Patent Application
20120322577
This Application claims priority from Japanese Patent Application No. 2011-132441 filed Jun. 14, 2011, which is incorporated herein by reference in its entirety.
The present invention relates to a golf club head, more particularly to a golf club head which has an improvement by being providing with a back surface thereof with a thick portion.
In most of recently marketed wood club heads, at least a face portion thereof is formed of metallic material. The face portion needs to be so thick as to maintain strength capable of withstanding an impact when a ball is hit. Although currently the size of the head has tended to be increased, large heads of 460 cm3, which is near the upper official limit stipulated by golf rules, have taken most of the share of marketed driver heads because the driver head must be formed in a volume smaller than 460 cm3+allowance of 10 cm3.
If the head size is so expanded, the weight of the face portion is increased. Thus, generally, while reduction of the weight of the face portion has been currently attempted, the thickness of the face portion has been decreased in order to maintain strength of the face portion and a measure of providing the back side of the face portion with ribs has been adopted. For example, Japanese Patent Application Publication No. 2006-141806 discloses that a golf club head includes six ribs extending from a central portion of the face toward the periphery of its face.
If a rib is provided in the shape of a letter X on the central portion of the back surface of the face portion, resilience property of the face portion drops drastically when a ball is hit on the sole side or the crown side off the face center, as compared to a case where a ball is hit on the face center. To solve this problem, Japanese Patent Application Publication No. 2008-36050 discloses that the thickness of four division faces on the back side of the face, which are defined by dividing with ribs is so determined that the thicknesses of the divided faces on the sole side and the crown side are smaller than those on the toe side and the heel side.
Conventionally, a number of highly resilient heads having coefficients of restitution considerably increased have been invented. However, it has been officially determined that the high-restitution heads whose coefficient of restitution is 0.830 or more cannot be used in a game from 2008 onward. Accordingly, a golf club whose coefficient of restitution at a center of its face portion is suppressed has been currently developed. However, it has been verified that if the coefficient of restitution at the center of the face portion is suppressed, the resilience property of face surface areas other than the center is lower on the sole side than on the crown side.
In view of the above-described problem, accordingly, an object of the present invention is to provide a golf club head in which with the weight of its face portion reduced and the strength of its face portion maintained, the resilient property of its face center is held within a range complying with the golf rule and even if a ball is hit off the face center, substantially the same resilience property as when the ball is hit at the face center can be
To achieve the above object, the present invention provides a golf club head having a hollow internal structure, the golf club head comprising a face portion, a crown portion, a sole portion, and a hosel portion, wherein the face portion contains, on an internal surface, a central portion Of the face portion, a C-shaped outer peripheral portion having an opening on the side of the hosel portion, at least four main ribs extending from the central portion to an outer edge of the face portion and an intermediate portion located between the central portion and the outer peripheral portion or the hosel portion, wherein the intermediate portion is divided into at least four areas: toe side area, heel side area, crown side area and sole side area with the at least four main ribs, wherein the thicknesses of the toe side area and the heel side area in the intermediate portion are greater than the thickness of the outer peripheral portion and the thicknesses of the crown side area and the sole side area in the intermediate portion are less than the outer peripheral portion.
The thickness of the crown side area of the intermediate portion may be defined to be greater than the thickness of the sole side area of the intermediate portion. The thickness of the heel side area of the intermediate portion may be defined to be greater than the thickness of the toe side area of the intermediate portion.
The face portion may contain, on the internal surface, reinforcement ribs extending from the central portion toward the outside of the face portion.
According to the present invention, the C-shaped outer peripheral portion having the opening on the side of the hosel is provided on the internal surface of the face portion. Then, the intermediate portion located on the central side relative to the outer peripheral portion is divided into four areas with at least four main ribs extending from the central portion to the outer edge of the face portion. The thicknesses of the toe side area and the heel side area in the intermediate portion are defined to be greater than the thickness of the outer peripheral portion. The thicknesses of the crown side area and the sole side area in the intermediate portion are defined to be less than the thickness of the outer peripheral portion. Consequently, with a current trend of reducing the weight of the face portion maintained, the strength of the face portion can be secured and the resilience property of the face can be held within a range complying with the golf rules. Furthermore, even if a ball is hit off the face center, a substantially uniform resilience property can be exerted.
