GOLF CLUB

Abstract: A golf club for improving the flying distance by removing phenomenon of pulling the shaft occurring as a reaction to phenomenon of prostrated toe liable to occur particularly to a skilled player enjoying a high head speed and further improving the head speed, and for improving the directional stability of a hit ball by removing phenomenon of prostrated toe and changing the design such as in the face resulting therefrom, the golf club being characterized in that the center of gravity of the head is shifted from the toe end to the shaft end by modifying the head shape by decreasing the volume of the head by a certain amount at the toe end on the rear side thereof ad increasing the head volume at the shaft end on the rear side by an amount equal to the amount decreased, thereby reducing the rotational radius of the head about a vertical line, as a rotational center line, when the golf club is suspended at the upper end of the shaft thereof. Furthermore, with a metal wood club, a head is provided with a face which comprises a spherical face formed in such a manner that the curvature in the transverse width direction becomes substantially equal to that in the vertical width direction. Moreover, with an iron club, the shape of the back of the face portion is formed by extending the central axis a of the above hosel substantially to a position where it passes through in the transverse direction, and the increase in thickness of the back of the neck portion is effected by moving a part of the weight at the toe end.

Description: The present invention relates to a golf club by use of which the directional stability and flight distance of a shot ball can be improved. In a conventional wooden club, as well as a metal wood club, the head is in such a shape that, as shown by a two-dashed line in Fig. 1, it gradually expands from a shaft side to a toe side. The centre of gravity of the head is set at a position toward the toe side rather than at the centre of the projection plane of the head, so that the head speed of the golf club may be maximised at the time of impact with the ball. Also, in a conventional golf club of an iron type, according to a similar theory, the shaft end of the back face of a club head is, when seen in plan view, smoothly connected to the hosel, through a neck part, forming a curve and thus the centre of gravity of the club is set at a position slightly toward the toe end. However, when the centre of gravity of the head lies toward the toe end, and when the head B is rotated whilst holding an end A of the club shaft, a radius R0 of the rotation, from a centre line of rotation positioned on the vertical line made by suspending an upper end of the shaft, increases as shown by double-dashed lines in Figure 2. Therefore, the clubs are apt to give a covering motion (which means that the toe end moves faster than the shaft end as if the toe rotates around the shaft) at the club head toe just before impact. For the purpose of inhibiting a hooked stroke, caused by the covering motion, the known metal wood-type clubs, as shown by a double-dashed line in Fig. 1, usually have a head striking face surface of such a shape that the shaft side expands slightly more at the shaft end than the toe end. Accordingly, curvatures along the transverse direction of the face surface and curvature along the longitudinal direction of the face surface are not the same; usually curvature in the longitudinal direction is larger than that along the transverse direction. Accordingly, for the purpose of overcoming the defects of the conventional club head, the inventor, as a result of his research, has altered the basic concept of designing the club head in order to provide a golf club head by use of which improvement in the directional stability and flight distance of the shot ball can be realised. That is the object of the present invention. The present invention is based upon the effect of the sling motion of the club head round the centre of gravity thereof, in which a heavier part goes faster and a lighter part lags behind the heavier part. This results in the parts rotating around the centre of gravity, so that the conventional club head is subjected not only to the above-mentioned covering movement but also to a pull-back phenomenon at the shaft end of the head as a reaction to the covering movement, resulting in a substantial decrease of the speed of the head. The present invention, therefore provides a metal wood-type golf club comprising a club head connected to a shaft via a hosel, the head extending from a heel end adjacent the hosel to a toe end, characterised in that the centre of gravity of the club head lies closer to the heel end than to the toe end of the head. This is achieved by shaping the club head with an increased mass at the shaft end and with the mass of the head toe end decreased by an equivalent amount, by adopting the shape, seen from above, showin in full lines in Figure 1. Thus the maximum radius of rotation, centred on a vertical line made by suspending an upper end of a shaft, is decreased. Furthermore, the striking face of the club is part-spherical, with substantially the same curvatures in the longitudinal and transverse directions. Mere shift of the centre of gravity of the head toward the shaft side is not enough to overcome the covering motion of the head; at the same time, the weight balance of the head must be maintained. Therefore, it is advantageous to increase the mass of the shaft end of the head as much as that of the toe end decreases so as to maintain the weight balance of the head. Due to this, the centre of gravity of the head is moved toward the shaft area by the amount having been shifted. In clubs embodying the present invention, since the centre of gravity of the head lies toward the shaft side, when the head is rotated by