Switching device for disconnection of a load from a direct-current supply

Claim 1

SWITCHING DEVICE FOR DISCONNECTION OF A LOAD FROM A DIRECT-CURRENT SUPPLY, COMPRISING DIRECT-CURRENT LINE TERMINALS, A LOAD CIRCUIT CONNECTED BETWEEN SAID TERMINALS, A SEMI-CONDUCTOR CONTROLLABLE DEVICE OF THE FOURLAYER TYPE HAVING TWO TERMINAL ELECTRODES AND AN INTERMEDIATE CONTROL ELECTRODE, A CONTACTOR HAVING CONTACTS AND CONTROL COIL MEANS FOR CAUSING SAID CONTACTS TO OPEN, SAID DEVICE HAVING SAID MAIN ELECTRODES SERIES CONNECTED WITH SAID CONTACTS IN SAID LOAD CIRCUIT, A FIRING CIRCUIT CONNECTED TO SAID CONTROL ELECTRODE AND ONE OF SAID MAIN ELECTRODES FOR RENDERING SAID SEMI-CONDUCTOR DEVICE CONDUCTIVE WHEN SAID CONTACTS ARE CLOSED, AN EXTINGUISHING CIRCUIT CONNECTED BETWEEN SAID MAIN ELECTRODES FOR CONTROLLING SAID SEMI-CONDUCTOR DEVICE TO SWITCH THE DIRECT CURRENT IN SAID LOAD CIRCUIT DOWN TO A RESIDUAL BLOCKING VALUE, A RESISTIVE MEMBER IN SAID LOAD CIRCUIT, A CONTROL SWITCH HAVING AN "ON" POSITION AND AN "OFF" POSITION, CURRENT SUPPLY LEADS CONNECTED TO SAID SWITCH, SAID COIL MEANS COMPRISING TWO COIL-ENERGIZING CIRCUITS OF WHICH ONE IS CONNECTED THROUGH SAID SWITCH WITH SAID SUPPLY LEADS ONLY WHEN SAID SWITCH IS IN THE "ON" POSITION TO THEN CAUSE CLOSING OF SAID CONTACTOR CONTACTS, SAID OTHER ENERGIZING CIRCUIT BEING CONNECTED ACROSS SAID RESISTIVE MEMBER FOR HOLDING SAID CONTACTS CLOSED UNTIL SAID SEMICONDUCTOR DEVICE IS EXTINGUISHED AFTER SAID SWITCH IS PLACED FROM "ON" TO "OFF" POSITION, SAID CONTACTOR HAVING AUXILIARY CONTACT MEANS CONNECTED WITH SAID FIRING CIRCUIT FOR CONTROLLING IT TO FIRE SAID SEMICONDUCTOR DEVICE UPON CLOSING OF SAID CONTACTS, AND SAID CONTROL SWITCH HAVING AUXILIARY CONTACT MEANS CONNECTED WITH SAID EXTINGUISHING CIRCUIT FOR CONTROLLING IT TO EXTINGUISH SAID SEMICONDUCTOR DEVICE WHEN SAID SWITCH IS PLACED TO "OFF" POSITION.