Patent Application
20050101406
The present invention relates to an iron type golf club head that is helpful to gain a large carry.
Conventionally, the orientation of a hit ball and the ease of lifting a ball has been thought more important than on the carry of a hit ball where an iron type golf club is concerned. However, in recent years, the technology for wood type golf clubs has improved, significantly increasing carry, and therefore, the difference in carry between iron type golf clubs and wood type golf clubs has been enlarged. As a result of this, recently, many golfers tend to place importance on the function also of iron type golf clubs in terms of carry.
In order to increase the function of golf clubs in terms of carry, it is considered to be effective to increase the coefficient of restitution of the head. The prior arts of Japanese published patent application No. 2001-129131, and No. 2001-29523 are examples, and describe that a dent or the like is provided on the back side of the face portion which hits a ball, so that a portion having a small thickness is provided.
However, there are many restrictions about a the head shape and the thickness of an iron type golf club head in comparison with a wood type golf club head, and it is not easy to increase the coefficient of restitution of an iron type golf club head.
An increase in the coefficient of restitution is a factor for increasing the initial speed of a hit ball, while the carry of the hit ball is not actually determined exclusively by the coefficient of restitution, but rather is significantly affected by the angle of the hit ball and the amount of backspin. In addition, the above described angle of the hit ball and the amount of backspin change depending on the point of the face where the ball is hit, thus, causing a variation in the carry.
Accordingly, it becomes important in order to gain a stable large carry, that a carry in the case where the hitting point of the face is shifted upward or downward from the sweet spot does not cause so different carry in comparison with the case where the hitting point is on the sweet spot of the face.
It is therefore, an object of the invention is to provide an iron type golf club head that makes it possible to gain a carry that is not so different from the case where the sweet spot hits a ball even in the case where the point of the face which hits a ball is shifted upward or downward from the sweet spot.
According to the present invention, a first aspect of the present invention is to provide an iron type golf club head in which an annular trench surrounding a central region that includes the sweet spot is provided on the back surface of the face portion, characterized in that, in the standard condition wherein the head is placed on a horizontal surface with prescribed lie angle and loft angle, the trench includes:
In the head of the present invention, the average trench width of the upper side trench portion in the trench is increased so as to secure a large range of a thin head portion region above the above described border plane in the face portion, and thereby, the rigidity of this region is relatively reduced in the head. As a result of this, in the case where a point above the sweet spot of the face surface hits a ball, a recoil effect is strongly exhibited in the ball so that the amount of backspin thereof can be reduced. Thus, even when the angle of the hit ball is large, the height of flight can be reduced, gaining a large carry.
Contrarily, the average trench width of the lower side trench portion in the trench is reduced so as to provide a thin head portion region in a small range below the above described border plane, and thereby, a reduction in the rigidity of this region is restricted. As a result of this, even in the case where a point on the face surface beneath the sweet spot hits a ball, the amount of backspin of the ball is increased and even a small angle of the hit ball allows the ball to gain a large carry. In addition, the center region that includes the sweet spot is surrounded by the annular trench, and therefore, the entirety of this center region is flexed due to the trench, and thereby, a large carry can be gained in the case where the sweet spot hits a ball.
Furthermore, the limitation of the numerals wherein the ratio (Wu/Wd) of the average trench width Wu of the upper side trench portion to the average trench width Wd of the lower side trench portion ranges from 2.5 to 5.0, allows the control of the above described amount of backspin to be suitably modified even in the case where a point above or below the sweet spot hits a ball, and thus, a effect can be expected, such that the reduction in the carry can be reduced in comparison with the case where the sweet spot hits a ball.
FIGS. 6(A) and FIGS. 6(B) are cross-sectional views illustrating the gear effect when a point on the upper and lower side, respectively, of the sweet spot SS hits a ball B:
In the following, the preferred embodiments of the present invention are described in reference to the drawings.
As shown in
A face attachment portion 10 having a cross-section in step form is formed in the periphery of the opening O. This face attachment portion 10 includes: an inside surface 7 that faces, for example, the outer peripheral surface e of the face member 2, and that is engaged with this outer peripheral surface e; and an annular support surface 9 that forms a wall that stands toward the center of the head on the rear end side of this inside surface 7, and that supports the peripheral portion of the rear surface 2B of the face member 2. The inside surface 7 has substantially the same contour as the outer peripheral surface e of the face member 2, and has substantially the same depth as the thickness of the outer peripheral surface e.
