Double-wall plastic tubing in which the outer wall has transverse corrugations and the inner wall is smooth
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United States of America Patent
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-
Dec 1, 1981
Issued Date -
N/A
app pub date -
Jun 2, 1980
filing date -
Aug 24, 1976
priority date (Note) -
Expired
status (Latency Note)
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Abstract
In the manufacture of double-wall plastic tubing in which the outer wall has transverse corrugations and the inner wall is smooth, in the case of annular transverse corrugations the air pressure between the two walls cannot be balanced with the external air pressure, resulting in deformations of the inner tube. To permit an equilibrium of pressure before the inner wall hardens, openings are pierced in the outer wall or openings are produced between the two walls for communication between the inner chambers of the transverse corrugations. After the hardening of the inner tube, these openings are reclosed by fusion.
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