Couplings for securing golf shaft to golf club head

A coupling for securing a golf shaft to a golf club head includes a first component configured to contact, and engage with, the golf shaft, and a second component bonded to the first component and configured to space the first component from the golf club head. The second component includes a second material having a Young's modulus less than a first material of the first component. In another aspect, a coupling includes a shaft engagement element, and a spacer configured to space the first component from the golf club head so that the golf shaft is above the golf club head in its entirety. The spacer includes a material having a Young's modulus no greater than about 10 Gpa. In another aspect, a kit includes a first coupling and a second coupling with at least one of a structural configuration or a material of a vibration dampening element differing.

BACKGROUND

Golf equipment designers traditionally have been interested in improving the “feel” of a golf club head, “feel” being the combination of impact effects between a golf club and a golf ball capable of being sensed by the golfer. The feel of a golf club can include at least in part vibrations emanating through the golf club when contacting the golf ball. These vibrations can be particularly apparent to the golfer when using a putter, which may involve a generally slower and more finely controlled motion than when using other types of golf clubs.

The materials used for a golf club (or club head) or the total weight of a golf club (or club head) may provide a softer or harder feel when striking a golf ball. For this reason, some putters may include an insert material on a striking face of the golf club head that is made of a different material than a remaining portion of the golf club head, or may include a milled striking face to give the putter a softer feel upon impact with a golf ball. Golfers may also add tape, such as a lead tape, to a golf club head to increase the weight of the golf club head and attempt to provide a softer feel when contacting a golf ball. However, such features often fall short of adequately isolating undesirable vibrations resulting from impact and inadequately provide vibration dampening in a manner tailorable to a particular golfer or class of golfer.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one of ordinary skill in the art that the various embodiments disclosed may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the various embodiments.

FIG. 1Ais a partial perspective view of a golf club including golf shaft20and golf club head10according to an embodiment. As shown inFIG. 1A, golf shaft20is coupled to hosel12of golf club head10. In addition, spacer102acts to space golf club head10from golf shaft20so that when operably secured to golf shaft20, a majority of, and preferably an entirety of, an exterior surface of the golf shaft20isolated from the interior surface of the hosel12of the golf club head10. As will be discussed in more detail below, spacer102can serve as a hosel sleeve that acts as a vibration dampening element between golf club head10and golf shaft20to attenuate vibrations, preferably high frequency vibrations, excited from impact with a golf ball. This arrangement can ordinarily provide a softer feel perceived by a golfer holding a grip (not shown) of golf shaft20.

In more detail, spacer102can be bonded to an internal shaft engagement element (e.g., engagement element104inFIGS. 1B and 1C) configured to engage with golf shaft20and provide the coupling100with a similar strength and bending stiffness or flexural rigidity to a tip portion of golf shaft20(of which it may substitute). A shaft engagement element having comparable bending stiffness to the tip portion of golf shaft20can help reduce curvature at the coupling between golf shaft20and golf club head10when a bending moment is applied to the golf club.

According to beam theory, the relationship between an applied bending moment and the curvature of a beam is:

M=EI⁢d⁢2⁢wdx2
where M is the bending moment, E is the Young's modulus or elastic modulus of the material, I is the area moment of inertia of the beam cross section about the bending axis, w is the deflection of the beam, and x is the distance along the beam. Accordingly, if a golf club is treated as a beam, the curvature,

d⁢2⁢wdx2,
of the golf club at a given cross section due to a moment applied to the golf club is proportional to the product of E and I, which is the bending stiffness at the cross section. The selection of material and treatment of the material (if any) where the golf shaft couples to the golf club head affects the bending stiffness by its Young's modulus, as does the cross-sectional area of the material, which affects the area moment of inertia, I.

In view of the foregoing, it is generally desirable in terms of reducing curvature and possible plastic deformation of a golf club where the golf club head couples to the golf shaft to attempt to match as close as possible the bending stiffness and strength of the coupling to the tip portion of the golf shaft. However, materials typically used for golf shafts for their higher bending stiffness and strength, such as treated steel, do not provide much, if any, vibration dampening due to their relatively high Young's modulus (i.e., stiffness). As discussed in more detail below, the present disclosure includes couplings that provide greater vibration damping for a softer feel, while still providing a bending stiffness and strength comparable to the tip portion of a golf shaft.

FIG. 1Bis an exploded perspective view of the golf club inFIG. 1A. As shown inFIG. 1B, golf shaft20can be secured to golf club head10using coupling100, which includes a first component, shaft engagement element104, and a second component, spacer102. Coupling100is configured such that, when operably secured to golf club shaft20and golf club head10, golf shaft20is located above the hosel of the golf club head10in its entirety. For all purposes herein, unless otherwise stated, “above” and “below” are relative terms to be considered along a directional axis corresponding to the virtual central longitudinal axis of a hosel (e.g. hosel12) of a golf club head (e.g. club head10, whereby “up” refers to the direction, along the central longitudinal axis from a sole-touching location of the axis to a hosel tip-touching location of the central longitudinal axis. Accordingly, “above the hosel of the golf club head” corresponds to being upward of the hosel as measured along the central longitudinal hosel axis.

