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Talking of the operating characteristics of the various rock crusher types we shall avoid, as far as possible, burdening the reader with mechanical details, which are covered quite thoroughly in catalogues and bulletins printed for that purpose. A brief general description of the essential features of each type will serve to clarify the action, for those who are not familiar with crushing equipment.
Fig. 1 shows a sectional view of a typical gyratory crusher. This type of machine is, by virtue of chronological priority gyratory, known as the “standard” gyratory crusher. Although it incorporates many refinements in design, it is fundamentally the same crusher that first bore the name of “gyratory” its crushing chamber is very much the same shape; the motion is identically the same, and the method of transmitting power from belt to crushing head is similar. It is an interesting fact that the same similarity in essential features of design exists in the case of the “standard” or Blake type, jaw crusher, which is something in the way of a tribute to the inspiration and mechanical ability of the men who originated these machines.
Essentially, the gyratory crusher consists of a heavy cast-iron, or steel, frame which includes in its lower part an actuating mechanism (eccentric and driving gears), and in its upper part a cone-shaped crushing chamber, lined with wear-resisting plates (concaves). Spanning the crushing chamber across its top is a steady-rest (spider), containing a machined jour¬nal which fixes the position of the upper end of the mainshaft. The active crushing member consists of the mainshaft and its crushing- head, or head-center and mantle. This assembly is suspended in the spider journal by means of a heavy nut which, in all but the very large machines, is arranged for a certain amount of vertical adjustment of the shaft and head. At its lower end the mainshaft passes through the babbitted eccentric journal, which offset s the lower end of the shaft with respect to the centerline of the crusher. Thus, when the eccentric is rotated by its gear train, the lower end of the mainshaft is caused to gyrate (oscillate in a small circular path) , and the crushing head, likewise, gyrates within the crushing chamber, progressively approaching, and receding from, each element of the cone shaped inner surface.
The action of the gyratory crusher, and of the other member of the reciprocating pressure family, the jaw crusher, is fundamentally a simple one, but as will be seen a great deal of thought and so me very progressive engineering has been ex pended upon the design of crushing chambers to increase capacities and to permit the use of closer discharge settings for secondary and fine-reduction crushing.
Referring to the table, always available from the manufacturer, it will be noted that standard gyratory crushers are manufactured in commercial sizes ranging from 8 in. to 60 in. receiving openings. Capacities are listed, for minimum and maximum open-side discharge settings, in short tons per hour, and the horsepower requirements for soft and hard materials are listed for each size. The capacities, and the minimum settings, are based upon the use of standard (straight-face) con caves.
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