YW-K400/E121 Series Normally-Open Electro-Hydraulic Drum Brake

The YW-K400/E121 Series Normally-Open Electro-Hydraulic Drum Brake is a specialized industrial braking system with a distinct operational mode, designed for applications where a fail-safe closed state is not the primary requirement, or where the brake must be disengaged for extended periods. Here is a description of its main features and operation:

Core Operating Principle:

This brake series operates on a "normally-open" (N.O.) or "de-energized-to-release"​ principle, which is the opposite of the more common spring-applied (normally-closed) brake. Its actuation is provided by an electro-hydraulic thruster (E121 model).

Normal State (Brake Released):​ When the system is in a resting state with no electrical power supplied to the thruster, the brake is in the open (released) position. The mechanical load on the shaft is free to rotate.

Brake Applied (Energized State):​ When the thruster's electric motor is energized, it drives a hydraulic pump to build pressure. This pressure activates a piston or mechanism that applies the braking force, forcing the brake shoes against the drum to stop and hold the load.

Release (De-energized):​ When power is cut, the hydraulic pressure drops, and an internal return mechanism (often a light spring) retracts the shoes, releasing the brake.

Key Features:

Model Designation:

YW-K400:​ Likely indicates the brake series and frame size. "K" may denote a specific "normally-open" design variant, and "400" could refer to a torque rating or drum diameter.

/E121:​ Specifies the model of the integrated electro-hydraulic thruster, designed for this application.

Normally-Open Design:​ This is its defining characteristic. It is used in scenarios where the machinery operates frequently and the brake is primarily used for controlled stopping rather than zero-power holding. It reduces spring fatigue and heat generation from continuous energization required in normally-closed brakes.

Electro-hydraulic Thruster (E121):​ Provides the smooth, cushioned force application typical of hydraulic systems, allowing for controlled engagement. The E121 thruster is sized for the specific force and stroke requirements of the K400 brake.

High Torque Capacity:​ The "400" designation suggests a substantial braking torque rating suitable for medium to heavy-duty applications.

Optional Features:​ May include manual release mechanisms, wear indicators, and automatic wear compensation to maintain shoe-to-drum clearance.

Typical Applications:

This brake is used in situations where the driven equipment is meant to be free to rotate when not actively being braked, or where holding is not required in a power-off state. Examples include:

Controlled Stopping on Conveyors:​ For precise stopping at stations without the need to hold the load against gravity or drift.

Tensioning Systems:​ In applications like paper, film, or textile webs, where a braking force needs to be variably applied during operation.

Some Cranes or Hoists:​ For secondary or service braking functions where a separate, independent holding brake (often spring-applied) is used for safety.

Industrial Machinery Drives:​ Where braking is needed for process control, not for safety parking.

Summary:

The YW-K400/E121 is a normally-open electro-hydraulic drum brake. Unlike fail-safe brakes, it is released when de-energized and applied when energized. This design is chosen for applications demanding controlled, on-demand braking during operation​ rather than automatic, power-off holding. It combines the reliable force of a drum brake with the smooth, adjustable actuation of an E121 electro-hydraulic thruster.

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