Patent Publication Number: US-2022221216-A1

Title: Refrigerator

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2021-0003647, filed Jan. 11, 2021, the entire contents of which are incorporated herein for all purposes by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a refrigerator. 
     BACKGROUND 
     A refrigerator may lose cool air therein due to frequent opening of a door. In some cases, to reduce or prevent the loss of cool air, the refrigerator may allow a user to see the inside of the refrigerator without opening the door of the refrigerator, thereby reducing the number of times of opening and closing the door of the refrigerator. For instance, a refrigerator door may include a panel assembly made of glass enabling the inside of the refrigerator to be seen, and a door frame supporting the panel assembly. 
     In some cases, the door frame may be made of only a metal material or a synthetic resin, and the parts may be fixed to each other by screw fastening. In some cases, in order to reduce the weight of the door to increase the convenience of using the door, the door frame of the door may be made only of synthetic resin material, not metal material. The synthetic resin door frame may be light in weight, but have weak strength compared to the metal door frame. Therefore, it may be difficult to stably support the door panel made of heavy glass. 
     For instance, it may be difficult to strongly fasten components of the synthetic resin door frame by a fastening device such as a bolt. In some case, a foam solution may leak through the assembly part of the part. 
     In some examples, the refrigerator door may be made by foaming and filling a foam solution such as polyurethane into the door for insulation performance. In some examples, where the door for a refrigerator through which the inside of the refrigerator is visible, it may be difficult to provide the foam solution because the foaming space and the foaming passage are relatively small compared to a general door for a refrigerator. In some cases, to avoid a glass portion through which the inside of the refrigerator is visible and to provide the foaming space in an outer part of the door, the foaming space and the foaming passage may be limited to a part of the door except for the see-through part. For instance, the foam space and the foaming passage may be provided in the door frame. 
     In some cases, it may be possible to provide a sufficient foaming space by increasing the thickness of the door frame of the door, but the see-through part through which the inside of the refrigerator is visible may be relatively reduced. In some cases, the door frame may be exposed through a see-through window to spoil aesthetic of the door. In some cases, foaming resistance may be reduced in foaming a foam solution into a temporarily assembled door. 
     In order to secure the foaming space and the foaming passage, the door frame may be thick, and an area of the see-through window may be relatively small. 
     SUMMARY 
     The present disclosure describes a refrigerator that includes a transparent panel assembly applied to a door assembly to enable the inside of the refrigerator to be seen through, and a door frame that supports the panel assembly and includes synthetic resin components engageably assembled to each other. 
     The present disclosure further describes a refrigerator that includes a transparent panel assembly applied to a door of the refrigerator to enlarge an area through which the inside of the refrigerator is visible, where an entire front surface of the panel assembly can be exposed forward and have only a transparent front panel of the assembly to be seen from an outside. 
     According to one aspect of the subject matter described in this application, a refrigerator includes a cabinet that defines a storage chamber and a door configured to open and close at least a portion of the storage chamber. The door includes a panel assembly including a front panel and a rear panel that are connected to each other, where the front panel defines a front surface of the door, and the rear panel is spaced apart from the front panel and defines a rear surface of the door. The door further includes an upper frame that defines an upper surface of the door and is coupled to a rear surface of the front panel, a lower frame that defines a lower surface of the door and is coupled to the rear surface of the front panel, side frames that define lateral surfaces of the door, respectively, and are coupled to the rear surface of the front panel, a door liner that is in contact with the upper frame, the lower frame, the side frames, and the rear panel, and an insulator provided in a foaming space defined by the panel assembly, the upper frame, the lower frame, and the side frames. The door further includes a rod that connects the front panel to the rear panel, a heater housing that covers the rod and is attached to the rear surface of the front panel, and a heating device coupled to the heater housing, the heating device being in contact with the rear surface of the front panel. 
     Implementations according to this aspect can include one or more of the following features. For example, the heater housing can define a heater mounting groove that faces the rear surface of the front panel and receives the heating device, and a plurality of attachment grooves that are spaced apart from the heater mounting groove and arranged in parallel to another along the heater housing. 
     In some implementations, the heater housing can include a frame that has an L-shaped cross-section extending toward the rear panel, where a part of the heater housing covers a lateral side of the rear panel, and the rod is disposed adjacent to the lateral side of the rear panel. 
     According to another aspect, a refrigerator includes a cabinet that defines a storage chamber and a door configured to open and close at least a portion of the storage chamber. The door includes a panel assembly including a front panel and a rear panel that are connected to each other, where the front panel defines a front surface of the door, and the rear panel is spaced apart from the front panel and defines a rear surface of the door. The door further includes an upper frame that defines an upper surface of the door and is coupled to a rear surface of the front panel, a lower frame that defines a lower surface of the door and is coupled to the rear surface of the front panel, side frames that define lateral surfaces of the door, respectively, and are coupled to the rear surface of the front panel, a door liner that is in contact with the upper frame, the lower frame, the side frames, and the rear panel, and an insulator provided in a foaming space defined by the panel assembly, the upper frame, the lower frame, and the side frames. The door liner includes a center portion that defines an opening that faces the rear panel in a thickness direction of the door, a foam boundary portion that protrudes relative to the center portion and covers a periphery of the center portion, and a damping plate disposed between the foam boundary portion and the rear panel. 
     Implementations according to this aspect can include one or more of the following features. For example, the upper frame, the lower frame, and the side frames define a door frame, where an outer portion of the door liner can be in contact with edges of a rear surface of the door frame, and an end of the foam boundary portion can be coupled to a rear surface of the rear panel. 
     In some implementations, the door liner can further include a locking arm that protrudes from an upper portion of the door liner and is coupled to a lower end of an upper rear surface of the upper frame, and a locking hook disposed at a lower portion of the door liner and coupled to the lower frame, the locking hook extending forward relative to a lower rear surface of the lower frame. 
     In some implementations, the foam boundary portion can be in contact with a rear surface of the rear panel to thereby define a boundary of the foaming space along a contact region between the foam boundary portion and the rear surface of the rear panel. In some implementations, the foam boundary portion can define a damping space that is recessed rearward relative to the rear panel. In some examples, the damping plate can be disposed in the damping space and protrudes toward the rear panel to thereby divide the damping space. 
     In some implementations, the upper frame, the lower frame, and the side frames define a door frame, where an edge of the door liner is in contact with a rear surface of the door frame. The door liner can further include a division fence that protrudes from an inner surface of the door liner toward the foaming space, where the division fence is disposed adjacent to an edge of the rear surface of the door frame. 
