CRUSHING AND GRINDING MA CHINERY. This article describes the class of crushers and grinders used to break up and reduce rock, stone, ore pigments, etc., to frag ments or to powder.
Crushing machines are used for purposes of coarse reduction. They consist of various forms of "stamps" or stamp-mills, crushing rolls, gyratory crushers, etc., and are employed to reduce metal ores for subsequent treatment by the processes of amalgamation and concen tration; for stone-breaking as for road-metal, and for crushing coal and coke.
For preliminary crushing, that is, for pre paring material for finer crushing by various forms of stamps, rolls and rotary mills such as those described in detail under the title MINING AND MILLING MACHINERY, the types of machines usually employed are the jaw crushers and the gyratory crushers. Of the former, the "Blake," the "Dodge," and the "Buchanan" crushers are among the most familiar and extensively used types.
the top of the main toggle bearing and the bottom of the steel lugs cast on the frame so that the angle of the toggle can be increased for lengthening the stroke, or it may be flattened to diminish the same. For increasing the stroke one or more liners are added, and by this means a variation of about 50 per cent is ob tained in the throw of the jaw. The receiving openings of these crushers range in size from 1% x 3 inches to 24 x 30 inches; their weight ranges from 160 to 60,000 pounds; they require from 4 to 65 horse power to operate them at 250 revolutions per minute, and are capable of re ducing the rock supplied to them into fragments ranging from 1 to 3 inches in size at a rate ranging from 4 to 35 tons per hour, according to the size of the machines. The capacity of a rock breaker depends on the distance between the jaws, and the number of revolutions of the power wheel. The amount of product is also affected by the kind of rock, the hard, brittle variety will go through faster than the sand ,Fig. 1 illustrates a vertical section and a top view of a eBuchanana stone crusher. It consists of a cast steel frame carrying two steel jaws, one fixed and one movable, e which are arranged to form a V-shaped opening. The movable or swing jaw is hinged at the top and is connected with suitable mechanism by which it is alternately pushed forward and backward, to and from the fixed jaw, thus alternately reducing and enlarging the V-shaped opening.
The material to be crushed is introduced at the an top of the opening, and is reduced by the reciprocating motion of the swing jaw to a size fine enough to allow it to pasi through the smaller outlet at the bottom of the opening. The adjustment to crush fine or coarse is made by means of removable steel liners placed be tween the planed surfaces of the frame and the main toggle block. The stroke is adjusted by means of jaw liners of steel placed between stones and other tough rock. The accompany ing table of "Relative Hardness of Elements and Ores" will serve to give a general idea of the relative powers required to crush them. It is important to note, however, that the power required will depend very much on the relative proportions of the mineral to the gangue matter; for example, galena may occur in a quartz gangue, and if the proportion of galena is very large, the hardness of the ore will be near the scale for galena as shown in the table; but, if the proportion is very small, the hardness of the ore will be near the scale for quartz.
Compounds of the heavy metals, such as gold, silver, copper, lead, etc., are soft, their hardness rarely exceeding 2.5 to 3; while that of the compounds of the arsenides and oxides of iron, nickel and cobalt are relatively hard, ranging from 6 to 6.5. Most of the sulphides, carbonates, sulphates and phosphates are soft. The conspicuously hard minerals are found chiefly among the oxides and silicates. The weights of the various ores differ within very wide limits. A spongy dry quartz containing of forms, and are used for the production of a much finer grade of crushed material than that obtained by the use-of the machines already described. In some of them the rolls are equipped with removable steel teeth. Such ma chines are used by the smelters for the coarse crushing of slag shells from slag cars and pots. Other forms have corrugated rolls, while the coal crushers and the coke crushers and sizers have rolls equipped with teeth of special design adapted for the crushing and sizing of the product according to the sizes demanded by the very little metallic sulphurets is naturally much lighter than a wet dense quartz heavily charged with galena. Broken quartz sent to the mill generally ranges from 15 to 22 cubic feet per ton, and a convenient size of truck for handling the same is one having a capacity of about half a ton.