Hereinafter, an embodiment of a golf club head according to the present invention will be described in detail with reference to the accompanying drawings. The sectional views of
As show in
As shown in
Main ribs 12 are formed on the surface on the rear side of the face member 10 such that they extend from the intersection portion 17 to an outer edge of the face portion 11. A first main rib 12a extends from the intersection portion 17 toward the toe side of the crown portion, a second main rib 12b extends from the intersection portion 17 toward the heel side of the sole portion 21, a third main rib 12c extends from the intersection portion 17 toward the heel side of the crown portion 22, particularly toward the hosel portion, and a fourth main rib 12d extends from the intersection portion 17 toward the toe side of the sole portion 21. These main ribs 12 are connected to each other via the intersection portion 17 disposed in the center of the face portion 11. The four main ribs 12 extend from the intersection portion 17 located in the center of the face portion 11 to suppress the resilience property at the central portion of the face portion 11.
The intermediate portion 15 is divided into four areas by the first to fourth main ribs 12a to 12d. That is, the four areas are a toe side area 15a located between the first main rib 12a and the fourth main rib 12d, a sole side area 15b located between the second main rib 12b and the fourth main rib 12d, a crown side area 15c located between the first main rib 12a and the third main rib 12c and a heel side area 15d located between the second main rib 12b and the third main rib 12c. On the other hand, although the outer peripheral portion 14 is separated by the main rib 12, the separated areas of the outer peripheral portion 14 have an equal thickness, so that they can be handled as an integral part.
As shown in
Of the four main ribs 12, at least one main rib may be formed so that the thickness of its thickest portion is different from the thickness of the other main ribs. As shown in
Preferably, a difference in thickness of the main rib between the crown side and the sole at the thickest portion of each rib is approximately 0.2 mm or more, more preferably approximately 0.3 mm or more. On the other hand, the upper limit of the difference in thickness is preferred to be approximately 0.7 mm or less, more preferably approximately 0.6 mm or less. Furthermore, of the first to fourth main ribs 12 to 15, a difference in thickness between a thickest portion of the thinnest main rib and a neighboring peripheral portion 19 is required to be at least approximately 0.3 mm or more, is preferred to be approximately 0.5 mm or more, and is more preferred to be approximately 0.6 mm or more. On the other hand, the upper limit of this difference in thickness is preferred to be approximately 2.0 mm or less and is more preferred to be approximately 1.8 mm or less.
Preferably, the four main ribs 12 are formed in a substantially equal width. The width of the main rib 12 is preferred to be approximately 2 mm or more at a portion in contact with the face back surface, and is more preferred to be approximately 3 mm or more. On the other hand, the upper limit of the width of the main rib 12 is preferred to be approximately 12 mm or less and is more preferred to be approximately 10 mm or less.
Reinforcement ribs may be formed on the back surface of the face portion 11. As the reinforcement rib, as shown in
The reinforcement rib 13 is formed like the main ribs so that the thickness thereof in the center is the greatest while the thickness decreases toward the intermediate portion. On the other hand, as shown in
The reinforcement rib 13 may be formed from the center of the face portion up to a halfway position relative to the outer edge. The length of the reinforcement rib 13 is preferred to be approximately 45% or more a distance from the center of the face portion 11 up to the outer edge, and is more preferred to be approximately 50% or more. On the other hand, the upper limit of the length of the reinforcement rib 13 is preferred to be approximately 90% or less and is more preferred to be approximately 85% or less. Thus, the reinforcement rib 13 may be formed in only the intermediate portion 15 as shown in
The thickest portion of the reinforcement rib 13 may be formed in the same thickness as a thickest portion of the thickest main rib of the four main ribs 12 or in a lesser thickness or in a greater thickness. Both in the case of increasing and decreasing the thickness, a difference in thickness therebetween is preferred to be approximately 0.1 mm to approximately 0.5 mm. The width of the reinforcement rib 13 is preferred to be approximately 2 mm or more at the thickest portion and is more preferred to be approximately 3 mm or more. On the other hand, the upper limit of the width of the reinforcement rib 13 is preferred to be approximately 12 mm or less and is more preferred to be approximately 10 mm or less.
