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Inventor: Eli H. Janney, a former Confederate soldier and dry-goods clerk, patented the knuckle coupler in 1873 (U.S. Patent 138,405).

The Janney coupler operates through a sophisticated yet reliable mechanical system that ensures secure train connections. 

Here’s a detailed breakdown of its working mechanism:

1. Key Components

 The coupler consists of:

 Knuckle – A pivoting, claw-like component that interlocks with another coupler.

Locking Mechanism – Includes a lock lifter, lock, and pulling face to secure the knuckle.

Draft Gear – Absorbs shock and buffering forces during coupling and train movement.

Coupler Head & Shank – The main body that transfers pulling and pushing forces.

2. Coupling Process (Connection)

When two rail cars approach each other, their coupler heads make contact.

The knuckles are forced open by the impact and then swing into the locked position.

The lock drops into place behind the knuckle, preventing accidental uncoupling.

The pulling face of the coupler ensures a tight, rigid connection.

3. Uncoupling Process (Separation)

A worker lifts the uncoupling lever (either manually or via a remote system).

The lock lifter raises the lock, freeing the knuckle.

 When the train moves, the knuckles swing open, disengaging the couplers.

4. Self-Adjusting & Safety Features

Automatic Centering – The coupler head aligns itself even if slightly misaligned.

Fail-Safe Locking – The lock prevents unintended opening under tension.

Draft Gear Absorption – Compresses to cushion impacts during coupling and braking.

5.Variations and Modern Designs

While the core knuckle-and-lock mechanism remains, different versions exist for specific needs:

A. AAR (Association of American Railroads) Standards

Type E: Most common in North America, used for freight trains.

Type F: Lighter version for passenger trains.

Type H: Heavy-duty variant for extreme loads.

B. International Variations

Russian SA-3: A stronger, square-shaped coupler used in ex-Soviet countries.

European Tightlock Coupler: Used in passenger trains, allowing closer connections than buffers.

Chinese DF Coupler: Adapts Janney’s principles with local modifications.

C. Specialized Couplers

Dual-Height Couplers: Allow compatibility between different rail systems (e.g., U.S. and Mexico).

Sliding/Articulated Couplers: Used in articulated trains (e.g., trams, subway cars).

6.Comparison with Other Coupler Systems