Escalator : is a moving staircase – a conveyor transport device for carrying people between floors of a building. The device consists of a motor -driven chain of individual, linked steps that move up or down on tracks, allowing the step treads to remain horizontal.

Moving walk way : is a slow moving conveyor mechanism that transports people across a horizontal or inclined plane over a short to medium distance. Moving walkways can be used by standing or walking on them. 

1- Step Drive System

2- Handrail Drive System.

The variation on how these two systems are combined is dependent upon the type of escalator. The Drive Machine used to drive the pinion gear or the main drive chain may directly or indirectly drive the Handrail Drive System.

The main drive machine is located in the upper pit area or in a separate

machine room located below the upper section of the escalator. An external drive located in the upper

pit area may employ a direct motor to gearbox drive, or a motor to gear

reducer with a chain drive. An external drive escalator with the

drive unit located within a machine room beneath the upper landing

will normally employ a motor/gearbox with a chain drive

extending to the upper landing.

The Drive machine is located outside the truss.

The Drive machine is located at the upper landing

within the truss between the step bandsThe main drive machine is located at the upper landing within the truss, between the step bands of the escalator. It employs a motor to gearbox drive with a direct drive axle connection. A separate dual drive machine within the step band is not uncommon with one machine used to directly drive the step chains located a few feet below the upper incline and one above the lower incline.

The Drive machine is located within the incline of the truss between the step bands.

The main drive is located within the incline of the truss within the step band. The motor may be directly connected to the gearbox or it may transfer power through a belt drive. The gearbox will have a direct connection to the drive axle. A modular escalator may have a single drive or a multiple drive depending on the overall length of the escalator.

The Drive machine provides the torque to drive the step

band at a constant speed.The drive motor shall be integrally mounted, A.C. squirrel cage, three phase induction motor of continuous rating, reversible type with high starting torque and low starting current and specially designed for escalator application.

It is either directly or flexibly coupled to the reduction gear. The motor is usually protected by thermal and/or electro-magnetic overload devices as well as thermistors in the motor winding.

Today’s drive systems incorporate a solid-state soft-start controller These new types of power control offer the ability to adjust the motor power to match the load. Modular soft-starters allow for gradual smooth starting of three-phase squirrel cage motors. Unlike conventional (older) electromechanical starting systems, these devices allow precise adjustment of motor starting torque, eliminating mechanical shocks to the system’s components.

The drive motor, together with the gear reducer, deliver the necessary torque.

The Main Drive Gear or gear reducer assembly may be a single-stage type gear reducer. This is an enclosed, mechanical device that takes the drive motor torque and transmits this torque to the bull gear through a gearbox shaft (pinion) or the main drive chain. The gear reducer assembly contains a steel worm gear that is coupled or directly sleeved onto the motor shaft and it meshes with the pinion (bronze) gear.

When looking up the escalator you are facing the riser of the step. The length of the step is measured from both ends of the step tread (front and rear) and the width is from both sides of the step. The step frames, treads, and riser excluding their attachment or inserts (yellow demarcations) are a die-cast aluminum design and form the Step Unit Assembly.

Each step in the escalator has two sets of wheels, which roll along two separate tracks. The upper set (the wheels near the top of the step) are connected to the rotating chains, and so are pulled by the drive gear at the top of the escalator. The other set of wheels simply glides along its track, following behind the first set.

The tracks are spaced apart in such a way that each step will always remain level. At the top and bottom of the escalator, the tracks level off to a horizontal position, flattening the stairway. Each step has a series of grooves in it, so it will fit together with the steps behind it and in front of it during this flattening

The Step Chains are endless links connected with link pins to make a complete loop and are attached to an axle on each side of the steps forming a loop which runs for the whole escalator length.

The step motion is achieved by a direct step assembly connection to the step chains.

Two-step chains; one for each side of the escalator are directly coupled to the Main Drive axle, the bull gear shaft, through the step chain sprockets. The step chain form a loop for the length of the truss, from the step chain sprockets at the upper end down to the tension carriage gear or turnaround (depending on the manufacturer) at the lower end or the lower reversing station.

The Main Drive Axle is driven by the motor and reducer assembly. Sprockets or bull gears (depending on the manufacturer). On both ends of the Main Drive Axle transfer power to the Step Drive System. These sprockets or bull gears drive two step chains, one each for the right and left sides of the escalator, which are connected at the lower end of the escalator to the step chain sprockets of the Tension Carriage.

SizeWidth (between

balustrade panels)Single-step

capacityApplications

Energy consumption

Very small 400 mm (16 in)One passenger, with feet together

A rare historic design found mostly in older department stores

3.7 kW (5.0 hp)

Small 600 mm (24 in) One passenger

Low-volume sites, uppermost levels of department stores, when space is limited

3.7 kW (5.0 hp)

Medium 800 mm (31 in)One passenger + one package or one piece of luggage

Shopping malls, department stores, smaller airports

7.5 kW (10.1 hp)

Large 1,000 mm (39 in)Two passengers – one may walk past another

Mainstay of metro systems, larger airports, train stations, some retail usage

7.5 kW (10.1 hp)

Escalator step widths and energy usage

The Circle Tracks provide smooth step travel at the end of the tracks.

