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Iron golf club

Iron golf club description/claims

1. Field of the Invention

The present invention relates to an iron golf club that enhances the gear effect, and more particularly to an iron golf club that lowers the rigidity of the sole portion of the head, reduces the head moment of inertia, enhances the gear effect, and accelerates ball spin.

2. Description of the Related Art

Various improvements have been made to the golf club over time for enabling stable shots to thereby increase carry and hit the ball to a precise location. In particular, iron-type golf clubs include, for example, a pitching wedge or sand wedge. These iron-type golf clubs, as a rule, are constituted such that the pitch of the face is predetermined, and a sole surface is provided in the lower portion relative to a face surface, which is the ball-hitting surface, and are golf clubs used when ball-hitting accuracy is demanded in particular.

A variety of iron golf club structures have been proposed, and a player selectively uses an iron golf club in accordance with his preferences. Examples include the flat back type, cavity type, pocket cavity type, and hollow construction type. These types of iron golf clubs all commonly have score lines formed in the surface of the face, and feature measures for stabilizing the amount of backspin imparted to the ball. In a shot to place the ball on the green, the hitting stroke is carried out so as to impart backspin (reverse rotation) to the ball and hit the ball high into the air, making it possible to stop the ball at a predetermined location on the target green.

With regard to prior art for increasing the gear effect in order to impart greater backspin to the ball, this applicant has also proposed a golf club of a construction that forms the height-distance, from the horizontal plane on which the surface of the sole of the head makes contact with the ground to the center of gravity of the head, larger than the radius of the ball, making it easier to impart spin to the ball (Refer to Japanese Patent Laid-open Number 2006-149478). Further, this applicant has proposed a golf club of a construction that either increases the flexibility of the face or the relative displacement of the face relative to the head at impact, thereby making it easier to impart spin to the ball (Refer to Japanese Patent Laid-open Number 2007-44445). Furthermore, as an example of improvement technology related to score lines, an iron golf club that forms sharp edges on the score lines to impart backspin to the ball is known (for example, Japanese Patent Laid-open Number 2004-141277).

Generally speaking, a golf club that imparts spin to the ball has score lines formed in the surface of the face as described above. Upon impact, the ball moves relatively along the surface of this face as it spins, and the ball is gripped by the edges of the score lines at this time, imparting stable spin to the ball. To put more spin on the ball, various improvements have been proposed for the surface of the face on which effective score lines are formed.

However, groove profile (marking) rules designed to establish certain restrictions on the formation of this score line groove have been studied internationally, and regulations were recently proposed. That is, as a new regulatory proposal for club face marking and spin generation, first, the value obtained by dividing the gross cross-sectional area of the score line groove by the pitch of the groove (groove width+spacing) will be restricted to 0.0025 square inches per inch (0.0635 mm2/mm). Second, the sharpness of the edge (angle) of a groove will be restricted to a lowest effective radius of 0.010 inches (0.254 mm).

A certain degree of regulation has been applied to score lines for some time, but now stricter regulations are going to be put into place. Therefore, changing the score line groove, for example, carrying out an improvement that makes the angle of the edge of the groove sharper so as to heighten the spin effect will be restricted in the future.

As mentioned above, improvements applied to the score lines of the surface of the face of a golf club will be restricted in the future, and an improvement designed to make the groove edges sharper will be substantially impossible. Therefore, other methods will have to be considered. Enhancing the gear effect to impart more backspin to the ball improves the performance of the golf club, and is not limited to the surface of the face alone. However, even though there are score line regulations that restrict improvements thereto, there is still room for improvement to aspects other than the score line, and this is what is required.

The present invention has been developed to solve for the problems inherent in the prior art as described hereinabove, and achieves the following object. An object of the present invention is to provide a golf club, which is an iron golf club designed to enhance the gear effect to make it easier to impart spin to a golf ball.

The present invention employs the following means for achieving the above-mentioned object.

An iron golf club of a first invention comprises: a head having, in a lower portion thereof, a sole part which has a ground-contact plane, and having, in an upper portion thereof, a top part, and a face part which has a ball-hitting surface for striking a ball, and, at one end thereof, a hosel part which is a shaft connector; and a shaft, which is connected at one end thereof to the hosel part, a ground-contact plane side of the head being configured to have low rigidity.

An iron golf club of a second invention according to the first invention, the top part side of the head being configured to have relatively higher rigidity than the ground-contact plane side.

An iron golf club of a third invention according to the first invention, the ground-contact plane side of the head having a relatively higher coefficient of rebound than the top part side of the head.

An iron golf club of a fourth invention according to the first through the third inventions, the ground-contact plane side of the head being in an area nearer to the sole part side than to an approximate horizontal plane which is parallel to the score lines, and which passes through the center of gravity.

An iron golf club of a fifth invention comprises: a head having, in a lower portion thereof, a sole part which has a ground-contact plane, and having, in an upper portion thereof, a top part, and a face part which has a ball-hitting surface for striking a ball, and, at one end thereof, a hosel part which is a shaft connector; and a shaft which is connected at one end thereof to the hosel part, and when the length of the above-mentioned hosel part is 50 mm or longer, the value of a moment of inertia centering on the axis that passes horizontally through center of gravity of the above-mentioned head in the toe-heel direction is less than 800 g·cm2. Preferably, this moment of inertia can be 770 g·cm2 or less.

An iron golf club of a sixth invention comprises: a head having, in a lower portion thereof, a sole part which has a ground-contact plane, and having, in an upper portion thereof, a top part, and a face part which has a ball-hitting surface for striking a ball, and, at one end thereof, a hosel part which is a shaft connector; and a shaft which is connected at one end thereof to the hosel part, and when the length of the above-mentioned hosel part is less than 50 mm, the value of a moment of inertia centering on the axis that passes horizontally through the center of gravity of the above-mentioned head in the toe-heel direction is less than 750 g·cm2.

An iron golf club of a seventh invention according to the first through the sixth inventions, the specific gravity of the material that constitutes the main part of the above-mentioned head being 6.5 g·cm2 or greater.

An iron golf club of an eighth invention according to the first through the seventh inventions, the above-mentioned head being either the head of a short iron or the head of a wedge.

All of these inventions lower the rigidity of the lower portion of the head and reduce the moment of inertia of the head, thereby increasing the gear effect and making it easier to impart spin. Means such as those described below are effective for achieving this.

• Provisional Patent
• Utility Patent

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