Mother-son type drainage device

The utility model discloses a mother-son type drainage device which comprises a flexible ring, the upper end and the lower end of the flexible ring are fixedly connected with a top plate and a bottom plate respectively, one side of the upper end of the top plate is fixedly connected with a liquid inlet pipe, the other side of the upper end of the top plate is fixedly connected with an air inlet pipe, and the middle position of the lower end of the bottom plate is fixedly connected with a liquid discharge pipe. According to the negative pressure drainage device, the device can be fixed through the connecting rope, the fixing base and the hook, negative pressure drainage can be conducted through the flexible ring, the top plate, the bottom plate and the spring, after drainage is finished, the first valve can be closed, the second valve, the third valve and the fourth valve can be opened, and air enters through the air inlet pipe; drainage liquid can enter the liquid collecting bag through the liquid drainage pi