Golf club head with uniform response front face

Abstract

A golf club head has a face insert the effective resiliency of which varies across a striking surface on a front face of the club head. The face insert, which is disposed in a cavity formed in the club head, is supported from beneath by a substrate which is formed of one or more materials to form a low resiliency region near a central of the cavity and a high resiliency region near heel and toe regions of the cavity. By varying the resiliency of the substrate behind the face insert, the effective resiliency, which is a composite of the face insert and the substrate, may be manipulated so that the effective coefficient of restitution between the club head and a golf ball may be made uniform across the entire front face.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to golf equipment and, in particular, to golf club heads.

As is well known to golf manufacturers and many golfers, the “sweet spot” of a golf club head is the point on the front face at which a line drawn normal to the front face passes through the center of gravity of the golf club head. If a golfer swings a golf club so that the club head impacts the golf ball at the sweet spot, few if any harmonic vibrations are excited within the golf club head and shaft system. Consequently, the maximum amount of energy from the golfer's swing is available for momentum transfer to the golf ball. Conversely, if the golfer swings the golf club so that it impacts the golf ball away from the sweet spot, the impact frequently excites various torsional and bending oscillations. Such a mis-hit has two deleterious consequences. The harmonic oscillations are felt as unpleasant vibrations transmitted to the golfer's hands and the energy lost through the harmonic oscillations is not available for momentum transfer to the golf ball thus resulting in a shorter distance of travel for the golf ball for the same swing speed. This effect is compounded by the fact that in many cases the sweet spot on the front face is at or near the point of the front face which has the highest compliance and therefore, the highest effective coefficient of restitution. Thus, a golf ball hit at the sweet spot will travel substantially further than a golf ball hit at a point on the front face away from the sweet spot. Accordingly, it would be advantageous to provide a golf club head having a lower resilience toward the center of the club head and a higher resiliency toward heel and toe ends of the club head so that the energy transferred to the golf ball would be uniform across the front face irrespective of where the impact occurs.

U.S. Pat. No. 5,807,190 to Krumme, et al. discloses a club head in which the face insert is composed of many small rods arranged in a closely packed array. According to the Krumme patent, use of individual rod segments to form the front face allows the properties of the front face to vary in any pattern over the impact area, simply by varying the materials out of which the individual rods are made. Use of multiple materials within the array of rods could render a front face having the desired distribution of resiliency. Such use of multiple materials would, however, render the club hard non-conforming, for Rule 5(b) of Appendix II of the United States Golf Association requires that the whole of the impact area of a club head be of the same material. Accordingly, what is needed is a golf club head in which the resiliency of the face may be varied across the front face without varying the rod material.

SUMMARY OF THE INVENTION

The present invention comprises a golf club head having a face insert the effective resiliency of which varies across a striking surface on a front face of the club head body. According to an illustrative embodiment, the club head body has a cavity for receiving a face insert. The face insert, which is disposed in the cavity, is supported from beneath by a substrate sandwiched between a back surface of the face insert and a bottom surface of the cavity. The substrate is formed of one or more materials to provide the substrate with low resiliency near a central region of the cavity and higher resiliency near either a heel region or a toe region of the cavity. By varying the substrate, the effective resiliency, which is a composite of the face insert and substrate, may be manipulated so that the effective coefficient of restitution between the club head and a golf ball may be made uniform across the entire front face.

DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawings figures in which like references designate like elements and, in which:

FIG. 1 is a front perspective view of a golf club head incorporating features of the present invention;

FIG. 2 is a cross-sectional view of the golf club head of FIG. 1 taken along line 2-2; and

FIG. 3 is a cross-sectional view of an alternative embodiment of a golf club head incorporating features of the present invention.

DESCRIPTION OF THE INVENTION

The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and the detailed description are not intended to limit the invention to the particular form disclosed but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention.

With reference to FIGS. 1 and 2, a golf club head 10, preferably a golf putter head, comprises a club head body 12 attached to a golf club shaft 14. Typically, the club head body 12 is made of a suitable metal such as steel formed by an investment casting process, however, metal materials such as titanium, aluminum, tungsten, brass, bronze and beryllium copper may be used to form club head body 12. Those skilled in the art will recognize also that the club head body 12 may be made of other metallic or non-metallic materials without departing from the spirit and scope of the present invention. Club head body 12 has a front face 16, a rear surface 18, a heel end 20 and a toe end 22, as well as a top rail 24 and sole 26.

