Many types of crushers use rotating hammers and other crushing elements to reduce materials by impact, shear or attrition. jaw crushers however, crush by compression of material between two opposing forces, the jaws. The movable jaw (the swing jaw) compresses the material against the stationary jaw.
The DT (Double Toggle) Model jaw crusher is unique in that it has its hinge point directly above the center of the crushing chamber. The advantage of this design is that when the movable jaw strokes, its motion is as nearly perpendicular as possible to the stationary jaw. This action produces a pure compression action that minimizes wear of the jaw plates.
Pennsylvania Jaw Crushers
For crushing of hard, abrasive materials, Jaw Crushers are often preferred, since this type of machine will crush virtually any mineral.
Jaw Crushers differ substantially from other types of crushers. There is no rotary motion in the crushing cycle, and all crushing is done by compression of the feed material between two massive jaws, which in effect are a type of breaker plate. Jaw plates can be either smooth or corrugated.
While one jaw is fixed, the other jaw pivots about a top hinge. This moving jaw is shaped to move firmly and squarely against the material, at 250 to 400 strokes per minute. There is no rubbing or grinding, only compression, which produces a generally cubical product with minimum fines.
The moving jaw is so balanced that fully 95% of the drive motor power is used for crushing, while only 5% of the power is needed to move the jaw itself. As a result of this high mechanical efficiency, smaller motors may be used, keeping power costs down.
Behind the stationary jaw are shims, used to compensate for plate wear and to adjust the closed side setting. For protection from uncrushables, there is also an automatic drive disengagement feature that acts instantaneously on the moveable jaw assembly.
Pennsylvania Jaw Crushers accept feed sizes up to 24″ (600mm) and produce a nominal product size as small as 3/4″ (19mm). Product size is determined by the distance between the lower end of the jaws. This gap dimension may be adjusted by shims behind the stationary jaw assembly. These crushers may be choke-fed from hoppers or conveyors.