Patent ID: 6708946
Filing Date: 2004-03-23
Classification: E21B,F16K

Abstract:
A method of minimising the ingress of debris between a ball valve element and valve seat as a ball valve is moved between an open and a closed position, the method comprising the steps of,compressing a first compression spring means having a first uncompressed spring force in a first position, to a second position having a second compressed spring force greater than said first spring force, and simultaneously rotating said apertured ball element to said open position, biasing a valve seat into contact with said ball element as the ball element rotates from the open to the closed position by a first resilient means having a resilient spring force, providing a second resilient means for applying an upward force to an assembly comprised of a mandrel means, a ball cage and ball element and said valve seat, said upward force being less than the second compressed spring force of said first compression spring means when said valve element is in said open position but being greater than said spring force of said first resilient means, moving the first compression spring means upwardly in the absence of an applied force to cause the ball element to rotate through 90Â° to a just-closed piston, retaining said valve seat in contact with said ball element by said first resilient means, and providing an upward biasing force flowing through said mandrel assembly, said ball cage and said ball element so as to move the assembly upwards by a relatively small amount to provide an intensifying effect between said ball element and said valve seat.