GB1005018A - Pneumatic impact tool - Google Patents

Abstract

1,005,018. Percussive drills. SKIL CORPORATION. Dec. 14, 1962 [Sept. 11, 1962], No. 47239/62. Heading B4C. A pneumatic impact tool 10 comprises a barrel 22 having a chamber 23 in which a hammer piston 30 is adapted to strike the shank 28 of a tool bit 29, the tool having passageways 20, 50 for directing air from a pressure source to a pressureactuated valve 55, of a lightweight non-metallic material arranged to control the flow of air to opposite ends of the chamber via passages 48, 35, 37 in order to reciprocate the piston. The barrel 22 is screwed into a handle portion 11, a valve body 40 being clamped thereby so as to define an annular chamber 41 communicating, via a passage 20 and a valve 17, with a chamber 14 fed with compressed air. The valve body is formed with a spigot portion 43 in which a groove 46 is cut in order to accommodate a valve member 55 made from a canvas or linen base impregnated with resin; the groove communicates with the chamber 41 via grooves 53 formed in the end surface of the barrel. In operation, upon opening the valve 17 air is fed via passage 20, chamber 41, grooves 53, groove 46 and a port 48 into the rear end of the chamber 23 thereby driving the piston forward. After a certain travel of the piston an exhaust port 32 is closed, the air trapped in front of the piston being compressed until the latter strikes the shank 28. The compressed air in front of the piston acts, via the passage 37, 35 and 50, on the valve member 55 thereby moving it to close off the port 48 and thus allow the air from the groove 46 to flow via passages 50 and 36, 37 into the front end of the chamber to reverse the piston the air in the rear end of the chamber being exhausted via a port 33. In order to form the port 37, a hole is drilled through the wall of the barrel until the drill breaks into the passage 35, this operation thereby simultaneously producing the exhaust port 32. Specification 1,005,019 is referred to.