Safety interlock system for microwave ovens

Abstract

A safety interlock system is disclosed for microwave ovens or other high voltage electrical apparatus incorporating sensor means for detecting any malfunction. Means are provided for interrupting line input power or actuating a failure indicating device or a combination of both. Thermally actuated means, such as bimetallic or meltable elements, as well as circuit breakers, relays and fuses are described. The sensor means are associated with each of the interlocks and do not carry regular equipment-load current until such time as a malfunction of the companion interlock occurs. Replacement of the faulty equipment by authorized personnel and manual resetting of the interrupt or indicating means before the oven is energized again reduce the risk of accidental radiation, electrical shock or damage to the apparatus.

I claim: 
     
       1. A safety interlock system for electrical apparatus comprising: .[.an.]. electrical circuit .[.including.]. .Iadd.means for coupling .Iaddend.a .[.connected.]. voltage source .[.and.]. .Iadd.to a load;   said circuit means comprising .Iaddend.interlock switch means actuated by predetermined means .Iadd.coupled between one terminal of said voltage source and one terminal of said load.Iaddend.;   sensor means .Iadd.coupled in series with said interlock switch means and said voltage source .Iaddend.for detecting the malfunction of said interlock switch means .[.with.]..Iadd.; .Iaddend.   said interlock switch means .Iadd.being .Iaddend.normally closed and said sensor means .Iadd.being .Iaddend.normally open when said apparatus is operative; and   .Iadd.resettable switch .Iaddend.means .[.operatively associated with.]. .Iadd.actuated in response to current through .Iaddend.said sensor means to .[.deenergize.]. .Iadd.disable .Iaddend.said .Iadd.electrical .Iaddend.circuit .Iadd.means .Iaddend.upon the detection of an unsafe operating condition .[.with.]. .Iadd.when .Iaddend.both said interlock switch and sensor means .Iadd.remain .Iaddend.in closed positions.   
     
     
       2. .[.The system according to claim 1.]. .Iadd.A safety interlock system for electrical apparatus comprising: electrical circuit means for coupling a voltage source to a load;   said circuit means comprising interlock switch means actuated by predetermined means coupled between one terminal of said voltage source and one terminal of said load;   sensor means coupled in series with said interlock switch means and said voltage source for detecting the malfunction of said interlock switch means;   said interlock switch means being normally closed and said sensor means being normally open when said apparatus is operative; and   resettable switch means actuated in response to current through said sensor means to disable said electrical circuit means upon the detection of an unsafe operating condition when both said interlock switch and sensor means remain in closed positions .Iaddend.wherein said circuit .[.deenergizing.]. .Iadd.disabling .Iaddend..[.comprise.]. .Iadd.comprises .Iaddend.thermally actuated means coupled in series with said sensor means and said voltage source.   
     
     
       3. .[.The system according to claim 1.]. .Iadd.A safety interlock system for electrical apparatus comprising: electrical circuit means for coupling a voltage source to a load;   said circuit means comprising interlock switch means actuated by predetermined means coupled between one terminal of said voltage source and one terminal of said load;   sensor means coupled in series with said interlock switch means and said voltage source for detecting the malfunction of said interlock switch means;   said interlock switch means being normally closed and said sensor means being normally open when said apparatus is operative; and   resettable switch means actuated in response to current through said sensor means to disable said electric circuit means upon the detection of an unsafe operating condition when both said interlock switch and sensor means remain in closed positions .Iaddend.wherein said circuit .[.deenergizing.]. .Iadd.disabling .Iaddend.means .[.comprise.]. .Iadd.comprises .Iaddend.a thermally .[.disintegratable.]. .Iadd.actuated .Iaddend.element coupled in series with said sensor means.   
     
     
       4. A safety interlock system for electrical apparatus comprising: an electrical circuit including a .[.connected.]. voltage source and interlock switch means actuated by predetermined means .Iadd.directly coupled to one side of said voltage source.Iaddend.;   sensor means .Iadd.coupled to the other side of said voltage source .Iaddend.for detecting the malfunction of said interlock switch means ,.[.with.].  said interlock switch means .Iadd.being .Iaddend.normally closed and said sensor means .Iadd.being .Iaddend.normally open when said apparatus is operative; .[.and.].   .Iadd.circuit deenergizing means .Iaddend..[.operatively associated.]. .Iadd.coupled in series .Iaddend.with said sensor means .Iadd.and said voltage source .Iaddend.to .[.deenergize.]. .Iadd.disable .Iaddend.said circuit upon the detection of an unsafe operating condition .[.with.]. .Iadd.when .Iaddend.both said interlock switch and sensor means .Iadd.remain .Iaddend.in closed position.Iadd.s.Iaddend.; and   warning means for indicating the occurrence of said unsafe operating condition.   
     
     
       5. The system according to claim 4 wherein said warning means are audible. 
     
     
       6. The system according to claim 4 wherein said warning means are visible. .Iadd. 7. A safety interlock system for electrical apparatus comprising: electrical circuit means for coupling a voltage source to a load;   said circuit means comprising mechanically actuated interlock switch means connected in said circuit means between one terminal of said voltage source and one terminal of said load;   sensor switch means mechanically actuated and connected in series with said interlock switch means, resistive heating means, and said voltage source for detecting a malfunction of said interlock switch means;   said interlock switch means being normally closed and said sensor means being normally open when said apparatus is operating; and   thermally actuated switch means responsive to thermal energy from said resistive heating means and connected in said electrical circuit means in series with said voltage source and said load and in series with said sensor means, said resistive heating means, said interlock switch means, and said voltage source and which opens in response to said thermal energy produced by current through said sensor means and said resistive heating means to disable said electrical circuit means when both said interlock switch and said sensor means remain in closed positions. .Iaddend..Iadd.   
     
     
            The safety interlock system according to claim 7 wherein: said thermally actuated switch means comprises a thermally disintegratable element. .Iaddend..Iadd. 9. The safety interlock system according to claim 7 wherein:   said thermally actuated switch means comprises a resettable switch. .Iaddend.