| 摘要 |
<p>A method for forming a heated end of a plastic pipe into a bell having a sealing groove therein arranged to receive a seal so that it may be sealingly joined with a plain end of a second pipe inserted therein. The apparatus comprises a mandrel base rigidly secured to a mandrel core having annular grooves formed thereabout communicating with a vacuum source through a passage formed in the core and base. A mandrel shell comprising four separable segments is secured on the core. The mandrel shell has a plurality of apertures formed therein communicating with the annular groove on the core such that a vacuum may be drawn through the apertures. A heated plastic pipe is forced over the mandrel shell until it engages a tapered shoulder formed on the mandrel base, thus forming a seal between the end of the pipe and the base. A vacuum is drawn on the cavity formed between the plastic pipe and the mandrel shell thus drawing the plastic pipe to the shell, forming an annular internal groove in the pipe. Segments of the mandrel shell are removed from the end of the pipe after withdrawing the mandrel core therefrom.</p> |
