The Mechanical Handling and Storing of Material

Ioo THE MECHANICAL HANDLING OF MATERIAL as to make a leakage between adjacent sections impossible, as the strip is just over the butt joint of the two sections. This strip is curved to allow the segments to bend freely when passing the terminals. In Fig. 128 the surface of the plates is not convex but flat, with the exception of a slight curve at the joint just mentioned to allow of the plate ends interlocking. Conveyors of this type are mostly used to handle large coal in collieries, and are often employed as picking tables for sorting coal and other materials whilst they are being conveyed. They also take the place of ordinary band conveyors, where the nature of the material to be conveyed would injure a rubber or textile band. The belt is often supported at intervals by stationary rollers over which it travels. In more modern types (see Fig. 127) the rollers are attached to the links and travel with them, an arrangement which has the advantage of economising the driving power. The screeching of belts of the ordinary type, caused by the edges of the belt rubbing on the side angles, is avoided. Moreover, the points of the support being fixed relatively to the belt, there is none of the irregular up-and-down motion sometimes met with on inferior bands, and the whole action is much smoother. Fig. 129 represents a steel plate conveyor built by the Steel Cable Engineering Co., which is used for the purpose of sorting chips in wood pulp mills. These conveyors very much resemble colliery picking bands, and beyond the fact that the framework is of timber, they might be used for the same purpose. Every second section of the band has its own guide pulleys, which run on angle-iron tracks in the side of the framework, as seen in the cross siection. The different plates overlap each other to make leakage impossible. Unlike other conveyors of this type here mentioned, the one in question is driven by cables instead of by chains. The tightening of these conveyors is effected in a similar manner to that of band conveyors, and the speed at which they run is 60 to 120 ft. per minute, according to the purpose for which they are employed.1 The lower speed is adopted when the material is to be picked over. See Tightening Gears, page 191.