US 3770930 A
Disclosed is a safety switch apparatus for microwave ovens that insures that the microwave generator is enabled only when the oven door is closed. The switch is responsive only to an irregularly shaped actuator that is operable only when the oven door is closed so that protection is afforded against exposure to microwaves generated while one is tampering with the oven as well as against accidental irradiation resulting from an open door.
Description (OCR text may contain errors)
United States Tang [ MICROWAVE OVEN APPARATUS  Inventor: Arthur Y. C. Tang, 4 Amy Rd. Framingharn, Mass. 01701  Filed: Jan. 3, 1972 21 Appl. No.: 215,050
 US. Cl. 219/1055, 200/44  int. Cl. 1105!) 9/06  Field of Search 219/1055; 200/44  References Cited UNITED STATES PATENTS 3,699,299 10/1972 Umezu et a1 219/1055 3,715,552 2/1973 Umezu et al.... 219/1055 3,715,554 2/1973 Umezu et al.... 219/1055 3,666,904 5/1972 Krajewski 219/1055 3,576,417 4/1971 Tingley 219/1055 Nov. 6, 1973 Mitchell 200/44 Wilson et a1 219/1055 Primary Examiner-J. V. Truhe Assistant Examiner-Hugh D. Jaeger Attorney-John E. Toupal  ABSTRACT Disclosed is a safety switch apparatus for microwave ovens that insures that the microwave generator is enabled only when the oven door is closed. The switch is responsive only to an irregularly shaped actuator that is operable only when the oven door is closed so that protection is afforded against exposure to microwaves generated while one is tampering with the oven as well as against accidental irradiation resulting from an open door.
10 Claims, 6 Drawing Figures PATENTEBIQY 6l975 3770.930
SHEET 10$ 2 1 MICROWAVE OVEN APPARATUS BACKGROUND OF THE INVENTION In recent years quick cooking characteristics have increased the popularity of microwave ovens. However, a disadvantage of microwave cooking is that exposure to microwave radiation can produce serious injury. Such radiation exposure can occur if the microwave generator is operated while the oven chamber is open. Although safety interlock switches of various forms have been used to prevent generation of microwave power when the oven door is open, accidents may still occur because conventional switches can be bypassed, as for example, by the prodding fingers of a curious child thereby exposing him to dangereous radiation. Likewise, a homeowner with a defective oven may wish to attempt the repairs himself and purposely defeat the safety switch. Such tampering is most difficult to prevent and can result in irradiation of the human body.
Accordingly, the object of this invention is to provide a safety switch system for microwave ovens that prevents accidental exposure to microwave radiation and cannot be subverted by tampering of unauthorized personnel.
SUMMARY OF THE INVENTION This invention is characterized by a microwave oven with a housing that defines a cooking chamber, one side thereof being defined by a movable oven door. Microwave energy is supplied to the cooking chamber by an energy source that is selectively enabled by a switching system including a switch operator that is functional only when the oven door is in a closed position. An irregularly shaped key in the switch operator is inserted into a key responsive switching device only when the oven door is in the closed position. Coat hangers, screw drivers and other items commonly found around the home cannot successfully be used to defeat the safety switch since actuation occurs only in response to the irregularly shaped key.
Another feature of the invention is the inclusion of two switches in the switching system that are connected in series so that both switches must be activated before the microwave energy source is enabled. The dual switch arrangement renders the switching circuit less susceptible to tampering in that an object such as a screwdriver or piece of wire may possibly actuate one of the switches if the key responsive device is prodded thereby, but successfully closing both switches simultaneously with any object other than the key is highly improbable. In addition, should one switch become defective or stick in the actuated position, the second switch still provides interlock protection to the user of the oven.
Yet another feature of the invention is the inclusion of a latch in the switch operator so that the oven door must be closed and latched before actuation of the switches is possible. Sufficient coupling for a radiation shield between the door and the housing is thereby insured.
