Introduction to Lifts
The lift is a type of vertical transport equipment that efficiently moves people or goods between floors (levels, decks) of a building, vessel or other structure: generally powered by electric motors that either drive cables, hoist, or pump hydraulic flaid to raise a cylindrical piston like a jack. For multi-storeyed buildings the installation of lifts is a must to avoid fatigue in climbing up the stairs and for quick vertical circulation between different floors. The architect normally appoints a specialist engineer for the design of lifts. The following load capacities are laid down for passenger lifts in residential building.
(i) 400 kg (small lift) - for passengers, who may be carrying loads.
(ii) 630 kg (medium lift) for passengers with wheelchairs.
(iii) 1000 kg (large lift)- suitable for the transport of stretchers, furniture.
The waiting area in front of the lift shaft must be laid out and designed, so that:
(a) Lift users entering and leaving the lift do not obstruct each other more than necessary even if carrying luggage.
(b) The heavy loaded items to be transported by the lift, can be loaded and unloaded without risk of injury to people or damage to the building or the lift and causing least possible obstruction to other users.
Previously collapsible doors were provided both for the lift car (cage) and for the opening in the shaft at the floor level. Now-a-days flush doors of sliding type are provided.
Location of Lift
The most efficient method of locating lifts to serve an individual building is to group them together. A group has a lower average interval between car arrivals than a single lift. Groups should be located:
(1) For easy access to and from the main building entrance.
(ii) Centrally for general ease of passenger journey.
If a building has areas which give long distance to the central group elevator, then it may be efficient to provide an additional elevator for local areas.
In larger multi-storey building, it is usual to locate the lifts at a central pedestrian circulation point.
It is recommended that the walking distance between the entrance and the lift group should not be greater than 60 m, preferably this should be kept to 45 m maximum.
When lifts are arranged in a group it is recommended that all the lifts in that should serve the same floors.
Important Definitions Related to Lift
Components of lift) (1) Control room, (2) Guides, (3) Lift car, (4) Counter weight. (5) Control panel, (6) Lift pit. (7) Buffer. (8) Hoist way. (9) Hoist rope.
Car: This is the load carrying element of an elevator, including car platform, car frame, enclosure and car door.
Lift Car: The load carrying unit with its floor or platform, car frame and enclosing bodywork.
Lift Landing: Lif landing is the portion of a building or a structure used for discharge of passengers or goods or both into or from lift car.
Lift Shaft
Details of Lift & Lift ShaftTotal Headroom: Total headroom is the vertical distance from the level of the top lift landing to the floor bottom of the machine room slab.
Lift Landing Door : Lift landing door is the hinged or sliding portion of a lift well enclosure, controlling access to a lift car at a lift landing.
Structure of an Electric Lift
Cross-section of Shaftshows the major components of an electric lift. The vertical void in which the lift travels up and down is called "hostway" or "lift shaft. The bottom of the lift shaft is called "lift well" or "lift pit". The cabin in which passengers are being carried is called the "lift car. The lift car has its own doors, called "car doors. At each landing, there are "landing doors The landing doors are not powered as they are opened or closed by the car doors under mechanical engagement when the car is within the unlocking zone of each floor. The landing indicator, or called hall lantern, is used to inform the passengers a certain car arrives serve that particular floor. The car doors are powered by a door operator which is essentially a small DC or AC motor. The car is lifted up or down by suspension rupes terminated at the top of the car frame The ropes go up from the car frame to the machine room which is normally at the top of the hoistway and are laid on the drive sheave, down to the counterweight frame The drive sheave is mechanically driven by the traction motor which can be DC or AC, with or without a gear box. For high speed lifts, the drive is usually gearless. A brake is installed between the sheave and the drive motor and it is mechanically applied, electrically released The space between the two terminals of the ropes can be increased by diverter pulleys. At the bottom of the hoistway, there are buffers for the car and the counterweight. The communication between the car and the controller inside the machine room for control and display functions is via a ribbon of travelling cables. The horizontal movement of the car is constrained by the guide rails using guide shoes for low speed or guide rollers for high speed.
Lift door:
The lift door may be any of the following type:
(i) Centre Opening Sliding: A door which slides horizontally and consists of two or more panels which open from the centre and are usually so interconnected that they move simultaneously.
(ii) Mid-bar Collapsible: A collapsible door with vertical bars mounted between the normal vertical members.
(iii) Multi-panel: A door arrangement whereby more than one panel is used such that the panels are connected together and can slide over one another by which means the clear opening can be maximized for a given shaft width.
(iv) Single Slide: A single panel door which slides horizontally. Two speed sliding
(v) Two-Speed Sliding: A door which slides horizontally and consists of two or more panels, one of which moves at twice the speed of the other.
