Weight control system for a rotary drill assembly

摘要

A system for controlling the weight on a rotary drill bit includes an hydraulic cylinder and piston assembly. Pressurized hydraulic fluid acting on the bottom of the piston provides an upward force on the drill string which is connected to the rotary drill bit. A profiled central drive shaft running through the piston conveys the rotary motion from a power swivel to a piston rod attached to the bottom of the piston which in turn is connected to the drill string.