U.S. patent application number 10/042541 was filed with the patent office on 2002-10-24 for golf club shaft having wave shaped reinforced part.
Invention is credited to Ryu, Suk-Ho.
Application Number | 20020155899 10/042541 |
Document ID | / |
Family ID | 27573798 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020155899 |
Kind Code |
A1 |
Ryu, Suk-Ho |
October 24, 2002 |
Golf club shaft having wave shaped reinforced part
Abstract
The present invention relates to a golf club shaft having
improved torsion characteristics comprising a base shaft having an
internal surface and an external surface, and at least one wave
shaped reinforced part on at least one of said surfaces, said wave
shaped reinforced part comprising a plurality of reinforcement
pieces. The wave shaped reinforced part is located on at least one
of the upper portion, midpoint or lower portion. The golf club
shafts of the present invention can be made by applying a base
section of a prepreg sheet or assembly having a plurality of finger
like elements to a portion of a base shaft, wrapping the finger
like elements around the base shaft to provide a wave shaped
reinforced part having a plurality of reinforcement pieces, and
curing the shaft having the wave shaped reinforced part thereon to
produce a golf club shaft having a wave shaped reinforced part.
Golf clubs made with the shafts of the present invention impart
greater flying distance and/or directional accuracy to golf balls
struck by the golf clubs. The wave shaped reinforced part provides
a means of moving the kick point of the shaft to achieve a desired
effect on flying distance and/or accuracy. The present invention
provides a convenient means of adjusting the characteristics of a
golf club shaft according to the skill level of the intended
user.
Inventors: |
Ryu, Suk-Ho; (Seoul,
KR) |
Correspondence
Address: |
Maria Parrish Tungol
Suite 500
2231 Crystal Drive
Arlington
VA
22202
US
|
Family ID: |
27573798 |
Appl. No.: |
10/042541 |
Filed: |
October 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10042541 |
Oct 19, 2001 |
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09472219 |
Dec 27, 1999 |
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09472219 |
Dec 27, 1999 |
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08896722 |
Jul 18, 1997 |
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09472219 |
Dec 27, 1999 |
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29061700 |
Oct 29, 1996 |
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D401981 |
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09472219 |
Dec 27, 1999 |
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08760079 |
Dec 4, 1996 |
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60047697 |
May 23, 1997 |
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Current U.S.
Class: |
473/316 ;
473/318 |
Current CPC
Class: |
A63B 60/00 20151001;
A63B 60/06 20151001; A63B 53/12 20130101; A63B 60/48 20151001; A63B
60/08 20151001; A63B 2209/023 20130101; A63B 53/10 20130101; A63B
60/14 20151001; A63B 60/10 20151001 |
Class at
Publication: |
473/316 ;
473/318 |
International
Class: |
A63B 053/10; A63B
053/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 1996 |
KR |
96-17367 |
Nov 28, 1996 |
KR |
96-58614 |
Dec 24, 1996 |
KR |
96-27842 |
Claims
What is claimed is:
1. A golf club shaft comprising a base shaft having an internal
surface and an external surface, and at least one wave shaped
reinforced part on at least one of said surfaces, said wave shaped
reinforced part comprising a plurality of reinforcement pieces.
2. The golf club shaft of claim 1 wherein said golf club shaft
includes an upper portion, a midpoint m, and a lower portion, said
wave shaped reinforced part located on at least one of said upper
portion, said midpoint m, and said lower portion.
3. The golf club shaft of claim 2 wherein said wave shaped
reinforced part is located on said upper portion.
4. The golf club shaft of claim 2 wherein said wave shaped
reinforced part is located on said lower portion.
5. The golf club shaft claim 2 wherein said wave shaped reinforced
part is located on said midpoint m.
6. The golf club shaft of claim 1 wherein said plurality of
reinforcement pieces is at least three reinforcement pieces.
7. The golf club shaft of claim 6 wherein said wave shaped
reinforced part is on said external surface of said base shaft.
8. The golf club shaft of claim 7 wherein said wave shaped
reinforced part has a length of about 2 cm to about 20 cm.
9. The golf club shaft of claim 8 wherein said wave shaped
reinforced part has a sinusoidal configuration.
10. The golf club shaft of claim 1 wherein said reinforcement
pieces comprise a carbon fiber prepreg sheet and a glass fiber
prepreg sheet.
11. A golf club shaft having an external surface, comprising a base
shaft having a tip end for receiving a club head and a grip end for
receiving a grip, and a wave shaped reinforced part on said
external surface of said base shaft, wherein said wave shaped
reinforced part has a length of about 20 cm and includes at least 3
reinforcement pieces, said wave shaped reinforced part having a
sinusoidal configuration, and wherein said reinforcement pieces
comprise carbon fiber prepreg.
12. The golf club shaft of claim 11 wherein said waved shaped
reinforced part has at least 5 reinforcement pieces.
13. The golf club shaft of claim 11 wherein said reinforced part is
located on said upper portion.
14. The golf club shaft of claim 11 wherein said base shaft has a
length of about 1143 mm and a kickpoint located at about 44 cm from
said tip end of said base shaft.
15. The golf club shaft of claim 11 wherein said reinforcement
pieces further comprise glass fiber prepreg.
