Parts Of An Elevator

The parts of an elevator are spread through the building from top to bottom (Fig. 47-1). The landing is the part of the floor adjacent to the elevator where passengers and freight are received and discharged. The elevator's rise or travel is the vertical distance traversed by the elevator cab (also called the car) from the lowest to the highest landings.

The cab rides up and down in the elevator shaft or hoistway. The hoistway is the vertical space for travel of one or more elevators. There are guide rails—vertical steel tracks that control the travel of the elevator car or the counterweight (see below)—on the side walls of the shaft. They are secured to each floor with support brackets. Guide shoes on the sides of the cab fit onto the guide rails and guide the cab vertically in the shaft. The elevator pit is the part of the shaft that extends from the level of the lowest landing to the floor of the hoistway.

The cab is lifted in the shaft by cables, which connect to the top beam of the elevator. The cables are steel wires that pass over a motor-driven cylindrical sheave at the traction machine, then down to the counterweights. The hoisting cable is a wire cable or rope used for raising and lowering the elevator car. A traveling cable is an electrical cable connecting the elevator car to a fixed electrical outlet in the hoistway.

Counterweights are rectangular cast-iron blocks mounted in a steel frame, and attached to the other end of the hoisting cable to counterbalance the elevator cab. The counterweights ride in two guide rails on the back wall of the shaft. Their weight equals the weight of the cab plus an allowance for the people in the cab. The counterweight creates traction at the sheave and balances the weight of the cab. There are also cables attached to the bottom of the cab and the counterweight, to balance the weight of the hoist cable.

At the top of the shaft is a structural platform for the elevator machinery. A penthouse or elevator machine room on the roof houses the elevator machine that turns the sheave, which lifts or lowers the cab. The penthouse rises one or two levels directly above the shaft. Heavy steel beams support the hoisting machin-

Figure 47-1 Parts of an elevator

ery. A control panel with switches and buttons regulates the hoisting machine. The drive or motion control governs velocity, acceleration, position determination, and keeping the car level with each floor.

The elevator includes a speed governor to detect excessive speed or freefall and signal brakes to clamp onto guide rails to slow down and stop the elevator car. A limit switch automatically cuts off the current to an electric motor when the elevator passes a point near the top or bottom of its travel. The buffer is a piston or spring device that absorbs the impact of the descending car or counterweight at the extreme lower limit of travel.

The hoistway door between the elevator landing and hoistway is normally closed except when a car is stopped at a landing. Hoistway doors are typically 214 cm (7 ft) or 244 cm (8 ft) high.

Operating controls for the elevator control the car door operation and the function of car signals. Car signals include floor call buttons and other indicators. Supervisory controls allow group operation of multiple car installations.

Elevators can be noisy. Noise-sensitive areas, such as sleeping rooms, should be located away from elevator shafts and machine rooms. Using vibration isolators between guide rails and the structure can reduce elevator noise. Properly designed controls also reduce system noise. Solid-state equipment eliminates the clatter and whirring sound of older machine rooms.

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