The Mechanical Handling and Storing of Material

BAND CONVEYORS 95 substances should lodge between the terminals and the belt, some scrapers are arranged on the band to prevent this. The driving and tail terminals are shown to a small scale in Figs. 118 and 119. With a combined band there are three terminal drums, one for each of the bands, and to Fig. 120. Idlers for Sandvik Steel Band Conveyor. overcome the difficulty of any alteration in speed of the middle band, the drum for this is not keyed to the spindle, but runs freely on it. At the tail end one of the side sheaves is keyed to the spindle, and the other two are loose. The tail or tightening terminal is fitted with a movable tension frame of timber, which is held taut by a weight in order to compensate for any expansion which may be caused by the load or tempera- ture. Idlers. — It has already been mentioned that these con- veyors can work without idlers, but such an arrangement is only for a limited number of pur- poses. For more important in- stallations idlers are used ; they are 12 in. in diameter, and much narrower on the face than the pjg_ 122. Idlers for Sandvik Compound Steel Band width of the band. Such idlers Conveyor. are shown in Figs. 120, 121, and 122 for single band and compound band conveyors. At intervals flanged idlers are used to prevent the belt from travelling to one side. The distance between the idlers varies from 6 to 16 ft., according to the weight of the material to be carried, and the return idlers may be as far as 40 ft. apart. On account of their rigidity steel bands can never be troughed.