     According to another aspect, a refrigerator a cabinet that defines a storage chamber and a door configured to open and close at least a portion of the storage chamber. The door includes a panel assembly comprising a front panel and a rear panel that are connected to each other, where the front panel defines a front surface of the door, and the rear panel is spaced apart from the front panel and defines a rear surface of the door. The door further includes (i) an upper frame that defines an upper surface of the door and is coupled to a rear surface of the front panel, the upper frame having an upper front surface, an upper main part, and an upper rear surface, (ii) a lower frame that defines a lower surface of the door and is coupled to the rear surface of the front panel, the lower frame having a lower front surface, a lower main part, and a lower rear surface, (iii) side frames that define lateral surfaces of the door, respectively, and are coupled to the rear surface of the front panel, each of the side frames having a side front surface, a side main portion, and a side rear surface. 
     The door further includes a door liner that is in contact with the upper rear surface, the lower rear surface, the side rear surfaces, and the rear panel, and an insulator provided in a foaming space defined by the panel assembly, the upper frame, the lower frame, and the side frames. At least one of the upper front surface or the lower front surface defines a stepped assembly surface that is recessed relative to the front surface of the door, where the side front surface is in contact with the stepped assembly surface such that the upper front surface or the lower front surface defines a plane parallel to the side front surface. 
     Implementations according to this aspect can include one or more of the following features. For example, each of the upper front surface and the lower front surface can define the stepped assembly surface, where the side frames are coupled to the stepped assembly surfaces, respectively, and define a common plane with the upper frame and the lower frame. In some examples, the side frames can include one of a locking hole or a first locking hook, and the upper frame can include the other of the locking hole or the first locking hook, where the first locking hook is coupled to the locking hole. 
     In some implementations, a cross-section of each of the side frames, the upper frame, and the lower frame has a U-shape. The side frames and the upper frame can be perpendicularly arranged and coupled to each other, where each of the side frames has at least three surfaces in contact with the upper frame. The side frames and the lower frame can be perpendicularly arranged and coupled to each other, where each of the side frames has at least three surfaces in contact with the lower frame. 
     In some implementations, the upper frame and the side frames can be assembled to each other along an assembly direction, and where each of the upper front surface and the upper rear surface can include a first locking hook that is inclined downward along the assembly direction. In some implementations, the upper frame can define a sensor mounting part that receives a door sensor, and the upper frame can include transfer ribs that are connected to a portion between the sensor mounting part and the upper front surface. 
     In some implementations, the upper frame can include a reinforcement rib that connects inner sides of the upper front surface, the upper main part, and the upper rear surface to one another, where the inner sides face the foaming space. In some examples, the upper main part of the upper frame can include a stepped surface that defines an inlet through which the insulator is provided into the foaming space, and a shield cover that covers the inlet. The shield cover can include (i) a cover body that is disposed at the stepped surface of the upper main part and (ii) a cover hook that is disposed at a lower portion of the cover body and coupled to a lower surface of the inlet. 
     In some implementations, the side front surface of each of the side frames and a rear surface of the front panel can define a first attachment surface. The upper front surface of the upper frame and the rear surface of the front panel can define a second attachment surface. The lower front surface of the lower frame and the rear surface of the front panel can define a third attachment surface, where the first attachment surface, the second attachment surface, and the third attachment surface define a continuous surface together. 
     In some implementations, at least one of the upper frame, the lower frame, or one or both of the side frames can define a contraction prevention groove that extends in a longitudinal direction thereof. 
     In some implementations, the transparent panel assembly can be applied to the door for a refrigerator, and the door frame supporting the panel assembly can include synthetic resin components that are engageably assembled to each other. Therefore, in comparison to the metal door frame, the total weight of the door is reduced, so that weight lightening of the door assembly can be realized. 
     In some implementations, the frames (side frames, upper frame, and lower frame) constituting the door frame can be engageably assembled with each other without a fastening device such as a screw, and the door liner assembled in rear of the door frame can be also assembled to the door frame by the locking structure. Therefore, the assembly process of the door can be simplified and the assembling property can be improved. 
     In some implementations, the panel assembly is supported only by the door frame without adding a separate outer frame other than the door frame, so that the supporting structure of the door can be thinned. An area (see-through part) through which the inside of the refrigerator is visible through the panel unit can be secured relatively wide. Therefore, even when the door is not opened, the user can see the storage space in the refrigerator and aesthetics of the door can be improved. 
     In some implementations, the front panel providing a frontmost surface in the multi-layered glass panel unit can be configured such that edges thereof are not surrounded by the door frame, and an entire front surface thereof is exposed forward. Therefore, only a glass part (front panel) is exposed at the front of the door, and the aesthetic of the refrigerator can be improved. 
     In some implementations, when the frames (side frames, upper frame, and lower frame) constituting the door frame are assembled to each other, the front surface of the door frame can be formed in a continuous surface. Therefore, an adhesive force between the panel assembly attached to the front surface of the door frame and the front surface of the door frame can be improved, and the durability of the door can be improved. The wide attachment area can improve sealing performance of the foaming space can be improved. 
     In some implementations, the rear surface of the door frame is formed in a continuous surface so as to secure a wide contact area between the door liner and the door frame, so that sealing performance of the foaming space can be improved. 
     In some implementations, when the bezel part of the front panel is formed half-transparent, the bezel part can cover the assembly part such as the door frame arranged in rear of the front panel so as to improve the aesthetic of the door. The bezel part can transmit light emitted from a lighting device or a touchable operating device located at a rear surface of the bezel part, so that the bezel part can be used as a part of a display device. 
     In some implementations, when the side, upper, and lower frames constituting the door frame are made of synthetic resin material by injection molding, a relatively complicated shape of the door frame can be realized in comparison to when the side, upper, and lower frames are made of a metal material. Therefore, an installation structure for installing various electrical components such as a lighting device and a touch button can be implemented to the door frame. 
     In some implementations, the side, upper, and lower frames constituting the door frame can be engageably assembled in surface-contact with each other at various surfaces. Therefore, the more solid door frame can be provided, and leakage of the foam solution between the components can be reduced or prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an example of a refrigerator including a door. 
         FIG. 2  is a perspective view showing an example of the door. 
         FIG. 3  is a perspective view showing the door at another angle from  FIG. 2 . 
         FIG. 4  is a perspective exploded view showing example parts of the door. 
         FIG. 5  is a perspective exploded view showing the parts of the door at another angle from  FIG. 4 . 
         FIG. 6  is a perspective view showing the door without a panel unit. 
         FIG. 7  is a rear-perspective view showing an example of a door frame of the door. 
         FIG. 8  is a perspective view showing an inside structure of an example of an upper frame of the door. 
         FIG. 9  is a front view showing a front structure of the upper frame of the door. 
         FIG. 10  is a sectional view taken along line I-I′ in  FIG. 2 . 
         FIG. 11  is a perspective view showing an example of side frames and a lower frame of the door frame of the door. 
         FIG. 12  is a sectional view taken along line II-II′ in  FIG. 2 . 
         FIG. 13  is a sectional view taken along line in  FIG. 2 . 
         FIG. 14  is a perspective view showing an example of a lower structure of the door without the panel unit and the side frames. 
         FIG. 15  is a sectional view showing an example of an upper lateral structure of the door. 
