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Golf club headGolf club head description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080113825, Golf club head. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to a golf club head with improved ball-hitting directionality, and more specifically, relates to a golf club head having a large moment of inertia and improved stability of direction of a hit ball. [0003]2. Description of the Related Art [0004]Various improvements have been made to golf clubs, to extend flight distances, and to enable stable hitting of the ball. Flight distances directly affect scores, and so through improvements so as to broaden the effective range ("sweet" area) of the striking point on a golf club head (hereafter also simply called a "head"), improvements in the position of the effective area, improvements in the material of the face surface, and similar, the probabilistic ball flight distance has been extended; consequently scores have improved, and players using such heads have found them beneficial. Moreover, in order to improve scores, golf clubs have been sought for which the direction of ball-hitting is stably determined even when there is deviation of the striking point. For this reason, normally the moment of inertia must be made large. In particular, the lateral moment of inertia is an important factor determining the direction of the ball. [0005]This is because, if the moment of inertia is made large, when the striking position at which the ball is struck is shifted, so that for example the ball is struck on the toe side of the golf club head, the club does not readily bend. That is, if the moment of inertia of the golf club head is made large, then as explained above, even when the ball is hit off-center there is little shake of the head, and the ball is driven in a comparatively straight direction. Hence the average flight distance is extended, and as a result scores are improved. [0006]The wood material (persimmon) of the woods used from long ago had a tendency to cause the head to rotate easily when the ball was stuck; but modern woods, made of metal and with a hollow interior, have a larger moment of inertia compared with wooden woods, so that there is little rotation and no similar tendency, so that at present such clubs are used by many players and have become the mainstream. These hollow metal-type woods have grown in volume, but current rules stipulate a maximum volume of 460 cm.sup.3 (with a tolerance of 10 cm.sup.3). [0007]There is a trend toward larger heads, but the masses of the constituent parts of a head adds up, and the swing balance, which is a criterion for ease of swinging of a club, becomes heavy. As a result, head masses have in the prior art been no greater than approximately 210 g. That is, given the configuration of the prior art, although heads have tended to increase in size the total mass has been limited, and so excess mass to control the position of the center of gravity, or in other words, excess mass to increase the moment of inertia has in the prior art been limited to approximately 10 g, due to the constraint that the total mass should not be increased. [0008]According to R&A rules, the pendulum test method is adopted to measure the restitution coefficient of the face surface. This testing method entails fixing the club, causing a steel sphere to collide with the face surface, and measuring the contact time; the contact time is called the characteristic time, and the rule limits this characteristic time to 257 .mu.s (microseconds) or less (including a tolerance of 18 .mu.s). In order to keep this characteristic time at or less than the time stipulated by the rules, the thickness of the face portion sheet tends to become thick, but there is a limit to the extent to which the face portion mass can be reduced. Further, the hosel portion connected to the shaft is positioned on one end of the face portion, and the weight of this portion is also relatively great. [0009]Further, the above-described rules also impose various constraints on external dimensions, such as that the length from the heel portion to the toe portion must not be longer than the length from the face portion to the rear surface; that the length from the heel to the toe must be 127 mm (5 inches) or less; and that the length from the sole to the crown must be 71.12 mm (2.8 inches) or less. And, there is the further constraint that the volume must be 470 cm.sup.3 (including a tolerance of 10 cm.sup.3) or less. Given these constraints as well, the center of gravity position cannot be located in a position so as to increase the "sweet" area, and moreover the overall head mass becomes large. Due to such constraints, it is extremely difficult to increase the weight or other excess mass so as to increase the moment of inertia. [0010]Despite such engineering difficulties, various proposals to increase the moment of inertia have been made. For example, heads are known in which mass is distributed in at least one direction among the three major inertial axes in orthogonal coordinates passing through the center of gravity, or in sites in proximity thereto, or with masses distributed in such a manner (see for example Japanese Patent Laid-open No. 5-57034). And, clubs are known in which the golf club head comprises metal material members and fiber-reinforced resin members, with the head bonded