Abstract: An improved linear fluid motor system, which is adapted to be driven by pressurized hydraulic fluid from a hydraulic pump, includes a piston rod having a first head interacting with product fluid and a second head interacting with hydraulic fluid, a first spool valve and a second spool valve interacting with the second piston head to control a third spool valve which reverses the displacement of the piston rod at its limits of travel, a first accumulator, and a second accumulator for cushioning abrupt pressure changes in the hydraulic fluid, a heater for heating the hydraulic fluid, a control valve for controlling the product fluid pumping rate of the system, interconnections for connecting the various components of the system, stops for defining the various configurations of the system, a detent mechanism for restraining the third spool valve in its switching configurations, and a coaxial conduit for conveying the hydraulic fluid between the hydraulic pump and the system whereby the product fluid is pumped f

Abstract: An automatically-reversing, fluid-actuated piston-and-cylinder unit includes a cylinder with a first section reciprocably receiving a piston and a second section reciprocably receiving a spool valve member. The piston is connected to a piston rod that extends slidably through the valve member. The valve member includes a plurality of lands that subdivide the cylinder second section into a plurality of fluid chambers. In a first position the valve member directs fluid to one side of the piston and in a second position it directs fluid to the other side of the piston. The valve member is automatically shifted between its first and second positions when the piston reaches its limits of travel.

Abstract: A wellhead assembly especially suited for oil wells has a wide working pressure range and employs three components which fit together to seal the well casing, hold the tubing against high wellhead pressures, and provide a connection to the tubing through which the sucker rods are operated. The primary casing seal is formed by the mating contact of metal surfaces that are not subject to deterioration. The actuator for the subsurface pump is a vertically disposed hydraulic cylinder unit aligned with the sucker rods and forming the uppermost section of an elongated cylindrical housing, which also has a lowermost section on the wellhead that provides the outlets for the fluid pumped from the well, and an intermediate, control section that contains a spool valve for controlling the hydraulic actuator. The spool is shifted by the piston and rod of the hydraulic actuator at the upper and lower limits of their stroke to thereby reciprocate the sucker rods and operate the subsurface pump.