Pneumatic stapler device

Claim 1

In a pneumatically operated stapler device having a body with a compressed air reservoir, a working cylinder, and a working piston and staple drive reciprocably disposed in said cylinder and adapted to be driven in a working stroke from an initial position to a terminal position in said cylinder; the improvement which comprises the combination of: an air chamber adjacent said cylinder, said cylinder having a wall with first port means for admitting compressed air from said cylinder to said chamber after completion of said working stroke and second port means for admitting compressed air from said chamber to said cylinder for returning said working piston from said terminal position to said initial position; control valve means regulating the passage of compressed air from said reservoir to said cylinder and the venting of air from said cylinder, said control valve means being manually operable for initiating operation of the device; air passage means communicating between said chamber and said control valve means; auxiliary valve means interposed in said air passage means and comprising a valve housing, a valve piston movably disposed in said valve housing, spring means acting on one side of said valve piston, and adjustable means for regulating the spring force, and said valve housing having port means for subjecting the opposite side of said valve piston to the air pressure in said chamber so as to admit compressed air from said chamber to said control valve means for actuating the latter when the air pressure in said chamber overcomes the force of said spring, whereby to obtain automatic repetitive operation of the device, and said valve piston being nonresponsive to the air pressure in said chamber in one position of said adjustable means for obtaining nonautomatic operation of the device.