GB653769A - Improvements in the manufacture of hollow reinforced concrete products - Google Patents

Abstract

653,769. Concrete pipes. FRANJETICH, Z. July 1, 1948, No. 17789. Convention date, July 5, 1947. [Class 99(ii)] [Also in Group X] Prestressed concrete pipes are made by securing concrete bars having tensioned wire reinforcement, around the expansible core of a mould, winding a wire around the bars and core to form a transverse reinforcement, tensioning the latter by expanding the core and then applying concrete to embed the reinforcements and form the walls of the pipe. The apparatus consists of a mould having an expansible core, shown in Fig. 4. A number of T- section bars 4 are arranged symmetrically around a rod 1, provided at the ends with left and right hand threads. The ends of bars 4 bear on cones 2 which are engaged on the threads on rod 1 so that turning the rod causes the cones to approach one another and the bars 4 to spread apart. Concrete bars 5 having tensioned, "twisted pair" wire reinforcements, are laid on the core so as to bridge the spaces between. the bars 4 and a wire reinforcement 6 is wound around the bars. The cone is then expanded to produce the required tension in wire 6 and the assembly inserted into a cylindrical outer shell. Concrete is poured into the annular space between the core and shell to form the pipe which is removed after setting by contracting the core.