HIGH-FREQUENCY COOKER AND METHOD OF MANUFACTURING THE SAME

Abstract: It is an object to obtain a high frequency heating cooking apparatus capable of preventing from rusting and reducing the cost substantially at the same time. The heating compartment of the high f requency heating cooking apparatus of the invention comprises a side wall, a top panel, and a bottom panel. By folding and plating one plated steel plate, the side wall having a left sid e wall, a right side wall, and a back side wall is formed. The plated steel plate has a function of preventing from rusting. The top panel is made of a stainless steel material, and this top panel has a power feed port, an intake hole, and an exhaust hole. The side wall made from a plated steel plate does not have opening ends of holes such as intake hole and exhaust hole.

Description: Technical. Field The present invention relates to a high frequency heating cooking apparatus with a heater or a microwave oven, and more particularly to the constitution of its heating compartment and method of manufacturing the same. Background Art A high frequency heating cooking apparatus according to the preamble of claim is known from JP-A-586397. The constitution of a heating compartment of a conventional high frequency heating cooking apparatus is described below while referring to Fig. 3and Fig. 4. A structural diagram of the heating compartment of the conventional high frequency heating cooking apparatus is shown in Fig. 3. A front sectional view of the conventional high frequency heating cOoking apparatus is given in Fig. 4. In Fig. 3 and Fig. 4, the heating compartment is composed of an assembly of a left side wall 101, a right side wall 101, and an upper wall 103, a bottom panel 102, and a back panel 104. Each member is joined by welding or crimping. The side wall 101 is provided with a power feed port 107 for feeding high frequency electromagnetic waves generated by a magnetron 108 into the heating compartment, and an intake hole 105 for ventilation. The back panel 104 is provided with an exhaust hole 106 for exhaust. The outer side of the bottom panel 102 is provided with a lower heater 111, and the outer side of the upper wall 103, with an upper heater 112. At the junction end of the bottom panel 102, there is a flange 110 for preventing the water escaping from a junction 109 from propagating into the direction of the lower heater 111. In such conventional constitution of the heating compartment, however, since the upper wall 103 and bottom plate 102 in which the upper heater 112 and lower heater 111 are provided are exposed to high temperature, stainless steel materials of high heat resistance are needed. On the other hand, the right and left side walls 101 are low in temperature, and do not need expensive stainless steel materials. In the conventional constitution, since the left side wall 101, right side wall 101, and upper wall 103 are in an integral structure, stainless steel materials must be used, which resulted in a cost increase. In the side wall 101 and back panel 104, if plated steel plates other than stainless steel are used. rust is formed in the side wall 101 in other portions than the plated layers in the end portion of the holes of the power feed port 107, intake hole 105, and exhaust hole 106. Another problem is the increase of material cost of the flange 110 for avoiding insulation failure by preventing water leak from the junction 109 of the side wall 101 and bottom panel 102 from propagating into the lower heater 111. It is hence an object of the invention to provide a high frequency heating cooking apparatus capable of preventing rusting, reducing cost, and insulating the heater easily. This is accomplished by the heater according to claim 1 and the manufacturing method according to claim 8. Preferably, each one of the left side wall, the right side wall, and the back side wall does not have a cut section end portion of hole or opening. Preferably, the surface treated steel plate is a plated steel plate having a function of preventing from rusting. Preferably, the surface treated steel plate is an aluminum plated steel plate. Preferably, the surface treated steel plate is a painted steel plate. Preferably, the surface treated steel plate is a fluorine resin coated steel plate. Preferably, the top panel is formed of a stainless steel having a function for preventing from rusting. Preferably, the top panel forms an intake hole, an exhaust hole, and a power feed port for feeding the high frequency electric power into the heating compartment formed at specified positions. In the above constitution, the side wall of the heating compartment composed of left side wall, right side wall, and back side wall is a surface treated steel plate integrally formed in a pi-form or U-form. Hence, rusting is prevented, and the manufacturing cost is reduced at the same time. More particularly, notable effects are obtained when the surface treated steel plate aluminum plated steel plate or fluorine resin coated steel plate. Moreover, the top panel is formed of stainless steel, and penetration holes such as power feed opening, intake hole and exhaust hole are formed in the stainless steel, and the side wall made of steel plate does not have penetration hole. Accordingly, if inexpensive plated steel plate is used in the side wall, since it does not have cut section end portion of penetration hole or opening, the high frequency heating cooking apparatus preventing from rusting is obtained. Still more, the heater is installed outside of the top panel or bottom panel made of stainless steel, and is not installed at the side wall made of steel plate. Hence, if inexpensive plated steel plate is used in the side wall, the high frequency heating cooking apparatus highly reliable in heat resistance can be obtained. As a result, the manufacturing cost is lowered. In addition, the heater is installed at the lower side of the bottom plate, and a bead form reducing portion is formed near the end of the surface of inside of the bottom panel, which prevents water generated inside from passing through