US3770929A

US3770929A - Actuator for operating an alarm device to inform the completion of cooking in a microwave oven

Info

Publication number: US3770929A
Application number: US00205811A
Authority: US
Inventors: K Kobayashi
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1970-12-28
Filing date: 1971-12-08
Publication date: 1973-11-06
Anticipated expiration: 1990-11-06

Abstract

An actuator for operating an alarm device to inform the completion of cooking in a microwave oven is provided and includes an oscillation source for generating microwave energy, the oscillation source being connected through a pair of transmission lines to a source of commerical electricity. A door switch is inserted in one of the transmission lines and the same is opened by the opening of a door which provides access to an oven portion. A first relay is provided which includes a main contact which is inserted within one of the transmission lines and the same will control the operation and stopping of the microwave energy oscillation source. The first relay additionally includes an excitation coil and a self sustaining contact for maintaining operation of the first relay once the same is properly actuated. A timer is provided for setting a predetermined time for cooking and the same includes a contact which is connected between the pair of transmission lines and in series to the excitation coil of the first relay and the self sustaining contact and is further connected to the door switch and the main contact of the first relay. The contact of the timer is provided with a back contact portion which upon closure will be connected to a circuit which includes a self sustaining contact of a second relay which will maintain operation of the second relay once actuated by excitation of the excitation coil of the first relay, a main contact of a second relay which is also actuated by excitation of the excitation coil of the first relay and an alarm device which is enabled by the main contact of the second relay and operated upon closure of the back contact portion such that the alarm device for informing the completion of cooking is continuously actuated from the time of completion of cooking until the opening of the door. The contact of the timer includes a pair of interlocked and simultaneously operated contacts one of which includes the back contact portion for operating the alarm upon closure of the back contact.

Description

United States aent 91 Kobayashi ACTUATOR FOR OPERATING AN ALARM DEVICE TO INFORM THE COMPLETION OF COOKING IN A MICROWAVE OVEN [75] Inventor: Kyozo Kobayashi, Shizuoka, Japan [73] Assignee: Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan [22] Filed: Dec. 8, 1971 [2]] Appl. No.: 205,811

[30] Foreign Application Priority Data Dec. 28, 1970 Japan 45/135813 [52] US. Cl. 219/1055, 340/309.1 [51] Int. Cl. 1105b 9/06, G08b 1/00 [58] Field of Search 219/1055; 99/344; 340/309.1, 309.4, 309.5, 392, 393; 200/38 FA, 38 FB [56] References Cited UNITED STATES PATENTS 2,876,344 3/1959 Miller ZOO/38 FB Primary Examiner-J. V. Truhe Assistant Examiner-Hugh D. Jaeger Att0rney-Norman F. Oblon et al.

[57] ABSTRACT An actuator for operating an alarm device to inform the completion of cooking in a microwave oven is provided and includes an oscillation source for generating microwave energy, the oscillation source being connected through a pair of transmission lines to a source Nov. 6, 1973 of commerical electricity. A door switch is inserted in one of the transmission lines and the same is opened by the opening of a door which provides access to an oven portion. A first relay is provided which includes a main contact which is inserted within one of the transmission lines and the same will control the operation and stopping of the microwave energy oscillation source. The first relay additionally includes an excitation coil and a self sustaining contact for maintaining operation of the first relay once the same is properly actuated. A timer is provided for setting a predetermined time for cooking and the same includes a contact which is connected between the pair of transmission lines and in series to the excitation coil of the first relay and the self sustaining contact and is further connected to the door switch and the main contact of the first relay. The contact of the timer is provided with a back contact portion which upon closure will be connected to a circuit which includes a self sustaining contact of a second relay which will maintain operation of the second relay once actuated by excitation of the excitation coil of the first relay, a main contact ofa second relay which is also actuated by excitation of the excitation coil of the first relay and an alarm device which is enabled by the main contact of the second relay and operated upon closure of the back contact portion such that the alarm device for informing the completion of cooking is continuously actuated from the time of completion of cooking until the opening of the door. The contact of the timer includes a pair of interlocked and simultaneously operated contacts one of which includes the back contact portion for operating the alarm upon closure of the back contact.

