JP2002200204A - Metal/composite material golf club shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf club shaft formed by combining the respective advantages of a metallic shaft and a composite material shaft into a single hybrid design. SOLUTION: The golf club shaft having a metallic front end section and a composite material grip side section is provided. The grip side section has a small-diameter segment to be nested into the axial direction bore of the front end section. An adhesive for integrally fixing the front end section and the grip side section is arranged between these sections. An insulating layer for preventing pitting effect corrosion can be arranged between the front end section and the grip side section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf club shaft having excellent performance characteristics, and more particularly, to a two-piece golf club shaft combining a metal part and a composite material part, which has advantages of both materials. And a two-piece golf club shaft that eliminates the disadvantages of both materials.

[0002]

BACKGROUND OF THE INVENTION Control and accuracy in golf games are affected by the torsional rigidity of the shaft. The torsional stiffness of the shaft resists torsion of the club head during swing, especially when the golf ball and club head do not make complete contact. Metal golf club shafts (the most popular metal being steel) are used by many golf players. The advantage of a steel shaft is its high torsional stiffness, which is known in the art as a "low torque" shaft.

[0003] Many golf shaft manufacturers provide composite shafts (often referred to as graphite shafts).
And these composite shafts are usually made of graphite, carbon fiber or epoxy resin. Although composite shafts can be much lighter than metal shafts, the torsional stiffness of conventional graphite shafts is less than that of steel shafts. Thus, graphite shafts are known in the art as being "higher torque" than steel shafts.

[0004] In an attempt to increase the torsional stiffness of composite shafts, manufacturers have used various fibers such as high modulus carbon fibers, aramid fibers and boron fibers. Manufacturers have also changed the structure by winding the fiber at various angles in an attempt to improve torsional stiffness. Most of these changes increase cost and often playability of the shaft.
It also has a negative effect on

[0005] Recent studies have shown that only the tip section of the shaft provides torsional resistance which prevents torsion of the club head due to poor ball / head contact. Contact between the club head and the ball is a very brief dynamic event during which only the tip section of the shaft is loaded. This event is
The entire length of the shaft is effectively lost before it is loaded. Thus, it is desirable to construct the tip section of the shaft from a metal with high torsional stiffness, such as steel, while the proximal section can be constructed from a composite such as graphite with low torsional stiffness. In this manner,
The effective torque characteristics of the shaft can be improved while maintaining lightness.

US Pat. No. 4,836,545 to Pompa discloses one attempt to combine the advantages of a metal shaft with the advantages of a composite shaft. However, the patent does not disclose the effect of two shaft sections on shaft performance. The length and weight of the two sections of the shaft of this US patent are arbitrarily selected. Testing revealed that the weight of the metal tip section was much higher than the weight of the composite hand section. Because the tip section is very heavy, the center of gravity (CG) of the shaft moves to the tip side,
The swing weight of the club has been undesirably increased.

[0007] Swing weight is measured for the finished club (assembled cl) around a location usually 14 inches from the grip end.
ub) is the measured value of the static moment. The absolute weight and balance position (CG position) of the head, shaft and grip all affect the swing weight of the club.
It is common for large club manufacturers to know the specifications of the shaft and grip to determine the head weight to achieve the desired club swing weight, but this approach is not always possible. Generally, component suppliers offer club head weights that match an industrially accepted weight range. What is highly desired, therefore, is to provide a shaft used for such a head to achieve a popular club swing weight.

Also, accepting secondary weighting to achieve the desired club swing weight is undesirable for the head. The secondary weight is typically introduced at the tip of the shaft (where the shaft is inserted into the hosel of the head). This position is not optimal as it is far from the center of gravity of the head, thus reducing the moment transfer to the ball at a given swing speed. When the moment transmission to the ball is reduced, the flight distance of the ball is reduced.

No. 4,836,545 also does not recognize the difficulty of joining the metal section and the composite section of the shaft. The joint must be aesthetically acceptable and of sufficient strength to prevent breakage.

As is apparent from the foregoing, it is desirable to provide an improved golf club shaft that can exhibit the advantages of both a metal shaft and a composite shaft, while eliminating the disadvantages of both.

[0011]

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide advantages of each of a metal shaft and a composite shaft.
It is to provide a golf club shaft combined with a single hybrid design.

Another object of the present invention is to eliminate the disadvantages of metal shafts and composite shafts of a single hybrid design.

It is another object of the present invention to provide a method of manufacturing a golf club shaft having a tip section made of a metal material and a hand section made of a composite material.

It is yet another object of the present invention to provide a method and apparatus that can achieve the above objects while conforming to the golf rules set by the American Golf Association.