(vi) Vertical Bi-Parting: A door which slides vertically and consists of two panels or sets of panels that move away from each other to open and are so interconnected that they move simultaneously.
(vii) Vertical Lifting: A single panel door, which slides in the same plane vertically up to open.
(viii) Swing: A swinging type single panel door which is opened manually and closed by means of a door closer when released.
Call Indicator :
Call indicator is a visual and audible device in the car to indicate to the attendant about the lift landings from which calls have been made
Lift Suspension Ropes :
Lift suspension ropes is the ropes by which the car and counter weight are suspended.
Lift guides :
Guide Rails: Guide rails are fixed members truly vertical in the shaft, and of steel, used to guide the movement of a lift car or counterweight in a vertical direction.
Guide Rails Fixing: The complete set comprising the guide rails bracket and its fastenings.
Guide rails shoe: An attachment to the car frame or counterweight for the purpose of guiding the lift car or counter weight frame.
Lift well :
Lift well is the unobstructed space within an enclosure provided for the vertical movement of the lift car and any counterweight, including the lift pit and the space for top clearance.
Lift pit :
Lift pit is the space in the lift well below the level of the lowest lift landing served
Lift Well Enclosure :
Any structure which separates the lift well from its surroundings is called lift well enclosure.
Lift Machine :
Lift machine is the part of the lift equipment comprising the motor and the control gear, reduction gear, brake and winding drum or sheave, by which the lift car is raised or lowered Safety springs or buffers are placed in the pit, to bring the car or counterweight to a safe stop. A buffer is a device designed to stop a descending car or counterweight beyond its normal limit and to soften the force with which the elevator runs into the pit during an emergency. They may be of polyurethane or oil type in respect of the rated speed.
There are two principal types of buffers in existence :
• Energy accumulation accumulate the kinetic energy of the car or counterweight.
• Energy dissipation dissipate the kinetic energy of the car or counterweight.
Lift Rated Load :
Lift rated load is the maximum load for which the lift car is designed and installed to carry safely at its rated speed.
Lift Rated Speed :
Lift rated speed is the mean of the maximum speed attained by the lift car in the upward and downward direction with rated load in the lift car.
Lift Contact Speed :
Lift contact speed is the mean of the maximum speed attained by the lift car while moving from one landing to another.
Lift Overhead Beams :
Lift overhead beams is the members, usually of steel, which immediately support the lift equipment at the top of the lift well.
∆ Classification of Lift :
The lifts are classified into following types based on the purpose of use:
(a) Passenger lifts
(b) Goods lifts
(c) Hospital lifts
(d) Dumb waiter
(e) Service lifts
(f) Fireman's lift
These lifts are designed to move people between floors of a building. Their capacity is related to available floor space. Upto 8-10 floors these operate at Im/s and above 10 floors the speed starts at 2.5 m/s to 10 m/s.
Goods Lift∆ Goods lifts :
A lift designed primarily for the transport of goods, but which may carry lift attendant or other persons necessary for the loading or unloading of goods.
∆ Hospital Lifts :
A lift normally installed in a hospital/dispensary/clinic and designed to accommodate one number bed/stretcher along its depth, with sufficient space around to carry a minimum of three attendants in addition to the lift operator.
Dumb Waiter Lift∆ Dumb Waiter :
Dumb waiter is a lift with a car which moves in guides in a vertical direction, has a net floor area of 1 m², total inside height of 1.2 m; has a capacity not exceeding 250 kg and is exclusively used for carrying materials and shall not carry any person (whether or not provided with fixed or removable shelves).
Dumbwaiters are small freight elevators that are intended to carry food rather than passengers They often link Kitchens with other rooms. When installed in restaurants, schools, kindergartens hospitals, retirement homes or in private homes, the litts generally terminute in a kitchen. These lifts are self-contained, these lifts can be easily moved to where they are needed.
∆ Service lift :
Service Lift is a passenger cum goods lift meant to carry goods along with people. These lifts are used in an office building: these may be required to carry food or stationeries, in a residential building to carry a bureau or accommodate a stretcher and in a hotel to be used for food trolleys or baggage.
∆ Fireman's lift :
Fire lift is passenger lift provided with minimum capacity for 8 passengers and fully automated with emergency switch on ground level. in the event of fire, the emergency switch is used to move directly to the ground floor with maximum speed of lift.
In general, buildings 15 m in height or above shall be provided with fire lifts.
In case of fire, only fireman shall operate the fire lift. In normal course, it may be used by other persons. Each fire lift shall be equipped with suitable inter-communication equipment for communicating with the control room on the ground floor of the building.
The number and location of fire lifts in a building shall be decided after taking into consideration various factors like building population, floor area, compartmentation, etc.