The outer peripheral portion 14 of the face portion 11 and the four divided intermediate portions 15, i.e., the toe side area 15a, the sole side area 15b, the crown side area 15c and the heel side area 15d have a substantially equal thickness in each portion. However, as shown in
The width of the C-shaped outer peripheral portion 14 is preferred to be approximately 20% or more a distance from the intersection portion 17 of each main rib 12 up to the outer edge of the face portion 11 and is more preferred to be approximately 25% or more. On the other hand, the upper limit of this width is preferred to be approximately 40% or less and is more preferred to be approximately 35% or less.
The difference in thickness between the toe side area 15a or the heel side area 15d in the intermediate portion and the outer peripheral portion 14 is preferred to be approximately 0.025 mm or more, more preferred to be approximately 0.05 mm or more and further preferred to be approximately 0.1 mm or more. On the other hand, if the difference in thickness is excessive, no uniform resilience property may be obtained in some cases. Therefore, the upper limit of the difference in thickness is preferred to be approximately 0.5 mm or less and is more preferred to be approximately 0.4 mm or less. Furthermore, the difference in thickness between the sole side area 15b or the crown side area 15c and the outer peripheral portion 14 is preferred to be approximately 0.025 mm or more, is more preferred to be approximately 0.05 mm or more and is further preferred to be approximately 0.1 mm or more. On the other hand, if the difference in thickness is excessive, no uniform resilience property may be obtained in some cases. Therefore, the upper limit of the difference in thickness is preferred to be approximately 0.5 mm or less and is more preferred to be approximately 0.4 mm or less.
The thicknesses of the sole side area 15b and the crown side area 15c may be equal to or different from each other. However, preferably, to equalize the coefficient of restitution of the sole side with that of the crown side as much as possible, preferably, the thickness of the sole side area 15b is less than that of the crown side area 15c as shown in
The thicknesses of the toe side area 15a and the heel side area 15d may be equal to or different from each other. However, preferably, to equalize the coefficient of restitution of the toe side with that of the heel side as much as possible, the thickness of the toe side area 15a is less than that of the heel side area 15d as shown in
As shown in
The thickness of the central portion 18 is greater than the thickness of a thickest portion of the main rib having the largest thickness of the four main ribs 12. A difference in thickness is preferred to be approximately 0.1 mm to approximately 0.5 mm. Furthermore, as shown in
As shown in
Although the thickness of the intermediate portion 15 in the face member 10 differs between the toe side area 15a, the sole side area 15b, the crown side area 15c and the heel side area 15d as described above, it is preferred to be approximately 1.0 mm or more and is more preferred to be approximately 1.5 mm or more. On the other hand, the upper limit of the thickness of the intermediate portion 15 is preferred to be approximately 3.0 mm or less and is more preferred to be approximately 2.5 mm or less. There exists a difference in thickness between the outer peripheral portion 14 of the face member 10 and the intermediate portion 15 as described above, and the thickness of the outer peripheral portion 14 is preferred to be approximately 1.0 mm or more and is more preferred to be approximately 1.5 mm. On the other hand, the upper limit of the thickness of the outer peripheral portion 14 is preferred to be approximately 3.0 mm or less and is more preferred to be approximately 2.5 mm or less.
Although there exists a difference in thickness between one main rib and another main rib, and between the main rib and the intermediate portion 15 or the outer peripheral portion 14, the thickness of the thickest portion of each of the four main ribs 12a to 12d of the face member 10 is preferred to be approximately 3.0 mm or more and is more preferred to be approximately 3.2 mm or more. On the other hand, the upper limit of the thickness of the four main ribs 12a to 12d is preferred to be approximately 4.2 mm or less and is more preferred to be approximately 4.0 mm or less. Furthermore, the thickness of the thickest portion of the reinforcement rib 13 of the face member 10 is preferred to be approximately 3.0 mm or more and is more preferred to be approximately 3.2 mm or more. On the other hand, the upper limit of the thickness of the reinforcement rib 13 is preferred to be approximately 4.2 mm or less and is more preferred to be approximately 4.0 mm or less. There exists a difference in thickness between the central portion 18 of the face member 10 and the main rib 12 as described above, and the thickness of the central portion 18 is preferred to be approximately 2.5 mm or more and is more preferred to be approximately 2.7 mm or more. On the other hand, the upper limit of the thickness of the central portion 18 is preferred to be approximately 4.0 mm or less and is more preferred to be approximately 3.8 mm or less.
