JPH0675607B2 - Floating practice golf ball - Google Patents

Description

The present invention relates to a floating practice golf ball.

[Conventional technology]

Generally, the performance required of a practice golf ball is first of all that it has a feeling that is not different from that of a round ball and that it has a trajectory shape similar to that of a round ball. It is thought that the skill of a golfer who practiced with a practice ball will be improved by providing the.

In other words, by being able to reproduce the trajectory during golf play on the practice field, it becomes easier to improve inconvenient parts such as swing and address, and unless the trajectory during golf play can be reproduced on the practice field, It is considered that a nice shot does not necessarily lead to a nice shot in golf play.

By the way, practice golf balls are roughly classified into two types according to the location conditions of the practice field. One of them is a so-called normal range ball that is hit into an area usually surrounded by a net called a golf range (not necessarily surrounded in foreign countries), and the other one is
A water golf ball that is driven into a pond or lake. In water golf that is adopted due to this geographical or economic factor, it is called floating ball because it is the first essential condition that the ball used is to float on the water in order to facilitate its recovery. Has been.

On the other hand, a round golf ball has a set standard, and the weight and outer diameter of the ball are regulated. That is, the ball outer diameter is 1.680 for large size balls.
Inches (42.67mm) and up, ball weight 1.62 oz (45.
92g) or less. A golfer's dream is to extend the flight distance even further by 1 m, so the ball outer diameter is usually set to the minimum limit and the ball weight is set to the maximum limit in order to give a slight advantage in the flight distance. There is. As a result, the specific gravity of the round golf ball is about 1.1 to 1.2 in the case of the large size ball, and the specific gravity is higher in the small size ball, and the normal round ball does not float on water.

In comparison, floating balls have a specific gravity of 1.0
Since it needs to be below, even if the specific gravity is at the upper limit of 0.99, a large size ball weighs 39 to 40 g.
It is 5 to 6g lighter than the round ball.

By the way, golf balls have dimples to extend the flight distance, which makes them about
A flight distance increase of nearly 100m has been achieved. The role of these dimples is generally to promote turbulent transition in the boundary layer and cause turbulent flow separation, so that the separation point decreases backward and the separation area is smaller than in laminar flow separation without dimples. There are two points: that the pressure resistance can be reduced and that the lift can be improved by promoting the vertical difference between the peeling points.

However, with a floating ball, even if it is a large size ball as downward gravity, only 39-40 g weight works, and if the lift similar to that of the round ball works, the trajectory of the floating ball is more than that of the round ball. If the ball has an upward trajectory and is hit under the same conditions, the floating ball will have a clearly different trajectory than the round ball. Nevertheless, in the prior art, the physical properties peculiar to the floating ball were not deeply sought, and the floating ball was merely provided with the dimples similar to those of a normal round ball.

[Problems to be solved by the invention]

As described above, since the conventional floating ball has dimples similar to those of a normal round ball, the trajectory will be different from that of the round ball. Cannot be reproduced with a floating ball, and as a result, there is a problem that the technique learned by using a floating ball is not always useful for a round ball.

[Means for solving problems]

The present invention aims to improve the trajectory by introducing dimples having a small lift force into the floating ball so that the trajectory of the floating ball approaches that of the round ball.

That is, according to the present invention, in a floating ball having a specific gravity of 1 or less, the dimple has a diameter of 3.5 to 4.0 mm,
It is characterized by providing dimples having a total volume of 400 to 600 mm ³ .

More specifically, if the weight and diameter of the golf ball are the same, it is considered that the major factor that influences the lift and resistance of the golf ball is the dimple.

By the way, in the first-class round balls, considerable research has recently been conducted on the influence of dimples on the trajectory of the ball, and proper dimples have been proposed. However, it is no exaggeration to say that dimples have not been researched at all in range balls including floating balls, and as described above, the fact that dimples used for round balls are used for floating balls is the actual situation. Is.

Therefore, in the present invention, as a means for reducing the lift without significantly changing the drag force, it was devised to make the total volume of the dimples larger than the range adopted for the round ball, and an experiment showed that a good flight ballistic shape was obtained. We have found that they can be obtained.

