Electrohydraulic drive for process line winders, unwinders and other

Abstract

An electrohydraulic drive for process line equipment, especially a spooler that winds and pays out an indefinite length of metallic strand, varies the output torque of a hydraulic motor by controlling its displacement and the pressure differential between its inlet and outlet. A valve controlled by a proportional actuator reduces the supply pressure of the hydraulic fluid in a feed line for the motor. A sequence valve located in a return line from the motor maintains the pressure at the motor outlet at a preselected and adjustable value. During braking, fluid from the return line is directed to a regeneration circuit that includes a flow divider returning one portion of the flow to the feed line and another portion to a supply reservoir. A servo-amplifier circuit includes an integrating amplifier that compares the actual rotation speed of the motor to a speed command signal. An analog multiplier produces a control signal for the proportional actuator. In the preferred form a tensiometer monitors strand tension and produces an input signal to a computer that modifies the pressure limit signals. The computer also controls the speed command and displacement of the motor. A hydraulic cylinder controls the linear traversing movement of the spooler under the control of a high speed servo valve that in turn is controlled by electronic circuitry. Position, velocity and rotation speed transducers for the spooler and a position transducer for the strand provide input signals to the circuitry.