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TECH TIPS: INSTALLATIONSBACKGROUND ON ELEVATORS

Ever since the fi rst multilevel buildings were built the concept of vertical transportation has been on man's mind. The oldest forms of this desire can be found in the creation of simple ladders, stairways, animal-driven hoists and manually powered windlases or capstans. Some ancient Roman buildings even reveal evidence of shaftways where the use of manually hoisted moveable platform is indicated. However the fi rst documented use of advanced geared techniques used in hoisting materials is often credited to architect and engineer Filippo Brunelleschi in the 15th century AD, during the creation of the dome of Florence's Basilica de Santa Fiore. From the Renaissance period to the 19th century, development of what we would call an elevator evolved slowly from simple baskets hauled by ropes to steam-driven hoists. Unfortunately the result of these efforts were occcasionally less than successful (and sometimes fatal). Many of these failures can be attributed to their lack of understanding of basic engineering principles and how to calculate materials stresses, a reliance on the use of simple fi ber ropes to provide lift, and a failure to implement safety devices that could reliably stop a car in case of a linkage failure. It was not until 1857 that the modern passenger elevator began to win public acceptance through its use in the store of of E.V. Haughwort & Company in New York. Traveling at a speed of 40 fpm (0.20 mps) the device incorporated a novel elevator safety device by Elisha Graves Otis that would immediately engage should the hoist rope fail. This safety device, coupled with advances in steam powered hoisting engines and improvements in wire hoisting rope, offered architects the ability to satisfy the growing demand for convenient, cheap offi ce space by allowing them to be able to build skywards. This led to the development of the familiar modern steel/glass skyscraper, which have become a familiar, visual metaphor for progress throughout the world today. Due to recent advances in metallurgy, electronics, computer technology, the future potential for elevator design remains wide open. Indeed, not only for its use conveying customers and freight in increasingly tall buildings, but in the possibilities it offers in lifting payloads into low Earth orbit. The idea of a "Space Elevator" was fi rst proposed by author Arthur C. Clark in the mid 20th Century, and it is a concept that is being seriously reviewed in various symposiums throughout the world today.

Early Elevators

Until 1903 elevators were of drum or hydraulic-type design (both roped and direct plunger). Though

useful both possessed design limitations as well. For instance, to meet the needs of even higher buildings drum-type machines required enormous cylindrical drums to hold the vast wound coils of hoist rope required. In addition, drum-type machines needed costly back-up equipment to prevent the car from being drawn into overhead areas should primary electrical methods fail. The effi ciency of a hydraulic elevator's design for high-rise buildings was often hampered by the length of the cylinder used to raise or lower the cab, and the size of the hole (often as large as the height of the rise) needed by direct-plunger-driven hydraulic elevators. These factors, in addition to the desire by planners to dedicate as little fl oor space as possible to the actual placement of elevator machinery (creating even more profi table, usable fl oor space), the availablity of low-cost commercial electricity, and the need to convey passengers more quickly, led to the development of a far more effi cient and versatile form of elevator design—the traction elevator.

Traction Elevators

Basically traction elevators work by using hoist ropes to transmit the lifting force created by rope friction as a rope makes contact with the grooved surface of the drive sheave. Through the use of an electrical motor, the speed and direction of an elevator car is maintained. From the top of the car, the ropes wrap simply around the drive sheave (nestling within the grooves of the sheave) where they then proceed to the counterweight area and are fi nally terminated (this is called a Single-wrap roping). Often one fi nds that only the simple combined weight of the car and the counterweight is used to keep the ropes seated safely within the grooves of the drive sheave. However higher speed elevators often use a Double-wrap design, where the ropes pass over the sheave twice. Traction elevators provide architects with the ability to use multiple ropes (which improves traction as well as increasing safety factors) and their design greatly lessens the chance of a car or counterweight being drawn into overhead equipment areas should an electrical stopping switch ever fail. In addition, traction elevators are capable of extremely high rises (which can be seen both in deep mine conditions and in today's newer high-rise buildings). Major critical factors one must consider are rope weight and the load those ropes place on the sheave shaft and surrounding machinery. Over the years engineers have tried to address these factors through the use of modifi ed sheave groove profi es, implementation of multiple defl ector sheave arrangements, more complicated roping

Double-wrap Gearless Machine

Gearless Machine

Geared Machine

Typical geared machine (Single Wrap)

