GB2126060A

GB2126060A - High-frequency heating apparatus

Info

Publication number: GB2126060A
Application number: GB08322011A
Authority: GB
Inventors: Nobuo Ikeda
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-08-18
Filing date: 1983-08-16
Publication date: 1984-03-14
Also published as: GB8322011D0; JPS5933793A; NL8302865A; ATA292983A; FR2532145A1; GB2126060B; DE3328748A1; CH661829A5; FR2532145B1; AT398875B

Abstract

High-frequency heating apparatus comprises a heating chamber for receiving a heating load, a high-frequency oscillator for feeding high-frequency waves to the heating chamber, heating means for elevating the temperature in the heating chamber, and a door installed at an opening of the heating chamber so that it can be opened and closed and provided in its inner periphery with a choke groove (11) with a depth of 1/4 of a wavelength to be used. An outer plate (12) of the door is provided with a recess (20) which, when the door is closed, is opposed to a peripheral plate (21) around the opening of the heating chamber and in which is disposed a gasket (22) of heat- resistant resilient material. <IMAGE>

Description

SPECIFICATION High-frequency heating apparatus The present invention relates to high-frequency heating apparatus and has particular reference to a seal arrangement for the door of high-frequency heating apparatus having an electric heater as a means for elevating the temperature in the heating chamber.

A conventional high-frequency heating apparatus having an electric heater is provided with a gasket between a peripheral plate around the opening to a heating chamber and an outer door plate, the gasket preventing leakage of highfrequency waves. The gasket, which is made of heat-resistant silicone rubber, glass fibre or the like, requires a clearance between the outer door plate and the peripheral plate around the opening of the heating chamber to enable installation of the gasket therein. Further, a temperature rise in the heating chamber causes thermal deformation of the outer door plate and the peripheral plate around the opening, thus increasing the leakage of waves from the surface contact between the outer door plate and the peripheral plate.In addition, the volume to be heated increases by an amount corresponding to the great distance between the gasket and the opening of the heating chamber, so that the efficiency of heating is low.

There is accordingly a need for high-frequency heating apparatus which eliminates the aforesaid drawbacks of the prior art and which is free from leakage of high-frequency waves and superior in thermal efficiency.

According to the present invention there is provided high-frequency heating apparatus comprising a heating chamber for receiving a heating load, a high-frequency oscillator for feeding high-frequency waves to the heating chamber, heating means for elevating the temperature in the heating chamber, and a door installed at an opening of the heating chamber so that it can be opened and closed and provided in its inner periphery with a choke groove with a depth of 1/4 of a wavelength to be used, an outer plate of the door being provided with a recess which, when the door is closed, is opposed to a peripheral plate around the opening of the heating chamber and in which is disposed a gasket of heat-resistant resilient material.

An embodiment of the invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a side view, in section, showing the door of prior art high-frequency heating apparatus; Fig. 2 is a perspective view of high-frequency heating apparatus embodying the present invention; and Fig. 3 is a side view, in section, of the door of the apparatus shown in Fig. 2.

Referring now to the drawings, a conventional high frequency heating apparatus having an electric heater, as shown in Fig. 1, is provided with a gasket 22 between a peripheral plate 21 around the opening of a heating chamber 2 and an outer door plate 12, for preventing leakage of high-frequency waves. The gasket 22, which is made of heat-resistant silicone rubber, glass fibre or the like, requires a clearance C between the outer door plate 12 and the peripheral plate 21 around the opening in the heating chamber 2 to install the gasket therein. Further, a temperature rise in the heating chamber 2 causes thermal deformation of the outer door plate 1 2 and the peripheral plate 21 around the opening, thus increasing the leakage of waves from the surface contact between the outer door plate 1 2 and the peripheral plate 21 around the opening.In addition, the volume to be heated increases by an amount corresponding to the great distance between the gasket 22 and the opening in the heating chamber 2, so that the efficiency of heating is low.

In the embodiment of the present invention, as shown in Figs. 2 and 3, high-frequency heating apparatus comprises a main body 1 with a door 3 openably and closably installed at the opening in a heating chamber 2 provided in the main body.

Numeral 4 denotes an operating panel installed on the front surface of the main body 1, which is provided with fluorescent display lamps 5 used to give a display of timer settings and output settings, program selection keys 6, a start button 7 and a cancel button 8. The numeral 9 denotes an inner door, plate installed inside the door 3 and forming a portion of a choke wall, and 10 denotes a see-through window provided in the door 3.

In Fig. 3, the numeral 11 denotes a choke groove 11 provided around the inner periphery of the door 3, the choke groove being defined by the inner door plate 9, an outer door plate 12, and a separate metal member 1 3 fixed to the inner door plate 9 as by spot welding, the depth of the choke groove being 1/4 of a wavelength to be used.

Numeral 14 denotes a punched plate formed with a number of small holes to form a see-through window 10, and numeral 1 5 denotes a glass plate for preventing particles of food from clogging the small holes. Numeral 16 denotes another glass plate installed at the outside of the door 3, and 17 denotes a handle to be gripped for opening and closing the door 3. The assembly of inner door plate 9 and separate metal member 13 is screwed to the outer door plate 12, and the punched plate 14 and glass plate 1 5 are clamped and fixed therebetween. Numeral 1 8 denotes a gasket which prevents cracking of the glass plate 1 5 and leakage of vapour which emanates from the food being cooked.

