GB2313760A

GB2313760A - Microwave oven with inwardly projecting waveguide

Info

Publication number: GB2313760A
Application number: GB9711091A
Authority: GB
Inventors: Woo-Keumjun
Original assignee: Daewoo Electronics Co Ltd
Current assignee: WiniaDaewoo Co Ltd
Priority date: 1996-05-31
Filing date: 1997-05-29
Publication date: 1997-12-03
Also published as: GB9711091D0; KR200150292Y1; JPH1055886A; KR970063309U

Abstract

A microwave oven has a magnetron 130 mounted to a wall of the heating chamber 112, with an antenna 132 connected to the magnetron for emitting the microwaves produced. A waveguide means is formed on the wall of the chamber, which comprises a first section 122 formed on the wall of the chamber, and a second section 124 attached to the wall opposite the first section, wherein the second section supports the magnetron. The first section preferably projects into the chamber, so that the two sections define a pathway for the microwaves. A transparent cover may be provided over the first section to prevent food contamination of the waveguide. Because part of the waveguide projects into the heating chamber, the magnetron may be positioned closer to the chamber allowing the overall size of the oven to be reduced. The shape of the waveguide also allows the microwaves to reach even to the comers of the chamber.

Description

MICROWAVE OVEN HAVING AN IMPROVED WAVEGUIDE The present invention relates to a microwave oven, and more particularly to a microwave oven in which a structure of a waveguide is improved such that a size of the microwave oven can be reduced and microwaves can reach a corner of a heating chamber thereof.

As is wefi known, a microwave oven is an appliance for heating food by passing microwaves through the food. In general, the microwave oven has a magnetron which generates, by a high-voltage, microwaves which are applied within the microwave oven.

In the microwave, the magnetron generares approximately 2,450 MHz microwaves. When the microwaves are applied to the food contained in a heating chamber, molecules of the food are rapidly moved so that a frictional heat is generated due to a friction between the molecules. The microwave oven heats the food by using the frictional heat.

Such microwaves are generated when a high-voltage by primary and secondary induction coils of a transformer disposed at a bottom wall of a cabinet is supplied to the magnetron, and are radiated into a heating chamber through a waveguide.

U.S. Patent No. 5,438,183 (issued to Katsuaki hayami et al. on August 1, 1995) discloses a microwave oven capable of radiating microwaves into a heating chamber so as to uniformly heat a food.

FIG. 1 is a sectional view of a microwave oven 10 having a waveguide according to the patent of Katsuaki hayami et al. Referring to FIG. 1. microwave oven 10 according to the patent of Katsuaki hayami includes cavity 12, magnetron 13, waveguide 14, and an antenna for radiation.

FIG. 2 is an enlarged sectional view of magnetron 13 and waveguide 14 of microwave oven 10, shown in FIG. 1. Referring to FIG. 2, magnetron 13 includes an output antenna 16 for generating microwaves. A food 17 to be heated is placed in cavity 12. Waveguide 14 provides microwaves emitted from output antenna 16 of magnetron 13 into cavity 12. Waveguide 14 has substantially a truncated cone configuration in which the cross sectional area at cavity 12 is greater than that at magnetron 13. Output antenna 16 of magnetron 13 is disposed to project from a bottom side with respect to waveguide 14 into an inner space of waveguide 14. Antenna 15 for radiating microwaves is fixed within the inner space of waveguide 14 around output antenna 16 of magnetron 13 while maintaining distances from waveguide 14 and output antenna 16 of magnetron 13 so that no spark is generated between waveguide 14 and output antenna 16 of magnetron 13.

Microwave oven 10 includes a fixed plate 18 of a dielectric material which is secured to waveguide 14 and has an aperture substantially at the center thereof through which output antenna 16 of magnetron 13 passes. Radiation antenna 15 is fixed around the aperture of the fixed plate 18.

In microwave oven 10 according to the patent issued to Katsuaki hayami et al. as constructed above, because microwaves are emitted by an electric field generated between output antenna 16 of magnetron 13 and radiation antenna 15 and also by an electric field generated between radiation antenna 1S and a side wall of waveguide 14, an emitting area of microwaves is greater than that of a conventional case where microwaves are emitted only by an electric field generated between output antenna 16 of magnetron 13 and the side wall of waveguide 14. Therefore, nonuniformity in the radiation of the microwaves in cavity 12 can be suppressed. which in turn suppresses unevenness in heating a food product.