Hoist Rope

Drive Motor

Drive Sheave

Defl ector Sheave

Double-wrap sheave

Drive Motor

Hoist Rope

Drive sheave

Bedplate

Brake

BrakeDrum

Brugg Wire Rope, LLCBrugg Wire Rope, LLC


Gearless Machines

Geared Machines and ComponentsDefl ector Sheave

Drive SheaveHoist Rope

Gearless Machine MG 28 Compact Gearless Machine (Double Wrap) Baby Gearless Machine GH 330

Worm, ring gear and traction sheave(detail from drawing at left)

EPD machine with planetary gearing

Longwrap traction machine with helical gear

A low-speed shaft supported by twobearings on either side of the sheave

1. AC driving motor2. DC brake3. Worm and worm shaft machined in one piece

4. Worm wheel5. Traction sheave

6. Tapered roller bearings

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Typical under-driven worm gear


Drive MotorBrake

BrakeBrake

Hoist Rope

Hoist RopeHoist Rope

Drive Motor Drive Motor

Drive SheaveDriveSheave

DriveSheave

Bed Plate

Defl ector Sheave

Hoist RopesHoist Ropes

Drive SheaveDrive Sheave

Drive Sheave

Drive Motor

Drive Motor

Brake


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Machine-Room-Less (MRL) Elevator Machines

Geared Machines

Machine MX 06 EcoDisc™ MiniSpace™ MX 18 EPM Machine for roomless elevatorsseen mounted in wall niche

SR 3006 Worm Gear Machine (vertical position) Titan 1 Machine


Drive Sheave

Drive Sheave

Drive Sheave

Drive Sheave

Hoist Ropes

Hoist Ropes Hoist

Ropes

Hoist RopesDrive

Motor

Drive Motor

Drive Motor

Drive Motor

Guide Rail

Brake

Brake

Brake

Brake



GearlessInstallation

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1. Hoist Ropes2. Compensation Rope/Chain3. Governor Rope4. Door Closing Ropes5. Machine6. Counterweight7. Secondary/Deflector Sheave

8. Governor 9. Governor Tension Sheave10. Travelling Cable11. Drive Sheave

arrangements, and the use of new materials in installation component manufacture. Unfortunately many of these advances have had a negative impact both on the life expectancy and performance of the hoist ropes themselves.

Gearless Machines

Gearless Traction machines now serve as the accepted standard for high-rise, high-speed (over 400 fpm/2.0 mps) high-performance elevator installations. On higher speed gearless traction machines (800 fpm/4.0 mps), ropes are typically applied in a double-wrap arrangement in order to increase traction and minimize rope wear. A gearless traction elevator typically comprises a large slow-speed (50 to 200 rpm) DC (though some AC motors are used) motor connected to a drive sheave ranging in size from 30 to 48 in. (750 to 1200 mm) diameter. To stop the drive sheave, an electrically released spring-applied brake is applied. Though expensive and bulky, slow-speed DC motors are necessary to drive large diamerter sheaves. And on the whole, larger drive sheaves better conform to the bending radius of elevator hoist ropes and promote longer hoist rope life overall. Normally, Single-Wrap roping arrangements are perferred in either gearless or gearless traction arrangements, as this offers 180° of rope contact with the sheave, removes the need for defl ector sheaves, and can eliminate diffi cult fl eet angles when used with large sheaves.

Geared Machines

Geared Traction machines use a high-speed AC or DC motor with a reduction gear to drive the traction sheave. Such a design creates slow sheave speeds and high torque, which offers advantages in elevator performance Geared meachines are used in elevators and dumbwaiters from 25 to 30,000 lbs (10 to 14,000 kg) or more, and speeds from 25 to 450 fpm (0.125 to 2.3 mps). The true advantage in a geared design lies in its complete fl exibility as to worm gear ratios, motor speeds, horsepower, drive sheave diameters, and roping arrangements. Indeed, in some materials handling applications geared machines are used for speeds of up to 600 fpm (3.0 mps) or more. Geared and (and a number of Gearless machines as well) commonly utiltize various types of agressive undercut grooving to

increase traction and this has led to evidence of dramatically increased sheave and rope wear. Though some manufacturers have tried to correct this situation through the use of protective polyurethane sheave liners (which also seeks to improve rope traction), such remedies have only met with limited success.

