Fluid actuated jack mechanism

Abstract From the Canadian patent

A well pipe jacking mechanism in which a reversible variable displacement pump acts in one condition to deliver pressure fluid in parallel with another pump to the lower end of a jacking cylinder, while receiving and metering fluid from the upper end of the cylinder to regulate upward piston movement. In a second condition, flow through the variable displacement pump is reversed to lower the piston and a variable, restriction valve regulates discharge of fluid from the lower end of the cylinder. In a third condition the variable dis-, placement pump discharges fluid to the lower end of the cylinder and exerts an upward force of increased power on the piston.