7 Claims, 2 Drawing Figures PATENTEUImV 6191s 3770.929

Flefl INVENTOR KYOZO KOUAYASHI BY m ATTORNEYS ACTUATOR FOR OPERATING AN ALARM DEVICE TO INFORM THE COMPLETION OF COOKING IN A MICROWAVE OVEN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to an improved actuator for operating an alarm device to inform the completion of cooking in a microwave oven and more particularly to an improved actuator for operating an alarm device such that the alarm device once operated will continue until the door of the microwave oven is opened so as to correctly inform the completion of cooking and to increase the reliability of determining when a cooking operation is completed.

2. Description of the Prior Art In the past an alarm device, such as a chime, to inform one of the completion of cooking has been used and actuated only for a given instant of time by the physical force caused when a contact within the timer is opened.

Also, in the past, an alarm device, such as a chime, has been used and actuated by using two separate contacts within the timer in such a manner that the same are differentially actuated and serve to ring the chime during the differential time.

While somewhat satisfactory, one disadvantage of the former alarm device, is that the same may be opened either in the users absence or without his notice. A disadvantage of the latter alarm device is that by having two cam mechanisms in the timer for enabling differential actuations thereof, the structure of the timer is complicated, the cost is expensive and the reliability is limited. Another disadvantage of the latter type alarm device is that the timer thereof being complicated and unreliable will often accidentally misoperate and thereby cause an overheating of a material being cooked within the microwave oven and sometimes even cause a serious disaster, such as a fire to occur. Accordingly, a need existed for an actuator for an alarm device which is a simple and reliable structure.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a new and improved unique actuator for operating an alarm device to inform the completion of cooking in a microwave oven.

It is a further object of this invention to provide a new and improved unique actuator for continuously actuating an alarm device from the time of completion of cooking until the time of opening of the door of the microwave oven.

It is still another object of this invention to provide a new and improved unique actuator that includes a timer which has two contacts that are simultaneously operated to thereby provide high reliability for an alarm device associated with a microwaveoven.

It is yet one other object of this invention to provide a new and improved unique actuator for a microwave oven which has a timer that includes two contacts in series whereby the safety and reliability of operation of the microwave oven against over-heating is improved.

It is yet one further object of this invention to provide a new and improved unique actuator for operating an alarm device to inform the completion of cooking in a microwave oven which is relatively simple, compact and inexpensive.

Briefly, in accordance with this invention the foregoing and other objects are attained by the provision of an actuator for operating an alarm device to inform the completion of cooking in a microwave oven which includes an oscillation source for generating microwave energy to an oven portion and which source is connected through transmission lines to an electric source. A door switch is inserted within at least one of the transmission lines and will open in accordance with the opening of a door which provides access to an oven portion. A first relay is provided and includes a main contact which is inserted and connected to at least one of the transmission lines and the same serves to control the operation of the oscillation source. The first relay further includes an excitation coil and a self-sustaining contact for maintaining the operation of the first relay once actuated. A timer for setting a predetermined time for cooking is provided and the same includes a contact which is connected in series to the excitation coil of the first relay and the self-sustaining contact and is further connected to the door switch and to the main contact of the first relay. The contact of the timer is provided with a back contact portion which upon closure will be connected to a circuit which includes a self sustaining contact of a second relay which will maintain operation of said second relay once actuated by excitation of the excitation coil of the first relay, a main contact of the second relay which is also actuated by excitation of the excitation coil of the first relay, and an alarm device which is enabled by the main contact of the second relay and operated upon closure of the back contact portion to inform the completion of cooking such that the alarm device is continuously actuated from the time of completion of cooking until the opening of the door.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the present invention will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view of a conventional microwave oven which is equipped with an actuator according to the present invention; and

FIG. 2 is a diagram of an electric circuit of one preferred embodiment of an actuator according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings wherein like reference numerals indicate identical or corresponding parts throughout the several views and more particularly to FIG. 1 thereof wherein a microwave oven 11 is shown as including an outer sheath 13 which has an oven portion 12 on the interior thereof for holding a cooking material such as food and a door 15 which enables a front opening 14 to open and shut and thereby provide access to the oven portion 12. It should be understood that since the main construction of the microwave oven 11 itself is the same as that of conventional microwave ovens, a further detailed description of the general construction of the microwave oven 11 is not needed for an understanding of this invention and will not be given.

