KR102596131B1 - Improved iron type golf club head - Google Patents

Abstract

An iron golf club head is disclosed that achieves improved performance through a specific effective stiffness area ratio between the perimeter of the iron golf club head and the face of the iron golf club head. More specifically, the present invention discloses a golf club head, wherein the iron golf club head comprises a specific iron golf club that results in an effective stiffness area ratio of about 4.5 to 5.5 and a coefficient of restitution value that varies depending on the effective stiffness area ratio. The head chassis has a variable face profile.

Description

Improved iron type golf club head {IMPROVED IRON TYPE GOLF CLUB HEAD}

Cross-reference to related applications

This application claims the benefit of U.S. Provisional Patent Application No. 63/065,310, filed August 13, 2020, the disclosure of which is incorporated by reference in its entirety.

Overall, the present application provides an effective stiffness area of a certain ratio between the boundary of the iron golf club head and the face of the iron golf club head and also achieves an improved Coefficient of Restitution. It relates to an improved iron type golf club head. More specifically, the present invention relates to the integration of iron golf clubs with variable face profiles into specific iron golf club head chassis resulting in an effective stiffness area ratio of about 4.5 to 5.5 and a coefficient of restitution in accordance with the effective stiffness area ratio described above. It's about.

Iron golf club heads, similar to their wood counterparts, have benefited significantly from technological advancements taking place in the industry. Although, visually, modern metalwood looks more different than persimmon wood when comparing a modern hollow iron to a traditional mashie or niblick, the technological advancements are perhaps groundbreaking. will be.

U.S. Patent No. 4,826,172 to Antonious teaches a perimeter weighted iron-type golf club head with a recessed or cavity back and a peripheral mass having an improved weight configuration formed by a weight member within the cavity, comprising: Describes one of the previous advancements in iron golf club head design and technology. Moving the golf club head mass to the perimeter to create a cavity back allows the golf club head to be more forgiving of off center shots.

US Patent No. 5,362,047 to Shaw et al. describes another previous example of improving the performance of an iron type golf club head, wherein the thickness of the face-piece is determined from the toe of the head of at least one iron of the set. Increased to the heel and increased from heel to toe in at least one other iron in the set. Varying the thickness of the face-piece can further improve the performance of a golf club head by reducing material from portions of the striking face that do not need material.

Kosmatka's U.S. Patent No. 5,971,868 describes a golf club head face such that areas of the face that are subjected to approximately similar loads resulting from the application of a particular force have approximately similar thicknesses, such that stresses are approximately uniform upon application of similar forces. Other previous attempts to create a contoured back surface of the golf club shown with a surface of varying thickness are described to result in .

Takeda's U.S. Patent No. 6,200,228 provides a golf club head in which a cavity is formed in the rear surface, a back member securely fits within the cavity, and the bodies are in intimate contact with each other. This backing allows for increased head strength and allows the head to be improved so that the face thickness can be made thinner.

Most recently, U.S. Patent No. 7,169,057 to Wood et al. discloses an iron golf club head having a hollow inner portion formed from two different casings, with the thickness and hardness of the first casing varying between long and short iron golf club heads. do.

Such technology has improved the design of iron-type golf club heads, progressively moving away from the traditional muscle back configuration toward a more cavity-like rear end and hollow cavity type configuration, as described by the aforementioned patent. As they become more advanced, and as the striking faces of iron-type golf club heads become thinner; An opportunity arises to further improve the performance of the hitting face of that type of golf club head.

Accordingly, based on the foregoing, there is a need in the art to develop improved iron type golf club heads that can utilize new modern club head chassis designs. More specifically, there are many opportunities to design a golf club head with a striking face of variable thickness depending on the current club head chassis, thereby creating a golf club head of optimal performance.

