Rotary hydraulic coupling

A rotary hydraulic coupling for use in an engine having a camshaft, a hydraulic phaser for driving the camshaft having hydraulic working chambers and rotating oil ducts leading to the hydraulic working chambers, and an oil feed manifold secured to the body of the engine and incorporating oil galleries for supplying oil to and from the phaser, the rotary coupling serving to connect the oil galleries of the oil feed manifold to the rotating oil ducts leading to hydraulic working chambers of the phaser and comprising a cylindrical first element having axially extending oil passages;

• an annular second element surrounding and sealed relative to the first element, annular grooves in a mating surface of at least one of the two elements, and bores in each of the first and second elements that communicate with the annular grooves to establish fluid flow communication between the bores in the two elements, the bores in the first element being connected to the axially extending oil passages in the first element, wherein the first element is formed of an outer tube and an inner spool assembly of at least one part, and the axially extending oil passages in the first element are formed by at least one of the group comprising channels and holes in the inner spool.