EP0593486B1 - Golf club head - Google Patents

Abstract

A golf club head having, on the outside thereof, a lower ground-engaging portion forming the sole (2), a substantially planar forward portion forming the striking surface (3), and a rear portion forming the body (4). Said head comprises an internal cavity (5) which is at least partially defined by the walls of a steel shell (6) in said lower rear portion, and said striking surface (3) consists, at least in the striking area, of a fibre-based composite material having a modulus of elasticity of at least 230 Gpa.

Description

The present invention relates to a golf club head, and more particularly, a "wood" type head.

Currently, the clubs used by golfers from the tee or teeing ground to carry the ball for long distances are called the "woods". Originally, the "woods" were built entirely from wooden materials such as persimmon, or other varieties. These clubs are still appreciated by many players, but are not very tolerant, given the low density of the material used, and its homogeneous distribution behind the impact face of the club head.

To overcome this drawback, the "wood-metal" appeared, a club taking the form of wood, but whose head is entirely made of steel. Given the high density of the material used and the mass constraints imposed, the wood-metal generally comprises a hollow steel head, generally produced by lost wax casting. In this type of construction, the mass, which is mainly distributed around the periphery of the impact face, gives the club a tolerance much higher than that of conventional "woods". This tolerance concerns both the angle of departure of the ball, also called "loft" angle, defining the vertical trajectory of the ball, as the deflection of the ball, that is to say the lateral trajectory of the ball .

A first disadvantage of wood-metal concerns the unpleasant sensations felt by the player during impact, due to the metallic contact of the face on the ball.

Another drawback stems from the fact that the stiffness of the steel impact face, the thickness of which must be sufficient to withstand the impact during the blow, is not optimum. It can be demonstrated that a reduction in the face stiffness increases the speed of restitution thus generating a greater flight distance. However, it can be demonstrated that the rigidity of the face depends on the thickness of the impact face and on the elastic modulus of the material. With a given modulus of elasticity, the reduction in rigidity is therefore directly linked to a reduction in the thickness of this face. However, it now appears that the optimum point of rigidity of the impact face of a "metal wood" corresponds to a too small thickness, less than 3 mm, causing its irreversible deformation.

The prior art has proposed golf heads to improve the sensations felt by the player and the speed of restitution.

For example, document GB-A-2 162 431 proposes a "wood" type head, the striking face of which is formed by a stack of layers of ceramic and layers of composite materials. However, the thick walls of this head give it a low tolerance which affects the quality of the trajectories of the balls.

Another example is provided by document GB-A-2,132,902. This document relates to an "iron" type head, the masses of which are offset towards the heel and the toe. The too thin striking face is thickened by at least one layer of composite materials added to the striking face. However, the striking face has become very thick and this solution is not applicable to a "wood" type head.

Yet another example is proposed by document WO 92/22356 a document of the state of the art according to Article 54 (3) EPC. This document relates to a golf club head, the metal front face of which has a cavity for receiving an insert of composite material. The presence of a peripheral lip of the cavity prevents the entire front face from being covered with a layer of composite material, therefore considerably attenuating the beneficial effects provided by the composite material.

The aim of the present invention therefore consists in proposing a golf club head of new construction, in particular of the "wood" type, giving the player good sensations during impact and allowing good work of the ball. Another object is to propose a head whose tolerance is identical to that of a head of a club of the same type of current construction, in particular of wood-metal, but whose stiffness can be chosen in an optimum way, thus allowing d '' increase the contact time of the ball on the impact face, and thus simultaneously the starting speed and the feeling of control of the ball.

To this end, the present invention provides a golf club type head "wood" externally comprising a lower part intended to rest on the ground, constituting the sole, a substantially flat front part constituting the impact face and a rear part constituting the body; said impact face being produced, in the impact zone at least, in a fiber-based composite material whose elastic modulus is greater than or equal to 230 GPa, characterized in that a closed internal cavity is limited , at least, by the lower and rear walls of a steel shell and by the front part made of fiber-based composite material.

Advantageously, the composite material consists of carbon fibers and / or aramid impregnated with a thermoplastic or thermosetting resin. The specific choice of these materials in the construction of the face makes it possible in particular, because of the high resistance properties of the fibers, to reduce the stiffness of the impact face in an optimum manner, while maintaining a sufficient thickness comparable to that of a classic steel face.

The presence of a steel shell has the effect of keeping the golf club sufficient mass and distributed around the periphery of the head, thereby increasing the tolerance of the club.

