Patent Publication Number: US-8986136-B2

Title: Method of making golf ball with material-filled grooves

Description:
TECHNICAL FIELD 
     The present invention relates generally to golf balls and, more particularly, to golf balls having surface grooves with compressible materials in the grooves. 
     BACKGROUND 
     A golfer typically selects a golf ball that has a combination of features and performance characteristics based on his or her preferences and/or skill. The various performance characteristics may be provided by selection of materials and structural configurations, as well as manufacturing techniques. Different portions of the ball (for example the inner core and the outer surface layers) may be formed to have differing mechanical properties and other physical attributes. These differing properties and attributes determine the performance characteristics of the ball. For example, a ball having more weight toward the outer surface will maintain more spin during flight, which may be desired by the player. In addition, the hardness and/or compressibility of different portions of the ball influence the distance, control, and feel of the ball when played. 
     Golf balls have been developed that utilize relatively soft and/or compressible outer layer materials to improve spin and/or feel. However, soft and/or compressible materials may lack desired levels of durability for use in a surface layer of a golf ball, which experiences significant amounts of abuse from contact with golf club heads and from the ground. In addition, golf balls having soft and/or compressible outer layers may not provide desired levels of distance when struck. 
     In addition, the aerodynamics of the golf ball outer surface also influences the performance characteristics of the ball. Golf balls have been developed having dimples or grooves to provide desired aerodynamic effects. However, such balls have not taken advantage of the discontinuity in the outer surface of the ball by incorporating different materials in the dimples and/or grooves. 
     Some golf balls have been developed that include inner materials that penetrate the outer cover layer at some points, for example, to provide indicia on the outer surface of the ball. These golf balls are provided with a minimal difference between the hardness of the inner material and the outer cover layer material, for example, for example no greater than 15%, in order to provide consistency in the performance characteristics of the outer surface of the ball. Thus, such exposed inner materials are not implemented to provide an enhanced performance attribute, but rather, are merely for aesthetic benefit (as indicia). In other cases, hard material inlays, such as stripes, have been provided on golf balls, to provide different play characteristics depending on where on the outer surface the ball is struck. However, such differing play characteristics are prohibited by some rule-making golf organizations. 
     Some golf balls have been developed that utilize plugs that extend through the outer cover layer. The plugs may have a higher or lower hardness than the outer cover layer material. However, these plugs are flush with the outer surface of the outer cover layer. Accordingly, embodiments having softer plugs may be susceptible to wear of the plugs, since the softer materials may be less durable than the harder outer cover layer. 
     The present disclosure is directed to improvements in golf balls. 
     SUMMARY 
     In one aspect, the present disclosure is directed to a golf ball. The golf ball may include an inner core layer and an outer cover layer disposed radially outward of the inner core layer. The outer cover layer may be formed of an outer cover layer material having one or more grooves extending radially inward from an outer surface of the outer cover layer. In addition, the golf ball may include a groove material disposed within the one or more grooves. The groove material may have a compressibility that is different from a compressibility of the outer cover layer material. Also, the outer surface of the groove material may extend radially outward beyond the outer surface of the outer cover layer. 
     In another aspect, the present disclosure is directed to a golf ball. The golf ball may include an inner core layer and an outer cover layer disposed radially outward of the inner core layer. The outer cover layer may be formed of an outer cover layer material having one or more grooves extending radially inward from an outer surface of the outer cover layer. In addition, the golf ball may include a groove material disposed within the one or more grooves. The groove material may have a compressibility that is different from a compressibility of the outer cover layer material. Also, an outer surface of the groove material may be recessed from the outer surface of the outer cover layer. 
     In another aspect, the present disclosure is directed to a golf ball. The golf ball may include an inner core layer and an outer cover layer disposed radially outward of the inner core layer. The outer cover layer may be formed of an outer cover layer material having one or more grooves extending radially inward from an outer surface of the outer cover layer. In addition, the golf ball may include a groove material disposed within the one or more grooves and forming a portion of an outer surface area of the golf ball. The groove material may have a compressibility that is less than a compressibility of the outer cover layer material. Also, the outer cover layer material may constitute a substantial majority of the outer surface area of the golf ball. Further, an outer surface of the groove material may be substantially flush with the outer surface of the outer cover layer. 
     In another aspect, the present disclosure is directed to a method of making a golf ball. The method may include molding at least one core layer and molding an outer cover layer radially outward of the at least one core layer, from an outer cover layer material, including forming one or more grooves extending radially inward from an outer surface of the outer cover layer. The method may also include molding a groove material within the one or more grooves, the groove material having a compressibility that is different from a compressibility of the outer cover layer material. In addition, molding the groove material may include forming the groove material such that an outer surface of the groove material extends radially outward beyond the outer surface of the outer cover layer. 
     In another aspect, the present disclosure is directed to a method of making a golf ball. The method may include molding at least one core layer and molding an outer cover layer radially outward of the at least one core layer, from an outer cover layer material, including forming one or more grooves extending radially inward from an outer surface of the outer cover layer. In addition, the method may include molding a groove material within the one or more grooves, the groove material having a compressibility that is different from a compressibility of the outer cover layer material. Also, molding the groove material may include forming the groove material such that an outer surface of the groove material is recessed from the outer surface of the outer cover layer. 
     In another aspect, the present disclosure is directed to a method of making a golf ball. The method may include molding at least one core layer and molding an outer cover layer radially outward of the at least one core layer, from an outer cover layer material, including forming one or more grooves extending radially inward from an outer surface of the outer cover layer. In addition, the method may include molding a groove material within the one or more grooves, the groove material having a compressibility that is less than a compressibility of the outer cover layer material. Also, molding the groove material may include forming the groove material such that an outer surface of the groove material is substantially flush with the outer surface of the outer cover layer, and such that the outer cover layer material constitutes a substantial majority of the outer surface area of the golf ball. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  shows a cutaway, partial cross-sectional view of an exemplary golf ball having a three-piece construction; 
         FIG. 2  shows a cutaway, partial cross-sectional view of an exemplary golf ball having a four-piece construction; 
         FIG. 3  shows a cutaway, partial cross-sectional view of an exemplary golf ball having material-filled spiral grooves in an outer layer; 
         FIG. 4  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 5  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 6  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 7  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 8  shows a cutaway, partial cross-sectional view of an alternative golf ball embodiment having material-filled spiral grooves in an outer layer; 
         FIG. 9  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 10  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 11  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 12  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 13  shows a partial cross-sectional view of an exemplary alternative golf ball embodiment; 
         FIG. 14  shows a cutaway, partial cross-sectional view of an exemplary golf ball having material-filled, circular grooves in an outer layer; 
         FIG. 15  shows a cutaway, partial cross-sectional view of an alternative golf ball embodiment having material-filled, circular grooves in an outer layer; 
         FIG. 16  shows a cutaway, partial cross-sectional view of an exemplary golf ball having a material-filled recessed grid in an outer layer; 
         FIG. 17  shows a cross-sectional view of a mold for a golf ball; 
         FIG. 18  shows a partial cross-sectional view of an apparatus and method for molding components of a golf ball; 
         FIG. 19  shows a partial cross-sectional view of a mold for an outer cover layer of a golf ball; and 
         FIG. 20  shows a partial cross-sectional view of an alternative apparatus and method for molding components of a golf ball. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     The present disclosure relates generally to grooved golf balls. More specifically, the present disclosure relates to grooved golf balls having material in the grooves that is softer than other portions of the outer layer. 
