Abstract: The retractable stop associated with the valve (14) of the female element (2) consists of a spring (26) in catch (hook) form (26), of which the branches (26a) are engaged on the stem (14a) of the valve (14), so as to grip it constantly between two zones, diametrically opposite each other, while the sliding ring (24) has, at its end turned toward the collar (20), a cylindrical segment (24b) of diameter (D3) greater than that of the first section (14'a) of the stem (14a) of the valve (14), and between its end (24a), designed to come in contact with the shoulder (23) of the stem (14a) and the said cylindrical segment (24b), a truncated cone segment (24c), of which the small diameter is equal to the diameter (D1) of the first section (14'a) of the stem (14a), and which is designed to be situated between the branches (26a) of the catch (26) when the ring (24) is supported against the shoulder (23) of the stem (14a) of the valve (14), and this latter is in normal opening position.