Iron type golf club head and iron type golf club set

An iron type golf club head has a club face provided with face lines and comprises an external weight member secured to a sole portion of a head main body and having a specific gravity larger than the head main body. The external weight member has a center of gravity located on the toe side of the middle point in the toe-heel direction of the face lines, and comprises a wide portion and a narrow portion located on the heel side of the wide portion. The wide portion is located on the toe side of the above-mentioned middle point. The wide portion has a front edge extending along the leading edge of the sole portion, and the narrow portion has a front edge extending along the leading edge and located backward of the front edge of the wide portion.

TECHNICAL FIELD

The present invention relates to an iron type golf club head and a set of iron type golf clubs excellent in flight distance performance.

BACKGROUND ART

The following Patent Document 1 discloses an iron type golf club head in which a weight member is attached to a sole of a main body of the head and extends in the toe-heel direction of the head. The weight member integrally includes a toe-side portion and a heel-side portion, and the toe-side portion extends from the sole into a back portion of the head. The heel-side portion extends only in the sole. Such iron type golf club head can provide a lower and deeper center of gravity of the head.Patent Document 1: Japanese Patent Application Publication No. 2018-000471

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In general, when a golf ball is hit by an iron type golf club at the sweet spot of the club face, a long flight (driving) distance can be obtained.

Incidentally, the sweet spot is, as well known in the art, a point on the club face at which a straight line, which is drawn perpendicularly to the club face from the center of gravity G of the head, intersects the club face.

On the other hand, many golfers try to hit a golf ball at a middle point in the toe-heel direction of the face lines (or score lines) formed in the club face because such middle point is easily recognizable when addressing the ball. Further, an iron type golf club often hits a golf ball placed directly on the ground. Therefore, in order to improve the flight (driving) distance performance of an iron type golf club head, it is important to bring the sweet spot close to the middle point in the toe-heel direction of the face lines and also to lower the position of the sweet spot.

On the other hand, an iron type golf club head has a hosel portion having a relatively heavy weight. Thereby, the center of gravity of the head occurs on the heel-side of the middle point in the toe-heel direction of the face lines. Therefore, in order to provide an iron type golf club head with excellent flight distance performance, it is necessary to design the center of gravity of the head as close to the toe as possible.

Thus, in order to shift the center of gravity of the head toward the toe, it is required to add a large weight member in a toe-side of the sole portion.

In the case of an iron type golf club head, however, the sole portion is usually formed so as to extend upward as the position approaches to the toe. For this reason, when trying to arrange a weight member toward the toe as much as possible, the weight member will be arranged at a higher position. This results in a problem such that the position of the center of gravity of the head becomes higher and the position of the sweet spot also becomes higher.

In view of the above problem, the present invention was made, and a primary objective of the present invention is to provide an iron type golf club head and an iron type golf club set in which the center of gravity of the head is positioned toward the toe and deeper from the club face, while maintaining the center of gravity of the head at a low position.

According to the present invention, an iron type golf club head has a club face provided with face lines extending in the toe-heel direction of the head, and comprises a head main body and an external weight member secured to a sole portion of the head main body and extending in the toe-heel direction, wherein

the specific gravity of the external weight member is larger than the specific gravity of the head main body,

the center of gravity of the external weight member is located on a toe-side of the middle point in the toe-heel direction of the face lines,

wherein

the external weight member comprises a wide portion and a narrow portion where the width of the external weight member in the front-back direction of the head is larger in the wide portion than in the narrow portion,

the wide portion is located on the toe side of the middle point in the toe-heel direction of the face lines, and

the narrow portion is located on a heel side of the wide portion,

wherein

the wide portion has a first edge on a club face side which extends along a leading edge of the sole portion,

the narrow portion has a second edge on the club face side which extends along the leading edge of the sole portion, and

the first edge is located on the club face side than the second edge.

The wide portion may be disposed such that the extent in the toe-heel direction of the wide portion includes the position in the toe-heel direction of a most toe-side end of the face lines.

The narrow portion may be disposed such that the extent in the toe-heel direction of the narrow portion includes the position in the toe-heel direction of the middle point in the toe-heel direction of the face lines.

