Abstract:
A cooking chamber assembly in a microwave oven for improved which improves air tightness in the cooking chamber, and reduces assembly complexity, time, and cost. A tray which essentially forms a bottom surface of a cooking chamber of the microwave oven is surrounded by a unitary gasket. A groove formed in an inner edge of the unitary gasket is designed to receive an outer edge of the tray, and a lip formed on an outer edge of the unitary gasket is designed to provide an air tight seal with an inner surface of a case of the cooking chamber. An air duct which guides circulating air is attached to an inner portion of the case with a series of hooks, allowing the air duct to be attached without separate fastening members such as screws or bolts, thus further reducing manufacturing time and cost.

Description:
This application claims the benefit of the Korean Application Nos. P2002-85106 filed on Dec. 27, 2002, and P2002-86907 filed on Dec. 30, 2002, which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to microwave ovens, and more particularly, to a cooking chamber assembly in a microwave oven of which ceiling and air duct assembly are improved. 
   2. Background of the Related Art 
   The microwave oven defrosts or heats food by directing a microwave to the food, that causes molecules in the food to vibrate to generate frictional heat for the defrosting or the heating. 
     FIG. 1  illustrates a partly disassembled perspective view of a related art microwave oven. As shown, the microwave oven is provided with a base plate  10 , a front plate  15  and a rear plate  13  mounted on a front end and a rear end of the base plate  10  vertical thereto respectively, an inner case  17  between the front plate  15  and the rear plate  13  to form a cooking chamber  20  therein, an outfit chamber  30  formed over the base plate  10  and sides of the inner case  17 , a front panel  40  attached to the front plate  15 , a plurality of electric components in the outfit chamber  30 , and an outer case  45  for enclosing the inner case  17  and the outfit chamber  30 . 
   The front plate has an opening  16  for making the cooking chamber  20  in communication with an exterior, and a door  41  on the front panel  40  for closing the opening  16 . 
   The outfit chamber  30  is provided with a magnetron  31  for generating and directing a microwave to the cooking chamber  20 , a transformer  32  for boosting a voltage of an external power and supplying to the magnetron  31 , and a cooling fan  33  for cooling various components. 
   The cooking chamber  20  of the microwave oven may sometimes be provided with a ceramic tray  50  on a bottom thereof and an air duct  60  on a ceiling thereof for circulating air in the cooking chamber  20 . Structures for mounting the ceramic tray  50  and the air duct  60  to the cooking chamber  20  will be described, briefly. 
     FIG. 2  or  3  illustrates a structure for mounting the tray  50  in the cooking chamber  20 . As shown in  FIG. 2 , the tray  50  is mounted on the bottom of the cooking chamber  20  together with a plurality of gaskets  55 . The gaskets  55 , for an example, of silicone rubber, are provided to four sides of the tray  50 . The gaskets  55  are put inside of the cooking chamber  20 , together with the tray  50 , and sealant  56  is applied to corners of the tray  50  where the gaskets  55  abut. 
   However, the application of the sealant is not convenient in above structure, failing to cover the abutting parts of the gaskets  55 , perfectly. Then, as shown in  FIG. 3 , there may be a small gap  57  formed between the gaskets  55 , a corner of the cooking chamber  17 , and the sealant  56 . Then, water or dirt may infiltrate therein, which is not sanitary, and may caused rust, or out of order of components when intensive. Moreover, the applied sealant  56  or the gap  57  harms a sense of beauty of the cooling chamber  20 , and drops consumer satisfaction. 
   In the meantime, referring to  FIG. 4 , the air duct  60  is mounted on an underside of a ceiling of the cooking chamber  20 . The air duct  60  draws in external air, circulates the air inside of the cooking chamber  20 , for prevention of formation of dew on the door  41  during cooking, and discharging smell and smoke from food to an exterior. To do this, the air duct  60  has inlets  61  for introducing the external air passed through the outfit chamber  30  into the cooking chamber  20 , and outlets  62  for drawing the air circulated inside of the cooking chamber  20  and discharging to an exterior. 
   Such an air duct  60 , in general formed of plastic, is fastened to an underside of ceiling with fastening members  63 , such as screws, as shown in FIG.  4 . However, such a fastening structure requires many assembly components, and a complicated assembly process, and time, which drops productivity. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a cooking chamber assembly in a microwave oven that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
   An object of the present invention, designed for solving the foregoing problems, lies on providing a cooking chamber assembly in a microwave oven, which has an improved structure that can prevent formation of a gap between a wall of a cooking chamber case and a tray. 
