DESCRIPTION

The present invention relates to a golf club head, which is provided with advantageous head alignment capabilities and an enhanced polar moment of inertia.

It is known that the performance of certain golf club heads, such as golf putter heads, is largely determined by alignment and stability.

The stability of a golf club head is largely influenced by the so-called polar moment of inertia

(PMOI) of the golf club head.

The higher is the PMOI value of the golf club head, the larger is the resistance offered by the golf club head to change its position.

The alignment of the golf club head is facilitated or hindered by geometric features that enable the golfer to align the golf club head face toward the intended target.

Basically, the golf club can vary in its position relative to five degrees of freedom: a) translation parallel to the shooting direction; and b) translation perpendicular to the shooting direction; and c) rotation about a horizontal axis perpendicular to the shooting direction; and d) rotation about a horizontal axis parallel to the shooting direction; and e) rotation about a vertical axis.

A variety of features and techniques have been proposed during years to facilitate the golfer's ability to align the head of a golf club for a shot.

These typically require lining up multiple pairs of symbols formed or painted on the golf club head. The golfer must look from one pair of symbols to another to carry out the alignment process.

Frequently, the symbols are relatively difficult to see because they are small or have fine features.

Existing golf club head designs tend to be unstable because they are easily rotated around a vertical axis. When this occurs during a shot, the golfer loses control over the direction of the ball.

Thus, there exists a continuing need for an improved golf club head that has the combined features of improved alignment capabilities and stability.

In order to satisfy this need, the present invention provides a golf club head, according to the claim 1 proposed in the following.

In a general definition, the golf club head, according to the invention, comprises a front portion, a rear portion, an upper portion and a lower portion.

The upper portion of the golf club head comprises an upper port that is formed therethrough and is defined by a first inner edge thereof.

The lower portion of the golf club head is arranged below the upper portion, from which it is vertically spaced.

The lower portion of the golf club head comprises a lower port, which is formed therethrough and is defined by a second inner edge thereof.

Said upper and lower ports are arranged such that when an eye of a user of the golf club head is aligned therewith along a predetermined alignment axis, the second inner edge and the first inner edge appear to the user in a predefined mutual spatial relationship.

The mentioned vertically-displaced ports of the golf club, according to the invention, are arranged such that they remarkably aid in the alignment of the club head.

The shape of said ports may be any, according to the needs.

Preferably the upper and lower ports are oval in shape with the major axis of each port perpendicular to the golf club head face.

According to a first embodiment of the present invention, the upper and lower ports are arranged such that when an eye of a user of the golf club head is aligned therewith along a predetermined alignment axis, the second inner edge defining said lower port is fully visible to the user through said upper port.

In this case, the lower port is advantageously sized slightly smaller than the upper port so that when proper alignment of the golf club head is achieved, the two ports are positioned concentric to each other and the edges of the lower port are visible through the upper port.

When the golfer adjusts the position of the golf club head relative to his line of sight to align the two ports, the bottom port is visible to him within the top port, and is concentrically positioned.

By doing so, the golfer may control the golf club head position and orientation relative to five degrees of freedom as described below:

Translation parallel to the shooting direction: if the golf club head is positioned too far to the right, the left end of the bottom port will not be visible, and vice versa;

Translation perpendicular to the shooting direction: if the golf club head is positioned too far away from the golfer, the nearest edge of the bottom port will not be visible, and vice versa;

Rotation about a horizontal axis parallel to the shooting direction: if the hands of the golfer are positioned too far away from the golfer, the nearest edge of the bottom port will not be visible, and vice versa;

Rotation about a horizontal axis perpendicular to the shooting direction: if the hands of the golfer are positioned too far to the right, the left edge of the bottom port will not be visible, and vice versa;

Rotation about a vertical axis: if the club head is rotated about the axis of the shaft, the concentricity of the bottom port with the top port will not be maintained.

According to an alternative embodiment of the present invention, said upper and lower ports are arranged such that when an eye of a user of the golf club head is aligned therewith along a predetermined alignment axis, the second inner edge defining said lower port is fully hidden to the user by said the upper port.

In this case, the lower port is advantageously formed so that it is slightly larger than the upper port. Consequently, the golfer achieves alignment of such a golf club head by adjusting the position of the head so that the edges of the golf club head are obscured by the edges of the upper port.

