Patent Application
20050020379
The present invention relates to a golf club head, more particularly to a hybrid structure of a metal component and a fiber reinforced plastic component being capable of generating a favorable high-pitched hitting sound.
In case of wood-type golf clubs in particular, metal heads made of one or more kinds of metal materials are nowadays widely used. In this type of club heads, there is a strong tendency towards a very large head volume, adopting a hollow structure. A hollow metal head having a relatively large head volume can generate a high-pitched ball hitting sound which gives a favorable hitting impression to many golfers, and thus this is one of the reasons for the preference of the large-sided metal heads.
In this type of heads, however it is very difficult to lower the center of gravity while maintaining a large head volume because the design freedom of weight distribution is small due to the limited overall weight and large volume.
On the other hand, golf club heads made of fiber reinforced plastic (FRP) have been proposed. In case of such all-FRP club heads, however, although the design freedom may be increased, in comparison with all-metal head, the hitting sound becomes lower in the peak sound pressure frequency, and thus hit feeling is not good for many golfers. Further, the rebound performance and durability are inferior to all-metal head.
It is therefore, an object of the present invention to provide a golf club head whose hitting sound is rendered a high-pitched sound from which good hit feeling can be obtained, without sacrificing the durability, while increasing the design freedom of weight distribution for a large-sized head.
According to the present invention, a golf club head comprises:
FIGS. 15(a) and 15(b) are schematic cross sectional views for explaining a method of manufacturing the FRP component.
Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.
In the following embodiments, club head 1 according to the present invention is a wood-type hollow club head (#1 driver). A hollow structure is preferable to a filled structure with an expanded plastic or the like because a relatively long reverberation time can be obtained.
AS shown in
In case of a wood-type club head, the head volume is set in the range of not less than 300 cc, preferably more than 350 cc, more preferably more than 380 cc, more preferably more than 400 cc, but not more than 600 cc, preferably less than 500 cc. Such a large head volume is preferred from a point of view of performance advantage as well as improvement in the hitting sound because high frequency components of the hitting sound can be enhanced and the decay time thereof is prolonged.
According to the present invention, the club head 1 is made up of at least a face component M1 made of a metal material, an FRP component M2 made of a fiber reinforced resin and an elastomeric insert 8.
Firstly, the example show in
The face component M1 comprises a face plate 9 and a turnback 10 extending backward from the edge (at least an upper edge) of the face plate 9.
The face plate 9 forms at least a major portion (preferably more than 80% in area) of the club face 2 so as to include the sweet spot. The face plate 9 in this example forms the entirety of the club face 2.
The optimum thickness for the face plate 9 may be somewhat varied depending on the metal material used, but in most case, it is preferable that the thickness is set in a range of from 2.0 mm to 3.0 mm. The thickness may be a substantially constant value throughout the face portion 3, but in this example, the face portion 3 has a variable thickness such that a central region 9a including the sweet spot is surrounded by a thinner peripheral zone 9b as shown in
The face plate 9 provided with such thinner peripheral zone 9b can increase the flexural deformation of the face portion 3, and improve the rebound performance, while providing an impact strength and durability.
The above-mentioned turnback 10 includes at least an upper turnback 10a, and in this example further includes a lower turnback 10b, a toe-side turnback 10c and a heel-side turnback 10d. In this example, therefore, the turnback 10 as a whole extends continuously around the face plate 9.
The upper turnback 10a extends backward from the upper edge (2a) of the face plate 9 to form a front end zone of the crown portion 4. The toe-side turnback 10c extends backwards from the toe-side edge (2t) of the face plate 9 and forms a front end zone of the side portion 6 on the toe-side. The heel-side turnback 10d extends backwards from the heel-side edge (2e) of the face plate 9 and forms a front end zone of the side portion 6 on the heel-side. The lower turnback 10b extends backward from the lower edge (2b) of the face plate 9 and forms at least a front end zone of the sole portion 5.
