GB1302728A - - Google Patents

Abstract

1302728 Fastener driving tools FASTENER CORP 22 June 1970 [30 June 1969] 30240/70 Heading B4C A fluid actuated fastener driving tool 10 comprises a housing 12, a reservoir 16, e.g. for compressed air, a cylinder 18 having a reciprocable piston 26 bearing driving means 28 for staples 34 &c., a resilient bumper 74, a control valve assembly 22 for governing piston movement, and means for inactivating the control assembly 22 in the event of deterioration of the bumper 74. In inactive condition, air from the reservoir 16 acts around the lower edge of a valve ring 40, being balanced by pressure acting on an upper surface through a passage 48. On actuating the valve 22 the passage 48 is connected to atmosphere, the ring 40 rising under the reservoir pressure out of sealing relationship with an upper end 18a of the cylinder 18, so that pressure enters the cylinder 18 to actuate the piston and the driving means 28. At the end of the stroke, the piston 26 engages the bumper 74, a piston passage 70 aligning with an inlet port 62 of a return chamber 60 so that pressure enters the chamber 60, Fig. 2 (not shown). Release of the valve 22 restores pressure to the passage 48, the ring 40 being urged into sealing relationship with the piston end 18a, while disengagement of a lip 40a of the ring 40 from a resilient valve element 52 connects the upper end of the piston 26 to atmosphere through passages 58. Pressure from the chamber 60 then acts through ports 64 to return the piston to its upper position. In the event of deteri oration of the bumper 74, the end of the piston stroke falls at a lower level, the ports 62 then opening into the cylinder 18 above the level of the piston 26, Fig. 3 (not shown). On releasing the valve 22, pressure in the chamber 60 exhausts to atmosphere directly through the ports 62, so that the piston 26 fails to rise to its upper position.