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US 4,957,687 AGranted
Method for making profiled plastic tubes such as corrugated tubes
OwnerBulent Akman, Bernard de Curraizeinventors
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OwnerBulent Akman, Bernard de Curraizeinventors
Estimating the term…
A tube or hollow body of a plastic material having memory characteristics is formed in a mold body having interior undulations or grooves. Pressure is applied to the interior of the plastic tube, while the tube is at a temperature above its softening point, to expand the tube into the configuration of the interior of the mold body. The pressure is maintained while the tube is cooled. After cooling, the tube is extracted axially from the mold body, and is reheated to cause the tube, by virtue of its memory characteristics, to return to the shape it had while in the mold, thereby eliminating the distortion and stretching occurring during removal from the mold. The mold body can be a tubular corrugated casing or stainless steel with a relatively thin wall, which cannot be taken apart. End assemblies are provided to hold and seal the tube ends while the tube is expanded in the mold body, by pressure applied through one of the end assemblies. The preferred plastic material is PTFE (TEFLON).
A method of making profiled hollow bodies from a plastic material having memory return characteristics upon heating comprising the steps of positioning a tube of memory characteristic plastic material in a hollow mold body having an internal surface corresponding to the desired external profile shape of the tube, applying internal fluid pressure to the tube while the tube is at a temperature above its softening point to deform the tube against the inner surface of the mold body, cooling the tube while within the mold body and while maintaining the internal pressure, releasing the internal pressure after cooling, removing the tube from the mold body by pulling the tube axially out of the mold body, and then heating the tube to a temperature sufficient to cause the memory characteristics of the plastic material to return the tube to substantially the same profile as the internal surface of the mold body, to thereby substantially eliminate the stretching and deformations caused by pulling the tube out of the mold body.
Dependencies are inferred from the claim text.