WO2008035077A1

WO2008035077A1 - Golf club

Info

Publication number: WO2008035077A1
Application number: PCT/GB2007/003567
Authority: WO
Inventors: James Stephen Boyd Mather; David Fletcher; Dennis Vardy
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-09-20
Filing date: 2007-09-20
Publication date: 2008-03-27
Anticipated expiration: 2009-03-20
Also published as: GB0618450D0; GB2441973A

Abstract

A golf club head comprising a rigid box section (20) with an extending rear base plate (240) which is provided with an additional primary weight (242).

Description

GOLF CLUB

Field of the invention

The present invention relates to golf clubs and more particularly to golf clubs of the type known as woods.

Background of the invention

The game of golf has been the subject of many patents for inventions which claim to improve the performance potential of the golfer. It is clear that the majority of golfers find achievement of satisfactory shot making difficult and most accept this situation. The manufacturers of golf equipment, be it balls or clubs, are aware of the deficiencies of players yet still continue to produce equipment which is mainly beneficial to the professional and good golfer. The less proficient golfer is left to make the best of what is available, to compromise their shot-making in order to be able to participate in the game.

An aim of this invention is to offer a better solution to this level of golfer, whilst not adversely affecting its usefulness to the better and elite player.

Golf clubs traditionally come in sets, comprising "irons and woods", so named because of the materials from which they were originally constructed many years ago. The woods, hereinafter referred to as the wood type, are divided into two categories, drivers and fairway woods, the first to be used off the tee at the start of a hole, and the latter off the fairway if long distances are still to be required.

To achieve these long distances, the speed of the club head must be large and the angle of the loft on the club face must be low. The former obviously depends on the abilities and strength of the golfer but can also be aided by making the shaft longer. Unfortunately, this increases the inertia of the club about the wrists and the shoulders of the golfer so making the club more difficult to swing. It is often the case that, perversely, the head speed does not increase, and the golfer loses control of the club resulting in a poor impact and shot. To compensate, the mass of the head is sometimes decreased but insufficiently to recover control. Previous patented designs by the inventors present methods by which control can be mainly recovered without loss of distance. This involves the use of added mass within the area of the hands to balance the reduced head mass. The results in play are very satisfactory for the golfer. These patented designs will be incorporated into these new designs in order to enhance the playing performance of the clubs.

Statistical surveys of the playing performances of both amateur and professional golfers consistently show that the most important parameters in improving play are accuracy and distance, the former being slightly more important than the latter.

It is an intention of this design to create a club that enables both accuracy and distance to be improved.

Design of the driver and fairway woods

The earliest drivers were made from briar or hickory and take their bulbous shape from the only methods available for construction in the 17^th century. Persimmon ' wood from the USA replaced hickory and was the common material used for "woods" until 30 years ago. The development of modern casting techniques allowed the heads to be made from stainless steel. Since this material is some 8 times heavier than persimmon, the wood needed to be made hollow with a very thin wall thickness.

The overall size of the head was also limited by the use of this material. Designers sought other materials with a lower specific gravity than steel, yet with equivalent specific strength. This was found in Titanium and its alloys. The head size could be, and indeed was, increased to the very large units now available on the market. Some manufacturers still use steel as their design material and, by careful stress analysis, have produced larger heads with a very thin wall thickness.

The bulbous head offers a further advantage particularly to the weaker golfer. The large flat area on the base of the club prevents the leading lower edge of the face digging into the ground. With poorly executed shots, the club can "bounce" along the floor and still make reasonable contact with the ball. This is an important facet of the design of both the driver and the fairway clubs.

Impact process It is important to understand the impact process of ball and club to appreciate the designs which are proposed in this invention. The velocity with which the driver head approaches the stationary ball vary from 30 m/s for a weak amateur player to over 45 m/s for the professional. The ball is elastic and is compressed during the early stage of impact. The peak force between ball and the face of the club can be as large as 15kN. As well as compressing the ball, the head of the driver is deformed. Such deformations have been measured by various researchers, who show that the face becomes concave, and the crown or top and the sides of the club becomes more convex. Inevitably, this results in a loss of energy which could usefully be used to propel the ball forward. The larger heads with thinner walls clearly deform more.

