Golf club heads with internal undercuts

Abstract

To address to the necessity for producing golf club head having a construction which expands a limit of modifications to a face to improve energy transfer from the club to a ball at impact.SOLUTION: Described herein is a hollow body iron-type golf club head 100 having a sole 110 and ballast configured to relieve stress within a forward region of the sole. In a first configuration, the golf club head comprises a ballast undercut for relieving stress. In other configurations, the ballast undercut is combined with additional stress relief features, such as a cascading sole near a face sole juncture, for further reductions in face thickness.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 013,341, filed April 21, 2020, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to golf equipment, and more particularly to a flexure structure for obtaining improved performance characteristics of hollow body irons and a method of manufacturing hollow body irons having the flexure structure. [Background technology]

[0003] A hollow body iron ideally acts as a springboard, deflecting backward during impact. In club design, the degree to which a hollow body iron behaves as a springboard or a spring is constrained by peak stress values. To ensure that a conventional golf club does not exceed its maximum stress limit, the face and sole are thickened to make the club stiffer. The stiffness of a conventional golf club results in a reduced springboard or a spring behavior of the club head.

[0004] Therefore, there is a need in the art to push the boundaries of modifications to the face to produce golf club heads having structures that improve the transfer of energy from the club to the ball upon impact. [Brief explanation of the drawings]

[0005] [Figure 1] 1 depicts a perspective view of the toe end of a hollow body club head according to one embodiment.

[0006] [Figure 2A] The hollow body club head of FIG. 1 is depicted along transverse line II.

[0007] [Figure 2B]2B depicts a view of a portion of the hollow body club head of FIG. 2A.

[0008] [Figure 3] 2 depicts a front view of the internal cavity of FIG. 1;

[0009] [Figure 4A] 2 depicts a cross-sectional view of a hollow body club similar to that of FIG. 1 taken along a cross-sectional line similar to cross-sectional line II-II of FIG. 1 according to another embodiment.

[0010] [Figure 4B] 4B depicts a view of a portion of the hollow body club of FIG. 4A.

[0011] [Figure 5] 2 depicts a cross-sectional view of a prior art hollow body club along a transverse line similar to transverse line II of FIG. 1 according to another embodiment.

[0012] [Figure 6] 1 depicts a cross-sectional view of a hollow body club similar to that of FIG. 1 taken along a cross-sectional line similar to cross-sectional line II of FIG. 1 according to another embodiment.

[0013] [Figure 7] 1 depicts a comparative graph of 7-iron ball speed, measured in mph, for various undercut embodiments described in this disclosure.

[0014] [Figure 8] 8 depicts a comparative graph of vertical launch angle in degrees for the 7-iron of FIG. 7 for various undercut embodiments described in this disclosure.

[0015] [Figure 9] 8 depicts a comparative graph of spin rate in rpm for the 7-iron of FIG. 7 for various undercut embodiments described in this disclosure.

[0016] [Figure 10] 1 depicts a comparative graph of pitching wedge vertical launch angle in degrees for various undercut embodiments described in this disclosure.

[0017] [Figure 11] 11 depicts a comparative graph of spin rates for the pitching wedge of FIG. 10 for various undercut embodiments described in this disclosure.

[0018] [Figure 12] 12 depicts a comparative graph of ball speeds for the pitching wedge of FIG. 11 measured in mph for various undercut embodiments described in this disclosure.

[0019] For simplicity and clarity of illustration, these drawings illustrate general modes of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. Additionally, elements in the drawings are not necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help improve understanding of embodiments of the present disclosure. The same reference numbers in different drawings refer to the same elements.

[0020] It should be understood that the terms "first," "second," "third," "fourth," "fifth," etc. in the specification and claims, if any, are used to distinguish between similar elements and are not necessarily used to describe a particular sequence or chronological order, and that terms so used are interchangeable under appropriate circumstances; for example, the embodiments described herein may operate in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprise," "have," and any variations thereof are intended to encompass a non-exclusive inclusion, such that a process, method, system, article, device, or apparatus comprising a list of elements is not necessarily limited to those elements, but may include other elements not descriptively listed in such process, method, system, article, device, or apparatus.

[0021] If any, the terms "left," "right," "front," "rear," "upper," "lower," "above," "under," etc. in this specification and claims are used for descriptive purposes and not necessarily to describe permanent relative positions. It should be understood that terms so used are interchangeable in appropriate circumstances such that the embodiments described herein are operable, for example, in orientations other than those illustrated or otherwise described herein.

[0022] The terms "couple," "coupled," "couples," "coupling," and the like, should be understood broadly and refer to connecting two or more elements or signals electrically, mechanically, and / or otherwise. The terms "loft" or "loft angle" of a hollow body golf club (hereinafter "hollow body", "hollow body iron", "iron-type golf club head", or "golf club head") as described herein refer to the angle formed between the club face and shaft as measured by any suitable loft and lie machine. The loft plane is located tangent to the striking face at the geometric center. The loft angle is measured between the contact plane and the loft plane. The loft angle is measured between the contact plane and the loft plane. In many embodiments, the loft angle of the club head is less than about 50 degrees, less than about 49 degrees, less than about 48 degrees, less than about 47 degrees, less than about 46 degrees, less than about 45 degrees, less than about 44 degrees, less than about 43 degrees, less than about 42 degrees, less than about 41 degrees, less than about 40 degrees, less than about 39 degrees, less than about 38 degrees, less than about 37 degrees, less than about 36 degrees, less than about 35 degrees, less than about 34 degrees, less than about 33 degrees, less than about 32 degrees, less than about 31 degrees, less than about 30 degrees, less than about 29 degrees, less than about 28 degrees, less than about 27 degrees, less than about 26 degrees, less than about 25 degrees, less than about 24 degrees, less than about 23 degrees, less than about 22 degrees, less than about 21 degrees, less than about 20 degrees, less than about 19 degrees, less than about 18 degrees, or less than about 17 degrees. Additionally, in many embodiments, the loft angle of the club head is greater than about 16 degrees, greater than about 17 degrees, greater than about 18 degrees, greater than about 19 degrees, greater than about 20 degrees, greater than about 21 degrees, greater than about 22 degrees, greater than about 23 degrees, greater than about 24 degrees, greater than about 25 degrees, greater than about 26 degrees, greater than about 27 degrees, greater than about 28 degrees, greater than about 29 degrees, greater than about 30 degrees, greater than about 31 degrees, greater than about 32 degrees, greater than about 33 degrees, greater than about 34 degrees, greater than about 35 degrees, greater than about 36 degrees, greater than about 37 degrees, or greater than about 38 degrees. DETAILED DESCRIPTION OF THE INVENTION

[0023] This disclosure describes technology for an improved hollow body iron-type golf club head (hereinafter "hollow body," "hollow body iron," "iron-type golf club head," or "golf club head") having a sole and ballast configured to relieve stress within a forward portion of the sole. In a first configuration, the golf club head includes a ballast undercut for stress relief. In other configurations, the ballast undercut is combined with additional stress relief features, such as a cascade sole, near the face-sole junction to obtain a further reduction in face thickness.

