| 摘要 |
Plastic pipe is belled under pressure by inserting what is, in effect, a telescoping mandrel into a heat-softened pipe end with great axial force immediately after two mold halves with cavities defining the desired bell configurations have been brought together under pressure. The softened pipe end is not only expanded to a bell configuration by the mandrel, but is compressed by the radial annular end wall of a sleeve which slides axially over the mandrel into the spacing between the mandrel and the mold halves defining the bell-shaped cavity. Thereby, not only may the heat-softened pipe end be molded to assume an exact configuration to a high degree of tolerance, but the normal thinning of the walls of the pipe end which occurs with its belling may be re-thickened by the axial compression of the sleeve to the original pipe wall thickness. After such radial expansion and axial compression of the heat-softened pipe end to the precise bell shape and tolerance, the mold halves are first cooled, the sleeve is first withdrawn axially, then the mandrel is withdrawn, and lastly the mold halves are separated to permit the belled pipe to be removed.
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