Abstract: A hydraulic system which includes a pump for supplying hydraulic fluid to a load by a fluid supply line and receiving hydraulic fluid from the load by means of a fluid return line. The pump, as well as a drive motor therefore is enclosed within a pressure vessel, having a gas interior which forms an acoustic impedance mismatch so that the pump is acoustically isolated from the surrounding water medium. The fluid return line is connected to a reservoir having a moveable piston which separates the reservoir into two compartments, one filled with oil and the other with gas. The reservoir is sealed so that its internal pressure which is relatively low, for example between 10 and 100 psia is completely independent of the pressure of the surrounding water medium and maintains the return line pressure at that same low value.

Abstract: A hydraulic system which includes a pump for supplying hydraulic fluid to a load and receiving hydraulic fluid therefrom wherein the pump is acoustically isolated from the surrounding water medium. The pump and a motor which drives the pump is enclosed in a pressure vessel, the interior of which is supplied with a gas at a certain pressure less than the ambient water pressure. The pressure of the hydraulic fluid in the return line is maintained at a pressure less than the ambient by a reservoir arrangement which includes a piston and rod assembly with the rod being subject to the ambient water medium. A certain pressure within an oil filled compartment of the reservoir is maintained at a fraction of the ambient water medium pressure by making the ratio of the cross sectional area of the piston to the rod equal to that predetermined fraction. This reduced pressure compartment is hydraulically connected to the fluid return line as well as to a gas regulator.

Abstract: An hydraulic liquid system wherein a pump moves liquid from one location to another such as in supplying one or more loads in an underwater environment. The system includes two hydro-pneumatic chambers utilized such that one is filled by liquid from the pump while the other supplies the load, and as one hydro-pneumatic chamber empties, valves reconfigure the system such that the hydro-pneumatic chamber reverse roles. Each hydro-pneumatic chamber includes a liquid side and a gas side separated by a movable barrier with the gas sides of the hydro-pneumatic chambers being connected to one another thereby providing a large acoustic transmission drop across a liquid-gas boundary and subsequent gas-liquid boundary to interrupt the liquid noise path from the pump to the load.