Abstract:
A control system for an icemaker utilizes a control scheme in which various operating conditions of the icemaker are monitored sand the icemaker is shut down if a fault condition is sensed. In response to detection of the fault condition, steps are taken to actively remove the fault. Restarting of the icemaker is then attempted if sensors indicate that normal continued operation should be possible. The operating conditions sensed include the temperature of refrigerant at an outlet from a condenser, the rate at which a water pan fills with water while water is delivered to it for subsequent delivery to and over an evaporator to freeze the water into ice on the evaporator. and the time required to harvest ice from the evaporator.

Description:
[0001]     This application claims benefit of provisional application Ser. No. 60/455,103, filed Mar. 13, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to commercial icemakers, and in particular to control systems therefore.  
       BACKGROUND OF THE INVENTION  
       [0003]     Commercial ice making machines are well known in the art and provide for the manufacture of ice in various forms, such as cubed and flaked. Cube type icemakers typically make ice by running a flow of water over a vertically oriented evaporator until ice of a sufficient thickness has formed thereon. When the ice is of harvest size, a hot gas defrosting procedure is typically used to remove the ice from the evaporator. It has long been recognized that icemakers are prone to a variety of malfunction events. In response thereto icemakers were first designed to include different control systems that shut down the icemaker in response to a sensor indicating that a problem exists. Examples of such malfunctions include the condenser being too cold or too hot, ice not being successfully harvested from the evaporator, or insufficient water in the water pan. It is also well understood that certain of the malfunctions can be due to causes that are transient in nature. Thus, control strategies have been proposed that allow the ice machine to shut down if a problem is sensed and then to restart and attempt to again make ice. In case the malfunction is not due to a transient problem, these restarts are usually limited to some predetermined number so that the icemaker does not vainly attempt an unlimited number of restarts. It is also well known to add a time delay between each restart in order to increase the total time period over which the limited number of restarts is attempted. This approach can provide more time for the transient problem to go away, while not increasing the number of restarts. At the end of the number of predetermined restart attempts after which a normal cycle of functioning is not restored, it is known to put the machine into a permanent shut-down and activate an indicator light to summon a service technician. Likewise, it is known to reset the counting of restarts to zero if a full ice making cycle results and is followed by a successful harvest.  
         [0004]     A problem with the foregoing control approaches is that the restarts simply occur right after the error is sensed or after the predetermined time delays. In either case, the restart is essentially “mechanical”, that is, without any regard to the actual conditions of the machine. Thus, as long as the particular problem that initiated the shut down continues to exist, each restart attempt during that time is futile and can result in a needless waste of water and/or energy. Efficiency of energy and water use is of critical concern to owners and operators of ice making machines. Accordingly, it would be very desirable to have a control system that is better responsive to the actual operating condition of the ice maker so that restart attempts are minimized and are only initiated when there is a greater chance of a successful ice making cycle occurring. A further problem with the prior art controls concerns the fact that nothing is done in an attempt to actively remove or clear the problem causing the fault condition. Restart attempts are simply repeated in hopes that the error condition goes away or is somehow eliminated by the restart process itself Thus, it would also be desirable to have a more active control strategy that can take specific and more positive steps to eliminate an error condition.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention concerns a control system for an ice maker wherein various operating condition thereof are continually monitored and where the ice maker is shut-down if a fault condition is sensed. A restart is attempted if sensors indicate that normal continued operation should be possible. Also, certain control steps are taken to actively remove the error condition.  
         [0006]     A condenser routine is shown wherein operation of the ice maker is discontinued if a predetermined high temperature thereof is sensed. The ice maker is only restarted when a suitably low condenser temperature is sensed indicating that a subsequent full cycle ice making operation is attainable. If the predetermined high temperature is nevertheless again encountered, the control will again shut-down the ice maker and wait again for the desired low temperature to be sensed. A predetermined number of theses restarts will result in a permanent shut down condition being instructed. Thus, the control of the present invention does not attempt a restart unless and until the condenser temperature has come down to a predetermined low temperature. Thus, the restart has a much greater likelihood of leading to a successful completion of an ice making cycle.  
