Detector for ferromagnetic material in an elevator well and an elevator control system operated thereby

Claim 1

A DETECTOR SYSTEM FOR MAGNETIC MATERIAL INCLUDING (A) A FIRST CIRCUIT, (B) MEANS PRODUCING AN ALTERNATING CURRENT IN THE FIRST CIRCUIT, (C) A COIL IN SAID FIRST CIRCUIT IN A MAGNETIC FIELD WHICH IS DISTORTED BY PRESENCE OF MAGNETIC MATERIAL TO REDUCE THE FLOW OF CURRENT IN SAID FIRST CIRCUIT, (D) A FIRST TRANSISTOR IN THE FIRST CIRCUIT NORMALLY BIASED TO BE NON-CONDUCTING WHEN CURRENT IN THE FIRST CIRCUIT IS BELOW A GIVEN VALUE, (E) A CAPACITOR CONNECTED ACROSS THE FIRST TRANSISTOR IN PARALLEL WITH SAID TRANSISTOR, (F) A SECOND CIRCUIT CONNECTED WITH A SOURCE OF POWER, PART OF THE SECOND CIRCUIT BEING CONNECTED IN PARALLEL WITH THE FIRST TRANSISTOR AND THE CAPACITOR, (G) A SECOND TRANSISTOR IN THE SECOND CIRCUIT, AT LEAST A PORTION OF THE SECOND TRANSISTOR BEING IN THE PART OF THE SECOND CIRCUIT THAT IS CONNECTED IN PARALLEL WITH THE TRANSISTOR OF THE FIRST CIRCUIT, (H) A POWER RELAY FOR A CIRCUIT THAT IS TO BE CONTROLLED, SAID RELAY HAVING AN ACTUATING COIL IN THE SECOND CIRCUIT, (I) AND MEANS IN THE SECOND CIRCUIT BIASING THE SECOND TRANSISTOR IN AN OFF CONDITION WHEN THE FIRST TRANSISTOR IS CONDUCTING, THE CAPACITOR BEING OF SUFFICIENT CAPACITY TO AVOID FULLY CHARGING ON ANY HALF CYCLE OF THE TIME THAT THE FIRST TRANSISTOR IS CONDUCTING AS THE RESULT OF FLOW OF ALTERNATING CURRENT IN THE FIRST CIRCUIT, AND THE CAPACITOR HAVING A POTENTIAL, WHEN CHARGED MORE FULLY DURING A PLURALITY OF CYCLES WHEN THE FIRST TRANSISTOR IS NOT CONDUCTING, TO OVERCOME THE MEANS IN THE SECOND CIRCUIT BIASING THE SECOND TRANSISTOR BECOMES AN OFF CONDITION WHEREBY THE SECOND CIRCUIT BECOMES CONDUCTING AND ENERGIZES THE POWER RELAY WHEN THE FIRST TRANSISTOR BECOMES NON-CONDUCTING AS THE RESULT OF DECREASE IN THE ALTERNATING CURRENT IN THE FIRST CIRCUIT CUIT, CHARACTERIZED BY THE COIL IN THE FIRST CIRCUIT BEING A SECONDARY COIL OF A TRANSFORMER, AND THE MEANS FOR PRODUCING AN ALTERNATING CURRENT IN THE FIRST CIRCUIT BEING A PRIMARY COIL OF THE TRANSFORMER THAT PRODUCES THE MAGNETIC FIELD IN WHICH THE SECONDARY COIL IS LOCATED, AND CHARACTERIZED BY THE PRIMARY AND SECONDARY COILS BEING LOCATED ON AN ELEVATOR CAR THAT TRAVELS UP AND DOWN IN A SHAFTWAY, VANES OF FERROMAGNETIC MATERIAL AT SPACED LOCATIONS ALONG THE SHAFTWAY IN POSITION TO PASS BETWEEN THE PRIMARY AND SECONDARY COILS AT THE ELEVATOR CAR TRAVELS PAST THE VANES, A MOTOR FOR THE ELEVATOR CAR, AND AN ELECTRIC CIRCUIT FOR THE MOTOR CONTROLLED BY SAID POWER RELAY.