Patent Publication Number: US-2012023996-A1

Title: Twist tray ice maker system

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to ice maker systems, and more particularly to improved techniques for harvesting ice from the ice mold body in which the ice is formed. 
     Existing twist tray ice maker systems have been used to automatically produce ice inside the freezer compartments of domestic refrigerator products. They operate by filling a flexible plastic ice mold (tray) with water. Once the water freezes, the mold is rotated upside down and twisted until the ice cubes fall out by gravity. The tray is then rotated back to its upright position and the cycle is started again. 
     These existing twist tray ice maker systems have several known failure modes. First, calcium deposits form on the plastic tray causing the ice cubes to stick inside the mold. When the tray is refilled, water overflows into the ice storage bucket. The overflow water freezes the cubes in the ice storage bucket causing the ice dispensing mechanism to jam. Second, because the ice mold is made of plastic, the rate of ice making is low due to the low thermal conductivity of plastic. Third, the plastic ice trays are known to break causing the entire system to jam or overflow. 
     BRIEF DESCRIPTION OF THE INVENTION 
     As described herein, the exemplary embodiments of the present invention overcome one or more disadvantages known in the art. 
     One aspect of the present invention relates to an ice tray apparatus comprising: an ice mold body formed substantially of a metal material; and a holder for holding the ice mold body, the holder comprising a rotation-stopping feature formed thereon. In one illustrative embodiment, the holder may be formed substantially of a plastic material. 
     Another aspect of the present invention relates to an ice making apparatus comprising: an ice tray assembly; a frame for supporting the ice tray assembly; and a rotation assembly for rotating the ice tray assembly within the frame. The ice tray assembly comprises an ice mold body formed substantially of a metal material, and a holder for holding the ice mold body, the holder comprising a first rotation-stopping feature formed thereon. The frame comprises a second rotation-stopping feature formed to engage the first rotation-stopping feature on the holder. 
     Yet another aspect of the present invention relates to a refrigerator appliance comprising: a compartment; and an ice maker assembly mounted in the compartment. The ice maker assembly comprises: an ice tray assembly; a frame for supporting the ice tray assembly; and a rotation assembly for rotating the ice tray assembly within the frame. The ice tray assembly comprises an ice mold body formed substantially of a metal material, and a holder for holding the ice mold body, the holder comprising a first rotation-stopping feature formed thereon. The frame comprises a second rotation-stopping feature for engaging the first rotation-stopping feature on the holder. 
     Advantageously, in accordance with illustrative techniques of the invention, the use of a metal material for the ice mold body, which has a thermal conductivity significantly higher than that of plastic, improves the transfer of heat away from the water thereby increasing the amount of ice that can be made in a given period of time. The metal ice mold body is also more resistant to mineral deposit buildup. Furthermore, the use of a plastic holder for holding the metal ice mold body with a positive stop on the plastic holder provides for the flexibility and elastic deformation desirable to twist the ice mold body to release the ice there from without leading to significant fatigue fracture problems. 
     These and other aspects and advantages of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not necessarily drawn to scale and, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a diagram of an ice maker assembly, in accordance with an embodiment of the invention; 
         FIG. 2  is a diagram of an ice maker assembly, in accordance with another embodiment of the invention; 
         FIG. 3  is a diagram of the ice maker assembly of  FIG. 1  in a storage compartment of a refrigerator appliance, in accordance with an embodiment of the invention; 
         FIGS. 4A to 4E  are various views of the ice maker assembly of  FIG. 1 , in accordance with an embodiment of the invention; 
         FIGS. 5A to 5E  are various views of the ice maker assembly of  FIG. 2 , in accordance with another embodiment of the invention; 
         FIGS. 6A to 6G  are various views of an ice tray assembly of the ice maker assembly of  FIG. 1 , in accordance with an embodiment of the invention; 
         FIGS. 7A to 7G  are various views of an ice tray assembly of the ice maker assembly of  FIG. 1 , in accordance with another embodiment of the invention; 
         FIGS. 8A to 8G  are various views of an ice tray assembly of the ice maker assembly of  FIG. 2 , in accordance with an embodiment of the invention; 
         FIGS. 9A to 9G  are various views of an ice tray assembly of the ice maker assembly of  FIG. 2 , in accordance with another embodiment of the invention; 
         FIG. 10  is a diagram illustrating the operation of the ice maker assembly of  FIG. 1 , in accordance with an embodiment of the invention; 
         FIG. 11  is a diagram illustrating the operation of the ice maker assembly of  FIG. 2 , in accordance with another embodiment of the invention; and 
         FIG. 12  is a diagram illustrating an example of twisting or deformation of the ice tray assembly, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION 
     One or more of the embodiments of the invention will be described below in the context of an ice maker system in a refrigerator appliance, such as a household refrigerator. However, it is to be understood that techniques of the invention are not intended to be limited to ice maker systems in household refrigerators. Rather, techniques of the invention may be applied to and implemented in any other suitable environments in which it would be desirable to improve the reliability and ice making performance of an ice maker system. 
