Device for controlling the flow of fluid to a fluid unit

A device for controlling the flow of hydraulic fluid from a high-pressure source to a fluid-actuable unit, comprising a supply conduit operatively connected with the high-pressure source, means including an on/off valve substantially without any throttling effect located in the supply conduit for permitting an average supply velocity to be adjusted by cyclic opening and closing of the on/off valve with a ratio between periods of the cyclic opening and closing to cause a transfer of kinetic energy to the fluid-actuatable unit, and a non-return valve means operatively arranged in an unthrottled manner between the fluid-actuatable unit and one of a low-pressure connection and low-pressure reservoir for preventing a flow to one of the low-pressure connection and low-pressure reservoir and in a location where high flow velocities occur when the on/off valve is open so that dynamic vacuum peaks occurring after the closing of the on/off valve are of sufficient magnitude to open the non-return valve means and to continue the transfer of kinetic energy to the fluid-actuatable unit.