Referring now to FIG. 2, it is seen that a commerical frequency electric source 16 and a source 17 for providing an oscillating microwave energy within the oven portion 12 are provided. The oscillating microwave energy source 17 is connected through transmission lines L and L to the electric source 16. A door switch 18 is provided and is connected within the transmission line L,. The door switch 18 will be in an open position when the door is opened and will be in a closed position when the door 15 is shut. A pushbutton 19 is provided for a cooking operation and the contact thereof will close only when the button is pushed. A first relay RY .is provided and has a main contact 21 which is connected in the transmission line L so as to control the operation of the oscillation source 17, and a selfsustaining contact 22 which is connected in parallel to the push-button 19 for forming a by-pass circuit. The two

contacts

21 and 22 will be closed when an excitation coil 30 of the relay RY is actuated.

A timer 25, which is shown in FIG. 1, is provided for setting the cooking time and the same includes two

contacts

23 and 24 which are interlocked so as to simultaneously actuate. When the two

contacts

23 and 24 are closed, the excitation coil of the first relay RY will be actuated for the cooking time set by the timer 25. The two

contacts

23 and 24 are connected in series with the push-button switch 19 and the excitation coil 20. The two

contacts

23 and 24 are further connected between the transmission lines L and L and to the main contact 21 of the first relay RY, and the door switch 18.

A second relay RY is provided and has amain contact 28 which is connected in series to an alarm device 27 for infonning the completion of cooking and a selfsustaining contact 29. An excitation coil 26 for the second relay RY is provided and is connected in series to the self-sustaining contact 29, which series combination is connected between the transmission lines L, and L The self-sustaining contact 29 of the second relay RY is further connected to the door switch 18, to the series circuit 30 which includes the

contacts

23 and 24 of the timer and to the main contact 21 of the first relay RY,.

A conductive line 31 is provided and serves to connect the series circuit between the excitation coil 26 of the second relay RY and the self-sustaining contact 29 so as to form a by-pass for the self-sustaining contact 29.

A back contact 32 is provided and is connected to at least one of the contacts of the timer 25, such for example as the contact 24. The back contact 32 is closed when the operation of the timer 25 is stopped and the

contacts

23 and 24 are open.

Theoperation of the actuator of the present invention, as described above, is as follows. Initially, a material for cooking is inserted in the oven portion 12 and the door 15 is shut. The door switch 18 is thereby closed. The timer 25 is set to a predetermined cooking time and the

contacts

23 and 24 are closed. Under such conditions, the push-button 19 is pushed for initiating the cooking operation and in accordance therewith the excitation coil 20 of the first relay RY, is actuated and the main contact 21 is closed. The oscillation source 17 is thereby actuated to radiate microwave energy within the oven portion 12 and the cooking material is thereby heated. The contact 22 of the first relay is simultaneously closed. Thus, even though the push-button switch 19 is returned to its normally open position, the excitation coil 20 of the first relay RY will be selfsustained, so that the oscillation source 17 will be continuously operated.

During the above operation, a voltage will also be impressed through the conductive line 31 to the excitation coil 26 of the second relay RY and the

contacts

28 and 29 will thereby close. Since the contact 29 is closed, the excitation coil 26 will be self-sustained. Since the contact 28 is closed, the alarm device 27 will be held in a condition such as to be capable of conduct- After the predetermined time of the timer 25 has elasped, the

contacts

23 and 24 of the timer will be opened and the electric current to the excitation coil 20 of the first relay RY will be stopped. The

contacts

21 and 22 will then open and the operation of the oscillation source will stop. The excitation coil 20 will be sustained in its non-excitation condition and the cooking operation will have been completed. When the

contacts

23 and 24 of the timer 25 are opened, the back contact 32 will be closed whereby the alarm device 27 is actuated to indicate the completion of the cooking operation. The alarm device 27 will continue to operate until the door 15 is opened at which time the cooked material can be removed from the oven portion 12. The door switch 18 is opened by the opening of the door 15 and in accordance therewith the excitation coil 26 of the second relay RY is then deactivated, whereby the

contacts

28 and 29 are opened and the operation of the alarm device 27 is stopped.

