GB1172224A - Improvements relating to Pneumatic Devices for Driving Fasteners or like purposes - Google Patents

Abstract

1,172,224. Fastener driving tools. GASTON E. MARBAIX Ltd. 29 Dec., 1966 [29 Dec., 1965], No. 55142/65. Heading B4C. A pneumatically-actuated fastener driving tool comprises a piston 7 reciprooable in a cylinder 5 which is mounted in a housing 1, the open ends of the cylinder being controlled by first and second main valves 10 and 14. The main valve 10 is in the form of a differential piston slidable in bores 3, 4 formed in a cap 3 and the body 1, a sealing ring lOC being fitted in the valve for engagement with the end of the cylinder; a piston-actuated exhaust valve 11 is located in the valve 10. The main valve 14 is provided with an opening 14H through which a driving blade 8 moves, a groove 8A being formed in the blade for controlling a ball valve 16 located in the main valve 14. In operation, with the tool in the position shown in Fig. 1, air from a chamber 2A flows through a triggeroperated valve 21, passages 21B, a chamber 15, passage 1A and a chamber 13A to maintain both main valves in contact with the ends of the cylinder. Due to the pressure in the chamber I3A, the valve 11 is opened so that the air above the piston is exhausted. Upon actuation of the valve 21, the air pressure is cut-off from the chambers 13A, 15 so that the main valves move away from the ends of the cylinder thereby allowing air to act on the driving piston 7. At the start of its downward stroke, the ball valve 16 is opened thereby allowing the air below the piston to be initially exhausted through passages 14K, 14J, chamber 15, passage 21B, valve 21 and passage 23. When the valve 14 drops the remaining air is exhausted through ports and an annular groove 14L in the valve 14 and ports 1B in the body 1. In the modification shown in Fig. 6, the trigger-operated valve 35 is adapted to control the air in chambers 13A, 15 and is arranged to operate in conjunction with a valve 37A in order to exhaust the pressure in the chamber 13A, the valve 37A having to be opened by pressure on the workpiece before the tool can be fired; the ball valve 16 is replaced by a valve 30 movable in the main valve 10 and body 13. The piston 7 may be retained in its raised position by means of a magnet (40, Fig. 4) or by a spring- clip and detent device and a resilient buffer ring 14C provided; alternatively, the buffer ring may be dispensed with and the valve 14 itself made of a resilient material (Fig. 8). In the further embodiment shown in Fig. 13, the main valve 206 is of annular form and is slidable on a boss 201 formed on a cylinder cap 200 secured to the body 101. The control of the exhaust above and below the drive piston 108 is controlled by means of a valve 203 in the boss 201. The lower main valve 128 is urged away from its seat by means of small pistons 130.