JPS6117510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a racket frame having an outer shell structure made of fiber-reinforced plastic (hereinafter abbreviated as FRP), such as a box-shaped cross section, with a core material made of foamed synthetic resin. In simultaneous molding of a concave groove for protecting the gut on the outer peripheral side surface of the ball hitting part of the frame in the direction in which the gut is stretched, the core material constituting the frame molding material is formed of at least three sliced materials stacked and stacked in the ball hitting direction. By doing so, the moldability of the groove is improved.

In general, this type of racket frame has a frame in which a ball-striking part 1, a neck part 2, and a shaft part 3 are continuously integrally formed, and the outer periphery of a foamed synthetic resin core material 4 is formed, as illustrated in FIGS. 1 and 2. FRP5 on the surface
In particular, a concave groove 6 for protecting the gut is provided in the outer circumferential side surface 1a of the frame ball-hitting portion 1 in the direction in which the gut is stretched over at least the upper half of the frame. By forming the ball along the frame, the gut that is folded back and stretched on the frame ball-hitting portion 1 is protected.

Conventionally, when molding such a racket frame, as illustrated in FIGS. 3 to 5,
A rod-shaped frame molding material 10 in which an FRP molding prepreg 12 is wrapped around a foamed synthetic resin core material 11 having a rectangular cross section is fit into a mold 13 while being bent into a predetermined racket shape.
By later clamping the split mold 14 having a shape and performing hot-press molding, the concave groove can be press-formed at the same time as the frame molding, or as illustrated in FIG.
In the core material 11 that constitutes the frame molding material 10,
A concave portion 11a corresponding to a concave groove is formed in advance, and the prepreg 12 for FRP molding of the outer skin layer is pressed into the concave portion 11a by the convex portion 14a of the split mold 14. In the former case, the seed molding means uses a split mold 14.
The entire corresponding surface of the core material 11 is drawn inward due to the compression effect caused by the pushing, and the corners become rounded.
The overall cross-sectional shape is deformed, and accordingly, the prepreg 12 for FRP molding is similarly drawn in, making it difficult to mold the FRP shell structure into a box-shaped FRP shell structure with a sharp cross section. Since it is difficult to match the convex portion 14a of the split mold 14 with high precision through the prepreg 12 for FRP molding, the shape of the groove after molding becomes incomplete, and moreover, air bubbles and Not only are voids likely to occur, but pressure and heat are not sufficiently transmitted to the molded part of the FRP, which can easily cause molding defects.
Various inconveniences occurred.

Therefore, in this invention, the core material constituting the frame forming material is formed of a plurality of sliced materials stacked one on top of the other in the direction of ball hitting, and the laminated state of the sliced materials corresponding to the groove forming part for protecting the gut etc. The above-mentioned drawbacks of the conventional method are attempted to be overcome by making the spacing match in advance to a range corresponding to the formed width of the groove.

Next, the present invention will be explained based on the embodiments shown in FIG. 7 and below.

7 to 10 show a first embodiment of the present invention, in which reference numeral 20 denotes a rod-shaped frame molding material, which is attached to the outer peripheral surface of a foamed synthetic resin core material 21 having a rectangular cross section.
It has a structure formed by winding and covering an FRP molding prepreg 22. The core material 21 is formed from at least three slice materials 21a, 21b, 21c, and each slice material 21a, 21b,
The intermediate sliced material 21b is formed by laminating the layers 21c in a non-adhered state in the direction of ball hitting, and corresponds to the surface side such as the outer circumferential side in the direction in which the string is stretched, which corresponds to the forming part of the concave groove for protecting the string. , and is formed to have a thickness corresponding to the width of the groove. This frame molding material 20 is bent into a predetermined racket shape, fit into a mold 23, and hot-press molded, and as shown in FIG. 8 and FIG. Due to the pressing mold clamping action of the mold 24, the intermediate slice material 21 constituting the core material 21 is
This is made by compressing one side of the frame ball hitting part 30 and forming a concave groove 31 in a frame ball hitting part 30 having a cross-sectional structure as shown in FIG.

