Patent Publication Number: US-6220038-B1

Title: Ice maker

Description:
This is a divisional of U.S. patent application Ser. No. 09/499,011, filed Feb. 4, 2000, which is a continuation-in-part of U.S. patent application Ser. No. 09/285,283 filed Apr. 2, 1999, now U.S. Pat. No. 6,082,121. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to freezers, and, more particularly, ice-making devices. 
     2. Description of the Related Art 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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 
     The present invention provides an ice maker which, without heat, mechanically breaks the bond between the ice cubes and the mold cavities before the water is completely frozen. This method of breaking the bond increases throughput, conserves energy and allows the ice cubes to freeze on the outside first and continue freezing in an inward direction. By eliminating the melting procedure, the ice maker substantially reduces vaporization of water within the freezer, which is further reduced by sealing the water in the mold cavities from the ambient air. 
     The invention comprises, in one form thereof, an ice making apparatus including a mold having a cavity with a bottom surface. The mold cavity is configured for containing water therein for freezing into ice. An auger extends substantially vertically through the mold cavity. The auger is configured for rotating to thereby push the ice out of the mold cavity. The auger includes a rotatable surface at least partially defining the bottom surface of the mold cavity. The rotatable surface includes at least one ramp configured for lifting the ice off of the bottom surface of the mold cavity. 
     The invention comprises, in yet another embodiment thereof, an ice maker which includes a mold and an auger. The mold has at least one cavity with a bottom surface, and the at least one mold cavity is configured for containing water therein for freezing into ice. The auger includes a shaft having a longitudinal axis and having at least one flight attached thereto, the shaft including a top end and a base end with the base end being rotatably mounted in the bottom surface of the at least one mold cavity. The shaft extends substantially vertically through said at least one mold cavity and is configured to rotate and thereby push the ice out of said at least one mold cavity. The shaft and/or at least one flight has a radius that decreases relative to the longitudinal axis in a direction heading from the base end to the top end of the shaft and thereby has a radially inward taper in that direction. 
     An advantage of the present invention is that heat is not needed in order to break the bond between the ice cubes and their mold cavities, thereby conserving energy and reducing operational costs. 
     Another advantage is that, since the mold cavities are not heated, and since the ice cubes are not completely frozen before being removed from their cavities, the time spent freezing the water in the cavities is reduced, and the throughput rate is increased. 
     Yet another advantage is that, since the mold cavities are not heated, the water freezes from the outside in, thereby pushing impurities to the inside of the cube, where they are less conspicuous and do not plate out on the mold surface. 
     A further advantage is that, since the step of melting the outer surface of the ice is eliminated, and since the water is sealed from ambient air while freezing, vaporization of the water is greatly reduced, resulting in less frost on the wall of the freezer and less water that the refrigerator must remove. 
     A still further advantage is that the provision of at least one inward taper allows an ice cube to automatically become separated from at least a portion of the auger upon movement of the ice cube in an output direction. Even though the ice cube has an inward taper to match that of the auger, the inner diameter of the ice cube at a given location therein has its own specific value. Meanwhile, the diameter of at least a portion of the auger adjacent to that given location, the diameter of the shaft and/or the outer diameter of the at least one flight, continually decreases relative to the inner diameter of that given location as the ice cube is moved in the output direction. Consequently, since the contact area per unit length between the auger and an ice cube decreases as the ice cube moves along the auger, the friction per unit length therebetween also decreases. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a top view of the mold and auger of the ice making apparatus of FIG. 1; 
     FIG. 2 is a front, partially sectional view of one embodiment of an ice making apparatus of the present invention; 
     FIG. 3 is a front, enlarged, fragmentary, partially sectional view of another embodiment of an ice making apparatus of the present invention; 
     FIG. 4 is a front, partially sectional view of yet another embodiment of an ice making apparatus of the present invention; 
     FIG. 5 is a side view of another embodiment of an auger for the ice making apparatus of the present invention; 
     FIG. 6 is an end view of the auger shown in FIG. 5; and 
     FIG. 7 is an exaggerated, fragmentary, sectional view of the auger shown in FIGS. 5 and 6 as viewed alone line  7 - 7  of FIG.  6 . 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and particularly to FIG. 2, there is shown an ice making apparatus  10 including a mold  12 , a rotatable auger  14 , a housing  16  and a drive mechanism  18 . For ease of illustration, ice making apparatus  10  is shown as including only a single mold  12 . However, it is to be understood that ice making apparatus  10  may include multiple molds  12  for delivering multiple ice cubes. 
