Non-return device for air intake of outer pipe of double-wall pipe

The utility model provides a non-return device for air inflow of an outer pipe of a double-wall pipe. The non-return device is installed at the air inlet end of the outer pipe of the double-wall pipe. The device comprises a pipe body, a valve plate and a mandrel. Wherein the valve plate and the mandrel are arranged in the pipe body; the valve plate is a circular plate with the diameter equal to the inner diameter of the pipe body, the mandrel is fixed to the pipe body and connected to the valve plate, and the valve plate can rotate relative to the mandrel to the position perpendicular to the axial direction of the pipe body so as to completely block the pipe body. In addition, the mandrel and the valve plate are eccentrically arranged, the valve plate can fall back to the horizontal position through the gravity of the valve plate, then the pipe body is blocked, and the situation that residual gas in an outer pipe communicated with the pipe body leaks out along the gas inlet due to the fact that the specific g