Note: Descriptions are shown in the official language in which they were submitted.
CA 02231908 1998-03-12
THERMOPLASTIC POLYMER SHAFT HAVING AN
INTEGRALLY FORMED REINFORCING MEMBER
FOR USE IN GOLF CLUBS AND THE LIKE
SCOPE OF THE INVENTION
The present invention relates to an improved thermoplastic shaft for use
in sports equipment such as a golf club or fishing rod, and more particularly,
a
composite polymer shaft having an integrally formed reinforcing member for
increased rigidity.
BACKGROUND OF THE INVENTION
The use of graphite composites and other carbon polymer fibers to
reinfor~;,e shafts used in sports equipment such as golf clubs and fishing
rods is well
known.. Graphite or carbon polymer shafts (hereinafter collectively also
referred to
as graphite shafts) are being increasingly used in various different types of
sporting
goods ;is they possess both the properties of increased strength and light
weight.
Typically, conventional graphite shafts are formed as an elongated
hollow tube which often is characterized by a marginally tapering
construction.
In the case of golf clubs, the graphite shafts are lighter than
conventional steel golf club shafts. Graphite golf club shafts have been
found,
however, to suffer the disadvantage of a loss in rigidity, particularly where
the shaft
diameter narrows below 1.5 centimeters. Fishing rods which incorporate
graphite
shafts ,also suffer a loss in rigiadity where narrower diameter shafts are
used. To
provide: graphite fishing rods with the desired rigidity near the grip or
handle, it is
known to form the fishing rod shaft so as to have an enlarged diameter of 2.5
centimeters or more at the grip end. In addition to being unsightly and making
the
mounting of the fishing rod grip more complex, the larger diameter of the
shaft
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necessitates the use of additional graphite material, increasing the overall
manufacturing costs of the rod.
SUMMfARY OF THE INVENTION
Accordingly, the: present invention overcomes at least some of the
disadvantages of the prior art by providing a light weight thermoplastic
polymer shaft
which may be used in sports equipment, such as a golf club or fishing rod, and
which
includes an axially positioned reinforcing member to provide at least part of
the shaft
with increased rigidity and structural integrity.
Another object of the invention is to provide an elongated graphite shaft
which, for example, is suitable for use as a golf club shaft or fishing rod
shaft, and
which is reinforced structurally i.n the direction of bend, impact and/or
loading forces.
Another object of the invention is to provide an improved method of
manufacturing a marginally tapering cylindrical graphite shaft, so as to
incorporate
an inte;~rally formed elongate rE~inforcing member.
Another object o1~ the invention is to provide a light weight reinforced
shaft which is made from a thermoplastic material and is suitable for use as
part of
a golf club or fishing rod, and 'which may be formed from a single integral
casting.
The shaft of the present invention is formed as an axially elongated
member for use in sports equipment. The shaft is made from a composite
polymer,
and preferably a thermoplastic carbon polymer such as a graphite composite.
The
shaft is characterized by an outer sidewall having a preferred diameter of
less than
about 2 cm and which extends radially about the axis to define a shaft core.
At least
part of the core is divided into t:wo or more longitudinally extending hollow
or resin
filled cavities by a reinforcing web or member which spans between radially
separate
points along the shaft sidewall.
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The reinforcing member is preferably elongated and extends
longitudinally along the axis at least part way along part of the shaft core.
Most
preferably, the reinforcing member has an I-beam type construction and
includes a
flat web which is joined along each of its longitudinal edge to the sidewall.
The
reinforcing member divides the: core of the shaft most preferably through its
axial
center, although other configurations of reinforcing webs are also possible.
The I-beam is preferably oriented in the shaft so as to increase the shaft
rigidity against bending in the direction of bending, load and/or impact
forces. As
such, in the case of a golf shaft, where an I-beam type reinforcing member is
used,
the reinforcing member is oriented with its lateral width aligned parallel to
the
direction along which the club is swung. The reinforcing member is therefore
preferably aligned perpendicular to the club face and parallel to the club
swing
direction, so as to provide maximum rigidity on ball impact. Similarly, where
the
shaft is to be used on a fishing rod, the lateral width of the reinforcing
member is
oriented in alignment with the direction at which the rod eyelets project from
the
periphery of the ~ shing rod .shaft, thereby providing maximum rigidity in the
direction of load forces.
Preferably, the shaft sidewall has an overall cylindrical exterior profile,
although other configurations such as a hexagonal, octagonal or other
polygonal
profiles are also possible. Although not essential, where the shaft is to be
used as a
golf club or fishing rod shaft, the shaft may taper marginally from one
enlarged
diameter end at the club or rod grip or handle, towards a smaller diameter
remote
end. The reinforcing member need not extend along the entire axial length of
the
shaft. if material costs are to be reduced, the reinforcing member could
extend only
along the part of the shaft which is to be provided with increased rigidity.
