JPS5933392B2 - Racket frame molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a racket frame whose entire outer shell is made of fiber-reinforced plastic (hereinafter abbreviated as FRP) such as glass or carbon. By embedding the mass body in the outer shell FRP layer at the same time as molding, the mass body can be easily and reliably fixed.

In general, the suitability of a racket frame is determined intuitively based on the player's own arm strength, especially grip strength, the overall weight of the frame, and the position of the center of gravity.The suitability of a racket frame is determined intuitively based on the player's own arm strength, especially grip strength, the overall weight of the frame, and the position of the center of gravity. ing.

In particular, the position of the center of gravity of the racket frame has a thick influence on the feel of the swing; the closer it is to the grip, the lighter it feels and the sharper the swing.

By the way, in conventional molding of a racket frame having this type of FRp outer shell structure, for example, a foamed synthetic resin such as polyurethane resin or polystyrene resin is used as the core material, and the FRP strength member is used as the core material. FRp
A method in which a prepreg sheet of molding material is coated, or glass fiber is individually wrapped around a core material during foaming, and then a rod-shaped frame material coated with or dipped in a matrix synthetic resin solution is mold-fitted while being bent and heated and pressurized. Alternatively, a rubber tube serving as a core material is coated with glass fiber, coated or dipped in a synthetic resin liquid for matrix, and placed in a mold.
A method of heating the rubber tube by pumping high-pressure air into it, an injection molding method of wrapping glass fiber around a suitable core material and fitting it into a mold, and then injecting a synthetic resin liquid for the matrix, and a flexible mold. By centrifugal molding, etc., the cylindrical rod-shaped frame material obtained by arranging glass fibers and injecting a matrix synthetic resin liquid and rotating the mold is bent together with the mold into the shape of a racket frame. The entire frame outer shell is continuously integrally molded from FRP, and the racket frame molded product obtained by this manufacturing method &! ,
They all have the same characteristics or are standard products, and it is not possible to obtain a balanced product in stages according to the suitability of each individual player.

Conventionally, in order to adjust the balance of a racket frame with such an FRP outer shell structure in accordance with the player's requirements, it is necessary to wrap tape or the like around the grip to make it thicker to strengthen the grip. A weight made of cylindrical metal with an appropriate weight is driven into the core material at the end of the frame shaft, which will become the grip part, and the hardened FRP layer after molding is cut to form a plate-like mass. The center of gravity was adjusted by embedding the body and gluing it together.

However, this type of adjustment means, especially one using a method of driving a weight into the core material, tends to cause cracks in the shaft part due to the driving pressure of the weight, and the bending stress or impact that acts on the end part of the shaft during long-term use. As a result, the foamed synthetic resin surrounding the weight breaks due to shearing, which creates a gap around the weight, causes it to rattle, and causes an abnormal noise when the ball is hit.

In addition, in cases where the mass body is installed by cutting the hardened FRP layer after molding, the installation work is troublesome and requires a lot of labor, and the FRP layer of the frame outer shell is only about 1 inch thin. Therefore, embedding the mass body is very difficult and increases the process and time.

Furthermore, since the reinforcing fibers in the FRP layer of the most important part of the strength member are cut, this is disadvantageous in terms of strength design, and the fatigue resistance of the frame is greatly reduced, resulting in major problems with the method of installing the mass body. .

This invention eliminates the above-mentioned conventional drawbacks and simultaneously embeds the mass body in the outer FRP layer, which is a strength member, at the same time as molding the racket frame. This is intended to ensure secure fixation and to prevent adverse effects on the FRP shell material due to the installation of the mass body.

The following explanation will be based on one embodiment shown in the drawings. As shown in Figs. 1 and 2, 1 in the drawings indicates a continuous ball-striking part 2, neck part 3, and shaft part 4 by the molding method of the present invention, which will be described later. The racket frame is integrally molded with a frame material having a substantially prismatic cross section, with a core material 5 made of foamed synthetic resin and a strength member made of FRp as an outer shell 6, and a grip part of the shaft part 4. Terminal section 4
A mass body 9 made of a flat metal material such as a lead plate or an iron plate is integrally buried in an intermediate FRp layer 63 which intersects in a shape between the FRP layers 61 and 62 on both the front and back face surfaces of a.

In addition, 10 in the figure is the shaft end portion 4 which becomes the grip portion.
1a is a yoke material.

