JP2854790B2 - Racket frame manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a racket frame for a racket which can be used for tennis, soft tennis, squash, badminton, racquetball, and the like. A method of manufacturing a racket frame for a racket that can be adjusted to meet requirements.

[0002]

2. Description of the Related Art The applicant discloses in Japanese Patent Application No. 5-166086 that injection molding of an outer structure made of a short fiber reinforced thermoplastic resin or the like is performed around an inner structure made of a long fiber reinforced thermosetting resin or the like. Has provided an unprecedented method of manufacturing a hybrid racket frame. According to this hybrid racket frame, the surface of the racket frame in terms of strength and rigidity and the surface of the vibration damping ability can be simultaneously held in an appropriate state.

[0003]

However, in the above-described hybrid racket frame, there remains a problem in the adhesive strength at the interface between the inner structure and the outer structure formed by injection molding around the inner structure. If the material compatibility of both layers is poor, sufficient adhesive strength cannot be obtained. For example, when an internal component is molded with a long fiber reinforced epoxy resin and an outer component is to be molded by injection molding a short fiber reinforced nylon resin around the internal component, the internal component using the long fiber reinforced epoxy resin is used. Plays a role of improving strength and rigidity, and the external structure made of nylon resin reinforced with short fiber plays a role of improving vibration damping performance, so long fiber reinforced nylon with short strength and good damping performance By adding epoxy resin, strength and rigidity can be increased without increasing weight and bulk too much, but the adhesion between the layers of nylon resin and epoxy resin is poor, and the features of both layers are fully utilized There were drawbacks that could not be done.

Accordingly, the present invention solves the above-mentioned drawbacks in the method of manufacturing a hybrid racket frame, enables the bonding strength between the two layers to be joined to be sufficient, and fully exerts the features of both layers. It is an object of the present invention to provide a method of manufacturing a racket frame that can have both good vibration damping performance and strength.

[0005]

In order to achieve the above-mentioned object, a method of manufacturing a racket frame according to the present invention is to press-mold a long fiber reinforced resin to form an internal structure, and to form a short around the internal structure. A method of manufacturing a racket frame in which an external component made of a short fiber-reinforced thermoplastic resin is integrally molded around the internal component by injection molding a fiber-reinforced thermoplastic resin, wherein the internal component is features during the press molding, the perform press forming an external structure of a resin of the same kind as granular resin in a state where dusted inside structure outside surface, that then performs the injection molding of the short-fiber-reinforced thermoplastic resin And

[0006]

The features of the method of manufacturing a racket frame of the present invention described above.
According to the remarks , by performing press molding in a state where the same type of powdery resin as the resin of the external component is dusted on the external surface of the internal component, simultaneously with the press-forming of the internal component, At least a part of the inner structure is joined while being pressed into the outer surface. For this reason, when the resin for molding the external component is subsequently injected around the internal component, the injected resin and the granular resin already bonded to the external surface of the internal component are mutually fused and solidified. .
As a result, the connection between the inner structure and the outer structure is made sufficiently strong, and the characteristics of both the inner structure made of the long fiber reinforced resin and the outer structure made of the short fiber reinforced resin are sufficiently exhibited. Racket frames that can be manufactured.

[0007]

1 and 2 show an example of a racket frame manufactured by the method of the present invention, and FIGS. 3 to 8 are views for explaining an embodiment of a method of manufacturing a racket frame of the present invention. 1 is an overall view of the racket frame, and FIG.
AA sectional view of FIG. 3, FIG. 3 is an overall view of the internal structure of the racket frame, FIG. 4 is a sectional view taken along line BB of FIG. 3, and FIG. 5 is a mold for injection-molding the external structure. FIG. 6 is a view showing one split mold, FIG. 6 is a view showing a state in which a positioning member is arranged in a space of one split mold of a mold for injection-molding an external component, and FIG. 7 is injection-molding the external component. Sectional view showing a state in which the internal structure is positioned and held in the space of the mold for molding,
FIG. 8 is a cross-sectional view of the racket frame taken out of the mold after injection molding of the outer component around the inner component.

