Golf club head

Abstract

To provide a golf club head which improves mass of a club head and performance characteristics while keeping a stress limit, an outer appearance, and mass of a head in an entire club.SOLUTION: A golf club head includes: a golf club head body having a toe 102, a heel on the opposite side of the toe 102, a sole 111, and a top portion on the opposite side of the sole 111, in facing a reference position; a loft angle LA; golf club head mass mh that satisfies mh=2.1 g / degree*LA+a and 109 g<a<210 g; a blade length BL of less than 80 mm; a striking face 109 which has a face center 14 and defines a face plane; a virtual center plane 10 which extends vertically through the face center and perpendicularly to the face plane; a center of gravity of the golf club head which is located 2.0 mm or less from the virtual center plane 10; and a moment Izz of inertia about a vertical axis extending through the center of gravity that satisfies Izz>mh*9.3 cm2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a golf club head.

Background Art

[0002] The head of a golf club has mass and performance characteristics that affect the quality and consistency of shots when hitting a golf ball. Such mass and performance characteristics are often related to the mass or mass distribution within the golf club head. Examples of such mass and performance characteristics include the position of the center of gravity (CG) of the club head, the coefficient of restitution (COR) or characteristic time (CT) at various locations on the striking face of the club head, and the moment of inertia (MOI) about various virtual axes passing through the CG.

[0003] As an example of a mass characteristic that affects performance, the position of the CG can affect, for example, how high a golf ball is hit, the amount of spin of the golf ball, or the tolerance of the club head with respect to ball speed and straightness of a shot that occurs off - center, away from the "sweet spot" of the striking face. Conventionally, as has been revealed, the sweet spot is the point on the striking face through which the vertical projection from the CG of the club head passes. For example, lowering the CG of an iron - type club head towards the sole side and moving it rearward from the striking face can increase the height of the shot so that the carry distance is extended and more backspin of the golf ball can result as a more controlled shot. Moving the sweet spot closer to the center of the striking face allows the sweet spot to be aligned with the position of the sweet spot expected by the player. Due to the asymmetric shape and mass distribution of a conventional iron - type golf club head, the position of the CG centered laterally typically requires, for example, the inclusion of high - density weights, which can be costly and may have an adverse effect on the swing weight.

[0004] As another example of a mass property that affects performance, a large MOI of the club head means that the club head is less likely to twist when the golf ball is struck at a location off-center from the center of the hitting face away from the sweet spot. Increasing the MOI of the club head generally makes the club head more stable or allows for off-center shots, and the larger MOI can make such off-center shots straighter and increase ball speed.

[0005] As an example of a performance characteristic, COR is a measure of the energy loss or energy transfer between the hitting face and the golf ball. The higher the COR measured at the hitting face, the less energy is lost or the more energy transfer improves when the hitting face impacts the golf ball. More energy is transferred to the golf ball at a higher COR, which is converted to a faster ball speed and usually results in increased carry distance. COR can be measured, for example, using the conventional cannon test in accordance with the method for determining COR specified by the United States Golf Association (USGA). In this regard, the USGA has shifted from the use of COR to the use of another performance characteristic called the Characteristic Time (CT) measurement to quantify the elasticity of the hitting face. For all purposes herein, CT refers to the characteristic time described in the USGA's "Procedure for Measuring the Flexibility of a Golf Clubhead" (Rev. 1.0.0, May 1, 2008).

[0006] Improvements in the mass and performance characteristics of the club head are considered in comparison with the structural requirements for the purpose of using the club head, such as stress characteristics. The mass and performance characteristics are also considered in comparison with other limitations, such as limitations specified by regulatory bodies such as the USGA, with respect to CT, dimensions, and the mass of the club head. Further, players generally have implicit expectations for the club head, such as the overall appearance with respect to size, or the overall expected weight of the club head relative to the type of golf club or the loft angle of the golf club. DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

[0007] The present inventors have recognized the need for various face thickness patterns for golf club heads, particularly iron-type club heads, that improve the mass and performance characteristics of the club head while maintaining similar stress limits, appearance, and overall club head weight. As will be described in more detail below, the improved mass and performance characteristics can include, for example, the coefficient of restitution (COR), characteristic time (CT), moment of inertia (MOI), and / or the position of the center of gravity (CG) of the club head. In some exemplary embodiments, an iron-type club head with a cavity back or hollow body includes an improved variable face thickness pattern that allows any weight to be moved from the striking face of the club head to other areas of the club head to improve the mass and / or performance characteristics of the club head. Advantageously, such club heads can improve mass and performance characteristics such as a high COR at the striking face, a higher MOI, and a deeper and lower CG position that is laterally centered relative to equivalent club heads while maintaining similar stress limits. Further, such club heads do not sacrifice the conventional appearance, dimensions (e.g., blade length, topline thickness), and overall club head weight (e.g., swing weight) that some players may prefer.

[0008] Reducing the weight of the face while maintaining the overall weight of the club head can be important for players who associate a particular loft of a golf club head with a particular mass and also have a preferred swing weight for their golf clubs. Generally, when provided in a set, iron-type club heads increase in mass with loft. For example, the mass of an iron-type golf club head may follow the following equation. mh = 2.1 (g / degree) * LA + a (Equation 1) Here, mh is the golf club head mass (g: gram), LA is the loft angle of the club head (degree: degree) when oriented towards the reference position, and a is between 109 g and 210 g. In one or more embodiments, the golf club head has an improved face thickness pattern while maintaining such a golf club head mass mh. Such a club head can have an improved face thickness pattern with a vertical MOI Izz extending through the CG, which satisfies the following. Izz > mh * 9.0 cm 2 (Equation 2)

[0009] In one or more aspects of the present disclosure, the golf club head includes a golf club head body including a toe, a heel opposite the toe, a sole, and a top portion opposite the sole when oriented towards the reference position. The golf club head mass mh satisfies Equation 1. Also, the blade length of the club head is less than 80 mm. The striking face of the club head defines a face plane and includes a face center and a virtual center plane perpendicular to the face plane and extending vertically through the face center. In this specification, the face center of the striking face is determined according to the procedure described in the USGA's "Procedures for Measuring the Flexibility of Golf Club Heads" (Rev. 2.0, March 25, 2005). The CG of the club head is located within 2.0 mm from the virtual center plane, and the MOI about a vertical axis extending through the CG, Izz, satisfies Izz > mh * 9.3 cm 2 satisfies.

[0010] In some embodiments, the striking face includes a central region including the face center, an intermediate region at least partially surrounding the central region, an upper region above the central region, a lower region below the central region, and a toe region on the toe side of the central region. Each of the central region, the upper region, the lower region, and the toe region includes a maximum width and an average thickness, and the intermediate region is disposed between the central region and each of the upper region, the lower region, and the toe region. The average thickness of the intermediate region is greater than the average thickness of each of the central region, the upper region, the lower region, and the toe region. In one or more embodiments, the intermediate region completely surrounds the central region.

[0011] According to some embodiments, at least one of the toe region, the upper region, and the lower region includes an elongated groove or recess having a width of about 2.0 mm or more on its back surface. Alternatively or additionally, the upper region, the lower region, and the toe region each include an upper groove or recess generally extending in the toe-heel direction, a lower groove or recess generally extending in the toe-heel direction, and a toe groove or recess generally extending in the vertical direction on its back surface.

[0012] In one or more aspects of the present disclosure, a golf club head includes a golf club head body having a toe, a heel opposite the toe, a sole, and a top portion opposite the sole when oriented in a reference position. The face insert of the club head has a mass mf fixed to the golf club head body and includes a striking face defining a face plane. The golf club head mass mh satisfies Equation 1. The blade length of the club head is less than 80 mm, and the moment of inertia Izz about the vertical axis passing through the CG of the club head satisfies Izz>mh*9.3 cm 2 and is satisfied. Also, the ratio mf / mh is 0.22 or less. In one or more embodiments, the ratio mf / mh of an iron-type golf club head is 0.20 or less.

