GB1080657A - Improvements in or relating to pneumatically operated percussion driving tools - Google Patents

Abstract

1,080,657. Nailing and stapling. JOH. FRIEDRICH BEHRENS. Dec. 24, 1965 [Dec. 28, 1964], No. 54818/65. Heading B4C. A pneumatically-operated percussion tool for driving fasteners, such as nails or staples 15, comprises a driving piston 80, reciprocable in a cylinder 30 which is displaceably mounted in a casing 20, inlet openings 37 being provided in the cylinder wall for pressurized air under the control of a piston valve 40 mechanically coupled to the cylinder. The cylinder 30 is formed with a flange 43 slidable in a chamber 44 and provided with a seal 45 adapted to contact the upper edge of the casing part in which the cylinder moves. A control piston insert 41 is movable within the flange 43 and is formed with an extension 42 arranged to abut a seal 55 in a head portion 11 of the easing. In operation, with the tool in the position shown, air is fed from a reservoir 13 through a port 116, passages 105, 109 into the chamber 44 to thereby maintain the flanges 43 and insert 41 in the closed position, air above the piston escaping through a bore 49 in the insert and ports 52 in the head 11. Upon actuating a valve 123, 124, the flow of air to the chamber 44 is prevented, thereby allowing air in a chamber 23 to raise the flange and insert so as to permit the piston to be driven downwardly on its working stroke. During this stroke, air in front of the piston is exhausted via an annular passage 65 and ports 28 in the casing; air is also forced through ports 36 in the cylinder, into a chamber 25. Towards the end of the stroke, the piston strikes a resilient member 60 sealingly held in the cylinder and thereby moves the latter downwardly so that the bottom end of the cylinder closes the outlet ports 28. When a trigger 125 is released the valve 123, 124 is opened and the piston returned by the air compressed in the chamber 25. In order to prevent the tool from being used until it is pressed against a workpiece, a feeler 135 is connected to rod 100 via a lever 132 such that when the tool contacts a workpiece the rod is moved into a position in which a pin 128 on the trigger can enter a recess 104 in the rod. A magnet 47 is mounted on the valve insert 41 in order to retain the piston in its raised position.