GB2200558A

GB2200558A - Golf iron club-head

Info

Publication number: GB2200558A
Application number: GB08717812A
Authority: GB
Inventors: Masashi Kobayashi
Original assignee: Maruman Golf Co Ltd
Current assignee: Maruman Golf Co Ltd
Priority date: 1987-02-03
Filing date: 1987-07-28
Publication date: 1988-08-10
Anticipated expiration: 2007-07-28
Also published as: GB2200558B; KR920002803B1; JPS63192474A; GB8717812D0; KR880009674A

Abstract

In a set of iron golf clubs each club comprises a shaft having a club-head on one end and a grip on the other end thereof. The horizontal length (L) of the hitting surface of the club-head is between 96 millimeters and 110 millimeters, while the vertical length (H) of the hitting surface of the club-head is between 45 millimeters and 80 millimeters. <IMAGE>

Description

GOLF IRON CLUB-FEAD BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf club, particularly to an improvement of club-heads for set of iron golf clubs.

ore particularly, the present invention is related to a set of iron golf clubs in which a specially adapted iron golf club is provided-which will meet the requirements of each stroke the player may make in the course of a game of golf, while maintaining like characteristics throughout a set of such golf clubs, despite the variations in their weight and shape.

2. Description of the Related Arts As is well known, there is a point on the club-head of an iron golf club, at the hitting surface of, at which the most effective impact with the ball can be made. This point can be defined as a point of intersection at the hitting surface of a perpendicular line drawn from the center of gravity of the club-head toward the hitting surface, and is generally called the "sweet spot". If the contact with the ball takes place at this point, the ball is hit in the most effective manner, i.e., a maximum initial velocity and a maximum flight distance are obtained. In addition, the most accurate delivery, i.e., most stable direction of flight (hereinafter, flight direction) of the ball, can be obtained.Conversely, if the contact with the ball takes place at a pbint other than the sweet spot, the club-head is apt to pivot around the center of the gravity of the club-head, due to the off-set impact of the ball thereon, and thus a reduced initial velocity and flight distance of the ball are obtained, in com- parison with the case where the impact between the ball and club-head occurs at the sweet spot. Further, the possibility of an undesired flight direction of the ball is greatly increased.

To reduce this possibility of a reduction of the initial velocity and flight distance, and inaccuracy in the flight drection of the ball, it is well known to provide the club-head with a relatively large moment of inertia (hereinafter, denoted as I), to minimize the pivoting motion around the center of gravity of the club-head.

Japanese Examined Utility Model Publication No. 53-288 discloses an iron club-head which is intended to eliminate the above-mentioned drawbacks, and in which the weight distribution of the club-head is deviated along the outer periphery thereof as far as possible, to increase the I value. However, the weight and size of the disclosed club-head is not substantially different from those of the conventional club-head, and thus the I value obtained by this construction is not as great as expected.

Japanese Unexamined Utility Model Publication No. 61-165762 also discloses club-heads for a set of iron golf clubs by which the above-mentioned drawbacks are eliminated, in which the horizontal and vertical lengths of the hitting surfaces of the respective iron golf clubs are made longer than those of conventional club-heads. However, this disclosure does not consider the relationship between the vertical length of the club-head and the height of the sweet spot thereof.

Since the vertical length of the hitting surface of the proposed club-head is considerably longer than that of the conventional club-head, the height of the sweet spot from the ground plane becomes remarkably larger than that of the conventional club-head. As a result, the impact between the ball and the hitting surface of the club-head is apt to occur at a point considerably lower than the location of the sweet spot thereof. Therefore, the maximum height of the trajectory of the ball in flight is low, and thus the flight distance of the ball is shortened.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an iron club-head with which the above mentioned drawbacks of the prior arts are eliminated.

Another object of the present invention is to provide an iron club-head which will minimize the reduction of the flight distance and the inaccuracy of the flight direction of the ball when the impact between the ball and the club-head is at a point other than the sweet spot of the hitting surface of the club-head.

