Turbo machine with a device for preventing a segment of nozzle guide vanes assembly from rotating in a casing; rotation-proofing peg

1. A turbo machine including a device preventing rotation of a segment of a distributor in a form of a ring sector housed inside a ring-shaped casing of the turbo machine, the ring sector including fixed blades integral with a section of the ring sector, with interposing of a heat shield sheet between an inside wall of the casing and an outside wall of the distributor segment, comprising:

a rotation-proofing peg mounted both in a notch provided on the distributor segment at a radially inner end of the peg and a housing arranged on the casing at a radially outer end of the peg, the heat shield sheet including, at a downstream end, a tab bearing against the rotation-proofing peg; and

a surface portion arranged radially between the tab and the inside wall of the casing, the surface portion forming an abutment in event of possible radial displacement of the heat shield sheet during operation of the turbo machine,

wherein an upper surface of the surface portion bears against the inside wall of the casing, and an upstream facing end of the surface portion is free of contact with the casing.

2. The turbo machine as claimed in claim 1 , wherein the rotation-proofing peg includes a head housed in the notch of the distributor segment and a rod entering the housing arranged on the casing, the surface portion being integral with the head of the rotation-proofing peg.

3. The turbo machine as claimed in claim 2 , wherein the surface portion includes a shoulder machined in the head of the rotation-proofing peg.

4. The turbo machine as claimed in claim 1 , wherein the surface portion is formed by a lug parallel to the axis of the distributor and bearing against the inside wall of the casing.

5. The turbo machine as claimed in claim 1 , wherein the distributor segment includes a rib at right angles to the axis of the distributor and bearing against the inside wall of the casing, the notch of which is formed in a protrusion provided on one side of the rib.

6. The turbo machine as claimed in claim 5 , wherein the heat shield sheet is in a form of a ring sector with an indentation corresponding to the protrusion, the tab being arranged in a bottom of the indentation.

7. The turbo machine as claimed in claim 5 , wherein the shield sheet is provided upstream with regard to the rib of the distributor segment and the rotation-proofing peg.

8. The turbo machine as claimed in claim 1 , wherein an axial length between the upstream facing end of the surface portion and a head of the rotating-proofing peg is less than an axial thickness of a rod of the rotating-proofing peg.

9. A turbo machine including a device preventing rotation of a segment of a distributor in a form of a ring sector housed inside a ring-shaped casing of the turbo machine, the ring sector including fixed blades integral with a section of the ring sector, with interposing of a heat shield sheet between an inside wall of the casing and an outside wall of the distributor segment, comprising:

a rotation-proofing peg mounted both in a notch provided on the distributor segment at a radially inner end of the peg and a housing arranged on the casing at a radially outer end of the peg, the heat shield sheet including, at a downstream end; a tab bearing against the rotation-proofing peg; and

a surface portion arranged radially between the tab and the inside wall of the casing, the surface portion forming an abutment in event of possible radial displacement of the heat shield sheet during operation of the turbo machine,

wherein an upper surface of the surface portion bears against the inside wall of the casing, and an upstream facing end of the surface portion is free of contact with the casing, and

wherein an axial length between the upstream facing end of the surface portion and a head of the rotating-proofing peg is less than an axial thickness of a rod of the rotating-proofing peg.

10. A rotating-proofing peg in combination with a turbo machine including a device preventing rotation of a segment of a distributor in a form of a ring sector housed inside a ring-shaped casing of the turbo machine, the ring sector including fixed blades integral with a section of the ring sector, with interposing of a heat shield sheet between an inside wall of the casing and an outside wall of the distributor segment, the turbo machine comprising the rotation-proofing peg mounted both in a notch provided on the distributor segment at a radially inner end of the peg and a housing arranged on the casing at a radially outer end of the peg, the heat shield sheet including, at a downstream end, a tab bearing against the rotation-proofing peg; and a surface portion arranged radially between the tab and the inside wall of the casing, the surface portion forming an abutment in event of possible radial displacement of the heat shield sheet during operation of the turbo machine, wherein an upper surface of the surface portion bears against the inside wall of the casing, and an upstream facing end of the surface portion is free of contact with the casing,

wherein the rotation-proofing peg includes a straight rod and a head with a first face parallel to the axis of the rod and a surface portion at right angles with respect to the first face on a side opposite the rod.

11. The peg as claimed in claim 10 , wherein the peg includes a lug at right angles with respect to the axis of the straight rod, the surface portion being formed by the lug.