Patent Application
20070105657
The present invention relates to a golf club head and a manufacturing method therefor, more particularly to a structure of the crown portion of a hollow head including a crown plate being capable of lowering the center of gravity of the head without deteriorating the durability of the joint of the crown plate.
A hollow golf club head (a) of which main body (b) is provided in the crown portion with an opening (o) closed by a crown plate (c) as shown in
Such club head is provided around the opening (o) of its main body (b) with an annular support (f) for the crown plate to be spliced with a peripheral edge part of the crown plate (c). Hitherto, it has been considered that the strength of the joint of the crown plate (c) and the head main body (b) becomes insufficient if the overlap width (A) therebetween is decreased. Therefore, the width is usually set in a range of more than 5 mm, for example, 15 mm.
Thus, due to the crown-plate support (f) having a relatively large width (A), the weight of the crown portion can not be fully reduced in spite of the lightweight crown plate, and as a result, maximal lowering of the center of gravity is not possible.
It is therefore, an object of the present invention to provide a golf club head, in which, the conventional crown-plate support provided around the opening can be minimized or almost cut out, without decreasing the durability of the joint of the crown plate, and thus, a further lowering of the center of gravity is possible.
According to the present invention, a golf club head having a hollow structure comprising a metallic main body provided in a crown portion with a crown opening and a metallic crown plate fitted in the opening, wherein
the edge of the crown plate is butt welded to the edge of the main body around the crown opening.
Therefore, the conventional crown-plate support provided around the opening can be cut out, without decreasing the durability of the joint. Accordingly, the weight of the crown part of the head can be reduced, and it becomes possible to lower the center of gravity of the head.
Incidentally, upon lowering the center of gravity of the head, the sweet spot shifts towards the sole portion of the head, and the probability of hitting a ball at a position on the upper side of the sweet spot SS becomes high. As a result, at impact, the club head makes a slight rotation (in
Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.
In the drawings, golf club head 1 according to the present invention is a wood-type hollow head 1.
As shown in
According to the present invention, the crown portion 4 is provided with a crown opening O1 which is closed by a crown plate 1B. In this embodiment, as shown in
In order to increase the moment of inertia of the club head 1 to minimize undesirable motions of the club head at a missed shot and thereby to improve the directional stability, and to allow to provide a larger crown opening to further the crown weight reduction, the head volume is preferably set in a range of not less than 400 cc, more preferably more than 420 cc, still more preferably more than 430 cc. However, in view of the club weight, swing balance, durability and the like, the head volume is preferably not more than 470 cc.
Further, in view of the swing balance, the weight of the club head 1 is preferably not less than 175 grams, more preferably more than 180 grams, but preferably not more than 210 grams, more preferably less than 205 grams.
*Face Plate*
The face plate 1C forms the substantially entirety of the face portion 3, and thus, the front face thereof defines the club face 2.
For the face plate 1C, titanium alloys such as Ti-15V-3Cr -3Al-3Sn, Ti-22V-4Al(DAT51), Ti-6Al-4V, Ti-13V-11Cr-3Al and Ti-4.5Al-2.0Mo-1.6V-0.5Fe are preferably used.
The thickness of the face plate 1C or the thickness t4 of the face portion 3 is preferably not less than 3.00 mm, more preferably not less than 3.05 mm, still more preferably not less than 3.10 mm. when the thickness t4 is increased, the depth GL of the center of gravity G decreases, and the moment of inertia tends to decrease. Therefore, the thickness t4 is preferably not more than 3.40 mm, more preferably not more than 3.35 mm, still more preferably not more than 3.30 mm.
The face portion 3 in this example has a substantially constant thickness t4. But, the thickness t4 may be variable. For instance, while maintaining the thickness in the central zone including the sweet spot SS to provide durability, the thickness in the peripheral zone surrounding the central zone can be reduced to improve the rebound performance.
In this embodiment, the face plate 1C is provided with a turnback 13 along at least partially of the edge 2a-2d of the club face 2. The turnback 13 is formed integrally with the face plate 1C by a pressing bend method, casting method, forging method or the like. In other words, they are not separate parts jointed.
The turnback 13 in this example is, as shown in
*Main Body*
In the
The head main body 1A in this example is a single piece of a metal material, although the main body 1A may be an assemblage of two or more separate pieces.
Metal materials having a relatively large specific gravity, for example, stainless steels and maraging steels, and further pure titanium, titanium alloys (for example Ti-6Al-4V) and the like can be preferably used to make the main body 1A.
In order to lower the center of gravity of the head by reducing the weight of the crown portion 4, the area of the crown opening O1 is preferably not less than 40 sq.cm, more preferably not less than 50 sq.cm. But, in view of the durability of the crown portion 4, the area is preferably not more than 75 sq.cm, more preferably not more than 65 sq.cm.
