US20040266549A1

US20040266549A1 - Iron club head and iron-headed golf club

Info

Publication number: US20040266549A1
Application number: US10/493,392
Authority: US
Inventors: Yasuhiro Iizuka
Original assignee: MacGregor Golf Japan Ltd
Current assignee: MacGregor Golf Japan Ltd
Priority date: 2001-11-05
Filing date: 2002-11-05
Publication date: 2004-12-30
Also published as: WO2003039684A1; JPWO2003039684A1

Abstract

The present invention relates to an iron club head for an iron golf club. The iron club head 1 includes a front area 2 having a front wall for defining a striking face, and a rear area 3 connected to the front area 2. The rear area 3 is formed from at least a sole portion 32, a toe portion 33 and a top blade portion 34. The front area has a rib 23 extending from the outer peripheral edge of the front wall toward the rear area at portions thereof corresponding to at least the sole portion, the toe portion and the top blade portion of the rear area. The rear area is joined to the front area at the end surface of the rib.

Description

FIELD OF THE INVENTION

The present invention relates to iron golf club heads. More particularly, the present invention relates to an iron club head that has high strength and a wide sweet area, and that makes it easy to hit a golf ball and send it high into the air. The present invention also relates to an iron golf club using such an iron golf club head.

DESCRIPTION OF THE RELATED ART

Club heads for iron golf clubs include cavity type iron club heads in which a face part for defining a striking face and a sole part for defining a sole surface are integrally formed with each other and which has a recess or cavity opening in the back thereof, as a head structure having a lowered center of gravity to make it easy to hit a golf ball and send it high into the air. Among cavity type iron club heads is one type which has a head structure in which a front part for defining a striking face and a rear part for defining a sole surface, which are produced separately from each other, are joined to each other. On the other hand in club heads for wood golf clubs, hollow type club heads are the mainstream, wherein a face part and a sole part, which are formed separately from each other, are joined together into a club head with a hollow inside.

Iron golf clubs are required to provide high strength and a wide sweet area. However, the conventional joined type iron club head has a structure as shown in FIG. 1, in which a flat plate-shaped front part a and a rear part b having a sole portion are joined directly to each other. Therefore, one problem which often occurs with the conventional joined type iron club head is that it is difficult to ensure that it has sufficiently high strength and it is impossible to widen the sweet area.

Iron golf clubs are required to perform in such a way that makes it easy to hit a golf ball and send it high into the air. For the latter requirements, deepening and lowering the center of gravity of the iron club head is extremely effective. If the center of gravity of the iron club head is deepened, the loft angle of the club head when impacting a golf ball increases. If the center of gravity of the iron club head is lowered, it is likely that a ball will be struck at a point near the center of gravity of the club head. In either case, it becomes easy to hit a golf ball and send it high into the air.

In this regard, the conventional integral cavity type iron club head is disadvantageous as follows. It is theoretically possible to deepen and lower the center of gravity of the iron club head by adding an extra weight thereto, for example, by fitting an insert into the sole surface. However, this causes the head to increase in weight. Consequently, the overall weight of the golf club and consequently the swing weight increase. Thus, addition of an extra weight exerts an influence upon the swing. Conversely, if the weight of the face part and its peripheral portion is reduced to decrease the overall weight of the club head, rigidity is reduced, resulting in an increase in distortion of the clubface. Accordingly, the iron club head becomes unfit for use.

Regarding hollow type club heads for wood golf clubs, club heads employing a cup-face design in which a rib is formed along the peripheral edge of the face part, and the face part is joined to the sole part at the rib are already available. However, the application of the cup-face type face part to wood club heads is aimed mainly at increasing the strength at the joint between the sole part and the face part and/or its vicinities. Moreover, in conventional cavity type wood club heads, the face part and the sole part are generally made of the same material.

Under these circumstances, the present inventors conducted exhaustive studies to overcome the above-described problems and to attain a structure that enables the sweet area to be widened while meeting the requirements of iron club heads, i.e. the requirements for rigidity of the club head body and the strength against an impact applied to the club head when striking a golf ball. As a result, it was found that it is possible, by radically modifying the club head structure, to widen the sweet area while meeting the requirements for the overall rigidity of the club head and the strength against an impact applied to the club head when striking a golf ball, and accomplished the present invention on the basis of this finding.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an iron club head with excellent strength and a wide sweet area by modifying the structure of the front area so that there is a front wall for defining a striking face and the structure of a rear area is joined to the front area.