   Another object of the present invention is to provide a cooking chamber assembly in a microwave oven, which has an improved air duct mounting structure that enables direct attachment of the air duct on an underside of ceiling of a cooling chamber case without separate fastening member. 
   Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the cooking chamber assembly in a microwave oven, includes a case, a tray, and a gasket. The case has a cooking chamber formed therein and an opening in a front part. The tray is provided in the case to form a bottom of the cooking chamber. The gasket formed as one unit has an inner edge surrounding an edge of the tray, and a part of outer surface in close contact with an inside surface of the case. 
   The gasket includes a groove caved along the inner edge for inserting the edge of the tray. 
   The gasket may further includes a lip projected from the outer edge of the gasket to outward to be continuous along the outer edge so as to be in contact with opposite insides and rear side of the inner case for enhancing close contact with an inside surface of the case. The lip is sloped such that an end thereof is directed, for an example, an outward upper side of the gasket. 
   The gasket has a top surface sloped such that a height of the outer edge is higher than a height of the inner edge. The gasket is formed of rubber. 
   The gasket is formed separate from the tray, or formed as a unit with the tray by insert molding. 
   The cooking chamber assembly may further include an air duct. The air duct is mounted on an upper part of an inside of the case to form a ceiling of the cooking chamber for providing an air circulation passage. 
   The air duct is fixed to the upper part of the inside of the case directly by means of hooks. The air duct includes a panel, walls, a plurality of apertures for passing circulating air, and a plurality of hooks. The panel forms a ceiling surface of the cooking chamber, and the walls are formed around the panel. The air duct may further include a flange extended horizontally to forward from a top of the front wall. The hooks are extended upward from the wall, elastically. 
   The case includes a plurality of inserting holes in an upper part for inserting, and fastening the hooks. 
   The air duct further includes a plurality of projections projected backward from the rear wall opposite to the front wall, and the case further includes a plurality of holes in an inside of rear wall for receiving and holding the projections. The hook is provided to the front wall. 
   The hook includes an elastic body extended upward from the wall, and a wedge formed head having a predetermined gap between a bottom surface of the head and a top surface of the flange. The gap is preferably the same with, or smaller than a thickness of a part the inserting hole is formed therein. Since the inserting hole is formed in the bracket attached to an inside surface of an upper part of the case, it is preferable that the gap is the same with, or smaller than the thickness of the bracket. 
   It is to be understood that both the foregoing description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention claimed. 

   
     BRIEF DESCRITPION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
       FIG. 1  illustrates a partly disassembled perspective view of a related art microwave oven; 
       FIG. 2  illustrates a disassembled perspective view of a sealing structure between walls of an inner case of a related art cooking chamber and a tray, schematically; 
       FIG. 3  illustrates a partial perspective view showing a gap between an inner corner of a related art cooking chamber assembly; 
       FIG. 4  illustrates a front view showing an inside of a related art cooking chamber assembly having an air duct provided thereto; 
       FIG. 5  illustrates a disassembled perspective view showing a ceiling structure between an inner case of a cooking chamber and a tray in accordance with a preferred embodiment of the present invention, schematically; 
       FIG. 6  illustrates a section across a line I—I in  FIG. 5 ; 
       FIG. 7  illustrates a section across a line II—II in  FIG. 5 ; 
       FIG. 8  illustrates a perspective view showing an air duct in a cooking chamber in accordance with a preferred embodiment of the present invention; 
       FIG. 9  illustrates an enlarged perspective view of the hook in  FIG. 8 ; and 
       FIGS. 10A and 10B  illustrate partial sections each showing the steps of fastening the air duct in FIG.  8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In describing the present invention, same parts will be given the same names and symbols, and repetitive description of which will be omitted. 
     FIG. 5  illustrates a disassembled perspective view showing a ceiling structure between an inner case of a cooking chamber and a tray in accordance with a preferred embodiment of the present invention schematically,  FIG. 6  illustrates a section across a line I—I in  FIG. 5 , and  FIG. 7  illustrates a section across a line II—II in FIG.  5 . Those drawings show a tray  400  mounting structure in a cooking chamber assembly of a microwave oven of the present invention, well. 
   Referring to  FIG. 5 , the cooking chamber assembly includes an inner case  200 , a tray  400 , and a gasket  500 . 
