Patent Application
20080096689
In the drawings, wood-type hollow golf club head 1 according to the present invention is a driver (#1 wood) head comprises: a face 3 whose front face defines a clubface 2 for striking a ball; a crown 4 intersecting the clubface 2 at the upper edge 2a thereof; a sole 5 intersecting the clubface 2 at the lower edge 2b thereof; a sidewall 6 between the crown 4 and sole 5 which extends from a toe-side edge 2c to a heel-side edge 2d of the clubface 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. The head 1 is provided with a hollow (I) and a shell structure with the thin wall. The hollow (I) in this example is a closed void space, but it may be filled with a foamed plastic, leaving a space from the backside of the face 3.
In the case of a driver, it is preferable that the head volume is set in a range of not less than 380 cc, more preferably not less than 400 cc, still more preferably 420 cc in order to increase the depth of the center of gravity and the moment of inertia around a vertical axis passing through the center of gravity G. 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, preferably not more than 460 cc.
The mass of the club head 1 is preferably set in a range of not less than 180 grams, more preferably not less than 185 grams in view of the swing balance, carry distance and strength or durability, but not more than 220 grams, more preferably not more than 215 grams in view of the directionality and traveling distance of the ball.
In order to obtain sufficient rebound performance and allow the center G of gravity to locate in a suitable position, the backside width w which is almost same as the clubface width is set in a range of not less than 90 mm, preferably not less than 93 mm, more preferably not less than 95 mm, but less than 125 mm, preferably not more than 122 mm, more preferably not more than 120 mm, and the backside height H which is almost same as the clubface height is set in a range of not less than 30%, preferably not less than 32%, but not more than 75%, preferably not more than 72% of the backside width w.
The clubface 2 may be a flat surface, but in this example, the clubface 2 is a slightly curved surface protruding frontward such as a part of a spherical surface whose center is positioned rearwards of the center G of gravity of the head. The clubface 2 can be provided with grooves or punch marks which are excluded from the considerations of the profile line Lf of the clubface 2 and the thickness of the face 3.
It is possible that the club head 1 has a three or four-piece structure. In this embodiment, however, the club head 1 has a two-piece structure made up of a metallic face plate 1A forming a major part of the face 3 at least, and a main body 1B forming the remaining part of the head.
In this embodiment, the face plate 1A has its main portion forming the entirety of the face 3, and the face plate 1A is provided along the edges 2a, 2b, 2c and 2d of the clubface 2 with a turnback 9 extending backwards of the club head.
The turnback 9 is integrally formed with the face plate main portion by plastic forming (e.g. press working, bending, casting and forging) a single metal material.
In this embodiment, the main body 1B is integrally molded from a metal material. In the case that the turnback 9 is formed, the main body 1B comprises the above-mentioned hosel portion 7, a major part of the crown 4, a major part of the sole 5, and a major part of the sidewall 6. In the case that the turnback 9 is not formed, the main body 1B comprises the hosel portion 7, the crown 4, the sole 5, and the sidewall 6. Regardless of the turnback 9, an opening is formed at the front of the main body, and the opening is covered with the face plate 1A.
The face plate 1A and the main body 1B are welded as shown in
As to the metal materials for the face plate 1A and main body 1B, preferably used are metals having a high specific tensile strength such as stainless alloys, maraging steels, pure titanium, titanium alloys, magnesium alloys and aluminum alloys. It is also possible to use a fiber reinforced resin in combination with such metal materials.
In this embodiment, the face plate 1A and main body 1B are made of the same metal material, but this is not critical.
According to the present invention, the face 3 is provided with a specific thickness distribution. The thickness distribution can be provided by molding, forging, milling and the like. In this example, NC milling is utilized.
As shown in
The nine portions are as mentioned above:
In general, the coefficient of restitution measured at a point on the clubface has a tendency to increase as the rigidity of the neighborhood of the measuring point is decreased. Therefore, by satisfying the conditions (a), (b) and (c):
If the average thickness tMTP and tMHP is too small, damage such as cracks becomes liable to occur along the boundary between these portions MTP and MHP and the sidewall 6, and there is possibility that the durability of the face 3 is decreased. If the average thickness tMTP and tMHP is too large, the coefficient of restitution can not be increased, and further the weight of the face 3 is unfavorably increased.
Therefor, each of the average thicknesses tMTP and tMHP is preferably set in a range of not less than 1.6 mm, more preferably not less than 1.7 mm, still more preferably not less than 1.8 mm, but not more than 2.6 mm,.more preferably not more than 2.5 mm, still more preferably not more than 2.4 mm.
If the average thickness tUCP and tLCP is too small, it becomes difficult to control the coefficient of restitution of the face 3 so as to comply with the golf rules or regulations. If the average thickness tUCP and tLCP is too large, there is a possibility that the coefficient of restitution of the face 3 decreases drastically.
Therefore, each of the average thicknesses tUCP and tLCP is preferably set in a range of not less than 2.5 mm, more preferably not less than 2.6 mm, still more preferably not less than 2.7 mm, but not more than 3.5 mm, more preferably not more than 3.4 mm, still more preferably not more than 3.3 mm.
