Abstract: A hydraulic drilling apparatus, especially a rock drill comprising a body, a cylinder in the body and a percussion piston reciprocating in the cylinder. A tool is connected to the body and a motor is provided for rotating the tool. A control valve is also provided for the percussion power. A control valve is also provided for regulating the motor speed. Both of these control valves are operated independently by one lever. A hydraulically operated flushing valve is also provided. A hydraulic pump and hydraulic channels coact to form a percussion circuit and a rotation circuit is parallelly coupled with the percussion circuit in relation to the hydraulic pump. A flushing valve circuit is controlled by the percussion circuit and a circuit for the free circulation of the hydraulic pump which is parallelly coupled with the percussion circuit in relation to the hydraulic pump. The circuits are connected to the hydraulic pump.

Abstract: A hydraulic percussion apparatus comprising a body, a cylinder in the body and a percussion piston reciprocating in the cylinder. A distributing valve moves in a valve housing. A valve for starting and stopping the percussion apparatus is provided. A hydraulic pump and hydraulic channels form a percussion circuit with a gas/liquid pressure accumulator. A distributing valve circuit and a free circulation circuit are provided for the pump which are parallelly coupled with the percussion circuit, which circuits are connected to the pump and to the start-and-stop valve which has positions for controlling pressure in the circuits. The start-and-stop valve has a middle position during which pressure in the percussion circuit rises up to a predetermined value while the distributing valve circuit remains closed independent of the pressure in the percussion circuit.