     The performance characteristics of a golf ball are determined, at least in part, by the structural configuration of the layers and/or the material compositions of the layers. The overall performance characteristics of the golf ball are affected in certain ways by the makeup of individual layers and also reflect the combination and arrangement of the layers and materials from which the golf ball is formed. The concepts discussed in the present disclosure may be applicable to golf balls having any construction, including any suitable number of layers. 
     Further, although the disclosure describes various grooved configurations for golf balls, a person having ordinary skill in the art will be able to adapt the disclosed concepts for implementation in other types of balls (other than golf balls) and other types of layered articles. For example, the disclosed concepts may be applicable to any layered article, such as a projectile, recreational device, or individual components of these articles. 
     Definitions 
     For purposes of this disclosure, the terms “compressible,” “compressibility,” and the like refer to the amount deformation exhibited by an object when compressed under a predetermined set of loading parameters. As used in the present disclosure, compressibility shall refer to compression deformation, which is the deformation amount (in millimeters) of an object when compressed by a force, specifically, the deformation of the object when the compression force is increased from 10 kg to 130 kg. The deformation amount of the object under the force of 10 kg is subtracted from the deformation amount of the object under the force of 130 kg to obtain the compression deformation value of the object. While compressibility (and compression deformation) is a parameter that may be measured for entire golf balls, compressibility can also be measured for individual components of golf balls. In the present disclosure, compressibility of a golf ball groove material is measured and discussed in detail. 
     Hardness of a golf ball layer is measured generally in accordance with ASTM D-2240. In some cases the hardness may be measured on a cross-sectional surface of a ball layer. In other cases, the hardness may be measured on the curved surface of a ball layer. 
     Golf Ball Structure Generally 
     The disclosed concepts may be applicable to golf balls having any internal structural configuration.  FIGS. 1 and 2  illustrate exemplary 3-layer and 4-layer golf ball constructions, respectively. 
     3-Layer Ball Structure 
       FIG. 1  illustrates a cutaway, partial cross-sectional view of an exemplary three-layer golf ball construction. As shown in  FIG. 1 , a golf ball  100  may include a cover layer  105 , an outer core layer  110  disposed radially inward of cover layer  105 , and an inner core layer  115  disposed radially inward of outer core layer  110 . The dimensions and materials of each layer may be selected to achieve desired performance characteristics. 
     Cover layer  105  may be formed of a relatively soft but durable material. For example, cover layer  105  may be formed of a material that compresses/flexes when struck by a golf club, in order to provide spin of the ball and feel to the player. Although relatively soft, the material may also be durable, in order to withstand scuffing from the club and/or the golf course. Exemplary cover layer materials may include urethane or ionomer blends, and/or any other suitable material. 
     In addition,  FIG. 1  illustrates the outer surface of cover layer  105  as having a generic dimple pattern. While the dimple pattern on golf ball  100  may affect the flight path of golf ball  100 , any suitable dimple pattern may be used with the disclosed embodiments. In some embodiments, golf ball  100  may be provided with a dimple pattern including a total number of dimples between approximately 300 and 400. 
     Outer core layer  110  may be formed of a relatively firm and suitably resilient material. Outer core layer  110  may be configured to provide a relatively high launch angle and a relatively low spin rate when the ball is struck by a driver, and a relatively higher spin rate and increased control when struck with irons. This may provide distance off the tee with spin and control around the greens. Inner core layer  115  may be formed of a relatively firm material in order to provide distance. 
     The thickness of the golf ball layers may be varied in order to achieve desired performance characteristics. In some embodiments, inner core layer  115  may have a diameter in the range of about 19 mm to 30 mm. For example, in some embodiments, inner core layer  115  may be spherical with a diameter  120  of approximately 24 mm to 28 mm. 
     4-Layer Ball Structure 
       FIG. 2  is a cutaway, partial cross-sectional view of a golf ball  200  having a four-piece construction. As shown in  FIG. 2 , golf ball  200  may have four layers that are positioned adjacent one another. For example, in some embodiments, golf ball  200  may include an outer cover layer  205  and an inner cover layer  210  disposed radially inward of outer cover layer  205 . Golf ball  200  may also include an outer core layer  215  disposed radially inward of inner cover layer  210 , and an inner core layer  220  disposed radially inward of outer core layer  215 . Any layer may surround or substantially surround any layers disposed radially inward of that layer. For example, outer core layer  215  may surround or substantially surround inner core layer  220 . 
     As shown in  FIG. 2 , golf ball  200  may dimples  230  which may be formed in outer cover layer  205 . As noted above, dimples  230  may have any suitable configuration. 
     In the present disclosure and drawings, golf ball  200  is described and illustrated as having four layers. In some embodiments, at least one additional layer may be added. For example, in some embodiments, a mantle layer may be added between outer core layer  215  and inner cover layer  210 . In some embodiments, an intermediate cover layer may be inserted between inner cover layer  210  and outer cover layer  205 . Further, in some embodiments, an intermediate core layer may be inserted between inner core layer  220  and outer core layer  215 . Other layers may be added on either side of any disclosed layer as desired to achieve certain performance characteristics and/or attributes. 
     In some embodiments, golf ball  200  may have a diameter of at least 42.67 mm (1.680 inches), in accordance with the Rules of Golf. For example, in some embodiments, golf ball  200  may have a ball diameter between about 42.67 mm and about 42.9 mm, and may, in some embodiments, have a ball diameter of about 42.7 mm. Golf ball  200  may have a ball weight between about 45 g and about 45.8 g and may, in some embodiments, have a ball weight of about 45.4 g. 
     The thickness of the layers of golf ball  200  may be varied in order to achieve desired performance characteristics. In some embodiments, outer cover layer  205  may have a thickness of approximately 0.5 mm to 2 mm. In addition, in some embodiments, inner cover layer  210  may have a thickness of approximately 0.5 mm to 2 mm. In some embodiments, outer cover layer  205  and/or inner cover layer  210  may have a thickness of approximately 0.8 mm to 2 mm. In some embodiments, outer cover layer  205  and/or inner cover layer  210  may have a thickness of approximately 1 mm to 1.5 mm. 
     In some embodiments, outer core layer  215  may have a thickness of at least about 5 mm. In some embodiments, inner core layer  220  may be a sphere having a diameter  225  in the range of approximately 21 mm to 30 mm. In some embodiments, diameter  225  of inner core layer  220  may be in the range of approximately 24 mm to 28 mm. For example, in some embodiments, diameter  225  may be 24 mm. In other embodiments, diameter  225  may be 28 mm. 
     In some embodiments, the inner core layer may be formed by any suitable process, such as injection molding or compression molding. Further the inner core layer may be formed of any suitable material, such as a thermoplastic material, for example. In some embodiments, suitable thermoplastic materials may include, for example, an ionomer resin, such as Surlyn, produced by E. I. Dupont de Nemous and Company. In some embodiments, the inner core layer may be formed from a highly neutralized acid polymer composition. Exemplary highly neutralized acid polymer compositions suitable for forming the inner core layer may include, for example, HPF resins such as HPF1000, HPF2000, HPF AD1024, HPF AD1027, HPF AD1030, HPF AD1035, HPF AD1040, all produced by E. I. Dupont de Nemous and Company. 