If the average thickness tMCP is too small, there is possibility that the coefficient of restitution of the face 3 increases over the limitation by the golf rules, and further the durability of the face 3 will be deteriorated. If the average thickness tMCP is too large, there is a possibility that the coefficient of restitution of the face 3 decreases to decrease the carry distance.
Therefore, the average thickness tMCP is preferably set in a range of not less than 2.3 mm, more preferably not less than 2.4 mm, still more preferably not less than 2.5 mm, but not more than 3.3 mm, more preferably not more than 3.2 mm, still more preferably not more than 3.1 mm.
If the average thicknesses tUTP, tLTP, tUHP and tLHP are too small, the coefficient of restitution of the face 3 is liable to increase over the limitation by the golf rules, and further strength or durability is liable to deteriorate along the boundary between these portions UTP, LTP, UHP and LHP and the crown 4 and sole 5. If the average thicknesses tUTP, tLTP, tUHP and tLHP are too large, the coefficient of restitution of the face 3 decreases to decrease the carry distance.
Therefore, the average thicknesses tUTP, tLTP, tUHP and tLHP are each preferably set in a range of not less than 1.8 mm, more preferably not less than 1.9 mm, still more preferably not less than 2.0 mm, but not more than 2.8 mm, more preferably not more than 2.7 mm, still more preferably not more than 2.6 mm.
Further, the ratio (tMCP/tMTP) and ratio (tMCP/tMHP) are preferably set in a range of not less than 1.1, more preferably not less than 1.2, still more preferably not less than 1.3, but not more than 2.0, more preferably not more than 1.8, still more preferably not more than 1.7.
If the ratio (tMCP/tMTP), (tMCP/tMHP) is less than 1.1, it becomes difficult to widen the high-restitution-coefficient area in the toe-heel direction. If the ratio (tMCP/tMTP), (tMCP/tMHP) is more than 2.0, the rigidity difference or thickness difference between (MCP and MTP), (MCP and MHP) increases, and deformation or stress concentrates on the boundary therebetween, thus the durability of the face 3 is liable to deteriorate.
The ratio (tUCP/tUTP), (tUCP/tUHP), (tLCP/tLTP) and (tLCP/tLHP) is preferably set in a range of not less than 1.1, more preferably not less than 1.2, still more preferably not less than 1.3, but not more than 1.9, more preferably not more than 1.7, still more preferably not more than 1.6.
If the ratio (tUCP/tUTP), (tUCP/tUHP), (tLCP/tLTP) or (tLCP/tLHP) is less than 1.1, it is difficult to improve the COR in the portion UTP, UHP, LTP, LHP, therefore, it is also difficult to widen the high-restitution-coefficient area. If the ratio (tUCP/tUTP), (tUCP/tUHP), (tLCP/tLTP) or (tLCP/tLHP) is more than 1.9, it is difficult to control the COR in the portion MCP so as to comply with the golf rules. Further, the rigidity difference or thickness difference between (UCP and UTP), (UCP and UHP), (LCP and LTP), (LCP and LHP) increases, and deformation or stress concentrates on the boundary therebetween, thus the durability of the face 3 is liable to deteriorate.
According to the present invention, taking the face 3 as a whole, the thickness is decreased in the toe and heel portions (UTP, MTP, LTP, UHP, MHP, LHP), because of the above-mentioned conditions (a), (b) and (c). Therefore, there is a possibility that the strength is decreased between the crown 40 and the portions UTP and UHP, and between the sole 5 and the portions LTP and LHP. However, by satisfying the conditions (d) and (e):
As to the condition (f), if the largest average thickness tMAX in the above-mentioned nine average thicknesses is less than 2.8 mm, the coefficient of restitution of the face 3 as a whole is very liable to increase over the limitation by the golf rules. Further, it becomes difficult to maintain the necessary durability for the face 3. If on the other hand, the largest average thickness tMAX is more than 3.5 mm, the coefficient of restitution of the face 3 is decreased, and the weight of the face 3 is increased and the design freedom of the center of gravity of the head is lost.
Thus, the largest average thickness tMAX is not less than 2.8 mm, preferably not less than 2.9 mm, but not more than 3.5 mm. Preferably not more than 3.4 mm.
As to the condition (g), if the smallest average thickness tMIN in the above-mentioned nine average thicknesses is less than 1.6 mm, it is difficult to provide necessary durability for the face 3. If the smallest average thickness tMIN is more than 2.3 mm, the coefficient of restitution of the face 3 is decreased, and it becomes difficult to widen the high-restitution-coefficient area. Further, the weight of the face 3 tends to increase.
Thus, the smallest average thickness tMIN is not less than 1.6 mm, preferably not less than 1.7 mm, but not more than 2.3 mm, preferably not more than 2.2 mm.
