Abstract: The invention provides a control valve for an air operated power assisted steering mechanism for a vehicle. The valve has a spiral scroll and nut connection. One of these elements is connected to the steering wheel and is rotated thereby as the steering wheel is turned in a steering motion and the resulting linear motion of one of the elements is transferred into relative movement of a ported sleeve and two valve spools respectively for controlling the two directions of power assistance of the steering of the vehicle. The valve preferably is located in a hub of the steering wheel, in the steering column, or drivingly connected to the steering column by means of a transmission.