The Blake Jaw Crusher, invented by Eli Whitney Blake in 1858, is one of the earliest and most widely used mechanical crushers for rock and ore processing. It operates based on a double-toggle mechanism, where the movable jaw exerts compressive force on the material against a fixed jaw.
Theory of Blake Jaw Crusher
1. Working Principle:
– The Blake crusher uses a pitman (eccentric) mechanism to generate reciprocating motion in the movable jaw.
– The swing jaw moves back and forth, crushing material between itself and the stationary jaw.
– Crushing occurs in a wedge-shaped chamber, where larger rocks are progressively broken down into smaller sizes.
2. Double-Toggle Mechanism:
– Unlike single-toggle crushers, the Blake design uses two toggle plates for better leverage and force distribution.
– The eccentric shaft drives the pitman, which moves the swing jaw in an elliptical motion.
– This design reduces wear and provides more uniform crushing.
3. Crushing Action:
– The material is fed from the top (feed opening).
– As the movable jaw moves towards the fixed jaw, compression crushes the rock.
– When it retracts, crushed material falls downward due to gravity (gravity discharge).
4. Advantages of Blake Jaw Crusher:
– High reliability and simple maintenance.
– Effective for hard and abrasive materials.
– Uniform particle size due to controlled movement.
5. Disadvantages:
– Higher energy consumption compared to modern designs.
– Bulky structure due to double-toggle mechanism.
Mathematical Theory (Crushing Efficiency)
– The crushing ratio is determined by:
\[
\text{Reduction Ratio} = \frac{\text{Feed Size}}{\text{Product Size}}
\]
– Power consumption can be estimated using Bond’s Law or Kick’s Law, depending on particle size reduction.
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Applications
– Primary crushing in mining and aggregate industries.
– Used for hard rocks like granite, basalt, and iron ore.
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