Abstract: An improved shiftable clamp (12) adapted for connection to a fixture (10) is provided, wherein the clamp (12) is selectively operable to engage and hold a workpiece (14) to the fixture (10). The clamp (12) includes a tubular body (22) and a piston (24) telescopically received within the body (22). Movement of the piston (24) is guided and controlled by way of a cam assembly (26) including a cam track (64) formed in the piston (24) and an associated cam track follower ball (66) mounted on the body (22). A spring unit (74) is also provided on the body (22) and includes a spring (82, 96) serving to self-center and bias the ball (66) into the track (64). This insures that the ball (66) smoothly rotates during movement of piston (22) and reduces wear and premature clamp failure.

Abstract: An improved shiftable clamp (12) adapted for connection to a fixture (10) is provided, wherein the clamp (12) is selectively operable to engage and hold a workpiece (14) to the fixture (10). The clamp (12) includes a tubular body (22) and a piston (24) telescopically received within the body (22). Movement of the piston (24) is guided and controlled by way of a cam assembly (26) including a cam track (64) formed in the piston (24) and an associated cam track follower ball (66) mounted on the body (22). A spring unit (74) is also provided on the body (22) and includes a spring (82, 96) serving to self-center and bias the ball (66) into the track (64). This insures that the ball (66) smoothly rotates during movement of piston (22) and reduces wear and premature clamp failure.

Abstract: A retract clamp (20) utilizes three clamp arm retraction enhancement mechanisms (26, 28, 63) to increase clamp arm (24) retraction consistency. The first retraction enhancement mechanism (26) is a bifurcated piston having a first piston member (68) and a second piston member (70). If the first piston member (68) becomes tilted and caught, the second piston member (70) continues to move allowing the first piston member (68) to right itself. The second retraction enhancement mechanism (28) comprises a clamp arm guide mechanism having a base (82), a pusher (84), and a plurality of resilient members (110-124) interposed between the base (82) and the pusher (84) to bias the pusher (84) against the clamp arm (24) and align the clamp arm (24) with a clamp arm receiving area (40) defined in a clamp arm holder (22). The third clamp arm retraction enhancement mechanism comprises a lift surface (63) on the clamp arm (24).

Abstract: A valve, having provision for replacing stem packing while the valve is under pressure, has a valve body with a flow passageway through it, a gate that is vertically positioned to open and close the passageway, a stem extending upwardly from the valve body, the lower end being attached to the gate, a bonnet secured to the valve body by which the valve body open top is closed, the stem extending through an opening in the bonnet, a packing box slidably positioned in an opening in the top of the bonnet and receiving the stem, a back seat ring is positioned within the opening of the bonnet below the packing box and having a circumferential sealing surface surrounding the valve stem, the valve stem having an integral enlarged diameter shoulder so that when the stem is in the full upward position the packing box can be moved downwardly in the direction towards valve body forcing the back seat ring sealing surface to seal against the stem shoulder formed on the valve stem to permit packing retained within the packin