Protective cover for a convection microwave oven

Abstract: A protective cover for a microwave oven prevents water from permeating the inside of the oven through venting holes, and also prevents insertion of foreign materials into the holes. The convection microwave oven includes an inner case 10 forming a cooking chamber 100, and an outer case 20 coupled to the inner case 10. A duct 50 is mounted on the rear plate 12 of the inner case 10. To an inside of the duct 50, a blower fan 61 is installed, and to the outside of the duct 50, a cooling fan 71 and a motor 63 are installed, these being covered by the protective cover 80. The protective cover 80 includes a central surface 81, top and bottom surfaces 82 and 85, and right and left surfaces 83 and 84. Exhaust holes 80b on the top surface 82 have outward guide projections 82a for preventing dripping water on the top surface 82 from entering the inside, and intake holes 80a on the central surface 81 have inward guide projections 81a for preventing foreign materials from penetrating into the inside.

Description: The present invention relates to a convection microwave oven having a cooking function using a forced convection of hot air heated by an electric heater in addition to a basic cooking function by means of high frequency energy, and more particularly, to a protective cover installed on the back side of a microwave oven to protect and cool a fan motor for forced convection of hot air. Generally, a microwave oven is a cooking appliance which cooks foods by frictional heat generated by letting the molecules of the foods being cooked move at high speeds by using high frequency energy. Recently, there has been developed a convection microwave oven having the cooking function by forced convection of hot air created by an electric heater and a blower fan in addition to the basic cooking function using high frequency energy. In such a convection microwave oven, cooking foods such as meat and fish are cooked evenly from surface to interior by the high frequency energy and at the same time, the surface of the food is browned to a crisp by the heating of hot air, so that the taste and flavour of the food is enhanced. Of course, the convection microwave oven can only use either method of the high frequency energy or the heating of hot air by the heater independently. EP 0,584,934 discloses a microwave oven having a convection heating function. Figure 5 illustrates a prior art convection microwave oven disclosed in Japanese Utility Model Publication No. 57-132118. As shown in Figure 5, the prior art convection microwave oven has an inner case 1a forming a cooking chamber 1 and an outer case 6 surrounding the inner case 1a, wherein an electric component compartment (not shown) for mounting various electrical components is located between the inner and outer cases 1a and 6. Especially, in the back of the cooking chamber 1, a duct 7a is provided between a back side plate 4a coupled to the rear portion of the inner case 1a and the outer case 6 to form a hot air chamber 7 in which a blower fan 8 and an electric heater (not shown) are provided. In an inner wall of the duct 7a, a thick insulating material 7b is fixed to prevent heat radiated from the heater from transferring backward. In the back of the duct 7a, a cooling fan 8a coaxially engaged with the blower fan 8 and a motor 8b for operating the cooling fan 8a and the blower fan 8 are also installed. The duct 7a, the cooling fan 8a and the motor 8b are surrounded by a back side plate 6a coupled to the rear portion of the outer case 6. The back side plate 6a has a plurality of air vents 9a and 9b for venting air in accordance with operation of the cooling fan 8a. In such a prior art convection microwave oven, since the plurality of air vents 9b, formed in the back side plate 6a of the outer case 6 surrounding the motor 8b, are made to pass through the surface of the back side plate 6a, water permeating through these air vents 9b can cause the electric leakage or electric breakdown of the motor 8b. That is, if water is dropped on the back side plate 6a of the outer case 6 due to careless usage, the water does not fall outside along with the back side plate 6a, but flows inside through the air vents 9b, thereby causing a dangerous short-circuit or breakdown. In addition, due to the air vents 9b through which foreign materials can permeate easily, the motor 8b and cooling fan 8a are apt to become damaged. Therefore, it is an object of the present invention to provide a protective cover for a convection microwave oven capable of preventing water dropped on the back side of an outer case from permeating through air vents and foreign materials from being able to penetrate inside. In order to achieve this object, this invention provides a protective cover for a convection microwave oven, for covering a duct located in the back side of a cooking chamber of the oven, said protective cover comprising: a central surface; a top surface extended aslant from the central surface; a right side surface extended aslant from the central surface; a left side surface extended aslant from the central surface; and a bottom surface extended aslant from the central surface; and a plurality of intake holes; characterised by: the plurality of exhaust holes being formed on the central surface to introduce the outside air to the inside by a cooling fan arranged to the outer wall the duct; a plurality of exhaust holes are formed on the top surface, the bottom surface, and one side surface, respectively, to exhaust the air circulated by the cooling fan to the outside; and a plurality of outward guide projections formed on each of the exhaust holes of the top surface for preventing the water flowing on the top surface fro entering the inside through each of the exhaust holes. Further, a plurality of inward guide projections are extended aslant toward the bottom in each of a plurality of intake holes formed in the central surface