Process for extruding tube having different sections and die for tube extrusion molding

A process for extruding a tube having different sections, comprising the steps of:

• superimposing a first die and a second die in a direction of extrusion;
• providing an outflow passage having 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;
• simultaneously forming the intermediate wall in an inside space of the tube, the intermediate wall 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;
• and
• causing the intermediate wall to partition the inside space into a plurality of independent partial spaces on the section of the tube, the intermediate wall being at least one connecting wall which connects two tube wall parts opposite in the second direction of the tube wall,
• wherein a width of the at least one connecting wall increases or decreases in the longitudinal direction from the extrusion start end.

A die for tube extrusion molding comprising:

• a first die and a second die which are superposed in a direction of extrusion and which are relatively movable in a set direction along the superposed surface,
• said first die having a first die hole formed by a void between a first peripheral wall of a first hole formed in the first die and a first core arranged in the first hole and integrated with the first die,
• said second die having a second die hole formed by a void between a second peripheral wall of a second hole formed in the second die and a second core arranged in the second hole and integrated with the second die;
• an outflow passage formed by the superposition in the direction of extrusion of the first die hole and the second die hole for extruding a material to form a tube;
• said first core being composed of a plurality of child cores arranged in parallel, having 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 forming a void between the plurality of child cores extended in a second direction crossing the first direction on the perpendicular plane;
• said outflow passage having an opening for a tube wall formed by a void between the first peripheral wall or the second peripheral wall and the first core or the second core, and also having an opening for a first intermediate wall defined by the void between the first cores and continuing to the opening for the tube wall;
• the first die and the second die being superposed so that the maximum interval in the first direction of the opening for the tube wall can be varied according to the amount of the relative movement in the set direction of the first die and the second die;
• the second core keeping at least one of the openings for the first intermediate wall in an open state by the predetermined width and in a blocked state;
• 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 at least one connecting wall increases or decreases in the longitudinal direction from the extrusion start end.