the junction part to contact with the heater. As a result, an excellent electric insulation of the heater is guaranteed. Brief Description of the Drawings Fig. 1 is a perspective view for explaining the assembling constitution of a heating compartment of a high frequency heating cooking apparatus in an embodiment of the invention. Fig. 2 is a front sectional view of a high frequency heating cooking apparatus in an embodiment of the invention. Fig. 3 is a perspective view for explaining the assembling constitution of a heating compartment of a high frequency heating cooking apparatus in a prior art. Fig. 4 is a front sectional view of a high frequency heating cooking apparatus in a prior art. Best Mode for Carrying Out the Invention An embodiment of a high frequency heating cooking apparatus of the invention is described below while referring to Fig. 1 and Fig 2. A perspective view for explaining the constitution of an embodiment of a high frequency heating cooking apparatus of the invention is shown in Fig. 1, and its front sectional view is given in Fig. 2. In Fig. 1 and Fig. 2, a heating compartment 20 for heating the food is composed of a nearly rectangular parallelepiped having a left side wall 1a, a right side wall 1b, a back side wall 4, a top panel 3, a bottom panel 4, and a door. A lower heater 11 is provided at the outside of the bottom panel 2, and an upper heater (not shown) at the outside of the top. panel 3. At the outside of the heating compartment 20, a magnetron 8 for generating high frequency electromagnetic waves, and a waveguide 15 are installed. The top panel 3 is manufactured from a stainless steel material. Stainless steel has a property of preventing from rusting and an excellent heat resistance. A power feed port 7, an intake hole 5, and an exhaust hole 6 are formed in the top panel 3. At the upper side of the top panel 3, the waveguide 15 is installed between the power feed port 7 and magnetron 8. The high frequency electromagnetic waves generated by the magnetron 9 are guided into the heating compartment 20 through the waveguide 15 and power feed port 7. The intake hole 5 has plural tiny penetration holes, and plays the role of taking in the air for ventilating inside the heating compartment 20. The exhaust hole 6 has plural tiny penetration holes, and plays the role of exhausting the steam or gas in the heating compartment 20 to outside. It is preferred that the intake hole 5 is formed at a position remote from the exhaust hole 6. The intake hole 5, exhaust hole 6, and power feed port 7 are formed, for example, by blanking. The left side wall 1a, right side wall 1b, and back side wall 1c are integrally composed into a pi-form or a U-form. That is, the side wall 1 composed of the left side wall 1a, right side wall 1b, and back side wall 1c is an integral structure manufactured by folding and processing one plate material. Moreover, the left side wall 1a, right side wall 1b, and back side wall 1c do not have holes such as intake hole and exhaust hole. The side wall 1 composed of the left side wall 1a, right side wall 1b, and back side wall 1c is manufactured from a surface treated steel plate. The door is installed as the front side of the heating compartment so as to be opened and closed. The side wall 1 and bottom panel 2 are joined by welding, caulking or crimping. The side wall 1 and top panel 3 are joined by welding or crimping. The surface treated steel plate used in the side wall 1 composed of the left side wall 1a, right side wall 1b, and back side wall 1c is preferably a surface plated steel plate for preventing from rusting. The plated steel plate is not particularly limited, but, for example, an aluminum plated steel plate is used. The bottom panel 2 is manufactured from a stainless steel material. Stainless steel has an excellent heat resistance and a property of preventing from rusting. In the bottom panel 2 near the junction 9 of the side wall 1 and bottom plate 2, a protruding reducing portion 13 in a bead form is formed. If moisture released from the food in the heating compartment or water used when cleaning the inside of the heating compartment escapes from the junction 9, it is captured by the reducing portion 13, and is not propagated to the lower heater 11. In this constitution, the cooking material is put into the heating compartment 20, and the cooking material is heated and cooked by application of the magnetron 8 or heater 11. At this time, the air in the heating compartment 20 flows by convection in the heating compartment 20. and part of the air is discharged outside of the heating compartment 20 through the exhaust hole 6, while fresh air flows into the heating compartment 20. At this time, part of the steam generated from the cooking material is discharged outside of the heating compartment 20 through the exhaust port 6. In this constitution, the following action and effect are obtained. Since the side wall 1 is remote in distance from the lower heater 11 and upper heater, it is not heated to high temperature. Therefore, the plated steel plate used in the side wall 1 can sufficiently maintain its reliability in terms of temperature. Moreover, since the plated steel plate is generally less expensive than the stainless steel, the material cost of the side wall 1 is saved. Generally speaking, rusting due to temperature and moisture is likely to occur in the cut section ends of the opening of the intake hole 5, exhaust hole 6, and power feed port 7. In this embodiment, however, since the intake hole 5, exhaust hole 6, and power feed power 7 are formed on the top panel which is made of stainless steel which prevents from rusting, rust is not formed. Moreover, since the side wall I made of plated steel plate does not have cut sections of penetration holes or opening, rust is not formed at the end face of holes. As a result, a rust-free heating compartment is obtained. By the constitution of forming the projecting reducing portion 13 in the bottom panel 2 near the junction 9 of the side wall I and bottom panel 2, water in the heating compartment 20 is prevented from escaping