Flow measuring apparatus

Claim 1

A FLUID FLOW METER FOR MEASURING THE FLOW OF FLUID THROUGH A CONDUIT COMPRISING: A CASING HAVING AN INLET AND AN OUTLET; A VENTURI IN SERIES FLOW RELATIONSHIP WITH SAID INLET AND OUTLET THROUGH WHICH THE FLUID FLOWS TO GENERATE A FLUID PRESSURE DIFFERENTIAL; A FLOW INDICATING DEVICE RESPONSIVE TO SAID FLUID PRESSURE DIFFERENTIAL; A VALVE MEMBER OPERATIVELY CONNECTED TO SAID VENTURI FOR VARYING THE THROAT AREA THEREOF TO CAUSE A CORRESPONDING VARIATION IN THE FLUID PRESSURE DIFFERENTIALFLUID FLOW RELATIONSHIP ASSOCIATED WITH SAID VENTURI; A FIRST FLUID CHAMBER COMMUNICATING WITH THE FLUID PRESSURE AT THE THROAT OF SAID VENTURI; A SECOND FLUID CHAMBER COMMUNICATING WITH THE FLUID PRESSURE UPSTREAM FROM SAID VENTURI; A MOVABLE WEALL SEPARATING SAID FIRST AND SECOND FLUID CHAMBERS AND RESPONSIVE TO THE FLUID PRESSURE DIFFERENTIAL THEREBETWEEN AND BEING OPERATIVELY CONNECTED TO SAID VALVE MEMBER FOR ACTUATING THE SAME AT A PREDETERMINED VALUE OF SAID FLUID PRESSURE DIFFERENTIAL TO CAUSE AN INCREASE IN THE THROAT AREA OF SAID VENTURI; A RESILIENT MEMBER OPERATIVELY CONNECTED TO SAID MOVABLE WALL FOR URGING SAID VALVE MEMBER TOWARD A CLOSED POSITION IN OPPOSITION TO SAID FLUID PRESSURE DIFFERENTIAL AND FOR ESTABLISHING A FORCE TO BE OVERCOME BY SAID PREDETERMINED PRESSURE DIFFERENTIAL; AND A FIXED STOP MEMBER ENGAGEABLE WITH SAID MOVABLE WALL FOR LIMITING THE MOVEMENT OF SAID VALVE MEMBER IN A CLOSING DIRECTION TO A PREDETERMINED POSITION.