Importance

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Abstract

An apparatus for making extruded tubing having one or more lumens therein with a variable outer diameter. The apparatus is useful for forming tubing of an extrudable material such as an elastomer or thermoplastic. The extrudable material is forced around a mandrel and through a die aperture over a mandrel wherein the inside surface of the tubing is of uniform diameter along its length but the wall thickness varies throughout its length. Such an apparatus may be used, for example, to make kink-resistant tubing. In one embodiment, the aperture in the extrusion die has a variable diameter while the mandrel remains constant. In a second preferred embodiment, a moveable ring with a central aperture is disposed within the extrusion chamber coaxially with the mandrel. The ring is capable of reciprocal motion in the direction of extrusion. During extrusion, when the moveable ring is moved toward the die opening, it constricts the outer diameter of the tubing thus formed. When the ring is moved away from the die opening, the outer diameter of the extruded tubing increases to the full diameter of the die opening.

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First Claim