Abstract:
An ice producing machine that has a cylindrical evaporator, a compressor that circulates refrigerant supplied to the evaporator, an auger that removes ice from the evaporator and an ice bin for holding the ice. Potential damage to the machine that might result from abnormal loading of the motor that drive the auger is prevented by monitoring the motor current and turning off the motor and compressor before abnormal loading can cause damage. False ice bin not full interpretations are avoided by setting the threshold of a light detector that senses whether the ice bin is full or not full to slightly less than the voltage developed by the light detector when subjected to ambient light only.

Description:
FIELD OF THE INVENTION 
     This invention relates to an ice producing machine and a method that produces ice. 
     DESCRIPTION OF THE PRIOR ART 
     An ice producing machine generally has a condensing unit and an ice making assembly that operate together to produce and harvest ice. Ice making assemblies operate either in a batch mode or a continuous mode. In the batch mode, operation alternates between freeze and harvest cycles. In the continuous mode, operation constantly makes and harvests ice simultaneously. Continuous mode ice producing machines that make flaked or nugget ice forms are commonly known as flaker ice producing machines. 
     The ice making assembly of a flaker ice producing machine generally includes a cylindrical evaporator that has an external surface surrounded by tubes through which a refrigerant flows. The refrigerant is circulated by operation of a compressor. As the cylindrical evaporator is being chilled, water is applied to its internal surface so that ice forms thereon. A layer of the ice is removed and conveyed to a top of the evaporator by an auger. The ice is then pushed through a head that defines the ice form and dispensed to an ice bin. 
     The auger drive train includes an electric motor and a gear reducer. The motor has typically included a centrifugal switch that closes when the motor attains normal operating speed. Closure of the centrifugal switch actuates a relay that turns the compressor on to circulate the refrigerant. The centrifugal switch remains closed and the relay remains actuated until the motor stops rotating. When the motor does stop rotating, the centrifugal switch opens, the compressor relay is deactuated and the compressor is turned off. 
     The motor stops rotating when it is turned off intentionally, when there is a power failure or when motor loading becomes so great as to prevent rotation. Motor loading can be caused by a number of circumstances including motor or gear reducer failure, bearing failure or ice clogging in the evaporator due to over chilling. Generally, motor loading due to any of these circumstances will occur over a considerable amount of time before it becomes so great as to stop rotation. During this time, the ice producing machine may be extensively damaged. For example, continued operation of the compressor during heavy motor loading can cause evaporator mounting bolts to break, the cylinder to rotate and the refrigerant tubes to break or leak, thereby releasing the refrigerant. 
     The ice making assembly of a flaker ice producing machine also includes an ice bin into which the ice is conveyed and stored. A light detector is positioned to detect and provide a bin full signal voltage when the ice bin is full. The ice making assembly responds to the ice bin full voltage to stop making ice until the light detector provides a voltage that represents a bin not full condition. One prior art method of setting a threshold for the light detector calculated the threshold at 50% of the voltage developed by the light detector with only ambient light incident thereon. During ice making, the software interprets voltage above the threshold as the bin being full and voltage below the threshold as the bin being not full. For a bin not full condition, the emitter beam is fully incident on the light detector and the light detector voltage tends toward zero volt. However, during ice making, water drops can form on the light detector window and provide a degree of obscurity that can provide false readings. That is, the light detector develops voltages above the threshold when the bin is not full. These readings re interpreted by the software as the bin being full. 
     There is a need for an ice producing machine and method that turns off the compressor and ice making operation thereof before motor loading can result in damage to the machine or the need for service calls. 
     There is also a need for an improved light detector threshold setting technique that is not subject to faulty interpretation by the system software. 
