JP2009095593A - Shaping mold for golf ball and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaping mold 2 which can obtain a golf ball excellent in aerodynamic symmetry and appearance. <P>SOLUTION: The shaping mold 2 includes upper and lower molds 4 and 6. The upper and lower molds 4 and 6 are put together to form a spherical cavity. Numerous pimples 10 are arrayed on the cavity surfaces of the upper and lower molds 4 and 6. The upper and lower molds 4 and 6 each have flat surfaces 14, protrusions 16 and recesses 18. The protrusions 16 protrude from the equator Eq and the recesses 18 are hollowed below the equator Eq. The protrusions contain some parts of the pimples 10. The center angle between a protrusion 16 and another protrusion 16 adjacent to the protrusion is 10° or more and 20° or less. The number of protrusions 16 are 18 or more and 33 or less. The height Hp of the protrusions 16 is O.2 mm or more and 1.5 mm or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a golf ball mold. More specifically, the present invention relates to a mold having a large number of pimples on the cavity surface for forming dimples.

  The golf ball has a large number of dimples on its surface. The dimples disturb the air flow around the golf ball during flight and cause turbulent separation. Turbulent separation shifts the separation point of air from the golf ball backwards, reducing drag. Turbulent separation promotes the deviation between the upper separation point and the lower separation point of the golf ball due to backspin, and increases the lift acting on the golf ball. The reduction of drag and the improvement of lift are referred to as “dimple effect”. Excellent dimples better disturb the air flow.

  Usually, a golf ball is molded by a mold composed of an upper mold and a lower mold each having a hemispherical cavity. When the upper mold cavity is assumed to be the northern hemisphere of the globe and the lower mold cavity is assumed to be the southern hemisphere of the globe, the upper mold and the lower mold are matched on the equator plane (plane including the equator). A large number of pimples are provided on the inner peripheral surface of the mold, and dimples are formed on the surface of the golf ball by the pimples. The dimple shape is a shape obtained by inverting the shape of the pimple.

  Since the molding material (for example, synthetic resin) leaks from the parting surfaces of the upper mold and the lower mold, burrs are generated at the equator portion of the golf ball surface. Burrs occur along the parting line. This burr is ground and removed with a grindstone or the like. It is difficult to remove burrs generated inside the dimples. For easy removal of burrs, no dimples are formed on the equator. In other words, no pimples are provided on the parting surface of the mold. A great circle is formed on the seam of the golf ball obtained by this mold. The great circle coincides with the equator. The great circle does not intersect with the dimples. When this great circle band coincides with the portion where the peripheral speed of backspin is the fastest (hereinafter also referred to as “the fastest portion”), a sufficient dimple effect cannot be obtained. The dimple effect when the great circle zone and the fastest portion coincide is smaller than the dimple effect when the great circle zone and the fastest portion do not coincide. The difference in the dimple effect impairs the aerodynamic symmetry of the golf ball. The great circle further hinders the appearance of the golf ball.

  Japanese Patent Application Laid-Open No. 2002-159598 discloses a mold in which a parting surface has a horizontal surface and an inclined surface. In this mold, pimples can be arranged on the equator avoiding the parting surface. With this mold, a golf ball having seam unevenness can be obtained. This golf ball does not have a great circle. A similar mold is also disclosed in Japanese Patent Application Laid-Open No. 2004-89549.

  Japanese Patent Application Laid-Open No. 10-99469 discloses a mold having a pin placed on a parting surface. The dimples are formed on the golf ball by the pins. With this mold, a golf ball having no great circle band is obtained.

Japanese Patent Application Laid-Open No. 11-137727 discloses a mold having a bulge on a parting surface. The bumps form dimples on the golf ball. With this mold, a golf ball having no great circle band is obtained.
JP 2002-159598 A JP 2004-89549 A Japanese Patent Laid-Open No. 10-99469 JP 11-137727 A

  In a golf ball obtained with a mold having a parting surface having a horizontal surface and an inclined surface, dimples are rough in the vicinity of the seam. There is room for improvement in the aerodynamic symmetry of this golf ball. Even with golf balls obtained with molds having pins or ridges, the aerodynamic symmetry and appearance are still not sufficient.

  An object of the present invention is to provide a golf ball excellent in aerodynamic symmetry and appearance.

  The golf ball mold according to the present invention comprises a pair of half dies. This mold includes a large number of dimples for forming dimples on the cavity surface. Each half mold includes a plurality of protrusions protruding from the equator. Each protrusion includes a part of the pimple. When one half mold and the other half mold are combined, all of the central angles between a certain protrusion and another protrusion adjacent thereto are 10 ° or more and 20 ° or less.