         FIG. 16  is a sectional view taken along line IV-IV′ in  FIG. 2 . 
         FIG. 17  is a rear-perspective view showing the lower structure of the door. 
         FIG. 18  is a sectional view showing the lower structure of the door. 
         FIG. 19  is a sectional view taken along line in  FIG. 2 . 
         FIG. 20  is a view showing an example of manufacturing the door. 
     
    
    
     DETAILED DESCRIPTION 
     One or more implementations of a refrigerator will be described with reference to the accompanying drawings. For example, a built-in type refrigerator having a door assembly will be described for an example, but the door assembly of the present disclosure can be applied to various devices having an inside storage space, such as a general refrigerator, a wine refrigerator, a kimchi refrigerator, a beverage storage, a plant cultivation apparatus, and a laundry processing apparatus. 
     In some implementations, as shown in  FIG. 1 , a cabinet  10  can define the exterior of the refrigerator and have a shape of a six-sided object, for example. The cabinet  10  can define a container that is open forward. The cabinet  10  can include a plurality of parts, and can include an outer casing  11 , as a major part, which provides an outside wall surface of the refrigerator. The opening of the cabinet  10  can be shielded by a door, which will be described later. 
     An upper portion of the cabinet  10  can have an upper plate  20 . The upper plate  20  can be connected to the door provided at a front surface of the cabinet  10  to cover a hinge device or constitute a part of the hinge device. 
     In some implementations, the cabinet  10  can have totally four storage spaces. A first upper storage chamber  30 A and a second upper storage chamber  30 B can be located at an upper portion in the cabinet  10 , and a first lower storage chamber  40 A and a second lower storage chamber  40 B can be located in a lower portion therein. Each of the four storage spaces can be shielded by each door. In some implementations, a door shielding the first upper storage chamber will be described as an example. 
     The second upper storage chamber  30 B can have a dispenser device  50 . A user can take out water or ices by using the dispenser device  50  without opening a door of the refrigerator. The dispenser device  50  can be removed. 
       FIG. 2  is a view showing an example of a door  100  for a refrigerator. As shown in  FIG. 2 , the door  100  is provided to open and close the first upper storage chamber  30 A. In some implementations, the door  100  can be configured to be opened and closed while being rotated. Specifically, the door  100  is brought into close contact with the front surface of the cabinet  10  to close the first upper storage chamber  30 A, or moves away from the front frame while being rotated to open the first upper storage chamber  30 A. 
     The refrigerator can achieve the sealed first upper storage chamber  30 A by the door  100 . The sealed first upper storage chamber  30 A can store foods while maintaining a constant temperature without loss of cold air. In some implementations, at least a part of the door  100  is formed in a transparent see-through part  115 . Therefore, the first upper storage chamber  30 A can be seen from the outside through the see-through part  115 . 
       FIGS. 3 to 19  show a detailed structure of the door  100 . In some implementations, a hinge can be mounted at one lateral portion of the door  100 . The hinge connects the door  100  to the cabinet  10  such that the door  100  is rotatable. The hinge can be assembled to a door frame, which will be described below. In some implementations, referring to  FIG. 2 , the hinge is provided at a right surface of the door  100 . Contrary to  FIG. 2 , the hinge can be provided at a left surface of the door  100 , and can be provided at a middle height of the door  100 , not at upper and lower portions of the door  100 . Reference numeral  131  indicates a hinge mounting part to which the hinge is mounted. 
     As shown in  FIG. 3 , a rear portion of the door  100  is shown without a door liner  160  and a gasket  190  that are assembled at the rear portion of the door  100 . As shown in the drawing, when the door liner  160  is omitted, an empty-rectangular-shaped foaming space S can be opened at the rear portion of the door  100 . The foaming space S can be shielded by the door liner  160  and foaming solution can be injected and foamed through an inlet H 1 , H 2  while the foaming space S being shielded. The foaming space S can be provided in a clearance between the door frame and a rear panel  116  spaced apart from each other, the door frame and the rear panel  116  will be described below. 
       FIG. 4  is a perspective exploded view showing disassembled parts constituting the door  100 . As shown in  FIG. 4 , in a direction from the front to the rear of the door  100 , a panel assembly  110 , a heater housing  180 , the door frame, the door liner  160 , and the gasket  190  are arranged in order. Among the parts, the heater housing  180  can be arranged between the rear panel  116  of the panel assembly  110  and the door frame. 
     In some implementations, the panel assembly  110  can include multi-layered glass panels. For example, a plurality of transparent-material panels can be laminated with spaces to provide the panel assembly  110 , and the user can selectively see the inside of the refrigerator through the panel assembly  110 . In some implementations, the panel assembly  110  is configured such that the plurality of glass panels is arranged while being spaced apart from each other to provide an insulation layer. However, a material is not limited to the glass, and can be made of various materials through which it is possible to see the inside of the refrigerator. 
     Among the plurality of panel layers, a front panel  111  providing a front surface of the panel assembly  110  can be made of a half glass material to enable the inside of the refrigerator to be selectively seen, or the front panel  111  can be covered with a film to be translucent. 
     Referring to  FIG. 5 , the panel assembly  110  includes the front panel  111  providing the front surface of the panel assembly  110  and the rear panel  116  layered on a rear surface of the front panel  111 . The rear panel  116  is layered on a rear portion of the front panel  111 . In some implementations, the rear panel  116  can include two layers  116   a  and  116   b , but can include one layer or less or of three layers or more. The panel assembly  110  can include the front panel  111  and the rear panel  116 . 
     The panel assembly  110  is made of glass or a material that enables the inside of the refrigerator to be visible, so that the user can selectively see the inside of the refrigerator through the panel assembly. The front panel  111  and the rear panel  116  can have an insulation material or an insulation structure to help to prevent leakage of cold air in the refrigerator. 
     The rear panel  116  can have the size smaller than the size of the front panel  111 . Specifically, the area of the front panel  111  can be larger than the area of the rear panel  116 . Therefore, an edge of the front panel  111  can protrude more than an edge of the rear panel  116 . For example, the edge of the front panel  111  can protrude more than lateral surfaces of the rear panel  116 . 
     The protruding portion of the front panel  111  can be referred to a bezel part  112   b . A portion in the bezel part  112   b  can be referred to the see-through part  115 . The see-through part  115  is a transparent portion as to allow the inside of the storage space to be seen through the panel assembly  110 . However, the bezel part  112   b  is not necessarily transparent. In some implementations, the bezel part  112   b  is provided only in the front panel  111 . However, the see-through part  115  is provided not only in the front panel  111 , and but also in the rear panel  116 . 
     The see-through part  115  is a transparent portion allow the storage space in the refrigerator to be observed through the panel assembly  110 , and can be referred to a center portion of the front panel  111  and the entire area of the rear panel  116 . Referring to  FIG. 3 , the see-through part  115  is provided inside the bezel part  112   b . The door frame, which will be described below, is provided on a rear surface of the bezel part  112   b , and various parts are located therein. The above structure will be described again below. 