     Mold  12  includes a front wall  20 , a back wall  22 , a base  24  and a side wall  26 . Another side wall  27  (FIG. 1) is also included in mold  12 , but is not shown in the partially sectional view of FIG.  2 . An inner surface  28  of each of perimeter walls  20 ,  22 ,  26  and  27  is slanted outwardly at an angle Θ relative to a vertical direction indicated by dotted line  30 . Angle Θ can be approximately between 1° and 5°, and is preferably approximately 3°. Walls  20 ,  22 ,  26  and  27  retain water within a cavity  32  of mold  12 . A level of the water&#39;s surface is indicated with a horizontal line  34  shown in an alternative embodiment in FIG. 3. A top edge  36  of side wall  26  is visible in FIG. 2, and is at the same vertical level as a top edge of side wall  27  and the respective top edges  38  and  40  of front wall  20  and back wall  22 . Auger  14  includes a shaft  42  and a lifter  44  which are fixedly joined together by set screws  46 . It is also possible for shaft  42  and lifter  44  to be formed together as a one-piece, monolithic auger. Auger  14 , including both shaft  42  and lifter  44 , rotates about a longitudinal axis  48  which extends vertically through the center of cavity  32 . Shaft  42  includes a continuous series of spiraling flights  50 , each of which is spaced approximately 0.2 inch from each vertically adjacent flight  50 . That is, there are five flights  50  per vertical inch. 
     Lifter  44  includes a rotatable surface  52  and a shank  54  having threads  55 . As best seen in FIG. 1, surface  52  is substantially circular with a diameter of approximately 1.0 inch. Surface  52  partially defines a bottom surface  56  of cavity  32 , with base  24  of mold  12  defining the remainder of bottom surface  56 . Rotatable surface  52  includes two ramps  58  and  60 , each of which forms one half of surface  52 . A bottom  62  of ramp  58  is adjacent to a top  64  of ramp  60 . Conversely, 180° away, a top  66  of ramp  58  is adjacent to a bottom  68  of ramp  60 . Each of ramps  58  and  60  has a drop of 0.1 inch in a clockwise direction as viewed in FIG.  1 . Thus, each of ramps  58  and  60  has a slope of 0.1 inch per half rotation, or 0.2 inch/rotation, matching the slope of flights  50 . Further, the vertical level of surface  52  along any radius is constant. For example, the vertical level of surface  52  along radius  70 , half way down ramp  60 , is 0.05 inch above bottom  68  of ramp  60  and 0.05 inch below top  64  of ramp  60 . Housing  16  supports mold  12  and contains drive mechanism  18 . Housing  16  includes an internally threaded cup  72  having threads  74  which interface with threads  55  of shank  54 . 
     Drive mechanism  18  functions to rotate auger  14  through an output shaft  76  which is coupled with shank  54 . Drive mechanism  18  may be in the form of an electrical motor, for example. 
     In operation, cavity  32  is filled with water to an appropriate level, such as that of the illustrated water surface  34 , by any suitable method. The air surrounding both ice making apparatus  10  and the water is cooled below 32° F. by refrigeration such that the water at least partially freezes. Mold  12  and auger  14  are maintained below freezing and thus absorb heat from the water that is adjacent to these parts in cavity  32 . Ice first forms in the areas of cavity  32  that are adjacent mold  12  and auger  14  to thereby form a shell  77  surrounding the remaining water  78  in cavity  32 . 
     Once an outer shell  77  of ice has formed in cavity  32 , drive mechanism  18  can be used to lift the ice out by rotating auger  14  in a clockwise direction, as viewed in FIG.  1 . Threaded cup  72  of housing  16  functions to allow auger  14  to rotate, while at the same time holding down auger  14 . 
     During the freezing process, a bond forms between the ice and mold cavity  32 . More particularly, a bond forms between the ice and each of bottom surface  56  and walls  20 ,  22 ,  26  and  27 . Before the ice cube can be lifted out of cavity  32 , these bonds must be broken while, at the same time, not breaking the relatively fragile outer shell  77  of the ice cube. 
     As auger  14  rotates, ramps  58  and  60  function as shearing devices which break the bond between the ice and bottom surface  56  of cavity  32 . Since the ice cube is approximately square-shaped, it cannot rotate within cavity  32 . Ramps  58 ,  60  and flights  50  work together to lift the ice upward at a same rate. By ramps  58 ,  60  and flights  50  operating conjunctively, the total upward force exerted on the ice cube is spread out over a greater surface area of the cube, thereby minimizing the chances of breaking the ice cube. The shearing and upward forces exerted on the ice cube by ramps  58  and  60  as they rotate, as well as the additional upward force exerted by flights  50 , is enough to break the bonds between the ice and mold  12 . The surface finish on inner surface  28  and rotatable surface  52  is also critical in shearing the bond between the ice and mold cavity  32 . 
