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FIG 2 in part III il1ustrated the cross section of a typical gyratory crusher. Fig. 3 il1ustrates the same crushing chamber we have been considering, except that, in place of the straight face concave, the non-choking type has been substituted. For the sake of direct comparison we have shown the same discharge setting in both diagrams, although a closer setting would be permissible for the non-choking- arrangement.
Inasmuch as the eccentric-throw is the same, and the concaves in the upper part of the chamber parallel those of the standard type, it follows that the successive drops of the material in this zone would be similar. This is true down to line 13. Then we note a difference in the new diagram; the drop per stroke increases much more rapidly than in the former case until, at stroke 16, the line has arrived at the discharge level.
The choke-point has been raised to point 13-14, instead of being at the discharge level. From the choke-point, on down to the discharge level, each successive volume is greater than volume 13-14, and greater than the volume immediately preceding. Therefore, the shape of the crushing chamber in the zone below the choke-point is favorable to choke-free operation. Under certain conditions choking can occur in this zone, however, as will be pointed out later.
The ratio-of-volume-reduction between volumes 0-1 and 18-19 in the figure previously discussed is obviously greater than the ratio between volumes 0-1 and 13-14 in the non-choking diagram; actually the ratio in the former case is about 4: 1, and in the latter about 1.75:1. Therefore, if we assume an equal percentage of voids in the feed for both cases, it is apparent that the non-choking arrangement will not, when the choke-point is reached, have compacted the material to as low a percentage of voids as the straight-face chamber. Also, the actual volume of 18-19, in the standard chamber, is substantially smaller than that of 13-14 in the no-choking chamber. Inasmuch as these volumes pass the choke-point in the same time-period, the capacity through the 13-14 zone is obviously the greater of the two. |