For
example, in the case of a fishing rod or golf club, only the twenty to sixty
centimeter
portion of the fishing rod which is adjacent the rod or club handle may be
provided
with the reinforcing member for increased rigidity.
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Accordingly, in cme aspect the present invention resides in an elongated
thermoplastic shaft member for use in sports equipment, the shaft member
including,
a radially extending sidewall defining a substantially open interior core,
and
a reinforcing web having a pair of spaced longitudinally extending
edges, said web spanning said open interior core and being joined along each
of its
edges to said sidewall.
BRIEF DESCRIPTION OF TH:E DRAWINGS
Further objects and advantages of the invention will now appear from
the following description taken together with the accompanying drawings in
which:
Figure 1 is a perspective view of a golf club incorporating a reinforced
shaft in accordance with a preff:rred embodiment of the invention;
Figure 2 is a schematic side view of the golf club shaft shown in
Figure 1;
Figure 3 is an enlarged cross-sectional view of the shaft shown in
Figure 2 taken along lines 3-3';,
Figure 4 shows an enlarged cross-sectional view of the shaft shown in
Figure 1 taken along line 4-4';
Figure 5 shows a perspective view of an inner mold used in the casting
of a shaft in accordance with a preferred embodiment of the invention;
Figure 6 shows a schematic side view of an outer mold casing for use
in conjunction with the inner mold shown in Figure 5; and
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Figure 7 shows a schematic view of the positioning of the inner mold
of Figure 5 positioned within the mold casing of Figure 6 during t he
formation of
a molded shaft in accordance with a second embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows an assembled golf club 4 having a handle or grip 6 and
club head 8 mounted at each end of a golf club shaft 10 in accordance with a
preferred embodiment of the invention. Figures 2 and 3 show best the
construction
of the golf club shaft 10. The shaft 10 consists of a carbon or graphite fiber
reinforced thermoplastic, which as will be described permits its manufacture
by
moldin ~. When the shaft 10 is to be used in the assembled golf club 4 (Figure
1),
the shaFt 10 has a generally cylindrical construction and preferably tapers at
an angle
of between about 3 to 15 ° from an enlarged diameter end 12 having a
preferred
diameter of between about 1.5 to 2 cm to a smaller reduced diameter end 14,
having
a diameter of about 3/4 to 1-114 cm. The shaft is elongated along its
longitudinal
axis A-A, (Figure 2), and depending on the particular golf club 4, will have a
length
of between about 1 to 1.4 meters. In assembly of the completed golf club 4 of
Figure
l, the golf club grip 6 is fitted over the portion of the shaft 10 adjacent
the enlarged
diametf:r end 12, and the club head 8 is mounted to the reduced diameter end
14.
Figure 3 shows best the shaft 10 as including an outer sidewall 20
which extends radially about thc: club axis A-A,. The outer sidewall 20 is
generally
cylindrical in shape and defines a substantially hollow core 22. A reinforcing
web
24 is integrally formed with the sidewall 20. The reinforcing web 24 is
provided in
an I-beam type configuration and consists of a thin planar member 28 extending
laterall_~ from a first longitudinal edge 30a joined along a first portion of
the sidewall
20 to longitudinal edge 30b joined along a second radially opposite portion of
the
sidewall 22. The web 24 has a lateral width W from edge 30a to edge 30b which
is
selected equal to the inner diarr~eter of the sidewall 22 so that the member
28 spans
across the shaft core 22. FigurE~ 2 shows the web 24 as extending
longitudinally the
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entire length of the shaft 10 from end 12 to end 14 with the planar member 28
extending through the axial center A, of the shaft 10. The web 24 thus divides
the
interior core 22 of the shaft 10 into two symmetrically disposed semi-circular
cavities
26a,26b.
To provide the shaft 10 with sufficient strength, the sidewall 20 and
planar member 28 preferably each have a thickness selected at between about 1
to 2
mm. It: is to be appreciated, however, that the sidewall 20 and/or web 24
thicknesses
may vary along their longitudinal length, or other thicknesses could be used
depending upon the intended function of the shaft 10.
Figure 4 shows best the cutaway end view of the golf club 4 shown in
Figure 1 taken through the shaft: 10. Figure 4 shows the golf club head 8
mounted to
the end 14 of the shaft 10. Thf~ shaft 10 is oriented so that the lateral
width of the
planar member 28 is parallel to the path along which the club 4 is swung, as
represented by arrow 32, and which is also perpendicular to the leading edge
34 of
the club head 8. It is to be appreciated, that with this orientation, the
reinforcing web
24 provides the shaft 10 with .enhanced rigidity in the direction of impact
forces.
