Abstract:
A method of making ice in an automatic ice maker includes the steps of: providing a mold including one cavity; filling the at least one mold cavity at least partially with water; providing an ice removal device at least partly within the at least one mold cavity; coupling a mechanical drive with the ice removal device; coupling a controller with the drive; measuring a temperature of the mold; measuring an ambient temperature associated with the mold; and controlling operation of the drive using the controller, dependent upon the measured temperature of the mold and the measured ambient pressure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part of U.S. patent application Ser. No. 09/748,411, entitled “ICE MAKER AND METHOD OF MAKING ICE”, filed Dec. 26, 2000, which is a continuation-in-part of U.S. patent application Ser. No. 09/499,011, entitled “ICE MAKER”, filed Feb. 4, 2000, which is a continuation-in-part of U.S. patent application Ser. No. 09/285,283, entitled “ICE MAKER”, filed Apr. 2, 1999, now U.S. Pat. No. 6,082,121. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to freezers, and, more particularly, to ice makers within freezers.  
           [0004]    2. Description of the Related Art  
           [0005]    The freezer portion of a refrigeration/freezer appliance often includes an ice cube maker which dispenses the ice cubes into a dispenser tray. A mold has a series of cavities, each of which is filled with water. The air surrounding the mold is cooled to a temperature below freezing so that each cavity forms an individual ice cube. As the water freezes, the ice cubes become bonded to the inner surfaces of the mold cavities.  
           [0006]    In order to remove an ice cube from its mold cavity, it is first necessary to break the bond that forms during the freezing process between the ice cube and the inner surface of the mold cavity. In order to break the bond, it is known to heat the mold cavity, thereby melting the ice contacting the mold cavity on the outermost portion of the cube. The ice cube can then be scooped out or otherwise mechanically removed from the mold cavity and placed in the dispenser tray. A problem is that, since the mold cavity is heated and must be cooled down again, the time required to freeze the water is lengthened.  
           [0007]    Another problem is that the heating of the mold increases the operational costs of the ice maker by consuming electrical power. Further, this heating must be offset with additional refrigeration in order to maintain a freezing ambient temperature, thereby consuming additional power. This is especially troublesome in view of government mandates which require freezers to increase their efficiency.  
           [0008]    Yet another problem is that, since the mold cavity is heated, the water at the top, middle of the mold cavity freezes first and the freezing continues in outward directions. In this freezing process, the boundary between the ice and the water tends to push impurities to the outside of the cube. Thus, the impurities become highly visible on the outside of the cube and cause the cube to have an unappealing appearance. Also, the impurities tend to plate out or build up on the mold wall, thereby making ice cube removal more difficult.  
           [0009]    A further problem is that vaporization of the water in the mold cavities causes frost to form on the walls of the freezer. More particularly, in a phenomenon termed “vapor flashing”, vaporization occurs during the melting of the bond between the ice and the mold cavity. Moreover, vaporization adds to the latent load or the water removal load of the refrigerator.  
           [0010]    Yet another problem is that the ice cube must be substantially completely frozen before it is capable of withstanding the stresses imparted by the melting and removal processes. This limits the throughput capacity of the ice maker.  
           [0011]    What is needed in the art is an ice maker which does not require heat in order to remove ice cubes from their cavities, has an increased throughput capacity, allows less evaporation of water within the freezer, eases the separation of the ice cubes from the auger and does not push impurities to the outer surfaces of the ice cubes.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention provides a control system and corresponding method of operation which allows ice cubes to be automatically harvested in an efficient manner.  
           [0013]    The invention comprises, in one form thereof a method of making ice in an automatic ice maker, including the steps of: providing a mold including at least one cavity; filling the at least one mold cavity at least partially with water; providing an ice removal device at least partly within the at least one mold cavity; coupling a mechanical drive with the ice removal device; coupling a controller with the drive; measuring a temperature of the mold; measuring an ambient temperature associated with the mold; and controlling operation of the drive using the controller, dependent upon the measured temperature of the mold and the measured ambient temperature.  
           [0014]    The invention comprises, in another form thereof, an ice maker including a mold with at least one cavity for containing water therein for freezing into ice. A mold temperature sensor is positioned in association with a mold and provides an output signal indicative of a temperature of the mold. An ambient temperature sensor provides output signal indicative of an ambient temperature associated with the mold. An ice removal device is at least partly positioned within the at least one mold cavity. The mechanical drive drives the ice removal device. A controller is coupled with each of the mold temperature sensor, the ambient temperature sensor and the drive. The controller controls operation of the drive dependent upon the output signal from the mold temperature sensor and the output signal from the ambient temperature sensor.  
