e oscillating jaw, D, is pivoted at the top as in the Blake crusher, but is much shorter. The crushing-plate, U, of this jaw is cor respondingly longer, and is hinged in the jaw at its upper end. On the frame of the machine, just behind the lower end of the hinged plate, is an ad justable cam, N, by which the stroke of the plate can be cut off to any desired proportion of the stroke of the oscillating jaw, the lower end of the plate resting against the eam during the time the stroke is cut off. The impact of the plate against this cam facilitates, it is claimed, the discharge of the crushed material. By this arrangement of the jaw proper and the plate, it is obviously possible to give approximately the same length of stroke throughout, which is an impossibility in any machine in which the jaw is pivoted at one end only.
The Blake-Marsden Crusher is another modification of the ordinary Blake crusher, in which the eccentric-shaft is placed at the extreme rear end of the machine, the motion of the pitman being transmitted to the toggles, and thence to the oscillating jaw through a bent lever. The fulcrum of the bent lever is a horizontal shaft through the center of the machine.
The toggles are seated in the short arm of the lever which extends upward ; the long arm projects backward, and is pivoted at its end with the lower end of the pitman. The oscillat ing jaw is pivoted at the top, as in the ordinary Blake crusher. It is claimed that greater power is gained by the pitman and lever construction of this machine, which is extensively used in England, but rarely, if at all, in this country.
The Nichols Crusher is a machine of the jaw type in which the fixed jaw of other ma chines of this class is replaced by a heavy cast-iron cylinder, supported upon a horizontal axis. The oscillating jaw is mounted on a revolving eccentric shaft, and works against the cylinder in a rotary oscillating motion, which causes the cylinder to move slowly around with each descending stroke of the jaw. The cylinder is prevented from moving back, as the jaw ascends, by small balls, which are placed in each end of the cylinder and against a wedge-formed projection on the inner face of the sides of the jaw, forming, in effect, a ratchet. The lower end of the oscillating jaw is secured to the shaft of the cylinder by flat con necting bars. In the ends of these bars are heavy set-screws, bearing against the cylinder shaft, by which the distance between the lower end of the jaw and the cylinder is adjusted for either coarse-crushing, reducing, or pulverizing, packing-blocks being placed against the opposite side of the eylinder-shaft. The oscillating jaw is provided with a shoe of either white-iron or steel, which can be reversed from center to side, or end for end, when worn. The eccentric shaft is fitted with two heavy balance-wheels and tight and loose pulleys.
The Forster Crusher (Fig. 4) is a coarse-crushing machine of the jaw type. The oscillat ing jaw is pivoted vertically, however, instead of horizontally, as in most machines of this class. The oscillating jaw is a heavy casting, pivoted centrally near the crushing end. A horizontal, reciprocating motion is communicated to the other end by an eccentric. This is a very efficient crusher for coarse work, being very powerful and having few wearing parts.
The Dodge Crusher (Fig. 5) differs from the Blake in that the oscillating jaw is pivoted at the lower instead of the upper end (resembling the Krom crusher in this respect), from which it results that the product is more uniform in size, as the discharge opening remains nearly constant. It is obvious from this that it can be used to crush finer than the Blake,
and that its capacity is smaller. The oscillating jaw projects in an arm to which an up-and down movement is communicated by means of the eccentric on the driving-shaft at the rear of the machine. The jaw-shaft rests in movable boxes. To change the size of the material crushed, it is only necessary to loosen or tighten the adjusting screws, placing packing blocks on either side of the movable boxes.
The Comet Crusher (Fig. 6) is a rotary coarse-crushing machine of large capacity. It consists of an upright spindle, G, carrying a cone-shaped crusher-head, F, which works in a circular hopper, P, fitted with a chilled-iron lining, E. The axis of the spindle is not coinci dent with the main axis of the machine or bevel-wheel, but intersects it in the jour nal at the top, while the lower end is from + in. to in. (depending on the size of the crusher) out of center. This arrangement causes it gyrating motion at the bot tom of the spindle, the top of the journal being practi cally stationary except in the slight motion due to the angularity, which is very small, and is compen sated for by the oscillating box, B. The spindle, with its fixed crusher-head, F, is not fastened into the bevel wheel, but is free to revolve in it. Crushing is caused by the moving of the crusher-head, le, to and from the liners, B, exactly as in a Blake or other simi lar crusher with reciprocat ing jaw motion, and as the entire space around the head is filled with rock, the crusher is doing duty at every point in revolution of the pulley and gears.
The machine does not have a grinding action, as the head does not turn while crushing. although it is free to do so when not crushing. The crushed rock drops into the inclined chute and immediately slides out. This machine is especially designed for crushing railroad ballast and street macadam, but has also been used for coarse-crushing of ores, phosphate rock, etc. Messrs. Fraser & Chalmers, the makers, state that machines with a 6 x 12 in. opening will crush from 4 to S tons of rock per hour to macadam size, consuming 8 horse power. while the largest machines made, 12 x 24 will crush from 40 to 60 tons per hour, with a consumption of 50 horse-power.
The Gates Crusher is similar in principle and construction to the Comet. Prof, H. 0. liofinatt states, in a paper on " Gold Milling in the Black Hills" (Trans. Am. Inst. Min ing Engrs., vol. xviii.) that one of these crushers, lately installed at the Caledonia mill, at Terrayille, S. D., with three receiving openings, each 12 x 18 in., attended by one man, crushed 200 tons of ore in 10 hours, with about the same horse-power as three No. 5 Mikes, and set to the same size as the latter. When the three Makes were in use, it required 20 hours and 5 men to pro duce the same result. The disadvantage of both the Gates and Comet crushers is their enormous weight, and the consequent diffi culty of transporting them, especially in many mining regions in rough and moun tainous parts of the country.