         [0007]     A water fill rate routine is shown wherein a sensor monitors the rate of filling of a water pan below the evaporator. If the fill rate falls below a predetermined rate, the ice maker shuts off the compressor and the fill valve remains on. Once the rate increases above the predetermined rate or the high level is obtained, the compressor turns on, and the ice maker resumes a normal ice making cycle. If the water fill rate goes below a predetermined low fill rate the ice maker is shut off and water filling is discontinued. In this manner the control of the present invention conserves energy by turning off the compressor if the water fill rate is low but otherwise acceptable. The compressor is then restarted when the water does eventually reach the desired full level.  
         [0008]     A failed harvest routine is shown and requires the monitoring of one or more proximity switches associated with a curtain that is pivotally positioned adjacent the evaporator. If ice is successfully harvested from the evaporator, it will fall there from into an ice bin there below, and in doing so, will contact and move the curtain to an open position. If the one or more curtain proximity switches do not all open in 4 minutes, thereby indicating a failed harvest, the compressor and hot gas valve shut off. The fill valve opens, allowing new warm water to enter the system and the circulating pump then runs for 10 minutes circulating that water over the evaporator. The control then causes the ice maker to enter into a hot gas cycle wherein hot gas from the compressor is sent through the evaporator. The control keeps track of the repeated failed harvests until a predetermined maximum value is reached and then stops any further restart attempts. Therefore, the control of the present invention includes the further and more aggressive steps of circulating warm water over the evaporator in order to more effectively dislodge ice that is resistant to being successfully harvested from the evaporator.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]     A better understanding of the construction and operation of the present invention as well as the objects and advantages thereof can be had by reference to the following detailed description which refers to the following figures, wherein:  
         [0010]      FIG. 1  shows a perspective view of an ice maker mounted atop an ice storage bin.  
         [0011]      FIG. 2  shows a partial cross-sectional view of the interior of the ice maker.  
         [0012]      FIG. 3  shows a schematic representation of the ice maker.  
         [0013]      FIG. 4  shows an enlarged view of the ice maker control board.  
         [0014]      FIG. 5  shows an enlarged partial cross-sectional view of the water pan and pressure fitting.  
         [0015]      FIGS. 6A and 6B  show a flow diagram of the general control strategy of the present invention.  
         [0016]      FIG. 7  shows a flow diagram of the condenser control routine of the present invention.  
         [0017]      FIG. 8  shows a flow diagram of the water fill control routine of the present invention.  
         [0018]      FIG. 9  shows a flow diagram of the failed harvest control routine of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     The ice maker of the present invention is seen in  FIG. 1 , and referred to generally by the numeral  10 . Ice maker  10  includes an exterior housing  12  and is positioned atop an insulated ice retaining bin  14 . As is further understood by referring to  FIGS. 2 and 3 , and as is conventional in the art, ice maker  10  includes a vertical ice forming evaporator plate  16 , a condenser and fan  18  and a compressor  20  connected by high pressure refrigerant lines  21   a  and low pressure line  21   b . As is also well understood, the refrigeration system herein includes an expansion valve  22  and a hot gas valve  24 . A water catching pan  26  is positioned below evaporator  16  and includes a partial cover  27 . A water distribution tube  28  having a water inlet  29  extends along and above evaporator  16 . A water supply solenoid valve  30  has an inlet connected to a source of potable water, not shown, and an outlet line  31  supplying water to pan  26 . A water pump  32  provides for circulating water from outlet  32   b  thereof to inlet  29  of distribution tube  28  along a water line  34 .  
         [0020]     A solenoid operated dump valve  36  is fluidly connected to line  34  and serves, when open, to direct water pumped thereto to a drain, not shown. An evaporator curtain  37  is pivotally positioned closely adjacent evaporator  16  and includes a magnetic switch  38  for indication when it has moved away from evaporator  16  to an open position indicated by the dashed line representation thereof. For purposes of clarity of the view of  FIG. 2 , the various fluid connections of pump  32 , dump valve  36  and water supply valve  30  are not shown, such being represented in schematic form in  FIG. 3 .  