[0015]

According to one embodiment of the present invention, a golf club shaft having a metal tip section and a composite hand section is provided. The cylindrical tip section is formed of a metallic material such as steel. The cylindrical hand section is formed of a composite material such as graphite and has a small diameter portion or plug formed at one end of the hand section. The proximal section plug is telescopically received without the distal section end, with the distal section end overlapping the small diameter section of the proximal section. An adhesive such as epoxy is disposed between the tip section and the hand section, and both sections are fixed together.

In another embodiment of the present invention, an insulating layer is disposed between the tip section and the proximal section to prevent metal-to-composite contact within the metal / composite joint.
By preventing metal-to-composite contact, the insulating layer eliminates or reduces the potential for galvanic corrosion within the joint. The insulating layer is formed as a plurality of insulating spacers, such as glass beads or layers, which are incorporated into the hand section within the joint.

[0017]

Other objects and advantages of the present invention are:
It will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

Referring to FIG. 1, a grip 1 is shown.
2, a golf club 10 with a head 14 and a tubular shaft 16 is shown. The club 10 is shown as wood, but may be iron or putter. The shaft 16 has a tip section 18 and a hand section 20. The tip section 18 is preferably formed from a metallic material such as high strength steel,
0 is preferably formed of a composite material such as graphite. It should be noted that while the shaft 16 is shown having smooth, tapered sidewalls 22, parallel or stepped sidewalls could be used instead.

The tip section 18 is secured to the head 14 by sizing the lower end 14 to fit into a standard club head hosel socket. The upper end 26 of the tip section 18 is telescopically slip fit over the lower end of the hand section 20.
The physical properties of the tip section 18 from the head 14 to the joint 30 where the tip section 18 and the proximal section 20 meet, the torsional stiffness, It is designed to achieve the desired balance of bending stiffness (flexibility), strength and weight.

The relationship between the physical properties of the tip section 18 and the operability of the shaft 16 is complex and many factors must be taken into account.

1) If the metal tip section 18 is shortened, the torsional stiffness provided by the tip section 18 will not be great. Increasing the length of the tip section 18 increases the weight of the tip section 18.

2) The lower end 24 of the tip section 18 must be capable of mating with a standard industry standard club head.
Preferably, it retains a standard industry standard diameter of 0.335 or 0.350 inches. However, this diameter increases both torsional and bending stiffness,
It can increase towards the upper end 26 of the tip section 18.

3) For a tip section 18 of the same weight, increasing the diameter of the upper end 26 reduces wall thickness and reduces durability.

4) To minimize the weight of the tip section 18, the wall of the tip section 18 can be made thinner. However, as the wall thickness decreases, the strength and rigidity of the tip section 18 decreases.

5) Changing the diameter and wall thickness of the tip section 18 changes the bending stiffness (flexibility). If the bending rigidity (flexibility) is too high or too low, the operability and feeling of the shaft become unacceptable.

Extensive testing of operability and durability has resulted in the definition of acceptable and preferred geometric ranges for the tip section 18 of a 46 inch wood shaft weighing 65-90 g. Was completed.

If the length of the tip section 18 is less than 6 inches, sufficient torsional rigidity to improve shot accuracy cannot be obtained. FIG. 2 was measured using a torque test and shows how the club torque decreases as the length of the tip section increases. FIG. 3 shows the small torque characteristics of the steel tip section compared to the graphite tip section.

If the tip section 18 is larger than 12 inches, the shaft weight will increase undesirably and the center of gravity of the shaft 16 will move significantly in the direction of the tip 24. FIG. 4 shows how the length of the tip section increases the shaft weight. FIG.
It shows the relationship of shaft length to tip section length of １２12 inches and that club swing weights in the range of D1 to D5 can be achieved using industry accepted head weights.

As the diameter of the upper end 26 of the tip section 18 increases beyond 0.415 inches, the bending stiffness becomes undesirable, adversely affecting the flexibility of the tip section, resulting in low ball trajectory and unpleasant feeling to the club. Give the ring. Similarly, tip section 1
As the diameter of the upper end 26 of the 8 decreases below 0.385 inches, the bending stiffness is undesirably reduced, giving a high ball trajectory and a too soft feel to the club.

Durability tests performed with an AirCanon have shown that the upper end 26 of the tip section 18 having a length in the range of 6 to 12 inches and a total shaft weight of less than 65 g has a diameter of 0.415 inches or more. Proved that a sufficiently durable tip section 18 could not be obtained.

