FR2704764A1 - Handle (shaft) for a golf club and method of manufacturing it - Google Patents

Abstract

Method for manufacturing a handle for a golf club of the type comprising a central conduit (15) limited by the inner surface (14) of a cylindrical wall (12) produced from composite material, the said central conduit comprising at least one weight, characterised in that the said method consists in rolling up, around a mandrel, a thickness of fibres which have been preimpregnated with resin and, in a stage prior to the rolling-up operation, in arranging, between the outer face of the mandrel and the said thickness, at least one weight (M1, M2, M3).

Description

GOLF CLUB HANDLE AND MANUFACTURING METHOD
The present invention relates to a golf club handle and its manufacturing process. It relates more particularly to a club handle made of composite materials and which comprises at least one concentrated mass of inertia.

 During the practice of the game of golf, the player strikes his ball to move it, with a tool called golf club, consisting of a handle, commonly called by its English term "shaft", and which comprises at its lower end, a head, while its upper end is equipped with a handle often called by its English term "grip".

 The golfer, to bring the ball into the hole, uses several types of clubs which differ from each other by the shape of their head with which the ball is struck, and the length of their sleeve.

During the movement preceding the impact of the club on the ball, the handle undergoes a bending which conditions the position at impact. I1 also spreads particularly unpleasant vibratory phenomena for the player, who feels, after the shock of the ball, a discomfort which reduces him the confidence which he carries in his club, for the next stroke.

 Thanks to developments in new composite materials, the torsional and bending stiffness characteristics can be more easily controlled and adjusted to the desired values. The manufacturers can play on the orientation of the fibers (0/450), on the nature of the fibers (glass, carbon, kevlar), on the quantity and the number of layers to carry out by drappage, sleeves with the desired characteristics.

The major drawback nevertheless remains that the taking into account of certain parameters, in particular stiffnesses, has the consequence of not being able to satisfy other requirements, in particular those concerning the balancing of the handle, and consequently of the mounted club. Balancing must be understood in the broad sense and consists in adjusting the desired value, the mass, and the desired values and positions, the center of gravity and the inertia of the handle. The simultaneous compliance with the stiffness and mass requirements is sometimes difficult. Thus, in the sleeves made of composite material, one way of adjusting certain balancing parameters may consist in adding, in the desired places, portions of additional fibrous plies. By this operation, it inevitably results from modifications of the stiffness characteristics initially chosen because the addition of material is important, given the low density of the composite material.

 One of the objects of the invention is therefore to propose a simple and economical solution making it possible to effectively modify the characteristics of the mass of the handle, without modifying the general characteristics of overall stiffnesses of the handle.

 Another object is to facilitate the balancing of a golf club whose handle is made of composite material.

 An additional object is to be able to easily modify the mass of the handle (and of the club) without changing the characteristics of the center of gravity and inertia.

 An additional object is to be able to easily modify the mass and inertia of the handle (and of the club) without changing the characteristics of the center of gravity.

 Thus, the method of manufacturing a handle for a golf club of the type comprising a central duct having a counterweight, and limited by the internal surface of a cylindrical wall made of composite material, is according to the invention characterized in that said method consists in winding around a mandrel, a thickness of fibers pre-impregnated with resin, and in a step prior to winding, to have at least one counterweight between the external face of the mandrel and said thickness.

 According to another characteristic, the method consists in winding around the mandrel, at least a first layer of fibers pre-impregnated with resin, and in a step prior to winding, in placing at least one weight on said first layer, said one or more weights being placed on the face of the ply intended to form the internal face of the handle.

 according to an additional characteristic, in another preliminary step, the weight or weights are prepared in the form of a strip of high density material which is bonded to the first sheet. Said strip of high density material advantageously comprising a layer of glue or a double-sided adhesive.

 In a complementary step, the winding of the sheet of prepreg fibers is around a mandrel which is before and before winding, covered with an elastic and tight tubular bladder, made of elastomeric material.

