Method for fixing resin tube to die and manufacturing method for resin-tube covered roller

A manufacturing method for a resin-tube covered roller including a cylindrical or columnar base, an elastic layer provided on a peripheral surface of the base and containing rubber, and a surface layer formed by a resin tube configured to cover a peripheral surface of the elastic layer, the manufacturing method comprising:

• (1) a step of producing a cylindrical die having an inner peripheral surface covered with the resin tube by a method for fixing the resin tube inserted in the cylindrical die to the die comprising:
• (a) placing the resin tube inside the cylindrical die so that both end portions of the resin tube protrude from both ends of the die;
• and
• (b) folding back the end portions of the resin tube protruding from the both ends of the die onto an outer peripheral surface of the die,
• wherein the step (b) includes the following steps (i), (ii), and (iii):
• (i) providing a diameter expanding unit having a plurality of diameter expanding claws which are movable in a radial direction between a diameter reduced position to be insertable in the resin tube and a diameter expanded position to extend the resin tube so that an inner diameter of the resin tube is larger than an outer diameter of the die, and which extend in an axial direction orthogonal to the radial direction;
• placing the diameter expanding unit so that the axial direction is substantially parallel to a center axis of the die;
• inserting the diameter expanding claws at the diameter reduced position into one end portion of the resin tube protruding from one of the ends of the die;
• and
• moving the diameter expanding claws to the diameter expanded position to expand a diameter of the one end portion of the resin tube so that an inner diameter of the one end portion is larger than the outer diameter of the die;
• (ii) moving the diameter expanding unit and the die relative to each other so that the diameter expanding unit approaches the other end portion of the resin tube while keeping the one end portion of the resin tube in a diameter expanded state by the diameter expanding claws;
• and
• (iii) applying a pressing force toward the other end portion of the resin tube to an end surface of the one end portion of the resin tube;
• disengaging the one end portion of the resin tube kept in the diameter expanded state with the diameter expanding claws from the diameter expanding claws;
• and shifting the one end portion of the resin tube onto the outer peripheral surface of the die, and
• (2) a step of forming the elastic layer by fixing the base in a hollow portion of the cylindrical die having the inner peripheral surface covered with the resin tube so that the base is substantially concentric with the die, pouring an uncured material into a cavity between an inner peripheral surface of the resin tube and an outer peripheral surface of the base, and curing the uncured material.