Patent Publication Number: US-2012031114-A1

Title: Method and system for producing clear ice

Description:
CROSS-REFERENCED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/370,422, filed on Aug. 3, 2010, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure generally relates to a method and system for producing clear ice by monitoring the conductivity of water (e.g., Total Dissolved Solids (TDS)) in an ice machine and adding additional water when conductivity exceeds a predetermined level, thereby reducing the TDS level of the water and enabling the formation of clear ice. In particular, the present disclosure provides for the formation of clear or clearer ice by monitoring or detecting the conductivity of water to ensure that the TDS level of the water is maintained below a predetermined level during the freeze cycle by the addition of fresh water from the water source. 
     2. Discussion of the Background Art 
     It is know in the ice making industry that excessive TDS concentrations in water can prevent the formation of ice cubes and also product undesirable cloudy appearing ice cubes. In addition, once of the causes for equipment failure in ice making and steaming equipment is water-borne dissolved minerals commonly referred to as TDS, measured in parts per million (ppm). Unacceptably large concentrations of TDS interfere with machine operation while in solution, and form deposits of unwanted scale when the water changes phase. Scaling in ice makers can also result in increased level of difficulty in harvesting ice cubes, as they will often become stuck to the evaporator plate, and eventually may damage the evaporator plate. 
     Furthermore, as TDS builds up in an icemaker, the pH of the water also increases, which decreases the ability of minerals to stay in solution. Thus, left unchecked, the scale forms progressively faster. 
     Conventional icemakers address the problem of TDS buildup by periodically flushing the water lines and other components during the harvest phase of the cube formation cycle. In addition, the storage sump, which retains a supply of chilled water recirculated to form ice cubes, is also emptied at this time, either partially or totally. 
     Other attempts to decrease TDS and scaling in the water supply of ice makers, steamers and other water phase changing devices include the use of more effective filters and the addition of feed phosphates or acidulates to stop the buildup of minerals. Although filtration is effective in substantially reducing suspended particles, the ionic particles in solution in the water are not significantly reduced. The addition of phosphates or acid to filtered water has also been found to further prolong the service interval as compared to filtration alone. The chemical additives assist in maintaining the ionic particles in solution longer. However, users of such equipment have still been forced to dump excessive amounts of chilled water from their units. 
     Another drawback of conventional ice making equipment is that the rate of scale buildup varies with the varying TDS concentration in different types of water sources, the level of water treatment, and the geographic region. 
     The problem with periodically flushing the water lines and water in the sump is that it costs additional money in terms of sewage disposal and new filtered water. This problem was addressed in U.S. Pat. No. 5,527,470 (Suda) which is directed to a method for monitoring and controlling an ice machine by monitoring the TDS concentration of the recirculating water in the machine. If the TDS has been determined to exceed a predetermined level, then after the harvest cycle has been completed, the system will discharge all or a portion of the water from the sump and then introduce new water. Rather than discharging all of the water, as in some of the earlier attempts to regulated TDS in ice making water, Suda attempts to discharge only a portion and then adds only enough refresh water to insure that the sump water is below the predetermined TDS level. Unfortunately, this is still wasteful, results in cloudy ice and not ecologically desirable. That is, once the ice making machine of Suda initiates the freeze cycle is utilizes whatever water is presently in the sump to make ice regardless of its TDS level during the freeze cycle. However, as the ice begins to form, the present inventors have discovered that the TDS level in the sump increases and may exceed the predetermined TDS level and, thus, causes the formation of cloudy ice. 
     Contrary to either of the prior art processes seeking to reduce TDS levels as discussed above, the present inventors have developed a unique method and system for formation of clear ice, which does not have to dump water to maintain the TDS level. To the contrary, the present disclosure monitors the conductivity level (e.g., TDS level) during the freeze cycle and when the TDS level exceed a predetermined level, the pump valve is energized so that fresh water is introduced into the ice making machine during the freeze cycle to ensure that the TDS level remains below the predetermined level during a substantial portion of the freeze cycle so that ice clear or substantially clear ice is produced. This reduces the amount of water used and also produces consistently clear ice during each freeze/harvest cycle, which is not possible using the monitoring and discharge systems disclosed in the prior art. 
     The present disclosure also provides many additional advantages, which shall become apparent as described below. 
     SUMMARY 
     A method for making clear ice comprising: filling a water sump to a predetermined level; contacting a refrigerant to an evaporator; circulating water from the sump over the evaporator to form ice on the evaporator; monitoring the water level in the sump; and monitoring the conductivity of the water in the sump to determine if the conductivity of the water is equal to or greater than a predetermined conductivity valve, (i) if the conductivity is not equal to or greater than the predetermined conductivity valve and if the water level reaches a predetermined lower water level, then complete the ice making cycle and initiate to the harvest cycle; or (ii) if the conductivity is equal to or greater than the predetermined conductivity valve and if the water level has not reached a predetermined lower water level, then add additional water to the water sump. 
