invention without having lateral access to one of the connection elements for example in the event of one of these elements being embedded as represented in dashed and dotted lines for element a in fig1 in addition the ring 33 is mechanically protected against shocks and pollution by the body 31 the catches 20 and 21 being in one piece with the body 11 the endpiece a is very robust and may be mounted at the end of a flexible pipe in order to improve reliability of the locking at the moment of passage of the catch 20 in the curved part 403 the outer surface 417 of this part may be provided to be incurved towards the inside of the ramp 40 as represented in dashed and dotted lines in fig5 this inducing an acceleration of the relative speed of the catch with respect to the ramp after the passage of the catch at the level of the apex of the incurved part 417 this avoids a release of the axial effort in the direction of the hollow 404 hence the insurance that the catch 20 comes into abutment in this hollow in the passage 402 there may be provided an elastic blade 418 fixed by a rivet 419 or any other means in the bottom 420 of the ramp 40 this blade 418 tending under the effect of its own.