Note: Descriptions are shown in the official language in which they were submitted.
- 2)~0533;
1 --
Racket and method for makin~ such a racket.
The invention concerns a racket and a method for making
such a racket.
In particular, it concerns a racket for tennis, squash
10 and badminton games, as well as for any other qames
whereby a racket is used, whereby this racket consists of,
~ f~ fo~-7d of ~ h~ n~ ~ g~iF, /~hor~y tho ~rar..o io
mà~y made of composite material.
15 Such ~acket, whereby the frama is entirely made of
composite\~terial, is known from US 3 . 999 . 756 .
Rackets whic~are made of fibre-reinforced composite
materials have ~en replacing the former wooden and
20 aluminium rackets ~ccessfully for quite a while now.
Indeed, composite \~aterials have a very good
stiffness/weight ratio ~d strength/weight ratio, which
makes it possible to const~t very performing rackets.
25 The superior strength/weight r~i~o of composite materials
has allowed for drastic developmen~, such as for example
what is called the oversize rack~ and the midsize
racket, of which examples are described~ US 3.999.756.
30 Moreover, composite materials allow for a ~e design of
the cross section of the frame, whereby ~is cross
section can vary. This has allowed for example\l~or the
construction of what is called wide body racket~ as
described in US 4 . 664 . 380 .
AMENDED SHEEr
2t 9~5~3 `` ``
-- 1 t 1
on the one hand, a frame formed of a head and a grip,
whereby this frame iB at least partly made of composite
material and, on the other hand strings provided in the
head, whereby the frame comprises a first part containing
at least a part of the head and being made of thermoplastic
material reinforced with fibres and/or bundles of fibres,
and a second part which is made of synthetic material.
Such a racket is known from NL-A-9201354. The racket
described in this document consists of several parts made
of a synthetic material some of which are reinforced with
continuous f ibres .
AMENOED SHEEr
533
ljZ
= = =
Rd-~}.e~ lU~I L~ IUI.;~I d rd-;3Ct~t. /
The invention concerns a racket and a~uPL~d for making
such a racket-
In particular, it cong~r~ racket for tennis, squash10 and badminton gy~ as well as for any other games
whereby a r~ is used, whereby this racket con8i8ts of
a f~rmed of a head and a grip, whereby the frame is
r- y ~d~ of ~ o~it~ -~t~
15 âuoh a racket, whereby the frame i5 entirely made of
composite material, is known from US 3.999.756.
~ackets which are made of fibre-reinforced composite
materials have been replacing the former wooden and
20 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.
25 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.
30 Moreover, 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 .
AMENDED SHEET
Woss/32029 21 9 ~53 r ~ 7~ c
.
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
5 always made of composite material.
Until recently, frames of rackets of composite material
were made with a matrix of epoxy resin, reinforced with
bundles of continuously orientated, long carbon, glass,
10 Revlar or boron fibres. Epoxy is a thermoset which is
cured in a mould during the production process by adding
heat. During the curing, the fibre reinforcement
impregnated with epoxy, called prepeg, is pressed against
the hot mould walls as a result of an internal pressure
15 and thus perf ectly adopts the shape of the mould . The
inter~al pressure is obtained by means of thin-walled
nylon pressure hoses around which the prepegs are wound.
After the curing, the rackets are taken out of the mould,
any epoxy flashes are removed, after which the rackets
20 are sanded, sandblasted and painted.
Placing the prepegs in the mould is a time-consuming job
because of the complicated connection between the oval,
closed racket head and the grip . Also the f; n i ch; n~ of
25 the racket, after it has been taken from the mould, is
time-consuming .
In order to avoid these time-consuming operations, one
has already tried to make rackets with a discontinuous,
30 randomly orientated short fibre reinforcement in a
thermoplastic matrix, among others as described in EP-A-
O. 188 . 127 .
The complete racket is hereby made in one piece by means
W0 95l321)29 2 ~ q ~3 5 3 3 ~ 6
of ~n injection technique. However, a seriou6
disadvantage of this method is that the short f ibre-
reinforced composite in the racket head relaxes because
of its viscoelastic behaviour under the influence of the
5 constantly working prestressing forces of the strings.
Thus, the permitted prestress and the size of the string
surface are rather limited in such rackets. The
structural damping of the rackets, however, is
considerably larger than that of rackets with a
continuously orientated fibre reinforcement.
~ore recently, one has tried to make complete rackets
with continuously orientated fibre reinforcement in a
thermoplastic matrix, as described for example in
W092/12847. 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
a~d reinforcement fibres, or by reinforcement fibres
powdered with plastic. This thermoplastic matrix saves
efforts during the finishing, because the surface quality
o~ 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 crder to obtain a large force of impact and
precision during the game.
