The phenomenon of elevator sliding and closing people is a topic often encountered and discussed by ordinary people in their daily lives, and media such as television and newspapers often report that an elevator in a certain residential area has slipped.


This article analyzes the types, characteristics, processes, and causes of elevator sliding phenomena, and further understands the reasons for elevator sliding through some practical cases, so that personnel and the public involved in elevator work can have a clearer understanding and comprehension of the phenomenon of elevator sliding and closing people.


    

The generation of slides

In the event of a malfunction during normal operation


The phenomenon of self-protection by sliding stairs


In general, during the operation of an elevator, if a malfunction occurs and the control system suddenly detects an abnormal signal, the elevator will automatically issue a command to stop running immediately. After receiving the stop command, the elevator will inevitably cause changes in its running speed or acceleration/deceleration during the short period of emergency stop, and it will not reach the destination stop level. As the running speed or acceleration/deceleration of the elevator changes, it will create a sense of physical weightlessness for passengers in the elevator car, giving them a feeling of "sliding".


If the fault signal is abnormal, the system can automatically address or correct it and eliminate it, and the elevator will automatically open the door and release people on the nearest level; If the abnormal signal of the malfunction cannot be automatically eliminated, it will cause people to be trapped, and due to untimely rescue, the elevator will be trapped for a long time. This is the phenomenon of elevator "sliding" to close or trap people reported in the media.


This kind of "slide" phenomenon is a self-protection slide phenomenon that occurs when an elevator malfunctions during normal operation. It is not only an abnormal operation of the elevator, but also a form of protection for the elevator itself against abnormal operation.




Caused by faults such as insufficient braking or traction force


The elevator loses control and experiences a sliding phenomenon of the car squatting at the bottom or hitting the top



This sliding phenomenon generally refers to the phenomenon where the potential energy generated by the quality difference between the elevator car and the counterweight causes the elevator car (or counterweight) to rise or fall when the elevator loses power drive and control.


The sliding phenomenon that occurs in special and serious situations is often due to reasons such as the brake not releasing, insufficient braking torque or traction force of the brake, causing the elevator to lose control at a certain speed, unable to stop at the landing station normally, until the car squats at the bottom or hits the top.


This is a serious phenomenon where the elevator loses control and slides for a long distance until the car squats at the bottom or rushes to the top due to faults such as brakes and insufficient traction during elevator operation or when the elevator stops at a flat level. The characteristics of this sliding phenomenon are manifested as the harm to passengers, significant damage to the elevator itself, and even life-threatening situations. When the elevator loses control and runs, if its speed exceeds the speed of the safety gear after a long sliding distance, the speed limiter safety gear system may be able to stop the elevator on the guide rail, or the elevator car may not be able to stop due to the safety gear; If the elevator speed does not exceed the operating speed of the safety gear, and the brake does not release or the traction force is insufficient, it is inevitable for the elevator car to squat or hit the top.


The reason for the occurrence of the slide


There are many reasons for the phenomenon of elevator sliding, and from a technical perspective, there are mainly the following aspects:


(1) The brake does not apply (do not apply) or the holding time is delayed.


① Mechanical jamming of brake spring (arm);


② The brake coil cannot be powered off;


③ Contact adhesion between two independent electrical devices controlling the brake;


④ Brake control circuit design error, after the motor is powered off, the brake cannot lose power;


⑤ The iron core has oil stains that are adsorbed and cannot be released;


⑥ The brake contactor has residual magnetism.


(2) The brake is applied but the braking torque is insufficient.


① The brake holding spring rusts and loses its elasticity or the elasticity adjustment is not in place, and the spring is too loose;


② Excessive clearance between brake wheels and brake shoes;


③ Wear of brake shoes;


④ The contact area between the brake wheel and brake shoe is too small;


⑤ The friction coefficient of the brake shoe is too small (wear, heat burning).


(3) Insufficient drag force.


① The traction wheel groove is severely worn;


② Excessive lubrication and severe oil stains on the traction steel wire rope;


③ Uneven tension of steel wire rope or severe insufficient tension of traction rope;


④ Improper or changing balance coefficient K, resulting in imbalance of counterweight and weight on both sides of the elevator car;


⑤ The elevator is severely overloaded (caused by secondary decoration, etc.), and the overload protection device is also ineffective;


⑥ The diameter of the traction rope is reduced due to wear.


(4) The speed limiter is malfunctioning.


① The electrical switch of the speed limiter is malfunctioning;


② The mechanical switch of the speed limiter is malfunctioning;


③ The lifting force of the speed limiter cannot make the safety gear work;


④ The actual operating speed of the speed limiter exceeds the prescribed value of relevant national standards;


⑤ The action mechanism of the speed limiter is malfunctioning or its action is blocked;


⑥ The linkage switch of the car roof safety gear is malfunctioning.


(5) The safety gear is malfunctioning.


① The gap between the safety clamp block and the side of the guide rail is too large, causing it to not reach the effective position or the safety clamps on both sides cannot move synchronously;


② The actual friction force between the safety clamp block and the side clamping of the guide rail cannot effectively stop the working load after the action of the safety clamp block;


③ The dirt and rust on the mechanical safety gear cause the safety gear to fail.


(6) Other reasons.


① The landing door or car door is not adjusted properly, causing the electrical interlocking device of the landing door or car door to be on and off during the operation of the elevator;


② The leveling sensor cannot sense the position of the elevator car, or detects that the position of the elevator car does not match the preset position, resulting in a phenomenon of misalignment;


③ The fixing of electrical wiring terminals is not firm, especially the wiring terminals of the main power supply and some electrical safety switches are not firm;


④ The end station protection switch (forced deceleration switch, limit switch, and limit switch) fails or cannot sense a signal, resulting in hitting the top or squatting at the bottom;


⑤ For sightseeing elevators, too strong sunlight and a lot of dust and dirt on the light curtain can affect the misoperation of the light curtain protection and cause the elevator to stop;


⑥ The call signal registration board in serial communication is damaged, causing a conflict of call addresses and resulting in chaotic elevator stops;


⑦ The frequency converter has malfunctioned and cannot receive the operating signal output from the I/O board in the control cabinet.