High speed riveting system

In a gun for upsetting the shank terminal of metallic rivet projecting through work, the rivet also having a head spaced from said terminal, the combination comprising

• a. structure including a plunger to be driven forwardly for transmitting upsetting force to be delivered to said terminal,
• b. means including a piston to drive the plunger forwardly after back-up force is applied to the rivet head,
• c. a chamber to store working fluid pressure, a control valve, and a trigger actuated valve for releasing the passage of control fluid pressure to operate the control valve for releasing working fluid pressure to actuate the piston,
• d. said structure including a forwardly extending tubular barrel, and an anvil element carried by and movable relative to the barrel between the plunger and rivet terminal to receive said upsetting force and to transmit same to the rivet terminal, there being a spring urging the anvil element forwardly relative to the plunger, the anvil extending in front of the plunger, the anvil element having generally frusto-conical recess means to receive and confine the tip of the rivet terminal during upset formation, said recess means including first and second conical recesses, the first recess located between the second recess and the forward end of the anvil, the first and second recesses defining respective generally conical angles .alpha. and .beta., and wherein .alpha. is substantially greater than .beta..