Patent GB-1305222-A (GB)
IPC: B25C1/04
Filed: 1970-02-03
Abstract: 1305222 Fastener driving tools JOH FRIEDRICH BEHRENS 3 Feb 1970 [19 Feb 1969] 4994/70 Heading B4C A pneumatically actuated fastener driving tool comprises a valve arrangement for providing "single" or "auto" fire, a chamber 30 for compressed air, a vent pipe 17, a working cylinder 2, a working piston 5 and a permanent magnet 7 for retaining the piston in an initial or starting position.  The valve arrangement comprises a body 11, a guiding sleeve 14, a slidable differential piston type main control valve 25 carrying a valve member 28, a slidable differential piston type auxiliary control valve 42, a trigger actuable valve 53, and a control sleeve 65 for selecting "single" or "auto" fire. In the position of Fig. 1 with the sleeve 65 set for "auto" fire, passage 29 communicates with the vent pipe 17 via annular passage 20, chamber 19, port 16 and annular chamber 84, and chamber 37 communicates with compressed air chamber 30 via bore 39, annular groove 93 and bore 48 to maintain valve member 28 against seat 86. When the trigger 50 is actuated the valve 53 is raised to permit compressed air to pass via channel 64 into chamber 55 to move the valve 42 to the position of Fig. 2. The chamber 37 now communicates via annular chamber 92 and vent passage 49 with atmosphere, and the valve 25 is forced downwardly to the position of Fig. 2 to open communication between the chamber 30 and the working cylinder. The piston will thus be moved on a working stroke. With the valve 25 in the position of Fig. 2 air will pass via passage 22 into a chamber 70 and thence via bore 71 into a chamber 47. Differential pressure on the valve 42 will cause that valve to automatically move downwardly, i.e. to position of Fig. 1, to open the chamber 37 to air supply chamber 30 so that the valve member 28 may move upwardly to its Fig. 1 position to open the working cylinder to atmosphere. The piston will thus move on a return stroke. As the valve 25 is moved upwardly the chamber 47 will via bore 71, chamber 70, and passage and annular space 20 communicate with vent pipe 17. Venting of the chamber 47 is delayed until the piston has returned to its initial position by air from the cylinder passing through the annular space 20. When the chamber 47 is vented the valve 42 will again be moved to the position of Fig. 2 and the cycle of operations will be repeated for as long as the trigger is actuated. By selective throttling of the passage 22 by a sealing ring 68 carried by the control sleeve 65, the speed of operation of the tool can be varied. Blocking of the passage 22 by the sealing ring 68 will condition the tool for "single" fire. With the passage 22 blocked and the trigger not actuated, the chamber 55 communicates with atmosphere via bore 98 and the valve 42 is in its lowermost position in which air passes from the chamber 30 into chamber 37 to maintain the valve member 28 against its seat 86. Actuation of the trigger will raise the valve 53 so that air from the chamber 30 may pass into the chamber 55 so as to raise the valve 42 and connect the chamber 37 to atmosphere so that the valve 25 will be forced downwardly to open chamber 30 to the working cylinder and close communication between the cylinder and the vent pipe 17. The piston will perform a working stroke. The piston return stroke will only be initiated when the trigger is released.