KR20220021429A - Improved iron type golf club head - Google Patents

Abstract

Disclosed is an iron golf club head that achieves improved performance through the area ratio of a specific effective stiffness between the boundary of the iron golf club head and the face thereof. More specifically, the present invention provides a golf club head, wherein the iron golf club head has a variable face profile, which can be changed to the chassis of a particular iron golf club head and results in an area ratio of a specific effective stiffness of about 4.5-5.5 and a coefficient of restitution value that is dependent on the area ratio of a specific effective stiffness.

Description

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 on August 13, 2020, the entire disclosure of which is incorporated by reference.

Overall, the present disclosure provides a method for achieving an improved Coefficient of Restitution with a certain ratio of Effective Stiffness Area between the perimeter of the iron golf club head and the face of the iron golf club head. An improved iron type golf club head. More specifically, the present invention relates to the incorporation of an iron golf club having a variable face profile into a particular iron golf club head chassis resulting in an effective stiffness area ratio of about 4.5 to 5.5 and a coefficient of restitution according to the effective stiffness area ratio described above. it's about

Iron golf club heads, like their corresponding wood golf club heads, benefit significantly from technological advances made in the industry. Although, visually, when comparing modern hollow irons to traditional mashes or niblicks, modern metalwoods look more different than persimmon woods, the technological advances are probably groundbreaking. will be.

U.S. Pat. No. 4,826,172 to Antonious teaches a circumferentially weighted iron-type golf club head having a recessed or cavity back and a peripheral mass, having an improved weight configuration formed of a weight member within a cavity, Describes one of the previous advances in iron golf club head design and technology. Circumferentially moving the golf club head mass to create a cavity bag allows the golf club head to be more forgiving of off center shots.

U.S. 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 in the set. increments from heel to toe and from heel to toe on at least one other iron in the set. Variation in the thickness of the face-piece can further improve the performance of the golf club head by reducing material from portions of the striking face that do not require material.

U.S. Pat. No. 5,971,868 to Kosmatka discloses a golf club head face such that areas of the face that are subjected to approximately similar loads from the application of a particular force have approximately similar thicknesses, such that upon application of similar forces the stresses are approximately uniform. Another previous attempt to create a contoured back surface of the depicted golf club having a surface of varying thickness is described.

U.S. Patent No. 6,200,228 to Takeda provides a golf club head in which a cavity is formed in the rear surface, a bag member securely fits within the cavity, and the body is in intimate contact with each other. This backing makes it possible to increase the strength of the head and to improve the head so that the thickness of the face can be made thinner.

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

Such technology improves the design of iron-type golf club heads, progressively toward a more cavity rear and hollow cavity-type configuration from a conventional muscle back configuration, as described by the aforementioned patent. As it evolves further, and as the hitting face of iron-type golf club heads becomes thinner; An opportunity arises to further improve the performance of the striking face of that type of golf club head.

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

One aspect of the present 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, the VFT profile further comprising a thick central portion, a transitional portion, and a thin perimeter portion. The thin perimeter 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 defines a boundary height (H _Boundary ) and boundary thickness (T _Boundary ), and the iron golf club head has an ESA ratio of about 4.5 to 5.5, the ESA ratio being defined as

,

,

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

Another aspect of the present 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, the VFT profile further comprising a thick central portion, a transitional portion, and a thin perimeter portion. The thin perimeter 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 defines 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 rate is defined as

