Patent ID: 6837141

Claim:
A hydraulic drive system comprising: (i) an input drive system comprising: (a) one or more hydraulic fluid lines; (b) a first cam element having a first wave-shaped profile; (c) a first plurality of hydraulically-driven piston units connected to said one or more hydraulic fluid lines, said first plurality of hydraulically-driven piston units having cam rollers which are disposed to act against said first cam element so that a movement of the first wave-shaped profile against the cam rollers produces a plurality of phases of oscillating fluid flow in said one or more hydraulic fluid lines, and said relative position of said cam rollers against said cam element determines a relative phase angle for said oscillating fluid flows; (ii) an output drive system comprising: (a) a second cam element having a second wave shaped profile; (b) a second plurality of hydraulically-driven piston units having cam rollers which are disposed to act against said second cam element so that a movement of the cam rollers against the second wave-shaped profile caused by said oscillating fluid flow produces a movement of said second cam element; and wherein piston units of the input drive system are directly connected by said hydraulic lines to piston units of the output drive system having the same relative phase angle; and wherein the movement of the input drive cam ring elicits the movement of the output drive cam ring.