The alignment process, according to which the golfer can control the golf club head position and orientation, relative to five degrees of freedom, now involves alignment criteria that are complementary with those described above.

In fact, the golfer may control the golf club head position and orientation relative to five degrees of freedom as described below:

Translation parallel to the shooting direction: if the golf club head is positioned too far to the right, the right end of the bottom port will be visible, and vice versa;

Translation perpendicular to the shooting direction: if the golf club head is positioned too far away from the golfer, the far edge of the bottom port will be visible, and vice versa;

Rotation about a horizontal axis parallel to the shooting direction: if the hands of the golfer are positioned too far away from the golfer, the far edge of the bottom port will be visible, and vice versa;

Rotation about a horizontal axis perpendicular to the shooting direction: if the hands of the golfer are positioned too far to the right, the right edge of the bottom port will be visible, and vice versa;

Rotation about a vertical axis: if the club head is rotated about the axis of the shaft, the concentricity of the bottom port with the top port will not be maintained.

The golf club head, according to the present invention, is advantageously structured such that its PMOI is remarkably enhanced.

Preferably, the golf club head comprises a plurality of inward components and one or more outward components, which are relatively farther away from the centre of gravity of the golf club head than the inward components.

According to the invention, the mass, weight, volume and/or density of the inward and outward components may be advantageously arranged such that the PMOI of the golf club head is improved.

For example, the outward components may be more massive and/or may weigh substantially more than the inward components.

For example, the outward components may comprise a material that is denser than a material comprised in the inward components, or at least one thereof.

Where the outward components comprise a denser material, this material may be selected as steel, tungsten, titanium or another suitable material.

Where the inward components comprise a relatively less dense material, this material may be selected as a polymer, a fibre reinforced composite such as carbon fibre reinforced epoxy or another suitable material.

In yet a further example, the outward components may have a greater volume than that of the inward components.

According to the present invention, a plurality of vertically-displaced ports are formed on the upper and lower portions of the golf club head, so that no mass of the golf club head is present at or near the vertical region defined by the ports.

As a consequence, in the golf club head, according to the invention, the PMOI/weight ratio is relatively high.

It should be noticed that the golf club head mass centre does in fact not need to necessarily coincide with the golf club head geometric centre. Nor, the mentioned alignment axis needs to necessarily coincide with the golf club head mass centre.

The golf club head may thus be arranged so that to improve the ball impact and reduce the arising of undesired spinning phenomena when shooting the ball.

According to the present invention, the upper portion and/or the lower portion of the golf club head may comprise a wall structure.

According to the present invention, the upper portion and/or the lower portion of the golf club head may comprise a tubular structure.

According to the present invention, the upper portion and/or the lower portion may comprise a tubular structure comprising at least one leg having at least one aperture, for example a port or a blind hole.

The present invention applies preferably to golf putter heads but it may be suitable also for heads of golf clubs of different type.

For a better understanding of the invention and its advantages, reference should be made to the accompanying drawings, in which there are illustrated preferred embodiments of the invention:

Figure 1 is an isometric view of an embodiment of the golf club head, according to the invention; and

Figure 2 is a top view of the golf club head of figure 1; and

Figure 3 is a side view of the golf club head of figure 1; and

Figures 4A-4D are some schematic views indicate how the golf club head of figure 1 should be reoriented or moved to achieve a proper alignment for a shot; and

Figure 5 is an top view of a further embodiment of the golf club head, according to the invention; and

Figure 6 is an top view of a further embodiment of the golf club head, according to the invention; and

Figure 7 is an top view of a further embodiment of the golf club head, according to the invention; and

Figure 8 is an isometric view of a further embodiment of the golf club head, according to the invention; and

Figure 9 is a top view of the golf club head of figure 8; and

Figure 10 is a side view of the golf club head of figure 8; and

Figure 11 is an isometric view of a further embodiment of the golf club head, according to the invention; and

Figure 12 is an isometric view of a further embodiment of the golf club head, according to the invention.

Referring now to the cited figures, the present invention relates to an improved golf club head

10, 100, 200, 300.

The golf club head 10, 100, 200, 300 comprises a front portion 16, 116, 216, 316, a rear portion 18, 118, 218, 318, an upper portion 12, 112, 212, 312 and a lower portion 14, 114,

214, 314 arranged below the upper portion and vertically spaced therefrom.