,

,

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

Another aspect of the present 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, the VFT profile further comprising a thick central portion, a transitional portion, and a thin perimeter portion. The thin perimeter 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 defines 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 , wherein 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 foregoing and other features and advantages of the present invention will become apparent from the following description of the invention shown in the accompanying drawings. The accompanying drawings, which are incorporated in and form a part of the specification, further serve to explain the principles of the invention and to enable those skilled in the art to make and use the invention.
1 of the accompanying drawings shows a rear view of a golf club head in accordance with an exemplary embodiment of the present invention.
2 of the accompanying drawings shows a rear view of a golf club head in accordance with an exemplary embodiment of the present invention, with the support member removed.
3 of the accompanying drawings illustrates a rear cross-sectional view of a golf club head in accordance with an exemplary embodiment of the present invention.
FIG. 4 of the accompanying drawings shows a cross-sectional view of a golf club head according to an exemplary embodiment of the present invention, taken along the cross-sectional line 4-4' shown in FIG. 3 .
FIG. 5 of the accompanying drawings illustrates a cross-sectional view of a golf club head according to an exemplary embodiment of the present invention, taken along the cross-sectional line 5-5' shown in FIG. 3 .
6 of the accompanying drawings illustrates a toe side view of a golf club head in accordance with an exemplary embodiment of the present invention.
7 of the accompanying drawings shows a plot illustrating the relationship between ESA ratio and COR of a golf club head for the present invention with a prior art golf club.

DETAILED DESCRIPTION The following detailed description sets forth the presently best considered mode of implementation of the present invention. Since the scope of the invention is best defined by the appended claims, the description is not to be taken in a limiting sense, but is merely intended to explain 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, the features of any one invention may not solve any or all of the problems described above, or may only solve one of the problems described above. Also, one or more of the above problems may not be completely solved by any of the features described below.

1 of the accompanying drawings shows a rear view of a golf club head 100 in accordance with an exemplary embodiment of the present invention. Golf club head 100 is generally the sole of golf club head 100 common to toe end 102 , heel end 104 , top line 106 , and iron type golf club head 100 . ) (108) portion. In addition to illustrating these common features and techniques thereof, FIG. 1 of the accompanying drawings also shows a portion of a hosel 110 of a golf club head, to which the shaft is coupled such that a shaft (not shown) is coupled. is composed

One feature worth noting here is that FIG. 1 of the accompanying drawings shows a golf club head 100 of the cavity bag type, with a rear opening 112 located in the rear portion of the golf club head 100 . is to do The cavity bag type golf club head 100 provides greater forgiveness as compared to a conventional blade type golf club head because the weight is shifted around the golf club head 100 . In addition to providing greater forgiveness, the cavity bag type golf club head 100 also often creates a "face mode" that can provide a greater coefficient of restitution (COR). By providing an opportunity to improve the ball speed of the standard blade type of golf club head.

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

As more and more efforts were put into more sophisticated engineering of this type of design, these clubs developed deeper and more complete cavities, even leading to the creation of a completely hollow body structure. In this type of performance driven platform for iron type golf club heads, the trend towards thinner striking faces is generally required to pair with increasingly stronger materials. Thinner faces of this type in irons, especially when incorporated into a chassis that offer a larger "face mode" such as a more complete cavity back and hollow body construction, in combination with being made of stronger materials, are generally more Larger face deflection, greater COR, all with the undesirable effect of increased stress.

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

In order to achieve the goal of reducing the stress of such a thin face iron golf club head having 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 present invention, may have a generally constant thickness. The thin perimeter can also, on the one hand, also have a taper, although it also has a generally constant thickness. A rear view of the golf club head 100 shown in FIG. 1 is shown as a finished product, with a support member 120 contacting the rear portion of the VFT profile 114 . To better illustrate the VFT profile 114, the support member 120 has been removed to provide FIG. 2 of the accompanying drawings.