According to a preferred arrangement of the process, after winding the sheet of fibers,
- the mandrel thus coated is placed in a mold whose imprint defines the final shape of the handle to be produced,
- then a molding operation is carried out by applying at least one internal pressure exerted by the introduction of a fluid inside the bladder between the latter and the mandrel, so as to compact the composite structure against the imprint of the mold, said mold being heated to allow the polymerization of the resin and thus, the production of the handle and the bonding of the weights.

 The invention also relates to a handle for a golf club of the type comprising a central duct limited by the internal surface of a cylindrical wall made of composite material, said central duct comprising at least one counterweight, which is characterized in that the one or more weights are formed by a sheet of high density deformable material from a shaped sheet which is glued to the internal surface of the wall of the handle.

 According to an additional characteristic, the density of the material of the weight or weights is greater than the density of the composite material constituting the wall of the handle, and advantageously the density of the material of the weight or weights is two to fifteen times greater than the density of the composite material constituting the wall of the handle.

 According to one embodiment, the counterweight constitutes an unclosed tubular wall on its periphery, while in a variant, it constitutes a tubular winding.

 According to another arrangement, the counterweight is constituted by at least two identical counterweights, arranged symmetrically on either side of the axis of the handle, while in a variant, the handle comprises three identical counterweights, distributed uniformly in the duct central.

 Other characteristics and advantages of the invention will emerge from the description which follows with reference to the appended drawings which are given only by way of nonlimiting examples.

 Figures 1 to 3 illustrate a first embodiment of a golf club handle according to the invention.

 Figure 1 is a general front view of a club equipped with the handle, Figure la being a detail view in longitudinal section.

 Figure 2 is a sectional view of the handle along II-II, on a larger scale.

 Figure 3 is a partial perspective view with cutaway.

 Figures 4 and 5 are views similar to Figures 2 and 3, showing an alternative embodiment.

 FIGS. 6 and 7 are views illustrating another variant in views similar to FIGS. 2 and 3.

 Figures 8 to 17 show different steps of the method of manufacturing a handle according to the invention.

 Figures 18 to 21 show in more detail, the area of the handle comprising the weights during the manufacturing process.

 Figures 18 and 19 show this area before pressurization, Figure 18 is a longitudinal section, while Figure 19 is a sectional view along AA.

 Figures 20 and 21 show this area after pressurization, Figure 20 being a longitudinal section, while Figure 21 is a sectional view along AA.

 Figures 22 to 24 illustrate an alternative embodiment.

 Figure 22 is a view similar to Figure 2.

 Figure 23 is a view similar to Figure 3.

 Figure 24 is a view similar to Figure 13.

 Before describing the manufacturing process according to the invention and in order to better understand the process, we will, first, describe several modes of execution of a club sleeve.

 As shown in Figure 1, a golf club consists of a handle (1) whose lower end comprises a head (2), while its upper end carries a handle (3). Generally, the lower end of the handle is engaged in a lateral extension of the head, called the neck (4), while the handle is constituted by a sleeve made of synthetic material, such as synthetic rubber. The handle (1) of the golf club consists of a slightly conical cylindrical tube, to be larger at its upper end (5) than at its lower end (6). It also comprises a lower part (7) intended to engage in the neck (4) of the head (2) of the club, while it comprises an upper part (8) engaged in the handle (3). central part (9) extends downwards through a lower intermediate zone (10), and upwards, through an upper intermediate zone (11).

 The tube constituting the handle is, in a manner known per se, formed by a cylindrical wall (12) comprising an external surface (13) and an internal surface (14) forming a central duct (15). According to a characteristic of the invention, the cylindrical wall (12) is made of composite materials and the central duct (15) comprises at least one inertia flyweight (M). Thus, the handle (1) is for example made of fibers embedded in a polymerized organic resin. The materials used are advantageously carbon fibers pre-impregnated with epoxy resin, but other fibers such as glass fibers or of the aramid type can of course be used.

