Composite golf club shaft

A golf club shaft has the usual handle portion at one end, a golf club head ounting portion at the opposite end, and a tapered intermediate portion therebetween. The tapered intermediate portion includes a substantially inflexible section adjacent the handle portion and a substantially flexible section adjacent the club head mounting portion. With this arrangement, rather than the entire shaft flexing in a substantially smooth curve during a normal swing of the club, the flexing is limited to the substantially flexible section of the club. This provides a club with increased control.

SPECIFICATION 
BACKGROUND OF THE INVENTION 
1. Field 
The invention is in the field of golf club shaft construction. 
2. State of the Art 
Golf club shafts generally include a handle portion at one end to which a 
hand grip is secured, and a club head receiving portion at the opposite 
end to which a club head is secured, with the intermediate portion of the 
shaft extending between the hand grip and the club head. The shaft is 
generally tapered between the hand grip and the club head. 
Most shafts will flex to some extent, with the newer shafts made of 
composite materials generally offering a greater degree of flex than older 
metal shafts. The shafts generally provide a relatively constant flex over 
their length, a least over the length from the hand grip to the club head. 
Flex in the club shaft is usually desirable because it provides increased 
speed as the club head hits the ball because the flex is usually highest 
at the start of the swing as the club head is initially moved, and as the 
club head gains speed during the swing, the initial flex decreases adding 
to the speed of the club. This provides a longer drive. However, when a 
shaft can flex, it generally also can twist. Upon initiating swing of the 
club, since the club head extends in unbalanced fashion from one side of 
the shaft, the shaft is subjected to torque forces which allow the club 
head and face of the club head to twist. This twisting lessens the control 
a golfer has when hitting the ball and can lead to slicing or hooking of 
the ball. Thus, while flex in a shaft is usually desirable to some extent, 
it affects the control a golfer has in achieving a straight shot. 
SUMMARY OF THE INVENTION 
According to the invention, a composite golf club shaft is constructed to 
modify the flex pattern of the shaft. Rather than providing a 
substantially constant flexing arc over the length of the shaft between 
the hand grip and the club head, the flexing characteristics of the shaft 
are modified so that the portion of the shaft adjacent the hand grip, and 
extending toward the club head, is stiffened so is resistant to flexing, 
leaving a shorter portion of the shaft toward the club head to flex. In a 
preferred embodiment of the invention, the club shaft is constructed so 
that a portion of the shaft extending between about fifteen inches to 
about eighteen inches from the hand grip end of the shaft resists bending 
or flexing during swing of the club, with the remaining portion of the 
shaft toward the club head flexing during swing. It has been found that 
reducing the length of the shaft over which the flexing of the shaft takes 
place during a swing does not substantially reduce the distance of a shot, 
but does substantially increase the control over the shot by the golfer. 
The shorter flexing portion of the club shaft reduces the twisting or 
torque of the club head which takes place. 
In a composite club shaft, the stiffening of a portion of the shaft to 
reduce the flexing and twisting or torque of that portion of the shaft is 
accomplished by thickening the composite material of the shaft through the 
stiffened portion adjacent the hand grip by adding additional layers of 
composite material through that portion.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
A golf club generally includes a golf club shaft 10, FIG. 1 with a handle 
portion 11 on which a hand grip 12 is mounted, and a club head mounting 
portion 13 on which a club head 14 is mounted. An intermediate portion 15 
extends between the handle portion 11 and club head mounting portion 13. 
As shown in FIGS. 2 and 3, the handle portion 11 of the shaft 10 is 
generally of constant diameter, as is the club head mounting portion 13. 
The intermediate portion 15 is generally tapered from the handle portion 
11 to the club head mounting portion 13. In prior art golf club shafts, 
the intermediate portion 15 generally tapers from a diameter equal to the 
diameter of the handle portion to the smaller diameter of the club head 
mounting portion. 
In the golf club shaft of the invention, the intermediate portion 15 
includes two sections, a substantially flexible lower section 20, and a 
substantially inflexible upper section 21. These two sections preferably 
blend together so that the flexibility of the shaft changes smoothly from 
one section to the other with no sudden or abrupt change. With a composite 
golf club shaft, i.e., a shaft made of fibers, such as carbon fibers, 
embedded in a resin material, the flexibility of the shaft can be 
controlled by the thickness of the composite materials. Thus, an extra 
thickness of fibers and resin are provided through the substantially 
inflexible section 21. This causes the substantially inflexible section to 
have an upper diameter adjacent the handle portion, as at 23, larger than 
the diameter of the handle portion 11 so that a bulge occurs on the shaft 
immediately below the hand grip mounted on the handle section. From this 
larger diameter portion 23, the intermediate portion of the club shaft 
tapers smoothly to the club head mounting portion 13. 