. .
2 11~5~
-- 4
To this aim, said first part i9 made of thermoplastic
material reinforced with continuous fibres and/or bundles
of fibres which extend according to ordened orientations,
while the second part is made of thermoplastic material
reinforced with discontinuous, randomly orientated fibres
and/or bundles of fibres
AMENDED SHtR
21~ 3~
. ~ .. ...
4~ 1
h i c ~; m t ~ nV~n~ j on ccnc~rn o ~ ~ck~t con ~ ~ 6t,~g
of, on the one hand, a frame formed of a head and,y~rip,
whereby this frame is mainly made of compos~material
and, on the other hand, strings provi,~in the head,
5 characterized in that the frame ma~y consists of two
parts, a first part which com~s at least a part of
the head and which is ma,~of thermoplastic material
reinforced with cont~us fibres and/or bundles of
fibres which exte~/ccording to specific orientations,
10 and a secon,s~part respectively which is made of
thermopl~c material which is reinforced with
d~inuous, randomly orien~ated fibres and/or bundles
o f;hr~c
15 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.
20 Said two parts will preferably overlap over at least
three centimetres and at the most up to the free end of
the grip .
Further, also a new production techLique is suggested to
25 produce such a racket. As opposed to already existing
techniques, this technique makes use of a major physical
quality of thermoplastic composites, namely that the
matrix or in other words the thermoplastic material can
be re-melted by adding heat without its chemical
30 qualities changing.
Also, the inventio~ concerns a method for making the
above-mentioned racket, characterized in that it mainly
consists i~ forming at least two U-shaped profile halves
AMENDED SHEET
-~ ~ `21q~533` ''
made of thermoplastic material which i5 reinforced with
discontinuous, randomly orientated fibres a~d/or bundles
of fibres; in forming a thimble-shaped element made of
thermoplastic material which is reinforced with
5 continuous fibres andlor bundles of fibres which extend
according to lipocific 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
10 to be put under pressure; in applying the flexible hose
with the thimble-shaped element around it i~ 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
15 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 and the overlapping part of the
thimble-shaped element can be enclosed between the two U-
20 shaped profile halves; in closing the production mould;in putting the above-mentioned f lexible hose under
pressure and simultaneously heating the production mould,
such that the above-mentioned thermoplastic material
melts, such that both U-shaped profile halves and the
25 thimble-shaped element are melted to one piece; in
interrupting the heat and pressure supply after a while;
in taking the thus formed frame, after the production
mould has cooled off to a temperature at which the
thermoplasti~ material has congealed again, out of the
30 mould; in providing strings.
In order to better explain the characteristics o the
invention, the following preferred . on~ ts are
described, as an example only without bei~g limitative in
~ME~IDE~ S~t'T
wo g~l32029 r~,D,
any way, with reference to the accompanyinq drawings in
which:
figure 1 schematically represents a racket according
~o the invention;
figures 2 to 4 schematically represent three
variants of a racket according to the invention;
figure 5 shows a 6ection 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;
f igure 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 XI I -XI I respectively in f igure 8 to a larger
scale;
figure 13 shows yet another part o$ a racket
according to the invention, which is meant to be
combined with the part of f igure 8;
figures 14 to 16 show sections of lines XIV-XIV to
XVI-XVI in figure 13 to a larger scale;
figure 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 f ormed are laid
down;
figures 20 to 22 show sections of lines XX-XX to
XXII-XXII respectively in figure 19 to a larger
scale .
As represented in figure 1, the invention concerns a
racket 1 consisting of, on the one hand, a frame 2 formed
21 ~3~
W095l320z9 r~l,
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 i~ the head 3.
5 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 ~he head 3 and which is m~de of
thermoplastic material reinforced with continuous bundles
of fibres which extend according to specific
10 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 bundle~
of f ibres .
The parts 6 and 7 are indicated schematically in that
they are hatched in opposite directions.
Preferably, the parts 6 and 7 overlap at least over a
20 certain distance, so that an overlap zone 8 is formed.
This Dverlap zone is at least 3 centimetres according to
a perpendicular projection on the longitudinal axis 9 of
the racket 1, and reaches ~srir-l ly to the free end 10 of
the grip 4. The overlap zones 8 on either side of the
25 head 3 are preferably situated symmetrically in relation
to the longitudinal axis 9.
In any case, the second part 7, irrespective of the size
of the overlap zone 8, pref erably entirely covers the
30 L~ -in;n~ part of the frame 2 next to the first part 6.
Figure l shows a configuration with a short overlap zone
8 . According to f igure 2, however, the overlap zone 8
extends to the free end lO of the grip 4.