Furthermore, because radiation antenna 15 is attached to fixed plate 18 of the dielectric material having the aperture through which output antenna 16 of magnetron 13 passes while maintaining constant distances from waveguide 14 and output antenna of magnetron 13, there is an advantage in that no spark will occur between radiation antenna 15 and oulput antenna 16.

In microwave oven 10 according to the patent issued to Katsuaki hayami et al, however, there is a problem in that a process of assembling is complicated because fixed plate 18 and radiation antenna 15 are mounted on output antenna 16 of magnetron 13.

Also, there is another problem in that a structure of waveguide 14 is increased due to elements to be mounted on output antenna 16 of magnetron, and as a result, a size of microwave oven 10 may be increased.

The present invention has been made to overcome the above described problems of the prior art. It is an object of the present invention to provide a microwave oven in which a structure of a waveguide is improved such that a size of the microwave oven can be reduced and microwaves can reach a corner of a heating chamber thereof.

To accomplish the above object of the present invention there is provided a microwave oven comprising: walls for defining a heating chamber; a magnetron attached ro one of walls of the heating chamber, for generating microwaves; an antenna which is connected to the magnetron at one end and is disposed to be opposite to rhe one of walls of the heating chamber, for emitting the microwaves generated by the magnetron: and a waveguide means which is formed on the one of walls of the heating chamber, for supporting the magnetron and for guiding microwaves emitted from the antenna.

The waveguide means includes a first waveguide section formed on the one of walls of the heating chamber and a second waveguide section which is attached to the wall of the heating chamber to be opposite to the first waveguide section so that the magnetrori is supported by the second waveguide section.

The first waveguide section projects into the heating chamber at a predetermined distance from the wall of the beating chamber.

A lower portion of the first waveguide section is spaced from a lower portion of the wall of the heating chamber by a predetermined distance so that an opening is fanned by the first waveguide section and the lower portion of the wall of the heating chamber.

The first waveguide section and the second waveguide section define a chamber which supplies a pathway for the microwaves emitted from the antenna.

A distance from the antenna to the first waveguide section is at least 5 mm.

The microwave oven according to the present invention further comprises a transparent cover at a front of the first waveguide section so that the microwaves transmit through the cover and a vapor and an alien substance can be prevented from flowing into the waveguide means.

In microwave oven 100 according to the present invention as constructed above, since first waveguide section 122 of waveguide 120 is formed to project into heating chamber 112, second waveguide section 124 and magnetron 130 is moved and disposed closer to the one of walls of heating chamber 112 as first waveguide section 122 projects into heating chamber 112. Therefore, a size of microwave oven 100 can be reduced in proportion to a width of side walls 124c and 124d of second waveguide section 124.

Furthermore, since the opening of the chamber defined by first waveguide section 122 and second waveguide section 124 declines to the center of the botrom wall of heating chamber 112, microwaves can be emitted to corners of heating chamber 112.

The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiment thereof with reference to the attached drawing in which: FIG. 1 is a sectional view of a microwave oven having a waveguide according to an embodiment of a conventional art; FIG. 2 is an enlarged sectional view of a magnetron and the waveguide of the microwave oven in FIG. 1; FIG. 3 is a perspective view of a microwave oven having a waveguide according to an embodiment of the present invention, in which the waveguide and a magnetron are schematically shown; FIG. 4 is a sectional view of the microwave oven in FIG. 3, in which a cabinet is not shown; and FIG. 5 is a perspective view of the waveguide according to the embodiment of the present invention, in which a waveguide cover is attached at a front of a first waveguide section projecting into a hearing chamber.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a perspective view of a microwave oven 100 having a waveguide 120 according to an embodiment of the present invention, in which waveguide 120 and a magnetron 130 are schematically shown. Referring to FIG. 3, microwave oven 100, in which waveguide 120 according to the embodiment of the present invention is installed, includes a cabinet 110. Cabinet 110 includes a heating chamber 112 in which a food to be cooked is placed and a control chamber 114 in which magnetron 130 and a transformer (not shown) are disposed. Heating chamber 112 and control chamber 114 are separated from each other by a partition 116 forming one of walls of heating chamber 112. A center portion of partition 116 projects into heating chamber 112 to form a first waveguide section 122. A second waveguide section 124 is opposite to first waveguide section 122 formed at the center portion of partition 116 and is attached to partition 116.

