GB728211A - An improved expansible mandrel for sinking tubes into the ground - Google Patents

Abstract

728,211. Piles. FRANKI FOUNDATION CO. Dec. 30, 1953, No. 36162/53. Class 68(2) In an expansible mandrel for driving sheet metal tubes into the ground, having a central member 12 and sectors 3 in which pneumatically controlled expansion chambers provide a radial thrust to support the tubes during driving, a separate set of pneumatic chambers is provided for the contraction of the mandrel. Preferably, each chamber is a longitudinally extending rubber pipe, each pipe 19 of one set being in radial alignment with a pipe 18 of the other set. The pipes are closed at their lower ends, and the admission of fluid under pressure to pipes 19 forces the arms 17 and 11 apart, contracts the mandrel, and flattens pipes 18 against their resilient tendency to assume a circular form. On inflating pipes 18, pipes 19 offer no resistance to flattening and the sectors 3 are guided radially outwards by arms 9. Upper casing 6 is attached by bolts 7 which allow for the radial movement of the sectors 3, and is provided with a wooden block 24 to receive hammer blows. These are transmitted to the central member 12 through resilient washer 15. Lugs 25 are provided for the with-, drawal of the mandrel, after which the tube 1 which may be conical or have a smooth wall, is filled with concrete or like. The lower end of the tube may be covered by a plate 2 of metal or concrete or may be sealed with a plug of concrete.