   The inner case  200  is mounted on the base plate  100 . A cooking chamber  210  is formed inside of the inner case  200 . The inner case  200  has an opening  215  in a front part for putting food into, and taking food out of the cooking chamber  210 . In the meantime, since a microwave is directed to the cooking chamber  210 , the inner case  200  is formed of a material through which no microwave leaks, such as a metal. 
   Of the upper space of the base plate  100 , a space adjacent to the space the inner case  200  occupies is used as an outfit chamber  300 . The outfit chamber  300  has a magnetron (not shown) mounted therein for directing a microwave to the cooking chamber. The outfit chamber  300  also has a plurality of electric components including a transformer (not shown) for providing a high voltage to the magnetron. The outfit chamber  300  also has a fan mounted therein (not shown) for cooling the electric components including the magnetron and circulating air inside of the microwave oven. 
   In the meantime,  FIG. 5  illustrates an embodiment the outfit chamber  300  is formed at a side of the inner case  200  of the cooking chamber  210 . However, position of the outfit chamber  300  is not limited thereto but the outfit chamber  300  may be formed at upper side or a rear side of the inner case  200 . 
   There is a front plate  150  in front of the inner case  200  and the outfit chamber  300 . The front plate  150  has an opening  155  in communication with the opening  215  in the inner case  200 . 
   Though not shown, there is a front panel having a door for closing the openings  215  and  155  in front of the front plate  150 . In the meantime, the inner case  200  and the outfit chamber  300  are covered with the outer case (not shown). 
   The tray  400 , in a form of, for an example, a plate, is placed in the inner case  200  and forms a floor of the cooking chamber  210 .  FIG. 5  illustrates an exemplary tray  400  of a square form to form the floor of the cooking chamber  210  of a hexahedral form. Of course, the tray  400  differs according to a form of the floor of the cooking chamber  210 . Though the tray  400  is formed of ceramic, the material of the tray  400  is not limited to the ceramic, but the tray  400  may be formed of a metal. 
   There is a gasket  500  around the tray  400 . As shown in  FIG. 5 , the gasket  500  has one body of rubber, such as silicone.  FIG. 5  illustrates a square gasket  500  having a central opening to surround edges of the tray  400 . Of course, a form of an inner edge of the gasket  500  is dependent on the edges of the tray  400 , and since a form of an outer edge of the gasket  500  is dependent on a form of an inside wall of the inner case  200  that forms the cooking chamber  210 , the form of the gasket  500  is not limited to one illustrated in FIG.  5 . 
   The inner edge of the gasket  500 , surrounding the edge of the tray  400 , has a groove  520  for enhancing fastening and air tightness. As shown in  FIGS. 5 and 6 , the groove  520  forms a caved channel along the inner edge of the gasket  500  such that the groove  520  is inserted on the edge of the tray  400 . 
   A part of the outer edge of the gasket  500  is brought into close contact with an inside surface of the inner case  200 , wherein a lip  510  is projected from the outer edge of the gasket  500  to outward for enhancing close contact and air tightness. The lip  510  is formed continuous so as to be in contact with opposite insides and rear side of the inner case  200 , as best shown in  FIG. 6  which is a section across a line I—I in FIG.  5 . As shown in  FIG. 6 , the lip  510  is sloped such that an edge thereof is directed an outward upper side. 
   In the meantime, there is no lip at a part of the outer edge of the gasket  500  in contact with the opening  155  of the front plate  150 . This is for smooth transition from the gasket  500  to the opening  155  of the front plate  150  for convenience of putting in and taking out food. However, when required, the lip  510  may be provided to the gasket  500  that comes into contact with the opening  215  of the inner case  200 . 
   A section of the gasket  500  adjacent to the opening  215  of the inner case  200  is best shown in FIG.  7 . As shown in  FIGS. 6 and 7  well, an upper surface of the gasket  500  is sloped such that the outer edge is higher than the inner edge, for guiding moisture, evaporated from the food and flowing down along an inside wall of the inner case  200 , toward a central part of the tray  400 , thereby preventing the moisture from staying on an inside surface of the inner case  200 . 