to prevent foreign materials from penetrating to the inside through each of the intake holes. In addition, a spacer is projected outward from the central surface so that the intake holes are spaced, at a predetermined interval, from an external wall. As mentioned above, since the top portions of the exhaust holes formed on the protective cover are surrounded by the outward guide projections, water does not permeate directly inside the microwave oven through the exhaust holes. The water bypasses along the outer surface of the protective cover by the outward guide projections and then drops down the bottom. Since the intake holes formed on the central surface of the protective cover have the inward guide projections extended aslant toward the bottom, each entrance of the intake holes is not opened to the outside directly, so that any foreign materials, such as a stick or a pin, can not be penetrated into the inside through the intake holes carelessly or intentionally. Further, the intake and exhaust holes are distant, by a predetermined interval, from an external wall by the spacer projected outward from the central surface of the protective cover, so that it guarantees free ventilation of the outside air. By way of example a specific embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which :- Figure 1 is an exploded perspective view of a convection microwave oven to which the present invention is applied; Figure 2 is a cross-sectional view taken along line II-II in Figure 1; Figure 3 is a back side view of a protective cover according to the present invention; Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3; and Figure 5 is a partial side cross-sectional view showing a schematic construction of a prior art convection microwave oven. As shown in Figure 1, a convection microwave oven to which the present invention is applied is comprised of an inner case 10, an outer case 20 which forms one assembly together with the inner case 10, and various kinds of electric components mounted between the inner and outer cases 10 and 20. In the back of the inner case 10, a duct 50 and a protective cover 80 are installed separably. The inner case 10 is comprised of a front plate 11, a rear plate 12, a left side plate 13, a right side plate 14, and a bottom plate 16 which form a cooking chamber 100. In the front plate 11, an opening 17, which functions as the inlet of the cooking chamber 100, is formed. The front plate 11 includes an upper extending plate 11a, a left extending plate 11c, and a right extending plate 11d, each being extended in the upper and left and right directions to a predetermined width. The rear plate 12 facing the front plate 11 also includes an upper extending plate 12a, a left extending plate 12c, and a right extending plate 12d, each being also extended in the upper and left and right directions to a predetermined width. The outer case 20 includes a top plate 21, a left side plate 23, and a right side plate 24. Edges of each plate forming the outer case 20 are coupled to edges of the extending plates forming the front and rear plates 11 and 12 of the inner case 10 to form a main body of the microwave oven. Here, lengths from the front to the rear of each plate forming the outer case 20 are equal to those of each plate forming the inner case 10 corresponding to each plate forming the outer case 20, respectively, and the outer case 20 is projected outward from the inner case 10 as the width of the extending plates of the inner case 10. The rear plate 12 of the inner case 10 also serves as the rear plate of the outer case 20, and thus the additional rear plate for the outer case 20 is not necessary. On the front plate 11 of the inner case 10, is a door 30 mounted to open and close the cooking chamber 100, and on the right extending plate 11d of the front plate 11d of the front plate 11, is a control panel 40 having a display 41 and bottoms 42 mounted thereon. In a space formed between the right side plates 14 and 24 of the inner and outer cases 10 and 20, and the right extending plates 11d and 12d of the front and rear plates 11 and 12, is provided an electric component compartment 200 in which electric components such as a magnetron 201 are mounted. As shown in Figure 2, an electric heater 101 functioning as a heating means is installed inside of the cooking chamber 100. The electric heater 101 is pivotally mounted on the upper portion of the cooking chamber 100. A plurality of intake and exhaust holes 121 and 122 for guiding forced convection of hot air are formed int he rear plate 12 of the inner case 10, and a duct 50 is arranged at the outside of the rear plate 12. Thus, the intake and exhaust holes 121 and 122 serve to communication the cooking chamber 100 with the duct 50. In the duct 50, a convecting means 60 and a cooling means 70 are provided. The convecting means 60 includes a blower fan 61 installed inside of the duct 50, a rotating shaft 62 passing through the duct 50 and connected to the blower fan 61, and a motor 63 connected to one end of the rotation shaft 62. The cooling means 70 includes a cooling fan 71 coupled to the shaft 62 between the duct 50 and the motor 63. To protect the duct 50, the cooling fan 71, and the motor 63, a protective cover 80 having a size large enough to fully cover these is also mounted on the rear plate 12 of the inner case 10. Figures 3 and 4 show the shape of the protective cover 80 in detail. As shown in Figure 3, the protective cover 80 has a central surface 81, a top surface 82, right and left side surfaces 83 and 84, and a bottom surface 85, which are angled aslant from the central surface 81. A plurality of intake holes 80a are formed on the central surface 81, and a plurality of exhaust holes 80b, 80c, and 80d are formed on the top surface 82, bottom surface 85, and left side surface 84, respectively (refer to Figure 3). The right side surface 83 has no exhaust holes. The reason for this is to prevent the hot exhaust air given