A further object of the present invention is to provide an iron club-head having a larger hitting surface area and a larger horizontal length thereof than that of the conventional club-heads, while maintaining a moderate vertical length of the hitting surface of the club-head to provide a stable impact with the ball.

The above objects of the present invention are achieved by the provision, of club-heads for a set of iron golf clubs, each of the iron golf clubs including a shaft having a club-head on one end and a grip on the other end thereof. According to the present invention, the horizontal length of the hitting surfaces of the club-heads of the set of iron golf clubs is between 96 millimeters and 110 millimeters and the vertical length of the hitting surfaces of the club-heads is between 45 millimeters and 80 millimeters.

According to one aspect of the present invention, the vertical length of the hitting surface of each of the club-heads of the set of iron golf clubs is between: No. 3 iron; 45 to 57 millimeters No. 4 iron; 46 to 58 millimeters No. 5 iron; 47 to 60 millimeters No. 6 iron; 48 to 61 millimeters No. 7 iron; 49 to 63 millimeters No. 8 iron; 50 to 64 millimeters No. 9 iron; S1 to öE millimeters PW iron; 52 to 75 millimerers SW iron; 53 to 80 millimeters The above club-heads of a et of iron golf clubs according to the present invention may be made of a metal having a low specific weight, such as aluminum, or magnesium or a whisker reinforced metal, that is, one of the above metals mixed with, for example, silicon carbide or a fiber reinforced metal, or one of the above metals combined with, for example, carbon fibers.

In order to properly adjust the weight and obtain an ideal location of the sweet spotg and to increase the value of moment of inertia I of each iron club-head, preferably a blind hole is provided on the rear surface of the club-head and a weight member, such as G lead or copper plug, is embedded in the blind hole.

Because of the increase of the horizontal length of the httting surface by 25 to 50%, while maintaining correct vertical length thereof, the height of the sweet spot in relation to the vertical length of the club-head is not very much different from that of the conventional club-head, and thus the properties of the iron golf club of the present invention are not deteriorated. In addition, even if the impact between the ball and the club-head occurs at a point other than the sweet spot, in the horizontal direction of the club-head, any reduction of the flight distance of the ball can minimized. Also, because the hitting surface area of the present invention is 40 to 60% larger than that of the conventional club-head, the player can strike the ball without unnecessary deliberation.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and advantages of the present invention will be better understood from the following description with reference to the preferred embodiments illustrated in the attached drawings; wherein Fig. 1 is a diagram sho;ino the comparat.tve dimensions of the iron club-head of the present invention and the conventional iron club-head, where symbols related to the conventional iron club-head have a dash attached thereto; Fig. 2 is a rear view of first embodiment of the present invention; Fig 3 is a cross sectIonal view taken along the line III-III of Fig. 2; Fig. 4 is a rear view of a second embodiment of the present invention; Fig. 5 is a cross sectional view taken along the line V-V of Fig. 4;; Fig 6 is a rear view of a third embodiment of the present invention; Fig. 7 is a cross sectional view taken along the line VII-VII of Fig. 6; Fig. 3 is a rear view of a fourth embodiment of the present invention; Fig. 9 is a cross sectional view taken along the line IX-IX of Fig. 8; Fig. 10 is a rear view of a fifth embodiment of the present invention; Fig. 11 is a cross sectional view taken along the line XI-XI of Fig. 10; Fig. 12 is a rear view of a sixth embodiment of the present invention; Fig. 13 is a cross sectional view taken along the line XIII-XIII of Fig. 12; Fig. 14 is a rear view of a seventh embodiment of the present invention; Fig. 15 is a cross sectional view taken along the line XV-XV of Fig. 14; and, Fig. 16 is a chart showing a comparison of a flight distance of a ball struck by the iron golf club of the present invention and that when struck by a conventional iron golf club.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Table 1 illustrates a comparison of the dimensions (in the horizontal and vertical directions)r the hitting surface areas and the value of the moment of inertia I of a set of iron club-heads manufactured by the present invention and those of the conventional iron club-heads.

