Cocks having rotating valves and sliding seats

A cock having a rotating valve and consisting of:

• a body defining a central chamber with cylindrical ducts for the passage of fluid, each duct having an axis and two opposing ends including a first end opening to the outside of the body and a second end opening into said chamber;
• a valve rotating about an axis which is located within said chamber, and through which a bore passes from one end to the other;
• annular seats carrying seals co-operating with said valve, each of the said seats being located near the second end of one of said ducts, coaxially therewith, and adapted to slide axially within said duct;
• an annular piston associated with each seat, but separate therefrom, said piston being accommodated in an annular space coaxial with said seat and located therebehind, on the opposite side of the valve;
• hydraulic means for displacing said pistons axially, including hydraulic means for pushing each of said annular pistons towards the seat with which it is associated, into a position such that the seat is applied to the valve;
• and mechanical means for locking said annular piston in this position;
• said body of the cock having a groove formed therein at the periphery of each of said fluid passage ducts;
• a split ring located in said groove;
• threaded holes drilled through said body and having two opposed ends including a first end opening at the external periphery of the body and a second end opening into said groove;
• and a screw in each of said threaded holes bearing against the external surface of said split ring when it is screwed into said hole.