Flowmeter

Claim 1

APPARATUS FOR MEASURING THE RATE OF FLUID FLOW THROUGH A PASSAGE COMPRISING A STRUCTURE ADAPTED TO BE POSITIONED WITHIN THE PASSAGE, PACKING MEANS EXTENDING OUTWARDLY FROM SAID STRUCTURE TO ENGAGE THE WALLS OF THE PASSAGE TO DIVIDE THE PASSAGE INTO FIRST AND SECOND REGIONS, FIRST CONDUIT MEANS CARRIED BY SAID STRUCTURE TO COMMUNICATE BETWEEN SAID FIRST AND SECOND REGIONS, SECOND CONDUIT MEANS CARRIED BY SAID STRUCTURE TO COMMUNICATE BETWEEN SAID FIRST AND SECOND REGIONS, A FIRST THERMAL SENSITIVE IMPEDANCE ELEMENT, A SECOND IMPEDANCE ELEMENT, SAID FIRST ELEMENT BEING POSITIONED IN SAID FIRST CONDUIT MEANS, SAID SECOND ELEMENT BEING POSITIONED EXTERNALLY OF SAID FIRST CONDUIT MEANS, MEANS FORMING AN ELECTRICAL BRIDGE CIRCUIT HAVING SAID FIRST AND SECOND ELEMENTS IN ADJACENT ARMS THEREOF, SAID BRIDGE CIRCUIT HAVING FIRST AND SECOND PAIRS OF OPPOSITE TERMINALS, A SOURCE OF VOLTAGE APPLIED ACROSS THE FIRST OPPOSITE TERMINALS OF SAID BRIDGE CIRCUIT, MEANS FOR MEASURING THE SIGNAL BETWEEN THE SECOND OPPOATIVE OF FLUID FLOW THROUGH SAID FIRST CONDUIT MEANS, AN IMPELLER POSITIONED IN SAID SECOND CONDUIT MEANS, A MOTOR TO ROTATE SAID IMPELLER TO DIRECT FLUID THROUGH SAID SECOND CONDUIT MEANS AT A RATE SO THAT THE FLOW THROUGH SAID FIRST CONDUIT MEANS IS ZERO AND MEANS TO MEASURE THE SPEED OF ROTATION OF SAID IMPELLER THE SPEED OF ROTATION OF SAID IMPELLER BEING A MEASURE OF THE RATE OF FLUID FLOW THROUGH SAID SECOND CONDUIT MEANS WHEN THE INDICATED FLOW THROUGH SAID FIRST CONDUIT MEANS IS ZERO.