Shaft engagement element104is configured to contact, and engage with golf shaft20, and made of a material having a greater Young's modulus than spacer102to provide coupling100with a comparable bending stiffness to the tip portion of golf shaft20. In this regard, shaft engagement element104can include a material with a Young's modulus no less than (i.e., greater than or equal to) 30 GPa, more preferably no less than 75 GPa, and even more preferably, no less than 100 GPa. In some examples, shaft engagement element104can include a material with a Young's modulus between 100 GPa and 200 GPa. Shaft engagement element104can be made of a material, such as steel, stainless steel, titanium, titanium alloy, aluminum, zinc, or copper. In the example ofFIG. 1B, shaft engagement element104is a hollow pin with internal pin bore105, but other embodiments may include a solid shaft engagement element, as in the embodiments ofFIGS. 6A to 6C and 7A to 7Cdiscussed below.

Spacer102, on the other hand, is configured to space shaft engagement element104from golf club head10in an operating position. In addition, spacer102comprises a material having a Young's modulus less than the Young's modulus of the material for shaft engagement element104to attenuate vibrations excited when golf club head10strikes a golf ball. In this regard, spacer102can include a material with a Young's modulus no greater than (i.e., less than or equal to) 10 GPa, more preferably no greater than 5 GPa, and even more preferably between 1 GPa and 5 GPa. The material for spacer102can include, for example, an elastomer, a natural rubber, a synthetic rubber, a polyurethane (e.g., Sorbothane), an acetal resin (e.g., Derlin), a thermoplastic material (e.g., polyethylene or polypropylene), a polyamide, or a fiber-reinforced resin. In addition, since spacer102is exposed to an exterior of the golf club, the material used for spacer102can have a hardness of Shore 20D to 70D, or higher, for durability.

In some implementations, a ratio of the Young's modulus of the material for shaft engagement element104to the Young's modulus of the material for spacer102can be no less than 3. For example, the Young's modulus of the material used for engagement element104may be no less than about 30 GPa, and the Young's modulus of the material used for spacer102may be no greater than about 10 GPa. More preferably, the ratio of the Young's modulus of the material for shaft engagement element104to the Young's modulus of the material for spacer102may be no less than 15. Even more preferably, the ratio of the Young's modulus of the material for shaft engagement element104to the Young's modulus of the material for spacer102may be no less than 25.

In some examples, engagement element104can include a titanium alloy with a Young's modulus of 105 to 120 GPas or steel with a Young's modulus of 180 to 200 GPa. Spacer102, in contrast, can include a plastic material with a Young's modulus of 1 GPa to 3 GPa, an aramid material with a Young's modulus of 70 to 112 GPa, or a composite material with a Young's modulus of 150 GPa.

FIG. 1Cis a further exploded perspective view of the golf club ofFIGS. 1A and 1Bdepicting the components of coupling100in more detail. As shown inFIG. 1C, shaft engagement element104is configured to fit within shaft internal bore22of golf shaft20. In some implementations, the inner diameter of the shaft internal bore22may be increased as compared to conventional golf shafts to allow for a larger outer diameter or cross-sectional area of shaft engagement element104. Increasing the cross-sectional area of shaft engagement element104can allow for a greater bending stiffness by increasing its area moment of intertia, I, as discussed above. Shaft engagement element104may be bonded, for example, by chemically adhering shaft engagement element104into shaft internal bore22using an epoxy resin. In other implementations, shaft engagement element104may be frictionally fitted into shaft internal bore22. Such frictional fitting implementations may allow for the addition and removal of coupling100or a golf club shaft by a golfer or retailer in the field.

Similarly, spacer102is configured to fit within hosel internal bore14of hosel12with hosel engagement portion110of spacer102fitting within hosel internal bore14. In some implementations, a diameter of hosel internal bore14may be increased as compared to conventional hosels to allow for more of the vibration dampening material of spacer102. Hosel engagement portion110may be bonded by, for example, chemically adhering hosel engagement portion110into hosel internal bore14using e.g. an epoxy resin. In other implementations, hosel engagement portion110may be frictionally fitted into hosel12. Such frictional fitting implementations may allow for the addition and removal of coupling100by a golfer or retailer in the field.

An outer sleeve portion106of spacer102extends radially from a hosel engagement portion110of spacer102and is located between hosel12and golf shaft20when assembled into an operating position. This arrangement allows outer sleeve portion106to prevent hosel12from directly contacting golf shaft20, which can help dampen vibrations emanating from golf club head10to golf shaft20.