According to the preferred embodiment, the weight of the handle is disposed at the central part (9) thereof, the weights (M1,
M2, M3) being located near the center of gravity (G) that would have the handle (1) alone, without the counterweight. Thus and for example, the flyweights are located at a distance (LM) from the upper end (5) of the handle, equal to approximately half of the total length (L) of the handle. According to a characteristic of the invention, the weights are arranged in the central duct (15) and according to the embodiment proposed in FIGS. 1 to 3, said central duct (15) locally comprises three identical peripheral weights (M1, M2, M3). Each of the weights consists of a wall of thickness (e), width (la) and length (lg) and is made for example of high density material, such as lead. Each counterweight is for example obtained by cutting from a lead plate a wafer with the dimensions of the counterweight and is secured to the internal surface (15) of the wall (12) of the handle. The three weights (M1, M2, M3) are advantageously distributed inside the handle regularly, so that their respective centers of gravity (g) are arranged on axes (a1, a2, a3) forming between them, a 120 degree angle. This distribution thus ensures symmetry around the general axis (XX ') of the handle.

 Each counterweight (Ml, M2, M3) can have a thickness (e) of between 0.1 mm and 1 mm, a width (la) of between 5 mm and 25 mm and a length (lg) of between 10 mm and 300 mm. The total mass of the three weights being between 3g and 10g for a handle with a mass of 50g to 90g. By way of example, for a handle of 70 grams and center of gravity (G), it is possible to provide a total mass of the flyweight (s), of 10 grams, the flyweight (s) being disposed near said center of gravity ( G).

 Figures 4, 5, 6 and 7 are views similar to Figures 2 and 3 showing two alternative embodiments of the weights. According to the variant illustrated in Figures 4 and 5, the handle (1) comprises only two identical weights (M1, M2) arranged symmetrically on either side of the axis (xi '), while according to the variant of Figures 6 and 7, it has only a single counterweight (M ') having the partial shape of an unclosed tube on its periphery to present an opening (O).

 The method of manufacturing the handle consists in placing and securing the mass or masses on the internal face of the first layer of fibers pre-impregnated with resin, which is wound around a mandrel with other layers of fibers of the same type, to form the handle after crosslinking and removal of the mandrel. The internal face of the first layer forming the internal surface (14) of the handle.

 The term "flyweight" is understood to mean an element of high density or at least of which the density is two to fifteen times greater than the average density of the material constituting the wall of the handle. But preferably, the density of the material constituting the counterweight is eight times greater than the average density of the wall, to limit its bulk. The material is advantageously lead, but can be of any material. Thus, weights can be used in plastic resin or in elastomer loaded with high density metal particles.

 We will describe below the manufacturing method according to the invention, in a preferred mode illustrated by FIGS. 8 to 24. It comprises a step of manufacturing an elastic tubular bladder (22) of length preferably at least equal to the desired handle length. The bladders are preferably made of elastomer which can be used by dipping. This technique is known to those skilled in the art, in particular gloves, bladders and rubber parts of small thickness, of complex shape, and the characteristics of which are essentially required are: great elongation ability and tightness perfect for gases and liquids. Among the elastomers which can be used in the context of the invention, mention may be made of silicone latexes, neoprenes or elastomers. The use of a latex bladder is preferred by the applicant.

 As shown in Figure 8, we use for this, a piece or template (20) which is immersed in a coagulating bath of calcium nitrate for example, then in a bath (21) of latex. After coagulation, the bladder (22) undergoes a cooking step of approximately 10 minutes between 700C and 800C.

This technique makes it possible to obtain bladders of small thickness, of the order of 0.2 to 0.3 mm. After cooling, the bladder is placed on a rigid molding mandrel (23) whose length is at least equal to that of the handle to be obtained (FIG. 10). In parallel with this bladder manufacturing step, the various layers of resin-impregnated fiber layers (N1, N2, N3, N4) are prepared, which are placed side by side, as illustrated in FIG. 11.

In another step, the three weights (Ml, M2,
M3), for example by cutting from a lead strip (24), one of the faces of the strip and for example the lower face comprising a layer of glue or a double-sided adhesive (25). The three weights thus cut and made of lead sheets, are glued to the first layer (N1) constituting the inner layer of the handle, as illustrated in Figure 13.

