Patent Publication Number: US-10323876-B2

Title: Refrigerator door ice maker and dispenser with a coupling unit for motor connection between the door and the main body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 13/911,307 filed on Jun. 6, 2013, which claims the benefit of Korean Patent Application Nos. 10-2012-0061060 and 10-2013-0036051, filed on Jun. 7, 2012 and Apr. 2, 2013, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the present disclosure relate to a refrigerator having an icemaker provided at a door. 
     2. Description of the Related Art 
     In general, a refrigerator is an appliance which has a storage compartment to store food therein and a cool air supply device to supply cool air to the storage compartment, to thereby keep food in a fresh state. A storage compartment is formed in a main body and has an opened front surface which is opened and closed by a door. 
     A refrigerator may include an icemaker to produce ice cubes, an ice bucket to store ice cubes produced by the icemaker, a feeding unit to feed ice cubes to the ice bucket, a driving motor to drive the feeding unit and a crushing device to crush ice cubes in the ice bucket into ice pieces. 
     The above components may be provided at a door as opposed to a storage compartment. A conventional exemplary refrigerator is disclosed in U.S. Pat. No. 6,082,130. The conventional refrigerator includes an ice bucket provided at a door to store ice cubes therein, and a feeding unit provided at the ice bucket to feed the ice cubes. 
     An ice storage space is provided above the ice bucket and an ice crushing space is provided below the ice bucket. The feeding unit has a rotation shaft extending vertically. A driving motor to drive the feeding unit is mounted to the door and located below the ice bucket. 
     SUMMARY 
     It is an aspect of the present disclosure to provide a refrigerator in which an ice bucket provided with a feeding unit is disposed at a door and the ice bucket has an increased capacity. 
     It is another aspect of the present disclosure to provide a refrigerator in which an ice bucket provided with a feeding unit is disposed at a door and the door has a simple structure. 
     It is a further aspect of the present disclosure to provide a refrigerator in which an ice bucket provided with a feeding unit is disposed at a door and ice feeding operation is smoothly performed. 
     It is a further aspect of the present disclosure to provide a refrigerator including a coupling device which is configured to transmit driving force from a driving motor disposed at a main body to a feeding unit disposed at a door and has a structure capable of easily accomplishing connection and disconnection. 
     It is a further aspect of the present disclosure to provide a refrigerator including a coupling device which is configured to transmit driving force from a driving motor disposed at a main body to a feeding unit disposed at a door and has an improved external appearance and safety. 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure. 
     In accordance with one aspect of the present disclosure, a refrigerator includes a main body having a storage compartment, a door rotatably coupled to the main body to open and close the storage compartment, an icemaker provided at the door, an ice bucket provided at the door to store ice cubes produced by the icemaker, the ice bucket being provided with a feeding device to feed the ice cubes stored therein, and a driving device provided at the main body to drive the feeding device. When the door is closed, the driving device is connected to the feeding device, and when the door is opened, the driving device is disconnected from the feeding device. 
     The driving device may include a driving motor to generate driving force and a driving coupler to be connected to the feeding device. The feeding device may include a feeding unit to feed the ice cubes and a driven coupler to be connected with or separated from the driving coupler. When the door is closed, the driving coupler and the driven coupler may be connected to each other, and when the door is opened, the driving coupler and the driven coupler may be separated from each other. 
     The driven coupler may include a support part and a pressurized part protruding from the support part. The pressurized part may have a proximal end located apart from a rotation center by a distance of a first radius and a distal end located apart from the rotation center by a distance of a second radius. The driving coupler may include a wing part and a pressurizing part protruding from the wing part. The pressurizing part may have a proximal end and a distal end, at least one of which is located apart from the rotation center by a distance between the first radius and the second radius. 
     The driving coupler and the driven coupler may be made of a resin material. 
     The driving motor may be disposed at a side wall of the main body, and the driving device may include a reducer to reduce rotation speed of the driving motor and transmit driving force from the driving motor to the driving coupler. 
     The driving motor may be disposed at a top wall of the main body, and the driving device may include at least one worm gear to transmit driving force from the driving motor to the driving coupler. 
     The ice bucket may include a storage space to store the ice cubes dropping from the icemaker and a crushing space in which the ice cubes are crushed into ice pieces. The crushing space may be horizontally arranged in the storage space. The feeding unit may include a rotation shaft horizontally extending to feed the ice cubes in the storage space to the crushing space. The driven coupler may be disposed at the rotation shaft of the feeding unit. 
     The ice bucket may include a storage space to store the ice cubes dropping from the icemaker and a crushing space in which the ice cubes are crushed into ice pieces. The crushing space may be disposed below the storage space. The feeding unit may include a rotation shaft vertically or slantedly extending to feed the ice cubes in the storage space to the crushing space. The feeding device may include at least one worm gear to transmit driving force from the driven coupler to the feeding unit. 
     The ice bucket may include a discharge port to discharge the ice cubes therethrough and a crushing device to crush the ice cubes into ice pieces. The crushing device may include a fixed blade fixed to the ice bucket, a rotational blade coupled to a rotation shaft of the feeding unit, a guide member rotatably coupled to the discharge port to crush the ice cubes, and a switching motor to rotate the guide member. 
     In accordance with another aspect of the present disclosure, a refrigerator includes a main body having an inner casing, an outer casing and an insulation wall provided between the inner casing and the outer casing, a storage compartment formed in the inner casing, a door rotatably coupled to the main body to open and close the storage compartment, an icemaker provided at the door, an ice bucket provided at the door to store ice cubes produced by the icemaker, the ice bucket being provided with a feeding unit to feed the ice cubes stored therein, and a driving motor provided at the main body to drive the feeding unit. 
     The inner casing may be formed with a concave-shaped motor receiving part which is depressed inside the insulation wall, and at least a portion of the driving motor may be received in the motor receiving part. 
     The driving motor may be fixed to an outer surface of the outer casing. 
     The driving motor may be fixed to an inner surface of the inner casing. 
     The refrigerator may further include a driving force transmission device to transmit driving force from the driving motor to the feeding unit. The driving force transmission device may include a driving coupler provided at the main body and a driven coupler provided at the door and configured to be coupled to the driving coupler when the door is closed and to be separated from the driving coupler when the door is opened. 
     The driving force transmission device may further include a worm gear to transmit driving force from the driving motor to the driving coupler. 