Both the conventional and the inventive club-heads are made of a whisker reinforced metal, such as an aluminum alloy mixed with silicon carbide whiskers, to improve the strength thereof.

As in Table 1, Table 2 illustrates a comparison of the location of the sweet spot and the distance from the axis of the shaft to the sweet spot of a set iron club-heads manufactured by the present invention and those of the conventional iron club-heads.

Table 1 Area of Hitting Surface of Club-Head and Moment of Inertia (I) Hitting Surface Area I Value in Horizontal Horizontal Length (mm) Vertikal Length (mm) (cm) Direction (g.cm) Iron Club Present Present Present Present Conventional Conventional Conventional Conventional Intervetion Intervention Intervention Intervention No. 3 72.0 96.0 48.5 55.0 24.5 36.1 2040 2700 No. 4 72.5 96.0 49.5 56.0 25.0 36.5 2110 2850 No. 5 73.5 96.0 50.5 56.5 25.5 37.2 2290 2980 No. 6 74.0 96.0 51.5 58.0 26.3 38.2 2380 3120 No. 7 74.5 96.0 52.5 59.5 26.7 39.3 2510 3190 No. 8 75.5 96.0 55.5 61.5 28.4 40.5 2580 3240 No. 9 76.0 96.0 65.5 64.5 29.1 42.5 2620 3300 PW 77.5 96.0 57.5 70.0 30.1 45.1 2670 3420 SW 79.0 96.0 95.5 72.5 32.0 47.0 2810 3510 Table 2 Location of Sweet Spot (mm) Present Present Present Conventional Conventional Conventional Invention Invention Invention Iron Club M' M N' N R' R No. 3 27.0 42.0 20.0 21.0 38.2 51.2 No. 4 27.5 42.0 20.3 21.5 39.4 52.7 No. 5 28.0 42.0 20.4 22.0 40.5 54.3 No. 6 28.0 42.0 21.7 22.5 42.0 55.8 No. 7 28.0 42.0 22.4 23.5 43.7 58.2 No. 8 29.0 41.5 23.1 24.0 44.7 58.0 No. 9 29.5 41.5 23.2 24.5 44.6 57.8 PW 30.5 41.0 24.0 25.0 45.4 58.6 SW 30.5 41.0 26.2 27.2 45.9 61.2 Referring tc Figure 1. hori?,ot,fttal lengths L, 1,1 Of the hitting surface c denote distances from the intersecting point 3 of the axis 5A of the shaft 5 and the sole 2 to the toe 1, 1'; vertical lengths H, Hw denote distances between the sole 2 and top ends 4, 4' of the hitting surfaces; and, areas A, A' of the hitting surfaces denote substantially flat surfaces between the iclnity of the point 3 and the toes 1, 1'.The locations of the sweet spots S, S' are generally represented by horizontal distances M, M' between the point 3 and the sweet spots S, S', by vertical distances N, N' between the sole 2 and the sweet spots S, S', and by the length of perpendicular lines R, R' drawn from the sweet spots S, S' to the axis 5 of the shaft 5.

Figures 2 and 3 are rear and cross sectional views, respectively, of the iron club-head according to a first embodiment of the prsent invention, in which a blind hole 7 for balancing the weight of the club-head is formed from the rear surface 2 thereof toward a hitting surface 6 and eccentric to the center of gravity of the club-head. A weight member 8 made of lead, copper or the like and having a predetermined volume is embedded in the blind hole 7, and then the blind hole 7 and the vicinity thereof are covered by a thin decoration plate 9 made of, for example, aluminum or plastic.

