Patent GB-1526532-A (GB)
Title: Safety firing control means for a fluid operated tool
IPC: B25C1/00
Filed: 1976-03-11
Abstract: 1526532 Time safety limit for fastener-driver tool SENCO PRODUCTS Inc and HEINRICH BUEHNEN KG 11 March 1976 [12 March 1975] 09769/76 Heading B4C A pneumatically powered fastener driving tool comprises a fastener magazine 11, two separate and independent triggering means 13, 15 shiftable independently and in any order between normal and firing positions, a firing sequence control means 12 requiring both triggering means to be concurrently in their firing positions to actuate the tool and a safety means which imposes a time limit within which both triggering means must achieve their firing positions to activate the tool. Pressurized air from reservoir 8 normally passes through valve 12 to press down firing valve 7. When valve 12 connects the space above firing valve 7 to atmosphere valve 7 lifts, allowing piston 5 to be driven downwards to apply a fastener. The piston is returned by air driven into return reservoir 9. The triggering means comprise finger trigger 13 and a workpiece responsive trip assembly 15, 15a, 15b. In the embodiment of Fig. 2 movement of either triggering means to the firing position raises trigger core 18 to the half stroked position (Fig. 3, not shown) thereby initiating the time limit by allowing compressed air from reservoir 8 to enter reservoir 111a via passage 110 and orifice 117, If the other trigger is moved to its firing position within the time limit trigger core 18 is raised to its fully stroked position (Fig. 4, not shown) in which air from reservoir 8 may pass through ports 49 and 84 to act on the underside of remote core 37 to raise it against the bias of spring 109 to the position of Fig. 5 (not shown). Air from reservoir 8 can no longer reach the space above firing valve 7 via passage 27. Instead the space is vented to atmosphere via passages 72, 69, 67 and 72 to lift valve 7 and drive a fastener. The air forced into return reservoir 9 opens valve (126, Fig. 8, 9, not shown) in passage 120 to vent passages 119, 118 and reservoir 111a and so resets the time limit to zero. Release of the triggers allows the trigger core 18 and remote core 37 to return to their starting positions shown in Fig. 2. If the second trigger is not moved to its firing position within the time limit the pressure in reservoir 111a becomes sufficient to raise valve housing 34 to a position (Fig. 6, not shown) in which reservoir 8 is able to continue pressurizing the space above firing valve 7 even if the second trigger is activated and remote core 37 raised (Fig. 7, not shown). Hence the tool cannot be fired until both triggers are returned to their normal positions and the air in reservoir 111a is vented via the lower annular space between trigger core 18 and trigger core housing 36.  The time limit may be adjusted by varying the size of the orifice. The orifice is formed by a V-shaped notch 117, Fig. 11, which decreases in depth as it extends rearwardly on threaded rod 112a, and threaded bore 110a. The orifice size increases and the rod is withdrawn from the bore. In the embodiment of Fig. 12, not shown, the time limit is adjusted by varying the size of the reservoir. An invariant time limit may be provided by using radial parts 46 or 85, Fig. 2, as the orifice.  In a non-exemplified embodiment the time limit is initiated and reset by the workpiece responsive trip. In the embodiment of Fig. 14 it is initiated (and reset) by finger trigger 151. On moving finger trigger 151 to the firing position (Fig. 16, not shown) valve 210 is opened to allow air from reservoir 8 to flow through metering orifice 231 to act on timing valve 225. After a time determined by the surge of the orifice the pressure in line 228 will be sufficient to move timing valve 225 to the left (Fig. 17, not shown) against the action of spring 226. Air will flow from reservoir 8 via lines 229, 230 to raise valve housing 157 to its lock-out position in which the tool cannot be fired. On returning finger trigger 151 to its normal position O ring 222 of valve 210 will shift out of sealing engagement with interior surface 219 of valve housing 213 causing line 228 to be vented to atmosphere via a bypass valve 233. Timing valve 225 is pushed to the right by spring 226 to vent line 230 and allow housing 157 to descend from its lock-out position. Autofire.-Plug 156, Fig. 17, may be replaced by a valve 234, Fig. 18. In the position shown valve 234 acts as a plug and the tool operates in the single fire mode of the previous examples. If valve 234 is turned so as to connect passages 136 and 119 the tool operates in an autofire mode. Thus if both triggers are activated within the time limit trigger core 160 will rise and cause remote core 161 to rise. The space above firing valve 7, Fig. 1, will be vented to fire the tool. Compressed air from return reservoir 9 will flow via passage 136 to move shuttle valve 236, Fig. 18, to the right. Lines 230b and 230c will be connected, causing valve housing 157 to shift upwards to close firing valve 7. Piston 5 will return, venting return reservoir 9, passage 136, valve 234, passage 119 and lines 230c and 230b so that valve housing 157 will fall. Provided both triggers are still activated the space above firing valve 7 will be vented, the tool fired again and the cycle continued until one of the triggers is deactivated.