     In accordance with a further aspect of the present disclosure, a refrigerator includes a main body having a storage compartment, a door rotatably coupled to the main body to open and close the storage compartment, an icemaker provided at the door, an ice bucket provided at the door to store ice cubes produced by the icemaker, a feeding unit including a driven coupler to receive driving force, the feeding unit configured to feed the ice cubes in the ice bucket in a horizontal direction, and a driving motor assembly provided at a side wall of the main body, the driving motor including a driving coupler which is connected to or separated from the driven coupler. 
     In accordance with a further aspect of the present disclosure, a refrigerator includes a main body having a storage compartment, a door rotatably coupled to the main body to open and close the storage compartment, an icemaker provided at the door, an ice bucket provided at the door to store ice cubes produced by the icemaker, the ice bucket being provided with a feeding unit to feed the ice cubes stored therein, a driving motor provided at the main body to generate driving force, and a coupling device to transmit driving force from the driving motor to the feeding unit, the coupling device including a driving coupler having a first coupling unit and a driven coupler having a second coupling unit which is engaged with the first coupling unit to receive driving force. The coupling device is configured to hide at least one of the first coupling unit and the second coupling unit when the door is opened. 
     The first coupling unit may include an insertion protrusion, and the second coupling unit may include an insertion recess into which the insertion protrusion is inserted. 
     The driving coupler may further include a first cover provided movably forward and backward around the insertion protrusion so as to hide the insertion protrusion when the door is opened. 
     The driving coupler may further include a first spring to elastically support the first cover so as to enable the first cover to hide the insertion protrusion. 
     The driven coupler may further include a second cover provided movably forward and backward in the insertion recess so as to hide the insertion recess when the door is opened. 
     The driven coupler may further include a second spring to elastically support the second cover so as to enable the second cover to hide the insertion recess. 
     If the insertion protrusion is located at a position incapable of being inserted into the insertion recess when the door is closed, the second coupling unit may move backward in an axial direction by pressurization of the insertion protrusion. 
     The driven coupler may further include a third spring to return the second coupling unit so that if the insertion protrusion moves to a position capable of being inserted into the insertion recess by operation of the driving motor in the state that the second coupling unit moves backward, the insertion protrusion is inserted into the insertion recess. 
     In accordance with a further aspect of the present disclosure, a refrigerator includes a main body having an inner casing, an outer casing and an insulation wall provided between the inner casing and the outer casing, a storage compartment formed in the main body, a door rotatably coupled to the main body to open and close the storage compartment, an icemaker provided at the door, an ice bucket provided at the door to store ice cubes produced by the icemaker, the ice bucket being provided with a feeding unit to feed the ice cubes stored therein, a driving motor provided at the main body to drive the feeding unit, and a motor housing to accommodate the driving motor, the motor housing including a first housing supported by the inner casing and the insulation wall and a second housing coupled to the first housing. 
     The first housing may be fixed to the inner casing by adhesive force of an insulation material used to form the insulation wall, and the second housing may be screw-coupled to the first housing. 
     The second housing may include a protruding part protruding toward the storage compartment so as to define a space to accommodate the driving motor. 
     The storage compartment may be provided with a mini-drawer to hide the protruding part. 
     The refrigerator may further include a first coupling unit coupled to a driving shaft of the driving motor and including an insertion protrusion configured to transmit driving force from the driving motor to the feeding unit, and a second coupling unit coupled to a rotation shaft of the feeding unit and including an insertion recess into which the insertion protrusion is inserted. 
     The refrigerator may further include a first cover provided movably forward and backward around the insertion protrusion so as to hide the insertion protrusion when the door is opened, and a second cover provided movably forward and backward in the insertion recess so as to hide the insertion recess when the door is opened. 
     The second housing may be formed with an opening which is blocked by the first coupling unit when the door is opened and through which the second coupling unit passes when the first coupling unit and the second coupling unit are coupled. 
     As described above, in the refrigerator constructed such that the ice bucket provided with the feeding unit is disposed at the door, the driving motor to drive the feeding unit may be mounted to the main body as opposed to the door. Accordingly, a capacity of the ice bucket may be increased. 
     Since the rotation shaft of the feeding unit is horizontally arranged, the ice feeding operation of the feeding unit may be smoothly performed. 
     In addition, the door may have a simple structure. 
     Repair or replacement of the driving motor may be easily achieved. 
     Further, in the coupling device to transmit driving force from the driving motor to the feeding unit, the driving coupler coupled to the driving motor disposed at the main body and the driven coupler coupled to the feeding unit disposed at the door may be smoothly connected. 
     Further, since the driving coupler and the driven coupler are concealed by the covers and are not exposed to the outside when the door is opened, external appearance and aesthetics may be improved, and the risk of injury from direct contact of a body of a user with the driving coupler or the driven coupler may be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view illustrating a refrigerator according to a first embodiment of the present disclosure; 
         FIG. 2  is a perspective view illustrating a door of the refrigerator depicted in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view illustrating a driving device of the refrigerator depicted in  FIG. 1 ; 
         FIG. 4  is a plan sectional view of the refrigerator depicted in  FIG. 1 ; 
         FIG. 5  is a sectional view illustrating a state in which a rotation center of a driven coupler and a rotation center of a driving coupler coincide with each other in the refrigerator depicted in  FIG. 1 ; 
         FIG. 6  is a side sectional view of a main body of a refrigerator according to a second embodiment of the present disclosure; 
         FIG. 7  is a perspective view illustrating a driving device of the refrigerator depicted in  FIG. 6 ; 
         FIG. 8  is a side sectional view of a main body of a refrigerator according to a third embodiment of the present disclosure; 
         FIG. 9  is a perspective view illustrating a door of a refrigerator according to a fourth embodiment of the present disclosure; 
         FIG. 10  is a plan sectional view of the refrigerator depicted in  FIG. 9 ; 
         FIG. 11  is a view to explain a refrigerator according to a fifth embodiment of the present disclosure; 
         FIG. 12  is a view illustrating a refrigerator according to a sixth embodiment of the present disclosure; 
         FIG. 13  is a view illustrating a rear of a door of the refrigerator depicted in  FIG. 12 ; 
         FIG. 14  is an exploded perspective view of a driving device of the refrigerator depicted in  FIG. 12 ; 
         FIG. 15  is a sectional view of a driving coupler of the refrigerator depicted in  FIG. 12 ; 
         FIG. 16  is a view illustrating a driven coupler of the refrigerator depicted in  FIG. 12 ; 
         FIG. 17  is an exploded perspective view of the driven coupler of the refrigerator depicted in  FIG. 12 ; 
         FIG. 18  is a sectional view of the driven coupler of the refrigerator depicted in  FIG. 12 ; 
         FIG. 19  is a sectional view illustrating a state in which a first coupling unit of the driving coupler pressurizes a second coupling unit of the driven coupler in the refrigerator depicted in  FIG. 12 ; and 
         FIG. 20  is a sectional view illustrating a state in which an insertion protrusion of the first coupling unit of the driving coupler is inserted into an insertion recess of the second coupling unit of the driven coupler in the refrigerator depicted in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a perspective view illustrating a refrigerator according to a first embodiment of the present disclosure. 
