DAMPING DEVICE FOR A FLUID-DRIVEN DOWN-THE-HOLE DRILL AND A FLUID-DRIVEN DOWN-THE-HOLE DRILL COMPRISING SUCH A DAMPING DEVICE

摘要

The invention concerns a damping device for a fluid-driven down-the-hole drill for the damping of the recoil from a drill bit (5A) connected to the machine, comprising a machine housing (2), an impact mechanism (3) driven by pressurised-fluid with a reciprocating hammer piston (8) that is arranged to give impacts onto a rear end, known as the "neck" (5B), of the drill bit, a chuck in which the drill bit (5A) is attached in a manner that allows rotation and axial reciprocating motion, means (4) to achieve rotation of the drill bit (5A), and a recoil damper. According to the invention, the means (4) for rotation of the drill bit (5A) is connected for direct operation of the neck (5B) of the drill bit, whereby the drill bit is mounted in bearings at the said chuck (37) fastening in a manner that allows rotation in the forward end of the machine housing, that the recoil damping device comprises a chamber (48, 49) filled with fluid under pressure, that a pressurised fluid cushion enclosed within the chamber is arranged to form axial bearings (41) for the drill bit during its rotation, and which pressurised fluid cushion is located in front of the means (4) for rotation of the drill bit.