Pipes and tubular conduits – Flexible – Braided – interlaced – knitted or woven
Patent
1995-11-16
1999-10-05
Brinson, Patrick
Pipes and tubular conduits
Flexible
Braided, interlaced, knitted or woven
138172, 138153, 138174, F16L 1100
Patent
active
059608340
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a curved pipe of fiber reinforced plastics material (hereinafter, also referred to as merely "FRP") and process and apparatus for producing the same, and more specifically to a structure suitable for an FRP racket and process and apparatus for its production.
BACKGROUND ART OF THE INVENTION
There are various problems as described hereunder in conventional FRP curved pipes such as FRP rackets and frames of bicycles.
For example, in a conventional process for producing a racket, after cutting a woven fabric prepreg or a unidirectional prepreg of reinforcing fibers such as carbon fibers or glass fibers or a cross-stacking prepreg formed by crossing and stacking the unidirectional prepregs at a predetermined width, the cut prepregs are wound and stacked one layer by one layer around a core material coated with an expansive tube made from resin or rubber (a tube made from a film-like material which has an expansion property), as described in JP-A-HEI-5-96030. Then, the core material is removed, a preform obtained is placed in a mold, and while the mold is heated, the preform is pressure-molded by injecting a pressurized medium (for example, a pressurized air) into the inside of the expansive tube (generally, called "internal pressure molding").
In such an internal pressure molding, the circumferential length of the periphery of the preform is set to be less than the circumferential length of the inner surface of the cavity of the mold so as to facilitate charge of the preform into the cavity. When heated and formed, the preform is pressed onto the inner wall surface of t he cavity by the pressure of the pressurized medium introduced into the expansive tube.
In such a conventional process, however, as shown in FIGS. 42 and 43, because prepregs 203 are wound and stacked one layer by one layer around a core material 202 coated with an expansive tube 201, a stacked portion (overlapped portion) is generated on each layer. Although all the layers must move (shift) in the circumferential direction ultimately at the time of heating and pressure molding in the mold, the movement is not completed in some portions because of the presence of many stacked portions. There fore, there occurs a case where an outer layer cannot reach the wall surface of the cavity, or a desired pressing force onto the wall surface cannot be generated even if the outer layer can reach the wall surface. Molding defects such as voids and lack of resin are frequently generated on an outer surface of a molded product from such causes. Therefore, there is a problem that nonuniformity of the surface quality and the strength of the molded product increases.
Moreover, in the formation of the preform, because prepregs 203 are wound one layer by one layer around the core material 202, the working efficiency is very bad.
In the above-described process, a molding in the mold is performed, for example, as shown in FIG. 44. In the figure, numeral 204 indicates an expansive tube after core material 202 is removed, numeral 205 indicates a preform, numerals 206 and 207 indicate a mold, and numeral 208 indicates a parting line. Numeral 209 indicates a core which forms a groove for gut strings of a racket and retreats at the time of mold opening.
A racket is generally constructed from complicated curved surfaces and molded in a closed cavity. Therefore, voids or pinholes 210 are likely to occur on a portion present at the farthest position from the meeting surface 208 of the mold and having a small curvature, as shown in FIG. 45. These defects must be filled with a putty, and this treatment deteriorates the productivity.
Further, in the conventional process, because an internal pressure is given to a preform composed of only woven fabric prepregs, unidirectional prepregs or a cross-stacking prepreg and having a high density of reinforcing fibers at the surface layer and the preform is heated and molded, when the internal pressure is given, the reinforcing fibers with a high density adhering to t
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patent: 3481369 (1969-12-01), Ganahl
patent: 3881522 (1975-05-01), Lewis et al.
patent: 4139025 (1979-02-01), Carlstrom
patent: 4217935 (1980-08-01), Grendelman et al.
patent: 4657795 (1987-04-01), Foret
patent: 5080943 (1992-01-01), Chulpsa
Isoi Shinya
Kanamori Hiromitsu
Kyono Tetsuyuki
Matsuura Ryoichi
Nishimura Kazuhiko
Brinson Patrick
Miller Austin R.
Toray Industries Inc.
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