Here, the area of the crown opening O1 is the area projected on a horizontal plane HP under the standard state of the club head as shown in
The standard state is such that the head is put on the horizontal plane HP, maintaining its lie angle and loft angle.
Although the crown opening O1 may be formed to protrude from the crown portion 4 to the side portion 6, in this embodiment, the crown opening O1 is formed within the crown portion 4, whereby the above-mentioned crown peripheral part 4A extends continuously and annularly around the crown opening O1.
As to the shape of the crown opening O1, preferably employed is a shape similar to but a little smaller than the shape of the crown portion 4 as shown in
*Crown Plate*
The crown plate 1B is made of a metal material having a specific gravity smaller than that of the head main body 1A in order to lower the center of gravity G of the head.
For example, titanium alloys are preferably used. Especially, Beta-type titanium alloys such as Ti-15V-3Cr-3A1-3Sn and Ti-4.5Al-3v-2Mo-2Fe(SP700) having a relatively large specific gravity and being excellent in ductility are preferably used in this embodiment.
The crown plate 1B is curved such that the curvature has, as shown in
In view of the durability and weight, the thickness t3 of the crown plate 1B is preferably not less than 0.30 mm, more preferably not less than 0.35, still more preferably not less than 0.40 mm, but not more than 0.70 mm, more preferably not more than 0.60 mm, still more preferably not more than 0.55 mm.
The ratio (t1/t3) of the thickness t1 of the crown peripheral part 4A to the thickness t3 of the crown plate 1B is preferably not less than 1.20, more preferably not less than 1.35, more preferably not less than 1.50, but not more than 2.00, more preferably not more than 1.80. If the ratio (t1/t3) is less than 1.20, the weight reduction in the crown portion 4 is liable to become insufficient. If more than 2.00, a weight increase or a decrease in the crown plate strength tends to occur.
The contour shape of the crown plate 1B is almost same as but a little smaller than the shape of the crown opening O1 so that, when the crown plate 1B is fitted in the crown opening 01, a micro gap is formed therebetween and the edge of the crown plate 1B and the edge of the crown peripheral part 4A can be butt welded as shown in
The fusion zone 19 extends from the outer surface of the crown portion 4 toward the inside of the head and reaches to the depth corresponding to the thickness t3 of the crown plate 1B.
If the fusion zone 19 is too narrow in width JW, the joint strength is liable to become insufficient. If too wide, the production efficiency tends to decrease because the quantity of finishing work such as grinding and polishing is increased thereby. Therefore, the width JW of the fusion zone 19 is preferably at least 1.5 mm, more preferably at least 2.0 mm, but at most 3.0 mm, more preferably at most 2.5 mm when measured at the outer surface of the crown portion 4.
*Process of Manufacturing Main Body*
The above-mentioned main body 1A can be manufactured by assembling two or more separate pieces which are prepared through appropriate methods such as forging, rolling and bending. However, the head main body 1A in this example is manufactured as a single casting of the above-mentioned metal material by a lost-wax precision casting.
Firstly, a casting 1Am is prepared in order to manufacture the head main body 1A. This primary casting 1Am is, as shown in
In either case, along the edge of the crown opening O1 to be formed, a thickness-increased part TI is molded. This thickness-increased part TI protrudes from the outer surface of the crown portion 4, and also protrudes from the outside to the inside of the edge 10ae of the crown opening O1 to be formed, as shown in
*Process of Forming Crown Opening*
Then, through the use of laser beam machining, the crown opening O1 is formed on the primary casting 1Am.
In this laser beam machining process, as shown in
If the above-mentioned crown peripheral part 4A on the outside of the thickness-increased part TI is too thin, it is difficult to provide durability for the crown portion 4 and it becomes difficult to cast such a thin plate. Therefore, the thickness t1 of the crown peripheral part 4A is preferably not less than 0.6 mm, more preferably not less than 0.7 mm. But, in view of the weight reduction in the crown portion 4, the thickness t1 is preferably not more than 0.9 mm, more preferably not more than 0.8 mm.
As explained above, the thickness t1 of the crown peripheral part 4A is very small. If there is no rib, the depth of the opening or hole in which the very thin crown plate 1B is fitted becomes very shallow. Accordingly, the crown plate 1B is easy to dislocate during assembling the head. However, by providing the rib 10t, such dislocation can be prevented. It is therefore, preferable that the maximum height TH of the rib 10t is at least 0.8 mm, more preferably 1.0 mm or more. But, in order to remove the rib from the finished head without consuming time, it is preferable that the maximum height TH is not more than 1.8 mm, more preferably not more than 1.5 mm. For the same reason, the maximum width TW of the rib 10t is preferably at least 0.6 mm, more preferably at least 0.7 mm, but at most 1.2 mm, more preferably at most 1.0 mm.
