This application claims the benefit of foreign priority to Japanese Patent Application No. JP2022-033819, filed Mar. 4, 2022, which is incorporated by reference in its entirety.
The present disclosure relates to a golf club head having a hollow portion therein and a method for manufacturing the same.
According to the Rules of Golf set forth by the United States Golf Association (USGA), golf club heads must not have a spring-like effect that exceeds the upper limit set forth in the Pendulum Test Protocol. Specifically, the CT (Characteristic Time) value of golf club heads is regulated to be less than a specified value. As a technology for controlling the CT value, the following patent document 1 has been proposed.
Japanese Unexamined Patent Application Publication No. 2019-181007
Various manufacturing errors may occur during the process of mass production of golf club heads. In consideration of such manufacturing errors, golf club manufacturers produce golf club heads with a CT value much lower than the upper limit of the Rules of Golf, and then adjust the CT so that it is below the upper limit of the Rules of Golf and close to the upper limit. For example, this adjustment includes a process of grinding the striking faces of golf club heads.
However, the shape of the striking face of golf club heads has a great influence on the trajectory of hit balls, such as the launch angle and the amount of spin. Therefore, the conventional process of adjusting the CT may cause changes in the trajectory of hit balls.
The present disclosure has been made in view of the above circumstances and has a main object to provide a golf club head capable of adjusting the rebound performance while suppressing changes in the trajectory of hit balls, and a manufacturing method thereof.
In one aspect of the present disclosure, a golf club head with a hollow portion therein, the head includes a face portion, and a main body including a crown portion and a sole portion each extending backwardly from the face portion. The main body is provided with at least one slit that penetrates the main body and extends in a head-front-back direction. The at least one slit includes a pair of slit inner walls extending in the head-front-back direction and at least one joint connecting the pair of slit inner walls to each other.
Hereinafter, one or more embodiments of the present disclosure will be described below based on the drawings.
Throughout the embodiments, the same elements and portions are denoted by the same reference characters, and duplicate explanations are omitted.
In
As used herein, an x-y-z coordinate system is associated with the head 1. The x-axis is defined as the axis orthogonal to the reference vertical plane VP and parallel to the horizontal plane HP. The y-axis is parallel to both the reference vertical plane VP and the horizontal plane HP. The z-axis is defined as the axis orthogonal to both the x-axis and y-axis. For the head 1, the direction along the x-axis is defined as the head-front-back direction, the direction along the y-axis as the toe-heel direction, and the direction along the z-axis as the head-up-down direction. The side of the face portion 2 is the front side and the opposite side is the back side with respect to the head-front-back direction.
The head 1 is essentially made of metal material and has a hollow portion (i) therein, as shown in
As metal materials for the head 1, stainless steel, maraging steel, titanium, titanium alloys, magnesium alloys, aluminum alloys, etc. are suitable, for example. Fiber-reinforced resin may be used as a part of the head 1.
As illustrated in
The head 1 includes the face portion 2 and a main body 3 extending backwardly from the face portion 2. The main body 3, for example, includes a crown portion 4, a sole portion 5 and the hosel portion 7, at least. In
The face portion 2 is the portion that strikes a ball and is formed on the front side of the head 1. The face portion 2 includes a striking face 2a that is in direct contact with the ball. The face portion 2 has a relatively large wall thickness to prevent damage during ball striking. In some preferred aspects, the face portion 2 has a greater thickness than those of the crown portion 4, the sole portion 5, and the like. The thickness of the face portion 2 is not particularly limited, but is, for example, equal to or more than 2.0 mm, preferably equal to or more than 2.2 mm. On the other hand, in order to allow the face portion 2 to flex sufficiently when striking the ball, the thickness of the face portion 2 is, for example, equal to or less than 4.0 mm, preferably equal to or less than 3.8 mm.
