Note: Descriptions are shown in the official language in which they were submitted.
~IrTI-101) c)~ E'l'ODUC_[i~G A P~CKI~T ~T~
F~CKGROIJND ()~ Tl-lE :LNVENTI()N
'I'his invention relates to a methocl of produc:ing a
racket frame in which a fiber r.e-inforced thermosetting resin
is molded into a racket frame.
Composite racket frames generally include a she]l
made of a plurality of layers of thermorsetting resin-
impregnated woven glass fibers or graphite fibers and a foam
core intimately bonding with the shell. During the processing
of such composite structure it usually need an internal
pressure to fo ce the shell to closely contact with the inner
wall of the mold cavity to take the shape thereof. There
are two met:hods of generating a sufficient internal pressure,
i.e. direct method (blow molding) and indirect method (foam
molding~. In the first: method the shell side -;s orced by
the compressecl air to closely contact with the inner wall
of the mold cavity to take a predetermined shape. The holloTi7
central portion is then provided with a foamable thermoplastic
composition which will then be foamed and cured therein by
heating. This additional step may incur further expenses
during processing.
In the second method, a plurality of resin-
impregnated woven`fibers layers are wrapped around a foamab]e
core composition and then put into a mold cavity for molding.
When heating the foaming agent activates the core composition
to generate a pressure to produce a desired molded shape
after curing. Although the latter method is more simpler
than the former one, the temperature Eor gelling and curing
the resin-impregna-ted fibers and for foarning the thermoplastic
resin are not -the same. Therefore the pressure generated
are not controllable and the resin from the core may pene~
trate into the shell layers, thereby destroying the orien-
tation of the fiber as well as the reinforcement thereof.
According -to the present invention there is pro-
vided a method for making a racket rrame comprising: the
steps of preparing two elongated strip members eachincluding
two racket handle portions and a racket head portion inter-
mediate said racket handle portions and defining an elongatedmold cavity section extending throughout its length, placing
a thermosetting resin composition and fibres for reinforcing
into the mold cavity sections, bringing said two s-trip mem-
bers together in face-to-face relation with the mold cavity
sections thereof in opposing relation to each other to form
a structural member defining an elongated mold cavity contain-
ing said thermoset-ting resin composi-tion and fibres, bending
said strip members to form a shape of a racket frame, curing
said thermose-tting resin composition, and removing the strip
members which comprise said structural member after curing.
The structural member may have its cross-section
in I-shape, concave lens shape or in the shape having a
notch like part. The fibers used may be carbon fiber,
glass fiber, boron fiber, kever or other reinforcing mater-
ials.
The removal of strip members from the formed
frame can be done either by grinding or by the use of a
mold releasing agent.
Desirably the strip members comprise flexible
members and said method includes the additional step of
- 2 -
placiny the structural member in a Fitt-ing.
Thus the present invention provides a method which
is applied for producing a fiber reinforced solid racket
frame with no internal pressure to be provided during mold-
ing so as to take the shape o-f the mold.
The present inven-tion will be fur-ther illus-tra-ted
by way o-F the accompanying drawings, in which:-
Fig. 1 is a perspective view o-F a racke-t frame
according to the present invention;
Fig. 2a is a perspective view of a flexible strip
member accor~ing to the invention;
Fig. 2b is a perspective view o-F a s-trip member
filled with a mold compound;
Fig. 2c is a cross-section of two abu-tted strip
members;
Fig. 2d is a plan view of a racket frarne;
Fig. 2e is a cross-section oF a racke-t frame in
a first embodimen-t according to -the invention;
Fig. 3 is a cross-section of a racke-t frame in a
second embodiment according -to the present invention;
Fig. ~ is a cross-section of a racket frame in a
third embodiment of the invention; and
Fig. 5 is a cross-section of a racket frame in a
fourth embodiment of the invention.
3i~3
As shown in Figs. I and 2 a racket frallle IU accord-
ing to the invent-ion is made oF a thermosetting resin rein-
forced with -fibers, such as carbon Fiber, ylass fibers,
- 3a -
i`:; k e~ f f~ J
~ bol-on fibers, k~ , eLc., by cast mo:Lding. Mo.Lds used -i.n
chi.s :invention are :Elexible strLp members 11 having a length
running from the handle portion, around the head port:lon and
then `back to the handle portion. Each of these strip members
11 has a mold cavity 13 throughout its length and two mold
cavities aEter bringing together can form a structural member
in the foms, such as I-shape (Fig. 2e), concave lens-Shape,
(Fig. 3), rectangle with one side thereof grooved, (Fig. 4),
rectangle with one side grooved and other side round (Fig.5).
These strip members 11 are used in place of rigid mol'ds which
may incur higher cost of molds fabrication. They are made
of materials such as plastics, wood pulp, paper pulp, wood
bamboo, etc. The plastic strip member can be made by extrusion
or injection molding 7 whereas wood or bamboo can be machined
to obtain a mold cavity.
During processing, the strip members 11 are fill.ed
with the thermosetting resin and fibers 14 and then two strip
members 11 are brought together and bent into a racket frame
shape which is then placed in a fitting for molding.
20 In Fig. 3 two strip members 21 provide a racket
frame 22 with its cross-section in a concave-lens shape. As
shown in Fig. 4 two strip members 31 and 41 provide a frame
having its cross-section in a combined rectangular shape 42
and U-shape 32. In Fig. 5 one strip member 51 has a groove
in U-shape 52 and another strip member 61 has a curved
groove 62. The groove 62 is firstly provided with a layer of
fibers reinforced resin 63 and then filled with a wooden
layer 6~. T~o strip membe~s 51 and 61 are brought t~gether
and bent lnto a racket frame shape.
Aften~ards, the resin is cured at a certain
temperature. After curing the strip members can be removed
by the use of a mold releasing agent or by grinding.
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