One aspect of the invention is an iron golf club head comprising a front portion having a striking face defining a face height (H _Face ), the striking face further comprising a substantially planar front surface and a non-planar rear surface. do. The non-planar rear surface of the striking face forms a VFT profile, which further includes a thick central portion, a transition portion, and a thin peripheral portion. The thin peripheral portion forms the face thickness (T _Face ), and the thick central portion forms the VFT height (H _VFT ) and VFT thickness (T _VFT ). The iron golf club head also includes a body portion attached to the rear portion of the front portion. The iron golf club head forms a boundary height (H _Boundary ) and a boundary thickness (T _Boundary ), and the iron golf club head has an ESA ratio of approximately 4.5 to 5.5, with the ESA ratio defined as:

,

A golf club head has a COR defined by the following relationship;

Another aspect of the invention is an iron golf club head comprising a front portion having a striking face defining a face height H _Face , the striking face further comprising a substantially planar front surface and a non-planar rear surface. do. The non-planar rear surface of the striking face forms a VFT profile, which further includes a thick central portion, a transition portion, and a thin peripheral portion. The thin peripheral portion forms the face thickness (T _Face ), and the thick central portion forms the VFT height (H _VFT ) and VFT thickness (T _VFT ). The iron golf club head also includes a body portion attached to the rear portion of the front portion. The iron golf club head has a boundary height (H _Boundary ) of about 35 mm to about 40 mm and a boundary thickness (T _Boundary ) of about 18 mm to about 24 mm, and the iron golf club head has an ESA ratio of about 4.5 to 5.5. , and the ESA ratio is defined as follows:

,

A golf club head has a COR defined by the following relationship;

Another aspect of the invention is an iron golf club head comprising a front portion having a striking face defining a face height H _Face , the striking face further comprising a substantially planar front surface and a non-planar rear surface. do. The non-planar rear surface of the striking face forms a VFT profile, which further includes a thick central portion, a transition portion, and a thin peripheral portion. The thin peripheral portion forms the face thickness (T _Face ), and the thick central portion forms the VFT height (H _VFT ) and VFT thickness (T _VFT ). The iron golf club head also includes a body portion attached to the rear portion of the front portion. The iron golf club head forms a boundary height (H _Boundary ) of about 35 mm to about 40 mm and a boundary thickness (T _Boundary ) of about 18 mm to about 24 mm. An iron golf club head has an ESA _Boundary of about 380 mm ² to about 420 mm ² , where the ESA _Boundary is defined as follows;

These and other features, aspects and advantages of the present invention will be better understood upon reference to the following drawings, description and claims.

The above and other features and advantages of the present invention will become apparent from the following description of the invention illustrated in the accompanying drawings. The accompanying drawings, which are included in and form a part of the specification, further serve to illustrate the principles of the invention and to enable those skilled in the art to make and use the invention.
Figure 1 of the accompanying drawings shows a rear view of a golf club head according to an exemplary embodiment of the present invention.
Figure 2 of the accompanying drawings shows a rear view of a golf club head according to an exemplary embodiment of the invention, with the support member removed.
Figure 3 of the accompanying drawings shows a rear cross-sectional view of a golf club head according to an exemplary embodiment of the present invention.
Figure 4 of the accompanying drawings shows a cross-sectional view of a golf club head according to an exemplary embodiment of the invention, taken along cross-section line 4-4' shown in Figure 3.
Figure 5 of the accompanying drawings shows a cross-sectional view of a golf club head according to an exemplary embodiment of the invention, taken along the cross-section line 5-5' shown in Figure 3.
Figure 6 of the accompanying drawings shows a toe side view of a golf club head according to an exemplary embodiment of the present invention.
Figure 7 of the accompanying drawings shows a plot showing the relationship between ESA ratio and COR of a golf club head for the present invention along with a prior art golf club.

The following detailed description describes the mode of implementation of the invention that is currently considered optimal. Since the scope of the invention is best defined by the appended claims, the description should not be taken in a limiting sense, but is prepared solely to illustrate the general principles of the invention.

Various inventive features are described below, each of which may be used independently of one another or in combination with other features. However, any one inventive feature may not solve any or all of the foregoing problems, or may solve only one of the foregoing problems. Additionally, one or more of the foregoing problems may not be completely solved by any of the features described below.

