GB739453A - Improvements in percussion tools having a reciprocable hammer piston actuated by combustion gases - Google Patents

Abstract

739,453. Percussive tools. AKTIEBOLAGET ATLAS DIESEL. Feb. 26, 1954 [March 2, 1953], No. 5750/54. Class 124. An internal-combustion engine operated percussive tool having a hammer piston, the return stroke of which is produced by pressure air or gas; and automatic means for rotating the bit, has a device for simultaneously preventing the rotation of the bit and preventing the production of the return stroke of the hammer piston. As shown, a hammer piston 30 of the differential type has its large diameter operating in a cylinder 35 to which compressed exhaust gas is supplied from a chamber 28 through a port 34 to produce upward movement of the piston. The chamber 28 may be supplied with compressed gas from a compression chamber 25 wherein operates a motor piston 17, 18. A ratchet and pawl mechanism operated by a rod 50 connected to a crankshaft 3 provides rotation of the bit 41. A valve member 55, Fig. 5, rotatably mounted in the lower casing 8 has three positions, in one of which the chamber 28 is vented to atmosphere and the upward movement of the piston 30 prevented and at the same time the pawl is held out of its operative position and rotation of the bit is also prevented, in a second position the pawl is maintained out of operative position but the chamber 28 is not vented to atmosphere and the hammer piston may operate, and in the third position both rotation of the bit and operation of the piston are permitted. Some gas from the chamber 28 may pass by way of a valve 44 to a chamber 38 and thence through a bore 45 to the hollow bit for clearing the borehole.