On-off valve fluid governed servosystem

Claim 1

A servosystem comprising in combination, a fluid-actuated double-acting piston-cylinder unit, two on-off electrically controlled valves for governing supply of fluid to said unit arranged between a high pressure source and a low pressure reservoir for said fluid, two conduits for supplying fluid form said source to the opposing sides of said piston each having a branch connection being branched off from a fluid connection between the said high pressure source and one of said valves, common controller means coupled for operating the valves with two separate alternating trains of electrical pulses of variable width synchronously emitted therefrom, fluid control means connected between each of the said conduits and the source for supplying fluid to said piston from the source, means governing the opening and closing of each of said valves by said two separate output pulse signal trains emitted from said common controller in a manner respectively tending to move said piston in opposite directions to a servo position established in response to difference in pulse width in the two said pulse trains, and means for influencing the controller output pulse trains to establish said servo position in response to a comparison of the position of the piston with a governing signal, wherein said fluid control means consist of on-off valves governed by said pulse trains and are coupled upstream between said conduits and the high pressure source, and wherein one valve upstream to the branch connection of one conduit to the said piston and the valve downstream to the branch connection of the other conduit to the said piston are connected to a first of said pulse trains for synchronous governing, and that the two remaining valves are connected to the second of said pulse trains.