     SUMMARY OF THE INVENTION 
     The present invention satisfies the aforementioned need with an ice producing machine and method that monitors current flow through the motor that drives the auger and turns off the motor and the compressor when a parameter proportional to the current flow exceeds a threshold that signifies a potential load problem. The method uses a three strike process by which the motor that drives the auger is subsequently turned on after a short wait. If the current flow parameter still exceeds the threshold, the motor is turned off a second time and then on again after a short wait. If the current flow parameter still exceeds the threshold, the motor is turned off a third time and the ice producing machine enters a wait status. If the current flow parameter is below the threshold, the three strike process is reset and the ice producing machine is free to perform normal ice making operations. Each time the motor is turned off an alert is signaled. If the motor is turned off a third time, the alert will remain on to alert the operator/owner that service is required. 
     The present invention also provides a threshold setting procedure for a light detector that detects ice bin full conditions. This procedure responds to an ambient light voltage produced by the light detector to set the threshold level of the detector to either of two levels dependent on the value of the ambient light voltage. If the ambient light voltage is less than a first value, the threshold is set to a fraction of the ambient voltage. If the ambient light voltage is equal to or greater than the first value, the threshold is set to the ambient voltage minus a fractional amount. For example, the first value may be about one volt, the fraction may be 0.75 and the fractional amount may be about 0.5 volt. In either case, the threshold is set near the ambient level, which results in higher thresholds than the prior art method, thereby avoiding the water drop obscurity problem. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure and: 
     FIG. 1 is a perspective view of the ice making machine of the present invention; 
     FIG. 2 is a block diagram, in part, and a schematic circuit diagram, in part, of the electrical control for the FIG. 1 ice making machine; 
     FIG. 3 is an over all flow diagram of the control program for the microprocessor of the FIG. 2 circuit; 
     FIG. 4 is a flow diagram of the initialization routine of the FIG. 3 control program; and 
     FIGS. 5 and 6 are flow diagrams of the gear motor routine of the FIG. 3 control program. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, an ice producing machine  20  includes an ice bin  22 , an evaporator  24 , a gear motor  26 , a gear reducer  28 , an auger  30 , a breaker head  32 , an ice sweep  34 , an ice chute  36 , an ice chute cover  38 , ice bin light detector  40  and an ice chute extender  42 , all of which fit together as shown by the dot dash line. Ice bin  22  has an ice chute hole  44 , in which ice chute extender  42  fits. Ice producing machine  20  also includes a condenser  46  and a compressor  48  that are connected in a refrigerant circuit with evaporator  24  and a water supply  49  that provides water to the interior of cylindrical evaporator  24 . An electrical controller  50  controls ice producing machine  20  to operate to make and harvest ice. Optionally, ice producing machine  20  may not have an ice bin  22 . 
     Referring to FIG. 2, electrical controller  50  includes a power on/off switch  51 , a microprocessor  62 , a gear motor switch  56 , a current sensor  58  and an ac/dc converter and voltage divider  60 . A pair of connectors  52  and  54  make connection to an ac power main, for example, 110 or 220 volts, 60 or 50 Hz. Connectors  52  and  54  are connected in an electrical circuit with gear motor  26 , power on/off switch  51 , microprocessor  62 , gear motor switch  56 , current sensor  58  and AC/DC converter and voltage divider  60 . AC/DC converter and voltage divider  60  converts the ac power line voltage to a dc operating voltage that is applied to microprocessor  62 . 
     Microprocessor  62  includes a control program  64  and a bus  66 . Bus  66  is connected with ice bin light detector  40 , a water sensor  68 , a compressor switch  72 , a fan switch  74 , a mode switch  76 , an a/d converter  78 , motor switch  56 , a freeze LED  80  and a service LED  82 . Control program  64  controls microprocessor  62  to communicate with these devices interconnected with bus  66  to operate ice producing machine  20  in ice making operations. 
     Water sensor  68  is associated with water supply  49  (FIG.  1 ). Compressor switch  72  is operable to turn compressor  48  (FIG. 1) on and off. Fan switch  74  is operable to turn condenser  46  (FIG. 1) on and off. Mode switch  76  is operable to set a freeze mode and a standby mode for ice producing machine  20 . The a/d converter  78  converts the output of current sensor  58  to a parameter, such as a digital voltage, that is usable by microprocessor  62 . Current sensor  58  is operable to monitor the current flow through gear motor  26 . Current sensor  58  may be any suitable current sensing device. For example, current sensor  58  may be a toroid in which the motor lead is threaded through its center and a voltage proportional thereto is developed in another winding on the toroid by transformer action. 
