Abstract: A reciprocating machine comprising a cylinder with a drive chamber and a return chamber; a piston arranged to move to and fro in the cylinder with a first piston area exposed to the drive chamber and being smaller than a second piston area exposed to the return chamber; a permanently open inlet for fluid to the drive chamber; a restricted outlet for fluid from the return chamber; a bore extending through the piston from a port in its first area to its second area; a first valve with a head adapted to seat on the port and a stem guided in the end wall of the drive chamber; and means for limiting the extent of travel of the first valve with the piston so that the first valve can travel with the piston only part of the way from the drive chamber toward the return chamber.

Abstract: The stabilizer comprises a generally tubular, metal body, the leading end of which has been hardened to rock-cutting strength in order that the stabilizer, according to the method of invention, can be impacted with a high frequency, low-blow actuator to cause the stabilizer to bore its own hole in the earth structure, this to eliminate a pre-boring, stabilizer installation step.

Abstract: A hydraulically operated reciprocating piston and a differential force operated valve are both in continuous fluid contact with a pressurized cushion chamber as well as the piston chamber pressure. The valve position is a function of the cushion chamber pressure. The cushion chamber pressure is a function of the axial position of the piston. The values of these functions are such that the piston is reciprocated when the machine is operated. The valve is a sleeve coaxial with the piston.

Abstract: A hydraulically operated reciprocating piston and a differential force operated valve are both in continuous fluid contact with a pressurized cushion chamber as well as the piston chamber pressure. The valve position is a function of the cushion chamber pressure. The cushion chamber pressure is a function of the axial position of the piston. The values of these functions are such that the piston is reciprocated when the machine is operated. The valve may, for example, be a sleeve coaxial with the piston or a valve transversely spaced from the piston.

Abstract: The stabilizer comprises an elongate element which is axially slit, and is circular in cross-section, for forced insertion into an undersized bore in a structure, such as a mine roof or wall, for stabilizing the structure. The stabilizer improvement comprises an annular, wire-rod flange made integral therewith for reinforcing the driven end of the stabilizer to enable such end to accept impact forces upon the stabilizer being forced into the bore.