     If the ice making cycle has ended and the conductivity of the water in the sump is not equal to or greater than the predetermined valve, adding additional water to the sump before initiating another ice making cycle. 
     If the ice making cycle has ended and the conductivity of the water in the sump is equal to or greater than the predetermined conductivity valve, dumping the water in the sump and adding freeze water to the sump before initiating another ice making cycle. 
     The step of monitoring the water level is via a water level probe comprising a first probe for detecting a high water level and second and third probes for detecting a low water level. 
     The water level probe measures the conductivity of the water by determining the conductivity difference between the second and third probes, wherein the third probe is a reference probe. The predetermined conductivity value is about 30 GPH. 
     A system for producing clear ice, the system comprising: a water supply; a water sump; an evaporator; a water inlet valve disposed between the water supply and the water sump; a pump for circulating water from the sump to the evaporate during an ice making cycle; a controller that monitors the water level in the sump and the conductivity of the water in the sump to determine if the conductivity of the water is equal to or greater than a predetermined conductivity valve, (i) if the conductivity is not equal to or greater than the predetermined conductivity valve and if the water level reaches a predetermined lower water level, then complete the ice making cycle and initiate the harvest cycle; or (ii) if the conductivity is equal to or greater than the predetermined conductivity valve and if the water level has not reached a predetermined lower water level, then add additional water to the water sump. 
     Further objects, features and advantages of the present disclosure will be understood by reference to the following drawings and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a water level probe function of the present disclosure; 
         FIG. 2  is a block diagram of the water system flow according to the present disclosure; and 
         FIG. 3  is logic diagram of the TDS sensing process and water fill used to form clear ice according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A system for making ice while controlling the water inlet and outlet based on the water conductivity in the sump trough. The water inlet valve is energized to bring all of the water in at one time prior to initiating the freeze cycle. Preferably, the amount of water is sufficient make a single batch of ice through one freeze and harvest cycle. And a conductivity measurement is made and depending upon the measurement the water valve may be energized again throughout the ice making or freezing cycle, as is necessary to maintain the conductivity or TDS level at or below a predetermined amount. During the freeze cycle, sensor readings are periodically taken of the water in the sump to determine if additional water needs to be added to reduce the TDS level, thereby producing substantially clear ice. 
     The system measures TDS of the supply water in the sump as water enters the system. If TDS is below the lower limit of normal, then no more water is brought into the sump and ice is made with that minimal amount of water. That is, the sump is initially filled until water contacts the lower level sensor which allows measurements of TDS. If the TDS measurement is between the lower and upper limit of normal, then an additional quantity of water is added to the sump by filling the sump until water contacts the upper level sensor and ice is continued to be made with that total water quantity. If TDS is above the upper limit of normal, then an additional quantity of water is added to the sump by filling the sump until water contacts the upper level sensor during the course of the ice making cycle. 
     The present disclosures can best be described by referring to the attached drawings, wherein  FIG. 1  is block diagram of water system  1  used in the system of the present disclosure. System  1  initiates the ice making process via control board  3  which sends output signals via electrical conduits  5  and  7  to energize water inlet valve  9  and de-energize water dump valve  11 , respectively. With water inlet valve  9  energized, water from water supply  13  passes through water inlet valve  9  via conduit  15  into water sump trough  17  where it is pump via pump  19  into conduit  21  and thereafter to water distributor  23 . Water from water distributor  23  is then distributed over evaporator  25  where it is formed into ice. Water that does not freeze onto evaporator  25  is then returned to water sump trough  17  for recycling to water distributor  23 . 
     A water level probe  27  is capable of measuring the water level in water sump trough  17 , as well as detecting the conductivity of the water in water sump trough  17 , so that the TDS level of the water can be monitored by control board  3 .  FIG. 1  depicts water level probe  27 , wherein probe ‘A’ is disposed at the level of water needed to for the ice making cycle to make a desired quantity of ice. Probes ‘B’ and ‘C’ are both disposed at the low level and measure conductivity of the water. As the water level drops during the ice making cycle from level ‘A’ where is registered low TDS or low conductivity toward levels ‘B’ and ‘C’, then conductivity tends to increase. When the water&#39;s conductivity reaches a predetermined level, i.e., an undesirable TDS level, control board  3  opens water inlet valve  9  so that fresh or additional water from water supply  13  passes through conduit  15  into water sump trough  17 . This additional water is then pumped to water distributor  23  via pump  19  and conduit  21  so that the ice being formed on evaporator  25  remains substantially clear. If additional water is not added when the conductivity or TDS level reaches an undesirably high level, then the ice being formed would tend to get cloudy which is not appealing to consumers. See Table 1 below: 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 TDS/CONDUCTIVITY 
                   