That is, the total volume of the dimples adopted in the round ball is 200 to 370 mm ³ according to the actual measurement, but in the present invention, by increasing this to 400 to 600 mm ³ , a large change in drag is not caused. It was possible to reduce the lift and control the lift to be suitable for floating balls. In addition, since the floating ball is light, it has a drawback that the trajectory fluctuates between the highest point of the trajectory and the landing, but in the present invention, the dimple diameter is 3.0 to 3.4 mm which is adopted in the conventional floating ball. By increasing the size to 3.5-4.0 mm, the critical Reynolds number is lowered, and the drag coefficient in the low speed region from the highest point of the trajectory to the landing is kept low to prevent the above wobble, and to increase the growth of a light ball. I was able to get a trajectory similar to that of a round ball.

In the present invention, the total volume of the dimples is set as described above.
Although the 400~600mm ^3, this is the total volume of the dimples 400
If it is less than mm ³ , the effect of reducing the lift of the ball is not sufficiently exerted, and the trajectory becomes high, which is different from the trajectory of the round ball, and if the total dimple volume exceeds 600 mm ³ , the lift is extremely reduced. Moreover, the improvement of the drag force cannot be ignored, the trajectory is low, and the trajectory becomes drop-like, which is different from the trajectory of the round ball, and the loss of the flight distance becomes large. In view of the above, the total dimple volume is desirably in a more narrow range in the above-mentioned range 400 to 600 mm ^3, the range of 450～520Mm ³ can be said to be particularly preferred. Further, in the present invention, the diameter of the dimples is 3.5 to 4.0 mm, but when the diameter of the dimples is smaller than 3.5 mm, the fluctuation of the trajectory cannot be sufficiently eliminated, while the dimple diameter is 4.0 If it is larger than mm, the adjacent dimples will overlap and the effect of the dimples cannot be fully exhibited.

As described above, by setting the total dimple volume to 400 to 600 mm ³ and the dimple diameter to 3.5 to 4.0 mm, it is possible to reduce the lift and prevent the fluctuation of the ball from the highest point to the landing, Such an effect is exhibited regardless of the total number of dimples. For example, in a floating golf ball, generally 250 to 450 dimples, and especially 300 to 400 dimples are provided for each ball. The above effect is that the total number of dimples is 250 to 4 dimples.
Not only when the number of dimples is within the range of 50, but also when the total number of dimples deviates from the above range due to brand printing or manufacturing, the same effect is obtained regardless of the total number of dimples.

In addition, the total dimple volume of 400 to 600 mm ³ and the dimple diameter of 3.5 to 4.0 mm can be applied to both one-piece golf balls and golf balls having a multi-layer structure, and good results can be obtained. The golf ball to be applied is not particularly limited as long as it can be used for a floating ball, and those conventionally used can of course be used, but in particular obtained by crosslinking the following rubber composition. A one-piece ball or a golf ball having a multi-layer structure using an inner core obtained by crosslinking the following rubber composition is preferable because it has good durability and good hitting sound and feel.

That is, as a rubber composition for obtaining a one-piece ball or an inner core, a polybutadiene rubber containing 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene ( Below, VC
The average particle size is 50
Compared with conventional floating balls, the one in which a fine particle ultra-high molecular weight polyolefin having a particle size of less than or equal to μm, an inorganic filler, a crosslinkable monomer and an initiator is blended has a better durability, and has a better hitting sound and feel. It is preferable because a good floating golf ball can be obtained.

In the above rubber composition, using VCR as an essential component of the base rubber is because VCR contains highly crystalline, high melting point syndiotactic-1,2-polybutadiene,
Unlike the case where cis-1,4-polybutadiene is used alone, it gives a golf ball an appropriate hardness (ball compression) without adding a large amount of an inorganic filler, which leads to an increase in specific gravity. This is because it is possible to impart a hitting sound and improve durability.

Specific examples of such a VCR include UBEPOL-VCR309 (trade name, composition: syndiotactic-1,2-polybutadiene 9% by weight, cis-1,4-
Polybutadiene 89% by weight, trans-1,4-polybutadiene 2% by weight), UBEPOL-VCR412 (trade name, composition: syndiotactic-1,2-polybutadiene 12% by weight, cis-1,4-polybutadiene 86% by weight, There are commercial products such as trans-1,4-polybutadiene (2% by weight).

The VCR is an indispensable rubber component in the rubber composition, and the more VCR contained in the base rubber, the better the golf ball will be in physical properties. Therefore, it is possible to use only this VCR as the base rubber, and, in view of processability and price, etc., natural rubber, cis-1,4-polybutadiene, and styrene-butadiene rubber can be used as VCR with this VCR as an essential component. Etc. may be blended. VC as above
When R is blended with natural rubber, cis-1,4-polybutadiene, styrene-butadiene rubber, etc. to form a base rubber,
VCR is preferably 30% by weight or more in the base rubber. That is, VCR preferably accounts for 30 to 100% by weight of the base rubber.