         [0021]     As particularly seen in  FIG. 4 , and also by referring to  FIG. 2 , an electronic control board  40  is located within a separate housing  41  at a position remote and physically isolated from pan  26  and evaporator  16 . Control board  40  includes a microprocessor  42  for controlling the operation of ice maker  10 . Board  40  includes a pressure sensor  44 , such as manufactured and sold by Motorola, Inc. of Phoenix, Ariz., and identified as model MPXV5004G. As understood by also viewing  FIG. 5 , a plastic pneumatic tube  46 , shown in dashed outline, is connected to sensor  44  and on its opposite end to a cylindrical air cup or fitting  48 . Those of skill will understand that housing  41  includes a cover, not shown, that provides for the enclosing and protection of control  40  and sensor  44  therein and through which tube  46  passes prior to connecting to sensor  44 . A temperature sensor  47  is positioned on the outlet refrigerant line of condenser  18  and is connected to control  40 .  
         [0022]     Fitting  48  resides in pan  26  at the bottom thereof and is press fit within a circular ridge  49  that is formed as an integral molded portion of the bottom surface of pan  26 . Fitting  48  includes an outer housing  48   a  defining an inner air trapping area  48   b  and a tube connecting portion  48   c . Four water flow openings  50  exist around a bottom perimeter of housing  48   a.    
         [0023]     The operation of the present invention can be better understood by referring to the flow diagram of  FIGS. 6A and 6B  wherein the basic operation of the present invention is shown. At start block  51  power is provided to control  40 . At block  52  compressor  20  is turned on and substantially simultaneously at block  54  fill valve  30  and dump valve  36  are opened. Thus, cooling of evaporator  18  begins and water flows into pan  26 . At decision block  56 , once a predetermined pump-on water level is reached in pan  26 , as indicated by the level line represented by the letter P in  FIG. 5 , circulatory water pump  32  is turned on at block  58 . The pump-on point is sensed by sensor  44 . In particular, as water fills pan  26 , water flows through holes  50  of fitting  48 . As that occurs, air trapped in area  48   b  is slightly compressed and forced into tube  46  which communicates such pressure increase to sensor  44 . That pressure is then input as a voltage to microprocessor  42  which assigns a numerical value thereto corresponding to a pressure scale. Therefore, when the predetermined pressure value is sensed that corresponds to the pressure at level P, pump  32  is turned on. Because of the fluid connections of pump  32  and dump valve  36 , the action of pump  32  serves to move any water in pan  26  to valve  36  causing the draining away thereof. Thus, a minimum water level, indicated by the level line represented by the letter M in  FIG. 5 , is sensed in the same manner as described above for level P. When that predetermined volume of the water has been removed from pan  26 , pump  32  is stopped at block  62 . As the water supply valve remains on, the level in pan  26  begins to rise and when the P level is again sensed at block  64 , then at block  66 , pump  32  is re-started and fill valve  30  closed. As dump valve  34  remains open, water will again be pumped from pan  26 . At block  68  control  40  again senses for the attainment of the M level. When that occurs, then, at block  70 , water pump  32  is stopped, dump valve  34  is closed and fill valve  30  is opened. It can be appreciated that blocks  52 - 68  serve as a dump cycle whereby any contaminants that have accumulated in pan  26  are agitated by the action of pump  32  and the inflow of water and are twice flushed in this manner and removed from the system.  
         [0024]     At block  72  control  40  monitors for the attainment of a maximum fill level for pan  26  indicated by the level line denoted by letters MX. When this highest pressure level is sensed, then at block  74  fill valve  30  is closed. At block  76 , a 45 second clock is initiated to provide for some pre-cooling of the water delivered to pan  26  through flow over evaporator  16 . At block  78  pump  32  is again turned on. A further  45  second clock is set at block  80 , and when that has timed out, fill valve  30  is opened. It will be understood by those of skill that action of pump  32  will serve to fill fluid line  34  and distribution tube  28  which will slightly lower the level of water in pan  26  below that of the desired maximum water volume indicated by level MX. Thus, fill valve  30  is opened at block  82 , to replenish that volume as is determined at block  84 . At block  86 , fill valve  30  is closed when the desired starting maximum level MX is again attained.  