               
               
                 SCALE B/C READING 
                 FUNCTION 
               
               
                   
               
             
            
               
                 High (30-45 GPH) high 
                 If B/C probe readings are within this range, fill 
               
               
                 conductivity (low 
                 to level A, when water drops to B/C refill to A 
               
               
                 resistance) 
                 again for additional water and dump every 
               
               
                   
                 cycle 
               
               
                 Normal (15-29 GPH) 
                 If B/C level is within this range, fill to level A 
               
               
                   
                 and dump every cycle 
               
               
                 Low (0-14 GPH) low 
                 If B/C level is within this range, fill to level A 
               
               
                 conductivity (high 
                 and do not dump every cycle 
               
               
                 resistance) 
               
               
                   
               
            
           
         
       
     
       FIG. 1  is a diagram showing the relative probe location. The high level probe is identified as “A” in this figure and is used to determine the high water level of the water sump. Probes “B” and “C” are low water level probes and are used to identify the low water sump level, as well as to measure the conductivity of the water present in the sump. 
       FIG. 3  is a logic diagram that depicts the ice making method of the present disclosure. The user will initiate the start of the ice cycle  31 . The system then check to see if ice cycle is beginning  33 . If the ice cycle does not begin, then the system returns to  31 . If the ice cycle does begin, then the conductivity of the water in sump trough  17  is measured  35  by water level probe  27  and control board  3 . Control board  3 , then compares  37  measured conductivity (M) to preset conductivities (H,N,L). Conductivity is a measurement of a materials ability to conduct electricity. In this present disclosure the water level probe is also measuring the conductivity of the water in the water sump. The resistance between the probes indicates the water&#39;s concentration of total dissolved solids (TDS) and scale. The table in  FIG. 1  describes the threshold levels for low to high levels of TDS and scale. The controller measures the conductivity of the water via probes “B” and “C” ( FIG. 1 ) and compares the measurement to a stored value resident in the controller. 
     Control board  3  will then determine if the measured conductivity is equal or less than a preset or predetermined conductivity valve L≦Preset Value  39 . If the conductivity is low and value L≦Preset Value then end ice formation  41  and end of ice making cycle  43 . This again refers to the block diagram “end of ice formation” which is the completion of the ice freeze cycle. If L is greater than the Preset Value, then the system checks to see if measured conductivity (M) is NORMAL  45  (15-29 GPH), i.e., M=N. If conductivity is NORMAL, then end of ice formation  47 . If conductivity is not NORMAL, then the system determines if the measured conductivity (M) is high  49 , i.e., M≧H preset valve. If the measured conductivity is not high, then the system returns to compare measured M to preset (H,N,L)  37 . If the measured conductivity is high where M≧H, then control board  3  energize water inlet  9  such that additional or fresh water is supplied to water sump trough  17  via water supply  13  during the freeze cycle  51  and then ends the ice formation  47 . End of ice Formation  47  means that the machine operates until it is signaled from the Ice Thickness Probe (ITP) at which point the machine enters into harvest cycle and ultimately the completion of the complete cycle. If the system has measured high conductivity, then after the freeze cycle has been completed, control board  3  energizes the water dump valve  11 , such that all of the water in sump trough  17  is dumped at the end of the ice making cycle  53  and then the freeze cycle is ended  43 . 
     In normal operation, the Ice Thickness Probe (ITP) determines when the machine is to enter into the harvest mode. When the ice forms on the evaporator to a point where the individual cubes are interconnected (bridged) the ice contacts the ITP and a signal is sent to the control board which initiates harvest. That is, the system continues its&#39; normal freeze cycle and is terminated when the Ice Thickness Probe (ITP) signals the controller. 
     While we have shown and described several embodiments in accordance with our invention, it is to be clearly understood that the same may be susceptible to numerous changes apparent to one skilled in the art. Therefore, we do not wish to be limited to the details shown and described but intend to show all changes and modifications that come within the scope of the appended claims.