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Golf club head

Golf club head description/claims

The present invention relates to a golf club head capable of reducing the variation in the carry distance of a struck ball and thereby increasing the carry distances in totality.

The directional stability of a struck ball is an important factor for stabilizing the carry distance. If the ball is struck off-center, the club head is moved or rotates around the center of gravity of the head more or less. If such a rotational movement of the club head at the time of off-center shot is reduced, then the lunching direction of the struck ball is stabilized.

In recent years, on the other hand, large-sized various wood-type golf club heads have been proposed. Usually, the large-sized golf club heads are increased in the lateral moment of inertia and vertical moment of inertia.

If the vertical moment of inertia is increased, then the vertical gear effect becomes reduced, therefore, if the ball hitting position is off the sweet spot upward or downward, the carry distance tends to decrease.

AS well known in the art, the vertical gear effect is as follows. If the ball hitting position is off the sweet spot SS upwards or downwards, then as shown in FIG. 6, with respect to a horizontal axis extending in the toe-heel direction passing through the center of gravity G of the head, there is caused a moment which is a product of the impact force F received from the golf ball (b) and the distance L1 or L2 between the hitting position and the center of gravity G measured perpendicular to the direction of the force F. As a result, the club head is rotated around the horizontal axis by a small angle.

Due to the frictional engagement between the golf ball and the club face (f), the contact surface of the golf ball receives a force in the reverse direction to the rotational direction of the club head like a gear. As a result, the backspin of the struck ball is decreased in the case of an upper hitting position or increased in the case of a lower hitting position.

In consequence, in the case of the golf club heads whose vertical moment of inertia is large where the rotational movement is decreased as explained above, if the ball hitting position is off the sweet spot upward, the backspin can not be fully decreased.

On the other hand, due to the face roll having a radius of curvature Y, in the case of the upper hitting position, when compared with the sweet spot SS, the loft angle becomes increased and the launch angle of the struck ball is also increased. As a result, the ballistic course is very liable to become a rising trajectory and thereby the carry distance is decreased.

Contrary, in the case of the lower hitting position, the backspin can not be fully increased, and the launch angle of the ball is decreased. As a result, the ball tends to drop quickly and thereby the carry distance is decreased.

Thus, in the case of a large-sized golf club head, due to the relatively large vertical moment of inertia, there is a tendency that the carry distance varies wide depending of the ball hitting position.

It is therefore, an object of the present invention to provide a golf club head in which, by increasing the lateral moment of inertia and decreasing the thickness of the club head, the vertical moment of inertia is decreased on the whole, and thereby the variation in the carry distance can be reduced.

According to the present invention, a hollow golf club head has a head volume of not less than 430 cc, a lateral moment of inertia of from 5000 to 5900 g sq·cm, and a club head thickness of from 45 to 58 mm.

Therefore, the vertical moment of inertia is decreased. As a result, even if the ball hitting position is off the sweet spot upward or downward, the struck ball benefits from the vertical gear effect and the decrease in the carry distance is controlled.

Further, since the lateral moment of inertia is very large, even if the ball hitting position is off the sweet spot toward the toe or heel, the lateral movement of the club head becomes very small, and the directional stability of the struck ball is improved, therefore, the decrease in the carry distance is controlled.

In this specification, sizes, positions, directions and the like relating to the club head refer to those under a standard state of the club head unless otherwise noted.

Here, the standard state of the club head 1 is such that the club head is set on a horizontal plane HP so that the center line CL of the club shaft (not shown) is inclined at the lie angle (alpha) while keeping the club shaft center line CL on a vertical plane VP1, and the club face 2 forms its loft angle (beta) with respect to the horizontal plane HP. Incidentally, in the case of the club head alone, the center line of the shaft inserting hole (h) can be used instead of the center line of the club shaft.

Lateral moment of inertia Ma is the moment of inertia around a vertical axis A1 passing through the center of gravity G in the standard state.

Vertical moment of inertia Mb is the moment of inertia around a horizontal axis A2 passing through the center of gravity G in the heel-and-toe direction of the head in the standard state.

Sweet spot SS is the point of intersection between the club face and a straight line N drawn normally to the club face 2 passing the center of gravity G of the head.

Back-and-forth direction is a direction parallel with the above-mentioned straight line N projected on the horizontal plane HP.

• Provisional Patent
• Utility Patent

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