The upper portion 12, 112, 212, 312 comprises at least an upper port 26, 126, 226, 227, which is formed therethrough and is defined by a first inner edge 27, 127, 227, 327 thereof.

The lower portion 14, 114, 214, 314 comprises at least a lower port 28, 128, 228, 328, which is formed therethrough and is defined by a second inner edge thereof 29, 129, 229, 329.

According to the invention, said upper and lower ports are arranged such that when an eye of a user of the golf club head is aligned therewith along a certain predetermined alignment axis

61, the second inner edge 29, 129, 229, 329, which defines the mentioned lower port, can be seen by the user in a predefined spatial relationship with respect to said first inner edge 27,

127, 227, 327 defining the upper port.

Advantageously, the front portion 16, 116, 226, 326 and the rear portion 18, 118, 218, 318 may be made of one or more relatively denser materials with respect to one or more materials of the upper portion 12, 112, 212, 312 and the lower portion 14, 114, 214, 314.

Alternatively, the front portion 16, 116, 216, 316, the rear portion 18, 118, 218, 318 and the lower portion 14, 114, 214, 314 can be made of one or more relatively denser materials with respect to one or more materials of the upper portion 12, 112, 212, 312.

According to some embodiments of the present invention (figures 1-7), the upper portion and/or the lower portion of the golf club head 10 may comprise wall structures, such as a top wall 12 and a bottom wall 14.

Figures 1-3 show a first embodiment of the golf club according to the invention.

The golf club head 10 comprises the front portion 16 and the rear portion 18.

At the front portion 16, the golf club head comprises a front face 20 and a recessed cavity 22 located within the front portion 16 to accommodate a golf club shaft.

The golf club head 10 of figure 3 comprises a top wall 12 and a bottom wall 14 respectively forming the upper portion and the lower portion.

Between the top wall 12 and bottom wall 14 is a hollow interior.

The top and bottom walls 12 and 14 are preferably made of a low weight material, such as a polymer plastic, or fibre reinforced resin such as carbon fibre reinforced epoxy.

This creates a light central region for the golf club head 10, so that a relatively greater weight can be located on the front portion 16 and rear portion 18 to increase the PMOI of the golf club head 10.

The top wall 12 or the bottom wall 14 may also be manufactured of a heavier material such as steel to change the centre of gravity vertically. For example, if the bottom wall 14 were made from steel, this would lower the centre of gravity toward the ground plane.

Optional recessed areas 24 may be used to further reduce the weight of the central region of the golf club head 10. The recessed areas 24 may be present at the bottom wall 14 and/or the upper wall 12.

Further recessed areas may be present also at the front portion 16 and/or the rear portion 18.

A port 26 is formed in the top wall 12, which passes through the top wall thickness and is defined by the first inner edge 27. The port 26 is advantageously oval shaped with the major axis in line with the direction of shooting and in the desired strike location of the golf ball.

The port 26 removes all weight from the centre portion of the top wall 12, creating a zero mass state for this zone.

A further port 28 is formed in the bottom wall 14, passing through said bottom wall, and it is defined by the second inner edge 29.

In this case, the port 28 is similar in shape, orientation and relative location as port 26.

As with the port 26, the port 28 removes all weight from the centre zone of the bottom wall

14, creating a zero mass state for this zone.

The front portion 16, the bottom wall 14 and the rear portion 18 may be made of the same material, while the top wall 12 may be made of a different material.

For example, the front portion 16 and the rear portion 18, as well as the bottom wall 14 may be made of steel with a density of approximately 8g/cm ³ .

As an alternative, at least one of the golf club head portions 14, 18 and 16 may be made of tungsten with a density of approximately 19 g/cm and/or titanium with a density of approximately 4.7 g/cm .

Preferably, the top wall 12 is made of carbon fibre/epoxy with a density of approximately 1.7 g/cm ³ , or glass fibre/epoxy at 2.7 g/cm ³ .

Figures 1-5 show embodiments of the present invention, according to which the upper and lower ports 26 and 28 are arranged such that when an eye of a user of the golf club head is aligned therewith along a predetermined alignment axis 61, the second inner edge 29 defining the lower port 28 is fully visible to the user through the upper port 26.