     As exemplarily shown in  FIG. 1 , a refrigerator  1  according to the first embodiment of the present disclosure includes a main body  10 , storage compartments  20  and  30  formed in the main body  10 , and a cool air supply device (not shown) to supply cool air to the storage compartments  20  and  30 . 
     The main body  10  includes an inner casing  11  (refer to  FIG. 4 ) to define the storage compartments  20  and  30 , an outer casing  12  (refer to  FIG. 4 ) coupled outside of the inner casing  11  and an insulation wall  13  (refer to  FIG. 4 ) disposed between the inner casing  11  and the outer casing  12 . 
     The inner casing  11  may be made of a resin material by injection molding and the outer casing  12  may be made of a metal material for high design quality and durability. The insulation wall  13  may be formed of rigid urethane foam, or may be formed by injecting a raw urethane material into a space between the inner casing  11  and the outer casing  12  that are coupled to each other. 
     The main body  10  may be formed in a substantially box-shaped configuration having an opened front surface. The main body  10  may include a top wall  14 , a bottom wall  15 , a pair of side walls  16   a  and  16   b , a rear wall, and an intermediate wall  17 . The storage compartments  20  and  30  may be divided by the intermediate wall  17  into a freezing compartment  20  on the left and a refrigerating compartment  30  on the right. A temperature of the freezing compartment  20  may be about −18° C. and a temperature of the refrigerating compartment  30  may be about 0° C. to 5° C. The positions of the freezing compartment  20  and the refrigerating compartment  30  are not limited to this arrangement and various configurations are possible. 
     A freezing compartment door  21  may be rotatably coupled to the main body  10  by a hinge  22 , so as to open and close an opened front surface of the freezing compartment  20 . In addition, a refrigerating compartment door  31  may be rotatably coupled to the main body  10  by a hinge  32 , so as to open and close an opened front surface of the refrigerating compartment  30 . 
     The freezing compartment door  21  is provided with an icemaker  40  to produce ice cubes and an ice bucket  50  to store ice cubes produced by the icemaker  40 . The icemaker  40  may produce ice cubes using cool air in the freezing compartment  20 . 
     The ice bucket  50  is disposed below the icemaker  40  at the freezing compartment door  21 . The ice bucket  50  is provided with a feeding device  61  and  63  (refer to  FIG. 2 ) to feed ice cubes stored therein. The main body  10  is provided with a driving device  70  to drive the feeding device  61  and  63 . Hereinafter, a structure of the refrigerator according to the embodiment of the present disclosure will be described focusing on the feeding device and the driving device  70 . 
       FIG. 2  is a perspective view illustrating the door of the refrigerator depicted in  FIG. 1 ,  FIG. 3  is an exploded perspective view illustrating the driving device of the refrigerator depicted in  FIG. 1 ,  FIG. 4  is a plan sectional view of the refrigerator depicted in  FIG. 1 , and  FIG. 5  is a sectional view illustrating a state in which a rotation center of a driven coupler and a rotation center of a driving coupler coincide with each other in the refrigerator depicted in  FIG. 1 . 
     Referring to  FIGS. 2 through 5 , the refrigerator according to the first embodiment of the present disclosure includes the icemaker  40 , the ice bucket  50  to store ice cubes produced by the icemaker  40 , the feeding device  61  and  63  to feed ice cubes stored in the ice bucket  50  and the driving device  70  to drive the feeding device  61  and  63 . 
     The icemaker  40  may include plural ice making cells  41  to freeze water supplied thereto into ice cubes, an ejector  42  to separate the ice cubes produced in the ice making cells  41  from the icemaker  40  and a slider  43  to guide the ice cubes separated from the icemaker  40  through the ejector  42  to the ice bucket  50 . 
     The ejector  42  may include a rotation shaft and an ejector pin extending in a radial direction from the rotation shaft. As the ejector pin rotates about the rotation shaft, the ice cubes in the ice making cells  41  are pushed to the outside of the ice making cells  41 . The ice cubes separated from the ice making cells  41  by the ejector  42  may slide down to the ice bucket  50  through the slider  43 . 
     The ice bucket  50  may include a storage space  51  to store the ice cubes dropping from the icemaker  40  and a crushing space  52  in which the ice cubes are crushed into ice pieces. The storage space  51  and the crushing space  52  may be horizontally arranged. 
     A discharge port  55  may be formed at a bottom portion of the crushing space  52 , through which the ice pieces are discharged from the ice bucket  50 . The discharge port  55  may be connected to a chute  90  to guide the ice pieces to a dispensing space of a dispenser. 
     A crushing device may be provided in the crushing space  52  to crush ice cubes into ice pieces. The crushing device may include a fixed blade  58  fixed to the ice bucket  50 , a rotational blade  59  coupled to a rotation shaft  62  of a feeding unit  61  and configured to rotate together with the feeding unit  61  and a guide member  56  to hold the ice cubes so that the fixed blade  58  and the rotational blade  59  may crush the ice cubes into ice pieces and to guide the crushed ice pieces to the discharge port  55 . 
     The guide member  56  may be rotatably coupled to the discharge port  55  by a hinge, to selectively allow ice cubes to be discharged through the discharge port  55  without being crushed. The crushing device may include a switching motor  57  capable of rotating the guide member  56 . 
     The ice cubes dropping to the storage space  51  of the ice bucket  50  from the icemaker  40  may be fed to the crushing space  52  from the storage space  51  by the feeding device  61  and  63 . The ice cubes may be selectively crushed into ice pieces or not crushed in the crushing space  52  and may be discharged to the outside of the ice bucket  50  through the discharge port  55  formed at the bottom portion of the crushing space  52 . 
