Patent ID: 9334983
Filing Date: 2016-05-10
CPC Classification: B21D,B29C,E21B,F16L,Y10T

Claim Text:
1. A hoop winding method for manufacturing a reinforced tube, wherein the following operations are carried out: a) providing a metal tube, then b) depositing a reinforcing layer around the metal tube, the reinforcing layer comprising elongate internal pressure and axial traction reinforcement elements, by alternating deposition of the reinforcement elements forming an angle between 60 and 90° to the axis of the tube with deposition of the reinforcement elements forming an angle between 0 and 30° to the axis of the tube, then c) imposing a tensile force at the ends of the metal tube so as to plastically deform the metal tube, the tensile force being oriented parallel to the metal tube axis, wherein a residual deformation of the metal tube caused by the tensile force induces tensional stresses in the reinforcement elements forming an angle between 0 and 30° to the axis of the metal tube, and the reinforcement elements forming an angle between 0 and 30° to the axis of the metal tube induce an axial compressive stress in the metal tube after release of the force, and d) imposing a pressure onto the inner wall of metal tube so as to plastically deform the metal tube, wherein a residual deformation of the metal tube caused by the pressure induces tensional stresses on the reinforcement elements forming an angle between 60 and 90° to the axis of the tube, and the reinforcement elements forming an angle between 60 and 90° to the axis of the tube induce a radial compressive stress in the metal tube after release of the pressure, the method being characterized in that the value of said pressure is set independently of the value of said tensile force.