Patent Grant
7297074
This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 2003-204764 and 2004-131712 filed in Japan on Jul. 31, 2003 and Apr. 27, 2004 respectively, the entire contents of which are hereby incorporated by reference.
The present invention relates to a golf club head, more particularly to a joint structure of a metal part made of a metal material and a FRP part made of a fiber reinforced resin.
In recent years, golf club heads made of a metal material and fiber reinforced resin have been proposed.
The laid-open Japanese utility model application JP-U5-51374 discloses a club head made of a metal material or a fiber reinforced resin, wherein the crown portion is cut out to form a window which can be either left opened or closed by a cover made of a lower specific gravity material.
The laid-open Japanese patent application JP-P2003-62130A discloses a club head formed by integrating a face component made of a metal material and having a turnback along the edge thereof, and an aft-body made of a plurality of plies of prepreg. As shown in
In a golf club head having such a spliced structure, the spliced portion is subjected to a large sharing force as the face portion receives a large impact force, and the bonded surface is very liable to come unstuck. This is especially true in case of a large-sized hollow golf club head such as wood-type golf club heads because the wall thickness is thin and thus deformation at impact is relatively large.
It is therefore, an object of the present invention to provide a golf club head, in which the joint portion is increased in the strength, and thereby the durability of the club head is improved.
According to one aspect of the present invention, a hollow golf club head is composed of a metal part made of at least one kind of metal material and a FRP part made of a fiber reinforced resin, the metal part having a first lap joint part, and the FRP part having a second lap joint part being lap-jointed with the first lap joint part, wherein one of the first lap joint part and second lap joint part is provided with at least one securing hole, and the other is provided with at least one protrusion engaging with the at least one securing hole.
Therefore, the strength of the lap joint is greatly increased by the mechanical engaging force between the securing hole and protrusion in addition to the bonding force which will be generated between the surface of the metal part and the surface of the FRP part by means of an adhesive agent, welding (melting) of the matrix resin or the like. Thus, the durability of the club head can be improved, and a further decrease in the material thickness becomes possible which will lead to not only a weight reduction but also a possibility of a large elastic deformation at impact to improve the rebound performance.
a) and 13(b) are cross sectional views for explaining a method of manufacturing a FRP part.
Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.
In the drawings, club head 1 according to the present invention is a wood-type club head such as #1 driver and fairway wood. The club head 1 comprises: a face portion 3 whose front face defines a club face 2 for striking a ball; a crown portion 4 intersecting the club face 2 at the upper edge 2a thereof; a sole portion 5 intersecting the club face 2 at the lower edge 2b thereof; a side portion 6 between the crown portion 4 and sole portion 5 which extends from a toe-side edge 2t to a heel-side edge 2e of the club face 2 through the back face of the club head; and a neck portion 7 to be attached to an end of a club shaft (not shown).
The volume of the club head 1 is set in a range of not less than 300 cc, preferably not less than 350 cc, more preferably 350 to 600 cc, still more preferably 370 to 550 cc. The head 1 has a cavity (i) immediately behind the face portion 3, and in the following embodiments, the cavity (i) is left void although it is also possible to fill it with a light-weight material such as foamed plastic, foamed rubber or the like. The combination of such a large head volume and hollow structure can improve the ball hitting sound because it can enhance high-frequency components of the ball hitting sound, and prolong the reverberation time of such enhanced sound.
For example, when the head volume of more than 300 cc, the depth GL of the center of gravity is preferably set in the range of not less than 35 mm, preferably not less than 37 mm, more preferably not less than 38 mm, but not more than 43 mm. The height GH of the center of gravity G is preferably set in the range of not less than 25 mm, but not more than 35 mm, preferably not more than 32 mm, more preferably not more than 30 mm. In case of a club head all made of metal material(s), it is very difficult to make a club head having such specifications, while achieving practical durability. However, according to the present invention, it is easy to make such a golf club head. By setting the depth GL of the center of gravity more than 35 mm, the sweet spot area of the head is remarkably increased, and the directionality may be improved. Further, as the height GH of the center of gravity is low, it becomes easer to decrease the backspin and to increase the launching angle of the ball and thereby to obtain an ideal ballistic course.
