GB1281262A - Pneumatically powered fastener driving device - Google Patents

Abstract

1281262 Fastener driving devices J M REICH 20 March 1970 [21 March 1969] 13600/70 Heading B4C A fastener driving tool having a fastener driving means (not shown) includes a control valve for controlling supply of air to the driving means, and a trigger 35 and a workpiece sensor 40 which must both be moved to their operative positions to effect movement of a member 27, (103) of the valve against a restoring force from an inoperative position to an operative position, the valve including means for delaying return of the member to its inoperative position when the trigger and/or sensor have been returned to their inoperative positions. When the member is in the inoperative position air passes via the control valve and passage 23 to a main valve for the driving means to maintain the main valve in a first position thus preventing actuation of the driving means, and when the member is in the operative position air is vented from the main valve via the control valve, thus the main valve moves to a second position to permit driving of a fastener by the driving means. As illustrated (Figs. 1 and 6) when the member 27 is in its inoperative position (Fig. 6) air is supplied to the main valve via port 66, bores 62, chamber 77 and passage 23. Also air is supplied via restricted bores 76 in a piston 73 carried by the member 27 to a chamber 75. Depression of the trigger 35 and movement of the workpiece sensor effects movement of the member 27 via a pivoted lever 29 to its operative position (Fig. 7) in which position the port 66 is closed by piston 80 carried by the member 27 and passage 23 is vented via bores 79, 78 in the member 27. The main valve thus moves to its second position to permit the driving means to be operated to drive a fastener. When the trigger is released or the sensor no longer contacts a workpiece, return of the member 27 to its inoperative position will be delayed by air in chamber 75 acting on the lower face of piston 77 overcoming pressure on the upper face of the piston 77 and on the upper face of the piston 80. When the pressure in chamber 75 drops to a certain level by bleeding via bores 76, return of the member 27 to its inoperative position will occur. In the embodiment of Fig. 8 the movable member 103 carries a piston 137 provided with restricted bores 142 and a sealing ring 138, and a second piston 150 is movably mounted on the member and is provided with a surface 160 which co-acts with a surface 148 on the member to open or close access between an air reservoir 21 and the passage 23 via bores 116, 159 and 118. In the inoperative position of the member 103 as shown in Fig. 8, air passes to the passage 23 and also via bores 147 and 146 enters a space above the piston 137. Air thus enters space 140 via bores 142 and around the periphery of the piston. Movement of the member towards its operative position effects first sealing of ring 138 with cylinder surface 109, and then contact of surfaces 148, 160 to close access between the reservoir and the passage 23 and opening of a vent valve comprised by sealing ring 119 and surface 155 of the second piston. The passage 23 is thus vented via vent opening 122. Return of the member 103 to its inoperative position is delayed in a manner similar to that previously described. An adjustable stop 38 limits pivotal movement of the trigger.