Patent GB-1284002-A (GB)
Title: Fastener driving device
IPC: B25C1/00
Filed: 1970-02-19
Abstract: 1284002 Fastener driving devices TEXTRON Inc 19 Feb 1970 [22 July 1969] 8068/70 Heading B4C An"auto -fire'' fluid pressure operated fastener driving device comprises a piston 38 having a fastener driving element 20 reciprocable in a cylinder 32, a control valve member 76 for permitting connection between the upper end of the cylinder on the one hand and a fluid pressure reservoir 26 or atmosphere on the other, a pilot valve member 92 movable to an operative position only upon actuation of a trigger 198 and upward movement of a motion transmitting member 234 in response to the device being pressed against a workpiece, and an "auto-fire" valve 108. The "auto-fire" valve includes a diaphragm 128, and a fixed plate 130 having an aperture 140 therein which communicates via passageways (not shown) and bores 110, 102, with pilot chamber 90. Chamber 126 communicates via a needle valve 196 (Fig. 3) and bores 182, 184, 186 and 188 with a piston return chamber 158. A work engaging member 210 is connected by a spring 232 to the motion transmitting member 234 which is urged to its inoperative position by a spring 252. The spring 232 is such that a slight recoil of the device is permitted without the motion transmitting member 234 moving from its operative position (Fig. 2). In the inoperative condition of the device spring 94 and fluid pressure acting on the valve member 76 will maintain the latter and the pilot valve member 92 in the positions of Fig. 1. Fluid within the pilot chamber 90 will be at the same pressure as that in the reservoir due to the communicating port 96. The upper end of the cylinder 32 is open to atmosphere via passage 72, port 74 and outlets in cap 156, and the return chamber 158 (and thus the chamber 126) and the lower end of the cylinder are open to atmosphere via passageways 174, and 179. Upon actuation of the trigger and presentation of the device to the workpiece, the pilot valve member 92 will be moved to the Fig. 2 position to permit fluid pressure to pass to the aperture 140. The diaphragm 128 will then be displaced to permit the fluid to pass to atmosphere via bore 148 and passageways 150, 152 and the outlets in the cap 156. The port 96 is such that reservoir fluid cannot immediately replenish fluid exhausted from the pilot chamber 90, and thus the pressure differential acting on the control valve member 76 will now urge the latter downwardly (Fig. 2). Fluid will now pass into the upper part of the cylinder 32 to drive the piston to its driven position in which it abuts a buffer 172 and closes exhaust passageways 174, 179. Fluid now passes into the return chamber 158 (and thus into chamber 126) via a port 180 to bias diaphragm 128 downwardly to prevent escape of fluid from the aperture 140 to exhaust, so that the pilot chamber 90 can be replenished with fluid from the reservoir via the port 96. When the pressure in the pilot chamber 90 reaches a certain value the control valve member 76 will be returned to its upper position (Fig. 1) and the cylinder space above the piston 38 will be opened to atmosphere. The fluid pressure in the return chamber 158 will now act on the lower surface of piston 38 and return it to its firing position (Fig. 1). As soon as the piston return is commenced the exhaust passageways 174, 179 will be opened to permit exhaust of  the return chamber 158 and thus of the chamber 126, exhaust of the latter being controlled by the needle valve 196. When the pressure in the chamber 126 drops to a certain value fluid will again escape from the aperture 140 to exhaust and a further cycle will be initiated. The fasteners may be nails (as shown), pins or staples.