GOLF CLUB BY REVERSE INTERLAMINAR PLACEMENT (RIP) TECHNOLOGY

Abstract

A golf club shaft is formed having a flexural rigidity layer at last one third the length of which is encased in an outer layer. The shaft is formed by applying sheets of composite material to a mandrel. Sheets forming the flexural rigidity layer include unidirectional fibers oriented substantially in parallel with the longitudinal axis of the shaft. The outer layer may include composite material sheets each having unidirectional fibers oriented at an angle with respect to the shaft's longitudinal axis. An innermost layer of the shaft may be formed of composite material sheets having fibers oriented at an angle with respect to the shaft's longitudinal axis.

Description

This Nonprovisional application claims priority under 35 U.S.C. §119(e) on U.S. Provisional Application No(s). 61/350,446 filed on Jun. 1, 2010, the entire contents of which are hereby incorporated by reference.

FIELD OF INVENTION

This disclosure relates to golf club shafts, and more particularly to unique disposition of fiber layers in composite golf club shafts having elongated tubular bodies composed of fiber-and-resin composite materials.

BACKGROUND OF THE INVENTION

Composite golf club shafts typically have hollow tubular bodies that taper longitudinally from larger, so-called “butt” or “grip” ends toward smaller, so-called “tip” ends upon which golf club heads are mounted in the completed golf clubs. Such shafts typically are generally circular in transverse cross-sectional shape, both at the outside and inside surfaces of the shaft, having walls that are of selected thicknesses and compositions to provide the strength, flexibility and weight desired for a particular golf club.

The design and manufacture of composite golf club shafts are highly developed arts, providing a wide variety of different shafts with characteristics that are intended to suit the abilities and personal preferences of a wide variety of golfers. Typically, composite shafts are designed to be concentric about their longitudinal axis while varying substantially in outside diameter from the larger grip end to the smaller tip end. The concentricity of the inside and outside surfaces is designed to be very precise, to produce the desired wall thickness and flexing characteristics, and remains stable when at rest, that is, when not loaded and stressed by outside forces.

During the swing, however, the forces acting on the shaft as the club is swung through the golf stroke are great enough to deform the shaft, longitudinally in flexing of the length of the shaft and torsionally in twisting of the shaft, and also transversely, causing the cross-sectional shape of the shaft to deform and become oval or elongated. Thus deformation is resisted by the wall strength of the shaft, referred to as “hoop strength”, but occurs in different degrees and directions, first in the so-called “swing plane (or planes)” of the golfer's swing and secondarily in the so-called “droop plane” that is generally perpendicular to the swing plane. The amounts of these deformations are functions of the forces applied throughout the swing and ball impact, and the physical properties of the shaft resisting these forces.

In the industry, various approaches are available to provide the desired properties in the shaft for improved performance, including increasing the wall thickness and the amounts of different composite materials in the wall, and varying the angles of the fibers in the composite materials relative to the longitudinal axis of the shaft.

However, conventional composite golf shafts typically include bias plies with fibers substantially oriented plus and minus 45° to the shaft axis to influence torsional (twisting) flexibility, and longitudinal plies with fibers parallel to the shaft axis to influence longitudinal (bending) flexibility. The bias plies 30a, 30b illustrated in FIG. 7 are applied closest to the center core of the golf shaft and the longitudinal fiber plies 32a to 32d are applied concentrically about the inner bias plies 30a, 30b last, and furthest from the core of the shaft. Although the figure shows two bias plies and four longitudinal plies, the number may vary. After curing, an amount of material is removed from the outermost longitudinal ply 32d of the golf shaft (e.g., by sanding) to obtain a desired shaft stiffness. A significant portion of the longitudinal fibers are thus sanded away. The conventional composite golf shaft loses approximately 5.75% of its stiffness during this material removal process.

SUMMARY OF THE DISCLOSURE

Consistent with one or more embodiments described in detail herein, a golf club shaft includes an elongated, generally tapered shaft having a generally circular transverse cross-sectional shape. The circular wall of the shaft has at least one flexural rigidity layer and at least one outer layer. The flexural rigidity layer(s) are disposed around the entire length of the shaft, and reinforcement fibers of the flexural rigidity layer(s) are substantially oriented in the longitudinal direction of the shaft. The outer layer(s) have no longitudinally-oriented fibers and are disposed concentrically about the outermost flexural rigidity, and extend at least one third the length of the shaft from a tip end of the shaft.