     Referring to  FIG. 19 , a rod  118  can be inserted in a spacing between the glasses constituting the panel assembly  110 . The rod  118  is provided to maintain a spacing between the glass panels. The glass panels and a plurality of rods  118  can be attached to each other by an adhesive. A sealant can be coated to maintain the airtightness of the space between the front panel  111  and the rear panel  116 . 
     A low emissivity coating layer can be formed on a rear surface of the rear panel  116  in order to reduce heat transfer into the storage chamber by radiation. A glass on which the low emissivity coating layer is formed is referred to a Low-E glass. The low emissivity coating layer can be formed by depositing a surface of a glass by sputtering or the like. The space between the front panel  111  and the rear panel  116  sealed by the rod  118  is formed in a vacuum state and thus is insulated. 
     In some examples, the sealed space between the front panel  111  and the rear panel  116  can be filled with inert gas such as argon gas for insulation. The inert gas is excellent in insulation property compared to normal air. 
     To describe the door frame, the door frame can be configured such that separate frames are assembled to each other. As the separate frames respectively constituting four sides of the door frame are assembled to be engaged to each other, the door frame is achieved. Among the separate frames, a plurality of inlets H 1  and H 2  connected to the foaming space S are provided in an upper frame  130  or a lower frame  140 . The inlet H 1 , H 2  can be open in a height direction of the door frame. In some implementations, the inlet H 1 , H 2  can be formed in the upper frame  130 . 
     In some implementations, as will be described below, a side frame  120  and the upper frame  130  can be in surface-contact with each other at three surfaces and the side frame  120  and the lower frame  140  can also be in surface-contact with each other at three surfaces. Therefore, a shielding area for sealing the foaming space S can be enlarged. 
     The door frame can include a pair of side frames  120 , the upper frame  130 , and the lower frame  140 . The side frames  120 , the upper frame  130 , and the lower frame  140  can be made of a synthetic resin material. The total weight of the door frame can be relatively lightened compared a metal door frame. 
     As shown in  FIGS. 5 to 7 , the side frame  120  can be arranged in a direction in which the side frame stands up on the door frame, that is, in a vertical direction. The side frame  120  can have a U-shape cross-section, and can lengthen in one direction. The above structure can improve the durability of the side frames  120  with respect to distortion or bending. 
     Specifically, a side body  121  constituting the side frame  120  can include a side front surface  121   a , a side main portion  121   b , and a side rear surface  121   c . The side front surface  121   a , the side main portion  121   b , and the side rear surface  121   c  are perpendicularly connected to each other to form the U-shaped cross-section. An upper end and a lower end of the side body  121  can be open in the vertical direction. 
     The side front surface  121   a  can be in surface-contact with the bezel part  112   b . The side front surface  121   a  can be formed in a continuous surface with a lower front surface  143   a  and an upper front surface  133   a , which will be described below. The side front surface  121   a , the lower front surface  143   a , and the upper front surface  133   a  can be attached to the bezel part  112   b  by the adhesive to be fixed to each other. The side front surface  121   a , the lower front surface  143   a , and the upper front surface  133   a  can form a continuous surface together, whereby an attachment area can be secured sufficiently wide. 
     The side front surface  121   a  can have a hook arm  124 . The hook arm  124  can hold a lower end of the upper frame  130 . As shown in  FIG. 7 , the hook arm  124  can have a cantilever shape extended upward from a rear surface of the side front surface  121   a . The hook arm  124  can hold the upper frame  130  while supporting the lower end of the upper frame  130 . 
     The side main portion  121   b  can provide a lateral surface of the door frame. The side main portion  121   b  can be in surface-contact with the upper frame  130  and the lower frame  140 . As shown in  FIG. 7 , an upper portion of the side main portion  121   b  overlaps with the upper frame  130 . 
     The side rear surface  121   c  can be perpendicularly connected to the side main portion  121   b  and face the side front surface  121   a . The side rear surface  121   c  can be narrower than the side front surface  121   a . In some examples, in order to provide a contact area between the side front surface  121   a  and the panel assembly  110 , the side front surface  121   a  can be narrower than the side front surface  121   a.    
     The side rear surface  121   c  can have a locking hole  123  into which a first locking hook  133   d  of the upper frame  130  is inserted. The locking hole  123  can be a portion formed by perforating the upper portion of the side rear surface  121   c . When the first locking hook  133   d  is locked in the locking hole  123 , the side frame  120  and the upper frame  130  can be assembled to each other. The hook arm  124  of the side front surface  121   a  and the locking hole  123  of the side rear surface  121   c  are assembled with the upper frame  130 , so that the side frame  120  and the upper frame  130  can be restricted from being easily separated from each other and can be secured. 
     Upper portions of the pair of side frames  120  can be connected to each other by the upper frame  130 . The upper frame  130  is formed in a bar shape connecting the pair of side frames  120  to each other, and the upper frame  130  can be arranged in a direction in which the upper frame  130  is placed on the door frame, i.e., in a transverse direction. The upper frame  130  can have a U-shaped cross section as the side frame  120 , and can lengthen in one direction. The above structure can improve the durability of the upper frame  130  with respect to distortion or bending. 
     Specifically, the upper frame  130  can include the upper front surface  133   a , an upper main part  133   b , and an upper rear surface  133   c . The upper front surface  133   a , the upper main part  133   b , and the upper rear surface  133   c  can be perpendicularly connected to each other to form a U-shaped cross section. Left and right ends of the upper frame  130  can be open in left and right directions, respectively. 
     The upper front surface  133   a  can be in surface-contact with the side front surface  121   a . Referring to  FIG. 7 , the upper front surface  133   a  overlaps with the side front surface  121   a . The upper front surface  133   a  can include a first front surface  133   a   1  and a second front surface  133   a   2 . The second front surface  133   a   2  can define an assembly surface  133   a   2  that is stepped from the first front surface  133   a   1 . The stepped assembly surface  133   a   2  can be a portion stepped rearward from the upper front surface  133   a , and the rearward stepped portion can be filled with the side front surface  121   a  of the side frame  120 . Therefore, the upper front surface  133   a  of the upper frame  130  and the side front surface  121   a  of the side frame  120  can form a continuous surface together. 
     As shown in  FIGS. 6 and 9 , the first locking hook  133   d  can be projected on the upper front surface  133   a . The first locking hook  133   d  can be inserted into the locking hole  123  of the side frame  120 . The first locking hook  133   d  can be formed to be inclined downward in an assembly direction of the upper frame  130  and the side frame  120 . Therefore, when the upper frame  130  is assembled to the side frame  120 , the first locking hook  133   d  can be easily inserted into the locking hole  123 . In some implementations, the first locking hook  133   d  can be projected on the stepped assembly surface  133   a   2 . 
