US3699299A

US3699299A - High frequency heating apparatus

Info

Publication number: US3699299A
Application number: US147460A
Authority: US
Inventors: Shiro Umezu; Tetsuo Hashimura; Akira Sekido
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1970-05-30
Filing date: 1971-05-27
Publication date: 1972-10-17
Anticipated expiration: 1989-10-17

Abstract

In a high frequency heating apparatus comprising a cabinet defining therein a heating chamber, a high frequency oscillator for radiating a high frequency electromagnetic wave in the heating chamber, a door mounted on the cabinet for closing the heating chamber, a door operating handle, and a locking member housed in the cabinet for locking the door in the closed position, there is provided a switch disposed in the cabinet for controlling the operation of the high frequency oscillator, and means interlocked with the handle for operating the switch to deenergize the high frequency oscillator when the locking device releases the door.

Description

United States Patent 1 ,699,299

Umezu et al. [451 Oct. 17, 1972 [541 HIGH FREQUENCY HEATING 3,243,565 3/1966 Sutton ..200/172 A APPARATUS 3,504,144 3/1970 Horner ..2 1 9/l0.55 x

[72] Inventors: Shiro Umezu, Kanagawa-ken; Tet- Primary Examiner Robert K. Schaefer Hashimura Tokyo; Akita Assistant Examiner-M. Ginsburg SekIdo, Kanagawa-ken, all of Japan An0mey Flynn & Frishauf [73] Assignee: Tokyo Shibaura Electric Co. Ltd., Kawasaki-shi, Japan ABS RACT 22 i M 27, 1971 In a high frequency heating apparatus comprising a cabinet defining therein a heating chamber, a high [21] Appl. No.: 147,460 frequency oscillator for radiating a high frequency electromagnetic wave in the heating chamber, a door [30] Foreign Application Priority Data mounted on the cabinet for closing the heating chamber, a door operating handle, and a locking May 30, 1970 Japan "4552967 member housed in the cabinet for locking the door in the closed position, there is provided a switch [52] U.S. Cl 119/1055, 200/50 A disposed in the cabinet for controlling the operation of [51] Int. Cl. ..H05b 9/06 the high frequency oscillator, and means interlocked [58] Field of Search ..200/50 A, 172 A; 219/ 10.55; with the handle for operating the switch to deenergize 340/274 the high frequency oscillator when the locking device releases the door.

[5 6] References Wed 13 Claims, 9 Drawing Figures UNITED STATES PATENTS 2,752,464 6/1956 Seeger ..200/l72

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FIG. 6

BACKGROUND OF THE INVENTION This invention relates to high frequency heating apparatus.

While the invention can be applicable to any type of high frequency heating apparatus, for heating and drying various objects and cooking foodstuffs, in the following, for the sake of description, the invention will be discussed in terms of a high frequency electronic oven utilizing a high frequency electromagnetic wave of about 2,450 MHz, for example.

In such an electronic oven, presence of an air gap between the cabinet and the door of the oven causes leakage of the electromagnetic wave thus adversely affecting nearby communication apparatus, for example, a television receiving set and human bodies. For this reason, it is highly desirable to deenergize the high frequency oscillator provided in the cabinet for radiating the high frequency electromagnetic wave in the cabinet whenever the door is opened, so that the prior art electronic oven is provided with a switch so interlocked with the door for deenergizing that the high frequency oscillator is deenergized whenever the door is opened. However, due to the operating characteristic of the switch and a mechanically idle coupling between the switch and the v door, the operation of the switch does not closely follow the opening and closing operation of the door. Accordingly, when the door is opened inadvertently the electromagnetic wave in the cabinet leaks out from an instant of opening of the door to an instant at which the switch is actually opened. Further, when the switch fails to operate due to welding of its contact, for example, a large quantity of the electromagnetic wave leaks out, thus causing a serious hazard.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improved high frequency heating apparatus which can positively lock the door to the cabinet whenever the high frequency oscillator is in operation and unlock the door when the door is opened intentionally or inadvertently.

Another object of this invention is to provide an improved high frequency heating apparatus including a switch in circuit with the high frequency oscillator and a door locking device which are operated by a door operating lever.

According to this invention, in a high frequency heating apparatus of the class comprising a cabinet defining therein a heating chamber having an access opening at one side thereof, a high frequency oscillator for radiating a high frequency electromagnetic wave in the heating chamber, a door mounted on the cabinet for closing the access opening, a door operating handle mounted on the door, and a locking device housed in the cabinet for locking the door in the closed position, there are provided a switch disposed in the cabinet, for controlling the operation of the high frequency oscillator, and means interlocked with thehandle for operating the switch to deenergize the high frequency oscilla tor when the locking device releases the door.