If the difference in the average thickness between the upper portions (UTP, UHP, UCP) and the lower portions (LTP, LHP, LCP) is large, the rigidity balance is lost, and deformation/distortion tends to concentrate in the upper portions or lower portions. From this point of view, the ratios (tUCP/tLCP), (tUTP/tLTP) and (tUHP/tLHP) are preferably set in a range of not less than 0.8, but not more than 1.3.
On the other hand, if a ball is struck at a point in the lower portions (LTP, LHP, LCP), there is a tendency that a large amount of backspin is given to the struck ball due to a vertical gear effect which results in a loss of the carry distance. This type of carry loss can be reduced by making the average thicknesses of the lower portions smaller than the average thicknesses of the upper portions, respectively. From this standpoint, therefore, it is preferable that the above-mentioned ratios (tUCP/tLCP), (tUTP/tLTP) and/or (tUHP/tLHP) are more than 1.0, more preferably not less than 1.1.
Furthermore, if the difference in the average thickness between the heel portions (UHP, MHP, LHP) and the toe portions (UTP, MTP, LTP) is large, the rigidity balance is lost, and deformation/distortion tends to concentrate in the heel portions or toe portions. Therefore, the ratios (tMTP/tMHP), (tUTP/tUHP) and (tLTP/tLHP) are preferably set in a range of not less than 0.8, but not more than 1.3.
In general, the head speed at the ball impact point becomes lower in the heel portions than in the toe portions, and as a result, the carry distance has a tendency to decrease when hitting at the heel portions than the toe portions. This type of decrease in the carry distance can be minimized by increasing the coefficient of restitution in the heel portions. From this point of view, it is more preferable that the radios (tMTP/tMHP), (tUTP/tUHP) and (tLTP/tLHP) are more than 1.0, preferably not less than 1.1.
In
In
The thickness transitional zones 11 in this example include a toe-side thickness transitional zone lit and a heel-side thickness transitional zone 11h. The toe-side thickness transitional zone lit extends from the upper edge to the lower edge of the backside 3i through the five portions UTP, UCP, MCP, LCP and LTP. The heel-side thickness transitional zone 11h extends from the upper edge to the lower edge of the backside 3i through the five portions UHP, UCP, MCP, LCP and LHP, three of which are common to the toe-side thickness transitional zone 11t.
The thick part 13 is formed between the toe-side and heel-side thickness transitional zones 11t and 11h so as to includes: a upper thick part 13a extending along the upper edge of the backside 3i from a middle point of the UHP to a middle point of the UTP; a lower thick part 13b extending along the lower edge of the backside 3i from a middle point of the LHP to a middle point of the LTP; and a narrower vertical thick part 13c extending between the upper and lower thick parts 13a and 13b through the MCP. As a result, the thick part 13 has a shape of capital H rotated by 90 degrees.
In order to satisfy the above-mentioned condition (a) “tUTP<tUCP>tUHP”, with respect to the percentage of the occupied area of the thick part 13 in each of the portions UTP, UHP and UCP, a relationship “UTP<UCP>UHP” is satisfied. Further, in order to satisfy the condition (c) “tLTP<tLCP>tLHP”, with respect to the percentage of the occupied area of the thick part 13 in each of the portions LTP, LCP and LHP, a relationship “LTP<LCP>LHP” is satisfied.
Furthermore, to satisfy the condition (b) “tMTP<tMCP>tMHP”, with respect to the percentage of the occupied area of the thick part 13 in each of the portions MTP, MCP and MHP, a relationship “MTP<MCP>MHP”, particularly “MTP=0<MCP>MHP=0”, is satisfied.
similarly, a relationship “UTP>MTP<LTP” and a relationship “UHP>MHP<LHP” are satisfied to meet the other conditions (d) and (e).
Wood-type golf club heads (volume 460 cc, loft 11 degrees) were made and tested for the carry distance and durability.
Except for the thickness distributions, all the heads had identical two-piece structures each composed of an open-front main body and a face plate with a turnback as shown in
In Exs. 1 to 3 and Refs. 1 and 2, as shown in
Ex. 4 had a H-shaped thick part as shown in
The heads were attached to identical FRP shafts to make 45-inch drivers, and each club was attached to a swing robot and repeatedly struck a ball at a head speed of 45 m/s while changing the impact point. The impact point was the following five points at (1) the sweet spot SS in MCP, (2) 30 mm toe-side of SS in MTP, (3) 30 mm heel-side of SS in MHP, (4) 15 mm upside of SS in UCP and (5) 15 mm downside of SS in LCP. At each of the impact points, five shots were made to obtain the average carry distance. The results are shown in Table 1.
Further, using the same swing robot and club, a durability test was carried out with an increased head speed of 54 m/s and the impact point fixed to the sweet spot SS. In the test, golf balls were struck successively up to 5000 times. The results are indicated in Table 1, wherein “OK” means that there was no damage after the 5000 shots. “NO” means that the face was broken before reaching to 5000 shots.
As apparent from the test results, the average carry distances of the example heads were significantly increased when compared with the reference heads, and with respect to the durability, the example heads compared favorably with the reference heads.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-285348 | Oct 2006 | JP | national |
