If the gate is in the closed position, that is, the lower edge of the gate has contacted the bottom of the gate, the hanging head bolt on the screw is at the lower part of the long elliptical screw hole, and the travel switch is still in the initial state, opening the gate at this time will not cause accidents even if the direction is reversed (including changes in the power phase sequence). Because the gate does not move, the screw can still descend and trigger the travel switch action, sending an alarm signal to remind the operator to terminate the misoperation or change the operation direction. It is an electric opening and closing and can automatically stop the machine. When an alarm signal and automatic shutdown are issued, if the operator does not immediately correct the erroneous operation (manual must be corrected immediately) or eliminate obstacles to reset the protection system, the alarm will continue to sound continuously. For electric opening and closing, if the fault is not eliminated and the travel switch is reset, it will not be able to repeat opening and closing, effectively preventing the occurrence of top gate accidents.

The opening and closing protection measures for submerged gates without door closing force. For this type of gate that is submerged in water for a long time, the screw lifting hole is still changed from circular to elliptical, but the position of the travel switch needs to be installed above the highest water level. Therefore, the stopper needs to be changed to a force transmission rod, and one end of the force transmission rod needs to be welded to the gate lifting seat. The force transmission rod is parallel to the screw and connected to the screw with a circular ring, so that the force transmission rod can move up and down inside the circular ring. The length of the force transmission rod should meet the requirement of extending to the highest water level. In addition to strengthening the work responsibility education and skill training of operators, requiring them to operate according to the opening and closing procedures, the key is to improve technical measures to prevent the occurrence of top gate accidents.

To solve this problem, the following conditions must be met technically: firstly, it must be able to issue a misoperation alarm to the opening and closing personnel, reminding them to stop the misoperation, and the electric opening and closing should be able to automatically stop the machine, terminating the occurrence of misoperation accidents; The second requirement is that the gate should automatically sound an alarm when encountering obstacles during the descent process, reminding the operator to stop the machine. Electric opening and closing should be able to automatically stop the machine; Thirdly, regardless of the type of operational accident, the automatic shutdown can only be resumed after the operator has eliminated the shutdown fault, which can avoid the possibility of accidents caused by repeated operations when the screw type opening and closing machine product has not eliminated the fault.