This mold is
(A) one protrusion,
(B) includes another protrusion adjacent to the protrusion (a), and (c) includes another protrusion adjacent to the protrusion (a). Preferably, the central angle θ1 between the protrusion (a) and the protrusion (b) is different from the central angle θ2 between the protrusion (a) and the protrusion (c). Preferably, the ratio P1 of the number of protrusions (a) having a central angle θ1 with another protrusion (b) different from the central angle θ2 with another protrusion (c) to the total number of protrusions is 50% or more. is there.

  Preferably, the mold includes a protrusion adjacent to the protrusion belonging to one half mold and adjacent to the protrusion belonging to the other half mold. Preferably, the ratio P2 of the number of protrusions adjacent to the protrusion belonging to one half mold and also adjacent to the protrusion belonging to the other half mold to the total number of protrusions is 50% or more.

  Preferably, the diameter of the pimple whose part is included in the protrusion is 4.0 mm or more. Preferably, the number of protrusions is 18 or more and 33 or less. Preferably, all the protrusions have the same height from the equator. Preferably, the diameter of all pimples existing in a region where the latitude is 20 ° or less is 4.0 mm or more.

  Preferably, the average diameter Dx of the upper 10% pimples and the average diameter Dn of the lower 10% pimples when all the pimples existing in the region where the latitude is 20 ° or less are listed in descending order of diameter. The ratio (Dx / Dn) is 1.15 or less.

  Preferably, the standard deviation of the diameters of all the pimples existing in the region where the latitude is 20 ° or less is 0.15 or less. Preferably, a plurality of types of pimples having different diameters are present in a region where the latitude is 20 ° or less.

A golf ball manufacturing method according to the present invention includes:
It consists of a pair of halves and has many dimples for forming dimples on its cavity surface, each halve has a plurality of protrusions protruding from the equator, and each protrusion includes part of the pimple When one half mold and the other half mold are combined, the material is put into a mold having a central angle of 10 ° or more and 20 ° or less between a certain projection and another projection adjacent thereto. And a step of forming a dimple having a shape in which the shape of the pimple is reversed by flowing the material in the mold.

  The golf ball obtained with the mold according to the present invention is excellent in aerodynamic symmetry and appearance.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view showing a golf ball mold 2 according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a part of the mold 2 of FIG. The mold 2 includes a pair of half dies 4 and 6. Specifically, the mold 2 includes an upper mold 4 and a lower mold 6. By combining the upper mold 4 and the lower mold 6, a spherical cavity is formed. A large number of pimples 10 are provided on the cavity surface 8 of the upper mold 4 and the lower mold 6. The outline of the pimple 10 is a circle. In FIG. 1, only some pimples 10 are shown. Actually, a large number of pimples 10 are arranged over the entire cavity surface 8. As is clear from FIG. 1, the parting surfaces 12 of the upper mold 4 and the lower mold 6 are uneven. 2 indicates that the uppermost part of the cavity surface 8 of the upper die 4 is assumed to be the north pole Pn (see FIG. 1) of the globe, and the lowermost part of the cavity surface 8 of the lower die 6 Is the equator when assumed to be the south pole Ps of the globe.

  FIG. 3 is a perspective view showing the lower mold 6 of the mold 2 of FIG. The parting surface 12 of the lower mold 6 includes a flat surface 14, a protrusion 16, and a recess 18. As also shown in FIGS. 1 and 2, the flat surface 14 is along the equator Eq. The protrusion 16 protrudes from the equator Eq. The recess 18 is recessed from the equator Eq. A group of two protrusions 16 and a group of two recesses 18 are alternately arranged along the circumferential direction. The number of protrusions 16 is twelve. The number of recesses 18 is twelve. The number of protrusions 16 is the same as the number of recesses 18. Although not shown, the upper mold 4 is similarly provided with a number of protrusions 16 and a number of recesses 18. When the upper mold 4 is combined with the lower mold 6, the protrusion 16 of the lower mold 6 is fitted into the recess 18 of the upper mold 4, and the protrusion 16 of the upper mold 4 is fitted into the recess 18 of the lower mold 6.

  Since the protrusions 16 of the lower mold 6 are fitted into the recesses 18 of the upper mold 4, the number of the recesses 18 of the upper mold 4 is the same as the number of the protrusions 16 of the lower mold 6. Since the protrusions 16 of the upper mold 4 are fitted in the recesses 18 of the lower mold 6, the number of the protrusions 16 of the upper mold 4 is the same as the number of the recesses 18 of the lower mold 6. In the mold 2, the number of the protrusions 16 of the upper mold 4, the recesses 18 of the upper mold 4, the protrusions 16 of the lower mold 6, and the recesses 18 of the lower mold 6 is twelve. The mold 2 has a total of 24 protrusions 16. The mold 2 has 24 dents 18 in total.

