Abstract: A valve acting as a gate valve or as a cock, whose body is divided into two chambers that communicate respectively with the inlet and the outlet. A fixed tubular sealing element is arranged therein, which consists of a flexible sleeve that, when in its swollen configuration, seals the holes of a riddled hollow cylinder in which it is housed, said sleeve acting thus on the flow from the first chamber to the second one through said holes. A third chamber is obtained within said tubular sealing element, a small part of the total flow passing through said chamber; thus, by the regulation of the flow rate of said mirror flow, by means of a stem valve assembly, the automatic regulation is corresondingly obtained of the main flow passing to the outside part of said sleeve, so that the regulation is obtained of the whole fluid stream.