Here, as shown in
The club head 1 is composed of a metal part M1 and a FRP part M2 attached to the metal part M1.
The metal part M1 comprises a face wall 9, a sole wall 10 and a side wall 11 forming at least part of the face portion 3, sole portion 5 and side portion 6, respectively, and the neck portion 7, whereby its top is opened and the metal part M1 has an opening O1.
The metal part M1 is made of at least one kind of metal material having a large specific tensile strength. For example, titanium alloys such as alpha+beta titanium alloys and beta titanium alloys are preferred. Specifically, Ti-6Al-4V, Ti-4.5Al-3V-2Fe-2Mo, Ti-2Mo-1.6V-0.5Fe-4.5Al-0.3Si-0.03C, Ti-15V-3Cr-3Al-3Sn, Ti-15Mo-5Zr-3Al, Ti-15Mo-5Zr-4Al-4V, Ti-15V-6Cr-4Al, Ti-20V-4Al-1Sn and the like can be preferably used. However, aside from titanium alloys, various metal materials, e.g. aluminum alloy, pure titanium, stainless steel and the like can be used. The metal part M1 shown in
The face wall 9 is to form at least 60% of the club face 2 in area, also forming the entire thickness from the club face 2 to the back face 2B. In this example, in view of the durability and high-pitched hitting sound, the face wall 9 forms substantially 100% of the club face 2.
The thickness of the face wall 9 or face portion 3 can be a substantially constant value. But, in this embodiment, to achieve a balance between durability and rebound performance, the thickness is increased in a central region 9a in comparison with the surrounding peripheral zone 9b.
The thickness Tc in the central region 9a is set in a range of not less than 2.5 mm, preferably more than 2.7 mm, but not more than 3.0 mm, preferably less than 2.9 mm.
The thickness Tp in the peripheral zone 9b is set in a range of not less than 2.0 mm, preferably more than 2.3 mm, but not more than 2.5 mm.
It is preferable that the peripheral zone 9b has such a width that the area of the peripheral zone 9b is in a range of about 20% to about 50% of the area of the central region 9a.
The sole wall 10 extends backwards from the lower edge of the face wall 9 to form at least a major front part of the sole portion 5. In view of the durability of the head, the area thereof is preferably set in a range of at least 60%, more preferably at least 80% (in this embodiment 100%) of the sole portion 5, and the thickness Ts of the sole wall 10 or sole portion 5 is preferably set in a range of not less than 0.9 mm and not more than 3.0 mm, more preferably more than 1.2 mm but less than 2.0 mm.
The side wall 11 extends upwards from the edge of the sole wall 10 along the entire length of the edge continuously from the toe-side edge to the heel-side edge of the face wall 9 through the back face. The thickness Tb thereof is preferably set in the range of not less than 0.8 mm, more preferably more than 1.0 mm, but not more than 6.0 mm, more preferably less than 5.0 mm to achieve a balance between strength or durability and a large moment of inertia around the center of gravity.
The metal part M1 is provided around the above-mentioned opening O1 with a first lap joint part F1 which overlaps with a second lap joint part F2 of the FRP part.
If there is a ridge line E or edged boundary between the crown portion 4 and side portion 6, the side wall 11 is made somewhat lower in vertical height than the ridge line E.
In the metal part M1 shown in
In the metal part M1 shown in
The crown joint part 20 is formed as a part of the crown portion 4 around the opening O1.
In
The crown joint part 20 and side joint part 21 are sunken from the adjacent outer surface through a step corresponding to the thickness of the FRP part M2 so that the outer surface of the FRP part M2 becomes flush with the outer surface of the metal part M1 at the boundary therebetween.
If the crown joint part 20 is too narrow in width, the bonding strength to the FRP part M2 becomes insufficient. If too wide, the weight unnecessarily increases. Therefore, the width L1 is set in the range of not less than 5.0 mm, preferably not less than 8.0 mm, more preferably not less than 12.0 mm, but not more than 25.0 mm, preferably not more than 20.0 mm. Here, the width L1 is a minimum distance across the objective part.
