Abstract: A breakstem rivet installation tool includes a jaw mechanism (12) for gripping the stem of a rivet, and a pneumatically actuated piston and cylinder device (13) for applying pulling force to the jaw mechanism. It is provided with a damping valve (22) for damping the flow of air from the piston and cylinder device (13) when the force is suddenly released on breaking of a rivet stem (23), thereby to reduce mechanical shock to the tool, and noise of fast-escaping air. The damping valve (22) comprises a resilient steel circular disc (32) which is secured at its center to the apex of a domed member (28) provided with vent holes (26). The undeformed shape of the disc (32) is flat. When, in use of the tool, a rivet stem breaks and the restraining force on the piston (15) is released, the velocity of air flow past the disc (32) urges the disc to bend towards the domed surface of the member (28), thereby restricting the air flow through the vents (26).

Abstract: A hand-held pneumatically-powered breakstem rivet placing tool comprises a pulling head (12) driven by a pneumatic piston and cylinder device (13). The drive is transmitted by way of a chain (15), one end (45) of which is secured to the body (11) of the tool and the other end (49) of which is secured to the piston rod (35) of the pneumatic device. Between its two ends the chain forms a loop which passes over a roller (52) which is connected to the pulling head (12) by way of a link mechanism (54, 58). When the pneumatic device (13) is actuated, the movable end (49) of the chain is pulled down, thus pulling the roller (52) and driving the head (12) to place a rivet. The roller (52) is carried on the top of a plunger (56) which is continuously urged upwards by air pressure in the cylinder (63) in which it slides, thereby to return the mechanism to its original position after a rivet has been placed.

Abstract: A breakstem river installation tool includes a jaw mechanism (12) for gripping the stem of a rivet, and a pneumatically actuated piston and cylinder device (13) for applying pulling force to the jaw mechanism. It is provided with a damping valve (22) for damping the flow of air from the piston and cylinder device (13) when the force is suddenly released on breaking of a rivet stem (23), thereby to reduce mechanical shock to the tool, and noise of fast-escaping air. The damping valve (22) comprises a resilient steel circular disc (32) which is secured at its center to the apex of a domed member (28) provided with vent holes (26). The undeformed shape of the disc (32) is flat. When, in use of the tool, a rivet stem breaks and the restraining force on the piston (15) is released, the velocity of air flow past the disc (32) urges the disc to bend towards the domed surface of the member (28), thereby restricting the air flow through the vents (26).