JPS5934273A - Tubular frame structure for tennis racket and production thereof - 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 The present invention generally relates to a high-strength film having an amorphous core or fillet surrounded and welded to an outer shell of resin-covered high-tensile composite filaments or fibers. 1 Concerning the structure.

In particular, the present invention provides improved energy absorption properties.

The present invention relates to a lightweight, high strength and robust tennis racquet with durable construction suitable for competition, in which the amorphous core is comprised of a flexible foamed polymer and a lightweight honeycomb reinforcing layer or structure.

Currently, tennis players have access to many types of tennis racquets. These racquets are made of a variety of materials and come in a number of different weights and shapes.

One of the most popular tennis frames recently developed uses resin-coated composite filament materials, such as graphite fibers, glass fibers, boron filaments, Kölwer filaments, or any combination thereof.

The most popular composite racquets are made from graphite fibers impregnated with insulating resin.

Graphite fiber composites were first developed for aerospace applications such as high-performance aircraft and hismizile structures. Graphite composites have also been found to be ideal for sports equipment due to their permanent light weight and high strength. As a result, graphite composites have become widely used in lightweight, high strength, and high performance tennis racket frames. When cured at elevated temperatures, resin-impregnated graphite fibers form a high-strength, robust, and lightweight structure (7), which is particularly suitable for manufacturing high-performance tennis rackets.

Basically, graphite composite tennis frames include a tubular, rigid composite frame structure or shell.

The hollow core present within the overcast tubular frame structure is typically filled with various core materials. The properties and shape of both this robust composite shell and core structure are important in providing the desired performance to the tennis racquet. FFL fibers of various sizes impregnated with various types of resin materials are commercially available. Many of these commercially available graphite composite materials have been used to provide tubular tennis frame structures that are quite robust.

However, with respect to core structure, sufficient core materials or structures have yet to be developed for use in high performance graphite tennis racquets.

An optimal core structure should provide good energy absorption properties to reduce shocks and vibrations that would otherwise occur in the hollow tubular frame 4FW construction during impact. Furthermore, the fluid distribution of the core material throughout the tennis frame tubular structure should be easily altered. This variable weight distribution allows for fine tuning and balancing of mass between the frame head and handle, enhancing desired performance characteristics. The core structure also ensures that over long-term use of the racket,
It should resist deterioration and disassembly due to shock and vibration.

Additionally, the core material is preferably melted or bonded to a robust composite shell to ensure a robust, vibration-free feel during use of the racquet.

One desirable structural property for an optimal core material is the ability of the core material to expand. The graphite racket is molded with 7' machining to apply pressure inside the cabinet and prevent it from collapsing by 1°. Typical Graf-Aite composite core tennis racket 11! ! The structure includes surrounding the core graphite fibers in a particular direction. The graphite fiber core structure is then heated and molded to give the desired shape. The internal pressure required to ensure that the robust graphite shell is properly molded is typically and most conveniently
provided by the wick itself. The ability of the core material to expand and generate internal pressure is therefore an important property and desirable in the commercial process of manufacturing such graphite composite tennis racquets.

Foamable or expandable resin mixtures have been used as suitable core materials. Foamed materials are desirable because they provide the necessary internal pressure during molding operations. Typically, the resin mixture is
Barium sulfate, cork shavings.

It is mixed with various additives such as glass, asbestos, fibers, mica flakes, etc. These additives control the density inside the core,
Used for a variety of reasons, ranging from low-density filling to manufacturing lighter racquets.

These resin core mixtures typically include phenolic epoxies. Core properties range from solid, hard and brittle mixtures to mixtures with the consistency of a stiff putty or molding clay. Although it has been discovered that many of the core materials currently used in Graphite Flano® are sufficient for their intended purpose, the core materials deteriorate prematurely and become crumbly, resulting in rackets). Problems have been experienced with string holes and other holes being damaged.

In response to the desire for an optimal core material and structure, one of the co-inventors of the present invention developed a flexible core structure from plasticized vinyl chloride, which was found to have enhanced racket performance characteristics. Elastic cores and composite structures based thereon are the subject of Belgian Patent Application No. 288,999, ``Elastic Core Composite Structures'', filed concurrently with the present application.

The novel elastic or flexible polymer core is based on flexible expanded vinyl, most preferably made from plasticized vinyl chloride dispersed with a suitable blowing agent.

