GB828667A - Pneumatically operated fastener driving machine - Google Patents

Abstract

828,667. Percussive tools. MODERNAIR CORPORATION. Nov. 14, 1956, No. 37334/57. Divided out of 826,645. Addition to 826,646. Class 124. The driving piston of a pneumatic driving unit as claimed in claim 1 of the parent Specification has an upwardly extending rod carrying a return piston of small diameter working in a cylinder in an upper closure, the underside of the return piston being connected alternately with the container and with the atmosphere. As shown, a container 215 for air under pressure is connected to a cylinder 244 having a working piston 228 carrying a rod 269 fitted with a return piston 268. A control piston 239 closes the cylin. der 244 with its underside and its upper side is in communication with the container through a channel 249. On closing a valve 253 to prevent pressure air acting on the top of the piston 239 and at the same time opening the space above the piston to atmosphere, the pressure air in the container acts on an annular area on the bottom side of the piston 239, raising it and allowing pressure air to force the 'piston 228 downwardly to a working stroke. As the piston 239 rises pressure air is admitted below the piston 268 through channels 278 and drives the return piston upwards thus returning the piston 228 to its original position, the air above the piston 228 escaping to atmosphere through passages 274 and 288. In a modification, Fig. 10 (not shown), the working piston of a driving unit as claimed in claim 2' of the parent Specification has a downward annular extension forming an arrow annular space which is in constant communication with the container, the pressure air in which produces the return stroke.