GB2029757A

GB2029757A - Sports Equipment

Info

Publication number: GB2029757A
Application number: GB7836675A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-22
Filing date: 1978-09-13
Publication date: 1980-03-26
Also published as: DE2841412A1; GB2029757B; BE871307A; FR2437847A1; FR2437847B1

Abstract

A method of producing racket frames comprises impregnating carbon or other fibrous material with high polymer epoxy resin to form sheets therefrom, shaping said sheets into a pipe, introducing a solid foaming material into the center of said pipe and shaping the pipe by hot- pressing it in a mould whereby the epoxy resin is hardened and the foaming material fills and unites with the pipe.

Description

SPECIFICATION Sports Equipment The present invention relates to sports equipment and particularly to a method for producing a racket frame using carbon fiber reinforced plastics or fiber reinforced plastics.

The carbon fiber reinforced plastics (CFRP) and fiber reinforced plastics (FRP) have the advantages of high strength, good elasticity, high rigidity, good moisture-resistance, light weight, and good resistance to collision, damages, high temperature, and corrosion. Due to the above said advantages, the CFRP and FRP are utilized very widely.

One type of known racket frame has been made of CFRP or FRP material to utilize the advantage of said materials especially for their good strength, elasticity, rigidity, moisture resistance, creep-resistance, and shock attenuation. However, the method for producing the known racket frame is not ideal and results in high manufacturing costs and low manufacturing speed.

There are two conventional methods for producing FRP or CFRP racket frames in the art.

The first one adopts a mould which can form the frame, throat piece, shaft, and handle of the racket integrally by a single operation, a rubber tube filled with high-pressured gas is used there as the core of the mould. The CFRP or FRP prepreg material in the tube shape is placed in the mould and becomes hard by hot-pressing. The rubber tube is then pulled out from the mould and a kind of liquid foam plastics is poured into the core of the mould. Although this is a rather precise method, these complex manufacturing processes have caused this method to be discarded.

The second method for producing the conventional CFRP or FRP racket frames comprises a first process to insert the prepreg material in the mould and then a plastics film pipe filled with foaming material is arranged as the core of the mould. The whole racket frame can be hot-pressing moulded integrally by a single operation. This second method has become very popular recently. However, it still has some disadvantages. Referring to Fig. 1 which shows a sectional view of a racket frame manufactured by this method, there are a plurality of layers of plastics film 103 between the CFRP or FRP layer 101 and the foaming material core 102, therefore the whole racket frame is not a single body.

Besides, the foaming material core 102 can not be reinforced by the CFRP or FRP layer 101.

When an external force F is applied to the frame as shown in Figs. 2 and 3, the foaming material core 102 breaks from time to time causing the center of gravity of the racket to deviate from its normal position and causing an unpleasant noise.

The reason for why there must be equipped with layers of plastics film 103 is to protect the foaming material from leakage and losing internal pressure. There is a string hole 13 on the frame of Fig. 1.

The second method for producing the known racket frame is much simpler than that of aforesaid first method. The cost will be lowered too.

However the quality of the racket products is decreased. In addition, the two methods have a common disadvantage, that is, a thin shaft, such as a badminton racket shaft with a core having a diameter around one millimeter can not be produced by said two conventional methods.

The present invention provides a method for producing a frame for a racket, comprising soaking CFRP or FRP materials in a high polymer epoxy resin to form prepreg sheets; forming a pipe from said prepreg sheets; introducing a solid independent foaming material in to the center of said prepreg pipe; and hot-pressing moulding said materials under high temperature whereby to cause the CFRP or FRP prepreg sheets to become hard and foaming material therein to foam simultaneously to form said frame wherein said CFRP or FRP material and the foaming material are closely constructed.

Preferably the racket frame has a thin racket shaft with a core having a diameter around one millimeter.

Advantageously the racket frame has a CFRP or FRP external layer integrally formed with the internal foaming material to achieve a reinforcing effect.

