JPH06126005A - Multilayer structure shaft with damping layer - Google Patents

Abstract

PURPOSE: To provide a multilayer structural shaft in which torsional rigidity and longitudinal rigidity are controllable respectively and independently. CONSTITUTION: A multilayer structural shaft having an attenuating layer consists of an inner structural part and an outer structural part. There is arranged a viscoelastic shear film, i.e., an attenuating layer 26, between the inner structural part and the outer structural part. The attenuating layer 26 increases torsional attenuating characteristics and an amplifying ratio at a resonance time during torsional impacting. The shaft is formed as an inner core consisting of a fibrous layer with high strength. Most of the fibrous layer inclines at a certain spiral angle, that is +45 degrees and -45 degrees against a longitudinal axis of the shaft, to make the inner core having high torsional rigidity. An outer shell surrounds the inner core, and the shell is formed of a fibrous layer with high strength, which gives appropriate rigidity in a longitudinal direction. The viscoelastic attenuating layer controls attenuation and rigidity between the core and the shell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to multi-layered shafts, and more particularly to shafts capable of controlling torsional and longitudinal stiffness and related properties.

Golf clubs are generally constructed from a club shaft having predetermined performance characteristics and a club head having auxiliary performance characteristics. In order to ensure optimum performance when hitting a golf ball, many factors need to be considered when designing the club head and club shaft. Many of the factors in designing club heads and club shafts are dimensional and static mass characteristics. For example, the main design parameters of a club head are total mass, moment of inertia, club face angle and surface characteristics, "envelope" size, and center of gravity location.
Similarly, the main design parameters for a club shaft are the length of the shaft, its diameter and the change in shaft diameter along its length, total mass, and its flexural characteristics. The flexural and torsional damping properties play a direct and major role in determining the "feel" of the golf club over its entire stroke, which is commonly referred to as the "flexibility" of the shaft. The bending rigidity and the torsional rigidity in the longitudinal direction are included.

The stroke of a golf club can be divided into several distinct parts. Takeaway, backswing, downswing, impact, and follow-through. During the takeaway, the golf club is swung behind the ball, with the shaft flexing somewhat so that the club head lags behind the club shaft. When the takeaway is full and downswing begins, the direction of movement of the shaft and the direction of movement of the club head are reversed and the club head lags behind the shaft again. The amount of club head delay is, in part, a function of the longitudinal flex characteristics of the shaft and the location of the design flex points (ie, high flex, mid flex, or low flex). . The club head is located at the tip of the club shaft,
During downward acceleration, the club head is accelerated more than any part of the club shaft, and, in most club shafts, the club head precedes the club shaft at the point of downswing prior to impact. Due to the flex characteristics of the club shaft, the club head has downswing flight characteristics somewhat similar to their purpose in tether flights. Among the results of the club head flight characteristics prior to impact, there is little change in the angle of the club face with respect to the longitudinal axis of the undeflected shaft. This angle change is
It affects the engagement between the club surface and the ball during impact and the resulting flight trajectory. Upon impact, the golf ball is pressed to form a contact surface or "patch" between the club surface and the pressed surface of the golf ball. A part of the coupling moment between the club head and the club shaft is given to the golf ball through this patch. As a result of the movement of the moment from the club face to the ball at impact, the club shaft flexes rearward and the club head again lags behind the club shaft and follows the club shaft.
During the follow-through after impact, the club head oscillates between the lag position and the lead position as a result of the natural frequency of the club shaft. These vibrations include some modal orders above the lowest order. Determining most of the "feel" of a golf club is the flexural characteristic of torsion in the longitudinal direction.

The flight trajectory of a golf ball can be partially controlled by the direction of the club surface at the time of impact. In addition to the angular change due to the flex characteristics of the club shaft, the position of the contact patch between the ball and the club surface at impact also affects the flight direction. The flight direction is the intended direction when the impact location is at the intersection of the node lines with respect to the critical mode of vibration of the club, ie the so-called "sweet spot". Impact position is "off" from "sweet spot"
When it is moving, that is, when it is deviated to the front end or the rear end side of the club surface, the flight locus deviates to the left or right of the intended flight direction. If the impact position is off center, the club shaft will experience a torsional moment. This twisting moment causes the club shaft to twist in either direction of rotation. As a result, due to the torsional rigidity of the club shaft,
The flight trajectory at the time of an off-center impact is affected.