Much has been said in research papers and in patents on clubs about the "trampoline effect." In this, the head and ball stiffnesses are chosen so that the deformed face returns to its normal undeformed state at exactly the same time as the ball returns to its undeformed state thereby increasing the velocity of the ball over that achieved using current conventional head designs. It is as though the ball reacts as a gymnast on a trampoline, hence the name given.

Unfortunately, recent research shows that the impact period depends on the speed of impact and the nature of the materials making up the ball. This is in contrast to the long-held maxim that all impacts were roughly 500μseconds. Thus it is concluded that a given club design will only achieve the trampoline effect for a specific ball hit at a specific speed. Universality for all golfers is not possible. It has also been shown that the trampoline effect is a maximum when the impact is at a certain point in the face. Away from the point and the effect reduces significantly. Published tests show that the amateur golfer, even a good one, varies the hit by ± 1.5 cms. We conclude that, for the everyday golfer, it is better to have a club which produces a consistent shot over a large area of the face. During the impact period, the head rotates three dimensionally and this movement imparts rotation to the ball. Some of this is desirable - backspin, which creates lift thus making the ball fly higher and longer than the loft on the face would dictate and some undesirable side-spin, which creates side forces on the ball causing a curved flight to the left or right. Since accuracy is a desired feature of the design, side-spin must be controlled. Elite and professional golfers sometimes wish to curve the ball left or right in flight to negotiate obstacles or counter the wind, and this desire also needs to be satisfied by the design.

The degree of three-dimensional rotation depends mainly on two factors, the stiffness of the shaft and the inertia of the head. The laws of Mechanics show that a stiffer shaft and a higher rotational inertia will both reduce the rotations. The larger heads obviously have larger rotational inertias since their mass is placed peripherally well away from the centre of gravity of the head and the impact point with the ball.

In addition, the location of the centre of gravity will affect spin generation. When the impact point on the face is not in line with the centre of gravity, side-spin and back-spin will be created. In irons, where the centre of gravity is close to the face of the club where the ball impact takes place, this added effect on spin is small and the face can be made flat. In woods, where the centre of gravity is well back, the spins generated will be large and, to counter this, the face is made in a convex curve both across and down the face. The degree of curvature controls the effect.

It now remains to consider the optimum location of the Centre of Gravity. A recent paper by Iwatsubo et al confirms that side-spin is reduced if the CG is closer to the face than a standard design and if the rotational inertia about a vertical axis is increased. They also show that backspin is reduced if the rotational inertia about the horizontal axis is reduced. Their work is entirely theoretical based on a Finite Element analysis of the impact of a standard ball and a variety of head designs where the location of the CG and the rotational inertia are varied. No confirmatory experimental evidence is given in their research publications. The inventors have concluded that the following actions need to be incorporated into the proposed design to increase accuracy and distance and to match the design to the ability of the player: 1. Reduce head deformation allowing all the energy of the head to be used to propel the ball;

2. Reduce the unwanted elements of the three dimensional rotation of the head during impact;

3. Reduce the deformation of the shaft; 4. Maintain those elements of driver and fairway wood design which ease the playability of the club for the golfer; 5. Incorporate the requisite amount of curvature in the face to suit the player.

Summary of the invention

The present invention provides a golf club of the wood type including a shaft and head, the head comprising a box section having a front face, a bottom face, a top face and a rear face, a rear plate rigidly attached to and integrally formed with the bottom face of the said box section, said rear plate extending in a direction away from said rear face, and including a selected primary weight attached to or integrally formed with said rear plate at a predetermined position in relation to said front plate, said rear face of said box section being provided with one or more reinforcing ribs connecting said face of said box to said rear plate at a position adjacent to said selected primary weight to secure said primary weight in position during said use of said golf shaft.

Preferably each said club is provided with three ribs, two being positioned at the outer edges of the rear face and one positioned centrally therebetween, their location and dimensions being sufficient to provide no movement between the said rear face and the said rear plate.

In a preferred embodiment each said club is provided with four ribs, two being positioned at the outer edges of the read face and two equi-distantly positioned therebetween, their location and dimensions being sufficient to provide no movement between the said rear face and the said rear plate.

