The pair of high-tensile roller chains attached to both sides of every escalator step, forming a continuous closed loop that transmits drive force from the sprockets and maintains precise step spacing and orientation throughout the escalator.
Full Definition
Step chains are the primary power transmission and step-positioning elements in an escalator. Supplied in pairs (one on each side): (1) Chain pitch — distance between successive roller pin centres; standardised pitches (e.g. 133.33 mm) ensure synchronisation with step tread spacing and comb plate tooth pitch; (2) Construction — high-tensile alloy steel link plates, hardened pins and bushes, and roller bearings to minimise friction in guide tracks; (3) Step attachment — each step axle is bolted to the inner link plates of both chains, keeping all steps parallel and at equal spacing; (4) Tension device — adjustable idler sprocket at the lower landing maintains correct tension and takes up chain elongation from wear; (5) Lubrication — continuous or periodic automatic lubrication required; (6) Safety — EN 115-1 requires chain slack/break sensors on both chains; if tension falls below a threshold, the escalator stops immediately. Periodic elongation measurement is required; when cumulative elongation exceeds 2% of original pitch length, replacement is mandatory.
