Relay control circuit

Claim 1

A THERMAL PROTECTION SYSTEM FOR ELECTRIC POWER CONSUMING APPARATUS COMPRISING, IN COMBINATION, A RELAY HAVING AN ENERGIZING WINDING AND FIRST NORMALLY OPEN CONTACTS CONTROLLING SUPPLY OF ELECTRIC POTENTIAL FROM A SOURCE THEREOF TO SAID APPARATUS; AN ENERGIZING CIRCUIT FOR SAID RELAY WINDING INCLUDING A CONTROL SWITCH AND A CONDENSER CONNECTED IN SERIES BETWEEN SAID SOURCE AND SAID RELAY WINDING, THE CHARGING CURRENT OF SAID CONDENSER BEING OF A VALUE SUFFICIENT TO ENERGIZE SAID WINDING TO TRANSFER SAID RELAY TO CLOSE ITS NORMALLY OPEN CONTACTS; THE CURRENT FLOW THROUGH SAID RELAY WINDING AND SAID CONDENSER, EXCEPT DURING CHARGING OF THE LATTER, BEING INSUFFICIENT TO MAINTAIN SAID RELAY TRANSFERRED; A RELATIVELY LARGE RESISTANCE IN SHUNT WITH SAID CONDENSER AND INEFFECTIVE DURING CHARGING OF THE LATTER; A HOLDING CIRCUIT FOR SAID RELAY INCLUDING A NORMALLY CLOSED THERMOSTATIC SWITCH AND A RELATIVELY SMALL RESISTANCE, IN SERIES WITH SECOND NORMALLY OPEN CONTACTS OF SAID RELAY AND SAID RELAY WINDING, AND IN SHUNT WITH SAID CONDENSER AND SAID RELATIVELY LARGE RESISTANCE; SAID THERMOSTATIC SWITCH OPENING WHEN THE TEMPERATURE OF SAID APPARATUS EXCEEDS A PRE-SET VALUE; SAID CONDENSER DISCHARGING THROUGH SAID RELATIVELY LARGE RESISTANCE WHEN SAID HOLDING CIRCUIT IS CLOSED; WHEREBY, WHEN SAID CONTROL SWITCH IS CLOSED WITH SAID THERMOSTATIC SWITCH CLOSED, SAID RELAY WILL BE TRANSFERRED TO CONNECT SAID APPARATUS TO SAID SOURCE; SAID RELAY UPON OPENING OF SAID THERMOSTATIC SWITCH, REMAINING TRANSFERRED DURING RECHARGING OF SAID CONDENSER, AND SAID RELAY WINDING BEING DEENERGIZED TO DROP SAID RELAY TO OPEN ITS NORMALLY CLOSED CONTACTS AS SAID CONDENSER APPROACHES FULL CHARGE.