Intrinsically safe electrical device control systems

Claim 1

A SYSTEM FOR SAFELY CONTROLLING FROM A CONTROL STATION LOCATED IN A HAZARDOUS AREA WHERE EXPLOSIVE GAS OR DUST MAY BE PRESENT AN ELECTROMAGNETIC RELAY LOCATED IN A NON-HAZARDOUS AREA AND ALLOWING THE USE OF ECONOMICAL SWITCHING MEANS AT THE HAZARDOUS AREA COMPRISING: GENERAL PURPOSE SWITCHING MEANS AT THE HAZARDOUS AREA OF THE TYPE THAT IS NOT SEALED OR PROVIDED WITH EXPLOSION PROOF ENCLOSING MEANS OR THE LIKE; AN ALTERNATING CURRENT POWER SUPPLY SOURCE AT THE NONHAZARDOUS AREA; A CONTROL CIRCUIT AT THE NON-HAZARDOUS AREA; A HERMETICALLY SEALED ELECTRICAL CONDUIT BETWEEN THE HAZARDOUS AND NON-HAZARDOUS AREAS FOR PREVENTING SEEPAGE OF EXPLOSIVE GAS THEREBETWEEN; CONDUCTOR MEANS EXTENDING THROUGH SAID SEALED CONDUIT CONNECTING SAID CONTROL CIRCUIT TO SAID GENERAL PURPOSE SWITCHING MEANS AT THE HAZARDOUS AREA; SAID CONTROL CIRCUIT COMPRISING: A STEPDOWN TRANSFORMER SUPPLIED FROM SAID SOURCE FOR SUPPLYING A REDUCED AMOUNT OF ELECTRICAL POTENTIAL TO SAID CONTROL CIRCUIT; A SENSITIVE ELECTRORESPONSIVE DEVICE HAVING AN OPERATING COIL AND SELF-ENCLOSED CONTACTS FOR CONTROLLING SAID ELECTROMAGNETIC RELAY; RECTIFIER MEANS FOR SUPPLYING UNIDIRECTIONAL ENERGY TO THE OPERATING COIL OF SAID ELECTRORESPECTIVE DEVICE; AND A LOOP CIRCUIT HAVING MEANS COMPRISING SAID RECTIFIER MEANS AND SAID GENERAL PURPOSE SWITCHING MEANS AND SAID CONDUCTOR MEANS SUPPLIED FROM THE LOW POTENTIAL SIDE OF SAID TRANSFORMER FOR SUPPLYING A SMALL AND INTRINSICALLY SAFE AMOUNT OF ELECTRICAL ENERGY THROUGH SAID GENERAL PURPOSE SWITCHING MEANS INSUFFICIENT TO IGNITE THE GAS THEREAT WHEN SAID SWITCHING MEANS IS OPERATED TO CAUSE ENERGIZATION OF SAID OPERATING COIL TO CLOSE SAID CONTACTS WHEN SAID GENERAL PURPOSE SWITCHING MEANS IS CLOSED.

Claim 2

A SYSTEM FOR SAFELY CONTROLLING FROM A CONTROL STATION LOCATED IN A HAZARDOUS AREA WHERE EXPLOSIVE GAS OR DUST MAY BE PRESENT AN ELECTROMAGNETIC RELAY LOCATED IN A NON-HAZARDOUS AREA AND ALLOWING THE USE OF ECONOMICAL SWITCHING MEANS AT THE HAZARDOUS AREA COMPRISING: GENERAL PURPOSE SWITCHING MEANS AT THE HAZARDOUS AREA OF THE TYPE THAT IS NOT SEALED OR PROVIDED WITH EXPLOSION PROOF ENCLOSING MEANS OR THE LIKE; AN ALTERNATING CURRENT POWER SUPPLY SOURCE AT THE NONHAZARDOUS AREA; A CONTROL CIRCUIT AT THE NON-HAZARDOUS AREA; A HERMETICALLY SEALED ELECTRICAL CONDUIT BETWEEN THE HAZARDOUS AND NON-HAZARDOUS AREAS FOR PREVENTING SEEPAGE OF EXPLOSIVE GAS THEREBETWEEN; CONDUCTOR MEANS EXTENDING THROUGH SAID SEALED CONDUIT CONNECTING SAID CONTROL CIRCUIT TO SAID GENERAL PURPOSE SWITCHING MEANS AT THE HAZARDOUS AREA; SAID CONTROL CIRCUIT COMPRISING: A STEPDOWN TRANSFORMER SUPPLIED FROM SAID SOURCE FOR SUPPLYING A REDUCED AMOUNT OF ELECTRICAL POTENTIAL TO SAID CONTROL CIRCUIT; A SENSITIVE ELECTRORESPONSIVE DEVICE HAVING AN OPERATING COIL AND SELF-ENCLOSED CONTACTS FOR CONTROLLING SAID ELECTROMAGNETIC RELAY; RECTIFIER MEANS FOR SUPPLYING UNIDIRECTIONAL ENERGY TO THE OPERATING COIL OF SAID ELECTRORESPECTIVE DEVICE; AND A LOOP CIRCUIT HAVING MEANS COMPRISING SAID RECTIFIER MEANS AND SAID GENERAL PURPOSE SWITCHING MEANS AND SAID CONDUCTOR MEANS SUPPLIED FROM THE LOW POTENTIAL SIDE OF SAID TRANSFORMER FOR SUPPLYING A SMALL AND INTRINSICALLY SAFE AMOUNT OF ELECTRICAL ENERGY THROUGH SAID GENERAL PURPOSE SWITCHING MEANS INSUFFICIENT TO IGNITE THE GAS THEREAT WHEN SAID SWITCHING MEANS IS OPERATED TO CAUSE ENERGIZATION OF SAID OPERATING COIL TO CLOSE SAID CONTACTS WHEN SAID GENERAL PURPOSE SWITCHING MEANS IS CLOSED.