is such that a part of the countersunk feature 33 is located outside of the pusher 12 the dimensions of the different parts comprising the device are such that when the pusher 12 is in the highest possible position namely when the annular flange 15 of the pusher 12 substantially contacts the shoulder 11 between the second cavity 8 and the aperture 9 the flange 22 is substantially supported on an entire perimeter thereof against the added on part 23 advantageously an elastic element 35 is provided to ensure this support this elastic element 35 is also used to make the annular flange 15 of the pusher 12 approach the shoulder 11 between the second cavity 8 and the aperture 9 the elastic element 35 is for example a helical spring placed between the pusher 12 and the flange 22 the central longitudinal axis of the helical spring is substantially merged with the central longitudinal axis 10 of the body 1 it is clearly not possible to obtain perfect contact simultaneously between the flange 22 and the added on part 23 the end 25 of the second finger 24 and the ramp 30 and the annular flange 15 and the shoulder 11 between the second cavity 8 and the aperture 9 advantageously a functional.