Figure 1 of the accompanying drawings shows a rear view of a golf club head 100 according to an exemplary embodiment of the present invention. Golf club head 100 generally has a toe end 102, a heel end 104, a top line 106, and a sole of the golf club head 100 that are common in iron type golf club heads 100. )(108) may have a part. In addition to illustrating these common features and techniques, Figure 1 of the accompanying drawings also shows a portion of the hosel 110 of a golf club head, relative to which a shaft (not shown) is coupled. It is composed.

One feature worth noting here is that Figure 1 of the accompanying drawings shows a golf club head 100 of the cavity back type, with a rear opening 112 located in the rear portion of the golf club head 100. It means doing it. The cavity back type golf club head 100 provides greater forgiveness compared to a conventional blade type golf club head because the weight is moved to the circumference of the golf club head 100. In addition to providing greater forgiveness, cavity back type golf club heads 100 are also often used by creating a “face mode” that can provide a greater coefficient of restitution (COR). Improves the standard blade type golf club head by providing the opportunity to improve ball speed.

As players of larger handicaps require greater forgiveness, modern golf clubs have fully embraced this cavity back technology, although this type of cavity back iron type golf club head has previously been associated with golfers of larger handicaps. did. In fact, modern golf players, regardless of handicap and even tour players, often carry cavity back irons in their bags, especially in the case of long irons; This is because these clubs have been transformed into very playable golf clubs that offer advantages to all types of players.

As more and more effort was put into engineering these types of designs, these clubs developed deeper and more complete cavities, even leading to the creation of completely hollow body structures. In these types of performance-driven platforms for iron-type golf club heads, the trend toward increasingly thinner striking faces typically requires pairing them with increasingly stronger materials. In irons, this type of thinner face, combined with being made from stronger materials, typically results in a stronger face, especially when integrated into the chassis to provide larger "face mods" such as fuller cavity backs and hollow body configurations. The greater the face deflection, the greater the COR, all of which have the undesirable effect of increased stresses.

Therefore, one of the main objectives of the present invention is to balance performance needs by taking full advantage of the "face mode" created from the chassis that can benefit from such advantages, while fully managing the increased stresses associated with that design. To create a high-performance iron-type golf club head 100.

To achieve the goal of reducing the stress of these thin-faced iron golf club heads with a large unsupported area of the face creating a "face mode", the present invention provides a variable face thickness at the rear surface of the striking face 111. (VFT) profile 114 is used. VFT profile 114 may generally consist of a thick central portion, a transition region, and a thin perimeter. The thick central portion, in this present exemplary embodiment of the invention, may have a generally constant thickness. The thin perimeter may, on the other hand, also have a taper, although it generally also has a constant thickness. A rear view of the golf club head 100 shown in FIG. 1 is shown as a finished product and has a support member 120 contacting the rear portion of the VFT profile 114. To better illustrate the VFT profile 114, support member 120 has been removed to provide Figure 2 of the accompanying drawings.

2 of the accompanying drawings shows a golf club head 200 according to an exemplary embodiment of the present invention, with a support member (shown at 120, removed from FIG. 1) for clearer illustration of the VFT profile 214. A rear view is shown. First, it can be immediately seen that the VFT profile 214 includes two more sub-components that were previously described. More specifically, the VFT profile 214 further includes a thick central portion 214a and a transition portion 214b.

The thin peripheral portion 216 of the striking face 111 shown in FIG. 2 (previously shown in FIG. 1) also attaches to three sub-components, e.g., the heel 204 of the golf club head 200. a heel circumference portion 216a positioned proximately, a toe circumference portion 216c positioned proximate the toe 202 of the golf club head 200, and between the heel circumference portion 216a and the toe circumference portion 216c. It may be separated into a juxtaposed central peripheral portion 216b. In a preferred embodiment of the invention, the entirety of peripheral portions 216a, 216b, and 216c may be continuously tapered from the toe peripheral portion 216c toward the heel peripheral portion 216a, with the toe peripheral portion 216c It is thickest and the heel circumference part (216a) is the thinnest. However, in alternative embodiments of the present invention, this tapering need not be constant, but rather within the toe peripheral portion 216c, a central peripheral portion ( It may be present only within 216b), within heel perimeter portion 216a, or any combination thereof. In other words, it can be said that the toe portion of the peripheral portion is thicker than the heel portion of the peripheral portion. In further alternative embodiments of the present invention, all of the peripheral portions 216a, 216b, and 216c may be of the same thickness, without departing from the scope and content of the present invention.

