Abstract: A tapered mould consisting essentially of a rigid outer frame formed of a set of radially arranged longitudinally extending guide members and a set of axially spaced encircling rings, and a gapped frustoconical tubular casing of resilient sheet material having a set of longitudinal stiffening members arranged thereon for sliding engagement with the respective guide members. The gap in the wall of the tubular casing, extending along a longitudinal line on the periphery of the casing, is opened and closed automatically as the tubular casing inserted in the outer frame is moved axially in opposite directions. Labor - consuming bolt - clamping and releasing operation is completely eliminated and the mould operation can be mechanized with ease, as desired. Packing means interposed between a pair of stiffening members arranged on the opposite sides of the gap further ensures leak - proof gap closing.

Abstract: Labor-consuming bolting operation as required with conventional forms of the gapped or split type has been ingeniously expelled by the provision of a form structure comprised essentially of a rigid tubular frame, a resilient gapped tubular casing arranged therein as a form in which concrete is to be placed, and camming means arranged on the inside of the rigid frame and on the outside of the resilient casing and cooperable to act upon the resilient tubular casing radially and circumferentially thereof with axial movement of such resilient casing relative to the rigid frame so as to close the gap in the resilient casing while holding the latter in coaxial relation to the rigid frame, any loss of moisture content of concrete during centrifugal forming operation can be effectively prevented by arranging an appropriate packing element on the resilient casing along the gap therein.

Abstract: This invention relates to prestressed concrete piles, poles or the like pillers covered with an outer shell of steel pipe on a circumferential surface of a cylinderical prestressed concrete tube or a piller shaped prestressed concrete pole at least one end of said steel pipe being in an independent state to the concrete article. The invention provides the joint effects of the good compressive strength of the said prestressed concrete tube or pole and the good bending strength and a small frictional surface resistance of the steel pipe. One of the advantages of providing the steel pipe as the outer shell of the said prestressed concrete tube or pole relates to increasing the compressive strength of the said concrete tube or pole by preventing the generation of lateral stress within the said concrete tube or pole in a radial direction.