[0024] The hollow body can include a striking face, a rear portion opposite the striking face, a heel portion, a toe portion opposite the heel, a sole, and a top rail, defining an interior void. The rear portion can further include ballast extending forward from the rear portion into the interior void. In many embodiments, the ballast is an internal component that is not visible from the outside of the golf club. The ballast can also have a geometry configured to increase the interior surface area of ​​the sole. For example, the ballast can include a top surface, a front surface, and a bottom surface defined as an undercut region. The undercut is formed by the concave geometry of the bottom surface relative to the face when viewed from a toe-side cross section. The undercut allows a thinner, forward portion of the sole to extend below the ballast. A ballast with a bottom undercut surface, as opposed to a front surface that meets the inner surface of the sole at a right angle, (1) prevents stress from concentrating along the sole between the face and the ballast, and (2) increases the area of ​​the sole that can store strain energy. Thus, hollow body irons with undercuts have sole and face geometries with greater areas of thinning compared to hollow irons without undercuts.

[0025] The sole of a hollow-body iron can be divided into two regions: a forward portion and a rear portion. The forward portion defines a thinned area of ​​the sole adjacent to the striking face, which can store strain energy. The rear portion of the sole describes the area of ​​the sole adjacent to the rear portion of the body, which does not store strain energy. In other words, the forward portion 132 of the sole is the portion of the sole 110 that behaves as a spring. As a result of the ballast undercut, a hollow-body iron with a thinner face and an extended forward sole portion stores more strain energy (i.e., potential energy) than the face and forward sole portion of a club without an undercut. Consequently, the undercut improves the spring-like energy transfer between the club body and the golf ball (compared to a golf club without an undercut). This energy transfer can be further improved in a hollow-body iron if the forward sole portion also includes a cascade in addition to the undercut. The Cascade Sole improves stress flow within the forward portion of the sole near the face-sole junction, while the Undercut improves stress flow near the ballast. Therefore, the application of the Undercut and / or the combined application of the Undercut and Cascade Sole can result in a golf club head that can tolerate a thinner face by 3-8%. Thus, a previously unattainable thinner face results in improved flight trajectory and distance. I. Undercut

[0026] 1 of the drawings depicts an exterior perspective view of an iron-type golf club head 100 having an internal stress-relieving sole 110 and a ballast 114 having an undercut 102 as shown in FIG. 2A. The golf club head 100 has a hollow body structure having an internal void 104. The hollow body structure of the golf club head 100 is further defined by a striking face 106, a rear portion 108 opposite the striking face 106, a heel portion 103, a toe portion 105 opposite the heel portion 103, a sole 110, and a top rail 112 opposite the sole 110.

[0027] FIG. 2A illustrates a heel cutaway view of the golf club head 100 of FIG. 1 taken along cross-sectional line II. FIG. 2A shows the internal void 104 and stress relief features of the golf club head 100. The rear portion 108 further includes a ballast 114 positioned within the internal void 104. As shown in FIG. 2, the ballast 114 is an integral weighted element required for optimal CG (center of gravity) positioning in the golf club head 100. The ballast 114 is a solid structure that protrudes perpendicularly from the sole 110, forward from the rear portion 108, and extends along the sole 110 in a heel-to-toe direction. A forward portion 132 of the sole is defined between the striking face 106 and the ballast 114.

[0028] 2B , the ballast 114 includes a top surface 116, a front surface 118, and a bottom surface 120. As illustrated, the bottom surface 120 is contoured to create an undulation that defines an undercut region 128 having the undercut 102. The undercut region 128 of the ballast 114 can be considered as the undercut region 128 of material removed from the ballast 114 adjacent the inner surface 122 of the sole 110. The undercut region 128 includes the undercut 102 and an undercut transition 141. The undercut region 128 extends laterally in a heel-to-toe direction across the heel-to-toe length 124 of the ballast 114. In the illustrated embodiment, the undercut 102 is generally centered within the club head 100 between the heel portion 103 and the toe portion of the golf club 100. 2B, the undercut 102 extends below the ballast 114, causing a forward portion 132 of the sole 110 to interface between the face and the undercut 102 / bottom surface 120 of the ballast 114. The forward portion 132 of the sole 110 is effectively lengthened compared to a golf club head without the undercut (i.e., the forward portion defined between the striking face and the forward surface of the ballast). Thus, the undercut 102 not only reduces stress in the forward portion 132 of the sole, but also creates a larger spring (i.e., the forward portion of the sole) for transferring energy back to the ball upon impact.

[0029] FIG. 2B depicts an expanded view of the ballast 114 and undercut 102 shown in cross-section in FIG. 2A. As shown in FIG. 2B, the ballast 114 includes a top surface 116, a forward surface 118, and a bottom surface 120. The ballast 114 protrudes perpendicularly from the medial surface of the sole 106 along the medial surface of the rear portion 108. The bottom surface 124 has a contoured geometric shape that extends inward from the forward surface 118 toward the rear portion 108, defining the undercut 102, which extends in a heel-to-toe direction. Continuing to refer to the cross-section of FIG. 2B, the ballast bottom surface 120 further includes an undercut junction 130, which is defined as the junction between the ballast bottom surface 120 and the medial surface 122 of the sole 110. The undercut junction 130 is the aft-most point of the ballast bottom surface 120 that defines the undercut 102. As shown, the forward portion 132 of the sole is defined between the striking face 106 and the undercut junction 130, rather than between the striking face 106 and the forward surface 118 in hollow body irons that do not have the undercut 102.

[0030] 2B, the undercut 102 is defined by four parameters: undercut depth 134, undercut height 136, undercut length 138, and undercut sole thickness 123. Additionally, the ballast bottom surface 120 can be curved such that the undercut 102 is defined between an undercut bottom edge 139 and an undercut top edge 137. The undercut depth is measured as the vertical distance between the ballast forward surface 20 and the undercut junction 130 (i.e., the rearmost point of the undercut). The undercut height 136 is defined as the vertical distance between the undercut top edge 137 and the undercut bottom edge 139. The undercut length is measured parallel to the ground contact patch 10 between the undercut toe end 133 and the undercut heel end 135. Finally, the undercut sole thickness 123 is measured as the vertical distance between the sole outer surface 121 and the sole inner surface 121. In the first embodiment, the undercut 102 has a depth 134 of 0.065 inches, a height 136 of 0.083 inches, and a length of 1.16 inches.

