Patent ID: 7357198

Claim:
Downhole apparatus for selectively isolating the interior of a downhole assembly from the exterior thereof, the downhole apparatus comprising: a body defining a longitudinally extending bore and incorporating a wall having at least one aperture therein for providing fluid communication between said bore and the exterior of the downhole apparatus; a piston located within the body and slidable longitudinally therein so as to allow movement of the downhole apparatus between an open configuration, in which said at least one aperture is open to permit fluid communication between said bore and the exterior of the downhole apparatus via said at least one aperture, and a closed configuration, in which said at least one aperture is occluded by the piston to restrict fluid communication between said bore and the exterior of the downhole apparatus via said at least one aperture; a control groove and a pin received within the control groove for determining whether or not a longitudinal movement of the piston in a given direction will move the downhole apparatus between open and closed configurations; and a control member located between and movable relative to the body and the piston, the control groove being defined in one of the piston and control member, and the pin being provided on the other of the piston and control member; the downhole apparatus being characterized in that means are provided for constraining movement of the piston relative to the body to longitudinal movement only.