Fastener driving device having full cycle valve

A pneumatically operated fastener driving device comprising:

• a housing assembly including a cylinder therein, said housing assembly defining a fastener drive track,
• a drive piston slidably sealingly mounted in said cylinder for movement through an operative cycle including a drive stroke and a return stroke,
• a fastener driving element operatively connected to said piston and mounted in said fastener drive track for movement therein through a drive stroke in response to the drive stroke of the piston and a return stroke in response to the return stroke of the piston,
• a fastener magazine assembly carried by said housing assembly for feeding successive fasteners laterally into the drive track to be driven therefrom by said fastener driving element during the drive stroke thereof,
• a piston chamber defined at one end of said cylinder and communicating with said drive piston,
• an air pressure reservoir communicating with said piston chamber,
• an exhaust path defined in said housing assembly communicating the piston chamber with the atmosphere when the exhaust path is in an opened condition,
• a pilot pressure operated main valve movable from a normally closed position into an opened position closing the exhaust path and allowing a supply of air under pressure from the air pressure reservoir to be communicated with the piston chamber to initiate and effect the movement of the piston and fastener driving element through the fastener drive stroke thereof, said main valve having a first pressure responsive surface defining with a portion of said housing assembly a pilot pressure chamber, and a second pressure responsive surface in opposing relation to said first pressure responsive surface, said second pressure responsive surface being exposed to the supply of air under pressure,
• a feed orifice communicating the air pressure reservoir with the pilot pressure chamber,
• an actuator mounted for movement with respect to an exhaust port for controlling pressure in the pilot pressure chamber, said actuator being (1) normally disposed in an inoperative position closing the exhaust port such that pressure within said air pressure reservoir may communicate with said pilot pressure chamber as pilot pressure therein, and (2) movable in response to a manual actuating procedure into an operating position opening the exhaust port and exhausting the pilot pressure in said pilot pressure chamber through the exhaust port to atmosphere,
• a trigger member mounted with respect to said housing assembly for manual movement from a normal inoperative position to an operative position for moving the actuator to its operating position,
• first passage structure between the pilot pressure chamber and the exhaust port,
• a pressure responsive secondary valve member movable between a normally opened position and a closed position,
• second passage structure communicating said piston chamber with said secondary valve member, said second passage structure communicating with said exhaust path when said exhaust path is in the opened condition, said secondary valve member being mounted with respect to said first passage structure so as to be movable between an opened position biased by said air under pressure via said first passage structure permitting communication between said pilot pressure chamber and said exhaust port, and a closed position biased by air over the drive piston communicated from said piston chamber via said second passage structure preventing communication between said pilot pressure chamber and said exhaust port,
• an operative cycle being initiated upon movement of said trigger member to its operative position which moves said actuator to its operating position exhausting pilot pressure in said pilot pressure chamber through said exhaust port and causing said main valve to move to its opened position thereby initiating the fastener drive stroke, pressure over said drive piston in said piston chamber and said second passage structure communicating with said secondary valve member to move said secondary valve member from the opened position thereof to the closed position thereof causing said main valve to move to its closed position thereby completing one said operative cycle while said trigger member remains in the operative position thereof,
• said secondary valve member being constructed and arranged to return to the opened position thereof when said trigger member is permitted to move to the normal inoperative position thereof.