Metering mechanism for a pump, methods for locking and unlocking such a mechanism

A metering mechanism (7) comprising a body (70) mounted to translate in a sleeve (77) which is itself mounted in an adjustment nut (71), said adjustment nut being capable of cooperating by screwing with said sleeve, said screwing then causing a rotation of the adjustment nut relative to the body of the metering mechanism, said body being extended by a valve seat (75) that can be closed by a valve (76) and that is capable of accommodating a plunger (8), the reciprocating movement of which allows at least a suction at the valve (76), the travel of the plunger being a function of the position of screwing between the adjustment nut and the sleeve, the metering mechanism further comprising means (M) for activating the blocking of the rotation between the adjustment nut (71) and the body of the metering mechanism (70) so as to prohibit the screwing and the unscrewing between the adjustment nut and the sleeve, said means comprising a ring (1) housed in a locking nut (2) mounted to rotate around the body (70), said ring cooperating by screwing with said locking nut, said ring being mounted to translate only around and along the body of the metering mechanism between a first position of abutment at the bottom of the locking nut and a second position of abutment against the adjustment nut involving the rotational blocking of the adjustment nut rendered secured by complementarity of form with the ring.