Accordingly, when viewed as a whole of striking face 211, golf club head 200 has a variable thickness profile 214, which has two sub-components: It can be said to have a thick central portion 214a with the thickest thickness, and a transition portion 214b with variable thickness transitioning from the thick central portion 214a to the peripheral portions 216a, 216b, and 216c. Peripheral portions 216a, 216b, and 216c may, in preferred embodiments, be generally thicker at the toe than at the heel and may gradually taper throughout. To achieve this, without departing from the scope and spirit of the present invention, the heel perimeter portion 216a may be flat or tapered, the center perimeter portion 216b may be flat or tapered, and the toe perimeter portion 216c may be flat or tapered. It may be flat or tapered; Or any combination thereof may be used. Finally, in alternative embodiments of the present invention, the entirety of the peripheral portions 216a, 216b, and 216c may be constant, as described above, and without departing from the scope and content of the present invention.

To provide a clearer view of the various dimensions of the variable thickness profile 214, a cutaway view of the golf club head 200 is provided with the rear portion of the golf club head 200 removed. Figure 3 of the accompanying drawings shows an enlarged cutaway view of a golf club head 300 according to an exemplary embodiment of the present invention, allowing certain additional features to be highlighted.

First, in this cutaway view of the golf club head 300 shown in FIG. 3, the variable thickness profile 314 can be seen more clearly. The thick central portion 314a shown in FIG. 3 allows its dimensions to be identified, as these dimensions are important to the performance of the golf club head 300 itself. In this embodiment of the invention, thick central portion 314a may have a width W _VFT of about 15 mm to about 35 mm, more preferably about 20 mm to about 30 mm, and most preferably about 26 mm. there is. The thick central portion 314a may have a height (H _VFT ) of about 10 mm to about 27 mm, more preferably about 15 mm to about 22 mm, and most preferably about 18 mm. Figure 3 also shows the center point 333 of the thick central portion 314a.

In addition to the dimensions of the thick central portion 314a, Figure 3 of the accompanying drawings also shows the distance H _Face corresponding to the height of the striking face 311 at the center of the face. The height of striking face 311, as indicated by the distance H _Face , may be about 50 mm to about 54 mm, more preferably about 51 mm to about 53 mm, and most preferably about 52 mm.

Finally, Figure 3 of the accompanying drawings also identifies two specific points within the thick central portion 314a, the maximum stress location 332 and the maximum deflection location 334. In the present invention, it is important that the thick central portion 314a includes both the maximum stress location 332 and the maximum deflection location 334, since these locations generally approximate the locations where the greatest stress occurs. This is because it is possible to take advantage of the increased material thickness associated with the thick central portion 314a. As referred to in this embodiment of the invention, maximum deflection location 334 generally refers to a point that coincides with a hotspot on the face, which hotspot also coincides with the face geometry of golf club head 300. It is the center. The maximum deflection position 334 can generally be determined by physical measurement of the geometric center of the face of the golf club head 300. Alternatively, this position can be determined using modal analysis to try and capture the maximum deflection position, based on a prediction of the actual deflection expected to occur upon impact of the golf club head 300 with the golf ball. It can be decided through The maximum stress location 332, on the other hand, generally occurs at a location immediately behind the impact location with the golf ball. This position is generally slightly towards the heel of the maximum deflection position 334 and slightly lower than the maximum deflection position 334 on the face. This location is generally assumed to be at the midpoint of the scoreline in the heel-to-toe direction, approximately 15 mm or less from the leading edge of the golf club head 300. Once again, it is necessary to reiterate here that the thick central portion 314a, which contains both the maximum stress location 332 and the maximum deflection location 334, is important to the present invention when colliding with a golf ball. , because all of these locations experience greater stress than the rest of the face, and the increased thickness of the thick central portion 314a actually helps the durability of the golf club head 300.