Due to the forming process, the rib 10t extends continuously and annularly along the edge 10ae of the crown opening O1, but it may be possible to form the rib 10t discontinuously.
*Process of Forming Crown-Plate Support*
Further, through the use of the laser beam machining, the crown-plate support 10b protruding to the crown opening O1 as shown in
In the present invention, the crown-plate support 10b is prepared for the purpose of temporarily supporting and positioning of the crown plate during welding the crown plate to the head main body. Accordingly, a protrusion of at most 0.8 mm is sufficient to such purpose.
In the present invention, therefore, the width RW of the crown-plate support 10b measured perpendicularly to a tangent to the edge 10ae of the crown opening O1, namely, the amount of protrusion from the edge 10ae of the crown opening O1 is set in a range of at most 0.8 mm, preferably not more than 0.70 mm, more preferably not more than 0.65 mm, but at least 0.3 mm, preferably at least 0.40 mm, more preferably at least 0.50 mm. In the
In order that the width RW satisfies the above limitation, by irradiating the laser beam LB at the position corresponding to RW, the inner end or side face 10be of the crown-plate support 10b is formed.
Furthermore, by the laser beam machining, the outer face 10bo of the crown-plate support 10b on which the crown plate 1B is placed is formed at a certain depth so that the outer surface of the crown plate 1B becomes substantially flush with the outer surface of the crown peripheral part 4A when the crown plate is fitted in the crown opening O1.
As the width RW and the depth of the outer face 10bo are very small, it is very difficult to form the crown-plate support 10b with precision by the casting method only without utilizing the laser beam machining.
In
However, as shown in
The maximum thickness t2 of the crown-plate support 10b is preferably at least 0.60 mm, more preferably not less than 0.65 mm, but at most 0.85 mm, more preferably not more than 0.70 mm. To secure the thickness t2, the above-mentioned thickness-increased part TI also protrudes from the inner surface of the crown peripheral part 4A as shown in
*Process of Manufacturing Crown Plate*
The crown plate 1B may be formed by casting or forging a metal material. But, in such a case, as the crown plate 1B is unusually thin, structural defects or uneven residual stress distribution inherent in such processes tends to deteriorate the durability of the plate. Therefore, the use of a rolled metal material gradually extended into the predetermined uniform thickness is preferred because the structural defects and uneven residual stress distribution are minimized.
In this embodiment, therefore, the crown plate 1B is manufactured from a rolled metal plate.
As shown in
Next, as shown in
Then, as shown in
Finally, edge trimming is made as needed.
*Rolled Metal Plate*
In general, a rolled metal plate is extended a plurality of times, changing the extending. direction in order to eliminate anisotropy of characteristics. In this embodiment, however, the rolled metal plate is extended more in one direction K than other directions to intentionally provide anisotropy. since the crystal grains in the rolled metal plate are oriented in the extended direction K, the resultant crown plate 1B has a strength anisotropy and the Young's modulus increases in the direction K. The crown plate 1B is, at impact, subjected to a large stress in the back-and-forth direction Y. Therefore, the strain of the crown portion 4 at impact can be reduced by substantially aligning the directions K and Y. This will improve the durability and can decrease the energy loss to improve the rebound performance. In the heel-and-toe direction orthogonal to the back-and-forth direction Y, on the other hand, the Young's modulus of the crown plate 1B becomes relatively small. As a result, the shock at impact can be mitigated and the shot feeling may be improved.
Therefore, the angle θ between the extended direction K and the back-and-forth direction Y is set in a range of not more than 20 degrees, preferably not more than 10 degrees, more preferably not more than 5 degrees, most preferably 0 degree.
The back-and-forth direction Y of the club head is, as shown in
In the crown plate 16, the above-mentioned extended direction K is defined at the centroid of the contour shape of the crown plate 1B projected on the horizontal plane HP under the above-mentioned standard state of the head.
The extended direction K of the rolled material M can be determined as the major elongated direction of crystal grains in the metallic crystal structure, which can obtained by making an observation about the crystal grains with the use of an electronic microscope.
*Welding of Crown Plate and Main Body*
As explained above, the edge 1Be of the crown plate 1B is butt welded to the edge 10ae of the main body around the crown opening O1 by utilizing laser welding.
As the crown plate 1B is very thin, if another welding method, for example, plasma welding is employed, the heat during welding spreads to a wide range around the welded joint. As a result, the crown plate 1B tends to burn through or deform. Further, the metallic crystal structure is liable to be metamorphosed. These problems, however, can be solved by utilizing laser welding because a pinpoint irradiation is possible.