In addition, since the surface of the glass plate 1 6 is formed with a coating 19, the screwed portion is hidden and cannot be seen from the surface.

Numeral 20 denotes a recess formed in the outer door plate 1 2 in opposed relation to a peripheral plate around the opening of the heating chamber 2. A gasket 22 made of a heat-resistant resilient material is positioned in the recess 20 and installed on the outer door plate 1 2 or the peripheral plate 21 around the opening. The outer peripheral portion of the outer door plate 12 is in surface contact with the peripheral plate 21 with the mechanical clearance set to zero, and at least one of the plate 12 and the plate 21 is provided with an enamel coating of a dielectric material.The clearance A in the communicating region between the recess 20 in the outer door plate 12 and the clearance B between the inner door plate 9 and the heating chamber wall 23 has a depth less than the depth of the recess and is smaller than the clearance B.

The function of the aforesaid arrangement will now be described. First, a heating load is placed in the heating chamber 2. Then, either cooking by high-frequency waves or cooking by electric heater is seiected by means of the program selection keys 6, and the start button 7 is pushed. For example, if the selection key for highfrequency heating is pushed, high-frequency waves generated by a high-frequency oscillator (not shown) are fed into the heating chamber 2 to dielectrically heat the heating load. The choke groove 11 in the inner peripheral edge of the door 3 prevents leakage of the high-frequency waves fed into the heating chamber 2.Further, since the clearance A which establishes communication between the clearance B defined between the heating chamber wall 23 and the inner door plate 9 and the recess 20 formed in the outer door plate 12 is shallower than the recess 20 and smaller than the clearance B, the high-frequency waves are reflected into the heating chamber 2 by a change in impedance. Since the peripheral plate 21 around the opening in the heating chamber 2 is in surface contact with the outer door plate 1 2 to make the mechanical clearance zero, a sharp change in impedance attenuates the highfrequency waves to prevent waves from leaking from the heating chamber 2 to the outside.

If the electric heater (not shown) is used to heat the heating chamber 2 and the heating load, the heated air and the water vapour emanating from the heating load flow into the recess 20 through the clearance B and A, but the provision of the gasket 22 of heat-resistant resilient material in the recess 20 prevents them from flowing outside the main body 1. Further, since the gasket 22 is positioned adjacent the heating chamber, there is no possibility of unnecessary portions being heated, so that the heating efficiency can be increased.

Thus, with the high-frequency heating apparatus of this embodiment, even if the highfrequency waves fed into the heating chamber 2 tend to leak outside the main body 1, they are attenuated by the choke groove 11 formed in the inner peripheral edge of the door and by the clearance A which is smaller than the clearance B and is shallower than the recess 20. Further, since the peripheral plate 21 around the opening in the heating chamber 2 is in surface contact with the outer door plate 12 to make the mechanical clearance zero, it is possible to prevent leakage of high-frequency waves from the heating chamber 2.

In addition, the provision of the gasket 22 of heat-resistant resilient material in the recess 20 of the outer door plate 12 eliminates the possibility of hot air and vapour flowing out of the heating chamber 2 to the outside of the main body 1. Since the gasket 22 is positioned closer to the opening in the heating chamber 2, the excess volume and area to be heated are decreased and hence the efficiency of heating is increased.

Moreover, the high-frequency heating apparatus is free from leakage of electric waves.

In summary, high-frequency heating apparatus embodying the present invention allows the following effects to be obtained: (1) Because of the provision of the recess in the outer door plate and the provision of the gasket in the recess, leakage of high-frequency waves, vapour and hot air from the heating chamber during cooking can be prevented.

(2) Positioning of the recess in the outer door plate so that it is closer to the heating chamber decreases the excess volume and area to be heated, thus increasing the heating efficiency.

Claims

1. High-frequency heating apparatus comprising a heating chamber for receiving a heating load, a high-frequency oscillator for feeding high-frequency waves to the heating chamber, heating means for elevating the temperature in the heating chamber, and a door installed at an opening of the heating chamber so that it can be opened and closed and provided in its inner periphery with a choke groove with a depth of 1/4 of a wavelength to be used, an output plate of the door being provided with a recess which, when the door is ciosed, is opposed to a peripheral plate around the opening of the heating chamber and in which is disposed'a gasket of heat-resistant resilient material.

2. Apparatus as claimed in claim 1, wherein the peripheral plate and the outer door plate are in surface contact with each other when the door is closed and at least one of the plates is provided with an enamel coating of a dielectric material, the mechanical clearance between the peripheral plate and the outer door plate being substantially zero.

3. Apparatus as claimed in either claim 1 or claim 2, wherein the gasket is arranged on the peripheral plate or on the outer door plate.

4. Apparatus as claimed in any one of the preceding claims, wherein a clearance defined between an inner door plate forming the choke groove and the wall of the heating chamber communicates with the recess, the clearance in the communicating region having a depth less than the depth of the recess and being smaller than the clearance defined in the remaining region between the heating chamber and the inner door plate.

5. High-frequency heating apparatus substantially as hereinbefore described with reference to Figs. 2 and 3 of the accompanying drawings.