Due to the importance of the "feel" of a golf club, many design efforts have been made to date regarding the longitudinal flex characteristics of golf club shafts. For example, a part of the shaft is provided with a bending zone, that is, a high shaft bending zone, an intermediate shaft bending zone, a low shaft bending zone, or the diameter of the shaft gradually changes along the length direction of the shaft, Some change in stages. Since shafts are typically made from a single material, such as steel, aluminum, titanium, etc., a compromise must be made between torsional stiffness and longitudinal flexural characteristics to create optimal feel and characteristics. I won't. As is known, high torsionally stiff shafts may also have longitudinal flex characteristics, which provides a suboptimal "feel".

Club shaft designs have been advanced by using bicomponent fibers. Composite fiber shafts are made with directional non-metallic fibers such as graphite, boron, glass, etc. as a cement matrix. For example, the inner core of the shaft is made from a laminate of fibers. The fiber laminate is oriented at an auxiliary angle with respect to the longitudinal axis of the undeflected shaft, such as an angle in the range of -45 degrees to +45 degrees, which provides some torsional and longitudinal stiffness. To be An outer lamina having fibers parallel to the axis of the shaft is formed around the inner core, forming a shell that is substantially longitudinally rigid. As is well known, longitudinal stiffness can be adjusted by changing the size and number of longitudinal fibers, and torsional stiffness can be adjusted by changing the orientation angle of the fibers. And thus some degree of independence can be provided between these two properties. Although much effort has been made in the past to improve the static torsional rigidity, it has been difficult to achieve a large torsional rigidity with conventional length shafts having sufficient flexural characteristics. For this reason, many shafts do not have the highest torsional rigidity of metal or alloy golf shafts.

[0007]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a multi-layered shaft whose torsional rigidity and longitudinal rigidity can be adjusted independently.

Another object of the present invention is to provide a multi-layered shaft having a dynamic torsional rigidity that does not adversely affect the longitudinal rigidity of the shaft.

Yet another object of the present invention is to provide a multi-layer shaft having dynamic torsional stiffness that mitigates the effects of off-center impact.

Yet another object of the present invention is to provide a multi-layer shaft having damping characteristics that reduces the amplification ratio at resonance. Here, the amplification ratio refers to the relationship between the input to the shaft and the amplification of the output displacement of the shaft.

In view of these objectives, the present invention provides a multi-layered shaft of conventional dimensions. This shaft has the dynamic torsional rigidity achieved by a damping shear layer during torsional impact. The multi-layered shaft is composed of an inner structural portion and an outer structural portion, one of which mainly provides longitudinal rigidity characteristics and the other of which mainly torsional rigidity characteristics. A viscoelastic shear film or damping layer is provided between the inner structural portion and the outer structural portion, which damping layer reduces to some extent the relationship between the dynamic phenomena of bending and torsion. The damping layer contributes both to stiffness and to damping of shear forces between the two layers, while maintaining a balance between shear stiffness and shear damping that produces the desired dynamic properties. This damping layer contributes to the improvement of the torsional damping characteristic that effectively increases the dynamic torsional rigidity at the time of torsional impact.

In an embodiment of the invention, the shaft is formed as an inner core made of a high strength fiber layer.
This high strength fiber layer is -4 with respect to the longitudinal axis of the shaft.
The helix angle is in the range of 5 degrees to +45 degrees, so that the inner core has high torsional rigidity. The outer shell surrounds the inner core and is formed as a high strength fiber layer oriented for maximum stiffness in the longitudinal direction (eg, oriented parallel to the longitudinal axis). The viscoelastic damping or shear layer is located between the inner core and the outer shell and forms part of the length of the shaft, blocking some of the bond between the inner core and the outer shell. The damped shear layer increases the dynamic torsional damping properties, resulting in a disproportionately large increase in dynamic torsional stiffness against transient impact torques.

In another embodiment of the invention, the shaft is made from an alloy such as steel, aluminum or titanium and is formed as an inner core having high torsional rigidity. The outer shell surrounds the inner core and is oriented for maximum rigidity in the longitudinal direction (eg, oriented parallel to the longitudinal axis).
It is formed as a high-strength fiber layer. A damping shear layer is located between the inner core and the outer shell and forms part of the length of the shaft, effectively separating the inner core and the outer shell from each other. The damping shear layer increases the torsional damping properties, resulting in a disproportionately large increase in dynamic torsional stiffness over transient impact torques.

With respect to golf club shafts, the shear layer can be provided between the layers of the multi-layered shaft or between the lower end of the shaft and the hosel of the club head.

