PLASTIC CORE TUBE HAVING RING-SHAPED CORRUGATIONS

摘要

A core tube comprising a combination of a smooth outer tube, a second tube with ring-shaped corrugations arranged inside the first tube, and optionally a further smooth tube inside the second tube. Both or all three tubes are made of plastic extruded in one or more steps, and together provide the core tube with the required solidity and mechanical strength while minimizing its weight and cost.