     After one-half rotation of auger  14 , flights  50  and ramps  58 ,  60  have lifted the ice approximately 0.1 inch from its original position and the ice loses contact with rotatable surface  52 . As auger  14  continues to rotate, flights  50  push the ice cube further upward along shaft  42 . 
     Since there are five flights  50  per vertical inch on shaft  42 , it follows that five full rotations of auger  14  will raise the ice by approximately one inch such that the bottom of the ice cube is approximately at the same vertical level as the top edges  36 ,  38  and  40  of walls  20 ,  22  and  26 , respectively. At this vertical level, or at any other level at which the bottom of the ice cube is above filling level  34 , cavity  32  is again filled with water to the level of  34 . 
     As the newly inserted water in cavity  32  begins the freezing process, the ice cube  81  disposed immediately above on shaft  42  begins to freeze more completely. Stress cracks which may have formed in the ice cube due to the forces of auguring are again filled with water seeping in from the middle of the cube. After the water in cavity  32  has partially frozen, the auguring process is recommenced to thereby push the newly formed second cube  83  upward along shaft  42 . As the second cube  83  makes contact with the first cube  81 , the first cube  81  is pushed further up and off of a top  79  of auger shaft  42 . As the first cube  81  comes off of shaft  42 , the inner radial walls  85  defining the center through hole  87  in the cube lose the support of shaft  42 . Since the first cube may still not be completely frozen at this point, the water inside the cube may expand and rupture the inner radial walls  85 , thereby at least partially filling in the center through hole  87 . After the first cube has completely slid off of auger  14 , it can then drop into a dispenser tray (not shown) below apparatus  10 . 
     In other embodiments, an extension wall  80 , a deflector  82 , a cube guide wire  84 , a cooling device  86  and/or a fin  88  may be included in the ice making apparatus. Extension wall  80  is attached to top edge  40  of back wall  22 . Extension wall  80  serves to prevent the ice cubes from rotating along with auger  14  as the cubes progress along the upper portion of shaft  42 . Thus, an ice cube can be released off of top  79  of shaft  42 , even without the benefit of a second cube below it to provide an upward pushing force. 
     Deflector  82  is attached to a top edge  90  of extension wall  80 . Deflector  82  serves to direct the ice cubes in a predetermined direction, i.e., over front wall  20 , as the cubes come off of shaft  42 . Thus, the ice cubes may be directed into a dispenser tray, for example, that is positioned below front wall  20 . 
     Cube guide wire  84  is an elongate guiding element attached to top  79  of auger shaft  42 . Cube guide wire  84  is received in the center through hole in the ice cube as the cube comes off of shaft  42 . Cube guide wire  84  slidingly guides the ice cube in a predetermined direction, indicated by arrow  92 , possibly towards a dispenser tray. 
     Cooling device  86  is in the form of a refrigeration coil  94  and a tube  96  extending through back wall  22  and extension wall  80  of mold  12 . Thus, cooling device  86  directly contacts and directly cools mold  12 , rather than indirectly cooling mold  12  by cooling the air surrounding mold  12 . The direct cooling of mold  12  ensures that the water adjacent to mold  12  in cavity  32  freezes first, thereby forming an outer shell of ice surrounding an inner core of water. 
     Fin  88  extends vertically along inner surface  28  of back wall  22 . Fin  88  functions to increase the surface area of inner surface  28  that is in contact with the water in cavity  32 . The increased surface area provides improved heat transfer between mold  12  and the water, and results in quicker freezing of the water. If the mold cavity is substantially circular, fin  88  has the additional advantage of preventing rotation of the ice as auger  14  rotates. 
     In one embodiment, each of perimeter walls  20 ,  22 ,  26  and  27  extends vertically approximately to the vertical level of top  79  of auger shaft  42 , as indicated at  98 . As is evident in FIG. 3, an inner surfaces  100  of the extended portions of perimeter walls  20 ,  22 ,  26  and  27  do not continue the outward flare of inner surfaces  28 . Rather, inner surfaces  100  are oriented substantially vertically, i.e., parallel to shaft  42 . 
     In operation, if cavity  32  is filled with water substantially to the level of top edges  36 ,  38  and  40 , and a top of a first cube  81  is substantially adjacent to level  98  when a second cube  83  is being formed in cavity  32 , the first cube  81  can substantially seal off cavity  32  from the ambient air outside of mold  12 . Thus, the water in cavity  32  can be prevented from vaporizing and thereby forming frost on the walls (not shown) of the freezer in which mold  12  is located. That is, the extension of perimeter walls  20 ,  22 ,  26  and  27  to the level of  98  allows the first ice cube  81  to seal cavity  32  from the ambient air after cavity  32  has been refilled with water, thereby substantially inhibiting the formation of frost within the surrounding freezer. 
