A sectional view of the Dodge-type jaw crusher is shown in right. The mechanism of this machine is so simple that it is hardly necessary to enlarge upon what can be gained from an examination of the cut.
In one respect, the Dodge machine is a reversal of the actions we have been discussing; its movable jaw, being pivoted at a point below the discharge opening, has minimum movement at that opening, and maximum movement at the receiving opening.
Because the choke-point and the point of least motion coincide in this crusher, it is to be expected that it would be lacking in capacity, as compared to similar sizes of the Blake-type crusher. The Dodge machine has the virtues of simplicity, low cost, and ease of adjustment and maintenance, but, due to its low capacity, its field is restricted to rather narrow limits.
By reason of the small movement at the discharge opening, the natural expectation would be that the Dodge crusher would deliver a very uniform product, but this would hold true for only a very limited feed rate. The rapid action at the top of the crushing chamber tends to crowd material into the lower zone; this, as we have seen, tends to promote a packed condition, with accompanying production of fines by attrition. The machine works well on hard, clean-breaking rock, or ore, but does not have characteristics suitable to the handling of soft, friable materials which incline to cling and pack.
The Dodge crusher fits into a number of low-capacity applications, such as small mining operations, sampling plants, laboratory work, and numerous special applications where a small product is required, but where the tonnage involved does not justify a two stage operation. The machine is capable of making a very large ratio-of reduction, which is an important feature for the types of application outlined. A table of ratings of Dodge crushers is given.