AS to the amount of backward extension of the turnback (hereinafter, the “backward length”), in this embodiment, the backward length Lc of the upper turnback 10a, the backward length Lt of the toe-side turnback 10c and the backward length Lh of the heel-side turnback 10d are substantially same values along the edges 2a, 2t and 2e. But the backward length Ls of the lower turnback 10b is more than the backward length Lc, Lt and Lh. AS the lower turnback 10b extends backward in a significantly larger amount, unlike the upper, toe-side and heel-side turnback, the lower turnback 10b forms not less than 60%, preferably not less than 80% (in this example 100%) in area of the sole portion 5. Furthermore, it is also possible that the lower turnback 10b forms more than 100% of the sole portion 5. This means that the lower turnback 10b forms a lower part of the side portion 6. Therefore, the sole portion 5 of the head can be improved in the resistance to external injury and durability, while lowering the center of gravity G.
In this example, further, in order to deepen the center of gravity, the lower turnback 10b gradually increases in thickness from its front end to rear end as shown in
In
The face component M1 is preferably formed as a casting of a metal material. However, it may be also possible to make the face component M1 by assembling two or more parts formed by casting, forging, pressing, rolling, cutting or the like and joining them by welding and the like.
AS to the metal material for the face component M1, various materials, e.g. titanium alloys, pure titanium, aluminum alloys, stainless steel and the like may be used. But, titanium alloys having a high specific tensile strength are preferably used. Especially, alpha and beta titanium alloys such as Ti-6Al-4V, Ti-4.5Al-3V-2Fe-2Mo and Ti-2Mo-1.6V-0.5Fe-4.5Al-0.3Si-0.03C, and beta titanium alloys such as Ti-15V-3Cr-3Al-3Sn, Ti-15Mo-5Zr-3Al, Ti-15Mo-5Zr-4Al-4V, Ti-15V-6Cr-4Al and Ti-20V-4Al-1Sn are preferred.
In this example, the face component M1 is formed as a casing of Ti-6Al-4V, an alpha and beta titanium alloy suitable for casting, using a lost-wax precision casting method.
The above-mentioned FRP component M2 comprises: a major crown portion 20 which forms the crown portion 4 together with the upper turnback 10a; and a major side portion 21 which extends from its toe-side edge 21a to heel-side edge 21b through the back face and forms the side portion 6 together with the toe-side turnback 10c and heel-side turnback 10d; and in case of example shown in
The FRP component M2 is provided with an overhang 24 and an overhang 25 along the edge of the front part 01 and bottom part 02 of the opening.
The overhang 25 is disposed near the lower end of the major side portion 21 to overlap with the lower turnback 10b on the inside of the head.
The overhang 24 is disposed at the front end of the major crown portion 20 and major side portion 21 to overlap with the turnback 10a, 10c, 10d on the inside of the head.
The overhang 24 in this example is made up of a crown-side overhang 24a, a toe-side overhang 24b and a heel-side overhang 24c, and thus the overhang 24 extends continuously from the toe to the heel. It is however, possible to form discontinuously as one of modifications.
AS show in
In order for obtaining a high-pitched hitting sound at impact, it is important to make the major crown portion 20 to vibrate easily. Therefore, the thickness (tc) of the major crown portion 20 is set in the range of not more than 2.0 mm, preferably less than 1.5 mm, but not less than 0.3 mm, preferably more than 0.5 mm, more preferably more than 1.0 mm.
If the thickness (tc) is less than 0.3 mm, it is difficult to obtain necessary strength and durability for the major crown portion 20. If the thickness (tc) is more than 2.0 mm, the major crown portion 20 becomes difficult to vibrate at impact, and thus it is difficult to obtain high-pitched hitting sound. Further, it is not preferable as the weight increases in the upper part of the club head.
The thickness (ts) of the major side portion 21 is set in the range of not less than 0.3 mm, preferably more than 1.0 mm, but not more than 8.0 mm, preferably less than 5.0 mm.
