| 摘要 |
Appts. for forming and HF welding tubes or sleeves in an endless plastic sheet is as follows: the endless sheet is unreeled from a roll and moved forward in steps corresp. to the size of a roof sheet through a welding press; the tools in the press both form the tubes and also weld them, and each finished sheet, as it leaves the press, pulls the next one into place after it. Pref., the sheet is formed into a series of upstanding transverse folds or ridges by upper and lower clamps, within the welding press; an upper frame then moves downwards and a short distance longitudinally along the sheet, thus sweeping the folds flat into a position where they are welded to form closed sleeves. |
