I. Working Principle of Jaw Crusher
The jaw crusher, commonly known as "jaw breaker," is widely used in mining, metallurgy, building materials, highways, railways, water conservancy, and chemical industries for crushing various ores and large-sized materials. With a relatively simple structure, a complete range of models, and large-scale applications, it is a commonly used primary and secondary crushing machine. Its specifications are identified by the width and length of the feed opening (B × L mm).
Jaw crushers are divided into coarse crushing (PE series) and fine crushing (PEX series). The PE series coarse jaw crusher is mainly used for primary crushing, capable of processing large-sized materials and breaking them into medium-sized particles. The PEX series fine jaw crusher is suitable for secondary crushing, with both feed and discharge sizes being relatively small.
The jaw crusher consists of a movable jaw and a fixed jaw, forming a crushing chamber that simulates the chewing motion of animals to crush materials. The movable jaw periodically reciprocates against the fixed jaw. When the jaws come closer, the material is crushed between them; when they move apart, the crushed material is discharged from the crushing chamber due to gravity.
The frame is generally a rigid structure composed of side plates, front box assemblies, and rear box weldments. Since the frame bears significant impact loads during operation, it must have sufficient rigidity and strength. Medium and small crushers are usually integrally cast, while those larger than 1200 mm × 1500 mm adopt a combined upper and lower frame structure.
The supporting device is mainly used to hold the eccentric shaft in place on the frame. Modern jaw crushers typically use rolling bearings to reduce friction, facilitate maintenance, and ensure lubrication.
To minimize wear and extend the service life of the jaw plates, both the fixed and movable jaws are equipped with liners featuring tooth-like structures, often cast in wave or triangular patterns to aid in material crushing. These liners, made of high-strength wear-resistant manganese steel, protect the jaws from abrasion.
The fixed jaw liner is secured with bolts, with its lower end welded to a steel plate on the frame and its upper end clamped by a pressure plate to prevent movement.
The movable jaw liner is supported at the bottom by a boss on the movable jaw and tightened at the top with a wedge.
The eccentric shaft is the main shaft of the jaw crusher, driving the movable jaw in its reciprocating motion. Flywheels and belt pulleys are mounted on both sides of the eccentric shaft to balance dynamic loads and ensure stable operation.
The tensioning device consists of springs, tie rods, and adjusting nuts. One end of the tie rod is hinged to the bottom of the movable jaw, while the other end passes through a lug on the frame and is tensioned by springs and nuts. This mechanism maintains close contact between the toggle plate, movable jaw, and thrust seat.
During the working stroke, the spring is compressed.
During the discharge stroke, the spring expands.
The tie rod uses spring tension to balance the inertial force of the forward-swinging movable jaw and toggle plate, ensuring timely reverse motion.
The discharge opening width of a jaw crusher can be adjusted via the adjustment device:
Large and medium-sized crushers: Use toggle plates of different lengths, with shims of varying thicknesses placed between the rear frame wall and thrust seat to compensate for jaw plate wear.
Small crushers: Typically employ a wedge adjustment mechanism.
To protect critical components (e.g., movable jaw, frame, eccentric shaft) from damage, jaw crushers are equipped with safety mechanisms:
Most designs split the toggle plate into two segments connected by bolts engineered to fail under excessive load.
Some toggle plates have predesigned weak points (e.g., holes or cast iron sections) that fracture when overloaded, halting the movable jaw’s motion.
Hydraulic jaw crushers incorporate a hydraulic cylinder in the connecting rod for overload protection.