Consistent with one or more method embodiments described in detail herein, a golf club shaft is produced by steps including providing an elongated mandrel, applying flexural rigidity layer(s) and applying outer layers. The mandrel has an outside surface shaped to form the inside surface of the shaft. The flexural rigidity layer, of composite material, is applied about the entire length of the mandrel and includes reinforcing fibers which are oriented substantially parallel to the longitudinal axis of the mandrel to form a tubular body for the shaft. The outer layer(s) are applied concentrically about the flexural rigidity layer(s), and at least one outer layer has no longitudinally-oriented fibers. The at least one outer layer is disposed over at least one third the longitudinal length of the shaft.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a plan view of a golf club shaft incorporating features consistent with some embodiments of the present disclosure;

FIG. 2 is a transverse cross-section view near the tip end of a golf club shaft incorporating features consistent with some embodiments of the present disclosure;

FIG. 3 is a transverse cross-section view near the butt end of a golf club shaft incorporating features consistent with some embodiments of the present disclosure;

FIG. 4 is a plan view illustrating unidirectional fiber plies used in construction of a golf club consistent with some embodiments of the present disclosure;

FIG. 5 is a plan view of unidirectional fiber plies used in construction of a golf club consistent with other embodiments of the present disclosure;

FIG. 6 is a plan view of unidirectional fiber plies used in construction of a golf club consistent with other embodiments of the present disclosure;

FIG. 7 is a plan view of materials used in conventional construction of golf club.

FIG. 8 is a plan view of a mandrel used in construction of a golf club consistent with embodiments of the present disclosure.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents thereof.

As shown in the drawings for purposes of illustration, a composite golf club according to at least some embodiments of the invention is indicated generally by the reference number 10, having an elongated tubular body 11 that has a butt or grip end 12, the upper right hand end in FIG. 1, and a tip end 13. A club head (not shown) will be mounted on the tip end, and a grip (not shown) will be disposed around the butt end portion to complete the golf club in the conventional fashion.

The body 11 of the golf club shaft 10 shown in FIG. 1 has a longitudinal taper, as is typical in such shafts, from the larger butt end 12 toward the smaller tip end 13, and has a conventional cross-sectional shape that normally is circular or annular as shown in FIG. 2 when at rest, having inside and outside surfaces 14 and 15 that are circular in transverse cross-section and are generally concentric about the longitudinal axis of the shaft, indicated by the line 17 in FIGS. 1-3. It is to be understood that shafts may be designed and manufactured with variations in the wall thickness along the length of the shaft, for purposes of variations in the performance of the shaft in a golf club.

As discussed in general in the Background section, composite golf club shafts are composed of fiber-and-resin materials that are formed into the desired tubular shape on a tapered mandrel, typically composed of metal and having an outside shape that is the shape desired for the inside surface of the shaft to be produced, usually longitudinally tapered and of circular cross-sectional shape. The fiber-and-resin material is wrapped around the mandrel, usually in sheet form that is cut into selected geometric shapes and applied to form a plurality of layers of the sheet materials to make up a body of selected wall thickness and length, which may be in the range of thirty to sixty inches before being cut down to final size. Various materials, with various fiber types and orientations, are used according to the design of each shaft, in accordance with principles and methods that are well known in the industry. The term “composite material” is used in the broad sense used in the industry, and the types of fibers in the composite materials may be of a variety of types, including, but not limited to, graphite, fiberglass, boron, various metallics and spectra, according to the principles that are well known by those skilled in the art.

Typically, the assembled shaft then is wrapped in a shrink wrap film and cured in an oven (not shown) to form the hardened hollow composite body of the golf club shaft. The mandrel then is withdrawn from the assembly, leaving the shaft with its inside surface matching the outside surface of the mandrel. Subsequently, the shaft can be cut to a desired length for assembly into a golf club. It is to be noted that other procedures, such as filament winding of fiber-and-resin tape or roving onto a mandrel, may be used for applying the composite material, wrapping of sheet material being the illustrative manner of forming the shaft body described herein.

