WO1991014480A1

WO1991014480A1 - Method for manufacturing a golf-club shaft of a fibre material and golf-club shaft made of a fibre material

Info

Publication number: WO1991014480A1
Application number: PCT/FI1991/000087
Authority: WO
Inventors: Heikki Ratia; Matti Suominen
Original assignee: Exel Oy
Priority date: 1990-03-28
Filing date: 1991-03-28
Publication date: 1991-10-03
Also published as: FI901538A0; FI901538A

Abstract

The invention relates to a method for manufacturing a golf-club shaft of a fibre material. The method includes operations (I, VI) for supplying lengthwise and (II-V) crosswise fibre layers on top of a core, said layers consisting of continuous fibres, as well the application of heat or radiation for curing a shaft formed by fibre layers moistened with a resin or a like binder. According to the method, in at least two superimposed crosswise layers the fibres are wound at an angular position relative to the longitudinal shaft axis, said angle being within the range of circa (+)30° - circa (+)60° or circa (-)30° - circa (-)60°, the (+) angle referring to an angle which opens anticlockwise from said longitudinal axis and the (-) angle referring to an angle which opens clockwise from said longitudinal axis. The invention relates also to a golf-club shaft made of a fibre material, comprising a plurality of various fibre layers consisting of continuous fibres. The shaft element is provided with at least two superimposed crosswise fibre layers whose fibres are wound at an angular position relative to the longitudinal shaft axis, the size of said winding angle being within the range of circa (+)30° - circa (+)60° or circa (-)30° - circa (-)60°.

Description

Method for manufacturing a golf-club shaft of a fibre material and golf-club shaft made of a fibre material.

The present invention relates to a method as set forth in the preamble of claim 1 for manufacturing a golf- club shaft of a fibre material as well as to a golf- club shaft made of a fibre material, as set forth in the preamble of claim 6.

At present, the golf-club shafts made of a fibre mate¬ rial are usually manufactured by manual lamination from a pre-preg material, i.e. resin-moistened fibre mats. A problem with these is to achieve a desired adjustment of the properties repeatedly required of a club, in¬ cluding e.g. the twist, torsion, vibration and ri¬ gidity and especially the position of the centre of gravity of a club shaft. In a manually laminated shaft, the position of the centre of gravity will be indefinite and, thus, the ultimate centre of gravity must be lo¬ cated by changing the weight of a head portion attach¬ ed to the shaft of a club. Such a procedure is rela¬ tively slow. An object of the present invention is to provide a method for manufacturing a golf-club shaft formed of continuous fibres, said method facilitating the adjustment of shaft properties and the determina¬ tion of the centre of gravity of a shaft for any given club head portion whereby, after finishing a shaft, said head portion can be attached as such to the shaft portion. At the same time, it is also possible to ob¬ tain a product having a reduced total weight. In order to achieve this object, a method of the invention is characterized by what is set forth in the character¬ izing clause of claim 1. On the other hand, a golf- club shaft of the invention is characterized by what is set forth in the characterizing clause of claim 7. The most important advantage gained by a method of the invention is that the shaft properties can be adjusted simply by varying the angle of winding the fibres at various locations of a shaft. This angle of fibres is varied or changed in a manner that the winding angle of a pair formed by any given two superimposed trans¬ verse fibre layers is mutually equal but reversed at each lengthwise location of a shaft. The shaft may consist of a plurality of such pairs formed by two transverse layers, whereby the winding angle of one pair at least over a portion of the shaft length can be different from that of the other pair at the cor¬ responding location of the shaft for adjusting the desired properties of a shaft. For example, the ad¬ justment of the centre of gravity is preferably effect¬ ed by means of inner pairs of transverse fibre layers and the adjustment of torsional rigidity, in turn, by means of fibre layers located close to the surface.

In terms of increasing longitudinal rigidity and pro¬ duct strength, the inner and outer layers preferably comprise longitudinal fibre layers whose fibres are substantially parallel to the longitudinal shaft axis, i.e. the winding angle is appr. 0°. By means of these lengthwise layers, the longitudinal rigidity and pro¬ duct strength can be increased with a minimum amount of fibre.