Figure 4 of the accompanying drawings shows a cross-sectional view of the golf club head 300 shown in Figure 3, as shown by cross-section line 4-4'. This cross-sectional view allows the thickness of the striking face 411 to be seen more clearly. In this view, it can be seen that striking face 411 has a substantially planar front surface and a non-planar rear surface, creating a VFT profile. More specifically, the VFT profile consists of a thick central portion 414a transitioning to a peripheral portion 416c, as described above. The thick central portion 414a according to this exemplary embodiment of the invention has a thickness ( _T ) can have. Because this cross-sectional view of golf club head 400 is taken along cross-sectional line 4-4' shown in FIG. 3 located in the central portion of golf club head 400, the peripheral portion thickness shown here is substantially This is the thickness of the central peripheral portion 416b. The central peripheral portion 416b, located both above and below the thick central portion 414a, generally has a thickness of about 1.6 mm to about 2.0 mm, more preferably about 1.7 mm to about 1.9 mm, and most preferably about 1.8 mm. You can have (T _Face ). Additionally, the transition region 414b located above and below the thick central portion 414a gradually tapers in thickness from the thick central portion 414a toward the thickness of the central peripheral portion 416b.

Figure 5 of the accompanying drawings shows a cross-sectional view of the golf club head 500 taken along the cross-section line 5-5' shown in Figure 3. This cross-sectional line is taken along the toe portion of the golf club head 300 at the point representing the highest face height value. Therefore, by not having a reference point from the side view, it can be seen that the H _Face , as described above in Figure 3, together with this cross-sectional view, does not provide all the information needed in Figure 3 to provide an accurate measurement. . More specifically, the face height distance (H _Face ) is measured along the loft of the golf club head 500 parallel to the striking face and not parallel to the ground plane, as Figure 3 appears to have initially suggested. do. Obtaining an accurate definition for measuring the face height distance (H _Face ) is an important parameter in the determination of the effective boundary stiffness area (ESA) of the face (ESA _Face ), which is important in the present invention. ESA _Face , according to the present invention, is defined by the following equation (1):

Based on Equation (1), the golf club head 500 according to an exemplary embodiment of the present invention has a size of about 80 mm ² to about 110 mm ² , more preferably about 90 mm ² to about 100 mm ² , most Preferably, it may have an ESA _Face of about 95 mm ² .

FIG. 6 of the accompanying drawings shows a toe side view of a golf club head 600 according to an exemplary embodiment of the present invention, allowing the overall size of the golf club head 600 to be confirmed. Figure 6 further identifies additional dimensions and measurements that are important in determining the ESA _Boundary . Finally, a golf club according to the present invention will have a specific ESA _Face to ESA _Boundary ratio. First and foremost, Figure 6 of the accompanying drawings shows a golf club with the height of the chassis, defined as H _Boundary , measured from the top of the golf club head 600 to the bottom of the club head 600 at the address position. shows. Golf club head 600 can generally have an H _Boundary of about 35 mm to about 40 mm, more preferably about 36 mm to about 39 mm, and most preferably about 37 mm to about 38 mm. Once the H _Boundary is determined, the geometric center 634 of the face, at least up to the face, can be determined by dividing the H _Boundary distance by 2. Once the center of the face 634 is determined, the thickness of the chassis boundary (T _Boundary ) can be determined by measuring backward from the center of the face 634 at an angle perpendicular to the angle of the striking face itself. The T _Boundary as shown in this present exemplary embodiment may generally be from about 18 mm to about 24 mm, more preferably from about 19 mm to about 23 mm, and more preferably from about 20 mm to about 22 mm.

Once the values for H _Boundary and T _Boundary are obtained, ESA _Boundary can be calculated based on equation (2) below:

Based on Equation (2), the golf club head 600 according to an exemplary embodiment of the present invention has a size of about 380 mm ² to about 420 mm ² , more preferably about 390 mm ² to about 410 mm ² , most Preferably, it may have an ESA _Boundary of about 400 mm ² .