In referring to a substantially flexible section and a substantially 
inflexible section, it is meant that the flexibility of such sections are 
such that during a normal swing of the club, the substantially flexible 
section will flex to some extent while the substantially inflexible 
section will resist flexing. Thus, as shown in FIG. 4, during a normal 
swing with a club using the shaft of the invention, the substantially 
flexible section will flex into an arc as shown at some time during a 
normal swing, the extent of the arc depending upon the particular swing of 
the golfer using the club and the stage of the swing, the flex and the arc 
generally being greater during the initial phases of the swing. During 
this flexing of the club shaft, the substantially inflexible section 
remains relatively straight and unflexed. Substantially inflexible does 
not mean inflexible under other conditions or pressures that might be 
applied to the club under abnormal circumstances or tests, but only that 
it is substantially inflexible during a normal swing. 
In a typical shaft of the invention, the handle section of constant 
diameter will be about twelve-and-one-quarter inches long. The 
substantially rigid section of the intermediate portion will be from about 
three to five inches long to provide a total length at the upper end of 
the shaft that does not bend or flex during a normal swing of from about 
fifteen to about eighteen inches (this section being the total of the 
length of the handle portion and the substantially inflexible section). 
The intermediate portion of the club will be about twenty-three to about 
twenty-eight inches in length, while the club head mounting portion will 
be about four to about six inches in length. The diameter of the handle 
portion will be about 0.60 inches in outside diameter while the maximum 
diameter of the substantially inflexible section will be about 0.70 inches 
in diameter. The intermediate portion will taper from its maximum diameter 
to a diameter of about 0.335 inches which is the diameter of the club head 
mounting portion. These are typical dimensions and may vary considerably 
depending upon materials used in constructing the shaft, the actual 
construction of the shaft, and the expected loads on the shaft. 
It is preferred that the shaft be configured to make a transition between 
the handle portion and the maximum diameter of the substantially 
inflexible section in the form of a smooth curve, as shown. 
While the handle portion and the club head mounting portion have been shown 
and described as being of constant diameter, either could be tapered as 
desired. 
The composite shaft can be constructed in any desired manner, the 
construction of such shafts being well known. Generally the shaft is 
constructed on a mandrel which tapers from a large diameter at the handle 
end of the shaft to a smaller diameter at the club head mounting end of 
the shaft. This taper is generally necessary so that once the shaft is 
constructed, the mandrel can be removed from the center of the shaft 
leaving a hollow shaft with the hollow area 25, FIG. 3, having the same 
taper as the mandrel. Layers of fiber (such as graphite fibers) and resin 
material, generally in the form of "prepreg" (a fiber mat material coated 
with resin) are wrapped around the mandrel and the resin is allowed to 
harden to form the shaft. The majority of fibers are generally arranged 
along the length of the shaft, although various wrapping and fiber 
arrangements can be used. With the normal composite construction, as 
indicated above, the flexibility of the shaft at any point is a function 
of its thickness, thicker portions generally being less flexible. Thus, in 
order to have a one-piece shaft where the shaft can be removed from the 
mandrel in normal manner, the substantially inflexible section is formed 
by providing additional wraps of fiber and resin on the outside of the 
shaft to increase the thickness of the wall of the shaft through that 
section of the shaft. However, there may be other ways of reducing the 
flexibility of a section of the shaft without increasing the outside 
diameter of the shaft through that section. 
The construction of the shaft of the invention moves the balance point of 
the shaft upwardly toward the handle of the club as compared to the 
traditional shaft construction because additional material is added to the 
shaft adjacent the handle portion. 
Whereas this invention is here illustrated and described with reference to 
embodiments thereof presently contemplated as the best mode of carrying 
out such invention in actual practice, it is to be understood that various 
changes may be made in adapting the invention to different embodiments 
without departing from the broader inventive concepts disclosed herein and 
comprehended by the claims that follow.