Drainage device for closed chamber containing liquid

A drainage device, comprising:

• a closed chamber filled with an amount of liquid and gas, the closed chamber defining a fluid channel and a gas channel in a top end, and a slag discharge hole in the bottom end thereof;
• a liquid pumping mechanism pumping the liquid in the closed chamber, and preventing the liquid in the liquid pumping mechanism from flowing back to the closed chamber, the liquid pumping mechanism comprising a drive assembly, a telescopic assembly, and a first sealing assembly, the telescopic assembly defining a telescopic chamber, the driving assembly comprising a connecting pole;
• and
• a liquid discharge mechanism discharging the liquid in the liquid pumping mechanism to outside, and preventing outside air from entering into the closed chamber, the liquid discharge mechanism comprising a second sealing assembly, the second sealing assembly comprising an action piston fixed to an end of the connecting pole and a flexible member sleeved on the connecting pole and attached to the action piston;
• wherein the first sealing assembly and the second sealing assembly are received in the telescopic assembly and a major portion of the telescopic assembly is positioned within the closed chamber, the drive assembly drives the action piston to move, thereby pumping the liquid in the closed chamber into the telescopic chamber through the first sealing assembly, and discharging to the outside through the second sealing assembly.