Process for manufacturing filler tube and filler tube

A process for manufacturing filler tube to be welded onto a fuel tank, the filler tube made of thermoplastic resin, the process comprising the steps of:

• extruding a cylindrical workpiece comprising multiple layers by an extruder;
• and
• forming the filler tube by adhering the cylindrical workpiece onto an inner peripheral face, which a plurality of dividable molds form, while moving each of the dividable molds sequentially, thereby giving the filler tube a configuration copying the inner peripheral face;
• the filler tube having an end comprising a cylindrical body, and a flange elongating outward diametrically from the cylindrical body at one of opposite ends thereof;
• the flange including a first end face to be welded onto an outer face of the fuel tank, an outer peripheral face, and a second end face making a rear-face side of the first end face;
• the first end face, the outer peripheral face, and the second end face formed of a material for forming an outermost layer of the cylindrical workpiece;
• the step of forming the filler tube including moving the dividable molds at a movement speed, which is set at a first speed, upon adhering the cylindrical workpiece onto a site in the dividable molds for molding the cylindrical body, thereby giving the cylindrical body a predetermined diametrical thickness;
• and
• the step of forming the filler tube further including moving the dividable molds at another movement speed, which is set at a second speed being slower than the first speed, upon adhering the cylindrical workpiece onto another site in the dividable molds for molding the flange, thereby making a diametrical thickness of the flange greater than the predetermined diametrical thickness of the cylindrical body in conjunction with filling up the flange with the material for forming the outermost layer and other materials for forming the flange over a diametrical range thereof to be welded onto the outer face of the fuel tank.