GB1340747A - Pneumatic piston device such as impact tools - Google Patents

Abstract

1340747 Fastener driving tools SIGNODE CORP 10 May 1971 [11 May 1970] 14029/71 Heading B4C A pneumatically operable tool for driving fasteners, e.g. staples (as shown), nails or pins comprises a compressed air reservoir 92, a chamber 80 to which air from the reservoir can pass via port 116 to drive piston 28 on a working stroke, and a valve assembly 22 for controlling supply of air to and exhaust of air from the chamber. The valve assembly, which may be removed from the tool after removal of cap 16, gasket 72 and pin 109, comprises a sleeve 104, a first member 114 movable in the sleeve between a first or normal position in which the port 116 is blocked and the chamber communicates with a vent passage 112 via bore 160 and ports 172, and a second position (as shown) in which the port is open. In the second position a sealing ring 162 on a second member 134 of the valve assembly engages a seat 164 to block communication between the bore 160 and the vent passage. The first member is maintained in its first position by pressure air acting on its lower surface 120, communication between the reservoir and the surface 120 being by way of duct 124, ports 136, bore 138 and a passage between ball 140 and upper seat 142. Upon actuation of trigger 152 the ball 140 is raised against bias of spring 170 to abut against the upper seat 142 thus terminating communication between the reservoir and the surface 120 and communicating the surface with atmosphere via passage between the ball and lower seat 156. The first member will thus be moved to the illustrated position against bias of spring 121. When the port 116 is opened pressure air can pass to chamber 80 and therefrom via a one way valve formed by annular ring 94 directly into annular chamber 50, and chamber 54. When the trigger is released, the first member 114 returns to its first position and thus the space above the piston is vented. Pressure air in chambers 50, 54 will then return the piston to its initial position. When the initial position is attained, i.e. when annular ring 62 is positioned above shoulder 69, air in the chamber 54 can be vented via bores 68, 66 and past the annular ring 62 which is expanded by the air.