     The feeding device, which serves to feed ice cubes to the crushing space  52 , may include a feeding unit  61  and a driven coupler  63  receiving driving force to rotate the feeding unit  61 . 
     The feeding unit  61  may be formed in an auger configuration, which includes a rotation shaft  62  and a spiral blade  64  extending in a radial direction from the rotation shaft  62 . 
     The driven coupler  63  may include a support part  63   a  extending in a radial direction from the rotation shaft  62  and a pressurized part  63   b  protruding from the support part  63   a.    
     As exemplarily shown in  FIG. 5 , the pressurized part  63   b  includes a proximal end located apart from a rotation center O by a distance of a first radius D 1  and a distal end located apart from the rotation center O by a distance of a second radius D 2 . 
     A driving coupler  73 , which serves to rotate the driven coupler  63 , may be provided at the main body  10 . The driving coupler  73  includes a wing part  73   a  extending in radial direction from a rotation shaft and a pressurizing part  73   b  protruding from the wing part  73   a . The pressurizing part  73   b  includes a proximal end and a distal end, at least one of which is located apart from the rotation center O by a distance between the first radius D 1  and the second radius D 2 . As exemplarily shown in  FIG. 5 , the proximal end of the pressurizing part  73   b  may be spaced from the rotation center O by a distance of a third radius D 3  and the distal end of the pressurizing part  73   b  may be spaced from the rotation center O by a distance of a fourth radius D 4 . 
     When the rotation centers of the driving coupler  73  and the driven coupler  63  are aligned with each other, if the driving coupler  73  rotates, the pressurizing part  73   b  of the driving coupler  73  pressurizes the pressurized part  63   b  of the driven coupler  63  and thus the driven coupler  63  rotates. 
     The driving coupler  73  and the driven coupler  63  are engaged with each other when the door  21  is closed and are disengaged from each other when the door  21  is opened. Accordingly, in order to prevent damage due to frequent engagement and disengagement, the driving coupler  73  and the driven coupler  63  may be made of a resin material. 
     As exemplarily shown in  FIGS. 3 and 4 , a driving motor  71  to rotate the driving coupler  73  may be provided at the side wall  16   a  of the main body  10 . A reducer  74  to reduce rotation speed of the driving motor  71  may be connected to the driving motor  71 , and the driving coupler  73  may be connected to an output shaft  74   a  of the reducer  74 . 
     The inner casing  11  may be formed with a concave-shaped motor receiving part  80  which is depressed inside the insulation wall  13 , so that at least a portion of the driving motor  71  may be received in the motor receiving part  80 . As exemplarily shown in  FIG. 4 , the driving motor  71  may be wholly received in the motor receiving part  80 . 
     By virtue of the motor receiving part  80  in which at least a portion of the driving motor  71  is received, the driving device  70  may not excessively protrude inside the freezing compartment  20 , which may prevent decrease in the capacity of the freezing compartment  20  and interference with the driving device  70  when a user accesses the freezing compartment  20 . 
     The driving motor  71  may be shielded by a cover  75 . The cover  75  may include a coupling part  75   a  that comes into close contact with the inner casing  11  so as to be coupled to the inner casing  11 . The coupling part  75   a  may be formed with a fastening hole  75   b  and the inner casing  11  may also be formed with a fastening hole  81  corresponding to the fastening hole  75   b  of the coupling part  75   a . A fastening member  76  may be fastened to the fastening holes  75   b  and  81 , thereby securely fixing the driving device  70  to the inner casing  11 . 
     When the driving device  70  malfunctions, a user or technician may easily repair or replace the driving device  70  simply by releasing the fastening member  76  and separating the driving device  70  from the inner casing  11 . 
     The driving device  70  is positioned such that the rotation center of the driving coupler  73  is aligned with the rotation center of the driven coupler  63  in the door-closed state. 
       FIG. 6  is a side sectional view of a main body of a refrigerator according to a second embodiment of the present disclosure, and  FIG. 7  is a perspective view illustrating a driving device of the refrigerator depicted in  FIG. 6 . Some parts in this embodiment are substantially the same as those in the first embodiment and thus denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As exemplarily shown in  FIGS. 6 and 7 , in a refrigerator according to the second embodiment of the present disclosure, a driving motor  171  is disposed at an outer surface of the outer casing  12  of the top wall  14 . The driving motor  171  may be fixed to the outer surface of the outer casing  12  using a motor fastening part  171   a . The motor fastening part  171   a  is not limited to the configuration illustrated in the drawings and may have various configurations capable of fixing the driving motor  171  to the outer surface of the outer casing  12 . 
     An accommodation space  180   a , in which a driving shaft  172  of the driving motor  171  is disposed, is formed between the inner casing  11  and the outer casing  12 . The driving shaft  172  may extend downward from the top wall  14  through the accommodation space  180   a.    
     The driving shaft  172  is arranged perpendicularly to a rotation shaft of a driving coupler  173 . A worm gear  172   a  and  174   a  may be provided to transmit driving force of the driving shaft  172  to the driving coupler  173 . Instead of the worm gear  172   a  and  174   a , a bevel gear may be used. The structure of the worm gear  172   a  and  174   a  is capable of reducing rotation speed of the driving shaft  172  and thus does not require an additional reducer. Further, the worm gear  172   a  and  174   a  may have a smaller size than a bevel gear. 
     The worm gear  172   a  and  174   a  may include a worm  172   a  formed at the driving shaft  172  and a worm wheel  174   a  formed at a transmission shaft  174 . The driving coupler  173  may be connected to the transmission shaft  174 . The worm gear  172   a  and  174   a  may be disposed in an accommodation space  180   b  formed between the inner casing  11  and the outer casing  12 . 
     Bearings  172   b  and  174   b  may be provided in the accommodation space  180   b  to enable the driving shaft  172  and the transmission shaft  174  to smoothly rotate. The accommodation space  180   b  may be covered by a cover  175 . The cover  175  may be coupled to the inner casing  11  using a fastening member  176 . 
     As described above, since this embodiment is structured such that the driving shaft  172  and the worm gear  172   a  and  174   a  are disposed in the spaces between the inner casing  11  and the outer casing  12  and are not exposed to the outside, the external appearance of the refrigerator is improved. 