Although this new flexible foam core structure provides the tennis racquet with desirable high performance properties, an all flexible foam core structure does not provide the desired high strength and stiffness required for the application. Thus, 2I provides enhanced structural reinforcement that not only includes the advantages of an elastic or flexible core as described above, but also provides a particularly strong reinforced composite tapered frame structure.
Something that can be seen is desired.

According to the invention, a composite structure is provided, the core of which is
It has all the desirable comfort properties provided by an elastic or flexible core material, plus includes structural reinforcement.

The present invention is directed to a tubular frame for a tennis racquet that includes a core structure surrounded by a rigid composite shell. The core structure includes a resilient polymer reinforced by one or more lightweight honeycomb structures or layers. A flexible or elastic polymer core is prepared according to the previously mentioned co-filed patent application, the contents of which are also used in the present invention. The improved core structure is essentially perforated to sink the central flexible core and string the racquet through it. Additionally, the core structure includes a honeycomb structure on both sides of the flexible central core. The honeycomb structure is oriented such that the string holes do not penetrate or touch the honeycomb structure. A preferred honeycomb structure is a conventional honeycomb reinforcement layer made of a lightweight metal such as aluminum. Lightweight metal honeycomb structures are well known for use in various structurally reinforced articles requiring high strength and light weight.

The use of honeycomb reinforcement structures in tennis racquets is by no means new. U.S. Patent Application No. 4,175,745, issued to Gevers et al. on November 27, 1979, discloses an improved metal racquet in which a honeycomb structure is utilized for reinforcement. To prevent blistering and fraying of tennis strings passing through the honeycomb structure, plastic or other smooth inserts are provided so that the tennis strings are in continuous contact with the relatively jagged surfaces of the holes drilled in the honeycomb structure. It is necessary to prevent rubbing due to this. As a feature of the invention, the elastic core and honeycomb layer are oriented to prevent tennis racquet strings from contacting the honeycomb structure. Although this provides an improved tennis racket construction,
It not only includes the desirable properties of a honeycomb reinforced racket, but also the desirable properties of an elastic core. These features include increased shock absorption, variable mass distribution and protection from jagged metal edges of racquet strings. Although it is preferred that the honeycomb reinforcement according to the invention is used with a flexible foam core, the honeycomb reinforcement
It may be used with other conventional rigid or semi-rigid foam core materials.

According to the present invention, a method of manufacturing an improved racquet frame structure is disclosed. The method involves forming an elastic F-core (a core that is expanded and hardened, a predecessor of the core) containing a suitable expanding agent in a distributed manner, and placing appropriate honeycomb layers on both sides of the core. Agency. This elastic ulterior motive / Hanikano・
The structure is then surrounded by suitably woven resin-impregnated fibers.

This composite fiber-surrounded elastic layer and honeycomb layer are then placed into a suitable mold and cured by conventional internal pressure molding techniques.

The above-mentioned and other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings.

A tennis racket according to the present invention (see generally in FIG. 1).

((Not indicated by α.The tennis racket (10) has a head part +21, a neck part (141 and a handle 1.1fi)
Get 3 t. The neck portion (14) includes lower transverse struts (18I and 4), which not only provide strength and rigidity to the neck and spatula 1 portions, but also provide strength and rigidity to the racket string. Shrine and 71 (Ro.

The upper horizontal strut C (second is also part of the racket head part (121).

Anis racket (101 is preferably a conventional tubular structure made of resin-impregnated graphite fibers. The use of graphite fibers to produce tubular structures is well known. The preferred tennis racket U is made of graphite fibers. However, composite materials such as boron legs, glass fibers, polyamide fibers (Kevlar), and others may also be utilized in accordance with the present invention.

The racket head section (+21) is shown in cross section in Figure 2.
2 foam core t2 (1) and/or nicam reinforcement layer t7! Q,
(Including 7! (to).

As shown in the second and third figures, the racket head part (one part) includes a plurality of racket string holes G0.
The string hole C301 is used to attach the racket string (not shown) necessary to complete the racket. Racket string holes extend laterally 1171 through the tubular frame structure.

An important feature of the present invention is that the two layers (1,!6
), C2A should be oriented as shown in the second diagram, with the racket string hole (to) connected to the composite shell (2z) and the foam core (24).
Although it passes through the no-nikum layer f2fil, G! 8) should not be passed. This feature is important, as it prevents the racquet string passing through the racquet string hole from coming into contact with the relatively rough jagged edges that would be present in the string hole passing through the multi-chambered layer. 11- Do. Passage of the racquet string through the honeycomb layer results in premature chafing and breakage of the racquet string.

Thus, the present invention prevents such premature failure by preventing any possible contact between the honeycomb layer Qliil, (28) and the racquet string.