[0031] The undercut depth 134 between the ballast forward face 20 and the undercut junction 130 ranges from 0.010 inches to 0.100 inches. For example, the undercut depth 134 may be 0.010 inches, 0.015 inches, 0.020 inches, 0.025 inches, 0.030 inches, 0.035 inches, 0.040 inches, 0.045 inches, 0.050 inches, 0.055 inches, 0.060 inches, 0.065 inches, 0.070 inches, 0.075 inches, 0.080 inches, 0.085 inches, 0.090 inches, 0.095 inches, or 0.100 inches. Alternatively, the undercut face depth 131 may be measured as the vertical distance between the striking face 106 and the undercut junction 130. In some embodiments, the undercut depth from the face ranges from 0.200 inches to 0.500 inches. For example, the undercut depth from the face can be 0.200 inches, 0.220 inches, 0.240 inches, 0.260 inches, 0.280 inches, 0.300 inches, 0.320 inches, 0.340 inches, 0.360 inches, 0.380 inches, 0.400 inches, 0.420 inches, 0.440 inches, 0.460 inches, 0.480 inches, or 0.500 inches.

[0032] The undercut height 136, measured between the undercut bottom edge 137 and the undercut top edge 139, can range from 0.030 inches to 0.200 inches. For example, the undercut height 136 can be 0.030 inches to 0.040 inches, 0.040 inches to 0.050 inches, 0.050 inches to 0.060 inches, 0.060 inches to 0.070 inches, 0.070 inches to 0.080 inches, 0.080 inches to 0.090 inches, 0.090 inches to 0.100 inches, 0.100 inches to 0.110 inches, 0.110 inches to 0.120 inches, 0.120 inches to 0.130 inches, 0.130 inches to 0.140 inches, 0.140 inches to 0.150 inches, 0.150 inches to 0.160 inches, 0.160 inches to 0.170 inches, 0.170 inches to 0.180 inches, 0.180 inches to 0.190 inches, 0.190 inches to 0.200 inches, 0.190 inches to 0.210 inches, 0.190 inches to 0.220 inches, 0.190 inches to 0.230 inches, 0.190 inches to 0.240 inches, 0.190 inches to 0.250 inches, 0.260 inches to 0.270 inches, 0.270 inches to 0.280 inches, 0.280 inches to 0.290 inches, 0.290 inches to 0.300 inches, 0.300 inches to 0.310 inches, 0.310 inches to 0.320 inches, inch to 0.120 inch, 0.120 inch to 0.130 inch, 0.130 inch to 0.140 inch, 0.140 inch to 0.150 inch, 0.150 inch to 0.160 inch, 0.160 inch to 0.170 inch, 0.170 inch to 0.180 inch, 0.180 inch to 0.190 inch, or 0.190 inch to 0.200 inch.

[0033] 3 shows a front view of the golf club 100 with the striking face 106 removed to expose the undercut length 138 extending from the undercut heel end 135 to the undercut toe end. In some embodiments, the undercut length 138 ranges from 0.5 inches to 3.0 inches. In other embodiments, the undercut length ranges from 0.050 inches to 0.075 inches, 0.075 inches to 0.100 inches, 0.100 inches to 0.125 inches, 0.125 inches to 0.150 inches, 0.150 inches to 0.175 inches, 0.175 inches to 0.200 inches, 0.200 inches to 0.225 inches, 0.225 inches to 0.250 inches, 0.250 inches to 0.275 inches, or 0.275 inches to 0.300 inches. 3 further shows ballast length 124, which may be measured from ballast heel end 125 to ballast toe end 127. In some embodiments, ballast length 124 ranges from 1.0 inch to 3.0 inches. In other embodiments, ballast length 124 is 1.2 inches, 1.4 inches, 1.6 inches, 1.8 inches, 2.0 inches, 2.2 inches, 2.4 inches, 2.6 inches, 2.8 inches, or 3.0 inches.

[0034] The undercut length 138, measured as the distance between the undercut heel end and the undercut toe end, may further define a percentage of the ballast length 124 that describes the portion of the ballast 114 that comprises the undercut 102. In iron-type golf club head embodiments that comprise the undercut 102, the undercut 102 can increase the surface area that receives impact loads. The ballast length percentage may be calculated by dividing the undercut length 138 by the ballast length 124. In some embodiments, the undercut percentage of the ballast length ranges from 20% to 100%. The undercut length may range from 10% of the ballast length up to the same length as the ballast length (i.e., 100%). For example, the ballast length percentage may be 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0035] Additionally, an undercut transition height 142 is defined as the vertical distance between the medial surface of the sole 122 and the front surface lower edge 140, as shown in Figure 2B. In some embodiments, the transition height 142 may range from 0.150 inches to 0.300 inches. The transition height can range from 0.150 inch to 0.160 inch, 0.160 inch to 0.170 inch, 0.170 inch to 0.180 inch, 0.180 inch to 0.190 inch, 0.190 inch to 0.200 inch, 0.200 inch to 0.210 inch, 0.210 inch to 0.220 inch, 0.220 inch to 0.230 inch, 0.230 inch to 0.240 inch, 0.240 inch to 0.250 inch, 0.250 inch to 0.260 inch, 0.260 inch to 0.270 inch, 0.270 inch to 0.280 inch, 0.280 inch to 0.290 inch, or 0.290 inch to 0.300 inch. In the first embodiment described above, the transition height is 0.185 inch. An undercut transition 141 having a transition height 142 and a contoured profile allows the undercut 102 to smoothly transition to the ballast forward surface 118. This smooth transition promotes an even flow of stress through the undercut 102 and the ballast 114.

[0036] As discussed above, undercut 102 and undercut region 128 may be thought of as areas where ballast material has been removed, as compared to an iron-type golf club head lacking an undercut. Undercut volume 146 is defined by surface 146 of undercut region 128 and ballast forward face 20. For example, in one embodiment, undercut region surface 146 and ballast forward face 20 define undercut volume 146 of 0.018 cubic inches. In other embodiments, the undercut volume ranges from 0.018 cubic inches to 0.050 cubic inches. For example, undercut volume 146 may be 0.018 cubic inches, 0.020 cubic inches, 0.022 cubic inches, 0.024 cubic inches, 0.026 cubic inches, 0.028 cubic inches, 0.030 cubic inches, 0.032 cubic inches, 0.034 cubic inches, 0.036 cubic inches, 0.038 cubic inches, 0.040 cubic inches, 0.042 cubic inches, 0.044 cubic inches, 0.046 cubic inches, 0.048 cubic inches, or 0.050 cubic inches. Undercut volume 146 may be utilized to account for the mass removed from ballast 114 by undercut region 128. Mass is calculated by multiplying undercut volume 146 by the material density of ballast 114. For example, the undercut volume ranges from 0.018 cubic inches to 0.030 cubic inches. The undercut volume can be 0.018 cubic inches, 0.020 cubic inches, 0.021 cubic inches, 0.024 cubic inches, 0.026 cubic inches, 0.028 cubic inches, or 0.030 cubic inches. The material removed from the ballast to form the undercut is less than 6.0 g / cm. 3 to 7.75 g / cm 3 The material density ranges from 1.75 grams to 2.40 grams. The material removed from the ballast to form the undercut has a density of 6.0 g / cm. 3 , 6.5g / cm 3 , 7.0g / cm 3 , or 7.5g / cm 3The material density of the ballast 114 is 1.75 grams, 2.0 grams, 2.20 grams, 2.32 grams, or 2.40 grams.