In addition, the sole portion 3b of the head body portion 3 is provided with a back wall portion 11. As shown in
The face member 2 has a substantially flat surface 2A (though in some cases a narrow trench such as a face line may be provided) on the face surface F side, the back surface 2B which is the surface on the side opposite to this surface 2A, and the annular outer peripheral surface e which extends between these surfaces 2A and 2B. The outer peripheral surface e of the face member 2 is supported by the inside surface 7 provided on the face attachment portion 10 of the head body portion 3, and the peripheral portion of the back surface 2B is supported by the support surface 9 provided in the face attachment portion 10, respectively, so as to be attached to the attachment portion 10 by means of, for example, caulking, adhesive or other fixation means. As a result of this, the surface 2A of the face member 2 and the front surface of the head body portion 3 form a face portion FP that partitions the face surface F.
The face member 2 of the present embodiment is formed of a titanium alloy (e.g. Ti—6Al—4V). The titanium alloy has a small specific weight in comparison with the stainless steel or the like that may form the head body portion 3, and therefore, the weight of the head can be allocated more in the periphery of the face member 2, helping to increase the sweet area. Here, a material other than a titanium alloy, for example, SUS 450 (maraging steel) or the like, may of course be utilized for the face member 2.
In addition, as shown in
In addition, according to the present invention, the ratio (Wu/Wd) of the average trench width Wu of the upper side trench portion 4a to the average trench width Wd of the lower side trench portion 4b is limited to a range between 2.5 and 5.0. An excellent working effect of such a head 1 at the time when the head hits a ball is gained by effectively utilizing a gear effect and a recoil effect in the vertical plane of an iron type golf club head.
As shown in
In addition, it is known that the restitution of the face portion FP is increased when the rigidity of the face portion is reduced (so-called as impedance matching theory). In the case where such a face portion FP hits a ball, the flexed amount due to the elastic transformation of the face portion FP increases, leading to an increase in the time of contact between the face surface F and the ball. As shown in
In the case where a region Fa on the face surface, which is a region on the upper side of the border plane DP on the face surface F, hits a ball as shown in
Therefore, the average trench width Wu of the upper side trench portion 4a is made larger than the average trench width Wd of the lower side trench portion 4b, thereby reducing the rigidity of the upper region Fa of the face surface (an increase in the restitution) in the head 1 of the present invention. Accordingly, the time of contact between a ball and the face surface F can be lengthened at the time when the upper region Fa of the face surface hits the ball, and thereby, a high level of the internal friction f2 that accompanies the recoil effect can be greatly generated, thus making it possible to reduce the amount of backspin more effectively.
On the other hand, in the case where a lower region Fb of the face surface, which is a region on the lower side of the border plane DP of the face surface F, hits a ball as shown in
In the head 1 of the present invention, the average trench width Wd of the lower side trench portion 4b is made smaller than the average trench width Wu of the upper side trench portion 4b, thus relatively increasing the rigidity of the lower region Fb of the face surface (no increase in the restitution). Accordingly, the time of contact between the ball and the face surface F is shortened as much as possible at the time when the lower region Fb of the face surface hits the ball, and the friction f2 inside the ball that accompanies the recoil effect is restricted, and thereby, the reduction in the amount of backspin can further be prevented. Here, in the case where the rigidity of the lower region Fb of the face surface is enhanced, by completely eliminating the lower side trench portion 4b, the rigidity of the center region 5 that includes the sweet spot SS is also enhanced, and as a result, an increase in the carry cannot be expected at the time, even when the sweet spot hits a ball, failing to achieve an object of the present invention.
As described above, the average trench widths Wu and Wd of the trench 4 with the border plane DP are made to be different from each other, and thereby, the gear effects and the recoil effect are effectively matched, making it possible to gain a maximum carry as a whole even in the case where a point which is shifted upward or downward from the sweet spot SS hits the ball. Next, the technical reason for limiting the numeral of the ratio (Wu/Wd) of the above described average trench widths is described.