Now, once the ESA _Face and ESA _Boundary have been defined and obtained, an ESA Ratio is generated, which represents one of the key features of the present invention, illustrating one way to quantify what face mode the golf club head 600 will experience. To do this, you can create a ratio between two numbers. The ESA ratio is defined by equation (3) below:

Golf club heads according to the present invention may have an ESA ratio generally from about 4.5 to about 5.5, more preferably from about 4.7 to about 5.3, more preferably from about 4.8 to about 5.2. Alternatively, equation (3) can be combined with equations (1) and (2) to produce a more specific definition of the ESA ratio, as seen in equation (4) below:

Figure 7 of the accompanying drawings shows a plot showing the ESA ratio versus coefficient of restitution (COR) of four different prior art clubs as well as several embodiments of the present invention. In Figure 7, shown here, the ESA ratio is plotted along the X-axis and the COR of the golf club head is plotted along the Y-axis. Focusing on three prior art golf club heads, none of the data points for these three prior art have ESA ratio values between 4.5 and 5.5; It can be seen that it has ESA ratio values of about 3.4, about 4.25, and about 4.0. Another fourth prior art data point has an ESA ratio between 4.5 and 5.5, but does not achieve a sufficiently large COR above 0.828 for a given ESA ratio value. To capture the range of increased performance achieved by the present invention, a mathematical equation is provided in Figure 7, where y ≥ 0.0196x + 0.7211. In order to apply the above-mentioned relationship to the context of the values related to the current content, the following equation (5) is provided:

Combining these descriptions, it can be said that the golf club head of the present invention has an ESA ratio of about 4.5 to about 5.5 and a COR value greater than 0.0196 (ESA ratio) + 0.7211.

Lastly, any discussion of thin face irons here would not be complete without acknowledging the importance of durability. The durability of a golf club is generally related to the amount of stress it experiences upon impact with a golf ball. Typically, in iron type golf club heads made from steel, the durability of the golf club deteriorates significantly at any value above about 2.2 GPa. In other words, a golf club head according to the present invention may be said to have a stress value of less than about 2.2 GPa, more preferably less than about 2.1 GPa, and most preferably less than about 2.0 GPa.

All figures, such as those for amounts of material, moments of inertia, centers of gravity, lofts, draft angles, various performance ratios, and others in the foregoing parts of the specification, other than as operating examples or unless otherwise explicitly specified. Ranges, amounts, values and percentages may be read as if preceded by the word “about” even if the term “about” is not explicitly indicated in such value, amount or range. Accordingly, unless stated to the contrary, the numerical parameters set forth in the foregoing specification and appended claims are approximate values that may vary depending on the desired properties sought to be achieved by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed to reflect the number of significant figures indicated and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters that set the broad scope of the invention are approximate values, the numerical values set forth in specific examples are written as precisely as possible. However, any numerical value inherently contains certain errors resulting from the standard deviation found in each testing measurement. Additionally, when variable ranges of numerical ranges are described herein, it is contemplated that any combination of such values, including the recited values, may be used.

Of course, it is to be understood that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the scope and content of the invention as set forth in the claims below.

Claims (20)

Iron golf club heads include:
A frontal portion having a striking face forming a face height (H _Face ),
The striking face further comprises a planar front surface and a non-planar rear surface,
the non-planar rear surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transition portion, and a thin peripheral portion;
The thin peripheral portion forms the face thickness (T _Face ),
a frontal portion, wherein the thick central portion defines a VFT height (H _VFT ) and a VFT thickness (T _VFT );
comprising a body portion attached to a rear portion of the front portion,
The iron golf club head forms a boundary height (H _Boundary ) and a boundary thickness (T _Boundary ),
The iron golf club head has an ESA ratio of 4.5 to 5.5, and the ESA ratio is defined as follows,
, and
The golf club head has the following relational formula

An iron golf club head with a COR defined by . According to paragraph 1,
The iron golf club head has an ESA _Face of 80 mm ² to 110 mm ² , and the ESA _Face is

