FINE-CRUSHING MACHINES.— The Blake _Multiple -jaw Crusher (Fig. 7) is constructed upon the same principle as the ordinary Blake crusher, but is designed for finer crushing. In this machine the crushing is done between a series of sliding jaws supported upon the main tension-rods. The jaws are sep arated and held by 'libber rings placed between them on the tension-rods. In Fig. 7 this crusher is shown with the jaws thrown open, as if to put in new crushing-plates, or the like. The method of imparting motion is the same as in the regular Blake crusher—i.e., by means of eccentric, pitman, and toggles. The revolution of the shaft bringing the toggles more nearly into line, throws the main sliding jaw forward, thus compressing the whole series of sliding jaws, the crushing pressure being transmitted through the material to be crushed, with which the jaws arc supposed to be filled. It is evident that if a piece of iron or steel should by- accident get into one of the jaws, the only result would be to ren der that yaw for the time inoperative, the motion that it would have with respect to the next succeeding one being taken up and distributed through the other jaw openings. The size of the jaw openings in the machines ordinarily used varies from 15 x 4 in. to 30 x 2 in. These crushers have not yet come into general use, but they promise much for the future. The construction admits of a great area of discharge opening, and since the breaking of each fragment of rock is accomplished by the approach of two opposing surfaces, which can never meet, all particles sufficiently fine are at once removed. They give a more direct blow than rolls, and the die and shoe do not come together, as in the case of stamps; hence, they make a comparatively small proportion of fines, and would seem to be particularly adapted for use in dressing-works. According to Mr. Theo. A. Blake, the pres ent limit of crushing with this machine is from 14-mesh to 20-mesh, although it may be possible to carry it to 30-mesh. The largest installation of multiple-jaw crushers that has yet been made is at the dressing-works of the Chateaugay Ore and Iron Co., Lyon Mountain, N. Y., where all the ore is crushed by Blake machines, beginning with a single-jaw crusher of the ordinary type, and finishing with a series of multiple-jaw crushers of gradually diminishing size. The efficiency of this system is shown by the coal consumption, which was 1 ton of coal to 00 tons of ore, crushing from 15-in. size to size, on a fifteen months' run, from September 26, 1880, to January 1, 1883, a total of 137,551 tons of ore being worked.
The Improved Steam Stamp (Fig. 8).—One of the most important machines developed in the history of American ore-dressing machinery is the steam stamp, which, although in vented in 1856, and manufactured ever since, has but lately been improved. These stamps are used exclusively for crushing ore for concentration at Lake Superior, and are extensively used in crushing copper-sulphide ore at the large dressing-works at Anaconda, Mont. A steam stamp has also been used in the Homestake sold-mill, at Lead City, S. D., with, it is said, poor commercial results. At Broken Hill, New South
Wales, steam stamps have been erected for crushing silver-lead ores, but the results ob tained there have not yet been published. The improved steam stamp is built entirely of iron and steel, the entire framing of the machine consisting of four massive cast-iron col umns, braced to one another, and securely bolted together and to the heavy cast-iron sills or bed-plates, with body-bound bolts. The stamp is operated by a vertical steam cylinder, which can he made of any diameter or length of stroke, according to capacity required. The shaft operating the valves, by means of eccentrics and rods, is worked by a pair of machine-cut elliptical steel spur-wheels, receiving their motion from a countershaft driven from the mill line-shaft by a belt. This countershaft has a balance-wheel to insure steady motion. The irregular motion conveyed by the elliptical gears moves the valves in such a manner as to keep the top steam-port fully open for admitting the full steam press ure during the down stroke, and a small opening of the lower steam-port for the up stroke. The mortar has four discharge openings, and rests on a heavy cast-iron anvil or bed plate 20 in. thick, weighing about 11 tons, which is carried by spring timbers that rest upon the lower sills. Between the anvil and spring timber is a rubber cushion, 1 in. thick. Tire angle guide-pieces cast on the columns hold the mortar in place. These guides are planed and fitted with gibs adjustable by set-screws and jam-nuts. Neither mortar nor anvil is held down by bolts. This construction gives a yielding foundation, and, consequently, a certain amount of vertical elasticity. Within the past two years the innovation has been made of doing away with the spring timbers under the mortar bed, and setting the anvil block on a solid, unyielding base of masonry, and the results at Lake Superior seem to have demonstrated that an increase in capacity is gained in this manner. With the anvil and mortar springing away from the hammer a certain percentage of the force of the blow is lost, while, with the solid foundation, the whole is utilized for pulverizing the material in the mortar. The upper and lower guides for tire stamp-stems consist of cast-iron brackets fitted with removable bronze bushings, which can be replaced when worn. The stamp stem is slowly revolved by means of a horizontal pulley on a cast-iron sleeve between the upper and lower guide-brackets. This sleeve is brass-bushed, and contains two feathers fitting in corresponding slots in the stamp-stein, by which the latter is rotated. The piston rod is made of steel, and is connected to the stamp-stem by a circular disk, which is encased by a cast-iron bonnet bolted to the flange of the stamp-stem. The space between is filled with pure gum-rubber packing. This arrangement relieves the shock on the piston, and also permits removal of the piston for repairs without disturbing the stamp.