JPS5838572A - Production of reinforced composite racket - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improved method of manufacturing a racquet frame reinforced with glass or graphite fibers. That is, a shell made of laminated layers of directional graphite fibers impregnated with resin is compressed during a heating period, and a foamed elastomer mixture, i.e., a foamed rubber mixture, compressed air, and K. The present invention relates to a method in which two internal pressures generated separately are brought into complete contact with the inner surface of the shell mold cavity.

Many methods for manufacturing composite laminated fiber reinforced racket frames have been developed. In manufacturing known racket frames as described above, the shell of the racket frame is generally formed by winding a thin plate of oriented fibers impregnated with a thermosetting resin;
It is then placed into the mold cavity. Thereafter, the shell is compressed and squeezed by internal expansion pressure to contact the mold cavity. There are two conventional methods suitable for generating such internal inflation pressures. One is a direct method, that is, a compressed air method, and the other is an indirect method, that is, a foam core method.

The known direct method will be explained using FIGS. 1 and 2.

A racket frame shell 2 consisting of a top, a head, a throat, a shaft, and a grip is placed in the half mold cavity, and a corresponding cellophane tube 3 is wrapped in the cavity. The sealed end 30 of the cellophane tube 3 is the racket carrying part 2
5, and the other end 31 of the cellophane tube 3 passes through the racket frame, extends in an open state, and projects from the mold 1. When the mold 1 is heated to gel and harden the shell 2, a desired amount of compressed air is blown into the cellophane tube 3 through its free end by means of an air compressor to apply radial internal pressure, thereby forming the shell 2. 2 is expanded so that it comes into contact with the surface of the mold cavity. As a result, a desired racket frame can be obtained after the curing process is completed. Since racquet frames manufactured by this known method have a hollow shell, the entire frame tends to vibrate when used to hit the pole. Therefore, a lightweight foamed thermoplastic material such as polyvinyl chloride, polyethylene, or polypropylene is injected into the hollow portion of the racket frame to overcome the above-mentioned drawbacks. but,
It is inevitable that manufacturing costs will increase due to the second injection process required to manufacture the racket frame. moreover,
Since it is difficult to inject the most outstanding vibration-absorbing materials into the shell after hardening, such as elastomer or rubber, the materials injected into the hollow portion of the shell are generally limited to thermoplastic materials.

The indirect method, that is, the foam core method, will be explained using FIG.

This foam core system is disclosed in the following US patents: In other words, A? Ld44v? 4th, 0th outside M-C41i
No. 70,021 and No. 4゜124.670, prj
No. 4,070.020 and No. 4,1 of Done
No. 28,963.

A%d44. tP M, outside 046Aa and p t j
This is No. 4,129,634 of D6 Milk C. In the foam core method described above, to prepare the racket frame, an outer shell made of laminated layers of unidirectional graphite fibers and a core made of a seamless sleeve containing a foamed resin mixture are placed inside the mold cavity. You can place it in Thereafter, the mold is sealed to activate the foamed resin formulation and create pressure within the mold cavity, thereby tightly bonding the core to the shell. Although this method significantly reduces manufacturing steps, it requires precise control of the resin formulation to generate sufficient internal pressure before the curing process is complete. Unfortunately, the normal implementation @
There are many factors that influence the magnitude of the compression internal pressure, such as curing temperature, type and amount of blowing agent, type and amount of crosslinking agent, and type of resin compound. In other words, unless the above factors are accurately controlled, it is quite difficult to obtain the desired product.

Therefore, the main objective of the invention is to provide an improved manufacture that overcomes the above-mentioned drawbacks. That is, in the present invention, there are two internal compression pressures which are each continuously applied by the rubber compound located in the shell and by the compressed air.

Another object of the present invention is to provide an economical manufacturing method for manufacturing a racket frame with excellent vibration absorption properties and a clean outer surface.