The shear layer is made of a viscoelastic material such as a polymer. The thickness of the viscoelastic material is typically 0.015 inches or less, but the exact dimensions are determined based on the particular design requirements. The energy absorption of viscoelastic material is
It is determined as a function of its shear properties, the contact surface between the inner core and the outer shell, the time / magnitude properties of the impact profile.

The multilayer shaft provided by the present invention is provided with a damping layer, and it is possible to adjust both characteristics of torsional rigidity and longitudinal rigidity to some extent independently. This is not possible with a shaft made of a single material, and it can achieve high dynamic torsional rigidity suitable for golf club shaft applications.

Other objects and scope of application of the present invention will become apparent from the following detailed description given with reference to the drawings. The same parts in the drawings are represented by the same numbers.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a golf club 10 having a multilayer shaft according to the present invention. Golf club 10
Has a substantially cylindrical shaft 12 formed along the longitudinal axis Ax, and the shaft 12 is provided with a grip 14 at its upper end and a club head 16 at its lower end. The shaft 12 is tapered from its upper end to its lower end, and the lower end of the shaft 12 has a hosel 18
Is fitted into. Shaft 12 has a damping zone 20 extending a predetermined length along shaft 12 and further has a torsion damping layer (not shown in FIG. 1). The torsion damping layer improves the dynamic torsional rigidity of the shaft 12 and the golf club 10.

As shown in FIG. 2, the shaft 12 comprises a hollow core 22, an outer shell 24, and a viscoelastic damping layer 26. The damping layer 26 is located between the hollow core 22 and the outer shell 24, and the shaft 12 It has a predetermined length along the length direction and forms an attenuation zone 20. As described below in connection with FIG. 6, the hollow core 22, the outer shell 24 and the damping layer 26 are formed as a single laminated structure. The hollow core 22 consists of at least two layers L1 and L2 of a fiber reinforced matrix. Two layers L1, L
The orientation of the fibers at 2 forms a predetermined helix angle with respect to the longitudinal axis Ax. For example, +45 degrees and -45 degrees. The two layers L1 and L2 can also be formed from a plurality of subsidiary layers. The hollow core 22 has a large static torsional rigidity due to the directivity of its fibers. The outer shell 24 consists of at least one layer L3 of fiber-reinforced matrix, the main orientation of the fibers being along the longitudinal axis Ax. That is, it is 0 degree. The outer shell 24 has a large bending rigidity due to the directivity of the fibers in the longitudinal direction. The damping layer 26 is in the form of a thin sheet of viscoelastic material sandwiched between the hollow core 22 and the outer shell 24 and functions as a shear layer between the outer shell 24 and the hollow core 22 at impact. .
As described below, the damping layer 26 has the function of increasing the dynamic torsional rigidity at the time of impact, so that the desired rigidity value can be obtained without increasing the mass or the total length of the shaft 12. Has been done.

As shown in the cross-sectional view of FIG. 3, the damping layer 26 is sandwiched between the outer surface of the hollow core 22 and the inner surface of the outer shell 24 so that both the core 22 and the shell 24 and the surfaces are in close contact. Is in contact with. In general, maintaining contact between surfaces is extremely important because damping efficiency is related to the degree of surface contact. As described below, the outer surface of the hollow core 22 is preferably polished or machined to allow the desired surface contact. As shown in the enlarged view of FIG. 4, if necessary, a filler 28 such as epoxy cement may be used on the outer surface of the hollow core 22 to fill the concave portion of the surface before the surface treatment process. By this surface treatment step, the surface of the other party to which the damping layer 26 is bonded can be made smooth and uniform.

