pregripper of a sheet - fed printing press includes a drive unit for pivotally driving a pregripper bar secured to a pregripper support device , the drive unit having main and auxiliary cam elements disposed on a drive shaft so as to be fixed against rotation relative thereto , and cam follower members cooperatively engaging with the cam elements so as to produce a movement of the pregripper bar , the pregripper support device engaging the pregripper bar approximately centrally for introducing a force to produce the pivoting movement .