It should be understood that when the door 15 is opened after the cooking operation is completed that neither the excitation coil 20 of the first relay RY nor the excitation coil 26 of the second relay RY will be actuated and accordingly neither the oscillation source 17 nor the alarm device 27 will be actuated.

It should now be apparent that the actuator for the alarm device of this invention will enable the operation of the alarm device to continue from the completion of cooking in the microwave oven until the door thereof is opened at which time the cooked material can be removed by the user. As such, any accidental failure in overlooking the completion of a cooking operation is impossible.

Moreover, it should be apparent that in the actuator of this invention, the two contacts of the timer are connected in series with each other. Accordingly, even though difficulties are occurring with the operation of one of the two contacts of the timer, such as fusion, the operation of the oscillation source can be stopped by the operation of the other contact, or the alarm will be actuated to separately inform, such as by a specially provided pilot light or the like, that difficulties are occurring with the operation of one of the contacts yet the operation of the oscillation source cannot be stopped. In this manner the safety and reliability of heating by the microwave oven is improved. The above operation is illustrated with reference to FIG. 2 wherein it is seen that when the contact 24 of the timer is fused, the operation of the oscillation source 17 will be stopped by the operation of the contact 23 whereby an overheating condition is prevented and the faulty operation is made readily apparent by non-operation of the alarm 27. On the other hand, when the contact 23 of the timer is fused, the operation of the oscillation source 17 will not be stopped, however, the alarm 27 will be actuated to indicate the faulty operation and thereby prevent a serious accident which could be caused by overheating.

In addition, differing from conventional timers wherein a timer differential operation of two contacts is used to continuously operate an alarm device, the

timer used according to this invention has two interlocking contacts which are simultaneously actuated. Accordingly, the actuator of the present invention has a relatively simple structure, is economical and is highly reliable.

Obviously numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein. Accordingly,

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An actuator for operating an alarm device to inform the completion of cooking in a microwave oven which comprises:

an oven portion;

an oven door which provides access to said oven portion;

an electric source;

an oscillation source for generating microwave energy, said oscillation source being connected through transmission lines to said electric source;

a door switch which is inserted in and connected to at least one of said transmission lines, said door switch being opened by opening said oven door;

a first relay having a main contact which is inserted in and connected to at least one of said transmission lines for controlling the operation of said oscillation source, said first relay having an excitation coil and a self-sustaining contact for maintaining operation of said first relay once actuated;

a timer for setting a predetermined time for cooking,

said timer having a contact which is connected between said transmission lines and in series to said excitation coil of said first relay and said selfsustaining contact and is further connected to said door switch and to said main contact of said first relay; and,

wherein said contact of said timer is provided with a back contact portion which upon closure will be connected to a circuit which includes a selfsustaining contact of a second relay which will maintain operation of said second relay once actuated by excitation of said excitation coil of said first relay, a main contact of said second relay which is also actuated by excitation of said excitation coil of said first relay, and an alarm device which is enabled by said main contact of said second relay and operated upon closure of said back contact portion to inform the completion of cooking such that the alarm device is continuously actuated from the time of completion of cooking until the opening of said door.

2. An actuator for operating an alarm device to inform the completion of cooking in a microwave oven as in claim 1, wherein the contact of said timer includes two contacts which are connected to each other in series and which are interlocked with each other so as to simultaneously operate.

3. An actuator for operating an alarm device to inform the completion of cooking in a microwave oven as in claim 1, wherein the contact of said timer includes two contacts which are connected to each other in series and which are interlocked with each other so as to simultaneously operate and wherein one of said two contacts includes said back contact portion which when closed will supply current to said alarm device for operating the same.

4. An actuator for operating an alarm device to inform the completion of cooking in a microwave oven as in claim 2, wherein upon a faulty operation of one of said contacts of said timer said oscillating source will stop and said alarm will not actuate when expected.

5. An acutator for operating an alarm device to inform the completion of cooking in a microwave oven as in claim 2, wherein upon a faulty operation of one of said contacts of said timer said oscillating source will continue to operate, but said alarm will be prematurely actuated.