Hydraulic Elevators

Another major type of elevator design used today is a more advanced variation of the hydraulic elevator concept. One variety (Holed Hydraulic) uses a direct-plunger-driven from below device where the cylinder extends into the ground as deep as the elevator rises. Today's hydraulic elevators use hydraulic oil as their operating fl uid, as opposed to water steam, which is moved under pressure through high-speed pumps. Should the rise required not be too great, many engineers prefer designs that feature the use of telescoping pistons such as "holeless" hydraulic-type elevator designs (Holeless or Telescoping Holeless). The Roped Holeless arrangement (depicted) features the use of both an underslung rope arrangement and a piston arrangement. In general, hydraulic-drive machines are used for low-rise uses and are common for two to four-fl oor elevators (though some have been used for nine-fl oor installations). Hydraulic installations are generally considered to be impractical for facilities of more than fi ve fl oors due to speed and space limitations, and the high construction costs incurred from digging holes deep enough to house larger pistons. Another potential drawback to hydraulic elevator designs are that they often use two to three times more energy than traditional electric traction designs. In addition, much of the energy used to push the mass of the jack, and maintain oil pressure, is converted to heat in the machine room area. This in turn necessitates the need for expensive cooling procedures to be taken in the machine room area. Hydraulic elevators also create potential environmental concerns due to the need to be able to secure hydraulic oils contained in buried cylinders on-site and avoid groundwater contamination.


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1. Hoist Rope2. Compensation Rope/Chain3. Governor Rope4. Door Closing Ropes5. Machine6. Counterweight

7. Secondary/ Deflector Sheave8. Drive Sheave9. Governor 10. Governor Tension Sheave11. Traveling Cables

12. Above ground Cylinders13. Piston and Piston Guides

Geared Installation Hydraulic Installation (Roped indirect hydraulic confi guration)

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Compact Machine Room Elevators

The drive to reduce the total amount of fl oorspace dedicated to elevators has led to the rise of the Compact Machine Room installations. In essence, a CMR design can be thought of as hybrid arrangement whereby the total amount of space used by a conventional Machine Room is reduced by up to 50%. Such a design can be used in low, mid and hi-rise installations and offers designers wide line-ups, greater layout fl exibility (which can be useful in modernizations). Compact Machine Room designs (sometimes referred to as "MiniSpace designs) use smaller PMSM (Permanent Magnet Synchronous Motor) Gearless Traction machines which offer energy savings, high-effi ciency, reduce carbon dioxide emissions dramatically and provide enhanced ride comfort.

Machine-Room-Less (MRL) Elevators

The latest innovation in elevator design involves gearless electric traction driving machines that are installed within the hoistway itself. These systems are referred to as MRL (Machine-Room-Less) elevators. Despite their name, these traction elevators still require certain amounts of room dedicated to house various controllers, selectors and drives that can be accessed outside the hoistway area by maintenance personel. MRL elevators utilize a gearless traction type machine, meaning they offer faster operating speeds, superior performance and better ride quality compared to hydraulic elevators. Due to the naturally conservative nature of the elevator industry the popularity of MRL elevators has grown slowly; nevertheless, they have now become the standard option to be used for low to mid-rise buildings. Though the roping factor of the suspension system varies according to installation design, commonly you will fi nd 2:1 roping factors and underslung suspension used in MRL designs. Though manufactures insist that MRL elevators save major amounts of building space and reduce operations costs signifi cantly (through energy savings of up to 70-80% compared to hydraulic elevators), these benefi cial claims are still being evaluated by the industry. Such units often incorporate Permanent Magnet Motors (PMM) in their design and use fl at belts made of steel wire cores covered with polyurethane coatings. This rallows for the use of smaller sheaves and smaller surrounding equipment as well. Though still in their design infancy, the potential for new advancements in materials research, motor design and electronics, offers MRL installations a very promising future.

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1. Drive2. Overspeed Governor3. Hoist Rope4. Door Closing Rope5. Counterweight6. Governor Tension Sheave7. Traveling Cable8. Governor Rope9. Wedge Sockets10. Car Sheave(s)

Machine Roomless (MRL) Installation

(Underslung rope arrangement shown)

Compact Machine Room(CMR) Installation

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Mini-Gearless design represented

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1. Drive2. Overspeed Governor3. Hoist Rope4. Counterweight5. Governor Rope6. Wedge Sockets 7. Car Sheaves8. Car Crosshead

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Machine Roomless (MRL) Installation

(Underslung rope arrangement shown)

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