[0013] In some aspects, the striking face includes a sweet spot corresponding to a first coefficient of restitution, COR1, and an auxiliary position spaced at least 7.5 mm from the sweet spot corresponding to a second coefficient of restitution, COR2, where COR2 ≧ 0.98 * COR1. In some embodiments, the variable thickness of the striking face can provide a higher COR near the sweet spot, increase the COR in the region including the sweet spot, and / or provide a larger region of higher COR near the sweet spot. In another aspect, the repositioning of mass from the striking face can be configured to move the CG so that the sweet spot corresponds to a region having a higher COR and / or a region of the striking face more frequently struck by the player. For example, the central region of the striking face may include a heel-side region that is thicker than the toe-side region to improve the COR of the region of the striking face more commonly struck by the player.

[0014] The grooves or recesses on the back of the striking face of the present disclosure not only increase the COR of the striking face but also improve the weight distribution of the club head by repositioning mass from the striking face to other regions of the club head to increase the MOI or more appropriately position the CG of the club head to improve performance. Despite the reduced mass of the striking face, the stress limits of the striking face can be used as a constraint to determine the recesses or grooves so that when the striking face is tested for durability, it is comparable to prior art club heads.

[0015] In one or more aspects of the present disclosure, a method of manufacturing a golf club head includes forming a golf club head body having a striking face, a heel portion, a toe portion opposite the heel portion, a sole, a top portion opposite the sole, and a blade length of 80 mm or less. The thickness pattern of the striking face is formed by defining, on the striking face, a central region including a face center, an intermediate region at least partially surrounding the central region, an upper region above the central region, a lower region below the central region, and a toe region on the toe side of the central region. The intermediate region can be disposed between the central region and each or at least one of the upper region, the lower region, and the toe region. The central region is recessed such that the central region has a thickness that is thinner than that of the intermediate region. At least one of the toe region, the upper region, and the lower region is recessed such that the recessed region has a thickness that is thinner than the thickness of the central region. The variable face thickness pattern is formed such that the striking face includes a sweet spot corresponding to a first coefficient of restitution, COR1, and an auxiliary position spaced from the sweet spot by at least 7.5 mm corresponding to a second coefficient of restitution, COR2, where COR2 ≧ 0.98*COR1.

[0016] In one or more aspects of the present disclosure, a method of manufacturing a golf club head includes forming a golf club head body having a striking face, a heel, a toe opposite the heel, a sole, and a top portion opposite the sole. A variable thickness pattern is determined using a computing device by defining a plurality of parameterized zones on the striking face, including a central zone having a face center. Each parameterized zone includes at least one of a variable first parameter and a variable second parameter. A target value is set to at least one of a first constraint, a second constraint, and a third constraint. Each of the at least one variable first parameter and second parameter varies for each parameterized zone. An impact of a golf ball on the striking face is simulated and the resulting value is evaluated against a target value of at least one of the first constraint, the second constraint, and the third constraint. The determined variable thickness pattern is formed on the striking face based on the evaluation. In some implementations, the first constraint is the mass of the striking face, the second constraint is the mechanical stress of the striking face, and the third constraint is a weighted COR representing the overall effective or predicted COR of the striking face based on the COR of various portions of the striking face, which is weighted by the predicted impact probability of the golf ball. Further, in some embodiments, the variable first parameter and the variable second parameter may include a variable maximum width and a variable thickness of the parameterized zone or region.

[0017] In one or more aspects of the present disclosure, a method of manufacturing a golf club head includes forming a golf club head body having a striking face, a heel, a toe opposite the heel, a sole, and a top portion opposite the sole. A variable thickness pattern is determined by defining, using a computing device, a central region including a face center of the striking face, an intermediate region at least partially surrounding the central region, an upper region above the central region, a lower region below the central region, and a toe region on a toe side of the central region on the striking face. Each of the central region, the upper region, the lower region, and the toe region includes a variable width parameter and a variable thickness parameter. The intermediate region is disposed between the central region and each of the upper region, the lower region, and the toe region. A target value is set to at least one of a first constraint, a second constraint, and a third constraint. Each of a variable first parameter and a variable second parameter varies for each region of the striking face. An impact of the golf ball on the striking face is simulated and a resulting value is evaluated against a target value of at least one of a first constraint, a second constraint, and a third constraint. The determined variable thickness pattern is formed on the striking face based on the evaluation.

[0018] The various exemplary aspects described above can be implemented individually or in various combinations. The foregoing features and advantages of the golf club head of the present disclosure, as well as other features and advantages, will become apparent to those of ordinary skill in the art after considering the following description, the accompanying drawings, and the appended claims.

Brief Description of the Drawings

[0019] The features and advantages of embodiments of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings. The drawings and the related description are provided to illustrate embodiments of the present disclosure and are not intended to limit the scope of the claims.

[0020]

Figure 1

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[0021] One or more exemplary, novel, and non-obvious aspects and features of a golf club head, and methods of manufacturing such club heads as disclosed below, are not intended to be limited in any way. Further, the various aspects and features of the present disclosure can be used alone or in various novel and non-obvious combinations and sub-combinations with each other.

[0022] FIG. 1 is a front view of an exemplary golf club head 100 according to one or more embodiments. As shown in FIG. 1, the club head 100 includes a toe portion 102, a heel portion 104, a topline portion 106, and a sole portion 111. The club head 100 also includes a hosel 110 extending from the heel portion 104. The hosel 110 can include an open end for receiving a golf club shaft (not shown) of a golf club. A hosel axis 20 extends axially through the center of the hosel 110 and is within a virtual vertical hosel plane (e.g., the virtual vertical hosel plane 21 shown in FIG. 3). The club head 100 including a striking face 109 can be formed of, for example, a steel material.

[0023] In FIG. 1, the club head 100 is oriented in a reference position such that the sole portion 111 contacts a virtual ground 13 and the central hosel axis 20 is within the virtual vertical hosel plane. As used herein, a club head is "oriented in a reference position" when its sole (e.g., sole portion 111) contacts a virtual ground (e.g., virtual ground 13), its central hosel axis (e.g., central hosel axis 20) is disposed within a vertical plane, and its score line (e.g., score line 112) is parallel to the ground. In this reference position, the club head 100 is disposed at a predetermined loft angle (LA) (i.e., LA in FIG. 3) and a predetermined lie angle (i.e., α in FIG. 2). Unless otherwise specified, all parameters of the various embodiments in the present disclosure are specified for a club head oriented in the reference position.

[0024] In one or more embodiments, the loft angle LA ranges from about 18 degrees to about 40 degrees. In other embodiments, the golf club head is a wedge type golf club head and the loft angle LA ranges from about 40 degrees to about 64 degrees.

[0025] As shown in FIG. 1, the club head 100 includes a striking face 109 configured to strike a conventional golf ball. In some implementations, the striking face 109 may form part of a face insert fixedly attached to the body of the club head 100. In other embodiments, the striking face 109 may be integrally formed as part of the body of the club head 100. The striking face 109 is provided with one or more grooves or score lines 112 that impart additional spin to the golf ball upon impact. In FIG. 1, the striking face 109 includes a face center 14, which is perpendicular to the face plane (e.g., face plane 22 of FIG. 3) defined by the striking face 109 and is located on a virtual center plane 10 that extends vertically through the face center 14. As used herein, the "face center" of the striking face is determined in accordance with the procedure described in the United States Golf Association (USGA) "Procedure for Measuring the Flexibility of a Golf Clubhead" (Revision 2.0, March 25, 2005). In the example of FIG. 1, the face center 14 indicates a point on the striking face 109 that is midway between the heel and toe of the score line 112 and midway between the sole and topline of the striking face 109. In other embodiments, the score line may extend to the toe side edge of the striking face. In such embodiments, the lateral position of the face center is determined as the midpoint between the most heel position of the score line and a club face apex such as the club face apex 107 of FIG. 1.