     The upper front surface  133   a  can be in surface-contact with the bezel part  112   b . The upper front surface  133   a  and the rear surface of the bezel part  112   b  can be attached to each other by an adhesive and an adhesive tape. In order to achieve the above structure, the upper front surface  133   a  needs to have a sufficiently wide area. 
     The upper front surface  133   a  can be connected to the upper main part  133   b . The upper main part  133   b  can be perpendicularly connected to the upper front surface  133   a  and provide an upper surface of the door frame. As shown in  FIG. 5 , the upper main part  133   b  can have a hole, the hole can be the inlet H 1 , H 2 . The inlet H 1 , H 2  can include two inlets spaced apart from each other in the upper main part  133   b . The inlet H 1 , H 2  can be open in the height direction of the door frame, i.e., in a vertical direction. 
     In some implementations, any one of the pair of inlets H 1  and H 2  can be arranged to overlap with the side frame  120  and another inlet can be arranged at a location deviating from the side frames  120 . The above structure is provided to correspond to a flow speed of foam solution injected through the pair of inlets H 1  and H 2 . For example, since the foam solution passing through a locking device  150 , which will be described below, is delayed in progress, the inlets H 1  and H 2  are arranged at the location wherein the side frame  120  and thus increase the flow speed of the foam solution. 
     As shown in  FIG. 10 , a shield cover C covers the inlets H 1  and H 2 . The shield cover C can serve to shield the inlets H 1  and H 2  after the foam solution is all filled. A cover body C 1  of a shield cover C can cover the inlets H 1  and H 2 , and cover hooks C 2  can be provided on a lower portion of the cover body C 1 . The cover body C 1  can be seated on a stepped surface  136  formed in the upper main part  133   b , and the cover hooks C 2  can be held by lower surfaces of the inlets H 1  and H 2 . 
     The upper main part  133   b  can have a contraction prevention groove  135 . The contraction prevention groove  135  can be continuously depressed in a longitudinal direction of the upper main part  133   b . The contraction prevention groove  135  is provided to prevent contraction and deformation in a manufacturing process of the upper frame  130  made by injection of synthetic resin material. The contraction prevention groove  135  can be formed on any one surface of the side frame  120 , the upper frame  130 , and the lower frame  140 . A predetermined space can be formed between the upper main part  133   b  and the upper front surface  133   a . As shown in  FIG. 10 , a first front protruding end  133   a ′, which is an end of the upper main part  133   b , protrudes more than the upper front surface  133   a , so that a first mounting space A 1  can be located below the first front protruding end  133   a ′ of the upper main part  133   b . The first mounting space A 1  can be filled with at least part of the front panel  111  of the panel assembly  110 . 
     The upper main part  133   b  can be connected to the upper rear surface  133   c . The upper rear surface  133   c  can be perpendicularly connected to the upper main part  133   b  and can face the upper front surface  133   a . As shown in  FIG. 7 , the upper rear surface  133   c  can be in surface-contact with the side rear surface  121   c . The upper rear surface  133   c  can also have the first locking hook  133   d.    
     In some implementations, the first locking hook  133   d  is provided on a front surface of the upper front surface  133   a , and the hook arm  124  of the side frame  120  can be locked to a rear surface of the upper front surface  133   a . Furthermore, the first locking hook  133   d  can be provided on a rear surface of the upper rear surface  133   c , and the hook arm  124  of the side frame  120  can be hooked by a front surface of the upper rear surface  133   c . Therefore, the upper frame  130  and the side frame  120  are engaged with each other at various portions thereof, so that firm fixation between the upper frame  130  and the side frame  120  can be achieved. 
     As shown in  FIG. 10 , a first rear surface protruding end  133   c ′ can be provided on an upper end of the upper main part  133   b . The first rear surface protruding end  133   c ′ is a portion protruding more than the upper rear surface  133   c , and an empty second mounting space A 2  can be provided between the first rear surface protruding end  133   c ′ and the upper rear surface  133   c . The second mounting space A 2  can be filled with the door liner  160 . 
     As shown in  FIG. 8 , the upper frame  130  can have a sensor mounting part  132 . The sensor mounting part  132  can be a portion to which a door sensor is installed. In some implementations, the sensor mounting part  132  can be provided in the upper main part  133   b , and the sensor mounting part  132  can be depressed on the upper main part  133   b .  FIG. 8  is a perspective view showing a lower portion of the upper main part  133   b , and referring to  FIG. 8 , the sensor mounting part  132  can be projected downward. A sensing hole  132   c  can be provided on a center portion of the sensor mounting part  132 , and at least of part of the door sensor can be exposed outward. 
     Referring to  FIG. 6 , a sensing part  132   a  can be exposed from a front surface of the sensor mounting part  132 . The sensing part  132   a  can be arranged in rear of the bezel part  112   b  of the panel assembly  110 . In some implementations, the sensor mounting part  132  can be located on a center portion of an upper end of the door  100 . As an example, D in  FIG. 4  refers to a sensor cover covering the sensor mounting part  132 . 
     Referring to  FIG. 8 , the sensor mounting part  132  can have transfer ribs  132   b . The transfer ribs  132   b  can be a structure protruding from a lower surface of the upper main part  133   b . In some implementations, the transfer ribs  132   b  can be provided such that a plurality of transfer ribs  132   b  is spaced apart from each other. The transfer ribs  132   b  can connect the upper front surface  133   a  on which the sensing part  132   a  is exposed to the sensor mounting part  132 . The transfer ribs  132   b  can efficiently transfer an impact generated on a front surface of the door  100  to the sensor mounting part  132 . 
     As shown in  FIGS. 7 and 9 , surfaces in the upper front surface  133   a , the upper main part  133   b , and the upper rear surface  133   c , the inner surfaces facing the foaming space S, can be connected to each other by a first reinforcement rib  134 . A plurality of first reinforcement ribs  134  can be arranged on the upper frame  130  with intervals. The reinforcement rib can help to reduce or prevent twisting or bending of the upper frame  130 . Particularly, in the foam process of the foam solution, the reinforcement rib can help to reduce or prevent the deformation of the upper frame  130 . In some implementations, since the upper front surface  133   a  is wider than the upper rear surface  133   c , the reinforcement rib can have an asymmetrical structure. Among the first reinforcement ribs  134 , a portion  134   a  connected to the upper front surface  133   a  can be wider than a portion  134   b  connected to the upper rear surface  133   c.    
     To describe the lower frame  140 , lower portions of the pair of side frames  120  can be connected to each other by the lower frame  140 . The lower frame  140  is formed in a kind of bar connecting the pair of side frames  120  to each other. The lower frame  140  can be arranged in a direction in which the lower frame  140  is placed on the door frame, i.e., in the transverse direction. The lower frame  140  can have a U-shaped cross section as the side frame  120 , and can lengthen in one direction. The above structure can improve the durability of the lower frame  140  with respect to distortion or bending. 
