A control valve for connection unit for flexible pipes, comprising a plurality of sectors, (slices or petals), rotatable between a complete opening position and a complete closing position is described. The aforesaid plurality of rotatable sectors comprises at least two series of rotating sectors of different shape and dimensions disposed in an alternate way along the circumference of the connection unit. The smaller sectors can be controlled in such a way to close slower than the bigger ones. The shape and dimensions of the rotational sectors are such to consent a partial overlapping of the borders of the adjacent sectors for a better tightness between the sectors themselves.