[0026] In the example of FIG. 1, the sweet spot 16 is located on the hitting face 109 at a horizontal distance CGH from the virtual center plane 10 toward the heel portion 104. The sweet spot 16 is located on the virtual vertical CG plane 12, and the sweet spot 16 is located on the hitting face 109 where a virtual line passing through the CG of the club head 100 (e.g., CG18 in FIG. 2) is perpendicularly projected onto the face plane of the hitting face 109 (e.g., face plane 22 in FIG. 3). As used herein, the “sweet spot” of a club head is defined as the position on the hitting face of the club head where a virtual line perpendicularly projected onto the face plane of the hitting face passes through the CG position of the club head.

[0027] As will be described in more detail below, the hitting face 109 is formed with a variable thickness in different regions or parameterized zones of the hitting face 109 to provide improved mass and / or performance characteristics of the club head 100. Such characteristics include, for example, a larger coefficient of restitution (COR) and / or a larger characteristic time (CT) in a wider area and / or in the hitting area of the more general hitting face 109, a larger moment of inertia (MOI) around the virtual vertical CG axis (e.g., virtual vertical CG axis 24 in FIG. 4) and / or around the virtual horizontal CG axis (e.g., virtual horizontal CG axis 15 in FIG. 2), and / or an improved CG position of the club head 100. These improvements in mass and performance characteristics can be achieved by selective thinning or thickening of different regions or parameterized zones, and / or by any repositioning of mass from the hitting face to other parts of the club head. As used herein, the thickness of the hitting face is measured perpendicularly to the face plane defined by the hitting face (e.g., face plane 22 in FIG. 3 and face plane 42 in FIG. 6).

[0028] The total mass of the club head may function as a target total mass consisting of a structural mass and an optional mass. As used herein, the structural mass generally refers to the mass necessary to establish a minimum structural integrity for the club head to be operable for its intended use. On the other hand, the optional mass can refer to the remaining mass that is not required to establish the minimum structural integrity of the club head when a target mass is given, and thus can be disposed mainly to adjust the mass and / or performance characteristics of the club head.

[0029] In order to provide a higher MOI of the club head 100 and an improved position for the CG of the club head 100 (e.g., CG18 in FIG. 2) while increasing the COR value at a specific location of the striking face, for example, the thickness of different regions or parameterized zones of the striking face 109 may result in the mass moving from such regions or parameterized zones to other locations within the club head 100. For example, the mass removed from a specific region of the striking face can improve the COR of the striking face, and the removed mass can be repositioned within the club head. As a result, the CG of the club head 100 can be advantageously disposed closer to the virtual center plane 10, closer to the virtual ground 13, and further behind the striking face 109. As a result, the sweet spot 16 can be advantageously disposed near the face center 14 to better correspond to the player's expected sweet spot position and / or the striking area of the face that is struck more frequently, and also to provide a more forgiving club head that achieves better off-center shots in terms of shot height, straightness, and distance. In this regard, in some embodiments, the sweet spot 16 can be disposed horizontally within 2.0 mm from the face center 14 as a result of the repositioning of the mass from the striking face 109 according to the present disclosure. In other words, the CG of the club head 100 (e.g., CG18 in FIG. 2) in such an implementation can be disposed within 2.0 mm from the virtual center plane 10. In one or more embodiments, the golf club head having this lateral CG position does not include a high-density material (e.g., tungsten alloy).

[0030] As described above, the variable thickness pattern of the hitting face, discussed in more detail below, increases the COR in the more commonly hit locations, or in a broader area of the hitting face, and provides better energy transfer for off-center shots or statistically more shots. Additionally or alternatively, the variable thickness pattern disclosed for the hitting face can increase the area of the hitting face having a relatively high COR. For example, in some implementations, the hitting face 109 of FIG. 1 can include a maximum COR of 0.80 or greater at a first location and a COR of 98% or greater of the maximum COR at an auxiliary location of the hitting face that is 7.5 mm or more away from the first location. In such an implementation, the first location corresponding to the maximum COR can be at or near the sweet spot 16, such as within 5 mm of the sweet spot 16. Some implementations of the variable thickness pattern discussed below to improve the COR of the hitting face include, for example, a central region of the hitting face where the thickness on the heel side is greater than the toe side region.

[0031] FIG. 2 is a rear view of an exemplary cavity back club head according to one or more embodiments. In this regard, the club head 100 of FIG. 2 includes a rear cavity 114 behind at least a portion of the hitting face 109 and a rear muscle 116 near the sole portion 111. For ease of explanation, FIG. 2 provides a rear view of the club head 100 from FIG. 1. However, those skilled in the art will understand, with reference to the present disclosure, that the club head 100 can include different structures in other implementations, such as the hollow body structure shown in FIG. 6.

[0032] As shown in FIG. 2, CG18 is on the virtual horizontal CG axis 15. Ixx, which is the horizontal MOI of the golf club head 100, is shown about the virtual horizontal CG axis 15, which extends through CG18 and is parallel to the striking face 109. As described above, the mass reduction achieved by varying the thickness of the striking face 109 can allow an increase in Ixx, thereby improving the performance of the golf club head 100 for shots off-center in the vertical direction along the striking face 109 (e.g., on the side of the topline portion 106 or on the side of the sole portion 111).

[0033] The club head 100 of FIG. 2 has a blade length (BL) measured between the toe portion of the club head 100 in the virtual vertical toe plane 25 and the intersection of the hosel axis 20 and the ground 13 (which also defines the lie angle α). In some implementations, the club head 100 can have a blade length BL of less than 80 mm. This blade length may, for example, match the expected blade length BL of an iron-type club head. In this regard, the thickness of the striking face 109 can be changed without sacrificing the conventional outer dimensions of the club head 100, such as the blade length BL or the topline thickness of the topline portion 106 (e.g., TLT in FIG. 3). Further, the overall or target club head mass (e.g., swing weight) of the club head 100 in some implementations can match the expected mass of an iron-type club head.

[0034] As described above, the mass of an iron-type club head typically varies based on the loft angle (LA). When provided in a set, the iron-type club head can increase in mass according to the loft. For example, the mass of an iron-type club head may follow the following equation. mh = 2.1 (g / degree) * LA + a (Equation 1) Here, mh is the golf club head mass (g), LA is the loft angle (degrees) of the club head when oriented towards the reference position, and a is from 109 g to 210 g. In some implementations, the club head 100 maintains such a head mass mh while having an improved face thickness pattern.

[0035] FIG. 3 is a side view of the heel side of the club head 100 according to one or more embodiments. As shown in FIG. 3, the LA of the club head 100 is defined between the face plane 22 and the virtual vertical hosel plane 21. As described above, the hosel axis 20 extends axially through the center of the hosel 110 and is within the virtual vertical hosel plane 21. The face plane 22 is defined such that the striking face 109 is within the face plane 22. Referring to Equation 1 above, the club head mass of the club head 100 can vary according to the loft angle LA of the club head 100 such that the club number with a larger LA angle has a larger club head mass.

[0036] As shown in FIG. 3, the distance between the face plane 22 and the rear face 26 defines the topline thickness (TLT), which corresponds to the thickness of the topline portion 106 shown in FIG. 1. The topline thickness TLT of the club head 100 is 6.5 mm or less. This topline thickness TLT can correspond to the topline thickness TLT expected for an iron-type club head. In this regard, the thickness pattern of the striking face 109 can be changed without sacrificing the conventional outer dimensions of the club head 100, such as the topline thickness TLT of the club head 100, which may be preferred by some golfers.

[0037] FIG. 4 is a cross-sectional view of the club head 100 taken along the cross-section line 4 of FIG. 1 according to one or more embodiments. As shown in FIG. 4, the rear surface of the striking face 109 facing the rear cavity 114 and the rear muscle 116 includes an upper region groove (upper groove) 118, a central region recess 120, and a lower region groove (lower groove) 122. In embodiments where the striking face 109 includes a face insert, the rear surface of the face insert can include the upper region groove 118, the central region recess 120, and the lower region groove 122.

[0038] The back surface of the striking face 109 also includes an intermediate region 108 that at least partially surrounds a central region that includes the central region recess 120. In this regard, the intermediate region 108 includes an upper intermediate region 108 U and a lower intermediate region 108 L above and below the central region recess 120, respectively. Each of the central region, the upper region, and the lower region that includes the central region recess 120, the upper region groove 118, and the lower region groove 122, respectively, has an average thickness that is thinner than the average thickness of the intermediate region 108 and may have a substantially uniform thickness. The upper region groove 118 and the lower region groove 122 can each extend generally in the toe-heel direction, such as in the examples of the upper region grooves 318 and 418 and the lower region grooves 322 and 422 of FIGS. 7 and 8.