In a preferred embodiment, a 46 inch wood shaft weighs 75 grams, an 8 inch long tip section 18, a 0.4 inch diameter top end 26, 0.335 or 0.350. And the diameter of the lower end 24 of inches. Such a preferred tip section 18 has a torque of less than 0.6 degrees (°) over an 8 inch length as measured using a torque test. This is for a typical graphite shaft tip section measured using the same test method.
Equivalent to torque greater than 5 degrees.

Referring now to FIG. 5, the joint 30 of FIG. 1 is shown in greater detail. An important factor affecting the durability of the vehicle 6 is the strength of the joint 30 between the metal tip section 18 and the composite hand section 20. As shown, the tip section 18 is in the form of a hollow metal cylinder and the hand section 20 is formed as a hollow composite cylinder. Hand section 20 has a small diameter cylindrical portion or plug 32 for insertion into tip section 18. The small diameter portion 32 can be formed during lay-up of the composite hand section 20, or after initial molding, the hand section material can be formed by grinding a predetermined annular amount. Small diameter part 3
2 is dimensioned to ensure a sufficient amount of overlap on the tip section 18 and a durable interconnect with the tip section 18.

The metal tip section 18 and the composite hand section 20 are joined together by an adhesive, such as an epoxy adhesive 31. The thickness of the adhesive 31 is carefully adjusted, and the surface area of the tip section 18 and the proximal section 20 along the adhesive 31 is large enough to ensure sufficient strength. The bond strength is selected so that the joint 30 does not break due to shear from torsional loads applied through generally acceptable abuse levels during golf game play. By limiting the maximum thickness of the adhesive 31 and increasing the surface area of the joint 30, the highest straightness specification of the assembled shaft 16 can be maintained.

[0034] Static and dynamic durability tests have demonstrated that the adhesive thickness should be adjusted to be between 0.003 and 0.006 inches. These tests also
For a metal tip section 18 having a diameter of the upper end 26 in the range of 0.385 to 0.415 inches, the composite hand section 20 should be about 0.75 to 1.5 in order to obtain sufficient bonding area. Metal tip section 1 in inches long
8 also proved to be inserted. In a preferred embodiment, the 46 inch shaft driver is 0.0045
The composite hand section 20 having an adhesive thickness of 20 inches
Is inserted into the metal tip section 18 for a length of 1.25 inches. Such a geometry has been shown to provide sufficient strength and straightness to the assembled shaft 16.

The overall bending stiffness of the shaft 16 (this is
Defining the flexibility of the shaft) includes a tip section 18,
It is influenced by the design of the geometry of the hand section 20 and the joint 30. The local stiffness of the joint 30 can be high, and the joint 30 must be sufficiently durable but have no excessive stiffness.

The range of flexibility for different categories of players with different swing characteristics is generally based on the True Temper Dynamic ™ which is often used as a reference point.
The range of flexibility provided by these shafts is accepted throughout the industry. For those using the geometric range and the total shaft weight defined above,
FIG. 6 shows that the bending stiffness of the shaft 16 through the joint is such that the Dy can ensure good feel and favorable ball flight.
It shows that it is comparable to the bending rigidity of the namic shaft. The stiffness in FIG. 6 was measured as the deflection of the tip section in a simple cantilever load test.

FIGS. 7 and 8 illustrate the wall thickness along the length of the metal tip section 18 and composite wrist section 20 of the preferred embodiment of the shaft 16 and the popular True
FIG. 4 compares wall thickness found on Temper Dynamic ™ steel shaft and popular Grafalloy Prolite ™ graphite shaft. It is clear that the wall thickness of the shaft 16 is very different from the wall thicknesses of the available True Temper steel shafts and Grafalloy graphite shafts. This indicates that the shaft 16 cannot be made by joining a tip section and a hand section cut from commercially available steel and graphite shafts.

Referring again to FIG. 5, the small diameter portion 3
The formation of 2 is shown to form an edge in the form of a radial wall of the hand section 20. Although the radial wall 34 is shown as being orthogonal to the small diameter portion 32, it can be formed at an acute or obtuse angle with the small diameter portion 32. A tip section 18 and a proximal section 20 along the circumference of the shaft 16 adjacent the fitting 30
The dimension of the radial wall 34 is equal to or equal to the thickness of the end 38 of the tip section 18 plus the thickness of the adhesive 31 such that a smooth concentric wall transition is formed between It is preferable to set it to be slightly larger.

