Fastener driving device having full cycle valve

Abstract

A pneumatically operated fastener driving device includes a pilot pressure operated main valve movable from a normally closed position into an opened position closing an exhaust path and allowing a supply of air under pressure to be communicated with a piston chamber to initiate and effect the movement of a piston and fastener driving element through a fastener drive stroke. First passage structure is provided between a pilot pressure chamber and an exhaust port. A secondary valve member is mounted with respect to the first passage structure so as to be movable between an opened position permitting communication between the pilot pressure chamber and the exhaust port and a closed position preventing communication between the pilot pressure chamber and the exhaust port. Second passage structure communicates the piston chamber with the secondary valve member and with the exhaust path. Pressure over the drive piston in the piston chamber communicates with the secondary valve member to move the secondary valve member to its closed position preventing communication between the pilot pressure chamber and the exhaust port thereby causing the main valve to move to its closed position. The secondary valve member permits one full cycle of operation to be performed while the trigger member remains actuated thereby minimizing exposure of the fastener driving element and thus, damage thereto.