           [0015]    An advantage of the present invention is that ice cubes may automatically be harvested depending upon the temperature of the mold, thereby increasing the throughput rate of the ice maker.  
           [0016]    Another advantage is that the time period necessary for freezing the ice may be calculated without continuously sensing and memorizing the temperature of the mold.  
           [0017]    Yet another advantage is that the time period necessary for freezing the ice may be adjusted automatically based upon changing environmental conditions within the freezer which affect the temperature gradient of the freezing. That provides for better cube quality: no soft cubes, no hollow cubes, no broken cubes.  
           [0018]    A further advantage is that filling of the mold cavity does not occur until the temperature of the mold has decreased to a point where freezing may begin occurring after filling, so no double fills will occur.  
           [0019]    Another advantage is that a frozen or blocked fill tube may be sensed and heat applied thereto for the purpose of clearing the fill tube. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0021]    [0021]FIG. 1 is a schematic illustration of a freezer including an embodiment of an ice maker of the present invention; and  
         [0022]    [0022]FIG. 2 is a flow chart of a method of making ice of the present invention.  
         [0023]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Referring now to the drawings, and more particularly to FIG. 1, there is shown an embodiment of a freezer  10  including an ice maker  12  disposed within a freezer unit  14 . Freezer unit  14  may be, e.g., a side-by-side arranged or vertically stacked freezer unit in a household freezer appliance.  
         [0025]    Ice maker  12  generally includes a mold  16 , an auger  18 , a mechanical drive  20 , a controller  22 , a fill tube  24 , a mold temperature sensor  26  and an ambient temperature sensor  28 . Mold  16  includes at least one mold cavity  30  for containing water therein for freezing into ice. In the embodiment shown, mold  16  includes a single mold cavity  30  with interior walls having a slight draft to allow the ice to be more easily removed therefrom. Auger  18  includes an auger shaft  32  about which a continuous flighting  36  extends from one end to the other. Auger  18  is tapered in a discharge direction to allow easier decoupling from the at least partially frozen ice cube which is formed within mold  16 . For more details of a mold and tapered auger which may be utilized with ice maker  12  of the present invention, reference is hereby made by to U.S. patent application Ser. No. 09/499,011, entitled “Ice Maker”, which is assigned to the assignee of the present invention and incorporated herein by reference. Drive  20  rotatably drives auger  18  within mold  16 . In the embodiment shown, drive  20  is in the form of an electric motor, such as an alternating current or direct current motor, having an output shaft  38  which is coupled with and drives auger  18 . Drive  20  is electrically coupled with controller  22  via line  40 .  
         [0026]    Fill tube  24  is coupled with a water line  42  and receives water from a water source (not shown), such as a common pressurized household water supply line. Fill tube  24  selectively receives water such as by using a control valve  52  for supplying water to cavity  30  within mold  16 . Control valve  52  is coupled with controller  22  via line  54 . Fill tube  24  includes a heater  44  therein which is selectively energized to melt any accumulation of ice which may build up in fill tube  24  during operation. In the embodiment shown, heater  44  is in the form of an electrical wire which is over molded within fill tube  24 , and electric controller  22  via line  46 . For more details for a heated fill tube  24  which may be utilized with the present invention, reference is hereby made to U.S. patent application Ser. No. 09/130,180, entitled “Heater Assembly For a Fluid Conduit With an Internal Heater”, which is assigned to the assignee of the present invention and incorporated herein by reference.  
         [0027]    Mold temperature sensor  26  is positioned in association with mold  16  to sense a temperature of mold  16 . In the embodiment shown, mold temperature sensor  26  is embedded within or carried by a sidewall of mold  16  to thereby sense a temperature of the sidewall and provide an output signal to controller  22  via line  48 . Ambient temperature sensor  28  is positioned in association with mold  16  and provides an output signal indicative of the sensed ambient temperature. Ambient temperature sensor  28  may be mounted to suitable structure within freezer  14 , and is preferably mounted to ice maker  12 . For example, ice maker  12  may include a mounting flange for mounting to a wall within freezer  14 , and ambient temperature sensor  28  may be mounted to the flange of ice maker  12 . Other suitable mounting locations on ice maker  12  which are not in contact with mold  16  are also possible.  
         [0028]    Sensor  29  is used to detect whether or not ice is present within an ice holding tray or bin in freezer unit  14 . Sensor  29  provides an output signal to controller  22  indicative of whether the ice tray is already full.  
         [0029]    Compressor  31  is also coupled with controller  22  and provides an output signal to controller  22 . In particular compressor  31  provides a signal to controller  22  indicating whether compressor  31  is running or not running.  
         [0030]    Controller  22  is used to selectively accuate drive  20 , heater  44  and/or valve  52 . The control of drive  20 , heater  44  and valve  52  is at least in part dependent upon one or more output signals which are outputted from first temperature sensor  26 , second temperature sensor  28  and/or sensor  29  to controller  22 .  