DESCRIPTION OF THE DRAWINGS These and other features and objects of the present invention will become more apparent upon a perusal of the following description taken in conjunction with the accompanying drawings wherein:
FIG. 1 shows a perspective view of a microwave oven utilizing the subject switch;
FIG. 2 shows a sectional elevation view of a switch actuator used in the embodiment of FIG. 1 with the door in a closed position and the switch inactivated;
FIG. 3 shows a sectional elevation view of the switch actuator shown in FIG. 2 with the switch actuated;
FIG. 4 shows a sectional view of the switch shown in FIG. 3 taken along the line 4-4,
FIG. 5 shows a perspective view of a microwave oven utilizing another preferred embodiment of the subject switch; and
FIG. 6 shows a detailed elevation view of the switching apparatus used in the embodiment shown in FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1, 2 and 3 there is shown a microwave oven 21 including a housing 22 with a movable door 23 that defines one side of a cooking chamber 24. Retained within another portion of the housing 22, but not shown in FIG. 1 in order to preserve clarity, is a conventional microwave energy source that is operatively coupled to the cooking chamber 24 to supply microwave energy thereto in response to selective enabling signals from a safety switching apparatus 25. Included in the switching apparatus 25 is a lower switch 26 and an upper switch 27 in series that supply the enabling signals when both are actuated. Also included in the switching apparatus is an operator 28 including a handle 31 and an actuator 29 that rides in a shaft 32 within the door 23. If the door 23 is in a closed position as shown in both FIGS. 2 and 3, an opening 33 within a latching block 34 is directly above the shaft 32 and, as shown in FIG. 2, the opening is blocked on an upper end by a blocking spring 35 transverse thereto. When the actuator 29 is in an upper position passing through the opening 33, as shown in FIG. 3, the door 23 is locked. An irregularly shaped wedge 36 at the top of the actuator 29 forces the blocking spring 35 from the path of the actuator 29 as it is moved upward. As shown in FIG. 3, blocking spring 35 is pushed to the left by the wedge 36, and upon further upward motion of the actuator 29 eventually comes to rest in a groove 37 within the actuator 29. Only when the blocking spring 35 is within the groove 37 is the actuator rod 29 in contact with a button 38 on the upper switch 27, causing actuation thereof.
Referring now to FIG. 4 there is shown the blocking spring 35 mounted on a shaft 41. Normally the blocking spring 35 is disposed over the center of the opening 33 in the block 34. However, when the actuator 29 is in the upper position and the spring is in the groove 37, it is displaced as shown in FIG. 4. This displacement, which is in the downward direction when seen as in FIG. 4, and towards the front or left as shown in FIGS. 2 and 3, depresses a button 42, thereby actuating the switch 26.
During operation of the oven 21 as shown in FIGS. 1-4, the actuator 29 must be in the lowered position as shown in FIG. 2 in order to open the door 23. When the door 23 is opened, as shown in FIG. 1, the actuator 29 may be moved to the upper position as shown in FIG. 1 with no effect on the energy source, which is not enabled. However, when the door 23 is closed and the handle 31 is moved to the upper position as shown in FIG. 3, the wedge 36 displaces the blocking spring 35 against the button 42 actuating the switch 26 as shown in FIGS. 3 and 4. In addition, the actuator 29 presses upward against the button 38, actuating the switch 27 and consequently the microwave energy source is enabled for cooking. However, the actuator 29 passing through the block 34 securely latches the door 23 closed. The actuator responsive buttons 38 and 42 respond only to the predetermined shape of the actuator 29 because only a wedge shaped object can displace the spring 35 and travel upward sufficiently to actuate the switch 27. In addition, the wedge must be of the proper size and length and must be sloped toward the left as shown in FIGS. 2 and 3. If an attempt is made to energize the switches 26 and 27 with a wedge sloped to the right the point of the wedge will not strike the button 38, therefore the switch 27 will remain inactivated. Only a remote possibility remains that tampering with an object such as a screw driver or coat hanger will simultaneously displace the spring 35 properly and simultaneously actuate the switch 27.