This tolerance can be optimized on such a construction, and provision can be made for the shell to include an extra thickness of material forming an additional mass of inertia in the region near and behind the periphery of the impact face. This mass can in particular extend in a homogeneous and continuous manner over the entire region behind the periphery of the face, thus conferring tolerance in the vertical and horizontal trajectory of the ball.

On the other hand, the head according to the invention is also characterized in that the internal cavity is entirely limited by the lower, rear and upper walls of the steel shell and by the front part made of fiber-based composite material.

• la figure 1 est une vue en perspective d'une tête de club selon l'invention,
• la figure 2 est une vue de dessous de la tête de la figure 1,
• la figure 3 est une vue de la face de la tête selon la figure 1 ou 2,
• la figure 4 est une vue en coupe transversale selon I-I' de la figure 3,
• la figure 5 est une vue en perspective et éclatée de la tête de la figure 1,
• la figure 5a est une vue en perspective d'un détail de la figure 5,
• la figure 5b est une vue en élévation du détail de la figure 5a.

Other characteristics and advantages of the golf club head according to the invention will emerge from the description below, relating to nonlimiting examples of implementation, as well as from the appended drawings which form an integral part of this description.

• FIG. 1 is a perspective view of a club head according to the invention,
• FIG. 2 is a bottom view of the head of FIG. 1,
• FIG. 3 is a view of the face of the head according to FIG. 1 or 2,
• FIG. 4 is a cross-sectional view along II ′ of FIG. 3,
• FIG. 5 is a perspective and exploded view of the head of FIG. 1,
• FIG. 5a is a perspective view of a detail of FIG. 5,
• Figure 5b is an elevational view of the detail of Figure 5a.

The club head according to the invention comprises, as shown in FIGS. 1 to 3, representing a "wood" type head (1), a substantially planar front part (AV) constituting the impact face (3), a rear part (AR) constituting the body (4) proper, and a lower part intended to rest on the ground (S), constituting the sole (2). The body (4) is extended on the side by a neck (40) forming an integral part of said body (4).

In the embodiment of Figure 4, a closed internal cavity (5) is arranged in the head (1). It is limited on the one hand, by the lower wall (60), the rear wall (61) and the upper wall (62) of a shell (6) of high density material, in particular steel, and on the other hand part, through the wall (30) of the impact face (3). The wall (30) is entirely made of composite material. The assembly can in particular be carried out by gluing, screwing or any other means.

By composite material, the applicant intends to use webs woven from carbon and / or aramid fibers impregnated with a thermoplastic or thermosetting resin material. Among the fibers preferred by Applicant, there are long carbon fibers with high mechanical strength and whose elastic modulus can vary from 230 to 590 GPa and the breaking strength from 2450 to 7000 MPa. Such values are of course higher than those of conventionally known steels. The matrices or resins can be of the polyphenylene sulfide (PPS), polyether imide (PEI), polyether-ether-ketone (PEEK), or epoxy type.

Advantageously, the shell (6) comprises an additional thickness (64) of material constituting an additional mass of inertia positioned in a region close to and behind the periphery of the impact face (3). This additional thickness (64) extends substantially over the entire said region, so that the mass is distributed as far as possible, on either side of the horizontal axis of symmetry (X, X ') and of the vertical axis of symmetry (Y, Y '). These axes are perpendicular to each other, and pass through the center of gravity O of the head (1). The axis (X, X ') is parallel to the impact face on the one hand and to the ground on the other hand when the head rests on the sole (2), and the rotation of the head relative to this axis defines the angle of "loft" which directly influences the starting angle of the trajectory of the ball. Consequently, the distribution of an additional mass of inertia on either side of O on this axis, directly influences the tolerance of the club compared to the vertical trajectory of the ball.

Similarly, the vertical axis (Y, Y ') perpendicular to (X, X') defines the angle of the face, and defines the lateral trajectory of the ball. An additional mass distribution on this axis on either side of (Y, Y '), directly influences the tolerance with respect to the lateral trajectory of the ball.

To achieve optimal tolerance, the mass will therefore preferably be distributed in a homogeneous and continuous manner, around the periphery of the impact face (3). This distribution advantageously compensates for the loss of mass due to this type of construction in comparison with a "wood-metal" type construction, the impact face of which is made of high density material. The difference in mass is therefore best used in the regions as defined above.