     Principles of the invention realize that to improve reliability and ice making performance, it is desirable to form the ice mold body or tray out of a metal material. Metal has a thermal conductivity much higher than that of plastic. This improves the transfer of heat away from the water thereby increasing the amount of ice that can be made in a given period of time. The use of metal also allows for the use of several non-stick coatings such as, by way of example only, a nanoceramic coating, a Teflon (trademark of DuPont) coating, or a Thermolon (trademark of Thermolon) coating. These coatings improve reliability by preventing a failed ice harvest, i.e., ice remaining in the tray after the ice harvesting cycle. 
     Furthermore, in order to provide for the flexibility and elastic deformation desirable to twist the metal ice mold body to release the ice during an ice harvesting cycle, principles of the invention realize that it is desirable to form the holder for holding the metal ice mold body out of a plastic material. However, materials other than plastic may be used to form all or substantial portions of the holder, by way of example, metals. 
     Accordingly, in embodiments of the invention, the ice tray assembly (ice mold body and holder) is manufactured from metal and plastic components. A metal tray can be formed from a flat metal sheet. The cups or cavities used to hold water while it freezes (ice formation cavities) are easily formed by common manufacturing processes. To twist the tray to release ice during an ice harvesting cycle, the metal tray is held in a plastic holder that provides the geometry desirable to flex the tray and harvest ice there from. 
     Illustrative embodiments of the inventive ice maker system will now be described. Embodiments with ice mold bodies having cube-shaped ice formation cavities are illustrated and described in the context of  FIGS. 1 ,  3 ,  4 A to  4 E,  6 A to  6 G,  7 A to  7 G and  10 . Embodiments with ice mold bodies having hemisphere-shaped ice formation cavities are illustrated and described in the context of  FIGS. 2 ,  3 ,  5 A to  5 E,  8 A to  8 G,  9 A to  9 G and  11 . Both sets of embodiments operate in a similar manner, as will be described below. It is to be understood that principles of the invention are not limited to the shape of the ice formation cavities of the ice mold body. 
       FIG. 1  shows an ice maker assembly, in accordance with an embodiment of the invention. As shown, ice maker assembly  100  comprises an ice tray assembly  110  and a frame  120 . The ice tray assembly  110  comprises an ice mold body  112 . The ice mold body  112  is formed of a metal material. The ice tray assembly  110  also comprises a holder  114  for holding the ice mold body  112 . The holder  114  is formed of a plastic material. The frame  120  supports the ice tray assembly  110 . 
     It is to be appreciated that the ice mold body  112  need not be formed of a single type of metal. Also, the entire ice mold body  112  need not be completely formed of a metal material. That is, the ice mold body  112  may be substantially formed from a metal material so long as the ice mold body exhibits, for example, the comparatively high thermal conductivity, the ability to apply a non-stick coating, and the mineral deposit buildup prevention advantages afforded by a metal material. Examples of metal material that the ice mold body  112  include but are not limited to aluminum, stainless steel, or a copper, nickel, tin combination (e.g., C72500 in accordance with Unified Numbering System). 
     Likewise, it is to be appreciated that the holder  114  need not be formed of a single type of plastic. Also, the entire holder  114  need not be completely formed of a plastic material. That is, the holder  114  may be substantially formed from a plastic material so long as the holder exhibits, for example, the flexibility and elastic deformation desirable to twist the metal ice mold body to release the ice during an ice harvesting cycle. Examples of plastic material that the holder  114  include but are not limited to polypropylene. 