     Referring to FIG. 3, control program  64  begins when power on switch  51  is closed at start step  90 . Control program  64  next performs an initialization routine  92  that sets various thresholds and other parameters used by control program  64 . Control program  64  next performs a water supply routine  94  to determine the availability of water. Control program  64  next performs an ice bin full routine  96 . Control program  64  next performs a mode routine  98 . If in a run mode, compressor  48 , condenser  46  and gear motor  26  are turned on to begin making ice. If not in a run mode, control is returned to water supply routine  94 . Control program  64  then performs a gear motor routine  100 . 
     Referring to FIG. 4, initialization routine  92  includes a step  102  that measures voltage of ice bin light detector  40  with ambient light only. Step  104  determines if the measured voltage is greater than a predetermined value, which is determined by the design of light detector  40 . The predetermined value is preferably in the range of about 0.75 volt to about 5 volts. The predetermined value is shown as one volt, by way of example. If not greater, step  106  sets the threshold of light detector  40  to a fraction of the measured voltage. The fraction is preferably in a range of about 0.6 or 60% to about 0.85 or 85%. For this example, the fraction is about 0.75 or 75%. If greater, step  108  sets the threshold to the measured voltage minus a predetermined amount. The predetermined amount is in a range of about 0.25 volt to about 0.75 volt. For this example, the predetermined amount is about 0.5 volt. Step  110  performs other initializations. This procedure sets the light detector threshold nearer to ambient than the prior art technique of setting the threshold at 50% of ambient. This provides a greater margin for water drop obscurity voltage readings, thereby preventing such readings from exceeding the threshold when the bin is not full. 
     Referring to FIG. 5, gear motor routine  100  begins with step  122  that checks the gear motor current. Step  124  then determines if a parameter proportional to the gear motor current is over the threshold. The parameter, for example, is the output voltage of a/d converter  78 . If not, control is returned to step  92  (FIG.  3 ). If the gear motor current parameter is more than the threshold, step  126  (with reference to FIG. 2) turns off gear motor  26  (opens motor switch  56 ), turns off compressor  48  (opens compressor switch  72 ) and flashes the service LED  82 . This is the first strike of a three strike and you&#39;re out process conducted by gear motor routine  100 . A strike count is incremented at this time. Step  128  times out a wait interval before step  130  turns on gear motor  26  and checks the gear motor current. If the gear motor current parameter is not over the threshold, step  134  performs a start up sequence in which compressor  48  is turned on. Step  136  checks the gear motor current. Step  138  then determines if the gear motor current parameter is over the threshold. If not, the strike count is reset, service LED  82  is turned off and control passes to water supply routine  94  (FIG.  3 ). 
     If either step  132  or step  138  determine that the gear motor current exceeds the threshold, step  142  turns off the gear motor, flashes service LED  82  and increments the strike count to two. Referring to FIG. 6, step  144  times out a short wait interval before step  146  turns on the gear motor and checks the gear motor current. Step  148  then determines if the gear motor current parameter is over the threshold. If not, step  150  turns on the compressor. Step  152  checks the gear motor current. Step  154  then determines if the gear motor current parameter exceeds the threshold. If not, step  156  resets the strike count, turns off service LED  82  and passes control to water supply routine  94  (FIG.  3 ). 
     If either step  148  or step  154  determines that the gear motor current parameter exceeds the threshold, step  158  increments the strike count to three, turns off gear motor  26 , the condenser fan, freeze LED  80  and flashes service LED  82 . Step  160  then causes control program  64  to enter a wait status. The flashing service LED  82  alerts an operator/owner that ice producing machine needs service. 
     Thus, the ice producing machine and method of the present invention detects abnormal loading of the gear motor and turns off the gear motor and the compressor before catastrophic events occur that can cause extensive damage. 
     The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.