   The tray  400  and the gasket  500  may be fabricated separately. In this instance, as described with reference to FIGS.  5 ˜ 7 , the tray  400  and the gasket have fastening structures. However, the present invention is not limited to this, but the tray  400  and the gasket  500  may be fabricated as a unit. Because the tray  400  of ceramic or a metal and the gasket  500  of rubber, such as silicone, can be insert molded into one body. That is, after fabricating the tray  400 , by putting the tray  400  in a metal mold or the mold, and injecting and hardening liquid rubber, the tray  400  and the gasket  500  can be fabricated as one body. As this process of insert molding is known well, no more description will be given. 
   When the tray  400  and the gasket  500  of the present invention are mounted on the inside of the inner case  200 , that prevents formation of the gap between the gasket  500  and the inner case  200  in advance, water leakage can be prevented. Therefore, the cooking chamber assembly, having the gasket  500  of the present invention applied thereto, even permits washing of the cooking chamber  210 , i.e., an inside space of the inner case  200 , with water. According to this, the cooking chamber  210  for cooking the food can be maintained much cleaner. 
   FIGS.  8 ˜ 10 B best shown fastening structures of an air duct  600 , which forms a ceiling of the cooking chamber  210  and circulating air in the cooking chamber assembly of the present invention, referring to which a structure for mounting the air duct  600  will be described in more detail. 
   The air duct  600  is attached to an upper side of an inside of the inner case  200 . The panel  610 , forming a ceiling surface of the cooking chamber  210 , is substantially in a square form. There are a plurality of walls at edges of the panel  610 , i.e., one pair of side walls  630 , a front wall  620 , and a rear wall  640  substantially in vertical. The side walls  630  are in contact with the side walls of the inner case  200 . 
   The air duct  600  has a plurality of apertures  625  and  635  for passing circulating air, for introducing the air used to cool the components in the outfit chamber  300  into the air duct  600 , and therefrom into the cooking chamber  210 , and therefrom to an exterior after the air is circulated through the cooking chamber  210 . As shown in  FIG. 8 , the apertures are formed in the sidewalls  630  and the front wall  620 , and though not shown, may be formed in the panel  610 . 
   In the case of the apertures  625  and  635  in  FIG. 8 , the apertures  635  in the sidewalls  630  introduce air from the outfit chamber  300  to the air duct  600 , and the apertures  625  in the front wall  620  supply the air introduced into the air duct  600  to the cooking chamber  210 . In the meantime, the air circulated in the cooking chamber  210  is exhausted through a plurality of apertures (not shown) in the wall of the inner case  200 , such as the rear wall, or in the panel  610 . When the air is exhausted through the apertures in the panel  610 , there may be a partition (not shown) provided for preventing the exhausting air from mixing with the air introduced into the air duct  600  through the sidewall  630 . 
   In the meantime, as shown in  FIG. 8 , a flange  650  is extended in a forward direction horizontally from an upper part of top of the front wall  620 . Hooks  700  are extended upward from the front wall  620  to have an elasticity, for fastening the air duct  600  to the upper part of the inside of the inner case  200 , directly. Detail of the hook  700  is shown in  FIGS. 8 and 9 . 
   Referring to  FIG. 8 , at least two hooks  700  are formed on the front wall  620 . However, positions of the hooks  700  are not limited to the front wall  620 , but the hooks  700  may be formed on the sidewalls  630  or the rear walls  640 , together with the front wall  620 . Nevertheless, the hook  700  will be described limited to a case when the hooks  700  are formed on the front wall  620 , with reference to  FIGS. 8 and 9 . 
   A body  710  of the hook  700  is extended upward from the front wall  620  to a predetermined length. Since the body  710  of the hook  700  has its own elasticity, the body  710  deformed in a front or rear direction, elastically. There is a head  720  on top of the body  710  of the hook  700 , and, as shown in  FIG. 9 , a bottom  725  of the head  720  is flat. There is a gap between the bottom  725  of the head  720  and a top surface of the flange  650 . 
   Referring to  FIGS. 8 and 9 , there is a cutaway part  655  continuous between the flange  650  and the front wall  620 , for enhancing the elasticity of the body  710 , and securing a space for the hook  700  to move when the body  710  is deformed, elastically. That is, body  710  of the hook  700  is freed from the flange  650  and the front wall  620  by the cutaway part, thereby permitting the body  710  to move in the front or rear direction, elastically. 