[0037] The forward portion 132 of the sole 110, which extends from the striking face 106 to the ballast 114, affects the impact response of the golf club head 100 with a golf ball. As shown in FIG. 2 , the undercut junction 130 is spaced further rearward from the striking face 106 than the ballast forward surface 118. The undercut junction's additional distance from the striking face 106 means that the thinner forward portion 132 of the sole 110 is effectively lengthened (relative to the overall front-to-rear sole width) such that a portion of the forward sole portion extends below the ballast 114 (compared to a conventional golf club head lacking the undercut 102). The forward sole length can be measured as the vertical distance between the undercut junction 130 and the face surface 130. In some embodiments, the effective increase in length ranges from 6% to 12%. For example, the undercut 102 can increase the length of the forward sole portion 132 by 6% to 7%, 7% to 8%, 8% to 9%, 9% to 10%, and 11% to 12%. Increasing the length of the thinned forward portion 132 of the sole 110 reduces peak stress values ​​in the golf club head 100. The undercut 102 creates stress relief at the face-sole transition 126 by allowing the forward portion 132 of the sole 110, between the striking face 106 and the ballast 114, to deflect to a greater extent under impact loads rather than behaving as a rigid connection. The effective increase in the length of the forward sole 132 due to the undercut increases the total surface area over which impact loads are distributed, resulting in a stress reduction of 1000 to 2000 psi within the forward portion 132 of the sole. The undercut 102 both reduces stress concentrations in the forward sole portion 132 and increases the bending / spring effect of the forward sole portion 132. Additionally, the undercut 102 reduces the peak stress values ​​in the striking face 106 by 2000 psi to 3500 psi.For example, the undercut can reduce peak stress values ​​at the striking face by between 2000 psi and 2100 psi, between 2100 psi and 2200 psi, between 2200 psi and 2300 psi, between 2300 psi and 2400 psi, between 2400 psi and 2500 psi, between 2500 psi and 2600 psi, between 2600 psi and 2700 psi, between 2700 psi and 2800 psi, between 2800 psi and 2900 psi, between 2900 psi and 3000 psi, between 3100 psi and 3200 psi, between 3200 psi and 3300 psi, between 3300 psi and 3400 psi, or between 3400 psi and 3500 psi.

[0038] This reduction in stress within the sole 110 and striking face 106 alone can lead to improved wear life for the golf club head 100. In other words, a golf club head 100 with a ballast 114 having an undercut 102 can take more hits and play for longer periods of time than a conventional golf club head without an undercut. For example, a hollow-body golf club with an undercut 102 can experience an increased failure count of 50, 100, 150, 200, 250, or even 300 hits. Fatigue failure in a golf club subjected to cyclic loading occurs over time at points of peak stress where small cracks form in the material. The cracks then amplify stress. Therefore, a golf club head 100 with reduced peak stress experiences crack growth and resulting fatigue failure at a slower rate.

[0039] Alternatively, the stress reduction achieved by the ballast 114 and undercut 102 described above can be utilized to improve club performance and ball speed. In some embodiments, the ballast 114 having the undercut 102 can be provided in conjunction with a thinned striking face 106. To the extent that the striking face of a golf club head without the undercut 102 is limited by peak stress levels at the face-sole transition, in other words, it is not possible to improve the performance of a conventional golf club with a thinner face because the added stress from the thinner face would result in peak stresses exceeding the limit K value. As discussed above, the golf club head 100 includes the ballast 114 having the undercut 102 for stress reduction. Thus, in some embodiments, the striking face 106 can be thinned without increasing the peak stress levels at the sole-face transition above the limit K value.

[0040] The thinning may be applied to the entire face. For example, at the geometric center of the face of an undercut club, the thickness of this region of the face may range from 0.080 inches to 0.150 inches. The face thickness at the geometric center of the face may be 0.150 inches, 0.140 inches, 0.130 inches, 0.120 inches, 0.110 inches, 0.100 inches, 0.090 inches, or 0.080 inches. In the peripheral toe region of the face of an undercut club, the face thickness may range from 0.050 inches to 0.090 inches. The face thickness in the peripheral toe region can be 0.0500 inch, 0.060 inch, 0.065 inch, 0.070 inch, 0.071 inch, 0.074 inch, 0.076 inch, 0.077 inch, 0.079 inch, 0.080 inch, 0.082 inch, 0.084 inch, 0.086 inch, 0.088 inch, or 0.090 inch. The face thickness in the peripheral heel region of an undercut club can range from 0.045 inch to 0.090 inch. The face thickness in the peripheral heel region can be 0.045 inch, 0.050 inch, 0.055 inch, 0.060 inch, 0.065 inch, 0.070 inch, 0.075 inch, 0.080 inch, 0.085 inch, or 0.090 inch.

[0041] In some embodiments, the ballast 114 with the undercut 102 reduces the thickness of the face by 0.003 inches. In other examples, the striking face 106 may be thinned by the undercut 102 by 0.004 inches, 0.005 inches, 0.006 inches, 0.007 inches, 0.008 inches, 0.009 inches, or 0.010 inches. For a thin striking face 106, this reduction equates to approximately a 6% thinning, or an increase in ball speed of 0.5 mph to 0.7 mph. In some embodiments, the undercut 102 makes the striking face 3 to 8% thinner than the striking face of a golf club head without the undercut. For example, the striking face 106 may be thinned by 3% thinning, 4% thinning, 5% thinning, 6% thinning, 7% thinning, or 8% thinning.