       FIG. 8  is a side sectional view of a main body of a refrigerator according to a third embodiment of the present disclosure. Some parts in this embodiment are substantially the same as those in the first and second embodiments and thus denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As exemplarily shown in  FIG. 8 , in a refrigerator according to the third embodiment of the present disclosure, a driving motor  271  is disposed at an inner surface of the inner casing  11  of the top wall  14 . The driving motor  271  may be fixed to the inner surface of the inner casing  11  using a motor fastening part  271   a . The motor fastening part  271   a  is not limited to the configuration illustrated in the drawings. 
     A driving shaft  272  of the driving motor  271  may penetrate the inner casing  11  and may be disposed in a space between the inner casing  11  and the outer casing  12 . The driving shaft  272  may be formed with a first worm  272   a . The driving shaft  272  may also be coupled with a bearing  272   b  for smooth rotation thereof. 
     A first worm wheel  274   a , which is engaged with the first worm  272   a , may be formed at a first transmission shaft  274 . The first worm  272   a  and the first worm wheel  274   a  may compose a first worm gear  272   a  and  274   a . An accommodation space  280   a  to accommodate the first worm gear  272   a  and  274   a  may be formed between the inner casing  11  and the outer casing  12 . 
     In addition, an accommodation space  280   b  may be formed between the inner casing  11  and the outer casing  12 . The accommodation space  280   b  may extend vertically to accommodate the first transmission shaft  274 . The first transmission shaft  274  may be coupled with a bearing  274   c  and may be formed with a second worm  274   b.    
     A second worm wheel  275   a , which is engaged with the second worm  274   b , may be formed at a second transmission shaft  275 . The second transmission shaft  275  may be connected with a driving coupler  273  and may be coupled with a bearing  275   b . The second worm  274   b  and the second worm wheel  275   a  may compose a second worm gear  274   b  and  275   a . An accommodation space  280   c  to accommodate the second worm gear  274   b  and  275   a  may be formed between the inner casing  11  and the outer casing  12 . 
     The accommodation space  280   c  may be covered by a cover  276 , and the cover  276  may be coupled to the inner casing  11  using a fastening member  277 . 
     As described above, using the plural worm gears  272   a ,  274   a ,  274   b  and  275   a , driving force from the driving motor  271  disposed at the inner surface of the inner casing  11  of the top wall  14  may be transmitted to the driving coupler  273 . The driving force transmission structure is not limited to this embodiment using the plural worm gears  272   a ,  274   a ,  274   b  and  275   a . Various other driving force transmission methods, using a single worm gear, a bevel gear, a belt-pulley system, or the like, may be applied, and such methods also fall within the scope of the present disclosure. 
     This embodiment has features that the worm gears  272   a ,  274   a ,  274   b  and  275   a , the first transmission shaft  274  and the second transmission shaft  275  are disposed in the spaces between the inner casing  11  and the outer casing  12  and are not exposed to the outside. Further, the worm gears  272   a ,  274   a ,  274   b  and  275   a  eliminate the need for any additional reducer. 
       FIG. 9  is a perspective view illustrating a door of a refrigerator according to a fourth embodiment of the present disclosure, and  FIG. 10  is plan sectional view of the refrigerator depicted in  FIG. 9 . Some parts in this embodiment are substantially the same as those in the first through third embodiments and thus denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As exemplarily shown in  FIGS. 9 and 10 , in a refrigerator according to the fourth embodiment of the present disclosure, a rotation shaft of a feeding unit  361  is vertically arranged. An ice bucket  350  includes a storage space  351  to store ice cubes produced by the icemaker and a crushing space  352  to which the ice cubes are fed from the storage space  351  and in which the ice cubes are crushed into ice pieces. The crushing space  352  is disposed below the storage space  351 . 
     Although a separated state of the storage space  351  from the crushing space  352  is illustrated in  FIG. 9 , the storage space  351  and the crushing space  352  may be formed separately or integrally. 
     In the crushing space  352 , there are provided a discharge port  355  through which ice pieces are discharged, a fixed blade  358  fixed to the ice bucket  350 , a rotational blade  359  configured to rotate together with the feeding unit  361 , and a guide member  356  to hold the ice cubes so that the fixed blade  358  and the rotational blade  359  may crush the ice cubes into ice pieces and to guide the crushed ice pieces to the discharge port  355 . The guide member  356  may rotate about a hinge shaft  356   a  by a switching motor  357 . 
     The storage space  351  and the crushing space  352  are partitioned by a partition plate  353 . The partition wall  353  is formed with a communication hole  354  to communicate the storage space  351  and the crushing space  352  with each other. The partition plate  353  is horizontally arranged. Accordingly, a rotation shaft  362  of the feeding unit  361  may be vertically arranged. 
     The feeding unit  361  may include a rotation shaft  362  and a stirrer  364  provided above the rotation shaft  362  so as to stir ice cubes in the storage space  351  and feed the same to the crushing space  352  through the communication hole  354  while preventing the communication hole  354  from becoming blocked. 
     The rotation shaft  362  may be formed with a worm wheel  362   a , and a worm  365   a  engaged with the worm wheel  362   a  may be formed at a transmission shaft  365 . The transmission shaft  365  may be connected with a driven coupler  363 . 
     As described above, by using the worm gear  362   a  and  365   a , driving force may be transmitted from the driven coupler  363  to the feeding unit  361  having the vertically arranged rotation shaft  362 . 
       FIG. 11  is a view to explain a refrigerator according to a fifth embodiment of the present disclosure. Some parts in this embodiment are substantially the same as those in the first through fourth embodiments and thus denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As exemplarily shown in  FIG. 11 , in a refrigerator according to the fifth embodiment of the present disclosure, a rotation shaft of a feeding unit  461  is slantedly arranged. An ice bucket  451  and  452  includes a storage space  451  to store ice cubes produced by the icemaker and a crushing space  452  to which the ice cubes are fed from the storage space  451  and in which the ice cubes are crushed into ice pieces. A partition plate  453  to partition the storage space  451  and the crushing space  452  is slantedly arranged. The partition plate  453  may be formed with a communication hole  454  to communicate the storage space  451  and the crushing space  452  with each other. 
     The feeding unit  461  may include a rotation shaft  462  arranged slantedly with respect to a horizontal plane or perpendicularly to the partition plate  453  and a stirrer  464  provided above the rotation shaft  462  so as to stir ice cubes in the storage space  451  and feed the same to the crushing space  452  through the communication hole  454  while preventing the communication hole  454  from becoming blocked. 