holding the end of the club shaft, the radius R1 of rotation is smaller, as shown in full lines in Figure 2, than the conventional radius R0 of rotation. Moreover due to the increased mass of the shaft end of the head, there is an improvement in the speed of the head upon impact when a ball, which results from the reduced sling motion (in which the heavier part tends to go forward and the lighter part tends to be pulled backward just before impact, as shown in Fig. 3(b)). In clubs according to the invention it is difficult to cause the covering motion which in conventional clubs is apt to take place in the toe end and the draw phenomenon apt to take place in the shaft end of conventional clubs. In the present invention the curvatures along the transverse direction and along the longitudinal direction of the striking face surface are made substantially the same. Since the flight direction of the shot golf ball is dominated by both curvatures along the transverse direction and along the longitudinal direction of the face surface at the point where the impact is made, when the curvatures are not the same, as in conventional clubs, the flight is not controlled to the desired direction. In the present invention, however, the covering motion of the head at the time of the impact is inhibited by shifting the centre of gravity of the head toward the shaft side, and the head face surface is formed by a sphere having substantially the same curvatures along both directions of the face surface, which spherical face is most suitable for giving an impact causing control of the hit ball. Moreover, since it is difficult to cause the covering motion of the head upon giving an impact, the ball tends to be directed along the extension of a radius connecting the centre C of a spherical body defining the spherical face and the position where the impact was made, thus superior directional stability of the ball is ensured. The club face can be designed so as to slightly open by about 1.5° against the ball upon addressing the ball, so that a defect of the conventional club, in which the head easily turns after the impact and therefore golfers are apt to "duff", can be overcome. The impact is made in a slightly open position and immediately after this the position becomes square and then the head turns little by little, which makes the ball fly in a high draw trajectory. Fig. 1 is a plan view comparing the plan shape of a metal head according to the present invention with that of a conventional metal head. Fig. 2 is a comparative view showing sling motions of wood-type clubs with the metal head according to the present invention and with the conventional metal head. Fig. 3(a) is an explanatory view showing motion of the conventional metal head before and after an impact. Fig. 3(b) is an explanatory view showing motion of the metal head according to the present invention before and after impact. Fig. 4 is a perspective view showing the idea of designing a face surface of the metal head according to the present invention. The present invention will now be explained in detail, in which the present invention is applied to a metal wood-type club. Fig. 1 is a plan view illustrating a projected plan of a metal head according to the present invention, comparing with a conventional metal head. A metal head 1 is a hollow casting, having a spherical face 2 and a hosel part 3 connecting with an unshown shaft. The weight distribution 11 of the toe end is shifted to the back of the shaft end 12 and expanded (See the extent of oblique shading). On the whole, the distribution of the amount is not symmetrical, but lies toward the shaft end rather than the toe end. Therefore the centre of gravity of the head shifts from G0 towards the shaft end G1, and the distribution of the mass in the shaft side is increased. As a result, superior weight distribution which, at the moment of impact, suppresses the covering motion in the toe side and the draw phenomenon in the shaft side, can be obtained. As for the face surface 2, as shown in Fig. 4, the curvature R along the transverse direction and the curvature R along the longitudinal direction are the same and the face 2 surface is so designed that it forms a part of a sphere with radius R round a centre C as illustrated. The hosel part 3 obliquely protrudes upward from a position adjacent to the face surface translated in parallel to the centre of the sphere. The loft angle of the face surface generally falls in the range from about 9° - 12° and both curvatures along the transverse and longitudinal directions of the face are selected from the range from 9 - 12R so that they are the same. Use of such a golf club makes a golf ball and the face surface collide with each other at the time of impact as if a small ball and a large ball collided with each other and the golf ball is directed along a line extending the radius connecting the spherical centre C and the position where the impact was given.

Claims: A metal wood-type golf club comprising a club head (1) connected to a shaft via a hosel (3), the head extending from a heel end adjacent the hosel to a toe end, characterised in that the shape (11,12) seen from above of the rear surface of the club head is as shown by full lines in Figure 1 so that the centre of gravity of the club head lies closer to the heel end than to the toe end of the head (1) and in that the head (1) has a striking face (2) spherical surface with substantially the same curvatures along the transverse direction thereof and along the longitudinal direction thereof. A metal wood-type club according to claim 1 wherein the striking face (2) has a loft angle of 9° -12°.

Inventors: SASO MITSUHIRO, SASO, MITSUHIRO
Applicants: KABUSHIKIGAISHA HIMEJI LODGE H, KABUSHIKIGAISHA HIMEJI LODGE HAKUBA
Application year: 1992
Main classification: A63B53
IPC codes: A63B53