Abstract: A pressure sensitive valve for a fluid-actuated percussive drill includes passageways for fluid flow to expose a valve surface to a burst of short-interval, high pressure fluid from a drive chamber to cause early closing of the valve.

Abstract: A fluid actuated percussion rock drill comprising a hollow wear sleeve and a piston slidingly disposed within the wear sleeve. Drive and return pressure surfaces bias the piston between drive and return positions, respectively. A high pressure port is included. A return chamber is exposed to the return pressure surface. A drive chamber is exposed to the drive pressure surface. A pressure sensitive valve is movable between an open and a closed position. When the valve is in the open position, the high pressure port is connected to the drive chamber. The valve includes a first valve pressure surface for exposure to the drive chamber and a second pressure surface for exposure to the high pressure port. A third valve pressure surface is exposed to an outlet pressure port. The volume of fluid travels between the high pressure port and the drive chamber when the valve is in an open position can be limited as desired for different drill applications.

Abstract: Broadly, the invention comprises defining a friction rock stabilizer with a configuration which will allow its insertion into an earth structure bore with minimal thrust force, and then deforming the inserted stabilizer, for instance, by forcing an insert thereinto to cause radial expansion of the stabilizer to increase its frictional engagement with the bore surface and produce a high anchorage thereof. The stabilizer set of the invention comprises a stabilizer and at least one oversized expansion insert therefore.