FIG. 2Ais a perspective view of coupling100fromFIGS. 1B and 1Cin isolation.FIG. 2Bis a cross-section view of coupling100along cross-section line2B inFIG. 2Awhen in contact with golf shaft20. As shown inFIGS. 2A and 2B, coupling100includes annular groove116between shaft engagement element104and spacer102for receiving and securing golf shaft20. In addition, outer sleeve portion106of spacer102includes chamfer107to provide a safer, more durable, and/or more aesthetic construction for outer sleeve portion106, which is exposed on an exterior of the golf club when it is assembled in the operating position shown inFIG. 1A.

As shown inFIG. 2B, spacer102shrouds or encircles a lower portion of shaft engagement element104, and also shrouds or encircles a tip portion of golf shaft20where shaft engagement element104and the tip portion of golf shaft20overlap. Spacer102can be bonded to shaft engagement element104and golf shaft20. In some implementations, spacer102may be bonded to shaft engagement element104by co-molding spacer102with shaft engagement element during a molding process. In other implementations, spacer102may be bonded to shaft engagement element104by gluing spacer102to shaft engagement element104. Spacer102may be bonded to golf shaft20, for example, by glue (e.g., an epoxy glue).

Shaft engagement element104fits within shaft internal bore22of golf shaft20with the tip portion of golf shaft20interiorly contacted or supported by shaft engagement element104and exteriorly contacted or supported by lateral shaft support surface114of spacer102. Shaft engagement element104is also in contact with base113of spacer102and interior surface112of hosel engagement portion110of spacer102. Indentations in base113of spacer102can provide better engagement between shaft engagement element104and spacer102.

A wall thickness of spacer102encircling shaft engagement element104(e.g., hosel engagement portion110) may be selected in some implementations to allow for a larger outer diameter of shaft engagement element104for a greater bending stiffness. However, the thinness of a wall of spacer102encircling shaft engagement element104may also be balanced against the amount of vibration dampening material in spacer102to meet, for example, a vibration damping design specification.

The foregoing arrangement of shaft engagement element104, spacer102, and golf shaft20can ordinarily provide a sufficiently strong and stiff coupling between golf shaft20and golf club head10via shaft engagement element104, while isolating golf shaft20from golf club head10via spacer102to serve as a vibration dampening element. In this regard, coupling100isolates golf shaft20in its entirety from golf club head10when in an operating position with golf shaft20located above golf club head10in its entirety.

FIG. 3Ais a perspective view of coupling200for securing golf shaft20to golf club head10according to an embodiment.FIG. 3Bprovides a cross-section view of coupling200along cross-section line3B when in contact with golf shaft20. As shown inFIGS. 3A and 3B, coupling200includes shaft engagement element204and spacer202bonded to shaft engagement element204to isolate golf shaft20from a golf club head (e.g., golf club head10inFIGS. 1A to 1C). In this regard, coupling200isolates golf shaft20in its entirety from a golf club head when in an operating position with golf shaft20located above the golf club head in its entirety. Spacer202may be bonded to shaft engagement element204by co-molding spacer202with shaft engagement element204during a molding process. In other implementations, spacer202may be bonded to shaft engagement element204by, for example, glue.

As with shaft engagement element104and spacer102of coupling100inFIGS. 2A and 2Bdiscussed above, the material used for spacer202in coupling200can include a material having a lower Young's modulus than the material of shaft engagement element204to attenuate vibration from when the golf club head strikes a golf ball. The same ratios, limits, and preferred ranges for the Young's moduli of the materials used for spacer102and shaft engagement element104discussed above for coupling100may be used in selecting materials for spacer202and shaft engagement element204of coupling200. For example, the material for shaft engagement element204may be selected from steel, stainless steel, titanium, titanium alloy, aluminum, zinc, and copper. Similarly, the material for spacer202may be selected from an elastomer, a natural rubber, a synthetic rubber, a polyurethane, an acetal resin, a thermoplastic material, a polyamide, and a fiber-reinforced resin. As with coupling200inFIGS. 2A and 2B, coupling300inFIGS. 3A and 3Bis at least partially hollow with sleeve internal bore205, which receives and secures golf shaft20.

As shown inFIGS. 3A and 3B, coupling200differs from coupling100in one aspect in that shaft engagement portion204is exposed to an exterior of the golf club and externally shrouds or encircles the tip portion of golf shaft20instead of fitting within shaft internal bore22. Shaft engagement portion204includes chamfer207to provide a safer, more durable, and/or more aesthetic construction for shaft engagement portion204, which is exposed on an exterior of the golf club when it is assembled in the operating position.

