The Mechanical Handling and Storing of Material

CONVEYORS C—APPLIANCES IN WHICH THE TROUGH CONTAINING THE MATERIAL MOVES BODILY WITH THE MATERIAL CHAPTER VII BAND CONVEYORS Historical and Introductory.—The credit of this invention, at all events the under- lying principle of its present form, is due to Mr George Fosbery Lyster, engineer of the Mersey Dock and Harbour Board, who in 1868 carried out a series of experiments on behalf of that body in order to ascertain what type of conveyor was most suitable for the mechanical handling of grain. The experiments were initiated on worm conveyors of different types, which, however, proved altogether inadequate for large granaries and silo warehouses, principally on account of their small capacity and the great driving power required. Mr Lyster then began to experiment with endless travelling bands, and after a few preliminary trials with small canvas bands, made further trials with a band 12 in. broad. This band was run at different speeds to ascertain the highest velocity at which such conveyors could be worked with safety and economy. It was also desired to practically test the most suitable speeds for different kinds of grain. A speed of 8 ft. per second was found to be the maximum for light grain, such as oats, while careful experiments showed that even bran and flour could be conveyed at this speed without such material being thrown off the band by the resistance of the air to its passage. A speed of about 9 ft. per second was found suitable for heavier grain, such as Indian corn, peas, etc. The capacity of this 12-in. band when fed to its fullest extent was found to be about 35 tons of grain per hour, the band then travelling at the speed of 8 ft. per second.1 Mr Lyster found by his experiments that grain had no tendency to fall off the band, and that even single grains when placed near the edge remained in position while passing over the carrying rolls at the speeds mentioned. Like other mechanical inventions, the band conveyor had to pass through a period of disappointments. It was feared that a flat band would spill the grain, and the supporting rolls were therefore hollowed out in the middle to give the band the form of a trough. This was all right as far as conveying was concerned; but on the other hand, the bands employed, which were composed of cotton webbing covered with rubber, wore out in a very short time, because, owing to the varying diameters of the curved roller and the consequent variation of the circumferential velocity at different points of the roller, a grinding action was set up between the rollers and the band, the velocity of the latter being of course the same for the whole of its width. This grinding action destroyed the bands. Later on further trials confirmed Mr Lyster’s experiments, showing 1 Proceedings Meeh. Eng., August 1869. 75