  As is apparent from FIG. 2, the protrusion 16 includes a part of the pimple 10. The outer edge of the protrusion 16 is an arc. The outer edge substantially coincides with the contour of the pimple 10. Since the protrusion 16 protrudes from the equator Eq, the pimple 10 included in the protrusion 16 intersects the equator Eq.

  FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. This cross section is along the equator Eq. FIG. 4 shows a flat surface 14 of the lower mold 6, two protrusions 16 a and 16 b of the lower mold 6, and two protrusions 16 c and 16 d of the upper mold 4. The protrusion 16b is adjacent to the protrusion 16a. The protrusion 16a and the protrusion 16b belong to the same half mold. The protrusion 16c is adjacent to the protrusion 16a. The protrusion 16a and the protrusion 16c belong to different half dies. Two other protrusions are said to be “adjacent” when there are no other protrusions between the two protrusions.

  In FIG. 4, what is indicated by the symbol O is the center point of the cavity. The center lines CLa, CLb, and CLc shown in FIG. The center line CLa passes through the center of the protrusion 16a in the longitude direction. The center line CLb passes through the center of the protrusion 16b in the longitude direction. The center line CLc passes through the center of the protrusion 16c in the longitude direction. In FIG. 4, what is indicated by reference sign θ1 is the central angle between the protrusion 16a and the protrusion 16b. In FIG. 4, what is indicated by reference sign θ2 is a central angle between the protrusion 16a and the protrusion 16c.

  This mold 2 is used for molding a golf ball. The mold 2 can be used for compression molding, injection molding, cast molding, and the like. In any method, the material is put into the mold 2. This material flows in the mold 2 to form dimples having a shape obtained by reversing the shape of the pimple 10.

  FIG. 5 is a plan view showing the golf ball 20 obtained with the mold 2 of FIG. 1, and FIG. 6 is a front view thereof. The golf ball 20 has a large number of dimples 22 on the surface. All the dimples 22 are circular. 5 and 6, the types of the dimples 22 are indicated by reference signs A to E. The golf ball 20 includes dimples A, dimples B, dimples C, dimples D, and dimples E. The number of dimples A is 26, the number of dimples B is 88, the number of dimples C is 102, the number of dimples D is 94, and the number of dimples E is 14. The golf ball 20 includes 324 dimples 22.

  In FIG. 6, what is indicated by the symbol Ln1 is a latitude line at 20 ° north latitude, and what is indicated by the symbol Ls1 is a latitude line at 20 ° south latitude. On the surface of the golf ball 20 or the cavity surface 8, a region surrounded by the latitude line Ln1 and the latitude line Ls1 is a low latitude region. On the surface of the golf ball 20 or the cavity surface 8, the region other than the low latitude region is a high latitude region. FIG. 5 shows the types of dimples 22 present in the high latitude region. The dimple 22 whose center latitude exceeds 20 ° is a “dimple existing in a high latitude region”. FIG. 6 shows the types of dimples 22 present in the low latitude region. The dimple 22 whose center latitude is 20 ° or less is a “dimple existing in a low latitude region”.

  The dimple 22 has a shape obtained by inverting the shape of the pimple 10. The dimple A is formed by pimple A. The dimple B is formed by the pimple B. The dimple C is formed by the pimple C. The dimple D is formed by the pimple D. The dimple E is formed by the pimple E. The mold 2 shown in FIGS. 1 to 4 includes 26 pimples A, 88 pimples B, 102 pimples C, 94 pimples D, and 14 pimples E. The diameter of the pimple A is 4.50 mm. The diameter of the pimple B is 4.40 mm. The diameter of the pimple C is 4.30 mm. The diameter of the pimple D is 4.10 mm. The diameter of the pimple E is 3.60 mm.

  As described above, the mold 2 includes the pimple 10 that intersects with the equator Eq. Therefore, the golf ball 20 obtained with the mold 2 includes dimples 22 that intersect with the equator Eq of the golf ball 20. In this golf ball 20, no great circle is formed on the equator Eq. The dimple 22 that intersects with the equator Eq enhances the dimple effect when the equator Eq coincides with the fastest part of backspin. This golf ball 20 is excellent in aerodynamic symmetry. This golf ball 20 does not have a great circle which does not coincide with the equator. This golf ball 20 is excellent in appearance.

