Patent ID: 7584801

Claim:
A drill string flow control valve comprising: a valve housing characterized by a wall defining a valve interior, wherein the valve housing has an internal housing flow path formed therein with a housing outlet flow port disposed along said internal housing flow path; a valve sleeve disposed at least partially in the interior of the valve housing, the valve sleeve having a sleeve flow port and a valve sleeve wall, wherein the valve sleeve is axially movable within the valve housing from a closed position to an open position, such that the valve sleeve wall substantially impedes fluid flow from the housing outlet flow port to the sleeve flow port when the valve sleeve is in the closed position and wherein the sleeve flow port and the housing outlet flow port are in substantial alignment when in the open position; wherein the valve sleeve has an upper pressure surface defined thereon so as to provide a first surface area upon which a first fluid pressure from the internal housing flow path may act to provide a downward force on the valve sleeve and wherein the valve sleeve has a lower pressure surface defined thereon so as to provide a second surface area upon which a second fluid pressure may act to provide an upward force on the valve sleeve; a spring wherein the spring biases the valve sleeve to the closed position by exertion of a biasing force on the valve sleeve; an upper pressure port split off from said internal housing flow path, said upper pressure port disposed to allow the first fluid pressure to act upon the upper pressure surface; and a lower pressure port that allows the second fluid pressure to act upon the lower pressure surface from external the valve housing.