If the thickness (ts) is less than 0.3 mm, the strength decreases, and the directional stability is liable to deteriorate. If the thickness (ts) is more than 8.0 mm, as the weight increases although the total weight of the club head is limited, it becomes difficult to reallocate a weight to a lower portion such as sole portion in order to lower the center of gravity. Further, the vibration is resisted.
In
In this embodiment, the FRP component M2 is manufactured at once by integral moulding. But, multi-stage methods, for example, firstly making two or more discrete parts and then joining these parts together for example using adhesive agent or the like, can be employed to manufacture the FRP component M2.
As shown in
The thermosetting resin is, for example, epoxide resin, nylon resin or the like. It is preferable that the amount of resin is in the range of 20 to 30% of the overall weight.
AS to the reinforcing fibers, organic fibers such as carbon fibers and aramid fibers, having a modulus of elasticity of not less than 200 GPa, preferably not less than 240 GPa, more preferably not less than 290 GPa, but preferably not more than 500 GPa, are preferably used. Specifically, the following carbon fibers may be preferably used.
The modulus of elasticity of carbon fibers was measured according to Japanese Industrial Standard R7601:1986, “Testing method for carbon fibers”.
Aside from the above-mentioned prepreg molding, other manufacturing methods such as injection molding may be employed. In this case, by mixing short fibers with the injected resinous material, random orientation may be obtained. If the fibers are disposed in the mold in advance, an ordered fiber arrangement may be obtained.
In the example shown in
The above-mentioned additional fourth part M3 is made up of the excluded hosel neck portion 7 and hosel tubular portion 11 (hereinafter the “hosel component M3”). The hosel component M3 is formed by casting in the same way as the face component M1, but it is of course possible to make it by another method such as lathing.
The above-mentioned elastomeric insert 8 is made of an elastomeric material and disposed at least between the upper turnback 10a of the face component M1 and the FRP component M1.
If the hardness of the elastomeric insert 8 is too small, the amplitude of impulsive force applied to the FRP component M2 from the face component M1 increases, and the durability is liable to deteriorate. If the hardness is too large, the vibration of the face plate at impact is controlled and it becomes difficult to obtain the high-pitched hitting sound. Further, the durability is liable to deteriorate.
Preferably, the shore-A hardness of the elastomeric material is set in the range of not more than 80, preferably less than 70, more preferably less than 60, still more preferably less than 50, but not less than 30, preferably more than 35.
For example, polymer alloy of esters polymer(s) and halogen polymer(s), styrene block copolymer, block copolymer of polystyrene and vinyl polyisoprene, chlorinated polyethylene, acrylonitrile-butadiene rubber (NBA), acrylic rubber (ACR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), norbornene-based polymer and the like may be used.
In this example, the elastomeric insert 8 is disposed between the overhang 24 and the upper, toe-side and heel-side turnback 10a, 10c and 10d.
In the example shown in
The main portion 8A is sandwiched between the inner surface 10i of the turnback 10(10a) and the outer surface 24o of the overhang 24. Between the rear end 10 at of the turnback 10 and a step 24t at the rear end of the overhang 24, the perpendicular portion 8B extends to and flushes with the surface of the club head. Between the front end of the overhang 24 and the back side 2B of the face plate, a small space K is left to allow a relative displacement of the face component M1 towards the FRP component M2 at impact.
If the thickness of the main portion 8A is too small, the amplitude of impulsive force received by the FRP component M2 from the face component M1 increases, and the durability is liable to deteriorate. Further, the vibration of the face plate due to impact is liable to be damped. If the thickness is too large, the durability of the junction is again liable to deteriorate, and also in view of the weight increase it is not preferable. Therefore, the thickness (tm) of the main portion 8A is set in the range of not less than 0.8 mm, preferably more than 1.0 mm, more preferably more than 1.2 mm, but not more than 5.0 mm, preferably less than 3.0 mm, more preferably less than 2.0 mm. Also, the thickness of the perpendicular portion 8B is set in the same range as above.