     Specifically, the lower frame  140  can include the lower front surface  143   a , the lower main part  143   b , and a lower rear surface  143   c . The lower front surface  143   a , the lower main part  143   b , and the lower rear surface  143   c  can be perpendicularly connected to each other to form a U-shape cross section. Left and right ends of the lower frame  140  can be open in left and right directions, respectively. 
     The lower front surface  143   a  can provide a front surface of the door frame together with the side front surface  121   a  and the upper front surface  133   a . The lower front surface  143   a  can forma continuous surface together with the side front surface  121   a  and the upper front surface  133   a , and the continuous surface can be in surface-contact with the bezel part  112   b.    
     As shown in  FIG. 11 , the lower front surface  143   a  can be wider than the lower rear surface  143   c . The hook arm  124  of the side frames  120  can be hooked by on an upper end of the lower front surface  143   a . A second locking hook  143   d  can be projected on the lower front surface  143   a , and the locking hole  123  of the side frame  120  can be fastened by second locking hook  143   d . In some implementations, an assembly structure between the lower frame  140  and the side frame  120  can be the same as the assembly structure between the upper frame  130  and the side frames  120 . 
     In some implementations, the second locking hook  143   d  is provided on a front surface of the lower front surface  143   a , and the hook arm  124  of the side frame  120  can be hooked to a rear surface of the lower front surface  143   a . Furthermore, the second locking hook  143   d  can be provided on a rear surface of the lower rear surface  143   c , and the hook arm  124  of the side frame  120  can be hooked by a front surface of the lower rear surface  143   c . Therefore, the upper frame  130  and the side frame  120  are engaged with each other at various portions thereof, so that firm fixation between the upper frame  130  and the side frame  120  can be achieved. 
     The lower front surface  143   a  can be in surface-contact with the side front surface  121   a . The lower front surface  143   a  can include a first front surface  143   a   1  and a second front surface  143   a   2 . The second front surface  143   a   2  can define an assembly surface  143   a   2  stepped from the first front surface  143   a   1 . The assembly surface  143   a   2  is a portion stepped rearward from the lower front surface  143   a , and the rearward stepped portion can be filled with the side front surface  121   a  of the side frame  120 . Therefore, the lower front surface  143   a  of the lower frame  140  and the side front surface  121   a  of the side frame  120  can form a continuous surface. 
     A predetermined space can be formed between the lower main part  143   b  and the lower front surface  143   a . As shown in  FIG. 11 , a second front protruding end  143   a ′, which is an end of a lower main part  143   b , protrudes more than the lower front surface  143   a , so that the first mounting space A 1  can be located above the second front protruding end  143   a ′ of the lower main part  143   b . The first mounting space A 1  can be the same as the first mounting space A 1  provided between the upper main part  133   b  and the upper front surface  133   a.    
     The lower front surface  143   a  can be connected to the lower main part  143   b . The lower main part  143   b  can provide a bottom surface of the door frame. The lower main part  143   b  can have a hinge housing  141  to which a hinge device can be mounted. The hinge housing can be projected toward the inside of the foaming space S. 
     The lower main part  143   b  can be connected to the lower rear surface  143   c . The lower rear surface  143   c  can be perpendicularly connected to the lower main part  143   b  and can face the lower front surface  143   a . The lower rear surface  143   c  can be in surface-contact with the side rear surface  121   c.    
     The lower rear surface  143   c  can include a first rear surface  143   c   1  and a second rear surface  143   c   2  as the lower front surface  143   a . The second rear surface  143   c   2  and the first rear surface  143   c   1  can define a stepped assembly surface  143   c   2 . The assembly surface  143   c   2  is a portion stepped rearward from the lower rear surface  143   c , and the rearward stepped surface can be filled with the side rear surface  121   c  of the side frame  120 . Therefore, the lower rear surface  143   c  of the lower frame  140  and the side rear surface  121   c  of the side frames  120  can form a continuous surface. 
     A second rear surface protruding end  143   c ′ can be provided at a lower end of the lower rear surface  143   c . The second rear surface protruding end  143   c ′ can be a portion protruding from the lower rear surface  143   c . The empty second mounting space A 2  can be provided between the second rear surface protruding end  143   c ′ and the lower rear surface  143   c . The second mounting space A 2  can communicate with the second mounting space A 2  provided between the upper rear surface  133   c  and the upper main part  133   b . The second mounting space A 2  can be filled with the door liner  160 . 
     Surfaces in the lower front surface  143   a , the lower main part  143   b , and the lower rear surface  143   c , the inner surfaces facing the foaming space S, can be connected to each other by the second reinforcement rib  144 . A plurality of second reinforcement rib  144  can be arranged on the lower frame  140  with intervals. The second reinforcement rib  144  can help to prevent twisting or bending of the lower frame  140 . Particularly, in the foaming processing of the foam solution, it can be possible to reduce or prevent deformation of the lower frame  140  by the second reinforcement rib  144 . In some implementations, since the lower front surface  143   a  is wider than the lower rear surface  143   c , the second reinforcement rib  144  can have an asymmetrical structure. Among the second reinforcement ribs  144 , a portion  144   a  connected to the lower front surface  143   a  can be wider than a portion  144   b  connected to the lower rear surface  143   c.    
     A push hole  146  can be formed in the lower rear surface  143   c . The push hole  146  is a portion to which a push device  147  is mounted. A part of the push device  147  can be projected rearward through the push hole  146 .  FIG. 17  is a view showing a part of the push device  147 . The push device  147  can provide an elastic force in a direction in which the door  100  is pushed from the cabinet  10 . When the user releases the locking device  150 , the door  100  can rotate forward to some degree. 
     The lower main part  143   b  can have a contraction prevention groove  145 . The contraction prevention groove  145  can be continuously depressed in a longitudinal direction of the lower main part  143   b . The contraction prevention groove  145  can help to prevent contraction and deformation in a manufacturing process of the lower frame  140  made by injection of synthetic resin material. 
     The front surface of the door frame assembled as described above can provide an attachment surface with respect to the rear surface of the front panel  111  of the panel assembly  110 . Specifically, (i) the side front surface  121   a  of the side frame  120  can provide a first attachment surface K 1  (referring to  FIGS. 16 and 19 ) with respect to the rear surface of the front panel  111 , (ii) the upper front surface  133   a  of the upper frame  130  can provide a second attachment surface K 2  (referring to  FIGS. 12 and 15 ) with respect to the rear surface of the front panel  111 , and (iii) the lower front surface  143   a  of the lower frame  140  can provide a third attachment surface K 3  (referring to  FIG. 18 ) with respect to the rear surface of the front panel  111 . The first to third attachment surfaces K 1  to K 3  are formed in a continuous surface. Therefore, a sufficiently wide attachment area can be secured between the front surface of the door frame and the rear surface of the front panel  111 . 
