Patent Application
20070287552
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 hollow head for a wood-type golf club such as driver (#1) or fairway wood, and the 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 2c to a heel-side edge 2d of the club face 2 through the back face BF of the club head; and a hosel portion 7 at the heel side end of the crown to be attached to an end of a club shaft (not shown) inserted into the shaft inserting hole 7a. Thus, the club head 1 is provided with a hollow (i) and a shell structure with the thin wall.
In the case of a wood-type club head for a driver (#1), it is preferable that the head volume is set in a range of not less than 360 cc, more preferably not less than 380 cc in order to increase the moment of inertia and the depth of the center of gravity. However, to prevent an excessive increase in the club head weight and deteriorations of swing balance and durability and further in view of golf rules or regulations, the head volume is preferably set in a range of not more than 470 cc, more preferably not more than 460 cc.
The mass of the club head 1 is preferably set in a range of not less than 170 grams, more preferably not less than 180 grams in view of the swing balance and rebound performance, but not more than 250 grams, more preferably not more than 240 grams, still more preferably not more than 200 grams in view of the directionality and traveling distance of the ball.
As shown in
The crown plate 1C is a slightly convexly curved thin plate made of a metal material.
For example, maraging steels, aluminum alloys, pure titanium and titanium alloys can be used. Preferably, titanium alloys such as Ti-15V-3Cr-3Al-3Sn, Ti-3Al-2.5V, Ti-15Mo-5Zr-3Al, Ti-10V-2Fe-3Al and Ti-6Al-4V can be used.
The crown plate 1C has a shape similar to but smaller in size than the shape of the contour of the crown portion 4.
The projected area of the crown plate 1C on the horizontal plane HP is set in a range of 0.4 to 0.6 times the projected area of the head 1 on the horizontal plane HP as shown in
The length RL of the crown plate 1C is set in a range of 0.5 to 0.7 times the length EL of the crown portion 4, when measured in the back-and-forth direction on the plane VP1 including the center G of gravity of the head and the sweat spot SS.
The thickness t3a of the crown plate 1C is preferably set in a range of not less than 0.2 mm, more preferably not less than 0.3 mm, still more preferably not less than 0.4 mm, but not more than 1.0 mm, more preferably not more than 0.8 mm, still more preferably not more than 0.7 mm.
If the thickness t3a is less than 0.2 mm, the strength and durability becomes insufficient, and further it is difficult to provide the necessary rebound performance. If more than 1.0 mm, on the other hand, it becomes difficult to increase the carry and the centre G of gravity of the head tends to become higher. In this embodiment, the thickness t3a is constant throughout the crown plate 1C. But, the thickness t3a can be varied within the above-mentioned range, for example, such that the central part has a reduced thickness small than the periphery edge.
In any case, the thickness t3a at the front edge 21 is referred to as “thickness t3”.
As the crown plate 1C is formed with a small thickness to reduce the weight thereof, the crown plate 1C is formed by a process including plastic forming the above-mentioned metal material because the plastic forming can provide a high-strength homogeneous material in comparison with casting.
In this embodiment, the crown plate 1C is formed by:
preparing a rolled sheet of the above mentioned metal material having a constant thickness;
punching out a plate from the rolled sheet with punch cutting dies, which plate has a shape slightly larger than the finished shape of the crown plate 1C;
pressure molding the plate with shaping molds to provide the convex curvature; and
trimming the edge of the plate with a NC milling machine to have the exact finished shape.
Of course, another method is also possible. For example, the crown plate 1C can be formed by: preparing a rolled sheet; cutting out a plate having the exact finished shape from the rolled sheet by lasering; and pressure molding the plate with shaping molds to provide the convex curvature.
The face plate 1F is provided with a turnback 13 integrally with its main part 12.
The main part 12 defines a major part of the face portion 3 including the sweat spot SS in its center. In this embodiment, the main part 12 defines the entirety of the face portion 3.
The turnback 13 is formed along at least the upper edge 2a. In this embodiment, the turnback 13 is formed along the almost entire length of the edge (2a, 2b, 2c, and 2d) of the face portion 3 excepting a part corresponding the hosel portion 7 as shown in
The face plate 1F is made of a metal material having a large specific tensile strength such as titanium alloys, e.g. Ti-15V-6Cr-4Al, Ti-6Al-4V, Ti-13V-11Cr-3Al, Ti-5.5Al-1Fe, Ti-4.5Al-3V-2Fe-2Mo, Ti-4.5Al-2Mo-1.6V-0.5Fe and the like.