The width of the wide portion measured at the position in the toe-heel direction of the most toe-side end of the face lines may be not less than 1.35 times the width of the narrow portion measured at the position in the toe-heel direction of the middle point in the toe-heel direction of the face lines, both widths measured in the front-back direction of the head.

The width of the wide portion measured at the position in the toe-heel direction of the most toe-side end of the face lines may be 23 mm or more.

An internal weight member having a specific gravity greater than that of the external weight member, may be disposed between the head main body and the external weight member, wherein, in the toe-heel direction of the head,

the center of gravity of the internal weight member is located on the toe side of the middle point in the toe-heel direction of the face lines.

The iron type golf club head may comprises a height of the sweet spot of the club face which is less than 19 mm, a depth of the center of the gravity of the head which is not less than 8 mm, and

a distance in the toe-heel direction between the sweet spot and the middle point in the toe-heel direction of the face lines which is less than 4 mm.

According to another aspect of the present invention, an iron type golf club set includes a plurality of iron type golf clubs having different loft angles and respectively comprising the iron type golf club heads as described above, wherein

the distance in the toe-heel direction of the head between the center of gravity of the external weight member and the middle point in the toe-heel direction of the face lines becomes larger as the loft angle becomes smaller.

The iron type golf club head according to the present invention includes the head main body and the external weight member extending in the toe-heel direction in the sole portion of the head main body, and the specific gravity of the external weight member is larger than the specific gravity of the head main body. Therefore, the iron type golf club head according to the present invention can provide a low position for the center of gravity of the head. The lowered center of gravity of the head lowers the position of the sweet spot.

By lowering the position of the sweet spot, the sweet spot approaches to the ball hit position in such a situation that the iron type golf club head hits the ball placed directly on the ground. This helps to increase the flight distance of the hit ball.

In general, due to the structural nature of the iron type golf club head, when a ball placed directly on the ground is hit, the ball hit position becomes lower than the sweet spot. As a result, when the ball hits the club face, the golf club head is liable to rotate toward such a direction that the club face inclines downward. However, by making the position of the sweet spot lower so as to approach the ball hit point, such rotation of the head can be suppressed, and as a result, the resultant decrease of the ball launch angle is also suppressed. This also helps to increase the flight distance of the hit golf ball.

The external weight member includes the wide portion and the narrow portion located on the heel side of the wide portion. The wide portion is located on the toe side of the middle point of the toe-heel direction of the face lines.

Such iron type golf club head can shift its center of gravity toward the toe, and as a result, the sweet spot approaches to the middle point of the face lines from the heel side. As the middle point of the face lines is a common hitting position of the golfers, the flight distance of the hit ball may be further increased.

Further, the first front edge of the wide portion is located closer to the club face than the second front edge of the narrow portion, and

in the toe side of the sole portion, the wide portion extends in a wider range in the front-back direction. As a result, more weight can be distributed to the toe side of the head. This helps to shift the center of gravity of the head toward more toe-side.

Further, in the heel side of the sole portion, more weight can be distributed to the rear side of the head. This helps to shift the center of gravity of the head to a rear side of the head, increasing the depth of the center of gravity of the head from the club face.

As described above, in the iron type golf club head according to the present invention, the center of gravity of the head can be positioned toward the toe and to a deeper position from the club face, while maintaining the center of gravity of the head at a lower position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described in conjunction with accompanying drawings.

FIGS. 1, 2 and 3are a front view, a rear view and a bottom view, respectively, of an iron type golf club head1(hereinafter simply referred to as the “head”1) as an embodiment of the present invention.

In this application including the description and claims, dimensions, positions, directions and the like relating to the club head refer to those under a reference state of the club head unless otherwise noted.

As shown inFIG. 10, the reference state is a state of the head which is set on a horizontal plane HP so that face lines7formed in the club face2of the head become parallel to the horizontal plane HP,

the center line CL of the club shaft inserting hole8of the head (corresponding to the axis of the club shaft) lies within a vertical plane VP perpendicular to the horizontal plane HP, and the face lines7become parallel to the horizontal plane HP and parallel to the vertical plane VP.