     The acid polymer may be neutralized to 80% or higher, including up to 100%, with a suitable cation source, such as magnesium, sodium, zinc, or potassium. Suitable highly neutralized acid polymer compositions for use in forming the inner core layer may include a highly neutralized acid polymer composition and optionally additives, fillers, and/or melt flow modifiers. 
     Suitable additives and fillers may include, for example, blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, acid copolymer wax, surfactants. In some embodiments, the additives and fillers may include, for example, inorganic fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay, silica, lead silicate, and other types of organic fillers. In some embodiments, the additives and fillers may include, for example, high specific gravity metal powder fillers, such as tungsten powder, molybdenum powder, and others. In some embodiments the additives and fillers may include regrind, that is, core material that is ground and recycled. 
     Any suitable melt flow modifiers may be included in the highly neutralized acid polymer composition. Exemplary suitable melt flow modifiers may include, for example, fatty acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof. 
     The outer core layer may be formed by any suitable method, such as compression molding. Further, the outer core layer may be formed of any suitable material, such as a thermoset material. For example, in some embodiments, outer core layer  215  may be formed by crosslinking a polybutadiene rubber composition. When other rubber is used in combination with a polybutadiene, polybutadiene may be included as a principal component. For example, a proportion of polybutadiene in the entire base rubber may be equal to or greater than 50% by weight and, in some embodiments, may be equal to or greater than 80% by weight. In some embodiments, outer core layer  215  may be formed of a polybutadiene rubber composition including a polybutadiene having a proportion of cis-1,4 bonds of equal to or greater than 60 mol %. For example, in some embodiments, the proportion may be equal to or greater than 80 mol %. 
     In some embodiments, cis-1,4-polybutadiene may be used as the base rubber and mixed with other ingredients. In some embodiments, the amount of cis-1,4-polybutadiene may be at least 50 parts by weight, based on 100 parts by weight of the rubber compound. Various additives may be added to the base rubber to form a compound. The additives may include a cross-linking agent and a filler. In some embodiments, the cross-linking agent may be zinc diacrylate, magnesium acrylate, zinc methacrylate, or magnesium methacrylate. In some embodiments, zinc diacrylate may provide advantageous resilience properties. 
     In some embodiments, the filler may include zinc oxide, barium sulfate, calcium carbonate, or magnesium carbonate. In some embodiments, zinc oxide may be selected for its advantageous properties. In some embodiments, the filler may be used to increase the specific gravity of the material. For example, metal powder, such as tungsten, may alternatively be used as a filler to achieve a desired specific gravity. In some embodiments, the specific gravity of outer core layer  215  may be in the range of about 1.05 g/cm^3 to about 1.35 g/cm^3. 
     In some embodiments, a polybutadiene synthesized using a rare earth element catalyst is preferred. Using this polybutadiene may provide golf ball  200  with increased resilience. Examples of rare earth element catalysts include lanthanum series rare earth element compound, organoaluminum compound, and almoxane and halogen containing compound. A lanthanum series rare earth element compound is preferred. Polybutadiene obtained by using lanthanum rare earth-based catalysts usually employ a combination of a lanthanum rare earth (atomic number of 57 to 71) compound, but particularly preferred is a neodymium compound. 
     In some embodiments, the polybutadiene rubber composition may comprise at least from about 0.5 parts by weight to about 5 parts by weight of a halogenated organosulfur compound. In some embodiments, the polybutadiene rubber composition may comprise at least from about 1 part by weight to about 4 parts by weight of a halogenated organosulfur compound. The halogenated organosulfur compound may be selected from the group consisting of pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol; pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol; pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol; 2,3,5,6-tetraiodothiophenol; pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol 4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol; 3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; and their zinc salts, the metal salts thereof and mixtures thereof. 
     One or more cover layers may be molded to enclose the outer core layer. The cover layers may be formed of any suitable materials. For example, in some embodiments, cover layers may be formed from thermoplastic or thermoset materials. In some embodiments, inner cover layer  210  and/or outer cover layer  205  may be made from a thermoplastic material including at least one of an ionomer resin, a highly neutralized acid polymer composition, a polyamide resin, a polyester resin, and a polyurethane resin. In some embodiments, an ionomer resin, polyurethane resin, or highly neutralized acid polymer composition may be more preferred for inner cover layer  210  or outer cover layer  205 . In some embodiments, inner cover layer  210  may be formed of the same type of material as outer cover layer  205 . In other embodiments, inner cover layer  210  may be formed of a different type of material from outer cover layer  205 . 
     The disclosed concepts may be implemented in golf balls having three-layer construction, four-layer construction, five-layer construction, or any other suitable configuration. Exemplary such concepts are discussed below. 
     Grooved Configurations 
     In some embodiments, an exemplary disclosed golf ball may include features that provide increased spin and/or feel when struck. In order to provide such characteristics, the golf ball may be provided with one or more components formed of a material having an increased compressibility. That is, the material may deflect a greater amount when exposed to a given amount of force than a relatively less compressible material. In order to provide increased spin and/or feel, such compressible material may be disposed radially outward from the center of the ball, for example at or near the outer surface of the ball. 
     It is generally desirable for a golf ball to exhibit minimal spin when struck with a driver. Further, when a golf ball is struck with a club moving at a relatively high club head speed, such as a driver, the amount of deformation of the ball is significant, such that the properties of the core and other inner layers of the ball determine the playing characteristics, particularly distance. For these reasons, it may be desirable to provide a golf ball with a relatively hard and incompressible outer cover layer. An outer cover layer that is too compressible may be too “grippy” and thus produce more spin, even when struck with a driver. Further, a compressible outer cover layer would tend to absorb some of the energy of the impact with the club head and, therefore, reduce the distance achievable with the ball. 
     During short game play, however, it may be desirable for a golf ball to exhibit greater amounts of spin and feel. Greater amounts of spin facilitate greater control of the ball. During short game play, where club head speeds are relatively slower, the compressibility of the cover layers of the ball determine the playing characteristics, since the ball is not typically struck hard enough to compress the inner layers of the ball. Increased spin may be provided by a compressible outer cover layer material. Further, such a compressible outer cover layer may also provide improved feel of the ball when struck at relatively slow club head speeds. Thus, the desirability of having a compressible cover for short game play (e.g., playing with irons) may be in conflict with the desirability of having a relatively incompressible cover for long game play (e.g., hitting with a driver). 
     The present disclosure provides ball configurations, which implement both compressible and incompressible materials in the cover in order to produce a ball that has both good distance with low spin when struck with a driver, and increased spin and feel when struck with a short game club (e.g., irons, pitching wedge, sand wedge). In some embodiments, an exemplary disclosed golf ball may include one or more core layers and one or more cover layers. In some embodiments, an outermost cover layer, formed of a first material, having formed therein one or more grooves. For example, such grooves may include one or more channels, which may be formed in any suitable configuration. In some embodiments, for example, the outermost cover layer may include at least one spiral channel. In some embodiments, the cover layer may include circular grooves or circumferential grooves, which may be arranged in a grid about the outer surface of the ball. 
