Patent ID: 7395708

Claim:
A flow measuring apparatus connectable to a flow of fluid, comprising: a barrel having an interior area; a piston movable in the barrel between first and second positions, the piston divides the interior area into first and second portions; a biasing member coupled to the piston and urging the piston toward the first position; a first fluid passageway having an inlet, an outlet and an intermediate portion therebetween; a second fluid passageway in fluid communication with the first fluid passageway and with the first portion of the barrel, the second fluid passageway being configured to provide fluid from the intermediate portion of the first fluid passageway to the first portion of the barrel to move the piston toward the second position; a valve assembly coupled to the first fluid passageway downstream of the intermediate portion, the valve assembly being movable between an open position that allows fluid to pass through the first fluid passageway to the outlet and a closed position that causes fluid to flow into the second flow passageway and into the first portion of the chamber to move the piston from the first position to the second position, the valve assembly being movable away from the closed position to release pressure from the barrel in an overpressure condition; a latch mechanism coupled to the valve assembly and being movable between an activated position and a released position, the latching mechanism in the activated position moves the valve assembly to the closed position, and the latching mechanism in the released position allowing the valve assembly to move to the open position, the latching mechanism being configured to move to the released position at least when the piston reaches the second position; an actuator coupled to the latching mechanism and configured to activate the latch mechanism to move the valve assembly to the closed position to cause the fluid to move the piston to the second position; and a measuring device configured to monitor the movement of the piston through a stroke between the first and second positions and the time to complete the stroke.