Swingweight adjusted golf club shaft   

This application is a divisional of co-pending U.S. application Ser. No. 12/342,617, filed on Dec. 23, 2008, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to an improved golf club shaft. More particularly, the present invention relates to a golf club shaft for a set of clubs wherein the internal wall thicknesses of the shafts are shaped in a way that allows the golf club shafts to be cut down to an individually desirable length while minimizing or eliminating the undesirable change in the swingweight within the set of clubs.

BACKGROUND OF THE INVENTION

Golf club shafts have always been an important component of every golf club. Although many would argue that finding a correct golf club head makes the most significant impact on an individual\'s golf swing, finding the correct golf club shaft to go with the correct golf club head is also just as important. Currently in the art, conventional golf club shafts have been made out of various materials such as steel, metal alloy, or composites that change the various characteristics of the golf club shaft. These materials, although provide significant differences in swing characteristics of a golf club in and of themselves, are incapable of addressing the weight consistency issue within a set of golf clubs. With the development, understanding, and focus on the weight consistency issue of the golf club, it has become known that the consistency of a weight and feel of a golf club depends on more than just the weight of the shaft alone. The weight of the golf club and the way it feels when being swung are generally dependent on two factors; the actual weight of the golf club and the moment of the club around an arbitrary location; which has been called the “swingweight” of a golf club. Understanding swingweight and maintaining the same swingweight is extremely beneficial and desirable to a golfer in order to find a set of golf clubs that feels natural to the individual no matter which club is chosen.

The concept of swingweight is a well known concept within the golfing industry. Swingweight can be generically simplified as the weight relationship of a golf club about a fixed fulcrum point. More specifically, the swingweight is the measurement of a golf club\'s moment about the fixed fulcrum, generally placed at an arbitrary location fourteen inches away from the butt end of the grip. The swingweight is important to a golf swing because it affects how heavy the club feels during the swing regardless of its actual weight. Golf club sets that are put together without any conscious effort on maintaining the swingweight often have a major flaw in that each club feels and performs differently due to swingweight variations. This swingweight variation described above could be as little as one swingweight, but in severe situations, such variation could result in as much as four swingweights. Major differences in swingweight can significantly affect the feel of a golf club, and is often an undesirable effect. Hence, it can be seen from above that there is a need for a set of golf clubs that maintains a consistent swingweight through the various clubs.

The need for consistent swingweight is particularly prevalent within a set of irons, as they often come in a set of multiple clubs and they are expected to perform consistently within the set. In order to address the swingweight issue within a set of irons, a prevalent approach within the golf industry has been using constant weight shafts. A constant weight shaft aims to maintain the swingweight of each individual shaft within an iron set regardless of the length of the shaft. This constant weight shaft approach is generally achieved by independently manufacturing each shaft to their individual weight, length, and swingweight specifications. As a result of the individualized complicated manufacturing process, all of the shafts within a set of irons will have the same weight and swingweight regardless of the length of the shaft. This individualized and independent manufacturing process takes in consideration the weight of each of the club head, the weight of each of the grip and grip tape, the length of the shaft, and the weight of the shaft to achieve a consistent swingweight. This approach of individually manufacturing each shaft within a set of irons, although effective in maintaining swingweight, can be slow, burdensome, and expensive to manufacture.

In order to minimize production costs while still achieving constant swingweight, it is also common in the golf club industry to adapt a descending weight shaft approach as an alternative to the constant weight shaft approach. The descending weight shaft approach ignores any attempt to maintain individual shaft weight and swingweight across the set of irons. Thus, as the length of the shaft get shorter and shorter, the weight and swingweight of each shaft begin to differ across the set of clubs. Ultimately, as each individual shaft is cut down to their appropriate length, their weights are reduced by the amount of weight lost from the length reduction. In order to address the issue of the difference in swingweight, the descending weight shaft approach adjusts and modifies the weight of other components of a golf club such as the head or the grip. Because no attempt is made to adjust the weights and swingweights of the shaft themselves, all the shafts within a set of irons can be manufactured together utilizing the same manufacturing specifications, reducing the manufacturing costs. The descending weight shaft approach, although effective in reducing manufacturing costs, is ineffective in adjusting the swingweight of the individual shafts, and relies on adjustments of other components of the golf club that requires added design complexity of one or more of the other components and additional steps at the assembly stage. This additional design complexity and the additional manual assembly step can often be undesirable as it increases production cost of a golf club.

