| 摘要 |
The local film thickness is measured (31) and the data passed to a controller (34), which adjusts the volume and/or temperature of the air supplied (18, 18') to the cooling channels (13, 13'). Segmented valves (14, 14') ensure that the control is exercised sector by sector to give a uniform thickness. Cooling air is preferably fed through two cooling channels, one of which supplies a stream that is constant round the periphery while the other acts as sector by sector control stream. An independent claim is included for a tubular film blowing plant containing cooling rings (13, 13') with independent sector by sector control. Two cooling rings are fitted above each other, the lower cooling ring having a smaller diameter than the upper ring. |