16. A method of making a golf club shaft having a base shaft and a
wave shaped reinforced part thereon comprising, applying a base
section 2B of a prepreg sheet having a plurality of finger like
elements 2A to a portion of a base shaft, wrapping said finger like
elements 2A around said base shaft to provide a wave shaped
reinforced part having a plurality of reinforcement pieces on said
base shaft, and curing said shaft having said wave shaped
reinforced part thereon to produce a golf club shaft having a wave
shaped reinforced part thereon.
17. The method of claim 16 wherein said wave shaped reinforced part
comprises at least 3 reinforced pieces.
18. The method of claim 16 wherein said base shaft has an upper
portion, a midpoint m, and a lower portion, and wherein said wave
shaped reinforced part is located on at least one of said upper
portion, said midpoint m, and said lower portion.
19. The method of claim 16 wherein said prepreg sheet comprises a
carbon fiber prepreg sheet.
20. The method of claim 16 wherein said prepreg sheet comprises a
glass fiber prepreg sheet joined to a carbon fiber prepreg
sheet.
21. A golf club comprising a golf club shaft comprising a base
shaft having an internal surface and an external surface, and at
least one wave shaped reinforced part on at least one of said
surfaces, said wave shaped reinforced part comprising a plurality
of reinforcement pieces.
22. The golf club of claim 21 wherein said golf club shaft includes
an upper portion, a midpoint m, and a lower portion, said wave
shaped reinforced part located on at least one of said upper
portion, said midpoint m, and said lower portion.
23. The golf club of claim 22 wherein said wave shaped reinforced
part is located on said upper portion.
24. The golf club of claim 22 wherein said wave shaped reinforced
part is located on said lower portion.
25. The golf club claim 22 wherein said wave shaped reinforced part
is located on said midpoint m.
26. The golf club of claim 21 wherein said plurality of
reinforcement pieces is at least three reinforcement pieces.
27. The golf club of claim 26 wherein said wave shaped reinforced
part is on said external surface of said tubular shaft member.
28. The golf club of claim 22 wherein said wave shaped reinforced
part has a length of about 2 cm to about 15 cm.
29. The golf club of claim 28 wherein said wave shaped reinforced
part has a sinusoidal configuration.
30. The golf club of claim 21 wherein said reinforcement pieces
comprise a carbon fiber prepreg sheet and a glass fiber prepreg
sheet.
Description
[0001] This application is a continuation of Ser. No. 09/472,219
filed on Oct. 26, 1999 which is a continuation of Ser. No.
08/896,722 filed on Jul. 18, 1997, now abandoned which was a
continuation-in-part of Ser. No. 29/061,700 filed on Oct. 29, 1996,
now U.S. D No. 401,981 and Ser. No. 08/760,079 filed on Dec. 4,
1996, now abandoned. This application claims the benefit of U.S.
Provisional Application No. 60/047,697 filed on May 23, 1997.
BACKGROUND OF THE INVENTION
[0002] Since a carbon (graphite) shaft is lighter than a
conventional steel shaft, the head speed of a golf club while
swinging is increased, thus increasing the flying distance of a
ball struck by the golf club. However, a graphite shaft has a
disadvantage in that its torsion characteristics are poor. If the
torsion characteristics of the shaft are poor, the sweet spot of
the club head typically does not strike the ball during impact.
When the ball is impacted by areas of the club head other than the
sweet spot, the direction of the ball in flight is not exact.
[0003] According to conventional methods for improving torsion
characteristics of a shaft, first, the fiber orientation (angle
formed by the axis of the shaft with the textile tissue of carbon
fiber within prepreg sheet) of torsion layer should be
.+-.45.degree. and the prepreg sheets are used for rolling the
shaft several times; however, this method has disadvantages in that
flex strength is significantly reduced and the weight of the shaft
is increased, even though torsion characteristics are improved.
[0004] Second, steel or aluminum alloy is installed internally and
on top of it, prepreg sheets are laminated in such a manner that
the textile tissue of carbon fiber (mesh) is at the same position
as the axial direction of the shaft; however, the use of steel-type
internal conduit may be responsible for increasing weight, thus
adversely affecting the light weight of a carbon shaft.
[0005] Meantime, for the improvement of flying distance of a golf
ball, much research has focused on the enhancement of golf club
head shape and material instead of the golf club shaft. However,
the shaft is one of the important factors which influences the
flying distance of a golf ball. The relevant conventional methods
are as follows:
[0006] Korean Patent Open-Laid No. 96-1936 describes a method of
forming the hollow part within the shaft with a hexagon or octagon
but its manufacturing process is very complicated over the enhanced
effects of flying distance.
[0007] Although these methods of the prior art provide shafts which
may be used in golf clubs, these shafts suffer from the
disadvantages described above. A need therefore exists for golf
club shafts and golf clubs which overcome disadvantages such as
those described above.
SUMMARY OF THE INVENTION
[0008] The present invention relates to a golf club shaft
comprising a base shaft having an internal surface and an external
surface, and at least one wave shaped reinforced part on at least
one of the surfaces wherein the wave shaped reinforced part has a
plurality of reinforcement pieces. The wave shaped reinforced part
is located on at least one of the upper portion, midpoint or lower
portion.
