Electric cooking apparatus with safety control

Abstract

The improved operating-safety control uses an operating contactor and a safety contactor each having normally open switch contacts and means connect these switch contacts on opposite sides of and in main power series circuits with the electric heating elements of the cooking apparatus effective for controlling electric input to same. An actuating coil is effective for closing each contactor switch contacts, and the control includes an operating thermostat and a safety thermostat each having a heat sensor in the cooking environment and each having a heat sensor in the cooking environment and each having normally closed contacts opened responsive to a set sensed high temperature. The control connects main on and off switch means operatively in series with a parallel hookup connection of the safety contactor actuating coil as one leg and the serially connected operator contactor actuating coil and operating thermostat controlled contacts as the other leg. Thus actuation of said main on and off switch means effectively opens and/or closes the switch contacts of both contactors. The control further connects the safety thermostat controlled contacts operatively with a power series connection through said mentioned parallel hookup connection and in series with the main on and off switch means and operates responsive to the opening of said contacts for deenergizing the actuating coils of both contactors, and means hold the safety thermostat controlled contacts open until reset means is actuated. A signal device is hooked across the main power input lines at locations between the safety contactor switch contacts and heating elements effective to indicate both a power on condition and a faulted closed condition of the operating and/or safety contactor switch contacts.

What is claimed is: 
     
       1. In an electric cooking unit having electric heating .[.elements.]. .Iadd.element means .Iaddend.disposed to heat a cooking environment, an improved operating-safety circuit comprising main on and off switch means, an operating contactor and a safety contactor each including normally open switch contacts and an actuating coil effective for closing same, an operating thermostat and a safety thermostat each having a heat sensor in the cooking environment and each having .[.normally closed contacts opened.]. .Iadd.contact means shifted between operative dispositions .Iaddend.responsive to the sensed .[.set high temperature.]. .Iadd.temperature demand and higher temperature satisfied and overheat conditions, .Iaddend.means connecting the operating contactor switch contacts and the safety contactor switch contacts on opposite sides of and in main power series circuits with the heating .[.elements.]. .Iadd.element means .Iaddend.effective for controlling electric input to same, an operate control including means connecting the main on and off switch means operatively in series with a parallel hookup connection of the safety contactor actuating coil as one leg and the serially connected .[.operator.]. .Iadd.operating .Iaddend.contactor actuating coil and operating thermostat controlled .[.contacts.]. .Iadd.contact means .Iaddend.as the other leg, so that .Iadd.in the temperature demand conditions .Iaddend.actuation of said main on and off switch means simultaneously energizes and deenergizes both actuating coils and thereby opens and closes the switch contacts of both contactors, a safety control including means connecting the safety thermostat controlled .[.contacts.]. .Iadd.contact means .Iaddend.operatively with .[.power series connection through.]. said mentioned parallel hookup connection and in series with the main on and off switch means operable responsive to the .[.opening of said contacts for.]. .Iadd.shifting of said controlled contact means for opening the parallel hookup connection and thereby .Iaddend.simultaneously deenergizing the actuating coils of both contactors, .Iadd.and .Iaddend.means effectively holding said parallel hookup connection open and manual reset means for releasing the said holding means.[., and a signal device hooked across the main power input lines at locations between the safety contactor switch contacts and heating elements effective to indicate both a power on condition and a faulted closed condition of the safety and operator contactor switch contacts.].. 
     
     
       2. An operating safety circuit according to claim 1, wherein the means effective for holding the parallel hookup connection open includes having the safety thermostat of the type that remains in its set position until shifted by an outside force so that once the same has been operated responsive to the .[.set high.]. .Iadd.sensed .Iaddend.temperature .Iadd.overheat condition .Iaddend.and the thermostat .[.contacts are opened and.]. .Iadd.contact means are shifted .Iaddend.the same .[.contacts remain open.]. .Iadd.contact means remain shifted .Iaddend.until manually reset by actuation of the reset means. 
     
     
       3. An operating safety circuit according to claim 1, wherein the means effective for holding the parallel hookup connection open includes a safety relay having a coil in a circuit including normally opened contacts of the safety thermostat .Iadd.contact means .Iaddend.which relay is energized upon a sensed .[.over.]. .Iadd.overheat .Iaddend.temperature condition and said relay having normally closed contacts opened upon the energizatio of the relay coil, and means operatively connecting the said normally closed relay contacts in a circuit that precludes actuation of .Iadd.the .Iaddend.operate contactor actuating coil. 
     
     
       4. An operating safety circuit according to claim 3, wherein the means precluding actuation of the operate contactor actuating coil includes an operate relay having a coil operatively connected in series with the safety relay normally closed contacts and having normally open contact means operatively connected in series with the operating contactor actuating coil, effective when the safety relay is energized to preclude energization of the operate relay and thus the actuation of the operating contactor actuating coil. 
     
     
       5. An operating safety circuit according to claim 3, wherein circuit means is provided through the safety relay normally opened contact means and the safety relay coil and the main on and off switch means effective when the safety relay is energized to hold the same as such until it is released by actuation of the main on and off switch means. 
     
     
       6. An operating safety circuit according to claim 5, wherein said cooking unit is a deep fat fryer having a cooking container for the fat and a wall forwardly disposed from the cooking container, and wherein said main on and off switch means is located on the said forwardly disposed wall to allow actuation of same without reaching over the cooking container. .Iadd. 7. An operating-safety circuit according to claim 1, further providing that the operating and safety contactors each has two pairs of such switch contacts simultaneously closed by said respective actuating coil, that there are two such electric heating element means, and that said connecting means provide through the pairs of operating and safety contactor switch contacts a pair of independent main power circuits for controlling electric inputs to the heating element means, and further including a signal device hooked across the main power input circuits at locations between the safety contactor switch contacts and the operating contactor switch contacts where said circuits are normally at different potentials when the switch contacts are closed, effective to indicate both a power on condition and a faulted closed condition of the safety and operating contactor switch contacts. .Iaddend..Iadd. 8. An operating safety circuit according to claim 7, wherein the signal device comprises a neon type glow lamp. .Iaddend. .Iadd. 9. In an electric cooking unit having at least two electric heating element means disposed to heat a cooking environment, an improvement operating-safety circuit comprising the combination of two contactors, each contactor including at least two sets of switch contacts and means effective for opening and closing same, means establishing an independent power series circuit through each of the heating element means by connecting one set of switch contacts of each contactor on each side of the respective heating element means between the different electric potentials and the heating element means whereby at least two such independent power series circuits are defined, and a signal device connected across two such power series circuits at locations between the contactor switch contacts relative to the different electric potentials and where a diffferential in potential exists between the circuits when all switch contacts are closed, effective to indicate both a power on condition when both contactors are closed and a faulted closed condition of either contactor.