[0039] In some implementations, at least one of the upper region groove 118 and the lower region groove 122 can be an elongated groove having a width of about 2.0 mm or more. Further, in some embodiments, the thickness of the central region recess 120 can be tapered such that, as in the example of the central region recess 320 of FIG. 7, the region on the heel side of the central recess can be thicker than the region on the toe side of the central recess. As another example, the central region recess can include a heel-side region that is thicker than the toe-side region, such as in the examples of the heel-side region 435 and the toe-side region 433 of FIG. 8. In some implementations, the thickness of the central region can decrease stepwise from the heel side of the central region toward the toe side of the central region.

[0040] In FIG. 4, Izz is centered about the virtual vertical CG axis 24. Optional mass removed from or maintained on the hitting face 109 to form the upper region groove 118, central region recess 120, and lower region groove 122 can be repositioned to the heel portion 104 and toe portion 102 to increase Izz. In some implementations, Izz may satisfy the following condition. Izz > mh * 9.3 cm 2 (Equation 2) Here, mh is the mass of the golf club head 100. As described above, increasing the MOI about the virtual vertical CG axis 24 that extends through CG18 improves the tolerance of the club head 100 to reduce the bending of the club head 100 about the virtual vertical CG axis 24 during off-center shots (e.g., shots more towards the toe or heel side of the sweet spot 16) in the horizontal direction along the hitting face 109.

[0041] Furthermore, the variable thickness pattern of the hitting face 109 can increase the COR at positions on the hitting face 109 corresponding to more commonly struck locations or a wider area of the hitting face, providing better energy transfer for off-center shots or statistically more shots. The variable thickness pattern of the hitting face 109 having the upper region groove 118, central region recess 120, and lower region groove 122 can increase the area of the hitting face having a relatively high COR.

[0042] For example, the mass removed from a specific region of the hitting face 109 can improve the COR of the hitting face 109, and the removed mass can be repositioned to the club head 100, whereby the CG18 can be advantageously positioned closer to the lateral center of the hitting face 109, closer to the virtual ground 13, and further rearward of the hitting face 109. In such an example, the mass removed or retained from the hitting face 109 to form the upper region groove 118, the lower region groove 122, and the central region recess 120, such as by machining (e.g., grinding, milling) or known casting or forging processes, can lower the position of the CG18 and reposition it further rearward of the hitting face 109 by repositioning it to the rear muscle 116. As another example, the mass removed from the hitting face 109 can be repositioned from the heel side of the hitting face 109 to the toe side of the hitting face 109, and the CG18 can be moved from the heel portion 104 to the side of the toe portion 102.

[0043] Those skilled in the art will understand, with reference to the present disclosure, that other implementations may differ from the arrangement shown in FIG. 4. For example, other implementations of the cavity back club head may include different shaped rear cavities 114 or rear muscles 116. As another exemplary variation, the cross-sectional shape of one or more of the upper region groove 118, the central region recess 120, and the lower region groove 122 may be different from that shown in FIG. 4 in another embodiment. As yet another exemplary variation, some implementations may not include the central region recess 120 and may include only one or more grooves adjacent to the periphery of the rear surface of the hitting face 109, such as the upper region groove 118 and / or the lower region groove 122.

[0044] FIG. 5 is a rear view of an exemplary hollow club head 200 according to one or more embodiments. The club head 200 including a striking face 209 can be formed of, for example, a steel material. Similar to the club head 100 of FIGS. 1-4, the club head 200 includes a hosel 210, a toe portion 202, and a heel portion 204. However, instead of having a rear cavity such as the rear cavity 114 for the club head 100 of FIGS. 2 and 4, the club head 200 of FIGS. 5 and 6 includes an internal cavity 224 behind at least a portion of the striking face 209, as shown in FIG. 6. In some implementations, the striking face 209 may form part of a face insert fixedly attached to the body of the club head 200. In other embodiments, the striking face 209 may be integrally formed as part of the body of the club head 200. For ease of explanation, FIG. 5 provides a rear view of a club head 200 that can have an appearance similar to the club head 100 of FIG. 1. However, those skilled in the art will understand, with reference to the present disclosure, that the club head 200 may include different structures in other implementations different from those shown in FIGS. 5 and 6.

[0045] As shown in FIG. 5, the CG48 is disposed on a virtual horizontal CG axis 45. The Ixx, which is the horizontal MOI of the club head 200, is shown about the virtual horizontal CG axis 45, which extends through the CG48 and is parallel to the striking face 209 shown in FIG. 6. The mass reduction achieved by varying the thickness of the striking face 209 can allow for an increase in Ixx by repositioning the mass to other parts of the club head 200, thereby improving the performance of the golf club head 200 for off-center shots (e.g., shots off to the side of the topline portion 206 or off to the side of the sole portion 211) in the vertical direction along the striking face 209.

[0046] In some embodiments, the club head 200 may have a blade length BL of less than 80 mm. This blade length may, for example, match the expected blade length BL of an iron-type club head. In this regard, the thickness of the hitting face 209 can be changed without sacrificing the conventional outer dimensions of the club head 200, such as the blade length BL or the topline thickness of the topline portion 206. Further, in some embodiments, the overall or target club head mass (e.g., swing weight) of the club head 200 may match the expected mass of an iron-type club head.

[0047] As described above, the mass of an iron-type club head typically varies based on the loft angle (LA). As shown in FIG. 6, the loft angle LA of the club head 200 is defined between the face plane 42 and the virtual vertical hosel plane 41. The virtual vertical hosel plane 41 includes a hosel axis 40 that extends axially through the center of the hosel 210. The face plane 42 is defined such that the hitting face 209 lies within the face plane 42. The mass of the club head 200 can satisfy Equation 1 provided above with respect to the loft angle LA while having an improved face thickness pattern. Further, the club head 200 can have a shallower depth than a typical hybrid-type golf club head. For example, the club head 200 may have a depth of less than 30 mm as measured from the leading edge to the trailing edge of the sole portion 211 of the club head 200. As described above, the repositioning of mass from the hitting face 209 can enable improvements in performance and mass characteristics such as an increase in MOI, a better CG position, an increase in COR or CT, without changing the expected dimensions, footprint, or appearance of a conventional iron-type golf club head.

[0048] FIG. 6 is a cross-sectional view of the club head 200 taken along the section line 6 of FIG. 5 according to one or more embodiments. As shown in FIG. 6, the rear surface of the hitting face 209 facing the internal cavity 224 and the rear muscle 216 includes an upper region groove 218 and a central region recess 220. In embodiments where the hitting face 209 includes a face insert, the rear surface of the face insert can include the upper region groove 218 and the central region recess 220.

[0049] The back surface of the hitting face 209 also includes an intermediate region 208 that at least partially surrounds a central region including the central region recess 220. In this regard, the intermediate region 208 is respectively above and below the central region recess 220, an upper intermediate region 208 U and a lower intermediate region 208 L including. Each of the central region including the central region recess 220 and the upper region including the upper region groove (or recess) 218 has an average thickness that is thinner than the average thickness of the intermediate region 208. In some implementations, the intermediate region 208 may have a substantially uniform thickness. The upper region grooves 218 can generally extend in the toe-heel direction, such as in the examples of the upper region grooves 318 and 418 in FIGS. 7 and 8 respectively.

[0050] In some implementations, the upper region groove 218 may have an elongated groove with a width of about 2.0 mm or more. Further, the thickness of the central region recess 220, such as in the example of the central region recess 320 in FIG. 7, in some implementations, the region on the heel side of the central region recess may be tapered so as to be thicker than the region on the toe side of the central region recess. As another example, the central region recess can include a heel-side region that is thicker than the toe-side region, such as in the examples of the heel-side region 435 and the toe-side region 433 in FIG. 8.

