the member 12 is so designed as to have a diameter at 16 which is equal at a maximum to the internal diameter of the tube 10 said tube is thus capable of sliding over said member without being subjected either to any effort of extension or to any stress the end portion 17 of the tube 10 being intended to come into position substantially at the level of the terminal edge of the conical surface 15 the member 12 is further provided with an internal bore 18 which serves to ensure continuity of the passage through the tube 10 and the coupling connector 11 finally said member 12 is provided at the opposite end with a cylindrical extension 19 having an externally threaded portion 20 the design function of which will be explained in detail hereinafter the end portion 17 of the flexible tube 10 which surrounds the member 12 is secured to this latter by means of a second member 13 which is intended to fit over the end portion of said tube 10 and serves to apply said end portion against the conical surface 15 to this end said member 13 which forms a ring and is placed initially in the position of fig2 is progressively thrust into position by means of an extension member 21 provided with an internally threaded portion 22 for securing said ring 13 on the externally threaded portion 20 of the member 12 this has the effect of applying an axial effort on said ring which is brought into the position illustrated in fig3 at the end of travel the extension member.