In another aspect, coupling200differs from coupling100inFIGS. 2A and 2Bin that shaft engagement element204constitutes a female-type mating element complementary to the male-type mating element constituted by the tip end of the shaft20(whereas the shaft engagement element104of the coupling100is solely insertable within the interior bore of the tip end of shaft20). In addition, the coupling200vertically supports or contacts golf shaft20at base215instead of spacer202vertically supporting or contacting golf shaft20.

In yet another aspect, coupling200differs from coupling100inFIGS. 2A and 2Bin that spacer202shrouds or encircles a smaller portion of shaft engagement element204that overlaps golf shaft20. Instead, more structural support is provided externally from shaft engagement element204. Coupling200may therefore provide for a greater bending stiffness and/or strength than coupling100when using the same materials as for shaft engagement element104and spacer102, since shaft engagement element204has a greater radial area than shaft engagement element104for the same size golf shaft20. In addition, hosel engagement portion210of spacer202is filled by insert portion222of shaft engagement element204to provide additional strength and bending stiffness to coupling200than the hollow center of hosel engagement portion110inFIGS. 2A and 2B. Shaft engagement element204is also vertically supported or contacted by additional internal surfaces of spacer202, with support surfaces220,218, and212providing vertical support or contact between spacer202and shaft engagement element204. In terms of material properties, shaft engagement element204preferably comprises attributes similar to those described with regard to the like shaft engagement element104of the embodiment ofFIG. 1, whereas spacer202preferably comprises attributes similar to those described with regard to the like spacer102of the embodiment ofFIG. 1.

FIG. 4Ais a perspective view of coupling300for securing golf shaft20to golf club head10according to an embodiment.FIG. 4Bprovides a cross-section view of coupling300along cross-section line4B when in contact with golf shaft20. As shown inFIGS. 4A and 4B, coupling300is similar to coupling100in its receiving and securing of golf shaft20between shaft engagement portion304and outer sleeve portion306in annular groove316of coupling300. However, coupling300differs from couplings100and200discussed above in that coupling300is made from a single material.

As shown inFIGS. 4A and 4B, outer sleeve portion306of coupling300includes chamfer307to provide a safer, more durable, and/or more aesthetic construction for outer sleeve portion306, which is exposed on an exterior of the golf club when it is assembled in an operating position. Outer sleeve306shrouds or encircles a lower portion of shaft engagement portion304, and also shrouds or encircles a tip portion of golf shaft20where shaft engagement portion304and the tip portion of golf shaft20overlap. Shaft engagement portion304fits within shaft internal bore22of golf shaft20with the tip portion of golf shaft20interiorly contacted or supported by shaft engagement portion304and exteriorly contacted or supported by lateral shaft support surface314. Hosel engagement portion310is configured to fit within a hosel internal bore (e.g., hosel internal bore14inFIG. 1C), and includes base313. In the example ofFIGS. 4A and 4B, coupling300is hollow in that sleeve internal bore305is open and internal base surface312does not contact another material.

The foregoing arrangement of coupling300can allow for a simplified and/or less expensive construction for coupling300than for couplings100and200discussed above, since coupling300is made of a single material and may be made of a single component. In addition, coupling300can still provide for vibration dampening by selecting a material that has a high enough strength for structural integrity and a Young's modulus for both sufficient bending stiffness (as compared to the tip portion of golf shaft20) and vibration dampening. A material for coupling300can include, for example, a material with a Young's modulus that is less than the Young's modulus for the material used for golf club head10. In this regard, coupling300isolates golf shaft20in its entirety from golf club head10when in an operating position with golf shaft20located above golf club head10in its entirety.

FIG. 5Ais a perspective view of coupling400for securing golf shaft20to golf club head10according to an embodiment.FIG. 5Bprovides a cross-section view of coupling400along cross-section line5B when in contact with golf shaft20. As shown inFIGS. 5A and 5B, coupling400is similar to coupling100in its receiving and securing of golf shaft20between shaft engagement portion404and outer sleeve portion406in annular groove416of coupling400.

As shown inFIGS. 5A and 5B, coupling400differs from coupling300inFIGS. 4A and 4Bin that insert element409fills an internal space defined by an internal surface of shaft engagement portion404and internal base surface412of base413. In some implementations, insert element409can be bonded to a remaining portion of coupling400by co-molding insert element409with the remaining portion of coupling400during a molding process. In other implementations, insert element409can be bonded to the remaining portion of coupling400with glue.

The addition of insert element409can ordinarily increase the strength and bending stiffness of coupling400, which may allow for the selection of a material for the remaining portion of coupling400that has a lower Young's modulus to provide improved vibration dampening.