       FIG. 2  shows an ice maker assembly  200  similar to the ice maker assembly  100  of  FIG. 1  with the exception that the ice tray assembly  210  shown in  FIG. 2  comprises an ice mold body  212  that comprises hemisphere-shaped ice formation cavities as opposed to the cube-shaped ice formation cavities in the ice mold body  112  of  FIG. 1 . Otherwise, the ice maker assembly  200  is preferably formed and operates similar to the ice maker assembly  100 . 
       FIG. 3  shows the ice maker assembly  100  of  FIG. 1  deployed in a freezer compartment  300  of a refrigerator appliance. Of course, ice maker assembly  200  of  FIG. 2  could be deployed in the freezer compartment  300  in a similar manner. Note that the ice maker assembly  100  is located in the freezer compartment  300  such that the ice formation cavities of the ice mold body can be filled with water supplied by the water inlet assembly  302 . Also, as shown, ice formed and then harvested by the ice maker assembly  100  is deposited in the ice storage bucket  304 . Auger assembly  306  rotates and moves the ice in the ice storage bucket  304  away from the ice maker assembly  100  so that newly made ice can drop into the ice storage bucket unimpeded. 
     It is also to be appreciated that while  FIG. 3  shows the ice maker assembly  100  located in a freezer compartment of a refrigerator appliance, the ice maker assembly  100  can, more generally, be located in any suitable storage compartment of a refrigerator appliance. Another example of such a storage compartment is an ice making compartment in the door of a fresh food compartment. 
       FIGS. 4A to 4E  show various views of the ice maker assembly  100  of  FIG. 1 . Note that, as compared to  FIG. 1 ,  FIG. 4A  shows the ice tray assembly  110  in a rotated position such that the bottom of the ice tray assembly  110  is visible in  FIG. 4A . 
       FIGS. 4B ,  4 C,  4 D and  4 E show features formed on the holder  114  and the frame  120 . As shown in  FIGS. 4B and 4C , the holder  114  comprises a first rotation-stopping feature  402  formed thereon. In one embodiment, the first rotation-stopping feature  402  comprises a tab protruding from the holder  114 . As shown in  FIGS. 4B ,  4 D and  4 E, the frame  120  comprises a second rotation-stopping feature  404  formed thereon. In one embodiment, the second rotation-stopping feature  404  comprises a stopper block protruding from the frame  120 . As will be explained below, as the ice tray assembly  110  rotates in the frame  120 , the feature (tab)  402  on the holder  114  contacts (i.e., engages) the feature (stopper block)  404  on the frame  120  causing the ice tray assembly  110  to resist rotation so as to twist and thus temporarily deform the ice mold body  112 . It is to be understood that the rotation-stopping features may be formed in alternate shapes and arrangements other than a tab and stopper block illustrated in the figures. One of ordinary skill in the art will realize other shapes and arrangements for providing a positive stopping mechanism for the ice tray assembly within the frame. 
       FIG. 4C  shows other features formed on the ice mold body  112  and on the holder  114 . A plurality of ice formation cavities  405  are shown formed on the ice mold body  112 . In this embodiment, the cavities  405  are cube-shaped. Note that each cavity  405  is connected to adjacent cavities by grooves  407 . The grooves fill with water and the water freezes along with the water in the cavities. In this way, the ice cubes are connected, and thus tend to come out due to gravity in groups or completely connected as a single group. 
     As also shown in  FIG. 4C , the holder  114  comprises first and second rotation-enabling features respectively formed at distal ends of the holder  114 . That is, at one end of the holder  114  is formed a rotation-enabling feature  406 , and at the other end of the holder  114  is formed a rotation-enabling feature  408 . The features  406  and  408  are formed at a centerline of the ice tray assembly  110 . In one embodiment, the rotation-enabling feature  406  comprises a shaft feature and the rotation-enabling feature  408  comprises a slot feature. These features are formed on the holder  114  to enable rotation of the ice tray assembly during ice harvesting. 
