Plastic article or earthenware shaping or treating: apparatus – Female mold and means to shape parison directly by internal... – Including means to prepare parison
Patent
1977-12-21
1979-08-21
Rosenbaum, Mark
Plastic article or earthenware shaping or treating: apparatus
Female mold and means to shape parison directly by internal...
Including means to prepare parison
425539, 425393, 425812, B29D 2303
Patent
active
041652142
ABSTRACT:
In order, in the molding of corrugated thermoplastic tubing, to overcome the disadvantage that pressurized air which is supplied to a zone within the tube of thermoplastic material as it is extruded from an extrusion head into the entrance of a tubular mold tunnel may tend to cause rupturing of the tube at the area immediately adjacent to the extrusion head where the tube is unsupported by the wall of the tubular mold tunnel the pressurized gas is supplied at a low pressure to a first zone within the tube of thermoplastic material to support the tube against the wall of the tunnel, and pressurized gas at different, successively higher pressures is supplied to second and third zones within the tube to urge the tube outwardly into the corrugations of the tubular mold tunnel. A gas leakage path between the second and third zones permits leakage from the third to the second zone, the pressure in the second zone being controlled by venting gas therefrom at a controlled rate.
REFERENCES:
patent: 3677676 (1972-07-01), Hegler
patent: 3924992 (1975-12-01), Hegler
patent: 3981663 (1976-09-01), Lupke
patent: 4003685 (1977-01-01), Maroschak
Lupke Gerd P. H.
Lupke Manfred A. A.
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