In the reference state of the club head, the following orthogonal directions are defined as shown inFIG. 10:

“Toe-heel direction” is a direction y parallel to the horizontal plane HP and parallel to the vertical plane VP;

“up-down direction” is a direction z perpendicular to the horizontal plane HP; and

“Front-back direction” is a direction x orthogonal to the direction y and the direction z.

In the reference state, the center line CL is inclined at the specified lie angle α with respect to the horizontal plane HP, and

the club face2is inclined at the specified loft angle β with respect to the vertical plane VP.

In the present embodiment, the head1has a shape of a typical iron club head as shown inFIGS. 1 to 6, and the head1comprises a club face2, a top portion3, a sole portion4, and a toe portion5, a hosel portion6and a back portion9.

The club face2is a substantially flat surface for striking a ball.

The club face2is provided with face lines (or grooves)7in order to increase the friction between the club face2and the ball. The face lines7extend parallel with each other and parallel to the toe-heel direction y of the head1.

The top portion3is an upper surface part of the head1extending backward from the upper edge of the club face2.

The sole portion4is a lower surface part of the head1defined between a leading edge Le and a trailing edge Te in the bottom view of the head as shown inFIG. 3.

The leading edge Le is at a position where the club face2and the lower surface part of the head1intersect with each other in a cross section of the head perpendicular to both the vertical plane VP and the horizontal plane HP.

The trailing edge Te is at a position where the lower surface part of the head1and the back portion9intersect with each other in the above-said cross section of the head.

If such demarcation position can be identified from the appearance by a clear edge, the trailing edge Te is defined by the clear edge.

If there is no clear edge in the appearance, then the radius of curvature of the contour of the sole portion4is measured in the above-said cross section of the head, to find the position at which the radius of curvature first becomes less than 15 mm in the course from the leading edge Le side toward the rear of the head. The trailing edge Te can be defined as existing at the found position.

The back portion9is a rear surface part of the head1extending upwardly from the trailing edge Te of the sole portion4.

The toe of the head is a farthest point from the hosel portion6, and the toe portion5is a surface part of the head1including the toe and smoothly connecting between the top portion3and the sole portion4.

The hosel portion6is a part of the head provided with a club shaft inserting hole8(shown inFIG. 10) into which the tip end of a club shaft (not shown) is inserted.

The hosel portion6in this example is formed as a cylindrical tubular portion.

When the tip end of the club shaft (not shown) is inserted and secured into the club shaft inserting hole8, the center line CL of the club shaft inserting hole8coincides with the axis of the club shaft.

In the present embodiment, as shown inFIGS. 4 to 6, the golf club head1is composed of a head main body10and an external weight member20.

The head main body10constitutes a major part of the head1, and in this example, comprises the club face2, the top portion3, the sole portion4, the toe portion5, the hosel portion6and the back portion9.

The head main body10is made of one or more kinds of metal materials, for example.

Preferably, the head main body10includes a face plate12and a face plate receiving part14as shown inFIGS. 5 and 6.

Preferably, the face plate12and the face plate receiving part14are made of different metal materials.

For example, the face plate12is made of a metal material having the smallest specific gravity among metal materials constituting the golf club head1.

For the face plate12, a titanium alloy excellent in specific strength which has a specific gravity of 4.5 or less can be used preferably. This helps to position the center of gravity of the head more backward and downward as well as helps to increase a weight margin for adjusting the center of gravity of the head when designing the head.

The face plate receiving part14has a through hole penetrating the face plate receiving part14in the front-back direction of the head so as to be surrounded by the top portion3, the sole portion4and the toe portion5, and thereby having a front opening O.

The face plate receiving part14is provided around the opening O with a club face mounting portion16to which the peripheral portion of the face plate12is fitted and fixed. The opening O is closed by the face plate12fixed to the club face mounting portion16.

In order to fix the face plate12and the face plate receiving part14together, various fixing means, for example, welding, brazing, adhesive, caulking and the like can be used alone or in combination.