As shown inFIGS. 5A and 5B, outer sleeve portion406of coupling400includes chamfer407to provide a safer, more durable, and/or more aesthetic construction for outer sleeve portion406, which is exposed on an exterior of the golf club when it is assembled in an operating position. Outer sleeve portion406shrouds or encircles a lower portion of shaft engagement portion404, and also shrouds or encircles a tip portion of golf shaft20where shaft engagement portion404and the tip portion of golf shaft20overlap. Shaft engagement portion404fits within shaft internal bore22of golf shaft20with the tip portion of golf shaft20interiorly contacted or supported by shaft engagement portion404and exteriorly contacted or supported by lateral shaft support surface414. Hosel engagement portion410is configured to fit within a hosel internal bore (e.g., hosel internal bore14inFIG. 1C), and includes base413. In terms of material properties, shaft engagement element404preferably comprises attributes similar to those described with regard to the like shaft engagement element104of the embodiment ofFIG. 1, whereas insert element409preferably comprises attributes similar to those described with regard to the like spacer102of the embodiment ofFIG. 1.

FIG. 6Ais a perspective view of coupling500for securing golf shaft20to golf club head10according to an embodiment.FIG. 6Bprovides a cross-section view of coupling500along cross-section line5B when in contact with golf shaft20. As shown inFIGS. 6A and 6B, coupling500includes shaft engagement element504, spacer502, and a third component, hosel insert509. In some implementations, hosel insert509can be made of a material with a different Young's modulus than the materials used for spacer502and/or shaft engagement element504. In such implementations, the Young's modulus of the material used for hosel insert509can be greater than the Young's modulus of the material used for spacer502to provide for added bending stiffness in the connection between coupling500and the hosel. In addition, the material used for hosel insert509may be selected for better adhesion or frictional ft with the hosel, such as by using a metal material to contact a metal material of the hosel. In some implementations, hosel insert509and shaft engagement element504may be made of the same material.

As with shaft engagement element104and spacer102of coupling100inFIGS. 2A and 2Bdiscussed above, the material used for spacer502can have a lower Young's modulus than the Young's modulus for a material used for shaft engagement element504. The same ratios, limits, and preferred ranges for the Young's moduli of the materials used for spacer102and shaft engagement element104discussed above for coupling100may be used in selecting materials for spacer502and shaft engagement element504of coupling500. For example, the material for shaft engagement element504may be selected from steel, stainless steel, titanium, titanium alloy, aluminum, zinc, and copper. Similarly, the material for spacer502may be selected from an elastomer, a natural rubber, a synthetic rubber, a polyurethane, an acetal resin, a thermoplastic material, a polyamide, and a fiber-reinforced resin.

As shown inFIGS. 6A and 6B, coupling500includes annular groove516between shaft engagement element504and spacer502for receiving and securing golf shaft20. In addition, outer sleeve portion506of spacer502includes chamfer507to provide a safer, more durable, and/or more aesthetic construction for outer sleeve portion506, which is exposed on an exterior of the golf club when it is assembled in the operating position.

As shown inFIG. 6B, spacer502shrouds or encircles a lower portion of shaft engagement element504with outer sleeve portion506, and also shrouds or encircles an upper portion of hosel insert509with hosel contact portion510. In addition, spacer502shrouds or encircles an extreme tip portion of golf shaft20when located in annular groove516. Coupling500may be bonded to golf shaft20by, for example, gluing shaft engagement element504into shaft internal bore22and/or gluing golf shaft20into annular groove516. In other implementations, shaft engagement element504may be frictionally fitted into shaft internal bore22. Such implementations may also allow for the addition and removal of coupling500or a golf club shaft by a golfer or retailer in the field.

Shaft engagement element504fits within shaft internal bore22of golf shaft20with the tip portion of golf shaft20interiorly contacted or supported by shaft engagement element504and partially exteriorly contacted or supported by annular groove516of spacer502. Shaft engagement element504is also in contact with interior surface512of spacer502.

Hosel insert509is configured to fit within a hosel internal bore (e.g., hosel internal bore14inFIG. 1C). Hosel insert509may be bonded with a hosel, for example, by gluing hosel insert509into the hosel internal bore. In other implementations, hosel insert509may be frictionally fitted into the hosel. Such implementations may also allow for the addition and removal of coupling500or a golf club head by a golfer or retailer in the field.

FIG. 7Ais a perspective view of coupling600for securing golf shaft20to golf club head10according to an embodiment.FIG. 7Bprovides a cross-section view of coupling600along cross-section line7B inFIG. 7Awhen in contact with golf shaft20. As shown inFIGS. 7A and 7B, coupling600includes shaft engagement element604, spacer602, and a third component, hosel insert609. In some implementations, hosel insert609can be made of a material with a different Young's modulus than the materials used for spacer602and/or shaft engagement element604. In such implementations, the Young's modulus of the material used for hosel insert609can be greater than the Young's modulus of the material used for spacer602to provide for added bending stiffness in the connection between coupling600and the hosel. In some implementations, hosel insert609and shaft engagement element604may be made of the same material.