The cross-sectional shape of the tubular structure shown in the second figure is not critical. A relatively rectangular tubular structure with grooves (34)
Preferred for aesthetic as well as performance properties. The actual final molding 1 cross-sectional shape of the tubular structure is not critical, as long as the honeycomb reinforcing layer and the foam core can be oriented appropriately within the cross-section.

A preferred method for preparing a tubular structure according to the invention is:
This involves the well-known method of hot molding the composite material in an outer mold utilizing foam core 2 material to provide the internal pressure necessary to force the composite layer outwardly into the mold interior surface. The first step is to create a suitable foam core. A suitable foamed lower core is the fourth
It is shown as C34) in the figure.

Any type of expandable material may be utilized. The foamable compound has a composite curing temperature of approximately 107.2 U to 17
No special mold is required as long as it produces the desired foam and provides sufficient internal pressure when heated to 6.6C.

Although any foaming compound that produces a rigid or robust foam may be utilized, it is not possible to produce a flexible or resilient foam (
Preferably, a foamable elastic polymer is used. Even more preferred is a helically wrapped core of plastic or flexible polyvinyl chloride. As previously discussed in the Background of the Invention, the use of elastic foam vinyl as a base material for tubular graphite racquets is disclosed in the application, which is incorporated by reference. Preferably, the ulterior motive is prepared according to the disclosure. A thin (i.e., between 0.025 and 0.381) flexible vinyl chloride sheet is prepared by impregnating it with a suitable chemical swelling agent. A preferred swelling agent is 2.2'. azobisisobuzarnitri/l, (AZ i)N ). AZ
The DN is added to the polyvinyl chloride film, preferably as a powder. The polyvinyl chloride sheet is then spirally wrapped to form a core (34). As shown in Figure 5, the spiral wrap of resin-impregnated polyvinyl sheet intersperses a series of polyvinyl chloride layers, dispersing the blowing agent between each layer. Wrapping the blowing agent dispersed between polyvinyl chloride sheets is a particularly suitable and convenient means of achieving the desired final foam core structure. If desired, 1
Wrap it in multiple layers.℃・.

As a second step in the preparation of the preferred tubular frame structure, the lower core (34) is coated with two honeycomb reinforcement layers (2fil, (
It is sandwiched between 281. As shown in Figure 7, the honeycomb layer includes a plurality of honeycomb chambers (40) bounded at both ends thereof by bonding. Lightweight honeycomb reinforcement structures are well known and have a light weight, high It is widely used where a strong and rigid structure is required.A suitable honeycomb layer is made of aluminum or an aluminum alloy (
Ru.

Other lightweight materials may be utilized if desired. Additionally, non-metallic honeycomb structures may be utilized as well.

For example, it may be made from resin-treated aramid fibers sold by DuPont under the trademark NEM8X. Additionally, glass fiber reinforced honeycomb cells such as HltI (372) may be used as well. IRH372 is a glass fiber bias weave reinforced plus deck honeycomb containing a polyimide resin system. Any other suitably strong and lightweight honeycomb chamber may also be used in accordance with the present invention. The honeycomb cells preferably have their axes perpendicular to the longitudinal axis of the tubular structure.

Suitable honeycomb cells have a cross-sectional diameter of 1.59 mm to 6.35 wag, preferably 3.18 m. The preferred width of the honeycomb layer, or the preferred width of the honeycomb chamber, is 3.18 mI+ and 12.7 mm, and preferably,
Flare 1 is approximately 6.35flIII+. 'Both the core and the honeycomb reinforcing layer are sized appropriately and have dimensions consistent with those of conventional tennis racket structures. A preferred honeycomb structure is $6n O52-001 manufactured by IIEXEL.

Honeycomb layer (2h), ulterior heart sandwiched between ClkO (
(4) is then wrapped or surrounded by composite fibers.

The composite fiber has an uncured outer shell structure (41;
) to form. Tennis racket frame structure and I-te,
Approximately 21,000 kg/1rys2 maybe 28,000
Graphite fibers with intermediate modulus between kg/1 mn20 are preferred.

The fibers are conventional resin-impregnated graphite fibers, supplied in either wire or woven sheet form. Although the diameter of the graphite fiber is not critical to the present invention, it is preferably extremely thin, on the order of 0.0076 fin. Additionally, if high strength and stiffness are desired, high modulus graphite fibers may be utilized. The direction of N'J trl is from +45° to -45° with respect to the length direction of the tubular structure.
It is preferable that the shape is wrapped while changing the direction alternately.