     The rotation shaft  462  of the feeding unit  461  may be formed with a worm wheel  462   a , and a worm  465   a  engaged with the worm wheel  462   a  may be formed at a transmission shaft  465 . 
       FIG. 12  is a view illustrating a refrigerator according to a sixth embodiment of the present disclosure, and  FIG. 13  is a view illustrating a rear of a door of the refrigerator depicted in  FIG. 12 . Some parts in this embodiment are substantially the same as those in the first through fifth embodiments and thus denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     As exemplarily shown in  FIGS. 12 and 13 , a refrigerator  501  according to the sixth embodiment of the present disclosure includes a main body  510 , a storage compartment  520  formed in the main body  510  and a cool air supply device (not shown) to supply cool air to the storage compartment  520 . The cool air supply device may maintain a temperature of the storage compartment  520  below zero. That is, the storage compartment  520  may be a freezing compartment. 
     The main body  510  includes an inner casing  511  to define the storage compartment  520 , an outer casing  512  coupled outside of the inner casing  511  and an insulation wall  513  (refer to  FIG. 18 ) disposed between the inner casing  511  and the outer casing  512 . The insulation wall  513  may be formed of rigid urethane foam, or may be formed by injecting a raw urethane material into a space between the inner casing  511  and the outer casing  512  that are coupled to each other. 
     A door  521  may be rotatably coupled to the main body  510  by a hinge  522 , so as to open and close an opened front surface of the storage compartment  520 . The door  521  is provided with an icemaker  540  to produce ice cubes and an ice bucket  550  to store ice cubes produced by the icemaker  540 . The icemaker  540  may produce ice cubes using cool air in the storage compartment  520 . 
     The icemaker  540  may include plural ice making cells  541  to freeze water supplied thereto into ice cubes, an ejector  542  to separate the ice cubes produced in the ice making cells  541  from the icemaker  540  and a slider  543  to guide the ice cubes separated from the icemaker  540  through the ejector  542  to the ice bucket  550 . 
     The ice bucket  550  is provided at a rear of the door  521  and is positioned below the icemaker  540 . The ice bucket  550  may include a storage space  551  to store the ice cubes dropping from the icemaker  540  and a crushing space  552  in which the ice cubes are crushed into ice pieces. 
     The storage space  551  and the crushing space  552  may be horizontally arranged next to each other. A discharge port  555  may be formed at a bottom portion of the crushing space  552 , through which the ice pieces are discharged from the ice bucket  550 . The discharge port  555  may be connected to a chute  560  to guide the ice pieces to a dispensing space of a dispenser. 
     The ice bucket  550  may be provided with a feeding device  561  and  700  to feed ice cubes and a crushing device  556 ,  557 ,  558  and  559  to crush the ice cubes into ice pieces. 
     The feeding device may include a feeding unit  561  and a driven coupler  700  to which driving force to rotate the feeding unit  561  is transmitted. The driven coupler  700  is disposed outside of the ice bucket  550 , and the feeding unit  561  may be connected to the driven coupler  700  through an opening  553  of the ice bucket  550 . 
     The feeding unit  561  may include a rotation shaft  562  and a helix  563  extending from the rotation shaft  562 . 
     The driven coupler  700  may include a second coupling unit  710  formed with an insertion recess  720  and a second cover  730  provided in the insertion recess  720  so as to hide the insertion recess  720 . A detailed constitution of the driven coupler  700  will be explained later. 
     The crushing device may include a fixed blade  558  fixed to the ice bucket  550 , a rotational blade  559  coupled to the rotation shaft  562  of the feeding unit  561  and configured to rotate together with the feeding unit  561  and a guide member  556  to hold the ice cubes so that the fixed blade  558  and the rotational blade  559  may crush the ice cubes into ice pieces. The guide member  556  may be rotatably coupled to the discharge port  555  by a hinge and may rotate by a switching motor  557  to selectively allow the ice cubes to be discharged through the discharge port  555  without being crushed. 
     The main body  510  is provided with a driving device to drive the feeding device and the crushing device. 
     The driving device includes a driving motor  571  (refer to  FIG. 17 ) to generate driving force and a driving coupler  600  to transmit the driving force from the driving motor  571  to the feeding device. 
     When the door  521  is opened, the driving coupler  600  and the driven coupler  700  are disengaged from each other. When the door  521  is closed, the driving coupler  600  and the driven coupler  700  are engaged with each other and, accordingly, driving force transmission therebetween is accomplished. 
     The refrigerator according to the sixth embodiment of the present disclosure has features that the driving coupler  600  and the driven coupler  700  are smoothly engaged with each other when the door  521  is closed, the external appearance and aesthetics in the door-opened state is improved and the risk of injury from direct contact of a body of a user with the driving and driven couplers  600  and  700  is prevented. Constitution of the driving coupler  600  and the driven coupler  700  will now be described. 
       FIG. 14  is an exploded perspective view illustrating the driving device of the refrigerator depicted in  FIG. 12 , and  FIG. 15  is a sectional view of the driving coupler of the refrigerator depicted in  FIG. 12 . 
     As exemplarily shown in  FIGS. 14 and 15 , the driving device of the refrigerator according to the sixth embodiment of the present disclosure includes a driving motor  571  to generate driving force and a driving coupler  600  to transmit the driving force from the driving motor  571  to the feeding device. 
     The driving force of the driving motor  571  is transmitted to a driving shaft  572  with a rotation speed of the driving motor  571  being adequately reduced by a transmission part  575 . The transmission part  575  may include a reduction gear or belt. 
     The driving coupler  600  may be configured to be coupled to the driving shaft  572  and rotate together with the driving shaft  572 . The driving coupler  600  may be coupled to the driving shaft  572  through a connection bracket  573 . 
     The connection bracket  573  may have a substantial U shape and may be coupled to the driving shaft  572  so as to rotate together with the same. The driving shaft  572  may have a rectangular cross section, and the connection bracket  573  may be formed with a rectangular shaft hole, through which the driving shaft  572  is inserted. The driving shaft  572  may be coupled via a nut  574  to fix the connection bracket  573  to the driving shaft  572 . 
     The driving coupler  600  may include a first coupling unit  610 , a first cover  630  and a first spring  640 . The first coupling unit  610  may be coupled to the connection bracket  573  so as to rotate together with the same. 
