Patent ID: 7743787

Claim:
A mud saver valve for retaining drilling fluid in the kelly of a rotary drilling rig, comprising: a kelly sub defining an open-ended elongated body having threaded ends for forming a connection between the Kelly and a drill pipe string; an enlarged bore formed in said elongated body; a tubular body received within said enlarged bore of said elongated body; a hollow piston axially disposed within said tubular body, said piston being axially movable relative to said tubular body and defining a fluid passage there through; a valve removably mounted within said tubular body, said valve cooperating with said piston to normally close the fluid passage through said piston, wherein said hollow piston is movable between a first closed and second open position; a stop member removably connected to said tubular body, said stop member including a first internal circumferential tapered shoulder for limiting downward movement of said valve; and a magnetized spring for urging said hollow piston into engagement with said valve, said magnetized spring being responsive to flow in a first direction through said mud saver valve to move said hollow piston from a first closed position to a second open position compressing said magnetized spring to the stack height position of said magnetized spring, said magnetized spring being sufficiently magnetized to cause said magnetized spring to urge said magnetized spring to remain in said stack height position when said flow is reduced and thereby to tend to resist said mud saver valve from moving from said second open position to said first closed position.