Defined as: iron golf club head. According to paragraph 2,
An iron golf club head with an ESA _Face of 90 mm ² to 100 mm ² . According to paragraph 3,
An iron golf club head with an ESA _Face of 95 mm ² . According to paragraph 2,
The iron golf club head has an ESA _Boundary of 380 mm ² to 420 mm ² , and the ESA _Boundary is

Defined as: iron golf club head. According to clause 5,
An iron golf club head where the ESA _Boundary is 390 mm ² to 410 mm ² . According to clause 6,
An iron golf club head with an ESA _Boundary of 400 mm ² . According to paragraph 1,
The thick central portion has a VFT thickness (T _VFT ) of 1.9 mm to 2.3 mm, a VFT height (H _VFT ) of 10 mm to 27 mm, and a VFT width (W _VFT ) of 15 mm to 35 mm. Golf club head. According to clause 8,
An iron golf club head wherein the VFT thickness (T _VFT ) is 2.0 mm to 2.2 mm, the VFT height (H _VFT ) is 15 mm to 22 mm, and the VFT width (W _VFT ) is 20 mm to 30 mm. According to clause 9,
An iron golf club head wherein the VFT thickness (T _VFT ) is 2.1 mm, the VFT height (H _VFT ) is 18 mm, and the VFT width (W _VFT ) is 26 mm. Iron golf club heads include:
A frontal portion having a striking face forming a face height (H _Face ),
The striking face further comprises a planar front surface and a non-planar rear surface,
the non-planar rear surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transition portion, and a thin peripheral portion;
The thin peripheral portion forms the face thickness (T _Face ),
a frontal portion, wherein the thick central portion defines a VFT height (H _VFT ) and a VFT thickness (T _VFT );
comprising a body portion attached to a rear portion of the front portion,
The iron golf club head forms a boundary height (H _Boundary ) of 35 mm to 40 mm and a boundary thickness (T _Boundary ) of 18 mm to 24 mm,
The iron golf club head has an ESA ratio of 4.5 to 5.5, and the ESA ratio is defined as follows,
, and
The golf club head has the following relational formula

An iron golf club head with a COR defined by . According to clause 11,
An iron golf club head wherein the boundary height (H _Boundary ) is 36 mm to 39 mm, and the boundary thickness (T _Boundary ) is 19 mm to 23 mm. According to clause 12,
An iron golf club head wherein the boundary height (H _Boundary ) is 37 mm to 38 mm, and the boundary thickness (T _Boundary ) is 20 mm to 22 mm. According to clause 13,
The iron golf club head has an ESA _Boundary of 380 mm ² to 420 mm ² , and the ESA _Boundary is

Defined as: iron golf club head. According to clause 14,
An iron golf club head where the ESA _Boundary is 390 mm ² to 410 mm ² . According to clause 15,
An iron golf club head with an ESA _Boundary of 400 mm ² . Iron golf club heads include:
A frontal portion having a striking face forming a face height (H _Face ),
The striking face further comprises a planar front surface and a non-planar rear surface,
the non-planar rear surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transition portion, and a thin peripheral portion;
The thin peripheral portion forms the face thickness (T _Face ),
a frontal portion, wherein the thick central portion defines a VFT height (H _VFT ) and a VFT thickness (T _VFT );
comprising a body portion attached to a rear portion of the front portion,
The iron golf club head forms a boundary height (H _Boundary ) of 35 mm to 40 mm and a boundary thickness (T _Boundary ) of 18 mm to 24 mm,
The iron golf club head has an ESA _Boundary of 380 mm ² to 420 mm ² , and the ESA _Boundary is

Defined as: iron golf club head. According to clause 17,
An iron golf club head where the ESA _Boundary is 390 mm ² to 410 mm ² . According to clause 18,
An iron golf club head with an ESA _Boundary of 400 mm ² . According to clause 19,
The thick central portion has a VFT thickness (T _VFT ) of 1.9 mm to 2.3 mm, a VFT height (H _VFT ) of 10 mm to 27 mm, and a VFT width (W _VFT ) of 15 mm to 35 mm. Golf club head.

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