   Referring to  FIGS. 10A and 10B , the inner case  200  has an inserting hole  810  for fastening the air duct  600  to the inner case  200  with the hook  700 . Though the inserting hole  810  can be formed in the inner case  200  directly, the inserting hole  810  may be formed in a separate bracket  800 .  FIGS. 10A and 10B  illustrate an embodiment in which the inserting hole  810  is formed in a bracket  800  attached and fixed to an upper inside surface of the inner case  200 , and the hook  700  is inserted in the inserting hole  810 . No inner case  200  is shown in the drawings. 
   It is preferable that the gap between the bottom  725  of the head  720  and the flange  650  is the same or slightly smaller than a thickness of a part in which the inserting hole  810  for inserting the head  720  of the hook  700  is formed therein. In the case of embodiment shown in  FIGS. 10A and 10B , it is preferable that the gap is the same with, or slightly smaller than the thickness of the bracket  800 . If the gap has a thickness as described above, since a part of the bracket  800  is inserted between the bottom  725  of the head  720  of the hook  700  and the top surface of the flange  650  tightly, a fastening force of the hook  700  can be increased more. 
   The cooking chamber assembly of the present invention may also include a plurality of projections  645 , and a plurality of holes (not shown) for receiving the projections  645 . As shown in  FIG. 8 , the projections  645  are projected backward from the rear wall  640  of the air duct  600 . The holes are recessed in an inside surface of the rear of the inner case  200  for receiving and holding the projections. Because the structure having, and joining the projections and the holes thus is apparent to those skilled in the art only with above description, no more detailed description or drawings will be given. 
   In the cooking chamber assembly of the present invention having the foregoing structure, a process for attaching the air duct  600  to an inside of an upper side of the inner case  200  with the hook  700  will be described, with reference to  FIGS. 10A and 10B . 
   Though not shown, after positioning a mounting position of the air duct  600  by inserting the projections  645  from the rear wall  640  of the air duct  600  in the holes, a front part of the air duct  600  is lifted until the hooks  700  are inserted in the inserting holes  810 . In this process, since the top of the head  720  of the hook  700  is sloped, the head  720  of the hook  700  is pushed backward slightly, when an upper part of the body  710  is slightly pushed backward, elastically. 
   As the head  720  of the hook  700  keeps moving upward, the head  720  is inserted in the inserting hole  810  fully, when the upper part of the body  710  moves forward by an elastic restoring force, according to which the head  720  also moves forward. Then, as shown in  FIG. 10B , the bracket  800  is fastened between the bottom of the head  720  and the top surface of the flange  650 , the hook  700  is fastened very firmly. 
   Since there are at least two hooks  700  formed on the front wall  620  of the air duct  600 , stable lateral fastening is possible, and a rear side of the air duct  700  is held by the holes and the projections  645 , the air duct  600  can maintain the mounted state stably in a state the hooks  700  are inserted in the inserting holes  810 . 
   Because the cooking chamber assembly of the present invention in which the air duct  600  is mounted with the hooks  700  requires no separate fastening members, such as screws or bolts for assembly, assembly and fabrication work are improved very much, to enhances a productivity. 
   The cooking chamber assembly of the present invention having the foregoing structure has the following advantages. 
   First, the unitary gasket in the cooking chamber assembly of the present invention provided for prevention of water leakage forms no gap between the inside wall of the cooking chamber and the tray. According to this, a perfect waterproof state can be maintained between inside and outside of the bottom of the cooking chamber, thereby permitting to protect the various electric components against becoming out of order caused by moisture. 
   Second, the perfect waterproof state maintained between inside and outside of the bottom of the cooking chamber permits cleaning of the cooking chamber assembly with water, that permits to maintain the cooking chamber cleaner. 
   Third, the unitary gasket permits an easy fitting to the tray, and reduces a fabrication time period as no gap is formed to dispense with sealant application, that permits improvement in productivity. Moreover, if the gasket and the tray are insert molded, the productivity can be improved more. 
   Fourth, the no necessity for application of sealant to an inside of the cooking chamber improves a sense of beauty. 
   Fifth, the mounting of the air duct with hooks can dispense with additional fastening members, such as screws or bolts, permitting to reduce an assembly and components costs. 
   Sixth, the very easy and fast assembly work of the cooking chamber assembly of the present invention permits a fast fabrication without delay, that improves productivity. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. For an example, it is possible that the air duct can be mounted to the inner case only with the hooks without the projections and the holes. In this case, it is preferable that the hooks are formed not only on the front wall, but also sidewalls and rear walls, and according to which the bracket the inserting holes are formed therein are provided additionally for inserting of the additional hooks. 
   Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.