This feature is apparent from figure 2, where it is shown a top plan view of the golf club head

10 in proper position and alignment relative to the viewpoint of a golfer preparing to take a shot using the golf club head 10.

Both the upper port 26 and lower port 28 are visible and the lower port 28 is concentric and slightly smaller with respect to the upper port 26.

If the golfer has not positioned or oriented the golf club head properly, ports 28 and 26 will not appear concentric.

When the golf club head 10 has been properly positioned relative to the golfer's eye, as in figure 2, it will be seen that the inner edge defining the lower port 28 is fully visible to the golfer through the upper port 26, so that the inner edges defining the ports 26 and 28 provide a predetermined image to the golfer.

It will be appreciated that the edges 27 and 29 of the ports 26 and 28 define a closed plane figure when viewed from above by the golfer and that said curved edges 27, 29 bear a predetermined relationship to each other that is readily recognized by the golfer and indicates proper alignment of the golfer with the golf club head.

Since the edges 27 and 29 are curved, aligning one with the other thereby aligns the golf club head in two dimensions.

It should be appreciated how this feature simplifies the alignment process.

Figures 4A through 4D can be considered to understand how the golf club head of figure 2 should be reoriented or moved to achieve proper alignment for a shot.

With reference to Figure 4A, either the golf club head 10 is forward of the correct position so that the right side of the edge 29 of the lower port 28 is obscured, or else the golfer has rotated the golf club head so that its rear portion 18 is high relative to its face 20.

Therefore, the edge 29 of the lower port 28 appears to be too far to the right relative to the edge 27 of the upper port 26.

An appropriate reorientation or movement of the golf club head will bring the two oval ports

26 and 28 into a concentric alignment so that the whole edge 29 of the lower port 28 will be visible to the golfer.

It will be seen that only two features of the golf club head 10, that is, the edges 27 and 29 of the two oval ports 26 and 28, need be seen by the golfer to achieve alignment.

It will also be appreciated that these features are sufficiently large and prominent to enable the golfer to view them with ease in the process.

Figure 4B illustrates the condition where the golf club head 10 is behind the correct position or the head 10 has been rotated relative to a horizontal axis parallel to the golf club head's face 20, so that the edge 29 of the lower port 28 appears to be shifted to the left relative to the edge 27 of the upper port 26.

Figure 4C illustrates the condition where the golf club head 10 is too far from the golfer or the head 10 has been rotated relative to a horizontal axis perpendicular to the golf club head's face 16, so that the edge 29 of the lower port 28 appears to be shifted down relative to the edge 27 of the upper port 26.

Figure 4D illustrates the condition where the golf club head 10 is too close to the golfer or the head 10 has been rotated relative to a horizontal axis perpendicular to the golf club head's face 20, so that the edge 29 of the lower port 28 appears to be shifted upwardly relative to the edge 27 of the upper port 26. In each of the cases 4A-4D, the golfer can readily adjust the position or orientation of the putter's head to correctly align it for a shot as indicated by the golfer's ability to view the edge 29 of the lower port 28 in its entirety, as well as an axial alignment of the upper and lower ports 26 and 28.

In figure 5, it is shown an embodiment of the golf club, according to the invention, in which the upper port 26 and the lower port 28 have different shapes.

When the golf club head 10 has been properly positioned relative to the golfer's eye, as in figure 5, it will be seen that the inner edge 29 defining the squared lower port 28 is fully visible to the golfer through the oval upper port 26, so that the inner edges 27 and 29 defining the ports 26 and 28 provide a predetermined image to the golfer.

It will be appreciated that the curved edges of the ports 26 and 28 still bear a predetermined relationship to each other that may be readily recognized by the golfer and indicates proper alignment of the golfer with the golf club head.

Also in this case the edges 26 and 28 are curved so as to allow an easy aligning of the golf club head in two dimensions.

Figures 6-7 show alternative embodiments of the present invention, according to which the upper port 26 and the lower port 28 are arranged such that when an eye of a user of the golf club head 10 is aligned therewith along a predetermined alignment axis, the second inner edge

29 defining the lower port 28 is fully hidden to the user by the upper port 28.

To this aim, the lower port 28 is preferably formed so that it is slightly larger than the upper port 27. The golfer can thus achieve alignment of the golf club head 10 by adjusting the position of the head 20 so that the edge 29 of the lower port 28 is obscured by the edge 27 of the upper port 26.

