| Golf club shaft -> Monitor Keywords |
|
|
 
Golf club shaftRelated Patent Categories: Games Using Tangible Projectile, Golf, Club Or Club Support, ShaftGolf club shaft description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060128494, Golf club shaft. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This Nonprovisional application claims priority under 35 U.S.C. .sctn. 119(a) on Patent Application No(s). 2004-357416 filed in Japan on Dec. 9, 2004, the entire contents of which are hereby incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to a golf club shaft and particularly a golf club shaft, composed of a metal tube, which is lightweight and has a high strength. DESCRIPTION OF THE RELATED ART [0003] In recent years, to increase the speed of a hit golf ball and hit the golf ball stably, there is a tendency for golf club shaft manufacturers to manufacture a lightweight golf club shaft by making the head heavy concentratedly. Therefore a carbon shaft composed of fiber reinforced resin such as carbon prepreg which is lightweight and has a high specific strength and specific rigidity is most widely used. [0004] The carbon shaft has a low torsional rigidity and is unstable in the direction of a hit ball. Thus in recent years, high-class players take a new look at the directionality and the feeling they have when they hit a ball with a shaft made of metal. Recently it is possible to manufacture a shaft composed of metal tube having a weight of 85 g to 90 g. [0005] Regarding the problem of making a lightweight golf club shaft made of metal and improving the strength thereof, in Japanese Patent Application Laid-Open No. 2002-58764 (patent document 1), there is disclosed the golf club shaft composed of the cold-rolled plate made of maraging steel having a higher strength and toughness than ordinary steel as a material for the golf club shaft made of metal. According to the disclosure, the golf club shaft composed of the above-described material has a high strength and a high torsional rigidity and is lightweight. [0006] In Japanese Patent Application Laid-Open No. 7-51416 (patent document 2), there is disclosed the material made of stainless steel whose surface is coated with the hard ceramic layer such as titanium carbide or titanium nitride formed by sputtering. According to the disclosure, the golf club shaft composed of this material is firm, flexible, and capable of hitting a ball a long distance. [0007] However, to manufacture a shaft that allows female and senior players to swing easily, these conventional arts are required to reduce the weight of the shaft by thinning the material. When the material is thinned, it has a low strength. Considering the balance between the strength of the material and the thickness thereof, there is a limitation in further thinning the material. [0008] In the conventional art, the degree of flexibility of the shaft is adjusted and designed by reducing (stepped portion is formed) the diameter of the metal shaft. In the vicinity of the stepped portion, there is a point at which the thickness of the shaft changes. Thus a bending stress is applied concentratedly to the change point. Consequently the shaft has a low strength. SUMMARY OF THE INVENTION [0009] The present invention has been made in view of the above-described problems. Therefore it is an object of the present invention to provide a metal golf club shaft which has a high strength, is lightweight, and has a proper degree of flexibility. [0010] To solve the above-described problems, the present invention provides a golf club shaft composed of a metal tube and having a weight not less than 50 g and less than 85 g. A rib is formed on an inner peripheral surface of the golf club shaft and/or a peripheral surface thereof. A rigidity value (EI value) of the golf club shaft at a position spaced at 90 mm from a head-side front end thereof is set to not less than 1.0 kgmm.sup.2 nor more than 2.5 kgmm.sup.2. An outer diameter of the golf club shaft at a position spaced at 30 mm from the head-side front end thereof is set to not less than 9.5 mm nor more than 15.0 mm. [0011] As described above, by forming the rib on the inner peripheral surface of the golf club shaft (hereinafter often referred to as merely shaft) and/or the peripheral surface thereof, the shaft is capable of securing a proper degree of strength and flexibility. Thereby the shaft can be thinned entirely and made as light as 50 g. Further it is possible to design the shaft having a low rigidity by thinning the shaft at its head-side front end which affects the flight distance of a hit ball. Thus the shaft of the present invention is more flexible than the conventional shaft. Thereby female and senior players can swing it easily and increase the head speed, thus hitting a ball a longer distance. Further in addition to the formation of the rib, the outer diameter of the shaft at the position spaced at 30 mm from the head-side front end is set to not less than 9.5 mm nor more than 15.0 mm. That is, the outer diameter of the head side of shaft of the present invention is set larger than that of the head side of the conventional shaft. Thereby it is possible to enhance the strength of the head-side front