[0001] The present invention is related to composite sheet naterial, particularly a thermoset
resin impregnated fiber reinforced plastics skin for a wooden racket.
[0002] It is well known that the playing characteristics
3f a game racket such as a tennis racket, including the design and the material from
which the frame of the racket is constructed, for example, a tennis racket which is
constructed with a wooden frame has good torsional stiffness characteristics enabling
the player to maintain touch control during strong play, especially when the ball
is hit off- center. On the other hand, metal rackets generally have better bending
stiffness characteristics than wood rackets, thereby enabling the player to hit the
ball with a considerable degree of power and often without feeling the vibrational
stress. Thus, in the past, the choice of a racket having a metal frame required the
player to sacrifice the torsional characteristics of wood rackets while the choice
of a racket having a wood frame meant the loss of the better bending characteristics
of the metal rackets. It has been attempted to bond a fiber reinforced plastics skin
on each of the opposing faces of the wooden frame to combine the best properties of
wood and metal racket.
[0003] A conventional method for manufacturing the fiber reinforced plastics skin is illustrated
in Fig. 1; the fiber reinforced plastics skin 10 is formed by press punching a cured
fiber sheet according to the outline of the wooden frame. Then, the respective fiber
reinforced plastics skin is adhered to the surface of the wooden frame. It is no doubt
that some reinforcement might be achieved in this way. Yet inherent effect possessed
by the reinforced material is not completely manifested. Further it is not economical
to adhere same thickness of the fiber reinforced plastics skin to each portion of
the racket frame. Another drawback is that since before tailoring the reinforced fiber
sheet has been cured so that the orientation of the fiber has been - fixed and can
not be pre-arranged to meet the desired angle. Besides, after press punching, very
high percentage of the precured reinforcing fiber sheet will be left unused, hence
increasing the production cost.
[0004] In accordance with the present invention a method for manufacturing a thermoset resin
impregnated fiber reinforced plastics skin for a wooden racket comprises steps of:
tailoring a first uncured thermoset resin impregnated fiber sheet with the fiber thereof
being arranged in cross-ply pattern, each- fiber oriented at an angle ranging from
+ 25° - + 45
0 with respect to a longitudinal axis of a racket, into the flat shape of respective
portion of the racket; tailoring a second uncured thermoset resin impregnated fiber
sheets with the fiber thereof being arranged in cross-ply pattern, each- fiber oriented
at an angle ranging from 0° + 90° with respect to the longitudinal axis of the racket,
to the proper portion of the first fiber sheet; and bending the first tailored fiber
sheet with the second tailored fiber sheet. by curing to form a predesigned laminated
racket reinforced plastics skin.
[0005] It is an object of the present invention to provide a method for producing a fiber
laminate for reinforcing a wooden racket, in which each fiber of the fiber laminate
has definite orientation to manifest the effect of reinforcement.
[0006] Another object of the present invention is to provide a method for producing a fiber
laminate, in which before tailoring to adapt to the shape of the frame, the resin
impregnated.fiber is not yet cured so that the resin impregnated fiber sheet is very
easily and economically cut and laminated to the mold.
[0007] These and other objects will be apparent by illustrating a preferred embodiment with
reference to the following drawings, in which:
Fig. 1 is a schematic view illustrating a prior method for manufacturing fiber reinforced
layer for racket frame;
Fig. 2 is a schematic elevational view of a preferred embodiment manufactured by a
method according to the present invention; and
Fig. 3 is a schematically exploded view illustrating respective layer of a fiber laminate
produced by a method according to the present invention.
[0008] As shown in Fig. 2, when starting to manufacture a fiber laminate, a first uncured
thermoset resin impregnated carbon fiber sheet 26 is firstly tailored into a semi-annular
shaped layer 23 and a substantially Y-shaped layer 22 which includes a throat portion
and a shaft portion corresponding to the respective portion of a wooden racket frame.
Each fiber of the semi-annular shaped layer 23 is arranged in cross-ply pattern and
the orientation of each fiber is at an angle ranging from ± 25° ± 45
0, with respect to a longitudinal axis of a racket. The orientation of the - fiber
of the Y-shaped layer 22 is identical to that of the semi-annular shaped layer 23
and the fibers of both layers are overlapped at their juncture24. Thereafter, several
uncured resin impregnated carbon fiber strips 25 with different length which have
their fiber oriented at an angle ranging from 0° - 90°, with respect to the longitudinal
axis of the wooden racket, are separately adhered to the necessary part of the surface
of the Y-shaped layer 22 and the semi-annular shaped layer 23.. Since each layer is
an as yet uncured resin impregnated carbon fiber sheet, the number of layers of the
laminate can be varied to cater to the need, and the center of gravity of the whole
frame-can be adjusted by means of adding additional weight to the Y-shaped layer 22
or to the same annular shaped layer 23. Additionally, the throat portion which is
most commonly subjected to the largest impact, can be reinforced by a further layer
of strip-shaped carbon fiber sheet to meet this need. Finally, placing the uncured
laminate in the mold cavity 21 of the lower mold 20 and subsequently a upper mold
thereupon with heat treatment together with applying pressure, a unique pre-designed
laminated racket reinforcing sheet is then formed.
[0009] With the invention thus explained, it is apparent that various modifications might
be made within the spirit of the scope of the invention, it is intended that the invention
be defined only as indicated in the appended claims.
1. A method for manufacturing a thermoset resin impregnated fiber reinforced plastics
skin for a wooden racket including, the steps of tailoring a first thermoset resin
impregnated fiber sheet(26) with the fiber thereof being arranged in cross-ply pattern
and oriented at first predetermined angles, tailoring a second thermoset resin impregnated
fiber sheet(25)with the fiber thereof being arranged in cross-ply pattern and oriented
at second predetermined angles, and bonding the first and second tailored fiber sheets(25,
26)characterized in that either said first and second resin impregnated fiber sheet(25,
26) is tailored before the resin is cured ; said first and second tailored resin impregnated
fiber sheets are laminated and cured in a mold(20).
2. A method as claimed in Claim 1, wherein said first and second tailored resin impregnated
fiber sheets (25, 26) are laminated in alternate layers.
3. A method as claimed in Claim 1, wherein said first . predetermined angles ranges
from ±25° to ±45° and'said second predetermined angles ranges from O° to ± 90°.
4. A method of manufacturing a wooden racket of the kind including the step of bonding
a shaped skin of fibre reinforced plastics to the wooden frame of the racket to improve
its characteristics, characterised in that the shaped skin is formed by the steps
of tailoring to the shape of the racket a first uncured fibre impregnated thermosettable
resin sheet (26) with the fibres thereof arranged in cross-ply array and oriented
at first predetermined angles, tailoring to the shape of the racket a second uncured
fibre impregnated thermosettable resin sheet (25) with the fibres thereof arranged
in cross-ply array and oriented at second predetermined angles, bonding together the
first and second uncured sheets (25,26), and curing the bonded sheets in a mould (20)
to form a laminated shaped skin.
