Defintion • An escalator is a moving staircase – a conveyor transport device for carrying people between floors of a building.
History • In 1889, Leamon Souder successfully patented the "stairway", an escalator-type device that featured a "series of steps and links jointed to each other". No model was ever built. • In November, 1898, Piat installed its "stepless" escalator in Harrods Knightsbridge store in England.
Benefits • The capacity to move large numbers of people. • Can be placed in the same physical space as one might install a staircase. • No waiting interval (except during very heavy traffic). • They can be used to guide people toward main exits or special exhibits.
Main components: • Landing Platforms. • Truss. • Steps and Tracks. • Handrail. • Wheel track & step chain. • Driving & control unit.
Landing Platforms: • The top platform contains the motor assembly and the main drive gear. • Each platform contains a floor plate and a combplate. • The floor plate provides a place for the passengers to stand before they step onto the moving stairs. • The combplate is the piece between the stationary floor plate and the moving step.
Truss • Assembly of structural steel that supports the weight and load of an escalator. • A Control Panel, Drive Units for Steps and Moving Handrails and other components are housed inside the structure. • Main parts: - Top Machine Room/Bottom Machine Room. - Main Track. - Trailing Track. - Moving Handrail Drive Unit.
Top Machine Room/Bottom Machine Room 1) Control Panel: Controls stop/start operation and also supplies electric power to the Drive Unit. 2) Drive Unit: A unit to drive the escalator, comprised of electric motor, decelerator, electromagnetic brake, V belt, Sprocket, and other components. 3) Drive Chain: A chain that transmits the Drive Unit's power to the drive wheel (Sprocket). 4) Sprocket (top/bottom): Drive wheels installed at top and bottom to drive the Steps. The top Sprocket drives the moving Steps, while the bottom sprocket turns the Steps.
Steps & Tracks: • The track system is built into the truss to guide the step chain, which continuously pulls the steps from the bottom up and the other way around. • Every step has 4 wheels: 2 step-wheels and 2 trailing-wheels. • For both type of wheels there’s a separate track: the step-wheel track (on the outer side) for the step wheels and the trailing wheel track (on the inner side) for the trailing wheels.
Steps & Tracks: • The wheels on the step-wheel track are the ones that are connected to the rotating step chain and so are pulled by the main drive gear at the top of the escalator. The other set of wheels just glide along its track, following the other ones.
Steps & Tracks: • The steps themselves are solid, one piece, die-cast aluminum or steel. • Yellow demarcation lines may be added to clearly indicate their edges.
Step Chain: • A chain, located on both sides of an escalator, connecting the Steps and driven by the Step Chain Sprocket.
Handrails: • The handrail provides a convenient handhold for passengers while they are riding the escalator. • Moves along the top of the Balustrade in synchronization with the Steps.
Handrail Driver: • The handrail drive system is directly driven by the step drive system by adding an extra belt around the main drive gear that also drives the steps. • Like this, both the steps and the handrail move at the same speed, making the ride for the passengers on the escalator more comfortable.
Driving Unit: • The motor is a three phase squirrel cage AC induction motor specifically developed for escalator service. • High starting torque. • Minimal vibration. • Reversing Type.
Motor starting: • Direct-on-line. • Star-Delta starter. • Soft-starter(variable source voltage). • VVVF Control (Variable Voltage, Variable Frequency)
VVVF energy optimizer Controller: • Its soft starting feature also lowers excessive starting current and prevents wearing of mechanical gears, chains, belts etc. So it prevents mechanical shocks. • Reduces losses in AC induction motors by way of voltage reduction and soft starting capability. • It provides the required motor operating voltage to suit various loading conditions, resulting in higher power factor (i.e. better power efficiency) and reduced motor losses.
Braking: • An intelligent braking system would require a brake that can be proportionally controlled. • The most widely used brake types on escalators are either hydraulic or electromagnetic.
Electromagnetic Braking: • 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 Braking: • Hydraulic brakes on the other hand can be controlled by varying the oil pressure that acts against the springs. • So modern escalators and intelligent braking systems use hydraulic brakes.
Hydraulic Braking: • 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.
Hydraulic Braking: • 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.
Case Study: • Swafyyeh Mall (Avenue):
Main Wheel: Main Chain Step chain Main Wheel
References: • Wikipedia. • www.mitsubishielectric.com • www.howstuffworks.com • buckylab.blogspot.com • Intelligent Braking Systems for Public Service Escalators by Dr. Lutfi Al-Sharif.
Thanks for your attention. Done by : Ahmad Alammouri 0094295