Similarly, the first layer has fibers running along the length of the tubular structure.
The line is IjI. While any number of layers may be utilized in preparing a suitably robust dual shell, for tennis racquet applications, approximately three layers of graphite fiber sheets provide the best strength, light weight, and performance. It turns out that it gives a combination.

When utilizing three sheets or layers, the preferred fiber orientation is such that the fibers of one layer are parallel to the longitudinal axis of the tubular structure and 1.
, the fibers of another layer are at a 45° angle to the longitudinals of the tubular structure, and the fibers of the third layer are orthogonal to the fibers of the second layer.

The uncured tubular structure shown in FIG. 8 (4) is then placed 16 into a suitable mold as shown in FIG.
) and the lower mold plate (52). The mold plate (!i
ll, Ciυ, and 62 are clamped together by a suitable high-power lamp or other conventional means. The mold is then heated to the curing temperature of the graphite composite. This temperature is usually about 107.6 C or about 176.6 T;
It is between. At these temperatures, the blowing agent decomposes or undergoes chemical changes to create foaming gas. This gas is necessary to force the graphite composite outwardly into the mold and also to force the honeycomb layer shell and shell outwardly into position.

This gas generation also creates a flexible polyvinyl chloride foam core. The heating period may vary depending on the temperature used and the particular resin and polyvinyl chloride utilized. Typically, however, this heating period is between half an hour and two hours.

Foam expansion is usually between 100 and 200%.

The cured and molded tubular structure is shown in FIG.

After cooling, the frame structure is removed from the mold. It is clear that any suitable tubular structure can be created by the shape of the mold. But l.

Therefore, since this preferred tubular structure has particular application in tennis racquets, it is preferred to use a conventional tennis racquet mold.

Racquet string holes C30) may be drilled through the hardened composite shell 021 and the flexible foam core after the racquet is removed from the mold. Also, prior to molding, the bottle may be stretched out laterally through a single core and an uncured composite shell. After molding and curing, the bottle is removed to create a suitable racquet string hole.

Although exemplary embodiments of the invention have been described, those skilled in the art will appreciate that the disclosure is merely an example and that various modifications may be made without departing from the scope of the invention. .

Therefore, the invention should not be limited to the particular embodiments illustrated in FIG.

[Brief explanation of the drawing]

Fig. 1 is an overall view of one embodiment of the tubular frame tennis racket according to the present invention, Fig. 2 is a cross-sectional view in the T'' plane of Fig. Ii, and Fig. 3 is an improvement in the l-lft plane of Fig. 1. A diagram of the tubular frame structure, FIG. 4 is a perspective view of a preferred helical wrapping, FIG. 5 is a cross-sectional view in the v-■ plane of FIG. 4, and FIG. 6 is a honeycomb layer and elastic collapse. FIG. 7 is a partially cutaway view of the uncured core structure as seen from the ■l-V11 direction in FIG. A perspective view of the structure; FIG. 9 is a cross-sectional view of the uncured tubular structure in a suitable racquet mold; FIG. 10 shows a thermoset tubular frame structure according to the present invention after being cured and molded in an exemplary racquet mold. Cross-sectional view. (121 is the head part, (14) is the neck part, (!The body is the upper horizontal strut, (211 is the upper horizontal strut, t221 is the outer shell, 041 is the foam core, (261, (-the body is the honeycomb layer, 1
31σ is string hole, fi (41 is F core, α;) is polyvinyl chloride layer, (vertical is expansion agent, (4G is honeycomb chamber, (squid), (44) is boundary layer, (46) is uncured outer layer. Shell structure, l”1(1)r +!'in + 'S'21
C is the upper + center, lower mold plate.

Claims (1)