Another object of the present invention is to provide an iron club head with a deepened and lowered center of gravity by making the front area material have a smaller specific gravity than that of the material of the rear area.

A further object of the present invention is to provide an iron golf club having an iron club head with the above-described structure.

The present invention provides an iron club head for an iron golf club. The iron club head includes a front area with a front wall for defining a striking face, and a rear area connected to the front area. The rear area is formed from at least a sole portion, a toe portion and a top blade portion. The front area has a rib extending from the outer peripheral edge of the front wall toward the rear area at portions thereof corresponding to at least the sole portion, the toe portion and the top blade portion of the rear area. The rear area is joined to the front area at the end surface of the rib.

According to the present invention, it is possible to increase the overall rigidity of the club head and to improve strength against the impact applied to the club head when striking a golf ball. In addition, the sweet area can be widened.

In the above-described iron club head, the front area may be made of a material with a smaller specific gravity than that of the material of the rear area. Thus, the center of gravity can be deepened and lowered.

The material for the front area and the material for the rear area may be adopted on the basis of the strength, specific gravity, etc. thereof. For example, the material of the front area may be titanium or a titanium alloy, and the material of the rear area may be a stainless steel. The specific gravity of titanium is 4 to 5 g/cm ³. The specific gravity of the stainless steel is 7 to 10 g/cm³.

Further, the sole portion of the rear area may be weighted to deepen and lower the center of gravity. For example, an insert made of a material having a larger specific gravity than that of the material of the rear area may be joined to the sole portion.

Another application of this invention is to provide an iron golf club which has an iron club head. The iron club head includes a front area with a front wall for defining a striking face, and a rear area connected to the front area. The rear area is formed from at least a sole portion, a toe portion and a top blade portion. The front area has a rib extending from the outer peripheral edge of the front wall toward the rear area at portions thereof corresponding to at least the sole portion, the toe portion and the top blade portion of the rear area. The rear area is joined to the front area at the end surface of the rib.

Thus, it is possible to increase the overall rigidity of the club head of the iron golf club and to improve the strength against the impact applied to the club head when striking a golf ball. In addition, the sweet area can be widened.

In the above-described golf club, the front area of the club head may be made of a material with a smaller specific gravity than that of the material of the rear area. Thus, the center of gravity can be deepened and lowered.

The material for the front area and the material for the rear area may be adopted on the basis of strength, specific gravity, etc. thereof. For example, the material of the front area may be titanium or a titanium alloy, and the material of the rear area may be a stainless steel. The specific gravity of titanium is 4 to 5 g/cm ³. The specific gravity of the stainless steel is 7 to 10 g/cm³.

