Method and apparatus for making concrete pipe

Abstract

A method and apparatus for making concrete pipe and, more particularly, for the vibration treatment of concrete pipe for compaction and residual stress relief. A concrete pipe is formed within an external jacket employing a rotary packerhead method wherein the jacket is positioned vertically and the packerhead is moved progressively upwardly within the jacket rotating and distributing mix radially outwardly and troweling the internal surface of pipe under formation. On completion, the green pipe is removed from the pipe making machine and transported to and above a hollow vertically split and radially expandable and contractable cylinder. The pipe is lowered about the cylinder with the latter in a contracted condition, the cylinder is expanded into engagement with the pipe internal surface, and a vibrating means within the cylinder is actuated to vibrate the pipe throughout its length. The pipe is then returned to the pipe making machine, the packerhead is lowered, and a finish forming upward pass of the head deposits mix and/or trowels the pipe internal surface and fills any void which may have formed at the top of the pipe. The pipe is then removed from the machine and cured. The apparatus comprises the expandable and contractable cylinder, rollers mounted the same for intermittent relative rotation within the pipe, guide means at the top of the cylinder, fluid operable cylinders and an associated linkage within the cylinder for expanding and contracting the same, and a plurality of vibrators mounted within and on the cylinder wall.