     As also shown in  FIG. 4C , the ice maker assembly  100  comprises a rotation assembly  410  for rotating the ice tray assembly  110  within the frame  120 . In one embodiment, the rotation assembly  410  is a motor assembly with a shaft (not shown) that inserts into the rotation-enabling feature  408  (slot feature) formed in the holder  114 . The other end of the holder  114  is supported by the frame  120  by way of the rotation-enabling feature  406  (shaft feature) being inserted into an opening  412  formed in frame  120  as shown in  FIG. 4E . The shaft feature of the holder  114  fits in the opening  412  of the frame  120  such that the shaft feature can rotate therein. Thus, as the shaft of the motor inserted in the slot feature of the holder  114  rotates, the entire ice tray assembly  110  rotates within the frame  120 . 
     As will be explained in accordance with  FIG. 10 , the rotation of the ice tray assembly is stopped by the engaging of the rotation-stopping features on the frame  120  and the holder  114 . Note that these rotation-stopping features are on the end of the ice tray assembly  110  opposite to the location of the rotation (motor) assembly  410 . 
       FIGS. 5A to 5E  show various views of the ice maker assembly  200  of  FIG. 2 . The views of  FIGS. 5A ,  5 B,  5 C,  5 D and  5 E are similar to the views of  FIGS. 4A ,  4 B,  4 C,  4 D and  4 E with the exception that the ice tray assembly  210  comprises an ice mold body  212  with hemisphere-shaped cavities  505 . 
     Returning to the ice maker assembly  100 ,  FIGS. 6A to 6G  show various views of the ice tray assembly  110 , in accordance with an embodiment of the invention.  FIG. 6A  shows an exploded view.  FIGS. 6B and 6C  show respective top and bottom views of the ice tray assembly  110 .  FIGS. 6D ,  6 E,  6 F and  6 G show respective top, front, side and back views of the ice tray assembly  110 . 
     In this embodiment, the ice mold body  112  is held to the holder  114  via removable fasteners  602 . Such removable fasteners may be any suitable type of removable fastener, for example, as shown in  FIG. 6A , screws that pass through holes formed in the corners of the ice mold body  112  and fasten into corresponding four corners of the holder  114 . Of course, more or less fasteners can be used and placed in alternate locations formed on the ice mold body  112  and the holder  114 . 
       FIGS. 7A to 7G  show various views of an ice tray assembly  110 ′ of the ice maker assembly of  FIG. 1 , in accordance with an alternative embodiment of the invention.  FIG. 7A  shows an exploded view.  FIGS. 7B and 7C  show respective top and bottom views of the ice tray assembly  110 ′.  FIGS. 7D ,  7 E,  7 F and  7 G show respective top, front, side and back views of the ice tray assembly  110 ′. 
     In this embodiment, the ice mold body  112 ′ is held to the holder  114 ′ via support features  702  formed as part of the holder  114 . Such support features may be any suitable type of support features, for example, as shown in  FIGS. 7A and 7C , tabs formed on the holder  114  that support the ice mold body  112 ′ as it is inserted in the holder  114 . Corresponding tabs are formed on the top and bottom of the holder as shown. The ice mold body  112 ′ may also fit within channels that run along the length of the sides of the holder  114 . Thus, the ice mold body  112 ′ is held firmly within the holder  114 . While a certain number of support features are shown in  FIGS. 7A to 7G , more or less support features can be used and formed in alternate locations on the holder  114 . 
     Also, it is to be appreciated that the support features and holder shown in  FIGS. 7A to 7G  may be formed as an over-molded plastic frame (i.e., molded over the ice mold body). In any case, the embodiment of  FIGS. 7A to 7G  eliminates the need for the fasteners of  FIGS. 6A to 6G . 
       FIGS. 8A to 8G  and  9 A to  9 G show respective embodiments (views A through G) of the ice tray assemblies  210  and  210 ′ that correspond to and are similar to ice tray assemblies  110  and  110 ′ of  FIGS. 6A to 6G  and  7 A to  7 G, with the exception that the ice mold bodies ( 212  and  212 ′) have hemisphere-shaped cavities rather than cube-shaped cavities. Otherwise, the assemblies of  FIGS. 8A to 8G  and  9 A to  9 G are formed and operate in a similar manner to those shown in  FIGS. 6A to 6G  and  7 A to  7 G. 