Hence, it can be seen that there is a need in the field for a golf club shaft that is capable of minimizing or eliminating the variations in the swingweight of a golf club by focusing on the shaft itself without the expensive manufacturing expenses associated with independently manufacturing each golf club shaft or expensive adjustment weights associated with final adjustments in other components or the finished product. More specifically, there is a need for a golf club shaft that can be uniformly manufactured and cut down to the desirable length to match the various length of an iron set all while minimizing or even eliminating the variations in the swingweight of the golf club shaft.

SUMMARY

In one aspect of the present invention is a plurality of golf clubs comprising of a first golf club containing a first shaft, and a second golf club containing a second shaft; wherein the second shaft is formed by cutting down the length of the first shaft; and wherein an internal wall profile within the first shaft allows the second golf club to have a total moment about a second fulcrum to be similar to a total moment about a first fulcrum of the first golf club.

In another aspect of the present invention is a golf club comprising of a grip connected to a first end of the golf club, a head connected to a second end of the golf club, and a shaft interposed between the head and the grip containing an internal wall profile; wherein the internal wall profile causes a moment of the shaft about a fulcrum to change from 10 gram·inchs to 50 gram·inchs for each half inch reduction in the shaft length.

In a further aspect of the present invention is a method of minimizing a swingweight variation within a plurality of golf clubs comprising of reducing the length of a first shaft by a half inch to produce a second shaft, and adjusting an internal wall profile of the first shaft; wherein the second shaft has a second shaft moment about a fulcrum that varies 10 gram·inchs to 50 gram·inchs when compared to a first moment about a fulcrum of the first shaft.

These and other features, aspects and advantages of the present invention will become better understood with references to the following drawings, description and claims.

The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and faun a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.

FIG. 1 shows an exemplary golf club head wherein demonstrating the calculation of moment about a fulcrum;

FIG. 2 shows a prospective view of a golf club in accordance with the present invention;

FIG. 3a shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with the present invention;

FIG. 3b shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an alternative embodiment of the present invention;

FIG. 4 show a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with a further alternative embodiment of the present invention;

FIG. 5 shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an even further alternative embodiment of the present invention;

FIG. 6a shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an even further alternative embodiment of the present invention;

FIG. 6b shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an even further alternative embodiment of the present invention;

FIG. 7 shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an even further alternative embodiment of the present invention; and

FIG. 8 shows a cross-sectional view of an internal wall thickness profile of a golf club shaft in accordance with an even further alternative embodiment of the present invention.

DETAILED DESCRIPTION

The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any or all of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below.

The present invention generally provides a golf club shaft that has a pre-formed internal wall thickness profile geometry shaped in a way that minimizes or eliminates the changes in the swingweight within a set of golf clubs; hence allowing an uniform manufacturing technique for all shafts within a set of golf clubs. More specifically, the present invention relates to a shaft with a unique pre-formed internal wall profile that can be cut down to the desired length to match the required length of a specific iron without the need to make external adjustments to the swingweight. The current invention is unlike the prior art golf club shafts, where in order to achieve a constant swingweight within a set of golf clubs has to either individually manufacture each shaft to a different specification or make significant external adjustments to other components before or after assembly to compensate for the difference in swingweight.

Turning now to FIG. 1 which shows an embodiment of the present invention wherein calculation of the center of gravity, the moment of inertia for each of the individual components of a golf club, and the total moment about the entire golf club can be shown. More specifically, FIG. 1 is capable of establishing a relationship between the moment of a golf club and the swingweight. Here, golf club 100, has a grip 102 at a first end 101 of golf club 100. Connected to the grip 102 is a shaft 104 which may serve as a connecting apparatus between grip 102 and the head 106. The head 106 may be connected to the distal or second end 103 of the golf club 100. Each of the above mentioned components has its own center of gravity, which in theory is a point where the system\'s mass behaves as if it were concentrated at that point. Alternatively speaking, the center of gravity of a golf club component can often be the balance point of the individual components along the lengthwise direction. Here, as shown in the current exemplary embodiment, center of gravity of grip 108 may be located near the grip 102, the center of gravity of the shaft 110 may be located near the shaft 104, and the center of gravity of the head 112 may be located near the head 106 all without departing from the scope and content of the present invention.