The inventors conducted carry tests by preparing a variety of iron type golf clubs of the same type as that of
It should be specially mentioned that a further limitation of the ratio (Wu/Wd) and the depth d of the center of gravity of the head 1 are related to each other. Concretely speaking, it is preferable for the lower limit of the ratio (Wu/Wd) to be 2.5 or higher, preferably 3.0 or higher and it is more preferable for the lower limit to be 3.5 or higher. It is preferable for the upper limit to be 5.0 or less, preferable 4.4 or less when being combined with any of the lower limit values. In addition, it is desirable for the depth d of the center of gravity of the head 1 to be 4.6 or greater, preferably 5.0 mm or greater, and it is more preferable for the depth d to be 5.2 mm or greater. The combination of these parameters allows the above described working effects to occur in a so-called peak manner, and a critical effect can occur in such a manner that the loss in carry at the time of a ball hit upwardly or downwardly is restricted to approximately 5% (in case of 3.5-4.4% of the ratio (Wu/Wd), more than 5.2 mm depth d) of the case when the sweet spot hits a ball. It is inferred that this results from synergetic effects between the combined effects of the gear effects and the recoil effect gained by limiting the depth d of the center of gravity of the head 1 to a constant length, and the working effects gained by limiting the ratio (Wu/Wd) of the trench width to the above described value. Here, in the case where the depth d of the center of gravity of the head 1 is excessively increased, the head shape tends to be warped, and the weight of the head tends to increase significantly. It is preferable for the upper limit of the depth d of the center of gravity to be 7.0 mm or less when being combined with any of the above described lower limit values, and furthermore, it is more preferable for the upper limit to be 6.0 mm or less.
Here, though the thickness t0 of the center region 5 of the face member 2 is not particularly limited, it is preferable for the lower limit to be 2.5 mm or greater, and it is more preferable for the lower limit to be 2.7 mm or greater, while it is preferable for the upper limit to be 3.5 mm or less when being combined with any of the above described lower limits, and it is more preferable for the upper limit to be 3.2 mm or less. In the case where the thickness t0 is 2.5 mm or less, the durability of the center region 5 which is subjected to a large impact tends to be reduced, and contrarily, in the case where the thickness t0 exceeds 3.5 mm, the rigidity of the entirety of the face member 2 tends to be enhanced, causing the restitution to be deteriorated. Though the thickness of this center region 5 of the present embodiment and of the above described tested clubs is a substantially uniform thickness of 3.0 mm, the thickness can be varied.
In addition, though the minimum thicknesses t0 and t2 in the upper side trench portion 4a and lower side trench portion 4b of the face member 2 are not particularly limited, it is preferable for the lower limit of the thickness t1 to be 1.6 mm or greater, and it is more preferable for the lower limit to be 1.7 mm or greater, while it is preferable for the upper limit of the thickness t1 to be 2.3 mm or less when being combined with any of the lower limits, and it is more preferable for the upper limit to be 2.0 mm or less. In addition, it is preferable for the lower limit of the thickness t2 to be 1.8 mm or greater, and it is more preferable for the lower limit to be 2.0 mm or greater, while it is preferable for the upper limit of the thickness t2 to be 2.5 mm or less when being combined with any of the above described lower limits, and it is more preferable for the upper limit to be 2.3 mm or less.
In the case where the thickness t1 is 1.6 mm or less or the thickness t2 is 1.8 mm or less, the strength in the trench 4 tends to lack, causing the durability of the face portion FP to be reduced. Contrarily, in the case where the above described thickness t1 is greater than 2.3 mm or the thickness t2 is greater than 2.5 mm, it becomes difficult to control the rigidity of the upper region Fa or the lower region Fb of the face surface. In the present embodiment and in the above described tested clubs, the thickness t1 in the upper side trench portion 4a is set at 1.8 mm and the thickness t2 in the lower side trench portion 4b is set at 2.3 mm, which are both substantially uniform in thickness.
