is open and protrudes inside the annular portion 13 a frustum shaped circumferential expansion 19 is formed on the outer lateral wall of the cylindrical portion 14 its smaller end face is directed towards the upper end 14 a and its larger end face is coupled to the annular base 15 at the prefracture line 16 a downward axial pressure on the cylindrical portion 14 is sufficient to uncouple it from the annular portion 13 by breaking the sealing means formed by the line 16 fig1 illustrates a bottle 1 as packaged before the preparation of the product s in which the annular portion 13 is fixed to the neck 3 and is still rigidly coupled to the cylindrical portion 14 whose lower end 14 b is partially inserted in the top of the perforator 9 by applying a downward pressure to the cylindrical portion 14 fig2 the sealing means formed by the line 16 are broken and the cylindrical portion 14 is uncoupled from the annular one 13 which remains anchored to the neck 3 by continuing to apply the pressure the uncoupled cylindrical portion 14 slides inside the annular portion 13 and the lower end 14 b penetrates further into the perforator 9 until the larger end face of the expansion 19 abuts against the collar 10 then the perforator 9 pushed by the cylindrical portion 14 slides inside the reservoir 5 descending and piercing the diaphragm 6 along the line 8 the sliding stroke of the perforator 9 is determined by a stroke limiting.