Golf ball

Abstract

Provided is a golf ball that is suitable for golf players who can achieve a sufficiently high trajectory due to initial elements and is also suitable for golf players who cannot achieve a sufficiently high trajectory due to initial elements. The golf ball has a core, a cover, and a paint layer. The golf ball has a variable dimple on a surface thereof. The cover has a hole. A space is formed by the hole. The cover and the paint layer are not joined at a location directly below the dimple. A space is formed between the cover and the paint layer. The volume of the space varies due to a centrifugal force caused by backspin.

What is claimed is: 
     
         1 . A golf ball comprising a plurality of dimples on a surface thereof, wherein
 the dimples include one or more variable dimples, and   each of the variable dimples has a structure that makes a shape thereof during flight different from a shape thereof at rest.   
     
     
         2 . The golf ball according to  claim 1 , wherein transition from the shape at rest to the shape during flight is achieved by a centrifugal force resulting from spin of the golf ball. 
     
     
         3 . The golf ball according to  claim 1 , wherein a volume V2 of the variable dimple with the shape during flight is different from a volume V1 of the variable dimple with the shape at rest. 
     
     
         4 . The golf ball according to  claim 3 , wherein the volume V2 with the shape during flight is smaller than the volume V1 with the shape at rest. 
     
     
         5 . The golf ball according to  claim 3 , wherein the golf ball includes
 a first variable dimple in which the volume V2 with the shape during flight is smaller than the volume V1 with the shape at rest, and   a second variable dimple in which the volume V2 with the shape during flight is larger than the volume V1 with the shape at rest.   
     
     
         6 . The golf ball according to  claim 3 , wherein
 the golf ball includes the variable dimple for which an absolute value of a volume change rate Pv calculated by the following mathematical formula is not less than 5%,
     Pv =( V 2− V 1)/ V 1·100
 
   
       where V1 represents a volume of the dimple with the shape at rest, and V2 represents a volume of the dimple with the shape during flight when a rate of the spin is 2500 rpm. 
     
     
         7 . The golf ball according to  claim 1 , wherein
 the golf ball has a main part and a membrane covering the main part,   a surface of the membrane has a plurality of dimples including the variable dimple and a land that is a part other than the dimples, and   a distance between the membrane and the main part at a location directly below the variable dimple can vary.   
     
     
         8 . The golf ball according to  claim 7 , wherein
 the golf ball has a fluid between the membrane and the main part at the location directly below the variable dimple, and   the distance between the membrane and the main part can vary due to expansion or contraction of the fluid.   
     
     
         9 . The golf ball according to  claim 7 , wherein
 the golf ball has a fluid between the membrane and the main part at the location directly below the variable dimple, and   the distance between the membrane and the main part can vary due to increase or decrease of the fluid.   
     
     
         10 . The golf ball according to  claim 9 , wherein the golf ball has
 a first variable dimple directly below which the golf ball has the fluid between the membrane and the main part,   a second variable dimple directly below which the golf ball has the fluid between the membrane and the main part, and   a passage that allows the fluid present directly below the second variable dimple to move to a location directly below the first variable dimple.   
     
     
         11 . The golf ball according to  claim 1 , wherein a ratio of a number of the variable dimples to a total number of the dimples is not less than 50%. 
     
     
         12 . The golf ball according to  claim 1 , wherein the golf ball has a core, a cover positioned outside the core, and a paint layer positioned outside the cover, and wherein the variable dimple comprises a space between the cover and the paint layer. 
     
     
         13 . The golf ball according to  claim 12 , wherein the cover has a hole, and the space is formed by the hole. 
     
     
         14 . The golf ball according to  claim 1 , wherein the golf ball comprises:
 a first variable dimple that decreases in volume during flight, and   a second variable dimple that increases in volume during flight.   
     
     
         15 . The golf ball according to  claim 14 , wherein the golf ball has a passage connecting the first variable dimple and the second variable dimple, and a fluid moves between the first variable dimple and the second variable dimple through the passage during flight. 
     
     
         16 . The golf ball according to  claim 15 , wherein the fluid is a non-compressible liquid. 
     
     
         17 . The golf ball according to  claim 1 , wherein the variable dimple has a volume change rate Pv calculated by the formula Pv=(V2−V1)/V1×100, where V1 is the volume at rest and V2 is the volume during flight at 2500 rpm, and an absolute value of the volume change rate Pv is at least 10%. 
     
     
         18 . The golf ball according to  claim 1 , wherein at least 80% of the dimples are variable dimples. 
     
     
         19 . A golf ball comprising:
 a spherical body having a core and a cover; and   a plurality of dimples on a surface of the spherical body, wherein   the dimples include variable dimples having a structure that allows the depth of the variable dimples to change in response to centrifugal force during spin of the golf ball.   
     
     
         20 . A golf ball comprising:
 a golf ball body having a core and a cover;   a membrane covering the golf ball body, the membrane having dimples and lands on a surface thereof; and   fluid positioned between the membrane and the golf ball body at locations corresponding to the dimples, wherein   a distance between the membrane and the golf ball body varies during flight due to centrifugal force acting on the fluid.