Radially engageable leakproof coupling

A sealed coupling comprising first and second tubular endpieces each having an end provided with an orifice, beyond its own end, the first endpiece has a U-shaped axial extension provided with a transverse groove with a bottom that comprises a semicircular portion of a radius greater than a radius of the orifice of the first endpiece, together with two rectilinear portions situated at opposite ends of said semicircular portion, said groove having a first radial wall situated adjacent to the end of the first endpiece and a second radial wall facing the first, the end of one of the endpieces being provided with a circular sealing gasket that projects axially beyond said end and that comings into sealing contact with the end of the other endpiece, the second endpiece being provided with a substantially circular radially outwardly extending flange and with a radial collar that is resiliently flexible in an axial direction and that has a radial face facing away from the end of said second endpiece, said flange, together with said radial collar, engaged into the groove during relative transverse displacement of the two endpieces for the purpose of coupling said endpieces together, said radial face of the radial collar bearing against the second radial wall of the groove when the flange and the radial collar are engaged in said groove, one of the first and second endpieces having an axial projection situated in the vicinity of the edge of the orifice thereof, while the other of said endpieces has an axial setback situated in the vicinity of the edge of the orifice thereof, said setback receiving said axial projection when the endpieces are in a coupled-together position, said axial projection cooperating with the end of said other endpiece during an engagement stroke of the flange and the radial collar into the groove so that said radial collar is resiliently urged in a direction increasing separation between the ends of the two endpieces and is received in said axial setback under an effect of resilience of the radial collar at the end of said engagement stroke.