According to at least one embodiment of the shaft shown in FIGS. 2 and 3, transverse cross-sections of the shaft at areas near the tip end and the butt end, respectively, reveal the different layers constituting the shaft at the respective portions. One or more sheets of bias material form inner bias layer 22. Each sheet of bias material includes unidirectional reinforcing fibers oriented at an angle selected between +35° and +55° or −35° and −55° with respect to longitudinal axis 17. When two or more bias layers are applied as the inner-most layer, each sheet includes unidirectional reinforcing fibers oriented at a substantially equal but opposite angle with respect to an adjacent bias layer. For example, if a first bias layer has fibers oriented at +45° with respect to the longitudinal axis, fibers of a next bias layer are oriented at −45° with respect to the longitudinal axis.

A flexural rigidity layer 20 is, in the embodiment illustrated in FIGS. 2 and 3, disposed on the inner bias layer 22. Each of one or more sheets of composite material constituting the flexural rigidity layer includes unidirectional fibers oriented substantially parallel to the longitudinal axis 17.

FIG. 2 includes an outer material layer 24 which may include one or more outer bias layers similar to the inner bias layers or a coating of non-fibrous material. The outer material layer 24 is disposed along at least one third the length of the shaft, typically from the tip end to at least one third the length of the shaft. It will be appreciated by those of skill in the art, however, that the outer material layer may be disposed at other locations, and may include lengths between one third and full length of the shaft. As shown if FIG. 3, a length near the butt end of the shaft may be devoid of outer material layer 24.

FIGS. 4-7 illustrate sheets of materials used in manufacture of a golf club shaft according to the present disclosure. In the Figures, the materials shown from top to bottom respectively correspond to layers beginning at the inner surface 14 and concluding with the outer surface 15. Although particular numbers of sheets are illustrated, it will be appreciated by one having ordinary skill in the art that the number of sheets may be varied according to design. For example, the Figures show four sheets of flexural rigidity material in each figure, whereas the number of sheets may be as few as one or have many more.

FIG. 4 provides sheets of composite materials according to one embodiment of the invention in which no inner bias layers are included. Thus, the inner surface 14 of the golf club shaft 10 is formed by flexural rigidity layer 20, comprising sheets 20a, 20b of composite material having unidirectional fibers oriented substantially in parallel with the longitudinal axis 17. Outer surface 15 is formed by outer layer 24, comprising sheets 24a and 24b of composite material, each alternately having fibers unidirectionally oriented at an angle between +35° and +55° or at an equal but opposite angle between −35° and −55°. Alternatively, outer layer 24 may instead comprise a non-fiber coating as described above. In either case the outer surface may be sanded or otherwise diminished without substantially affecting the flexural rigidity layers. Because at most only a portion of the flexural rigidity layer(s) is exposed, removal of portion of the outer surface decreases flexural rigidity far less than the approximately 5.75% decrease resulting from removal in the conventional method. (In some disclosed embodiments, for example, only 1.9% of flexural rigidity is lost during sanding.) Although the FIG. 4 illustrates the outer layer having a length similar to that of the flexural rigidity layers, it will be appreciated in view of this disclosure that the outer layer 24 may be as short as one third the length of the shaft.

FIG. 5 provides sheets of composite materials for forming another embodiment of golf club shaft 10. In addition to the flexural rigidity layer 20 and outer 24, this embodiment includes inner bias layer 22 comprising bias material sheets 22a, 22b, each alternately having fibers unidirectionally oriented at an angle between +35° and +55° or at an equal but opposite angle between −35° and −55°. In this embodiment, it is clear that outer layer 24, including sheets 24a, 24b, has a length n greater than or equal to one third the shaft length m.

FIG. 6 illustrates an embodiment similar to that of FIG. 5 except the outer layer 24, including sheets 24a, 24b has a length equal to that of the flexural rigidity sheets 20a-d and inner bias sheets 22a, 22b.