If the face portion 3 is too thick, the centre G of gravity of the head becomes shallow and the moment of inertia of the head becomes small. Therefore, the thickness tf of the main part 12 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. However, if the main part 12 is too thin, it is difficult to provide a necessary strength and durability. Therefore, the thickness tf is not less than 3.00 mm, more preferably not less than 3.05 mm, still more preferably 3.10 mm.
In this example, the thickness tf is substantially constant throughout the face portion 3. But, it is also possible that the face portion 3 has a variable thickness.
The turnback 13, especially upper turnback 13a is subjected to a large stress at impact. If the upper turnback 13a is too thin, the durability of the face portion is decreased. Further, if too thin, as the rigidity is decreased, the deflection at impact increases to increase the energy loss, and the rebound performance is deteriorated. If the upper turnback 13a is too thick, it goes against the lowering of the centre G of gravity.
Therefore, the thickness t1a of the upper turnback 13a is preferably set in a range of not more than 2.0 mm, more preferably not more than 1.5 mm, still more preferably not more than 1.2 mm, but, not less than 0.8 mm, more preferably not less than 0.9 mm.
The thickness t1a can be varied within this range so as to gradually decrease from the front to the rear. But, in this embodiment, the thickness t1a is substantially constant in the back-and-forth direction as well as the widthwise direction. In any case, the thickness t1a at the rear edge 20 is referred to as “thickness t1”.
If the size of the upper turnback 13a in the back-and-forth direction of the head is too small, as the rigidity is decreases, the durability is decreased, and the energy loss at impact increases. If too large, it becomes difficult to increase the carry and the centre of gravity becomes high. Therefore, the length FL of the upper turnback 13a is preferably set in a range of not less than 0.05 times, more preferably not less than 0.07 times, but not more than 0.3 times, more preferably not more than 0.2 times the length EL of the crown portion 4.
Here, the length EL is the length in the back-and-forth direction measured under the standard state of the head horizontally along the vertical plane VP1 including the straight N from the upper edge 2a of the club face 2 to the extreme rear end of the head.
The length FL of the upper turnback 13a is measured in the back-and-forth direction of the head from the upper edge 2a of the club face 2 to the rear edge 20 of the upper turnback 13a.
In this embodiment, the length FL of the upper turnback 13a is substantially constant in the widthwise direction from the toe to the heel. But, it is not always necessary to have such constant length from the toe to the heel. It will be sufficient that the length FL is substantially constant within a range Y which is defined as having the width corresponding to the face height FH and centered on the sweat spot SS in the toe-heel direction when viewed from above the head as shown in
The face plate 1F is formed by a process including plastic forming of the above-mentioned metal material because the face plate 1F, which is subjected to a large stress at impact, requires strength and durability, and the plastic forming can provide a high-strength homogeneous material in comparison with casting.
In this embodiment, as the turnback 13 is formed along the almost entire length of the edge of the main part 12, the crown plate 1C is formed by forging. More specifically, the crown plate 1C can be formed by: preparing a rolled sheet of the metal material having a constant thickness; punching out a plate from the rolled sheet with punch cutting dies; forging the plate with dies to provide the turnback 13 and also provide the above-described specific thickness distribution; and trimming the edge of the turnback with a NC milling machine to have the exact finished size and shape.
The crown plate 1C can be formed by bending without using dies in the case of for example the turnback 13 formed along the upper edge 2a only.
Since the turnback 13 can keep the weld junction position away from the club face 2, the effects of the heat during welding on the club face can be minimized.
Since the above-mentioned turnbacks (13a, 13b, 13c, 13d) form the front zones of the respective portions (3, 4, 5), the main shell 1M forms the remainder of the head.
In this embodiment, accordingly, the main shell 1M integrally includes: a major part 5A of the sole portion 5; a major part 6A of the side portion 6; a peripheral part 4B of the crown portion 4; and the above-mentioned hosel portion 7.