[0051] As will be discussed in more detail below with reference to FIGS. 7-10, such a taper or variation in the thickness of the central region or the central region recess can also typically improve the COR of the central region and / or increase the area of the hitting face 209 having a larger COR. Further, the thickness of different regions or parameterized zones of the hitting face 209 results in a mass that moves from such regions or parameterized zones to other locations within the club head 200, providing a higher MOI of the club head 200 and an improved location of the CG48 while increasing the COR value at a particular location on the hitting face.

[0052] For example, the mass removed from a particular region of the hitting face 209 can improve the COR of the hitting face 209, and the removed mass can be repositioned within the club head 200 such that the CG48 is advantageously positioned closer to the lateral center of the hitting face 209, closer to the virtual ground 13, and further rearward of the hitting face 209. In such an example, the mass removed from the hitting face 209 to form the upper region groove 218 and the central region recess 220 can be repositioned to the rear muscle 216, for example, by machining, known casting or forging processes, etc., to lower the position of the CG48 and move the CG48 further rearward of the hitting face 209. In some implementations, the hitting face 209 may be separately formed and attached to the body of the club head 200 by welding or other known methods. As another example, the mass removed from the hitting face 209 can be repositioned from the heel side of the hitting face 209 to the toe side of the hitting face 209, moving the CG48 from the heel portion 204 to the side of the toe portion 202.

[0053] As a result, the sweet spot on the hitting face 209 (e.g., sweet spot 16 in FIG. 1) can be advantageously disposed closer to the face center (e.g., face center 14 in FIG. 1) so as to better correspond to the expected sweet spot position of the player or the more frequently hit position of the hitting face 209. In this regard, the sweet spot of the club head 200 in some implementations can be disposed horizontally within 2.0 mm from the face center as a result of the repositioning of mass from the hitting face 209.

[0054] As described above, the variable thickness pattern of the hitting face can increase the COR at a location on the hitting face 209 corresponding to the more commonly struck location, provide better energy transfer for statistically more shots, and improve the weighted COR of the hitting face. Additionally or alternatively, the variable thickness pattern disclosed for the hitting face can increase the area of the hitting face having a relatively high COR. For example, in some implementations, the hitting face 209 can include a maximum COR of 0.80 or greater at a first location and a COR of 98% or greater of the maximum COR at an assist location of the hitting face 209 that is 7.5 mm or more from the first location. In such an implementation, the first location corresponding to the maximum COR can be at or near the sweet spot, such as within 5 mm from the sweet spot. Some implementations of the variable thickness pattern discussed below to improve the COR of the hitting face include, for example, a central region of the hitting face where the thickness on the heel side is greater than the region on the toe side.

[0055] In FIG. 6, Izz is centered about the virtual vertical CG axis 44. An optional mass removed from or saved from the hitting face 209 to form the upper region groove 218 and the central region recess 220 can be repositioned to the heel portion 204 and the toe portion 202 to increase Izz. In some implementations, Izz may satisfy Equation 2 above. Increasing the MOI about the virtual vertical CG axis 44 extending through the CG 48 improves the tolerance of the club head 200 such that there is less bending of the club head 200 about the virtual vertical CG axis 44 during a horizontal, off-center shot (e.g., a shot on the toe side or the heel side of the sweet spot) along the hitting face 209.

[0056] Those skilled in the art will understand, with reference to the present disclosure, that other implementations may differ from the configurations shown in FIGS. 5 and 6. For example, other implementations of the hollow club head can include internal cavities 214 or rear muscles 216 of different shapes. As another exemplary variation, the cross-sectional shape of the upper region groove 218 or the central region recess 220 may be different from that shown in FIG. 4 in other embodiments. In this regard, other implementations may also include grooves in the lower region, as in the example of FIG. 4 discussed above. In yet other embodiments, the central region recess 220 may be omitted, such that the recess on the back surface of the hitting face 209 may include only one or more grooves or channels adjacent to the periphery of the back surface, such as the upper region groove 218.

[0057] FIG. 7 shows an exemplary back surface 328 of a cavity back club head, such as the cavity back club head 100 of FIGS. 2 - 4, according to one or more embodiments. As shown in FIG. 7, the back surface 328 includes recesses in an upper region, a central region, a toe region, and a lower region. More particularly, the back surface 328 includes an upper region groove or channel 318 adjacent to the periphery of the back surface 328, a toe region groove (toe groove) or channel 326, and a lower region groove or channel 322. The central region recess 320 is formed in the central region between the upper region groove 318, the toe region groove 326, and the lower region groove 322. The intermediate region 308 surrounds the central region recess 320 and is disposed between the central region recess 320 and each of the upper region groove 318, the toe region groove 326, and the lower region groove 322. Further, the intermediate region 308 has an average thickness greater than the average thickness of each of the central region recess 320, the groove 318 of the upper region, the groove 326 of the toe region, and the groove 322 of the lower region.

[0058] The preferred dimensions of the central region recess 320 have a face thickness of 2.5 mm or less, which preferably tapers from 2.3 mm on the heel side of the central region recess 320 to 1.9 mm on the toe side of the central region recess 320. The preferred dimensions of the upper region groove 318 have a face thickness of 1.5 mm or less and a maximum width of 5.0 mm or more. The preferred dimensions of the toe region groove 326 have a face thickness thinner than the upper region groove 318 and a maximum width of 2.0 mm or more. The preferred dimensions of the groove 322 of the lower region have a face thickness of 1.5 mm or less, i.e., preferably larger than the toe region groove 326 and a width of 2.5 mm. As used herein, the width of a groove or channel is defined by the maximum vertical distance between the longer opposing faces of the groove or channel. The preferred thickness of the intermediate region 308 surrounding the recesses of the central region recess 320, the upper region groove 318, the toe region groove 326, and the lower region groove 322 is less than 3 mm and greater than 2.5 mm, preferably having a thickness of about 2.7 mm.

[0059] Some preferred dimensions of the recesses on the back surface 328 of FIG. 7 can include the dimensions in Table 1 below. As used below, thickness refers to the thickness of the striking face 309, width refers to the distance measured perpendicular to the longer opposing face of the recess, and radius refers to the radius of curvature between the bottom of the recess having the face thickness shown in the recess and the adjacent wall of the recess. [Table 1]

[0060] The aforementioned preferred dimensions of the central region recess 320, upper region groove 318, toe region groove 326, and lower region groove 322 improve characteristics related to the performance and mass of the cavity back club head. Such performance and mass-related characteristics include, for example, the CG position of the club head, COR or CT at various positions of the striking face, and MOI with respect to various virtual axes passing through the CG. The recesses on the back surface 328 not only increase the COR of the striking face 309 with a reduction in the mass of the striking face 309 at specific locations, but also, as described above, improve the weight distribution of the club head to increase the MOI and more appropriately position the CG for performance. The recesses on the back surface 328 can also determine that, with the maximum face stress as a constraint, the striking face 309 can match a prior art club head when tested for durability despite the reduced mass of the striking face 309.

[0061] Those skilled in the art, referring to the present disclosure, will understand that other embodiments of the back surface of the striking face of the cavity back club head may differ from the arrangement shown in the example of FIG. 7. For example, other configurations may optionally not include one or more of the recesses shown in FIG. 7.

[0062] FIG. 8 shows an exemplary back surface 428 of a hitting face 409 of a hollow body club head, such as the hollow body club head 200 of FIGS. 5 and 6, according to one or more embodiments. As shown in FIG. 8, the back surface 428 includes recesses in an upper region, a central region, a toe region, and a lower region. However, unlike the example of the back surface 328 of FIG. 7, the back surface 428 of FIG. 8 includes a different thickness pattern in the central region recess 420. More specifically, a central portion 437 of the central region recess 420 is thicker than a heel side portion 435 and a toe side portion 433. Such an arrangement typically further improves the COR or CT of a wider area of the hitting face 409 in the central region.

