| 摘要 |
1,190,802. Automatic thickness control. HARTE & CO. Inc. May 11, 1967 [May 13, 1966], No.22039/67. Heading G3R. Sheet material after manufacture is pulled from calender rolls by a pick-off roll partly wrapped by the sheet, and the difference between the signal from a detector responsive to sheet thickness downstream of the pick-off roll, and a reference signal, automatically controls the speed ratio of the rolls to maintain thickness constant. As shown, plastics material in a semi-liquid state is fed to a set of driven calender rolls 2, 3, 4, 5 to form a sheet which passes round roll 5 and is pulled off by a rubber surfaced friction roll 6. The sheet then passes through driven embossing and cooling rolls 10, 11, 12 on its way to a driven wind-up roll 13. Back-scatter radiation gauges 14, 15 automatically control, through controllers 21, 22, screw-down units 23, 24 which adjust the gap between rolls 4, 5 and thereby maintain a constant thickness of material on roll 5. Pick-off roll 6 runs at a higher speed than roll 5 so that the material is reduced in thickness by stretching, and the wind-up thickness is measured by a radiation gauge 26 which repeatedly scans across the sheet and supplies signals which are averaged at 32 to control a servo-operated speed regulator 35 for a D.C. motor 38 driving roll 6 so that wind-up thickness is maintained constant. This regulator operates intermittently with intervals allowing sufficient time for the effect of each correction to be felt by detector 26 before the next correction. Scanning of radiation gauges 14, 15, and additional control of bending or axial position of the calender rolls is referred to, |
