Digital servo-valve

Claim 1

A rotary valve comprising: (a) a valve body; (b) a pluraltiy of fluid conduits passing through the valve body comprising supply ports and service ports, each port presenting an orifice to one plane of the valve body; (c) a rotatable valve plate for directing multiple flow paths from the plurality of supply ports to the plurality of service ports, the valve plate having a plurality of fluid channels abutting the one plane of the valve body for rotational alignment of the fluid channels with the supply ports and service ports; (d) a stepper motor having an output shaft mechanically coupled to the valve plate, the output shaft rotatable to rotate the valve plate through a range of predetermined positions; (e) mechanical centering means for returning the valve plate to a predetermined closed position whenever the power is turned off or lost to the stepper motor, and (f) machine intelligence means for controlling the operation of the stepper motor linked to the valve plate, the machine intelligence means including means for registering the position of the valve plate when mechanically returned to a predetermined closed position, determining the required number of electrical pulses at the desired frequency sufficient to activate the stepper motor for a predetermined number of degrees of rotation of the output shaft to advance or return (in clockwise or counterclockwise rotation) the valve plate to a desired position, whereby the stepping motor will advance and stop the valve plate at the desired position without feedback sensors to constantly measure the actual position of the valve plate.