| 摘要 |
A method and apparatus are described for flanging a tubular article of a crystallizable thermoplastic polymer, particularly of a saturated linear polyester material such as polyethylene terephthalate, which has been heat-set to an elevated temperature, e.g. for producing bodies for processable food and beverage containers. The open end of the tubular body is applied to a flanging die and heated to a flanging temperature above the glass transition temperature but below the heat-set temperature of the polymer. The tubular body and the die are forced together so that the softened end of the tubular article is forced to move outwards until it abuts against a stop ring to form the flange. The residual shrinkage in the polymer material helps it to take up the precise contours of the die and to form a well-defined flange. The flanged end is then cooled, preferably to a temperature at least 20 DEG C. below the flanging temperature, before releasing the tubular body 10 from the die. |
