Abstract: A downhole valve comprises a body defining a through bore and a valve member for location in the body and movable between an open position and a closed position. The valve has a first configuration in which the valve member is normally closed, and will hold a pressure differential in a first direction, and a second configuration in which the valve member is closed and will maintain a pressure differential in the first direction and also in an opposite second direction and a third configuration in which the valve member is locked in the open position until it is deliberately closed.

Abstract: A downhole tool comprises a tubular body (12) for location in a tubular member, such as a drill string, and defines a through bore (20) and a number of circumferentially spaced ports (26). A valve member which may be in the form of a piston sleeve (24) is mounted in the bore (20) and is movable relative to the body (12) between a first position in which fluid may flow through the port (26) and a second position in which the valve member (24) closes the port (26), the valve member being movable between the first and second positions by application of differential fluid pressure. Movement of the valve member (24) is provided by a cam arrangement including a circumferentially extending cam groove (56) and a cam follower (57).