[0009] The golf club shafts of the present invention can be made by
applying a base section of a prepreg sheet or assembly having a
plurality of finger like elements to a portion of a base shaft,
wrapping the finger like elements around the base shaft to provide
a wave shaped reinforced part having a plurality of reinforcement
pieces, and curing the shaft having the wave shaped reinforced part
thereon to produce a golf club shaft having a wave shaped
reinforced part thereon.
[0010] Golf clubs made with the golf club shafts having at least
one wave shaped reinforced part impart greater flying distance
and/or directional accuracy to golf balls struck with the golf
clubs. The wave shaped reinforced part improves the torsion
characteristics of the golf club shaft and provides a means of
changing the location of the kick point of the shaft to achieve a
desired effect on flying distance and/or directional accuracy. The
present invention provides a convenient means of adjusting the
characteristics of a golf club shaft according to the skill level
of the intended user.
[0011] Having summarized the invention, the invention will now be
described in detail by reference to the drawings, detailed
description and non-limiting examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a front view of a golf club shaft in accordance
with a first embodiment of the invention in which a wave-shaped
reinforced part is provided at the lower part of the shaft.
[0013] FIG. 2 is a front view of a golf club shaft in accordance
with a second embodiment of the invention in which a wave-shaped
reinforced part is provided at the upper part of the shaft below
the grip end.
[0014] FIG. 3 is a front view of a golf club shaft in accordance
with a third embodiment of the invention in which wave-shaped
reinforced parts are provided at both the lower part and the upper
part of the shaft.
[0015] FIG. 4 is a front view of a golf club shaft in accordance
with a fourth embodiment of the present invention in which a
wave-shaped reinforced part is provided at the middle part of the
shaft.
[0016] FIG. 5 is a front view of a golf club shaft in accordance
with a fifth embodiment of the present invention in which a
wave-shaped reinforced part is provided at a location midway
between the grip end of the shaft and the middle point of the
shaft.
[0017] FIG. 6 is a partial longitudinal sectional view of a portion
of the shaft according to the invention having a wave shaped
reinforcement part that has a sinusoidal configuration.
[0018] FIG. 7 shows frontal views of other possible shapes of waves
of wave shaped reinforcement parts useful in the invention.
[0019] FIG. 8 shows the preparatory state of forming the wave
shaped reinforced part before wrapping finger like elements of the
prepreg sheet around the shaft. The base section of the prepreg
sheet or assembly is attached to the base shaft and the finger like
elements are shown in an extended state.
[0020] FIG. 9 is a perspective view of a section of a reinforced
part of a golf club shaft according to the invention prior to
curing of a wave shaped reinforced part showing some of the finger
like elements of a prepreg sheet wound around the base shaft to
form reinforcement pieces. FIG. 9 also shows some of the finger
like elements-in an extended state prior to winding around the base
shaft.
[0021] FIG. 10 shows shaped reinforcement pieces that are formed by
wrapping the finger like elements of the prepreg sheet around the
shaft. One of the finger like elements is shown in an extended
state to illustrate the effect of forming the finger like elements.
The figure also shows a view of tape that is wrapped around the
reinforcement pieces prior to curing.
[0022] FIG. 11 shows a golf club shaft having a wave shaped
reinforcement part that partially encircles a base shaft.
[0023] FIG. 12 shows a golf club shaft that has rib shaped
reinforcement pieces.
[0024] FIG. 13 shows a golf club shaft having a wave shaped
reinforcement piece on the interior of the shaft.
[0025] FIG. 14 is a frontal view of a golf club made with a first
embodiment of a golf club shaft of the invention in which a
wave-shaped reinforced part is provided at the lower part of the
base shaft above the hosel.
[0026] FIG. 15 is a frontal view of a golf club made with a second
embodiment of a golf club shaft of the invention in which a
wave-shaped reinforced part is provided at the upper part of the
shaft below the grip.
[0027] FIG. 16 is a frontal view of a golf club made with a third
embodiment of a golf club shaft of the invention in which
wave-shaped reinforced parts are provided at both the lower part
and the upper part of the shaft.
[0028] FIG. 17 shows a golf club made with a fourth embodiment of a
golf club shaft of the invention in which a wave-shaped reinforced
part is located at the midpoint of a base shaft.
[0029] FIG. 18 shows a golf club made with a fifth embodiment of a
golf club shaft of the invention in which a wave-shaped reinforced
part is located between the midpoint and the grip end of the
shaft.
DETAILED DESCRIPTION OF THE INVENTION
[0030] FIG. 1 shows a first embodiment of the golf club shaft 25A
of the present invention, in which a wave shaped reinforced part 1
is formed in the lower portion of the golf club shaft. The lower
portion of the shaft that portion between the midpoint of the
entire length of the shaft and the upper edge 12 of the hosel
section. FIG. 1 shows the preferred location a of the reinforced
part near hosel section 15. The wave shaped part 1, however, may be
located at other positions between the upper edge of the hosel
section and the midpoint of the lower portion of the shaft. When
wave shaped reinforced part 1 is provided at location a of base
shaft 5, there is a significant improvement in torsion
characteristics of the golf club shaft.