off by the cooling fan 71 from being drawn into the electric component compartment 200 (refer to Figure 1) through intake holes 12e, because the intake holes 12e are formed on the right extending plate 12d of the inner case 10. As shown in Figure 4, on the exhaust holes 80b are formed guide projections 82a projected outward from the exhaust holes 80b, so that if water drips on the exhaust holes 80b, the outward guide projections 82a prevent the water from running into the exhaust holes 80b. The intake holes 80a formed on the central surface 81 have inward guide projections 81a sloped toward the center direction of the intake holes 80a, so that foreign materials such as toothpicks or pins can not be inserted into the intake holes 80a. Further, a spacer 81b projected outward from the central surface 81 to a predetermined length is formed, so that the intake and exhaust holes 80a and 80b formed on the protective cover 80 are spaced, at a predetermined interval, from an external wall by which the microwave oven is placed. The outward guide projections 82a the inward projections 81a, and the spacer 81b are formed integrally with the protective cover 80. The operation of the convection microwave oven according to the present invention will now be described. If the start button is depressed to cook the foods by high frequency heating, a cooling fan (not shown) located in the electric component compartment 200 automatically turns on to draw the outside air in, thereby removing moisture from the inside of the cooking chamber 100. Simultaneously, a high voltage is applied to the magnetron 201, so that high frequencies radiate from the magnetron 201 to the food in the cooking chamber 100 to execute the cooking process. Also, the food can be cooked by the forced convection of hot air together with the high frequency heating as follows. At first, when the electric power is supplied to the electric heater 101, heat is generated from the heater 101. At the same time, by the operation of the blower fan 61, the air inside the cooking chamber 100 is drawn in the area where the blower fan 61 is placed through the intake holes 121 and it is guided upward by the duct 50. The air is again exhausted to the cooking chamber 100 through the exhaust holes 122, so that the heat generated from the electric heater 101 is forced to transfer to the food to be cooked by the air. Therefore, the heat is dispersed and transferred to the cooking chamber 100 to cook the food evenly. With the operation of the electric heater 101 and the blower fan 61, the cooling fan 71 is also operated. When the cooling fan 71 rotates, the outside air is drawn in the protective cover 80 through the intake holes 80a to cool the motor 63, and then it is exhausted through the exhaust holes 80b, 80c, and 80d. At this time, since no holes are formed on the right surface 83 of the protective cover 80, the high temperature exhaust air can not enter the electric component compartment 200. As mentioned above, according to the convection microwave oven, because water flowing down the top surface of the protective cover bypasses the exhaust holes formed on the top surface of the protective cover by the outward guide projections formed on the exhaust holes, it does not permeate inside the microwave oven an runs down the bottom. Therefore, breakdown and short-circuit of the motor installed in the inside of the protective cover can be prevented. Further, because the intake holes formed in the central surface of the protective cover have the inward guide projections extended aslant toward the bottom, foreign materials such as small sticks or pins can not be inserted into the intake holes. Furthermore, because by the spacer formed on the central surface of the protective cover, the intake and exhaust holes are distant, at a predetermined interval, from an external wall by which the microwave oven is placed, radiation of heat by the cooling fan is achieved effectively. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Claims: A protective cover (80) for a convection microwave oven, for covering a duct (50) located in the back side of a cooking chamber (100) of the oven, said protective cover comprising: a central surface (81); a top surface (82) extended aslant from the central surface (81); a right side surface (83) extended aslant from the central surface (81); a left side surface (84) extended aslant from the central surface (81); and a bottom surface (85) extended aslant from the central surface (81); and a plurality of intake holes (80a); characterised by : the plurality of exhaust holes (80a) being formed on the central surface (81) to introduce the outside air to the inside by a cooling fan (71) arranged to the outer wall the duct (50); a plurality of exhaust holes (80b), (80c), and (80d) are formed on the top surface (82), the bottom surface (85), and one side surface (84), respectively, to exhaust the air circulated by the cooling fan to the outside; and a plurality of outward guide projections (82a) formed on each of the exhaust holes (80b) of the top surface (82) for preventing the water flowing on the top surface (82) from entering the inside through each of the exhaust holes (80b). A protective cover according to claim 1, further comprising a plurality of inward guide projections (81a) extended aslant from each of the intake holes (80a) formed on the central surface (81) for preventing foreign materials from penetrating to the inside through each of the intake holes (80a). A protective cover according to claim 1 or 2, further comprising a spacer (81b) projected outward from the central surface (81) in order that the intake holes (80a) are distant, at a predetermined interval, from an external wall. A convection microwave oven, having a protective cover as claimed in any one of the preceding claims.

Inventors: LIM GYU SIK, LIM, GYU SIK
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1996
Main classification: H05B6
IPC codes: H05B6, F24C7