Rotary percussion hydraulic drilling machine

A rotary percussion hydraulic drilling machine has striker piston slidably mounted inside a cylinder which defines a first annular chamber connected to a one-way valve slidably mounted inside a chamber connected to an accumulator comprising a diaphragm, leading to which is a hydraulic fluid inlet pipe and a second annular chamber connected to a control valve. This control valve, governed by the movements of the piston, connects the second chamber alternately to the high pressure pipe and to the return pipe. The valve, constructed in the form of a sleeve and subject to the force of a spring has a lateral connection allowing the direct passage of fluid to the return pipe, a rotary motor being located in the inlet pipe. Thus solely rotary operation for a rate of flow less than a certain threshold value and rotary/percussive operation for rates of flow beyond this threshold value may be obtained.