In order to determine the swingweight of a golf club, it is important to recognize the concept of the fulcrum 114 and its location relative to a golf club 100. In this current exemplary embodiment, the fulcrum 114 may generally be at a location that is fourteen inches away from the first end 101 or the butt end of the golf club 100. The fulcrum 114 relates to the swingweight of a golf club 100 in a way such that the swingweight is determined as the sum of all the moment of each of the components about the above mentioned fulcrum point 114. In this current exemplary embodiment containing three components, the total moment of golf club head 100 may generally be simplified as follows:

Wgrip(d1−14)+Wshaft(d2−14)+Whead(d3−14)=Total Moment  (1)

As it can be seen from FIG. 1, the distances d1, d2, and d3, are distances of the center of gravity of each of the components, as measured from the first end 101 or the butt end of the golf club 100. The weight of each of the components, depicted by the symbol W is depicted as Wgrip, Wshaft, and Whead. The moment of each of the components of a golf club 100 such as the grip 102, the shaft 104, and the head 106 may be calculated by multiplying the weight of each of the component such as Wgrip, Wshaft, and Whead with each of their respective distance relative to the fulcrum 114. For identification purposes, the moment of each of the components may also be identified as a singular variable simplified as Mgrip, Mshaft, and Mhead. The sum of all the total moments within the golf club head 100 such as Mgrip, Mshaft, and Mhead, as depicted in Equation (1) by the product of the weight and distances, is directly correlated to the swingweight of a golf club 100 based on the Table 1 below.

TABLE 1 Swingweight Total Moment (Gram · Inches) C-0 5600 C-1 5650 C-2 5700 C-3 5750 C-4 5800 C-5 5850 C-6 5900 C-7 5950 C-8 6000 C-9 6050 D-0 6100 D-1 6150 D-2 6200 D-3 6250 D-4 6300 D-5 6350 D-6 6400 D-7 6450 D-8 6500 D-9 6550 E-0 6600

It should be noted that although the current exemplary embodiment depicted in FIG. 1 may only the contain 3 essential elements to golf club 100; namely the grip 102, the shaft 104, and the head 106; various other minor components could also contribute to the moment and swingweight of golf club 100 such as a ferrule, a shaft tip insert, a tape, an epoxy, or any other minor components generally installed in a golf club all without departing from the scope of the present invention.

As it can be seen from above in Table 1, each 50 gram·inches variation of the total moment equates to one swingweight shift. The current invention, through the adjustment of the internal wall profiles, may allow various golf clubs within a set of irons to minimize the variation in the swingweight, or even maintain the swingweight of each of the golf clubs within a set of irons despite its variations in length. More specifically, the current invention may achieve this by utilizing a shaft with a unique internal wall thickness profile throughout the entire range of the set of irons, wherein the unique internal wall thickness profile will allow each individual shaft to be cut down to the desirable length while minimizing swingweight variations.

In order to determine the unique internal wall profile required, a focus may be placed on the calculation of the total moment variations of each of the golf clubs within a set of irons, especially paying close attention to the moment changes for each of the individual components such as the grip 102, the shaft 104, and the head 106. Table 2 below shows an exemplary calculation of the moment changes across an exemplary set of irons ranging from a 2 iron to a 9 iron. Here, as it can be seen, the weights and moments are determined based on each of the components of a golf club 100 as depicted in the FIG. 1 setup. Ultimately, the moment of each of the individual components of grip 102, shaft 104, and head 106 can be seen below:

TABLE 2 Mgrip Total Mshaft Mhead Club Grip (Moment Shaft Shaft (Moment Head (Moment Number Weight d1 of Grip) Weight Length d2 of Shaft) Weight

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