Speed reducer sealing device for construction hoist

The utility model discloses a speed reducer sealing device for a construction hoist. The device comprises a step input shaft penetrating a box body, a bearing block and an iron flange cover, wherein a bearing for realizing radial positioning is arranged between the inner wall of the bearing block and the outer wall of the input shaft; an oil baffle disc and a brake gasket which are fixed by locking nuts are arranged at the step section of the input shaft; the iron flange cover, the bearing block and the box body are fastened by a plurality of screws; an annular groove for placing an O-shaped ring is formed around the input shaft; an aluminum ring is arranged outside the O-shaped ring in an interference way; a dynamic ceramic ring is arranged on the inner ring of the aluminum ring; a magnetic ring is embedded in the middle part of the aluminum ring; a convex ring is formed at the end, opposite to the inner wall of the iron flange cover, of the dynamic ceramic ring; a static ceramic ring in contact with the convex ring is embedded in the central hole of the iron flange cover. Axial compression on the dynamic ceramic ring and the static ceramic ring can be realized through magnetic adsorption between the magnetic ring and the iron flange cover, and the dynamic ceramic ring is mechanically sealed along with the rotation of the input shaft, so that the sealing effect is very good, the corrosion resistance is high, and the heat resistance and the high pressure resistance are high.