In this embodiment, the face plate receiving part14integrally includes the hosel portion6as one body.

The face plate receiving part14is, for example, made of a metal material having a specific gravity greater than that of the face plate12.

The face plate12is preferably made of an iron-based alloy, specifically stainless steel or carbon steel, as a metal material having basic strength and good workability, which has a specific gravity of more than 7.0, preferably 7.5 or more.

When the face plate receiving part14is made of a metal material having a specific gravity more than that of the face plate12, the center of gravity of the head can be located further backward and lower.

The head main body10is not limited to the structure composed of two different kinds of materials. The head main body10may be composed of a single material or three or more kinds of materials.

When the head main body10is made of one kind of material, it is usually of a one-piece structure in which the face plate12and the face plate receiving part14are integrally formed as one piece or member. But, it may be of a multi-piece structure in which, for example, the face plate12and the face plate receiving part14made of the same material are formed separately and then fixed to each other.

When the head main body10is made of three or more kinds of materials, the head main body10may be of a multi-piece structure in which the face plate12is fixed to the face plate receiving part14, for example, composed of two or more members. In this case, the face plate12and the members constituting the face plate receiving part14are respectively made of three or more kinds of materials different from each other.

In the sole portion4of the head main body10(specifically, the face plate receiving part14in this example), a reentrant portion18is formed for example as shown inFIGS. 4 and 6.

In the reentrant portion18, an external weight member20is disposed.

The external weight member20is exposed to the outside of the head so as to form a part of the outer surface of the sole portion4as shown inFIGS. 3 and 4.

In the sole portion4, the external weight member20extends in the toe-heel direction.

For example, the external weight member20has a substantially constant thickness as shown inFIG. 5.

For example, the external weight member20is made of a metal material having a specific gravity greater than that of the head main body10, to help to bring the position of the center of gravity of the head closer to the position of the center of gravity of the external weight member20.
Since the external weight member20is disposed in the sole portion4so as to be exposed to the outside of the head, it helps to lower the position of the center of gravity of the head.

Incidentally, when the head main body10is made of one kind of material, the specific gravity of the head main body10equals to the specific gravity of the material.

When the head main body10is made of plural kinds of materials having different specific gravities, the specific gravity of the head main body10equals to a weighted average obtained by weighting the specific gravities of the materials constituting the respective members by the volumes of the respective members.

Preferably, the external weight member20is made of a tungsten-nickel-iron alloy containing W, Ni and Fe.

The specific gravity of such tungsten-nickel-iron alloy can be increased by increasing the ratio of the content of w to the content of Fe in its chemical components.

Such alloy containing Fe may be welded to the head main body10made of an iron-based alloy such as soft iron or stainless steel. In the external weight member20in this example, the content of W is increased to the extent that its weldability to the head main body10is maintained.
The specific gravity of the external weight member20is not particularly limited as long as it is larger than that of the head main body10, but it is preferably 8.0 or more, more preferably 9.0 or more.

As shown inFIGS. 1 and 3, the center of gravity g1of the external weight member20is located on the toe side of the middle point C in the toe-heel direction y of the head1of the face lines7.

In this example, the external weight member20extends in the toe-heel direction y across the middle point C of the face lines7as shown inFIG. 3.

The middle point C is a point in the toe-heel direction y which is, as shown inFIG. 1, at the same distance from the position P1in the toe-heel direction y of the most toe-side end of the face lines7and from the position P2in the toe-heel direction y of the most heel-side end of the face lines7.
InFIG. 1, “FC” denotes the center of the club face which is the middle point in the up-down direction of the head, of the club face2at the middle point C in the toe-heel direction y of face lines7.

By configuring the external weight member20as described above, it is possible to shift the center of gravity of the head toward the toe at a lower position. By lowering the position of the center of gravity of the head, the position of the sweet spot of the club face2is also lowered. Therefore, when the iron type golf club head hits a ball placed directly on the ground, the position of the sweet spot approaches to the ball hit position of the club face20. This helps to increase the flight distance of the hit ball.

