Heating control cock

A control cock operative to be mounted between the ends of four pipes, said pipes comprising first fluid supply and return pipes on one side of the cock and second fluid supply and return pipes on the other side, said control cock comprising a cylindrical shell rotatably and sealingly mounted about its axis between the ends of the pipe, said cylindrical shell being rotatable through intermediate conditions between a fully opened position and a fully closed position;

• said cylindrical shell having disposed therein at least two longitudinal passages which in said fully opened position enable fluid communication between said first and second supply pipes and said first and second return pipes, respectively;
• said cylindrical shell having a first by-pass channel for enabling fluid communication only between said first fluid supply and return pipes when said cylindrical shell is in said closed position, said first by-pass channel being separated from the ends of the second pipes by a confined space at least partially surrounding the by-pass channel, said space containing a thermal insulating agent;
• and said cylindrical shell having a second by-pass channel for enabling partial fluid communication between said first fluid supply and return pipes as well as two through-going openings for enabling partial fluid communication between said first and second fluid supply pipes and said first and second fluid return pipes, respectively, while the shell is disposed intermediately between the fully opened and fully closed position.