     In order to provide the increased spin and/or feel, a relatively compressible material may be disposed within the one or more grooves. Such material may have a compressibility that is less than the compressibility of the outermost cover layer material. In some embodiments, the outer cover layer material may constitute a substantial majority of the outer surface area of the golf ball and the outer surface of the material disposed in the grooves may constitute a substantial minority of the outer surface area of the golf ball. 
     In some embodiments, the golf ball may include features that affect the aerodynamics of the ball. For example, in some embodiments, the outer surface of the material disposed in the grooves may extend beyond or may be recessed from the outer surface of the outermost cover layer. Therefore, the ball may include either bulges and/or recesses in the outer surface, which may have an effect on aerodynamics. In some embodiments the aerodynamic effect may be a reduction in drag coefficient, to improve distance and/or spin. In other embodiments, the effect may be an increase in drag coefficient, possibly in exchange for increased or decreased spin and/or control. In some embodiments, the orientation of the bulges and/or recesses may induce spin during flight. For example, a spiral arrangement of elongate bulges and/or recesses may cause a particular spin of the ball during flight. 
       FIG. 3  illustrates an exemplary golf ball  300 . Ball  300  may include an inner core layer  310  and an outer core layer  315  disposed radially outward of inner core layer  310 . In addition, ball  300  may include an inner cover layer  320  disposed radially outward of outer core layer  315 , and an outer cover layer  325  disposed radially outward of inner cover layer  320 . These layers may be configured generally as discussed above with respect to  FIGS. 1 and 2 . In some embodiments, ball  300  may have more or fewer layers. Suitable materials for inner core layer  310 , outer core layer  315 , inner cover layer  320 , and outer cover layer  325  are discussed above. Other suitable materials will be recognized by those having ordinary skill in the art. 
     For purposes of this disclosure and claims, the outer cover layer shall be referred to, in some cases, as the “outermost layer” of the golf ball. Similarly, the term “outermost surface area” of the golf ball is used in reference to the outer surface of the disclosed layers. It will be understood by those having ordinary skill in the art, however, that one or more finish coatings, including paint or other colorations, as well as one or more topcoats or clearcoats may be applied to an outer surface of the disclosed layers. These finish coatings have relatively insignificant thickness and, therefore, the outer surfaces of the disclosed layers are effectively the outermost surfaces of the golf ball, from a structural standpoint. 
     According to exemplary disclosed embodiments, spin and/or feel of the golf ball may be increased by the inclusion of a relatively compressible material at and/or near the outer surface of the outer cover layer. In some embodiments, a second material may be molded into the grooves of the outer cover layer, wherein the second material has a compressibility that is different than the compressibility of the outer cover layer material. For example, in some embodiments, a material that is more compressible than the outer cover layer material may be molded into the grooves. In other embodiments, the outer cover layer material may be more compressible than the material molded into the grooves. Although the material molded into the grooves (“groove material”) may be more or less compressible than the outer cover layer, for purposes of discussion, the embodiments discussed below, unless otherwise noted, will be described as having a groove material that is more compressible than the outer cover layer material. 
     In some embodiments, the outer surface of the groove material forms a portion of the outer surface of the ball. The surface area and thickness of the groove material may be factors in the extent to which the groove material affects the spin and feel of the ball. Generally, the greater the amount of exposed surface area and/or thickness of a compressible material, the greater the increases in spin and feel will be. A compressible material will exhibit more grip against the club face, much like a soft compound tire provides more road grip. Therefore the amount of compressible material surface area will affect the amount of grip the ball will have against the club face. This increase in grip provides more spin and feel when striking the ball. In addition, the thickness of the compressible material has a similar effect on grip, the thickness of the compressible material is related to the amount of compressible material present at the outer portion of the ball. The more compressible material present at the outer portion of the ball, the more the outer portion deforms when struck, even on short game strikes, which tend to be less forceful. 
     In order to limit the increase in spin provided by the inclusion of compressible groove material, the groove material may constitute a limited amount of the outer surface area of the ball. For example, in some embodiments, the outer surface of the outer cover layer may constitute a substantial majority of the overall surface area of the ball, and the outer surface of the groove material may constitute a substantial minority of the outer surface of the ball. In other embodiments, the outer surface of the groove material may constitute a substantial majority of the outer surface area of the ball, and the outer surface of the outer cover layer may constitute a substantial minority of the outer surface area of the ball. This configuration may be advantageous, for example, when the outer cover layer material is more compressible than the groove material. 
     In addition, the extent to which the groove material extends radially beyond the outer surface of the outer cover layer may also influence the spin and feel. In some embodiments, the groove material may partially fill the grooves, and thus, may have an outer surface that is recessed from the outer surface of the outer cover layer. In some embodiments, the groove material may completely fill the grooves. For example, in some embodiments, the outer surface of the groove material may be substantially flush with the outer surface of the outer cover layer. In some embodiments, the outer surface of the groove material may overfill the grooves, bulging out such that the outer surface of the groove material extends radially outward beyond the outer surface of the outer cover layer. Generally, the greater the distance of a groove material from the center of the ball (relative to the outer surface of the outer cover layer), the greater the increases in spin and feel. The further the groove material extends radially, the more surface area of the groove material will be engaged by the club face and the less surface area of the outer cover layer will be engaged by the club face, thus providing increased grip against the club face, resulting in increased spin and feel. 
     In some embodiments, outer cover layer  325  may include a groove  330  extending radially inward from an outer surface  340  of outer cover layer  325 . In some embodiments, groove  330  may have the form of an elongate channel. Such channels may have any suitable configuration, such as, for example a spiral arrangement, as shown in  FIG. 3 . As further illustrated in  FIG. 3 , groove  330  may be a continuous spiral groove encircling golf ball  300  and extending substantially from one side of the golf ball to an opposite side of the golf ball. Other embodiments may incorporate more than one channel, such as a plurality of spiral grooves. Other arrangements are also possible. In addition, groove  330  may have any suitable shape, length, width, and depth. Exemplary alternative groove configurations are shown in the figures and discussed below. 
     Ball  300  may include a groove material  335  disposed within groove  330 . In some embodiments, groove material  335  may have a compressibility that is different from the compressibility of the material from which outer cover layer  325  is formed. In some embodiments, groove material  335  may be more compressible than the material of outer cover layer  325 . In other embodiments, groove material  335  may be less compressible than outer cover layer  325 . 
     In some embodiments, groove material  335  may have a hardness that is different than the hardness of outer cover layer  325 . For example, in some embodiments, groove material  335  may have a hardness that is lower than the hardness of outer cover layer material  325 . In such embodiments, the harder outer cover layer material may provide durability to the outer surface  345  of ball  300 , while the softer groove material  335  may provide increased spin and/or feel. In other embodiments, groove material  335  may have a hardness that is greater than the hardness of outer cover layer  325 . 
     The placement of the relatively compressible groove material  335  in the cover region of ball  300 , radially displaced from the center of ball  300 , may enhance the increase in spin and/or feel provided by compressible groove material  335 . In addition, the compressible groove material  335  may further enhance the increase in spin and/or feel in some embodiments where groove material  335  extends radially outward beyond outer surface  340  of outer cover layer  325 . For example, as shown in  FIG. 3 , an outer surface  350  of groove material  335  may extend radially outward beyond outer surface  340  of outer cover layer  325 . A bulge dimension  355 , shown in  FIG. 3 , illustrates an exemplary amount by which outer surface  350  of groove material  335  may extend beyond outer surface  340 . Exemplary alternative configurations with respect to the relative placement the outer surfaces of the groove material and the outer cover layer are shown and discussed in greater detail in conjunction with other disclosed embodiments. 
