| 摘要 |
A pneumatically operated fastener driving device includes a pilot pressure operated main valve movable from a normally closed position into an opened position 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. An operative cycle is initiated upon exhausting pilot pressure in the pilot pressure chamber causing the main valve to move to its opened position thereby initiating the fastener drive stroke. 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 is constructed and arranged to move in response to changes in pressure occurring in the piston chamber to cause the main valve to reciprocate thereby causing the drive piston to move through repeated operating cycles as long as the trigger member is in its operative position.
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