What Goes Up, Also Comes Down: Escalators

What goes up, also comes down: Escalators

Abstract

There are so many mechanisms we consider as a black box. We always take these for granted and really don’t know how they work. An escalator is a fairly simple concept, but no one really seems to know the specifics. They simplify travel to higher floors and allow for space to be more efficiently used. This article discusses the escalator’s history, the individual components’ functionality, and the future escalators.

Keywords: escalator, escalators, up, down, travel, elevators, stairs, moving stairs

Multimedia Suggestions: Refer to [3] for an animated image of the motor system, refer to [8] for a video about curved escalators.

Biography: I’m a petroleum chemical engineer at the University of Southern California. I’m currently in my second year as an undergraduate. I’ve like figuring out why and how something works, especially if it’s something so simple that we take it for granted. I work at the USC bookstore and we have this escalator inside running from open to close, which is where I got this idea.

Introduction

We’re always moving from place to place. However our natural movement is restricted vertically without some tool to aid us. Today most buildings have multiple floors to more efficiently utilize space. In order to reach various different heights a large tool called an escalator is installed. An escalator is a moving set of stairs that allows people to travel to upper and lower heights efficiently. Escalators do not have a waiting interval unless there is a large amount of traffic. However it was initially intended for people’s amusement instead of commercial use [1]. The escalator is an alternative means to using the elevator or stairs. You would only have to walk onto a step, stand, and wait. Once you arrive at the top of the escalator simply step off onto the platform. You have arrived at your destination. The Umeda Sky building escalator is an example of an aesthetically pleasing design and is for commercial use (see Fig. 1).

There are over 30,000 escalators in the U.S., some are weather-proofed for the outdoors. An estimated 90 billion passengers ride the escalator each year. [2]

History

The first escalator-like machine was patented in 1859 in Massachusetts by Nathan Ames. He called it the Revolving Stairs, but it was never actually built [2]. Several years later in 1895 a man named Jesse Reno created a novelty ride at Coney Island called an incline elevator, a moving stairway that elevated passengers [2]. Charles Seeberger of the Otis Elevator Company redesigned it and made it practical. Seeberger dubbed the moving stairway, an escalator from the latin root ‘scala’ for steps and combined it with ‘elevator’. The first commercial escalator was created in 1899 at the Otis factory in Yonkers, N.Y. At the Paris 1900 Exposition, the Seeberger-Otis wooden escalator won first prize. [1]

Jesse Reno’s ride success gave him the title of the “escalator designer”; he was able to found a company with this success called Reno Electric Stairways and Conveyors in 1902. Eventually the company Otis bought Seeberger’s and Reno’s patent rights to the escalator and they dominated the market for escalator production. Before 1950 the escalator was considered a proper noun for a product Otis made so it was called the ‘Escalator’. In 1950 the patent office ruled that ‘escalator’ was just a descriptive term for moving stairways due to various other companies coming into the market. [1]

The Escalator and its Parts

The escalator consists of four main components, the truss, the steps, the handrail, the wheel tracks, and the motor system which consists of an electric motor, pulleys, and gears which pull the track. The tracks, gears, stair assembly, and pulleys are attached to the truss before shipping. The location and specifics of the escalator need to be determined beforehand since the foundation has to be prepared [4]. An image of the escalators is shown below along with a slight view of its mechanics underneath; there are labels for various parts of the escalator (see Fig. 2).

The Truss

It is a metal frame with cross braces that runs along both sides of the escalator and connects at the top and bottom platform. It supports the overall structure and connects everything together. Before it is shipped out, many components such as the gears, stair assembly, pulleys, and tracks are already attached to the truss. The steel framework installed in the foundation will hold the truss in place. [4]

The Steps

The steps are all individual pieces made out of a die-cast aluminum with a comb-like top and front. They most closely resemble a triangular prism. Each step has a set of two wheels, upper and lower. The upper wheel is attached to the ‘back’ of the step. It’s held level by a chain guide that runs through the upper half of each step which is pulled by the drive gear. The lower set of wheels glides on the inner rail stabilizing it further. [3] The steps attach to the motor system and have the ability to collapse onto one another at both of the landing platforms. There may also be yellow paint on the sides of each step to warn passengers about getting too close to the sides. [4]

The Track

The track consists of both the chain guide and the inner rail which are attached to the truss. It loops the entire system and pulls the steps throughout in an endless cycle. The chain guide is attached the upper wheel of each step and the motor pulls the chain guide through. The inner rail stabilizes the step by having the wheel glide on it all the way around. The chain guide and inner rail are parallel at all times in order to allow it to collapse on the top and bottom platform and become steps on the incline. The steps are always level with the track. After the steps reach the top landing platform the steps go about a curve and travel upside down until they reach the bottom platform and follow the path to turn right-side up again. [4]

The Handrail

The handrail consists of a black rubber material that one can hold for stability for going up the escalator. The outside layer of the handrail is made out of rubber and polymer material. Underneath this outer layer are other layers that help move the railing. The first layer is called the ‘slider’ or ‘glider ply’ which consists of cotton or synthetic textile. This layer allows the railing to move smoothly on its track. The layer on top of that is the ‘tension member’ which is either steel cable or steel tape. It provides the necessary tensile strength and flexibility for the railing [4]. The purpose of the tension and textile would allow it to move smoothly along the track. It would also help reduce friction so the handrail system does not get overheated. The outer layer covers these and protects them from natural wear, the environment, and human acts in general. The motor pulls the railing as well to match its timing with the rest of the escalator. [4]

