Gas turbine engines

Claim 1

In a gas turbine engine, the improvement in structure for controlling clearance between blade tips of a turbine rotor having a predetermined rate of expansion and shroud means surrounding the blade tips, the combination comprising: an engine casing; a hollow annular control ring concentrically positioned within said casing; a plurality of shroud segments defining said shroud means about the blade tips of the turbine rotor, said shroud segments being secured to said hollow annular control ring for expansion and contraction with the same; means operatively supporting said hollow annular control ring and the shroud segments supported thereby from said casing while mechanically isolating said control ring from deformation or expansion of said casing, said support means permitting said control ring to expand and contract independently of said casing while being maintained concentric with the same, and said support means providing means to supply a fluid to the interior of said hollow annular control ring, and means thermally insulating the exterior of said hollow annular control ring, said thermally insulating means and said support means cooperating to control the rate of expansion of said control ring to match the rate of expansion of the turbine rotor whereby clearance between the shroud means and the blade tips of the turbine rotor is a predetermined amount during at least a portion of the operating cycle of the engine.