Differential pre-tightening mechanism applied to sleeve unfolding

The differential pre-tightening mechanism comprises an upper pre-tightening mechanism, a lower pre-tightening mechanism, a differential mechanism and a power assembly, and the input end of the differential mechanism is in transmission connection with the output end of the power assembly; the output ends of the upper pre-tightening mechanism and the lower pre-tightening mechanism are both provided with the driving assemblies, and the power assembly drives the upper pre-tightening mechanism and the lower pre-tightening mechanism through the differential mechanism so as to drive the corresponding driving assemblies to make contact with the inner surface of the sleeve. According to the differential pre-tightening mechanism, a single power source is used for achieving variable-diameter self-adaption of multiple pre-tightening mechanisms, the upper driving assembly and the lower driving assembly can make contact with the inner surface of a sleeve in any form at the same time, the effective contact force of the driv