GB1373178A - Expansible mandrels for use in driving or withdrawing tubular piles - Google Patents

Abstract

1373178 Pile driving mandrels C L GUILD and W B GOODMAN 10 Jan 1972 1219/72 Heading E1H An expansible pile driving or extracting mandrel includes opposed arcuate ribbed sections 10 interconnected by an upper driving head 11, biasing means urging the sections together into a pile entering position and means for forcing the sections apart into a pile gripping position. The latter means comprises groups of sheaves 44, 45, alternate sheaves being mounted on one or other of the mandrel sections, and anchored cables, chains or the like 43 trained over the sheaves 44, 45 and passing round upper travelling sheaves 37, so that on movement of sheaves 37, derived from a fluid pressure actuator 27, in a direction to tighten the cables 43, the groups of sheaves 44, 45 and so the mandrel sections to which they are secured, are forced apart. The biasing means urging the sections together comprise wedge shaped shims 17 clamped between the upper flanged ends 14 of the arcuate sections and the driving head 11. Further biasing means in the form of spring loaded bolts 56, Fig. 6, may also be provided. Alternatively (Fig. 8 not shown) the further biasing means may comprise cable runs trained about the sheaves in an opposed way to the runs of the first mentioned cable, a tightening of these cable runs pulling the groups of sheaves and so the mandrel sections together. In a further modification (Fig. 9 not shown) a plurality of the means for forcing the sections into the pile gripping position are provided at spaced intervals along the mandrel, the means operating sequentially from the bottom end upwards. In this case the further biasing means are provided by pivoted lever systems (66-68).