As shown most clearly in FIG. 2, club head body 12 is formed with a cavity 28 that extends from the front face 16 toward the rear surface 18 and is defined by side wall 30 and bottom wall or surface 32. A striking surface 34 on the front face 16 of club head body 12 is provided by a front face insert 36 supported by a substrate 38 disposed in cavity 28. Substrate 38 is preferably composed of additional face inserts 40, 42 and 44. Face insert 36 preferably comprises a plurality of individual rod elements 46. Rod elements 46 are all of substantially identical geometry except for their individual lengths. Accordingly, the individual rod elements 46 are not separately described herein in detail. Rod elements 46 are packed together in an array such that each side surface 48 is in contact with the side surface of an adjacent rod element 46. Face insert 36 is positioned in cavity 28 such that the bottom ends 50 of the rod elements 46 are supported by the upper surfaces 52, 54 and 56 of face inserts 40, 42 and 44. The exposed ends 58 of rod elements 46 are finished flat to form the striking surface 34 on the front face 16. Face insert 36 may be formed of individual rod elements of circular cross-section (not shown), but preferably comprises a plurality of metal alloy rod elements 46 of hexagonal cross-section (as seen in FIG. 1) arranged in a close-packed array surrounded by an epoxy binder 60 that holds the rod elements 46 in place.

Face insert 40, which is positioned in a central region 62 of cavity 28 is preferably made from an elastomer such as polyurethane having a resiliency of between 0.5 and 0.85. Face inserts 42 and 44 may be made of a metal alloy, ceramic or elastomer having a resiliency greater than that of face insert 40. The material choices for face inserts 40, 42 and 44 will vary from club head to club head depending on the location of the vibrational nodes and anti-nodes of the golf club head.

Where a principal node of the club head is located in the central region 62 of cavity 28, little energy is lost due to the excitation of harmonic vibrations within the club head 10. Accordingly, a golf ball will travel a greater distance for a given club head speed. Conversely, if a golf ball is struck in a heel region 64 of cavity 28 proximal face insert 42, energy will be lost due to the excitation of harmonic vibrations in club 10 and the ball will not travel as far. Similarly, if a golf ball is struck in a toe region 66 of cavity 28 proximal face insert 44, energy will be lost due to the excitation of harmonic vibrations in club head 10. The energy lost in a “toe hit” versus a “heel hit” may or may not be the same. Therefore, in order to compensate separately for a “toe hit” or “heel hit”, the material chosen for face inserts 42 and 44 may be of different resiliencies so as to dissipate different amounts of energy.

The effective coefficient of restitution, as used herein, is the ratio of the velocity of a golf ball struck by the golf club head at various locations on the front face as compared to the velocity of the golf ball in a perfectly elastic collision. The apparent coefficient of restitution C for a golf club of mass M1 travelling at a velocity V1 and striking a stationary golf ball of mass M2 may be described by the following equation:
C=(V_2b−V_2c)/(V_1c−V_1b)
Where V_1c is the the club head velocity before impact, V_1b is the ball velocity before impact, V_2c is the club head velocity after impact, and V_2b is the ball velocity after impact.

The effective coefficient of restitution will be a function of not only the composite resiliency of face insert 36 and any one of face inserts 40, 42 and 44 but also the energy lost due to the aforementioned excitation of vibrations within the club head. Since the material of face insert 36 must be the same across the entirety of striking surface 34, and since the losses introduced as a result of exciting harmonic vibrations within golf club head 10 are difficult to control, the effective coefficient of restitution can be made uniform across the striking surface 34 most effectively by reducing the resiliency of face insert 40 relative to face inserts 42 and 44 so that the sum of the energy lost due to the resiliency of the face inserts 42, 44, 46 plus the energy lost due to the excitation of harmonic vibrations is equal across the front face 16 of the body 12. Although the resiliency of face insert 36 has some effect on the overall resiliency, the overall resiliency of striking surface 34 is dominated by the resiliency of substrate 38. Therefore, the overall resiliency of striking surface 34 can be manipulated by altering the resiliency of substrate 38 notwithstanding the presence of face insert 36. The result is that, for a given club head velocity, the golf club head will impart the same initial velocity to a golf ball irrespective of where on the front face the golf ball is hit.

With reference to FIG. 3, an alternative embodiment of a golf club head incorporating features of the present invention comprises a club head body 312 having a front face 316, a rear surface 318, a heel end 320 and a toe end 322. A cavity 328 with a side wall 330 extends from the front face 316 toward the rear surface 318 and terminates in a bottom wall 329. As with the illustrative embodiment of FIG. 2, a face insert 336 is supported by a substrate 338 composed of face inserts 340, 342 and 344. In order to provide a smoother transition from the high resiliency heel and toe regions 341, 343 proximal face inserts 342 and 344 to the low resiliency region 345 proximal face insert 340, transition regions 346 and 348 are provided in which face insert 340 is partially supported by face inserts 342 and 344, which causes the effective coefficient of restitution in transition regions 346 and 348 to be a composite that includes the resiliency of face insert 340 as well as the resiliency of face insert 342 and face insert 344.

Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. For example, first face insert may be a solid insert or a veneer rather than a plurality of rod elements. Accordingly, it is intended that the invention should be limited only to extent required by the appended claims and the rules and principals of applicable law.

Claims

1. A golf club head comprising:

a body having a front face, a rear surface and a cavity extending from the front face toward the rear surface, said cavity having a bottom surface;

a first face insert formed of a first material, said first face insert having a front surface and a back surface, said first face insert disposed within the cavity with the back surface of said first face insert adjacent the bottom surface of the cavity;

a second face insert formed of a second material, said second face insert having a front surface and a back surface, said second face insert disposed within the cavity with the back surface of said second face insert adjacent the bottom surface of the cavity; and

a third face insert disposed within the cavity atop said first face insert and said second face insert, said third face insert including a plurality of elongate rod elements each having a first end, a second end and a side surface, said plurality of elongate rod elements arranged in a parallel closely packed array such that the side surface of each of said plurality of elongate rod elements is in contact with the side surface of an adjacent one of said plurality of elongate rod elements, the first ends of said plurality of elongate rod elements abutting the front surface of one of said first face insert and said second face insert, and said second ends of said plurality of elongate rod elements exposed to form a striking surface on the front face of the body.

2. The golf club head of claim 1, wherein the second material forming said second face insert has a lower resiliency than the first material forming said first face insert.

3. The golf club head of claim 2, wherein said second material is an elastomer.

4. The golf club head of claim 3, wherein said first material is a metal alloy.

5. The golf club head of claim 1, wherein said cavity comprises a central region, a heel region and a toe region, and wherein said first face insert is disposed in one of said heel and toe regions and said second face insert is disposed in said central region.

6. The golf club head of claim 5, wherein the second material forming said second face insert has a lower resiliency than the first material forming said first face insert such that said front face proximal said central region will exhibit the same effective coefficient of restitution as said front face proximal said one of said heel and toe regions.

7. The golf club head of claim 1, wherein said cavity comprises a central region, a heel region and a toe region, and wherein said first insert is disposed in said heel region of said cavity and said second face insert is disposed in said central region of said cavity.

8. The golf club head of claim 7, further comprising a fourth face insert disposed in said toe region of said cavity and formed of the first material.

9. The golf club head of claim 8, wherein the second material forming said second face insert has a lower resiliency than the first material forming said first face insert and said fourth face insert, such that said front face proximal said central region will exhibit the same effective coefficient of restitution as said front face proximal said heel region and said toe region.

10. A golf club head comprising:

a body having a rear surface, a front face, a heel end, a toe end and a cavity extending from the front face toward the rear surface, said cavity having a central region and a bottom surface;

a face insert having a front surface and a back surface, said front surface including a striking surface on the front face of said body; and

a substrate disposed in said cavity sandwiched between the back surface of said face insert and the bottom surface of said cavity, said substrate having a resiliency that varies from a high resiliency value proximal the toe end of said body to a low resiliency value proximal the central region of said cavity such that said golf club head exhibits a substantially uniform effective coefficient of restitution across the face insert when striking a golf ball.

11. The golf club head of claim 10, wherein said face insert comprises a plurality of elongate rod elements each having a first end, a second end and a side surface, and said plurality of elongate rod elements arranged in a parallel closely packed array such that the side surface of each of said plurality of elongate rod elements is in contact with a side surface of an adjacent one of said plurality of elongate rod elements.

12. The golf club head of claim 10, wherein said substrate comprises a first insert and a second insert, said first insert being formed of a first material having a first resiliency value, said second insert being formed of a second material having a second resiliency value less than said first resiliency value, and said second insert being located proximal the central region of said cavity.

13. The golf club head of claim 11, wherein said substrate comprises a first insert and a second insert, said first insert being formed of a first material having a first resiliency value, said second insert being formed of a second material having a second resiliency value less than said first resiliency value, and said second insert being located proximal the central region of said cavity.

14. The golf club head of claim 13, wherein said first material is a metal alloy and said second material is an elastomer.

15. The golf club head of claim 10, wherein said substrate also has said high resiliency value proximal the heel end of said body.