Pneumatically actuated fastener driving device with improved piston return air system

Claim 1

A fastener driving device comprising a housing, means within said housing defining a reservoir for receiving and containing fluid under pressure supplied thereto from a source of fluid under pressure, means within said housing defining a cylindrical drive chamber having one end arranged for communication with said reservoir, a piston mounted within said drive chamber for movement from a first position adjacent said one drive chamber end through a drive stroke into a second position adjacent the opposite end of said drive chamber and from said second position through a return stroke into said first position, means carried by said housing defining a drive track, means carried by said housing for receiving a supply of fasteners and for feeding successive fasteners from said supply laterally into said drive track, a fastener driving element slidably mounted within said drive track and operatively connected with said piston for movement thereby through a drive stroke in response to the drive stroke of said piston to drive a fastener in said drive track outwardly into a workpiece and through a return stroke in response to the return stroke of said piston, main valve means movable between a first position communicating said one drive chamber end with the atmosphere and preventing communication between said one drive chamber end and said reservoir and a second position communicating said one drive chamber end with said reservoir and preventing communication of said one drive chamber end with the atmosphere so that said piston and fastener driving element will be moved through the drive stroke thereof in response to the movement of said main valve means into said second position and through the return stroke thereof in responSe to the movement of said main valve means into said first position, means within said housing defining a pilot pressure chamber pneumatically operatively connected with said main valve means for effecting movement of said main valve means into said first position and in response to the communication of pilot pressure therein and for effecting movement of said main valve means into said second position in response to the exhaust of pilot pressure therefrom, means defining an exhaust outlet for said pilot pressure chamber, manually operable valve means mounted for movement between a normally closed position preventing communication of said pilot pressure chamber with said exhaust outlet and a manually actuated opened position communicating said pilot pressure chamber with said exhaust outlet to thereby exhaust said pilot pressure chamber to atmosphere so as to effect movement of said main valve means into said second position and hence said piston through said drive stroke in response to the movement of said manually operable valve means into said opened position, means within said housing defining a return air plenum chamber, means establishing communication between the pressure air within said one drive chamber end acting on said piston to effect the drive stroke of the latter and said plenum chamber when said piston reaches the end of said drive stroke and for communicating the plenum chamber with the opposite end of said drive chamber so that the air under pressure in said plenum chamber can effect the return stroke of said piston when said main valve means is moved into said first position, means defining a flow path for air under pressure from said plenum chamber to said pilot chamber operable when said manually controlled valve means is moved into said closed position to establish a pilot pressure in said pilot chamber sufficient to effect movement of said main valve means into said first position and hence said piston through said return stroke only after said plenum chamber has received sufficient air under pressure to insure completion of said piston return stroke and said manually controlled valve means has been moved into said closed position, means for dissipating the air under pressure within the opposite end of said drive chamber and said plenum chamber to atmospheric pressure in conjunction with the completion of said piston return stroke, and means in said flow path for preventing flow of air under pressure from said pilot chamber into said plenum chamber so as to prevent exhaust of the air under pressure within said pilot chamber through said plenum chamber and to permit such exhaust solely through said exhaust outlet in response to a subsequent manual movement of said manually controlled valve means into said opened position.