Detailed Explanation of Elevator Weight Balance System
The elevator weight balance system is mainly composed of two parts: the counterweight device and the weight compensation device. Its function is to keep the elevator stable during operation, ensuring the normal operation of the elevator system and the safety of passengers.
The composition of the elevator weight balance system is generally composed of two parts: the counterweight device and the weight compensation device.
The counterweight device, as an essential part of the elevator weight balance, is referred to as the counterweight, which is mainly composed of a counterweight frame, a counterweight block, a guide shoe, a clamping device, etc., as shown in Figure 2. It is suspended on the other side of the traction rope relative to the car, and plays a role in relatively balancing the weight of the car. The weight of the counterweight and the car acts on the traction wheel through the wire rope to ensure that the elevator has a suitable traction capacity. The counterweight frame is mainly made of channel steel welded or bolted, and its space is sufficient to place a counterweight block of appropriate weight. The counterweight block is often made of cast iron castings or mixed castings of ore sand, cement, and steel bars. The installation requirements of the centering weight meet the elevator weight balance coefficient between 0.4 and 0.5, or according to the weight specified by the manufacturer.
●Example of counterweight calculation:
The rated load of a traction passenger elevator is 1000 kg, the traction ratio is 1:1, the rated speed is 1.75 m/s, and the car weight is 800 kg. What is the range of its counterweight?
Solution: Because the balance coefficient is between 0.4 and 0.5
According to the counterweight balance formula:
Counterweight = car weight + balance coefficient × rated load
So the minimum counterweight = 800 + 0.4 × 1000 = 1200 kg
The minimum counterweight = 800 + 0.5 × 1000 = 1300 kg
This shows that proper elevator weight balance ensures smooth operation and prevents excessive load on the traction machine, improving both safety and energy efficiency.
●Weight compensation device:
There are mainly several forms of compensation chain, compensation cable, and compensation rope, as shown in Figure 3. Its two ends are suspended on the bottom beam of the car and the lower part of the counterweight frame. It mainly balances the weight difference on both sides caused by the movement of the wire rope during the operation of the elevator. If the car is at the lower end station, the counterweight runs to the upper end station, and the wire rope moves to the car side. The weight deviation on both sides caused by the wire rope itself is mainly balanced by the weight of the compensation device. This compensation system is also an important component of the elevator weight balance design.
●Safety requirements for counterweight and compensation devices:
The counterweight should be fixed in a frame.
For metal counterweights and elevators with a rated speed greater than 1m/s, at least two pull rods should be used to fix the counterweight. The pulley installed on the counterweight should be equipped with a protective device to prevent the rope from falling off or foreign objects from entering. For elevators with a rated speed greater than 3.5m/s, a compensation rope should be used. The compensation rope is mainly made of steel wire rope and is equipped with accessories such as a tensioning device for the compensation rope and an anti-jumping device. When using the compensation rope, the following conditions should be met:
a) Use a tensioning wheel;
b) The ratio of the diameter of the tensioning wheel to the nominal diameter of the compensation rope is not less than 30;
c) The tensioning wheel is equipped with a protective device as required;
d) Gravity is used to keep the tension of the compensation rope;
e) An electrical safety device that meets the requirements is used to check the minimum tension position of the compensation rope.
All these measures ensure the elevator weight balance system operates smoothly, providing comfort, efficiency, and reliability during elevator operation.