The Mechanical Handling and Storing of Material

!Ö2 the mechanical handling of material than is the usual practice. As regards inclines, up-gradients of 5 per cent., and down- ward gradients of 12° are within working limits. .... The advantages of these belt conveyors are their suitability for an uneven floor, as the band can accommodate itself to the bends in the floor and roof. The power for driving them is considerably less than for other appliances, and the working is both noiseless and dustless, which is of great importance. The disadvantages are the great wear and tear caused not only, as already mentioned, by the atmosphere, but as these conveyors, in common with all other coal face conveyors, have to be removed and re-erected constantly nearer the receding face, the re-erection does not always get the caie necessary to ensure all idlers being at right angles to the band and parallel with each other and in consequence the band travels with a snake like side motion, whereby the edges are injured and frayed by contact with other objects. The loading is not so easy Fig. 216. Blackett Conveyor Delivering Coal into Main Gateway. as with other appliances, and an occasional dropping off of pieces of coal is also com- plained of, and finally, for wet mines they are quite unsuitable. Class C.—Appliances in which the coal is dragged along in a fixed trough by a chain or scrapers. The best known and oldest conveyor of this type is that of Blackett1 2 (Fig. 216). These machines are to all intents and purposes scraper conveyors (which have already been fully dealt with in Chapter Vthe principal feature being that they are built as low and compact as possible in order to leave sufficient head room for the coal to be put in and conveyed even in thin seams. The chain scrapers are now of the form of very large Ewart or Lee type of chain. Other scraper conveyors are by Greaves/ Vinton,3 Ritchie & Sutcliffe.4 In order to still further reduce the height of the conveyor, 1 Fully described in The Colliery Guardian, I., 1905, page 580. 2 Fully described in The Colliery Guardian, II., 1906, page 7. 3 Fully described in “ Mines and Minerals,” 1907, page 230. 4 Fully described in “The Coal Age,” 1912, page 644.