     The first coupling unit  610  may include a circular plate part  611  formed in a substantially circular-plate shape and an insertion protrusion  620  protruding from the circular plate part  611 . The circular plate part  611  may be formed with a spring support part  612  to support the first spring  640 . 
     The insertion protrusion  620  may be inserted into an insertion recess  720  formed at a second coupling unit  710  of the driven coupler  700 , which will be described later. In the inserted state of the insertion protrusion  620  into the insertion recess  720 , if the driving motor  571  is driven, rotational force of the driving motor  571  is transmitted to the feeding device. 
     The first cover  630  serves to hide the insertion protrusion  620  so as not to be exposed to the outside when the door  521  is opened. Here, “to hide” means to cause the insertion protrusion  620  to appear not to protrude from the surrounding objects. That is, the first cover  630  moves to a position on an identical plane to a front surface portion of the insertion protrusion  620 , so that a side surface portion of the insertion protrusion  620  is not exposed. 
     Such a structure of hiding the insertion protrusion  620  may improve the external appearance and aesthetics, prevent injury from direct contact of a body of a user with the insertion protrusion  620  and enhance convenience in use. 
     The first cover  630  is formed with an opening  631  through which the insertion protrusion  620  passes. So as to hide or expose the insertion protrusion  620 , the first cover  630  is provided movably forward and backward around the insertion protrusion  620  in an axial direction of the motor driving shaft  572 . 
     The first cover  630  may be elastically supported by the first spring  640 . As exemplarily shown in the drawings, the first spring  640  may be provided in two separate parts disposed adjacent to both sides of the insertion protrusion  620 . The first spring  640  elastically biases the first cover  630  in order to hide the insertion protrusion  620 . The first spring  640  may be configured as a compression coil spring. 
     The first cover  630  may move backward in the axial direction by being pressurized by the second coupling unit  710  of the driven coupler  700 , which will be described later. Accordingly, the insertion protrusion  620  may be exposed to the outside. If the pressurization is released, the first cover  630  may return to a position of hiding the insertion protrusion  620  by elastic restoring force of the first spring  640 . 
     The refrigerator may further include a motor housing  581  and  585  to accommodate the driving motor  571 . The motor housing  581  and  585  may include a first motor housing  581  and a second motor housing  585 . 
     The first motor housing  581  is disposed inside of the insulation wall  513  between the inner casing  511  and the outer casing  512 . Therefore, the first motor housing  581  may be supported by the inner casing  511  and the insulation wall  513 . The first motor housing  581  has an opening directed toward the storage compartment  520 . 
     Before injecting an insulation material, the first motor housing  581  is temporarily fixed to the inner casing  511 . Then, the insulation material is injected into the space between the inner casing  511  and the outer casing  512 , thereby securely fixing the first motor housing  581  to the inner casing  511  through adhesive force of the insulation material itself. 
     The second motor housing  585  is coupled to the first motor housing  581  to cover the opening of the first motor housing  581 . The second motor housing  585  and the first motor housing  581  have coupling holes  589  and  582  respectively, and are coupled to each other by fastening a fastening member, such as a screw, to the coupling holes  589  and  582 . 
     The second motor housing  585  has a protruding part  587  protruding toward the storage compartment  520  so as to define an accommodation space  586  to accommodate the driving motor  571 . 
     In addition, the second motor housing  585  is formed with an opening  588 , through which the second coupling unit  710  passes when the first coupling unit  610  and the second coupling unit  710  are coupled. 
     In the storage compartment  520 , there may be provided a mini-drawer  590  to store thin or small food items. The mini-drawer  590  may be designed to hide the protruding part  587  of the second motor housing  585  so as not to be exposed to the outside, thereby improving the external appearance. 
       FIG. 16  is a view illustrating the driven coupler of the refrigerator depicted in  FIG. 12 ,  FIG. 17  is an exploded perspective view of the driven coupler of the refrigerator depicted in  FIG. 12 , and  FIG. 18  is a sectional view of the driven coupler of the refrigerator depicted in  FIG. 12 . 
     Referring to  FIGS. 16 through 18 , the driven coupler may include a base part  701 , a second coupling unit  710 , a second cover  730 , a second spring  740 , and a third spring  750 . 
     The base part  701  is formed in a substantially cylindrical shape having an opening at one side. The base part  701  serves to support the second coupling unit  710  and the third spring  750 , and is coupled to the rotation shaft  562  of the feeding unit so as to rotate together with the same. The rotation shaft  562  of the feeding unit may have a rectangular cross section, and the base part  701  may be formed with a rectangular shaft hole  703 , through which the rotation shaft  562  is inserted. The base part  701  may be provided with a flange part  702  protruding from an outer circumferential surface thereof. The flange part  702  is supported by the ice bucket  550  and serves to fix the position of the base part  701 . 
     The second coupling unit  710  serves to receive driving force by being coupled to the first coupling unit  610  of the driving coupler. The second coupling unit  710  includes a body part and an insertion recess  720  formed at the body part. 
     The insertion protrusion  620  of the first coupling unit  610  is inserted into the insertion recess  720  of the second coupling unit  710 . Thus, the insertion recess  720  may have a cross-sectional shape substantially identical to or larger than the insertion protrusion  620 . 
     Here, the coupling of the first coupling unit  610  and the second coupling unit  710  means insertion of the insertion protrusion  620  of the first coupling unit  610  into the insertion recess  720  of the second coupling unit  710 . 
     The second coupling unit  710  is formed with a shaft hole  711  into which the rotation shaft  562  of the feeding unit is fitted and is coupled to the rotation shaft  562  of the feeding unit so as to rotate together with the same. The rotation shaft  562  of the feeding unit may have a rectangular cross section, and the shaft hole  711  may also have a rectangular shape. 
     The second cover  730  serves to hide the insertion recess  720  so as not to be exposed to the outside when the door  521  is opened, by moving to a position on an identical plane to a front surface portion of the second coupling unit  710 . Here, “to hide” means to cause the second coupling unit  710  to appear not to be formed with the insertion recess  720  when viewed from the outside. 
     Such a structure of hiding the insertion recess  720  may improve the external appearance and aesthetics and prevent inconvenience or injury to fingers of a user caused by becoming caught in the insertion recess  720  during use of the refrigerator. 
     So as to hide or expose the insertion recess  720 , the second cover  730  is provided movably forward and backward in the insertion recess  720  in an axial direction of the rotation shaft  562  of the feeding unit. 
