1. Field of the Invention
The present invention relates to apparatus and methods for scanning and sorting tobacco leaves. More particularly, the present invention relates to apparatus and methods for processing tobacco leaves by scanning the leaves and removing unacceptable leaves and other contaminants that are detected.
2. Description of the Related Art
Tobacco leaves obtained from farmers include discolored or damaged leaves and other contaminants which must be removed during the initial processing of the tobacco. Initial processing of tobacco leaves includes dividing the flow of tobacco over many slow moving conveyors. One or more inspectors were stationed at each conveyor to visually inspect each leaf and manually remove undesirable leaves and other contaminants, such as stems, stone, or portions of latex gloves used by tobacco leaf harvesters. This system of initial processing was costly as it required a lot of space, equipment and manpower. The system was also inefficient and inconsistent because the inspectors are unable to give full attention to every leaf and particle, despite the generally slow moving conveyors. The system also relied on the subjective judgment of the inspectors to identify and remove discolored or damaged leaves and other contaminants.
Machines were developed in the early 1970's to scan the flow of tobacco leaves on the multiple conveyors. The machines scanned the flow using light at different wavelengths. The machines were able to detect and reject different colors, as selected by the operators. Although the machines performed adequately, they were subject to changes in the light source, effects of ambient lighting, shadows and drift of the calibration parameters, which resulted in inconsistent performance. The machines were largely abandoned in the 1980's and human inspectors returned at a reduced level.
Technology improved in the 1990's and more efficient and consistent scanning devices were developed. These scanning devices used traditional optics with independent light sources and lasers. The scanning devices are used in many industries, and proved successful in scanning strip-tobacco and stems. However, each device is extremely expensive.
A need exists for a machine for scanning tobacco leaves to reject unacceptable (e.g., discolored or damaged) leaves and/or other undesirable particles before they are threshed into multiple small pieces. To divide the product over multiple conveyors in order to thin the flow enough so that each leaf can be viewed individually would require 50-100 machines per plant. The conveyor speed would also be limited because beyond a certain speed the leaves become airborne and cease to be conveyed. The cost of this many machines, the slow processing speed, and the space required would make plant construction and operation prohibitively expensive.