Abstract: A method of breaking rock, concrete or other hard compact material adjacent to a hole drilled thereinto and an apparatus for performing the method wherein the apparatus contains a notch-forming means to form a circumferential notch in the drillhole wall, a hydraulic jack means which is located inside the drillhole to exert a force to actuate the notch-forming means and to react against the bottom of the drillhole and develop an outwardly directly axial force on the notcher to break one or more pieces of material from the face and a hydraulic supply means to supply hydraulic fluid to actuate the hydraulic jack. The hydraulic supply means is located outside the drillhole.

Abstract: What follows is a description of a hydraulically powered actuator for producing a reciprocating output and a method which produces a reciprocating output in response to the controlled flow of a hydraulic fluid. The hydraulic actuator includes, in one embodiment, a cylinder within which a piston assembly is reciprocated, the cylinder being itself displaceably mounted within a housing so that it can periodically introduce a unique flow passage through which a rapid fluid flow occurs, the provision of the passage reduces the hydraulic power lost during reciprocating movement of the piston assembly and ensures a high energy output.