  The central angles θ1 and θ2 of all the pimple pairs on the equator Eq are 20 ° or less. In the golf ball 20 obtained from the mold 2 having the central angles θ1 and θ2 of 20 ° or less, the dimples 22 are densely arranged on the equator Eq. This golf ball 20 is excellent in aerodynamic symmetry and appearance. In this respect, the central angles θ1 and θ2 are preferably 19 ° or less, and more preferably 18 ° or less. From the viewpoint of easy manufacture of the mold 2, the central angles θ1 and θ2 are preferably 10 ° or more, more preferably 11 ° or more, and particularly preferably 12 ° or more.

  The golf ball 20 in which the dimples 22 are arranged at unequal intervals on the equator Eq is obtained by the molding die 2 having different central angles θ1 and θ2. In the golf ball 20, a high dimple effect is obtained when the equator Eq coincides with the fastest part of backspin. This golf ball 20 is excellent in aerodynamic symmetry. From the viewpoint of aerodynamic symmetry, the absolute value of the difference (θ1−θ2) between the central angle θ1 and the central angle θ2 is preferably 3 ° or more, and more preferably 6 ° or more. The absolute value of the difference is preferably 10 ° or less. It is preferable that all the central angles θ1 are the same. It is preferable that all the central angles θ2 are the same.

The ratio P1 of the number of protrusions 16 satisfying the following condition 1 to the total number of protrusions 16 is preferably 50% or more.
Condition 1: The central angle θ1 between one adjacent protrusion 16 is different from the central angle θ2 between the other adjacent protrusion 16.
The golf ball 20 obtained with the mold 2 in which the ratio P1 is 50% or more is excellent in aerodynamic symmetry. In this respect, the ratio P1 is more preferably equal to or greater than 60%, and particularly preferably 100%. The ratio P1 of the mold 2 shown in FIG. 1 is 100%.

  As is clear from FIG. 6, a large number of dimples B intersect with the equator Eq of the golf ball 20. The dimple B has a large diameter. In the golf ball 20 in which the dimple 22 having a large diameter intersects the equator Eq, a high dimple effect is obtained when the equator Eq matches the fastest part of the back spin. This golf ball 20 is excellent in aerodynamic symmetry. From the viewpoint of aerodynamic symmetry, the diameter of the pimple 10 that intersects the equator Eq is preferably 4.0 mm or more, more preferably 4.2 mm or more, and particularly preferably 4.4 mm or more. From the viewpoint that the deformation of the dimples 22 due to the removal of burrs is not noticeable, the diameter of all the pimples 10 that intersect the equator Eq is preferably 5.0 mm or less. It is preferable that the diameters of all the pimples 10 intersecting the equator Eq are within the above range.

  From the viewpoint of aerodynamic symmetry, the diameters of all the pimples 10 existing in the low latitude region are preferably 4.0 mm or more, and more preferably 4.1 mm or more. In the golf ball 20 shown in FIG. 6, dimples B, dimples C, and dimples D exist in a low latitude region. The diameters of all the pimples 10 existing in the low latitude region of the mold 2 are 4.1 mm or more.

  The golf ball 20 in which a large number of dimples 22 intersect with the equator Eq is excellent in aerodynamic symmetry. In this respect, the number of pimples 10 intersecting with the equator Eq is preferably 18 or more, more preferably 20 or more, and particularly preferably 24 or more. From the viewpoint that a large dimple 22 can be disposed on the equator Eq, the number of the pimples 10 that intersect with the equator Eq is preferably 33 or less, and more preferably 30 or less. In the mold 2 shown in FIG. 1, 24 pimples 10 intersect with the equator Eq. Therefore, in the golf ball 20 shown in FIG. 6, 24 dimples 22 intersect with the equator Eq.

As described above, the protrusion 16a (see FIG. 4) is adjacent to the protrusion 16b belonging to the same half mold, and is also adjacent to the protrusion 16c belonging to a different half mold. In the golf ball 20 obtained with this mold 2, when the fastest part is located on the equator, the affiliation of the dimples 22 that appear sequentially by backspin is:
"Southern Hemisphere, Southern Hemisphere, Northern Hemisphere, Northern Hemisphere, Southern Hemisphere, Southern Hemisphere, Northern Hemisphere, Northern Hemisphere ---"
It is. Due to the appearance of the dimples 22 in this pattern, a large dimple effect is obtained. This golf ball 20 is excellent in aerodynamic symmetry.

The ratio P2 of the number of protrusions 16 satisfying the following condition 2 to the total number of protrusions 16 is preferably 50% or more.
Condition 2: Adjacent to the same half-shaped protrusion 16 and also adjacent to a different half-shaped protrusion 16.
The golf ball 20 obtained with the mold 2 in which the ratio P2 is 50% or more is excellent in aerodynamic symmetry. In this respect, the ratio P2 is more preferably equal to or greater than 60%, and particularly preferably 100%. The ratio P2 of the mold 2 shown in FIG. 1 is 100%.