[0042] As discussed above, the undercut region 128 has a volume 146 that represents mass removed from the ballast 114. The ballast 114 functions as a mass pad to control the center of gravity (CG) for the golf club head 100, thereby allowing the undercut 102 to modify the club head CG. The CG can be defined relative to the geometric center 126 of the striking face 106. The geometric center 126 of the striking face 118 can be determined in accordance with Section 6.1 of the USGA's Procedure for Measuring the Flexibility of a Golf Club Head (USGA-TPX3004, Rev. 1.0.0, May 1, 2008) (available at http: / / www.usga.org / eqipment / testing / protocols / Procedure-For-Measuring-The-Flexibility-Of-A-Golf-Club-Head / ) ("Flexibility Procedure"). The anterior-posterior CG depth 144 can be defined as the horizontal distance between the geometric center 126CG. For example, the anterior-posterior CG depth 144 can range from 0.080 inches to 0.110 inches. The anterior-posterior CG depth can be 0.080 inches, 0.082 inches, 0.084 inches, 0.086 inches, 0.088 inches, 0.090 inches, 0.092 inches, 0.094 inches, 0.096 inches, 0.098 inches, 0.100 inches, 0.105 inches, or 0.110 inches.

[0043] The ratio of the undercut face depth 146 to the fore-aft CG location is constrained to be between 3.0 and 5.5. For example, the face depth ratio may be 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0. In this range, the undercut 102 improves peak stresses in the forward sole portion 132 without removing material from the ballast to the extent that the CG location is compromised.

[0044] Furthermore, due to the location of the CG, the undercut does not affect the overall MOI of the club. For purposes of determining the club head's moments of inertia, a coordinate system may be defined at the CG via mutually orthogonal axes (i.e., x-, y-, and z-axes) (not shown). The y-axis extends perpendicular to the ground plane 10 through the head CG from the top rail 112 to the sole 110 when the club head is in the address position. The x-axis extends perpendicular to the y-axis through the head CG from the heel 103 to the toe 105. The z-axis extends perpendicular to the x- and y-axes through the head CG from the striking face 106 to the rear portion 108.

[0045] Moments of inertia exist about the x-axis Ixx (i.e., top rail to sole moment of inertia), the y-axis Iyy (i.e., heel to toe moment of inertia), and the z-axis (i.e., striking face to rear). In many embodiments, a golf club head with an undercut has a 96 g-in 2 from 130g·inch 2 In many embodiments, the golf club head having an undercut has a top rail to sole moment of inertia, Ixx, of about 95 g·in. 2 Larger than approx. 98g·inch 2 Larger than 100g·inch 2 Larger than approx. 102g·inch 2 Larger than approx. 103g·inch 2 Larger than 104g·inch 2 Larger than approx. 105g·inch 2 Larger than approx. 106g·inch 2 Larger than 110g·inch 2 Larger than 115g·inch 2 Larger than 125g·inch 2 Larger than approx. 135g·inch 2 Larger than 140g·inch 2 Greater than or about 145g·inch 2Further, in many embodiments, the golf club head having an undercut has a top rail to sole moment of inertia, Ixx, that is greater than about 350 g·in 2 Larger than 360g·inch 2 Larger than 370g·inch 2 Larger than 380g·inch 2 Larger than 390g·inch 2 Larger than 400g·inch 2 Larger than 410g·inch 2 Larger than 420g·inch 2 Greater than or about 430g·inch 2 In many embodiments, the golf club head having an undercut has a heel-to-toe moment of inertia, Iyy, that is greater than 350 g·in. 2 From 420g·in 2 Furthermore, the clubhead with the undercut has a heel-to-toe moment of inertia of approximately 400 g·in. 2 Larger than 410g·inch 2 Larger than 420g·inch 2 Larger than approx. 430g·inch 2 Larger than approx. 440g·inch 2 Larger than approx. 450g·inch 2 Larger than approx. 460g·inch 2 Larger than approx. 470g·inch 2 Greater than or about 480g·inch 2 In many embodiments, the golf club head having an undercut has a striking face-to-rear moment of inertia, Izz, that is greater than 400 g·in. 2 to 450g·in 2 The striking face has a rear moment of inertia, Izz, which can range from 1 / 2 to 1 / 4. The undercut in the golf club head does not significantly change the moments of inertia Ixx, Iyy, Izz relative to a golf club head without an undercut. II. Undercut and cascade sole

[0046] FIG. 4A illustrates another embodiment of a golf club head 200 including a ballast 214, an undercut 202, and a cascading forward portion 232 of the sole 210. FIG. 4 depicts a cross-sectional view of the golf club head 200. The golf club head 200 is substantially similar to the golf club head 100 and includes a thinned forward portion 232 of the sole 210 that is effectively lengthened via the undercut 202. The golf club head 200 is further defined by a striking face 206, a rear portion 208 opposite the striking face 206, a heel portion 203, a toe portion 205 opposite the heel portion 203, a sole 210, and a top rail 212 opposite the sole 210. These components together define a hollow body club having an interior void 204. The rear portion 206 further includes a ballast 214 positioned within the interior void 204. 4, the ballast 214 includes a top surface 216, a forward surface 218, and a bottom surface 220. The ballast bottom surface 220 is similar to the ballast bottom surface 120. The contoured bottom surface 220 is recessed toward the rear portion 208 to create the undercut 202.

[0047] FIG. 4B provides an expanded view of the ballast 214 and sole 210 illustrated in FIG. 4. As shown, the forward portion 232 of the sole 210 extends from the undercut 202 in the ballast 214 to the striking face 206. The forward portion 232 of the sole further includes an inner region 260 and a cascade region 262. The cascade region 262 can include an inner radius transition 264 between the inner surface of the striking face 206 and the inner surface of the sole 210. The cascade region 262 can include at least two thickness steps or stages. The stepped structure results in a continuous thinning of the forward sole portion 132. In some embodiments, the cascade region 262 can include an inner radius transition 264 having 2, 3, 4, 5, 6, or 7 steps.

[0048] 4B , cascade region 262 includes a first step 266, a second step 268, and a step transition 270 between first step 266 and second step 268. Cascade region 262 of forward sole portion 232 can have a thickness measured as the perpendicular distance between sole lateral surface 221 and sole medial surface 222. The thickness can decrease in the fore-to-aft direction across cascade region 262. First step 266 can have a first thickness 272 defined as the perpendicular distance between sole lateral surface 221 and sole medial surface 222 within first step 266. Second step 268 can have a second thickness 274 defined as the perpendicular distance between sole lateral surface 221 and sole medial surface 222 within second step 268. In some embodiments, the first thickness 272 is greater than the second thickness 274, such that the overall thickness of the cascade region 262 decreases in the anterior-posterior direction. The first thickness 272 and / or the second thickness 274 can have a constant thickness over the step length in the anterior-posterior direction. In other embodiments, the first thickness 272 and / or the second thickness 274 can be tapered to decrease in thickness over the step length in the anterior-posterior direction.

