the damper discs 70 71 but from hereon the valve according to the embodiment of fig7 will be described without talking the thickness of the damper discs 70 71 into consideration when the valve is set for a small air flow also the total opening y is small for very small flows y is less than x i e all suspension means 73 74 are collapsed and the damper discs 70 71 rest against the flow reducing device 18 in this setting it is the upper most damper 70 which by its upper surface forms the damper surface 76 for increased flow the flow reducing devise 18 and the tube are displaced away from each other in the illustrated embodiment by displacing the dynamic tube member 12 into the stationary tube member 11 when y exceeds x the first suspension means 73 will be stretched and lift with it the upper damper disc 70 when the opening y is more than x but less than 2x the lower damper disc 71 will remain against the flow reducing device 18 therewith the total opening y will be split into two openings an upper opening with height x limited by the flange surface 31 and the upper damper surface 76 of the upper damper disc 70 and a lower opening with height y x limited by the lower damper surface 77 of the upper damper disc 70 and the upper damper surface 78.