Transportation Systems: Elevators and Dumbwaiters PDF

TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.1 Definition of Elevators It is a conveying equipment, with car or platform, used to move people or freight vertically Serves two or more floors of a building or structure Movement of the car may be controlled by gravitational, manua...

TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.1 Definition of Elevators It is a conveying equipment, with car or platform, used to move people or freight vertically Serves two or more floors of a building or structure Movement of the car may be controlled by gravitational, manual or mechanical power. Used in buildings where several peak periods of traffic occur each day, i.e in office buildings, hospitals, and apartment buildings Consider capacity, number of floors, travel time and wait interval TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.2 Classification of Elevators Passenger Elevators Used to carry people and small packages; with typical capacity of 600-2300lbs.; typically required for 5 storey buildings up; one for every 30,000-40,000 area of office buildings, and every 60-75 rooms for condominium or hotels TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.2 Classification of Elevators Freight Elevators Used to carry materials, goods, equipment and vehicles; with typical capacity of 2300-4500 but can be up to 13 tons; typically required for every 300,000 ftsq area of office space, each 100 beds in a hospital and 200 rooms in a hotel or condominium TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.2 Classification of Elevators Dumbwaiter Used to carry lightweight freight such as food, laundry, books, documents, and other small items with a maximum width of 340 (277 based on NBC)mm x 1200mm height TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.2 Classification of Elevators Manlift Used by authorized personnel and their tools and equipment only, typically installed in radio antennas, bridge towers, underground facilities, dams, power plants; with typical capacity of 140 to 647kg TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Oil Hydraulic Elevators Raised /lowered simply by means of a movable rod plunger rigidly fixed to bottom of the elevator car; can be used from 5-7 storey TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Types of Hydraulic Elevators 1. Oil Hydraulic Elevators The hole is usually drilled into the ground and cased with plastic or metal casing. The holed type is the most balanced type of hydraulic elevator. It is raised by means of a movable rod or plunger rigidly fixed to the bottom of the car. The system is hydraulic and operates the same way as a hydraulic automobile jack. Oil from a reservoir is pumped under the plunger thereby raising it and the car. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Types of Hydraulic Elevators 1. Oil Hydraulic Elevators The pump is stopped during downward motion, the car being lowered by gravity and controlled by action of bypassed valves which also controls the positioning of the car during the upward motion. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Types of Hydraulic Elevators 2. Roped Hydraulic Elevator Use a combination of ropes and hydraulics TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Types of Hydraulic Elevators 3. Telescopic Elevators Has a telescopic plunger consisting of concentric tubes that slide within one another, allowing a shallow hole below the lowest floor. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators Types of Hydraulic Elevators 4. Hole less Hydraulic Does not require holes to be dug for the hydraulic cylinder. In most designs, the cab is lifted by a pair of hydraulic jacks, one on each side of the elevator. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.3 Types of Elevators The absence of cables, drums, MG set and penthouse equipment, makes this system inexpensive and often the choice for low speed, low rise applications where construction of the plunger pit do not present difficulties and where absence of a penthouse is desirable. Electric Elevators Also known as Traction Elevator, they have a drive machine (geared/gearless) with an electric motor and pulley-like (grooved) drive sheave that holds the cables that move the elevator car up or down. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.4 Types of Traction Machine Geared Traction Machines are driven by AC or DC electric motors. This type of machine employs a worm and gear between the driving motor and the sheave. It is considered to be less superior to the gearless traction machine since it has more moving parts and requires more maintenance. They are used for low and medium speed passenger and freight elevators. These machines are generally the best option for the basement or overhead traction use for speeds up to 1000ft/min (5m/s). TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.4 Types of Traction Machine Gearless Traction High speed, low torque electric motors powered by AC or DC motor, the shaft of which is directly connected to the brake wheel and to the driving sheave, which is directly attached to the end of the motor. The elevator cables are placed around this sheave. This type of machine is used for medium and high speed elevators for office and residential condominiums of 10 storeys or more; where high speeds and smooth quality operation are desired.  TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System  TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System A. Parts of a Hydraulic Elevator 1. Hydraulic Jack- a cylinder and plunger 2. Pump- powered by an electric motor that increases the pressure in the hydraulic fluid 3. Control Valve- located between the cylinder and fluid reservoir that controls the pressure in the jack 4. Tank- a fluid reservoir TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System B. Parts of an Electric/ Traction Elevator 1. Shaft / Hoistway- vertical passageway for car and counterweights 2. Hoisting Ropes/Cables- are steel cables that support the elevator and counterweights. Usually 3 (min) to 8(max) cables placed in parallel fastened to top of the car by cable sockets passing over a motor driven cylindrical sheave to the counterweights; are means for lifting or lowering the car. 3. Counterweights- set of steel, cast- iron, or pre-cast blocks fastened to the end of the hoisting cable that counterbalances the car. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System B. Parts of an Electric/ Traction Elevator 4. Guide Rails- are vertical tracks that guide the car and the counterweights. 5. Car- a cage of light metal supported on a structural frame, the top member of which the cables, that carry the car, are fastened. 6. Machine Room- a room usually placed directly above the shaft in which the elevator machine is housed; may also be located at the sides or at the bottom. It contains the motor- generator (MG) set which supplies energy to the elevator machine, the control board and the control equipment. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System B. Parts of an Electric/ Traction Elevator 7. Elevator Machine- is an electric machine connected to an electric motor (AC or DC) in which the friction between the hoist ropes and drive sheave is used to move the elevator car with the cable. 8. Controls- a combination of push buttons, contacts, relays, and devices, operated manually or automatically to initiate door opening, starting acceleration, retardation, levelling and stopping of the car. 9. Governor- controls the speed. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System B. Parts of an Electric/ Traction Elevator 10. Safety Devices a. Main Break- mounted directly on the shaft of the elevator machine. The elevator is first slowed down by dynamic braking action of the motor and the brake then operates to clamp the brake drum, thus holding the car still at the floor. b. Safety Switch- is designed to stop an elevator car automatically before car speed becomes excessive. On over speed, the speed governor will cut off power to the motor and set the brake. This usually stops the car, but should speed still increase, the governor will actuate rail clamps mounted at the bottom of the car one on each side. This will clamp the guide rails bringing the car to a switch stop. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.5 Basic Components of Elevator System B. Parts of an Electric/ Traction Elevator 10. Safety Devices c. Electric Final Limit Switches- are located a few feet below and above safe travel limits of elevator car. If car over-travels, either down or up, these switches de-energizes the motor and sets the main brake. (landing switches) d. Oil or Spring Buffers- an energy absorber located at the bottom of the hoistway to soften the force with which a car runs into the pit during an emergency; these can be in a form of spring or oil-spring combination. TRANSPORTATION SYSTEMS 1 ELEVATORS AND DUMBWAITERS 1.6 Architectural Section of an Electric Elevator Shaft