Further, the sole portion of the rear area may be weighted to deepen and lower the center of gravity. For example, an insert made of a material having a larger specific gravity than that of the material of the rear area may be joined to the sole portion. It should be noted that the iron club head and a club shaft may be connected through a hosel inserted into the neck portion, for example. The hosel may be formed as a part separate from the iron club head from a material with a smaller specific gravity than that of the material of the rear area of the iron club head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a conventional joined type iron club head. [0021]
FIG. 2 is a front view of one embodiment of the iron club head according to the present invention. [0022]
FIG. 3 is a side view of the iron club head shown in FIG. 2. [0023]
FIG. 4 is a sectional view of the iron club head shown in FIG. 2 as seen along the arrow A-A. [0024]
FIG. 5 is a sectional view of the iron club head shown in FIG. 2 as seen along the arrow B-B. [0025]
FIG. 6 is a sectional view as seen along the arrow D-D in FIG. 3, showing a hosel mounting portion of the iron club head in FIGS. 2 and 3 and a hosel secured to the hosel mounting portion. [0026]
FIG. 7 is a sectional view similar to FIG. 4, showing another embodiment of the iron club head according to the present invention. [0027]
FIG. 8 is a graph showing the results of a test for measuring the coefficient of restitution of a conventional club head and a club head according to one embodiment of the present invention.[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the iron club head according to the present invention will now be described below with reference to the accompanying drawings. [0029]
FIGS. [0030] 2 to 5 show an iron club head 1 as one embodiment of the present invention. The iron club head 1 has a front area 2 for defining a striking face and a rear area 3. The front area 2 and the rear area 3 are joined together into an integral iron club head. The front area 2 has a front wall 22 for defining a striking face 21 and a rib 23 extending from the peripheral portion of the front wall 22 rearward (toward the rear area). The front wall 22 and the rib 23 are formed in an integral structure. In this embodiment, the rib 23 is not formed over the entire perimeter of the front wall 22. That is, the rib 23 is formed on the sole side, toe side and top blade side of the iron club head but not on the heel side thereof. A rear area-side end surface (left end surface in FIG. 4) 26 of the rib 23 forms a joint surface for connection with the rear area 3. Another joint surface 27 for connection with the rear area 3 is formed at the hosel mounting side of the front area. The striking face 21 is formed with a plurality of scorelines 24 extending horizontally (laterally in FIG. 2). In this embodiment, the front part is made of titanium or a titanium alloy, but it may be made of an aluminum alloy or a magnesium alloy. It should be noted that the front wall for forming the striking face need not always have a uniform thickness over the entire area thereof but may be formed to be thick at the center and thin at the peripheral portion thereof to improve the spring characteristics of the clubface while maintaining the required strength. In this case, the back of the striking face may be convexly curved, by way of example. Alternatively, the thickness of the front wall may be changed stepwisely or continuously so that the center of the front wall is thickest.
The [0031] rear area 3 has a sole portion 32 for defining a sole of the iron club head, a toe portion 33 for defining a toe, a top blade portion 34 for defining a top blade, and a hosel mounting portion 35. These portions are integrally formed with each other. In this embodiment, the above-described portions of the rear area 3 are integrally made of a stainless steel material. Respective end surfaces 36 of the sole portion 32, the toe portion 33 and the top blade portion 34, which are closer to the front area 2, are in the same plane and constitute a joint surface for connection with the front area 2. Another joint surface 37 for connection with the front area 2 is formed on the side of the rear area 3 closer to the hosel mounting portion 35. The front area 2 and the rear area 3 are joined together at the end surfaces 26 and 36 and the joint surfaces 27 and 37 by a publicly known joining method and are thus formed into an integral structure. Accordingly, the iron club head 1 has a cavity C defined by the front wall, the rear wall, the sole portion, the top blade portion, the toe portion, etc.
Thus, no part of the sole portion is formed in the [0032] front area 2 of the iron club head 1. Therefore, it is possible to reduce the amount of material used to form the front area. Accordingly, it is possible to save on material costs even in the case where the front area is made of a costly material having high impact strength, such as titanium or a titanium alloy. Further, it is possible to deepen and lower the center of gravity of the iron club head by forming the rear area from a material having a larger specific gravity than that of the material of the front area, such as a stainless steel material. Further, because the rib is substantially formed over the entire perimeter of the front area, strength can be increased, and the clubface area can be widened. Thus, it is possible to minimize distortion of the striking face which occurs when striking a golf ball.
The [0033] hosel mounting portion 35 has, as shown in FIG. 6, a stepped hole 38 with a circular cross-sectional configuration. The distal end 41 (lower end in FIG. 6) of a hosel 4 is inserted in the stepped hole 38. In this embodiment, the rear area 3 and the hosel 4 are joined together by combining thread engagement and welding to increase the joint strength. However, the rear area 3 and the hosel 4 may be joined together by a publicly known joining method. The hosel 4 is formed in a tubular shape as a whole from a material having a smaller specific gravity than that of the material of the rear area 3, such as titanium or a titanium alloy. The hosel 4 has an axial hole 42. The lower end of a golf clubshaft 5 is fitted and secured in the axial hole 42. Because the hosel 4 is formed as a member separate from the rear area by using a material with a smaller specific gravity than that of the material of the rear area, it is possible to lower the center of gravity of the head part of the iron golf club.
It should be noted that in the foregoing embodiment the [0034] joint surfaces 26 and 27 of the front area and hence the joint surfaces 36 and 37 of the rear area are joined to the mating joint surfaces at respective plane surfaces as illustrated in the figures. To increase the joint strength, however, the arrangement may be as follows. A projection is formed on the rib of the front area, and a recess fittable with the projection is formed in a corresponding portion of the rear area, or alternatively, a recess is formed in the rib of the front area, and a projection fittable in the recess is formed on a corresponding portion of the rear area, and the projection and the recess are fitted to each other to join the front area and the rear area together. Further, the rib may be formed also on the heel mounting side of the front area to make the joint surfaces flush with each other.
FIG. 7 shows a modification [0035] 1 a of the iron club head according to the present invention. The iron club head 1 a also comprises a front area 2 for defining a striking face 21 a, and a rear area 3 joined to the front area 2. The iron club head 1 a in this embodiment differs from the above-described embodiment only in the structure of the rear area 3 a. Therefore, only the part in which the iron club head 1 a differs from the foregoing embodiment will be described below, and a description of the rest of the iron club head 1 a is omitted.
The rear area [0036] 3 a has a cut portion 311 a formed in the lower corner edge (in FIG. 7) of the sole portion 32 a. An insert 6 is fitted into and joined to the cut portion 311 a. The insert 6 has the same configuration as that of the cut portion and is made of a material with a larger specific gravity than that of the material of the rear area (specific gravity: approximately from 10 to 20 g/cm³), e.g. tungsten. With this arrangement, the specific gravity of the material forming the sole portion of the iron club head increases, and the center of gravity of the iron club head shifts rearward in relation to the mounting position of the insert 6. Accordingly, it is possible to further deepen and lower the center of gravity of the iron club head.
The following is a description of the results of a test carried out to compare the conventional cavity type iron club head shown in FIG. 1 [hereinafter referred to as “the conventional club head” (Model: MACTEC NV No. 5 Iron)] with the cavity type iron club head according to one embodiment of the present invention [hereinafter referred to as “the club head of the present invention” (Model: MACTEC NV2 No. 5 Iron) in terms of the coefficient of restitution (COR) and the extent of the sweet area. [0037]