In the example shown in
If the backward length Lc of the upper turnback 10a is too small or too large, then the vibration is controlled and it becomes difficult to generate a high-pitched hitting sound.
Thus, the length Lc is set in the range of not less than 4.0 mm, preferably more than 6.0 mm, more preferably more than 8.0 mm, but not more than 30 mm, preferably less than 25.0 mm, more preferably less than 12.0 mm.
In this example, between the lower turnback 10b and the overhang 25 around the bottom opening part 02, the elastomeric insert 8 is not disposed, and they are directly joined with an adhesive. But, it is also possible to dispose the elastomeric insert 8 therebetween.
In assembling the head, the lower turnback 10b is placed to close the bottom opening 02, and the lower turnback 10b and the overhang 25 are joined with an adhesive agent.
In case of
The face plate 9 is placed so as to close the front opening 01, with the elastomeric insert 8 disposed between the turnback 10 and overhang 24. Using an adhesive agent between the elastomeric insert 8 and the turnback and between the elastomeric insert 8 and the overhang, they are joined.
AS to the adhesive agents, for example, epoxy adhesive, polyurethane adhesive, rubber-based adhesive and the like may be used. In this example, epoxy adhesive used.
In order to increase the adhesive strength, it is preferable that surface roughening is made on the bonding face of the turnback 10 especially upper turnback 10a by shot blast, shot peening or the like. Preferably, the roughness of the roughened surface R is in the range of not less than 10 micrometers, preferably more than 15 micrometers, but not more than 40 micrometers, preferably less than 35 micrometers. In general, the roughness of the casting surface of a lost-wax precision casting is less than 10 micrometers. Here, the roughness means the “ten point height of roughness profile” measured according to the Japanese Industrial Standard B0601 (ISO 4287).
The elastomeric insert 8 allows the face plate 9 to lean back at impact as shown in
Especially preferably, by decreasing the thickness of the major crown portion 20 in a range of 0.4 to 0.8 mm, using high modulus fibers having a modulus of elasticity of not less than 230 GPa preferably in a range of from 300 to 500 GPa, not only the crown portion 4 but also the face portion become liable to vibrate at impact and heightening of the hitting sound can be promoted.
In anyway, it is preferable that the maximum sound pressure level occurs within a frequency band of not less than 4000 Hz, preferably more than 4500 Hz, but not more than 7000 Hz, preferably less than 6000 Hz. The frequency can be changed by adjusting the shore-A hardness, thickness and width of the insert 8. Further, through the use of increased design freedom, it is proffered to design the head as follows.
In order to increase the sweet area, the depth of the center of gravity is preferably set in the range of not less than 40 mm, preferably more than 42 mm, more preferably more than 45 mm, but not more than 55 mm, preferably less than 50 mm.
Further, in order to have greater vertical gear effect, the sweet spot height is set in the range of not more than 30 mm, preferably less than 25 mm, more preferably less than 20 mm, but not less than 15 mm.
In case of all-metal club head having a head volume of more than 300 cc, it is very difficult to achieve the above-mentioned deep gravity point and low sweet spot while maintaining the satisfactory durability. However, according to the present invention, it can be easily achieved.
Furthermore, it is preferable that the restitution coefficient (e) is set in the range of not less than 0.800, preferably more than 0.820, but not more than 0.860, preferably less than 0.850. Here, the restitution coefficient (e) is measured according to the “Procedure for Measuring the velocity Ratio of a club Head for conformance to Rule 4-1e, Appendix II, Revision 2 (Feb. 8, 1999), united states Golf Association”.
In this case, the elastomeric insert 8 comprises the above-mentioned main portion 8A and a perpendicular portion 8B and further a fixing portion 8c protruding towards the other side of the main portion 8A from the portion 8B to have a T-shaped cross sectional shape. To adapt thereto, the overhang 24 of the FRP component M2 is modified such that the above-mentioned step 24's surface 24t at the rear end of the overhang 24 is provided with a groove 36 into which the fixing portion 8c is inserted.
