Patent ID: 9689513
Date: 2017-06-27
CPC Classifications: F16L,Y10T

Claim:
1. A tubular article having a longitudinal axis, wherein the tubular article comprises: a first inner strip and a second outer strip that are separate from one another, wherein the first inner strip and the second outer strip are each made of spirally wound overlapping material; wherein the first inner strip has a longitudinal axis, a first edge, and a second edge, the first and second edges of the first inner strip being at a common first radius; wherein the second outer strip has a longitudinal axis, a first edge, and a second edge, the first and second edges of the second outer strip being at a common second radius; wherein the first inner strip comprises two or more longitudinally extending inner ridges, each of which extends along the longitudinally extending axis of the first inner strip in parallel to each other and in which the inner ridges of the first inner strip each comprise asymmetric ridges having a leading edge extending from the first radius and forming a contact portion and a non-contact trailing edge portion terminating at the first radius; wherein the second outer strip comprises two or more longitudinally extending outer ridges, each of which extends along the longitudinally extending axis of the second outer strip in parallel to each other and in which the outer ridges of the second outer strip each comprise asymmetric ridges having a leading edge extending from the second radius and forming a contact portion and a non-contact trailing edge portion terminating at the second radius; and wherein the leading edges of the first inner strip and the second outer strip are in contact with each other, and the non-contact trailing edge portions of the first inner strip and the second outer strip are spaced apart from each other.