Referring to FIG. 1 and FIG. 2, a racket frame F obtained by the manufacturing method of the present invention has an internal structure 10.
And an external component 20 made of resin formed around the internal component 10. Internal component 10 is hollow 11
It has become. Reference numeral 50 denotes a resin positioning pin described later.

The internal structure 10 is made of a long fiber reinforced thermosetting resin and has a thickness of, for example, about 0.25 to 2 mm. The internal structure 10 is made of a prepreg in which a cloth or braid made of long reinforcing fibers such as glass fiber or carbon fiber is impregnated with a matrix resin such as an epoxy resin or an unsaturated polyester resin. Cure and mold. The outer structure 20 is made of a short fiber reinforced thermoplastic resin and has a thickness of, for example, about 1 to 2 mm, and is integrally formed by injection molding around the inner structure 10. The short fiber reinforced thermoplastic resin of the external structure 20 is
Resins such as nylon resin, polycarbonate resin, and polyphenylene oxide resin reinforced with short fibers such as glass fibers and carbon fibers or chopped fibers can be used.

Next, an embodiment of a method of manufacturing a racket frame according to the present invention will be described with reference to FIGS. First,
By using a sheet-shaped prepreg made of a long fiber reinforced thermosetting resin, cutting the prepreg into an appropriate size and shape, and winding it into a hollow, a hollow body portion 10 as shown in FIG.
A prototype of the internal structure composed of a and the flat plate portion 10b is formed. 13 is a hole for fixing to a mold, and 14 is a grip end portion. On the outer surface of the prototype of the internal structure obtained in this way,
Spray (spray) a powdery resin 80 made of the same resin as the short fiber reinforced thermoplastic resin serving as the external structure 20 (see FIGS. 3 and 4). The prototype of the internal structure 10 in which the powdery resin 80 is coated on the outer surface is mounted in the mold 30 and is hollowed by the internal pressure method.
Press molding is performed with the mold in a heated state while introducing a gas into the inside 11 and applying internal pressure. Thereby, the internal component 10 having a predetermined shape is completed. The prototype of the internal structure 10 does not necessarily have to be hollow. A prototype may be formed by winding a sheet-like material around a lightweight member such as a foamed core material or a tube. The internal structure 10 itself is preferably hollow in terms of lightness, but may be solid.

When using an epoxy resin having a large elastic modulus of about 13000 kgf / mm ² , which greatly contributes to strength and rigidity, as the long fiber reinforced thermosetting resin of the internal component 10, the temperature is 140 ° C.
By performing the press working at about the temperature, the internal structure 10 having a predetermined shape can be completed in a hardened state. When a nylon resin having an elastic modulus of about 2000 kgf / mm ² is used as the powdery granular resin 80, that is, as a short fiber reinforced thermoplastic resin of the external component 20, an elastic modulus with a good vibration damping performance is about 20.
When a nylon resin of 00 kgf / mm ² is used, the nylon resin remains cured at about 140 ° C.
At the time of the press molding, at least a part of the granular resin 80 of nylon is forcibly pushed from the outer surface of the inner structure 10 and is bonded to the outer surface of the inner structure 10. Regarding the size of the powdery resin 80, the thickness of the internal component 10 on which the resin
It is necessary to be changed depending on the thickness of, for example, not less than at least a fraction of the thickness of the internal structure 10,
Since the adverse effect on the internal structure 10 is large, an appropriate size smaller than that and an appropriate shape are experimentally determined as necessary. For example, when the thickness of the internal structure 10 is about 1 mm, a spherical powdery resin 80 having a size of about 0.2 mm is used.
Can be adopted. Of course, the resin of the internal structure 10 is not limited to an epoxy resin. Further, the resin of the external structure 20 is not limited to the nylon resin. The resin of the external component 20 is a thermoplastic resin suitable for injection molding, and does not soften at the temperature at which the internal component 10 is molded, so that it can bite into the outer surface of the internal component 10 and be bonded. What kind of resin should be selected?

