METHOD AND APPARATUS FOR CONTROLLING THE THICKNESS OF A FILM PRODUCT

摘要

The present invention relates to a method and apparatus for controlling the thickness of an extruded, biaxally elongated film product.
In apparatus for producing such film product an adjustment to remove thickness deviation in the film needs to be effected when production is started or restarted and is normally done by a skilled worker, in a bad working environment.
An object of the present invention is to provide a method and apparatus in which thickness deviations are controlled automatically without supervision.
The invention is characterised by a method in which correlation between positions along the widthwise direction of a film sheet and positions of die manipulation bolts of an extrusion die is obtained, initially a profile of the film sheet prior to lateral elongation is converged into a tolerable range, and thereafter the thickness of the film sheet after lateral elongation is measured, and if there are thickness deviations outside the tolerable range, thickness regulation is affected by transmitting a signal corresponding to the thickness deviations to appropriate ones of the die manipulation bolts.
The invention is also characterised by apparatus for producing the product film in which means are provided for measuring the thickness of the film sheet over its width and for correlating positions along the widthwise direction of the film sheet with positions of die manipulating bolt spaced over the width of the extrusion die so that the profile of the film sheet prior to lateral elongation can be regulated in accordance with the method defined above.