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US-12623120-B2 - Golf ball

US12623120B2US 12623120 B2US12623120 B2US 12623120B2US-12623120-B2

Abstract

A golf ball can include a core, a mid layer, and a cover. In the golf ball, a hardness Ho at a central point of the core, a core surface hardness Hs, a hardness H1 at a point to which a distance from the central point of the core can be equal to 25% of a radius of the core, a hardness H2 at a point to which a distance from the central point of the core can be equal to 75% of the radius of the core, a hardness Hm of the mid layer, and a hardness Hc of the cover can satisfy all of the following relational expressions: Ho ≤ H ⁢ 1 ≤ H ⁢ 2 ≤ Hs ( 1 ) Ho < Hs ( 2 ) ( Hm - Hc ) ≤ ( Hs - Ho ) ( 3 ) ( Hs - Hc ) ≤ ( Hm - Hs ) . ( 4 )

Inventors

  • Daijiro KOJIMA
  • Takahiro Sajima

Assignees

  • SUMITOMO RUBBER INDUSTRIES, LTD.

Dates

Publication Date
20260512
Application Date
20240207
Priority Date
20230215

Claims (20)

  1. 1 . A golf ball comprising: a spherical core, a mid layer positioned outside the core, and a cover positioned outside the mid layer, the golf ball satisfying the following relational expressions (1) to (4): Ho ≤ H ⁢ 1 ≤ H ⁢ 2 ≤ Hs , ( 1 ) Ho < Hs , ( 2 ) ( Hm - Hc ) ≤ ( Hs - Ho ) , and ( 3 ) ( Hs - Hc ) ≤ ( Hm - Hs ) , ( 4 ) wherein Ho: Shore-C hardness at a central point of the core, Hs: Shore-C hardness at a surface of the core, H1: Shore-C hardness at a point to which a distance from the central point of the core is equal to 25% of a radius of the core, H2: Shore-C hardness at a point to which a distance from the central point of the core is equal to 75% of the radius of the core, Hm: Shore-C hardness of the mid layer, and Hc: Shore-C hardness of the cover, wherein a difference between Hm-H1 is not less than 37 and not greater than 42, and wherein a difference between Hc−H2 is not greater than 0 and not less than −10.
  2. 2 . The golf ball according to claim 1 , further satisfying the following relational expression (7): Ho ≤ Hc . ( 7 )
  3. 3 . The golf ball according to claim 1 , wherein a material of the mid layer is a resin composition, and a base polymer of the resin composition is an ionomer resin.
  4. 4 . The golf ball according to claim 1 , wherein a material of the cover is a resin composition, and a base polymer of the resin composition is an ionomer resin.
  5. 5 . The golf ball according to claim 1 , wherein the core has an amount of compressive deformation De of not less than 3.40 mm and not greater than 5.40 mm, and the golf ball has an amount of compressive deformation Db of not less than 3.0 mm and not greater than 3.40 mm.
  6. 6 . The golf ball according to claim 5 , wherein the mid layer has a thickness Tm of not less than 0.5 mm and not greater than 3.0 mm, and the cover has a thickness Tc of not greater than 2.0 mm and not less than 0.1 mm.
  7. 7 . The golf ball according to claim 2 , wherein a difference Hc−Ho is not less than 18 and not greater than 30.
  8. 8 . The golf ball according to claim 1 , wherein a second difference Hm−Hc subtracted from a first difference Hs−Ho is not less than zero and not greater than 20.
  9. 9 . The golf ball according to claim 1 , wherein a second difference Hs−Hc subtracted from a first difference Hm-Hs is not less than 0 and not greater than 15.
  10. 10 . The golf ball according to claim 1 , wherein the hardness Hc is smaller than the hardness Hm by not less than 20 and not greater than 33, the hardness Hc is smaller than the hardness Hs by not less than 7 in Shore-C hardness and not greater than 13, and the hardness Hm is larger than the hardness Hs by not less than 12 and not greater than 18.
  11. 11 . A method comprising: providing a golf ball including: a spherical core, a mid layer positioned outside the core, and a cover positioned outside the mid layer, the golf ball satisfying the following relational expressions (1) to (4): Ho ≤ H ⁢ 1 ≤ H ⁢ 2 ≤ Hs , ( 1 ) Ho < Hs , ( 2 ) ( Hm - Hc ) ≤ ( Hs - Ho ) , and ( 3 ) ( Hs - Hc ) ≤ ( Hm - Hs ) , ( 4 ) wherein Ho: Shore-C hardness at a central point of the core, Hs: Shore-C hardness at a surface of the core, H1: Shore-C hardness at a point to which a distance from the central point of the core is equal to 25% of a radius of the core, H2: Shore-C hardness at a point to which a distance from the central point of the core is equal to 75% of the radius of the core, Hm: Shore-C hardness of the mid layer, and Hc: Shore-C hardness of the cover, wherein Hm-H1 is not less than 37 and not greater than 42, and wherein a difference between Hc−H2 is not greater than 0 and not less than −10.
  12. 12 . The method according to claim 11 , wherein the golf ball further satisfies the following relational expression (7): Ho≤Hc (7).
  13. 13 . The method according to claim 11 , wherein a material of the mid layer is a resin composition, and a base polymer of the resin composition is an ionomer resin.
  14. 14 . The method according to claim 11 , wherein a material of the cover is a resin composition, and a base polymer of the resin composition is an ionomer resin.
  15. 15 . The method according to claim 11 , wherein the core has an amount of compressive deformation De of not less than 3.40 mm and not greater than 5.40 mm, and the golf ball has an amount of compressive deformation Db of not less than 3.0 mm and not greater than 3.40 mm.
  16. 16 . The method according to claim 15 , wherein the mid layer has a thickness Tm of not less than 0.5 mm and not greater than 3.0 mm, and the cover has a thickness Tc of not greater than 2.0 mm and not less than 0.1 mm.
  17. 17 . The method according to claim 12 , wherein a difference Hc−Ho is not less than 18 and not greater than 30.
