GB1423899A - Portable pneumatic percussive tool - Google Patents

Abstract

1423899 Percussive tool INSTITUT GORNOGO DELA SIBIRSKOGO OTDELENIA AKADEMII NAUK SSSR and SVERDLOVOSKY ZAVOD "PNEUVMOSTROIMASHINA" IMENI ORDZHENKIDZE 31 July 1973 [3 Oct 1972 18 Jan 1973 (2)] 36451/73 Heading B4C A pneumatic percussive tool of the kind having a reciprocating piston 4 delivering blows to a tool bit 5 has a handle 34 slideable on the tool body 1 against the influence of shock-absorbing means 37, and chuck elements 10 engaged by a tapered portion 11 of a coil spring 8 which includes a cylindrical portion 9 embracing the tool body, the spring being expanded to urge the chuck elements into engagement both with the bit shank 6 and the tool body. Either the chuck inner surface or the bit surface may be coated with material to increase friction. The means 57 may be a multi-strand spring, Fig. 4. When the handle is pushed down, a cam surface 36 opens a valve 32 admitting pressure to passages 27, 28 leading to beneath the piston 4. The piston rises, exhausting air above it through ports 38, jacket 40 and holes 41 when it passes the ports 38, pressure beneath the piston is released. Pressure builds up above the piston causing a valve ring 25 to rise and cut off communication between passages 27, 28, thus admitting pressure to the upper cylinder end via ports 26 to return the piston and deliver a blow to the bit. As the descending piston passes the ports 38, pressure builds up beneath it for cushioning and loss of pressure behind it enables to ring 25 to again close the ports 26.