     The door frame can have the locking device  150 . The locking device  150  can be provided to restrict the door  100  from arbitrarily opening. The locking device  150  can be arranged in a vertical direction along the side frame  120 . Referring to  FIGS. 4 and 5 , the locking device  150  can include a handle  151  at a lower end thereof. The locking device  150  with a long bar shape can extend upward from the handle  151 . The locking device  150  can be covered by a locking housing  155 . Therefore, the locking device  150  can be protected in the foaming process. 
     A locking part  153  can be provided at a surface opposite to the handle  151 . The locking part  153  can be a kind of hook structure. When the user raises the handle  151 , the locking part  153  is operated in conjunction with the handle, and a locking state can be released. An elastic member provided in the locking device  150  can recover the handle  151  to the initial location of the handle  151 . 
     The door frame can be coupled to the door liner  160 . The door liner  160  can be assembled to the door frame to shield the foaming space S. Specifically, the foaming space S can refer to an empty space defined by the rear surface of the bezel part  112   b , an inside surface of the door frame, a lateral surface of the rear panel  116 , and a front surface of the door liner  160 . 
     When the door liner  160  is assembled to the door frame to shield the foaming space S and the foam solution is injected through the inlets H 1  and H 2 , the foam solution is filled and foamed in the foaming space S to form the insulator. 
     As shown in  FIG. 5 , a liner body  161  of the door liner  160  has a rectangular frame shape, and a center portion of the liner body  161  can be void. As the door liner  160  has a frame shape, the storage space in the cabinet  10  can be exposed to the outside while been seen through the see-through part  115  and the door liner  160 . 
     The door liner  160  can be assembled to the door frame. As shown in  FIG. 12 , the door liner  160  can have a locking arm  162  projected thereon. The locking arm  162  can be extended on the front surface of the door liner  160  while having a cantilever shape. The locking arm  162  can be extended to be inclined toward the upper side, i.e., toward the upper frame  130 . The locking arm  162  can be locked by a lower end of the upper rear surface  133   c  of the upper frame  130 . The locking arm  162  can have a plurality of locking pieces  162   a  to increase the elastic force of the locking arm  162 . 
     As shown in  FIG. 13 , the door liner  160  can have a locking hook  163  at a lower portion thereof. The locking hook  163  can be projected from the front surface of the door liner  160  while having a cantilever shape. The locking hook  163  can be assembled while passing through the lower rear surface  143   c  of the lower frame  140 . A locking step  163   a  can be provided at an end of the locking hook  163  to maintain a locking state of the locking hook  163 . 
     As described above, an upper portion of the door liner  160  can be locked to the upper frame  130  by the locking arm  162 . A lower portion of the door liner  160  can be locked to the lower frame  140  by the locking hook  163 . The worker firstly locks the locking arm  162  to the upper frame  130  and then rotates the lower end of the door liner  160  to lock the locking hook  163  to the lower frame  140 . Accordingly, the door liner  160  and the door frame can be simply assembled to each other. 
     When the door liner  160  is assembled to the door frame, the door liner  160  can be in surface-contact with the side frame  120 , the upper frame  130 , and the lower frame  140  constituting the door frame. As shown in  FIG. 16 , the door liner  160  is in surface-contact with the side rear surface  121   c  of the side frames  120  to form a first liner contact surface L 1 . As shown in  FIGS. 12 and 15 , the door liner  160  is in surface-contact with the upper rear surface  133   c  of the upper frame  130  to form a second liner contact surface L 2 . As shown in  FIG. 13 , the door liner  160  is in surface-contact with the lower rear surface  143   c  of the lower frame  140  to form a third liner contact surface L 3 . As described above, the door liner  160  is in surface-contact with the side frames  120 , the upper frame  130 , and the lower frame  140  constituting the door frame, whereby a shielding area for sealing the foaming space S can be wider. 
     As shown in  FIG. 13 , the door liner  160  can have the gasket mounting part B. The gasket mounting part B can be formed such that a part of the door liner  160  is recessed, and the gasket  190  can be assembled to the gasket mounting part B. A shape of the gasket mounting part B can be variously changed in response to a shape of the gasket  190 . 
     The gasket mounting part B of the door liner  160  can include a protrusion  165  and the protrusion  165  can include a gasket assembly groove  165   a . The gasket assembly groove  165   a  can be recessed from the rear surface of the door liner  160  deeper than the gasket mounting part B. A part of the gasket  190  can be inserted into the gasket assembly groove  165   a . In some examples, a fastening device can be assembled to the gasket assembly groove  165   a , so that the gasket  190  can be securely fixed to the door liner  160  by a beam. 
     As shown in  FIG. 17 , the gasket assembly groove  165   a  can have a plurality of air vents V 2  connected to the foaming space S. The air vents V 2  can be provided to discharge air in the foaming space S to the outside. The plurality of air vents V 2  can be formed along the gasket assembly groove  165   a . Since the inlets H 1  and H 2  can include the pair of inlets H 1  and H 2 , the foam solution injected through the pair of inlets H 1  and H 2  expands and solidifies to cause a gas trap, and the air vents V 2  can release the gas trap. 
     A push passing part  167  to which the push device  147  is mounted can be provided at the lower portion of the door liner  160 . A part of the push device  147  is projected rearward through the push passing part  167 , so that the push device  147  can be brought into close contact with the front surface of the cabinet  10 . 
     The door liner  160  can have an interference prevention part  169 . For example, the interference prevention part  169  can include a recessed space provided to avoid interference with the gasket  190  in a process in which the gasket  190  is depressed. In some implementations, the interference prevention part  169  can be formed at an edge portion of the gasket mounting part B adjacent to the protrusion. The interference prevention part  169  can have air vents V 2 . 
     As described above, the door liner  160  can include the first liner contact surface L 1 , the second liner contact surface L 2 , and the third liner contact surface L 3  between the door liner  160  and the door frame. The door liner  160  can be in contact with the rear surface of the rear panel  116  to form a boundary of the foaming space S. A part outside the door liner  160  can be in close contact with a rear surface edge of the door frame, and a part inside the door liner  160  can be in closed contact with the rear surface of the rear panel  116 . 
     As shown in  FIGS. 13, 18, and 19 , a foam boundary portion  166  can be provided inside the door liner  160 . The foam boundary portion  166  can be projected toward the rear of the door liner  160 , i.e., in a direction away from the rear panel  116 . In some implementations, the foam boundary portion  166  can have a triangular cross section. A damping space  166   a  can be provided inside the triangular space. A one end of the foam boundary portion  166  can be can be in close contact with a surface of the rear panel  116 . A portion where the foam boundary portion  166  and the rear panel  116  meet together can be provided as one boundary of the foaming space S. The damping space  166   a  can help to reduce or prevent excessive pressure on the foam boundary portion  166  by slowing a filling speed of the foam solution. 