  The ratio P3 of the number of protrusions 16 satisfying both of the above conditions 1 and 2 to the total number of protrusions 16 is preferably 50% or more. The golf ball 20 obtained with the mold 2 in which the ratio P3 is 50% or more is excellent in aerodynamic symmetry. In this respect, the ratio P3 is more preferably equal to or greater than 60%, and particularly preferably 100%. The ratio P3 of the mold 2 shown in FIG. 1 is 100%.

  It is preferable that the dimples 22 are densely arranged in the low latitude region of the golf ball 20. In the golf ball 20, a high dimple effect is obtained when the equator Eq coincides with the fastest part of backspin. This golf ball 20 is excellent in aerodynamic symmetry. The golf ball 20 is also excellent in appearance. By arranging a plurality of types of pimples 10 having different diameters in the low latitude region of the mold 2, a high density of the dimples 22 in the low latitude region can be achieved. From the viewpoint of aerodynamic symmetry and appearance, the number of pimples 10 present in the low latitude region is preferably 2 or more, and more preferably 3 or more. In the mold 2 shown in FIG. 1, the pimple B, the pimple C, and the pimple D exist in the low latitude region. In the low latitude region of the mold 2, the number of types of pimples 10 is three.

  The ratio (Dx1 / Dn1) of the average diameter Dx1 of the upper 10% pimples 10 and the average diameter Dn1 of the lower 10% pimples 10 when all the pimples 10 existing in the low-latitude region are listed in descending order. ) Is preferably 1.15 or less. In the golf ball 20 obtained with the mold 2, a high dimple effect is obtained when the equator Eq coincides with the fastest part of back spin. This golf ball 20 is excellent in aerodynamic symmetry. From the viewpoint of aerodynamic symmetry, the ratio (Dx1 / Dn1) is more preferably 1.10 or less, and particularly preferably 1.07 or less. The low latitude region of the mold 2 shown in FIG. 1 has 36 pimples B, 48 pimples C, and 36 pimples D. The number of dimples 22 in the low latitude region is 120. Accordingly, the twelve pimples B correspond to the upper 10% pimple 10 and the twelve pimples D correspond to the lower 10% pimple 10. The mold 2 has Dx1 of 4.40 mm, Dn1 of 4.10 mm, and a ratio (Dx1 / Dn1) of 1.07.

  The ratio (Dx2 / Dn2) of the average diameter Dx2 of the upper 10% pimples 10 to the average diameter Dn2 of the lower 10% pimples 10 when all the pimples 10 are listed in descending order is 1.30. The following is preferred. The golf ball 20 obtained with the mold 2 having a ratio (Dx2 / Dn2) of 1.30 or less is excellent in flight performance. From the viewpoint of flight performance, the ratio (Dx2 / Dn2) is preferably 1.20 or less, and more preferably 1.16 or less. The ratio (Dx2 / Dn2) of the mold 2 shown in FIG. 1 is 1.16.

The standard deviation Σ1 of the diameters of all the pimples 10 existing in the low latitude region is preferably 0.15 or less. In the golf ball 20 obtained with the mold 2, a high dimple effect is obtained when the equator Eq coincides with the fastest part of back spin. This golf ball 20 is excellent in aerodynamic symmetry. From the viewpoint of aerodynamic symmetry, the standard deviation Σ1 is more preferably 0.12 or less. In the low latitude region of the mold 2 shown in FIG. 1, the average diameter of the pimple 10 is 4.27 mm. Therefore, the standard deviation Σ1 is calculated by the following mathematical formula.
Σ1 = (((4.40-4.27) ²・ 36 + (4.30-4.27) ²・ 48 + (4.10-4.27) ²
・ 36) / 120) ^1/2
The standard deviation Σ1 of this golf ball 20 is 0.12.

  The standard deviation Σ2 of the diameters of all the pimples 10 is preferably 0.30 or less. The golf ball 20 obtained with the mold 2 having the standard deviation Σ2 of 0.30 or less has excellent flight performance. From the viewpoint of flight performance, the standard deviation Σ2 is more preferably 0.25 or less, and particularly preferably 0.20 or less. The standard deviation Σ2 of the mold 2 shown in FIG. 1 is 0.20.

  In FIG. 2, what is indicated by an arrow Hp is the height of the protrusion 16 from the equator Eq. From the viewpoint that a high dimple effect is obtained when the equator Eq coincides with the fastest part of backspin, the height Hp is preferably 0.2 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.4 mm or more. preferable. From the viewpoint of durability of the mold 2, the height Hp is preferably 1.5 mm or less, and more preferably 1.3 mm or less.

