Patent ID: 7431572

Claim:
A hydraulic oil well pumping installation, comprising: a down hole pump positioned down a well, the down hole pump including: a master cylinder wherein the master cylinder is below the slave cylinders; more than one slave cylinder in axial alignment with the master cylinder; a master piston positioned in the master cylinder and dividing the master cylinder into a first portion and a second portion; a slave piston positioned in each slave cylinder and dividing each slave cylinder into a first portion and a second portion, each slave piston being connected directly or indirectly by a rigid linkage to the master piston, such that movement of the master piston results in movement of the slave pistons; a first hydraulic fluid conduit selectively supplying hydraulic fluid to and drawing hydraulic fluid from the first portion of the master cylinder; a second hydraulic fluid conduit selectively supplying hydraulic fluid to and drawing hydraulic fluid from the second portion of the master cylinder; an intake port on each slave cylinder, each intake port having a one way intake valve permitting entry of fluids into the slave cylinder via the intake port and preventing well fluids from exiting each slave cylinder via the intake port; and an exhaust port on each slave cylinder, each exhaust port being controlled by a one way exhaust valve permitting well fluids from the well to exit each slave cylinder via the exhaust port and preventing fluids from flowing back into each slave cylinder, the fluids being drawn into a first slave cylinder via the intake port, pumped sequentially from one slave cylinder to another, and exhausted by conduit to the surface from a last slave cylinder via the exhaust port.