Detectors of fluid flow

Claim 1

AN OIL FLOW DETECTOR FOR A REFRIGERANT COMPRESSOR HAVING AN ELECTRIC DRIVING MOTOR, HAVING A PASSAGE THROUGH WHICH LUBRICATING OIL FLOWS WHEN SAID COMPRESSOR IS IN OPERATION, HAVING A FIRST PTC THERMISTOR IN HEAT EXCHANGE CONTACT WITH SAID MOTOR, HAVING A PROTECTIVE RELAY WITH AN ENERGIZING COIL, HAVING ELECTRIC SUPPLY CONNECTIONS, AND HAVING A CIRCUIT CONNECTING SAID COIL AND THERMISTOR IN SERIES TO SAID CONNECTIONS, SAID DETECTOR COMPRISING A SECOND PTC THERMISTOR IN SAID PASSAGE AND A HEATER RESISTOR IN SAID PASSAGE IN HEAT EXCHANGE CONTACT WITH SAID SECOND TRANSISTOR, AND COOLED BY OIL FLOW IN SAID PASSAGE, SAID RESISTOR BEING CONNECTED TO SAID CONNECTIONS, SAID SECOND THERMISTOR BEING CONNECTED IN SAID CIRCUIT IN SERIES WITH SAID COIL AND SAID FIRST THERMISTOR, SAID RELAY HAVING A SWITCH THAT IS CLOSED WHEN THE TEMPERATURE OF SAID MOTOR IS NORMAL, AND WHEN OIL FLOWS IN SAID PASSAGE, AND THAT OPENS WHEN THE TEMPERATURE OF SAID MOTOR HAS INCREASED TO AN ABNORMAL TEMPERATURE, AND WHEN THERE IS NO OIL FLOW IN SAID PASSAGE, AND MEANS INCLUDING SAID SWITCH FOR CONNECTING SAID MOTOR TO SAID CONNECTIONS.