Drill stem make-up and break-out system for earth drilling machines

Abstract

A system for use in the make-up or break-out of drill stem members of earth boring machines having a hydraulically operated power swivel to rotate the drill stem and hydraulic cylinders to raise and lower the swivel. A first, variable volume pump supplies fluid to the hydraulic cylinder through a four-way valve. A servo pump controller, connected with this valve and operable by variable resistors, establishes the linear make-up and break-out speeds for the power swivel. A second, variable volume and reversible pump supplies fluid to the power swivel means. A second servo pump controller, connected with the second pump and operable by variable resistors, establishes selected linear rotational travel speeds for the power swivel. Make-up torque is controlled by an electrical solenoid activated pressure compensator connected with the second pump, and linear speed is similarly controlled.

Dependencies are inferred from the claim text.