Flow control device for gas stream

A device for gas flow control which is adapted for disposition in a duct, comprising:

• a flap pivotal about an axis, said flap having an operative position with the duct in which it is adapted to be disposed and wherein the axis has a predetermined location with respect to the operative position;
• a drive element having an output shaft;
• and
• a receiving pocket into which the drive element can be slid, said receiving pocket being so sized and dimensioned that it positions the drive element with respect to said flap so that at least one of a drive connection between the output shaft and said flap is established or the axis of rotation is located in said predetermined location, when the drive element is slid to a seated position in said receiving pocket.