A percussion apparatus, including:
- a body delimiting a piston cylinder,
- a striking piston alternately movable inside the piston cylinder, and arranged to strike a tool during each operating cycle of the percussion apparatus,
- a control distributor arranged to control a reciprocating movement of the striking piston inside the piston cylinder reciprocally along a striking stroke and a return stroke,
- a control device arranged to vary the striking stroke of the striking piston depending on the hardness of the ground encountered by the tool, the control device comprising:
- a control cylinder,
- a plurality of first control channels each opening into the control cylinder, each first control channel also opening into the piston cylinder and being adapted to be put in communication with a high-pressure fluid supply circuit during at least one part of the reciprocating movement of the striking piston,
- a second control channel connected to the control distributor and opening into the control cylinder,
- a control slide movably mounted in the control cylinder between a plurality of control positions in each of which the control slide is configured to fluidly connect the second control channel with at least one of the first control channels,
- a first control chamber delimited by the control slide and the control cylinder, a first face of the control slide being located in the first control chamber, and
- a second control chamber delimited by the control slide and the control cylinder, a second face of the control slide, opposite to the first face, being located in the second control chamber,
- wherein the control slide delimits a receiving housing, the control device further comprises an adjusting slide mounted in the receiving housing, the control slide and the adjusting slide delimiting a first adjusting chamber permanently fluidly connected to the second control channel and a second adjusting chamber permanently fluidly connected to the high-pressure fluid supply circuit, and the adjusting slide is movably mounted in the receiving housing between a first position in which the adjusting slide is configured to fluidly connect the first control chamber and the second adjusting chamber and a second position in which the adjusting slide is configured to fluidly isolate the first control chamber and the second adjusting chamber, the control device being configured such that the adjusting slide is displaced towards the first position thereof when the second control channel is fluidly connected to the high-pressure fluid supply circuit via at least one of the first control channels.