[0049] The cascade region may include a first step 266, a second step 268, a third step (not shown), a first step transition 270 between the first step 266 and the second step 268, and a second step transition between the second step and the third step. As noted above, the cascade region of a forward sole region having three steps may have a thickness measured as the perpendicular distance between the outer surface of the sole and the inner surface of the sole. This thickness again decreases in the fore-to-aft direction across the cascade region. As noted above, the first step may have a first thickness. The second step may have a second thickness. The third step may have a third thickness, with the third step thickness (as with the first and second step thicknesses) measured as the perpendicular distance between the outer surface of the sole and the inner surface of the sole. In some embodiments, the first thickness is greater than the second thickness, and then the third thickness is greater than the second thickness, such that the overall thickness of the cascade region 262 decreases in the anterior-posterior direction. The first thickness and / or the second thickness and / or the third thickness can have a constant thickness over the step length in the anterior-posterior direction. In other embodiments, the first thickness and / or the second thickness and / or the third thickness can be tapered to decrease in thickness over the step length in the anterior-posterior direction.

[0050] The step transition 270 is between the aft edge of the first step and the forward edge of the second step and can be sloped in the anterior-posterior direction to consistently reduce the cascade region thickness between the first thickness 272 and the second thickness 274. Alternatively, in cascade regions having two step transitions (i.e., a first transition between the first and second steps and a second transition between the second and third steps), these transitions can be sloped in the anterior-posterior direction to consistently reduce the cascade region thickness between the first, second, and third thicknesses (or the first, second, and third steps). In some embodiments, such as FIG. 4B , the step transition 270 is linearly sloped at an angle less than 45 degrees between and adjacent the first step 266 and the second step 268. In some embodiments, the step transition 270 is linearly sloped at an angle ranging from 10 degrees to less than 45 degrees. The linear slope can be gradual, such as between 5 and 10 degrees, between 10 and 15 degrees, between 15 and 20 degrees, between 20 and 25 degrees, between 25 and 30 degrees, between 30 and 40 degrees, or between 40 and 45 degrees. Although not shown, in other embodiments, the step transition 270 can be steeper and more step-like. For example, the step transition 270 can be between 45 and 50 degrees, between 50 and 55 degrees, between 55 and 60 degrees, between 60 and 65 degrees, or between 65 and 70 degrees.

[0051] As described above, forward sole portion 232 further includes medial region 260 between cascade region 262 and ballast undercut 202. Uniform medial region 260 also has a medial thickness 276 defined as the vertical distance between sole outer surface 221 and sole inner surface 222. Medial thickness 276 is less than the thickness of an adjacent step or of the final step in cascade region 262. As shown in FIG. 4B , medial thickness 276 is less than second thickness 274.

[0052] Continuing to refer to FIG. 4B , medial region 260 of forward sole portion 232 can be effectively lengthened by ballast 214 including undercut 202. Ballast 214 has a geometry substantially similar to that of ballast 114. The ballast bottom surface defines undercut region 228 including undercut 202, undercut transition 241, and undercut junction 230. As shown in FIG. 4B , medial region 260 is positioned adjacent to undercut 202. Undercut region 228 functions in a substantially similar manner to undercut 202 and undercut region 228. Specifically, undercut region 228 reduces stress concentrations within forward sole portion 232 and also increases the bending / spring effect of forward sole portion 232.

[0053] In many embodiments, the performance improvements resulting from the cascade sole 262 and undercut 202 are even greater. In other words, a golf club head having both a cascade region and an undercut 202, such as hollow body club 202, experiences a greater reduction in peak stresses than a golf club head having either a cascade region or an undercut. The reduction in peak stresses in the forward sole portion 232 increases the region's tolerance for modification to improve ball speed. Specifically, a hollow body club 200 having a forward sole region 232 defined by an undercut 202 and a cascade region can have a thinner face (compared to a hollow body club lacking either or both an undercut and a cascade sole). This results in better ball speed and distance. In some embodiments, the undercut 202 and cascade sole 242 allow the forward portion 232 of the sole to be more responsive. Rather than remaining rigid, the forward portion 232 can be thinned, causing the forward portion 232 to behave as a spring under impact loads. This means the golf club head 200 is more efficient at transferring swing energy to the golf ball. The net increase in ball speed through the reduction in the average thickness of the sole forward portion 232 is a result of the stress reduction at the face-sole transition 226. The undercut and cascade sole work together to improve the flow of stress within the forward portion 232, thereby reducing the level of stress concentration at impact. [Example]

[0054] Example 1: Study of Undercut in Hollow Body Iron As described in detail above, ballast and undercuts can be applied to golf club heads, both alone and in combination with other features, such as a cascade sole, to improve club performance. In the following examples, the performance improvements resulting from the undercut 102 were examined by comparing a golf club head without an undercut (Golf Club A, hereinafter "Club A"), a golf club head with an undercut (Golf Club B, hereinafter "Club B"), a golf club head without an undercut and with a cascade sole (Golf Club C, hereinafter "Club C"), and a golf club head with an undercut and with a cascade sole (Golf Club D, hereinafter "Club D"). The performance improvements were measured and analyzed using finite element analysis (FEA). Specifically, FEA was used to measure peak stress values ​​within the forward section. The average peak stress, along with the measured surface area experiencing the peak stress, was used to determine each club's potential to efficiently transfer impact energy back to the ball. The reduction in average peak stress serves as an indicator for improved durability and potential performance gains through face and sole thinning.

[0055] Each of Example Clubs A, B, C, and D was substantially similar, having the same overall mass, material construction, and loft angle. Impact loads for each club were simulated at 105 mph. Each Example Club had the unique internal void configuration described above. The average peak stress between the striking face and the ballast within the forward portion of the sole was calculated for each Example. Similarly, the area of ​​average peak stress was calculated for each Example. Finally, the average peak stress within the striking face was calculated for each Example. Table 1 below shows the peak face stress, peak stress in the forward sole portion, and peak stress area within the forward portion of the sole for each Example Club discussed below. The stress values ​​were used to determine the effect of undercutting on club performance through the thinning of the face and sole. Example Club A was compared to Club B. Example Club C was compared to Club D. A control club head was similar to the Example Club Head but did not have any stress-relieving features. [Table 1] [Club A]

[0056] Club A represented a prior art golf club head lacking any stress relief features and was similar to FIG. 5. Club A, representing a conventional hollow-body golf club head, had a ballast with no undercut and did not have a cascade sole. Without the undercut, the forward portion of the sole and the ballast met at a substantially right angle. Similarly, without the cascade sole, the striking face transitioned smoothly to the forward portion of the sole.