A circular cooking tray 140, on which the food to be cooked is placed, is positioned in heating chamber 112 of microwave oven 100. Cooking tray 140 includes a shaft extending downward from the center of a bottom surface thereof. As shown in FIG 4, an annular groove is formed around central axis extending through the center of cooking tray 140 at a center of the bottom wall of heating chamber 112, on which cooking tray 140 is disposed. Furthermore, a through hole is perforated at the bottom wall of heating chamber 112 at a position corresponding to the center portion of cooking tray 140.

A chamber for receiving an electric motor 150 is formed at a bottom surface of microwave oven 100 under heating chamber 112. Electric chamber 150 is disposed in the chamber. A connecting member 152 is used for connecting a shaft of electric motor 150 to the shaft extending from the bottom surface of cooking tray 140. Accordingly, cooking tray 140, which receives and supports the food, can be rotated by electric motor 150.

Inner surfaces of the walls of heating chamber 112 is coated with reflecting layers as to effectively reflect the microwaves.

A door 160 is arranged at the front of an opening of heating chamber 112 in microwave oven 100. Door 160 includes a frame 162 and a window 164 through which heating chamber 112 can be seen. A side of frame 162 of door 160 is hinged to a front side of a body of microwave oven 100. A plurality of hoob 166 are attached to an inner surface of the other side of frame 162 so that door 160 is detachably attached to the body of microwave 100. An inner side of window 164 is coated with a semitransparent film so that the microwaves can be prevented from leaking to outside of heating chamber 112.

Waveguide 120, magnetron 130, a transformer (not shown), and a microcomputer (not shown) are disposed in control chamber 114. A control panel (not shown) is attached to a front surface of a front wall of cabinet r10 defining control chainber 114, on which a plurality of buttons are disposed to establish cooking conditions of foods to be cooked.

Referring to FIGs. 4 and S, as described above, waveguide 120 includes first waveguide section 122, which forms the one of walls of heating chamber and projects into heating chamber 112 from the center of partition 116 separating heating chamber 112 and control chamber 114, and includes second waveguide section 124, which is opposite to first waveguide section 122 and is attached to partition 116.

First waveguide section 122 includes an upper wall 122a, a front wall 122b. and first and second side walls 122c and 122d. Upper wall 122a and first and second side walls 122c and 122d project from partition 116 by a predetermined distance into heating chamber 112 and are connected by front wall 122b to each other. As shown in FIGs. 4 and 5, an opening 126, through which the microwaves pass, is formed between a lower end of first waveguide section 122 and partition 116, on which first waveguide section 122 is formed. First waveguide section 122 is formed in such a manner that after an opening is perforated by cutung a part of partition in a rectangular shape at a center of partition 116 forming the one of walls of heating charnber 112, an upper portion of the opening is pressed.

Second waveguide section 124 includes an upper wall 124a, a rear wall 124b, and first and second side walls 124c and 124d respectively having a trapezoidal shape. Rear wall 124b of second waveguide guide section 124 is inclined at a lower portion thereof. A thruhole is perforated at the center of an upper portion of rear wall 124b. Second waveguide section 124 is attached to partition 116 to correspond to first waveguide section 122 so that a chamber is defined between first waveguide section 122 and second waveguide section 123, to supply a pathway for microwaves emitted from antenna 132.

A transparent cover 170 may be disposed at a front of the first waveguide section 122 of waveguide 120 so that tbe microwaves transmit through cover 170 and a vapor and an alien substance can be prevented from flowing into waveguide 120.

Magnetron 130 is incorporated with an outer surface of second waveguide section 124 of waveguide 120. Also, antenna 132, which emits microwaves to waveguide 120, is integrally formed at a side of magnetron 130. Antenna 132 extends through the thruhole formed in rear wall 124b of second waveguide section 124.

A distance between a distal end of antenna 132 and first waveguide section 122 preferably is held at 5 mm since when the distance between a distal end of antenna 132 and first waveguide section 122 is less than 5 mm, microwaves emitted from antenna 132 is discharged by first waveguide section 122, and when the distance between a distal end of antenna 132 and first waveguide section 122 is more than 5 mm, a size of microwave oven 100 may be increased. The distance between a distal end of antenna 132 and first waveguide section 122 is held at 5 mm in order not to increase discharging and not to increase a size of microwave oven 100.

