Spool valve assembly

A flow control valve comprising:

• (a) main body having a central bore open at each end;
• (b) a two-position spool valve having no neutral operating position slidably supported in said bore for movement between first and second operating positions and adapted to be actuated in one axial direction to said second position via the open end of said central bore;
• (c) means at one end of said spool valve for actuating the same from said second position to said first position;
• (d) said spool valve having only first, second, third and fourth annular grooves separated by first, second and third annular lands;
• (e) said main body having (1) a pressurized fluid supply passage continuously in communication with said second groove, (2) separate fluid venting passages for venting only unpressurized fluid from a respective one of said first and third grooves and in continuous communication therewith, (3) a fluid passage in selective communication with either said first or said second groove depending upon the position of said spool valve axially of said bore, and in communication with said fourth groove when in communication with said second groove, and (4) a fluid passage in communication with either said second or said third groove depending upon the position of said spool valve axially of said bore;
• and
• (f) means at the other end of said spool valve for actuating the same to said second position.