A spring stores elastic energy.

Deforming a spring creates a restoring force. Within a linear spring’s working range, force rises in proportion to deflection: F = kx, where k is spring stiffness.

Springs can work in compression, extension or torsion. Their materials and geometry determine their limits; the linear model does not apply to every spring at every deflection.

Stiffness connects force and movement.

An ideal spring with stiffness 1,000 N/m

Compressing it by 0.02 m produces 20 N of restoring force and stores 0.2 J of energy: E = ½kx².

This example starts from an unloaded spring. An assembled mechanism may already contain preload, so additional movement does not start from zero force.

Holding is different from stopping.

A friction brake presses surfaces together to resist relative movement. Holding a stationary shaft requires sufficient resisting torque. Stopping a moving system also requires energy to go somewhere.

During friction braking, mechanical energy becomes heat. A holding torque rating alone does not describe the brake’s ability to absorb repeated stops.

One common electrically released arrangement.

Coil off: springs apply the brake.

Coil off: spring-applied brakeThe spring pushes the armature left. The armature clamps the lined rotor disc against a fixed plate, resisting shaft rotation. The coil is de-energised. The arrow shows the armature’s applying direction.1234

Coil on: magnet releases the brake.

Coil on: electrically released brakeThe energised coil attracts the armature right toward the fixed magnet body, compressing the spring. Exaggerated clearance beside the friction lining allows the shaft and rotor disc to turn. The arrow shows the release direction.1234
  1. Coil and magnet body. Current creates a magnetic field. Attraction pulls the armature towards the fixed body.
  2. Applying spring. Pushes the armature towards the friction disc when magnetic release force is absent. Release compresses the spring further.
  3. Armature. Moves a short distance axially. Applied, it clamps the disc; released, it leaves clearance.
  4. Friction interface. Linings on the rotor disc press against the fixed plate and armature to produce resisting torque. The disc is coupled to the shaft.
A generic spring-applied disc brake, shown in section. Clearances and movement are exaggerated. The shaft and rotor turn; the magnet body, fixed plate and armature do not turn. Actual lift brake arrangements vary.

This connects the solenoid principles from Module 02 to mechanical force. The electrical supply releases the brake; the springs provide the applying force.

A lift brake is part of a coordinated system.

In many traction systems, the drive controls normal deceleration and the machine brake holds the car once stopped. Brake operation and monitoring are coordinated with the controller.

The machine brake is distinct from lift safety gear. Spring application alone does not prove that a brake can hold: friction condition, mechanical travel and the complete design still matter.

A closer look

Stored spring energy can remain when electrical power is absent. Understanding a brake’s operating principle is separate from dismantling or adjusting it; the installed design determines its specified clearances, forces and checks.

Check your understanding

Does a stationary brake holding torque continuously turn that torque into heat?

Reveal the explanation

Not through frictional sliding if there is no movement. During a sliding stop, energy is dissipated as heat. Electrical coils may have separate heating losses.

Further reading.

Optional reading to explore this lesson in more detail.

  • OpenStax: spring force and stored energy

    Section 16.1 explains spring stiffness and elastic potential energy. Use the diagrams and worked examples to understand the limits of the linear-spring model.

  • KEB: a spring-applied brake in operation

    The video and transcript show one spring-applied, electrically released brake. Focus on the operating sequence; its construction and manual-release arrangement are specific to the illustrated product.

Connect this to motors.

See how electrical and mechanical principles meet in our introduction to how motors work.