| 摘要 |
The invention concerns a method of forming a flange or bellows in a plastic tube. The tube is preheated at a precise area and gripping dies are used to compress the heated area. Upon compression, the heated area is forced to bulge out and fold to form the flange or bellows. A mandrel inserted into the tube prior to compression ensures that the tube bulges outwardly. The invention may be used to form a variety of flanges, rims or bellows on plastic tubing. It is particularly useful in forming retaining rims on polyethylene tubing used for gas tank vents. Exposure to gasoline may cause such tubes to swell or bend. With a retaining rim formed in accordance with the present invention such swelling or bending can readily be accommodated.
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