  The intersection width between the dimple 22 and the equator Eq is substantially the same as the height Hp of the protrusion 16. In light of the dimple effect, the cross width is preferably equal to or greater than 0.2 mm, more preferably equal to or greater than 0.3 mm, and particularly preferably equal to or greater than 0.4 mm. From the viewpoint of easy manufacture of the golf ball 20, the cross width is preferably 1.5 mm or less, and more preferably 1.3 mm or less.

  From the viewpoint of easy manufacture of the golf ball 20 and the durability of the mold 2, the absolute value of the difference (Hp1−Hp2) between the height Hp1 of the highest protrusion 16 and the height Hp2 of the lowest protrusion 16 is 0.5 mm or less is preferable. Ideally, the difference (Hp1-Hp2) is zero. In other words, it is preferable that all the protrusions 16 have the same height from the equator.

  In FIG. 6, what is indicated by reference characters Ln2 and Ls2 is a latitude line. The latitudes of the latitude lines Ln2 and Ls2 are arbitrarily set within a range exceeding 20 ° and not more than 40 °. A region between the latitude line Ln2 and the pole point Pn on the surface of the golf ball 20 is a pole vicinity region. Of the surface of the golf ball 20, the region between the latitude line Ls2 and the pole point Ps is also the pole vicinity region. As is apparent from FIG. 5, the pattern of the dimple 22 whose center belongs to the pole vicinity region can be divided into five units. The dimple pattern of each unit is substantially the same. When the dimple pattern of one unit is rotated 72 ° around the pole, it substantially overlaps the dimple pattern of the other unit. The symmetric rotation angle of the dimple pattern in the pole vicinity region is 72 °.

  The pattern of the dimple 22 belonging to the low latitude region can be divided into six units. The dimple pattern of each unit is substantially the same. When the dimple pattern of one unit is rotated 60 ° around the pole, it substantially overlaps the dimple pattern of the other unit. The symmetric rotation angle of the dimple pattern in the low latitude region is 60 °. This symmetric rotation angle is different from the symmetric rotation angle (ie, 72 °) of the dimple pattern in the pole vicinity region. Due to the different symmetric rotation angles, this golf ball 20 can provide a large dimple effect. This golf ball 20 is excellent in flight performance.

  In FIG. 6, a region surrounded by the latitude line Ln1 and the latitude line Ln2 is an adjustment region. An area surrounded by the latitude line Ls1 and the latitude line Ls2 is also an adjustment area. The pattern of the dimples 22 belonging to the adjustment region is line symmetric with respect to the center line CL in FIG. This dimple pattern has no axis of symmetry other than the center line CL. In this dimple pattern, the dimple patterns do not overlap each other when the rotation is between 0 ° and less than 360 ° around the pole. In other words, the dimple pattern in the adjustment region cannot be partitioned into a plurality of units that are rotationally symmetric with respect to each other. The dimple pattern in the adjustment region may be divided into a plurality of units that are rotationally symmetric. In this case, the number of units in the adjustment area needs to be different from the number of units in the pole vicinity area, and further needs to be different from the number of units in the low latitude area.

  If the pole vicinity region is adjacent to the low latitude region across the boundary line, the dimples 22 cannot be densely arranged in the vicinity of the boundary line due to the difference in the number of units. In this case, there is a wide land in the vicinity of the boundary line. Wide lands inhibit the dimple effect. In the golf ball 20 according to the present invention, an adjustment area exists between the pole vicinity area and the low latitude area. In this adjustment region, since the dimples 22 can be arranged without being restricted by the number of units, the land area can be suppressed. By this adjustment region, a high occupation ratio of the dimple 22 is achieved.

  In this golf ball 20, the symmetrical rotation angle of the pattern of the dimples 22 intersecting with the equator Eq is 60 °. This symmetric rotation angle is different from the symmetric rotation angle (ie, 72 °) of the dimple pattern in the pole vicinity region. In the golf ball 20, a high dimple effect is obtained when the equator Eq coincides with the fastest part of backspin. This golf ball 20 is excellent in aerodynamic symmetry.

  In this golf ball 20, the symmetrical rotation angle of the pattern of the dimples 22 intersecting with the equator Eq is 60 °. Further, in this golf ball 20, the symmetrical rotation angle of the pattern of the dimple 22 belonging to the low latitude region and not intersecting with the equator Eq is 60 °. Both symmetrical rotation angles coincide. In the golf ball 20, a high occupation ratio of the dimples 22 is achieved in a low latitude region. In the golf ball 20, a high dimple effect is obtained when the equator Eq coincides with the fastest part of backspin. This golf ball 20 is excellent in aerodynamic symmetry.