Therefore, in this case when the golf club head 10 is not in the correct position the edge 29 of the lower port 28 will result partially visible to the eye of the user, who may move the golf club head 10 in order to obtain the full obscuration of the edge 29 of the lower port 28.

In the golf club head of figure 6, both the upper and the lower ports 26 and 29 have a same oval shape while in the embodiment of figure 7 the ports 26 and 28 have different shapes.

According to the present invention, the upper portion and/or the lower portion lower portion of the golf club head may comprise a tubular structure.

Figures 8-10 show different views of a golf club 100, according to the present invention, in which both the upper portion and the lower portion of the golf club comprise tubular structures.

The golf club head 100 comprises a top tubular structure 112, a bottom tubular structure 114, a front portion 116, and a rear portion 118.

The golf club head 100 further includes a front face 120 and a recessed cavity located within the front portion 116 to accommodate a shaft (not shown for purposes of simplicity and clarity).

Each of the tubular structures 112 and 114 has preferably a hollow interior.

The tubular structures 112 and 114 are made of a low weight material such as a polymer plastic, or fibre reinforced resin such as carbon fibre reinforced epoxy.

This creates a light central region so that relatively greater weight can be included in the front portion 116 and rear portion 118 to increase the PMOI of the golf club head 100.

Either the top tubular structure 112 or bottom tubular structure 114 may instead be manufactured of a relatively denser material such as aluminum, steel, or titanium to change the centre of gravity along a vertical axis of the golf club head.

For example, if the bottom tubular structure 114 were made from steel, this would lower the centre of gravity toward the ground plane.

Inner edge 127 of the top tubular structure 112 defines an upper port 126.

The port 126 is advantageously oval shaped with the major axis in line with the direction of shooting and in the desired strike location of the golf ball.

Of course, the port 126 may have a different shape.

The port 126 excludes all material from the central zone of the golf club 100, creating a zero mass state for this zone.

The bottom tubular structure 114 forms a lower port 128, which is similar in shape, orientation and relative location to port 126 but slightly smaller.

Nonetheless, the port 126 may have a different shape.

As with port 126, port 128 excludes all material from the centre area of the golf club head

100, creating a zero mass state for this zone.

The ports 126 and 128 are arranged such that when an eye of a user of the golf club head 100 is aligned therewith along a predetermined alignment axis 61, the second inner edge 129 defining the lower port 128 is fully visible to the user through the upper port 126.

Figure 9 is a top plan view of the golf club head 100 in proper position and alignment relative to the golfer for making a shot.

Both the upper port 126 and lower port 128 are visible.

In addition, the lower port 128 is concentric and slightly smaller with respect to the upper port

126.

If the golfer has not positioned or oriented the golf club head properly, ports 128 and 126 will not appear concentric as in figure 9.

When the golf club head 100 has been properly positioned relative to the golfer's eye, as in figure 9, it will be seen that the inner edge 129 defining the lower port 128 is fully visible to the golfer through the upper port 126, so that the inner edges defining the ports 126 and 128 provide a predetermined image to the golfer.

It will be appreciated that the edge of each of ports 126 and 128 defines a closed plane figure when viewed from above by the golfer and that the curved edges 127 and 129 of the ports 126 and 128 bear a predetermined relationship to each other that is readily recognized by the golfer and indicates proper alignment of the golfer with the golf club head 100.

Since the edges 127 and 129 are curved, aligning one with the other thereby aligns the golf club head 100 in two dimensions. This simplifies the alignment process.

According to an alternative embodiment (not shown), the ports 126 and 128 may also be arranged such that when an eye of a user of the golf club head 100 is aligned therewith along a predetermined alignment axis, the second inner edge 129 is fully hidden to the user by the upper port 126.

In this case, the lower tubolar structure 114 will be arranged to define a lower port 128 that is slightly larger than the upper port 126.

When the golf club head 10 is not in the correct position the edge 129 of the lower port 128 will be partially visible to the eye of the user, who can achieve alignment of the golf club head

100 by adjusting the position of the head so that the edge 129 of the lower port 128 is obscured by the edge 127 of the upper port 126.

