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Golf ballRelated Patent Categories: Games Using Tangible Projectile, Golf, Ball, Particular Unitary Or Layered ConstructionGolf ball description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060025239, Golf ball. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims priority on Patent Application No. 2004-221049 filed in JAPAN on Jul. 29, 2004, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to golf balls. More particularly, the present invention relates to multi piece golf balls having a core, a mid layer and a cover. [0004] 2. Description of the Related Art [0005] Top concern to golf players for golf balls is their flight performances. Golf balls that are excellent in flight performances are responsible for scores. The golf players particularly place great importance on flight distance attained upon shots with a driver. [0006] Golf players also place great importance on spin performances of golf balls. Great back spin rate results in small run. For golf players, golf balls which are liable to be spun backwards are apt to be rendered to stop at a targeted position. Great side spin rate results in easily curved trajectory of the golf ball. For golf players, golf balls which are liable to be spun sidewise are apt to allow their trajectory to curve intentionally. Golf balls that are excellent in spin performances are excellent in control performances. High-class golf players particularly place great importance on control performances upon shots with a short iron. [0007] In light of the flight performances and control performances, golf balls having a variety of structures have been proposed. For example, U.S. Pat. No. 6,106,415 discloses a golf ball having a core, a mid layer comprising an ionomer resin and a cover comprising polyurethane. [0008] Covers having high elasticity are advantageous in terms of the flight performance. However, highly elastic covers liable to deteriorate the control performance. Soft covers are advantageous in terms of the control performance. However, the soft covers are disadvantageous in terms of the flight performance. Demands from the golf players for golf balls have increasingly escalated in recent years. Highly balanced flight performances and control performances have been desired. An object of the present invention is to provide golf balls that are excellent in flight performances and control performances. SUMMARY OF THE INVENTION [0009] A golf ball according to the present invention has a spherical core, a mid layer positioned outside of this core, and a cover positioned outside of this mid layer. Principal component of the base polymer of this mid layer is an ionomer resin. This mid layer has a hardness Hm as measured with a Shore D type hardness scale of equal to or greater than 62. This cover has a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 55. This cover has a weight Wc of equal to or less than 3.2 g. Ratio (Hc/Wc) of the hardness Hc to the weight Wc (g) of this cover is equal to or greater than 10.0. [0010] Because low head speed is achieved upon shots with a short iron, amount of deformation of the golf ball is small. Upon shots with a short iron, spin rate primarily depends on the material of the surface of the cover. Because the golf ball according to the present invention has a cover having a hardness Hc of equal to or less than 55, slipping that occurs between the club face and the golf ball upon impact is suppressed. According to this golf ball, a great spin rate is achieved upon a shot with a short iron. This golf ball is excellent in a control performance upon a shot with a short iron. [0011] Upon shots with a driver, the mid layer and the core are also deformed greatly in addition to the cover. Covers having a low hardness Hc may be disadvantageous in terms of resilience performances. Less adverse effects from the cover are exerted on the resilience performance because the cover has a weight Wc of equal to or less than 3.2 g and the ratio (Hc/Wc) of equal to or greater than 10.0 in this golf ball. Great resilience performance is accomplished by providing the mid layer in which an ionomer resin is used, and which has a hardness Hm of equal to or greater than 62. This golf ball is excellent in a flight performance upon a shot with a driver. [0012] Preferably, principal component of the base polymer of the cover is a thermoplastic polyurethane elastomer. Preferably, the cover has a thickness Tc of equal to or less than 0.6 mm. [0013] Preferably, a reinforcing layer is provided which comprises a thermosetting resin as a base polymer between the mid layer and the cover. Preferably, this reinforcing layer has a thickness of 3 .mu.m or greater and 50 .mu.m or less. Preferably, this reinforcing layer has a tensile strength of 150 kgf/cm.sup.2 or greater and 500 kgf/cm.sup.2 or less. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is a partially cut off cross-sectional view illustrating a golf ball according to one embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0015] The present invention is hereinafter described in detail with appropriate references to the accompanying drawing according to the preferred embodiments. [0016] A golf ball 2 depicted in FIG. 1 has a spherical core 4, a mid layer 6 covering this core 4, a reinforcing layer 8 covering this mid layer 6, and a cover 10 covering this reinforcing layer 8. Numerous dimples 12 are formed on the surface of the cover 10. Of the surface of the cover 10, a part except for the dimples 12 is a land 14. Although this golf ball 2 has a paint layer and a mark layer to the external side of the cover 10, these layers are not shown in the Figure. [0017] This golf ball 2 has a diameter of from 40 mm to 45 mm. From the standpoint of conformity to a rule defined by United States Golf Association (USGA), the diameter is preferably equal to or greater than 42.67 mm. In light of suppression of the air resistance, the diameter is preferably equal to or less than 44 mm, and more preferably equal to or less than 42.80 mm. This golf ball 2 has a weight of 40 g or greater and 50 g or less. In light of attainment of great inertia, the weight is preferably equal to or greater than 44 g, and more preferably equal to or greater than 45.00 g. From the standpoint of conformity to a rule defined by USGA, the weight is preferably equal to or less than 45.93 g. [0018] The core 4 is usually obtained through crosslinking of a rubber composition. Examples of preferred base rubber include polybutadienes, polyisoprenes, styrene-butadiene copolymers, ethylene-propylene-diene copolymers and natural rubbers. In light of the resilience performance, polybutadienes are preferred. When other rubber is used in combination with polybutadiene, it is preferred that polybutadiene is included as a principal component. Specifically, the proportion of polybutadiene occupying in total base rubber is preferably equal to or greater than 50% by weight, and particularly preferably equal to or greater than 80% by weight. Polybutadienes having a percentage of cis-1,4 bond of equal to or greater than 40%, and particularly equal to or greater than 80%, are preferred. [0019] For crosslinking of the core 4, a co-crosslinking agent is usually used. Preferable co-crosslinking agent in light of the resilience performance is a monovalent or bivalent metal salt of an .alpha.,.beta.-unsaturated carboxylic acid having 2 to 8 carbon atoms. Specific examples of preferable co-crosslinking agent include zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. Zinc acrylate and zinc methacrylate are particularly preferred on the ground that a high resilience performance can be accomplished. [0020] Also, an .alpha.,.beta.-unsaturated carboxylic acid having 2 to 8 carbon atoms, and an oxidized metal may be blended as a co-crosslinking agent. Both components react in the rubber composition to give a salt. This salt is responsible for the crosslinking reaction. Examples of preferable .alpha.,.beta.-unsaturated carboxylic acid include acrylic acid and methacrylic acid. Examples of preferable oxidized metal include zinc oxide and magnesium oxide. Continue reading about Golf ball... Full patent description for Golf ball Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Golf ball 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. 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