That is, when the racket frame 1 having the above-described structure is manufactured by the molding method of the present invention (i, as illustrated in FIGS. 3 to 5, the outer circumferential surface of the core material 11 foam-molded, for example, from polystyrene resin). At the same time, a rod-shaped frame material 13 covered with a prepreg sheet 12, which is a material for FRP molding, is bent and fitted into a mold 14 consisting of an upper and lower mold, and at the same time, a rod-shaped frame material 130 is placed at a position corresponding to the end of the shaft that will become the grip part. After the mass body 9 is disposed on the mating surface of the both end mating parts 13a, when the mold is clamped, the prepreg sheet of the FRP molding material is sandwiched between the mold from the outside and the foamed resin of the core material from the inside, and pressure is applied. By heating and curing the rackets in this state, a racket frame as shown in FIGS. 1 and 2 is obtained.

Therefore, according to the above-described molding means according to the present invention, since the mass body 9 is integrally embedded in the FRP layer 63 of the shaft end portion 4a which becomes the grip portion of the racket frame 1 at the same time as the frame is molded, As the prepreg sheet hardens and is bonded to the mass body, the mass body 9 is securely fixed, and even if bending stress or vibration is applied to the end of the shaft during long-term use, there will be no wobbling (no wobbling), resulting in improved durability. The balance of the entire frame can always be stabilized.

In addition, if the prepreg sheet 12 is placed at a predetermined position on the rod-shaped frame material 13 during molding, the mass body 9 can be FR
Since it can be buried between the P layers 6, it destroys the reinforcing fibers of the FRp outer shell, which is the only strength member compared to the conventional method in which a mass body is installed by cutting the hardened FRP after molding. (Since it can be buried, it is advantageous in terms of strength design or fatigue resistance measures, and there is no need for a new process or work time for burying the mass body, and at this time, even if 90 volumes of the mass body are added to the FRP layer. Since the core material is made of foamed resin that can be deformed by pressure, the FRP layer can be absorbed by simply expanding to the inner surface, and the outer surface shape is only defined by the shape of the rigid mold, so it can be used as before. For the first time, it became possible to obtain a frame with a smooth surface.

In the above embodiments, the mass body was explained using a simple flat plate-shaped mass body, but a perforated plate-shaped mass body with corrugated or uneven parts formed on the surface, or with a large number of through-holes may also be used. If used, the resin liquid in the prepreg will pass through the through-holes during molding, which will improve the resin circulation, and can also be expected to have an anchoring effect, allowing for more secure fixation and improved durability.

Furthermore, the order in which the mass bodies are placed on the rod-shaped frame material during formation may be at the same time as the prepreg sheet is wrapped around the core material, after the prepreg sheet is wrapped around the core material, or after the mold fitting. The layer 63, that is, the area that becomes the mating surface of the rod-shaped frame material 13 during molding, is located at the center of the shaft axis, which is effective in terms of balance.

As explained above, in a racket frame in which the entire frame outer shell is continuously and integrally formed with FRp, the outer shell FRP on the shaft end portion side serving as the grip portion is
The mass body is embedded in the layer at the same time as it is formed, and the mass body can be fixed easily and reliably without damaging the FRP, improving durability and fatigue resistance during long-term use, and making it easier to adjust the balance. It is easy to use and has excellent practical effects.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the racket frame according to the present invention, Fig. 2 is an enlarged vertical cross-sectional view of main parts taken along line A-A in Fig. 1, and Figs. 3 to 5 show manufacturing steps. It is an explanatory diagram. 1... Racket frame, 2... Ball hitting part, 3... Neck part, 4... Shaft part, 4a... Shaft terminal part , 6, 61, 62
, 63... FRP layer, 9... Mass body,
11... Core material, 12... Prepreg sheet, 13... Bar-shaped frame material, 14...
...Molding mold.

Claims (1)

[Claims] 1 A rod-shaped frame material coated with an FRP molding material around the outer periphery of a core material made of foamed synthetic resin is fit into a mold while being bent, and the FRP molding material is clamped between the core material and the mold and heated. When integrally molding the entire frame outer shell with FRP, it is recommended to arrange a plate-shaped mass body within the FRP molding material at a position corresponding to the grip part of the rod-shaped frame material and embed it between the FRP layers at the same time as molding. Characteristic racket frame molding method.