Local correction of blown film thickness using variable air flow

摘要

In a process for the fine correction of the thickness profile in a blown film tube, the flow of cooling air is varied in individual regions of the film bubble periphery. At least part of the cooling air is introduced to the bubble by a circumferential slot which is divided into individually fed segments. The control of the additional cooling air is by means of radial blowers. In this manner it is possible to accurately control the cooling action and therefore film thickness in individual circumferential regions of the film bubbles. Equipment for achieving fine control of the additional air is also described.