Hydraulic actuator for well pumps

Claim 1

Hydraulic apparatus for actuating a subsurface reciprocating pump, comprising, in combination: I. a hydraulic actuator comprising, (a) a vertically disposed motor cylinder having first and second ends, (b) a guide tube coaxial within said cylinder and extending from said second end thereof along a major portion of the length thereof, (c) means mounting said guide tube at said second end of said cylinder and closing the space between said cylinder and said tube, so that said cylinder and said guide tube define a first annular hydraulic chamber, (d) an annular piston, having first and second surfaces, reciprocable along said tube in said cylinder between first and second limits of travel, to vary the volume of said first chamber, (e) an elongted lift tube within said cylinder and surrounding said guide tube, having a first end extending beyond said first end of said cylinder in sealing relation thereto and a second end secured to said first surface of said piston, to reciprocate with said piston in said cylinder and define with said cylinder a second annular hydraulic chamber of which the volume varies, with movement of said piston, oppositely to the variation in volume of said first chamber, (f) a lift rod secured to said first end of said lift tube and extending through said lift tube and said guide tube beyond said second ends thereof for connection to the pump rod of a subsurface pump, and (g) first and second port means affording communication to said first and second chambers respectively, at sites beyond the limits of travel of said piston; II. a hydraulic accummulator connected to said first port means; III. a continuous source of hydraulic fluid under pressure; IV. a receiver for hydraulic fluid; V. control means actuated when said piston moves to said limits of its travel; and VI. valvable means interconnecting said actuator, said accumulator, said pump, and said receiver so as to cause reciprocation of said piston, lift tube and lift rod in said cylinder, to cause continuous circulation of fluid for said actuator from and to said source, to repetitively store and release in said accummulator energy derived from the downward movement of a mass connected to said lift rod, and to cushion the reverse of said motor at the first limit of travel of the piston, said valvable means including (a) first valvable means for interconnecting said port means, (b) second valvable means for connecting said second port means with said receiver, (c) means connecting said accumulator and said second port means to said source, and (d) means enabling actuation of said valvable means by said control means.