The compression or tension spring in a traction machine brake that provides the clamping force to apply the brake pads or lining to the drum or disc surface when the brake coil is de-energised (fail-safe design).
Full Definition
Elevator brake springs are manufactured from oil-tempered alloy steel wire (to DIN EN 10270-2) and are designed for indefinite fatigue life at the operating load range, with a safety factor of ≥1.5 against ultimate load. The spring rate and pre-compression are set at commissioning to achieve the specified brake torque; adjustment is made by changing shim thickness or a spring tension nut. Over time, spring relaxation (set) reduces clamping force; inspection intervals should include a spring force measurement or brake torque verification test per EN 81-20 Annex F. Two independent springs per brake arm are required by some manufacturers as a redundancy measure. Springs must not be painted or subjected to temperatures above 200°C, as this affects tempering. In elevator brakes the spring acts as the primary safety element — its failure must be detectable before the next elevator trip.