[0031] The wave shaped reinforced parts of the golf club shafts of
the present invention are made up of reinforcement pieces. In wave
shaped reinforced part 1, the number of reinforcement pieces is 1
to 6 reinforcement pieces, more preferably 1 to 3 reinforcement
pieces. Although a larger number of reinforcement pieces may be
applied to the shaft, it is preferred to use at most 6 pieces to
minimize the possibility that the weight of the golf club shaft may
become excessive and thus reduce the flying distance of the
ball.
[0032] Typically, when the number of reinforcement pieces in wave
shaped reinforced part 1 is 3 pieces, about 10 percent improvement
in torsion characteristics may be expected. As a result, even
though the ball is not hit by the sweet spot of the golf club head
during impact, the ball generally goes in the desired direction and
a bad hook or slice is prevented. Also, when wave-shaped reinforced
part 1 is provided at the lower part a of base shaft 5, the kick
point moves upward.
[0033] The length of wave shaped reinforced part 1 is about 2 cm to
about 15 cm, preferably about 3 cm to about 10 cm.
[0034] FIG. 2 shows a second embodiment of the invention in which a
wave shaped reinforced part 1' is provided in the upper portion of
the golf club shaft. The upper portion of the golf club shaft is
that portion between the midpoint of the entire length of the shaft
and the lower edge of the grip section of the shaft. FIG. 2 shows
the preferred location b of the wave shaped reinforced part near
grip section 22. However, the wave shaped reinforced part 1' may be
located at other positions between the midpoint of the upper
portion of shaft and the lower edge of the grip section. When
wave-shaped reinforced part 1' is provided at location b, the kick
point of golf club shaft 25B moves down, away from the grip end
20.
[0035] The total length of wave shaped reinforced part 1' can range
from about 2 cm to about 20 cm, preferably about 3 cm to 15 cm. In
wave shaped reinforced part 1', the number of reinforcement pieces
is 1 to 7 reinforcement pieces, more preferably 3 to 5
reinforcement pieces. Although a larger number of reinforcement
pieces may be applied to the shaft, it is preferred to use no more
than 7 pieces to minimize the possibility that the weight of the
golf club shaft may become excessive and thus reduce the flying
distance of the ball.
[0036] Generally, if the kick point is located closer to the grip
end of the shaft, the flying distance of the ball is enhanced but
the direction of the ball is less accurate. In addition, it may
become very difficult to make a swing that will produce exact
impact at the point where the force of shaft is maximized, creating
much difficulty for amateur golfers.
[0037] However, since golf club shafts such as the shaft
illustrated in FIG. 2, cause the kick point to move down, the golf
club shafts of the invention overcome the aforementioned
shortcomings so as to make an exact swing and impact much easier
even for amateur golfers. In addition, any loss of flying distance
produced by the move-down of the kick point can be countered by
extending the length of the base shaft 5. The length of base shaft
5 therefore can be increased to cause the kick point of the
resulting golf club shaft to have the same height (from tip 10 of
the shaft) as the original height of the kick point on base shaft 5
prior to forming the wave shaped reinforced part thereon so that
the flying distance of the ball increases.
[0038] Without wishing to be bound by theory, the following Table 1
shows typical percentages of movement of the kick point which may
be expected depending on the number of reinforcement pieces in a
wave shaped reinforced part when applied to location b of a base
shaft.
1TABLE 1 PERCENTAGE OF MOVEMENT OF THE KICK NUMBER OF POINT (the
percent decrease in the height REINFORCEMENT of the kick point
measured from the club PIECES head tip of the shaft) 3 3% 5 5% 7
7%
[0039] Thus, if the height of the kick point of a base shaft
(measured from the club head tip 10) is 15 cm without a wave shaped
reinforced part 1', then forming a wave shaped reinforced part
having 3 reinforcement pieces at the upper part b of the base shaft
moves the kick point "down" to a height 14.5 cm (measured from club
head tip 10). This is a 3% decrease in height from the original
height of the kick point of the base shaft.
[0040] FIG. 3 shows a third embodiment of the invention in which
wave shaped reinforced parts 1 and 1' are located at both the lower
and upper portions of the golf club shaft. FIG. 3 shows the wave
shaped reinforced part at the preferred location a near hosel
section 15 and the preferred location b near grip section 22
respectively of base shaft 5. However, part 1 may be located at
other positions between the midpoint of the lower portion of the
shaft and the upper edge of the hosel section 15. Likewise, part 1'
may be located at other positions between the midpoint of the upper
portion of the shaft and the lower edge of the grip section. When
reinforced parts 1 and 1' are provided at both location a and
location b of the base shaft 5, improvement of ball flight
direction may be expected together with a more convenient and exact
swing.
[0041] In this embodiment, the total number of reinforcement pieces
in wave shaped reinforced parts 1 and 1' is 5 to 7 pieces. The wave
shaped reinforced part 1' located at upper part b preferably has a
larger number of reinforcement pieces than wave shaped reinforced
part 1 located at lower part a. Reinforced part 1 typically has 2
to 3 pieces and a length of about 2 cm to about 8 cm. Wave shaped
reinforced part 1' typically has 4 to 5 pieces and a length of
about 10 cm to about 15 cm.