[0057] FEA analysis was used to calculate values ​​for peak stress in the striking face of Club A, as shown in Table 1. Under an impact load of 105 mph, the peak stress in the striking face was 218,469 psi. Under the same impact load, the front portion of the striking face had a peak stress of 157,440 psi. [Club B]

[0058] Club B represented a hollow body golf club head having an undercut stress relief feature. Hollow body Club B was similar to Club A, except Club B included an undercut as a stress relief feature. The undercut allowed the forward portion of the sole to extend under the ballast rather than meeting at a right angle. The undercut in Example 1 was 0.065 inches deep, 0.083 inches high, and had undercut transition heights of 0.185 inches and 1.16 inches.

[0059] Values ​​for peak face stress, peak forward sole stress, and peak stress area were determined using FEA analysis and a simulated impact with a golf ball at 105 mph. The peak face stress was 217,117 psi, and the peak forward sole stress was 156,257 psi. Compared to Club A, the undercut reduced the peak stress in the striking face by 1,352 psi and the peak stress in the forward portion of the sole by 1,183 psi. This club demonstrated that the ballast and undercut allowed both the striking face and the forward portion of the sole to store more strain energy. This meant that Club B exhibited improved durability and improved spring response to impact loads. [Club C]

[0060] Hollow-body Club C represented a club head having only the forward portion of the sole with a cascade. Club C was similar to Clubs A and B, but had a cascade sole as a single form of stress relief. The face-to-sole transition included a first step, a second step, and a step transition between the first and second steps. The first step had a first step thickness, and the second step had a second step thickness that was less than the first step thickness. The step transition was sloped to provide a gradual transition from the first step thickness to the second step thickness. This example did not have an undercut, and the forward portion of the sole and the ballast met at a substantially right angle.

[0061] Referring again to Table 1, the hollow body golf club head of Example 2 had a peak face stress of 213,311 psi, or a reduction in peak stress of 5,158 psi in the striking face. The club of Example 2 had a peak forward sole stress of 154,742 psi (pounds per square inch), or a reduction in peak forward sole stress of 2,698 psi. This example demonstrated that the Cascade Sole reduced stress through increased strain energy storage, resulting in improved durability and spring response under impact loads. [Club D]

[0062] Club D (shown in FIG. 6) featured an undercut and a cascade sole as two forms of stress relief for the striking face and forward sole portion. The ballast included an undercut, which effectively lengthened the forward sole portion below the ballast. The cascade sole included a first step, a second step, and a step transition between the first and second steps. The first step had a first step thickness, and the second step had a second step thickness that was less than the first step thickness. The step transition was sloped to provide a gradual transition from the first step thickness to the second step thickness.

[0063] Club D was also subjected to FEA analysis under simulated ball impact at 105 mph. The peak face stress was 209,851 psi, resulting in a peak stress reduction in the striking face of 8,618 psi. In other words, Club D experienced a 4% reduction in peak stress within the striking face. The peak stress in the forward sole section was 154,689 psi. The forward sole section experienced a peak stress reduction of 3,480 psi, or a 2.2% reduction from Club A. This example demonstrated that the undercut and cascade sole worked together to reduce peak stress. Furthermore, this example demonstrated that the forward portion of the sole can tolerate additional load without reaching fatigue failure. This example demonstrated that improving ball speed is possible by thinning the face and sole to match the load capacity of the forward sole section.

[0064] The peak stresses in the forward sole portion of each of these club heads specifically indicated the potential for adjusting the thickness of the sole and face and the resulting change to ball speed. The peak stresses in the forward sole portion were compared to the critical K-yield stress value of the forward sole portion. Stresses that indicated the striking face and sole had to be thickened indicated that an internal void configuration would have reduced ball speed. Stresses that indicated the striking face and sole could be thinned indicated that an internal void configuration would have increased ball speed.

[0065] Club A and Club B were compared against a limiting K value of 156 ksi. The peak stress of Club A, which did not have an undercut, was 158,169 psi. This peak stress value suggested that the sole and face would have needed to be thickened by approximately 2.5% to achieve a stress value not exceeding 156 ksi. The thickened face and sole indicated that an internal void configuration would reduce ball speed. Club B, which had an undercut, improved the peak stress in the forward sole portion. Club B had a peak stress of 156,868 psi. The lower peak stress of Club B indicated that Club B did not require as much thickening of the sole and face as Club A's sole and face. These results indicated that after the modifications, Club B and the undercut exhibited better ball speed than Club A, which did not have an undercut.

[0066] Similarly, Club C and Club D were compared against the same critical K value of 156 ksi. Club C, which had a cascade sole and no undercut, had a peak stress of 155,416 psi. Club C's peak stress was slightly below the critical K stress, indicating that no modifications would be necessary to improve or reduce ball speed. The slightly lower peak stress indicated that the cascade sole in Club C would have increased durability. Club D, which had an undercut in addition to the cascade sole, had a peak stress of 154,689 psi. Club D indicated that the undercut provided a further reduction in peak stress. This reduction in stress indicated that Club D had a face and sole that could tolerate thinning to improve ball speed.

[0067] Comparisons of Club A and Club B, and Club C and Club D, showed that the undercut reduced the peak stress within the forward portion of the sole. These results further demonstrate that undercuts can be applied to hollow body golf club heads to improve ball speeds by utilizing stress reduction to thin the face and sole. [Example 2: Performance of a club having an undercut]

[0068] In a second example, the performance benefits of the undercut were examined using player testing of actual clubs. In this example, a 7-iron with an undercut was compared to a structurally similar 7-iron lacking the undercut. The sole and face of the 7-iron with the undercut were optimized to reduce thickness. Over 700 shots were hit with each golf club, and ball speed, launch angle, and spin rate were analyzed.

[0069] Figure 7 compares the average ball speed of a 7 iron with an undercut to a 7 iron without an undercut. The average ball speed of the iron with the undercut was 119.7 mph. The average ball speed of the iron without the undercut was 118.7 mph. Figure 8 compares the average vertical launch angle of a 7 iron with an undercut to a 7 iron without an undercut. This data shows that the 7 iron with the undercut and the 7 iron without the undercut have substantially similar launch angles. Figure 9 compares the average spin rate of the same 7 iron with an undercut to a 7 iron without the undercut. The 7 iron without the undercut had an average spin rate of 6079.9 rpm. The 7 iron with the undercut had a reduced average spin rate of 5990.6 rpm.

[0070] Finally, the statistical area (data not shown) of the 7 iron with undercut was compared with that of the 7 iron without undercut. The statistical area data was used to determine the consistency of each golf club head by plotting shot distance according to left and right deviation from a straight shot. The 7 iron without undercut had a distance deviation of 20 m, while the 7 iron with undercut had a distance deviation of 14 m. This data showed that the undercut 7 iron produced shots with more consistent distance.

