No_4_March_and_April__1949 — Page 82

80

VERTICAL TRANSPORTATION

By Philip J. Kessel, Manager of Otis Elevator Company, Hong Kong.

Historical records do not definitely state when the first man-carrying hoist was invented although Aristotle (384-322 BC) mentioned hoists in his writings. Later records handed down from the Monasteries had many drawings of hoists for the transportation of men and supplies.

In the middle of the 17th century a Frenchman invented the "Flying Chair" which was cranked up and down by ä servant, A hoistway was used with this device and a cage was raised and lowered by a rope passing around a drum and down to a lead counterweight it is stated that similar hoists were installed in Windsor Castle for Queen Anne in 1713.

not

It was not until a century later that there was any record of a power uriven hoist for passengers. These hoists were not hits as we know them to-day, they were not equipped with any automatic safety devices and never proved very popular. From 1835 onwards the advance of vertical transportation,

tor' passengers only

but aiso

nas for freight,

been excéeungly rapiu and during the course of those years many were the types of control and operation. We can trace the advance Irvin machines driven by belts, pulleys and spur Then came the gears to worm geared belt ariven machines. development of individual steam engines of many different All machines were drum type, operated by types for it use. a and rope in the car. The next development was the nyuraune it and with it came a building boom which was to last, with brief interruptions, for more than twenty-five year's.

In the late 1800's came the high commercial building called a "skyscraper. This was now possible because the it made buildings of more than six floors high convenient and acceptable, and also because improved bunding methods Inade It possible to erect on a framework of steel. It is interesting to note that the early hydraulics were capable of Speeds up to 600 FPM.

The geared hydraulic lift was operated by water pressure supplied by steam driven pumps. It took up a great deal of space, was extremely costly to operate, and left much to be desired from a salety standpoint; but it permitted high rises, and speeds up to 600 ft. per minute. Volumes could be, and have been, written about the many types of hydraulic lifts that were tried out. There were two general types that survived: the piston type (either vertical or horizontal) and the plunger type.

By the use of sheaves and complicated roping the piston types were geared as high as 12:1, so that the piston would not travel as far as the car. With the plunger type the lift car was pushed up, often 25 floors or more, by a steel tube sunk as far in the ground as the building was high. There are a few such installations still in operation to-day.

In 1889 the world's first successful electric lifts were installed in the Demarest Building, Fifth Avenue, New York City, and they served well until the building was torn down 30 years later.

In 1892 another electrical development took place that was to have its effect on the modern lift. After several months of experimenting on a belt-driven lift, the first lift was designed to operate on a plan suggested by Mr. H. Ward Leonard. To-day we know this method of operation as either Ward Leonard control or Unit-Multi-Voltage control. This type of control is used on all high speed lifts and gives the assurance of rapid and smooth acceleration and deceleration. Many are the advantages of this type of control and with its present day improvements it is used extensively with geared traction machines with speeds from 200 FPM and upwards.

Since the development which we have just traced and with the need for assuring both architects and owners of having the correct number of lifts, type of control and speed requirements for a given building, it is important that thorough study and traffic analysis be made at the time when preliminary drawings of the building are being prepared. In order to make a correct analysis it is important that the proper determination of the maximum traffic flow for any particular building be ascertained. Traffic peaks and popula- tion vary with different types of buildings, the most common type being a diversified tenancy office building.

When calculating the number of lifts for a building the net rentable area is used as a basis for estimating the popula- tion. In cases where the architect may not be able to supply the net rentable area until his plans are more developed, it is possible to take the net area as generally between 65 percent and 70 percent of the gross area. The number of square feet of net rentable area per person varies with the location and the type of occupancy of the particular building. We know that while in the United States and other countries a density ratio can be used of one person to one hundred square feet, here in the Far East we feel that is necessary to reduce the ratio to 70 sq. ft. per person or lower. In making a traffic analysis a five minute handling capacity per lift must be found. The correct number and speed of lifts should make it possible to empty or fill the building of its entire population within a 30 40 minute period.

Usually diversified tenancy office buildings have three important traffic peaks:-

1. The Morning Peak. This is the incoming peak. At this time the traffic is predominantly in the up direction with little or no down traffic.