The face portion 2 includes a periphery E defining the boundary of the striking face 2a. As used herein, the periphery E of the face portion 2 is the ridge line if it is visible to the naked eye as a clear ridge line. On the other hand, if such a ridge line is not clearly formed, the periphery E of the face portion 2 is obtained as follows. First, as illustrated in
The crown portion 4 extends from the periphery E of the face portion 2 backwardly of the head so as to form an upper surface of the head. The hosel portion 7 is provided on the heel side of the crown portion 4. The hosel portion 7 has the shaft insertion hole 7a for fixing a shaft (not illustrated). The crown portion 4 is the portion excluding the face portion 2 and the hosel portion 7 in a plan view of the head shown in
As illustrated in
The main body 3 is provided with at least one slit 10 that penetrates the main body 3. In some preferred embodiments, at least one of the crown portion 4 and the sole portion 5 is provided with a plurality of slits 10. The plurality of slits 10 is spaced in the toe-heel direction of the head. In the example of
Specifically, the crown portion 4 has two slits 10, which are located on the toe and heel sides with respect to the head-front-back direction line FCL of the head passing through the face center FC. In addition, the sole portion 5 has three slits 10, which are distributed on the toe side and heel side of the head-front-back direction line FCL and on the head-front-back direction line FCL. The face center FC is the position of each center in the toe-heel direction and the head-up-down direction of the striking face 2a. Alternatively, one or more slits 10 may be provided only in the crown portion 4 or only in the face portion 2. Further, only one slit 10 may be provided in the crown portion 4, or may be provided in the sole portion 5.
When the ball is struck with the striking face 2a of the face portion 2, the crown portion 4 and the sole portion 5, which are connected to the face portion 2, are subjected to tensile deformation in the toe-heel direction in addition to bending deformation in the head-front-back direction. On the other hand, one or more slits 10 can locally reduce the tensile stiffness of the main body 3 (e.g., the crown portion 4 and/or the sole portion 5) in the toe-heel direction. Thus, the main body 3 with one or more slits 10 can flex (stretch) more in the toe-heel directions, starting from the slits 10, and can contribute to the flexion of the face portion 2. This has the advantage of expanding the highly resilient area of the face portion 2 in the direction of the area provided with the slits.
In order to effectively promote the deflection in the toe-heel direction of the main body 3 as described above, the length L of the slits 10 is, for example, equal to or more than 10 mm, preferably equal to or more than 12 mm, more preferably equal to or more than 15 mm. On the other hand, if the length L of the slits 10 is excessively large, the durability of the main body 3 may decrease. From this point of view, the length L of the slits 10 is, for example, equal to or less than 40 mm, preferably equal to or less than 30 mm, more preferably equal to or less than 25 mm.
In order to effectively promote the deflection in the toe-heel direction of the main body 3, the width W of the slits 10 is, for example, equal to or more than 0.5 mm, preferably equal to or more than 1 mm, more preferably equal to or more than 2 mm. On the other hand, a larger width W of the slits 10 may decrease the durability of the main body 3. From this point of view, the width W of slits 10 is, for example, equal to or less than 10 mm, preferably equal to or less than 8 mm, more preferably equal to or less than 6 mm. The width W of the slits 10 can be constant or variable.
In order to effectively promote the deflection in the toe-heel direction of the main body 3, the slits 10 are preferably placed closer to the face portion 2. As illustrated in
As illustrated in
The joints 12 according to the present embodiment can be used as an adjusting member to adjust the tensile stiffness of the main body 3 in the toe-heel direction of the head. For example, after the head 1 has been manufactured, at least one joint 12 of at least one slit 10 may be at least partially removed, if necessary. The slit 10, from which the joint 12 has been removed partially, can reduce the tensile stiffness of the main body 3 in the toe-heel direction without substantially changing the bending stiffness of the main body 3 in the head-front-back direction, compared to other slits 10 where the joint 12 has not been removed. Such a slit 10 can help to provide a greater deflection (elongation) of the main body 3 in the toe-heel directions when striking the ball, and can increase the rebound performance, i.e., the CT, at the striking position corresponding to the slit 10. Although the tensile stiffness in the toe-heel direction of the main body 3 changes with the presence or absence of the joints 12 and the number of joints 12, the change in the bending stiffness in the front-back direction of the head can be very small. The present disclosure takes note of this point and changes the tensile stiffness in the toe-heel direction with little change in the bending stiffness of the main body 3 in the head-front-back direction, depending on the presence or absence and the number of joints 12. This makes it possible to adjust the rebound performance without changing the spin and launch angle of hit balls. The change (decrease) in the bending stiffness of the main body 3 in the head-front-back direction may change the orientation of the striking face 2a (increasing the rotation) when a ball is struck, changing the spin and launch angle of hit balls. Therefore, such changes are undesirable.