Figures 4 and 5 illustrate a second embodiment of the present invention A base member 10 of the clubhead is made of a metal having a low specific weight, such as aluminum, magnesium, or titanium so that the hitting surface area of the club-head can be increased, and a U-shaped cavity 11 having an upwardly opening aperture is formed on the rear surface of the club-head.

A weight member 12 made of a metal having a relatively high specific weight, such as steel, stainless steel, copper, or bronze is embedded in the cavity 11. In this embodiment, since the weight distribution of the weight member 12 is brought close t woe d bead surfaces ir.

the horizontal direction and cjoe to the sole surface in the vertical direction, the moment of inertia I of the club-head is increased and the height of the sweet spot S thereof is made lower than that in the first embodiment. The sweet spot S may be located anywhere on the club-head by a selection of combinations of the material composing the weight member 12 and the shape and the disposition thereof.

Figures 6 and 7 illustrate a third embodiment of the present invention. The club-head comprises a structural member 13 made of, for example, steel or stainless steel, attached to a fiber-reinforced plastic member 14 made of a plastic reinforced by fibers, such as carbon, aramid, or whisker fibers. Therefore, when the ball is hit by this club-head, an increased flight distance of the ball can be obtained because of the ei 5ticity of the reinforced plastic member 14. In this embodiment, the neck member and the sole member are integrated'into a structural member having substantially an L shape. However, the structural member 13 can be formed in a frame shape, having a hollow portion in which the fiber-reinforced plastic 14 is embedded to distribute the weight of the club-head along the outer periphery thereof. This construction provides a further increase of the value of the moment of inertia I of the club-head.

Figures 8 and 9 illustrate a fourth embodiment of the present invention. In this embodiment, a plate member 15 made of a ceramic, such as alumina or zirconia is firmly inserted in the middle portion of a ridge formed on the top surface of the sole member 2, to improve the strength of the club-head. In this embodiment, the ceramic plate is used as a part of the club-head, but it is possible for the entire club head 5 to be made of a ceramic.

Figures 10 and 11 illustrate a fifth embodiment of the present invention Ir this embodiment, a hollow interior space 16 is formed to give the club-head á hollow construction. A plurality of ribs 17, which are substantially paraliel with the top edge of the club-head, are formed behind the hitting surface 6 and projecting into the hollow interior 16 to improve the strength thereof. According to this embodiment, because of the hollow construction of the club-head, a material having a relatively high specific weight may be used for the club-head, without problems.

Figures 12 and 13 illustrate a sixth embodiment of the present invention. In this embodiment, the club-head is provided with a honey-comb construction 18 behind the hitting surface 6, to improve the strength thereof.

This construction also serves to increase the hitting surface area without increasing the weight of the club-head. Although the drawings show that the honey-comb construction is exposed at the rear of the club-head, this construction may be concealed within the club-head and not seen from the outside.

Figures 14 and 15 illustrate a seventh embodiment of the present invention. The club-head is made of a metallic material, such as steel, stainless steel, or bronze, as used in the conventional club-head. In this embodiment, the member 6 constituting the hitting surface and the sole member 2 are formed as a relatively thin L shape in cross section, to stabilize the movement of the club-head when the player is adressing the ball.

Many comparative tests were made between a set of iron golf clubs of the present invention and the conventional iron golf clubs (shown in the Tables 1 and 2) by utilizing a mechanical test machine. The results of these tests are shown in Table 3 and Fig. 16, in which only the results of a test with No. 5 irons is illustrated, to simplify the description. The No. 5 iron golf club of the present invention used in the test was manufactured according to the first embodiment shown in Figs, 2 and 3.

Table 3 Point of Impact Conventional Present Invention Ql Sweet spot 154.5 162.1 12 12 mm from sweet spot toward toe 150.4 160.4 Comparaison betwenn 1 and 2 4.1 1.7 The following conclusions can be made from the results shown in Table 3 and Fig. 16: (1) When the ball is struck at the sweet spot on the hitting surface of the iron golf club manufactured by present invention, the flight distance of the ball is 7.6 meters longer than that when struck by the conventional iron golf club.