In the example shown in
In order to engage with the undermentioned protrusions 8b of the FRP part M2, the first lap joint part F1 of the metal part M1 is provided with a plurality of securing holes 8a. The securing hole 8b is preferably a through-hole, and usually a circular hole as shown in
However, all or some of the securing holes 8b may be a blind hole having a closed inner end as shown in
In view of securing or engaging force, the depth of such a blind hole is set to be not less than 0.5 mm, preferably more than 0.8 mm. The upper limit therefor depends on the thickness of the first lap joint part F1. Therefore, to prevent thickening of the lap joint, the depth is limited to under about 2.0 mm, preferably under 1.5 mm.
In cases of blind hole, it may be formed in a shape of a groove extending continuously or discontinuously along the edge of the opening O1.
When the metal part M1 is formed using a mold like a casting, the holes 8a may be formed during the molding or casting process. It is also possible to form the holes 8a by machining, after molding, utilizing a numerical controlled machine tool for example. In anyway, by making the securing holes in the first lap joint part of the metal part, the corresponding weight reduction is possible.
As described above, as the face portion is made of a metal material, the ball hitting sound becomes a high-pitched sound, and by the large head volume and hollow structure, the reverberation time thereof is prolonged. Thus the club head can give an impression of good shot to the player.
The above-mentioned FRP part M2 is to cover the above-mentioned opening O1 of the metal part M1. Thus, the FRP part M2 has a crown wall 12 which forms the almost entirety of the surface of the crown portion 4.
In the example shown in
In the example shown in
The FRP part M2 is made of a fiber reinforced resin including fibers.
Preferably, fibers having a tensile modulus of elasticity of not less than 200 GPa, more preferably not less than 240 GPa, still more preferably not less than 290 GPa are used. Especially, fibers having a modulus of from 290 to 500 GPa are preferred. To give actual examples, the following carbon fibers may be suitably used.
Here, the tensile modulus of elasticity is measured according to Japanese Industrial standard R 7601-1986 “Testing methods for carbon fibers”.
The fibers in the FRP part M2 may be oriented toward one direction or dispersed in the resin in random orientation. But, in this example, the fibers are oriented toward orthogonal directions. As to the resin, various resins can be used. In this example, a thermosetting resin such as epoxy resin is used.
The thickness Tf of the crown wall 12 is set in the range of not less than 0.2 mm, preferably not less than 0.5 mm, more preferably not less than 0.8 mm, but not more than 3.0 mm, preferably not more than 2.5 mm, more preferably not more than 2.0 mm.
The thickness Te of the flange 13 is set in the range of not less than 0.2 mm, preferably not less than 0.5 mm more preferably not less than 0.7 mm, but not more than 2.0 mm, preferably not more than 1.5 mm, more preferably not more than 1.2 mm.
The FRP part M2 is provided with a second lap joint part F2 which makes a lap joint, together with the first lap joint part F1.
In the example shown in
In the example shown in
The second lap joint part F2 is provided with protrusions 8b. In order that the protrusions 8b can fit to the above-mentioned securing holes 8a provided on the first lap joint part F1, the positions and shapes thereof are so determined.
In order to make the FRP part M2, a molding method using prepregs can be employed, for example as shown in
The prepreg P is as well known in the art a combination of continuous reinforcing fibers that are preimpregnated with a thermoset or thermoplastic organic resin matrix. In this example, epoxy resin is used as a matrix resin. The fibers in a prepreg P may be oriented toward one direction or orthogonal directions. The prepreg is cut into a specific shape. By laying predetermined number of prepreg sheets one on top of another to have a required thickness, the prepregs are shaped into a specific shape, and the matrix resin is hardened. In case of unidirectional orientation, prepregs P are arranged such that the fibers in a prepreg cross those in the adjacent prepreg. Preferably, the resin content is set in a range of about 20 to 25%.
Here, the resin content is a percentage of the weight of the resin component to the overall weight of the object. The resin content can be obtained as follows. To separate the fibers, the resin matrix is removed from the measuring object by chemically dissolving the resin matrix only. If the measuring object is uncured prepreg, as the chemical, for example methyl ethyl ketone may be used. If the measuring object is a cured FRP material, for example hot nitric acid may be used. Then by subtracting the weight of the fibers from the total weight of the measuring object, the weight of the resin matrix can be obtained.
