Abstract: A pair of pumps which are joined by a flexible connection passing over a rotatable device positioned for rotation in a substantially vertical plane. The rotatable means is driven alternately in clockwise and counterclockwise directions whereby the lifting of one pump occurs as the other pump is lowered.

Abstract: A system is provided for maintaining a permanent reciprocatory movement of a mechanical arrangement, particularly a pump unit. A main driving wheel is coupled to the mechanical arrangement and fastened on the shaft of a hydraulic motor which is supplied by a variable delivery pump provided with control means. The control means is coupled to the wheel by a drive mechanism which comprises a rocking lever coupled to the control means and a cam carrier wheel rotationally fixed to the wheel. As the mechanical arrangement moves in one direction, the rotation of the driving wheel causes the cam wheel to change the position of the rocking lever thus permitting the control means to direct the flow of fluid from the variable delivery pump to the hydraulic motor to reverse the direction of travel of the mechanical arrangement.