Abstract: A hydraulic pump jack cylinder is coupled with a closed loop hydraulic circuit, which includes a hydrostatic pump that delivers hydraulic fluid under pressure to the pump jack cylinder. The pump jack cylinder includes an inner extension piston area and an outer retraction piston area which are configured to have substantially the same area to establish a cylinder ration at 1:1. The hydrostatic pump drives the cylinder rod connected to the oil well sucker rod at a constant velocity in both the extension and retraction strokes with a quick sinusoidal turn-around at the ends of the strokes to provide a change in stroke direction. The swash plate in the hydrostatic pump brake the flow of fluid from the pump jack cylinder during retraction to prevent free-fall. A programmable logic controller controls the swash plate angles to switch stroke direction before the cylinder rod bottoms out.

Abstract: A supporting frame mounting a work implement, such as a post hole digger, is disclosed wherein the supporting frame is connected to a standard snow plow mount at the front of a truck. The supporting frame includes a fixed base member affixed to the snow plow mount and supporting a rotatable base portion by a slew bearing. The supporting frame further includes a double arm boom member pivotally connected to the rotatable base member and a single arm boom member pivotally connected to the double arm boom member to provide a compact nesting configuration for transport. The work implement is affixed to the single arm boom member by a pivot and a swivel to permit a self-seeking vertical orientation by gravity. A hydraulic system powers the pivotal movement of the boom members and the rotatable base member, as well as the operation of the work implement.

Abstract: A supporting frame mounting a work implement, such as a post hole digger, is disclosed wherein the supporting frame is connected to a standard snow plow mount at the front of a truck. The supporting frame includes a fixed base member affixed to the snow plow mount and supporting a rotatable base portion by a slew bearing. The supporting frame further includes a double arm boom member pivotally connected to the rotatable base member and a single arm boom member pivotally connected to the double arm boom member to provide a compact nesting configuration for transport. The work implement is affixed to the single arm boom member by a pivot and a swivel to permit a self-seeking vertical orientation by gravity. A hydraulic system powers the pivotal movement of the boom members and the rotatable base member, as well as the operation of the work implement.