In addition, in the case where an iron type golf club head having a conventional size is assumed to be used, it is preferable for the lower limit of the average trench width Wu of the upper side trench portion 4a to be 3.0 mm or greater, and it is more preferable for the lower limit to be 4.0 mm or greater. In addition, it is preferable for the upper limit of the average trench width Wu of the upper side trench portion 4a to be 15.0 mm or less when being combined with any of the above described lower limits, and it is more preferable for the upper limit to be 12.0 mm or less. In the case where the average trench width Wu of the upper side trench portion 4a is 3.0 mm or less, it becomes difficult to sufficiently gain the effects of reducing the rigidity of the upper region Fa of the face surface, leading to the tendency where it is difficult to achieve a high level of the recoil effect. Contrarily, in the case where the average trench width exceeds 15.0 mm, the rigidity of the upper region Fa of the face surface tends to be excessively reduced, causing the durability to be deteriorated.
In the same manner, it is preferable for the lower limit of the average trench width Wd of the above described lower side trench portion 4b to be 1.0 mm or greater, and it is more preferable for the lower limit to be 3.0 mm or greater. In addition, it is preferable for the upper limit of the average trench width Wd of the lower side trench portion 4b to be 7.0 mm or less when being combined with any of the above described lower limits, and it is more preferable for the upper limit to be 5.0 mm or less. In the case where the average trench width Wd of the lower side trench portion 4b is 1.0 mm or less, the rigidity of the center region 5 tends to increase, making it difficult to expect an increase in the carry at the time when the sweet spot hits a ball. Contrarily, in the case where the average trench width exceeds 7.0 mm, the rigidity of the lower region Fb of the face surface tends to be reduced, allowing the recoil effect to occur to a exessive degree.
In the present embodiment and in the above described tested clubs, each of the trench widths Wu, Wd of the upper side trench portion 4a and the lower side trench portion 4b is substantially constant. Though the trench width naturally may vary, in the case where the trench width varies, it is preferable for each of the upper side trench portion 4a and lower side trench portion 4b to have a trench width that varies by a small amount in a manner where the difference between the maximum trench width and the minimum trench width is within 3 mm. In addition, in the case where the trench width varies, the above described average trench width Wu (Wd is also calculated in the same manner), for example, is calculated by weighing according to the length thereof, as described below:
Wu=Σ(WuiLi)/SLi (i=1, 2,)
where Wui indicates the trench width of an arbitrary region i of the upper side trench portion 4a, and Li indicates the length occupied by the above described trench width Wui.
In addition, it is desirable for the center region 5 to have a length Hs in the upward and downward directions along the face surface F passing through the sweet spot SS of 15 mm or greater in the above described standard condition. In the case that the length is 15 mm or less, the thin head portion region, due to the trench 4, tends to be too wide, and as a result, the durability is deteriorated. In addition, it is desirable for the length Hs of the center region 5 to be 35 mm of less. In the case that the length exceeds 35 mm, the thin head portion region tends to be reduced, making the control of the rigidity difficult. In particular, it is preferable for the lower limit of the length Hs to be 20 mm or greater, and it is more desirable for the upper limit to be 30 mm or less.
In addition, in order to respectively adjust the rigidities of the upper region Fa of the face surface and the lower region Fb of the face surface to more preferable values, it is preferable for the ratio (Su/Sd) of the trench area Su of the upper side trench portion 4a in the trench 4 to the trench area Sd of the lower side trench portion 4b to be 2.0 or greater, it is more preferable for the ratio to be 2.3 or greater, and it is still more preferable for the ratio to be 2.5 or greater, while it is preferable for the upper limit of the ratio to be 3.5 or less, it is more preferable for the upper limit to be 3.0 or less, and it is still more preferable for the upper limit to be 2.8 or less.
Though the border portion between the upper side trench portion 4a and the lower side trench portion 4b in the trench width varies in step form in the embodiment shown in
Iron type golf club heads having a loft angle of 25—were prototyped based on Table 1 and
An identical shaft was attached to each prototype head so as to manufacture an iron type golf club of which the entire length was 38.0 inches. Each club was attached to a swing robot, and the three points in total, the sweet spot and the points 5 mm above and below the sweet spot (in this test, shots missed by a comparatively small amount were assumed) hit the balls at a head speed of 34.5 m/s, in a manner that the angle of the hit ball, the amount of backspin and carry were respectively measured.
The results of the test are shown in Table 1.
As a result of the test, significant effects of the examples could be confirmed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-380217 | Nov 2003 | JP | national |
