Method and apparatus for automatically a saw for a soft prestressing

摘要

Apparatus and method for automatically roll tensioning saw as used on bandmill. Selected portion of saw is formed into known curve so that existing prestress distribution in saw causes selected portion to bow across width thereof. Saw profile is detected by a bow sensor traversing back and forth across saw, simultaneously feeding saw longitudinally, thus causing sensor to describe zig-zag locus on bowed saw face. Back crown sensor output signals reflect back crown as saw feeds past. Both sensor outputs are fed into computer where bow sensor readings are averaged and synchronized with average back crown to assess existing pre-stress distribution for that portion. Computer compare assessed distribution with desired distribution and outputs correcting signals to stretcher rolls to correct deviations of assessed distribution from desired distribution. Stretcher rolls are automatically positioned at desired location and roll with desired force at computed location on that particular portion of saw. Stretcher rolls are traversed by hydraulic positioning cylinder, and forced together by hydraulic loading cylinder, both cylinders controlled by servo valves responsive to computer output signals and signals from feedback sensors.