[0042] When wave shaped reinforced parts 1 and 1' are provided as
described in this embodiment, improvement of ball flight direction
also may be expected together with a more convenient and exact
swing. Also, the direction of the kick point moves down relative to
the kick point of the base shaft.
[0043] FIG. 4 shows a fourth embodiment of the present invention,
in which a wave shaped reinforced part 1A is provided at midpoint m
of the length of the base shaft 5. If the wave shaped reinforced
part 1A is provided at midpoint m, the kick point moves down
relative to the location of the kick point of the base shaft 5.
[0044] In this embodiment, reinforced part 1A typically has 5 to 7
pieces and a length of 2 cm to about 20 cm, preferably about 3 cm
to about 15 cm. When reinforced part 1A is provided at midpoint m
of base shaft 5, improvement of ball flight direction also may be
expected together with a more convenient and exact swing.
[0045] The position of wave shaped reinforced part 1A relative to
midpoint m may vary. For example, wave shaped reinforcement part 1A
may be provided so as to cause wave shaped reinforced part 1A to
extend equally on each side of midpoint m. Wave shaped reinforced
part 1A also can be positioned to have unequal portions thereof
extend on either side of midpoint m.
[0046] FIG. 5 shows a fifth embodiment of the present invention in
which a wave shaped reinforced part 1B is provided midway between
the lower edge of grip section 22 and midpoint m of the base shaft
5. In the golf club shaft shown in FIG. 5, the kick point moves
down relative to the location of the kick point of the original
base shaft 5. In this embodiment, reinforced part 1B typically has
5 to 7 pieces and a length of about 10 cm to about 20 cm. When
reinforced part 1B is provided at midpoint m of base shaft 5,
improvement of ball flight direction also may be expected together
with a more convenient and exact swing.
[0047] FIG. 6 is a partial cross sectional view of a portion of the
shaft according to the invention having a wave shaped reinforced
part that has a sinusoidal configuration, i.e., the surfaces of the
waves are curved as opposed to an angular or compressed wave
configuration. The reinforcement pieces of the wave-shaped
reinforced parts of the golf club shafts of the invention
preferably have a sinusoidal configuration as shown, for example,
in FIG. 6.
[0048] The shape of the waves formed by reinforcement pieces may
have alternative configurations such as, for example, square wave
configuration, triangular wave configuration, compressed wave
configuration, and trapezoidal configuration. Examples of these
alternative configurations are shown in FIG. 7 which shows frontal
views of other possible configurations of wave shaped reinforced
parts used in the invention.
[0049] Base Shaft
[0050] The base shafts that can be employed to make the golf club
shafts of the present invention include, but are not limited to,
commercially available graphite shafts, titanium shafts, steel
shafts, fiberglass shafts and other shafts that are suitable for
use in making golf clubs. Graphite shafts are preferred as the base
shaft. The base shaft can be in an unfinished state, i.e., prior to
application of finishing materials such as lacquers. Finished
shafts that have been treated with finishing materials can also be
used as the base shaft.
[0051] Many prior art golf club shafts such those disclosed in
Korean Patent Application No. 96-1939 require complicated
manufacturing processes. An advantage of the present invention over
golf club shafts of the prior art is that commercially available
base shafts can be used to produce the golf club shafts according
to the invention. The present invention provides a convenient means
of moving the kick point of the golf club shafts according to the
skill level of the intended user.
[0052] Prepreg Sheet Starting Material
[0053] Prepreg is the composite industry's term for continuous
fiber reinforcement material which is pre-impregnated with a
partially cured polymer resin. Prepreg sheets are well known in the
art. Prepreg sheets are produced by known methods such as that
disclosed in Callister, William D., Materials Science and
Engineering: An Introduction, John Wiley & Sons, Inc, N.Y.
(1994) herein incorporated by reference. Commercially available
prepreg sheets can be used to form wave shaped reinforced parts of
the golf club shaft according to the invention.
[0054] Prepreg sheets useful in the invention include carbon fiber
reinforced prepreg sheets wherein the carbon fibers run in a single
direction. Glass fiber reinforced prepreg sheets can also be used
wherein the glass fibers are woven to intersect each other in a
perpendicular orientation forming a criss-cross pattern. In a
preferred embodiment of the invention, the prepreg sheet starting
material is an assembly of a glass fiber prepreg sheet on top of a
carbon prepreg sheet so that the glass prepreg sheet is on the
outside surface of the reinforced part. This type of assembly
prevents the carbon fibers from leaking or peeling off during the
manufacturing process.
[0055] Prepreg sheets useful in the invention include but are not
limited to those which are impregnated with a thermoplastic resin,
preferably epoxy resin. The thickness of the prepreg sheet is
typically between about 0.1 mm to about 0.15 mm. An example of a
carbon fiber prepreg sheet useful in the invention is known as T700
and was obtained through Korea Fiber Co. of Korea.
