth motion. In the illustrated embodiment, agitation element  116  is rotated clockwise a specified amount about the vertical axis of the machine, and then rotated counterclockwise by a specified amount. The clockwise/counterclockwise reciprocating motion is sometimes referred to as a stroke, and the agitation phase of the wash cycle constitutes a number of strokes in sequence. Acceleration and deceleration of agitation element  116  during the strokes imparts mechanical energy to articles in basket  70  for cleansing action. The strokes may be obtained in different embodiments with a reversing motor, a reversible clutch, or other known reciprocating mechanism. 
   After the agitation phase of the wash cycle is completed, tub  64  is drained with pump assembly  72 . Clothes are then rinsed and portions of the cycle repeated, including the agitation phase, depending on the particulars of the wash cycle selected by a user. 
     FIG. 3  is a schematic block diagram of an exemplary washing machine control system  150  for use with washing machine  50  (shown in  FIGS. 1 and 2 ). Control system  150  includes controller  138  which may, for example, be a microcomputer  140  coupled to a user interface input  141 . An operator may enter instructions or select desired washing machine cycles and features via user interface input  141 , such as through input selectors  60  (shown in  FIG. 1 ) and a display or indicator  61  coupled to microcomputer  140  displays appropriate messages and/or indicators, such as a timer, and other known items of interest to washing machine users. A memory  142  is also coupled to microcomputer  140  and stores instructions, calibration constants, and other information as required to satisfactorily complete a selected wash cycle. Memory  142  may, for example, be a random access memory (RAM). In alternative embodiments, other forms of memory could be used in conjunction with RAM memory, including but not limited to flash memory (FLASH), programmable read only memory (PROM), and electronically erasable programmable read only memory (EEPROM). 
   Power to control system  150  is supplied to controller  138  by a power supply  146  configured to be coupled to a power line L. Analog to digital and digital to analog converters (not shown) are coupled to controller  138  to implement controller inputs and executable instructions to generate controller output to washing machine components such as those described above in relation to  FIGS. 1 and 2 . More specifically, controller  138  is operatively coupled to machine drive system  148  (e.g., motor  120 , clutch system  122 , and agitation element  116  shown in  FIG. 2 ), a brake assembly  151  associated with basket  70  (shown in  FIG. 2 ), machine water valves  152  (e.g., valves  102 ,  104  shown in  FIG. 2 ) and machine drain system  154  (e.g., drain pump assembly  72  and/or drain valve  130  shown in  FIG. 2 ). In a further embodiment, water valves  152  are in flow communication with a dispenser  153  (shown in phantom in  FIG. 3 ) so that water may be mixed with detergent or other composition of benefit to washing of garments in wash basket  70 . 
   In response to manipulation of user interface input  141  controller  138  monitors various operational factors of washing machine  50  with one or more sensors or transducers  156 , and controller  138  executes operator selected functions and features according to known methods. Of course, controller  138  may be used to control washing machine system elements and to execute functions beyond those specifically described herein. Controller  138  operates the various components of washing machine  50  in a designated wash cycle familiar to those in the art of washing machines. 
     FIG. 4  is a schematic of a washer overfill protection circuit  200 . Washer overfill protection circuit  200  includes a pressure sensor  210  electrically coupled to a frequency to voltage converter  215 . The output of frequency to voltage converter  215  is electrically coupled to at least a first circuit  220  and a second circuit  225 . In the exemplary embodiment, first circuit  220  is a back up circuit  220  and includes a first operational amplifier (op amp)  230  and a second op amp  235 . In one embodiment, first op amp  230  is a overfill comparator  230  and second op amp  235  is a sensor error comparator  235 . Overfill comparator  230  and sensor error comparator  235  are electrically coupled to a first gate  240 . First gate  240  is electrically coupled to a second gate  245  and a third gate  248 . Second gate  245  is electrically coupled to a first transistor  250 , such as a bipolar junction transistor. First transistor  250  is electrically coupled to a first relay driver  255 . First relay driver  255  is electrically coupled to a fluid valve coil  260 , such as a hot water valve coil  260 . 