2. The Noon Peak. In cities where lunch hours are staggered, i.e. 12:00 noon to 1:00 p.m. and 1:00 p.m. to 2:00 p.m., the noon peak has three phases, twelve o'clock when most of the traffic is down, one o'clock when the traffic is heavy in both directions and when the maximum traffic flow usually occurs, and two o'clock when most traffic is up. The maximum noon peak varies from 11.7 percent to 14.3 percent of the population in five minutes with

passengers being handled in both directions.

3. The Evening Peak. This is the outgoing peak and the traffic is predominantly down with little or no up traffic. As all traffic is directed to the Ground Floor, the lifts are generally filled to capacity at a few stops, so that they handle more people than the morning peak.

This is an important peak because people are anxious to get out of the building as quickly as possible. The peak is of short duration. However, if the building is adequately elevatored no trouble will be experienced with the evening peak.

Lift Machines: Gearless traction lifts are suitable for all types of buildings owing to their smoothness of operation, rapid acceleration and retardation, and long life. Gearless clevators have been operated up to 1,500 FPM and in some of the tall skyscrapers in New York, the code permits them to operate at 1,200 FPM.

Platforms: Platform sizes should conform to standards as set by Lift Manufacturers, viz.

2500 lbs.-7'-0" X 5'-0" outside 3000 lbs.-7′-0′′ X 5′-6′′ 3500 lbs.-7'-0" X 6′-2′′

"

FT

These platforms are in accordance with code ratings. Narrow and deep lift cars should be avoided whenever possible because the passenger transfer time is increased, resulting in slower service. The ideal opening is center opening doors 3′-6′′ wide X 7'-0" high and in order to install these a platform having a width of 7'-0" is necessary.

With a 3'-6" opening it is possible for two passengers to walk abreast in or out of the car and a wider opening (for passenger service) would be of little advantage. Arrangement of lifts-It is important that the lifts be accessible from all entrances to the building. For maximum efficiency it is recommended that they be grouped near the center of the building. It is not desirable that two banks of lifts located in different parts of the building serve the same floors, with a possible exception in the case of extremely tall buildings; generally the traffic cannot be equalized on the two banks and the bank nearer the principal entrance or street will handle most of the traffic.

It must be borne in mind that traffic analysis data varies greatly with the type of building, such as hotels, hospitals, single purpose buildings, professional office buildings and apartment houses.

In big office buildings where a large number of lifts is required it is recommended that an alcove arrangement be used. This reduces the amount of travel required by the waiting passenger to reach the lift stopping at his floor and passenger transfer time is considerably reduced. The alcove arrangement also permits the narrowest possible corridors and saves space on the upper floors.

Signal control passenger lifts are designed for maximum traffic handling efficiency in that the attendant has only two simple mechanical operations to perform:-

(1) pressing the buttons corresponding to the floors at

which passengers wish to stop and

(2) moving the lever which initiates the closing of the

doors and starts the car.

Other functions are performed automatically in response to the calls registered at the landings served and on the car operating panel. This leaves the operator free to concentrate on the wishes and safety of the passengers and eliminates mistakes due to forgetfulness. Automatic dispatching systems are recommended to provide the best possible service with the least number of lifts and are applicable to all installations where lifts operate in a group.

A very recent development by one of the world's largest lift manufacturers is "Autotronic Control." This may be furnished in connection with a bank of three or more lifts having a Peak Period control dispatching equipment. It provides automatic car balance, improved headway timing for morning peak and instant hall lantern transfer. Another combination includes the three features mentioned above plus automatic zone return, forgotten man pickup and hall call re-registration.

Regardless of the size and type of lift it is important that the equipment be so manufactured that complies with all safety codes even though lifts may be installed in cities like Hong Kong where no lift code is in force. The majority of lift manufacturers automatically comply with these standards. It is interesting to know, from the viewpoint of safety, that more than eight times the world's population is carried each year by the hundred and fifteen thousand lifts in the U.S. This involves an annual passenger load in excess of seventeen billion persons and an incalculable number of total miles of travel. Notwithstanding their heavy use passenger lifts have the lowest accident ratio of any form of transportation.