In general, when a ball placed directly on the ground is hit by an iron type golf club head, the ball hit position of the club face becomes lower than the sweet spot due to the structural nature of the iron type golf club head.

Therefore, from the hit ball, the head receives a force to rotate the head toward such a direction that the club face leans downward. By lowering the position of the sweet spot so as to approach to the ball hit position, it is possible to suppress such rotation of the head occurring at the time of hitting the ball. Thus, a decrease in the ball launch angle can be suppressed. This helps to increase the flight distance of the hit ball.

In addition, by shifting the center of gravity of the head toward the toe, in the toe-heel direction, the sweet spot approaches to the middle point C of the face lines7(namely, the position in the toe-heel direction y at which many golfers try to hit a ball), and as a result, the probability that the flight distance of the hit ball is further increased, is increased.

In order to achieve the above-described desirable position for the center of gravity g1of the external weight member20, the external weight member20is provided with a wide portion22and a narrow portion24as shown inFIG. 3.

The wide portion22has a large width W1in the front-back direction x of the head.

The narrow portion24has a width W2in the front-back direction x smaller than the width W1of the wide portion22.

In the case of the example of the external weight member20shown inFIG. 3, between the wide portion22and the narrow portion24, there is formed a step26(an edge) which is available to delimit a border between the wide portion22and the narrow portion24.

The step26in this example extends in the front-back direction x of the head on the toe side of the middle point C of the face lines7.

Thus, in the external weight member20in this example, the wide portion22is located on the toe side of the middle point C of the face lines7, and the narrow portion24is located on the heel side of the wide portion22.

And the wide portion22has a greater weight than the narrow portion24.

Therefore, the external weight member20can distribute more weight on the toe side than the heel side.

The wide portion22has a first edge22aon the club face2side which extends along the leading edge Le.

The narrow portion24has a second edge24aon the club face2side which extends along the leading edge Le.

In the head1in the present embodiment, the first edge22ais located closer to the club face2than the second edge24aas shown inFIG. 3.

In a toe-side part of the sole portion4, therefore, it is possible to make the wide portion22extend in a wider range in the front-back direction x. This makes it possible to distribute more weight to a toe-portion side lower position of the head.

In a heel-side part of the sole portion4, on the other hand, as the second edge24ais located backward of the first edge22a, it is possible to make the weight concentrate in a rear side part of the head.

With these effects, in the head1in the present embodiment, the center of gravity can be shifted toward the toe and to a lower position, therefore, it is possible to provide the head1having excellent flight distance performance.

As explained above, it is possible to shift the center of gravity of the head1toward the toe by using the wide portion22.

But, it is difficult to position the center of gravity of the head on the toe side of the middle point C of the face lines7as far as it is premised that the position of the center of gravity of the head1is lowered while adopting a conventional iron type golf club head shape for the head1.
Thus, the center of gravity of the head in the present embodiment is still positioned on the heel side of the middle point C.

It is preferable that, as shown inFIG. 3, the extent in the toe-heel direction y of the wide portion22includes the position P1in the toe-heel direction y of an end in the toe-heel direction y of the face lines7which end is the most toe-side end among those of the face lines7.

More preferably, the toe-side end20tof the external weight member20is positioned on the toe side of the position P1. Thereby, more weight is distributed to the toe-side part of the sole portion4.

It is preferable that, as shown inFIG. 3, the extent in the toe-heel direction y of the narrow portion24includes the position in the toe-heel direction of the middle point C of the face lines7. More preferably, the narrow portion24extends across the middle point C. Thereby, in a heel-side part of the sole portion4than the middle point C, more weight is distributed to the rear of the head.

Preferably, the heel-side end20hof the external weight member20is positioned on the heel side of the position P2in the toe-heel direction y of the most heel-side end of the face lines7.

The width W1of the wide portion22measured in the front-back direction of the head at the position P1is preferably not less than 1.35 times, more preferably not less than 1.40 times, still more preferably not less than 1.50 times the width W2of the narrow portion24measured in the front-back direction of the head at the middle point C. Thereby, the center of gravity of the head can be positioned toward more toe-side.

