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. .Iadd.

I claim: 
     
       1. Microwave oven apparatus comprising: a conductive enclosure having an access opening;   a door closing said access opening;   a microwave energy generator;   an electrical circuit for energizing said generator including safety interlock switch means;   said circuit including a voltage source .Iadd.and having said interlock switch means directly coupled to one side of said voltage source through thermally actuated circuit deenergizing means responsive to heat from resistive heating means; .Iaddend.   sensor .Iadd.switch .Iaddend.means .Iadd.coupled to the other side of said voltage source .Iaddend.for detecting the malfunction of said interlock switch .[.with.]. .Iadd.means, .Iaddend.said interlock switch means .Iadd.being .Iaddend.normally closed and said sensor .Iadd.switch .Iaddend.means .Iadd.being .Iaddend.normally open when said apparatus is operative; .[.and.]..Iadd.   said interlock switch means and said sensor switch means being mechanically actuated by movement of said door; and   said circuit deenergizing .Iaddend.means .[.operatively associated.]. .Iadd.being coupled in series .Iaddend.with .Iadd.said resistive heating means through .Iaddend.said sensor .Iadd.switch .Iaddend.means .Iadd.across said voltage source .Iaddend..[.to deenergize.]. .Iadd.to disable .Iaddend.said .Iadd.microwave .Iaddend.generator .[.upon detection of an unsafe operating condition with both said.]. .Iadd.when said .Iaddend.interlock switch .[.and sensor means in closed positions.]. .Iadd.means fails to open upon opening of said door. .Iaddend.   
     
     
       2. Microwave oven apparatus according to claim 1 and warning means for indicating the occurrence of .[.said.]. .Iadd.an .Iaddend.unsafe .Iadd.condition of said .Iaddend.interlock switch .Iadd.means .Iaddend.and .Iadd.said .Iaddend.sensor .Iadd.switch .Iaddend.means .[.condition.].. .Iadd. 3. Microwave oven apparatus comprising: a conductive enclosure having an access opening;   a door closing said access opening;   a microwave energy generator having its output coupled to the interior of said enclosure;   circuit means comprising interlock switch means mechanically actuated by movement of said door and connected in said circuit means between one terminal of a voltage source and one terminal of said load;   sensor switch means mechanically actuated by movement of said door 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 switch means being normally open when said apparatus is operating; and   thermally actuated switch means, which is connected in series with said interlock switch means, said voltage source and a transformer supplying said microwave generator during operation of said apparatus and which is connected in series with said sensor means, said resistive heating means, said interlock switch means and said voltage source when said interlock switch means fails to open upon opening of said door to thermally actuate said thermally actuated switch means and thereby disabling said microwave generator. .Iaddend..Iadd. 4. The microwave oven apparatus according to claim 1 wherein:   said thermally actuated switch means comprises a thermally disintegratable element. .Iaddend..Iadd. 5. The microwave oven apparatus according to claim 3 wherein:   said thermally actuated switch means comprises a resettable switch. .Iaddend.