HYDRAULIC DOWN-THE-HOLE DRILLING MACHINE

摘要

A hydraulic down-the-hole drilling machine including a piston (8) that seen from the inlet (24) of the machine has a first (9), a second (10) and a third (11) piston portion with consecutively increasing diameter. To the third piston portion (11) is connected a fourth piston portion (12) having a smaller diameter than the third piston portion. The first piston portion (9) has a first pressure surface (14) that together with a second pressure surface (15) of the second piston portion (10) has a larger area than a third pressure surface (16) of the third piston portion (11), said third pressure surface (16) facing in the opposite direction and having a larger area than the first pressure surface (14).