In addition to the winding angle of fibres, the shaft properties can also be affected by the selection of fibres used for each fibre layer, said fibres being continuous. For example, the fibre material may com¬ prise various types of carbon fibres (HS, IM, HM) , glass fibres, polyester, polyethylene, aramide, nylon and the like fibres suitable for reinforcement, e.g. metal-based fibres. The fibres have a filament thick¬ ness typically within the range of 5-30 um and the fibre weight is usually 0,1-2,4 g/m. As a useful bind¬ er it is possible to employ e.g. heat-setting resins, epoxies, vinyl esters, methacrylates, polyesters, phenols, polyides etc. The shaft fibre layers can be built e.g. in a manner that appr. 40 % of the total amount of fibres in a shaft include substantially straightforward fibres extending longitudinally of the shaft and the rest, appr. 60 %, include fibres wound transversely at varying angles. As for these longitudinal fibres, for instance 1/3 can be laid in¬ side the shaft and appr. 2/3 on top of the shaft, the transverse fibre layers being laid between said longi¬ tudinal fibre layers. For example, said innermost layer of longitudinal fibres may comprise carbon fibres having a modulus of 230 GPa and an elongation at rup¬ ture of 1,6 % and the outer layer of longitudinal fibres may accordingly comprise a composite including 10 % of carbon fibres having a modulus of 380 GPa and an elongation at rupture of 1,3 % and 90 % of carbon fibres having a modulus of 230 GPa and an elongation at rupture of 1,6 %. Accordingly, in the transverse¬ ly wound fibre layers, including e.g. four layers, a pair formed e.g. by the two innermost layers may com¬ prise e.g. carbon fibres having a modulus of 230 GPa and an elongation at rupture of 1,6 % and the outer pair may accordingly comprise a- composite having 40 % of carbon fibres with a modulus of 295 GPa and an elongation at rupture of 1,4 % and 60 % of carbon fibres with a modulus of 380 GPa and an elongation at rupture of 1,3 %. In addition, the mutual relationship of these pairs can be varied e.g. in a manner that the two innermost layers have a share of 10 % while the pair consisting of the top two layers has a share of 90 % or, for example, in a manner that these propor¬ tions are reversed, i.e. 90 %/10 %. Such use of vari¬ ous fibres and fibre compositions in various layers facilitates an almost limitless adjustment of various properties.

The invention will now be described with reference made to the accompanying drawing, in which

fig. 1 shows schematically the various operations in¬ cluded in a method of the invention,

fig. 2 shows the principle of one transverse or cross- winding unit applicable in a method of the in¬ vention,

fig. 3 illustrates a shaft element manufactured by means of a method of the invention,

fig. 4 shows a cross-section of the shaft element of fig. 3 in a larger scale, and

fig. 5 shows a definition for the direction of a wind¬ ing angle.

In reference to fig. 1, a method of the invention in¬ cludes the following operations:

I: supplying successive, joint cores 1 to a production line and supplying longitudinal fibres from a reel 5 through a resin vessel 6 into a longitudinal-fibre feeding unit 2 for feeding the longitudinal fibres on top of core 1.

II-V: winding transverse or crosswise fibre layers by means of cross-winding units 3 on top of the longitudi¬ nal fibres at a desired angular position in various locations of a shaft,

VI: feeding a top layer consisting of longitudinal fi¬ bres on top of crosswise layers, and

VII: curing a formed shaft element by the application of heat and radiation energy. Finally, the finished shaft elements are cut off of each other by means of cut-off points formed at core junctions. The method sequence shown in fig. 1 discloses two longitudinal- fibre feeding units 2 and four cross-winding units 3 , but of course the number thereof can be varied as de¬ sired. For example, the number of cross-winding units 3 can suitably be four to eight, but preferably al¬ ways an even number. Furthermore, there may be pro¬ vided a special cross-winding unit e.g. for making a decorative coating layer. Fig. 2 illustrates an exam¬ ple of one embodiment of cross-winding unit 3. Thus, the cross-winding unit comprises a circular disc 7 which is provided with eight fibre rollers 9 for feed¬ ing bundles of fibres 10 on top of core 1. In the centre of disc 7 is provided an opening 8 for said core 1. It is naturally possible to employ any other desired number of rollers, e.g. 4-16 rollers. During the operation of winding unit 3, said bundles of fi¬ bres 10 can be simultaneously supplied out of a desired number of rollers, e.g. 4-16 rollers. Each bundle of fibres 10 includes a large number of filamants, even tens of thousands of filaments.

