Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-04-14
2001-06-05
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C029S889720, C228S157000, C219S159000
Reexamination Certificate
active
06242715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for manufacturing a hollow turbomachine blade, particularly a large-chord fan rotor blade.
The advantages of using large-chord blades in turbomachines are particularly evident in the case of the fan rotor blades in bypass turbojet engines. These blades must, however, withstand severe conditions of use and, in particular, must possess satisfactory mechanical characteristics associated with antivibratory properties and resistance to impact by foreign bodies. The need for sufficiently high velocities at the tips of the blades has also led to research into reducing the mass of the blades, and this has been achieved, in particular, by the use of hollow blades.
2. Discussion of the Background
EP-A-0700738 describes a process for manufacturing a hollow turbomachine blade, especially a large-chord fan rotor blade. In this known process a first step (a) is to use a computer-aided design and manufacture (CAD/CAM) system to create, starting from the geometric definition of the blade to be obtained, a digital simulation of the primary parts of the blade in flat form and including a computation, for each part, of the lengths of the fibers on each side of the central fiber as a function of their position with respect to the axis of the part. Also carried out at this stage is a digital simulation of an operation to shape the parts by twisting, for comparison with the final result. After this first step EP-A-0700738 teaches a general operating procedure involving the following steps:
(b) die-forging the primary parts of the blade using a press;
(c) machining the primary parts;
(d) depositing diffusion barriers on at least one of the parts according to a predefined pattern;
(e) assembling the primary parts and diffusion welding them together under isostatic pressure;
(f) pressurized gas inflation and superplastic shaping of the welded assembly; and,
(g) final machining of the assembly.
One of the aims of the invention is to make it possible to carry out, during the above sequence of operations, an additional shaping of the parts by twisting, without the risk of causing buckling-type undulations along the central fibre. These undulations are generated by compressive stresses induced during elongation of the lateral fibers as a result of the differences in length between the initial flat part and the twisted part which is obtained.
SUMMARY OF THE INVENTION
Accordingly, the invention provides a process for manufacturing a hollow turbomachine blade of the type which is known generally from EP-A-0700738, wherein the process includes a step of hot twisting an element of the blade, which is made of a titanium alloy of the TA6V type, about a twist axis, the hot twisting step comprising prior attachment of collars to said element at positions distributed according to a predetermined twisting law, heating said element to a temperature above 700° C., and causing a plurality of bars to rotate about said twist axis so as to act on said collars to cause progressive twisting of the heated element, the distribution and number of said collars being such as to produce a linear twist development between each collar.
It is known to twist a part, in particular a turbomachine blade, by using means which requires at least one rotating jaw with or without prestressing and in either a hot or a cold state, and in particular by shaping by creep at 950° C., in the case of a blade made of TA6V-type titanium alloy, in an impression under the action of masses which are fixed to the ends of the part and create a torsional moment.
However, these known means are unsuitable for the highly progressive twisting encountered in a process for manufacturing a hollow turbomachine blade having a high compression ratio in the base region of the aerofoil portion of the blade, such as in the case of a large-chord fan rotor blade.
Accordingly, the invention also provides hot progressive twisting apparatus for use in the manufacture of a hollow turbomachine blade having a high compression ratio in the base region of the aerofoil portion of the blade, the apparatus comprising:
a metallic support structure;
a cylindrical electric furnace fixed vertically on said support structure, said furnace having a wall including a plurality of horizontal slots;
a circular frame surrounding said furnace;
a plurality of rings which are free to rotate about said frame;
bars disposed on said rings and projecting inwards through said slots in said furnace wall so as to act on the collars attached to the element which is to be twisted when said element is placed in said furnace; and
jaws for gripping opposite ends of said element to hold said element in position in said furnace and enabling a tensile force to be applied to said element along the axis thereof during twisting of said element.
The use of hot progressive twisting apparatus in accordance with the invention for the hot twisting step in the blade manufacturing process makes it possible to avoid the drawbacks of the earlier known processes and to obtain blades possessing improved geometrical and mechanical properties optimized to the conditions of use, and also enables repeat quality to be ensured while facilitating relatively low-cost manufacturing conditions.
Other features and advantages of the invention will become apparent from the following description of the preferred embodiments of the invention with reference to the appended drawings.
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Patent Abstract of Japan, vol. 8., No. 249 (M-338 [1686], Nov. 15, 1984 & JP 59 125230, Jul. 19, 1984.
Bichon Mathieu Philippe Albert
Costeplane Bernard Armand Rene
Lorieux Alain Georges Henri
Fuqua Shawntina
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Societe Nationale d'Etude et de Construction de Moteurs d&a
Walberg Teresa
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