Patent ID: 6652741
Filing Date: 2003-11-25
Classification: B01D,F04B,Y02A

Abstract:
Water pumping apparatus comprisingfirst and second pumps (3, 4, 60), each of the pumps having two chambers (18a, 18b, 20a, 20b) in alignment and receiving respective pistons (24, 26) movable in translation within the cambers, the pistons being interconnected by a sliding shaft (23), double-acting, hydraulic actuators (19a, 19b, 25, 61) respectively for driving the pumps and a loop (14, 15) for circulating driving hydraulic fluid therefrom, the loop being common to the hydraulic actuators, and valve means (12, 27, 68, 81) for pausing the sliding shaft and pistons of the first of the pumps for a prolonged period at an end of a stroke thereof, accelerating the sliding shaft and pistons of the second of the pumps while the first of the pumps is paused, and selectively putting each of the actuators into communication with the loop in such a manner that the sum of absolute values of hydraulic fluid flow velocities to the actuators for the driving is substantially constant.