Hollow roll for travelling on material web

PURPOSE: To provide a hollow roll for travelling on a material web, capable of reducing a difference between the diameter at both ends and the diameter at others when heated. CONSTITUTION: The temperatures of a calendar roll in use for machining a material web, a press roll and a hollow roll 1 in use for a drying cylinder at their ends are controlled. The roll 1 has an inner face heating device 20 and outer face heating devices 30, 30'. The inner face heating device 20 is arranged in the roll 1 for heating the inner face of the hollow roll 1 in a range smaller than the width of the material web 2 passing through the outer face of the roll 1. The outer face heating devices 30, 30' are arranged near both ends of the roll 1 for heating the outer face of the roll 1 at its ends.