In addition to the methods using prepregs, an injection molding method using a fluid compound material of short fibers, a resin matrix and additives can be employed to eliminate the need to form the protrusion 8b in separate operation.
After the FRP part M2 and the metal part M1 are made as discrete parts, they are assembled by lap jointing the first and second lap joint parts F1 and F2 with applying an adhesive agent to therebetween and inserting the protrusions 8b into the securing holes 8a.
If the holes 8a and protrusion 8b are too small, it is difficult to improve the shearing strength of the lap joint. If too large, the bonding area of the lap joint becomes decreased and it is difficult to obtain necessary strength and durability. Therefore, the maximum diameter D of the hole 8a and protrusion 8b is preferably set in the range of not less than 2.0 mm, more preferably not less than 3.0 mm, but not more than 8.0 mm, more preferably not more than 5.0 mm.
In addition to a circle, the holes 8a and protrusions 8b can be formed in a shape of an ellipse, elongated circle, polygon and the like. Thus, in case of not round shape, it is preferable to limit the hole in terms of the volume, instead of the diameter D. The volume of a hole 8a is set in a range of not less than 1.5 cu.mm, preferably not less than 5.6 cu.mm, but not more than 102.0 cu.mm, preferably not more than 30.0 cu.mm. Also it is preferable that the percentage of the total area S1 of all the holes 8a to the overall area S of the lap joint part F1 or F2 including the total area S1 is set in the range of not less than 20%, preferably not less than 30%, but not more than 70%, preferably not more than 60%. As a result, a balance between the adhesion force by the adhesive agent and the mechanical engaging force by the protrusion 8b and holes 8a can be achieved, and the strength of the joint can be remarkably increased.
Reversely to the above examples, as shown in
Further, it is possible to form both of the holes 8a and protrusions 8b on each of the first and second lap joint parts F1 and F2.
Furthermore, as shown in
In this example, the second lap joint part F2 is two-forked in the cross section, namely, this part F2 is provided with an inner lip F2i which is positioned on the inside of the first lap joint part F1, and thus the first lap joint part F1 is held between the inner lip F2i and the outside part F2o on the outside of the first lap joint part F1.
When this two-forked type second lap joint part F2 is formed on the above-mentioned discrete-type FRP part M2, it is preferable that the outside part F2o is provided with downwardly or inwardly protruding outer protrusions 8bo, and the inner lip F2i is provided with upwardly or outwardly protruding inner protrusions 8bi. In the respective securing holes 8a, the outer protrusions 8bo confront with the respective inner protrusions 8bi, and they are bonded each other.
In the above description, the FRP part M2 is first formed separately from the metal part M1, and they are integrated by bonding the lap joint parts F1 and F2.
It is however, also possible to do the formation of the FRP part M2 and its integration with the metal part M1 concurrently within a mold as follows.
Firstly, the metal part M1 is made, wherein a through hole O3 which is utilized to insert a bladder B into the hollow (i) of the metal part M1 is provided in an appropriate position, for example, in the side wall 11 on the toe side as shown in
Then, an inside prepreg Pi is applied to the inner surface of the first lap joint part F1 as shown in
On the outside of the inside prepreg Pi, an outside prepreg Po is applied to the outer surface of the first lap joint part F1 so as to completely cover the opening O1. The outside prepreg Po is a single sheet having a size and shape being capable of completely covering the opening O1. Between the peripheral part of the outside prepreg Pi and the outer surface of the first lap joint part F1, an adhesive agent 17 is again used to temporarily fix each other.
In this example, between the inside prepreg Pi and outside prepreg Po, an adhesive agent is not used. But, if need be, it is possible to use an adhesive agent.
For the adhesive agents 16, 17, those having superior adhesiveness between the metal material of the metal part M1 and the matrix resin in the inside and outside prepreg Pi and Po, for example, heat-hardening adhesive agents such as epoxy resin adhesives are preferably used.
As shown in
For that purpose, the content of the resin in each prepreg, namely, that in the FRP part M2 is set in the range of not less than 15%, preferably not less than 20%, but not more than 35%, preferably not more than 30%, more preferably not more than 25% when the matrix resins is fully hardened, the bladder B is deflated and pulled out from the hollow (i). The club head 1 is demolded. The through hole O3 is patched to close.
