Patent ID: 6863517

Claim:
An apparatus for extruding and cooling polymeric sheet materials, said apparatus comprising: a polymer sheet extruder producing polymeric sheets of predetermined thickness; a plurality of cooling rolls positioned downstream of a heating device, a gap between said cooling rolls being position in concert with said extruder for introducing said sheet into said gap, each said cooling roll having a longitudinal axis of rotation and being capable of cooling a polymeric sheet produced by said extruder; a positioning device connected to at least one of said rolls, said positioning device being mounted for selective positioning with respect to another of said cooling rolls; a laser source connected for measuring directly and without reflection, and while said sheet is processed through said gap, the thickness of said gap, said laser source being aimed in said machine direction and emitting a laser beam aimed and arranged for transmitting a beam of laser light into and directly through said gap; a corresponding laser beam detector positioned and aimed in line with said gap on a side of said cooling rolls opposite to said laser source for non-reflectively measuring, while said sheet is processed through said gap, the amount of laser light passing directly through said gap; a measuring and comparison device for comparing said measured value to a desired value corresponding to a desired gap width; and a controller responsive to said measured value for controlling said gap distance through selective linear roll displacement; wherein at least one of said cooling rolls has at least one end portion with a diameter less than the diameter of the roll portion having said extruded sheets thereon to provide space through which said laser beam can be sighted.