Classifications

• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B49/00—Stringed rackets, e.g. for tennis
  • A63B49/02—Frames
  • A63B49/10—Frames made of non-metallic materials, other than wood
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
  • A63B60/54—Details or accessories of golf clubs, bats, rackets or the like with means for damping vibrations
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B2209/00—Characteristics of used materials
  • A63B2209/02—Characteristics of used materials with reinforcing fibres, e.g. carbon, polyamide fibres
  • A63B2209/023—Long, oriented fibres, e.g. wound filaments, woven fabrics, mats
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B49/00—Stringed rackets, e.g. for tennis
  • A63B49/02—Frames
  • A63B49/10—Frames made of non-metallic materials, other than wood
  • A63B49/11—Frames made of non-metallic materials, other than wood with inflatable tubes, e.g. inflatable during fabrication

Definitions

• the invention concerns a racket and a method for making such a racket.
• racket for tennis, squash and badminton games, as well as for any other games whereby a racket is used, whereby this racket consists of a frame formed of a head and a grip, whereby the frame is mainly made of composite material.
• Rackets which are made of fibre-reinforced composite materials have been replacing the former wooden and aluminium rackets successfully for quite a while now. Indeed, composite materials have a very good stiffness/weight ratio and strength/weight ratio, which makes it possible to construct very performing rackets.
• the superior strength/weight ratio of composite materials has allowed for drastic developments, such as for example what is called the oversize racket and the midsize racket, of which examples are described in US 3.999.756.
• composite materials allow for a free design of the cross section of the frame, whereby this cross section can vary. This has allowed for example for the construction of what is called wide body rackets as described in US 4.664.380.
• the freedom regarding the design of the cross sections also allows for a better control of the vibrational behaviour and the mass distribution, so that it is found nowadays that the rackets of better quality are almost always made of composite material.
• frames of rackets of composite material were made with a matrix of epoxy resin, reinforced with bundles of continuously orientated, long carbon, glass, Kevlar or boron fibres.
• Epoxy is a thermoset which is cured in a mould during the production process by adding heat.
• prepeg the fibre reinforcement impregnated with epoxy
• the internal pressure is obtained by means of thin-walled nylon pressure hoses around which the prepegs are wound.
• the complete racket is hereby made in one piece by means of an injection technique.
• a serious disadvantage of this method is that the short fibre- reinforced composite in the racket head relaxes because of its viscoelastic behaviour under the influence of the constantly working prestressing forces of the strings.
• the permitted prestress and the size of the string surface are rather limited in such rackets.
• the structural damping of the rackets is considerably larger than that of rackets with a continuously orientated fibre reinforcement.
• thermosets with continuously orientated fibre reinforcements As described for example in 092/12847.
• the same method is used hereby as for thermosets with continuously orientated fibre reinforcements, but the above-mentioned impregnated fibre reinforcement is replaced by fabrics of synthetic fibres and reinforcement fibres, or by reinforcement fibres powdered with plastic.
• This thermoplastic matrix saves efforts during the finishing, because the surface quality of the rackets, when coming out of the moulds, is better than with thermosets, but the application of the reinforcement fibres in the mould remains a time- consuming occupation.
• the present invention aims a racket which combines a large structural damping, which is favourable for the comfort of the player, with a large stiffness in that part of the racket which contains the strings, the latter in order to prevent relaxation of the racket head under the influence of the prestressing forces of the strings and in order to obtain a large force of impact and precision during the game.
• the invention concerns a racket consisting of, on the one hand, a frame formed of a head and a grip, whereby this frame is mainly made of composite material and, on the other hand, strings provided in the head, characterized in that the frame mainly consists of two parts, a first part which comprises at least a part of the head and which is made of thermoplastic material reinforced with continuous fibres .and/or bundles of fibres which extend according to specific orientations, and a second part respectively which is made of thermoplastic material which is reinforced with discontinuous, randomly orientated fibres and/or bundles of fibres.
• the first part preferably extends from the free end of the head in the direction of the grip, so as to cover a part of the head, whereas the second part preferably covers the rest of the frame.
• Said two parts will preferably overlap over at least three centimetres and at the most up to the free end of the grip.
• thermoplastic composites namely that the matrix or in other words the thermoplastic material can be re-melted by adding heat without its chemical qualities changing.
• the invention concerns a method for making the above-mentioned racket, characterized in that it mainly consists in forming at least two U-shaped profile halves made of thermoplastic material which is reinforced with discontinuous, randomly orientated fibres and/or bundles of fibres; in forming a thimble-shaped element made of thermoplastic material which is reinforced with continuous fibres and/or bundles of fibres which extend according to specific orientations; in applying any of the above-mentioned U-shaped profile halves in a production mould; in applying the above-mentioned thimble-shaped element over a flexible hose which is fit to be put under pressure; in applying the flexible hose with the thimble-shaped element around it in the production mould, such that the thimble-shaped element at least partly overlaps the underlying profile half and such that at least one end of the flexible hose can be reached outside the production mould; in applying the second profile half at the height of the already provided U-shaped profile half, such that the part of the flexible hose situated here