In the golf club head 100, the bottom tubular structure 114 is on more than one level, as it is formed into the shape of a "W" with the outermost legs 114A a greater distance from the ground plane than the innermost legs 114B, forming the lower port 128.

In this way, the golf club head 100 is enabled to resist deformation about a horizontal axis perpendicular to the face 120.

In various alternative embodiments, the legs 114A-114B of the lower portion 114 are arranged at the same or various angles to the horizontal and/or vertical planes, and are attached to the front and rear portions 116 and 118 of the golf club head 100 at selected locations, in order to achieve either a more rigid or more flexible structure of the golf club head as a desired result.

According to the present invention (figures 11-12), the top tubular structure and/or the bottom tubular structure of the golf club head may comprise one or more legs having at least one aperture.

In figure 11, it is shown a golf club head 200, which has a similar construction to that one illustrated in figures 8-10.

The golf club head 200 comprises a front portion 216, a rear portion 218 and upper and lower tubular structures 212 and 214 respectively forming the upper and lower portions of the golf club head.

Ports 226 and 228 may be formed respectively by the tubular structures 212 and 214. Such ports may be arranged such that when an eye of a user of the golf club head 200 is aligned therewith along a predetermined alignment axis, the second inner edge 229 defining the lower port 228 is fully visible or hidden to the user through the upper port 226.

Both the tubular structures 212 and 214 comprise one or more legs 212A and 214A, which are provided with one or more apertures 250 extending along a main axis 250A substantially vertical, i.e. perpendicular with respect to the ground plane.

Each of the apertures 250 may be a port, which passes through the thickness of the corresponding leg 212A or 214A, or a blind hole.

The lower tubular structure 214 may have legs 214A at different heights from the ground plane.

In figure 12, it is illustrated a golf club head 300 that is basically similar to that one shown in figure 11. The golf club head 300 comprises a front portion 316, a rear portion 318 and upper and lower tubular structures 312 and 314, respectively forming the upper and lower portions of the golf club head.

Ports 326 and 328 may also in this case be arranged such that when an eye of a user of the golf club head 300 is aligned therewith along a predetermined alignment axis, the second inner edge 329 defining the lower port 328 is fully visible or hidden to the user through the upper port 326.

Both the tubular structures 312 and 314 comprise one or more legs 312A and 314 A, which are provided with one or more apertures 350.

In this case, the apertures 350 extend along a main axis 350A that is substantially horizontal, i.e. parallel with respect to the ground plane.

Each of the apertures 350 may be a port passing through the thickness of the corresponding leg or a blind hole.

The lower tubular structure 314 may have legs at different heights from the ground plane.

Apertures 250 and 350 on the upper and/or lower tubular structures of the golf club head 200,

300 provide remarkable advantages.

They may be used to accommodate properly shaped inserts in order to modify the weight distribution of the golf club head according to the needs.

Further, the apertures 250 and 350 may be properly arranged and designed to remarkably improve the aesthetic appearance of the golf club head. Variations of the embodiments shown in figures 11-12 are possible. For example, the apertures 250, 350 may extend along different orientations or they may a shape different than oval.

According to the present invention, certain portions or inward components of the golf club head 10, 100, 200, 300 are arranged close to its centre of gravity, such as the top wall 12 and/or the bottom wall 14, the top tubular structure 112, 212, 312 and/or the bottom tubular structure 114, 214, 314 may be fabricated of multiple layers of aligned carbon filaments held together with an epoxy binder, i.e., so-called "graphite" material.

The fibres in the various plies are parallel to one another, but the various plies preferably have varying fibre orientations.

This creates a low weight but strong structure.

Therefore, the mass of the golf club head closest to its centre of gravity is advantageously reduced both by forming ports in the central portion, as well as by forming the central portion of the putter body with relatively lightweight materials.

This weight savings can be redistributed to the perimeter of the golf club head, such as at the outward portions or components 18, 118, 218, 318 and 16, 116, 216, 316 to further increase the PMOI about a vertical axis, resulting in improved stability of the golf club head and better ball directional control.

In order to form the light portions of the golf club head a carbon fibre reinforced epoxy prepreg may be advantageously used.

A prepreg is formed by embedding the fibres, such as carbon, glass, and others, in resin.

This is typically done using a prepreg machine, which applies the non-cured resin over the fibres so they are all wetted out.

