GB1302759A - - Google Patents

Abstract

1302759 Rock drills INGERSOLL-RAND CO 20 April 1970 [22 May 1969] 18799/70 Heading B3C [Also in Division B4] In a percussive tool including a tool bit 15, and a hammer piston 10 reciprocable in a cylinder liquid, e.g. oil, is supplied alternately to chambers 8a, 8b (Fig. 3) to effect reciprocation of the piston and via each chamber to a respective accumulator 90, 91. The supply of liquid is controlled by grooves in the piston coacting with ports in the cylinder during reciprocation of the former. Liquid under pressure initially passes into a tank 100, and, with the hammer piston in the position illustrated in Fig. 2, passes via pipe 111, and grooves 68 into the chamber 8a and acts on shoulder 11a of the piston to urge the piston on a return stroke. At the same time liquid passes from chamber 8a via annular passage 54 and bore 94 into the accumulator 90, and chamber 8b communicates with an outlet pipe 121, which leads into an outlet tank (101) (Fig. 1, not shown), via grooves 66 and annular passage 53. As the piston moves on its return stroke, communication between inlet pipe 111 and chamber 8a, and between chamber 8b and outlet pipe 121 is terminated. Energy of the liquid accumulator 90 is then released into chamber 8a to continue the piston return, and liquid in chamber 8b will be compressed and forced into accumulator 91. As the piston continues its return motion grooves 65 will open communication between liquid inlet pipe 110 and chamber 8b so that the chamber 8b and accumulator 91 will be charged with liquid. Simultaneously chamber 8a communicates with the outlet pipe 121 via grooves 67. Return motion of the piston is then terminated and a drive stroke commences. The liquid stored in accumulator 91 will effect continuation of the piston's drive stroke when the liquid supply to chamber 8b is terminated. Communication between the inlet pipe 111 and chamber 8a via grooves 68 is effected before the piston impacts the tool bit 15. The force acting on the piston on its drive stroke is supplemented by air or hydraulic fluid compressed in chamber 131 at the end of the return stroke. A motor 20 via gearing and chuck 27 effects rotation of the bit which receives air for blowing cuttings out of a bore hole.