The Mechanical Handling and Storing of Material

ii6 THE MECHANICAL HANDLING OF MATERLAL Figs. 157 and 158 show the conveyor for draining purposes in connection with a coal-washing plant. The head end of the conveyor being fitted with a perforated plate, allows the water to at once escape, whilst the coal is conveyed to the further end. The conveyor has a slight upward incline; thus should any water remain with the coal, it will tend to run back towards the feed end where it can escape through the perforations. The conveyor can also be used as a picking table, as the oscillating motion of the trough does not inconvenience the pickers after the first few minutes, and it has this advantage, that the coal is always uniformly spread out over the whole surface. Hence picking is much easier work on this kind of conveyor than on the ordinary steel plate table, where the coal remains in heaps just as it has been deposited on the band, and has therefore to be spread for examination by the pickers. Figs. 157 and 158. Zimmer Conveyor as used for Draining Purposes in connection with Coal-Washing Plant. Fig. 159 shows two Zimmer conveyors at work, which are used for picking purposes, at the Amelia Pit of the Cramlington Coal Co., Ltd. This conveyor is also extensively used in collieries, etc., not only for conveying, but also for classifying or sorting coal and other minerals into different sizes. When used as a screen, the machine is fitted with an interchangeable sieve which divides the trough into an upper and lower deck or compartment; the fine material which has been sifted out by this perforated plate is conveyed on the bottom of the conveyor until an outlet is reached. The sifting action is so sharp, that a perforated plate of 6 or 8 ft. in length is sufficient in most cases to effect the separation. The sieves for different sized coal required can therefore be made of such lengths as to coincide with the row of sidings on which the trucks to be loaded can stand (see Fig. 160). Such a plant is at work in a Belgian colliery, where the coal is divided into a great number of sizes, each truck receiving coal of a different size. Fig. 161 shows a Zimmer Patent Balanced Screen of this kind to a larger scale.