Pressure reducing valve

A pressure reducing valve, whose output pressure is automatically controlled relative to ambient pressure, particularly for scuba breathing apparatus regulators, comprising two axially adjacent chambers (3, 4), separated by a partition (2), whereof one, the so-called compensation chamber (3), communicates with the outside environment and the other, the so-called pressure chamber (4), communicates with a pressurized gas source, whereas a tubular plug (8) slidably and tightly passes through the partition (2), which plug is open at both ends and has a widened piston-like head (9) which is arranged to slide in a tight manner in the compensation chamber (3), and which separates the latter from an outlet chamber (14) of the valve, in which the respective end of the tubular plug (8) opens, a helical pressure spring (12) being interposed between said piston-like head (9) of the tubular plug (8) and the partition (2), whereas the other end of the tubular plug (8) cooperates, in the pressure chamber (4), with a facing pad (13), which forms the valve seat and is mounted in such a manner as to slide axially for adjustment purposes in a corresponding housing, which pad (13) abuts axially, on the side opposite the plug (8), against an adjustment screw (17) to be tightened in the valve body (1) or in a part (16) fastened thereto, and preferably consisting of a threaded stem, by which screw (17) the pad (13) may be pushed and displaced axially inwardly, preferably against the force of a helical spring (15) accommodated in the pressure chamber (4), to adjust the axial position of the pad (13), characterized in that an antifriction member (18) is interposed between the pad (13) and the threaded stem (17), which is mounted in such a manner as to be free to rotate and to slide axially and to prevent any direct contact between the end of the adjustment screw (17) and the pad (13), and to further prevent the pad (13) from being driven along into rotation by the adjustment screw (17) when the latter is rotated.