28 of the inner cam body 14 is preferably provided as shown with a linear rib extension 54 which extends transverse to the inner cam body 14 as will appear infra with reference to fig5 the linear rib extension 54 serves to pinch the sleeve 12 when the outer cam body 16 is rotated and cams the inner cam body 14 towards the sleeve 12 this linear rib extension 54 as shown is preferably rectilinear and has a rounded lower edge and extension 54 extends between the inner ends of the ribs 48 and 50 so that a continuous protuberance extends about the sides and inner end 28 of the inner cam body 14 as seen in fig3 and 5 an integral lower ridge extension 56 is preferably provided on the inside of the valve body 10 this extension 56 cooperates with the inner end 28 of the inner cam body 14 or more specifically extension 56 cooperates with the linear rib extension 54 to pinch the sleeve 12 as best seen in fig5 referring now to the outer end of the inner cam body 14 this outer end of body 14 is provided with two opposed curved cam surfaces 58 and 60 these cam surfaces 58 and 60 consist of and are derived from two opposed cut out portions of the inner cam body 14 each of the portions having a cam surface 58 or 60 which cams the inner cam body 14 in the same direction as the other portion the outer cylindrical cam body 16 is also disposed within the chamber 26 and juxtaposed coaxially with the inner cam body 14 in the assembled.