In the case of laser welding, due to the pinpoint irradiation, if the gap between the crown plate 1B and the crown opening O1 is wide, it is difficult to weld. To achieve an effective wilding, the gap should be as small as possible. Accordingly, with respect to the shape, the crown opening as well as the crown plate has to be formed with a high degree of accuracy. Therefore, in this embodiment, lasering is utilized to form the crown opening O1 in the crown portion of the head main body 1A as described above.
As shown in
As shown in
As shown in
If the width RW is more than 0.8 mm, as shown in
Accordingly, not to form such unwelded part 20, the width RW is set in the above-mentioned very small value range of not less than 0.3 mm, but not more than 0.8 mm.
As to the extent of the fusion zone 19, as far as the fusion zone 19 reaches to the end 10be of the crown-plate support 10b, even if the outside of the crown-plate support 10b is remained almost intact as shown in
During irradiating the laser beam LB, the above-mentioned rib 10t facilitates to lessen the heat transmitted to the crown peripheral part 4A. Further, the fused rib 10t is utilized as the filler metal material between the gap. Usually, the rib 10t is removed by machining after the crown plate 1B is welded. But, it may be left to utilize for an ornamental propose or the like.
*Welding of Face Plate and Main Body*
The face plate 1C is attached to the head main body 1A by butt welding the turnbacks 13a, 13b, 13c and 13d to the crown peripheral part 4A, sole main part 5A, side main part 6A on the toe-side and side main part 6A on the heel-side of the main body 1A, respectively.
For the purpose of supporting and positioning the face plate 1C, the head main body 1A can be provided along the edge of the front opening O2 with projections 17.
As the method of welding, in this example, laser welding is employed.
Due to the turnback 13, the butt welding becomes possible without reducing the joint strength. Further, the welded butt joint 15 gets away from the edge of the club face 2. This will increase the durability of the butt joint, and further the rebound performance may be improved. Therefore, it is preferable that the depth FL of the turnback 13 in the back-and-forth direction of the club head is at least 3 mm, more preferably at least 5 mm, but at most 30 mm, preferably not more than 20 mm, more preferably not more than 15 mm.
In the above-described example, the crown opening O1 and crown plate 1B are almost semicircle as best shown in
In
In
In
Incidentally, carbon dioxide laser, especially YAG (yttrium, aluminum, garnet) laser is preferably used because a high-power, high-energy-density laser beam can be obtained. Laser beam irradiation can be made in the atmosphere or in an inert gas although electron beam irradiation requires to be carried out in a vacuum chamber. Thus, in view of the production efficiency, production cost and the like, the use of laser beam is preferred.
Comparison Tests
Hollow metal wood club heads (volume: 450 cc, Loft angle: 11.0 deg., Lie angle: 57.5 deg.) were made and tested for the durability and measured for the sweet spot height.
All the heads had the same structure except for the crown portion as shown in Table 1.
In each head, the crown plate having the shape shown in
The main body was formed as follows: An ingot of a titanium alloy Ti-6Al-4V was melted, and the primary casting as shown in
The face plate with the turnback as shown in
The crown plate was butt welded to the main body by the welding method shown in Table 1.
The weight of the club head Ex. 1 was 200 grams.
Sweet Spot Height:
As shown in
Durability Test:
The club heads were attached to identical FRP shafts (V-25, flex X, manufactured by SRI Sports Limited) and 45-inch wood clubs were made. Each club was attached to a swing robot (SHOT ROBO, manufactured by Miyamae Co., Ltd), and golf balls were hit 10000 times (max.) at the sweet spot at the head speed of 54 m/sec, while checking the joint of the crown plate and main body. If some kind of damage was found, the hitting was stopped and the number of total hits was recorded. The results are shown in Table 1.
Non-Defective Rate:
With respect to each head, twenty pieces was manufactured, and a percentage of non-defective products was obtained.
The non-defective product means a head satisfying the following conditions (A) and (B): (A) There is no pinhole in the welded butt joint between the crown plate and head main body. (B) The fused zone extends from the outer surface to the inner surface of the crown portion, and it is possible to identify the weld bead on the inner surface.
The inside of the head was observed using an endoscope passed into the head through the shaft inserting hole of the hosel. The outside of the head was observed with the unaided eye. The results are shown in Table 1.
From the test results, it was confirmed that the center of gravity can be lowered, while providing an excellent durability and without lowering the non-defective rate.
The present invention is suitably applied to a wood-type hollow head such as a driver (#1) and fairway wood. But, it can be also applied to iron-type, utility-type and patter-type golf club heads.
*Numerical value in parentheses:
Percentage of the total length of the crown-plate support to the inside perimeter of the crown opening.
C: continuous
D: discontinuous
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-321193 | Nov 2005 | JP | national |
