Abstract: Method and apparatus for controlling a percussive machine by determining, during the phase of rebound of a piston following impact, the existence of an instantaneous flow rate of fluid flowing from a top chamber toward the high-pressure fluid feed circuit. The instantaneous flow rate is determined on the basis of the differential pressure between the top chamber and the high pressure fluid feed circuit. If a flow rate is detected, a control device is fed with pressurized fluid so as to shift a selector piston in a direction for lengthening the stroke of the striking piston.

Abstract: This device is of the type in which the tool is mounted so as to slide, with interposition of upper and lower guide means, in a front guide. According to the invention, at least one of the guide means delimits a guide zone, the directrix of which comprises points of inflection forming separation angles between facets, which zone cooperates with a zone of complementary cross-section made, at least locally, on the tool in order to rotationally lock this tool.

Abstract: A hydraulic percussion device comprises a housing defining a longitudinal cylinder, a piston longitudinally reciprocal in the cylinder and subdividing same into a front compartment and a rear compartment, and a tool engageable longitudinally with the piston at the front compartment. The compartments are alternately and oppositely hydraulically pressurized to move the piston forward to strike the tool while traveling at an end speed and to move the piston backward away from the tool, the rate of alternation being a frequency parameter and the speed being a force parameter. A controller varies at least one of the parameters by detecting how much the piston rebounds from the tool after striking same and operating the control means in accordance with how much rebound is detected. How much the piston rebounds can be detected by sensing the pressure in one of the compartments immediately after the piston strikes the tool.