In a first embodiment, the cavities created by the ribs are filled with lightweight materials. In one form, the weight of the foam material filling the outside cavities are the same. In a variant, the weights of the outside cavities are different, enabling the Centre of Gravity (CG) to be moved from a central location and giving the clubhead an unequal mass distribution about the CG. It is already known that such a differential distribution can be used to correct or reduce a slice or a hook.

Preferably, the lightweight material would be plastics material, for example polyurethane foam. The attachment would be semi-permanent by gluing or similar process, thus complying with the regulations of not being alterable during the game, but removable by chemical action.

In a second embodiment, the rear face of said box section is provided with a plurality of holes. Advantageously, there are three or four holes. Preferably within each hole a small weight is placed forming an array comprising a plurality of smaller weights each said small weight being less in mass then said primary weight.

In one form, said smaller weights are all equal in mass. In another form, said smaller weights are of different mass. This will enable the clubhead to be unequally weighted in relation to the centre of gravity (CG) of the head.

Preferably the smaller weights are semi-permanently fixed into the box section but may be removable by suitable machine action. Thus the weight balance will be fixed, i.e. not alterable by a golfer during a game and thus complying with regulations, but could be altered, for example, to correct a slice, or to alter the club setting for a new player who may purchase the club second-hand. Embodiments of the present invention will now be described with reference to the accompanying drawings in which:-

Figure 1 shows in vertical cross-section a known traditional design of golf club head; Figure 2 shows in vertical cross-section a golf club head according to the present invention;

Figures 3 a, 3b and 3 c show modified embodiments of the head of Figure 2;

Figure 4 shows a rear profile of the box section of the head shown in Figure 2; Figure 5 shows a further modification of the golf club head shown in

Figures 2 and 3;

Figure 6 shows in rear elevation a further modification of a golf club head according to the present invention;

Figure 7 shows a heavy mass introduced into the handle of the club with the centre of gravity placed close to the centre of the two hands gripping the golf club;

Figures 8a and 8b picture the club.

With reference now to the drawings, Figure 1 shows a traditional design of golf club head comprising a solid or hollow box, 1, which is shown in cross-section and comprises a semi-elliptical shape with a substantially flat front face, 2, and a baseplate, 3. A hosel will be provided in a known position not shown in the cross- section and to this hosel a shaft and grip are fitted in known manner.

In the design according to a first embodiment of the present invention, a reduction of the head deformation is achieved by stiffening the main structure of the head as shown in Figure 2.

The club head designed as shown in Figure 2 comprises a rigid box section 20, having a front face 22, a bottom face 24, a top face 26, and a rear face 28. The box is formed with a front face formed integrally with the side and bottom faces with no additional insert in the front face thus forming a rigid structure. The baseplate 24 is extended in the direction away from the front face 22 as shown by a rear extension plate 240, which may be formed integrally with the baseplate 24. Figure 3 shows a selected primary weight 242 which is rigidly attached to or formed integrally with the rear extension plate 240. In the design, this weight can be adjustable in both mass and positioning relative to the front face 22.

The stiffening is achieved by the whole box section 20 being smaller than the normal bulbous structure of Figure 1 , and is therefore very much stiffer. The deformation on impact with a golf ball will be much smaller than in normal clubs and certainly much smaller than the heads with very large volumes and large unsupported areas. By maintaining a hollow structure, rather than a simple flat plate as in the design of "irons", a stiff structure can be created at low mass. This is not needed with irons whose mass is normally higher since the club lengths are shorter. This stiffness also eliminates any trampoline effect, which is one of our aims. Accepting the exclusion of the trampoline effect offers the possibility of a consistent hit over a larger area. Since the golf clubs are of the wood type, the impact speed when striking the golf ball will normally be very high in relative golf speed terms possible up to 65 m/s.

This impact speed will produce a tendency for the rear plate 240 to either bend or crack thus reducing the life-expectancy of the club. Also if the club is misused by, for example, hitting a very hard surface instead of the ball, then the impact force will be substantially increased leading possibly to severe cracking or bending of the rear plate due to the momentum generated by the deceleration of the primary weight 242. In order to prevent damage to the rear plate, the rear plate is provided with one of more stiffening ribs 2422 to 2424 as shown in Figure 3 a. Figure 3b shows four such ribs as visualised in Figures 9 to 14.

