Patent Application
20100179001
1. Field of the Invention
The present invention relates to a golf ball, and more particularly, to a golf ball having long flight distance and good hitting feel.
2. Description of the Related Art
The flight distance is regarded as one of the significant criteria for evaluation of a golf ball. Generally speaking, while different golf balls are hit by the same golf club with the same head speed under the same environment, the primary factors that the flight distance of every golf ball is subject to change contain initial velocity, spin rate, and launch angle of the ball. Among the factors, the initial velocity is the key. In the prior art of the golf ball, coefficient of restitution (COR) is a substitution parameter of the initial velocity. If the COR of the golf ball is higher, in general, the flight distance of the ball will be longer.
The popular golf ball sold in the market for the common amateur golfers are a two-piece ball having long flight distance and preferable durability. Such two-piece golf ball is composed of a solid core and a cover layer enclosing the solid core, wherein the core is made from polybutadiene and the cover layer is made from tough polymer, like ionomer. However, when the golfer strikes such ball with a short iron, the hitting feel is worse and the spin rate is low, such that the golfer has worse control of the ball and thus the two-piece ball is not popular for the low-handicappers or professionals. On the contrary, the popular golf ball for the professionals, such as wound golf ball, has better hitting feel and higher spin rate to have better controllability. However, the wound golf ball has shorter flight distance. For this reason, many patents for improvement of such drawback were presented as recited below.
U.S. Pat. No. 6,254,495 disclosed a multi-layer solid golf ball comprising a core, an enclosing layer, an intermediate layer, and a cover. Each of the core and the enclosing layer is made from thermoplastic resin or thermoplastic elastomer. The diameter of the core is defined between 3 mm and 18 mm. The intermediate layer is made from polybutadiene rubber. Such ball has good hitting feel but the diameter of the core is too small to provide long flight distance.
U.S. Pat. No. 5,556,098 disclosed a three-piece solid golf ball comprising a center core and an intermediate layer. The center core is made from polybutadiene, having a specific gravity of less than 1.4 and a diameter of at least 26 mm. The intermediate layer is made from polyester elastomer, having a specific gravity smaller than 1.2. However, such ball fails to produce sufficient moment of inertia (MOI) effectively and to have good hitting feel.
U.S. Pat. No. 5,899,822 disclosed a three-piece solid golf ball comprising an intermediate layer and a cover layer. The Shore D hardness of the intermediate layer is greater than the cover layer for at least 13 degrees. The MOI of such ball is at least more than 83 g·cm2. However, the Shore D hardness of the intermediate layer is too large to enable the golf ball to have good hitting feel.
U.S. Pat. No. 6,653,382 disclosed a thermoplastic copolymer for use in a golf ball. When a sphere is made from the thermoplastic copolymer to have a diameter between 1.5 inches and 1.54 inches and the sphere is tested at an initial velocity of 125 ft/s, its COR can reach 0.785 and higher and its Atti compression is lower than 100. Such ball comprising the 1.5 inches to 1.54 inches sphere inside has long flight distance but has a bad hitting feel because of overgreat diameter of the sphere thereof.
U.S. Pat. No. 6,458,046 disclosed a multi-layer wound golf ball comprising a solid center made from thermoplastic elastomer, an intermediate layer made from a thermoset material and enclosing the solid center, a wound layer enclosing the intermediate layer, and a cover layer enclosing the wound layer. Such ball though has good hitting feel but is devoid of long flight distance. Besides, it is not easy to produce the wound ball, so that such ball is not applicable to the mass production.
The golf ball of the present invention has a compression deformation of 2 mm to 4 mm and comprises a core made from a thermoplastic material, an intermediate layer made from a thermoset material, and at least one cover layer. The COR of the core falls between 0.78 and 0.89 and is higher than that of the whole golf ball.
Referring to
The core 10 is made from a thermoplastic material selected from a group consisting of ionomer resin, polyamide resin, polyester resin, polyurethane resin, and a mixture thereof. In this embodiment, ionomer resin is preferred for the core 10. The suitable ionomer resin includes HPF and Surlyn®, both commercially available from E.I. DuPont de Nemours and Company, or IOTEK®, commercially available from Exxon Corporation.
To increase the COR of the core 10 for longer flight distance, the core 10 is made from a primary material, like HPF 1000 or HPF 2000, and from an optional secondary material, like Surlyn® or IOTEK®. The secondary material of the core 10 is in an amount of 0 to 10 parts by weight, based on 100 parts by weight of the primary material of the core 10.
It is to be noted that the COR of the core 10 in this embodiment is defined between 0.78 and 0.89, preferably between 0.79 and 0.89, for longer flight distance. Also, the COR of the core 10 in this embodiment is higher than that of the golf ball 100. Preferably, the COR of the core 10 is higher by at least 0.01, more preferably at least 0.02, than that of the golf ball 100. The COR of the golf ball 100 in this embodiment is defined between 0.78 and 0.83, preferably between 0.795 and 0.83. Besides, the diameter and the specific gravity of the core 10 having longer flight distance in accordance with the aforesaid conditions are set forth below.
The diameter of the core 10 is defined between 19 mm and 37 mm, more preferably between 21 mm and 35 mm, and most preferably between 23 mm and 32 mm. The specific gravity of the core 10 is defined preferably between 0.9 and 1.2, more preferably between 0.92 and 1.1.
The core 10 is prepared by hot-press molding or injection molding, and the injection molding is preferred. When the core 10 is prepared by injection molding, the temperature of the injection machine is set between 190° C. and 220° C.
The core 10 of the present invention can alternatively be a multi-layer construction and be made from any other thermoplastic material except for the aforementioned materials, as long as the core 10 has the COR between 0.78 and 0.89.