     The damping space  166   a  can have a damping plate  166   b  projected toward a surface of the rear panel  116 . The damping plate  166   b  can have a plate structure extended along the damping space  166   a . The damping space  166   a  can be divided into left and right spaces with the damping plate  166   b  as the center. In some examples, one end of the damping plate  166   b  and the surface of the rear panel  116  may not be in close contact with each other, and can be spaced apart from each other at a predetermined interval, as shown in the enlarged view of  FIG. 19 . Therefore, the foam solution can be filled into the boundary over the damping plate  166   b . The damping plate  166   b  can slow the filling speed of the foam solution into the damping space  166   a  down. 
     As shown in  FIG. 19 , an edge of the door liner  160  can be in surface-contact with the side rear surface  121   c  of the side frames  120 . The first liner contact surface L 1  described above can be provided on the contact portion. A division fence  168  can be projected on an inner portion of the door liner  160  adjacent to the side rear surface  121   c  toward the side front surface  121   a  of the side frame  120 . The division fence  168  can slow a speed of the foam solution flowing toward the first liner contact surface L 1  to help to prevent the foam solution from leaking to the outside. The division fence  168  can be extend in the same direction as the damping plate  166   b.    
     As shown in  FIGS. 4 to 6 , the door frame and the rear panel  116  are spaced apart from each other, and a lighting device  178  can be installed in a part of the foaming space S. The lighting device  178  can be provide to light the see-through part  115  and be arranged in the transverse direction. The lighting device  178  can include a lighting part  178   a  such as a LED for emitting light, and a connector part  178   b  applying power and transmitting a signal. The lighting device  178  can be omitted or can be replaced with an input device for signal inputting. 
     The bezel part  112   b  can be coupled to the heater housing  180 . The heater housing  180  is provided to install the heating device such as a heater wire. In some implementations, heater housing  180  can be provided at a boundary portion between the front panel  111  of the heater housing  180  and the rear panel  116 . The heating device can help to prevent condensation generated on the door  100 . A housing body  181  constituting the heater housing  180  can have a rectangular frame shape. 
     As shown in  FIGS. 18 and 19 , the housing body  181  constituting the heater housing  180  can have a heater mounting groove  185  formed toward a rear surface of the bezel part  112   b . The heating device can be mounted in the heater mounting groove  185 . The heater mounting groove  185  can be provided at a location adjacent to the rear panel  116 . 
     The heater housing  180  can have attachment grooves  187  at a location adjacent to the heater mounting groove  185 . The attachment grooves  187  can be open toward the bezel part  112   b . The attachment grooves  187  can be provided to firmly attach the adhesive or adhesive tape, which holds the heater housing  180  to the bezel part  112   b , to the heater housing  180 . In some implementations, the attachment grooves  187  can include a plurality of attachment grooves  187  to form a continuously uneven structure. 
     Hereinbelow, an example of a process of manufacturing the door will be described. In some implementations, the front panel  111  and the rear panel  116  that constitute the panel assembly  110  can be layered together to constitute the single panel assembly  110 . Separately, the door frame can be assembled. The door frame can include the pair of side frames  120 , the upper frame  130 , and the lower frame  140 . The upper frames  130  can be assembled in a downward direction and the lower frame  140  can be assembled in an upward direction. In some implementations, the assembly structure between the side frames  120  and the upper frame  130  and the assembly structure between the side frames  120  and the lower frame  140  can be the same. 
     In some implementations, the first locking hook  133   d  can be provided at the front surface of the upper front surface  133   a . The hook arm  124  of the side frame  120  can be locked to the rear surface of the upper front surface  133   a . Furthermore, the first locking hook  133   d  can be provided on a rear surface of the upper rear surface  133   c , and the hook arm  124  of the side frame  120  can be hooked by a front surface of the upper rear surface  133   c . Therefore, the upper frame  130  and the side frame  120  are engaged with each other at various portions thereof, so that firm fixation between the upper frame  130  and the side frame  120  can be achieved. 
     When the door frame is assembled, the door frame and the panel assembly  110  can be coupled to each other. The panel assembly  110  can be laid down with the front panel  111  facing upward, and the door frame can be arranged to surround the rear panel  116 . As shown in  FIG. 20 , jigs J can be provided at four surfaces of the door frame to push the door frame in directions of edges thereof. Arrows {right arrow over ( 1 )} and {circle around ( 2 )} indicates the directions in which the jigs J push the door frame. 
     Then, when the front panel  111  is pressed in a downward direction by using a roller, etc., the rear surface of the bezel part  112   b  and the front surface of the door frame can be brought into contact with each other. As described above, (i) the side front surface  121   a  of the side frame  120  can provide the first attachment surface K 1  (referring to  FIGS. 16 and 19 ) with respect to the rear surface of the front panel  111 , (ii) the upper front surface  133   a  of the upper frame  130  can provide the second attachment surface K 2  (referring to  FIGS. 12 and 15 ) with respect to the rear surface of the front panel  111 , and (iii) the lower front surface  143   a  of the lower frame  140  can provide the third attachment surface K 3  (referring to  FIG. 18 ) with respect to the rear surface of the front panel  111 . The first to third attachment surfaces K 1  to K 3  can be formed in a continuous surface. Therefore, it can be possible to secure sufficiently firm attachment between the front surface of the door frame and the rear surface of the front panel  111 . 
     The assembly including the panel assembly  110  and the door frame can be turned over, and the heater housing  180  can be attached to the bezel part  112   b . The door liner  160  can be assembled in rear of the door frame. The upper portion of the door liner  160  can be locked to the upper frame  130  by the locking arm  162 . The lower portion of the door liner  160  can be locked to the lower frame  140  by the locking hook  163 . The worker firstly locks the locking arm  162  to the upper frame  130  and then rotates the lower end of the door liner  160  to lock the locking hook  163  to the lower frame  140 . 
     Then, the door liner  160  can be in surface-contact with the side frame  120 , the upper frame  130 , and the lower frame  140  constituting the door frame. The door liner  160  can be in surface-contact with the side rear surface  121   c  of the side frame  120  to provide the first liner contact surface L 1 , the door liner  160  is in surface-contact with the upper rear surface  133   c  of the upper frame  130  to provide the second liner contact surface L 2 , and the door liner  160  is in surface-contact with the lower rear surface  143   c  of the lower frame  140  to provide the third liner contact surface L 3 . As described above, the door liner  160  is in surface-contact with the side frames  120 , the upper frame  130 , and the lower frame  140  constituting the door frame, whereby a shielding area for sealing the foaming space S can be wider. 
     The foam solution can be filled through the inlets H 1  and H 2  and foamed to form the insulator. The foam solution can be filled into the foaming space without leakage to the outside by the structure of the surface-contact between the bezel part  112   b  and of the front surface of the door frame and the surface-contact between the rear surface of the door frame and the door liner  160 . 
     Hereinabove, although all components constituting the implementation are described as being coupled to each other or operated in combination as one, the present disclosure is not limited to the implementation. Within the scope of the purpose of the present disclosure, all of the components can be operated by selectively coupling one or more components together.