The shaft 12 is made according to the combination sequence shown in FIG. As shown in FIG. 5, a series of flags F1, F2, F3 having a pennant shape from the raw material dough.
Cut F4. The number and shape of the flags can be variously changed depending on the shape of the shaft as the final product. Suitable raw materials include curable epoxy,
Alternatively, there is a cement having a function equivalent to that using graphite, boron, or glass fiber. Further, it is possible to use fabrics having different kinds of fibers for one shaft. A preferred fiber reinforced fabric is a 36 inch wide roll of "HYE6048A1A tape" sold by ICI under the tradename "FIBERITE". The flags F1 and F2 are cut from the tape so as to form an auxiliary angle with respect to the main direction of the tape, that is, +45 degrees and -45 degrees. The flags F3 and F4 are cut from the raw material so that the fibers are arranged along the main direction of the tape. Each flag Fn is overlaid on a solid metal mandrel 30. Depending on the shape of the shaft 12, the diameter of the mandrel 30 tapers from its handle end side towards its lower hosel end. Apply sticky adhesive to the mandrel 30 and set the flag F1 on the mandrel
0 manually or mechanically, and the flag F2 is manually or mechanically superimposed on the flag F1. Flags F1 and F2 provide both longitudinal and torsional stiffness in the resulting shaft 12 due to their supplemental angular orientations. Then, the damping layer 26 is formed on the hosel end portion at the lower end. The damping layer 26 is 0.0005 to 0.
It is preferably a polymer elastomer having a film thickness of 006 inches. The properties and thickness of the viscoelastic material of the damping layer 26 are determined by the final properties desired for film thicknesses ranging from 0.0001 to 0.015 inches.
In general, the thicker the film, the smaller the shear and energy absorption rate as compared to the thinner film, and the energy absorption rate is also related to the contact surface area. In a cylindrical shaft, the contact surface area is empirically determined and is a function of the length of damping zone 20. Looking at one golf club application, the damping layer 26 extends about 8 inches along the lower end of the shaft 12. Also, attenuation zone 2
0 is a longer distance along the shaft 12 if desired,
Alternatively, it may be a shorter distance. A preferred film is an acrylic material such as poly (butyl acrylate: acrylic acid), sold by 3M as ISD110 or ISD113 film,
It has a film thickness of 00175 to 0.0045 inches. This damping film has a sticky surface,
The flags can be overlaid on the flags F1, F2. After forming the damping layer 26, the flag F3 is superimposed on the damping layer 26 at the lower end of the combination layer, and the flag F3 is added to the flag F3 in the remaining length of the combination layer.
Stack on the surface of 2.

After the flag superposition process is completed, a wrapping tape (not shown) is wrapped around the uncured shaft and the taped assembly is placed in an oven to cure the epoxy carrier. After curing, the outer surface of the shaft assembly is polished or machined to final dimensions. In addition, a protective coating is applied if necessary.

In the golf club, the presence of the damping layer 26 inside the shaft 12 greatly increases the dynamic torsional damping at the time of impact. FIG. 6 is a graph comparing the torsional mode damping of four shafts. The vertical axis represents torsional damping, and the horizontal axis represents frequency (Hz).
Graph S1 represents a shaft without a damping layer, graph S
2, S3 and S4 are each made of ISD110 and have a thickness of 0.0
1 illustrates a shaft having a 045 inch damping layer 26, a 0.00175 inch thick damping layer 26 of ISD 110, and a 0.002 inch thick damping layer 26 of ISD 113. As can be seen, the presence of the damping layer 26 increases the average 300% torsional damping. The flag or sheet stacking method shown in FIG. 5 is the preferred method, but is wound with filaments,
It is also possible to assemble the shaft using layers knitted with filaments.

In the embodiments described above, the shaft is made of reinforcing fibers, but the shaft can be made of other materials. For example, as shown in FIG. 7, the shaft 12 'may be formed from a hollow metal core 22',
A viscoelastic damping layer 26 'is arranged around 2'and the damping layer 2
It is also possible to form a fiber reinforced shell 24 around 6 '. The metal core 22 'can be made of a metal commonly used in golf club shafts. For example,
Steel, steel alloy, aluminum, titanium, etc. By providing the damping layer 26 ',
The same effect as the embodiment shown in FIG. 6 can be obtained. That is, dynamic torsional damping can be greatly increased by absorbing the impact energy resulting from an off-center impact.

The concept of the present invention can be extended to the entire golf club by providing a damping layer 26 between the outside of the conventional golf club shaft and the inside surface of the hosel, as shown in FIG.

As described above, the case where the present invention is applied to a golf club has been described as an example, but the present invention can be used for other purposes. For example, it can be applied to a bicycle frame in which the torsional rigidity and the longitudinal rigidity of the structural member are important issues.

As will be appreciated by those of ordinary skill, the multi-layered shaft with damping layer of the present invention is susceptible to various modifications and variations without departing from the scope of the present invention. And changes should be considered equivalent.

[Brief description of drawings]

FIG. 1 is a perspective view of a golf club having a multi-layered shaft with a portion of the length of the golf club forming a viscoelastic damping layer that increases the dynamic torsional stiffness of the shaft.

FIG. 2 is a partial perspective view of the shaft shown in FIG. 1, with other parts removed to show the internal structure.

3 is a lateral cross-sectional view of the shaft shown in FIG. 2 taken along line 2-2.

4 is a longitudinal cross-sectional view of the shaft shown in FIG. 2 taken along line 4-4.

