Patent FR-2863033-A1 (FR)
Title: Tubular joint shaped with lip extending male thread and curved seating on female threaded part so that after plastic deformation by radial expansion, joint is sealed
Inventor: DUBEDOUT LAURENT
IPC: E21B17/042
Filed: 2004-09-22
Abstract: Second and third butting surfaces are conical with identical angles, so as they press together, the internal and external surfaces of the first lip forming a first gripping sealing contact with the second external or third internal surface respectively. During radial plastic expansion of the joint, the first external and the third internal surface form a second gripping sealing contact. A first tubular element (EM) has a first part with a male thread and a second part (P2) extending the first part and including a first annular lip (L1) with a first axially butting surface (SB1), a first internal surface and a first external surface, and a second butting surface (SB2). A second tubular element (EF) has a female thread matching the male thread and screwing onto it, a second annular lip (L2) with a third butting surface (SB3) pressing against the second butting surface, a second external surface placed opposite the first internal surface and a second internal surface, a fourth butting surface (SB4) and a third internal surface facing the female thread and defining with the second external surface and the fourth butting surface an annular seating (LO) for the first lip. The conical surfaces of the second and third butting surfaces are respectively convex and concave so the first internal surface grips and seals radially against the second external surface. Alternatively, the conical surface of the second and third butting surfaces are respectively concave and convex so the first internal surface grips and seals radially against the third internal surface. The angles of the cones are between 5 and 30 deg. The first lip and the seating have shapes chosen so first contact is not made until after the second butting surface is pressing on the third butting surface. The first butting surface is designed to be constrained during tightening to press against the fourth butting surface in such a way as to provoke axial compression of the first lip in elastic deformation. The second external surface of the second lip has an angled annular portion near the third butting surface with an angle of between 8[deg] and 12[deg], preferably 10[deg]. The first internal surface of the first lip is initially inclined at an angle of between 0.1[deg] and 15[deg]. The male and female threads have threads with a bearing flank with a negative angle of between -3[deg] and -15[deg] and an engaging flank with a positive angle of between +10[deg] and +30[deg]. The threads are designed after screwing and before deformation to leave an axial play between their engaging flanks of between 0.05 and 0.3 mm. The first tubular element has at the level of its first external surface and before its first part, a conical chamfer defining a local annular seat inwards. This chamfer has a continuous slope of between 8[deg] and 12[deg]. A second part of the first tubular element has a local annular over- thickness at the level of a fourth internal surface extending the second butting surface in the direction of the first part, and a third internal surface with a groove in a selected place in which the local over-thickness will fit. At the level of the first external surface of the first lip, during radial expansion, an annular shoulder matching at least part of the groove is in gripping and sealing contact with the groove. The groove has two curvilinear portions with identical radii of curvature of between 2 and 60 mm, separated by a cylindrical central part. An independent claim is included for the production of the above joint by screwing the parts together and then expanding them radially using an axially displaced expansion tool.