The resin of the prepreg is at a "B Stage", meaning that only heat and pressure are required to complete cross linking to harden and cure the resin.

Thermoset resins like epoxy are popular because they are available in liquid form at room temperature, which facilitates the embedding process.

A thermoset is created by a chemical reaction of two components, forming a material in a non-reversible process.

Usually, the two components are available in liquid form, and after mixing together, will remain a liquid for a period of time before the cross-linking process begins.

It is during this "B Stage" that the prepreg production process is carried out, where the resin coats the fibres.

Common thermoset materials are epoxy, polyester, vinyl, phenolic, polyimide, and others. The prepreg sheets are cut and stacked according to a specific sequence, as described hereinbelow, paying attention to the fibre orientation of each ply.

Each prepreg layer comprises an epoxy resin combined with unidirectional parallel fibres selected from the class of fibres including but not limited to carbon fibres, glass fibres, aramid fibres, and boron fibres.

The prepreg is cut into strips at various angles and laid up on a table.

The strips are then stacked in an alternating fashion such that the fibres of each layer are different to the adjacent layers. For example, one layer may be +45 degrees, the next layer -45 degrees.

If more bending stiffness is desired, a fibre angle such as zero degrees is used.

If more torsional stiffness is desired, a higher proportion of higher angle strips such as +/- 45 degree strips are used. Other fibre angles may also be used.

This lay-up, which comprises various strips of prepreg material, is then prepared for moulding.

The walls 12 and 14 of the golf club head 10 may be formed by compressing the prepreg material between two plates having the desired contour of the surfaces of the walls 12 and 14.

Upon applying heat and pressure, the walls 12 and 14 are formed and the ports 26 and 28 can be moulded in or removed in a post-moulding machining operation.

The tubular structures 112, 212, 312 and 114, 214, 314 of the golf club head 100, 200, 300 may be formed by rolling the prepreg material into a tubular form. A polymeric bladder is inserted into the tubular form.

This is packed into a mould, which is then placed into a hot press that closes the mould.

Air pressure is applied to the bladders to internally pressurize them to expand and consolidate the prepreg form against the cavity of the mould.

The mould is heated up which allows the epoxy resin to flow and eventually cross link and cure.

The internal pressure of the bladder combined with the higher moulding temperature will cause the epoxy risen to lower in viscosity, allowing the prepreg to assume the shape of the mould cavity before cross-linking and setting.

Once the moulding operation is complete, the mould is opened and the tubular structure removed.

The apertures 250 and 350 can be moulded in or removed in a post-moulding machining operation.

The operation of fixing the walls or the tubular structures to the front portion and the rear portion of the golf club head may be accomplished by adhesive bonding or fixing with some mechanical fasteners.

For example, the front and rear portions could be provided as two pieces, which are then assembled with the walls or tubular structures using mechanical fasteners.

As an alternative, the fixing of the wall structures or the tubular structures can be performed directly in the mould by an over- injection or a co-moulding process or the like.

For example, the wall structures or the tubular structures can be fixed to the front portion and rear portion by means of a co-moulding operation in which the front and rear portions are provided as metal components and inserted into a mould, and the wall structures or tubular structures are formed of a carbon fibre composite material formed thereabout.

As a further option, the front and rear portions can be pressure fitted with the wall structures or the tubular structures.

The composite material used is preferably carbon fibre reinforced epoxy because the objective is to provide reinforcement at the lightest possible weight.

Other fibres may be used such as fibreglass, aramid, boron and others.

Other thermoset resins may be used such as polyester and vinyl ester.

Thermoplastic resins may also be used such as nylon, ABS, PBT and others.

As evidenced above, the ports 16, 126, 226, 326 and 28, 128, 228, 328 can have any desired shape.

In certain embodiments, the alignment ports, in particular the bottom ports 28, 128, 228, 328, may have open ends or open edges or straight lines to aid in the alignment of the golf club head.

In certain embodiments, the ports of the golf club head may have a circular shape.

In certain embodiments, they have a square, rectangular, diamond or other quadrilateral shape, or else a shape having more or less than four sides.

In certain embodiments, the shape of the alignment ports is a combination of one or more curved portions and one or more straight segments.

With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Although various embodiments have been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other embodiments, modifications and variations will be ascertainable to those of skill in the art.