Golf Club

1. Field of the Invention

The present invention relates to a golf club.

2. Prior Art

In a conventional process for producing a golf club provided with a head made of metal material such as aluminum, stainless steel or titanium, a tip end portion of a shaft is directly inserted into a shaft insertion portion of a head and securely fixed thereto with adhesives.

In the prior art, a shock generated in ball impact is not moderated and is transmitted to the player almost without reducing the magnitude of the shock. Thus, in many cases, the wrists, elbows or shoulders of the player might be damaged. Since the tip end portion of the shaft that has been inserted into the head is bound thereby so that it hardly flexes, it is difficult to exhibit the inherent performance of the shaft. In the golf play, the hit distance of the ball depends mainly on an initial velocity of the ball, an angle of the hit ball and a spinning amount of the ball. Also, it is effective to increase the head speed of the club by generating a flexible motion of the tip end portion of the shaft which transmits the energy to the ball to increase the repulsive force. However, such effect could not be expected in the club according to the prior art.

In view of the foregoing defects, an object of the present invention is to provide a golf club which enables to suppress a shock generated upon the ball impact, and which would hardly damage player's wrists, elbows, shoulders and the like.

It is another object of the invention is to provide a golf club wherein a tip end portion which has been inserted into a head may flex to thereby exhibit an inherent performance of the golf club.

Still another object of the present invention is to provide a golf club which increases a repulsive force to enhance a head speed and to increase a hit distance of the ball by generating a flexible motion of the tip end portion of the shaft.

In order to attain these and other objects, according to the present invention, there is provided a golf club wherein a shaft sleeve made of non-metallic material such as fiber reinforced plastic, wood or the like is mounted on a tip end portion of a shaft.

According to another aspect of the invention, there is provided a golf club wherein a shaft sleeve made of non-metallic material such as fiber reinforced plastic, wood or the like is mounted on a shaft insertion portion of a head.

If the shaft sleeve made of non-metallic material such as fiber reinforced plastic, wood or the like which has a suitable flexibility in comparison with metal is mounted on a shaft insertion portion of a head or a tip end portion of the shaft, by elasticity of the shaft sleeve 2, it is possible to suppress the shock generated upon the ball impact, to flex the tip end portion of the shaft inserted into the head, and to generate a flexible motion at the tip end portion of the shaft to increase the repulsive force thereby enhance the head speed of the club.

The above-described increment of the repulsive force may be explained as a so-called "kick back phenomenon" which may be generated by the provision of the above-described shaft sleeve. Namely, upon the swing of the golf club, the head is momentarily returned back, and at the same time, a large repulsive force is generated at the tip end portion of the shaft so that an acceleration is generated by the repulsive force to increase the head speed. Also, if the tip end portion of the shaft is flexed, the longitudinal gear effect of the club head is remarkable to suppress the generation of the back spin of the ball.

In the accompanying drawings:

FIG. 1 shows an overall view of the main part of the golf club according to an embodiment of the invention; and

FIG. 2 is a cross-sectional view of the main part shown in FIG. 1.

The present invention will now be described with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a shaft sleeve 2 made of non-metallic material such as fiber reinforced plastic (FRP), wood or the like is securely fitted around a tip end portion 1a (i.e., lower end portion) of a shaft 1. The tip end portion 1a of the shaft 1 provided with shaft sleeve 2 is securely inserted by threading or adhesives into a shaft insertion portion 3a of a metallic head 3 made of aluminum, stainless steel, titanium or the like. A length x of a flange 4 formed integrally with the head 3 is set at a short level. In assembling order, the shaft sleeve 2 is securely inserted first into the shaft insertion portion 3a of the head 3 and the tip end portion 1a of the shaft 1 may be securely inserted into the shaft insertion portion 3a to which the shaft sleeve 2 has been fixed. Incidentally, the shaft sleeve 2 may be fully inserted into the shaft insertion portion 3a of the head 3 or otherwise may be partially extruded out of the head 3.

As in the golf club having the structure described above, if the shaft sleeve 2 made of non-metallic material such as fiber reinforced plastic material wood or the like is mounted on the shaft insertion portion 3a of the head 3 or the tip end portion 1a of the shaft 1, it is possible to moderate a shock generated upon ball impact, by the elasticity of the shaft sleeve 2, to thereby reduce a magnitude of the shock to be transmitted to the player in comparison with the conventional golf club. Thus, the player's wrists, elbows, shoulders and the like would not be damaged. Also, the tip end portion la of the shaft 1 that has been inserted into the head 3 may be flexed together with other parts, the inherent performance of the shaft may readily be exhibited. Also, a flexible motion of the tip end portion 1a of the shaft 1 is caused to be generated, thereby increasing the repulsive force to enhance the head speed of the club, resulting in a long hit desitance of the ball.

The fact that shaft 1 is flexed also at the tip end portion 1a that has been inserted into the head 3 explains the phenomenon at the tip end portion of the overall flexure. This makes a remarkable difference in magnitude of the flexure of the overall shaft 1 and magnitude of repulsive force. Namely, a so-called "kick back phenomenon" is generated, and more specifically, the head 3 is momentarily returned by the shock of the ball impact, and at the same time, a large repulsive force is generated at the tip end portion 1a of the shaft 1. An acceleration is generated by the repulsive force to increase the head speed. As a result, the ball hit distance may be elongated. Also, when the tip end portion 1a of the shaft 1 is flexed, a longitudinal gear effect of the club head is remarkable and a so-called back spin would hardly be applied to the ball. Thus, it is possible to elongate the ball hit distance. This effect is further enhanced since the length x of the flange 4 formed integrally with the head is set at a short level.

In order to numerically confirm the above-described kick back phenomenon, the following comparison experiments were conducted. However, since it was difficult to directly measure the head speed accelerated in the moment of the impact, this was replaced by the speed (initial velocity) of the ball in the experiment. The test conditions, items and results of the measurement were shown as follows.

1. Test Conditions

(1) Head speed of Club (HV): 40 m/s or 45 m/s

(2) Club Used: BIG-LB Metal (Trade Name of Present Assignee)

#1 Wood

Loft Angle 10.5.degree.

(3) Ball Used: Two-Piece Ball

2. Measurement Items

(1) Ball Velocity (BV)

(2) Number of Back Spin (rpm) of the Ball

3. Measurement Results

As shown in Tables 1 and 2, the speed of the ball of the golf club of "shaft sleeve applied" where the shaft sleeve 2 made of non-metallic material such as fiber reinforced plastic, wood or the like was mounted on the shaft was faster than the conventional club of "no shaft sleeve applied" and the number of back spins according the present invention was more suppressed than that of the conventional club. Also, in the club of "shaft sleeve applied", the advantage was more remarkable in the case of higher head speed than in the case of lower head speed.

The present invention offers the following advantages.

According to the present invention, since the shaft sleeve made of non-metallic material such as fiber reinforced plastic, wood or the like is mounted on the shaft insertion portion of the head or the tip end portion of the shaft to suppress the shock generated upon the ball impact, the wrists, elbows, shoulders or the like of the player would hardly be damaged. Accordingly, it is possible to provide a golf club which may readily be used by anybody. Also, since the tip end portion of the shaft which has been inserted into the head may flex together with the other parts, it is easy to enjoy the inherent performance of the shaft. Therefore, it is possible to provide a high performance golf club which may sufficiently exhibit the inherent performance of the shaft. Also, since the tip end portion of the shaft may take a flexible motion to generate the kick back phenomenon to increase the repulsive force, it is possible to enhance the head speed of the club to increase the hit distance of the ball. In this sense, it is possible to provide a high performance golf club.