The main shell 1M is a casting of a metal material having a large specific tensile strength. Specifically, stainless steels (e.g. SUS630 etc.), maraging steels, aluminum base alloys, titanium alloys (e.g. Ti-6Al-4V etc.) and the like can be preferably used.
The thickness tp of the side major part 6A is not less than 0.50 mm, preferably not less than 0.60 mm in order to increase the moment of inertia of the head. But, if too thick, the weight margin of the head becomes too small. Therefore, the thickness tp is preferably not more than 2.0 mm, more preferably not more than 1.7 mm.
The thickness ts of the sole major part 5A is at least 0.60 mm, preferably not less than 0.80 mm to provide a necessary strength. But, if too thick, the weight margin of the head becomes too small. Therefore, the thickness ts is preferably not more than 1.5 mm, more preferably not more than 1.3 mm. Incidentally, a separate weight member may be fixedly provided on the sole major part 5A according to need.
The main shell 1M is formed by a process including casting. The main shell 1M can be formed by only casting such as lost-wax process precision casting. But, it is desirable that the sizes and shapes of the openings are adjusted with accuracy by utilizing machine work. Thus, it is preferable that the process of making the main shell 1M further includes machining.
In this embodiment, therefore, a primary casting 1Ma is first produced, which casting is provided with openings Of1, Oc1 smaller than the finished openings Of and Oc or alternatively provided with no opening. Thereafter, by machining the primary casting 1Ma, the provisional smaller openings Of1 and Oc1 are shaped into the openings Of and Oc, or alternatively the openings Of and Oc are formed. For that purpose, a numerical control machine tool is suitably used.
Of course it is also possible that one of the two openings Of and Oc is formed by casting and machining as explained above, and the other is formed by the casting only.
Either by the machining or by the casting only, the top opening Oc is formed within the crown portion 4, and thereby, the above-mentioned peripheral part 4B including a lateral frame 4A is formed.
The shape of the top opening Oc is almost same as but very slightly smaller than the shape of the crown plate 1C so that when the crown plate 1C is fitted in the top opening Oc the gap between their edges becomes less than about 0.5 mm, preferably almost zero. And the edges are butt-welded.
The lateral frame 4A is defined by a portion which is positioned between the top opening Oc and the front opening Of, and extends continuously from the toe to the heel to increase the stiffness of the main shell 1M.
Front Opening Of
The front opening Of has an edge including: the upper front edge 22 of the lateral frame 4A; the lower front edge 5Ae of the sole major part 5A; and the toe-side and heel-side front edges 6Ae1 and 6Ae2 of the side major part 6A.
The shape of the edge of the front opening Of is the same as the shape of the edge of the face plate 1F, namely, the rear edge of the turnback. And the edges are butt-welded.
The face plate 1F and crown plate 1C are fixed to the main shell 1 by: butt-welding the edge of the face plate 1F to the edge of the front opening Of; and butt-welding the edge of the crown plate 1C to the edge of the top opening Oc, as shown in
In order to facilitate the positioning of the face plate 1F during welding, the front opening Of is provided with clamping pieces 17 protruding from the edge of the opening and thereby being capable of fitting into the turnbacks of the face plate 1F. Also the top opening Oc is provided with clamping pieces 18 capable of fitting to the peripheral edge of the inner surface of the crown plate 1C and thereby positioning and supporting the crown plate 1C. The clamping pieces 17 and 18 are arranged along the edges of the openings at intervals. It is however, also possible to provide such clamping pieces on the face plate 1F and/or crown plate.
During welding, there is a possibility that a weld bead is formed on the outside of the head and also on the inside of the head. The weld bead on the outside of the head is removed by grinding and polishing. But, the weld bead on the inside of the head can be remained if it is difficult to remove. In this case, the weld bead is not included in the above-mentioned thicknesses.
Therefore, the crown portion 4 comprises the front zone defined by the upper turnback 13a, the middle zone defined by the lateral frame 4A, and the back zone defined by the crown plate 1C.
The crown plate 1C namely back zone is very thin. But, the upper turnback 13a namely front zone is relatively thick. If the upper turnback 13a becomes too thick relatively to the crown plate 1C, then the increase in the weight of the crown portion 4 becomes remarkable, or the durability of the crown plate 1C is decreased. If the thickness t1a of the upper turnback 13a becomes close to the thickness t3a of the crown plate 1C, then it difficult to increase the carry and further it becomes difficult to improve the durability or reduce the weight of the crown portion 4.