For example, in the crown portion 4 and/or the sole portion 5, if one or more joints 12 of the slit 10 on the toe side are removed, the CT of the toe side of the striking face 2a can be increased. Further, in the crown portion 4 and/or the sole portion 5, if one or more joints 12 of the slit 10 on the heel side are removed, the CT of the heel side of the striking face 2a can be increased. Furthermore, in the sole portion 5, if one or more joints 12 of the slit 10 in the center are removed, the CT near the face center FC can be increased. Therefore, it is possible to adjust the CT of the head 1 without grinding the face portion 2.
When a plurality of joints 12 is provided in each slit 10, one or more joints 12 may be removed. When a plurality of joints 12 is provided in the head-front-back direction, the margin of improvement of CT can be adjusted arbitrarily by changing the number of joints 12 to be removed.
The shape of the joint 12 is not particularly limited. For example, the joints 12 may have a cylindrical or prismatic shape extending in the toe-heel direction of the head. In the embodiment of
In this embodiment, the joints 12 extends in the toe-heel direction with a constant cross-sectional area. In another embodiment, the joints 12 may be formed with the same wall thickness as the main body 3. The joints 12 may also be varied such that their cross-sectional area is locally increased or decreased. Furthermore, the joints 12 and the slit inner walls 11 may be connected by a smooth circular arc surface (not illustrated) in order to reduce stress concentration thereon.
In order to effectively achieve the adjusting effect of the rebound performance, in a plan view of each slit 10a, a total joint projected area is preferably equal to or less than 0.8 times the total projected area of the slit 10 including the joints 12. In the embodiment of
In the example, the first portion 101 extends with a constant width. A plurality of joints 12 is formed in the first portion 101.
The width of the second portion 102 is larger than that of the first portion 101. Such a slit 10 can help to effectively suppress the stress increase near the backmost end 10b of the slit 10, where the deformation of the main body 3 is likely to increase. In some preferred embodiments, the width of the second portion 102 is equal to or more than 1.5 times the width of the first portion 101, more preferably equal to or more than 2.0 times.
Around the slit 10, a thick-walled portion 13 is formed by locally increasing the thickness of the main body 3. When the ball is struck, the area around the slit 10 of the main body 3 is subject to high stress due to the bending stress caused by bending in the head-front-back direction and the tensile stress caused by tensile deformation in the toe-heel direction. Strictly speaking, the slit 10 also slightly reduces the bending rigidity in the head-front-back direction. However, when the thick-walled portion 13 is formed as described above, the decrease in bending rigidity in the head-front-back direction can be suppressed while the tensile rigidity in the toe-heel direction is locally decreased. In addition, the slit 10 with the thick-walled portion 13 can disperse the stress in the periphery of the slit 10 and suppress the local increase in stress.
The thick-walled portion 13 is provided, for example, adjacent to the slit 10. The thick-walled portion 13 is formed by locally increasing the wall thickness of the main body 3, as shown in
As shown in
The inner thick-walled portion 13a is, for example, raised on the hollow portion (i) side. The inner thick-walled portion 13a is annularly formed around the slit 10. The inner thick-walled portion 13a is effective in relaxing the stresses around the slit 10 of the main body 3. The inner thick-walled portion 13a rises from the inner surface 4i of the reference thick-walled portion 13c formed by the reference thickness tc of the main body 3 (in this example, the crown portion 4) toward the hollow portion (i). The thickness boundary between the inner thick-walled portion 13a and the reference thick-walled portion 13c is a virtual boundary defined by a smooth extension of the inner surface 4i of the reference thick-walled portion 13c to the slit 10.
Although a thickness ta of the inner thick-walled portion 13a is not particularly limited, it is preferably, for example, equal to or more than 0.5 mm, preferably equal to or more than 1.0 mm, more preferably equal to or more than 1.5 mm, in order to fully demonstrate the stress reduction effect in the area around the slit 10. In order to suppress the weight increase of the head 1, the thickness ta of the inner thick-walled portion 13a is, for example, equal to or less than 5.0 mm, preferably equal to or less than 4.0 mm, more preferably equal to or less than 3.0 mm.