As the material of the internal structure 10, a thermoplastic resin reinforced with long fibers may be used in addition to the long fiber reinforced thermosetting resin. In this case, the internal structure 10
A yarn made of reinforcing fiber such as glass fiber or carbon fiber,
A filament made of thermoplastic resin is knitted into a sheet and wrapped around a lightweight member such as a foamed core material or a tube, then attached to a mold, press-formed in a heated state, and cooled. And then cured. In addition, the sheet knitted thing, the one formed by winding into a cylindrical shape, is mounted in a mold, press-molded in a heated state while introducing gas into the hollow and applying internal pressure, and cooled and cured. Alternatively, it may be formed. Further internal structure 10
Can be formed in the same manner as described above by hollowing a yarn made of a long fiber and a yarn made of a thermoplastic resin as a braid, and mounting this in a mold. Examples of the thermoplastic resin include a nylon resin, a polycarbonate resin, and a polyphenylene oxide resin.

Next, the internal component 10 with the powdery resin 80 biting into the outer surface is further placed around the external component 10.
In order to perform injection molding of the mold 20, a mold split 31 as shown in FIG.
And the short fiber reinforced thermoplastic resin is injected into the space inside the mold around the inner structure 10, thereby integrally forming the outer structure 20 made of the short fiber reinforced thermoplastic around the inner structure 10. I do. In this case, the resin of the short fiber reinforced thermoplastic resin of the external component 20 is the same resin as the powdery resin 80. By injecting the short fiber reinforced thermoplastic resin,
The powdery granular resin 80 pushed into the outer surface of the internal structure 10 has a protruding portion or the like from the outer surface melted by the heat of the injected resin to form the resin and the injected resin. Fused and then coagulated together to unite. As a result, the outer component 20 is integrally formed around the inner component 10 in a state where the outer component 20 and the interface with the inner component 10 are firmly joined (coupled). Since the two are sufficiently firmly connected to each other, a racket frame capable of actually exhibiting the characteristics of both can be manufactured.

[0014]

The continuation of the embodiment of the method of manufacturing the racket frame will be further described. Internal structure as described above
After the 10 is formed, the low melting point alloy 12 is injected into the hollow 11 of the formed internal structure 10 from the opening of the grip end portion 14 to fill the hollow 11. As the low melting point alloy 12,
Alloys made of lead, tin, bismuth, cadmium and the like can be mentioned. The melting point of the low melting point alloy 12 needs to be lower than the melting temperature of the thermoplastic resin described later. As the low melting point alloy 12, an alloy having a melting point of about 110 to 180 ° C. is usually used. Further, an internal structure filled with the low melting point alloy 12
10 is mounted on a mold 30 to form a racket frame. As shown in FIGS. 5 to 7, for example, the mold 30 includes split molds 31 and 32 that can be bisected by a surface perpendicular to the thickness direction of the racket frame (a surface parallel to the face surface of the racket) (FIG. 7).
), Grooves 33, 34 for forming a mold space 40 are provided in each of the split dies 31, 32. By combining the two grooves 33 and 34, a mold space 40 is completed in the mold 30, and the entire internal structure 10 shown in FIG. The internal component 10 is a core portion of the racket frame, and a resin is injection-molded into a space 40 around the core, so that a resin external component 20 is integrally molded around the internal component 10 to form a racket frame. Is formed. For this reason, the internal component 10 needs to be held and positioned without contacting the inner surface of the mold 30 around it.