The fine particle ultra-high molecular weight polyolefin having an average particle size of 50 μm or less plays a role of a reinforcing filler having a low specific gravity, enhances the hardness and durability of the golf ball, and improves the feel at impact and the impact sound. . As such a particulate ultra-high molecular weight polyolefin, for example, Miperon (trade name, particulate ultra-high molecular weight polyolefin having an average particle diameter of 20 μm and a molecular weight of 2,000,000 or more) manufactured by Mitsui Petrochemical Co., Ltd. is commercially available. The amount of such particulate ultrahigh molecular weight polyolefin having an average particle diameter of 50 μm or less is usually preferably 10 to 40 parts by weight with respect to 100 parts by weight of the base rubber.

As the inorganic filler, for example, zinc oxide (ZnO), silicon oxide (SiO ₂ ), calcium carbonate, aluminum silicate or the like is used. The main role of these is to increase hardness and impact strength, to increase the durability of the golf ball, and to improve the feel at impact and the sound at impact, but in some cases, α, β-monomers such as acrylic acid and methacrylic acid are used. It also has a role of reacting with an ethylenically unsaturated carboxylic acid to form a metal salt of those acids, which enables the rubber composition to be crosslinked as a crosslinkable monomer. When a large amount of these inorganic fillers are blended, the hardness and impact hardness are increased, but since the specific gravity becomes large and the particles do not float on water, the blending amount of these inorganic fillers is usually 5 per 100 parts by weight of the base rubber. It is preferably about 20 parts by weight.

The crosslinkable monomer is one that crosslinks the rubber composition to exert impact resilience and the like, and imparts hardness, durability, a suitable shot feeling, and a hitting sound to the golf ball, but as such a crosslinkable monomer, , Α, β-monoethylenically unsaturated carboxylic acids such as methacrylic acid and acrylic acid or metal salts thereof, polyfunctional methacrylic acid esters such as trimethylolpropane trimethacrylate, and polyfunctional acrylic acid esters such as trimethylolpropane triacrylate Etc. are used, and it is usually preferable that the compounding amount of these crosslinkable monomers is 5 to 25 parts by weight with respect to 100 parts by weight of the base rubber.

The initiator is for initiating the polymerization of the crosslinkable monomer to crosslink the rubber composition, and examples of such an initiator include dicumyl peroxide and 2,2-di (tert. -Butylperoxy) butane, peroxide such as -tert-butyl perbenzoate is used, and the compounding amount of these is usually 0.5 to 100 parts by weight of the base rubber.
It is preferably 5 parts by weight.

When the ball is a two-piece ball, the outer shell covering the inner core obtained by crosslinking the rubber composition is an ionomer resin, trans polyisoprene, a polyurethane resin as a base material, and an additive such as a pigment is appropriately added. Those added are preferable.

1 and 2 are views showing an example of a golf ball according to the present invention, and FIGS. 1 and 2 exemplify a one-piece ball. FIG. 1 is a front view thereof, and FIG. 2 is a sectional view thereof. is there.
In the figure, 1 is a golf ball body, 2 is a golf ball body 1.
Is a dimple provided on the surface of the. However, although the dimples 2 are usually provided at 250 to 450 as described above,
1 to 2 show the case where the total number of dimples is 336.

Then, the total volume of the dimples is arbitrarily selected from the dimples provided on the surface of the golf ball (usually 24 to 48,
Select 30 pieces in the below-mentioned example), cut the dimples in 1/1000 mm unit in the depth direction, add it assuming that it is a truncated cone and calculate the volume, and calculate it in proportion to the total number of dimples. It is a thing.

〔Example〕

Four types of floating golf balls having the specifications shown in the following Examples 1 to 4 were produced and compared with the balls of Examples 1 to 4, the balls of Comparative Examples 1 and 2, and the ball of the reference example. The ball of Comparative Example 1 is a one-piece floating golf ball in which the dimple specifications are the same as those conventionally used, the dimple diameter is 3.4 mm, the total dimple volume is 340 mm ³ , and the total number of dimples is 336. . Ball of Comparative Example 2, and 650mm ³ the total dimple volume, is a one-piece floating golf ball that was even larger than the upper limit 600mm ³ of the present invention, reference example is a wound golf ball for a round, in this ball is a specific gravity of 1.09 It does not float on water and cannot be used for water practice. Each ball is a large size ball, and its diameter is about 42.8 mm. In addition, all the blended compositions shown in Table 1 are based on parts by weight.