• figure 1 schematically represents a racket according to the invention
• figures 2 to 4 schematically represent three variants of a racket according to the invention
• figure 5 shows a section according to line V-V in figure 4 to a larger scale
• figures 6 and 7 show two variants of the section of figure 5
• figure 8 shows a part of a racket according to the invention, prior to the composition thereof
• figures 9 to 12 show sections according to lines IX- IX to XII-XII respectively in figure 8 to a larger scale
• figure 13 shows yet another part of a racket according to the invention, which is meant to be combined with the part of figure 8
• figures 14 to 16 show sections of lines XIV-XIV to
• FIG. 17 shows a part which is used during the manufacture of the racket
• figure 18 shows a section according to line XVIII- XVIII in figure 17 to a larger scale
• figure 19 shows a production mould in which a number of components of the racket to be formed are laid dow
• figures 20 to 22 show sections of lines XX-XX to XXII-XXII respectively in figure 19 to a larger scale.
• the invention concerns a racket 1 consisting of, on the one hand, a frame 2 formed of a head 3 and a grip 4, whereby this frame 2 is mainly made of composite material and, on the other hand, strings 5 provided in the head 3.
• the invention is special in that the frame 2 is mainly composed of two parts, a first part 6 which at least comprises a part of the head 3 and which is made of thermoplastic material reinforced with continuous bundles of fibres which extend according to specific orientations, and a second part 7 respectively, which is situated at the height of the grip 4 and is made of thermoplastic material which is reinforced with discontinuous, randomly orientated fibres and/or bundles of fibres.
• the parts 6 and 7 are indicated schematically in that they are hatched in opposite directions.
• the parts 6 and 7 overlap at least over a certain distance, so that an overlap zone 8 is formed.
• This overlap zone is at least 3 centimetres according to a perpendicular projection on the longitudinal axis 9 of the racket 1, and reaches maximally to the free end 10 of the grip 4.
• the overlap zones 8 on either side of the head 3 are preferably situated symmetrically in relation to the longitudinal axis 9.
• the second part 7, irrespective of the size of the overlap zone 8, preferably entirely covers the remaining part of the frame 2 next to the first part 6.
• Figure 1 shows a configuration with a short overlap zone 8. According to figure 2, however, the overlap zone 8 extends to the free end 10 of the grip 4. According to the most preferred embodiments, which offer optimum play characteristics for most players, the first part 6, to the exclusion of the overlap zones 8, will run on from the head end 11 to a point which, measured according to the perpendicular projection on the longitudinal axis 9, is situated at about 2/3 of the length of the strings measured according to the longitudinal axis 9. This is the case among others for the examples in figures 1 and 2, in other words the length LI amounts to 2/3 of the length L2.
• Figure 3 schematically represents a variant in which the first part 6, to the exclusion of the overlap zones 8, runs on to half of the strings 5, measured according to the longitudinal axis 9.
• the racket 1 as represented in figure 4, has two arms 12 and 13 and a reinforcement piece 14 provided in between, ⁇ which also forms a rounded completion of the head 3, the first part 6, to the exclusion of the overlap zones 8, will preferably never extend any further than those places where the reinforcement piece 14 and the two arms 12 and 13 come together.
• figure 4 shows a variant in which the second part 7 runs on right past the place where the arms 12 and 13 join the reinforcement piece 14.
• the frame 2 will be entirely or almost entirely hollow. It can hereby have different forms of sections, and this form may vary for one and the same racket in different places.
• Figures 5 to 7 show a number of embodiments with sections in the shape of an ellipse, a circle and a rectangle respectively.
• the reinforcement piece 14 is also made of composite material, this is preferably solid. According to a variant, it can also be made of another material, for example aluminium, whereby it matters little in this case whether it is solid or hollow.
• the first part 6 is preferably made of different layers, as will be further described in the description of the method.
• the second part 7 has randomly orientated reinforcement fibres with a length which can vary from 0.1 mm to 15 cm.
• the length of the fibres can hereby vary from one fibre to another and also as a function of the technique used to form the second part 7 or the components thereof, as will be further explained in the description.
• the volume of reinforcement fibres amounts to between 20% and 80% of the total composite material volume.
• the reinforcement fibres are preferably carbon fibres, but also other fibre sorts are possible, such as glass fibres or aramid fibres.
• the above-mentioned racket 1 is made according to the new method described in the introduction, which will be explained in further detail hereafter by means of figures 8 to 22.
• At least two U-shaped profile halves 15 and 16 in the shape of scale parts, are formed, for example as represented in the figures 8 and 13, which will later form the above-mentioned second part 7.
