Games using tangible projectile – Player held and powered – nonmechanical projector – per se,... – Racket or paddle; accessory therefor
Patent
1998-02-02
1999-04-27
Chiu, Raleigh W.
Games using tangible projectile
Player held and powered, nonmechanical projector, per se,...
Racket or paddle; accessory therefor
A63B 4910
Patent
active
058974474
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fibre reinforced plastic (hereinafter referred to as FRP) racket and its method of manufacture and, in particular, it relates to the optimum structure of the racket frame.
PRIOR ART
FRP tubes are lightweight and have high strength characteristics and so are employed in various fields such as sports and leisure applications like golf shafts and fishing rods, etc. Furthermore, FRP curved tubes are widely used as racket frames. A general method of manufacturing such a racket frame is to cut, to a prescribed width, carbon or glass reinforcing fibre woven fabric prepreg, unidirectional prepreg or angle plied prepreg in which such unidirectional prepreg is superimposed in a crosswise fashion. The prepreg is then laid-up one by one to form a laminate onto a core material, after which the preform thus obtained is introduced into a mold that is heated. Another general method is where the racket frame is molded by so-called internal pressure molding in which laying-up is performed by wrapping the prepreg one ply at a time around a mandrel covered by a flexible tube, after which the mandrel is then withdrawn. The preform obtained is then introduced into a mold and, while heating the mold, pressure is applied by means of a pressurized fluid (eg compressed air) within the flexible tube. Below, methods of molding a racket frame using a prepreg are referred to as the `prepreg method`.
Moreover, as a method for manufacturing the preform, there is also known the method in which the preform is produced by winding a reinforcing fibre bundle around a core material by a filament winding method (hereinafter referred to as the FW method), the preform then being set in the mold and the molding of the desired racket frame is made. Again, there is known method where winding is performed by the FW method around a core material covered with a flexible tube, after which the core material is withdrawn. The preform obtained is introduced into a mold along with the flexible tube, and the racket frame is molded by internal pressure molding.
A racket frame based on this FW method has the setting of the reinforcing fibre winding angle is easy and provides an increase in design flexibility which improves frame performance. Moreover, in the preparation of the preform by the prepreg method, there are numerous stages, namely prepreg preparation/ cutting/laying-up, in addition to many manual operations, in the FW method, the preform is prepared in a single stage comprising a winding with a dedicated machine, so from the point of view of manufacture the FW method also possesses the features of reducing working time and increasing produce stabilization.
As a method of manufacturing rackets by the FW method, there is also known a method in which the reinforcing fibre bundle is wound by the FW method in a dry state without applying resin onto a core material covered with a flexible tube, after which the core material is withdrawn and the preform obtained is introduced into the mold along with the flexible tube. While pressurizing the interior tube, molding is effected by injecting a low viscosity thermosetting resin and performing crosslinking (this is as described in Japanese Unexamined Patent Publication No. 6-286005, U.S. Pat. No. 5,540,877 and International Unexamined Publication WO95/25633. Further, there is known a molding method in which, using the same kind of preform, a thermoplastic resin is injected and a polymerization reaction
The winding of the reinforcing fibre in preform production based on the FW method is normally carried out as shown in, for example, FIG. 4, where one helical layer is formed by winding at a certain constant angle across the entire tube length, and then on top there are formed a prescribed number of superimposed wound layers by winding at other constant winding angles, as required. In the example shown in FIG. 4, (A) helically wound layer 101 is formed by winding the reinforcing fibre at a winding angle of .+-.30.degree. in terms of the tube axial direction, th
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Chiu Raleigh W.
Toray Industries Inc.
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