The outer thick-walled portion 13b is, for example, raised on the outer surface of the head. The outer thick-walled portion 13b may form the thick-walled portion 13 together with the inner thick-walled portion 13a or in place of the inner thick-walled portion 13a. The outer thick-walled portion 13b rises outwardly from the outer surface 4o of the reference thick-walled portion 13c formed by the reference thickness tc of the main body 3 (in this example, the crown portion 4). The thickness boundary between the outer thick-walled portion 13b and the reference thick-walled portion 13c is a virtual boundary defined by a smooth extension of the outer surface 4o of the reference thick-walled portion 13c to the slit 10.
As shown in
As shown in
A width TW of the inner thick-walled portion 13a and the outer thick-walled portion 13b (shown in
Referring now to
As shown in
The grooves 20 can provide the same advantages as the slits 10 of the first embodiment. That is, the grooves 20 can locally reduce the stiffness of the main body 3 (for example, the crown portion 4 and/or the sole portion 5) in the toe-heel direction without substantially changing the bending stiffness in the head-front-back direction. Thus, the main body 3 with the grooves 20 can flex more greatly in the toe-heel direction when the ball is struck, starting from the grooves 20. This expands the highly resilient area of the face portion 2 in the direction of area provided with the grooves 20.
As in the first embodiment, the joints 23 provided in each groove 20 can be used as an adjusting member to adjust the tensile stiffness of the head body 3 in the toe-heel direction of the head. For example, after the head 1 is manufactured, at least one joint 23 of any groove 20 may be at least partially removed, if necessary. The groove 20 from which one or more joints 23 have been removed will reduce the tensile stiffness of the main body 3 in the toe-heel direction more than the other grooves 20 from which the joints 23 have not been removed. Such a groove 20 can provide greater deflection of the main body 3 in the toe-heel directions when striking the ball, and can expand the high repulsion area (increase the CT value) in the direction where the groove 20 is located. Thus, the head 1 according to this example can also adjust the CT value without grinding the face portion 2. In other words, the rebound performance of the head 1 can be adjusted while preventing changes in the trajectory of hit balls.
When a plurality of joints 23 is provided in one groove 20, one or more joints 23 may be removed. When a plurality of joints 23 is provided in the head-front-back direction, the margin of CT improvement can be adjusted arbitrarily by changing the number of joints 23 to be removed. In addition, the length L, width W, and the location of the slits 10 described in the first embodiment can be applied to the length, width, and the location of the grooves 20 of the second embodiment, respectively.
In the head 1 according to the first and second embodiments, a cover (not illustrated) made of an elastic material such as rubber, resin, elastomer, etc. may be provided to cover a void of each slit 10 and/or each groove 20. Such a cover can prevent foreign objects from entering the slits 10 and/or grooves 20 without interfering with the deformation of the main body 3 in any way.
Next, a method for manufacturing a golf club head of the present embodiment will be described. The process procedure of this manufacturing method is shown in
As shown in
Next, the manufacturing method according to this embodiment includes a second step of measuring a CT value of the first golf club head (step S2).
Preferably, the CT value is measured at a plurality of positions on the striking face 2a of the head 1 in
Next, the manufacturing method according to this embodiment includes the process of determining whether one or more measured CT values are smaller than a predetermined threshold value (step S3). For example, if a manufacturer of the first golf club head try to improve the maximum CT value of the first golf club head (hereinafter referred to as “CTmax”), the CTmax of the first golf club head is compared with the threshold value. The threshold value, for example, can be determined in various ways based on the upper limit of CT value (239 µs) specified in the Rules of Golf. For example, the threshold value may correspond to the upper limit of the CT. In another case, the threshold value may be set to a value slightly smaller than the upper limit in consideration of measurement errors, etc.
The manufacturing method according to the present embodiment then includes the process of obtaining a second golf club head by at least partially removing at least one of the joints 12 of the first golf club head if the concerned CT value is smaller than the predetermined threshold value (Yes in step S3). Thus, the second golf club head has at least one slit 10 from which one or more joints 12 have been removed, as shown in
For example, if the CTmax of the first golf club head is smaller than the threshold value, one or more joints 12 at a given position may be removed. The number of joints to be removed is determined according to the difference between the CTmax and the threshold value. For example, it is preferable that the larger the difference is, the more the number of joints 12 to remove. Further, one or more joints 12 closest to the position of the CTmax in the toe-heel direction may be selected to be removed as joints 12 to be removed.
