The national standard for elevators stipulates that "power-driven automatic doors should have anti-entrapment devices." At present, the anti-pinch device is mainly realized by the safety contact plate and light curtain. Some elevators are equipped with one, and some elevators are equipped with both light curtains and touch plates. When a passenger enters or leaves the car, blocking the safety touch plate or light curtain, the elevator door cannot be closed, even if the safety touch plate or light curtain is suddenly blocked during the door closing process, the elevator door will stop and open by itself. Under normal circumstances, the elevator with set selection, parallel connection and group control will close the door and standby when there is no operation command. In the process of closing the door, especially when the door will be completely closed when the anti-pinch system (light curtain or safety contact plate connection) has poor contact and other faults, the elevator's control system will think that the passenger blocked the light curtain or contact plate, the door will be reversed pop open, a few seconds after the back door will be automatically closed, and then be popped open, repeatedly, affecting the normal use of the elevator. The solution is to check the light curtain and the safety contact plate, troubleshooting. 2, it may be the hall door or car door floor and on the can slide in the garbage Elevator national standard, "power-driven automatic door to prevent the closing force should be no greater than 150 Newton, this force measurement shall not be measured within 1/3 of the beginning of the closing stroke." Elevator door movement in the chute of the floor and upper cans, closing process, if the floor or upper cans in the garbage (such as dust, cloth, cigarette butts, small stones, etc.), resulting in chute blockage, preventing the normal closure of the elevator door, the door machine driving force of more than 150 Newtons can not overcome the resistance, then this is the elevator door will be reversed pop open (garbage in the upper cans, floor cans, not in the light curtains and safety contact plates within the scope of the work, the Cannot force the light curtain and safety contact plate to act). The door closes again and pops open again. The solution is to clean out the trash in the chute and make sure the chute is clean and smooth.