     In yet another embodiment, ramps  53  and  60  are replaced with another ice lifting device in the form of actuators  102 . Actuators  102  push up on the bottom of the ice cube in order to break the bond between the ice and rotatable surface  52  of auger  14 . Actuators  102  may be powered pneumatically, hydraulically or electrically, such as by drive mechanism  18 , for example. The vertical rise of the ice-interfacing, top surface  104  of actuators  102  can be synchronized with the rotation of auger  14  in order to match the vertical rise of the ice as provided by flights  50 . 
     In the embodiments shown, perimeter walls  20 ,  22  and  26  of mold cavity  32  are arranged in a non-circular shape. However, it is to be understood that it is also possible, in an alternative embodiment, for perimeter walls  20 ,  22 ,  26  and  27  to form a circular shape. In this alternative embodiment, auger  14  is eccentrically disposed, i.e., horizontally displaced from a the center of mold cavity  32 , in order to prevent the ice from rotating in mold cavity  32  along with auger  14 . 
     In another embodiment (FIG.  4 ), a shaft  106  includes an internal heat pipe  108  with a valve fill hole  110 . A fluid within heat pipe  108  absorbs heat in cavity  32  and vaporizes. The vapor rises in heat pipe  108 , releases the heat near top  109  of shaft  106 , condensates, and falls back into cavity  32  where the cycle repeats. Thus, the absorption of heat from cavity  32  by heat pipe  108  promotes the radially inward freezing of ice cube  81 . As such, heat pipe  108  is an active means of transferring thermal energy from cavity  32 . However, heat pipe  108  could be replaced with an auger  14  made of a material with a substantial heat transfer coefficient, thereby relying on the conductance of heat away from cavity  32  through auger  14  to chilled mold  12  to freeze ice cube  81  radially inwardly. 
     Drive mechanism  18  functions to rotate auger  112  through output shaft  76  which is coupled with shank  114  via a set screw  46 . An outer perimeter  116  of a lifter  118  has a clearance of approximately 0.005 inch from an inside surface  120  of a mold  122 . At a temperature of, for example, 25° F., any water which seeps in between perimeter  116  of lifter  118  and inside surface  120  of mold  122  freezes and thereby seals the gap. 
     A further embodiment of an auger  130  is shown in FIGS. 5-7. Shaft  132  of auger  130  has a single continuous flight  134  mounted thereon, for purposes of illustration. Of course, multiple flights, continuous or spaced, may instead be employed. Shaft  132  has a top end  138  and a base end  136  configured for coupling with drive mechanism  18  to rotate auger  130 . The direction from base end  136  to top end  138  constitutes an output direction  140 , the direction in which ice cube  81  is to be pushed out of mold  12 . In this embodiment, shaft  132  and/or flight  134  has an inward taper, thus becoming increasingly more narrow, in output direction  140 . The provision of at least one such inward taper allows ice cube  81  (FIG. 3) to automatically become separated from at least a portion of auger  130  upon movement of ice cube  81  in output direction  140 . 
     Both shaft  132  and flight  134  are shown to be tapered, as best shown in FIG. 7, the inward taper of shaft  132  being shown as angle α, and the inward taper of flight  134  being shown as angle β. Each of taper angle α and taper angle β may be between approximately 0.1° and 5°, preferably between about 0.2° and 0.8°, and more preferably about 0.5°. In achieving an inward taper of shaft  132 , maximum diameter  142  near base end  136  is greater than the minimum diameter  144  at top end  138 . Similarly, in achieving an inward taper of flight  134 , maximum outer diameter  146  near base end  136  is greater than the minimum outer diameter  148  at top end  138 . The maximum diameter in each instance should exceed the corresponding minimum diameter by between about 0.005 and 0.1 inch and preferably by between about 0.007 and 0.04 inch. For example, maximum outer diameter  146  of flight  134  near base end  136  may be about 0.33 inch and minimum outer diameter  148  thereof at top end  138  may be about 0.31 inch. 
     As best seen in the break-away longitudinal cross section of auger  130  (FIG.  7 ), flight  134  has a radial periphery a partially rounded portion  150 . Rounded portion  150  provides less surface area for ice cube  81  to contact upon movement thereof out of mold  12 , easing separation thereof from auger  130 . Additionally, the rounding eliminates potentially sharp surfaces upon which ice cube  81  could be damaged. 
     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.