     The cross-sectional shape and the depth of groove  330  within outer cover layer  325  may have a number of possible configurations, as shown and discussed with respect to several exemplary disclosed embodiments. In one possible configuration shown in  FIG. 3 , groove  330  may have a curved cross-sectional shape, such that a bulged groove material  335  appears to have an American football-shaped cross-sectional shape. In addition, in some embodiments, groove  330  may extend partially through outer cover layer  325 , thus forming a recess in outer cover layer  325 , such that a portion  360  of outer cover layer  325  may extend between an inner surface  365  of groove material  335  and an outer surface  370  of inner cover layer  320 , which may be a different material than outer cover layer  325  and groove material  335 . 
     The bulging of groove material  335  beyond outer surface  340  of outer cover layer  325  may provide at least two benefits. First, the bulging groove material  335  may provide ball  300  with a different surface area when struck hard, such as with a driver, than when struck more easily, such as on short game strokes. When struck hard, the compressibility of groove material  335  may allow groove material  335  to deflect (compress) such that outer surface  350  of groove material  335  becomes substantially flush with outer surface  340  of outer cover layer  325 . Thus, the surface area of outer surface  345  of ball  300  that contacts the club face when struck hard, will be constituted of all of outer surface  340  and outer surface  350  in the area of ball  300  struck by the club face. In such situations, since the surface area of outer cover layer  325  may constitute a substantial majority of outer surface  345  of ball  300 , when ball  300  is struck hard, more of the contact area between ball  300  and the club face will be constituted by outer surface  340  of outer cover layer  325 . Since outer cover layer  325  may be less compressible than groove material  335 , this may be beneficial when driving the ball, because less spin is desired for drives. 
     When struck lightly, groove material  335  may not compress completely. Accordingly, a larger proportion of the surface area of ball  300  contacting the club face will be constituted by outer surface  350  of groove material  335 . This may provide a grippier surface of ball  300 , thus producing more spin and providing increased feel. 
     A second benefit is that the bulging of groove material  335  may provide an aerodynamic effect. The bulges of groove material  335  may disrupt airflow around ball  300 , disrupting airflow in much the same way dimples do on a conventional golf ball. In addition, the pattern of bulging groove material  335  may induce other aerodynamic effects. For example, a spiral arrangement, such as that shown in  FIG. 3 , may induce a particular spin during flight. In some embodiments, this induced spin may enhance spin generated at club face contact. For example, a spiral groove material configuration may induce backspin, which enhances the backspin produced by the club face. In some embodiments, the induced spin may be counter to, or off angle from, the spin generated by the club face. For example, in some embodiments, the spiral configuration may produce a rotation about the axis of ball flight (like an American football). 
     In addition to aerodynamic effects provided by groove material  335 , ball  300  may be provided with other aerodynamic effects by other structural features. For example, in some embodiments, ball  300  may include dimples  375  on outer surface  340  of at least a portion of outer cover layer  325 . Alternatively, or additionally, in some embodiments, ball  300  may have dimples in outer surface  350  of groove material  335  (not shown). Dimples  375  may have any suitable configuration. In some embodiments, dimples  375  may have an arrangement that is based on one or more dimple patterns known to those having ordinary skill in the art. 
       FIG. 4  shows an enlarged cross-sectional view of a portion of an exemplary golf ball having an alternative groove configuration.  FIG. 4  illustrates an exemplary golf ball  400 . Ball  400  may include an inner core layer  410  and an outer core layer  415  disposed radially outward of inner core layer  410 . In addition, ball  400  may include an inner cover layer  420  disposed radially outward of outer core layer  415 , and an outer cover layer  425  disposed radially outward of inner cover layer  420 . These layers may be configured generally as discussed above with respect to  FIGS. 1 and 2 , as well as  FIG. 3 . 
     As shown in  FIG. 4 , outer cover layer  425  of ball  400  may include groove  430  extending radially inward from an outer surface  440  of outer cover layer  425 . Ball  400  may also include a groove material  435  disposed within groove  430 . Groove  430  may have any suitable configuration, such that the outer surface of groove material  435  may have any suitable shape, including for example, round, elongate, rectangular, oval, polygonal, or any other suitable shape. Groove material  435  may have performance characteristics, such as compressibility, that are the same or similar to those discussed above with respect to groove material  335 . 
     Similar to the embodiment shown in  FIG. 3 , groove material  435  may be bulged beyond an outer surface  440  of outer cover layer  425 , as shown in  FIG. 4 . Groove material  430  may be formed as a recess, such that a portion  460  of outer cover layer  425  may extend between an inner surface  465  of groove material  435  and an outer surface  470  of inner cover layer  420 . 
     Groove  430  may have side walls  445 . In some embodiments, side walls  445  may be angled with respect to outer surface  440  of outer cover layer  425 . For example, as shown in  FIG. 4 , side walls  445  may be oriented substantially radially, that is, substantially perpendicular to outer surface  440 . Other similar embodiments may implement side walls that are parallel to one another and, therefore, not precisely radial. Such radial and parallel configurations may provide durability under shear loads (loads on groove material  435  that are substantially tangential to the outer surface of the ball). Radially oriented side walls  440  may retain groove material  435  in groove  430  under shear loads by providing lateral support against groove material  435 . 
     Also unlike groove  330  in  FIG. 3 , groove  430  may have a substantially planar bottom surface  480 , as shown in  FIG. 4 . A planar bottom surface (as opposed to a curved bottom surface as shown in  FIG. 3 ) may accommodate a larger amount of groove material, which may be desirable to provide increased spin and/or feel. Additionally, a planar bottom surface may be easier to manufacture, for example, via molding or machining. 
       FIG. 5  illustrates a similar embodiment to that shown in  FIG. 4 .  FIG. 5  shows a golf ball  500  having an inner core layer  510 , an outer core layer  515 , an inner cover layer  520 , and an outer core layer  525 . Ball  500  may also include a groove  530 , and a groove material  535  disposed within groove  530 . As shown in  FIG. 5 , groove material  535  may be bulged beyond an outer surface  540  of outer cover layer  525 , and thus, may have an outward facing surface that is substantially similar to groove material  435  in  FIG. 4 . 
     As illustrated in  FIG. 5 , ball  500  may include side walls  545  that are angled with respect to outer surface  540  of outer cover layer  525 . In some embodiments, opposing side walls  545  may be angled closer to one another near outer surface  540  of outer cover layer  525 . Having side walls  545  angled in this manner may increase durability by providing additional retention of groove material  535  in groove  530  under loading. 
     As also illustrated in  FIG. 5 , an inner surface  565  of groove material  535  and mating bottom surface  580  of groove  530  may be curved in an arc about the center of ball  500 . Accordingly, the thickness of the portion  560  of outer cover layer  525  may be consistent across substantially the entire groove  530 . This may provide predictability regarding the structural properties of the assembly. 
     In some embodiments, grooves may extend completely through the outer cover layer of the golf ball. In some such embodiments, the inner surface of the groove material may be in contact with the outer surface of the inner cover layer. In other embodiments, a portion of an underlying, inner cover layer may extend radially outward into (and in some cases through) the groove to form the groove material. These configurations may provide still further increases in manufacturability and/or durability of the assembly. 
