Patent ID: 6405530
Filing Date: 2002-06-18
Classification: F04B

Abstract:
A hydraulic circuit comprising:a bi-directional flow variable displacement pump including a movable member therein for varying displacement; a servo mechanism including two servo chambers therein operatively opposing each other, the servo mechanism being connected to the movable member so as to position the movable member based upon a hydraulic pressure differential between the servo chambers; a two-stage non-feedback proportional electronic control assembly operatively connected to the pump through the servo mechanism for controlling the magnitude and direction of the displacement of the pump; the first stage of the non-feedback proportional electronic control assembly consisting of a single non-feedback proportional electronic control valve that generates a displacement magnitude hydraulic command signal that is proportional to an input current; the second stage of the electronic control assembly including a directional control valve operatively connected to the electronic control valve and the servo mechanism, the directional control valve includes a plurality of positions including a first position wherein the displacement magnitude signal is received from the electronic control valve and ported to one of the opposing servo chambers so as to vary the flow of the pump in a first direction and a second position wherein the displacement magnitude signal is received from the electronic control valve and ported to the other of the opposing servo chambers so as to vary the flow of the pump in a second direction.