DESCRIPTION OF THE METHOD

The method of the invention includes steps of applying to a mandrel 40, in a particular order, sheets of composite material each having reinforcing fibers oriented in a single direction. The applied sheets are cured, and the resulting tubular shaft is removed from the mandrel 40. Portions of material of the outer-most layer may be removed; for example, to achieve a particular target weight, stiffness, and/or size targets.

The mandrel 40, illustrated in FIG. 8, is conventional in its configuration. It has an elongated shape with an outside surface 42 shaped to form the inside surface 14 of a shaft, herein tapered and of circular cross section. A coupling 35 projects outwardly from the mandrel's larger end, and may be variously formed. The coupling 35 may have, for example, a hexagonal head on a coaxial stem 46 joined to the shaft, for engagement by a tool (not shown) for turning the mandrel as it is withdrawn endwise from the shaft 10. In some embodiments consistent with this disclosure, the first sheets of composite material applied to the mandrel have fibers oriented in a direction substantially parallel to the longitudinal axis of the mandrel, thus providing flexural rigidity to the shaft. The number of sheets, type of reinforcing fibers, and type(s) of composite material may be selected for their stiffness, thickness, weight, etc.

Concentrically disposed upon at least a portion of the flexural rigidity layers may be added one or more outer layers of material. The outer layers are disposed over at least one third the length of the shaft starting at the smaller, tip end of the shaft, although it will be appreciated that the outer layers may be disposed over portions of the shaft other than the tip end. In one embodiment, the outer layers may include sheets of composite material having unidirectional reinforcement fibers bias-oriented at an angle with respect to the longitudinal axis of the mandrel. The bias-orientation of reinforcement fibers contributes torsional stiffness to the shaft portion upon which it is applied. In this case, the unidirectional fibers of each subsequently applied sheet of composite material are oriented at an equal, but opposite, angle with respect to an adjacent outer layer sheet. For example, if the first outer layer sheet has fibers oriented at +45° with respect to the longitudinal axis, the reinforcement fibers of the next outer layer sheet thus may be oriented at −45° with respect to the longitudinal axis.

In another embodiment, the outer layer(s) may include one or more coatings of varnish, paint, plastic, or the like. Whether composite fiber sheets or coatings, the outer layers may be at least partially removed by sanding or other means to adjust the weight, size, stiffness, structural smoothness, or other characteristics.

In another embodiment, at least one inner, bias layer is applied to the mandrel prior to the addition of flexural rigidity layers. Each inner bias layer includes unidirectional reinforcement fibers oriented at an angle with respect to the mandrel's longitudinal axis such that the unidirectional reinforcement fibers of adjacent inner bias layers are oriented at more-or-less equal but opposite angles. For example, if an inner bias layer is applied to the mandrel such that the unidirectional reinforcement fibers of one inner bias layer are oriented at +45° with respect to the longitudinal axis of the mandrel and shaft, an adjacent inner bias layer is next applied such that its unidirectional reinforcement fibers are oriented at about −45° with respect to the longitudinal axis of the mandrel and shaft.

In the case of either the inner bias layers or outer layers that include reinforcing fibers, the complementary angles of fibers for adjacent layers may be in the range of +35° to +55° or −35° to −55°. That is, adjacent bias layers (inner or outer), for example, may be substantially oriented at +35° and −35°. It is to be appreciated that when a multiplicity of bias layers are applied, the complementary angles selected for the unidirectional fibers may all be the same equal, but opposite angles, or pairs of layers may have varying equal but opposite angles.

The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A golf club shaft, comprising:

an elongated, generally tapered shaft having a generally circular transverse cross-sectional shape, the circular wall of the shaft including: at least one flexural rigidity layer disposed around the entire length of the shaft, reinforcement fibers of the flexural rigidity layer substantially oriented in the longitudinal direction of the shaft, and an outer layer, having no longitudinally-oriented fibers, disposed concentrically about an outermost flexural rigidity layer and extending at least one third the length of the shaft from a tip end of the shaft.

