Expansible shaft for roll core

摘要

An elongate expansible shaft for a roll core has a peripheral surface defining multiple separate elongate slots helically intertwined and oriented at a pitch angle no greater than about 30 DEG measured from a longitudinal axis. Each slot is T-shaped in cross section and contains a respective separate, elongate, resilient bladder pneumatically expandable into frictional engagement with the core. The bladder has a unitary construction with hinge portions for minimizing the loss of force due to expansion of the bladder. An air inlet fitting is inserted in one end of each bladder and is independently connected to a respective separate valve for preventing the escape of air from the bladder irrespective of the air pressure in any other bladder.