from the bottom panel 2, so that the electric insulation of the lower heater 11 can be easily assured. In the embodiment, to enhance prevention of contamination of the inner wall of the heating compartment, it is also possible to apply a resin paint on the inner surface of the side wall. As the fluorine resin, for example, fluorocarbon can be used. For instance, as the material for the side wall 1, a painted steel plate of fluorine resin may be used on the surface of the steel plate. Application of fluorine resin on the steel plate is extremely easy. In this constitution, the same action and effect as mentioned above can be obtained. Industrial Applicability Thus, in the high frequency cooking apparatus of the invention, it is not required to use an expensive stainless steel in the side wall, and an inexpensive plated steel plate can be used, while preventing from rusting on the hole end surface, so that the cost is reduced substantially. Besides, by forming a bead form reducing portion near the junction of the bottom panel of the heating compartment, water escaping from the junction is not propagated up to the heater, so that insulation of the heater can be assured in a simple constitution. Reference Numerals 1 Side wall 1a Left side wall 1b Right side wall 1d Back side wall 2 Bottom panel 3 Top panel 5 Intake hole 6 Exhaust hole 7 Power feed port 8 Magnetron 9 Jonction 11 Heater 13 Bead form reducing portion 15 Waveguide 20 Heating compartment

Claims: A high frequency heating cooking apparatus comprising: a heating compartment having a left side wall, a right side wall, back side wall, a bottom panel, and a top panel, for containing and heating food therein, a magnetron installed at an outside of said heating compartment, for generating a high frequency electric power, a duct for leading said high frequency electric power into said heating compartment, and said left side wall, said right side wall, and said back side wall are formed integrally of one plate, characterised in that a heater is installed at an outside of said heating compartment, wherein said heater is installed at said outside of at least one of said bottom panel and said top panel, and each of said left side wall, said right side wall, and said back side wall is a plated steel plate on the inner side and said plated steel plate has a function of preventing from rusting. A high frequency heating cooking apparatus of claim 1, wherein said each of said left side wall, said right side wall, and said back side wall does not have a cut section end portion of hole or opening. A high frequency heating cooking apparatus of any preceding claim, wherein said plated steel plate is an aluminum plated steel plate. A high frequency heating cooking apparatus of any preceding claim, wherein said top panel is formed of a stainless steel having a function for preventing from rusting. A high frequency heating cooking apparatus of any preceding claim, wherein said top panel forms a penetration hole having functions of intake and exhaust formed at a specified position. A high frequency heating cooking apparatus of any preceding claim wherein said top panel forms an intake hole, an exhaust hole, and a power feed opening for feeding said high frequency electric power into said heating compartment formed at specified positions. A high frequency heating cooking apparatus of any preceding claim, wherein each one of said left side wall, right side wall, and back side wall has a junction portion bonded to said bottom panel, said heater is installed at the lower side of said bottom panel, a bead form reducing portion is formed near the end of surface of the inner side of said bottom panel, and flow of water generated inside of said heating compartment into said junction portion is arrested by said reducing portion. A manufacturing method of a high frequency heating cooking apparatus according to one of claims 1-7 comprising: 1) a step of manufacturing a heating compartment, having (a) a step of folding and processing one plated steel plate to form side walls having a left side wall, a right side wall, and a back side wall, wherein said steel plate is plated on the inner side, (b) a step of joining a top panel above said walls, (c) a step of joining a bottom panel below said side walls, and (d) a step of placing a door to be opened and closed, before said side walls, (2) a step of installing a magnetron for generating a high frequency electric power to an outside of said heating compartment, (3) a step of installing a duct for leading said high frequency electric power into said heating compartment, and (4) a step of installing a heater at an outside of said heating compartment; wherein said plated steel plate has a function of preventing rusting. A manufacturing method of high frequency heating cooking apparatus of claim 8, wherein said side walls do not have cut section end portion of hole or opening. A manufacturing method of high frequency heating cooking apparatus of claim 8 or 9, wherein said plated steel plate is an aluminum plated steel plate. A manufacturing method of high frequency heating cooking apparatus of claims 8, 9 or 10, wherein said top panel is formed of a stainless steel having a function for preventing from rusting. A manufacturing method of high frequency heating cooking apparatus of claim 8, 9, 10 or 11, wherein said top panel forms an intake hole, an exhaust hole, and a power feed opening for feeding said high frequency electric power into said heating compartment formed at specified positions. A manufacturing method of high frequency heating cooking apparatus of claim 8, 9, 10, 11 or 12, wherein said heater is installed at the lower side of said bottom panel, a bead form reducing portion is formed near the end of surface of the inner side of said bottom panel, and flow of water generated inside of said heating compartment into said junction portion is arrested by said reducing portion.

Inventors: HAYAKAWA YUJI, HORI ICHIRO, HAYAKAWA, YUJI, HORI, ICHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1997
Main classification: F24C7
IPC codes: H05B6, F24C7