[0056] Total Weight of Golf Club Shaft with Reinforced Part(s)
[0057] The desired total weight of the golf club shaft with wave
shaped reinforced part(s) is an important factor in determining the
appropriate thickness of the prepreg sheet and the thickness of the
reinforcement pieces. Typical total weights of the golf club shaft
can range from about 70 g to about 100 g. It is preferred that the
total weight of a golf club shaft for a driver in accordance with
the invention which has three or more wave shaped reinforced parts
is about 70 g to about 75 g. The preferred total weight for a golf
club shaft of the invention which has three or more wave shaped
reinforced parts, when used in a 5-iron, is about 68 g to about 72
g.
[0058] Prepreg Sheet Base Section and Finger Like Elements
[0059] FIG. 8 shows base section 2B of prepreg sheet 2A attached
vertically onto a portion of base shaft 5. As illustrated in FIG.
8, prepreg sheet 2A has finger like elements 2 that are formed by
removing sections from a prepreg sheet starting material. The base
section 2B of prepreg sheet 2A is attached to base shaft 5, and
finger like elements 2 are shown in a position for wrapping around
and onto base shaft 5. Generally, the length of base section 2B of
a prepreg sheet corresponds to the desired length of the wave
shaped reinforced part.
[0060] As discussed in more detail below, prepreg sheet 2A can be
made from a single prepreg sheet or an assembly of prepreg sheets
such as a glass fiber prepreg sheet on top of a carbon fiber
prepreg sheet. The assembly is cut to form a prepreg sheet 2A with
finger like elements 2.
[0061] The finger like elements 2 preferably have an elongated,
tapered shape as shown in FIG. 8. Although it is preferred to use
finger like elements 2 which have a tapered shape, finger like
elements 2 may have a variety of shapes depending on the
configuration of the waves desired in the wave shaped reinforced
part. The shape of the finger like elements 2 may be readily
determined by those of ordinary skill in the art depending on the
configuration of the waves desired in the wave shaped reinforced
part.
[0062] Finger like elements 2 are formed by cutting a prepreg sheet
or assembly by known means such as utility knives, carbide disk
cutters, and the like. More advanced cutting means includes die
cutting and laser cutting. In the example shown in FIG. 8, finger
like elements 2 are curved toward the grip end of the base shaft 5.
This configuration is useful to form reinforcement pieces which
yield a wave shaped reinforced part that has a sinusoidal
configuration. The degree of curvature of the finger like elements
used to form a wave shaped reinforced part that has a sinusoidal
configuration can readily be determined according to the size and
shape of a particular base shaft. For example, when the base shaft
tapers in the direction of the club head tip of the base shaft, the
length of finger like elements 2 can be increased as the radius of
the base shaft decreases toward the tip end of the shaft.
[0063] Shape of the Reinforcement Pieces
[0064] The outer shape of the reinforcement pieces which form a
wave-shaped reinforced part can be formed according to the type of
wave desired in the wave shaped reinforced part. For example, the
reinforcement pieces may have a sinusoidal shape to provide a wave
shaped reinforced part having a sinusoidal configuration as shown
in FIG. 6. Similarly, the reinforcement piece may have other shapes
to provide wave shaped reinforced parts which have, for example,
compressed wave configurations, triangular wave configurations,
square wave configurations and the like as shown in FIG. 7. Other
possible configurations include arc, tetragonal or spiral
configurations. A particular configuration can be formed by sanding
the waves to the desired configuration. A wave shaped reinforced
part that has a spiral form can be formed, for example, by forming
a "rope" from carbon fibers. The "rope" is wound spirally around a
base shaft to form the desired number of reinforcement pieces.
[0065] Thickness of the Reinforcement Pieces
[0066] FIG. 9 shows a section of a golf club shaft having a wave
shaped reinforced part prior to curing. FIG. 9 also shows finger
like elements 2 extended prior to winding around the shaft. During
manufacture, finger like elements 2 are wrapped around base shaft 5
to form reinforcement pieces 30 having thickness T and overall
diameter D. The thickness T of reinforcement pieces such as those
shown in FIG. 9 is a function of 1) the desired total weight of the
golf club shaft with the wave shaped reinforced part and 2) the
taper of the shaft. The thickness T of the reinforcement pieces is
at least about 0.5 mm. Typically, the maximum thickness of the
reinforcement pieces is about 1.5 mm to maintain the total weight
of the golf club shaft within current commercially desirable weight
limits.
[0067] In one embodiment of the golf club shaft of the invention,
the overall diameters D as shown in FIG. 9 of the base shaft and
reinforcement pieces in a wave shaped reinforced part are the same.
In this embodiment, the thickness T of each reinforcement piece can
vary depending on the taper of the shaft. For example, as the
diameter of the base shaft decreases, the thickness T of
reinforcement pieces can increase so that the overall diameters D
of the base shaft and reinforcement pieces is constant. In another
embodiment, the thicknesses of the reinforcement pieces is constant
and the overall diameters D of the base shaft and the reinforcement
pieces can vary.
[0068] Manufacture and Assembly
[0069] A golf club shaft of the invention is formed by bonding a
prepreg sheet or, preferably, a prepreg sheet assembly onto a base
shaft. The prepreg sheet or assembly includes a base section and
finger-like members joined to the base section. The finger-like
members are wrapped around the base shaft to provide a wave shaped
reinforced part.