   Second circuit  225  includes a microprocessor  270 . Microprocessor  270  is electrically coupled to second gate  245  of back up circuit  220  and a third gate  248 . Third gate  248  is electrically coupled to a second transistor  285 , such as a bipolar junction transistor. Second transistor  285  is electrically coupled to a second relay driver  290 . Second relay driver  290  is electrically coupled to a fluid valve coil  300 , such as a cold water valve coil  300 . 
   Microprocessor  270  is programmed to perform functions described herein, and as used herein, the term microprocessor is not limited to just those integrated circuits referred to in the art as microprocessor, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits, and these terms are used interchangeably herein. 
   Pressure sensor  210  generates a variable frequency signal that is proportional to the water level in washer tub  64 . Frequency to voltage converter  215  generates an analog voltage that is proportional to the frequency from the output of pressure sensor  210 . The analog voltage is then input to microprocessor  270 . Microprocessor  270  uses the analog voltage to calculate the water level and sends, for example, a hot water valve command signal to turn on and off hot water valve coil  260 . The hot water valve command and pressure sensor check signal are sent to the input of second gate  245 . If hot water command is high and the pressure sensor check signal is high, the output of second gate  245  is high, turning on first transistor  250 . If first transistor  250  is on, first relay driver  255  is energized, closing the normally closed contact for first relay driver  255  energizing hot water valve coil  260 . Energizing hot water valve coil  260  opens the hot water valve (not shown), allowing hot water to flow into washer tub  64 . If the hot water valve command and/or the pressure sensor check signal is low, the output of second gate  245  is low, turning off first transistor  250 . If first transistor  250  is off, first relay driver  255  is de-energized, opening the normally open contacts of first relay driver  255 , de-energizing hot water valve coil  260 . De-energizing hot water valve coil  260  shuts off the hot water valve, blocking hot water from entering the washer tub  64 . 
   The output of the frequency to voltage converter  215  is input into overfill comparator  230  and compared with an over fill reference voltage. If the frequency to voltage converter  215  output is less than the over fill reference voltage, the overfill comparator  230  output is high, indicating a normal tub water level. If the frequency to voltage converter  215  output is greater than the over fill reference voltage, the overfill comparator  230  output is low, indicating an over fill condition. 
   The output of the frequency to voltage converter  215  is also an input into sensor error comparator  235  and compared with a sensor error voltage. If the frequency to voltage converter  215  output is greater than the sensor error voltage, the sensor error comparator  235  output is high indicating a valid pressure sensor signal. If the frequency to voltage converter  215  output is less than the sensor error voltage, the sensor error comparator  235  output is low indicating an invalid pressure sensor signal. 
   Overfill comparator  230  output and sensor error comparator  235  output are connected to the input of first gate  240 . If overfill comparator  230  output and/or sensor error comparator  235  output is low, first gate  240  output is low. If the output of first gate  240  is low, second gate  245  and third gate  248  outputs are low, de-energizing first transistor  250  and second transistor  285 . De-energizing first transistor  250  and second transistor  285  de-energizes first relay driver  255  and second relay driver  290 , respectfully, de-energizing hot and cold water valve coils  260  and  300 , respectfully. De-energizing hot and cold water valve coils  260  and  300 , blocks the hot and cold water from entering washer tub  64 . 
   In one embodiment, pressure sensor  210  may output an analog voltage instead of a frequency signal, thereby removing frequency to voltage converter  215  from circuit  200 . In another embodiment, the logic performed by first, second, and third gates  240 ,  245 , and  248  may be performed by other logic that generates the same operation. In addition, the water valve driver circuits may be generated by any other switching device. In a further embodiment, hot and cold water valve coils  260  and  300  may be replaced by dc water valves, using a dc drive circuit instead of first and second relay drivers  255  and  290 . 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Technology Classification (CPC): 3