In radially centrifugally molding sections of concrete pipe with a bell at one end, the concrete is poured downwardly into an upwardly extending mold which forms the outer surface of the pipe section. The lower end of the mold is shaped to form the bell end of the pipe section. The concrete is centrifugally forced outwardly against the inner surface of the mold and then is pressed outwardly by a series of rotatable rollers. A pressure wheel is located within the mold above the position of the rollers for limiting the upward movement of the concrete pressed outwardly against the mold and for increasing the concrete pressure acting downwardly toward the bell end of the concrete pipe section.
A machine serves to cast pipes of concrete or a similar material substantially vertically. The machine includes an inner mould part (2) and an outer mould part (12). These mould parts are displaced axially with respect to each other during the casting process. A vibrator is preferably provided upwardly in the inner mould part (2), and an axially journalled distributor wheel (1) is rotatably mounted on the top of the mould part (2) the distributor wheel (1) having a plurality of blades (4) for distributing the material in the ring gap between the two mould parts (2, 12). The distributor wheel (1) and its mount are constructed so stiffly that the vibrations generated by the vibrator are transmitted to the material through the blades of the wheel. This ensures, when a firm profile ring is used for the casting of the spigot end, that area of difficult access below said ring is filled completely with concrete, and that the concrete obtains the prescribed quality. It is hereby possible to cast pipes which have very narrow longitudinal tolerances and also spigot ends which fully satisfy the requirements made of shape and quality.
A packerhead concrete pipe making machine having a rotatable packerhead operable to form a concrete pipe in an upright cylindrical mold about a wire cage. The packerhead has a plurality of rollers rotatably mounted on a circular plate operable to pack concrete into a cylindrical shape in the mold. Each roller has an outer sleeve of elastic rubber material. A cylindrical wall secured to the plate supports an annular troweling member operable to finish the inside surface of the concrete pipe.