[0071] The player results for Example 2 highlighted the performance benefits of the undercut. Specifically, the data showed that the undercut reduced spin on low-loft golf club heads, such as a 7-iron, while improving ball speed and resulting in improved distance. Reducing spin on low-loft golf clubs is desirable due to distance requirements and expectations for longer, lower-loft golf clubs. This example also highlighted a tighter statistical area for the irons with the undercut, indicating that the undercut irons performed more consistently for distance. [Example 3: Wet condition performance and dry condition performance due to undercut]

[0072] In a third example, actual player club testing was used to examine the performance benefits of the undercut under varying turf conditions. In this example, a pitching wedge with an undercut was compared to a similar pitching wedge lacking the undercut. Each golf club was hit in wet and dry conditions, and average launch angle, spin rate, and ball speed were measured.

[0073] Figure 10 compares the launch angles of wedges with and without undercuts in both wet and dry conditions. The wedges with undercuts had an average launch angle of 24.0 degrees in dry conditions and 24.5 degrees in wet conditions. The wedges without undercuts had an average launch angle of 23.6 degrees in dry conditions and 25.1 degrees in wet conditions. Therefore, the launch angles of the wedges with and without undercuts were comparable in wet conditions.

[0074] Figure 11 compares the spin rates of the same wedge with an undercut and a wedge without an undercut in both wet and dry conditions. The wedge with the undercut had an average spin rate of 8617 rpm (revolutions per minute) in dry conditions and 8031 ​​rpm in wet conditions. The wedge without the undercut had an average spin rate of 8310 rpm and 7144 rpm in wet conditions. Thus, the wedge with the undercut increased spin rate and provided better turf interaction in both wet and dry conditions relative to the undercut wedge.

[0075] Figure 12 compares the ball speeds of wedges with and without undercuts. The wedges with undercuts had an average ball speed of 97.3 miles per hour (mph) in dry conditions and 96.9 mph in wet conditions. The wedges without undercuts had an average ball speed of 97.4 mph in dry conditions and 96.9 mph in wet conditions. The ball speeds for the wedges with and without undercuts were comparable in both wet and dry conditions.

[0076] The above data showed that pitching wedges with undercuts performed more consistently than wedges without undercuts in variable turf conditions. The launch angle of the wedges with undercuts varied by only 0.5 degrees between wet and dry conditions, while the wedges without undercuts had a launch angle of 1.5 degrees. This data showed that the launch angle of the wedges without undercuts varied three times more than the wedges with undercuts. Similarly, the spin rate of the ball produced by the wedges with undercuts was more consistent than that of wedges without undercuts. The spin rate varied by only 586 rpm between dry and wet conditions for the wedges with undercuts, while it varied by 1166 rpm between dry and wet conditions for the wedges without undercuts. Consistent spin rates in wet and dry conditions are preferred for undercut wedges because the purpose of wedge-type golf clubs is to provide consistent ball delivery on the green regardless of weather conditions. The ball speeds for the wedges with and without undercuts were substantially similar.

[0077] Because the Rules of golf change from time to time (new Rules may be adopted, or old Rules may be repealed or modified, by golf standards organizations and / or governing bodies), golf equipment related to the methods, apparatus, and / or products described herein may or may not conform to the Rules of golf at any particular time. Accordingly, golf equipment related to the methods, apparatus, and / or products described herein may be advertised, offered for sale, and / or sold as conforming or non-conforming golf equipment. The methods, apparatus, and / or products described herein are not limited in this respect.

[0078] Although a particular order of acts is described above, these acts may be performed in other chronological orders. For example, multiple acts described above may be performed sequentially, in parallel, or simultaneously. Alternatively, multiple acts may be performed in the reverse order. Furthermore, one or more acts described above may not be performed at all. The apparatus, methods, and articles of manufacturing described herein are not limited in this respect.

[0079] While this invention has been described in terms of various embodiments, it will be understood that the invention is capable of further modifications. It will be understood that this application does not include any variation, use, or adaptation of the invention described below, generally The present invention is not limited to the principles of the present invention and is not intended to be limiting unless otherwise specified. This includes deviations from the present disclosure within the scope of the present disclosure.

Claims

1. A golf club head, a hollow body defining a sealed interior cavity; The body The striking face and The heel part and a toe portion opposite the heel portion; a sole having a forward sole portion and a rearward sole portion; a solid ballast extending substantially from the heel region to the toe region, the solid ballast region having a ballast top surface, a ballast forward surface, and a ballast bottom surface; The top rail and a rear portion of the internal void extending away from the striking face between the top rail and the sole; It is equipped with the ballast bottom surface is contoured toward the rear portion to define an undercut; The undercut is a bottom edge; a top edge; an undercut joint; A heel end portion; A toe end portion, a face depth of 0.300 inches, measured as the perpendicular distance between the face surface and the undercut junction; an undercut height, measured as the distance between the bottom edge of the undercut and the top edge of the undercut, of between 0.080 inches and 0.090 inches; An undercut volume of 0.018 cubic inches, It has The golf club head, wherein the undercut is configured to relieve stress at the forward sole portion by between 1000 psi and 2000 psi.

2. 2. The golf club head of claim 1, wherein the undercut further has an undercut length measured as the distance between the heel end and the toe end, the undercut length being between 1.00 inches and 1.25 inches.

3. 2. The golf club head of claim 1, wherein the sole comprises a forward portion and a rearward portion, and the undercut has a depth of 0.065 inches and extends the length of the forward portion by between 7% and 8%.

4. 2. The golf club head of claim 1, further comprising a cascade sole, the cascade sole comprising an interior transition region from the striking face to the sole, the interior transition region comprising a first step having a first thickness, a second step having a second thickness different from the first thickness, and a step transition region between the first step and the second step.

5. The golf club head of claim 5 , wherein the inner transition region further comprises a third step.

6. The golf club head of claim 6 , wherein the step transition is linearly tapered at an angle of less than 45 degrees.

7. The golf club head of claim 6 , wherein the step transition is linearly tapered at an angle ranging between 10 degrees and less than 45 degrees.

8. 2. The golf club head of claim 1, wherein the undercut depth between the ballast forward face and said undercut junction ranges from 0.010 inches to 0.100 inches.

9. 2. The golf club head of claim 1, wherein an undercut face depth measured perpendicularly between the inner surface of the striking face and the undercut junction ranges from 0.200 inches to 0.500 inches.

10. CG depth of 0.096 inches, MOI Ixx ranging from 95 g cm ２ From 130 g cm ２ and the heel-to-toe moment of inertia Iyy can be in the range of 350 g cm ２ From 420 g cm ２ The golf club head of claim 1 , wherein the range of the axial length of the club head is between 100 and 120 mm.

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