         [0031]    Referring now to FIG. 2, there is shown a flow chart illustrating an embodiment of a method of the present invention for making ice in automatic ice maker  12  shown in FIG. 1. Ice maker  12  generally freezes ice cubes in a batch manner such that ice cubes are sequentially frozen and discharged into a suitable holding tray (not shown). The method described hereinafter corresponds to the logic processes for forming a single ice cube within ice maker  12 . It will be appreciated that the method continues in a looped fashion for making additional ice cubes within ice maker  12 .  
         [0032]    Moreover, the embodiment of the present invention for making ice cubes described hereinafter is assumed to be carried out in software within suitable electronics, and thus may be easily implemented by a person of ordinary skill in the art. It is to be appreciated, however, that the embodiment of the method of the present invention described hereinafter may be carried out in software, firmware and/or hardware, depending upon the particular application.  
         [0033]    After start  60  of the control logic flow chart shown in FIG. 2, a mold temperature Tm and initial ambient temperature Tr are stored in a memory device (block  62 ). Mold temperature sensor  26  outputs a signal via line  48  to controller  22  corresponding to mold temperature Tm; and ambient temperature sensor  28  outputs a signal via line  50  to controller  22  corresponding to initial ambient temperature Tr. Mold temperature Tm and initial ambient temperature Tr may be stored in a non-volatile memory to form a history of stored temperatures over time.  
         [0034]    At block  64 , a maximum mold temperature Tmax is determined using mold temperature sensor  26 . The maximum mold temperature Tmax corresponds to the maximum temperature reached by mold  16  after being filled with water as a result of thermal inertia. Mold  16  is generally at a temperature corresponding the internal temperature within freezer unit  14  prior to an initial fill cycle (i.e., approximately the same as the ambient temperature sensed by ambient temperature sensor  28 ). The water which is injected into mold  16  is at an elevated temperature (e.g., 60° F.). After mold  30  is filled with water from fill tube  24 , the elevated temperature of the water within mold cavity  30  causes the temperature of mold  16  to increase according to the corresponding temperature gradient curve. At some point in time, however, the temperature of mold  16  reaches a maximum level Tmax and then again descends as a result of the colder temperature of the air within freezer unit  14 . Suitable control logic, such as that found in co-pending parent application Ser. No. 09/748,411 can be used to detect the maximum temperature Tmax of mold  16  after being filled with water.  
         [0035]    Blocks  66 ,  68 ,  70  and  72  basically define a wait state during which heat transfer is allowed to occur for freezing the water into ice within mold cavity  30 . At block  66 , a delay interval of fifteen seconds, or other suitable delay time period, occurs. A counter n, initially set to zero, is incremented by one at block  68 . A total harvest time consisting of the summation of the delay intervals is compared with a minimum time constant Th (block  70 ). Minimum time constant Th corresponds to an empirically determined value of a minimum amount of time necessary for freezing of the water to occur. If the total harvest time is less than the minimum time constant Th (line  72 ), then control loops back to the input side of block  66  and another delay interval occurs. On the other hand, if the total harvest time is greater than or equal to the minimum time constant Th (line  74 ), then a determination is made as to whether the temperature of the mold is approximately the same as the ambient temperature sensed by ambient temperature sensor  28  within freezer  14 .  
         [0036]    More particularly, the temperature of the mold increases above the internal ambient temperature within freezer  14  when water is injected into mold cavity  30 . As the water freezes, the temperature of mold  16  decreases and again approaches the internal ambient temperature within freezer  14 . Constant Tc2 is selected empirically to slightly raise the comparison value of the internal mold temperature Tr in decision block  76 . Since the mold temperature and the internal ambient temperature asymptotically approach each other over time after a fill cycle, it has been found necessary to slightly adjust the ambient temperature Tr by the offset constant Tc2 for the proper determination of whether freezing has occurred. If the mold temperature Tm is greater than the sum of the ambient temperature Tr and the constant Tc2 (line  78 ), control loops back to the input side of block  66  as shown. On the other hand, if the mold temperature Tm is less than or equal to the sum of the ambient temperature Tr and the constant Tc2 (line  80 ), control passes to the next group  82 - 108  for the purpose of determining an additional delay period during which freezing occurs prior to discharging an ice cube using drive  20  controlled by controller  22 .  
