Patent ID: 8734090

Claim:
A rotor blade tip clearance control apparatus for a gas turbine engine, the apparatus including: a plurality of circumferentially distributed segments which form an annular shroud surrounding outer tips of a row of rotor blades, a mechanical arrangement operatively connected to the segments, wherein actuation of the mechanical arrangement causes the segments to move in a radial direction thereby controlling a clearance between the segments and the outer tips, and a case cooling system which supplies cooling air to an engine case to which the segments are mounted, the cooling air regulating thermal expansion of the case and thereby also controlling the clearance between the segments and the outer tips, wherein: the case cooling system has a manifold ring which delivers the cooling air to the case, the mechanical arrangement is a unison ring operatively connected to the segments, circumferential movement of the unison ring causes the segments to move in a radial direction, and the unison ring forms the manifold ring.