What is the structure and working principle of a traction elevator?

What is the structure and working principle of a traction elevator?

Structure and working principle of the traction drive elevator.

The traction drive elevator consists of 8 systems, including traction, car, lift door, weight balance, safety protection, guidance, electric drag, and electrical control.

1. Traction system

Mainly consists of traction machine, guide sheave, car reverse sheave, wire rope, counter-weight reverse sheave, etc.


The function of the traction system is to drive the car and the counterweight to run up and down.

The principle of the traction system is the motor generates traction force on the traction steel rope through the friction between the traction sheave rope groove and the traction rope. 

The car and the counterweight are connected through the rope guide sheave and the reverse sheave. After the car reaches the target floors, the position of the car and the counterweight is kept unchanged by the brake. If the system fails, the sheave may roll back and the car may slip freely. Causes accidents such as abnormal downtime, shearing, dashing into pit or top. 


2. Car system

The car system is the container that transports passengers or goods from the floor to the destination floor. 

The function of the car is to isolate passengers or goods from all mechanical components in the elevator shaft to ensure the safety of passengers or goods.


3. Door system

The function of the elevator door system is to allow people or goods to enter and exit the car when the elevator reaches the target floor.

Door system includes car door system and landing door system.

The car door is a door provided at the entrance of the car. It is installed on the side of the car near the landing door, and is generally driven by a door operator installed on the top of the car to realize opening or closing. 

After the car door is closed, it forms a completely contained environment together with the car system, isolates all components in the hoistway, and prevents people or goods from colliding with the hoistway, or even falling into the hoistway.

The landing door is a door installed at the entrance of the landing. When the elevator is leveling, it is opened or closed with the drive of the car door cam or spear. Without the drive of the car door spear, the landing door cannot be opened automatically. 

After the landing door is closed, it forms a closed hoistway together with the hoistway wall to prevent people or goods from falling into the hoistway. 

In order to prevent shearing, all landing doors and car doors are equipped with electrical safety contacts, and the elevator can only run after all landing doors and car doors are completely closed.

The failure of the door system includes both mechanical and electrical aspects. If the door system is not mechanically strong enough or is not securely fastened, a slight bump can knock the door off. If the mechanical part of the door lock fails, the door cannot lock, allowing the door to be manually forced open even if the elevator car has departed. In both cases, people outside the landing door are prone to fall into the shaft.

If the electrical safety contacts of the door lock are short-circuited or bridged, the elevator may run with the door open, causing a shearing accident.


4. Counterweight balance system.

The elevator weight balance system is mainly composed of a counterweight device and a weight compensation device. 

The counterweight device is suspended from the other end of the car by the traction rope, which plays the role of balancing the car and part of the load. The traction machine can drive the elevator only by overcoming the weight difference between the car and the counterweight. 

The counterweight device is mainly composed of a counterweight frame, counterweight blocks and accessories. 

The compensation device mainly refers to the compensation chain, the two ends of which are respectively suspended at the bottom of the car and the bottom of the counterweight to compensate for the weight difference of the traction rope itself between the elevator car and the traction rope, especially when there is a large lifting height.

The weight balance system has an important influence on the elevator running and braking performance. Once an abnormality occurs, the safety of the elevator and home lifts will not be effectively guaranteed, and the car may slip, resulting in a shearing accident.


It would be a long paper if you put every system in one article. We will continue with the introduction  in the following section soon. Follow us House of Elevators.

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