In order to increase the CTmax more effectively, the relationship among the number and position of the joints 12 to be removed, the CT improvement margin, and the position at which the CT values is improved may be determined in advance by experiments or simulations. In some preferred embodiments, the dimensions of the joints 12 may be designed so that the CT improves in a range of 2 to 4 µs by removing one of the joints.
If necessary, one or more CT values of the second golf club head in which one or more joints 12 have already been removed may be measured. In this case, if the difference between the CTmax of the second golf club head and the threshold value is larger than a predetermined value, the third step may be repeated.
In the above embodiment, the case of further increasing the CTmax is described, but this manufacturing method can also be used to adjust a distribution of CT values. For example, in many cases, a CT value of golf club heads tends to be low at the striking positions that are shifted from the face center FC to the toe or heel side. Thus, if the CT value at a toe-side striking position is smaller than the predetermined threshold value, removing one or more joints 12 at the toe-side slit 10 can effectively increase the CT value at the toe-side striking position while suppressing an excessive increase in the CTmax. Similarly, if the CT value at a heel-side striking position is smaller than a predetermined threshold value, removing one or more joints 12 at the heel-side slit 10 can effectively increase the CT value at the heel-side striking position while suppressing the excessive increase of the CTmax.
In the above embodiment, the first golf club head is the head 1 according to the first embodiment, but in another embodiment, the first golf club head may be the head 1 according to the second embodiment. That is, the first golf club head may include the face portion 2 and the main body 3 extending backwardly of the head from the face portion 2, wherein the main body 3 is provided with one or more grooves 20, each groove 20 comprising a pair of groove walls 21 extending in the head-front-back direction, a groove bottom 22, and at least one joint 23 locally rising from the groove bottom 22 and connecting the pair of groove walls 21.
While the particularly preferable embodiments in accordance with the present disclosure have been described in detail, the present disclosure is not limited to the illustrated embodiments, but can be modified and carried out in various aspects within the scope of the disclosure.
A wood-type golf club head shown in
The slits in the crown portion are arranged 24 mm away from the face center to the toe and heel sides and extend parallel to the head-front-back direction.
The minimum distance D between the crown portion slits and the periphery E of the face portion is 1.0 mm.
The slits in the sole portion extend parallel to the head-front-back direction and are arranged such that one is in the central region and two are in the toe and heel regions away from the face center to the toe and heel by 26 mm.
First, a CT value of the first golf club head with all joints left was measured. The CT values at major hitting positions were shown in
Next, in the first golf club head, all three joints of the center slit of the sole portion were removed by cutting to obtain the second golf club head. The major CT values of the striking face of the second golf club head were as shown in
The following is an example of another manufacturing method. For the first golf club head described above, all three joints of the toe-side slit of the sole portion were removed by cutting to obtain another second golf club head.
Furthermore, Table 1 shows the results of the hitting test using a swinging robot. The first golf club head and the second golf club head were used for the hitting test, and the same golf balls were hit under the same conditions. The backspin and launch angle of each ball were measured.
As a result of the test, the second golf club head shows no substantial difference in the trajectory of hit balls compared to the first golf club head, while the CT value of the face center was increased by 13 µs with respect to the first golf club head.
The present disclosure includes the following aspects.
A golf club head having a hollow portion therein, the head comprising:
The golf club head according to note 1, wherein
The golf club head according to note 1 or 2, wherein
the at least one joint comprises a plurality of joints.
The golf club head according to any one of notes 1 to 3, wherein
the at least one joint has a cylindrical or prismatic shape extending in a toe-heel direction of the head.
The golf club head according to any one of notes 1 to 4, wherein
The golf club head according to any one of notes 1 to 5, wherein
in a plan view of the at least one slit, a total joint projected area is equal to or less than 0.8 times a projected area of the slit including the at least one joint.
The golf club head according to any one of notes 1 to 6, wherein
a thick-walled portion in which a thickness of the main body is locally increased is formed around the at least one slit.
A golf club head having a hollow portion therein, the head comprising:
The golf club head according to note 8, wherein
the at least one joint comprises a plurality of joints.
The golf club head according to note 8 or 9, wherein
A method for manufacturing a golf club head, the method comprising:
A method for manufacturing a golf club head, the method comprising:
Number | Date | Country | Kind |
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2022-033819 | Mar 2022 | JP | national |