Method and apparatus for controlling the thickness of extruded stock

In a process comprising an extruder for providing a continuous sheet length of elastomeric extrusion, a variable speed take-away belt to vary the thickness of the extrusion as it exits the extruder, a running-weigh-scale to measure the weight-per-unit-area of the continuous extrusion, a cooling train to set the extruded material, a skiver to cut the continuous extrusion into specific lengths, and a check-weigh-scale to measure the cut length weight, apparatus for controlling the thickness of the cut lengths of extruded elastomer comprising:

• A. means to sample the weight of extrusion passing over the running-weigh-scale each second;
• B. means to compute one-minute averages of of the running-weigh-scale samples;
• C. means to store the one-minute running-weight-scale averages;
• D. means to sample the weight of the cut lengths of extrusion at the check-weigh-scale;
• E. first comparator means to compare the check-weigh-scale samples to the oldest stored running-weigh-scale one-minute averages to obtain a targeted running-weight-scale average;
• F. second comparator means to compare the targeted running-weigh-scale average to the newest stored running-weigh-scale one-minute average to obtain a deviation from the targeted value if one exists;
• and
• G. converting means to convert the deviation from the targeted running-weigh-scale value to a control signal for increasing or decreasing the speed of the take-away belt to vary the thickness of the extrusion in accordance with the amount of deviation and the take-away speed of the belt.