The first main rib 12a is preferred to be inclined toward the toe side relative to vertical. Furthermore, the second main rib 12b is preferred to be inclined toward the heel side relative to the vertical. By inclining the first and second main ribs 12a, 12b in this way, the resilience property along a direction from the toe upper side to the heel lower side, where hitting points by amateur golfers concentrate, can be extracted to a maximum extent. More specifically, an angle θa of the central axis 31 of each of the first main rib 12a and the second main rib 12b with respect to a ground line 30 when the golf club head 1 is placed on an ordinary address position as shown in
The third main rib 12c is preferred to be inclined toward the crown side or the hosel side relative to horizontal. The fourth main rib 12d is preferred to be inclined toward the sole side relative to horizontal. By inclining the third main rib 12c and the fourth main rib 12d in this way, the resilience property in the upper area of the toe can be extracted to a maximum extent. More specifically, an inclination θb of a central axis 32 of the third main rib 12c and the fourth main rib 12d with respect to the ground line 30 is preferred to be approximately 5° or more and is more preferred to be approximately 10° or more. On the other hand, the upper limit of the rib inclination angle θb is preferred to be approximately 80° or less and is more preferred to be approximately 70° or less.
Preferably, a central axis 33 of the reinforcement rib 13 divides an angle formed by the central axis 31 of the first and second main ribs and the central axis 32 of the third and fourth main ribs to equal two parts (that is, the central axis 33 has an angle θc on each side with respect to both the central axes 31, 32). Preferably, an inclination of the long axis of the ellipse of the intersection portion 17 divides the angle formed by the central axis 31 of the first and second main ribs and the central axis 32 of the third and fourth main ribs to equal two parts like the central axis 33 of the reinforcement rib 13.
It is permissible to curve the first main rib 12a and the second main rib 12b smoothly in an S shape or a Z shape along the central axis 31 instead of a straight line. Furthermore, it is also permissible to curve the third main rib 12c and the fourth main rib 12d smoothly in an S shape or a Z shape along the central axis 32 instead of a straight line. By curving the main ribs 12 smoothly in this way, both the areas of the sole side area 15b and the crown side area 15c in the intermediate portion can be increased.
The face member 10 may be formed by forging or casting. As the material of the face member 10, titanium, titanium alloy or stainless steel may be used. The volume of the golf club head 1 is preferred to be approximately 100 cc or more and is more preferred to be approximately 150 cc or more. On the other hand, the volume of the golf club head 1 is preferred to be approximately 500 cc or less and is more preferred to be approximately 460 cc or less. Furthermore, the weight of the golf club head 1 is preferred to be approximately 170 g or more and is more preferred to be approximately 175 g or more. On the other hand, the weight of the golf club head 1 is preferred to be approximately 250 g or less and is more preferred to be approximately 245 g or less.
Although the above-described embodiment contains the reinforcement rib 13 as shown in
A golf club head according to the present invention was manufactured and the coefficient of restitution (COR) of its face portion was evaluated. In this embodiment, a characteristic time (CT) was measured instead of measuring the COR value actually. The CT value is a quantitative value capable of measuring the spring effect of the face adopted by the United States Golf Association (USGA) and the Royal and Ancient Golf Club of St. Andrews (R&A) and can be measured with a portable pendulum machine approved by the R&A Rules Limited. Generally, the more the face is deflected, the less energy is lost and the initial velocity of a ball is higher. Thus, the CT value indicates the deflection with a contact time between the ball and the face. Currently, the upper limit of the CT value is defined to be 257 (defined value of 239+allowance of 18) μseconds.
As the golf club head of this example, the configuration shown in
As the common conditions of the face portion, the width of the face portion was set to 75 mm and the height thereof was set to 43 mm. The first to fourth main ribs were tilted in the same way as
With this example and the comparative example, the CT values were measured at hitting points of a ball. As shown in
Under the above-described condition, the CT values of the respective hitting points of the example and the comparative example were measured. Table 2 and Table 3 show the measurement results. Based on those measurement results of the hitting points, the CT values of the entire face portion within the hitting area were calculated.
As shown in Table 2, Table 3,
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-132441 | Jun 2011 | JP | national |