[Scope of Claims] 1. A foam core (2) and at least one honeycomb reinforcing layer (26 (28)); a robust composite tubular shell surrounding the reinforcing layer and the foam core (24); and the above. The string hole C (01 is the string hole C) having a plurality of surfaces defining IJing holes (7) extending across and penetrating the foam core structure.
A tubular structure for a tennis racket that penetrates the 4+ and robust composite tubular outer shell (221 but not the upper R honeycomb reinforcing layer (26 (28)).2 The foam core (241 is elastic) A tubular frame structure for a tennis racket according to claim 1, which is a polymer core. 3. The resilient foam core (24) and the rigid outer shell (221)
4. A tubular frame structure for a tennis racket according to claim 2, in which the two honeycomb reinforcing layers (26-28) are arranged between the two honeycomb reinforcing layers (26-28). A tubular frame structure for a tennis racket according to claim 3, which is made of a lightweight metal. 5. A plurality of honeycomb reinforcing layers (26-28) having an axis perpendicular to the plane of the honeycomb layer (26-28). Honeycomb cells (including 40, above) and two-comb cells (4 (
5. A tubular frame structure for a tennis racket according to claim 4, wherein the negative is arranged between the boundary layers (42-4G) of the honeycomb layer. 6. The tubular frame structure for a tennis racket according to claim 5, wherein the honeycomb chamber (4G is orthogonal to the string hole (V) passing through the solid outer shell (2Z) and the elastic core (24). 8. The tubular frame structure for a tape racket according to claim 1, wherein the honeycomb reinforcing layer (26-28) is made of a non-metallic material. 8. The elastic core (24) is made of flexible foam vinyl. A tubular frame structure for a tennis racket according to item 2. 9. The strong composite shell is made of graphite fibers. Made of resin-impregnated fibers selected from the group consisting of borosilicate fibers, glass fibers, and polyamide fibers. 10. A tubular frame structure for a tennis racket according to claim 8 comprising: 10. a foam core surrounded by a robust composite shell (22);
24) The tubular frame structure for the Dennis Structs is
At least one honeycomb reinforcing layer (26 (2) disposed between the foam core (24) and the tough composite shell (221)
8) ) ; A string hole (including a plurality of surfaces defining 3α) passing through the frame structure laterally; It penetrates, but the above honeycomb layer (26
-28) is the shell threading 1゛, thereby the above string hole (
The racket string inserted through the honeycomb (30)
26-28) Tubular plate structures for tennis rackets. 11. The tubular frame structure for a tennis racket according to claim 10, wherein the foam core C2(a) is an elastic polymer. 12. The tubular frame structure for a tennis racket according to claim 11, wherein the Hanino J7 single layer (26-28) is made of lightweight metal. 13. The tubular frame structure for a tennis racket according to claim 12, wherein the lightweight metal is an aluminum alloy. 14. A reinforced foam core for a tennis racket having a robust tubular outer shell (27J) comprising a foam core sandwiched between parallel honeycomb reinforcing layers (26-28). 15. The foam core C241 is an elastic foam. the above)·
15. A reinforced foam core according to claim 14, wherein the nicum layer (26-28) is made of aluminum or an aluminum alloy. 16. Contains a heat-foamable base (b); the foamable base is sandwiched between the Nicum reinforcing layers (26-28) to form a reinforcing foamable base; The reinforced foamed core is surrounded by uncured composite fibers (4G); the foamed core G41 surrounded and reinforced with the fibers is placed in a suitable tennis racket mold, and the mold is heated to a suitable temperature to strengthen the foamed core. heating for a sufficient period of time to form the tubular frame structure comprising a foam core and a rigid composite tubular shell; The above honeycomb layer (26-2
8) A method for manufacturing a tubular frame structure for a tennis racket, which includes the step of providing holes (3(1+) in the tubular frame structure for string attachment that do not pass through J1. 17. The foamed core C44) is made of a flexible vinyl polymer and an appropriate amount of 16. The method for manufacturing a tubular frame structure for a tennis racket according to item 16, wherein the foamed core (4) is made of flexible polyvinyl chloride wrapped in a spiral shape; - The tennis racket according to claim 17, wherein the helical winding ((61) has the swelling agent dispersed between the layers. 19. A method for manufacturing a tubular frame structure for kerato. Agent (38 is AZ, DN Hiarl [¥πF
A method for manufacturing a two-structure tubular plate for a tennis racket according to claim 18. 20. F core C (4) is surrounded by uncured composite outer g (4fi). Place it in one mold (50-52), and then
Heat the Simold and press the shell against the mold to create the internal pressure necessary to form the composite shell. , the outer shell hardens to form the robust outer '+j, &12:', and the expanded F core C' (4J is the core f24).
In the manufacturing method of a composite 1-7-shaped frame structure having a strong outer shell and core layer, which forms a ,
The two layers are characterized in that the string holes, which may be provided in the upper frame structure, are oriented so that they pass through the outer shell and the core 24+, but not through the honeycomb layers (26-28). A method for manufacturing a composite tubular frame structure. 21. A method for manufacturing a composite tubular frame structure according to claim 20, wherein the core (24J is an elastic polymer). 22. The honeycomb layer (26-28) is made of aluminum or Claim 20 made of aluminum alloy
A method of manufacturing a composite tubular frame structure as described in Section 1.