JPS5918068B2 - Molding method for FRP racket frame with grooves - 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.
When simultaneously molding grooves for protecting the gut on the outer circumferential side surface of the ball-hitting part of the frame in the direction in which the gut is stretched, by providing a notch in the corresponding surface of the groove of the core material constituting the frame molding material, the groove can be formed. This is intended to improve moldability.

In general, this type of racket frame is shown in Figures 1 and 2.
As illustrated in the figure, the frame has a box-shaped outer shell structure in which a ball-striking part 1, a neck part 2, and a shut part 3 are continuously integrally formed, and the outer peripheral surface of a foamed synthetic resin core material 4 is coated with FRP5. In particular, by forming grooves 6 for protecting the gut along the circumferential direction of the frame over at least the upper half on the outer peripheral side surface 1a of the frame ball-hitting section 1 in the direction in which the gut is stretched, the frame ball-hitting section 1 is This is intended to protect the guts that are folded over.

Conventionally, in molding such a racket frame, as illustrated in FIGS. 3 to 5, a rod-shaped frame molding material is prepared by wrapping an FRP molding prepreg 12 around a foamed synthetic resin core material 11 having a rectangular cross section. 10 is fitted into a mold 13 while being bent into a predetermined racket shape, and in particular, the split mold 14 having the concave groove molding convex portion 14a is later clamped and hot-press molded, thereby forming the concave groove as a frame molding. At the same time, as illustrated in FIG. 6, a recess 11a corresponding to a groove is formed in advance in the core material 11 constituting the frame molding material 10, and the F"RP of the outer skin layer is formed in the recess 11a. The prepreg 12 for molding is pressed into shape by being pushed into the convex portion 14a of the split mold 14.However, in the former case, with this type of molding method, the core material is compressed by the compression effect caused by the pushing of the split mold 14. 11
The entire corresponding surface is drawn inward and the corners are rounded,
The overall cross-sectional shape is deformed, and the prepreg for FRP molding is also pulled in, creating a box-shaped FR with a sharp cross section.
It is difficult to mold into a P outer shell structure, and in the latter case, the recess 11a of the core material 11 and the protrusion 14a of the split mold 14 are made of FRP.
Prepreg 12 for molding is used to ensure good precision (because it is difficult to match, the shape of the groove after molding is incomplete, and not only are air bubbles and voids likely to occur between the core material and FRP, but also the FRP Since sufficient pressure and heat are not transmitted to the molded part, various problems have occurred, such as a tendency to cause molding defects.

Therefore, in this invention, incisions are made in advance in the frame circumferential direction at intervals corresponding to the width of the grooves formed on the surface of the core material constituting the frame molding material, which corresponds to the part where the grooves are formed to protect the guts. By cutting along the line, the above-mentioned drawbacks of the conventional method are attempted to be overcome.

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 20 is a rod-shaped frame molding material, and a prepreg 22 for FRP molding is attached to the outer peripheral surface of a foamed synthetic resin core material 21 with a rectangular cross section. It has a structure formed by winding and covering, and on the surface 21a side, such as the outer circumferential side in the direction in which the string is stretched, which corresponds to the forming part of the groove for protecting the string, there is a groove according to the width of the groove. Two notches 23, 23 are cut along the circumferential direction of the frame with a certain distance between them.

This frame molding material 20 is placed in a mold 24 by bending it into a predetermined racket shape, and then hot-press molded, and as shown in FIGS.
Due to the pressing mold clamping action of the split mold 25 having
The groove 31 is formed by compressing the space between the notches 23 and 23 and forming a groove 31 in a frame ball hitting portion 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. Four cuts 43 are made in the core material 41 of the coated frame molding material 40 according to the depth and width of the stepped groove.
While cutting 43 and 44°44 (see Figure 11),
The molding convex portion 46a of the mold 450 and the divided mold 46 is stepped into two stages.

By forming and hot-pressing (see FIG. 12), a frame ball-hitting portion 50 having two-stage grooves 51 as shown in FIG. 13 is formed.

Therefore, according to the above-described forming means, the outer peripheral side surface of the ball-hitting portion of the racket frame in the direction in which the string is stretched.

When molding a concave groove for protecting the guts, etc. along the circumferential direction of the frame at least in the upper half, a molded groove according to the molding width of the concave groove is formed on the compression molded part of the foamed synthetic resin core material that constitutes the frame molding material. Since the notches are cut in the interval range, when the groove is press-formed by the mold, the compression-molded part of the core material is separated and compressed by the notches, and the corners of the core material are not drawn in, preventing deformation of the core material itself. In addition, when the core material is compressed and dented, the compression pressure is relatively F
In addition to the prepreg for RP molding, this interaction allows sufficient molding pressure to be applied to the prepreg for FRP molding in the concave groove molding part, resulting in smooth heating action, good moldability, and high quality FRP. This makes it possible to mold a racket frame with excellent appearance, durability, and strength.

In addition, in each of the above embodiments, the cuts formed in the foamed synthetic resin core material constituting the frame molding material may be cut only in the range corresponding to the molded part of the groove, but the cuts may be made over the entire length of the core material. You can also cut it out.

Furthermore, in the above explanation, the present invention has been explained by taking as an example the molding of grooves for protecting gutts, but the present invention is not necessarily limited to forming grooves for protecting gutts, and can be applied to grooves or yokes in the shaft portion of a frame. It can also be applied to molding grooves on the inner circumferential surface of the frame for fixing, 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 conventional racket frame forming processes. FIG. 6 is a sectional view showing an example of another conventional frame molding material, and FIGS. 7 to 10 are explanatory diagrams showing a first embodiment of the racket frame molding process according to the present invention. 11 to 13 are explanatory views 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, 22...Prepreg for FRP molding, 23...Notch, 24...
Molding die, 25...Divided die, 30...Ball hitting portion of racket frame, 31...Concave groove.

Claims (1)

[Claims] 1 A concave groove is formed on at least part of the circumferential surface of the frame along the circumferential direction of the frame by hot-pressing a frame molding material in which a prepreg for fiber-reinforced plastic molding is wrapped around a core material made of foamed synthetic resin. When molding a racket frame having a fiber-reinforced plastic outer shell structure, at least two cuts are made in the frame's circumferential direction with an interval corresponding to the width of the groove in the core material portion corresponding to the groove of the frame. A method of forming a racket frame characterized by cutting along the line.