The Woodbury Concentrator is similar to the Frue vanner, but instead of the single smooth belt, thirteen narrow parallel belts are used. The pulp being equally divided be tween these belts, which prevent it from running to one side of the machine or the other, it is claimed that a thicker bed ofpulp can be worked, and that the machine has increased capacity in consequence. A revolving feed-bowl distributes to each belt its exact proportion of sand and water. The rims of the belts are corrugated to prevent cracking as they stretch in passing over the end rollers. The capacity of this machine is claimed to be from 12 to 15 tons per 24 hours. Several of them have been introduced recently, but no actual working results have been published.
The Golden Gate Concentrator consists of a tray about 11 ft. in length, resting upon supports, upon which it has a longitudinally reciprocating movement. This reciprocating movement varies in speed in such manner as to ca-use the pulp, fed upon the tray at one end, to travel slowly over its surface toward the other end. and the pulp is, by the shaking motion, kept in a loose condition, so that the mineral may settle out of the gangue upon the surface of the tray. The tray proper consists of two distinct parts, forming, however, one continuous surface. One part. being designed for the settling of the mineral, is horizontal, and has hardly any perceptible current of water, thus allowing the fine mineral to settle out of the water and reach the bottom of the tray ; the other part has an adjustable inclination upwards from its junction with the horizontal part, and over this part the current of wash! water flows, which washes away the gangue from the mineral. At the junction of the hori zontal with the inclined part of the tray, and extending across its width, is a protecting plate. set somewhat above its surface and parallel thereto. Above the protecting plate is an exhaust tube extending across the tray, and connected with two settling chambers, one on either side of the tray, within which a vacuum, sufficient to sustain a column of 4 in. or 5 in. of water, is constantly maintained by an exhaust fan. Just above the protecting plate, and connected with channels formed in the body of the exhaust tube, are exhaust mouths, into which the gangue and water are drawn by the vacuum maintained, being then discharged ot'er each side of the machine into the settling chambers, and thence into the tailing sluice. The operation of the concentrator is as follows : The crushed ore, with a suitable amount of water, is fed on to the horizontal part of the tray through the distributor at one end of the machine. The shaking motion of the tray causes the pulp to slowly travel toward the protecting plate. The heavy mineral, settling to the bottom, passes under the latter, together with sonic of the gangue. The larger part of the gangue and all the surplus water pass above the plate, the position of which is adjusted to suit the ore, and, arriving at the exhaust mouths. are drawn off and discharged into the tailings sluice. The pulp which
has passed under the plate continues on up the inclined part of the tray, where the gangue is separated from the mineral by a stream of wash-water from the head of the machine. The gangue and wash-water are taken up by the exhaust mouths, as before explained, and the mineral is delivered continuously over the head of the machine.
The Bertenshaw, or Gilpin County Concentrat r (Fig. 7), is an end bump table, the motion being imparted by a cam at the tailings end.
The cam w orks in a box, which can be filled with tallow or other grease, thus insur ing constant lubri cation at every revolution of the shaft. In this box is placed a steel shoe, with a bolt through its center for the cam to wear upon, which can he changed end for end as the wear may require. The spring is of torsional character. and easily adjusted, without stopping the machine, by the set-screw and clamp at each end. There is also a clamp bar attached to the center of the spring, which works in the cam box to give the bumping blow when the cam point leaves the shoe. The bed frame of the machine terminates in a solid block of wood at the headings end, against which the table bumps. The table is supported from four standards, swinging on knife-edge bearings. The pitch of the table is adjusted by bolts and set-screws on the front standards. The speed of the machine is governed by the character of the ore to be treated, varying from 130 bumps per minute upward.
The Rillinger Table, one of the oldest types of slime-washing machines. is much used in Germany, and to some extent in this country. it consists, in the single form, of a plain inclined table, hung from above in such manner as to move freely at right angles to inclina tion, and operated by a Call) and spring, which produce a quick succession of jars and shocks against a solid frame. The ore, in a stream of water, is fed on at one of the upper corners, and flows down the incline, but the successive shocks affect the particles of rock and mineral, tending to jerk them out in the direction of the shock with a force varying with specific gravity and size. The effect of the double force exerted by the downward current of water and jar at right angles thereto is to make the heavier particles take a diagonal course, and, by a few adjustable buttons on the lower end of the table, a separation according to specific gravity is brought about, the heaviest particles moving farther across than the lighter. Along the upper end of table unoccupied by the pulp discharge, water jets flow on the table in regulated quantity, so that its whole surface is washed and the line of the mineral particles controlled. The tables are usually hung in pairs, to save space and machinery. The tables are sometimes of wood, with rubber covering ; sometimes of slate, marble, or plate glass, about 4 ft. wide by 8 ft. long, and varying in number and intensity of shocks with the fineness of ore treated. These tables are well adapted for the treatment of the coarser slimes, but their capacity is small.