Fig. 3 illustrates a shaft element 11 manufactured by the application of a method of the invention, wherein the top lengthwise fibre layer is not shown for the sake of clarity. In addition, the individual bundles of fibres are shown at an exaggerated distance from each other, as in practice it is nevertheless possible to form a substantially continuous fibre layer thereof. Fig. 4 illustrates a cross-section of shaft 11 of fig. 3, whereby a top lengthwise fibre layer 12 is added thereto. In this example, there are four crosswise fibre layers 13-16 and two lengthwise fibre layers 12, 17. As shown in fig. 4, the club shaft is designed to be hollow.

The crosswise fibres have a winding angle

, prefer¬ ably within the range of circa (+)30 - circa (+)60 or within the range of circa (-)30 - circa (-) 60 . According to fig. 5, the (+)-angle refers to an angle which opens anticlockwise relative to a shaft element longitudinal axis 18 and the (-)-angle accordingly re¬ fers to an angle which opens clockwise relative to said shaft element longitudinal axis (18). For exam¬ ple, in a shaft 11 as shown in fig. 3, the top shaft end (thicker end) is provided with crosswise fibres having a winding angle of circa 30 , the bottom shaft end (thinner end) being provided with crosswise fibres having a winding angle of circa 45 . This variation of winding angleC - at a desired location of each cross¬ wise layer is effected for example in a manner that the advancing speed of cores 1 is maintained constant but the rotating speed of disc 7 of winding unit 3 is changed in order to obtain a desired angular position. Thus, the variation of angle proceeds in a stepless fashion. For example, reversal of the direction of a winding angle is effected in a manner that, in sequen¬ tially mounted winding units 3, the rotating direction of a downstream unit is reversed relative to that of the preceding winding unit while still maintaining the same rotating speed at the corresponding locations of a shaft, whereby said winding angle -Λ. will be equal at each location of a shaft. Thus, it is important to maintain an equal but oppositely directed winding angle in a pair formed by two superimposed crosswise layers so as to eliminate the stresses possibly generated in a shaft by fibres wound at an angular position. The winding angle can naturally be varied between various pairs of crosswise layers 12, 13; 14, 15 in shaft 11, as required by desired properties.

In a method of the invention, the centre of gravity can be adjusted quite accurately at a desired loca¬ tion which lies e.g. between appr. 40-60 % of the shaft length as measured from the bottom end of a shaft, preferably appr. 51 % of the shaft length. By effecting the crosswise winding e.g. as shown in fig. 3 in a manner that the winding angle at the bot¬ tom end of a shaft is larger than that at the top end of a shaft, it is possible to increase weight at the bottom end of a shaft and, thus, to displace the centre of gravity downwards. In addition, such transfer of weight to the bottom end of a shaft provides for a re¬ duction in the total weight of a shaft.

The above working examples are only intended to describe a few preferred embodiments of the invention and by no means to limit the scope of protection defined by the annexed claims. For example, lengthwise layers can also be laid between crosswise layers instead of only in the inner and outer surface layer.

Claims

1. A method for manufacturing a conical golf-club shaft (11) of a fibre material, said method including operations (1 , VI) and (II-V) for feeding lengthwise, and respectively crosswise fibre layers (12-17) of continuous fibres on top of a core (1), and curing a shaft formed by fibre layers moistened by a resin or a like binder, said curing being effected by the ap¬ plication of heat or radiation, c h a r a c t e r ¬ i z e d in that at least two layers of lengthwise fi¬ bre layers are formed, one serving as an outermost layer (12) of shaft (1) and another as an innermost layer (17), the latter being laid against core (1), said lengthwise fibre layers (12, 17) being substan¬ tially parallel to the longitudinal axis of core (1); that in at least two mutually touching superimposed crosswise layers (13, 14; 15, 16), which are laid be¬ tween said outermost (12) and innermost (17) length¬ wise layers, the fibres are wound at an angular posi¬ tion ((X) relative to the longitudinal axis of shaft

