Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Formed with main spar
Reexamination Certificate
1999-03-16
2001-05-08
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Formed with main spar
Reexamination Certificate
active
06227805
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a composite material blade. The invention is particularly applicable, but not exclusively, to variable pitch blades intended to be fitted to helicopter rear rotors.
BACKGROUND OF THE INVENTION
A composite material blade including a part forming the blade foot for the connection to driving means and an aerodynamically profiled main blade section is known, particularly from U.S. Pat. No. 6,035,531, which is incorporated by reference herein, said main blade section comprising at least one casing cover and two spars extending along the span of the blade and each located against the casing cover, one against the intrados side and the other against the extrados side of the blade, the spars extending into the part forming the blade foot, the part forming the blade foot including anchoring reinforcements located on either side of each spar.
The blade of the above mentioned type is obtained by the molding process commonly called Resin Transfer Molding or RTM.
Even if this molding technique enables the making, at moderate cost, of a blade having an excellent surface state coming out of the mold, so that very little touching up is necessary before this blade is painted, it is still necessary to improve its mechanical behavior, particularly in the spar, and to reduce the number of cut-outs in the covering and in the blade attachment zone.
SUMMARY OF THE INVENTION
To this end, according to the invention, a composite material blade of the above mentioned type, is mainly characterized in that the casing cover, the spars and the anchoring reinforcements are respectively constituted from at least one fabric cut-out which includes at least two folds of intersecting carbon fibers fabric, the folds being superposed on each other forming a pre-specified angle between them.
The invention thus enables, in controlling the folds in bundles, to reduce the number of carbon fabric templates entering into the manufacture of the blade and to reduce the blade manufacturing cost.
The blade according to the invention can possibly comprise in addition one or several of the following characteristics:
the casing cover, the spars and the anchoring reinforcements are each constituted from a stack of cut-outs of a first and/or second type;
the first type of cut-out includes two folds forming an angle equal to either 0° or 90° between them;
the second type of cut-out includes four folds forming successive angles equal, in absolute value, to 45°, 0° and 45° between them the folds are evenly distributed fabric folds;
the spars are constituted from a stack of two cut-outs of the first type, each cut-out forming an angle equal to 0° with the axis of the blade span;
the spars extend approximately to the blade leading edge
the transverse section of the spars varies along the blade span
the casing cover includes a cut-out of the first type oriented at 45° relative to the axis of the blade span;
the anchoring reinforcements comprise a stack of four cut-outs of the second type forming angles of 45° between them;
the four cut-outs are of different length and set back relative to each other so that the thickness of the stack, at the ends of the cut-outs, is approximately continuously variable;
the main blade section of the preform comprises a central light material filling body;
the blade includes, in the part forming the blade foot, at least one incident cylindrical guide portion which comprises a light material filling body on which are draped transverse cut-out stacks, which include, on the blade end side, two cut-outs of the first type oriented at 0° and a cut-out of the first type oriented at 45°, and on the end of the cylindrical portion as well as on the blade foot side, a cut-out of the second type oriented at 45°, one connecting cut-out of the first type being stacked on the previous cut-out, extending in the direction of the blade foot;
the resin proportion is different from one transverse section to another transverse section of the blade; and
the incident guide portion comprises adjustment means for the static moment of the blade which include two crimped nuts on at least one face of said portion which is turned towards the blade foot, balancing plates being fixed, by screws, on nuts.
The object of the present invention is also a manufacturing process for the blade as defined above and including stages consisting in
making a preform of the blade including a part forming the blade foot for connecting it to driving means and an aerodynamically profiled main blade section, said main blade section comprising at least one casing cover and two spars extending along the span of the blade and each located against the casing cover, one against the intrados side and the other against the extrados side of the blade, the spars extend into the part forming the blade foot, the part forming the blade foot including anchoring reinforcements located either side of each spar;
placing the preform in a mold;
injecting a liquid resin into the mold; and
heating the mold to make the resin take; characterized in that the making of the preform includes stages consisting in making an extrados half-shell and an intrados half-shell each including a spar, a casing cover and anchoring reinforcements which undergo a hot compacting stage in order to draw the anchoring reinforcements to an approximately continuously variable thickness.
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McCarthy R F J Et Al: “Polymer composite applications to aerospace equipment” Composites manufacturing, vol.5, No. 2, Jun. 1, 1994, pp. 83-93,XP000450078 * p. 84, col. 1, paragraph 3—p. 87, col. 1, paragraph 2 ; figures 5, 8-10 ; board 1 *.
Besse Jean-Luc Christian
Gaffiero Jacques Joseph
Eurocopter
Piper Marbury Rudnick & Wolfe
Ryznic John E.
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