[0070] In one embodiment of the manufacture of the golf club shafts
of the invention, the base section of a prepreg sheet or assembly
having finger like elements 2 as shown, for example, in FIG. 8, is
attached vertically along the length of a desired section of a base
shaft by an adhesive such as epoxy resin. Finger like elements 2
are wrapped around base shaft 5 to produce reinforcement pieces 30
such as those shown, for example, in FIG. 9.
[0071] FIG. 10 shows a section of a golf club shaft having a wave
shaped reinforced part wherein the reinforcement pieces are covered
by tape 40 prior to curing. FIG. 10 also shows a finger like
element 2 extended prior to winding around the shaft. During
manufacture, finger like elements 2 are wrapped around base shaft
to form reinforcement pieces 30 having thickness T and overall
diameter D. The resulting wave shaped reinforced part can be
covered with carbon tape 40 prior to curing as shown in FIG. 10.
The wave shaped reinforced part is cured by heat at an appropriate
temperature for the particular prepreg sheet. Generally, the curing
temperature and time are functions of the particular prepreg sheet
starting material. Curing temperatures and times are widely known
and published for various prepreg sheets that can be used alone or
in an assembly in the present invention. One skilled in the art can
readily determine the time and temperature values for the specific
prepreg sheet being used, the length of the reinforced part, and
the number and thickness of the reinforcement pieces. The time and
temperatures can be selected for full or limited cure.
[0072] Although it is preferred to bond a prepreg sheet or assembly
around a base shaft as described above, a wave shaped reinforced
part having a sinusoidal configuration shown in FIG. 6 or any of
the other configurations shown in FIG. 7 may be formed by well
known techniques such as compression molding, flame spraying,
plasma deposition and the like.
[0073] In a first embodiment of a compression molding method useful
in the invention, one or more layers of uncut prepreg sheet
material is wrapped onto the surface of the shaft. The wrapped
shaft then is compressed under heat and pressure in a mold having
the desired configuration of the waves in the wave shaped
reinforced part. Preferably, the wave shaped reinforced part such
as reinforced part 1, 1' is formed on the exterior surface of base
shaft 5.
[0074] As an alternative to compression molding, techniques such as
flame spraying may be employed to deposit material onto the surface
of the shaft to yield a wave shaped reinforced part having a
desired wave shape on selected portions of the base shaft.
[0075] Although it is preferred that the wave shaped reinforced
part completely encircle the base shaft as shown, for example, in
FIG. 10, a wave shaped reinforced part 32 may be formed on selected
portions of shaft 25I which only partially encircles the shaft as
shown in FIG. 11. Wave shaped reinforced parts which only partially
encircle the shaft may readily be formed by techniques such as
compression molding and flame spraying. Techniques such as
compression molding and flame spraying are especially suitable for
forming a golf club shaft 25F which has, for example, rib shaped
reinforcement pieces 31 as shown in FIG. 12.
[0076] Compression molding also may be used for example, to form a
wave shaped reinforcement pieces 30 on the internal surface of a
base shaft 25G as shown for example, in FIG. 13. In this aspect, a
rod having expandible sections may be inserted into a base shaft.
The expandible sections of the rod then are compressed against the
interior surface of the base shaft to form reinforcement pieces.
Preferably, the reinforcement pieces are wave shaped to produce a
wave shaped reinforced part that has a sinusoidal configuration.
Other wave shapes, e.g., any of those shown in FIG. 7, may be made
by compression molding.
[0077] FIG. 14 shows a golf club made from a first embodiment of
golf club shaft 25A of the present invention in which a wave shaped
reinforced part 1 is located at the lower part a of a base shaft 5
near hosel section 15. When wave shaped reinforced part 1 is
provided at the lower part a of base shaft 5, there is a
significant improvement in torsion characteristics of the golf club
shaft.
[0078] FIG. 15 shows a golf club made from a golf club shaft 25B in
accordance with a second embodiment of the invention in which wave
shaped reinforced part 1' is located at location b of the golf club
shaft near the grip 27. When wave-shaped reinforced part 1' is
provided at location b, the kick point of golf club shaft 25B moves
down, away from the grip 27.
[0079] FIG. 16 shows a golf club made from a golf club shaft 25C in
accordance with a third embodiment of the invention in which wave
shaped reinforced parts 1 and 1' are located at location a and
location b respectively of base shaft 5. When reinforced parts 1
and 1' are provided at both location a and location b of the base
shaft 5, improvement of ball flight direction may be expected
together with a more convenient and exact swing.
[0080] FIG. 17 shows a golf club 29D made from a golf club shaft
25D in accordance with a fourth embodiment of the invention in
which a wave shaped reinforced part 1A is located at the midpoint m
of base shaft 5. When reinforced part 1A is provided at midpoint m
of base shaft 5, improvement of ball flight direction also may be
expected together with a more convenient and exact swing.
[0081] FIG. 18 shows a golf club 29E made from a golf club shaft
25E in accordance with a fifth embodiment of the invention in which
a wave shaped reinforced part 1B is located between midpoint m and
the lower edge of grip 27 of base shaft 5. When reinforced part 1B
is provided at midpoint m of base shaft 5, the kick point moves
down and improvement of ball flight direction may be expected
together with a more convenient and exact swing.
