Principle of Elevators
2026-07-20 14:46:05
1. Working Principle of Elevators
Elevators are classified into various drive types based on their driving technology, including traction drive, forced drive, and hydraulic drive. Due to safety and energy efficiency considerations, traction-driven elevators are currently the most widely used.
The working principle of an elevator is similar to pulling water from a well using a windlass. The well represents the elevator hoistway, the windlass represents the elevator drive machine, the well rope represents the suspension steel wire ropes, the bucket represents the elevator car, and the water inside the bucket represents the passengers. A windlass lifts water by winding the rope around its axle. To save effort, a stone balancing the weight of both the bucket and the water can be suspended on the opposite side of the rope. During the lifting process, the bucket rises while the stone descends. At this point, the rope no longer winds around the axle; instead, the friction between the rope and the axle balances the weight difference between the two sides. This is the operating principle of a friction traction-driven elevator.
Almost all elevators currently in use are traction-driven (see Figure 1 for a schematic diagram of the working principle). The suspension steel wire rope suspends the elevator car on one side and a counterweight device for balancing on the other side. Based on safety, economic, and energy-saving considerations, the weight of the counterweight is usually equal to the weight of the empty car plus 40% to 50% of the maximum rated load.
2. Composition of an Elevator
An elevator is a piece of equipment that integrates mechanical, electrical, and electronic control technologies. Its mechanical components function like the human body, the electrical components act as the nervous system, and the microcomputer electronic control components serve as the brain. These parts work collaboratively with a clear division of labor to ensure the safe and reliable operation of the elevator.
An elevator mainly consists of components such as the traction machine, brake, control cabinet, speed governor, safety gear, buffer, car, car door, landing door, and guide rails.
- Traction Machine: Outputs power to drive the car up and down via the steel wire ropes, acting similarly to a car's engine.
- Brake: Part of the traction machine used to stop the car and keep it stationary, similar to a car's brakes.
- Control Cabinet: The brain of the elevator. It receives and processes various commands and signals to control and manage elevator operations, similar to a car's trip computer.
- Speed Governor, Safety Gear, and Buffer: These constitute the three major safety components of an elevator.
- Speed Governor: Monitors whether the elevator is overspeeding. If an anomaly occurs and the operating speed exceeds 1.15 times the rated speed, it issues both an electrical and a mechanical command. The electrical command is sent to the traction machine brake to stop the machine. The mechanical command is sent to the safety gear, triggering its braking mechanism to clamp the guide rails and stop the car.
- Safety Gear: The braking component that executes stops during accidental overspeeding.
- Buffer: As the name suggests, it restricts and prevents the car from exceeding its allowable upper and lower travel limits. Furthermore, if other safety components fail, it absorbs the kinetic impact of an overspeeding car that has overrun its limits, minimizing injuries to passengers or damage to cargo inside.
- Car: The box-like component that carries passengers or cargo, similar to a subway car.
- Car Door and Landing Door: The entrances and exits for passengers or cargo entering and leaving the car and landings. To prevent passengers from being crushed or sheared if the doors remain open during operation, both the car door and landing doors are equipped with electrical devices that detect closure and interlocking. This protective feature is similar to platform screen doors in a subway; if the screen doors fail to close, the subway will not run.
- Guide Rails: Restrict the degrees of freedom for both the car and the counterweight device, ensuring they can only move vertically along the rails to prevent tilting or swaying during operation.
3. Elevator Operation Process
When we take an elevator, we simply press the hall call button. Moments later, the elevator arrives at our floor and carries us to our destination. During this process, apart from pressing the direction button and the destination floor button, no other operations are required. Some highly intelligent elevators even support voice control or automatic floor selection via room card scanning. Relatively speaking, elevators are highly automated and intelligent products.
Elevators operate according to specific sequences. For every ride, an elevator must execute a complete cycle: responding to the call, starting, running, decelerating, leveling, opening the door, selecting the floor, determining direction, closing the door, restarting, running, decelerating, leveling, and opening the door again.
Each of these steps links sequentially to the next, corresponding to an independent control circuit or program operating under predefined safety conditions and environments. If a fault occurs in any single step, the elevator will automatically trigger its safety protection mode and take itself out of service. Therefore, if you notice the elevator stops responding to operations during a ride, it is actually a sign of self-protection and is safe. Danger only arises when an elevator runs with a fault due to a lack of protection.
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