2. The golf club shaft according to claim 1, wherein the outer layer comprises at least one outer bias layer, each outer bias layer having unidirectional reinforcement fibers angled with respect to the shaft's longitudinal axis, the unidirectional reinforcement fibers of each successive outer bias layer oriented at a substantially equal but opposite angle with respect to the orientation of fibers belonging to any adjacent outer bias layer.

3. The golf club shaft according to claim 1 or claim 2, wherein the at least one outer layer extends the entire length of the shaft.

4. The golf club shaft according to claim 2, further comprising:

at least two inner bias layers alternatingly disposed beneath the entire length of the innermost flexural rigidity layer, each inner unidirectional bias layer having unidirectional fibers angled complementarily to the fibers of the next of the inner unidirectional bias layers with respect to the shaft axis and disposed substantially from the tip end to the butt end of the shaft.

5. The golf club shaft according to claim 3, further comprising:

at least two inner unidirectional bias layers alternatingly disposed, for the entire length of the shaft, beneath an inner surface of the innermost base unidirectional flex layer, each inner unidirectional bias layer having unidirectional fibers angled complementarily to the fibers of the next of the inner unidirectional bias layers with respect to the shaft axis and disposed substantially from the tip end to the butt end of the shaft.

6. The golf club shaft according to claim 2, wherein the unidirectional fibers of the outer unidirectional bias layers are oriented between about +35° and +55° or between about −35° and −55° with respect to the longitudinal axis of the shaft such that the fibers of one outer unidirectional bias layer are oriented at a substantially equal but opposite angle with respect to the orientation of fibers belonging to the next outer unidirectional bias layer.

7. The golf club shaft according to claim 4, wherein the unidirectional fibers of the inner unidirectional bias layers are oriented between about +35° and +55° or between about −35° and −55° with respect to the longitudinal axis of the shaft such that the fibers of one inner unidirectional bias layer are oriented at a substantially equal but opposite angle with respect to the orientation of fibers belonging to the next inner unidirectional bias layer.

8. The golf club shaft according to claim 2, wherein the outer unidirectional bias layers are formed by a tape having unidirectional reinforcement fibers and wound spirally along the selected longitudinal portion of the shaft.

9. The golf club shaft according to claim 1 wherein the outer layer extends at least half the length of the shaft from a tip end of the shaft.

10. A method of producing a golf club shaft, comprising:

providing an elongated mandrel having an outside surface shaped to form the inside surface of the shaft;

applying about the entire length of the mandrel at least one flexural rigidity layer of composite material, reinforcing fibers of which are oriented substantially parallel to the longitudinal axis of the mandrel; to form a tubular body for the shaft; and

applying concentrically about the at least one flexural rigidity layer, at least one outer layer having no longitudinally-oriented fibers, the at least one outer layer disposed over at least one third the longitudinal length of the shaft.

11. The method according to claim 10, further comprising:

applying about the entire length of the mandrel at least one bias layer of composite material, unidirectional reinforcing fibers of which are oriented at an angle with respect to the shaft's longitudinal axis, the unidirectional reinforcement fibers successive bias layers oriented at substantially equal but opposite angles with respect to the orientation of fibers belonging to an adjacent bias layer, wherein

the at least one flexural rigidity layer is applied to the mandrel first, forming an innermost one or more bias layers of the shaft, the at least one flexural rigidity layer and at least one outer layer respectively disposed about the mandrel.

12. The method according to claim 10, wherein the at least one outer layer includes unidirectional reinforcement fibers oriented at an angle with respect to the longitudinal direction of the shaft, each adjacent outer layer having its reinforcement fibers oriented at a substantially equal but opposite angle with respect to reinforcement fibers of an adjacent outer layer.

13. The method according to claim 11 wherein the angle of the unidirectional reinforcing fibers of the at least one bias layer is between about +35° and +55° or between about −35° and −55° with respect to the longitudinal axis of the shaft.

14. The method according to claim 10 wherein at least one of the outer layers is formed by spirally wrapping a tape comprising the unidirectional fibers.

15. The method according to claim 11 wherein at least one of the bias layers is formed by spirally wrapping a tape comprising the unidirectional fibers of each bias layer.

16. The method according to claim 10 wherein the at least one outer layer is disposed over at least half the longitudinal length of the shaft.