Flow-control valve

A flow-control valve for operation with differential pressures below 100 p.s.i.g., including, in combination:

• a cylindrical casing having a first inside diameter;
• a cylindrical regulator including side exit ports, an end wall and a flow-controlling end-exit port axially disposed in said end wall and extending axially completely through said end wall for undiverted flow of fluid along the axis of said regulator through said end-exit port, said regulator having a second outside diameter and a third inside diameter;
• a piston having a fourth outside diameter which is less than said third inside diameter, said piston being in slidable engagement with said regulator and having side fluid inlet ports at the unstream end thereof and a skirt portion at the downstream end thereof, said skirt portion being adapted to engage said side ports in said regulator when said piston slides into said regulator in response to fluid pressure on side piston, said piston having a fifth inside diameter;
• a spring carried within said piston and regulator and positioned to urge said piston and regulator in opposite directions, said spring having a sixth outside and a seventh inside diameter and a first free length and a second solid length;
• said fifth inside diameter being approximately 0.67 times said first inside diameter;
• said sixth outside diameter being approximately 0.59 times said first inside diameter;
• said seventh inside diameter being approximately 0.51 times said first inside diameter;
• said first free length of said spring being approximately 1.4 times said first inside diameter;
• and,
• said second solid length of said spring being approximately 0.46 times said first inside diameter.