Therefore, the thickness t1a is preferably set in a range of not less than 1.5 times, more preferably not less than 1.7 times, but not more than 4.0 times, more preferably not more than 3.0 times, still more preferably not more than 2.3 times the thickness t3a of the crown plate 1C.
The thicker upper turnback has a higher rigidity than the thin crown plate, and the lateral frame 4A namely middle zone is disposed therebetween.
In order to make the rigidity change gradual from the front to the rear of the crown portion, the lateral frame 4A has a thickness gradually decreasing from the front to the rear. The lateral frame 4A has: a maximum thickness t2f at the front edge 22 welded to the rear edge 20 of the upper turnback 13a; and a minimum thickness t2b at the rear edge 23 welded to the front edge of the crown plate 1C.
In
In
In
In any case, the absolute value of the difference |t2b−t3| between the thickness t2b of the lateral frame 4A at the rear edge 23 and the thickness t3 of the crown plate 1C at the front edge 21 is set in a range of not more than 0.2 mm, preferably not more than 0.1 mm, more preferably not more than 0.05 mm.
Similarly, the absolute value of the difference |t2f−t1| between the thickness t2f of the lateral frame 4A at the front edge 22 and the thickness t1 of the upper turnback 13a at the rear edge 20 is set in a range of not more than 0.2 mm. Preferably not more than 0.1 mm, more preferably not more than 0.05 mm. other than those above, the thickness difference between the edges to be butt-welded, for example, the difference between the rear edge of the crown plate 1C and the rear edge of the top opening Oc, the difference between the rear edge of the sole-side turnback 13b and the sole-side front edge of the front opening Of and the like, can be preferably set in the same range as above.
Preferably, a rate of thickness change (t2f−t2b)/BL which is the thickness difference (t2f−t2b) divided by the length BL of the lateral frame 4A, is set in a range of not less than 0.02, more preferably not less than 0.03, but not more than 0.1, more preferably not more than 0.06.
In this embodiment, the length BL is substantially constant across the almost entire width of the lateral frame 4A. But, it is not always necessary. It will be sufficient that the length BL is substantially constant within the above-mentioned range Y. Here, the length BL of the lateral frame 4A is measured in the back-and-forth direction of the head from the front edge 22 to the rear edge 23.
The length BL is in a range of 0.5 to 2 times the length FL of the upper turnback 13a.
As explained above, in the golf club head according to the present invention, the crown portion is provided with a thickness distribution such that the thickness is gradually decreased from the front edge toward the rear of the head. In the above-embodiments, further, the thickness of the face portion is larger than that of the turnback; therefore, the thickness is gradually decreased from the face portion to the rear of the head through the crown portion.
In this embodiment, the edge of the front opening Of the main shell is positioned outside the face portion. But, it is also possible the edge of the front opening Of is partially positioned in the face portion.
Hollow metal wood golf club heads having the structure shown in
Common specifications of the heads are as follows:
Other specifications are shown in Table 1.
In each of the heads, the main shell, face plate and crown plate were laser welded or plasma welded as indicated in Table 1.
Each head was attached to a CFRP shaft (“MP-300”, SRI Sports Ltd.) to make a 45-inch wood club, and the golf club was mounted on a swing robot. Then, the head hit golf balls at the sweat spot five times at the head speed of 40 meter/second. The launch angle, backspin and carry of each ball were measured to obtain the respective mean values.
The results are shown in Table 1.
The durability test was made by an increased head speed of 50 meter/second, using the above-mentioned clubs and swing robot. The head hit golf balls at the sweat spot 10000 times Max., while checking the weld junction every 1000 times. The results are shown in Table 1, wherein “A” means that no damage was found after the 10000-time hitting test, and numerical values mean the number of hitting times at which a damage was observed at the weld junction.
From the test results, it was confirmed that, according to the invention, the strength and weight of the crown portion can be optimized, and the launch angle is increased while decreasing the backspin, and as a result, the carry is increased without sacrificing the durability.
In Ref. 1, although the durability was high, the backspin was increased and the carry became short. In Ref. 2, although the carry was long, the durability became remarkably lowered.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-158857 | Jun 2006 | JP | national |
