184,237. Schloemann, E., [Firm of], and Dobbelstein, O. April 29, 1921. Upward. - current classifiers.-In conveying loose material, such as coal, in a stream of liquid by means of compressed air mixed with the liquid, the pressure is regulated so that o n l y the lighter material is held in suspension while the heavier material such as rock separates by gravity. As applied to the raising of coal from mines, the coal is fed from a hopper l through a shoot f, g. h into an uptake pipe b where it meets a stream of water fed by a surface pump through a down pipe a. Compressed air enters the pipe b at o and forces the mixture of water and coal up the pipe b. The pressure is regulated so that heavy material such as rock separates by gravity and falls into a chamber p provided with valves q, r. If mine water is used, the pipe a may be dispensed with. The valve n of the hopper and the valves i, k of the shoot g are interdependent so that, when the valves n, k, of the shoot g are interdependent so that, when the valves n, k, are open, the valve i is closed, and vice versa. When not in use for convoying, the apparatus may be used for flushing by connecting to the pipe a a pipe t provided with a flap valve u. If used for conveying potash, mother lye is used as the conveying liquid.
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