Reduction of three dimensional rotational effects is achieved by moving the centre of gravity forwards to a point about 20 to 25 mm behind the face. This is forward to that of a conventional club and certainly even further forward to that of a large volume club. Having achieved these two aims, we need to match the club to the playing performance of the golfer. The location of the CG is altered by adding the mass 242 at or near to the rear of the base plate, as shown in Figure 2. This moves the CG rearwards, producing more reaction for the offset hit. This is then countered by the increased rotational inertia created by the addition of this mass. It may be seen that the mass 242 not only has momentum in the direction 2427 which would be expected in striking the ball, but if the ball is not struck accurately off the centre of the face it will have momentum in the direction of arrows 2428 and 2429. This momentum which appears as a shock force when the ball or ground is accidentally struck is countered or absorbed by the ribs 2420, 2422 and 2424. Without these, the weight 242 would act to bend or crack the plate 240 thus breaking the golf club. Although the mass 242 is typically only 20 to 30 g, the head speed of the golf club on impact of up to 65 m/s produces a shock sufficient to bend the base plate about its junction with the rigid box. Thus the ribs 2420, 2422, and 2424 must be of sufficient strength to withstand this force if the club were to come to rest virtually instantly as is the case when the club strikes the ground.

For an elite golfer, the mass would be placed away from the rear of the base plate which would enable the golfer to create the desired spin for manoeuvring the ball. In a further embodiment, the mass, 242, is added at any location as shown in Figure 3 a, to counter the effects of the golfers swing or to add to the effects needed by the elite golfer.

Alternatively or in addition, the rear face 28 shown in Figure 4 can be provided with holes 282, 284, and 286 which can further adjust the centre of gravity of the club.

The concentrated mass 242 is usually in the form of a block of steel or other dense material. Typically the mass of this block is 20 to 30 g and its location is 40 to 50 mm behind the front face 22. It is essential that the flat base is retained not only as a useful mount for the mass but also as an aid to the weaker golfer.

Where the golfer is used to a heavy club, the mass would be chosen to give the same overall weight, but it would be placed closer to the face so that the location of the CG is maintained. Where the golfer normally uses clubs with light heads, the mass is light and placed towards the extremity of the extended base.

In a preferred embodiment when the head weight is lower than normal, a weight 300 is provided within the shaft 30 as shown diagrammatically in Figure 7. The weight 300 is preferably provided by sliding a rubber/silicone (or other similarly flexible) material down the inside of the shaft which, as is the case with all modern clubs, is hollow. The weight is positioned such that its centre of gravity

(COG) is located within the region of the lower hand when both hands are placed on the club. The rubber/silicone insert also provides vibration damping for the player.

The clubs would be made with different lofts to accommodate the requirements of the golfer and these lofts would cover a range of at least 6 degrees, typically from 9 degrees to 15 degrees. Should it be necessary to fine tune the flight of the ball, particularly for an elite golfer, then the added mass can be split into 2 masses, 242, 244, and placed partly on the base and partly on the rear of the stiffened section as shown in Figure 5. This raises the centre of gravity of the head and thereby produces a higher trajectory.

To satisfy the Rules of Golf, these masses will be fixed firmly in place rendering them immovable for play in a round of golf, but alterable on the practice ground.

Reducing the shaft deformation is achieved by using stiffer shafts which are readily available. Because the CG is well forward, the use of a regular or weaker shaft is no longer necessary in order to increase the dynamic loft of the face. Clubs with a variety of lofts are made to suit the ability of the golfer. This is a more complex but better way of matching clubs to the player's needs. In a further embodiment shown in Figure 6, the rear plate 28 has been provided with four holes 281, 283, 285 and 287. These holes may be filled with lightweight plastic plugs, 281', 283', 285', and 287', each having a weight substantially less than said primary weight 242.

