Importance

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Abstract

A pneumatic press assembly 10 uses air pressure to power a piston 70 in a cylinder 52 through a power stroke. Springs 76, 78, 80, 82, 84, and 86 oppose the motion of the piston 70. A set of return springs (76 and 78) is effective over the entire stroke of the piston. The return springs are compactly mounted within the cylinder 52 between the bottom of the piston 70 and a shoulder 56 which extends radially inwardly from the cylinder wall. The shoulder also cooperates with a central portion 110 of the piston 70 to prevent rotation of the piston. A second set of springs (80, 82, 84, and 86) is effective only when the piston 70 is within a predetermined distance from the bottom of the power stroke. The second set of springs 80, 82, 84 and 86 is disposed between the bottom 230 of the cylinder 52 and a preload member 234. When the piston 70 approaches the bottom of its stroke, it contacts the preload member 234 which in turn compresses the springs 80, 82, 84, and 86 bringing the piston to a halt. These springs then expand, accelerating the piston 70 to a relatively high speed during an initial portion of the return stroke. During the initial portion of the return stroke, air displaced by the piston is permitted to escape freely from the cylinder. During a subsequent portion of the return stroke, the air displaced by the piston is forced through a restricted flow path to dissipate the kinetic energy of the piston. In addition, a spring loaded bumper is provided which contacts the piston at the end of the return stroke to cushion impact between the piston and the cylinder head.

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First Claim