  In the present invention, the ratio of the total area of all the dimples 22 to the surface area of the phantom sphere of the golf ball 20 is referred to as an occupation ratio. From the viewpoint of obtaining a sufficient dimple effect, the occupation ratio is preferably 75% or more, more preferably 76% or more, and particularly preferably 77% or more. The occupation ratio is preferably 86% or less, more preferably 85% or less, and particularly preferably 84% or less.

In the present invention, the “dimple volume” means a volume of a portion surrounded by a plane including the outline of the dimple 22 and the surface of the dimple 22. From the viewpoint of rising of the golf ball 20 is suppressed, the total volume of the dimples 22 is preferably 250 mm ³ or more, more preferably 260 mm ³ or more, 270 mm ³ or more is particularly preferable. In view of dropping of the golf ball 20 is suppressed, the total volume is preferably 400 mm ³ or less, more preferably 390 mm ³ or less, 380 mm ³ or less is particularly preferred.

  In light of suppression of hops in the golf ball 20, the depth of the dimple 22 is preferably 0.05 mm or more, more preferably 0.08 mm or more, and particularly preferably 0.10 mm or more. In light of suppression of dropping of the golf ball 20, the depth is preferably 0.60 mm or less, more preferably 0.45 mm or less, and particularly preferably 0.40 mm or less.

  The diameter of the dimple 22 is preferably 2.00 mm or greater and 6.00 mm or less. A large dimple effect can be obtained by setting the diameter to 2.00 mm or more. In this respect, the diameter is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. By setting the diameter to 6.00 mm or less, the original characteristic of the golf ball 20 that is substantially a sphere is maintained. In this respect, the diameter is more preferably equal to or less than 5.80 mm, and particularly preferably equal to or less than 5.60 mm.

  From the viewpoint of obtaining a sufficient dimple effect, the total number of dimples 22 is preferably 250 or more, and particularly preferably 270 or more. From the viewpoint that each dimple 22 can have a sufficient diameter, the total number is preferably 400 or less, and more preferably 370 or less.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
100 parts by weight of polybutadiene (trade name “BR-730” from JSR), 30 parts by weight of zinc acrylate, 6 parts by weight of zinc oxide, 10 parts by weight of barium sulfate, 0.5 parts by weight of diphenyl disulfide and 0.5 parts by mass of dicumyl peroxide was kneaded to obtain a rubber composition. This rubber composition was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity and heated at 170 ° C. for 18 minutes to obtain a core having a diameter of 39.7 mm. On the other hand, 50 parts by mass of ionomer resin (trade name “HIMILAN 1605” from Mitsui DuPont Polychemical Co.), 50 parts by mass of other ionomer resins (trade name “HIMILAN 1706” from Mitsui DuPont Polychemical Co., Ltd.) and 3 parts by mass Part of titanium dioxide was kneaded to obtain a resin composition. A half shell was molded from this resin composition. The core was wrapped with two half shells, and the core and the half shell were put into a mold shown in FIG. The pimple specifications of this mold are shown in Table 1 below. The cover having a thickness of 1.5 mm was formed by pressurizing and heating the half shell with this mold. A large number of dimples having a reversed pimple shape were formed on the cover. The burrs generated along the seam were removed by grinding. A clear paint based on a two-component curable polyurethane was applied to the cover to obtain a golf ball having a diameter of 42.7 mm and a mass of about 45.4 g. The golf ball has a PGA compression of about 85. This golf ball has the dimple pattern shown in FIGS.

[Examples 2 to 4 and Comparative Examples 1 to 3]
A golf ball was obtained in the same manner as in Example 1 except that a mold having the specifications shown in Tables 1 and 2 below was used.

[Flight distance test]
A driver equipped with a titanium head (trade name “XXIO”, Sumitomo Rubber Industries, Ltd., shaft hardness: X, loft angle: 9 °) equipped with a titanium head was attached to a swing machine manufactured by Golf Lab. A golf ball was hit under the conditions that the head speed was 49 m / sec, the launch angle was about 11 °, and the spin rate of backspin was about 3000 rpm, and the distance from the launch point to the rest point was measured. During the test, there was almost no wind. Measurement was performed 20 times for each of the pole hitting and the seam hitting. The average value of the flight distance is shown in Table 3 below. The seam hitting axis passes through both poles. The rotation axis of the pole hitting is orthogonal to the rotation axis of the seam hitting.

