Importance

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Abstract

A packerfoot includes a bladder assembly comprising an elongated generally tubular inflatable bladder having ends bonded to generally rigid bladder attachment portions. The bladder includes end portions bonded to the bladder attachment portions and a central inflatable portion. The bladder comprises multiple layers of rubber, one or more of which are reinforced by fibers, preferably S-glass. At each end of the bladder, the layers terminate at different longitudinal positions, forming annular steps on the exterior surface of the bladder. Conforming annular steps are formed on the interior surface of the bladder attachment portions. The bladder ends are bonded to the bladder attachment portions such that the annular steps of the bladder conform to the annular steps of the bladder attachment portions. The total bond length of the bladder to the bladder attachment portions is greater than or equal to twice the length of the inflatable portion of the bladder. The ratio of the bond length at each end of the bladder to the thickness of the fiber-reinforced portion of the bladder is greater than 25, and preferably greater than 50. A plurality of toes is retained on the exterior of the bladder by retaining rings that enclose the ends of the toes. Compressible strain-relief rings are positioned between the retaining rings and the ends of the toes to reduce stress concentrations in the bladder caused by the toe ends during inflation of the bladder.

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First Claim