Apparatus have evolved over the years for washing coal and concentrating ores in which materials of different specific gravities are separated by immersion in a fluid mass such as water of specific gravity high enough to effect the floatation of that portion of the materials of lower specific gravity. Characteristically, such type of apparatus have comprised either a rotating drum having inclined sidewalls and mounted for rotation about a horizontal axis or a cylindrical drum whose axis is inclined slightly with respect to the horizontal and wherein internally of the drum and on the inner surface of the drum, helical strips of limited height are provided and the direction of rotation of the drum is controlled such that upon rotation of the drum, the heavier mass materials seek by gravity the surface of the drum beneath the liquid mass causing floatation are driven towards a given open end of the drum itself. One such type of apparatus is illustrated in U.S. Pat. No. Re. 16,674 to Thomas M. Chance, reissued July 12, 1927, and entitled "Method and Apparatus for Separating Materials of Different Specific Gravities."
The apparatus of U.S. Pat. No. Re. 16,674, in one embodiment takes the form of a drum which rotates about a horizontal axis and which includes diverging portions from the end towards the center such that the drum is formed by two frustoconical portions joined at the center. The drum bears on the inner surface of both portions helical conveying elements which tend to drive, due to the rotation of the drum, the higher specific gravity material while the clean coal floats to the top of the surface of the water confined within the drum. Water and fine waste exits the drum at both the inlet and outlet ends through wire mesh covering openings within the drum wall and the water is separated from the fine waste and recirculated.
In a further embodiment of this invention, Chance discloses a cylindrical drum which is mounted for rotation about its axis and inclined to the horizontal, and wherein the drum bears internally thin spiral strips functioning as conveying elements tending to convey the higher specific gravity particles towards the open, upper end of the drum. The fines and water pass through an open mesh screen gate covering an opening within the drum wall, while the larger particles are discharged at that end of the apparatus. At the other end, the lighter particles of lower specific gravity float off through a screen cylinder onto a trough for removal from the rotating drum.
While such apparatus employed by Chance in the two different forms of FIGS. III and IV, permit satisfactory operation, the apparatus is complicated, maintained at a fixed geographical location, requires complicated water spray delivery pipes for agitating the accumulated water within the bottom of the drum, and fails to provide the desired separation of the high specific gravity material from the low specific gravity material and in terms of unwashed coal as the entry material, it fails to provide not only the desired degree of separating but also the washing of the coal to commercial satisfaction.
It is, therefore, a primary object of the present invention to provide a compact apparatus for improved separation of coal from waste material of higher specific gravity controlled washing of the coal during such process and wherein the apparatus is vehicle mounted to permit portability from site to site.