Referring next to FIG. there is shown an alternate microwave oven 51 including a housing 52 and a movable door 53 that define a cooking chamber 54. A conventional microwave energy source in the upper portion of the housing 52 in not shown in order to preserve clarity. A safety switch device 55 as shown in FIG. 6 includes a first switch 56 and a second switch 57 that are wired in series and selectively enable the microwave energy source. Both switches 56 and 57 must be activated for energization to occur. Shown in FIG. 6 is a portion of the housing 52 and a portion of the door 53. Protrnding from the door 53 through an opening 58 in the housing 52 is a latching bar 59 that is firmly affixed to the door 53 and defines an opening 61 near an end 62 thereof. A shaft 63 defined by the door 53 encloses a cylindrical extension 64 that couples a handle 65 and an irregularly shaped key 66. The shaft 63 is larger than the extension 64 to permit relative movement between the key 66 and the door 53. At the back of a cavity 67 defined by the housing 52 is a lock 68 with a locking pin 69 protrudingfrom the top thereof. The switches 56 and 57 are affixed to a rear section of the lock 68. Protruding from the rear of the lock 68 is a shaft 71 with two wings 72 and 73 thereon. As the shaft 71 rotates reciprocally the wings 72 and 73 translates to selectivcly activate the switches 56 and 57 respectively. The locking pin 69 is normally in the position shown in FIG. 6, but in response to actuation of the lock 68 by the key 67, it moves upward to the position shown by the dotted line in FIG. 6. Simultaneously, the wings 72 and 73 respond to the key 66 by actuation of the switches 56 and 57 respectively.
During operation of the embodiment 51, as shown in FIGS. 5 and 6, when the door 53 is open the key cannot possibly be inserted into the lock 68, therefore the switches 56 and 57 cannot be activated. When the door is closed as shown in FIG. 6, the key 66 rests in the cavity 67 so that proper manipulation of the handle 65 causes the key 66 to enter the lock 68. Turning the key 66 then actuates the lock 68 to displace the pin 69 to the position shown by the dotted line in FIG. 6, thereby securely locking the door. Simultaneously, the shaft 71 rotates causing activation of the switches 56 and 57, thereby enabling the microwave energy source.
It will be noted that in both embodiments 21 and 51 an operator must be actuated to both deenergize the energy source and unlatch the door before any opening movement thereof is possible. This is made possible by the arrangement wherein deenergization of the source is independent of oven door movement. Because of this feature, a complete termination of energy transmission is insured before any door opening movement can be initiated.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, some of the important features of both embodiments can be included in other embodiments. It is to be understood, therefore, that the invention can be practiced otherwise than as specifically described.
What is claimed is:
1. A microwave oven comprising:
a. a housing defining a cooking chamber with one wall thereof comprising a movable door means;
b. energy source means operatively coupled to said chamber for generating microwave energy and supplying said energy to said chamber;
c. first and second switching means connected to said energy source means so as to selectively enable said energy source means;
d. operator means comprising an actuator having an irregularly shaped portion for causing actuation of said first and second switching means and operatively coupled to said door means such that said operator means is functional only with said door means in a closed position but functions independently of door movement; and i e. actuator responsive means responsive to said actuator for actuating said first and second switching means and comprising blocking means to prevent actuation of said switching means by objects not having said irregularly shaped portion.
2. A microwave oven according to claim 1 wherein said operator means comprises latch means for latching said door in a closed position when said switching means is actuated.
3. A microwave oven according to claim 1 wherein said actuator is mounted in said door and said actuator responsive means is mounted in said housing.
4. A microwave oven according to claim 2 wherein said blocking means comprises a blocking spring disposed transversely in the path followed by said actuator during actuation and said actuator comprises a cam portion adapted to displace said spring during actuation of said switching means.
5. A microwave oven according to claim 4 wherein said actuator is slidably mounted in said door and said latch means comprises a latching block with a hole therethrough for receiving said actuator.
6. A microwave oven according to claim 3 wherein said actuator comprises a key, said actuator responsive means comprises a lock, and said blocking means comprise lock tumblers.
7. A microwave oven according to claim 1 wherein said operator means comprises latch means for latching said door in a closed position when said switching means is actuated.
8. A microwave oven according to claim 7 wherein said actuator is mounted in said door and said actuator responsive means is mounted in said housing.
9. A microwave oven comprising:
a. a housing defining a cooking chamber with one wall thereof comprising a movable door means;
e. actuator responsive means responsive to said actuator for actuating said switching means and comprising movable blocking means to prevent actuation of said switching means by objects not having said irregularly shaped portion, said blocking means being moved out of a blocking position by said irregularly shaped portion to allow actuation of said switching means.
10. A microwave oven according to claim 9 wherein said actuator is rectilinearly reciprocable.