Valve with wider opening and pressure regulator equipped with such a valve

Valve comprising:

• a valve body (1) comprising:
• an internal chamber (21) of axis (AA) comprising an upstream compartment (21a) and a downstream compartment (21b), the said upstream compartment (21) being of cylindrical cross section and of diameter (Dam) and the said downstream compartment (21b) being of cylindrical cross section and of diameter (Dav), with Dam<Dav,
• at least one fluid inlet orifice (10) formed in the wall of the said valve body (1) and opening into the upstream compartment (21a) of the internal chamber (21), and
• at least one fluid outlet orifice (20), and
• a piston body (2) that can move in translation along the axis (AA) inside at least one part of the said internal chamber (21) and is located between the said fluid inlet orifice (10) and the said fluid outlet orifice, the said piston body (2) having a front face (2a) located on the same side as the fluid inlet orifice (10), a rear face (2b) located on the same side as the fluid outlet orifice, and a lateral wall (2c) located between the said front face (2a) and the said rear face (2b), the said lateral wall (2c) of the piston body (2) having at least a first portion (P1) of cylindrical cross section and of first diameter (D1) and at least a second portion (P2) of cylindrical cross section and of second diameter (D2), with D1<D2 and D2<Dav,
• and in which the wall of the said valve body (1) has an internal face (a1) forming the end wall of the upstream compartment (21a), against which face the front face (2a) of the piston body (2) normally bears.