end which is subjected to a high shock when the ball is hit. Therefore the shaft of the present invention balances favorably among its flexibility, strength, and weight. [0012] The flexibility of the shaft can be varied by adjusting the interval between adjacent ribs or the angle of the rib with respect to the axis of the shaft. Therefore it is unnecessary to reduce the diameter of the shaft unlike the conventional shaft. Thus it is possible to prevent a stress from concentrating on a stepped point at which the thickness of the base is changed. Thereby it is possible to prevent the shaft from being damaged. [0013] The reason the weight of the shaft is set to not less than 50 g and less than 85 g is as described below: When the weight of the shaft is less than 50 g, it is impossible to manufacture a long shaft and make the shaft strong enough to withstand a stress for flexing of the shaft. When the weight of the shaft is more than 85 g, the player has difficulty in swinging the shaft and is incapable of increasing a head speed. Thus the player cannot hit a ball a longer distance. The weight of the shaft is favorably not less than 52 g nor more than 80 g, more favorably not less than 54 g nor more than 70 g, and most favorably not less than 55 g nor more than 65 g. [0014] The reason for specifying the rigidity value of the position spaced at 90 mm from the head-side front end is because a stress is liable to be applied to the position when the player swings. [0015] The reason the rigidity value of the shaft at the position spaced at 90 mm from the head-side front end 12 is set to not less than 1.0 kgmm.sup.2 nor more than 2.5 kgmm.sup.2 is as described below. If the rigidity value at the position is less than 1.0 kgmm.sup.2, the shaft is so soft and flexible that the shaft is liable to be broken owing to metal fatigue. On the other hand, if the rigidity value at the position is more than 2.5 kgmm.sup.2, the shaft is so hard at its head side that the degree of flexibility of the shaft is low when the ball is hit and thus the flight distance of the ball decreases. The lower limit of the rigidity value is favorably not less than 1.2 kgmm.sup.2 and more favorably not less than 1.3 kgmm.sup.2. The upper limit of the rigidity value is favorably not more than 2.4 kgmm.sup.2 and more favorably not more than 2.3 kgmm.sup.2. [0016] The reason for specifying the outer diameter of the position spaced at 30 mm from the head-side front end is because the position spaced at 30 mm from the head-side front end is inserted into the neck hole of the head and corresponds to the end surface of the neck hole of the head. The outer diameter of the shaft at the position spaced at 30 mm from the head-side front end is set to not less than 9.5 mm nor more than 15.0 mm is as follows: If the outer diameter of the shaft at the above-described position is set to less than 9.5 mm, the shaft is flexible but has a low strength. On the other hand, if the outer diameter of the shaft at the position thereof is set to more than 9.5 mm, the shaft is so thin that it has a low strength. The lower limit of the outer diameter of the shaft thereof at the position thereof is more favorably not less than 9.3 mm and most favorably not less than 9.4 mm. On the other hand, the upper limit of the outer diameter of the shaft at the position thereof is more favorably not more than 14.0 mm and most favorably not more than 13.5 mm. [0017] The rib may be formed on the inner peripheral surface of the shaft and/or the peripheral surface thereof. But it is preferable to form the rib on the inner peripheral surface thereof, because the peripheral surface thereof can be formed as a smooth surface. [0018] It is preferable to continuously form the rib on the entire circumference of the shaft and in the longitudinal direction thereof to provide the shaft with a strength uniformly for a torsion and bending applied to the shaft in right and left directions. [0019] The rib can be formed in the following configurations described in (1) to (5): [0020] (1): A meshed rib by intersecting with each other a spiral rib inclined in a plus direction with respect to the axis of the shaft and a spiral rib inclined in a minus direction with respect to that of the shaft. [0021] The angle of the rib with respect to the axis of the shaft is favorably not less than .+-.20.degree. nor more than .+-.60.degree. and more favorably not less than .+-.30.degree. nor more than .+-.45.degree.. Continue reading about Golf club shaft... Full patent description for Golf club shaft Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Golf club shaft patent application. ###  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 shaft or other areas of interest. ### Previous Patent Application: Divot indicating golf practice devices Next Patent Application: Lightweight, durable golf club shafts Industry Class: Games using tangible projectile ### FreshPatents.com Support Thank you for viewing the Golf club shaft patent info. IP-related news and info Results in 0.60677 seconds Other interesting Feshpatents.com categories: Software: Finance , AI , Databases , Development , Document , Navigation , Error 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
