Down-the-hole drill hammer having a piston follower valve

Abstract

A down-the-hole drill hammer including a drill bit about a distal end of the hammer and a piston for percussively contacting the drill bit. The drill hammer further includes a valve assembly for supplying and exhausting drive fluid to and from the piston, the valve assembly having a valve housing in fluid communication with drive fluid supply ports, drive ports and exhaust ports, and a control valve movable within the valve housing and in fluid communication with the valve housing. The drill hammer further includes a piston follower valve unconnected to the piston movable within the control valve for controlling positioning of the control valve and pressures applied to the piston via the drive ports and exhaust ports.

Dependencies are inferred from the claim text.