In addition to improvement of material, construction, and physical property of the core 10, the present invention also specifies that the specific gravity of the whole golf ball 100 falls between 0.97 and 1.2, preferably between 1 and 1.2, and that the MOI of the golf ball 100 is at least 79 g·cm2, preferably greater than 83 g·cm2, and most preferably between 83 g·cm2 and 86 g·cm2, for longer flight distance.
On the other hand, to enable the golf ball 100 having longer flight distance to have better hitting feel, the compression deformation of the whole golf ball 100 is kept between 2 mm and 4 mm, preferably between 2.7 mm and 3.7 mm. The compression deformation herein indicates the deformation amount of the ball under a force; specifically, when the force is increased to become 130 kg from 10 kg, the deformation amount of the ball under the force of 130 kg subtracts the deformation amount of the ball under the force of 10 kg to become the compression deformation of the ball. Such compression deformation is reached as per the following structure.
The intermediate layer 20 is made from a thermoset material, like rubber compound, and many base rubbers can be applied to the rubber compound. The base rubbers include 1,4-cis-polybutadiene, polyisoprene, styrene-butadiene copolymers, natural rubber, and a mixture thereof. For more resilience, 1,4-cis-polybutadiene is preferred for the intermediate layer 20. Alternatively, 1,4-cis-polybutadiene can be used as the base material for the intermediate layer 20 and mixed with other ingredients. However, the amount of 1,4-cis-polybutadiene should be at least 50 parts by weight, based on 100 parts by weight of the rubber compound. In addition, the base rubber can further include additives, like a cross-linking agent and a filler, to increase the specific gravity. For example, the cross-liking agent includes zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate, wherein zinc acrylate is preferable in consideration of more resilience. Furthermore, for more specific gravity, the intermediate layer 20 can include filler therein, such as zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate, wherein zinc oxide is preferable. Powder of metal, like tungsten, having a great specific gravity can also be the filler to enable the intermediate layer 20 to reach the required specific gravity. The Shore D hardness of an external surface 21 of the intermediate layer 20 is kept between 40 and 60 preferably. If the Shore D hardness of the external surface 21 is greater than 60, the golf ball 100 will not have good hitting feel. If the Shore D hardness of the external surface 21 is less than 40, the golf ball 100 will not have long flight distance.
The preparation of the intermediate layer 20 is not exceptionally limited and can be done by that of the cover layer of the conventional golf ball. For example, the above-mentioned rubber compound is mixed by kneader and roll mill and then molded to prepare two semi-spherical half-shells; next, the two semi-spherical half-shells encapsulate the core 10, and then they are treated by hot-press molding under the mold temperature between 125° C. and 165° C. for 270 to 390 seconds to finally prepare a sphere having the core 10 and the intermediate layer 20.
Further, the Shore D hardness of an external surface 31 of the cover layer 30 is kept between 40 and 75 for long flight distance and good hitting feel.
The preparation and material that the cover layer 30 is made by and from are not exceptionally limited and those of the conventional golf ball can be applied thereto.
Specified hereunder is the data mentioned in Tables 1 to 4 and the measuring method of the above-mentioned data.
The material that the core 10 is made from is selected from Table 1. The material that the intermediate layer 20 is made from is selected from Table 2. The material that the cover layer 30 is made from is selected from Table 3.
The amount of the materials listed in Tables 1 to 3 is shown in weight percentage. The test items and methods of the golf balls in Examples and Comparative Examples are set forth below and the test result is shown in Table 4, wherein
Compression deformation: As defined above;
Hardness: Shore D hardness values of the core, intermediate layer, and cover layer are measured on the spherical surface of the core, intermediate layer and cover layer respectively.
Method of measuring COR: A golf ball for test is fired by an air cannon at an initial velocity of 40 m/sec, and a speed monitoring device is located over a distance of 0.6 to 0.9 meters from the cannon. When striking a steel plate positioned about 1.2 meters away from the air cannon, the golf ball rebounds through the speed-monitoring device. The return velocity divided by the initial velocity is the COR;
MOI: Measured by Moment of Inertia Instrument (model number MOI-005-004) manufactured by Inertia Dynamics, Co.;
Flight performance: The test for carry and total distances is done in such a way that a driver club (W#1) is fixed to a swing robot manufactured by Miyamae Co., Ltd. and then swung at the head speed of 40 m/s; the golf club is SasQuatch, having a loft of 9.5° and manufactured by Nike, Inc.; and
Hitting feel: Let five low-handicap golfers swing the driver club (W#1) and the putter (PT) for practical strikes. If more than four golfers think that the ball has good hitting feel, the value is marked “◯”. On the contrary, if more than four golfers think that the ball has bad hitting feel, the value is marked “X”.
Known from the above data, when the core 10 is made from the thermoplastic material; the intermediate layer is made from the thermoset material; the COR of the core falls within a specific range and higher than that of the whole golf ball, the flight distance and hitting feel of the Examples are better than those of the Comparative Examples. Secondly, the compression deformation data show that the hitting feel is better when the compression deformation within a specific range is larger. As for the diameter of the core, when the diameter within a specific range is larger, the flight distance is longer. Thirdly, when the specific gravity of the core falls within the specific range of the present invention, the flight performance is better. Fourthly, when the MOI is higher, the flight distance is longer. Therefore, the golf ball of the present invention indeed includes good flight distance and hitting feel.
Although the present invention has been described with respect to a specific preferred embodiment thereof, it is no way limited to the details of the illustrated structures but changes and modifications may be made within the scope of the appended claims.