       FIG. 6  is an enlarged, partial cross-sectional view of a golf ball having a bulged groove material disposed within a groove that extends completely through the outer cover of the ball.  FIG. 6  shows a golf ball  600 , having an inner core layer  610 , an outer core layer  615 , an inner cover layer  620 , and an outer core layer  625 . Ball  600  may also include a groove  630 , and a groove material  635  disposed within groove  630 . As shown in  FIG. 6 , an outer surface  650  of groove material  635  may extend radially outward beyond an outer surface  640  of outer cover layer  625 . As illustrated in  FIG. 6 , groove  630  may extend completely through outer cover layer  625 . Accordingly, an inner surface  665  of groove material  635  may be in contact with an outer surface  670  of inner cover layer  620 . 
       FIG. 7  illustrates an enlarged, partial cross-sectional view of another golf ball embodiment featuring a bulging groove material disposed within a groove that extends completely through the outer cover layer.  FIG. 7  shows a golf ball  700 , having an inner core layer  710 , an outer core layer  715 , an inner cover layer  720 , and an outer core layer  725 . Ball  700  may also include a groove  730 , and a groove material  735  disposed within groove  730 . As shown in  FIG. 7 , in some embodiments, groove material  735  may be formed by a portion  760  of the inner cover layer material that extends radially outward into groove  730 . For purposes of illustration,  FIG. 7  includes a dashed line  765  to delineate a boundary between inner cover layer  720  and groove material  735 . 
     In some embodiments, groove material may be recessed from the outer surface of the outer cover layer. In some such embodiments, the outer cover layer may be formed of a more compressible material than the groove material. This configuration may operate on similar principles to embodiments, wherein a bulging groove material is more compressible than an outer cover layer into which it is molded. In some embodiments, this may provide a larger surface area of the ball formed of the more compressible material. Thus, such an embodiment could be implemented to provide even greater amounts of spin and/or feel. 
     In some embodiments, recessed groove material may be formed of a material that is more compressible than the outer cover layer. Such configurations may be implemented to provide a golf ball with a more durable outer surface. In a recessed groove material embodiment, contact between the outer surface of the groove material with clubs and the ground may be limited. By having a less compressible, and possibly harder, material disposed further radially outward than the more compressible groove material, and thus, exposed to more contact with the clubs and the ground, a more durable material may be subjected to a substantial majority of the abuse. 
     In addition to the benefits (discussed above) of adding a compressible material in the cover region of a golf ball having a recessed groove material, the recesses in the grooves may also provide an aerodynamic effect. As discussed above regarding the embodiment shown in  FIG. 3 , like bulged groove material, recesses in grooves may provide disruption of airflow at boundary layers (similar to dimples). Also like bulged groove material, recesses in grooves may be arranged to provide other aerodynamic effects, such as by inducing spin. 
       FIG. 8  illustrates an exemplary embodiment including a recessed groove material.  FIG. 8  shows a golf ball  800 , having an inner core layer  810 , an outer core layer  815 , an inner cover layer  820 , and an outer core layer  825 . Ball  800  may also include a groove  830 , and a groove material  835  disposed within groove  830 . As shown in  FIG. 8 , in some embodiments, an outer surface  850  of groove material  835  may be recessed from an outer surface  840  of outer cover layer  825 . 
     Groove material  835  may have a compressibility, and/or hardness, that are different than outer cover layer  825 . In some embodiments, outer cover layer  825  may be more compressible than groove material  835 . In other embodiments, groove material  835  may be more compressible than outer cover layer  825 . In determining whether to utilize a more compressible material for outer cover layer  825  or for groove material  835 , a ball designer may consider, as a factor, the desirability of performance characteristics provided by a more compressible material (e.g., spin, feel, control), and performance characteristics provided by a less compressible material (e.g., distance, durability). In order to achieve more compressible material characteristics, the more compressible material may be used to form outer cover layer  825 , which generally makes more contact with the club face. In order to achieve more incompressible material characteristics, the less compressible material may be used to form outer cover layer  825 . 
     Performance characteristics may also be determined by the relative surface areas of outer cover layer  825  and groove material  835  that make up the overall outer surface  845  of ball  800 . For example, although a more compressible material may be utilized for recessed groove material  835 , the ball may be provided with more compressible material characteristics by making grooves  830  wider and providing a higher ratio of groove material surface area to outer cover layer surface area. 
     Groove  830  may have any suitable shape. As shown in  FIG. 8 , groove  830  may be arranged in a spiral configuration similar to groove  330  in  FIG. 3 . In addition, groove  830  may have any suitable cross-sectional shape.  FIG. 9  is an enlarged view of a portion of ball  800 , showing an exemplary cross-sectional shape of groove  830 . As shown in  FIG. 9 , in some embodiments, groove  830  may have a curved bottom surface  885 . As further illustrated in  FIG. 9 , groove  830  may be formed as a recess in outer cover layer  825 . Therefore, a portion  860  of outer cover layer  825  may extend between an inner surface  865  of groove material  835  and an outer surface  870  of inner cover layer  820 . As can also be seen in  FIG. 9 , an outer surface  850  of groove material  835  may be recessed from outer surface  840 , as illustrated by a dimension  880 . 
     Golf ball  800  may also include other surface features. For example, in some embodiments, ball  800  may include dimples  875  on at least a portion of outer surface  840  of outer cover layer  825  or in other portions of golf ball  800 . 
       FIGS. 10 and 11  show enlarged, cross-sectional views of exemplary alternative groove configurations having recessed groove material.  FIG. 10  illustrates an embodiment wherein the groove has beveled or angled side walls.  FIG. 10  shows a golf ball  1000 , having an inner core layer  1010 , an outer core layer  1015 , an inner cover layer  1020 , and an outer core layer  1025 . Ball  1000  may also include a groove  1030 , and a groove material  1035  disposed within groove  1030 . As shown in  FIG. 10 , in some embodiments, an outer surface  1050  of groove material  1035  may be recessed from an outer surface  1040  of outer cover layer  1025 . 
     In some embodiments, groove  1030  may have sidewalls  1055  that are angled relative to outer surface  1040  of outer cover layer  1025 . In some embodiments, opposing sidewalls  1055  may be angled farther away from one another at outer surface  1040  of outer cover layer  1025 , as shown in  FIG. 10 . In some embodiments, a bottom surface  1085  of groove  1030  may be curved about the center of ball  1000 , as also shown in  FIG. 10 . 
       FIG. 11  illustrates an embodiment wherein the groove extends completely through the outer cover layer.  FIG. 11  shows a golf ball  1100 , having an inner core layer  1110 , an outer core layer  1115 , an inner cover layer  1120 , and an outer core layer  1125 . Ball  1100  may also include a groove  1130 , and a groove material  1135  disposed within groove  1130 . As shown in  FIG. 11 , in some embodiments, an outer surface  1150  of groove material  1135  may be recessed from an outer surface  1140  of outer cover layer  1125 . This is illustrated by a dimension  1145 . Outer surface  1150  of groove material  1135  is illustrated as being curved about the center of ball  1100 . However, it may also be possible for outer surface  1150  to be substantially planar. 