The wall (30) is preferably formed by the stack of several woven sheets of fibers. The particular orientation of the fibers constituting each woven ply is shown in the example of FIG. 5. In this case, the wall comprises first plies (31, 310, 311, 312, 313) whose fibers are oriented in a on the axis (X, X ') and on the axis (Y, Y'). The wall also includes second plies (32, 320, 321, 322, 323) oriented offset by + 45 ° and -45 ° relative to the axis (X, X '). Preferably, the wall comprises a successive stack of 10 to 25 layers (31, 32) of fibers.

In order to optimize the resistance of the wall (30), the applicant has defined a particularly advantageous sequence of the first plies (31) and second plies (32) according to a mode shown in Figures 5a and 5b. The wall therefore comprises a sequence of a first external layer (31a) of first plies (31) whose fibers are oriented along (X, X ') and (Y, Y'), of a second intermediate layer of second plies (32) whose fibers are oriented at + 45 ° and -45 ° from the axis (X, X '), and a third internal layer (31b) of first plies (31) whose fibers are oriented according to l 'axis (X, X') and (Y, Y '). The second intermediate layer comprises between 3 and 9 layers approximately.

The first external layer (31a) is intended to resist the compressive forces due to the impact of the ball and there the third internal layer (31b) is intended to resist the traction forces. The efforts are mainly oriented along the axes (X, X '') and (Y, Y '). The second intermediate layer (32) is intended to resist shear forces at the level of the neutral fiber, mainly oriented at +45 and -45 ° relative to (X, X ')

We can give an example of construction of a resistant wall (30) of composite material and its mechanical characteristics.

The wall consists of a stack of webs woven of carbon fibers in a balanced way and of epoxy resin. The volume ratio (fibers) / (resin) is equal to 1. The thickness of a sheet is equal to 0.2 mm. The fibers have a modulus of elasticity equal to 230 GPa and a breaking strength equal to 4410 MPa (fiber of the T300J type from TORAY®).

The stack consists of a first outer layer (31a) of 6 woven layers of fibers oriented along (X, X ') and (Y, Y') (so-called "0 °, 90 °" orientation); a second intermediate layer (32) of 5 woven sheets of fibers oriented at + 45 °, -45 ° from (X, X ') and a third internal layer (31b) of 6 woven sheets of fibers oriented at 0 °, 90 °.

The wall (30) has an elastic modulus according to (X, X ') or (Y, Y') equal to 60 GPa and a breaking strength of 500 MPa.

It can also be specified that a construction comprising a second intermediate layer of 3 plies or less of fibers only at the level of the neutral fiber does not withstand the impact of the ball sufficiently and leads to a rupture of the wall (30). This rupture phenomenon is also observed in a construction comprising a second intermediate layer of 9 or more woven plies of fibers at + 45 °, -45 ° in partial replacement of woven plies of fibers at 0 °, 90 °.

On the other hand, the internal cavity (5) can be filled with a very low density foam, of polyurethane type for example in each of the modes presented. In this case, the foam only serves to advantageously modify the noise of the impact of the ball by imparting a duller sound, often preferred by the players.

Of course, the invention is not limited to the embodiment described and shown by way of example, but it also includes all the technical equivalents as well as their combinations.

Claims (4)

1. A golf club head of the "wood" type externally comprising a lower portion adapted to bear on the ground, forming the sole (2), a substantially plane front portion forming the impact surface (3) and a rear portion forming the body (4), the impact surface (3) being formed, in at least the impact zone, from a fibre-based composite material whose modulus of elasticity is greater than or equal to
   230 GPa, a closed inner cavity being bounded, at least, by the lower (60) and rear (61) walls of a steel shell (6) and by the front portion (30) of fibre-based composite material.
2. A golf club head of the "wood" type as claimed in claim 1, characterised in that the inner cavity (5) is bounded integrally by the lower (60), rear (61) and upper (62) walls of the steel shell (6) and by the front portion (30) of fibre-based composite material.
3. A golf club head of the "wood" type as claimed in claim 1 or 2, characterised in that the shell (6) comprises an extra thickness of material (64) forming an additional inert mass in a region close to and to the rear of the periphery of the impact surface (3).
4. A golf club head of the "wood" type as claimed in any one of claims 1 to 3, the composite material of the head being formed by a stack of several woven layers of carbon and/or aramide fibres impregnated with a thermosetting resin material, characterised in that the stack comprises first woven layers (31, 310, 311, 312, 313) of fibres oriented along an axis (X, X') and a axis (Y, Y') and second layers (32, 320, 321, 322, 323) oriented in a manner offset by +45° and by -45° with respect to the axis (X, X').

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