[0082] The golf club shaft of the present invention has various
advantages such as: a) improvement of torsion characteristics of
the shaft, b) controllable movement of the kick point of the golf
club shaft to a desired location to improve the direction of a golf
ball with a more convenient and accurate swing, and c) the ability
to further extend the length of the reinforced shaft to improve the
flying distance of a golf ball without application of added force,
i.e., without the need to employ a higher swing speed. Another
advantage is the ability to use of commercially available base
shafts to produce the golf club shafts of the present invention
thus avoiding the complicated manufacturing processes required by
golf club shafts of the prior art.
[0083] Golf clubs made with the shafts of the present invention
impart greater flying distance and/or directional accuracy to golf
balls struck by the golf clubs. The reinforced part provides a
means of moving the kick point of the shaft to achieve a desired
effect on flying distance and/or accuracy. The present invention
also provides a convenient means of adjusting the characteristics
of a golf club shaft according to the skill level of the intended
user.
[0084] In addition, the wave-shaped reinforced part offsets the
impact wave induced when impacting a ball, thus protecting the
human body.
EXAMPLES
[0085] In an illustrative but non-limiting example, a commercially
available carbon fiber prepreg sheet known as T700 obtained through
Korea Fiber Company of Korea and a commercially available glass
fiber prepreg sheet are placed together and then the assembly is
cut to form a base section with finger-like elements having curved
edges as shown in FIG. 8. Base section 2B of the prepreg assembly
is attached along the length of the desired section of the base
shaft by epoxy resin and the finger-like elements are wrapped
tightly around the base shaft to form a wave shaped reinforced part
that has a sinusoidal wave configuration. The resulting wave shaped
reinforced part is covered with carbon tape. The covered wave
shaped reinforced part is then heat cured by placing the shaft
having the wave shaped reinforced part into an oven at 80.degree.
C. and then raising the temperature to 120.degree. C. over 30
minutes. Thereafter, the temperature is raised to 130.degree. C.
over 60 minutes. The shaft having the cured wave shaped reinforced
part thereon then is removed from the oven and cooled to room
temperature. After curing is completed, the tape is removed by
sandpaper, and the shaft is ground to remove any imperfections and
to give the resulting wave shaped reinforced part a smooth finish.
Grinding may also be employed to alter the shape of a reinforcement
piece or pieces in the cured wave shaped reinforced part to achieve
a desired wave configuration.
[0086] In another non-limiting example of the invention, a golf
club shaft such as that illustrated in FIG. 2 is produced. In this
example, the golf club shaft includes a base shaft that has a
weight of 62 gram, and total length of 1143 mm. The original kick
point is located 46 cm from the club head tip of the shaft. In
accordance with the invention, it is found that after adding a wave
shaped reinforced part having a length of 20 cm and having 5
reinforcement pieces, the kick point moves down to 44 cm from the
club head tip of the shaft. The weight of the shaft having the
reinforced part, measured prior to application of finishing
materials such as lacquers and the like, is 68 grams. If it is
desired to the same height of kick point as the original base shaft
prior to forming the reinforced part thereon, the length of the
base shaft may be extended by about 70 mm to about 110 mm.
[0087] The following Tables 2-4 show measurements of carry, and of
carry and roll distances (in yards) for a golf club made from a
commercially available golf club shaft ("CONTROL") and the same
type of golf club made from a golf club shaft according to the
invention ("INVENTION"). The specifications of the Test Clubs were
comparable. The clubs were tested in a mechanical swinging device
wherein the club head speed was 95 mph.
[0088] Control
[0089] Test Club Head: Tour Edge Titanium 950-Driver
(9.0.degree.)
[0090] Club Shaft: Aldila-R/S Flex
[0091] Invention
[0092] Test Club Head: Tour Edge Titanium 950-Driver
[0093] Club Shaft: Golf club shaft according to the invention with
the wave shaped reinforced part having five reinforcement pieces
near the grip section. The upper edge of the reinforced part was
located around 2.5 inches below a 103/8 inch grip. The shaft was
made from a graphite base shaft that was 45 inches long.
2 TABLE 2 Carry Carry and Roll CENTER HITS Distance (yds) Accuracy
Distance (yds) Accuracy CONTROL 235.0 -0.8 281.8 -6.0 Std. Dev. 1.4
4.5 7.4 6.4 INVENTION 244.0 2.4 272.8 2.4 Std. Dev. 3.5 4.5 3.6
4.2
[0094]
3 TABLE 3 Carry Carry and Roll 1/2 TOE HITS Distance (yds) Accuracy
Distance (yds) Accuracy CONTROL 221.4 13.4 271.2 12.8 Std. Dev. 4.7
2.1 8.3 1.9 INVENTION 240.0 2.4 268.8 0.3 Std. Dev. 1.9 2.2 4.8
2.9
[0095]
4 TABLE 4 Carry Carry and Roll 1/2 HEEL HITS Distance Accuracy
Distance Accuracy CONTROL 215.4 -18.8 265.0 -20.0 Std. Dev. 4.6 3.7
INVENTION 235.8 -27.6 271.0 -19.0 Std. Dev. 6.6 10.1 5.7 1.4
* * * * *