The Chain Wheel is used to maintain proper tracking of the step chain.

Most of the outer circle tracks have access windows for easy step

removal.

The Handrail provides a convenient handhold for passengers.

The Handrail is constructed of four distinct sections. At the center of the handrail is a "slider“. The next layer, known as the “tension member” consists of either steel cable or flat steel tape. On top of the tension member are the inner construction components. Finally, the outer layer, which is a blend of synthetic polymers and rubber.

The system uses a drive wheel with an uphill and downhill side.

The escalator handrail is wrapped around a portion of the drive wheel and two pressure rollers. The escalator handrail is driven by the drive wheel with the assistance of the uphill pressure roller and the downhill pressure roller applying pressure to the handrail as it passes through each of the first and second nips. There are also guide rollers with at least one positioned adjacent to the downhill and the uphill sides of the drive wheel.

The Handrail Take-Up Devices are located directly downhill from the handrail drive sheaves. The handrail take-up devices remove slack in the handrail to provide the proper amount of slack in the handrail required to drive the handrail.

There are a the mechanical link between the dual toothed drive chain sprockets. The drive chain sprockets and handrail drive chain coming to transfer power from the bull gear shaft to the handrail drive sheave. The Handrail drive chain has an adjustable take-up sprocket to keep the drive chain snug. The handrail drive chain receives lubrication from an enclosed bath system. 

The Automatic Lubrication System supplies oil to lubricate the main drive chain, step chain, and the handrail drive chains. Oil flow rate is adjustable by setting the automatic timer control “off” and “on” periods to supply more or less lubrication. The system dispenses pre-determined amounts of oil to the distribution network which delivers this oil to the bearing points.

Brakes in lift and escalator applications have to be fail-safe. For this reason, they are invariably spring applied and power lifted (either hydraulically or electromagnetically). The most widely used brake types on escalators are either hydraulic or electromagnetic (i.e., solenoid). An intelligent braking system would require a brake than can be proportionally controlled.

Hydraulic brakes are more amenable to proportional control than electromagnetic brakes. The problem with electromagnetic brakes is that they can either be set in the on or off positions, and it is not possible to keep them in intermediate positions in order to vary the pressure. Hydraulic brakes on the other hand can be controlled by varying the oil pressure that acts against the springs. So the decision was made to use hydraulic brakes for the intelligent braking system.

The pressure applied by the hydraulic brake is the result of the interaction between the spring force (trying to apply the brake pads on the disk) and hydraulic pressure (trying to keep the brake pads off the disk). The spring pressure is constant and cannot be varied, as it is a characteristic of the spring. By controlling the hydraulic pressure, the exact braking effort can be applied. The hydraulic pressure is varied by controlling the valves that control the flow of the oil. Such a control can be done via two methods: • Proportional valves.• Pulse width modulation (PWM) control of on/off valves.

The second method of PWM is the one used in this system. Although the switching is not proportional (i.e., only on and off), the duty cycle of the on/off proportions is varied such that a 50 % duty cycle leads to no change in pressure, while a duty cycle in excess of 50 % (i.e., with the valve feeding the oil staying open longer than 50 %) leads to an increase in pressure and reduction in braking (and vice versa). This requirement to increase or decrease the braking depends on the comparison between the reference ideal speed profile and the actual measured speed profile. 

Escalator speeds vary from about 90 feet per minute to 180 feet per minute (27 to 55 meters per minute). An escalator moving 145 feet (44 m) per minute can carry more than 10,000 people an hour -- many more people than a standard elevator.

-Step widths: 600, 800 & 1000 mm; min. step or tread length = 400mm

- Inclination: usually at angle 30° . 35° if rise < 6 m & speed < 0.5 m/s-Escalator handling capacity:

- Continuous operation is the optimal mode for the commercial sector in which customers are to be transported efficiently to the upper floors of the store.

- Stop-&-go operation is recommended for the intermittent arrival of passengers or for sporadic use outside peak times. Typical applications include movie theaters, airports, subway stations and railway stations. The unit remains ready for operation when there are no passengers, as signaled by a direction indicator. The Schindler entrance monitoring system detects approaching passengers and sets the escalator/moving walk into motion whenever required.

- continuous operation with crawling the escalator/moving walk continues to crawl along at 0.1 m/s in the absence of passengers, using a frequency converter. Unlike conventional stop-&-go operation, mechanical wear is considerably lower, and in this operating mode the readiness for operation and the direction of travel are indicated by the slowly moving steps.