Design and application of a rolling axial screening device for tobacco strip threshing and redrying

To address the issue of difficulty in popularization and application of strip structure regulation equipment for tobacco threshing and redrying due to its large footprint, an elevating screening process was designed. The new process consisted of a primary and secondary screening stage respectively and was installed above the tobacco strip receiving conveyer belt. Corresponding improvements were made to the tobacco strip structure regulation equipment based on the screening process, enabling strip size adjustment without occupying additional floor space. According to the process, the rolling axial screening device was installed above the receiving conveyor at a tilt angle of 30°. The distance between the screening roller shafts was 80 mm for the primary stage and 40 mm for the secondary stage. The primary stage screened out the smaller strips which were then transferred onto the receiving conveyer belt, while the larger strips were conveyed to the secondary stage. The secondary stage further screened out the smaller strips onto the conveyer belt, while the larger strips were transferred into a cutting device for size adjustment. The designed process replaced the original 8 cylindrical screening teeth on the roller shafts with the screening plates featuring 8 trapezoidal flake-shaped teeth, which stopped the cylindrical screening teeth from penetrating the strips, thereby solved the problem of low screening efficiency caused by ineffective rolling over. In production trials, operating at a motor frequency of 40 Hz and on the basis of stable threshing economic indicators, the large-strip rate was 35%-45%, and the medium-and-large strip rate was above 76%. The equipment demonstrated good stability, and compared to the regulation method involving the replacement with hexagonal frames, the energy consumption was reduced, and the structure and uniformity of processed tobacco strips were further improved, meeting the raw material processing requirements for cigarette manufacturing.