Control Valve

A control valve for use in liquid-carrying systems, and particularly for use in heating or cooling systems, having a valve housing (3) with an inlet side and an outlet side, and including an arrangement for maintaining a constant differential pressure between the inlet side and the outlet side independently of the liquid amount flowing therethrough, wherein a throttle elements sets itself in a balance under the influence of the inlet pressure on the one side and the outlet pressure and a spring pressure on the other side, characterized in that it additionally comprises an arrangement for adjusting the liquid amount flowing therethrough with two cooperating valve members (4, 6) arranged in the flow path, said valve members being constructed as two concentric rings which each have a recess extending approximately 180 degrees in the circumferential direction, wherein the outer one of the two concentric rings (4) is fixed relative to the valve housing (3), white the inner ring (6) is displaceable in the circumferential direction under the influence of a rotatable handle (10), whereby a greater or smaller overlap may be established manually in the circumferential direction between the recesses, and is also displaceable in the axial direction, so that a greater or smaller overlap may be provided between the recesses in the axial direction, as it is connected with an actuator for controlled or automatic adjustment of the axial overlap.