     Turning now to  FIG. 10 , the operation of the ice maker assembly  100  of  FIG. 1  is shown. Following an ice formation cycle (wherein water is added to the mold and frozen) and at the start of an ice harvesting cycle (wherein separation and release of the ice from the mold occurs), the rotation (motor) assembly  410  rotates the ice tray assembly  110  within the frame  120  (not shown in  FIG. 10  for clarity) in a rotational direction A (clockwise) around centerline B. 
     In one embodiment, the rotation assembly  410  applies a minimum rotational force (clockwise torque) of approximately 6 Newton meters (Nm) such that, when the first rotation-stopping feature (tab)  402  on the holder  114  and the second rotation-stopping feature (stopper block)  404  on the frame  120  engage or contact one another, the ice mold body  112  is twisted causing the ice mold body to temporarily deform and the ice formed therein to be released. That is, the tab on the holder contacts the stopper block on the frame causing the ice tray assembly to resist rotation so as to temporarily deform the ice mold body. 
     The rotational force applied by the motor causes the ice tray assembly  110  to rotate from a start position (e.g., horizontal) to a first rotational position at which the first rotation-stopping feature  402  and the second rotation-stopping feature  404  engage one another. This may be approximately 160 degrees in advance of the start position (which would be approximately 0 degrees). This first rotational position would be just short of the halfway position when the ice tray assembly is upside down (which would be approximately 180 degrees). This rotation-stopping contact position is shown in  FIGS. 4A and 4B  (and likewise in  FIGS. 5A and 5B ). 
     The rotation assembly  410  continues to apply a clockwise torque of approximately 6 Nm rotational force to the ice tray assembly  110  to attempt to rotate the ice tray assembly to a second rotational position beyond the first rotational position. In one embodiment, the second rotational position is approximately 10 degrees in advance of the first rotational position or approximately 170 degrees (160+10 degrees). 
     Note that the operation is described as “attempting” to rotate the ice tray assembly to the second rotational position. Recall that the first rotation-stopping feature (tab)  402  on the holder  114  contacts the second rotation-stopping feature (stopper block)  404  on the frame  120  at the first rotational position thus causing the ice tray assembly  110  to resist rotation so as to temporarily deform the ice mold body  112 . Thus, while the motor shaft of the rotation assembly  410  rotates about another 10 degrees past the first rotational position, the ice tray assembly  110  is resisting and thus the ice mold body  112  is axially flexing or twisting around the centerline B, causing the ice formed therein to be released and drop into an ice storage bucket (not shown) below the ice tray assembly. 
       FIG. 12  illustrates an example of the twisting or deformation of the ice tray assembly. For the sake of clarity,  FIG. 12  shows only the holder  114  so that it is easier to see an example of the twist or deformation that is caused by the engagement of the tab and stopper features described above. It is to be understood that the ice mold body held by the holder twists or deforms in a similar manner. As shown in the example, about five degrees (angle A) of twist/deformation results in about 0.15 inches of displacement (dimension B). However, it is to be understood that other angles and displacements may be realized using principles of the invention. 
     After the motor shaft of the rotation assembly  410  rotates to the second rotational position (about another 10 degrees past the first rotational position), the rotation assembly  410  applies a reverse rotational force (counterclockwise torque) to the ice tray assembly  110  to rotate the ice tray assembly back to the start position (and back to its non-deformed state) for a next ice formation cycle to begin. After the next ice formation cycle, the ice harvesting cycle described above is repeated. Thus, the ice maker system automatically generates ice until the ice storage bucket is filled, which is typically signaled by a stop arm (not shown). 
       FIG. 11  shows a similar operation as  FIG. 10  but for the ice tray assembly  210  that has the cube-shaped cavities formed in the ice mold body  212 . 
     It is to be understood that the rotational positions mentioned above are examples and that one skilled in the art will realize other rotational positions that can be implemented depending on the flexibility, rigidity, and/or deformation characteristics of the ice mold body of the ice tray assembly. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to exemplary embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. Moreover, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Furthermore, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.