Open and close protection device of mechanical crane span structure

The utility model relates to an open and close protection device of mechanical crane span structure, include: clamping screw and steel sheet, the steel sheet passes through clamping screw and installs the below at mechanical crane span structure, install the starting switch of control floodgate body switching on the upper surface of steel sheet, the steel sheet with the floodgate body is corresponding. The beneficial effects of the utility model are that: the position that corresponds through the below at the bridge plate and the floodgate body sets up the steel sheet, the starting switch of installation control floodgate body stop motion on the steel sheet, when the floodgate physical contact after the steel sheet, drive steel sheet upward movement, messenger's bridge plate touches starting switch to the motion of the time -out floodgate body prevents under the condition that the nobody controlled, and floodgate body bursting bridge plate perhaps damages the emergence of accidents such as lead screw.