Protecting device for universal shaft of straightening machine

The utility model provides a straightener cardan shaft protection device which comprises a connecting flange used for connecting a straightening roll and a universal coupling and a limiting assembly arranged on the outer circumferential wall of the connecting flange, the limiting assembly comprises at least two limiting clamping blocks evenly distributed in the circumferential direction of the connecting flange, each limiting clamping block is provided with an open end, and the open ends of the limiting clamping blocks are open. The open end is sleeved on the connecting flange; a fastening assembly is further arranged on the periphery of the limiting assembly in a surrounding mode, the fastening assembly comprises a first clamping sleeve and a second clamping sleeve, the two ends of the first clamping sleeve and the two ends of the second clamping sleeve are movably connected respectively, and the first clamping sleeve and the second clamping sleeve are tightened by the periphery of the limiting clamping bloc