     As shown in  FIG. 11 , in some embodiments, groove  1130  may be defined by side walls  1155  and may extend completely through outer cover layer  1125 . Also, in some embodiments, groove material  1135  may be formed by a portion  1160  of inner cover layer material that extends radially outward into groove  1130 . A dashed line  1165  illustrates a boundary between inner cover layer  1125  and portion  1160  forming groove material  1135 . 
       FIGS. 12 and 13  illustrate enlarged, cross-sectional views of exemplary groove configurations, wherein the groove material is substantially flush with the outer surface of the outer cover layer. The benefits and considerations of having groove material bulging or recessed are discussed above. The same considerations are also relevant to flush embodiments. In some cases, having flush groove material may provide a suitable compromise between bulged and recessed groove material configurations. Flush embodiments may also be easier to manufacture, and may produce a golf ball that appears to have a more traditional outer surface shape. 
       FIG. 12  shows a golf ball  1200 , having an inner core layer  1210 , an outer core layer  1215 , an inner cover layer  1220 , and an outer core layer  1225 . Ball  1200  may also include a groove  1230 , and a groove material  1235  disposed within groove  1230 . As shown in  FIG. 12 , in some embodiments, an outer surface  1250  of groove material  1235  may be substantially flush with an outer surface  1240  of outer cover layer  1225 . In addition, groove  1230  may include angled side walls  1255 . 
     As also shown in  FIG. 12 , in some embodiments, groove  1230  may extend completely through outer cover layer  1225 . Accordingly, an inner surface  1265  of groove material  1235  may be in contact with an outer surface  1270  of inner cover layer  1220 . 
       FIG. 13  shows a golf ball  1300 , having an inner core layer  1310 , an outer core layer  1315 , an inner cover layer  1320 , and an outer core layer  1325 . Ball  1300  may also include a groove  1330 , and a groove material  1335  disposed within groove  1330 . As illustrated in  FIG. 13 , in some embodiments, groove  1330  may be defined by side walls  1355  and may extend completely through outer cover layer  1325 . In addition, in some embodiments, groove material  1335  may be formed by a portion  1360  of inner cover layer material that extends radially outward from the center of ball  1300 . Portion  1360  is generally delineated by a dashed line  1365  in  FIG. 13 . 
       FIG. 14  illustrates an alternative embodiment having bulged groove material.  FIG. 14  shows a golf ball  1400 , having an inner core layer  1410 , an outer core layer  1415 , an inner cover layer  1420 , and an outer core layer  1425 . Ball  1400  may also include a groove  1430 , and a groove material  1435  disposed within groove  1430 . 
     As shown in  FIG. 14 , in some embodiments, grooves  1430  (and the bulging groove material  1435  associated with each groove  1430 ) may be substantially circular. It will be understood that grooves  1430  may have any other suitable shape, such as squares, rectangles, triangles, and any other suitable shape. 
     Outer surfaces  1440  of outer cover layer  1425  and outer surfaces  1450  of groove material  1435  may constitute an outer surface  1445  of ball  1400 . The size of grooves  1430  may vary and, accordingly, the ratio of surface area between outer surface  1440  and outer surface  1450  may also be varied to provide the desired performance characteristics. 
     Groove material  1435  may bulge beyond outer surface  1440  as indicated by a dimension  1460 . In addition, grooves  1430  may include side walls  1455  that are angled with respect to outer surface  1440  of outer cover layer  1425 . 
     As shown in  FIG. 14 , in some embodiments, grooves  1430  may extend completely through outer cover layer  1425 . Accordingly, an inner surface  1465  of groove material  1435  may be in contact with an outer surface  1470  of inner cover layer  1420 . 
     Golf ball  1400  may also include other surface features. For example, in some embodiments, ball  1400  may include dimples  1475  on at least a portion of outer surface  1440  of outer cover layer  1425  or in other portions of golf ball  1400 . 
       FIG. 15  illustrates a golf ball embodiment similar to ball  1400 , but having recessed groove material.  FIG. 15  shows a golf ball  1500 , having an inner core layer  1510 , an outer core layer  1515 , an inner cover layer  1520 , and an outer core layer  1525 . Ball  1500  may also include a groove  1530 , and a groove material  1535  disposed within groove  1530 . 
     As shown in  FIG. 15 , in some embodiments, grooves  1530  (and the groove material  1535  associated with each groove  1530 ) may be substantially circular. It will be understood that grooves  1530  may have any other suitable shape, such as squares, rectangles, triangles, and any other suitable shape. 
     Outer surfaces  1540  of outer cover layer  1525  and outer surfaces  1550  of groove material  1535  may constitute an outer surface  1545  of ball  1500 . The size of grooves  1530  may vary and, accordingly, the ratio of surface area between outer surface  1540  and outer surface  1550  may also be varied to provide the desired performance characteristics. 
     Outer surface  1550  of groove material  1535  may be recessed from outer surface  1540 . In some embodiments, outer surfaces  1550  of groove material  1535  may be substantially planar, as shown in  FIG. 15 . In other embodiments, outer surfaces  1550  may curve about the center of ball  1500 . In addition, grooves  1530  may include side walls  1555  that are angled with respect to outer surface  1540  of outer cover layer  1525 . 
     As shown in  FIG. 15 , in some embodiments, grooves  1530  may extend completely through outer cover layer  1525 . Accordingly, an inner surface  1565  of groove material  1535  may be in contact with an outer surface  1570  of inner cover layer  1520 . 
     Golf ball  1500  may also include other surface features. For example, in some embodiments, ball  1500  may include dimples  1575  on at least a portion of outer surface  1540  of outer cover layer  1525  or in other portions of golf ball  1500 . 
       FIG. 16  illustrates an alternative embodiment wherein the outer cover layer is formed as a grid defining grooves between the gridlines.  FIG. 16  shows a golf ball  1600 , having an inner core layer  1610 , an outer core layer  1616 , an inner cover layer  1620 , and an outer core layer  1625 . Ball  1600  may also include a groove  1630 , and a groove material  1635  disposed within groove  1630 . 
     As shown in  FIG. 16 , an outer surface  1640  of outer cover layer  1625  and an outer surface  1650  of groove material  1635  may form the overall outer surface  1645  of ball  1600 . In some embodiments, outer surface  1650  of groove material  1635  may extend beyond outer surface  1640  of outer cover layer  1625 . This configuration may operate on similar principles to the bulged groove material embodiments discussed above. 
     In some embodiments, outer cover layer  1625  may be formed as a grid, wherein the gridlines of the grid are formed by intersecting bands of material. For example, a first set of bands  1655  may intersect with a second set of bands  1660 . Grid bands  1655  and  1660  may have any suitable configuration and orientation. As shown in  FIG. 16 , grid bands  1655  may be oriented as latitudinal gridlines. In other embodiments, grid bands  1655  may be oriented differently, such as longitudinally. Also, as shown in  FIG. 16 , grid bands  1660  may be oriented longitudinally. In other embodiments, grid bands  1660  may be oriented differently, such as latitudinal. 
     The openings in the outer cover layer grid may define grooves  1630 . In some embodiments, as shown in  FIG. 16 , groove material  1635  may be formed by portions of inner cover layer  1620  that extend radially outward into grooves  1630 . 
     In some embodiments, groove material  1635  may be more compressible than outer cover layer  1625 . In other embodiments, groove material  1635  may be less compressible than outer cover layer  1625 . The advantages of each such configuration are discussed above in conjunction with other similar embodiments. 