[appearance]
The appearance of the golf ball was visually observed. Rating was performed according to the following criteria.
A: Appearance is good B: Appearance is slightly poor C: Appearance is poor This result is shown in Table 3 below.

  As shown in Table 3, the golf balls obtained with the molds of the examples are excellent in aerodynamic symmetry. From this evaluation result, the superiority of the present invention is clear.

  Golf balls having various structures can be manufactured by the mold according to the present invention.

FIG. 1 is a cross-sectional view showing a golf ball mold according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a part of the mold shown in FIG. FIG. 3 is a perspective view showing a lower mold of the mold of FIG. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a plan view showing the golf ball obtained with the mold shown in FIG. FIG. 6 is a front view showing the golf ball of FIG. FIG. 7 is a plan view showing a golf ball obtained with a mold according to Example 2 of the present invention. FIG. 8 is a front view showing the golf ball of FIG. FIG. 9 is a plan view showing a golf ball obtained with a mold according to Example 3 of the present invention. FIG. 10 is a front view showing the golf ball of FIG. FIG. 11 is a plan view showing a golf ball obtained with a mold according to Example 4 of the present invention. FIG. 12 is a front view showing the golf ball of FIG. FIG. 13 is a plan view showing a golf ball obtained with the mold according to Comparative Example 1. FIG. 14 is a front view showing the golf ball of FIG. FIG. 15 is a plan view showing a golf ball obtained with the mold according to Comparative Example 2. FIG. FIG. 16 is a front view showing the golf ball of FIG. FIG. 17 is a plan view showing a golf ball obtained with the mold according to Comparative Example 3. FIG. FIG. 18 is a front view showing the golf ball of FIG.

Explanation of symbols

2 ... Mold for golf ball 4 ... Upper die 6 ... Lower die 8 ... Cavity surface 10 ... Pimple 12 ... Parting surface 14 ... Flat surface 16 ... Projection 18 ... dent 20 ... golf ball 22 ... dimple

Claims (13)

Consisting of a pair of halves,
A lot of pimples for dimple formation are provided on the cavity surface,
Each half has a plurality of protrusions protruding from the equator,
Each protrusion contains a part of pimple,
A golf ball molding die in which all of the central angles between a certain projection and another projection adjacent thereto are 10 ° or more and 20 ° or less when one half die and the other half die are combined. (A) one protrusion,
(B) another projection adjacent to the projection (a), and (c) yet another projection adjacent to the projection (a), and a central angle θ1 between the projection (a) and the projection (b). The mold according to claim 1, which is different from a central angle θ <b> 2 between the protrusion (a) and the protrusion (c).   The ratio P1 of the number of protrusions (a) having a different central angle θ1 to the other protrusion (b) and a central angle θ2 to another protrusion (c) to the total number of protrusions is 50% or more. 2. The mold according to 2.   The mold according to any one of claims 1 to 3, comprising a protrusion adjacent to the protrusion belonging to one half mold and also adjacent to the protrusion belonging to the other half mold.   The mold according to claim 4, wherein a ratio P2 of the number of protrusions adjacent to the protrusion belonging to the one half mold and adjacent to the protrusion belonging to the other half mold to the total number of protrusions is 50% or more.   The mold according to any one of claims 1 to 5, wherein a diameter of a pimple including a part of the protrusion is 4.0 mm or more.   The mold according to any one of claims 1 to 6, wherein the number of the protrusions is 18 or more and 33 or less.   The mold according to any one of claims 1 to 7, wherein all the protrusions have the same height from the equator.   The mold according to any one of claims 1 to 8, wherein the diameter of all pimples existing in a region where the latitude is 20 ° or less is 4.0 mm or more.   The ratio (Dx) of the average diameter Dx of the upper 10% pimples and the average diameter Dn of the lower 10% pimples when all the pimples existing in the region where the latitude is 20 ° or less are listed in descending order. / Dn) is 1.15 or less, The shaping | molding die in any one of Claim 1 to 9.   The mold according to any one of claims 1 to 10, wherein the standard deviation of the diameters of all pimples existing in a region where the latitude is 20 ° or less is 0.15 or less.   The mold according to any one of claims 1 to 11, wherein a plurality of types of pimples having different diameters are present in a region having a latitude of 20 ° or less. It consists of a pair of halves and has many dimples for forming dimples on its cavity surface, each halve has a plurality of protrusions protruding from the equator, and each protrusion includes part of the pimple When one half mold and the other half mold are combined, the material is put into a mold having a central angle of 10 ° or more and 20 ° or less between a certain projection and another projection adjacent thereto. And a dimple having a shape in which the shape of the pimple is reversed and the material flows in the mold.

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