Method and apparatus for monitoring and evaluating the density of a

Abstract

A continuous stream of tobacco shreds is built at the underside of the lower reach of an air-permeable belt conveyor by conveying tobacco shreds in currents of air which impinge upon the lower reach of the conveyor at a variable angle and at a variable speed. The density of various layers of the stream at a plurality of points at different distances from the lower reach of the conveyor is monitored by a device which directs X-rays transversely across the stream and has a uni- or two-dimensional detector with one or more rows of diodes exposed to X-rays which have penetrated through the stream. The signals which are thereby generated by the diodes denote the monitored density at the plurality of points and are scanned, evaluated and processed to actuate one or more servomotors which vary one or more parameters that influence the orientation of shreds in the stream, the density and/or other characteristics of the stream. Such parameters can include the subatmospheric pressure at one side of the lower reach of the conveyor, the direction of flow, speed and/or quantity of air which transports the shreds to the conveyor, the rate of admission of tobacco shreds into the air current or currents, and/or the position of the trimming device which removes the surplus from the stream. The signals can be used to vary the parameters which influence the characteristics of the entire stream and/or to vary one or more parameters which influence the density and/or other characteristics of one or more layers of the stream.