Drag chain, protective cover has been widely used in CNC machine tools, electronic equipment, stone machinery, glass machinery, door and window machinery, injection molding machine, manipulator, lifting and transportation equipment, automated warehouse, medical equipment, automation equipment, robots, laser cutting, flame cutting, etc. The structure of the drag chain: the drag chain looks like a tank chain and is composed of many unit chain links, which can rotate freely. The same series of drag chains are high inside, high outside, the same pitch, high inside the drag chain, and the bending radius R can be selected differently. The unit chain link consists of left and right chain plates and upper and lower cover plates. Each section of the drag chain can be opened, which is convenient to assemble and disassemble without threading. After opening the cover plate, cables, oil pipes and air pipes can be put into the drag chain.