2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a high frequency electronic oven embodying the invention;

FIG.2 shows a vertical section of a portion of the high frequency electronic oven shown in FIG. 1, the section being taken along the line 11-11 of FIG. 3;

FIG.-3 shows a horizontal section of the portion shown in FIG. 2 taken along the line 111-111, with the spring 18b omitted for clarity;

FIG. 4 is an electrical circuit used in the high frequency electronic oven;

FIG. 5 is a view similar to FIG. 2 showing a modified embodiment of this invention;

FIG. 6 shows a horizontal section of the modified embodiment shown in FIG. 5, with the spring 18b omitted for clarity;

FIG. 7 shows a view similar to FIG. 2 showing another embodiment;

FIG. 8 shows a horizontal section taken along the line VIII-Viii of the modified embodiment shown in FIG. 1 taken along the line VIII-viii, with the spring I 18b omitted for clarity; and

FIG. 9 shows a perspective view of a switch box utilized in the embodiment shown in FIGS. 7 and 8.

Throughout the drawings like or corresponding parts are designated by the same reference characters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The high frequency electronic oven illustrated in FIGS. 1 to 3 comprises a cabinet 1 defining therein a heating or cooking chamber 2 with an access opening on one side thereof, a magnetron oscillator3 mounted on the top of the cooking chamber for radiating an electromagnetic-wave of 2,450 MHz, for example, a stirrer fan 4 for randomly distributing the electromagnetic wave throughout the cooking chamber 2 for uniformly heating a foodstuff, not shown, disposed in the cookingchamber, and a door 5 pivotally mounted by a hinge 6 on the lower edge of the cabinet for closing the door opening of the heating chamber 2. First and second door switches 7a and '7b (not shown) are disposed in a space defined between the side walls of the cabinet and thecooking chamber. To operate the door switches 7a and 712 (not shown) in accordance with the opening and closing operations of the door, there are provided first and

second levers

8a and 8b (not shown) extending through slots, not shown, of the front wall la of the cabinet. The ends on one side of these levers are pivotally connected to the door whereas springs 9a and 9b (not shown) are connected to the opposite or inner ends of the levers to normally urge them in the clockwise direction. When the door is closed, the inner ends of

levers

8a and 8b are brought into engagement with the operating members of

door switches

7a and 7b thus closing the same. On the other hand, when the door is opened, the

levers

7a and 7b are guided by said slots to disengage from the operating members of the door switches, thus opening the same. A panel board 11 carrying a timer 10 or the like is mounted on the front side of the cabinet above the door 5.

As best shown in FIGS. 2 and 3 the door 5 is provided with an operating handle 12 extending through an elongated opening 5a formed in the front wall of the door and supported by supporting members 13a and 13b secured to the inner side of the door. The handle is provided with

legs

16a and 16b at its opposite ends extending through perforations a and 15b in the front wall 1a of the cabinet and through perforations 14a and 14b of the rear wall of the door.

Hooks

17a and 17b are formed on the inner ends of the

legs

16a and 16b, respectively. These legs are normally biased in the clockwise direction as viewed in FIG. 2 by means of springs 18a and 18b connected between the legs and the inner wall of the door. At substantially the middle point of the handle 12 is connected a narrow switch operating lever 19 that extends through an opening 140 of the rear wall of the door and through an opening 150 of the front wall 1a of the cabinet 1. When the door is closed, the

hooks

17a and 17b of the legs of the handle are caused to engage catches 20a and 20b formed on the front wall 1a under the action of the springs 18a and 18b thus locking the door to the cabinet. At the same time, the switch operating lever 19 engages the operating member 210 of a micro-switch 21 disposed in the cabinet 1' thus closing the same. To open the door, the handle 12 is rotated in the counterclockwise direction against the action of springs 18a and 18b thereby to open the micro-switch 21 and to disengage

hooks

17a and 17b from catches 20a and 20b, thus unlocking the door.