together by an adhesive of thickness 0.05 to 1 mm (see for example Japanese Patent Laid-open No. 2003-320060). Also, technology is known in which an aperture portion is provided in the crown portion, and a fiber-reinforced resin with specific gravity smaller than metal materials is used in this aperture portion, to improve the ball-hitting directionality (see for example Japanese Patent Laid-open No. 2005-278838). [0011]Thus various measures have been taken to extend the flight distance of golf clubs, but at present club performance remains not entirely satisfactory. While the technologies described above have represented partial improvements, problems remain, and there is still room for improvement. Metal hollow golf club heads tend to increase in size, as described above, and if the moment of inertia is increased, the volume tends to increase as well; if the volume is increased while making efforts to limit mass, strength-related problems arise; and so there have been limits to the methods employed in the prior art. When for example using fiber-reinforced resins as described above, not only do strength-related limits appear, but there are the problems of unsatisfactory ball-hitting sounds and resistance to damage. On the other hand, insofar as is known by these inventors, there exist no golf clubs in the prior art, primarily comprising metal members, with a moment of inertia in the range 5000 to 6000 g-cm.sup.2. [0012]This invention was devised in order to resolve the above-described problems of the prior art, and attains the following objects. SUMMARY OF THE INVENTION [0013]An object of the invention is to provide a golf club with an increased moment of inertia of a metal hollow golf club head with large volume, and with improved ball-hitting directionality. [0014]A further object of the invention is to provide a golf club with an increased moment of inertia of a metal hollow golf club head with large volume without increasing the head mass, and with improved ball-hitting directionality. [0015]In order to attain the above objects, the following means are employed. [0016]The golf club of Invention 1 is a golf club having a metal hollow golf club head, comprising: a face portion positioned on a front surface of the metal hollow golf club head and having a striking face to strike a golf ball; a crown portion forming an upper surface of the club, and a sole portion forming a lower surface of the club, characterized in that the mass of the metal hollow golf club head is 210 g or less, characteristic time (CT value) of the metal hollow golf club head, relating to a restitution characteristic, is 257 .mu.s or less; and when a lie angle of the metal hollow golf club head is 60.degree., volume of the metal hollow golf club head is 470 cm.sup.3 or less, and moment of inertia about an axial line which is the center of a plumb line passing through the center of gravity of the metal hollow golf club head, is in the range 5000 to 6000 g-cm.sup.2. [0017]The golf club of Invention 2 is the golf club of Invention 1, characterized in that the metal is a titanium alloy sheet member, and a substantial center portion and an outer peripheral portion including sites of the plumb line within the curved surface of the crown portion and/or the sole portion constituting the body differ in thickness. [0018]The golf club of Invention 3 is the golf club of Invention 1 or Invention 2, characterized in that the metal hollow golf club head is formed by joining, by welding, the face portion, the sole portion, the crown portion, and a hosel portion to which the shaft is connected. [0019]The golf club of Invention 4 is the golf club of Invention 2, characterized in that a weight of 20 g or more is positioned at a position of a rotation radius most distant from the plumb line and at the crown portion and/or the sole portion. [0020]The golf club of Invention 5 is the golf club of Invention 4, characterized in that, in the golf club of Invention 4, the weight is positioned on the back side of the toe portion. [0021]The golf club of Invention 6 is the golf club of Invention 5, characterized in that the toe-side and back-side sites of the sole portion are formed in shapes protruding outward relative to the crown portion, and that the weight is positioned in this protruding sole portion. [0022]The golf club of Invention 7 is the golf club of Invention 1, characterized in that the metal hollow golf club head has: Continue reading about Golf club head... Full patent description for Golf club head Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Golf club head patent application. Patent Applications in related categories: 20090291772 - Golf club and golf club head with interchangeable body component - An iron type golf club head includes a club head having a first body component defining a striking face, and a second body component releasably secured to the first body component with a fastener. The second body component defines at least a perimeter portion of a rear face of the ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Golf club head or other areas of interest. ### Previous Patent Application: Adjustable golf putter Next Patent Application: Shock-absorbent golf club handle structure Industry Class: Games using tangible projectile ### FreshPatents.com Support Thank you for viewing the Golf club head patent info. 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