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

The thin perimeter portion 216 of the striking face 111 (previously shown in FIG. 1 ) shown in FIG. 2 also has three sub-components, for example the heel 204 of the golf club head 200 . Proximally positioned heel perimeter portion 216a, toe perimeter portion 216c positioned proximate toe 202 of golf club head 200, and between heel perimeter portion 216a and toe perimeter portion 216c It can be separated into a juxtaposed central perimeter portion 216b. In a preferred embodiment of the present invention, the entirety of the perimeter portions 216a, 216b, and 216c may continuously taper from the toe perimeter portion 216c towards the heel perimeter portion 216a, wherein the toe perimeter portion 216c is The thickest part and the thinnest part 216a around the heel. However, in an alternative embodiment of the present invention, this tapering need not be constant, as long as the toe-direction portion is thicker than the most heel-direction portion, within the toe perimeter portion 216c, the central perimeter portion ( 216b), within the heel perimeter portion 216a, or any combination thereof. In other words, it can be said that the toe portion of the perimeter portion is thicker than the heel portion of the perimeter 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 spirit of the present invention.

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

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. 3 of the accompanying drawings shows an enlarged, cut-away view of a golf club head 300 in accordance with an exemplary embodiment of the present invention, such that certain additional features may be emphasized.

First, in this cut-away view of the golf club head 300 shown in FIG. 3 , the variable thickness profile 314 may be more clearly identified. The thick central portion 314a shown in FIG. 3 allows its dimensions to be discernable because these dimensions are important to the performance of the golf club head 300 itself. In this embodiment of the invention, the 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. 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. 3 also shows the central point 333 of the thick central portion 314a.

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

Finally, FIG. 3 of the accompanying drawings also identifies two specific points within the thick central portion 314a, a maximum stress location 332 and a maximum deflection location 334 . In the present invention, it is important that the thick central portion 314a includes both a location of maximum stress 332 and a location of maximum deflection 334, which generally outline the locations where the greatest stresses occur. , and can benefit from the increased material thickness associated with the thick central portion 314a. As noted in this embodiment of the present invention, the position of maximum deflection 334 generally refers to a point coincident with a hotspot on the face, which hotspot is also concurrently with the geometry of the face of the golf club head 300 . is the center The maximum deflection position 334 may generally be determined by physical measurements of the geometric center of the face of the golf club head 300 . Alternatively, this position may be determined by modal analysis to try and capture the maximum deflection position, based on predictions of the actual deflection expected to occur upon impact of the golf club head 300 with a golf ball. can be determined through The maximum stress location 332, on the one hand, generally occurs at a location immediately following the impact location with the golf ball. This position is generally slightly heel-side in the maximum deflection position 334 and slightly below 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, at a location about 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 comprising both the maximum stress location 332 and the maximum deflection location 334 is important to the present invention, which is , because all of these locations are under greater stress than the rest of the face and the increased thickness of the thick central portion 314a actually aids the durability of the golf club head 300 .

FIG. 4 of the accompanying drawings shows a cross-sectional view of the golf club head 300 shown in FIG. 3, as shown by cross-sectional line 4-4'. This cross-sectional view allows the thickness of the striking face 411 to be seen more clearly. In this figure, 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 constitutes a thick central portion 414a that transitions to a perimeter portion 416c, as described above. Thick central portion 414a according to this exemplary embodiment of the present invention generally has a thickness (T _VFT ) of about 1.9 mm to about 2.3 mm, more preferably about 2.0 mm to about 2.2 mm, and most preferably about 2.1 mm. ) can have Since this cross-sectional view of the golf club head 400 is taken along the cross-sectional line 4-4' shown in FIG. 3 located in the central portion of the golf club head 400, the circumferential portion thickness shown herein is substantially The thickness of the central perimeter portion 416b. The central perimeter portion 416b positioned both above and below the thick central portion 414a is generally about 1.6 mm to about 2.0 mm thick, more preferably about 1.7 mm to about 1.9 mm thick, and most preferably about 1.8 mm thick. (T _Face ). Also, the transition region 414b positioned above and below the thick central portion 414a gradually tapers in thickness from the thick central portion 414a toward the central peripheral portion 416b thickness.