     Golf ball  1600  may also include other surface features. For example, in some embodiments, ball  1600  may include dimples  1675  on at least a portion of outer surface  1640  of outer cover layer  1625  or in other portions of golf ball  1600 . 
     Methods of Making Golf Balls 
     The disclosed golf ball embodiments may be manufactured in several different ways. The following discussion provides details regarding exemplary processes for making certain disclosed embodiments. Many of the provided details apply generally for making golf balls having grooves and groove material. 
     The layers of a golf ball may be made using any of a number of molding processes, such as injection molding and compression molding. In some embodiments, outer layers may be molded on top of pre-molded inner layers. In some embodiments, an inner layer may be injection molded within a pre-molded outer shell. 
     In addition, pre-formed inner and/or outer layers may be supported during the process of co-molding an adjacent layer using a plurality of support pins. In some embodiments, the support pins may be a retractable part of the mold apparatus. In some embodiments, the support pins may be extensions of the pre-molded layer. For example, in some embodiments, support mold pins may be formed as part of a core layer and may meld with inner cover layer material during injection of the inner cover layer material. In such embodiments, the support pins may be formed of a material that is readily compatible with the material of the layer to be added. This compatibility may prevent or inhibit the formation of voids and/or delamination at the pin sites. 
     Use of support pins in molding processes are well-known in the art and, accordingly, one of ordinary skill would readily recognize support pin configurations that may be suitable for use in the methods described below. 
     An exemplary method of making a golf ball according to the present disclosure may include molding at least one core layer. In some embodiments the method may include molding multiple core layers, such as an inner core layer and an outer core layer. The formation of these core layers may be accomplished by injection molding and/or compression molding. Various techniques for forming golf ball core layers will be readily recognized by those having ordinary skill in the art. 
     In addition, the method may also include molding an outer cover layer radially outward of the core layer. The molding of this outer cover layer may be performed using injection molding or compression molding. In some embodiments, the method may include formation of an inner cover layer radially inward of the outer cover layer. In some embodiments, the inner cover layer may be formed first, and the outer cover layer may be molded afterward. In other embodiments, the outer cover layer may be pre-molded as a shell and then the inner cover layer may be injection molded under the pre-molded shell between the outer cover layer and the core layers. In some embodiments, the shell may be formed as two hemispherical shells, in order to enable a pre-molded core to be placed inside the shell before injecting the inner cover layer material. 
       FIGS. 17 and 18  illustrate an apparatus and method for molding a golf ball according to the embodiment shown in  FIG. 16 , wherein an inner cover layer is injection molded under and through a pre-formed, grid-like outer cover layer.  FIG. 17  shows a cross-sectional view of a mold  1700 , including a first mold section  1705  and a second mold section  1710 . Mold  1700  may be used for injection molding groove material within a pre-formed grid-type shell. Accordingly, mold  1700  may include recesses  1715  which may be configured to receive injected groove material about a periphery of a pre-formed outer cover layer shell. Mold  1700  may also include one or more injection gates  1720  for injecting groove material into mold  1700 . 
       FIG. 18  illustrates mold  1700  with an outer cover layer shell  1725  placed inside. As shown in  FIG. 18 , shell  1725  may be formed as two hemispherical half-shells, as indicated by an equator line  1740 . In an exemplary method, the hemispherical half-shells may be snapped together about, or otherwise placed around one or more inner core layers (not shown) and then placed in mold  1700 , as shown in  FIG. 18 . It will be noted that, for purposes of illustration, mold  1700  is shown in cross-section, whereas shell  1725  is shown in an elevation view. 
     The method may further include injecting a groove material  1735  through gates  1720  into the cavity within mold  1700  where it may flow into the void under shell  1725 . Groove material  1735  may further flow radially outward through grooves  1730  (which may be formed completely through outer cover layer shell  1725 ), into recesses  1715 . Molding groove material  1735  in this manner may form the groove material from portions of inner cover layer material that extend radially outward into grooves  1730 . 
     As noted above, the groove material  1735  may be formed of a more or less compressible material than outer cover layer shell  1725 . 
     Processes for injection molding material under pre-molded outer layers that may be applicable to the present disclosure are discussed in detail in U.S. Ser. No. 61/580,549, filed on Dec. 27, 2011, and entitled “Golf Ball with Co-Molded Core and Medial Layer and Method of Making;” U.S. Ser. No. 61,580,537, filed on Dec. 27, 2011, and entitled “Method of Molding a Single-Piece Hollow Shell Including Perforations;” and U.S. Ser. No. 61/580,525, filed on Dec. 27, 2011, and entitled “Method of Recycling a Ball and Ball for Use in Recycling Method,” all of which are hereby incorporated herein by reference in their entirety. 
       FIGS. 19 and 20  illustrate an apparatus and method for making a golf ball according to the embodiment shown in  FIG. 3 , including molding a grooved outer cover layer and molding a groove material into recess grooves on the pre-molded outer cover layer.  FIG. 19  illustrates an outer cover layer mold  1900  configured to pre-mold the outer cover layer. Mold  1900  may include a first mold section  1905 , and a second mold section  1910 . Mold  1900  may further include spiral protrusions  1915 , which may be configured to form channel-type recess grooves, such as grooves  330  shown in  FIG. 3 . It will be noted that outer portions of mold  1900  are shown in cross-section, while a spherical inner void is shown in elevation to illustrate the arrangement of spiral protrusions  1915  along the walls of the spherical void. Mold  1900  may be used to injection mold outer cover layer material into injection gates  1920  to form an outer cover layer radially outward of one or more inner core layers and, in some embodiments, radially outward of one or more inner cover layers, thus forming a pre-molded golf ball component. 
       FIG. 20  illustrates an exemplary method of injecting a groove material into grooves  2030  formed in a pre-molded golf ball component  2025 .  FIG. 20  shows a groove material mold  2000 . Mold  2000  may include a first mold section  2005  and a second mold section  2010 .  FIG. 20  also shows pre-molded golf ball component  2025  disposed within mold  2000 . As shown in  FIG. 20 , mold  2000  may include a spiral groove  2015  configured to correspond with grooves  2030  in component  2025  to form a spiral void  2040  configured to receive groove material. In an exemplary method, groove material  2035  may be injected via injection gates  2020  into spiral void  2040 , as shown in  FIG. 20 . Molding groove material  2035  in this manner may form groove material  2035  in recess groove  2030  such that the outer cover layer material extends between an inner surface of groove material  2035  and an outer surface of the inner cover layer. 
     Similar molds and methods may be used to form golf balls having other features of embodiments discussed above. For example, exemplary methods of making golf balls may include forming the grooves completely through the outer cover layer, and molding the groove material such that an inner surface of the groove material is in contact with an outer surface of the inner cover layer. Further, similar molds and methods may be used for form the grooves in any suitable size, shape, and arrangement, including those discussed above. For example, such molds and methods may be used to form grooves having angled side walls, rounded bottom surfaces, planar bottom surfaces, and other configurations discussed above. Also, similar molds and methods may be implemented to form the groove material in any of the various configurations discussed above. 
     While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting, and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Features of any embodiment described in the present disclosure may be included in any other embodiment described in the present disclosure. Also, various modifications and changes may be made within the scope of the attached claims.