The invention concerns a device for supplying hydraulic power to a rotary apparatus for percussive drilling (2) whereof the tool (3) is driven in one direction or another and subjected to the action of an impact device (6) acting independently of the rotation, of a hydraulic device (9) with forward movement enabling the tool to generate a pressure force on the ground, and optionally of a suction device (14) for the drilling dusts, driven by a hydraulic motor, the various hydraulic actuating elements being driven from a hydraulic liquid source under pressure through a hydraulic flow divider (16), a set of distributors (17, 18, 19, 20) and an assembly of branch pipes outside the apparatus, such as hose pipes. Said device comprises a branch pipe external to the apparatus (24) for communicating the return branch pipe (22) of the hydraulic device (4) driving the tool in rotation and the supply line (23) of the impact device (6), to add to the supply rate of the impact device the return flow rate of the rotation driving device. |