A four - pyramid reel was designed to overcome the difficulty of unrolling solid reel. The expansion diameter of a tetragonal cone drum is directly driven by the expansion and contraction cylinder to produce radial displacement of the segment. Due to the lack of intermediate parts, the taper shaft has large diameter and high strength, and can withstand large tension (up to 400-600kn). The cone axis of a reel has positive and inverted cone. Figure 12-12 is the tetragonal cone reel of 1180 20 high rolling mill, which is mainly composed of pyramid shaft, umbrella block, clamp and expansion and contraction cylinder. The structure is relatively simple.

 

　　The tetrahedron is an open reel. When the drum expands, there is a gap between the fan pieces. Therefore, the volume expansion and contraction of the drum should not be too large, otherwise the gap between the fan-shaped blocks is too large, and the inner layer will be damaged when the coiling. The reel is cantilever structure, and the outer end is provided with movable support. Drum set jaw, jaw by six ¢45 plunger cylinder clamping, and by the spring to loosen, jaw is 5 mm. Drum pyramidal shaft taper Angle of 7 ° 45 ', it is greater than the friction Angle under the condition of normal lubrication, belong to automatic shrink diameter drum performance. The weak link of the drum is the tail hook of the fan-shaped piece. Under the action of axial force of the pyramid, the tail hook produces high bending and shear stress and is prone to fatigue damage. At the same time, the positive cone structure makes the connection bolt of the spindle and expansion cylinder in an unfavorable state of stress. The newly designed quad-pyramid coiler adopts the form of inverted cone, which greatly improves the force of the above parts and simplifies the fan-shaped structure. However, the working area of the expansion cylinder should be subtracted from the piston rod area, and the diameter of the expansion and contraction cylinder is slightly increased.