Referring now to FIG. 9, there is shown a second preferred embodiment of the present invention. In this embodiment, the same components as those used in the previous embodiment are:
It is indicated by a reference number obtained by adding 200 to the reference number used in the above-described embodiment. The second embodiment differs from the previous embodiments in that an insulating layer 252 in the form of a plurality of spacers is inserted between the tip section 218 and the proximal section 220. It is preferable that the insulating layer 252 be in the form of a bead and be formed of an insulating material such as ceramic or glass. Insulation bead 252
Prevents the metal in tip section 218 from contacting the graphite in hand section 220 to reduce or eliminate galvanic corrosion in joint 230.

The bead 252 can also be
Assists in adjusting the alignment and separation of tip section 218 to zero. In this regard, the diameter of the bead 252 is selected according to the gap 242 and the adhesive 23 between the beads
While providing enough space for 1
The tip section 218 and the proximal section 220 are coaxially aligned so as to ensure a smooth outer peripheral surface along the shaft 216 adjacent to 30. Preferably, the beads 252 are pre-mixed with the adhesive 231 prior to application in the fitting 230.

Referring now to FIG. 10, a third embodiment of the present invention is shown.
An embodiment is shown. In this embodiment, the same components as those in the previous embodiment are denoted by the same reference numbers plus 300. This third embodiment includes a distal section 318 and a proximal section 32.
0 is different from the previous embodiment in that an insulating layer 352 in the form of an upper layer is provided between 0 and 0. Upper layer 352
Is preferably in the form of an insulating layer integrally formed along the outer surface of the small diameter portion 332 and the tip section 3
The 18 metal is preferably formed of an insulating material, such as ceramic or glass, to prevent contact of the 18 metal with the graphite in the hand section 320 to reduce or eliminate galvanic corrosion within the joint 330. Layer 352 also includes
Assists in adjusting the alignment and separation of tip section 418 relative to proximal section 320.

Preferably, layer 352 includes a small diameter portion 332.
Is formed by forming the hand section 320 with a relatively thick layer of glass at one end of the hand section 320 before formation. Next, the layer 35 as the outer surface of the small diameter portion 332 is formed.
A small diameter portion 332 is formed by grinding a predetermined amount of the annular portion of the glass to leave 2. With this configuration, the fabric 352 isolates the remaining composite of the hand section 320 from the metallic material of the tip section 318.

As shown in FIGS. 11 and 12, during manufacture of the shaft, the joint 430 between the steel tip section 418 and the graphite hand section 420 includes:
A plastic ferrule 500 is incorporated. Ferrule 500 is formed of a suitable extruded or injection molded plastic and is used to accommodate any slight geometric mismatch between graphite section 420 and steel section 418. The outer diameter of ferrule 500 is sized to be slightly larger than the diameter of either graphite section 420 or steel section 418. After assembly, excess material can be removed from the plastic ferrule 500 by buffing with an abrasive belt or wiping with a solvent such as acetone. By removing material from ferrule 500 in this manner, a smooth transition can be formed on the outer surface between steel section 418 and graphite section 420.

Since the cross section of the ferrule 500 forms an inwardly inclined surface as shown in FIG. 12, the rectangular shape in FIG. 11 can be changed. Such a geometry of the ferrule is used to match the small radius of the corner of the machined graphite wrist section 420, which facilitates the manufacture of the shaft 416.

Referring to FIGS. 1 and 2 again, the manufacturing process of the shaft 16 will be described. The hollow cylindrical hand section 20 is formed to a given length by arranging a plurality of layers of preselected conjugate fibers such as carbon graphite at different angles from each other and joining these layers with a resin. Is done. The hand section 20 can be
It can be formed on parallel, tapered or stepped sidewalls.
The small diameter portion 32 is formed at one end of the hand section 20 by grinding a predetermined amount of the annular material portion at one end of the hand section 20 during assembly.

The hollow cylindrical tip section 18 is formed to a given length by drawing a material of a metallic material such as high-strength steel or aluminum through a mandrel. The tip section 18 can be formed with parallel, tapered or stepped sidewalls as desired. The length and weight of the tip section 18 are selected as described above.

An adhesive is applied to at least a portion of the small diameter portion 32 and the inner surface of the tip section 18. Next, the reduced diameter portion 32 is telescopically inserted into the tip section 18. As shown in FIGS. 9 and 10, an insulating layer 52 can be inserted between the tip section 18 and the proximal section 20 to prevent galvanic corrosion within the joint 30.

While the preferred embodiment of the present invention has been described above, it will be understood that other embodiments and modifications thereof are possible within the scope of the present invention described in the appended claims.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a golf club shaft incorporating the teachings of the present invention.

FIG. 2 is a graph showing the relationship between the length of the metal tip section and the torsional resistance.

FIG. 3 is a graph showing the relationship of torsional resistance for a metal tip section and a composite tip section.

FIG. 4 is a graph showing the relationship of shaft weight to tip section length and its effect on club swing weight.

