HYDRAULIC SEPARATORS.—Hydratilie separators are machines for classifying the fine material to be concentrated into groups of particles which, under like conditions, fall through the water together, the material thus being prepared for the jigs or other slime-washing ma chines. The hydraulic classifiers in general use are, with unimportant modifications, forms of the old German Spitzlutte or Spilzkasten, in which the particles of ore settle in pointed boxes against an upward current of clean water. They are regulated according to the work to be done by varying the velocity of the stream of ore and water passing through them, and the strength of the upward current of water.
The Calumet or Richards-Coggin separator (Fig. 3), which is generally used in the Lake Superior dressing works, con sists of four or five boxes. D, D, etc., or depressions in the bot tom of a continuous trough. The water and sand enter at m and undergo successive wash ings in each box until the fine sand overflows at n. The opera tion in each of the boxes is as follows : The heaviest sand at once finds its way to the bottom of the box; the wash-water is brought in through the pipe, a, in greater quantity than is sufficient to sup ply the spigot, B. No sand, there fore, can find its way out through E that has not weight enough to stem this water stream. This ex cess of water also acts by keeping the whole bottom of the box in a boil and turmoil, thus ever push ing up the lighter sands and allowing the heavier to keep near the bottom. The shield, c, prevents the stream from rising straight up, thereby confining the turmoil to the bottom of the box.
Ans.—This is the general name for the concentrating machine universally employed for separating the particles of mineral and gangue in sand and coarse meal sizes. The Hartz jig (Fig. 4), which, as is well known, consists of a wooden tank with a wedge-shape bottom, divided transversely into a number of compartments, these being further subdivided by a longitudinal partition not ex tending to the bottom, on one side of which is a sieve, and on the other a piston, remains the standard type of jig, and most of the other jigs in use are but modifications of it. In the Hartz jig the motion of the piston or plunger is given by an adjustable eccentric. The Collom jig, used at Lake Superior,
is a side-piston jig (Fig. 5), in which the plunger is depressed by a crank and lever tappet, a spring raising the plunger when the tappet is removed. This device gives a rapid rising cur rent through the jig sieve, and a more gentle descending cur rent, an action winch increases the sorting action of the jig. Other mechanical means for securing this slow return move ment of the piston have been introduced, but the Collom is the only jig of this type which has come into use in this country. The under-piston jigs have a piston working in a short cylinder placed in the longitudinal portion between two compartments, the piston rod extending out through the jig box through a stuffing-box, and receiving its reciprocating motion from an eccentric. Instead of the ordinary V-shape bottoms, jigs with rounded bottoms are sometimes used, es pecially as slime jigs, the rounded bottom aiding in the regu lar movement of the water. For very coarse material, and occasionally for iron ores, instead of giving motion to water through a fixed screen, sieves, either rectangular or circular, having a vertical reciprocating motion in a tub of water, are sometimes used, the effect being the same. Pneu matic jigs have been de signed and used experimen tally, but have rarely been regularly employed.
The Avail Jig is a double Hartz jig with a central pis ton working between two sieves. The reciprocating motion of the piston is given by an adjustable eccentric in the usual manner.
The Parsons Jig is a two.
sieve, under-piston jig, each sieve being 22 x 27 in. in the clear. The pulsating move ment of the water is given by a piston working in a short horizontal cylinder in the partition between the two jig boxes. The piston is 15+ in. in diameter ; the cylinder, 4+ in. long. The piston rodis horizontal and enters through a stuffing-box. The stroke of the piston is 2 in., and its speed 510 strokes per minute. The quantity of water required at the St. Joseph Lead Co.'s Works, at Bonne Terre, Mo., where this jig is extensively used, is about 32 gallons per minute, jigging about 9 tons of sand per 24 hours. For convenience the jigs are made double—i.e., four sieves, or two jigs. are united in one machine.