Opening/closing device for a container for pourable products

An opening closing device for a container for pourable products, having a perforable portion, said opening/closing device comprising a base combinable with said container at said perforable portion, a cutting element provided with a sharp end arranged on the lower side of said cutting element, and a first passage in said base, said cutting element being constrained translatably to said base inside said first passage between a first position (P1), in which said cutting element is combined separably with said base, and a second position (P2), in which said cutting element has reached and perforated said perforable portion, wherein said base comprises a second passage for pouring a pourable product when contained in said container, and wherein said first passage and said second passage are in a region of said base spaced from the upper surface of said perforable portion when said base is combined with said container, so as to define a cavity between the lower surface of said region and the upper surface of said perforable portion, said cutting element being shaped to impede, when it has reached said second position (P2), the passage of said pourable product through said first passage and to allow the outflow of said pourable product from said container to said second passage through said cavity.