Sealing device for turbine blades of a turbojet engine

Claim 1

In a turbojet engine having a compressor, an outer casing having a longitudinal axis and at least one turbine wheel rotatably mounted within the casing, the turbine wheel having a plurality of turbine blades attached thereto, an improved device for effecting a seal between the turbine blade tips and the outer casing during transitory and stabilized engine operating modes, comprising: (a). a plurality of first sector hook elements attached to the outer casing at a position upstream of the turbine blades so as to be movable in a radial direction with respect to the outer casing; (b). a plurality of second sector hook elements attached to the outer casing at a position downstream of the turbine blades so as to be movable in a radial direction with respect to the outer casing; (c). a one piece outer ring having an upstream end attached to the first sector hook elements and a downstream end attached to the second sector hook elements; (d). a one piece inner ring disposed between the first and second sector hook elements and located radially inwardly with respect to the outer ring, the inner ring having a greater coefficient of thermal expansion than the outer ring; (e). at least three resilient first connecting members each connected to the outer ring and the inner ring and extending in a generally circumferential direction; (f). a plurality of packing segments disposed bewteen the first and second sector hook elements, an inner sealing surface of the packing segments disposed in close proximity to the tips of the blades; (g). connecting means to connect each of the packing segments to the inner ring; (h). labyrinth seal means associated with an upstream and downstream edge of each packing segment to form a labyrinth seal in conjunction with the first and second sector hook elements; and, (i). means to direct air from a stage of the compressor onto the outer and inner rings such that thermal expansion/contractor of the outer and inner rings moves the packing segments radially outwardly/inwardly corresponding to the expansion/contraction of the turbine blade tips so as to maintain clearance bewteen the blade tips of the packing segments and to prevent excess air leakage therebetween.