         [0037]    To wit, at block  82  the slope V (represented by the temperature fall in degrees per unit of time, e.g., seconds) is calculated using the mathematical expression: 
           T max− Tm /15 Xn   
         [0038]    Where,  
         [0039]    Tm is the sensed current mold temperature using mold temperature sensor  26 , and the quotient 15 Xn represents in this example the total time for freezing to occur thus far within mold cavity  30 . Of course, the number  15  will vary if the delay interval in block  66  is selected differently. The slope V represents the rate at which freezing occurred within mold cavity  30 . If freezing occurs too rapidly, such as with a high value of the slope V, the outside of an ice cube may freeze while the interior may still remain in a liquid state as water.  
         [0040]    At decision block  84 , slope V of the temperature gradient is compared with a predetermined constant V1. If the slope V is less than the constant V1 (line  86 ), then an additional delay T 1  occurs to ensure that the water is frozen into ice. On the other hand, if the slope V is greater than or equal to the predetermined constant V1 (line  90 ), then the slope V is compared to a further predetermined constant V2. The constant V2 is selected with a value which is greater than the constant V1. If the slope V of the temperature gradient is less than the predetermined constant V2 (line  94 ), then an additional delay time T 2  occurs to ensure that the water is frozen into ice.  
         [0041]    On the other hand, if the slope V is greater than or equal to the predetermined constant V2 (line  98 ), then a determination is made as to whether the maximum mold temperature Tmax is greater than or equal to a predetermined constant Tc3 (decision block  100 ). If the maximum mold temperature Tmax is less than the constant Tc3 (line  102 ), then an additional time delay T 3  occurs to ensure that the water freezes into ice. The value of the time delay T 3  is greater than time delay T 2 , which in turn is greater than time delay T 1 .  
         [0042]    On the other hand, if the maximum mold temperature Tmax is greater than or equal to the constant T 3 , than this in general terms means that the mold warmed too much during the fill cycle and it is necessary to delay for a longer period to ensure that the interior of the ice cube freezes adequately. Thus, if the maximum mold temperature Tmax is greater than or equal to the constant Tc3 (line  106 ), then an additional time delay T 4  occurs to ensure that the water freezes into ice. The value of the additional time delay T 4  is greater than the value of time delay T 3 .  
         [0043]    The output from each of blocks  88 ,  96 ,  104  and  108 , each with a different time delay period, T 1 , T 2 , T 3  and T 4 , respectively, are inputted in a parallel manner to block  110 , wherein the value of counter N is reset to zero and the value of the maximum mold temperature Tmax is set to zero. At block  112 , controller  22  energizes drive  20  to discharge the ice cube from mold cavity  30  using auger  18 .  
         [0044]    Blocks  114  through  130  relate to the filling cycle of mold cavity  30  within mold  16 . Blocks  114  and  116  generally relate to determining whether the temperature of mold  16  has decreased to an extent allowing adequate freezing of the water to occur during the fill cycle. In block  114 , a current mold temperature Tm 1  and an ambient temperature Tr are sensed using mold temperature sensor  26  and ambient temperature sensor  28 , respectively. The ambient temperature Tr is compared with a constant Ts which is selected to be less than the freezing temperature of water. If the ambient temperature Tr is greater than the constant Ts (line  118 ), then a wait state occurs to the input side of block  114  while the mold continues to cool in freezer  14 . On the other hand, if the value of the ambient temperature Tr is less than or equal to the constant Ts (line  120 ), then the mold has cooled sufficiently and water is injected into mold cavity  30  using fill tube  34  (block  122 ).  
         [0045]    After being filled with water, the temperature Tm 2  of mold  16  is again sensed using mold temperature sensor  26  (block  124 ). The difference of the mold temperature Tm 2  after filling and the mold temperature Tm 1  immediately prior to filling are compared with a predetermined constant Tc 1  (decision block  126 ). If the difference of the mold temperature Tm 2  after filling minus the mold temperature Tm 1  immediately prior to filling is less than the constant Tc 1  (line  128 ), this means that the fill tube  24  has become frozen and water did not enter mold cavity  30  during the fill process of block  122 . Thus, heat is applied to fill tube  24  for thawing ice within fill tube  24  (block  30 ). On the other hand, if the difference of the mold temperature Tm 2  immediately after filling minus the mold temperature Tm 1  immediately prior to filling is greater than or equal to the constant Tc 1  (line  132 ), then control loops back to the input of block  62  at the top of the control logic flow chart.  
         [0046]    From the foregoing description of an embodiment of the method of the present invention for automatically making ice cubes, it will be appreciated that different logic steps may be implemented and/or interchanged and still effect the methodology of the present invention. The control logic effectively determines the amount of time necessary for adequate freezing of an ice cube, adjusts the time necessary using certain input parameters, and ensures that proper filling of water into the ice mold cavity occurs. The structure as well as the method of the present invention therefore combine to provide optimum harvest efficiency with minimum mechanical and electrical control hardware.  
         [0047]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.