Patent ID: 6681610
Filing Date: 2004-01-27
Classification: B21C,B62K

Abstract:
A process for extruding a tube having different sections where the tube is formed by using a die for tube extrusion molding having a first die and a second die which are superposed in a direction of extrusion, the first die and the second die being relatively movable in a set direction along the superposed surface, in order to permit the extrusion of a material via an outflow passage formed by the superposition in the direction of extrusion of a first die hole formed in the first die and a second die hole formed in the second die, and thereby causing a sectional form of the tube to be varied in the direction of extrusion by relatively moving the first die and the second die in the set direction, comprising the steps of:providing the outflow passage with an opening for a tube wall and at least one opening for an intermediate wall which continues to the opening for the tube wall inside the opening for the tube wall; extending the opening for the tube wall for a predetermined width in a first direction which is a direction when the set direction is projected on a plane perpendicular to the direction of extrusion, and extending the opening for the tube wall in a second direction crossing the first direction on the perpendicular plane; relatively moving the first die and the second die in the set direction; extruding the material from opening for the tube wall and the opening for the intermediate wall; forming the tube wall having a width in the first direction which varies in a longitudinal direction by varying the opening for the tube wall; and simultaneously forming the intermediate wall being formed in an inside space of the tube, and having a fixed thickness and a predetermined width in the first direction, extending in the longitudinal direction, and continuing to the tube wall in the inside space of the tube, wherein the intermediate wall is at least one connecting wall which connects two tube wall parts opposite in the second direction of the tube wall, and which partitions the inside space into a plurality of independent partial spaces on the section of the tube, and wherein a width of the connecting walls increases or decreases in the longitudinal direction from the extrusion start end.