What are the ways of speeding on the elevator

　　The traction elevator is driven by the traction machine, the friction between the traction wheel and the steel wire rope drives the car to run, and the brake is effectively closed to ensure that the car can be reliably stopped. Therefore, when the weight of the car is greater than the weight of the car, the failure of any link of transmission, traction and braking may cause the elevator to overspeed upward, and in serious cases will lead to the top rush. Therefore, there are many reasons for the elevator upward overspeed:

　　1. Brake spring relaxation, friction between brake shoe and brake wheel cause overheating of brake shoe and brake wheel, which leads to the decrease of brake capacity, brake seizure, brake arm, axle pin fracture and other faults, which lead to the failure of effective brake closure;

　　2. The main shaft, bearing, gear, worm and other mechanical parts of the traction machine are broken or damaged, and the traction force is seriously reduced;

　　3. The traction condition is damaged, and the traction wheel and wire rope slip;

　　4. Over speed caused by electrical control system fault, motor overheating, abnormal fluctuation of power voltage, etc.

　　2. Upward overspeed hazards of some elevators in use

　　Among the overspeed reasons analyzed above, the upward runaway caused by brake failure is the most common, which is mainly due to the fact that the brake previously used by some elevators is not a safety brake. Article 12, 4, 2 and 1 of safety code for elevator manufacturing and installation (gb7588-1995) clearly stipulates that "all brake components involved in the application of force to the brake wheel (or disc) shall be assembled in two parts and have appropriate dimensions to meet the following requirements: if a group of components does not work, the brake wheel (or disc) can still obtain enough brake force to slow down the car with rated load". Originally, this is a good rule, which requires that there must be redundancy in the design of mechanical parts of the brake, so that when a part fails to work, the brake can still make the elevator stop reliably. Unfortunately, in gb7588-1995, this provision was suspended. Due to the suspension of this regulation, some elevator brakes have congenital defects in design, which also creates conditions for the manufacture and application of non safety brakes.

　　The application of this kind of non safety brake in some elevators not only brings hidden danger to the elevator out of control, but also greatly reduces the protection effect of all electrical safety switches in the elevator safety circuit, because the electrical safety protection of the elevator finally functions through the reliable stop of the safety tongs. At present, in the use of elevators, this kind of non safety brake is not in a small number of applications. Because of the use of this brake, the accidents of the elevator upward rush have occurred in many parts of our country. Nowadays, more and more attention has been paid to the safe operation of elevators, this kind of non safety brake with congenital defects should be paid attention to. Whether to reform the brake or increase the upward overspeed protection device, or take other measures. This involves not only economy and safety, but also different structures of traction machine and various elevator structures, which is difficult to be generalized. However, no matter what, the upward overspeed of the elevator in use, especially the hidden danger of the upward overspeed of the elevator with non safety brake, should be paid attention to and taken seriously by our elevator counterparts and relevant departments.

　　3. Upward overspeed protection device

　　It is gratifying and gratifying that in the newly issued GB7588-2003, Article 12, 4, 2 and 1 are implemented as mandatory provisions, which will further promote the improvement of brake working reliability. Moreover, in the new standard, as an important safety component, the up speed protection device is clearly required to be used in the newly installed elevator, which will greatly reduce the up runaway accident of the newly installed elevator.

　　The car up overspeed protection device is a kind of safety protection device installed on the traction drive elevator, which is used to make the car stop or effectively decelerate when the elevator up overspeed reaches a certain degree. It is generally composed of speed monitoring device and deceleration device. Generally, two-way speed limiter is used as speed monitoring device to detect whether the car speed is out of control. Deceleration device includes safety gear, rope gripper and safety brake, which act on car or counterweight, wire rope system (suspension rope or compensation rope) and traction wheel respectively. The safety brake, as the upward overspeed protection device, must directly act on the traction wheel or the traction axle closest to the traction wheel. At present, the brake directly acting on the traction wheel is usually used as the upward overspeed protection on the permanent magnet synchronous motor of the inorganic room elevator. The mechanical structure of this kind of brake is designed redundantly, which meets the requirements of safety brake and does not need to consider its failure. At the same time, because it directly acts on the traction wheel, the damage of the main shaft, bearing and other mechanical parts of the traction machine will not affect its effective holding brake stop. Of course, it can not protect the upward overspeed caused by other reasons, such as the damage of traction conditions, slippage between traction wheel and wire rope, etc. This leads to a question: which type of upward overspeed protection device should work on? According to GB7588-2003 safety code for elevator manufacturing and installation, the upward overspeed protection device needs to work on the upper overspeed caused by brake failure and motor drive failure. Therefore, the current upstream overspeed protection device can not protect all the upstream overspeed elevators.