| 摘要 |
An unvulcanized rubber tube is mounted on a perforated mandrel and placed in an inflating box as described in Specification 647,084 and then subjected to a differential internal and external fluid pressure while being restrained by vanes at desired intervals to form circumferential swellings in the tube after which the tube is collapsed axially, preferably on a second mandrel, to produce the desired corrugations, and then vulcanized. A wrapping of flexible but virtually inextensible fabric is applied around the portions of the tube between the corrugations before the tube is placed in the inflating box, or after the tube has been removed from the box and immediately before the axial collapsing step. When swellings of a given outside diameter are desired the perforated mandrel may be placed concentrically within a larger unperforated mandrel to restrain the swellings.
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