Hoist

A Hoist is a mechanical device used for lifting and lowering a load, typically with a drum or lift-wheel around which a rope or chain is wrapped. In the context of industrial brakes, the hoist application is defined by one paramount, non-negotiable requirement: the absolute prevention of a dropped load.

Consequently, the brake on a hoist is the primary safety device. It is not principally a dynamic or service brake for slowing the load (this is largely managed by the motor and drive); its most critical function is static holding.

The key characteristics of a hoist brake are:

1. Fail-Safe Design: Hoist brakes are universally spring-applied and power-released. This is the essence of their fail-safe nature. Powerful mechanical springs provide the force to clamp the brake by default. Electrical or hydraulic power is required to actively release the brake.
2. Operational Principle:
   • When the hoist motor is commanded to lift or lower, the brake coil is energized at the same instant, releasing the brake and allowing the motor to turn.
   • The moment the motor is de-energized (either by command or by a power failure), the releasing force on the brake disappears. The springs instantly and automatically engage the brake with full force, securely holding the suspended load in a static position.
3. Location: The brake is typically mounted directly to the non-drive end of the hoist motor, on the high-speed side of the drivetrain before the gearbox. This placement takes advantage of the gearbox’s mechanical advantage, meaning a smaller, faster-acting brake can effectively hold the full load torque seen at the drum.

Whether it’s a small workshop chain hoist using an integrated DC electromagnetic brake or a massive steel mill crane with a large electro-hydraulic drum brake, the fundamental principle remains the same: the brake’s primary and most vital role is to fail into the “on” position, guaranteeing that the load will not fall.