Pulseless pump apparatus having pressure crossover detector and control

Abstract

A multi-cylinder pulseless pump mechanism is provided which incorporates a plurality of positive displacement pumps having their respective outlets coupled for sequentially delivering a continuous pulseless supply of fluid to an outlet line. To achieve pulseless fluid flow from the synchronously operating piston pumps and to achieve sensitive operation even under high pressure conditions a differential pressure sensor is provided having a pair of bridge type strain gauge transducers which render finite voltages above zero at all pressure conditions and thus provide transducer output signals that are free from electrical noise typically associated with zero voltage. One of the transducer signals is buffered to drive a recording device to show system pressure level. Both transducer signals are differentially summed to create a differential pressure which is also output to a recorder and which is electronically amplified and differentially summed to develop a differential switch output signal that is utilized for synchronous operation of a control valve for valve shifting at zero pressure during pump crossover to thus achieve continuous pulseless flow of fluid at the control valve outlet in response to sensed pressure conditions.