Abstract: A fluid pressure equalizing valve adapted for use in hydraulic systems includes a valve body having fluid inlet, working and vent ports, a valve plug in the valve body having a working passageway and a vent passageway formed therein and communicating with the peripheral wall thereof, the plug being rotatable in the valve body between a working position wherein the working passageway is aligned with the inlet and working ports and a vent position wherein the vent passageway is aligned with the inlet and vent ports. The valve plug includes a plurality of orifice passageways formed therein communicating the peripheral wall thereof with the vent passageway, each orifice passageway having a substantially smaller diameter than the working passageway. Means are provided for preventing fluid flow through the orifice passageways when the valve plug is in the working and vent positions.

Abstract: A petroleum pumping unit which is especially suitable for use in remote oil fields and under unpredictable pumping conditions is disclosed. The petroleum pumping unit of the present invention, which is easily movable between a folded, collapsed position for storage and shipment and an erect position for pumping operations, includes a horizontal support platform on which is pivotally mounted a mast assembly including a pair of masts spaced outwardly from the centrally positioned well polish rod. The polish rod is engaged by a notch in a horizontal, vertically movable bridle and is powered by at least one pair of flexibly mounted hydraulic cylinders and associated piston rods attached to the bridle and positioned between the polish rod and the masts and parallel thereto. Vertical movement of the bridle and, therefore, the stroke of the polish rod is defined by upper and lower limit switches which are actuated by actuating means on the bridle.