[0063] Further, the back surface 428 includes an upper region groove or channel 418, a toe region groove or channel 426, and a lower region groove or channel 422 adjacent to the periphery of the back surface 428. The central region recess 420 is formed in a central region between the upper region groove 418, the toe region groove 426, and the lower region groove 422. An intermediate region 408 surrounds the central region recess 420 and is disposed between the central region recess 420 and each of the upper region groove 418, the toe region groove 426, and the lower region groove 422. Further, the intermediate region 408 has an average thickness that is thicker than the average thickness of each of the central region recess 420, the upper region groove 418, the toe region groove 426, and the lower region groove 422.

[0064] Some preferred thicknesses in the hitting face 409 of the recesses of the back surface 428 of FIG. 8 include the following thicknesses of club heads 1B, 2B, 3B, and 4B in Table 2 below. The thickness of the central region provided in the comparative example club head B of Table 2 is a measured value of the thickness of the hitting face at the position where the central region recess of FIG. 8 (i.e., the heel side central region recess 435, the intermediate central region recess 437, and the toe side central region recess 433) would be disposed. The comparative example club head B includes a continuous peripheral groove or channel of uniform width and depth along most of the perimeter of the back of its hitting face. Table 2 also includes the preferred widths of the upper region groove 418, the toe region groove 426, and the lower region groove 422, measured perpendicular between two longer opposing faces of the groove.

Table 2

[0065] The aforementioned preferred dimensions of the central region recess 420 (i.e., the intermediate central region recess 437, the heel-side central region recess 435, and the toe-side central region recess 433), the upper region groove 418, the toe region groove 426, and the lower region groove 422 improve the performance and mass-related characteristics of the hollow club head. Such performance and mass-related characteristics include, for example, the CG position of the club head, the COR or CT at various positions on the striking face, and the MOI with respect to various virtual axes passing through the CG. In this regard, Table 4 below shows the mass removed from the striking face 409, the COR at the face center 54, the COR at a position 58 that is 7.5 mm off in the toe direction from the center of the sweet spot 56, and the weighted COR measurement or computer simulation value representing the expected or overall COR of the striking face 409 by weighting the COR at different locations on the striking face 409 using the probability that a golf ball is struck at that location.

[0066] In some embodiments, the hitting face 409 can include a maximum COR of 0.80 or greater at a first location such as the sweet spot 46 or within 5 mm of the sweet spot 46, and a COR that is 98% or greater of the maximum COR at a second location 48 that is 7.5 mm or more away from the first location. The thickness of the recess of the hitting face 409 can also be determined to increase the weighted COR. The weighted COR can be determined based on bin-by-bin or location-by-location probability of impact, as discussed in more detail in U.S. Patent No. 10,456,643, titled "Golf Club Head," filed December 28, 2018, the entire contents of which are incorporated herein by reference. The weighted COR, "expected COR," or "overall COR" can be considered to represent a probability-adjusted measure of the club head performance that a typical golfer would actually expect, considering how impacts are empirically distributed across the hitting face 409. Using such information, a golfer can make a more informed decision when selecting a golf club based on this weighted COR. Alternatively or additionally, a golfer can determine which golf club is more suitable for a particular handicap or skill level of the golfer.

[0067] The weighted COR can be determined by overlaying a rectangular virtual evaluation region on the hitting face 409 that includes a first pair of horizontal sides that are 35 mm in length, a second pair of vertical sides that are 25 mm in length, and a geometric center that coincides with the center of the face. The rectangular virtual evaluation region is divided into bins by dividing the rectangular virtual evaluation region into five rows (i.e., m = 5) of equal height 5 mm and seven columns (i.e., n = 7) of equal width 5 mm, thereby forming a matrix of bins having coordinates i and j. The average COR of each bin represented by the coordinates i, j is determined (e.g., measured or computer simulated), and the weighted COR can be determined by Equation 3 below. In other embodiments, the COR can be determined for the center position of each bin. [Number] Here, p ij represents the influence probability of the bin at coordinates i, j according to the influence probability matrix as shown in Table 3 below. [Table 3]

[0068] Other influence probability matrices can be used to determine the weighted COR in various implementations. For example, other influence probability matrices for determining the weighted COR or the expected COR can include those disclosed in U.S. Patent No. 10,456,643 incorporated by reference above. As another example of a variation, the measurement location of the COR can correspond to a boundary of a shape different from the points or the rectangular bins described in Table 3 above. In yet another variation, the COR measurement location can correspond to regions that are not adjacent and are spaced apart from each other. As another exemplary variation, the orientation of the bins or the COR measurement location may not form a rectangular matrix, but rather may form an irregular arrangement of different configurations such as an annular or a sunburst configuration.

[0069] The recess in the back 428 not only increases the COR of the hitting face 409 as the mass of the hitting face 409 decreases at a specific location, but also, as described above, improves the weight distribution of the club head, increases the MOI, or more appropriately positions the CG for performance. The recess in the back 428 also allows the hitting face 409 to be determined with the maximum face stress as a constraint to be comparable to prior art club heads when tested for durability, even though the mass of the hitting face 409 is decreased.

[0070] Referring to the dimensions in Table 2 above for the recess in the back surface 428 of FIG. 8, Table 4 below shows the computer simulation or measured mass and performance characteristics of the corresponding comparative example club heads B, club head 1B, club head 2B, club head 3B, and club head 4B. As shown in Table 4 below, as the face center COR, off-center COR, and weighted COR decrease from club head 1B to club head 4B, the amount of mass removed or saved from the striking face decreases from club head 1B to club head 4B. However, each of club head 1B to club head 4B has a larger value of removed mass, face center COR, off-center COR, and weighted COR than the comparative example club head B.

Table 4

[0071] One skilled in the art will understand, with reference to the present disclosure, that recess arrangements other than those shown in FIG. 8 are possible. In this regard, the removal of mass from the striking face 309 having the recess formed in the back surface 328 of FIG. 7 above can also result in a decrease in mass from the striking face 309, an increased COR at the face center, an increased COR at a location off-center 7.5 mm toward the toe of the sweet spot, and an increased weighted COR. As an example of another variation, some implementations may not include one or more of the upper region groove 418, toe region groove 426, lower region groove 422, or central region recess 420, and further may not include one or more of the portions of the central region recess 420 such as the heel side central region recess 435, middle central region recess 437, or toe side central region recess 433.

[0072] In this regard, Table 5 below shows the thickness and width of the hitting face suitable for the recesses of various variations of the hitting face 409 that does not include the lower region groove 422 but still includes the heel side central region recess 435, the intermediate central region recess 437, the toe side central region 433, the upper region groove 418, and the toe side region groove 426. All of the recesses in Table 5 below can have a radius of 0.4 mm between the bottom of the recess having the indicated thickness and the adjacent wall.

Table 5

[0073] FIG. 9 shows an exemplary back surface 528 of a hitting face 509 that includes an exemplary thickness pattern according to one or more embodiments. The thickness pattern of FIG. 9 includes regions or parameterized zones having various thicknesses, in contrast to the grooves described above that are surrounded by an intermediate region of greater average thickness. The hitting face 509 can be formed of, for example, a steel material.

[0074] As shown in FIG. 9, the back surface 528 includes an upper region 536, a peripheral region 538, a lower region 534, and a central region 520, which includes a toe side central region portion 533, an intermediate central region portion 537, and a heel side central region portion 535. The determination of the thickness of these regions can be determined using an iterative process such as the thickness pattern formation method of FIG. 11 described below, for example. The thickness can maintain a maximum hitting face stress limit or range as a constraint so that the hitting face 509 can provide an improved COR (e.g., a greater maximum COR and / or a weighted COR) while the mass of the hitting face 509 is reduced and still rivals prior art club heads when tested for durability.

[0075] Regarding this, for the parameterized zones or regions shown in FIG. 9 for the club head 1D, the preferred thicknesses are provided in Table 6 below, and the results of the yield stress limit (i.e., the von Mises stress of the hitting face), weighted COR, maximum COR, and the mass of the hitting face are shown in Table 7 below. The thicknesses of these regions are also shown below for the comparative example club head D in Table 6, and the results of the stress limit, weighted COR, maximum COR, and the mass of the hitting face are shown in Table 7 below for comparison. The thickness and width of the peripheral region 538 for both the comparative example club head D and the club head 1D may be the same, for example, in the case of a thickness of 2.4 mm and a width of 2.5 mm. The thicknesses shown below may vary between regions due to, for example, tapering or gradual transitions. In some implementations, the thicknesses provided below may represent the average thickness of the regions. In other implementations, the thicknesses provided below may represent the thickness at the center of the regions.