6. An actuator for operating an alarm device in response to the completion of cooking in an electronic oven, which comprises:

an oven portion;

an oven door which provides access to said oven portion; an electric source;

an oscillation source for generating microwave energy, said oscillation source being connected to said electric source through first and second transmission lines;

a door switch which is inserted in said first transmission line, said door switch being opened by opening said oven door;

a first relay having an excitation coil connected between said first and second transmission lines and having first and second contacts which are closed in response to the excitation of said coil, said first contact inserted in said first transmission line;

a timer for setting a predetermined time for cooking,

said timer having first and second switches interlocked with each other so as to be simultaneously closed upon the setting of said timer, said first and second switches connected in series with said excitation coil of said first relay; second relay having an excitation coil connected between said first and second transmission lines and having first and second contacts which are closed in response to the excitation of said coil, said first contact of said second relay inserted in series with said excitation coil of said second relay; an alarm device connected between said first and second transmission lines only upon the completion of said predetermined cooking time, whereupon said first switch of said timer is opened to deactivate said first relay and said second switch of said timer switches to connect said alarm device to said first transmission line, said second contact of said second relay connected in series between said alarm device and said first transmission line such that said alarm device is continuously actuated from the time of the completion of cooking until the opening of said door. 7. The actuator according to claim 6 further comprising push-button actuator means located in series with said first and second switches of said timer, said actuator means serving to initiate the cooking operation by closing the circuit between said first relay and said electric source after said timer has been set, said second contact of said first relay connected in parallel with said actuator means to bypass said actuator means upon the manual release of said push-button.

Claims

1. An actuator for operating an alarm device to inform the completion of cooking in a microwave oven which comprises: an oven portion; an oven door which provides access to said oven portion; an electric source; an oscillation source for generating microwave energy, said oscillation source being connected through transmission lines to said electric source; a door switch which is inserted in and connected to at least one of said transmission lines, said door switch being opened by opening said oven door; a first relay having a main contact which is inserted in and connected to at least one of said transmission lines for controlling the operation of said oscillation source, said first relay having an excitation coil and a self-sustaining contact for maintaining operation of said first relay once actuated; a timer for setting a predetermined time for cooking, said timer having a contact which is connected between said transmission lines and in series to said excitation coil of said first relay and said self-sustaining contact and is further connected to said door switch and to said main contact of said first relay; and, wherein said contact of said timer is provided with a back contact portion which upon closure will be connected to a circuit which includes a self-sustaining contact of a second relay which will maintain operation of said second relay once actuated by excitation of said excitation coil of said first relay, a main contact of said second relay which is also actuated by excitation of said excitation coil of said first relay, and an alarm device which is enabled by said main contact of said second relay and operated upon closure of said back contact portion to inform the completion of cooking such that the alarm device is continuously actuated from the time of completion of cooking until the opening of said door.

6. An actuator for operating an alarm device in response to the completion of cooking in an electronic oven, which comprises: an oven portion; an oven door which provides access to said oven portion; an electric source; an oscillation source for generating microwave energy, said oscillation source being connected to said electric source through first and second transmission lines; a door switch which is inserted in said first transmission line, said door switch being opened by opening said oven door; a first relay having an excitation coil connected between said first and second transmission lines and having first and second contacts which are closed in response to the excitation of said coil, said first contact inserted in said first transmission line; a timer for setting a predetermined time for cooking, said timer having first and second switches interlocked with each other so as to be simultaneously closed upon the setting of said timer, said first and second switches connected in series with said excitation coil of said first relay; a second relay having an excitation coil connected between said first and second transmission lines and having first and second contacts which are closed in response to the excitation of said coil, said first contact of said second relay inserted in series with said excitation coil of said second relay; an alarm device connected between said first and second transmission lines only upon the completion of said predetermined cooking time, whereupon said first switch of said timer is opened to deactivate said first relay and said second switch of said timer switches to connect said alarm device to said first transmission line, said second contact of said second relay connected in series between said alarm device and said first transmission line such that said alarm device is continuously actuated from the time of the completion of cooking until the opening of said door.

7. The actuator according to claim 6 further comprising push-button actuator means located in series with said first and second switches of said timer, said actuator means serving to initiate the cooking operation by closing the circuit between said first relay and said electric source after said timer has been set, said second contact of said first relay connected in parallel with said actuator means to bypass said actuator means upon the manual release of said push-button.