Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Producing multilayer work or article
Reexamination Certificate
1998-03-11
2001-07-24
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Producing multilayer work or article
C264S511000, C264S512000, C264S258000, C264S314000
Reexamination Certificate
active
06264877
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method of using composite material to make a part of large dimensions, such as a propeller blade, and in particular a blade for a wind turbine.
The invention also relates, more generally, to any part made of composite material by performing the method, and in particular tubular or non-tubular parts of large dimensions such as beams, wings, and masts.
BACKGROUND OF THE INVENTION
Such parts are difficult, or even nearly impossible, to make using conventional injection molding techniques, since a mold cavity of great length (e.g. greater than 10 meters) presents serious technical problems when it comes to filling it with injected plastics material, and requires injection tooling that is too expensive for short manufacturing runs.
That is why parts of large size, such as the blades of a wind turbine, for example, have until now been made by a molding method which consists in depositing successive layers of resin in a mold on successive layers of fiberglass cloth or the like, each layer of resin needing to be polymerized (cold, using a catalyst) before the following layer of resin is deposited, because of the heat given off by the resin polymerizing. By way of example, this can make it necessary to deposit and polymerize ten layers of resin each having a thickness of 5 mm in order to build up a wall having a thickness of 50 mm. Under such conditions, making a single wind turbine blade of great length (about 15 meters (m) to 35 m) can occupy one mold for three to four weeks.
In addition, if a low cost resin is used such as a polyester resin, it is necessary to protect personnel against the toxic vapor given off by the resin while the part is being made. Naturally, it is possible to use an epoxy resin instead of a polyester resin in order to eliminate the risks of pollution and toxicity, but to the detriment of cost price, since the cost of epoxy resins is about five times greater than the cost of polyester resins.
It is already known, e.g. from U.S. Pat. No. 5,037,599, to make a part out of composite material starting from a cloth made up of threads that are constituted by a mixture of thermoplastic fibers and of reinforcing fibers, the cloth being placed or draped in a mold and being thermoformed by applying heat and pressure, the heat causing the thermoplastic of the cloth to melt and the pressure pressing it against the wall of the mold. Nevertheless, that known method does not enable tubular parts to be made.
OBJECTS AND SUMMARY OF THE INVENTION
A particular object of the present invention is to avoid the drawbacks of known methods.
The method provides a method which makes it possible to make parts of large dimensions in about one-third to one-fourth of the time required by the above-mentioned methods, and at a cost that is substantially the same as for parts made out of polyester resin, but without any risk of pollution or of toxicity.
To this end, the invention provides a method of making a part out of composite material, the method consisting in placing in a mold at least one thickness of cloth made up of threads constituted by a mixture of fibers or threads of thermoplastic material and of reinforcing fibers or threads, in placing an inflatable envelope on the cloth in the mold, in closing the mold and inflating said envelope to press the cloth against the wall of the mold, in heating the mold-plus-cloth together under pressure up to the melting temperature of the thermoplastic material to embed the reinforcing fibers or threads in said material, in allowing it to cool, and in unmolding, wherein the mold is made of two mold portions, comprising a first portion that can be shut down on a second portion, the cloth is placed inside each of the mold portions, a film of the above-mentioned thermoplastic material is placed on the cloth in the first mold portion which is suitable for shutting down on the second mold portion, with the film and the cloth being pressed against the wall of said mold portion by pressure reduction or suction, said first mold portion is closed down on the second mold portion, and the above-mentioned heating under pressure is performed.
This makes it possible to obtain a tubular part of large dimensions in a single molding and heating operation, unlike the prior technique where it was necessary to proceed layer by layer.
In addition, there is no need to polymerize the plastics material during the method, it suffices to heat a thermoplastic material that has already been polymerized.
According to another characteristic of the invention, heating is performed under pressure in a closed enclosure which is fed with hot gas under pressure (e.g. superheated steam or hot air under pressure).
Since the mold is open at one of its longitudinal ends, the same pressure obtains both inside and outside the mold, thus making it possible to distribute the molten plastics material uniformly around the reinforcing threads or fibers and to make a uniform matrix of plastics material in which the reinforcing threads or fibers are completely embedded.
According to another advantageous characteristic of the invention, the above-specified plastics material is polypropylene which has the advantage of being low in cost and of not giving off a polluting or harmful gas when heated and melted.
The invention also provides a propeller blade, in particular a wind turbine blade, made in two parts, a leading or “upstream” part and a trailing or “downstream” part relative to the direction of fluid flow over the blade when it is in rotation, said two parts being made by performing the method as defined above, and being fixed together by adhesive.
In a preferred embodiment of the invention, its leading portion is in the form of a box section member of closed cross-section, and the trailing portion of the blade is of open, substantially V-shaped cross-section.
The length of a wind turbine blade of the invention may be about 15 m to 35 m and it takes about one week to make, i.e. it is made in about one-third to one-fourth the time required in the prior art. It can also be made out of a low cost thermoplastic material, without any risk of pollution or of toxicity for the personnel involved in manufacture.
REFERENCES:
patent: 2155375 (1939-04-01), Jablonsky
patent: 2202014 (1940-05-01), Lougheed
patent: 2202042 (1940-05-01), Blount
patent: 2945262 (1960-07-01), Petty
patent: 3205288 (1965-09-01), Bates
patent: 3523848 (1970-08-01), Huff et al.
patent: 4169749 (1979-10-01), Clark
patent: 4268571 (1981-05-01), McCarthy
patent: 4335182 (1982-06-01), Brand et al.
patent: 4471020 (1984-09-01), McCarthy
patent: 4568581 (1986-02-01), Peoples, Jr.
patent: 4720244 (1988-01-01), Kluppel et al.
patent: 5037599 (1991-08-01), Olson
patent: 5041182 (1991-08-01), Sekiguchi et al.
patent: 5087187 (1992-02-01), Simkulak et al.
patent: 5156786 (1992-10-01), Monroe
patent: 5176868 (1993-01-01), Davis
patent: 5248242 (1993-09-01), Lallo et al.
patent: 5262121 (1993-11-01), Goodno
patent: 5462408 (1995-10-01), Coffy
patent: 5505492 (1996-04-01), Nelson et al.
patent: 5547629 (1996-08-01), Diessen et al.
patent: 5624519 (1997-04-01), Nelson et al.
patent: 5638870 (1997-06-01), Takada et al.
patent: 5876054 (1999-03-01), Olson et al.
patent: 0 138 294 (1985-04-01), None
patent: 0 358 510 (1990-03-01), None
patent: 0 465 169 (1992-01-01), None
Patent Abstracts of Japan, Toshiaki, et al., JP 04-201241, Jul. 22, 1992.
Derwent Publications, Ono et al., JP 6-228 837, Aug. 16, 1994.
Alternatives Energies
Morrison & Foerster / LLP
Silbaugh Jan H.
Staicovici Stefan
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