Table 6

[0076] As shown above, the thickness of the entire hitting face of the comparative example club head D is substantially uniform, with slightly different thicknesses between different regions. In contrast, the middle central region 537 of the club head 1D is much thicker than the other regions, particularly thicker than the toe-side central region 535, the upper region 536, and the lower region 534. As shown in Table 7 below, such a change in the thickness of the hitting face 509 provides an increased weighted COR and an increased maximum COR compared to that of the comparative example club head D. Further, the variable thickness pattern of the club head 1D also reduces the mass of the hitting face 509 by 6 g, while maintaining an equivalent or improved stress limit, thereby providing equivalent or better durability than the equivalent club head D. As discussed above, the 6 g of mass removed or saved from the hitting face 509 can be redistributed to other parts of the club head, such as the rear muscle or the toe part, to increase the MOI and / or to more appropriately position the CG and sweet spot of the club head.

Table 7

[0077] Those skilled in the art referring to the present disclosure will understand that other implementations can include regions or parameterized zones of different shapes or arrangements different from those shown in the example of FIG. 9. In this regard, FIG. 10 provides different thickness patterns with different arrangements of regions or parameterized zones.

[0078] FIG. 10 shows an exemplary back surface 628 of the striking face 609 of a club head including different thickness patterns according to one or more embodiments. Similar to the exemplary thickness pattern of FIG. 9, the thickness pattern of FIG. 10 includes regions or parameterized zones having various thicknesses, in contrast to the grooves surrounded by an intermediate region of greater average thickness. The striking face 609 can be formed of, for example, a steel material.

[0079] As shown in FIG. 10, the back surface 628 includes a peripheral region 638, an outer region 630, and a central region 620, which includes an outer central region 644, a toe-side inner central region 642, and a heel-side inner central region 640. The determination of the thickness of these regions can be determined using an iterative process such as the thickness pattern formation method of FIG. 11 described below, for example. The thickness can maintain a limit or range of striking face stress as a constraint while providing an improved COR (e.g., a greater maximum COR and / or a weighted COR) such that the striking face 609 is comparable to club heads of the prior art when tested for durability, despite a reduction in the mass of the striking face 609.

[0080] Regarding this, for the parameterized zones or regions shown in FIG. 10 for club head 1E and club head 2E, the preferred thicknesses are provided in Table 8 below, and the resulting values of the yield stress limit (i.e., the von Mises stress of the hitting face), weighted COR, maximum COR, and the mass of the hitting face are shown in Table 9 below. The thickness and width of the peripheral region 638 of both club heads can be the same, for example, a thickness of 2.4 mm and a width of 3.5 mm. The thicknesses shown below may vary between regions due to, for example, tapering or stepwise transitions. In some implementations, the thicknesses provided below may represent the average thickness of the regions. In other implementations, the following thicknesses may represent the thickness at the center position of the regions.

Table 8

[0081] As shown above, the central region 620 is generally much thicker than the outer region 630, and the toe-side inner central region 642 and the heel-side inner central region 640 are even thicker than the outer central region 644. As shown in Table 7 below, such a change in the thickness of the hitting face 609 provides an increased weighted COR and an increased maximum COR compared to that of the comparative example club head D discussed above with reference to Table 7. Further, the variable thickness patterns of club heads 1E and 2E also reduce the mass of the hitting face 609 by 6 g and 7 g respectively compared to the comparative example club head D while maintaining a similar stress field, thereby providing a similar durability to the equivalent head D. The 6 g or 7 g of mass removed or saved from the hitting face 609 can be redistributed to other parts of the club head, such as the rear muscle or the toe part, in order to increase the MOI or to more appropriately position the CG and the sweet spot of the club head, as discussed above.

Table 9

[0082] FIG. 11 is a flowchart of an exemplary thickness pattern forming method for a striking face according to one or more embodiments. The method of FIG. 11 can be used, for example, with the parameterized zones or regions shown in FIGS. 9 and 10 described above. A computing device or other electronic processing device can be used to determine a variable thickness pattern in some implementations.

[0083] In block 1102, a plurality of parameterized zones or regions are defined for the striking face of the club head. The club head can form a golf club head body having a striking face, a heel portion, a toe portion opposite the heel portion, a sole, and a top portion opposite the sole. The club head can be formed, for example, of steel and can include a hollow body type club head or a cavity back type club head. Each parameterized zone or region can have a variable first parameter and a variable second parameter. In some implementations, the first and second parameters can include the thickness and width of the parameterized zone or region, or other dimensions.

[0084] In block 1104, a target value is set for each constraint value of the striking face. In some implementations, the first constraint value can be the mass of the striking face, the second constraint value can be the mechanical stress limit of the striking face, and the third constraint can be, as described above, the weighted COR value of the striking face. The target value for each parameterized zone or region can be set, for example, based on improvements desired for the club head, such as an increase in discretionary mass redistributed from the striking face, increased or minimum durability of the striking face, or an increase in weighted COR balanced with the maximum COR or CT rules set by a regulatory agency.

[0085] In block 1106, the parameters of each parameterized zone or region are varied. For example, the maximum width and maximum thickness can be varied as parameters for the central region, upper region, lower region, and toe region of the striking face. In some implementations, the parameters can be repeatedly varied to generate a set of values for one or more constraints based on the changes to the parameters.

[0086] In block 1108, the collision with the golf ball is optionally simulated for a plurality of collision positions. In some implementations, blocks 1106 and 1108 can be combined. For example, an impact probability matrix such as Table 3 above can be used with Equation 3 above to generate a weighted COR based on the variation of the first and second parameters of the parameterized zone or region within block 1106.

[0087] In block 1110, the constraint values resulting from the variation of the parameters within block 1106 are evaluated with respect to the target values of one or more constraint values. For example, the weighted COR value obtained as the result closest to 0.80 can at least partially determine the width and thickness of the parameterized zone or region. As another example, the maximum mass removal or mass savings from the striking face can be another factor considered in determining the size and / or thickness of the parameterized zone or region.

[0088] In block 1112, based on the evaluation in block 1110, a variable thickness pattern is formed on the striking face. In some cases, material can be removed using a cutting tool or other machining on the back of the striking face to form the variable thickness pattern. In other cases, the variable thickness pattern of the striking face may be formed by using a casting or forging process.

[0089] One of ordinary skill in the art will understand, with reference to the present disclosure, that the thickness pattern formation process of FIG. 11 may vary in other implementations. For example, the setting of one or more target values for one or more corresponding constraint values in block 1104 may be performed before the definition of the parameterized zone or region in block 1102. As another exemplary variation, the change of parameters for each parameterized zone within block 1106 can be combined with the evaluation of the resulting constraint values within block 1110. In some implementations, block 1108 may be omitted.

[0090] FIG. 12 is a flowchart of another exemplary thickness pattern formation method for a striking face according to one or more embodiments. The method of FIG. 12 can be used, for example, with the parameterized zones or regions shown in FIGS. 7 and 8 discussed above. A computing device or other electronic processing device can be used to determine a variable thickness pattern in some implementations.

[0091] In block 1202, the area of the striking face of the club head is defined to include a central area and an intermediate area, and at least one of an upper area, a lower area, and a toe area. The club head can be formed of a golf club head body having a striking face, a heel portion, a toe portion opposite the heel portion, a sole, and a top portion opposite the sole. The club head can be formed, for example, of steel material and can include a hollow body type club head or a cavity back type club head. The central area includes the face center of the striking face, and the intermediate area at least partially surrounds the central area. The upper area can be disposed above the central area, and the lower area can be disposed below the central area. The toe area can be disposed on the toe side of the central area. The intermediate area can be disposed between the central area and each, or at least one, of the upper area, the lower area, and the toe area.