(11), said angle ( ) being within the range of circa (+)30° - circa (+)60° or circa (-)30° - circa (-)60°, the (+) angle referring to an angle which opens anti¬ clockwise from said longitudinal axis and the (-) angle accordingly to an angle which opens clock¬ wise from said longitudinal axis whereby, in each layer formed by a pair (13, 14; 15, 16) consisting of said two mutually touching, superimposed crosswise layers, the winding angle (Λ-) is substantially equal but reversed at the corresponding locations of shaft (11).

2. A method as set forth in claim 1, c h a r a c ¬ t e r i z e d in that in said crosswise layers (13-16) the winding angle (θ ) is varied along the length of shaft (11) .

3. A method as set forth in claim 2, c h a r a c ¬ t e r i z e d in that said variation of the size of winding angle ( is effected by adjusting the re¬ lative velocities between the advancing speed of core (1) and a winding unit (3), the latter being used for crosswise winding and rotating around shaft (11) in a plane substantially perpendicular to the longitudi¬ nal direction of the shaft.

4. A method as set forth in claim 3, c h a r a c ¬ t e r i z e d in that the direction of winding angle

( CΛ- ) in a second crosswise layer is reversed relative to winding angle ( > ) in a crosswise layer therebelow by reversing the rotating direction of a following winding unit (3) relative to a preceding winding unit

(3).

5. A method as set forth in any of claims 1 - 4, c h a r a c t e r i z e d in that each cross-winding unit (3) is provided with a plurality of winding nozzles, preferably (4-16 units), each used for supplying a large number of filaments, whereby said shaft element (11) can be covered with substantially continuous crosswise fibre layers (13-16) .

6. A method as set forth in any of claims 1 - 5, c h a r a c t e r i z e d in that, in addition to an outermost (18) and innermost (17) lengthwise layer, said shaft (11) is provided with at least one length¬ wise layer laid between pairs of crosswise layers

(13, 14; 15, 16).

7. A golf-club shaft made of a fibre material, com¬ prising a plurality of fibre layers (12-17) formed of continuous fibres, c h a r a c t e r i z e d in that a shaft element (11) is provided with at least two superimposed fibre layers (13-16) , which extend cross¬ wise relative to the longitudinal axis of shaft (11) and whose fibres are wound at an angular position (CX. ) relative to the longitudinal axis of shaft (11) , the size of said winding angle ( ( ) being within the range of circa (+)30° - circa (+)60° or circa (-)30° - circa (-)60°, whereby the (+) angle refers to an angle which opens anticlockwise from said longitudinal axis and, accordingly, the (-) angle refers to an angle which opens clockwise from said longitudinal axis whereby, at each location of shaft (11) , said cross¬ wise layer winding angle ( & ) is equal to but inverted from the winding angle ( (? ) of a superimposed layer forming a pair therewith; and at least two lengthwise fibre layers, one being an outermost layer (12) and the other an innermost layer (17), said lengthwise layers being substantially parallel to the longitudi¬ nal axis of shaft (11).

8. A shaft as set forth in claim 7, c h a r a c t e r ¬ i z e d in that in each of said two superimposed cross¬ wise fibre layers said angular position ( 0^-) of fibres varies along the length of shaft (11).

9. A shaft as set forth in claim 8, c h a r a c t e r ¬ i z e d in that said shaft (11) is provided with a plurality of pairs (13, 14; 15, 16) formed by two super¬ imposed fibre layers whereby, at least over a portion of the length of shaft (11), the winding angle (o ) in one pair (13₇ 14) is different from winding angle (o . ) in another pair (15, 16) at a corresponding location along shaft (11).

10. A shaft as set forth in any of claims 7 - 9, c h a r a c t e r i z e d in that, in addition to an outermost (12) and innermost (17) lengthwise layer, said shaft (11) is provided with at least one length¬ wise layer laid between pairs of crosswise layers (13, 14; 15, 16).