Flow control valve

A flow control valve for holding a column of fluid until the pressure of said fluid reaches a preseleted cracking pressure, said control valve comprising:

• a valve body having an internal chamber, an inlet at one end of said chamber for receiving said column of fluid and an outlet at the opposite end of said chamber for discharging said fluid from said valve;
• a poppet axially movable within said internal chamber between an inlet-closing position and a retracted position, said poppet comprising a piston head having a face opposing said inlet and a plug projecting from said face, said plug closing-off said inlet from the remainder of said face when said poppet is at said inlet-closing position, said face being exposed to said fluid from said inlet when said poppet is moved from said inlet-closing position, said poppet further comprising at least one passage through said piston head for conveying said fluid from said face to a location on the backside of said piston head, an axially reciprocable, hollow connector extending from said backside and defining an interior channel in said poppet extending toward said other end of said valve body, said connector internally conveying fluid from said backside location to said oulet, and an annular hollow stem extending inward from said other end of said valve body slidably engaging the end of said connector to form a continuation of the interior channel defined by the connector;
• an annular stop at a fixed location within said chamber for peripherally engaging said backside of said piston head when said poppet is at said retracted position to thereby prevent further axial movement of said poppet and to form at least a partial seal about the periphery of said piston head, said piston-head passage providing enough pressure drop in the fluid conveyed therethrough to assure that the poppet remains in its retracted position;
• at least one hole in the wall of said stem for connecting the lower-pressure, other end of the valve body to a cavity between the backside of the piston head, the valve body and the hollow connector and for evacuating fluid leaking about the periphery of said piston head and
• biasing means for urging said poppet towards said inlet-closing position, said biasing means providing sufficient urging force to maintain said poppet at said inlet-closing position until said fluid achieves said cracking pressure,
• the surface area of said piston head being greater than that of said plug so that, when said plug is forced out of sealing contact with said inlet, said fluid pressure against said piston head exerts a substantially greater force on said piston head than the opposite force exerted thereon by said biasing means, thereby causing said poppet to snap into its retracted, fully open position.