A Comprehensive Analysis of the Components and Operating System of the Blake Jaw Crusher

The Blake Jaw Crusher, patented in 1858 by Eli Whitney Blake, stands as a monumental invention in the history of comminution. It represents the foundational architecture upon which modern jaw crusher design is based. Despite its age, the core principles of the Blake crusher remain relevant, particularly in understanding the fundamental mechanics of size reduction. This article provides a detailed examination of the key components that constitute a Blake Jaw Crusher and elucidates its distinctive double-toggle mechanical system.

Historical Context and Foundational Principle

Before delving into its components, it is crucial to understand the core operational principle that defines the Blake system. The Blake crusher is characterized as a double-toggle jaw crusher. In this configuration, the pivotal point (the toggle) is located at the top of the machine, near the center. This geometry causes the swinging jaw to have its maximum movement at the discharge opening (the bottom), which is opposite to another common design, the overhead eccentric or single-toggle crusher.

The primary objective of this machine is to apply compressive force to large rocks, breaking them into smaller, manageable fragments. The crushing action is intermittent—a reciprocating motion where the movable jaw presses the rock against the fixed jaw, creating immense pressure that causes fracture.

Detailed Breakdown of Key Components

A Blake Jaw Crusher is an assembly of several critical parts, each playing a specific role in its operation.

1. Frame
The frame is the robust, rigid structural backbone of the crusher. Typically constructed from heavy-duty cast steel or welded plate steel, it must withstand extreme cyclic stresses and vibrational loads generated during crushing. It houses and supports all other components, including the bearings for both pitman and toggle seats. The integrity of the frame is paramount; any deformation can lead to misalignment, premature wear, or catastrophic failure.

2. Fixed Jaw (Stationary Jaw Die)
This is a massive, immovable plate that forms one side of the crushing chamber. It is not part of the frame itself but is securely bolted or wedged to it. The working surface of this jaw is lined with a replaceable jaw die or cheek plate, typically made from austenitic manganese steel due to its excellent work-hardening properties and abrasion resistance.

3. Movable Jaw (Swing Jaw)
The movable jaw is assembled on a sturdy pitman and swings in an elliptical path towards and away from fixed jaw due to eccentric motion transmitted through toggle plates . Like fixed jaw , its crushing face also lined with replaceable manganese steel jaw die . Design swing jaw often includes reinforcing ribs maximize strength while minimizing weight .

4. Pitman (Eccentric Lever)
The pitman acts as connecting rod between eccentric shaft & movable jaw . It primary component responsible for transmitting crushing force from eccentric mechanism directly into swing jaw . Pitman subjected most severe stress entire machine must designed accordingly often box-shaped cross-section provide optimal strength-to-weight ratio . Upper end connected toggle plates while lower end mounted on main eccentric shaft .

5.Eccentric Shaft
Located bottom crusher frame , this large diameter rotating shaft heart motion system . Machined with offset section (eccentric) between two heavy-duty bearings . Rotation shaft causes pitman move up down combined with slight fore-aft motion creating necessary elliptical path for swing jaw . Made high-quality forged steel heat-treated withstand fatigue cyclic loading .

6.Toggle Plates & Seats
This component pair forms defining characteristic “double-toggle” system crucial safety feature .

• Toggle Plates: These flat rectangular bars usually cast iron or mild steel designed serve sacrificial link protect other expensive components from damage should uncrushable material like tramp iron enters chamber . Under extreme overload toggle plate will fracture relieving stress preventing damage pitman shaft frame etc .
• Toggle Seats: These hardened blocks provide seating surfaces ends toggle plates allowing pivoting action transmit motion force between pitman rear wall frame adjustment mechanism .

7.Cheek Plates (Side Liners)
These protective liners mounted inside frame sides adjacent crushing chamber protect frame walls from abrasive wear caused by rock material during compression cycle sliding downward discharge .

8.Discharge Setting Adjustment Mechanism
This system allows operator control size crushed product by changing distance between bottom fixed movable jaws at closed setting position .
In traditional Blake design adjustment achieved through use number interchangeable bronze shims inserted behind rear toggle seat block By adding removing shims operator can move entire toggle assembly forward backward consequently changing position swing jaw relative fixed jaw thereby altering discharge opening Modern versions might employ hydraulic or mechanical jacking systems for easier faster adjustment but principle remains same .

The “Sistim Blake” (Blake System) in Operation

The term “Sistim Blake” refers specifically to kinematic action double-toggle linkage Its operation can be broken down into distinct phases :

1.Feed & Initial Compression: Material fed top machine enters V-shaped chamber formed by fixed movable jaws As pitman moves upward due rotation eccentric shaft movable jaw moves towards fixed jaw compressing rock trapped between them Maximum force applied near top feed opening where largest rocks reside initiating primary breakage .

2.Progressive Crushing & Downward Travel: As crushing cycle continues rock fragments are pushed further down chamber Each successive reciprocating cycle applies compressive force but because pivot point located top movement magnitude greatest at bottom This creates progressive reduction size material as it descends smaller fragments being crushed in narrower sections chamber .

3.Discharge: At bottom stroke movable jaw reaches furthest point from fixed jaw creating maximum gap discharge opening This allows gravity pull crushed material fall through exit crusher Bottom location discharge facilitates gravity flow prevents choking promotes continuous throughput albeit via intermittent action .

Key advantage this “bottom-driven” system ability create “rock-on-rock” wear pattern within chamber where some material layers cushion direct contact between manganese steel liners significantly reducing wear rates compared designs where crushing focused primarily feed opening Furthermore geometry provides high mechanical leverage excellent nip angle effectively gripping particles without pushing them upward out chamber .

Advantages Limitations System

Understanding full context requires balanced view inherent strengths weaknesses design :

Advantages:

• Robust Simplicity: Mechanical design relatively straightforward highly reliable capable handling extremely hard abrasive materials
• High Mechanical Advantage: Double-toggle linkage generates tremendous crushing force at expense stroke making efficient powerful primary crusher
• Minimal Wear at Discharge: Since movement greatest discharge end liners experience less wear lower section compared single-toggle designs leading potentially longer service life
• Effective Nip Angle: Geometry naturally draws material into chamber without slippage

Limitations:

• High Profile & Weight: Due top-mounted pivot Blake crushers tend taller heavier than comparable single-toggle machines requiring more substantial foundations structures
• Lower Capacity per Unit Size: Intermittent action inherently less efficient continuous compression cycles meaning lower throughput for equivalent physical size modern alternatives
• Complex Foundation Loads: Reciprocating motion generates significant vertical horizontal forces necessitating robust dynamic foundation design
• Less Adjustable Under Load: Traditional shim adjustment system difficult perform while machine running unlike hydraulic systems found contemporary crushers

Conclusion

Blake Jaw Crusier represents brilliant engineering solution problem primary rock breaking Its enduring legacy lies elegant mechanical linkage double-toggle system which not only defines machine but also provides set performance characteristics—notably high leverage effective particle gripping While largely superseded more compact higher-capacity single-toggle hydraulic designs for new installations principles components “Sistim Blake” remain foundational knowledge anyone field mineral processing aggregate production Historical significance combined undeniable robustness ensures understanding these machines essential appreciating evolution development comminution technology today