The next step illustrated in FIG. 14 consists in covering the mandrel (23) with sheets of fibers impregnated with organic resin. The materials used in the context of the invention are carbon fibers pre-impregnated with epoxy from the company Hexcel-Genin of the T6T-135 type or
T6M-135, for example. Of course, the method can be applied to the molding of sleeves using other fibers such as glass fibers, polyaramides or others (ceramic, boron, polyethylene).

 The dressing of the mandrel (23) is carried out by winding a developed (26) of sheet (s) of fibers oriented according to the desired characteristics. A composite structure (27) is thus obtained in the form of a truncated cone of several layers of layers of fibers. The mandrel (23) formed and illustrated in FIG. 15 is for example coated with a covering (27) consisting of a stack of 12 to 15 layers of prepreg fibers.

 As shown in Figures 15 to 17, the mandrel (23) is then placed in a mold (28) whose imprint (29) will determine the final external shape of the handle. The molding operation is carried out by heating the mold and applying internal pressure exerted by the introduction of a gas inside the elastic bladder (22), so as to compact the composite structure (27) on the 'imprint (29) of the mold (28).

The molding cycle varies depending on the nature and the reactivity of the prepreg materials used. For example, for epoxy prepregs, the mold is heated to 1500C, then cooled to room temperature. The heating and cooling times are 7 and 2 minutes respectively. The pressurization takes place between 1200C and 1400C during the heating phase and is kept stabilized until the end of the molding cycle. For this, a compressed air pressure of between 10 and 12 bars is used.

 FIG. 17 shows the arrangement of the various constituents at the periphery of the mandrel after the injection of a compressed fluid, such as compressed air inside the bladder. After opening the mold, the mandrel (23) can be easily removed without special tools, simply because of the space provided by compaction, and cleared between the mandrel (23) and the bladder (22) surrounded by the composite structure ( 27).

 Figures 18 to 21 show in more detail, the area of the handle where the weights are located. Figures 18 and 19 show this area before pressurization and heating, Figures 20 and 21 showing it after pressurization. Before pressurization, it is noted that the composite structure (27) is wound with the weights (M1, M2, M3) around the mandrel (23) comprising the bladder (22). Said composite structure (27) locally includes, at the level of the counterweights, a projection (270). In addition, there is a space (e) between the composite structure and the surface of the external mold cavity. When pressurized, the bladder (22) inflates and then deforms the composite structure (27) in the 'space (e), to press it against the wall (29) of the mold (28), the three weights then taking their respective places and this, thanks to the flexibility of the material of the weights which can deform. The crosslinking of the resin of the first ply (N1) ensures the bonding of the weights on the internal surface (14) of the handle (1, 12).

 Figures 22 to 24 illustrate an alternative embodiment of a club handle according to which, the counterweight (M ") is constituted by a winding, over more than one turn, of a strip of high density material.

Figures 22 and 23 are views similar to Figures 2 and 3, Figure 24 being a view similar to Figure 13. Thus, the weight (M ") is for example initially formed by a strip cut from a lead sheet which is glued in part on the first layer (N1) constituting the inner layer of the handle. The gluing of said strip being such that the strip protrudes out of the first layer (N1) so that this strip, in the following operation, s 'wraps first around the mandrel and this, before said first layer (N1) is wound up. It will be noted that the counterweight (s) are therefore constituted by a sheet of high density deformable material, from a sheet laid shaped and glued to the internal surface of the wall of the handle.

 The term “winding process” means the rolling of plies or the filament winding. Furthermore, it would not be departing from the scope of the invention, if the counterweight (s) were, in a step prior to winding, arranged around the mandrel, that is to say arranged on its external face, and not glued to the first layer, as shown in Figure 13.

