The evolution of the western Sichuan foreland basin

An axial flow metering valve includes a valve body having an inlet, an outlet, a valve chamber therebetween and a passage for fluid between the inlet and the valve chamber. A valve member is movable in the valve chamber and includes a number of guide pins which extend axially through guide slots and into grooves in the valve body. The guide pins are threadedly engaged with a rotatable actuating member which encircles them. Rotation of the actuating member moves the valve member toward and away from the valve seat to regulate fluid flow. The valve member may carry a check valve member which checks reverse flow or may carry an inner bypass valve member which permits full unregulated reverse flow.