blake type jaw crusher

Blake Type Jaw Crusher: An Overview

The Blake type jaw crusher, named after its inventor Eli Whitney Blake in 1858, represents the foundational design of the modern overhead eccentric jaw crusher. It is characterized by a fixed vertical jaw and a swinging reciprocating jaw pivoted at the top. This article provides a detailed overview of its working principle, key components, advantages, and typical applications in primary crushing operations. We will also examine its evolution and compare it with other crusher types.

Working Principle and Key Components

The core action of a Blake crusher is compressive force. The movable jaw (swing jaw) is hinged at the top and moves back and forth via an eccentric shaft and toggle plates. As the swing jaw closes against the fixed jaw (stationary jaw), rock fed into the chamber (crushing chamber) is nipped and crushed. On the return stroke, crushed material descends by gravity until it is small enough to escape through the opening at the bottom, known as the discharge setting.

Key components include:

• Frame: Heavy-duty construction to withstand shock loads.
• Fixed & Swing Jaw Plates: Replaceable wear liners, often made from manganese steel.
• Eccentric Shaft: Transmits motion from the drive to the swing jaw.
• Toggle Plates: A safety mechanism that will fracture under uncrushable material (tramp iron) to protect other components from severe damage.
• Cheek Plates: Liners on the sides of the crushing chamber.

Comparison: Blake (Double Toggle) vs. Overhead Eccentric (Single Toggle) Design

While modern single-toggle crushers evolved from Blake's concept, distinct differences remain. The classic Blake design uses two toggle plates.

Feature	Blake Type (Double Toggle)	Modern Single Toggle Jaw Crusher
Toggle Mechanism	Two toggles: one for transmission, one for positioning.	One toggle plate integrated with the pitman.
Jaw Motion	More elliptical/reciprocating motion with less vertical movement.	More aggressive elliptical motion with significant vertical movement.
Wear on Jaw Plates	Generally lower wear due to less rubbing/abrasion.	Higher wear potential due to both compression and sliding/rubbing action.
Output & Shape	Traditionally produces fewer fines and a more uniform product shape.	Higher capacity for a given size; can produce more fines.
Construction & Weight	Heavier, more robust, and often more complex frame design.	Lighter, more compact design for equivalent capacity.
Typical Application	Heavy-duty primary crushing of hard, abrasive materials; less common in new installations but valued for longevity.	Dominant modern design for both stationary and mobile primary crushing plants.

The double-toggle principle remains highly regarded for its low wear cost and ability to handle extremely hard, abrasive materials with minimal rubbing action.

Real-World Application Case Study

A notable application of robust double-toggle style crushers is in hard rock aggregate mining.

• Project: Primary crushing station at a granite quarry.
• Challenge: Processing highly abrasive granite with high silica content, which causes rapid wear in crushing components.
• Solution: Installation of a heavy-duty double-toggle jaw crusher as the primary breaker.
• Outcome: The crusher's motion minimized abrasive sliding between the rock and jaw plates compared to some single-toggle designs. This resulted in significantly extended liner life—often 20-30% longer—reducing downtime for liner changes and lowering cost per ton for wear parts despite a potentially higher initial capital investment.

Frequently Asked Questions (FAQ)

1. Is the original Blake crusher still used today?
   While Eli Whitney Blake's exact 1858 model is not manufactured today, his double-toggle principle remains in production by several manufacturers (e.g., Kue-Ken/Kawasaki). These modern versions are engineered with advanced materials and precision but retain the fundamental kinematic motion he invented.

2. What are the main advantages of a double-toggle Blake-style crusher?
   Its primary advantages are exceptional durability when crushing hard, abrasive materials and lower wear costs over time due to its predominantly compressive crushing action with minimal friction between rock and liners.

3. Why are single-toggle crushers more common than double-toggle today?
   Single-toggle designs are generally lighter, less expensive to manufacture initially, have higher capacities per unit size due to their more aggressive stroke, and are simpler in design—making them ideal for mobile plants where weight matters.

4. Can a Blake-type crusher handle tramp metal?
   Yes, its design incorporates safety features like sacrificial toggle plates designed to break or shear upon encountering an uncrushable object like tramp metal or "tramp iron," protecting vital components like the eccentric shaft from catastrophic failure.

5. What type of product does it produce?
   Typically, it produces a well-graded product with fewer slabby or elongated particles compared to some other primary crushers because of its straight-line compressive action at both entry and exit points of the chamber