The test was performed 10 times for each of the conventional club head and the club head of the present invention at each of three points: the sweet spot, that is, the center of gravity (SS); a point (P _TOE) 10 mm away from the sweet spot toward the toe portion (TOE); and a point (P_HEEL) 10 mm away from the sweet spot toward the heel portion (HEEL). The conventional club head (club head A), had a front area made of titanium and a rear area made of a stainless steel. The overall weight was 255.4 g. Regarding the conventional club head, measured values in the test carried out 10 times for each of the above-described three points are as shown in Table 1 below. The club head of the present invention (club head B) also had a front area made of titanium and a rear area made of a stainless steel. The overall weight was 257.8 g. Regarding the club head of the present invention, measured values in the test carried out 10 times for each of the above-described three points are as shown in Table 2 below.

TABLE 1


Conventional club head A

	Test No.	SS	P_HEEL	P_TOE

1	0.775	0.746	0.749
2	0.773	0.744	0.747
3	0.771	0.741	0.744
4	0.758	0.736	0.739
5	0.757	0.734	0.738
6	0.756	0.732	0.735
7	0.754	0.730	0.734
8	0.754	0.728	0.732
9	0.751	0.725	0.730
10	0.751	0.724	0.730
Total COR	7.600	7.340	7.378
Average COR	0.760	0.734	0.738

TABLE 2


Club head of the present invention B

	Test No.	SS	P_HEEL	P_TOE

1	0.814	0.799	0.802
2	0.814	0.799	0.801
3	0.813	0.797	0.799
4	0.811	0.797	0.799
5	0.809	0.795	0.797
6	0.808	0.795	0.797
7	0.808	0.793	0.795
8	0.805	0.791	0.794
9	0.805	0.791	0.792
10	0.804	0.789	0.792
Total COR	8.091	7.946	7.968
Average COR	0.809	0.795	0.797

Average values of the measured values at each of the above-described three points obtained as the result of the test carried out 10 times for each of the above club heads are as shown in Table 3 below: [0040]

TABLE 3

Type Position Weight (g) COR

Club head A SS 255.4 0.760

P_HEEL 255.4 0.734

P_TOE 255.4 0.738

Club head B SS 257.8 0.809

P_HEEL 257.8 0.795

P_TOE 257.8 0.797
FIG. 8 is a graph which shows the results of the test by using the values shown in Table 3 to facilitate better understanding. It can be seen from the graph that the club head of the present invention exhibits a high coefficient of restitution as a whole in comparison to the conventional club head and is capable of sending the ball further than with the conventional club head. It can also be seen that the rate at which the value of the coefficient of restitution decreases at the point P[0041] _TOEand the point P_HEELwith respect to the coefficient of restitution at the sweet spot SS is lower in the club head of the present invention than in the conventional club head. This shows that the sweet area of the club head of the present invention is wider than that of the conventional club head.
The Present Invention Offers the Following Advantageous Effects [0042]
(a) The front area of the iron club head has a rib extending from the outer peripheral edge of the front wall toward the rear area at at least the sole portion, the toe portion and the top blade portion, and the rear area is joined to the front area at the end surface of the rib. Accordingly, it is possible to relieve the impact acting on the end surface of the striking face and to prevent breakage. Further, it is clear from the results shown in FIG. 8 that the sweet area can be widened. [0043]
(b) The coefficient of restitution of the striking face can be increased in comparison to the conventional structure. [0044]
(c) The center of gravity of the iron club head can be deepened and lowered by making the rear area of a material having a larger specific gravity than that of the material of the front area. [0045]
(d) Because the iron club head comprises the front area and the rear area and the volumetric capacity of the front area for defining the striking face is reduced, it is possible to save the material cost even in the case where the front area is made of a costly material which has high impact strength, such as titanium or a titanium alloy. [0046]
(e) The center of gravity of the iron club head can be further deepened and lowered by securing an insert in the sole portion of the rear area, said insert being made of a material having a larger specific gravity than that of the material of the rear area. [0047]
(f) By making the hosel of a material have a smaller specific gravity than that of the material of the rear area of the iron club head, the center of gravity of the head part of the iron golf club can be lowered further than that of the head part of a golf club using only the above-described iron club head. [0048]

