GB2240932A

GB2240932A - Iron golf club with round sole

Info

Publication number: GB2240932A
Application number: GB9003677A
Authority: GB
Inventors: Yutaka Katayama
Original assignee: Maruman Golf Co Ltd
Current assignee: Maruman Golf Co Ltd
Priority date: 1990-02-17
Filing date: 1990-02-17
Publication date: 1991-08-21
Also published as: GB9003677D0

Abstract

An iron golf club includes a sole with a bulger round 16, i.e. a convex curvature in the fore and aft section. The bulger round is formed by a curved surface having a radius of curvature R1 smaller than 20 millimeters between the leading edge and the trailing edge. The curve may be simple as shown or may have sections radiused about two distinct centres of curvature. <IMAGE>

Description

IRON GOLF CLUB WITH ROUND SOLE The present invention relates to an iron golf club with a round sole.

An iron golf club comprises a shaft and a head attached thereto, as is well known, and the head has a hitting surface, a rear surface, and a sole extending between the hitting surface and the rear surface. There have been several proposals to give the sole a special shape. For example, Japanese Unexamined Utility Model Publication No. 50-89453 discloses a golf club in which a concave groove is formed in a sole, in the central area thereof, and a leading edge is sharpened to thereby decrease resistance, and Japanese Examined Utility Model Publication No. 52-2528 discloses a golf club in which a plurality of parallel grooves are formed in a sole-to regulate the direction of the head during a swing.

In many conventional iron golf clubs, however, the soles are generally flat, so that the iron golf clubs can be rested close to the ground or turf during an address. If the leading edge of the sole is sharpened, as disclosed in the above Japanese Unexamined Utility Model Publication No. 50-89453, a problem arises in that the leading edge of the sole may stick into the ground or the turf, and further, that the golf ball may be damaged when hit by such a golf club. If parallel grooves are formed in a sole as disclosed in the above Japanese Examined Utility Model Publication No. 52-2528, a problem arises in that it is necessary for the grooved sole to be forcibly'engaged with the ground or the turf to regulate the direction of the head, and thus the resistance becomes greater.From these viewpoints, it is usual to chamfer or round off the leading edge of the sole, and further, to give the entire sole a rounded contour, as viewed in cross section. Such a sole having a rounded contour is sometimes called a camber sole, but here, such a rounded contour is referred to as a bulger round.

In an iron golf club with a sole having a bulger round, the loft of the iron golf club becomes unstable during the address, and thus the bulger round of the conventional sole is formed by a curved surface having a large radius of curvature so that the lowest portion of the sole becomes nearly flat and will closely engage the ground or the turf. In practice, and without exception, the bulger round of the conventional sole is formed by a curvature larger than a radius of curvature of 30 millimeters.

In addition, the sole of the iron golf club sometimes sinks into the turf during the address and the subsequent swing, and thus a problem arises in that the turf adheres to the head during the back swing and the forward swing so that the swing resistance is increased.

This problem occurs even in the case of an iron golf club having a bulger round with a larger radius of curvature.

The object of the present invention is to provide an iron golf club which can be swung smoothly.

According to the present invention, an iron golf club, includes a head having a hitting surface, a rear surface, and a sole extending between the hitting surface and the rear surface to define a leading edge and a trailing edge of the sole, the sole being configured to have a bulger round formed by a curved surface having a curvature smaller than a radius of curvature of 20 millimeters between the leading edge and the trailing edge.

By forming the bulger round of the sole by a curved surface having a curvature smaller than a radius of curvature of 20 millimeters, the leading edge or the trailing edge of the sole will be located above'the turf or as high as the top of the turf even when the sole of the iron golf club sinks into the turf during the address, so that the resistance of the turf to the iron golf club is reduced during a swing and the iron golf club can be swung more smoothly.

The present invention will become more apparent from the following description of the preferred embodiment with reference to the accompanying drawings, in which: Fig. 1 is a side elevational sectional view of a head of an iron golf club according to the first embodiment of the present invention, taken in section along the line I - I in Fig. 2; Fig. 2 is a front view of the head of the iron golf club of Fig. 1; Fig. 3 is a side elevational sectional view of a head of an iron golf club according to another embodiment of the present invention; Fig. 4 is a bottom view of the head of the iron golf club of Fig. 3; Figs. 5A and 5B are views of the head of the iron golf club according to the present invention, in relation to the turf; and Figs. 6A and 6B are views of the head of the iron golf club of the prior art, in relation to the turf.

Referring to Figs. 1 and 2, an iron golf club comprises a shaft 10 and a head 11 with a hosel 12 connecting the head 11 to the shaft 10 in a known manner. The head 11 has a hitting surface 14 for hitting a golf ball, a sole 16, and a rear surface 20.

A leading edge 18 is a portion at which the sole 16 connects with the lower end of the hitting surface 14, and a trailing edge 22 is a portion at which the sole 16 connects with the lower end of the rear surface 20.

As shown in Fig. 1, the sole 16 is provided with a roundness having a radius of curvature R1 , as viewed in cross-section. This roundness is referred to as a bulger round and is formed by a curved surface extending continuously from the leading edge 18 to the trailing edge 22. Figure 1 is a sectional view taken along the line I - I in Fig. 2, and it will be understood that the radius of curvature R1 of the bulger round is measured at the cross section passing the center of the scored area of the hitting surface 14.

As shown in Fig. 2, the sole 16 is also provided with a roundness having a radius of curvature R2 , as viewed longitudinally of the head 11. This roundness is referred to as a sole round.