By the method of molding and integrating a FRP part, the bonding strength between the metal part M1 and FRP part M2 and the durability can be greatly improved.
This method can be employed to make the FRP part M2 without the inner lip F2i as shown in
In the above examples, the metal part M1 is made of one kind of a metal material, and formed as an integral part. But, it is possible to use two or more kinds of metal materials, and the metal part M1 can be formed by assembling two or more parts which are formed by suitable methods, e.g. casting, forging, pressing, rolling, cutting and the like. As a modification of the above-described metal part M1, it can be made of two or more metal materials having different specific gravity. For example, the sole wall 10 may be formed of a different metal material having a larger specific gravity than the other portion.
In the above embodiments, as described above, as the specific gravity of the FRP part M2 is smaller than the metal part, the weight of the club head can be reduced to redistribute the reduced weight to the sole portion 5 and/or side portion 6 for example. Accordingly, the design freedom is greatly increased which makes it possible to lower and deepen the center of gravity and to increase the moment of inertia of a relatively large-sized hollow club head.
Comparison Tests (Discrete Type Club Head)
Wood-type golf club heads having the same outer shapes shown in
The metal parts had the structure shown in
Face Wall 9 (Face Portion 3)
Thickness Tc in the central region 9a: 2.8 mm
Thickness Tp in the peripheral zone 9b: 2.0 mm
Peripheral zone area/central region area: 20%
Sole Wall 10 (Sole Portion 5)
Thickness Ts: 1.3 mm
Side Wall 11 (Side Portion 6)
Thickness Tb: 1.0 mm
The securing holes were a 3.0 mm dia. circular hole, including a through-hole and blind-hole.
The ratio (S1/S) of the total area S1 of the securing holes to the overall area S of the first or second lap joint part F1, F2 was changed by changing the number of the securing holes. In Ref., the first and second lap joint parts were not provided with the securing holes and protrusions.
The FRP parts were made by using prepregs as shown in
Crown Wall 12 (Crown Portion 4)
Thickness Tf: 0.8 mm
Thickness Te: 0.8 mm
The prepregs used were carbon fiber prepregs: T-700S (resin: 37 weight %), T-800H (resin: 30 weight %), and M-40J (resin: 33 weight %) manufactured by Toray Industries Inc. which were used in combination so that the average resin content became 33%. The metal part and FRP part were fixed with an epoxy resin adhesive.
Durability Test
The club heads were attached to identical FRP shafts to make 45-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 54 meter/second, and the joint part and club face were visually checked for damage and/or deformation at every 1000 times hitting up to 9000 times.
The number of hitting times at which the junction was broken is shown in Table 2.
Ball Traveling Distance Test
Each of the clubs 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 indicated in Table 2 by an index based on Ref.A1 being 100, wherein the larger the index number, the longer the traveling distance.
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. The results are shown in Table 2.
From the test results, it was confirmed that the durability can be remarkably improved, while also improving the hitting sound and traveling distance.
Comparison Tests (Integral Type Club Head)
According to the method described in connection with
To make the club head 1, the metal parts shown in
The test results are also shown in Table 3.
From the test results, it was confirmed that the durability can be improved more than the above-mentioned discrete type club heads, and the hitting sound also has a tendency to be improved more than the discrete type club heads, while also improving the traveling distance.
The present invention can be applied to not only wood-type club heads but also iron-type, patter-type club heads.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-204764 | Jul 2003 | JP | national |
| 2004-131712 | Apr 2004 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5509659 | Igarashi | Apr 1996 | A |
| 5536011 | Gutowski | Jul 1996 | A |
| 5665014 | Sanford et al. | Sep 1997 | A |
| 6183377 | Liang | Feb 2001 | B1 |
| 6623378 | Beach et al. | Sep 2003 | B2 |
| 6663504 | Hocknell et al. | Dec 2003 | B2 |
| 7128662 | Kumamoto | Oct 2006 | B2 |
| Number | Date | Country |
|---|---|---|
| 5-51374 | Jul 1993 | JP |
| 2003-62130 | Mar 2003 | JP |
| 2004121395 | Apr 2004 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050026723 A1 | Feb 2005 | US |