FIG. 7Cis a perspective view of shaft engagement element604and hosel insert609in isolation (for purposes of showing further detail). Unlike coupling500shown inFIGS. 6A and 6Bdiscussed above, shaft engagement element604and hosel insert609include radial projections624and626, respectively, for improved adhesion with spacer602. In addition, shaft engagement element604and hosel insert609include flange portions618and620, respectively, for improved adhesion or frictional contact with spacer602. As will be appreciated by those of ordinary skill in the art, a flange portion and/or radial projections may be omitted from one or both of shaft engagement element604and hosel insert609in other embodiments.

As with shaft engagement element104and spacer102of coupling100inFIGS. 2A and 2Bdiscussed above, the material used for spacer602can have a lower Young's modulus than the Young's modulus for a material used for shaft engagement element604. The same ratios, limits, and preferred ranges for the Young's moduli of the materials used for spacer102and shaft engagement element104discussed above for coupling100may be used in selecting materials for spacer602and shaft engagement element604of coupling600. For example, the material for shaft engagement element604may be selected from steel, stainless steel, titanium, titanium alloy, aluminum, zinc, and copper. Similarly, the material for spacer602may be selected from an elastomer, a natural rubber, a synthetic rubber, a polyurethane, an acetal resin, a thermoplastic material, a polyamide, and a fiber-reinforced resin.

As shown inFIGS. 7A and 7B, coupling600includes annular groove616between shaft engagement element604and spacer602for receiving and securing golf shaft20. In addition, outer sleeve portion606of spacer602includes chamfer607to provide a safer, more durable, and/or more aesthetic construction for outer sleeve portion606, which is exposed on an exterior of the golf club when it is assembled in the operating position.

As shown inFIG. 7B, spacer602shrouds or encircles a lower portion of shaft engagement element604and flange618with outer sleeve portion606, and also shrouds or encircles an upper portion of hosel insert609and flange620with hosel contact portion610. In addition, spacer602shrouds or encircles an extreme tip portion of golf shaft20when located in annular groove616. Coupling600may be bonded to golf shaft20by, for example, gluing shaft engagement element604into shaft internal bore22and/or gluing golf shaft20into annular groove616. In other implementations, shaft engagement element604may be frictionally fitted into shaft internal bore22. Such implementations may also allow for the addition and removal of coupling600or a golf club shaft by a golfer or retailer in the field.

Shaft engagement element604fits within shaft internal bore22of golf shaft20with the tip portion of golf shaft20interiorly contacted or supported by shaft engagement element604and partially exteriorly contacted or supported by annular groove616of spacer602. Shaft engagement element604is also in contact with interior surface612of spacer602.

Hosel insert609is configured to fit within a hosel internal bore (e.g., hosel internal bore14inFIG. 1C). Hosel insert609may be bonded with a hosel, for example, by gluing hosel insert609into the hosel internal bore. In other implementations, hosel insert609may be frictionally fitted into the hosel. Such implementations may also allow for the addition and removal of coupling600or a golf club head by a golfer or retailer in the field.

FIGS. 8A to 8Cprovide examples of kits including different couplings to adjust the feel or vibration response of a golf club. The example couplings ofFIGS. 8A to 8Care substitutably securable to one or more different pairs of golf club heads and golf shafts. In some implementations, the shaft engagement elements and hosel inserts or spacers may fit a standardized shaft internal bore size and a standard hosel internal bore size to allow the couplings in the kits to be used interchangeably with golf clubs of different golf club manufacturers. The selection of a coupling from a kit for a golf club head and a golf shaft can be made by, for example, a golf club manufacturer upon request, such as with a customized order from a particular golfer or retailer for a certain level of feel (e.g., soft, medium, or hard). In other examples, a golfer may separately purchase a kit of couplings and select a coupling dependent on course conditions (e.g., a “stump” or “speed” of a putting green) and secure or have a retailer secure the coupling to a golf shaft and golf club head. In this regard, the couplings in the kits ofFIGS. 8A to 8Cmay include indicators of the dampening or feel provided by the coupling, such as by using a different color coding to identify soft (greatest dampening), medium (in between amount of dampening), and hard (least dampening) feels.

FIG. 8Ais a perspective view of a first example kit1000of couplings with each coupling including a vibration dampening element comprising a different material according to an embodiment. As shown inFIG. 8A, kit1000includes couplings700,800, and900. Couplings700,800, and900include shaft engagement elements704,804, and904, respectively, configured to contact, and engage with, a golf shaft. Couplings700,800, and900also include hosel engagement elements709,809, and909, respectively, configured to contact, and engage with, a hosel of a golf club head.