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

Claims (20)

 1. A method of manufacturing a handle for a golf club of the type comprising a central duct (15) bounded by the internal surface (14) of a cylindrical wall (12) made of composite material, said central duct comprising at least one counterweight, characterized in that said method consists in winding around a mandrel, a thickness of fibers pre-impregnated with resin, and in a step prior to winding, to be arranged between the external face of the mandrel (23) and said thickness, at least one counterweight (M, M ', M ", M1, M2, M3).  2. A method of manufacturing a golf club handle according to claim 1, characterized in that said method consists in winding around the mandrel (23), at least a first sheet (N1) of fibers preimpregnated with resin, and in a step prior to winding, placing at least one counterweight (M, M ', M ", M1, M2, M3) on said first ply, said one or more counterweights being placed on the face of the ply intended to form the inside of the handle.  3. A method of manufacturing a handle for a golf club according to claim 2, characterized in that in another preliminary step, the weight (s) (M, M1, M2, M3) is prepared in the form of a strip in high density material that is glued to the first layer (N1).  4. A method of manufacturing a golf club handle according to claim 3, characterized in that the strip of high density material comprises a layer of glue or a double-sided adhesive (25).  5. A method of manufacturing a golf club handle according to claim 4, characterized in that the mandrel (23) is before and before winding, covered with a tubular bladder (23), elastic and waterproof, made made of elastomeric material.  6. A method of manufacturing a golf club handle according to claim 5, characterized in that after the winding of the sheet of fibers,  the mandrel thus coated is placed in a mold (28) whose imprint (29) defines the final shape of the handle to be produced,  - A molding operation is then carried out by applying at least an internal pressure exerted by the introduction of a fluid inside the bladder between the latter and the mandrel (23), so as to compact the composite structure against the imprint (29) of the mold (28), said mold being heated to allow the polymerization of the resin and thus, the production of the handle and the bonding of the weights.  7. A handle for a golf club of the type comprising a central duct (15) bounded by the internal surface (14) of a cylindrical wall (12) made of composite material, said central duct comprising at least one counterweight (M, M ' , M ", M1, M2, M3), characterized in that the weight (s) (M, M ', M", M1, M2, M3) consist of a sheet of high density deformable material from a sheet shaped and which is glued to the internal surface (14) of the wall (12) of the handle (1).  8. A handle for a golf club according to claim 7, characterized in that the density of the material of the weight or weights is greater than the density of the composite material constituting the wall (12) of the handle.  9. Golf club handle according to claim 8, characterized in that the density of the material of the weight (s) is two to fifteen times greater than the density of the composite material constituting the wall (12) of the handle.  10. Golf club handle according to claim 9, characterized in that the density of the material of the weight (s) is seven times greater than the density of the composite material constituting the wall (12) of the handle.  11. A golf club handle according to any one of claims 7 to 10, characterized in that the counterweight (M ') constitutes an unclosed tubular wall on its periphery.  12. A handle for a golf club according to claim 7, characterized in that the counterweight (M ") constitutes a tubular winding.  13. A handle for a golf club according to claim 7, characterized in that the flyweight (M) consists of at least two flyweights (M1, M2).  14. A handle for a golf club according to claim 13, characterized in that the handle comprises two identical weights (M1, M2), arranged symmetrically on either side of the axis (xi ') of said handle.  15. A handle for a golf club according to claim 13, characterized in that the handle comprises three weights (M1, M2, M3) identical, uniformly distributed in the central duct (15).  16. Golf club handle according to any one of claims 7 to 15, characterized in that the weight (s) (M, M ', M ", M1, M2, M3) are located in the central part (9) of the handle (1).  17. A handle for a golf club according to claim 16, characterized in that the weight or weights (M, M ', M ", M1, M2, M3) are arranged substantially at the center of gravity (G) of the handle.  18. A handle for a golf club according to any one of claims 7 to 17, characterized in that the weight (s) consist of a lead sheet of thickness between 0.1 and 3 millimeters, of width between 5 and 40 millimeters and length between 10 and 300 millimeters.  19. A golf club handle according to any one of claims 7 to 17, characterized in that the weight (s) are constituted by a stack of layers of composite material comprising a resin loaded with high density metallic particles.  20. Golf club handle according to any one of claims 7 to 19, characterized in that it is manufactured according to the manufacturing method according to any one of claims 1 to 7.