5 is a schematic diagram showing a flag shape and a mandrel combination sequence when forming the shaft shown in FIG.

FIG. 6 is a graph showing the difference in torsional mode damping between a shaft without a damping layer and three test shafts with damping layers of three different thicknesses.

FIG. 7 is a cross-sectional view of another embodiment of a shaft having a metal core, a composite shell and a damping layer disposed therebetween.

FIG. 8 is a partial front view of an embodiment in which a damping layer is attached to a club head at different positions.

[Explanation of symbols]

 10 Golf Club 12 Shaft 14 Grip 16 Club Head 18 Hosel 20 Damping Zone 22 Hollow Core 24 Outer Shell 26 Damping Layer 28 Filler 30 Mandrel

Claims (26)

[Claims] 1. A shaft having an outer peripheral surface and extending in the axial direction, the shaft being made from a fiber matrix having a predetermined number of fibers at an angle to said axis. A damping layer disposed inside the fiber matrix between the axis and the peripheral surface and extending along at least a portion of the axis, the damping layer affecting torsional damping of the shaft; Shaft with. 2. The shaft comprises a first portion and a second portion, the first portion extending between the shaft and the second portion, the second portion between the first portion and the outer surface. The shaft according to claim 1, wherein the shaft extends. 3. The shaft according to claim 2, wherein the damping layer is disposed inside the fiber matrix between the first portion and the second portion. 4. The shaft according to claim 2, wherein the first portion has fibers that form an angle of 0 degrees or more with the axis. 5. The predetermined fibers of the first portion form an angle of +45 degrees with respect to the axis, and the other fibers of the first portion form an angle of −45 degrees with respect to the axis. The shaft according to claim 4, wherein: 6. The second portion comprises fibers having an angle of 0 degrees with respect to the axis.
Shaft described in. 7. The shaft according to claim 1, wherein the damping layer is made of a viscoelastic film. 8. The shaft according to claim 6, wherein the viscoelastic film is a film having a thickness of 0.015 inch or less. 9. The shaft according to claim 1, wherein the shaft is hollow. 10. A shaft having a first material extending along a longitudinal axis to form an inner portion and a second material surrounding the first material and forming an outer portion; and the inner portion. A damping layer between the outer portion and extending along at least a portion of the axis, the damping layer increasing torsional damping of the shaft. 11. The shaft according to claim 10, wherein the first material is a metal. 12. The shaft according to claim 11, wherein the second material is a directional fiber matrix. 13. The shaft according to claim 12, wherein the shaft is hollow. 14. The shaft according to claim 10, wherein the damping layer is made of a viscoelastic film. 15. The shaft according to claim 14, wherein the viscoelastic film is a film having a thickness of 0.006 inches or less. 16. A club head having a club surface for hitting a golf ball, and a shaft connected to the club head and formed of a directional fiber material around an axis extending in the longitudinal direction, the shaft comprising: A shaft having orthogonal cross sections, and a viscoelastic damping layer formed in the fibrous material between the axis and an outer surface, extending along at least a portion of the axis and increasing torsional damping of the shaft. A golf club equipped. 17. The shaft comprises a first portion and a second portion, the first portion extending between the shaft and the second portion, the second portion between the first portion and the outer surface. The golf club according to claim 16, wherein the golf club extends. 18. The golf club according to claim 17, wherein the damping layer is disposed inside the fiber matrix between the first portion and the second portion. 19. The golf club according to claim 17, wherein the first portion has fibers that form an angle of 0 degrees or more with the axis. 20. The predetermined fibers of the first portion form an angle of +45 degrees with respect to the axis, and the other fibers of the first portion form an angle of -45 degrees with respect to the axis. The golf club according to claim 18, wherein: 21. The golf club of claim 18, wherein the second portion comprises fibers that make an angle of 0 degrees with the axis. 22. The golf club according to claim 16, wherein the damping layer is made of a viscoelastic film. 23. The golf club according to claim 22, wherein the viscoelastic film is a film having a thickness of 0.015 inches or less. 24. The golf club according to claim 16, wherein the shaft is hollow. 25. A club head having a club surface for hitting a golf ball and a hosel, a shaft having a lower end fitted into the hosel, and a shaft disposed between the lower end of the shaft and the hosel. And a viscoelastic damping layer that increases the torsional damping of the golf club. 26. A step of forming a shaft core member made of a selected material, a step of overlaying a viscoelastic damping layer on at least a part of the core member, and a step of overlaying the viscoelastic damping layer and the core member. And a step of forming an outer shaft portion on the shaft.