[0092] In block 1204, the central region is recessed such that the central region has a thickness thinner than that of the intermediate region. In this regard, the intermediate region may have a uniform or substantially uniform thickness, for example, a thickness of at least 2.5 mm and 3.3 mm or less. The recess in the central region can be created, for example, by tapering the central region from the toe side of the central region towards the heel side of the central region. In other implementations, the thickness of the central region may vary by changing the thickness stepwise to form a recess. The recess in the central region may be formed, for example, by machining to remove mass or by forging or casting at least a part of the club head to save mass from the central region.

[0093] In block 1206, at least one of the toe region, the upper region, and the lower region is recessed, such as by a groove or a channel, such that the recessed region is thinner than the thickness of the central region. Such a groove may include, for example, an elongated groove having a width of about 2.0 mm or more in at least one of the toe region, the upper region, and the lower region. The groove can be formed, for example, by machining to remove mass or by forging or casting at least a part of the club head to save mass from at least one region. In some implementations, the upper region may include an elongated groove or channel having a width of 6.0 mm or more.

[0094] The recess in the central region formed in block 1204 and the recess in at least one of the toe region, the upper region, and the lower region of block 1206 are separated from the sweet spot corresponding to COR1, the first coefficient of restitution, by at least 7.5 mm from the sweet spot and have a COR, the second coefficient of restitution AUXresults in a hitting face that includes an auxiliary position corresponding to (COR2), where COR2 ≧ 0.98*COR1. In this regard, the addition of the aforementioned recess and the removal of mass or mass savings from the corresponding hitting face increases the area of the hitting face having a relatively high COR. In some implementations, the maximum COR of the hitting face can also be increased or more appropriately positioned to correspond to the sweet spot and / or the more frequently hit portion of the hitting face, as discussed above, such that it can be quantified with a weighted COR.

[0095] Furthermore, the removal or conservation of mass from the hitting face enables the redistribution of mass within the clubhead, such as to the rear muscle or toe portion of the clubhead, in order to increase the MOI and / or to more appropriately position the CG of the clubhead and the sweet spot of the hitting face. For example, the sweet spot can be positioned 2.0 mm or less from a vertical center plane that is perpendicular to the face plane and extends through the center of the face. As another example, the CG of the clubhead can be positioned 1.0 mm or less from the vertical center plane in order to more appropriately position the sweet spot on the face at a predicted or more frequently struck location.

[0096] The foregoing description of the disclosed exemplary embodiments is provided to enable one skilled in the art to make or use the embodiments in the present disclosure. Various modifications to these examples will be readily apparent to those skilled in the art, and the principles disclosed herein can be applied to other examples without departing from the scope of the present disclosure. For example, some alternative embodiments may include different sizes or shapes of the area of the striking face or the parameterized zone. Accordingly, the described embodiments should be considered exemplary in all respects and not restrictive, and thus the scope of the present disclosure is indicated by the following claims rather than the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope. The described embodiments should be considered exemplary in all respects and should not be regarded as restrictive. Further, the use of language in the following claims in the form of "at least one of A and B" should be understood to mean "only A, only B, or both A and B".

Description of the Reference Numerals

[0097] 10 Virtual center plane 14 Face center 16 Sweet spot 22 Face plane 100 Golf club head 102 Toe 108 Intermediate region 109 Striking face 111 Sole

Claims

1. A golf club head, when oriented towards a reference position, a golf club head body including a toe, a heel opposite the toe, a sole, and a top portion opposite the sole, a loft angle LA (degrees), mh = 2.1 (g / degree) * LA + a, and 109 g < a < 210 g, where mh (g) is the mass of the golf club head, a blade length of less than 80 mm, a striking face having a face center, the striking face defining a face plane, a virtual center plane perpendicular to the face plane and extending vertically through the face center, a center of gravity of the golf club head located within 2.0 mm of the virtual center plane, Izz > mh * 9.3 cm ２ including the moment of inertia Izz about the vertical axis passing through the center of gravity that satisfies the striking face includes a sweet spot corresponding to a first coefficient of restitution COR1 and an auxiliary position of the striking face at least 7.5 mm away from the sweet spot corresponding to a second coefficient of restitution COR2, the golf club head, wherein the first coefficient of restitution COR1 and the second coefficient of restitution COR2 satisfy the following formula. COR2 ≧ 0.98 * COR1

2. The striking face includes a central region including the face center, an intermediate region at least partially surrounding the central region, an upper region above the central region, a lower region below the central region, and a toe region on the toe side of the central region, each of the central region, the upper region, the lower region, and the toe region includes a maximum width and an average thickness, the intermediate region is disposed between the central region and each of the upper region, the lower region, and the toe region, The golf club head according to claim 1, wherein an average thickness of the intermediate region is greater than an average thickness of each of the central region, the upper region, the lower region, and the toe region.

3. The golf club head according to claim 2, wherein at least one of the toe region, the upper region, and the lower region includes an elongated groove having a width of about 2.0 mm or more on its back surface.

4. The golf club head according to claim 2, wherein the upper region, the lower region, and the toe region each include an upper groove generally extending in the toe - heel direction, a lower groove generally extending in the toe - heel direction, and a toe groove generally extending in the vertical direction on their back surfaces, respectively.

5. The golf club head according to claim 2, wherein the central region includes a heel - side region having a greater thickness than a toe - side region.

6. The golf club head according to claim 5, wherein the central region is tapered from the heel side region toward the toe side region.

7. The golf club head according to claim 1, wherein the auxiliary position is spaced at least 7.5 mm from the toe side of the sweet spot.

8. The golf club head according to claim 1, wherein the striking face has a weighted COR of 0.79 or more.

9. The golf club head according to claim 1, further including a topline thickness of 6.5 mm or less.

10. A golf club head, when directed toward a reference position, a golf club head body including a toe, a heel opposite the toe, a sole, and a top portion opposite the sole, a face insert having a mass mf fixedly attached to the golf club head body and including a striking face defining a face plane, a loft angle LA (degrees), a golf club head mass mh where mh = 2.1 (g / degree) * LA + a and 109 g < a < 210 g, a blade length of less than 80 mm, a center of gravity, including a moment of inertia Izz about a vertical axis passing through the center of gravity that satisfies Izz > mh * 9.3 cm2, where the ratio mf / mh is 0.22 or less, a golf club head.

11. The face insert includes a central region including a face center, an intermediate region at least partially surrounding the central region, an upper region above the central region, a lower region below the central region, and a toe region on the toe side of the central region, each of the central region, the upper region, the lower region, and the toe region includes a maximum width and an average thickness, the intermediate region is disposed between the central region and each of the upper region, the lower region, and the toe region, The golf club head according to claim 10, wherein the average thickness of the intermediate region is greater than the average thickness of each of the central region, the upper region, the lower region, and the toe region.

12. The golf club head according to claim 11, wherein the upper region, the lower region, and the toe region each include an upper groove generally extending in the toe - heel direction on their back surfaces, a lower groove generally extending in the toe - heel direction, and a toe groove generally extending in the vertical direction.

13. The golf club head according to claim 11, wherein at least one of the toe region, the upper region, and the lower region includes an elongated groove having a width of about 2.0 mm or more on its back surface.

14. The golf club head according to claim 11, wherein the central region includes a heel side region that is thicker than the toe side region.

15. The golf club head according to claim 14, wherein the central region is tapered from the heel side region toward the toe side region.

16. The striking face includes a sweet spot corresponding to a first coefficient of restitution COR1 and an auxiliary position of the striking face that is at least 7.5 mm away from the sweet spot corresponding to a second coefficient of restitution COR2, The golf club head according to claim 10, wherein the first coefficient of restitution COR1 and the second coefficient of restitution COR2 satisfy the following formula. COR2 ≧ 0.98 * COR1

17. The golf club head according to claim 16, wherein COR2 ≧ 0.99 * COR1 is satisfied.

18. The golf club head according to claim 10, wherein the striking face has a weighted COR of 0.79 or more.

19. The golf club head according to claim 10, further including a topline thickness of 6.5 mm or less.

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