The transformer (not shown) is mounted on a bottom wall of control chamber 114 and is connected by a cable to magnetron 130. The transformer generates a high-voltage and applies the high-voltage to magnetron 130.

Hereinafter. the operation of the elements of microwave oven 100 having the improved waveguide 120 according to the embodiment of the present invention will be described.

Firstly, when a user pushes an operating button attached to a front surface of cabinet 110, the microcomputer accommodated in microwave oven 100 sends an operating signal to the transformer. As a result, the transformer generates the high-voltage and transfers the high-voltage, so the microwaves are generated by magnetron 130. The microwaves emitted by antenna 132 are guided by first waveguide section 122 and second waveguide section 124 of waveguide 120 to transmit through the chamber defined by first waveguide section 122 and second waveguide section 124 and discharge through the opening into heating chamber 112. The microwaves emitted through waveguide 120 into heating chamber 112 directly are applied to the food, or are reflected by walls of heating chamber 112 and applied to the food.

During heating of the food, the microcomputer applies the operating signal to the electric motor to rotate the cooking tray, thereby heating the food placed on the cooking tray uniformly.

In the microwave oven according to the present invention as constructed above, since the first waveguide section of the waveguide is formed to project into the heating chamber, the second waveguide section and the magnetron are disposed closer to the one of walls of the heating chamber while the first waveguide section projects into the heating chamber. Therefore, a size of the microwave oven can be reduced in proportion to a width of the side walls of the second waveguide section.

Furthermore, since the opening of the chamber defined by the first waveguide section and the second waveguide section declines to the center of the bottom wall of the heating chamber, the microwaves can be emitted to corners of the heating chamber.

While the present invention has been particularly shown and described with reference to a particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be effected therein without departing from the invention as defined by the appended claims.

Claims

CLAIMS:

1. A microwave oven in which a structure of a waveguide is improved such that a size of the microwave oven can be reduced and microwaves can reach a corner of a heating chamber thereof characterized by comprising; walls for defining a heating chamber; a magnetron attached to one of walls of said heating chamber, for generating microwaves; an antenna which is connected to said magnetron at one end and is disposed to be opposite to the one of walls of said heating chamber, for emitting the microwaves generated by said magnetron; and a waveguide means which is formed on the one of walls of said heating chamber, for supporting said magnetron and guiding the microwaves emitted from said antenna.

2. A microwave oven in which a structure of a waveguide is improved such that a size of the microwave oven can be reduced and microwaves can reach a corner of a heating chamber thereof characterized by comprising: walls for defining a heating chamber; a magnetron for generating microwaves; an antenna, connected to said magnetron for emitting the microwaves generated by said magnetron and disposed opposite a selected wall of said heating chamber; and a waveguide means which is formed on the selected wall of said heating chamber, for supporting said magnetron and guiding the microwaves emitted from said antenna.

3 The microwave oven as claimed in claim 1 or claim 2, characterized in that said waveguide means includes a first waveguide section formed on the one of walls of said heating chamber and a second waveguide section which is attached to the wall of said heating chamber to be opposite to said first waveguide section so that said magnetron is supported by said second waveguide section.

4. The microwave oven as claimed in claim3, characterized in that said first waveguide section projects into said heating chamber by a predetermined distance from the wall of said heating chamber.

5 The microwave oven as claimed in claim 4, characterized in that a lower portion of said first waveguide section is spaced from a lower portion of the wall of said heating chamber by a predetermined distance so that an opening is formed bv said first waveguide section and said lower ponion of the wall of said heating chamber.

6. The microwave oven as claimed in claim 5, characterized in that said first waveguide section and said second waveguide section defines a chamber which supplies a pathway for the microwaves emitted from said antenna.

7 The microwave oven as claimed in claim 3, characterized in that a distance from said antenna to said first waveguide section is at least 5 mm.

8. The microwave oven as claimed in claim 1 or claim 2, characterized by further comprising a transparent cover at a front of said first waveguide section so that the microwaves transmit through said cover and a vapor and an alien substance can be prevented from flowing into the waveguide means.

9 The microwave oven constructed and arranged substantially as herein described with reference to or as shown in the accompanying drawings.