In this embodiment, as a positioning member for positioning the internal structure 10 in the space 40 of the mold 30, resin positioning pins 50 are inserted into the mold space 40 from above and below and from the left and right of the inner surface of the mold. They are arranged to protrude. Therefore, in the present embodiment, as shown in FIG. 7, insertion holes 35a and 35b are provided at appropriate intervals on the bottom surface 33a and the side surface 33b of the groove 33 of one split die 31, and the other split die 32 has Bottom of groove 34
An insertion hole 36a is provided in 34a. Each insertion hole 35a
, 35b, 36a, the positioning pins 50 abut on the internal component 10 from above and below and from left and right, and position the internal component 10 at a predetermined position in the mold space 40. can do.

As shown in FIG. 5, the groove 33 of the one split mold 31 is provided with two fixing projections 37 from the bottom surface 33a at positions corresponding to the grip positions of the racket frame. An attachment hole 13 is provided at a position corresponding to the grip of the internal component 10 with respect to the fixing protrusion 37. FIG.
In the figure, reference numeral 38 denotes a molten resin injection passage.

In the manufacture of the racket frame of the present embodiment, first, as described above, the hollow internal structure 10 is formed in which the powdery resin 80 is partially pressed into the outer surface and joined together.
A low melting point alloy (mp 140 ° C.) is melted and injected into the hollow of the internal structure 10 to fill the hollow 11 and solidify. Then mold
A positioning pin 50 made of resin is inserted into each of the insertion holes 35a, 35b, 36a for each of the split molds 31, 32 of 30. Next, the mounting hole 13 is fitted into the fixing projection 37 with the internal component 10 in one of the split dies 31, and the entire internal component 10 is
Attach to 33. And then the other split mold 32 is
Adjust to 31. Thus, the upper and lower surfaces and the left and right surfaces of the internal structural body 10 are divided into the resin-made positioning pins 50 of the split molds 31, 32.
Is positioned and arranged in the mold space 40 in a state of contact with the mold space 40. Thereafter, a thermoplastic resin reinforced with short fibers, for example, a nylon resin, is injected into the mold space 40 from the injection passage 38 to form a resin outer component 20 around the inner component 10.
Is formed. When the injection molding is completed, the split molds 31 and 32 are opened, and the molded racket frame is taken out. At this time, the positioning pin 50 made of resin is also taken out of the mold 30 together with the racket frame as a part of the meat of the external structure 20 of the racket frame (FIG. 8).

The internal structure 1 of the obtained racket frame
0 and the junction surface of the outer structure 20, since the embedding only the powder particulate resin 80 is applied during the molding of the internal structure 10, the joint interface is an external structure 20 resin and the internal structure 1
The resin has an uneven pattern due to the resin No. 0, and a sufficiently strong bonding state is achieved.

Next, the racket frame is heated to 150 ° C. in an oven (not shown) to remove the low melting point alloy 12 from the grip end portion 14. The heating temperature is equal to or higher than the melting point of the alloy and equal to or lower than the melting temperature of the thermoplastic resin of the outer structure 20. Further, the portion of the positioning pin 50 protruding from the outer surface of the racket frame (the insertion hole 35 of the mold 30).
a, 35b and 36a).
Thereafter, a gut hole is made with a drill, and a grip, an end cap, a gut and the like are attached to form a racket. The order of removing the low melting point alloy 12 and shaving off the positioning pin 50 is not limited to the above embodiment.

In the above embodiment, the internal structure 10 is placed in the mold space.
As a positioning member for positioning at 40, a positioning pin 50 made of resin is used, and this is inserted into the insertion hole 35a of the mold 30,
Although the description has been given of the example of insertion into 35b and 36a, the present invention is not limited to the above embodiment. First, when using a positioning member made of resin, the positioning pin 50 need not be used,
The internal structure 10 projects from the inner surface of the mold 30 to the space 40 side.
Any material may be used as long as it comes into contact with the surface. Second, the positioning member made of resin is provided with the insertion holes 35a, 35b, 3 of the mold 30.
It is also possible to attach to the inner surface of the mold 30 or to simply interpose the inner structure 10 between the inner surface of the mold 30 and the inner structure 10 without being inserted into the mold 6a. By configuring the positioning member made of resin in this way, the insertion holes 35a, 35b, and 36a do not need to be formed on the inner surface of the mold 30. In this case, since the positioning member does not protrude from the external structure 20 of the racket frame, a post-process of cutting off the protruding portion is not required. The technical scope of the present invention includes a manufacturing method having such a configuration of a resin positioning member and a mold.

