Abstract: A flow control valve has a housing with a gas outlet and contains a mobile shaft which can be moved towards or away from this gas outlet. A member for closing and opening the gas outlet is attached to a front end of the mobile shaft. At least a portion of the front surface of this member is formed as a curved surface such that when the mobile shaft is moved away from the gas outlet from the position where the gas outlet is completely closed by the closing member, a gap is formed more gradually between the gas outlet and the closing member such that a more accurate continuous control of the flow rate through the valve can be carried out.