         [0025]     At this point pump  32  is operating to flow water over evaporator  16  as such is being cooled by the action of compressor  20 , condenser and fan  18  and expansion valve  22 , all as operated by control  40 . As ice forms on evaporator  16 , the water level in pan  26  goes down as does the pressure sensed by sensor  44 . When a predetermined harvest water level is reached, as indicated by the level line denoted H, a corresponding predetermined pressure value is sensed by control  40  at block  88 . When the harvest point is indicated, pump  32  is stopped and hot gas valve  24  is opened at block  90 , causing evaporator  16  to warm resulting in the release of the ice slab formed thereon. Of course, those of skill will understand that other heating means known in the art could be employed, such as, an electrical heater integral with the ice forming evaporator. As is well understood, when the slab of ice falls from evaporator  16 , curtain  37  is opened and switch  38  is closed, signaling to the control  40  the release of the ice slab from evaporator  16 . As is also known, to insure that the slab of ice has fallen into bin  12  and is no longer in the vicinity of evaporator  16 , at block  96 , the control herein awaits the remaking of switch  38  which occurs when curtain  36  is free to swing back to its normal closed position unobstructed by any ice. At block  98  the control returns to start and initiates a further ice making cycle.  
         [0026]     It was found that the pressure-based water level sensing as described herein provides for very accurate and repeatable determination and control thereof, and hence, for very reliable control of the harvest cycle of an ice maker. In particular, the physical isolation of the pressure sensor  44  from pan  26  contributes to this improved performance by serving to prevent any degradation of the sensor due to the presence of water and/or the corrosive impact thereof.  
         [0027]     The operation of the high condenser temperature error control can best be understood by reference to  FIG. 7 . As seen therein at block  100 , ice maker  10  is in an ice making cycle where upon at block  102  the temperature of condenser  18  is sensed by temperature sensor  47 . If at block  104  the temperature is determined to be greater than 160 degrees Fahrenheit (F.) at block  106  a time period “C” is started. At block  108  the condenser temperature is read again, and if at block  110  the temperature of the condenser has gone below 160 Degrees F. normal ice making is continued after stopping the timing of period C at block  112  and resetting the time C timer at block  114 . If however, at block  116  time C has timed out, in the present case at 2 seconds, a counter is incremented once at block  118 . At block  120  it is determined if the counter equals three, i.e. that three successive time periods C have timed out without a successful return to an ice making cycle and the full completion thereof through harvest. If the C count is equal to 3, then at block  122  a high temp shut down code is flashed. All outputs are then turned off at block  124  which then requires that ice maker  10  be restarted by a manual restart at block  126  in order to re-enter the ice maker start-up or ice making routine at block  128 . If at block  120  the count is less than three, then at block  130  a high temperature waning code is flashed and all outputs are turned off at block  132 . The temperature of the condenser is monitored at block  134  and if at block  136  the temperature of the condenser goes to a predetermined low temperature, e.g. 100 degrees F., the ice malting start-up sequence is reinitiated at block  138 . It can be understood that the condenser temperature error control of the present invention only reinitiates if the condenser temperature is deemed to have gone to a suitably low temperature that restart makes sense, i.e. there is a greater likelihood that a successful ice making cycle will ensue.  