The electrical connection of the high frequency electronic oven is illustrated in FIG. 4. As shown, a series

circuit including fuses

32b and 32b, normally opened

contacts

33a and 33b of an electromagnetic contactor 33 and the primary winding of a high voltage transformer 34 is connected across a source 31. The secondary winding of the high voltage transformer 34 is connected across the anode and cathode electrodes of magnetron 3 through a rectifier 35 including a diode D and a capacitor C Junctures between fuse 32a and normally opened contact 33a and between fuse 32b and normally opened contact 33b are grounded through capacitors C and C respectively. The primary winding of a low voltage transformer 37 is connected across these junctures through a sourceswitch 36, while the secondary winding of the low voltage transformer 37 is connected to the cathode heater of the magnetron 3. In parallel with the primary winding of the low voltage transformer 37 are connected a fan motor 38, a source lamp 39, and a series circuit including a thermal switch 40 responsive to an excessive temperature rise of the magnetron, an electricmotor 10M for driving timer 10, a time limit contact 100 of the timer, micro-switch 21 and the first door switch 7a. Further, the operating coil of the electromagnetic contactor 33 and a motor 4M for driving the stirrer fan 4 are connected in parallel with the timer driving motor 10M. A series circuit including a buzzer 42 which informs the completion of the cooking operation and a normally closed contact 10b of timer 10 is connected in parallel with a series circuit comprising timer driving motor 10M and time limit contact 10a.

The high frequency electronic oven thus far described operates as follows: Closure of source switch 36 preheats the cathode heater of magnetron 3 from source 31 through the low voltage transformer 37. After changing a foodstuff in the cooking chamber 2,

the door 5 is closed and locked to the cabinet 1 in a manner described above. At this time, first and

second door switches

7a and 7b and micro-switch 21 are closed. When the timer 10 is preset to a predetermined time, its contact 10a is closed to energize the electromagnetic contactor 33 thus closing its normally opened

contacts

33a and 33b. Closure of these contacts applies a rectified voltage across the anode and cathode electrodes of the magnetron 3. Thus, the magnetron begins to oscillate to radiate the high frequency electromagnetic wave in the cooking chamber 2. After the elapse of the preset time of the timer, its time delay contact 10a is opened to deenergized the electromagnetic contactor 33. Opening of its normally opened

contacts

33a and 33b deenergizes the magnetron thus stopping its oscillation. Concurrently therewith, contact 10b of the timer is closed to energize buzzer 42 thus informing the completion of the cooking operation. The buzzer is deenergized by the opening of micro-switch 21 which is opened when the door is unlocked from the cabinet. In this manner, as the door is opened, since the magnetron oscillator 3 is deenergized it is possible to safely take out the cooked foodstuff from the cooking chamber. Further, even when it becomes necessary to open the-door during cooking operation concurrently with the disengagement of the

hooks

17a and 17b from catches 20a and 20b effected by the operation of door handle 12, switch operating lever 19 is disengaged from the operating member 21a of micro-switch 21, thus opening the same. Opening of micro-switch 21 also deenergizes the electromagnetic contactor 33 thus stopping the oscillation of the magnetron in the same manner as above described. Thus, whenever the door is opened intentionally or inadvertently, at the moment when the door is unlocked from the cabinet, or while the door is still closing the door opening of the cooking chamber, the operation of the magnetron is positively stopped, thus positively preventing the leakage of the electromagnetic wave.

In this embodiment, inasmuch as the micro-switch 21 is actuated by the switch operating lever 19 independent of

hooks

17a and 17b, the lever 19 is not required to have a large mechanical strength. Accordingly, it is possible to make sufficiently thin the switch operating lever 19. This enables the width of the perforation 15c through the front wall In of the cabinet to be sufficiently narrow, for example to be less than about 3mm. This prevents insertion from outside of a foreign member through perforation for actuating the switch 21. It will be clear that one of two

hooks

17a and 17b on the

legs

16a and 16b may be omitted.

In the modified embodiment shown in FIGS. 5 and 6, a perforation 50 for passing the switch operating lever 19 is formed at the bottom of a depression 51 formed in the front wall-1a of the cabinet. The depression 51 permits the easy insertion of the switch operating lever 19 into perforation 50.

In another embodiment shown in FIGS. 7 to 9, a switch box 60 of a synthetic resin is disposed in the cabinet 1. The switch box 60 contains a micro-switch 61 and is formed with opposed catches 62a and 62b on the outside for engaging

hooks

17a and 17b. The front end of the switch box is fitted in an opening formed in the front wall 1a of the cabinet 1 as best shown in FIG. 8. The front side wall of the switch box 60 is provided with a central opening 63'bounded by inclined surfaces 64. The inclined surface 64 performs the same function as the aforementioned depression 51. As the switch box is made of a synthetic resin, it does not generate a noise when engaged by hooks.