Claims

1. An iron club head for an iron golf club, comprising:

a front area having a front wall for defining a striking face; and

a rear area connected to said front area;

wherein said rear area is formed from at least a sole portion, a toe portion and a top blade portion; and

said front area has a rib extending from the outer peripheral edge of said front wall toward said rear area at portions thereof corresponding to at least said sole portion, toe portion and top blade portion of said rear area, said rear area being joined to said front area at an end surface of said rib.

2. An iron club head according to claim 1, wherein said front area is made of a material having a smaller specific gravity than that of a material of said rear area.

3. An iron club head according to claim 1, wherein a material of said front area is titanium or a titanium alloy, and a material of said rear area is a stainless steel.

4. An iron club head according to claim 1, wherein an insert made of a material having a larger specific gravity than that of a material of said rear area is joined to the sole portion of said rear area.

5. An iron golf club having an iron club head, said iron club head including:

a front area having a front wall for defining a striking face; and

a rear area connected to said front area;

6. An iron golf club according to claim 5, wherein said front area is made of a material having a smaller specific gravity than that of a material of said rear area.

7. An iron golf club according to claim 5, wherein the material of the front area of said iron club head is titanium or a titanium alloy, and the material of the rear area of said iron club head is a stainless steel.

8. An iron golf club according to claim 5 wherein an insert made of a material having a larger specific gravity than that of the material of the rear area of said iron club head is joined to the sole portion of said rear area.

9. An iron golf club according to claim 5, wherein a hosel for connecting together said iron club head and a clubshaft is formed as a member separate from said iron club head from a material having a smaller specific gravity than that of the material of the rear area of said iron club head.

10. An iron club head according to claim 2, wherein a material of said front area is titanium or a titanium alloy, and a material of said rear area is a stainless steel.

11. An iron club head according to claim 2, wherein an insert made of a material having a larger specific gravity than that of a material of said rear area is joined to the sole portion of said rear area.

12. An iron club head according to claim 3, wherein an insert made of a material having a larger specific gravity than that of a material of said rear area is joined to the sole portion of said rear area.

13. An iron club head according to claim 10, wherein an insert made of a material having a larger specific gravity than that of a material of said rear area is joined to the sole portion of said rear area.

14. An iron golf club according to claim 6, wherein the material of the front area of said iron club head is titanium or a titanium alloy, and the material of the rear area of said iron club head is a stainless steel.

15. An iron golf club according to claim 6, wherein an insert made of a material having a larger specific gravity than that of the material of the rear area of said iron club head is joined to the sole portion of said rear area.

16. An iron golf club according to claim 7, wherein an insert made of a material having a larger specific gravity than that of the material of the rear area of said iron club head is joined to the sole portion of said rear area.

17. An iron golf club according to claim 14, wherein an insert made of a material having a larger specific gravity than that of the material of the rear area of said iron club head is joined to the sole portion of said rear area.

18. An iron golf club according to claim 6, wherein a hosel for connecting together said iron club head and a clubshaft is formed as a member separate from said iron club head from a material having a smaller specific gravity than that of the material of the rear area of said iron club head.

19. An iron golf club according to claim 7, wherein a hosel for connecting together said iron club head and a clubshaft is formed as a member separate from said iron club head from a material having a smaller specific gravity than that of the material of the rear area of said iron club head.

20. An iron golf club according to claim 14, wherein a hosel for connecting together said iron club head and a clubshaft is formed as a member separate from said iron club head from a material having a smaller specific gravity than that of the material of the rear area of said iron club head.