By a News Reporter-Staff News Editor at Journal of Engineering -- Dunlop Sports Co. Ltd. (Kobe, JP) has been issued patent number 8998745, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.
The patent's inventors are Hasegawa, Hiroshi (Kobe, JP); Nakano, Takashi (Kobe, JP).
This patent was filed on October 4, 2012 and was published online on April 7, 2015.
From the background information supplied by the inventors, news correspondents obtained the following quote: "For golfers, flight distance of a ball is one of the important factors when selecting a golf club. Therefore, hitherto, in order to extend the flight distance of the ball, various improvements have been made with regard to shapes and materials of elements forming a golf club.
"However, in recent years, in order to suppress an excessive flight distance so as to increase fairness of game, a repulsion performance of a face, club length, and inertia moment of a head are regulated by rules. Thus, improvement of the flight distance is getting more difficult.
"Under such a situation, in consideration with the fact that initial velocity of the ball largely influences the flight distance, it is proposed to extend the club length close to an upper limit regulated by the rules so as to increase head speed of the club (for example, refer to Patent Literature 1)."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Technical Problem
"However, by a method of increasing the head speed of the club by extending the club length, a control property of the head is lowered by an extended amount of the club, so that the ball is not easily stricken by a sweet spot of the head. Therefore, a hitting ratio of the ball is deteriorated, the ball initial velocity cannot be stably increased, and as a result, the flight distance of the ball cannot be improved.
"In order to solve this, there are needs for suppressing the club length so as to increase the hitting ratio and increasing head weight so as to increase the initial velocity of the ball. However, when the head weight is simply increased, the inertia moment of the club is then increased, and there is a problem that swingability of the club is lowered.
"Thus, in order to prevent an increase in the inertia moment of the club without further increasing the club weight, it is thought that a gravity center point of a shaft is moved to the butt side (gripping side).
"Movement of the gravity center point of the shaft to the butt side can be achieved by increasing thickness of a butt side part of the shaft in general. However, by this method, a bending rigidity value EI (kgfm.sup.2) of the butt side part of the shaft is also increased, so that feeling at the time of hitting the ball and directivity of the hit ball are lowered.
"The present invention is achieved in consideration with such a situation, and an object thereof is to provide a golf club shaft capable of improving feeling at the time of hitting a ball and directivity of the hit ball while extending a flight distance of the ball.
"Solution to Problem
"(1) A golf club shaft of the present invention is characterized in that when a distance from a shaft front end to a shaft gravity center point is L.sub.G and a full length of the shaft is L.sub.S, 0.54.ltoreq.L.sub.G/L.sub.S.ltoreq.0.65 is satisfied, a shaft weight is 56 g or more, and a bending rigidity value EI at a point of 630 mm from the shaft front end to the shaft rear end side is 3.6 kgfm.sup.2 or less.
"In the golf club shaft of the present invention, when the distance from the shaft front end to the shaft gravity center point is L.sub.G and the full length of the shaft is L.sub.S, 0.54.ltoreq.L.sub.G/L.sub.S.ltoreq.0.65 is satisfied and a gravity center of the shaft is on the gripping side. Thus, when weight of a head is increased in order to increase initial velocity of a ball, an increase in inertia moment of the club can be suppressed. As a result, swingability of the club is increased and a hitting ratio can be improved, so that a flight distance of the ball can be improved. The bending rigidity value EI at the point of 630 mm from the shaft front end to the shaft rear end side serving as a part where flex of the club at the time of swing is felt is suppressed to be 3.6 kgfm.sup.2 or less. Thus, head speed can be improved by utilizing the flex. Since the swingability of the club is increased, the head speed can be further improved.
"(2) In the golf club shaft of (1) described above, a low elasticity material including fibers with a fiber elastic modulus of 20 t/mm.sup.2 or less may be used for a butt side part. It should be noted that the 'butt side part' in the present description indicates a part of 300 mm from a grip end of the club toward the head side.
"(3) In the golf club shaft of (2) described above, a fiber orientation angle of at least a part of the fibers in the low elasticity material may be 0.+-.10 degrees.
"(4) In the golf club shaft of (2) described above, a fiber orientation angle of at least a part of the fibers in the low elasticity material may be 45.+-.10 degrees.
"(5) In the golf club shaft of (2) to (4) described above, the low elasticity material may include 15 to 50 mass % of prepreg containing fibers with a fiber elastic modulus of 20 t/mm.sup.2 or less. It should be noted that '15 to 50 mass %' in this case indicates a ratio of weight of the fibers with the fiber elastic modulus of 20 t/mm.sup.2 or less contained in the butt side part with respect to weight of the fibers contained in the butt side part.
"Advantageous Effects of Invention
"According to the golf club shaft of the present invention, feeling at the time of hitting the ball and directivity of the hit ball can be improved while extending the flight distance of the ball."
For the URL and additional information on this patent, see: Hasegawa, Hiroshi; Nakano, Takashi. Golf Club Shaft. U.S. Patent Number 8998745, filed October 4, 2012, and published online on April 7, 2015. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8998745.PN.&OS=PN/8998745RS=PN/8998745
Keywords for this news article include: Dunlop Sports Co. Ltd.
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