(2) If the ball is struck at a point 12 millimeters from the sweet spot of the hitting surface and toward the toe of the iron golf club manufactured by the present invention, the flight distance of the ball is approximately 10 meters longer than if struck at the same point by the conventional iron golf club.

(3) According to the present invention, the reduction of the flight distance of the ball when struck at a point other than the sweet spot is relatively small in comparison with the case when the ball is correctly struck at th,e sweet spot.

(4) The flight distance by the iron golf club of the present invention when the ball is struck at the point other than the sweet spot is 5.9 meters longer than that when struck at the sweet spot by the conventional iron golf club.

The above excellent results 3re obtained because, in the present invention, the distance R from the axis of the shaft to the sweet spot is longer than the distance R' of the conventional iron golf club, with the result that the club length, i.e., the distance between the grip end and the sweet spot S of the iron golf club of the present invention, is longer by the amount K than that of the conventional iron golf club, and thus the swing velocity at the sweet spot of the iron golf club of the present invention is greater than that of the conventional iron golf club.

In addition, the height N of the sweet spot S of the iron golf club of the present invention is substantially the same as the height N' of the sweet spot S' of the conventional iron golf club, and thus the impact force of the iron golf club of the present invention with respect to-the sweet spot is not subsntially lower than with that of the conventional iron golf club.

Although particular embodiments shown in the Figures and disclosure of the present invention have been described, it will be understood as a matter of course that the present invention is not limited thereto, since modifications can be made by those skilled in the art in the light of the foregoing teachings.

Accordingly, the appended claims cover any such modifications which may incorporate those features which come within the spirit and scope of the present invention.

Claims

1. Club-heads for a set of iron golf clubs, each of said iron golf clubs including a shaft having a club-head on one end and a grip on the other end thereof; characterized in that, a horizontal length of hitting surfaces of said club-heads is between 96 millimeters and 110 millimeters, and a vertical length of hitting surfaces of said club-heads is between 45 millimeters and 80 millimeters.

2. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein said vertical length of the hitting surface of each of said club-heads is between: 45 millimeters and 57 millimeters for a No. 3 iron golf club; 46 millimeters and 58 millimeters for a No. 4 iron golf club; 47 millimeters and 60 millimeters for a No. 5 iron golf club; 48 millimeters and 61 millimeters for a No. 6 iron golf club; 49 millimeters and 63 millimeters for a No. 7 iron golf club; 50 millimeters and 64 millimeters for a No. 8 iron golf club; 51 millimeters and 66 millimeters for a No. 9 iron golf club; 52 millimeters and 75 millimeters for a pitching wedge iron golf club, and 53 millimeters and 80 millimeters for a sand wedge iron golf club.

3. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads is made of a light weight metal, such as aluminum or an aluminum alloy.

4. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads is made of a fiber-reinforced metal, such as aluminum or an aluminum alloy reinforced with whisker fibers or alunrna fibers.

5. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads comprises a member made of a metal having a low specific weight, such as aluminum, magnesium, or titanium and a member made of a metal having a high specific weight, such as steel, stainless steel, copper, or bronze.

6. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads comprises a structural member made of a metal and a member made of a fiber-reinforced plastic reinforced by carbon fibers, aramid fibers, or-whisker fibers.

7. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein at least one portion of each of said club-heads is made of a ceramic, such as alumina or zirconia.

8. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads has a hollow construction.

9. Club-heads for a set of iron gol clubs as claimed in claim 1, wherein each of said club-heads has a honey-comb construction formed behind a hitting surface thereof.~

10. Club-heads for a set of iron golf clubs as claimed in claim 1, wherein each of said club-heads has a thin-walled construction and is made of a metal, such as steel, stainless steel, or bronze.

11. Club-heads for a set of iron golf clubs, substantially as hereinbefore described with reference to the accompanying drawings.