Further, because the core 22 is substantially hollow, except for the
reinforcing web
24, the reinforcing web 24 does not add any appreciable increased weight or
material
cost to the finished golf club 4.
Figures 5 to 7 show a preferred mold assembly 36 (Figure 7) used in
the production of a thermoplastic shaft, having a construction to that shown
in Figure
1. The mold assembly 36 shown in Figure 7 would produce a shaft having a more
pronounced taper than that shown in Figure 1, and which, for example, could be
used
as the handle or stock portion of a fishing rod.
The mold assembly 36 consists of an inner mold 38 shown in Figure
5 and an outer mold casing 40 shown in Figure 6. The inner mold 38 is
characterized by a pair of projecting fins 42a,42b, each having a
complementary
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shape a.nd spacing to corresponding cavities 26a,26b to be formed in the
resulting
shaft, and a base 44. The fins 42a,42b are fixedly mounted to the base 44 so
as to
taper upwardly therefrom to a respective endmost tip 45a,45b.
Figure 6 shows the outer mold casing 40 as including a right casing
member 46 and a left casing member 48 which are adapted for movement into and
out of abutting contact. It is to be appreciated that the inner wall 49 of
each casing
member 46,48 is configured to provide the desired overall exterior shape and
taper
to the finished shaft. A pair of mating guide elements 50a,50b are provided in
the
top peripheral edge of each casing member 46,48. The guide elements 50a,50b
are
configured to move between the endmost tips 45a,45b of the fins 42a,42b to
assist in
the alignment of the casing members 46,48 as they are brought together.
Figure 7 shows the mold assembly 36 with the outer mold casing 40
assembled over the fins 42a,42b. The casing members 46,48 are preferably
coupled
to the mounting base 44 by a respective hinge 52a, 52b enabling their pivoting
movement together and apart in the direction of arrows 53.
With the outer casing members 46,48 joined together over the inner
mold fins 42a,42b in the position shown in Figure 7, the thermoplastic melt is
injected into the mold cavity 54 which is defined by the spacing between each
of the
fins 42a,42b, and that between the fins 42a,42b and the inner walls 49 of the
adjacent
casing members 46,48. After the thermoplastic has been injected and then
permitted
to cool in the mold 36, the casing halves 46,48 are swung apart on their
respective
hinges 52a,52b, and the cooled shaft is then lifted axially off of the inner
mold fins
42a,42b. A knock-out plug 56 ;Figure 7) may be fitted in a bore formed through
the
base 44~ between the fins 42a,42b. The knock-out plug 56 may be used to apply
an
axial force on the cooled shaft: to assist in its removal from the inner mold
fins
42a,42b.
While Figure 2 shows the reinforcing web 24 as extending along the
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entire length of the shaft 10, the invention is not so limited. If desired,
the golf club
shaft 10 could be formed so that the reinforcing web 24 extends only partway
along
its length. For example, the reinforcing web 24 could be provided only along
the
part of the shaft 10 immediately adjacent the grip 6. In this configuration,
the web
24 is provided where maximum shaft rigidity is required, and omitted from the
lower
part of the shaft 10 where increased flexibility may be desired.
Figure 1 shows the shaft 10 as tapering towards the shaft end 14. It
is to be appreciated that although preferred, it is not necessary that the
shaft 10 taper
at the approximate angle shown, or for that matter at all.
Although the preferred embodiment of the invention discloses a
reinforcing web 24 having a generally I-beam type configuration, the invention
is not
so limil:ed. If desired, the reinforcing web could be of an open diamond, V,
X, Y
or W shaped construction without departing from the scope and spirit of the
invention.
While Figures 1 to 4 disclose the use of the shaft 10 as part of a golf
club 4, the invention is not so limited. The shaft could equally be used in
other
sports equipment where an elongated lightweight member is required, including
by
way of non-limiting examples, as part of a fishing rod or in the handle
portion of a
tennis or squash racquet.
Although Figures 2 and 3 show the shaft 10 as having a pair of
symmevtrical open cavities 26a, 26b, the invention is not so limited. If
desired, the
cavities could be infilled with a resin to provide the shaft 10 with still
increased
rigidity.
Although the detailed description of the invention describes and
illustrates various preferred embodiments, the invention is not so limited.
Many
modifications and variations will now appear to those skilled in the art. For
a more
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precise definition of the invention, reference may be had to the appended
claims.