  18. 18 . The method according to claim 11 , wherein a second difference Hm−Hc subtracted from a first difference Hs−Ho is not less than zero and not greater than 20.
  19. 19 . The method according to claim 11 , wherein a second difference Hs−Hc subtracted from a first difference Hm−Hs is not less than 0 and not greater than 15.
  20. 20 . The method according to claim 11 , wherein the hardness Hc is smaller than the hardness Hm by not less than 20 and not greater than 33, the hardness Hc is smaller than the hardness Hs by not less than 7 in Shore-C hardness and not greater than 13, and the hardness Hm is larger than the hardness Hs by not less than 12 and not greater than 18.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) The present application claims priority to Japanese patent application JP 2023-021307, filed on Feb. 15, 2023, the entire contents of which is incorporated herein by reference in its entirety. BACKGROUND Technical Field The present specification discloses a golf ball. Specifically, the present specification discloses a golf ball including a core, a mid layer, and a cover. Background Art Skilled golf players may place importance on feel at impact when hitting a golf ball. Some golf players prefer soft feel at impact particularly upon an approach shot around the green. From the viewpoint of obtaining soft feel at impact, a golf ball including a flexible cover has been proposed. The golf ball including the flexible cover also has excellent controllability upon an approach shot. However, the flexible cover impairs the resilience performance of the golf ball. With a low-resilience golf ball, a large flight distance is not obtained upon a shot with a driver. To improve a flight distance upon a shot with a driver, a golf ball having a low spin rate when being hit is advantageous. In order to achieve both desired flight performance and desired controllability in a golf ball including a flexible cover, various attempts have been made to improve the structure and the material of a core. Japanese Laid-Open Patent Publication No. 2013-31640 discloses a golf ball in which, when the distances (%) from the central point of a core to nine points and JIS-C hardnesses at the nine points, such nine points being obtained by dividing a region from the central point of the core to the surface of the core at intervals of 12.5% of the radius of the core, are plotted in a graph, R2 of a linear approximation curve obtained by a least-squares method is not less than 0.95, and the Shore-D hardness of a mid layer is larger than the Shore-D hardness of a cover. Japanese Laid-Open Patent Publication No. 2012-130524 proposes a golf ball in which the difference between a JIS-C hardness H(5.0) at a point which is located at a distance of 5 mm from the central point of a core and a JIS-C hardness Ho at the central point is not less than 6.0, the difference between a JIS-C hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point and the hardness Ho is not greater than 4.0, the difference between a JIS-C hardness Hs at the surface of the core and the hardness H(12.5) is not less than 10.0, the difference between the hardness Hs and the hardness Ho is not less than 22.0, there is no zone in which the hardness decreases from the central point toward the surface of the core, and the Shore-D hardness of a mid layer is larger than the Shore-D hardness of a cover. Japanese Laid-Open Patent Publication No. 2013-248298 discloses a golf ball in which, in a spherical core including at least one rubber layer, when JIS-C hardnesses measured at nine points obtained by equally dividing the thickness of the rubber layer at intervals of 12.5% in the radius direction of the core are plotted relative to a distance (%) from the innermost point of the rubber layer, R2 of a linear approximation curve obtained by a least-squares method is not less than 0.95, the hardness at the outermost point of the rubber layer is larger than the hardness at the innermost point of the rubber layer, and the slab hardness of a mid layer is larger than the slab hardness of a cover. Japanese Laid-Open Patent Publication No. 2013-9895 proposes a golf ball which includes a core obtained by crosslinking a rubber composition containing a base rubber, a co-crosslinking agent, a crosslinking initiator, and a carboxylate and two or more covers and in which the JIS-C hardness of the innermost layer of the cover is larger than the JIS-C hardness at the surface of the core. Japanese Laid-Open Patent Publication No. 2015-77405 discloses a golf ball in which relational expressions of (1) D−C≥7, (2) C−B≤7, (3)(D−C)−(C−B)≥7, and (4) E−A≥16 are satisfied when the radius of a core is denoted by R (mm), a JIS-C hardness at the central point of the core is denoted by A, a JIS-C hardness at a position away from the central point of the core by R/3 mm is denoted by B, a JIS-C hardness at a position away from the central point of the core by R/1.8 mm is denoted by C, a JIS-C hardness at a position away from the central point of the core by R/1.3 mm is denoted by D, and a JIS-C hardness at the surface of the core is denoted by E. Japanese Laid-Open Patent Publication No. 2017-77355 proposes a golf ball in which, in a hardness distribution of a core, a JIS-C hardness Hc at the central point of the core, a JIS-C hardness H12 at a position away from the central point of the core by 12 mm, and a JIS-C hardness Ho at the surface of the core satisfy (1) 0≤H12−Hc≤15, (2) 15≤Ho−H12≤30, (3) (Ho−H12)−(H12−Hc)≥10, and (4) 20≤Ho−Hc≤40, and a spin index which is the product of (Ho−H12)−(H12−Hc) and the dynamic friction coefficient of the bal