Negative pressure pipeline opening and closing device

A negative pressure pipeline opening-and-closing device, wherein:

• the negative pressure pipeline opening-and-closing device comprises a blocking member for blocking a liquid outlet port of a liquid reservoir and a buoyant member connected to the blocking member;
• the buoyant member comprises two floats and a connection rod connected to the two floats,
• the liquid reservoir is provided with a guide therein, and the guide confines the two floats, the blocking member and the liquid outlet port in a same vertical line,
• a limiting member is arranged between the two floats and is fixed to an inner wall of the liquid reservoir,
• a maximum distance between the limiting member and a top wall of a lower float of the two floats is smaller than a maximum distance between a top wall of an upper float of the two floats and a top wall of the liquid reservoir;
• the connection rod has a length that is greater than one half the height of the liquid reservoir, and the total length of the blocking member and the buoyant member is smaller than the height of the liquid reservoir;
• and
• a valve box is arranged in the liquid reservoir, accommodates the buoyant member, and is communicated with the liquid reservoir through top and bottom of the valve box;
• a liquid inlet port is arranged in the sidewall of the valve box, the liquid inlet port extends down to a bottom wall of the liquid reservoir, and an air port is provided in a top of the liquid reservoir.