The width W1of the wide portion22is preferably not less than 23 mm, more preferably not less than 25 mm, still more preferably not less than 26 mm in order to position the center of gravity of the head toward more toe-side.

The upper limit of the width W1is not particularly limited, but it may be arbitrarily determined within the range of the width in the front-back direction x of the toe-side part of the sole portion4where the wide portion22is disposed.

The external weight member20has a third edge20eon the rear side of the head1as shown inFIG. 2. The third edge20eextends in the toe-heel direction along the trailing edge Te. The third edge20eextends in the toe-heel direction above the trailing edge Te. The third edge20eextends in the toe-heel direction smoothly along the trailing edge Te.

In order to distribute more weight toward the toe, the external weight member20comprises an end portion (20t) in the toe-heel direction y on the toe-side which extends upward slightly and then terminates. As shown inFIG. 2, the end portion (20t) extends along the contour of the toe portion5.

In order to maintain the lowered position of the center of gravity of the head, as shown inFIG. 2, the maximum height h of the external weight member20from the horizontal plane HP is preferably set to be not more than 35%, more preferably not more than 30% of the maximum height H of the club face2.

Further, as shown inFIGS. 5 and 6, an internal weight member30can be preferably disposed between the head main body10and the external weight member20.

The internal weight member30in this example is secured between the head main body10(the reentrant portion18) and the external weight member20as shown inFIG. 4A, and covered with the external weight member20. Thus, the internal weight member30is invisible from the outside of the head.

The reentrant portion18of the head main body10in this example includes, as shown inFIG. 4AandFIG. 6, a deep first reentrant portion18aaccommodating the internal weight member30, and a shallower second reentrant portion18bnot accommodating the internal weight member30.

As shown inFIG. 4B, the external weight member20(the narrow portion24) substantially fits the second reentrant portion18b.

The internal weight member30is made of a metal material having a specific gravity greater than that of the external weight member20.

Preferably, the internal weight member30is made of a tungsten-nickel-iron alloy containing W, Ni and Fe.

The specific gravity of the internal weight member30is not particularly limited, but preferably set to be not less than 11.0, more preferably not less than 12.0.

Preferably, the specific gravity of the internal weight member30is set to be not more than 18.5.

In this example, the tungsten-nickel-iron alloy whose specific gravity is increased by increasing the proportion of w up to such an extent that it cannot be welded to the head main body10, is used for the internal weight member30.

The position in the toe-heel direction y of the center of gravity g2of the internal weight member30is located on the toe side of the middle point C of the face lines7as shown inFIG. 3. Such arrangement helps to position the center of gravity of the head more toe-side.

Preferably, the entire internal weight member30is disposed on the toe side of the middle point C of the face lines7.

In this example, as shown inFIG. 6, the internal weight member30is provided with a through hole32, and the above-mentioned first reentrant portion18aof the head main body10is provided with a protrusion19at a position corresponding to the through hole32.

When the internal weight member30is set in the first reentrant portion18a, the protrusion19fits into the through hole32. Since the internal weight member30fits to the reentrant portion18, and the through hole32fits to the protrusion19, accurate positioning of the internal weight member30is possible.

In order to fix the internal weight member30to the head main body10, a weld bead (not shown) may be utilized when the internal weight member30cannot be welded to the head main body10. The weld bead (not shown) is disposed between the through hole32and the protrusion19. The weld bead fills the gap formed between the through hole32and the protrusion19, and by the friction or mechanical engagement therebetween, the internal weight member30is prevented from moving relatively to the head main body10. The weld bead is a hardened molten metal, and in this example, fused with the metal material of the protrusion19, namely, the metal material of the head main body10. Therefore, the vibration of the internal weight member30relative to the head main body10is suppressed, and the generation of abnormal noise due to the vibration is suppressed.

Owing to the above-described configuration of the head1, the center of gravity of the head can be positioned toward the toe and to a deeper position from the club face, while maintaining a lowered position.