     A guide leg  731  may be provided at a rear surface of the second cover  730 , in order to guide movement of the second cover  730  and prevent separation of the second cover  730 . 
     The second cover  730  may be elastically supported by the second spring  740 . That is, the second spring  740  elastically biases the second cover  730  in order to hide the insertion recess  720 . The second spring  740  may be configured as a compression coil spring. 
     The second cover  730  may move backward into the insertion recess  720  through pressurization provided by the insertion protrusion  620  of the first coupling unit  610 . If the pressurization is released, the second cover  730  may return to a position of hiding the insertion recess  720  by elastic restoring force of the second spring  740 . 
     When the door  521  is closed, the insertion protrusion  620  of the first coupling unit  610  is directly inserted into the insertion recess  720  of the second coupling unit  710 . However, the insertion protrusion  620  of the first coupling unit  610  may not be directly inserted into the insertion recess  720  of the second coupling unit  710  and may collide with the body part of the second coupling unit  710 . 
     Whether the insertion protrusion  620  of the first coupling unit  610  is directly inserted into the insertion recess  720  of the second coupling unit  710  or collides with the body part of the second coupling unit  710  depends on the position of the insertion protrusion  620  of the first coupling unit  610  and the position of the insertion recess  720  of the second coupling unit  710  when the door  521  is closed. 
     Such collision between the insertion protrusion  620  of the first coupling unit  610  and the body part of the second coupling unit  710  may cause shock and damage to the components. Further, because the first coupling unit  610  and the second coupling unit  710  are not completely coupled, the feeding device may not operate normally, or the door may not be closed completely. 
     Accordingly, the refrigerator according to the sixth embodiment of the present disclosure is equipped with a coupling device capable of preventing shock due to accidental collision between the insertion protrusion  620  of the first coupling unit  610  and the body part of the second coupling unit  710 , enabling the door to be completely closed and guiding the insertion protrusion  620  of the first coupling unit  610  to be fully inserted into the insertion recess  720  of the second coupling unit  710  if the driving motor  571  is driven in the collision state. 
     In order to achieve the above objectives, the second coupling unit  710  is provided movably forward and backward in an axial direction of the rotation shaft  562  of the feeding unit. The second coupling unit  710  is elastically supported by the third spring  750 . 
     When the door  521  is closed, if the insertion protrusion  620  of the first coupling unit  610  collides with the body part of the second coupling unit  710  and pressurizes the second coupling unit  710 , the second coupling unit  710  moves backward into the base part  701  against elastic force of the third spring  750 . 
     Subsequently, if the driving motor  571  is driven, the insertion protrusion  620  of the first coupling unit  610  rotates. If the insertion protrusion  620  of the first coupling unit  610  rotates to a certain extent and the position of the insertion protrusion  620  is aligned with the position of the insertion recess  720 , the second coupling unit  710  moves forward out of the base part  701  by elastic restoring force of the third spring  750  and eventually the insertion protrusion  620  of the first coupling unit  610  is inserted into the insertion recess  720  of the second coupling unit  710 . 
     The rotation shaft  562  of the feeding unit may be formed with a coupling hole  562   a  at an end portion thereof, and a separation-prevention member  760  may be coupled into the coupling hole  562   a  in order to limit movement of the second coupling unit  710 . 
       FIG. 19  is a sectional view illustrating a state in which the first coupling unit of the driving coupler pressurizes the second coupling unit of the driven coupler in the refrigerator depicted in  FIG. 12 , and  FIG. 20  is a sectional view illustrating a state in which the insertion protrusion of the first coupling unit of the driving coupler is inserted into the insertion recess of the second coupling unit of the driven coupler in the refrigerator depicted in  FIG. 12 . 
     Referring to  FIGS. 15 and 18 through 20 , operation of the coupling device of the refrigerator according to the sixth embodiment of the present disclosure will now be explained. 
     As exemplarily shown in  FIG. 15 , when the door is opened, the first cover  630  is elastically biased by the first spring  640  and hides the first coupling unit  610 . That is, the first cover  630  prevents the side surface portion of the insertion protrusion  620  of the first coupling unit  610  from being exposed to the outside. 
     As exemplarily shown in  FIG. 18 , when the door is opened, the second cover  730  is elastically biased by the second spring  740  and hides the second coupling unit  710 . That is, the second cover  730  prevents the insertion recess  720  of the second coupling unit  710  from being exposed to the outside. 
     When the door is closed, depending upon the position of the insertion protrusion  620  of the first coupling unit  610  and the position of the insertion recess  720  of the second coupling unit  710 , the first coupling unit  610  and the second coupling unit  710  may be coupled directly or by operation wherein the second coupling unit  710  is pushed backward and the driving motor is driven to rotate the insertion protrusion  620  of the first coupling unit  610 . 
     In detail, as exemplarily shown in  FIG. 19 , when the door is closed, if the insertion protrusion  620  of the first coupling unit  610  is located at a position incapable of being inserted into the insertion recess  720  of the second coupling unit  710 , the insertion protrusion  620  of the first coupling unit  610  is not inserted into the insertion recess  720  and collides with the body part of the second coupling unit  710 . Thus, the second coupling unit  710  is pressurized and moves backward into the base part  701  against elastic force of the third spring  750 . 
     As such, since the second coupling unit  710  moves backward when collision between the insertion protrusion  620  of the first coupling unit  610  and the body part of the second coupling unit  710  occurs, minimal shock is produced and the door is completely closed. 
     Next, as exemplarily shown in  FIG. 20 , if the driving motor is driven in the state of  FIG. 19 , the first coupling unit  610  and the insertion protrusion  620  rotate by the driving motor. If the insertion protrusion  620  rotates to a certain extent and the insertion protrusion  620  is located at a position capable of being inserted into the insertion recess  720 , the second coupling unit  710  moves forward out of the base part  701  by elastic restoring force of the third spring  750 . 
     At this time, the body part of the second coupling unit  710  moves forward while pushing the first cover  630  of the driving coupler back, and the insertion protrusion  620  of the first coupling unit  610  moves forward while pushing the second cover  730  of the second coupling unit  710  back. 
     If the driving motor is continuously driven even after the insertion protrusion  620  is inserted into the insertion recess  720 , the rotational force of the driving motor is transmitted to the feeding unit. 
     Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.