Yet another object of the invention is a racquet frame closely bonded to the inner surface of a shell that does not include a core molded from a rubber blend or elas-r compound, which is made from foamed rubber or foamed elastomer. To provide a method for manufacturing a reinforced composite racket frame, which is still flexible so that even if the racket frame is damaged, an accident due to its fragments can be avoided.

Yet another object of the invention is that the foamed rubber compound, i.e., the foamed elasto-r compound, is also cured to become thermosetting, so that the racquet frame is not foamed while being reheated during the coating process. To provide a method for manufacturing a fiber-reinforced racket frame that prevents the core from softening. The softened plastic is squeezed out of the thread holes by the reactivation of the remaining blowing agent that was incorporated into the plastic, resulting in a much finer finish.

These and other objects and advantages of the invention will become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings.

In the improved method of manufacturing a graphite fiber reinforced racket frame provided by the present invention, first an elongated plate 6 of the foamed elastomeric compound or foamed rubber compound type is inserted into the cellophane tube 3 and then a thermosetting resin By winding the pre-pre-lug 20 made of impregnated graphite fibers, an elongated article having a cross-section as shown in FIG. 4 is formed. Thereafter, the elongated article is placed in the mold cavity and bent so that one open end thereof protrudes from the mold.

Initially, while heating the mold, a desired amount of compressed air is fed into the cellophane tube 3 through its open end by an air compressor. As a result, a first internal pressure is applied that causes the elongated article to expand and come into tight contact with the inner surface of the mold. When the heating temperature becomes high enough to activate the foamed elastomer, ie, foamed rubber, the supply of compressed air is stopped. Then, a second internal pressure is generated due to expansion of the foamed elastomer compound, that is, the foamed rubber compound. Accordingly, the two successive internal pressure steps allow the elongated article to be formed into the shape of the mold cavity.

Referring to FIG. 4, it is clear that the foamed elastomer compound, i.e., the foamed rubber compound, is in a solid state and does not occupy the entire space within the tube 3 made of Nanaronon. The compressed air can be easily fed to uniformly expand the elongated article to obtain the desired shape.

Preferred examples of said foamed elastomer formulations or foamed rubber formulations are disclosed in the table below in accordance with this invention.

Composition Heavy duty rubber styrene-butadiene rubber 84.9 Foaming agent dinitrosopentamethylenetetramine 1.3 Crosslinking agent dicumyl peroxide 1.0 Filler zinc oxide 6.0 Filler carbon black 6.80
00

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a half-mold with a racket frame arranged to explain the manufacturing process of the fiber-reinforced racket frame, and Figure 2 is a diagram to explain the structure of the racket frame made by the known direct method. A cross-sectional view taken approximately along the A-AI line in FIG. 1, and FIG. 3 are as follows:
A sectional view taken along A-AI in FIG. 1 to explain the structure of another racket frame made by the known indirect method, and FIG. 4 shows a heating mold for a racket frame according to the present invention. FIG. 3 is a longitudinal cross-sectional view of a part of the sprout. Symbol explanation 1...Mold 2...Shell 3, Φ, 1, Cellophane tube Patent Applicant Kun Nan Rou "-"'
-) Figure 1

Claims (2)

[Claims] (1) A method for manufacturing a reinforced composite racket frame composed of an outer shell made of a thermosetting material and a foamed core, which comprises the following steps: (-) The foamed material is replaced with the thermosetting material #! Inserting the foam material into a shell, provided that the outer dimensions of the foam material are smaller than the inner dimensions of the shell to create a gap between the shell and the foam material. Inserting the foam material into the mold; (r-) a first compression process by compressing the void with compressed air to bring the shell into tight contact with the inner surface of the mold; (→
After the first compression step, heating the mold to expand the foam material, filling the void with the expanded foam material, and further pressurizing the mold. (2) The manufacturing method according to claim 1, wherein the foamed material is a foamed elastomer metal compound, that is, a foamed rubber compound.