• These profile halves 15 and 16 are made of thermoplastic material which is reinforced with discontinuous, randomly orientated fibres and/or bundles of fibres.
• the cross sections of the U-shaped profile halves 15 and 16 will usually have shapes as represented in figures 9 to 12 and 14 to 16. Basically, the parts which will form the arms 12 and 13 and the head 3 are elliptic, whereas the parts which are meant to form the grip 4 have a rectangular or polygonal shape.
• the reinforcement piece 14 will preferably be entirely part of one profile half, in this case the profile half 15.
• This reinforcement piece 14 can hereby be made, as represented in figure 12, of the same composite material as the rest of the second part 7 and in this case has a solid cross section.
• the profile halves 15 and 16 can be made in different ways. According to a first possibility, this can be done by means of an injection technique.
• the length of the reinforcement fibres is preferably 0.1 to 5 mm, as such short fibres allow for a smooth injection.
• thermoforming production technique a thermoforming production technique or a Sheet Moulding Compound (SMC) production technique.
• SMC Sheet Moulding Compound
• randomly orientated reinforcement fibres can be used, with a length which may vary between 0.1 mm and over 10 cm.
• a thimble- shaped element 17 is made of thermoplastic material which is reinforced with continuously orientated reinforcement fibres or bundles of fibres. These reinforcement fibres are surrounded with the matrix material in different forms, available in specialized trades in a form whereby the reinforcement fibre is enveloped with a thin layer of the thermoplastic material, or a form whereby the fibres are woven or bundled together with filaments of thermoplastic material, or yet another form whereby the fibres are powdered with fine granules of thermoplastic material.
• the thimble-shaped element 17 is preferably cylindrical, i.e. also in the shape of a hose. This element 17 is made in advance, possibly of different layers which either or not have a different fibre orientation. Preferably, the element 17 is made by means of a knitting machine or a winding machine.
• the thimble-shaped element 17 is, as represented in figures 17 and 18, provided around a flexible hose 18, in particular a hose which is fit to be put under pressure.
• This hose 18 preferably consists of nylon, rubber or any other material which resists the supplied heat and the supplied pressure, and it can be provided on both ends with connecting pieces 19 and 20 which allow for a pressure supply. Subsequently, the whole is assembled in a mould. This is illustrated by means of figure 19, which represents a mould half 21.
• one profile half in this case the profile half 15, is put in the mould half 21 first, in a recess 22 provided to this end, after which the flexible hose 18 with the thimble-shaped element 17 provided around it is also put in the mould half, such that the thimble-shaped element 17 at least partly overlaps the underlying profile half 15, in order to form the above-mentioned overlap zone 8, such that at least one end, but in this case both ends of the flexible hose 18, and in particular the above-mentioned connecting pieces 19 and 20, can be reached outside the mould.
• the second profile half 16 is provided on the first profile half 15, such that the part of the flexible hose 18 situated here and the overlapping part of the thimble- shaped element 17 can be enclosed between the two U- shaped profile halves 15 and 16. It is clear that one must see to it that the thimble-shaped element 17 overlaps the ends of the profile halves 15 and 16 symmetrically.
• the mould is closed, in other words the mould half 21 is closed off with a second mould half 23, which is also provided with a recess 24, as represented in figures 20 to 22.
• the figures 20 and 21 also show that the profile halves 15 and 16 overlap with their edges over a certain distance D.
• the above-mentioned flexible hose 18 is put under pressure and the mould is heated long and hard enough until all thermoplastic material present has become liquid, or at least very viscous, and a mutual fusion and/or adhesion has been obtained.
• the thermoplastic material of the thimble-shaped element 17 is melted to one piece and, on the other hand, an adhesion is realized between the thimble-shaped element 17 and the profile halves 15 and 16, as well as a mutual adhesion between the edges of the profile halves 15 and 16 overlapping over the distance D.
• the hose 18 is put under pressure by connecting it, as represented in figure 19, via connecting pieces 19 and 20 to a pressure source, for example a compressed air source 25, whereby the compressed air can be turned on by means of a suited valve 26.
• a pressure source for example a compressed air source 25
• the heating can for example be provided for by means of electrical heating elements 27.
• the mould can be opened and the formed frame can be removed from it. It is clear that this frame can be further finished, such as sanded and/or painted or such, and subsequently can be provided with the strings 5. It is also clear that the grip 4 can be wrapped around or provided with another covering.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Physical Education & Sports Medicine (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Moulding By Coating Moulds (AREA)
• Laminated Bodies (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=3888170

Family Applications (1)

Country Status (5)

Family Cites Families (5)

• 1994
  • 1994-05-19 BE BE9400515A patent/BE1008451A3/nl not_active IP Right Cessation
• 1995
  • 1995-05-16 WO PCT/BE1995/000046 patent/WO1995032029A1/en not_active Application Discontinuation
  • 1995-05-16 AU AU24015/95A patent/AU686379B2/en not_active Expired - Fee Related
  • 1995-05-16 CA CA002190533A patent/CA2190533A1/en not_active Abandoned
  • 1995-05-16 EP EP95917837A patent/EP0759798A1/de not_active Withdrawn

Non-Patent Citations (1)

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