The present invention is further described hereinafter by way of example, with reference to the accompanying drawings, in which: Fig 1 is a sectional view of the frame of a racket produced by the conventional method; Fig. 2 is a sectional view of the frame of a conventional racket showing the fracture or crack thereof; Fig. 3 is another sectional view of the frame of a known racket showing the crack produced by working; Fig. 4 is the perspective view of the mould and the embryo material of the racket frame according to the present invention; Fig. 5 is a sectional view of the frame taken along a line A~At in Fig. 4; Fig. 6 is a sectional view of the shaft taken along a line B-B' in Fig. 4; Fig. 7 is a sectional view of the frame after being hot-pressing moulded; and Fig. 8 is a sectional view of the shaft after being hot-pressing moulded.

Referring the Fig. 4 which shows a perspective view of the mould and the embryo material of the racket frame.

The mould is made of heat resistance metal and comprises a top mould 5, a bottom mould 6 and a pair of middle moulds 6a and 6b for moulding the frame 10, throat piece 20, shaft 30 and handle 40.

Referring to Figs. 5 and 6, which show the sectional view of the frame and shaft of the embryo material. The CFRP or FRP materials are soaked in the high polymer epoxy resin to form into prepreg sheets and then turned into a pipe shape. In the center of the CRFP or FRP prepreg sheet pipe, there is filled with a solid independent foaming material 102 which is made of thermoplastics mixed with foaming agent by pressing.

The pipe-shaped CFRP or FRP prepreg sheet together with the foaming material envolved therein is placed into the mould for hot-pressing moulding. The CFRP or FRP prepreg sheet will become hard and the foaming material therein will foam simultaneously under the same temperature.

The sectional view of the frame and the shaft of a racket frame after being hot-pressing moulded are shown in Figs. 7 and 8.

It is to be noted that the racket produced by the method according to the present invention is a integral article from the handle to the netting frame thereof. Besides, the CFRP or FRP layer is integrally formed with the internal foaming materials so as to achieve a perfect reinforcing effect. The process required by the present invention is quite simple, and in the meantime, a thin shaft with a core having a diameter around one millimeter can be produced directly from the present method.

As this invention may be embodied in several forms without departing from the spirit of the essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather chan by the description proceeding them, and all changes that fall within meets and bounds of the claims, or equivalence of such meets and bounds are therefore intended to be embraced by the claims.

Claims

1. A method for producing a frame for a racket, comprising soaking CFRP or FRP materials in a high polymer epoxy resin to form prepreg sheets; forming a pipe from said prepreg sheets; introducing a solid independent foaming material in to the center of said prepreg pipe; and hotpressing moulding said materials under high rdmperature whereby to cause the CFRP or FRP prepreg sheets to become hard and foaming material therein to foam simultaneously to form said frame wherein said CFRP or FRP material and the foaming material are closely constructed.

2. A method as claimed in Claim 1, wherein said solid independent foaming material is thermo-plastics material with foaming agent mixed therein by pressing.

3. A method as claimed in Claim 1 or 2 wherein soaking the CFRP or FRP material in the high polymer epoxy resin can be carried out after said CFRP or FRP material is formed into a pipe shape.

4. A method as claimed in Claim 1, 2 or 3 wherein said solid independent foaming material is further characterized by forming into a foaming center having a diameter about one millimeter for producing the thin shaft

4. A method as claimed in Claim 1, 2, 3 or 4 wherein said solid independent foaming material is further characterized by forming into a foaming center having a diameter about one millimeter for producing the thin shaft of a badminton racket.

5. A method of producing a frame for a racket substantially as hereinbefore described with reference to the accompanying drawings.

New Claims or Amendments to Claims filed on 26th April 1979.

Superseded Claims 1, 3, New or Amended Claims:~

1. A method for producing a frame for a racket, comprising soaking carbon fibre reinforced plastics or fibre reinforced plastics materials in a high polymer epoxy resin to form prepreg sheets; forming a pipe from said prepreg sheets; introducing a solid independent foaming material in to the center of said prepeg pipe; and hotpressing moulding said materials under high temperature whereby the carbon fibre reinforced plastics or fibre reinforced plastics prepreg sheets are caused to become hard and the foaming material therein caused to foam simultaneously to form said frame wherein said carbon fibre reinforced plastics or fibre reinforced plastics material and the foaming material are integrally moulded.

3. A method as claimed in Claim 1 or 2 wherein soaking the carbon fibre reinforced plastics or fibre reinforced plastics material in the high polymer epoxy resin can be carried out after said carbon fibre reinforced plastics or fibre reinforced plastics material is formed into a pipe shape.