In addition, couplings700,800, and900include vibration dampening elements702,802, and902, respectively, bonded to the shaft engagement element to serve as a spacer by spacing the engagement element from a golf club head in an operating position. As with the embodiments of couplings discussed above, vibration dampening elements702,802, and902are configured to isolate the engagement element from a golf club head when in an operating position. In this regard, when the couplings are operably secured to a golf shaft and a golf club head, the golf shaft is located entirely above the golf club head.

As shown inFIG. 8A, vibration dampening elements702,802, and902are made of materials having different Young's moduli. In more detail, the Young's modulus for vibration dampening element802(E2) is greater than the Young's modulus for vibration dampening element702(E1), and the Young's modulus for vibration dampening element902(E3) is greater than the Young's modulus for vibration dampening element802(E2). This variety of materials used for vibration dampening elements in kit1000ordinarily allows for varying amounts of frequency attenuation or levels of feel without changing the structural configurations among couplings700,800, and900. In some implementations, the materials used for vibration dampening elements702,802, and902can be selected from, for example, an elastomer, a natural rubber, a synthetic rubber, a polyurethane, an acetal resin, a thermoplastic material, a polyamide, and a fiber-reinforced resin.

FIG. 8Bis a perspective view of kit1100with each coupling in the kit including a vibration dampening element having a different structural configuration according to an embodiment. In this regard, other embodiments of kit1100may include a variety of structural configurations in common or similar to various couplings discussed above with reference toFIGS. 1A to 7C. As shown inFIG. 8B, kit1100includes couplings1200,1300, and1400. Couplings1200,1300, and1400include shaft engagement elements1204,1304, and1404, respectively, configured to contact, and engage with, a golf shaft. Couplings1200,1300, and1400also include hosel engagement elements1209,1309, and1409, respectively, configured to contact, and engage with, a hosel of a golf club head.

In addition, couplings1200,1300, and1400include vibration dampening elements1202,1302, and1402, respectively, bonded to the shaft engagement element to serve as a spacer by spacing the engagement element from a golf club head in an operating position. As with the embodiments of couplings discussed above, vibration dampening elements1202,1302, and1402are configured to isolate the engagement element from a golf club head when in an operating position. In this regard, when the couplings are operably secured to a golf shaft and a golf club head, the golf shaft is located entirely above the golf club head.

As shown inFIG. 8B, couplings1200and1300include inserts extending from center portions of the shaft engagement elements and hosel engagement elements. Coupling1200includes upper insert1230extending from a center portion of shaft engagement element1204and lower insert1232extending from a center portion of hosel engagement element1209. Coupling1300includes upper insert1330extending from a center portion of shaft engagement element1304and lower insert1332extending from a center portion of hosel engagement element1309. In some implementations, upper inserts1230and1330can form a single component or pin with lower inserts1232and1332, respectively, that extend through respective center portions of couplings1200and1300. These inserts may allow for the use of a different material within the shaft engagement element and/or the hosel engagement element to affect the bending stiffness or strength of the coupling. In the example of coupling1400, shaft engagement element1404and hosel engagement element1409may form a single component or pin that extends through a center portion of vibration dampening element1402.

Vibration dampening elements702,802, and902have different structural configurations that can allow for different amounts of vibration attenuation or different feels. In more detail, a cylinder height of vibration dampening element1302(H2) is greater than a cylinder height of vibration dampening element1202(H1), and the cylinder height of vibration dampening element1402(H3) is greater than the cylinder height of vibration dampening element1302(H2). This variety of structural configurations for vibration dampening elements in kit1100ordinarily allows for varying amounts of frequency attenuation or levels of feel without changing the material used for vibration dampening elements1202,1302, and1402. As will be appreciated by those of ordinary skill in the art, other structural configuration differences among vibration dampening elements1202,1302, and1402are possible in other implementations.

FIG. 8Cis a perspective view of kit1500with each coupling in the kit including a vibration dampening element that differs from another coupling's vibration dampening element with respect to a structural configuration or a material according to an embodiment. As shown inFIG. 8C, kit1500includes couplings1600,1700, and1800. Couplings1600,1700, and1800include shaft engagement elements1604,1704, and1804, respectively, configured to contact, and engage with, a golf shaft. Couplings1600,1700, and1800also include hosel engagement elements1609,1709, and1809, respectively, configured to contact, and engage with, a hosel of a golf club head.

In addition, couplings1600,1700, and1800include vibration dampening elements1602,1702, and1802, respectively, bonded to the shaft engagement element to serve as a spacer by spacing the engagement element from a golf club head in an operating position. As with the embodiments of couplings discussed above, vibration dampening elements1602,1702, and1802are configured to isolate the engagement element from a golf club head when in an operating position. In this regard, when the couplings are operably secured to a golf shaft and a golf club head, the golf shaft is located entirely above the golf club head.

