The Mechanical Handling and Storing of Material

8o THE MECHANICAL HANDLING OF MATERIAL conveyors is principally due to Mr Thomas Robins. At the present day thousands of installations are successfully at work, handling almost all kinds of material; hot and sticky substances being almost the only ones for which this method of transportation is unsuited The accompanying illustration, Fig. 108, represents a form of band conveyor con- structed by the Berlin Anhaitische Maschinenbau Aktien-Gesellschaft for conveying coa . The illustration shows clearly the type of tightening gear employed. It also gives the main drive with its two tightening pulleys in plan and elevation, the throw-off carriage and a cross section through one of the termini, as well as one intermediate section through the ^he difference in construction between conveyors for grain and minerals consists chiefly in the quality of the band and the form of the supporting idlers and whereas for grain curving rollers are only occasionally used, conveyors for minerals are fitted wi curving rolls for the entire length of the loaded strand, forming it into a continuous trough. The following is a more detailed description of the principal parts constituting a modern band conveyor. The Belt._____The most important part of a belt conveyor is undoubtedly the belt. Stitched canvas or woven cotton belts are often used, particularly for small installations, on account of the comparatively small first cost. They are usually saturated with some oily substance, the better to withstand the influence of the weather. Balata, and even woven wire bands are used at times, but for first-class work of a permanent character there is nothing to equal a good india-rubber belt. Rubber belts are composed of a foundation of cotton duck covered with rubber solution or “friction” pressed together, and the whole is then enclosed in a rubber covering, which may be rather thicker on the carrying side. The belt thus produced is then stretched and finally vulcanised. . Exhaustive experiments have been made by Mr Thos. Robins to ascertain the best class of rubber coverings to use for conveyor belts. Pure rubber is, no doubt, the most serviceable material, as it is almost indestructible, and as the rubber suffers very little wear from contact, even with sharp and cutting materials, but as pure rubber is exceedingly costly, it is practically beyond the reach of ordinary users, and the expen- ments alluded to were made to ascertain what kind of admixture to the rubber wi deteriorate its wearing qualities least. It is interesting to find from these tests that even steel wears faster than jobber under a heavy sand blast, and under conditions to which a belt would be exposed when handling minerals. The following diagram (Fig. 109) and table show the wear on the different materials subjected to a uniform sand blast for forty-five minutes : Rubber belt - - - -1'0 Woven cotton belt high grade - 6'5 Rolled steel- - - -15 Stitched duck high grade - - 8 0 Cast iron - - • 3’5 Woven cotton belt, low grade - 9 0 Balata belt, including gum cover - 5’0 j The object of the rubber covering is two-fold. The. thicker coveting on the upper side is to resist abrasion, and the remainder of the cover is for the purpose of protecting the body of the belt from moisture. Since the rubber solution, forming the friction with which the duck is held together, is not absorbed sufficiently by the fibres o tie cotton duck to make the body of the belt waterproof, and, as the cotton where exposed absorbs moisture as readily as the wick of a lamp, it is most important that the outer covering should be perfect, particularly if the belt is exposed to the wet. It is also necessary to see that the belt does not in any way rub against any hard