Negative pressure pipeline opening and closing device and application thereof

The invention relates to the technical field of liquid discharge, and discloses a negative pressure pipeline opening and closing device and application thereof. The device comprises a plug for plugging a liquid outlet and a buoyancy piece connected with the plug, wherein the buoyancy piece comprises two sets of floating blocks and a connecting rod for connecting the two sets of floating blocks; aguiding element is arranged in the liquid storage cavity and limits the two sets of floating blocks, the plug and the liquid outlet are located on the same vertical line, a limiting piece is arrangedbetween the two sets of floating blocks and fixedly connected with the inner wall of the liquid storage cavity, and the maximum distance between the limiting piece and the top wall of the floating block located below is less than that between the top wall of the floating block located above and the top wall of the liquid storage cavity. The buoyancy piece with the upper floating block and the lower floating block is adopte