GB1170675A - Compressed Air-Operated Apparatus for Driving Fasteners - Google Patents

Abstract

1,170,675. Nailing and stapling tools. J. F. BEHRENS, [trading as JOH. FRIEDRICH BEHRENS METALLWAREN - FABRIK]. 3 March, 1967 [11 March, 1966], No. 10127/67. Heading B4C. [Also in Division F2] A pneumatically-actuated tool for driving fasteners, such as nails or staples, comprises a driving piston 14 reciprocable in a cylinder 3 and a valve 34 adapted to control the admission and exhaust of air from the cylinder, the valve having a piston 38 movable in a chamber 59 to which compressed air is fed under the control of a second control piston 60 actuated by means of a trigger. The valve 34 is slidable over a fixed hollow stem (54, Fig. 2) having a flange 56 formed with a slot 58 communicating with a vent passage (71) via a slot (68) in a sealing disc (67). The disc rests on the head (66) of a rod 65 connected to the second control piston 60. In operation, with the tool in the position shown, compressed air fed to a reservoir 30 flows via a passage 53 in the valve 34, the hollow stem (54) and slot 58 into the chamber 59 thereby acting on the piston 38 to maintain the valve 34 closed; in this position of the valve air above the driving piston 14 is exhausted via a passage 26, ports (45, Fig. 3) and a passage 31 and, air below the driving piston is exhausted through a slot 8a in a resilient buffer 8. Upon actuation of the trigger, the rod is raised so that the disc (67) closes the hollow stem to cut-off the supply of air to the chamber 59 and open the latter to atmosphere via the slots 58, (68) and passage (71). The air now flows through passage 26 to act on the driving piston. When the piston contacts the buffer the slot 8a is closed and, due to a small clearance around the driving piston and a groove 16 therein, air flow through a port 22 into a chamber 21; instead of the air flowing through the clearance around the piston, the latter may be a close fit and a hole (18) provided in the cylinder wall, the size of the hole being controlled by a tapered screw or on O ring (19) compressed by a screw (20). From this chamber, the air passes into a chamber 63 via passage 75, 73, thereby moving the piston 60 downwardly so that the sealing disc (67) opens the stem (54) and causes the vent passage (71) to be closed and air to, again, be fed into the chamber 59 to close the valve 34; the speed at which the piston 60 is moved is determined by the setting of a throttle valve (81), (82). In a modification, instead of the piston 60 being moved initially by means of the rod 65, the latter is replaced by means of a ball-valve, in the piston 60.