W095132029 2 1 ~ a 533 r.~
.
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
5 according to the perpendicular pro j ection 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 f igures 1 and 2, in other words the
10 length L1 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
15 the longitudinal axis 9.
In the case where 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
20 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
reinfoL. 1 piece 14 and the two arms 12 and 13 come
together. Also, figure 4 shows a variant in which the
25 second part 7 runs on right past the place where the arms
12 and 13 ~oin the reinforcement piece 14.
In figures 1 to 4, the frame 2 is each time completely
hatched to clearly show the fields over which the parts
30 6 and 7 extend.
In reality, however, 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
21 90533
wogsl3~029 P~~ /ac
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
5 respectively.
In the case where the reinforcement piece 14 is al60 made
of composite material, this is preferably solid.
According to a variant, it can also be made of another
10 material, f or 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
15 method.
The second part 7 has randomly orientated reinforcement
fibres with a length which can vary from 0.1 mm to 15 cm.
~he length of the f ibres can hereby vary f rom one f ibre
20 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 cross section of the above-mentioned reinforcement
25 fibres, both of the first part 6 and of the second part
7, preferably amounts to 3 to 20 micrometers. The volume
of reinforcement fibres amounts to between 209~ and 8096 of
the total composite material volume.
30 The reinforcement fibres are preferably carbon fibres,
but also other fibre sorts are possible, such as glass
fibres or aramid fibres.
Preferably, the above-mentioned racket 1 is made
W0 9S~32029 ~ 1 ~ 0 5 3 3 P.~ ,C
according tQ the new method described in the
introduction, which will be explained in further detail
hereafter by means of figures 8 to 22.
5 ~ccording to this new method, 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
10 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
15 16 will usually have shapes as represented in figures 9
to 12 and 14 to 16. }3asically, the parts which will form
the arms 12 and 13 and the head 3 are elliptic, whereas
the parts which are meant to f orm 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
25 as the rest of the second part 7 and in this case has a
solid cross section.
The prof ile halves 15 and 16 can be made in dif f erent
ways. According to a first possibility, this can be done
30 by means of an injection techni~ue. In this case, the
length of the reinforcement fibres is preferably O.1 to
S mm, as such short fibres allow for a smooth injection.
According to another possibility, use can be made of what
wo 9sl3202~ P~ l l Dr7 c~ 9 ~ 5 3 3
.
11
i8 called a thermoforming production techni~ue or a Sheet
Moulding Compound (SMC) production technique. In this
case, also longer, randomly orientated reinforcement
fibres can be used, with a length which may vary between
5 0.1 mm and over 10 cm.
.
Moreover, as repre5ented in figures 17 and 18, a thimble-
6haped element 17 is made of thermoplastic material which
is reinforced with continuously orientated reinforcement
10 fibres or bundles of fibres. These reinforcement fibres
are sùrrounded with the matrix material in dif f erent
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
15 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 .
20 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
25 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.
30 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.
21 90533 --
wo 9sl32a29 12 . ~I/DI ~ C
Subsequently, the whole is assembled in a mould. This is
illustrated by means of figure l9, which represents a
mould half 21.
5 As represented in figure 19, 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
10 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
15 pieces 19 and 20, can be reached outside the mould.
In a following stage, which is no longer represented in
figure 19, but which can be derived from figures 20 to
22, the second profile half 16 is provided on the first
profile half 15, such that the part of the flexible hose
20 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
25 symmetrically.
Subsequently, 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
30 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.
~ 9~5~
Wo gsl32029 13 r~
At this stage, 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 viscou6, and a mutual
5 fusion and/or adhesion has been obtained. On the one
hand, 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
10 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
15 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.
The heating can for example be provided for by means of
20 electrical heating elements 27.
It is cleaf that, under the inf luence of heat and
pressure, the parts 6 and 7 will consolidate entirely and
assume the inner shape of the mould.
Subsequently, the heat supply is stopped and the mould is
cooled off for a sufficient length of time, whereby the
pressure can still be maintained for a while, until the
thermoplastic material has stiffened.
When the thermoplastic material has congealed, the mould
can be opened and the formed frame can be removed from
it .
2 1 ~33
w0 9sl32029 ~ r.
14
It is clear that this frame can be further finished, such
as sanded and/or painted or such, and 6ubsequently can be
provided with the strings 5. It is also clear that the
grip 4 can be wrapped around or provided with another
5 covering.
~he present invention is by no means limited to the
embodiments described by way of example and represented
in the accompanying f igures; on the contrary, such a
1~ racket and the above-mentioned method can be made in all
sorts of variants while still l. inin~ within the scope
of the invention.