The Motor System

The escalator’s motor system is shown above and its parts are labeled; it rotates clockwise and for an animated version refer to [3] (see Fig. 3). The concept of the motor system is fairly simple. One alternate current motor powers the entire escalator; depending on the height, size, and width, the horsepower of the motor will vary. The horse power can vary from 7.5 to 100 [7]. The motor is designed to be placed near the top of the escalator. There is one primary gear called the ‘drive gear’, it is directly powered by the motor. The drive gear handles the top platform where the steps begin to curve and it also runs two other gears. One is at the bottom of the escalator and is like the drive gear’s counterpart ensuring the steps turn there as well. The other gear is the handrail gear; since it’s powered by the drive gear it runs in sync with the rest of the escalator. [3]

Manufacturing the escalator

The prerequisite to installing an escalator has to deal with its foundation. Concrete fittings must first be poured and the steel framework must be installed to hold the truss in place. Primary and secondary suppliers collaborate in building and designing the escalator. They create the truss with several components already attached to it. Then they ship it out, various methods are then taken to fit the truss and its attached components into its molded foundation. The most common method seems to be with the use of a scissors lift. They jockey the escalator into position, in other cases the truss does not come completely assembled and it is fitted that way. [4] The rest of the components are then assembled like the attaching the steps onto the track. The final steps involve ensuring the power source is connected and everything is connected properly. Several tests are done and the Code of Federal Regulation (CRF) demands escalator quality control checks every year. [4]

The escalator vs. the elevator

The two main differences between an elevator and escalator is the efficiency in traveling to your destination and energy costs. The benefits in using an escalator are no wait interval, faster travel to the next immediate floor, and a larger carrying capacity than an elevator. However the elevator has a stronger potential to travel to higher floors faster than an escalator. The speed of the typical escalator moves at about 1-2 feet (0.3-0.6 m) per second and the maximum inclination of an escalator is 30 degrees with a standard rise of 60 feet (18m). [4]

The energy costs used for the escalator annually consume more than that of the elevator. Most of the time escalators rarely have a full load of passengers, which is when the energy is used most efficiently. The escalator also constantly consumes energy throughout the day while the elevator has the chance to conserve energy when not in use. For a comparison, enough escalators to maintain a six floor building would consume about 187,000 kWh annually while elevators would only consume 130,000 kWh annually [7]. Escalators can save energy based off of whether people use the escalator to go down or go up. When people go up, there is strain on the motor as it carries more weight against gravity. The passenger can walk up the escalator to mitigate the strain on the motor and therefore the cost, although for safety reasons that is not recommended. If the passenger takes the escalator down, there is less strain on the motor since it is assisted by gravity in this case, thereby saving energy.

The escalator is also considered safer since there’s less potential for injury if something goes wrong. If something gets caught in the escalator, the tension snaps, or someone just pushes the emergency stop switch, the escalator will stop moving so that further injuries can be prevented [9]. However in the case of an escalator, you’re most likely locked inside of it until help arrives, whereas with an escalator one could just walk off.

The future of escalators

Escalators have evolved and adapted since their conception. There is a green focus for installing more efficient engines to help conserve energy. New developments in design have been introduced such as the spiral staircase escalators, escalators that carry shopping carts, and escalators able to transport wheel chairs [4]. A company even creatively specializes in using escalators as advertisement space. Although escalators are common place in the U.S., other places such as China and Hungary have begun to realize the potential of escalators and therefore have a huge potential market. Hong Kong is one of the cities that have begun implementing the spiral staircases [8].

References:

[1] Bellis, Mary. The History of the Escalator: Jesse Reno, Charles Seeberger. About.com, n.d. Web. 9 April 2013.

http://inventors.about.com/library/inventors/blescalator.htm

[2] History of Escalators. Escalate.co.uk. n.p. , n.d. Web. 12 April 2013.

http://www.escalate.co.uk/History_of_Escalators.htm

[3] Harris, Tom. How Escalators Work. HowStuffWorks.com, 12 Dec. 2001. Web. 8 April 2013.

http://science.howstuffworks.com/transport/engines-equipment/escalator1.htm

[4] Escalator. MakeHow. n.p. , n.d. Web. 12 April 2013.

http://www.madehow.com/Volume-3/Escalator.html

[5] FEMA E-74 Reducing the Risks of Nonstructural Earthquake Damage. FEMA. N.p., 3 March 2013. Web. 12 April 2013.

http://www.fema.gov/earthquake/fema-e-74-reducing-risks-nonstructural-earthquake-damage-42

[6] Simon. Umeda sky building escalator. Flickr. 11 April 2005. Web. 12 April 2013.

http://www.flickr.com/photos/quaisi/9474729/

[7] Rastogi, Nina. Escalators vs. Elevators. Slate, 10 Aug. 2010. Web. 12 April 2013.

http://www.slate.com/articles/health_and_science/the_green_lantern/2010/08/escalators_vs_elevators.html

[8] The Levylator. YouTube.com. mycityunilondon, 22 Sep 2010. Web. 1 May 2013.

http://www.youtube.com/watch?feature=player_embedded&v=iC_se2zrmLM

[9] "escalator." Encyclopædia Britannica. Encyclopædia Britannica Online Academic Edition. Encyclopædia Britannica Inc., 2013. Web. 01 May. 2013. http://www.britannica.com/EBchecked/topic/192241/escalator