The illustrated iron golf club is preferably incorporated in an iron golf club set, and has the bulger rounds and the sole rounds constituted by circles with the dimensions (mm) in the following Table. Note, "a" and "b" are included in the Table, and is shown in Fig. 1, "a" represents a distance from the leading edge 18 to the lowest point of the sole 16 during the address, and" b" represents a width of the sole 16 from the leading edge 18 to the trailing edge 22. In this iron golf club set, a sand wedge is not shown since the sand wedge is not swung flat but in an explosive manner.

3i 4i 5i 6i 7i 8i 9i PW AW R1 8.5 9 10 11 11 11 12.5 14 15 2 110 to 130 a 7 7 6.8 7 5.6 5.4 5.2 5.1 4.4 b 15 15 16 17 18 19 20 21 25 As will be clear from this Table, in the case of the iron golf club set, the radius of curvature R1 of the bulger round becomes gradually greater as the length of the iron golf club in the set becomes shorter, i.e., from the long iron to the short iron, with a maximum of 15 millimeters for the approach wedge. Considering the case of an individual iron golf club, the design is such that the radius of curvature R1 of the bulger round of each iron golf club is smaller than 20 millimeters.

Also, the radius of curvature R2 of the sole round is smaller than 130 millimeters, so that the area of the sole 16 in contact with the ground or turf is very small.

In addition, the position of the lowest point (a) of the bulger round of the sole of the head 11 is displaced toward the hitting surface 14 as the length of the iron golf club in the set becomes shorter, so that the resistance of the iron golf club applied by the turf in the head advancing direction parallel to the turf is low. This feature is more advantageous for a short iron golf club, and for a player having a flat swing.

Alternatively, the position of the lowest point (a) of the bulger round of the sole of the head 11 can be displaced toward the rear surface 22 as the length of the iron golf club in the set becomes shorter. In this case, the head 11 is less likely to strike the ground and moves slidingly in the head advancing direction (direction parallel to the turf). Therefore, even if the head 11 hits the ground in front of the golf ball, the duff shot will be mitigated. This feature is useful to a player swinging a short iron golf club with a down blow swing.

In general, from the nature of the length of the golf club, it can be said that a short iron golf club is swung more in a down blow manner than is a long iron club.

As shown in Figs. 3 and 4, the bulger round of the sole 16 is formed not only by a curved surface based on a single circle but also by a continuously curved surface based on two circles (centers 01 and 02). In this case, this continuously curved surface is within the circle 0M of the maximum radius of curvature of 20 millimeters and the two circular surfaces continuously extend from the hitting surface 14 to the rear surface 22 with an interface 24 thereof extending longitudinally of the head 11 like a ridge.

Figure 5A and 5B schematically show the geometry of the soles of the number three iron and the approach wedge in accordance with the dimensions in the above table, and Figs. 6A and 6B schematically show the conventional geometry of the soles of the number three iron and the approach wedge in the prior art, with a larger bulger round. In these Figures, the heights "h" from the lowest point of the sole 16 to the leading edge 18 are important, and calculated examples thereof are shown in the following table. Appropriate typical values are given for the width "b".

Invention Prior Art 3I AW 31 AW R1 8.5 15 30 50 b 15 25 15 25 h 4.5 6.7 1.0 1.6 As will be apparent from this table and from Figs. 5A-5B and 6A-6B, in the conventional iron golf club with a bulger round R1 greater than 30 millimeters, the height "h" from the lowest point of the sole 16 to the leading edge 18 is at the most 1.6 millimeters, so that the leading edge 18 will probably sink into the turf. In the case of the present invention, it is possible to select the height "h" to be more than 4 millimeters, so that the leading edge 18 will be located above the turf or as high as the top of the turf on a normal fairway, and thus the iron golf club can be swang more smoothly and with less resistance even when the head 11 of the iron golf club sinks into the turf.

As explained above, it will be understood that, by making the radius of curvature of the bulger round smaller than 20 millimeters, as in to the present invention, the leading edge or trailing edge of the sole will be located above the turf or as high as the top of the turf even when a portion of the head of the iron golf club sinks into the turf during the address, so that the resistance by the turf is reduced during a swing and the iron golf club can be swung more smoothly.

In addition, by making the radius of curvature of the sole round smaller than 130 millimeters, the sole is in contact with the turf with a smaller area, so that it is possible to easily address and direct the hitting surface to a target even in a undesirable lie, such as an uphill lie, a downhill lie, a toeup lie, and a toedown lie.

Claims

1. An iron golf club including a head having a hitting surface, a rear surface and a sole extending between the hitting surface and the rear surface to define a leading edge and a trailing edge of said sole, said sole being configured to have a bulger round, said bulger round being formed by a curved surface having a curvature smaller than a radius of curvature of 20 millimeters between the leading edge and the trailing edge.

2. An iron golf club according to claim 1, wherein said curved surface forming said bulger round is constituted by two circular surfaces continuously extending from the hitting surface to the rear surface with an interface thereof extending longitudinally of said head like a ridge.

3. An iron golf club according to claim 1, wherein said sole is configured to have a sole round, said sole round being formed by a curved surface having a curvature smaller than a radius of curvature of 130 millimeters.

4. An iron golf club set comprising a plurality of iron golf clubs, each of said iron golf clubs including a shaft and a head attached thereto, said head having a hitting surface, a rear surface and a sole extending between the hitting surface and the rear surface to define a leading edge and a trailing edge of said sole, said sole being configured to have a bulger round, said bulger round being formed by a curved surface having a curvature smaller than a radius of curvature of 20 millimeters between said leading edge and said trailing edge, wherein the radius of curvature of said curved surface forming said bulger round becomes gradually greater as the length of the iron golf club in the set becomes shorter.

5. An iron golf club set according to claim 4, wherein the lowest points of said bulger rounds of said soles in the golf club set vary in the direction of the hitting surface and the rear surface.