Safety device for a small-size, electrically-driven winding and pulling apparatus or the like

Claim 1

A SAFETY DEVICE FOR USE FOR A THREE-PHASE ELECTRICAL SYSTEM COMPRISING, IN COMBINATION, FIRST, SECOND AND THIRD INPUT TERMINALS AND FIRST, SECOND AND THIRD LOAD TERMINALS; A REVERSING SWITCH DEVICE CONNECTED BETWEEN THE INPUT AND LOAD TERMINALS AND HAVING A FIRST POSITION WHEREIN IT CONNECTS THE FIRST, SECOND AND THIRD INPUT TERMINALS WITH THE FIRST, SECOND AND THIRD LOAD TERMINALS, RESPECTIVELY AND A SECOND POSITION WHEREIN IT CONNECTS THE SECOND, FIRST AND THIRD INPUT TERMINALS WITH THE FIRST, SECOND AND THIRD LOAD TERMINALS, RESPECTIVELY; A RELAY COIL OPERABLE, WHEN ENERGIZED, TO ACTUATE SAID REVERSING SWITCH DEVICE TO SAID SECSECOND POSITION; A PHASE SHIFTER CONNECTED ACROSS A PAIR OF SAID INPUT TERMINALS IN ADVANCE OF SAID REVERSING SWITCH DEVICE; A VOLTAGE DIVIDER CONNECTED ACROSS ANOTHER PAIR OF SAID INPUT TERMINALS IN ADVANCE OF SAID REVERSING SWITCH DEVICE; CIRCUIT MEANS OPERABLE TO APPLY, ACROSS SAID RELAY COIL, THE VECTORIAL SUM OF A FIRST VOLTAGE, WHICH IS THE AT SAID INPUT TERMINALS ARE IN ONE PHASE SEQUENCE, AND SUBSTANTIALLY NEUTRALIZING EACH OTHER WHEN THE VOLTAGES PAIR OF SAID INPUT TERMINALS; SAID FIRST AND SECOND VOLTAGES WHICH IS DERIVED FROM SAID VOLTAGE DIVIDER, WHICH IS SUBSTANTIALLY EQUAL TO THE OUTPUT VOLTAGE OF SAID PHASE SHIFTER, AND WHICH IS PROPORTIONAL TO THE VOLTAGE ACROSS SAID OTHER OUTPUT VOLTAGE OF SAID PHASE SHIFTER, AND A SECOND VOLTAGE, ADDING, TO ENERGIZE SAID RELAY COIL, WHEN THE VOLTAGES AT SAID INPUT TERMINALS ARE IN THE OTHER PHASE SEQUENCE.