What is claimed is:

1. A high frequency heating apparatus comprising:

a cabinet defining therein a heating chamber having an access opening at one side thereof;

a high frequency oscillator for radiating high frequency electromagnetic waves in said heating chamber;

a door mounted on said cabinet for selectively opening and closing said access opening;

a door operating handle mounted on said door, said handle being operable to release and lock positions to release and lock said door, respectively;

switch means including a switch disposed in said cabinetand coupled to said high frequency oscillator for controlling the operation of said high frequency oscillator;

switch operating means operatively coupled to and extending from said handle, and positively engaging and operating said switch means to a first position when said door is closed and locked to enable said high frequency oscillator, and operating said switch means to a second position to deenergize said high frequency oscillator when said handle is in its release position to release said door;

at least one lock arm extending from said handle toward the interior of said cabinet and operatively coupled to said handle; and

catch means interior of said cabinet for engaging saidlock arm when said door is in its closed position and said handle is in its lock position, and for releasing said lock arm when said handle is in its release position.

2. Apparatus according to claim 1 wherein said cabinet is provided with an opening and inwardly inclined surfaces defining said opening for guiding said switch operating means during closure of said door to securely operate said switch when said door is closed.

3. Apparatus according to claim 1 wherein said at least one lock arm has a hook at the end thereof which engages said catch means in the inside of said cabinet, and wherein said switch operating means comprises a switch operating lever secured to said door operating handle.

4. Apparatus according to claim 3 wherein said switch is housed in a housing having an opening therein for passing said switch operating lever.

5. Apparatus according to claim 4 wherein said housing includes means forming said catch means.

6. Apparatus according to claim 5 wherein said catch means has at least one projection extending from said housing so as to engage said at least one lock arm.

7. Apparatus according to claim 5 wherein said housing and said catch means are integrally formed of a synthetic resin.

8. Apparatus according to claim 4 wherein said opening is bounded by inwardly inclined surfaces of the front side of said housing.

9. Apparatus according to claim 2 wherein said switch means includes a lever pivotally mounted in said czilbinet for selectively operating said switch, and w erein said switch operating means includes a switch said inclined surfaces guiding said switch operating lever below said pivotally mounted lever during closure of said door, said switch operating lever engaging and pivoting said pivotally mounted lever when said lock arm engages said catch means to thereby operate said switch means to said first position.

10. Apparatus according to claim 1 wherein said lock arm includes means for guiding said switch operating means to positive engagement with said switch means to operate said switch means to said first position when said door is closed.

11. Apparatus according to claim 10 wherein said guiding means included in said lock arm engages a surface of said cabinet during closure of said door to guide said switch operating means into the positive engagement with said switch means.

12. Apparatus according in claim 10 wherein said switch operating means operates said switch means to said first position when said catch means is engaged with said lock arm.

13 Apparatus according to claim 9 wherein said lock

Claims

1. A high frequency heating apparatus comprising: a cabinet defining therein a heating chamber having an access opening at one side thereof; a high frequency oscillator for radiating high frequency electromagnetic waves in said heating chamber; a door mounted on said cabinet for selectively opening and closing said access opening; a door operating handle mounted on said door, said handle being operable to release and lock positions to release and lock said door, respectively; switch means including a switch disposed in said cabinet and coupled to said high frequency oscillator for controlling the operation of said high frequency oscillator; switch operating means operatively coupled to and extending from said handle, and positively engaging and operating said switch means to a first position when said door is closed and locked to enable said high frequency oscillator, and operating said switch means to a second position to deenergize said high frequency oscillator when said handle is in its release position to release said door; at least one lock arm extending from said handle toward the interior of said cabinet and operatively coupled to said handle; and catch means interior of said cabinet for engaging said lock arm when said door is in its closed position and said handle is in its lock position, and for releasing said lock arm when said handle is in its release position.

9. Apparatus according to claim 2 wherein said switch means includes a lever pivotally mounted in said cabinet for selectively operating said switch, and wherein said switch operating means includes a switch operating lever secured to said door operating handle and extending from said door inwardly of said cabinet, said inclined surfaces guiding said switch operating lever below said pivotally mounted lever during closure of said door, said switch operating lever engaging and pivoting said pivotally mounted lever when said lock arm engages said catch means to thereby operate said switch means to said first position.

12. Apparatus according to claim 10 wherein said switch operating means operates said switch means to said first position when said catch means is engaged with said lock arm. 13 Apparatus according to claim 9 wherein said lock arm, switch operating means and door operating handle are integral, said door operating handle simultaneously operating said lock arm and said switch operating means.