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A rotor blade for a gas turbine, in particular a turbojet, the blade comprising an airfoil, a platform connecting the airfoil to a blade root and having at least one stiffener extending under the downstream portion of the platform, together with means for cooling the blade by a flow of cooling fluid

A rotor blade for a gas turbine, in particular a turbojet, the blade comprising an airfoil, a platform connecting the airfoil to a blade root and having at least one stiffener extending under the downstream portion of the platform, together with means for cooling the blade by a flow of cooling fluid in ducts formed in the blade and in a cavity formed in the stiffener substantially in register with the trailing edge of the blade, and including outlet orifices facing downstream.

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What is claimed is: 1. A rotor blade for a gas turbine, the blade comprising: an airfoil having a trailing edge and a leading edge, said airfoil defining airfoil cooling fluid ducts, a blade root defining root cooling fluid ducts that are in fluid communication with said airfoil cooling fluid ducts

What is claimed is: 1. A rotor blade for a gas turbine, the blade comprising: an airfoil having a trailing edge and a leading edge, said airfoil defining airfoil cooling fluid ducts, a blade root defining root cooling fluid ducts that are in fluid communication with said airfoil cooling fluid ducts, a platform connecting the airfoil to the blade root, at least one stiffener between said platform and said blade root and including a plane web extending from the platform from its side opposite from the airfoil and passing under the trailing edge of the airfoil, and a cooling cavity formed in a trailing edge portion of the plane web of the stiffener, said trailing edge portion being adjacent to the platform and being situated substantially in alignment with the trailing edge of the airfoil, said cavity being in fluid communication with at least one of said root cooling fluid flow ducts formed in the blade root. 2. A blade according to claim 1, wherein said cavity is in fluid communication with at least one cooling fluid outlet orifice opening out downstream under the platform. 3. A blade according to claim 2, wherein the at least one outlet orifice from the cavity is oriented substantially parallel to the trailing edge of the blade. 4. A blade according to claim 2, wherein, when the blade is a blade for a high-pressure stage, the cavity of the stiffener presents dimensions of a few millimeters along the axis of the blade and in a direction perpendicular to said axis and to the axis of rotation of the turbine, and of about 1 mm or less in a direction that is perpendicular to the two above-specified directions. 5. A blade according to claim 2, wherein the cavity of the stiffener is made during casting. 6. A blade according to claim 2, wherein the at least one outlet orifice from the cavity is made during casting or by laser drilling or by electroerosion. 7. A blade according to claim 2, wherein said stiffener is a downstream stiffener, said blade further comprising an upstream stiffener, wherein said cavity is formed only in said downstream stiffener and not in said upstream stiffener. 8. A blade according to claim 7, wherein said upstream and downstream stiffeners define a housing for a sealing line that prevents air from passing radially outwards and inwards between platforms of adjacent blades. 9. A blade according to claim 2, wherein said at least one of said root cooling fluid flow ducts, which is in fluid communication with said cavity, is in further fluid communication with air exhaust slots formed in a trailing edge portion of a pressure surface of said airfoil. 10. A blade according to claim 9, wherein said cavity is substantially a rectangular parallelepiped. 11. A turbojet turbine, including a plurality of blades according to claim 1. 12. A turbojet, including a turbine according to claim 11. 13. A rotor blade for a gas turbine, the blade comprising: an airfoil having a trailing edge and a leading edge, said airfoil defining airfoil cooling fluid ducts, a blade root defining root cooling fluid ducts that are in fluid communication with said airfoil cooling fluid ducts, a platform connecting the airfoil to the blade root, said platform being connected to the trailing edge of the airfoil at a trailing edge connection, at least one stiffener between said platform and said blade root and including a plane web extending from the platform from its side opposite from the airfoil and passing under the trailing edge of the airfoil, and cooling means for reducing a temperature gradient between the trailing edge connection and the stiffener, said cooling means being formed in a trailing edge portion of the plane web of the stiffener, said trailing edge portion being adjacent to the platform and being situated substantially in alignment with the trailing edge of the airfoil, said cooling means being in fluid communication with at least one of the root cooling fluid flow ducts formed in the blade root.