As shown inFIG. 8C, coupling1600includes upper insert1630extending from a center portion of shaft engagement element1604and lower insert1632extending from a center portion of hosel engagement element1609. In some implementations, upper insert1630and lower insert1632can form a single component or pin that extends through a center portion of coupling1600. The insert or inserts may allow for the use of a different material within shaft engagement element1604and/or hosel engagement element1609to affect the bending stiffness or strength of the coupling in these locations. In the example of couplings1700and1800, shaft engagement elements1704and1804may each form a single component or pin with hosel engagement elements1709and1809, respectively, that extends through center portions of vibration dampening elements1702and1802.

Each of vibration dampening elements1602,1702, and1802in kit1500has a different structural configuration or includes a different material from at least one other coupling in kit1500. In this regard, vibration dampening elements1602,1702, and1802can vary with different combinations of structural configurations and material properties. In more detail, a cylinder height of vibration dampening element1602(H1) is less than cylinder heights of vibration dampening elements1702(H2) and1802(H3), which equal each other. On the other hand, a Young's modulus of vibration dampening element1802(E3) is greater than Young's moduli of vibration dampening elements1602(E1) and1702(E2), which equal each other. In some implementations, the materials used for vibration dampening elements1602,1702, and1802can be selected from, for example, an elastomer, a natural rubber, a synthetic rubber, a polyurethane, an acetal resin, a thermoplastic material, a polyamide, and a fiber-reinforced resin.

The variety of structural configurations and material properties for vibration dampening elements in kit1500ordinarily allows for varying amounts of frequency attenuation or levels of feel with more options for meeting bending stiffness or strength specifications. As will be appreciated by those of ordinary skill in the art, other structural configuration differences among vibration dampening elements1602,1702, and1802are possible in other implementations to fine-tune a frequency response of a golf club when hitting a golf ball.

FIG. 9Ais a graph comparing accelerometer data for a putter including a coupling as described above with reference toFIGS. 2A and 2B, and for a putter without such a coupling when hitting a golf ball. The coupling used for the putter includes a shaft engagement element configured to contact, and engage with, the golf shaft of the putter, and a spacer bonded to the shaft engagement element. The spacer comprises a material having a Young's modulus less than the shaft engagement element, and is operationally secured so that the golf shaft is located above the golf club head in its entirety.

In measuring the effect of using a coupling as described above, two otherwise identical golf putter models are used with an accelerometer mounted on a butt-end of the grip of the golf shaft to sense accelerations caused by vibration along the golf shaft. A robot is then used to consistently impact a golf ball with each putter. The golf ball is placed on a tee so that the impact location is near a center of a strike face of each golf club head. The raw accelerometer data is shown inFIG. 9Afor 2 ms prior to impact and 20 ms after impact for each putter.

As shown inFIG. 9A, the putter with the coupling has distinctly different vibration characteristics. In particular, the acceleration response to the impact decays quicker for the putter with the coupling and does not reach as high of an acceleration when impacting the golf ball at approximately 2 ms.

FIG. 9Bis a graph comparing the frequency responses for the putters ofFIG. 9Awhen hitting the golf ball. The frequency responses shown inFIG. 9Bresult from performing a Fast Fourier Transform (FFT) on the raw accelerometer data ofFIG. 9Aand plotting the responses on a logarithmic scale along the x-axis for frequency. As shown inFIG. 9B, there is a difference in primary mode frequencies and the maximum amplitudes for the frequency responses. The putter without the coupling has a primary frequency of 1587 Hz corresponding to point2000inFIG. 9B, with another significant peak at a slightly lower frequency. The putter with the coupling, on the other hand, has a peak frequency at 937 Hz corresponding to point2002inFIG. 9Bat a significantly lower amplitude.

The vibration dampening elements or spacers in the couplings described above can attenuate high frequency vibrations to provide a softer feel when contacting a golf ball, while the shaft engagement elements can provide a bending stiffness for the coupling that is comparable to the tip of a golf shaft. In addition, the above described couplings can ordinarily allow for a fine tuning of a golf club's feel, without having to solely rely upon golf club head face inserts or milling, which may not be as easy to customize for vibration dampening.

The foregoing description of the disclosed example embodiments is provided to enable any person of ordinary skill in the art to make or use the embodiments in the present disclosure. Various modifications to these examples will be readily apparent to those of ordinary skill in the art, and the principles disclosed herein may be applied to other examples without departing from the spirit or scope of the present disclosure. For example, some alternative embodiments may include a coupling allowing for some contact between a golf shaft and a golf club head while including a vibration dampening material with a lower Young's modulus than a shaft engagement portion of the coupling. Accordingly, the described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the disclosure is, therefore, indicated by the following claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.