And it is preferred that, as shown inFIGS. 7A and 7B, the sweet spot height SSH is lower than 19 mm, the gravity center depth SSD is not less than 8 mm, and the distance SSX in the toe-heel direction between the sweet spot SS and the middle point C is less than 4 mm.
Here, the sweet spot height SSH is a vertical distance from the horizontal plane HP to the sweet spot SS.
The gravity center depth SSD is the shortest distance from the club face2to the center of gravity G of the head.
The distance SSX is indicated as plus (+) values when the sweet spot SS is on the heel side of the middle point C, and minus (−) values when the sweet spot SS is on the toe side of the middle point C.

According to another aspect of the present invention, there is provided an iron type golf club set (simply golf club set) including a plurality of iron type golf clubs (simply golf clubs)100having different loft angles β.

In this specification, an iron type golf club set refers to a group of iron type golf clubs intended to be sold in combination or recommended to do so by the manufacturer of the golf clubs.

The golf clubs100included in the golf club set have unified designs for example, and are configured to achieve different flight distances and heights respectively by the different loft angles β.

The golf club set includes at least a golf club100whose loft angle β is smallest and approximately 19 to 27 degrees, and a golf club100whose loft angle β is largest and approximately 44 to 60 degrees.

It is preferable that the difference in the loft angle β between the golf clubs100adjacent to each other with respect to the club number is approximately 3 to 10 degrees, and in order to cover a wide range of flight distances by the golf clubs100included in the golf club set,

three or more, preferably four or more, more preferably five or more, and usually ten or less golf clubs100having different loft angles β are included in the golf club set.

FIGS. 8A, 8B and 8Care side views of the golf clubs100(100a,100band100c) included in the golf club set as an embodiment of the present invention, as viewed from the toe-side, showing their golf club heads under the respective reference states.

FIGS. 9A, 9B and 9Care front views of the golf club heads of the respective golf clubs100a,100band100c.

In term of the loft angle β, the golf club100bis larger than the golf club100aand smaller than the golf club100c(100a<100b<100c).

As to the club number, the same relationship (100a<100b<100c) exists.

The golf clubs100included in the golf club set, include a plurality of golf clubs100each composed of the above-described head1comprising the external weight member20and a club shaft s. This means that the golf club set may include one or more golf clubs whose golf club head does not include the external weight member20.

In the golf club set in this embodiment, with respect to the distance AX in the toe-heel direction y between the center of gravity g1of the external weight member20and the middle point C in the toe-heel direction y of the face lines7, the golf clubs100are configured such that the distance AX becomes larger as the loft angle β becomes smaller.

In general, a golf club100having a smaller loft angle β (so-called long iron) is required to provide a longer flight distance. Therefore, as in the present embodiment, by making the distance AX larger as the loft angle β becomes smaller, the sweet spot SS of the club face2becomes closer to the middle point C as the loft angle β becomes smaller, and higher rebound performance can be obtained.

With the above-described arrangement, the golf clubs100are desirably configured such that the distance SSX (shown inFIG. 7A) in the toe-heel direction y between the sweet spot SS and the middle point C becomes smaller as the loft angle β becomes smaller.

As to the distances SSX of the respective golf clubs100, it is preferable that the distances SSX are less than 4.0 mm, and the minimum among the values of the distances SSX is less than 1.0 mm, both in terms of the absolute value.

While detailed description has been made of preferable embodiments of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiments.

Examples

Based on the structure shown inFIGS. 1 to 6, six types of iron type golf club heads having different loft angles were experimentally manufactured. Then, various dimensions and distances relating to the position of the center of gravity of each head were measured. The results are shown in Table 1.

As can be seen from Table 1, it was confirmed that, in the iron type golf club heads according to the present invention, the center of gravity of the head is positioned toward the toe and deeper from the club face, while maintaining the center of gravity of the head at a lower position.

DESCRIPTION OF THE REFERENCE SIGNS

1iron type golf club head2club face4sole portion5toe portion7face line10head main body20external weight member22wide portion22afirst edge24narrow portion24asecond edge30internal weight member100golf clubC middle point in the toe-heel direction of the face linesg1center of gravity of the external weight memberg2center of gravity of the internal weight member