Abstract: The valve consists of a ring (1) enclosing hinged curved wings (2), the ring having diametrically opposite fixtures (1b-1c) designed to offset the means of hinging the wings so that in their maximum opened position of at least 85.degree., the latter only project beyond the plane of the ring by a small amount thus delimiting, in conjunction with the shape of the wings, three equivalent areas allowing a laminar, axial central flow, the means of hinging the said wings being integrated in the thickness of the ring so that the ends of the wings, at the level of fixtures (1b-1c), are spread apart thus delimiting a space which is completely unobstructed in order not to limit or interfere with the central flow. The ring (1) has an internal peripheral fixture (1a) suitable to provide a support surface corresponding to the external shaped edge (2b) of wings (2) in the closed position of the latter, thus creating a damping effect.