Example 1 A one-piece floating ball having a total of 336 dimples with a dimple diameter of 3.9 mm and a total dimple volume of 450 mm ³ was prepared according to the composition shown in the column of Example 1 in Table 1.

Example 2 In the composition shown in the column of Example 2 in Table 1 (however, the composition is the same as in Example 1), the dimple diameter was 3.
A one-piece floating ball having 7 mm, a total volume of dimples of 520 mm ³ , and a total of 392 dimples was produced.

Example 3 Inner core (diameter 3
8.3 mm) with Himilan 1707 (brand name, ionomer resin manufactured by DuPont Mitsui Polychemicals) as the base material, dimple diameter 3.7 mm, total dimple volume 520 m
m ^3, total number of dimples 392 (dimples specifications Example 2
(The same as the case of 2).

Example 4 With the compounding composition described in Example 4 of Table 1, dimple diameter 3.7 mm, total dimple volume 520 mm ³ , total number of dimples 392
Individual one-piece floating balls (the dimple specifications are the same as those in Example 2) were produced.

The floating golf balls of Examples 1 to 4 and the floating golf balls of Comparative Examples 1 and 2 and the wound thread golf ball of Reference Example were manufactured by using a golf ball hitting test machine (swing robot) manufactured by Trutemper Co., Ltd. Ball Association (USGA) ODS (Ove
In accordance with the test procedure of the rall Distance Standard), a flight test was performed at the No. 1 Wood club with a head speed of 45 m / sec, and the flight carry (flying distance) and the difference in ballistic height were evaluated. The results are shown in Table 1. Note that the evaluation values shown in Table 1 are numerical values obtained by testing 20 balls of each type and evaluating the average value.

As shown in Table 1, the ball of Comparative Example 1 largely floated and hopped before reaching the maximum ballistic point, and therefore, a great loss was also caused in the carry distance (carry). Also,
The trajectory was much higher than that of the wound ball for round of the reference example. Further, in the ball of Comparative Example 2 in which the total dimple volume was extremely large at 650 mm ³ , the total dimple volume was too large, the lift force did not act on the ball, the ball became a ball stalled, and the caliter became small.

On the other hand, the balls of Examples 1 to 4 all have a trajectory that is very similar to the wound thread for round of the reference example, and the carry is also larger than the balls of Comparative Examples 1 and 2,
The effect of the present invention is remarkable.

〔The invention's effect〕

As described above, in the present invention, by finding the optimum total dimple volume and dimple diameter for a floating ball, it is possible to improve the ballistic performance of the floating ball and bring it closer to that of a round ball.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a golf ball according to the present invention, and FIG. 2 is a sectional view thereof. 1 ... Golf ball body, 2 ... Dimple

Claims (5)

[Claims] 1. A floating practice golf ball having a ball specific gravity of 1.0 or less and a dimple diameter of 3.5 to 4.0.
mm, the total volume of dimples is 400 to 600 mm ^3. A floating practice golf ball. 2. The golf ball for floating practice according to claim 1, wherein the total number of dimples is 336. 3. A golf ball for floating practice according to claim 1, wherein the total number of dimples is 392. 4. A base rubber containing as an essential component a polybutadiene rubber in which the balls contain 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight of cis-1,4-polybutadiene rubber, Claims: An integrally molded one-piece ball obtained by crosslinking a rubber composition containing a particulate ultra-high molecular weight polyolefin having an average particle diameter of 50 μm or less, an inorganic filler, a crosslinkable monomer, and an initiator. A golf ball for floating practice according to the first, second or third range. 5. A base rubber containing polybutadiene rubber as an essential component, wherein the ball contains 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight of cis-1,4-polybutadiene rubber, An inner core obtained by cross-linking a rubber composition containing a particulate ultra-high molecular weight polyolefin having an average particle size of 50 μm or less, an inorganic filler, a cross-linking monomer and an initiator, an ionomer resin, trans polyisoprene or Claims 1 and 2 which are balls having a multi-layer structure using an outer cover made of a polyurethane resin as a base material.
The golf ball for floating practice according to the item 3 or 3.