Article 7- How do Escalators Work?

Introduction of Escalator Operation

In this article, we intend to explain how escalators work and introduce the main parts which play a vital role in operating the device.

Escalator Truss

The escalator has structural support which is called “Escalator Truss” where all the machinery is located and installed on. The escalator truss is divided into three main sections: Upper section, inclined section, and Lower section. Normally, the upper and lower sections are fixed and to provide variable height, the middle section can be altered.

There are two support angles at both ends of the escalator truss through which they are placed on the construction beams of the building. The support angles are not fixed (not welded, not screwed down, etc.) and are only held down by their own weight.

The escalator truss material is made of different steel alloys and shapes (Rectangle steel, Angle steel, and Channel steel) and combinations thereof in different sizes.

For the escalator truss coating, indoor escalators are coated with paint, and to provide a longer lifetime for semi-outdoor, fully-outdoor, and heavy-duty escalators (according to BS 729 - ISO1461) they are coated with hot-dip galvanized materials with a minimum thickness of 85µm

Track system

Inside the truss, there is a track system, which determines the direction of movement of the steps. The track system comprises three main sections: Upper track, inclined track, and Lower track. The track system holds the responsibility of guiding the step chain and the steps in order to make sure that they move properly in the direction of movement. It also helps the step chain and steps to rotate correctly at transition sections and creates a cycle.

Drive Unit

In the upper section of the escalator, there is the main drive shaft consisting of main parts such as step chain wheels, drive sprocket, and main axis including a sprocket installed on it. Drive Motor and gearbox transmit the motive force to the drive sprocket by a duplex drive chain and causes its movement at a specific speed mentioned in the standard called “Authorized Nominal Speed”. Rotation of the drive sprocket leads to rotation of the main drive shaft and consequently causes the turning of the step chain wheels. The step chain is composed of two sets of roller-chains joined together by several axles in regular intervals, mounted on step chain wheels. Eventually, the steps that are mounted on step chain axles will start rotating.

Handrail Unit

On both sides of the steps, there are safeguards called “Balustrade” made of glass or stainless steel based on the escalator utilization and customer taste, on which rubber rails are installed called “Handrails”. Handrails are provided to ensure passengers' safety so that they can hold onto them and keep their balance. 

Behind the main drive shaft, there is a handrail drive shaft comprised of main components such as a friction wheel and the handrail drive axis including a sprocket installed on it.

From the Main axis sprocket of the main drive shaft, a chain transfers the motive force to the Handrail drive axis sprocket and causes the turning of the handrail drive shaft. The friction wheel on both sides of the handrail drive shaft is located inside the handrail and makes it move. To hold the handrail firm to the friction wheel, a belt comprised of several rollers called” handrail pressure belt” is installed under the handrail. This pressure belt creates the friction force required for the handrail to rotate. In addition, A set of rollers are located before and after the friction wheel called “Handrail Tension Device” that undertakes the responsibility to tighten the handrail on both sides of the friction wheel.

To provide safety, there is a safety circuit consisted of safety contacts and monitoring devices that stop the device in case of emergency situations to protect passengers and prevent any damages to the escalator.