Pressure reducing valve assembly

A pressure reducing valve assembly comprising

• a main valve, wherein a valve housing (10) defines a cylindrical chamber (12) provided with annular grooves (17, 16, 15), each of which has an inlet port (A), an outlet port (B), and a return port (T), respectively, a spool (13) having at least three lands (13a, 13b, 13c) being slidably accommodated in said cylindrical chamber (12), so that at one end of said spool (13) is formed a pilot chamber (18) communicated to said outlet port (B) by way of a passage (24) while at the other end thereof is formed a control chamber (25, 250), whereby the fluid flow passing from the inlet port (A) to the outlet port (B) and between the corner of said land (13b) in the center and the rim of the end face of the annular groove (16) provided with said outlet port (B) diverges relative to the axial core of the spool (13) in the form of a trumpet, and the fluid flow passing from the pilot chamber (18) to the return port (T) and between the corner of said land (13a) on the side of said pilot chamber (18) and the rim of the end face of the annular groove (15) provided with said return port (7) diverges relative to the axial core of the spool (13) in the form of a trumpet;
• and
• a pilot valve, wherein a valve housing (39) defines a cylindrical chamber (40) provided with an inlet port (a), an outlet port (b), and a return port (t), a spool (41) equipped with lands being slidably accommodated in the chamber (40), so that at one end of the spool (41) is formed a chamber (45) communicated to said outlet port (b) by way of a passage (46) while an adjustable pushing means to push the other end of said spool is disposed at said other end,
• the chamber (45) containing a pressed biasing spring (47) to press the pilot spool (41) toward the adjustable pushing means (48), and the outlet port (b) being normally closed to the inlet port (a);
• wherein the inlet port (a) of said pilot valve (22) is connected with the inlet port (A) of said main valve (11) by way of a passage (51), while the outlet port (b) of said pilot valve (22) is connected with the control chamber (25, 250) of said main valve by way of a passage (52).