Gas-liquid hydraulic expandable chucks and shafts

摘要

A self-contained cylindrical expandable mandrel comprising a closed liquid hydraulic system pressurized by the smaller end of a piston, the larger end of which piston is compressed by a gas, such as compressed air from an outside source through a hose connectable to a pneumatic tire-type check valve on the unit. The closed liquid hydraulic system from the smaller end of the piston flexes a plurality of diaphragms directly urging plungers radially outwardly around the cylindrical mandrel for pressing buttons, bars, or leaves against the inside hollow cores of rolls of web or sheet material for positively grabbing these rolls for rotation directly with the shaft connected to the mandrel. Either a pair of these mandrels may be inserted in opposite ends of the core of a roll, or a complete shaft may be extended through the core of the roll from one end to the other, which shaft may be provided either with an air-type bag or accumulator for maintaining an even pressure on the hydraulic system at the end thereof opposite the piston-operating mechanism, or separate piston-operating mechanisms may be installed in each end of the shaft. Resilient means such as spring means may be provided for retracting each of the radially extending plungers and/or the piston to resist the fluid pressures and release the cores by contracting the expandable mandrels.