APPARATUS FOR MAKING ANNULARLY RIBBED PLASTIC PIPE AND METHOD OF MAKING SUCH PIPE

摘要

PCT No. PCT/CA93/00552 Sec. 371 Date Jun. 19, 1996 Sec. 102(e) Date Jun. 19, 1996 PCT Filed Dec. 20, 1993 PCT Pub. No. WO95/17295 PCT Pub. Date Jun. 29, 1995An apparatus for forming a thermoplastic pipe having a profiled surface includes a nozzle having an extrusion orifice feeding extrudate in a downstream direction to a mold path which extends from the nozzle and along which are provided a first mold block and a second mold block downstream of the first mold block. The mold blocks are closable around the extrudate to form the pipe and are openable to release the pipe. The mold blocks are moved together with one another and with the pipe in the downstream direction when the mold blocks are closed and are opened and sequentially moved in an upstream direction along an axis contiguous with the axis of the mold path while the extrudate continues to move in the downstream direction. The first mold block is moved in the upstream direction before the second mold block such that the mold blocks never pass one another on the mold path. After the mold blocks are moved in the upstream direction, they are then reclosed around the extrudate at a position to maintain consistency of the profile of the pipe.