Introduction

Topics: Elevator, Automobile, Transport Pages: 16 (2342 words) Published: July 29, 2013
Vertical Transportation: Elevators & Escalators
Dr. M. Zahurul Haq
Professor Department of Mechanical Engineering Bangladesh University of Engineering & Technology (BUET) Dhaka-1000, Bangladesh zahurul@me.buet.ac.bd http://teacher.buet.ac.bd/zahurul/

ME 415: Refrigeration & Building Mechanical Systems

c ­ Dr. M. Zahurul Haq

(BUET)

Vertical Transportation

ME 415 (2011)

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Introduction

Of the many decision that must be made by the designer of a multi-story building, probably none is more important than the selection of the vertical transportation equipment - that is the passenger, service, and freight elevators and the escalators. These items represent a major building expense; for a 25-story office building as much as 10% of the construction cost. The quality of elevator service is also an important factor in a tenant’s choice of space in competing buildings.

c ­ Dr. M. Zahurul Haq

(BUET)

Vertical Transportation

ME 415 (2011)

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Elevator Hardware

Electric Traction Passenger Lift

Electric Traction Passenger Lift
The car, cables, elevator machine, control equipment, counterweights, hoistway, rails, penthouse, and pit are the principle parts of a traction elevator installation. The car is a cage of some fire-resistant material supported on a structural frame, to the top member of which the lifting cables are fastened. By means of guide shoes on the side members, car is guided in its vertical travel in the shaft. The car is provided with safety doors, operating-control equipment, floor-level indicators, illumination, emergency exits, and ventilation. (BUET) Vertical Transportation ME 415 (2011) 3 / 32

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Elevator Hardware

Electric Traction Passenger Lift

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c ­ Dr. M. Zahurul Haq

(BUET)

Vertical Transportation

ME 415 (2011)

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Elevator Hardware

Electric Traction Passenger Lift

Four to eight cables, depending on the car speed and capacity, are placed in parallel; in general, each rope is capable of supporting the entire load. The minimum factor of safety varies from 7.6 to 12.0 for passenger lifts and from 6.6 to 11.0 for freight lift. The counter weight is made up of cut steel plates stacked in a frame attached to the opposite ends of the cables to which the car is fastened. Its weight equals that of the empty car plus 40% of the rated live load. It serves several purposes: to provide adequate traction at the sheave for car lifting, to reduce the size of the traction machine, and to reduce power demand and energy cost. Higher initial cost due to strengthen the overhead machine room floor, which must carry the additional structural load of the counter weight.

c ­ Dr.

The shaft or hoist-way, is the vertical passageway for the car and counterweights. On the side walls are the car guide rails and certain mechanical and electrical auxiliaries of the control apparatus. M. Zahurul Haq (BUET) The machine room isVertical Transportation above the ME 415 (2011) It 5 / 32 usually directly hoist-way.

Elevator Hardware

Electric Traction Passenger Lift

Gearless Traction Machines
A gearless traction machine consists of a DC or AC motor, the shaft of which is directly connected to a brake wheel and driving sheave. The elevator hoist ropes are placed around this sheave. The absence of gear means that the motor must run at the same relatively slow speed as the driving sheave, and these are generally used for high-speed lifts, i.e. speeds from 2.5 m/s to 10 m/s. A gearless traction machine is superior to geared machines because it is more efficient and quieter in operation, requires less maintenance, and has longer life. (BUET) Vertical Transportation ME 415 (2011) 6 / 32

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Elevator Hardware

Electric Traction Passenger Lift

Geared Traction Machines
A geared traction machine has a worm and gear interposed between the driving motor and the hoisting sheave. The driving motor...
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