| 摘要 |
<p>An oven for preheating continuous thermoplastic sheet prior to thermoforming the sheet with plunger assistance comprises a tower adjacent the forming press and through which the sheet passes up and down vertical paths while subjected to heat from between the two film paths. The heating pattern ensures that the underside of the film entering a conventional forming tool (base cavity, overhead plunger) is as hot or hotter than the upper face, so that (a) the moulding will adhere better to the mould than the plunger, (b) the underside can be hot enough to bond with mould inserts, e.g. labels without overheating the upper surface. The vertical oven requires relatively little floor space alongside a forming tool, and a chimney effect can be used to facilitate removal of volatiles more efficiently than from a long horizontal oven. The vertical sheet paths avoids risk associated with horizontal ovens of sheet sagging away from or towards horizontal banks of heaters.</p> |