Further, FIGS. 11 to 13 show a second embodiment of the present invention, in which grooves are formed in two steps on the outer circumferential surface of the ball-hitting part of the frame in the direction in which the string is stretched. The intermediate slice material 21B of the core material 21 constituting the coated frame molding material 20 is formed by overlapping three slice materials 43a, 43b, and 43c according to the width of the stepped groove (see FIG. 11). ), the molding convex portion 45a of the split mold 45 of the mold 44 is formed in two steps,
By hot pressing (see Figure 12), the first
It is formed by molding a frame ball hitting portion 50 having two-stage grooves 51 as shown in FIG.

Therefore, according to the above-mentioned forming means, when forming a concave groove for protecting the string on the outer peripheral side surface of the ball-hitting part of the racket frame in the direction in which the string is stretched, at least along the circumferential direction of the upper half of the frame, The foamed synthetic resin core material constituting the frame molding material is formed of at least three slices stacked in an unbonded state in the direction of ball hitting, and the intermediate slice material corresponding to the compression molding part is formed in the molding width of the concave groove. Because it is formed to the appropriate thickness, the intermediate slice material is separated and compressed without affecting other slice materials when pressing the concave groove with the mold, and compression by pressing with the conventional split mold as described above is possible. As a result of this action, the entire corresponding surface of the core material is drawn inward, making the corners rounded, and the overall cross-sectional shape is never deformed, which prevents deformation of the core material itself, and also prevents intermediate slices from deforming. When the material is compressed and dented, the compression pressure is applied relatively to the FRP molding prepreg, and due to this interaction, sufficient molding pressure can be applied to the FRP molding prepreg in the groove molding part. The heating effect is smooth and the moldability is good, resulting in high-quality FRP, which enables the molding of racket frames with excellent appearance, durability, and strength.

In addition, in each of the above embodiments, the core material constituting the frame molding material does not have to be a sliced material made entirely of foamed synthetic resin; for example, only the intermediate sliced material corresponding to the molded portion of the groove is made of a material with low buckling strength. The slice material may be made of a low foaming synthetic resin having a high buckling strength, and the other slice material may be made of a highly foaming synthetic resin such as a semi-rigid polyurethane resin having high buckling strength, or a non-foaming material such as a thermoplastic synthetic resin. Also, in the above explanation,
Although this invention has been described by taking as an example the molding of grooves for protecting gutts, this invention is not necessarily limited to the molding of grooves for protecting gutts; It can also be applied to molding surface grooves and the like, and similar effects can be produced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a racket frame, Fig. 2 is a partially enlarged cross-sectional perspective view of the frame ball hitting section taken along line A-A in Fig. 1, and Figs. 3 to 5 are views of a conventional racket frame. An explanatory diagram showing the molding process,
FIG. 6 is a sectional view showing an example of another conventional frame molding material, FIGS. 7 to 10 are explanatory views showing a first embodiment of the racket frame molding process according to the present invention, and FIG. 11 13 are explanatory diagrams showing a second embodiment of the racket frame forming process according to the present invention. 20...Material for frame molding, 21...Foamed synthetic resin core material, 21a, 21b, 21c...Slice material, 22...Prepreg for FRP molding, 23...
...Molding die, 24...Divided die, 30...Ball hitting portion of racket frame, 31...Concave groove.

Claims (1)

[Scope of Claims] 1. A frame molding material in which a prepreg for fiber-reinforced plastic molding is wrapped around a core material made of a foamed synthetic resin is placed in a mold, and the mold has a concave groove molding convex part. A fiber-reinforced plastic outer shell structure in which a concave groove corresponding to the concave groove molding convex portion of the divided type is provided along the circumferential direction of the frame on at least a portion of the circumferential surface of the frame by heat-pressing together with the pressing mold of the divided type. In molding a racket frame having a racket frame, the core material is formed of at least three sliced materials, which are overlapped in the direction of ball hitting, and an intermediate sliced material corresponding to the groove-forming portion of each sliced material is formed. An FRP having a groove, the thickness of which corresponds to the width of the groove.
Racket frame molding method.