Swing Jaw and Fixed Jaw Working Mechanism Knowledge

Swing Jaw and Fixed Jaw Working Mechanism Knowledge

The swing jaw (movable jaw) and fixed jaw form the core crushing cavity of a jaw crusher. Their coordinated reciprocating extrusion motion is the fundamental mechanism that breaks rock and ore. The fixed jaw stays stationary as one static crushing surface, while the swing jaw performs periodic back-and-forth swinging driven by the eccentric shaft. Their relative movement creates alternating compression and release space inside the V-shaped cavity to realize continuous stone crushing. This article elaborates on their individual structure, matching relation and complete collaborative working mechanism.

1. Basic Structural Layout of Fixed Jaw

  1. Installation position

    The fixed jaw assembly is firmly bolted to the front inner wall of the crusher main frame, with no displacement or swing during full operation. It acts as the static bearing surface for material extrusion.

  2. Core components
  • Fixed jaw plate: High manganese wear-resistant tooth plate with raised crushing teeth, directly contacting raw stones. The tooth ridges concentrate pressure to split brittle rock easily.
  • Fixing wedge blocks and lock bolts: Fasten the jaw plate tightly to the frame to prevent loosening under repeated strong impact and vibration.
  1. Structural feature

    Its vertical surface forms the right side of the wedge-shaped crushing cavity, maintaining a fixed inclined angle from top feeding inlet to bottom discharge outlet. The V-shaped space gradually narrows downward for layered automatic crushing.

2. Basic Structural Layout of Swing Jaw

  1. Installation position

    The swing jaw body is sleeved on the eccentric shaft at the top of the crusher, suspended freely inside the frame, opposite to the fixed jaw plate. It is the only moving component involved in direct stone extrusion.

  2. Core components
  • Swing jaw casting body: Heavy thick steel support carrier, bears all thrust transmitted by the toggle plate.
  • Movable jaw plate: Matched wear-resistant tooth plate, installed on the inner surface facing the fixed jaw; its tooth profile aligns crosswise with fixed jaw teeth to maximize splitting force.
  • Bearing housing: Fits the eccentric shaft to convert rotational motion into swing displacement.
  1. Motion characteristic

    Driven by the offset cam of the eccentric shaft, the swing jaw follows an elliptical reciprocating track (single toggle type) or pure horizontal linear swing track (double toggle type).

3. Matching V-Shaped Crushing Cavity Formed by Two Jaws

The gap between fixed jaw plate and swing jaw plate forms a unique V crushing chamber with three functional zones:
  1. Feeding zone (upper wide section): Large rock lumps fall in and receive preliminary squeezing and splitting.
  2. Intermediate crushing zone (middle narrow section): Medium-sized fragments are repeatedly extruded for secondary breaking.
  3. Discharging zone (bottom narrowest gap): Small particles meeting size standards drop out by gravity.

    The fixed jaw keeps its inclined angle unchanged; the swing jaw’s periodic swing changes the cavity volume repeatedly, which is the precondition for continuous crushing.

4. Complete Collaborative Working Mechanism Cycle

Stage 1: Compression Stroke (Crushing Stage)

The eccentric shaft rotates to its maximum offset position, pushing the top of the swing jaw toward the fixed jaw.
  • The clearance between the two jaw plates shrinks sharply; all trapped stones are clamped between tooth surfaces.
  • Combined forces of extrusion, bending and splitting act on rocks. Internal micro-cracks expand until lumps crack into small fragments.
  • The fixed jaw provides rigid counterforce without shifting, while the swing jaw delivers active thrust powered by the toggle plate and eccentric shaft.
  • Oversized blocks in the upper cavity cannot fall down and remain clamped for repeated compression.

Stage 2: Release Stroke (Discharging Stage)

The eccentric shaft rotates to the opposite offset position. The tension spring and tie rod pull the bottom of the swing jaw backward, separating the swing jaw plate from the fixed jaw plate.
  • The V cavity clearance widens instantly. Fragments smaller than the bottom gap slide down along both inclined jaw surfaces and exit the crusher.
  • Larger uncrushed rock chunks stay suspended in the middle cavity, waiting for the next compression stroke.
  • The fixed jaw still maintains static positioning to support residual materials during discharging.

Stage 3: Continuous Circulation

The eccentric shaft rotates nonstop, repeating compression and release strokes dozens of times per minute. The fixed jaw acts as a stable static counter-surface all the time, and the swing jaw performs cyclic swing. Raw materials complete layered crushing from top to bottom automatically without manual intervention.

5. Motion Difference: Single Toggle vs Double Toggle Swing Jaw Mechanism

Single Toggle Jaw Crusher (Mainstream Model)

  • Swing jaw motion track: Elliptical orbit with horizontal swing plus slight vertical up-and-down sliding.
  • Cooperation effect with fixed jaw: Vertical friction enhances material crushing efficiency and accelerates material downward sliding, raising hourly output.
  • Shortcoming: Vertical friction speeds up wear of both fixed jaw and swing jaw plates.

Double Toggle Jaw Crusher

  • Swing jaw motion track: Pure horizontal reciprocating movement, no vertical displacement.
  • Cooperation effect with fixed jaw: Only horizontal extrusion force exists, tooth plate abrasion is milder.
  • Advantage: Suitable for ultra-hard rock; uniform particle shape of finished aggregate.
  • Shortcoming: Complex transmission structure, higher manufacturing cost, lower throughput than single toggle type.

6. Key Coordination Rules Affecting Crushing Efficiency

  1. Cross tooth alignment

    The tooth ridges of swing jaw plate and fixed jaw plate must be staggered correspondingly. If teeth face each other flat, splitting force drops sharply and crushing capacity decreases.

  2. Uniform gap wear

    Long-term uneven abrasion on partial positions of fixed or swing jaw plate will form irregular cavity space, causing unqualified oversized finished stones. Timely turning over or replacement of jaw plates is required.

  3. Synchronized swing amplitude

    Malfunction of eccentric shaft, toggle plate or tension spring will change swing jaw travel distance, breaking matching clearance with fixed jaw and resulting in machine blocking or low production.

7. Failure Consequence of Abnormal Matching Between Swing Jaw and Fixed Jaw

  1. Loose jaw plate: Impact force makes fixed/movable tooth plate shift, leading to uneven extrusion and irregular stone output.
  2. Swing jaw stuck: Broken toggle plate or failed tension spring stops swing jaw reset, the cavity remains fully compressed and materials cannot discharge.
  3. Severe tooth plate wear: Flat tooth surfaces lose splitting capacity, more medium-size stones fail to be crushed, reducing finished product qualification rate.