In order to lower and deepen the center of gravity, as shown in
In
Comparison Tests
Wood-type golf club heads having the same outer shapes shown in
The face components were manufactured using titanium alloys (Ti-15V-6Cr-4Al), (Ti-4.5Al-3V-2Mo-2Fe) and (Ti-6Al-4V). The FRP component was manufactured, using prepreg pieces, a bladder and a mold as explained above. Carbon fibers used were “TR50S”, “MR40” and “HR40” shown in Table 1.
Firstly, the elastomeric insert was bonded to the FRP component, using epoxy adhesive “Araldite (AW106/HV953U)” Ciba-Geigy Japan Ltd. The thickness of the applied epoxy adhesive was about 0.5 to 1.0 mm. Then, the face component and the FRP component with the elastomeric insert were bonded using the adhesive.
Also the depth L of the center of gravity G and the height H of the sweet spot SS were measured. Here, the depth L is the horizontal distance of the center of gravity G of the club head from the leading edge E of the head measured in the back and force direction under the measuring state. The measuring state is as shown in
Ball Traveling Distance Test
The club heads were attached to identical carbon shafts to make 46-inch wood clubs. Each club was mounted on a swing robot, and three-piece balls (MAXFLI HI-BRID, Sumitomo Rubber Ind., Ltd.) were struck at a head speed of 45 m/s five times at the sweet spot to obtain the mean traveling distance (carry plus run). The results are shown in Table 2.
Hitting Sound Test (Feeling Test)
With those wood clubs, fifty average golfers having handicaps ranging from 15 to 25 struck the golf balls, and by the golfers' feeling the hitting sound was evaluated into five ranks from a point of view of whether the hitting sound was a favorable high-pitched sound. The higher the rank number, the more the favorable high-pitched sound.
Hitting Sound Test (Frequency Analysis)
Again using the swing robot instead of the golfers, the golf balls were hit at the sweet spot of each of the clubs five times at a head speed of 40 m/s, and the hitting sound was measured with a microphone fixed at a height of 160 cm and a distance of 80 cm sideways from the ball position.
The frequency spectrum of the measured hitting sound was analyzed at ⅓ octave band resolution to find out ten ⅓-octave-bands showing the largest ten sound pressure levels, and the mean value of the center frequencies of those ⅓-octave-bands was calculated. Such mean values are shown in Table 2, wherein the larger the value, the higher the frequency.
Durability Test
Using the swing robot, the club head struck the golf balls at the sweet spot 3000 times at a head speed of 51 meter/second, and thereafter the club face was checked for deformation and/or damage. The results shown are Table 2, wherein: “A” indicates that there was no damage; “B” indicates that damage occured between 3000 times and 2000 times; and “C” indicates that damage occured at less than 2000 times.
*1: Face plate: Ti—15V—6Cr—4Al (“DAT55G”, Daido Steel Co., Ltd.)
Else: Ti—6Al—4V
*2: Face plate: Ti—4.5Al—3V—2Mo—2Fe (“SP700”, Daido Steel Co., Ltd.)
Else: Ti—6Al—4V
*3: Face plate and neck portion: Ti—6Al—4V
Else: CFRP
From the test results, it was confirmed that a high-pitched hitting sound can be obtained together with increased traveling distance at the same time while maintaining the necessary durability. Furthermore, it was also confirmed that, when compared with the bonding surface not roughened in all the turnback, even by roughening the upper turnback only, the durability of the junction between the face component and FRP component against the impact force can be increased about 20% in case of the above-mentioned club head Ex. 1.
The present invention is suitably applied to wood-type hollow club heads for driver, fairway wood and the like, but in addition thereto, it may be applied to other-types of club heads such as utility-type, iron-type, patter-type club heads as far as the head has a hollow immediately behind the face portion comprising the metal face component M1 and FRP component M2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-155093 | May 2003 | JP | national |