In a preferred example, the total mass of the four plugs would be about 20 g. Normally these would each be 5 g and placed equally in all the holes. But it is intended that there would also be plugs of 2.5 g and 7.5 g. These, when located in certain holes, would alter the location of the centre of gravity and therefore the performance of the club.

For instance, for a player who normally draws or hooks the ball, the 7.5 g plug would be placed in hole 281, and the 2.5 g plug in hole 283. Two 5 g plugs would be placed in holes 285 and 287. For a golfer who slices, hole 283 would have a 7.5 g plug and hole 281 would have 2.5 g plug. For the player who hits the ball high but wants more penetration, hole 285 has 7.5 g, hole 287 has 2.5 g and the others 5 g each. For a player who drills the ball low, hole 287 is where the dominant mass will go.

As well as matching the mass distribution to the player, the club can be altered for a subsequent player who may purchase the clubs second-hand.

It may be envisaged that better players will require more sensitive systems and masses with lower differentials than 2.5 g can be made available.

If the head is made of steel, then the total mass available to be added in the plugs is about 20 g. If the head is made from titanium, then the mass available will be 40 or 50 g. Therefore the added mass in the plugs may then be between 20 and 50 g. The mass of the plugs could be equally divided and may have variations up to ± 5 g. The plugs would be typically of lightweight plastic and made with a lip which allows the plug to be clipped into place and only removed with some force. This is essential since the forces of impact are very large and might displace the plug. It is a Rule of Golf that the club must not be modified during a round although modifications between rounds is allowed.

The plugs, and plastic inserts may be provided with, for example, a maker's name or logo.

A practical embodiment is shown in Figure 8a. The face plate 22 may be cast in or pressed into the head in a later operation. The figure also shows the hosel and shaft connection 30.

Typically the width W is between 90 and 100 mm and the height H between 45 and 60 mm.

As shown in Figure 8b, the centre of gravity of the head unit is approximately 25 mm from the centre C of the face and 22 to 25 mm up the face from the base plate.

The overall mass of the driver head shown in this example is between 180 and 195 g-

Claims

1. A golf club including a shaft and head, the head comprising a box section having a front face, a bottom face, a top face and rear face, a rear plate rigidly attached to and integrally formed with the bottom face of said box section, said rear plate extending in a direction away from said rear face and including a selected primary weight attached to or integrally formed with said rear plate at a predetermined position in relation to said front plate, said rear face of said box section being provided with one or more reinforcing ribs connecting said face of said box to said rear plate at a position adjacent to said selected primary weight to secure said primary weight in position during said use of said golf shaft.

2. A golf club as claimed in Claim 1 in which each club is provided with three ribs, two being positioned at the outer edges of the rear face and one positioned centrally therebetween.

3. A golf club as claimed in Claim 1 in which each club is provided with four ribs, two being positioned at the outer edges of the rear face and two equidistantly positioned therebetween.

4. A golf club as claimed in any one of Claims 1 to 3 in which the cavities created by the ribs and rear face are each filled with a lightweight flexible plastic material.

5. A golf club as claimed in Claim 4 in which the said plastic material is of the same weight in the cavities.

6. A golf club as claimed in Claim 4 in which the said plastic material in the cavities is of different weight.

7. A golf club as claimed in Claim 3 in which the weight of the said plastic material is the same in the two outer cavities. 03567

8. A golf club as claimed in Claim 3 in which the weight of the said plastic material is not the same in each of the two outer cavities.

9. A golf club as claimed in Claim 3 in which the weight of the said plastic material is not the same in any of the three cavities.

10. A golf club as claimed in any one of Claims 1 to 3 in which the rear face of said box section is provided with a plurality of holes.

11. A golf club as claimed in Claim 10 in which there are three or four holes comprising the said plurality of holes.

12. A golf club as claimed in Claim 10 or Claim 11 in which within each hole a small weight is placed forming an array comprising a plurality of said smaller weights each said smaller weight being less in mass than the said primary weight.

13. A golf club as claimed in Claim 12 in which each of the said smaller weights are equal in mass.

14. A golf club as claimed hi Claim 12 in which one or more of the said smaller weights are of different mass.

15. A golf club as claimed in any one of the Claims 12 to 14 in which said smaller weights are semi-permanently fixed into position but are removable by machine action.