Method and apparatus for forming corrugations in tubing and a corrugated tube produced thereby
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United States of America Patent
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Jun 14, 1994
Issued Date -
N/A
app pub date -
Feb 10, 1992
filing date -
Oct 3, 1990
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Abstract
In a preferred embodiment, a method and apparatus for hydroforming thin-wall metal corrugated tubing which include first preforming the corrugated tubing in a conventional hydroforming operation of the type in which each convolution is formed separately. Semi-resilient spacers are then inserted between the sides of adjacent internal convolutions, while non-resilient washers are inserted between the sides of adjacent external convolutions. The corrugated tubing with the inserted spacers and washers is then highly compressed to the total thickness of the individual elements, with the spacers and washers controlling the radii formed at the crests and troughs of the convolutions. The resulting corrugated tubing has trough and crest radii on the order of 11/2 to 2 metal thicknesses, has an extension/compression ratio of 4 or greater, and can be compressed nearly flat. The sides of the convolutions are given a sine wave shape in cross-section to distribute stresses, so that they are not concentrated at the relatively sharp radii, and to eliminate noise when the corrugated tubing is flexed.
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