         [0028]     The water fill cycle control of the present invention is best understood by referring to the flow diagram of  FIG. 8 . At block  200  an ice making cycle is initiated and the control first determines at block  202  if water is at the maximum MX level. If it is, then at block  204  it is first determined that the hot gas valve  24  is closed and then at block  206  the ice making cycle is entered. If at block  202  the water level is not at the maximum, then a water fill timer is started at block  208  after which valve  30  is opened at block  210 . At block  212  the rate of flow in terms of inches of water depth increase in water pan  26  is determined by processor  42  as a function of the input of pressure communicated to sensor  44 . If, at block  212  it is determined that the water flow rate is increasing at a rate equal to or greater than 0.1 inch per 10 seconds it is then determined at block  214  if the MX water level has been reached. If that MX level has been achieved at block  214  then valve  30  is closed at block  216  and the hot gas valve  24  is checked at block  218 . If valve  24  is off, then an ice making cycle is entered at block  220 . Thus, as long as the flow rate of the water entering pan  26  correlates to a rate of fill of greater than or equal to 0.1 inch per 10 seconds of water level increase in pan  26 , ice maling proceeds once the MX level is reached. However, if at block  222  it is determined that the water level in pan  26  is less than one quarter of an inch, then at block  224  a failed water system shut down code is flashed and all outputs are turned off at block  226 . A manual restart at block  228  is then required to re-enter the ice making routine start-up at block  230 . If at block  212  it is determined that the pressure increase corresponds to a fill rate of pan  26  per 10 seconds as being less that 0.1 inch at block  232  the compressor is turned off and at block  234  an inlet water warning is flashed.  
         [0029]     It can now be understood that the water safety control of the present invention actively looks at the fill rate of pan  26  and has a built in tolerance for that fill rate. If the fill rate is above a certain predetermined rate, the compressor is left on. If the fill rate is low but otherwise acceptable, i.e. the filling of the pan will occur in a slower but nevertheless reasonable period of time, then that filling is allowed to continue. However, the compressor is turned off so as not to waste energy during the longer fill cycle. The water fill routine of the present invention is also an improvement over the prior art wherein a simple timer is used without regard to the actual fill rate. Thus, the water fill routine herein will not recognize as a “fault” what other systems may otherwise determine as such based upon the simple timing out of a timer. A threshold low or no fill rate is also determined below which the filling of pan  26  is exceedingly slow or not occurring at all, whereupon a manual restart should be required. If less than one quarter of an inch of water is seen in pan  26 , that would indicate that no water is flowing or that, for example, pan  28  is leaking water and not filling.  
         [0030]     The improved harvest cycle control of the present invention can best be understood in view of  FIG. 9 . At block  300 , a harvest cycle is signaled to begin and at block  302  hot gas valve  24  is opened. A harvest timer is then started at block  304 . If, at block  306  the harvest time is less than four minutes and at block  308  all the proximity switches  38  are open, indicating a successful harvest, then at block  310  a subsequent ice maling cycle is entered. If at block  306  the harvest time exceeds 4 minutes, then a harvest timer counter is reviewed at block  312  and if the count thereof equals 5, then a harvest time out shut down code is flashed at block  314 . At block  316  all outputs are turned off such that a manual restart is required at block  318  in order to re-enter an ice making cycle at block  320 . If at block  312  the count is less than 5, the counter is incremented at block  322  the compressor is turned off at block  324 , and a harvest time out warning code is flashed at block  326 . At block  328  a water fill timer is started and valve  30  is opened at block  330  letting warm water fill pan  26 . If at blocks  332  and  334  either the water fill timer equals 4 minutes or the water MX level is reached, then a water pump timer is started at block  336 . Water pump  32  is then started at block  338  and circulates the warm replacement water over the evaporator  16 . When the water pump timer reaches 10 minutes at block  340 , then the ice making restart cycle is entered at block  342 .  
         [0031]     It can be appreciated that the harvest control of the present invention uses a novel approach to circulate warm water over the evaporator for a predetermined period of time in order to melt and remove any recalcitrant ice from the evaporator. Thus, the control herein takes active measures to eliminate a fault resulting from a failed harvest, wherein ice is not seen to have fallen from the evaporator.  
         [0032]     While embodiments of the invention have been described in detail, one skilled in the art can devise various modifications and other embodiments without departing from the spirit and scope of the invention, as defined in the accompanying claims.