In the above embodiment, the resin-made positioning member including the resin-made positioning pin 50 is made of resin in order to make it easy to be compatible with the external component 20 formed by injection molding. In addition to the same resin as the external component 20, except for a resin having an extremely low softening temperature compared to the melting temperature of the resin of the external component 20, various thermosetting resins and thermoplastic resins can be selected. it can. Of course, if the positioning member made of resin can play the role of positioning, it should be such that it does not melt again during the injection molding of the external component 20 and does not generate an interface with the structure of the external component 20. Is preferred.

The inner structure 10 is made of a long fiber reinforced (thermosetting, thermoplastic) resin, and the outer structure 20 is made of a short fiber reinforced resin, so that the strength of the racket frame is improved by the inner structure 10. Thus, the adjustment of the attenuation characteristic can be adjusted by the material and thickness of the external component 20. Also, when the external component 20 is injection molded, the hollow component 11 of the internal component 10 is filled with the low melting point alloy 12 so that the internal component 10 can be molded even at a high injection pressure.
Can be prevented from being crushed. Thus the external construct
The injection amount of the thermoplastic resin for forming 20 can be accurately controlled. Therefore, the ratio of the thickness of the inner structure 10 to the thickness of the outer structure 20 and the weight of the racket can be arbitrarily changed.
As a result, appropriate strength and vibration damping performance can be obtained, and adjustments such as emphasizing one of the features can be made by changing the thickness ratio. Further, since the low melting point alloy 12 to be filled in the hollow 11 is heated and melted and injected, a casting step for forming a specific shape as in the prior art can be omitted, and most can be recovered. As a result, costs can be reduced.

[0024]

According to the method of manufacturing a racket frame according to the first aspect of the present invention, there is provided the present invention having the above configuration and operation.
At the time of press molding of the internal component, press molding is performed in a state where the same type of powdery resin as the resin of the external component is spread on the external surface of the internal component, and then injection molding of the short fiber reinforced thermoplastic resin is performed. Therefore, the connection between the internal component and the external component can be made sufficiently firm. Therefore, it is possible to actually manufacture a racket frame having both the improvement of the strength and rigidity of the internal structure made of the long fiber reinforced resin and the improvement of the damping performance of the external structure made of the fiber reinforced resin.

[Brief description of the drawings]

FIG. 1 is an overall view showing an example of a racket frame manufactured by the method of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an overall view of an internal structure for explaining an embodiment of a racket frame manufacturing method according to the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a view showing one split mold of a mold for injection-molding an external structure.

FIG. 6 is a view showing a state in which a positioning member is arranged in a space of one split mold of a mold for injection-molding an external component.

FIG. 7 is a cross-sectional view showing a state where an internal component is positioned and held in a space of a mold for injection-molding the external component.

FIG. 8 is a cross-sectional view of the racket frame taken out of the mold after injection molding of the outer component around the inner component.

[Explanation of symbols]

 10 Internal component 10a Hollow body 20 External component 30 Mold 40 Space 80 Powdery resin

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) A63B 49/10 B29C 45/14

Claims (1)

(57) [Claims] 1. A short fiber reinforced resin is press-molded to form an internal structure, and a short fiber reinforced thermoplastic resin is injection-molded around the internal structure to form a short fiber around the internal structure. A method for manufacturing a racket frame in which an external component made of a reinforced thermoplastic resin is integrally molded, wherein a powdery and granular resin of the same type as the resin of the external component is internally formed during press molding of the internal component. A method for producing a racket frame, comprising: performing press molding in a state of being covered with an outer surface of a structural body; and thereafter, performing injection molding of the short fiber-reinforced thermoplastic resin.