FIG. 5 is a detailed schematic cross-sectional view of the metal / composite joint of the golf club shaft of FIG. 1;

FIG. 6 is a graph showing the relationship between the tip section bending stiffness of a conventional steel shaft and the tip section bending stiffness of the shaft of the present invention.

FIG. 7 is a graph showing the relationship between the wall thickness of the tip section of the shaft of the present invention and the wall thickness of a conventional steel shaft.

FIG. 8 is a graph showing the relationship between the wall thickness of the proximal section of the shaft of the present invention and the wall thickness of a conventional graphite shaft.

FIG. 9 is a detailed schematic cross-sectional view of a metal / composite joint of the golf club shaft of FIG. 1 according to a second embodiment of the present invention.

FIG. 10 is a detailed schematic cross-sectional view of a metal / composite joint of the golf club shaft of FIG. 1 according to a third embodiment of the present invention.

FIG. 11 is a detailed schematic cross-sectional view of a metal / composite joint of the golf club shaft of FIG. 1 according to a fourth embodiment of the present invention.

FIG. 12 is a detailed schematic cross-sectional view of the metal / composite joint of the golf club shaft of FIG. 1 according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 golf club 16 shaft 18 tip section 20 hand section 30 joint 31 adhesive 32 small-diameter cylindrical portion (plug) 252 insulating layer (bead, fabric) 500 ferrule

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Michael Dee Walker United States Tennessee 38117 Memphis Sea Isle Road 1463 (72) Inventor Scott Dee Cokin United States Tennessee 38028 Eds North Lead Hocker Road 2430 (72) Inventor James S. Thomas United States Tennessee 38133 Bartlett Tina Cole 7436 (72) Inventor Graeme Howood United Kingdom Tennessee 38138 Germantown Cross Ridge Drive 7891 F-term (reference) 2C002 AA05 AA08 CS03 MM02 MM04 PP01 PP02 SS01 SS02 SS03

Claims (20)

[Claims] 1. A tip section formed of a metallic material and having a length of about 6 to 12 inches and a top diameter of about 0.385 to 0.415 inches; and a composite section and connected to said tip section. A shaft having a shaped hand section. 2. The shaft of claim 1, wherein said tip section has a lower end, said lower end having a diameter of about 0.335 to 0.350 inches. 3. The tip section may be about 0.0125 to
The shaft of claim 1 having a wall thickness of 0.0175 inches. 4. The hand section may be about 0.025-0.
2. The method of claim 1, wherein the wall thickness is 125 inches.
The shaft described. 5. The shaft according to claim 1, further comprising an adhesive disposed between the tip section and the proximal section. 6. The shaft according to claim 5, wherein said adhesive has a thickness of about 0.003-0.006 inches. 7. The shaft according to claim 1, wherein the proximal section has a plug nested within the distal section. 8. The tip section may include about 0.75-1.
The shaft of claim 1, wherein the shaft overlaps the plug over a length of 5 inches. 9. The shaft according to claim 1, further comprising a plastic ferrule disposed between the tip section and the proximal section. 10. The shaft according to claim 1, further comprising an insulating layer disposed between the tip section and the proximal section. 11. The insulating layer, wherein: the insulating layer includes a plurality of insulating spacers disposed between the distal section and the proximal section; and a glass layer formed as an outer surface of the distal section so as to be close to the proximal section. 11. The shaft of claim 10, further comprising one. 12. A plug having a distal section formed of a metallic material and a proximal section formed of a composite material, the proximal section extending from one end thereof and being telescopically received within the distal section. And wherein the tip section overlaps the plug over a length of about 0.75 to 1.5 inches. 13. The shaft according to claim 12, wherein said tip section has a length of about 6 to 12 inches. 14. The hand section may be about 0.025 to
13. The shaft of claim 12, having a wall thickness of 0.125 inches. 15. The tip section may be between about 0.0125 and
13. The shaft of claim 12, having a wall thickness of 0.175 inches. 16. The shaft according to claim 12, wherein said tip section has an upper end and a lower end, said upper end having a diameter of about 0.385 to 0.415 inches. 17. The tip section has an upper end and a lower end, the diameter of the upper end being about 0.385 to 0.415.
13. The shaft of claim 12, wherein the shaft is inches. 18. The shaft according to claim 12, further comprising an adhesive disposed between the tip section and the proximal section. 19. The method according to claim 19, wherein the adhesive is about 0.003-0.006.
19. The shaft of claim 18 having a thickness of inches. 20. The shaft according to claim 12, further comprising a plastic ferrule disposed between the tip section and the proximal section.