FIG. 5 of the accompanying drawings shows a cross-sectional view of the golf club head 500 taken along the cross-sectional line 5-5' shown in FIG. 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. Thus, as it does not have a reference point from the side view, it can be seen that H _Face , although described above in FIG. 3 , with this cross-sectional view, does not provide all the information needed in FIG. 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 rather than parallel to the ground plane, as FIG. 3 appears to have initially suggested. do. Obtaining an accurate definition for measuring the face height distance (H _Face ) is an important variable in the determination of the effective boundary stiffness area (ESA) of the face (ESA _Face ), which is important in the present invention. ESA _Face is, according to the present invention, defined by the following equation (1):

Based on Equation (1) above, a golf club head 500 according to an exemplary embodiment of the present invention has a thickness of from about 14 mm ² to about 25 mm ² , more preferably from about 16 mm ² to about 23 mm ² , most Preferably, it may have an ESA _Face of about 19 mm ² .

6 of the accompanying drawings depicts a toe side view of a golf club head 600 according to an exemplary embodiment of the present invention, allowing for ascertaining the overall size of the golf club head 600 . 6 further identifies additional dimensions and measurements that are important in determining the ESA _Boundary of a boundary. Finally, a golf club according to the present invention will have a specific ESA _Face to ESA _Boundary ratio. First and foremost, FIG. 6 of the accompanying drawings shows a golf club having a height of the chassis, defined as H _Boundary , measured from the upper end of the golf club head 600 to the lower end of the club head 600 at the address position. shows Golf club head 600 may generally have an H _Boundary of from about 35 mm to about 40 mm, more preferably from about 36 mm to about 39 mm, and most preferably from about 37 mm to about 38 mm. Once the H _Boundary is determined, the geometric center 634 of the face can be determined, at least up to the face, by dividing the H _Boundary distance by two. Once the center 634 of the face is determined, the thickness of the chassis boundary T _Boundary can be determined by measuring backwards from the center 634 of the face 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, more preferably from about 20 mm to about 22 mm.

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

Based on Equation (2) above, a golf club head 600 according to an exemplary embodiment of the present invention has a range from about 380 mm ² to about 420 mm ² , more preferably from 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, generate an ESA ratio, representing one of the key features of the present invention, which describes one way to quantify that the golf club head 600 will experience a face mode. To do this, we can create a ratio between two numbers. The ESA ratio is defined by the following equation (3):

Golf club heads according to the present invention may generally have an ESA ratio of from about 4.5 to about 5.5, more preferably from about 4.7 to about 5.3, and still 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 for the ESA rate, as seen in equation (4) below:

7 of the accompanying drawings shows plots showing the ESA ratio versus coefficient of restitution (COR) for several embodiments of the present invention as well as four different prior art clubs. 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, these three prior art data points do not have ESA ratio values of 4.5 to 5.5; It can be seen that they have ESA ratio values of about 3.4, about 4.25, and about 4.0. Another fourth prior art data point has an ESA ratio of 4.5 to 5.5, but does not achieve a sufficiently large COR of greater than 0.828 at a given ESA ratio value. Equation 7 is provided in FIG. 7 to capture the region of increased performance achieved by the present invention, where y to help narrow the range of previously unachieved performance values within the ESA ratio values discussed above. ≥ 0.0196x + 0.7211. In order to apply the above relation to the context of 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.

Finally, any discussion herein of thin face irons would not be complete without recognizing 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 of steel, the durability of the golf club degrades significantly at any value above about 2.2 GPa. In other words, a golf club head according to the present invention can 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 numerical values, such as for amounts of materials, moments of inertia, center of gravity, lofts, draft angles, various performance ratios, and others in the foregoing portions of the specification, other than in operating examples, or otherwise, unless explicitly specified otherwise. Ranges, amounts, values, and percentages may be read as preceded by the word “about,” even if the term “about” is not explicitly indicated for such value, amount, or range. Accordingly, unless stated to the contrary, the numerical parameters recited in the foregoing specification and appended claims are approximate values which may vary depending on the desired characteristics to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter should at least be construed in light of the recited significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting the broad scope of the invention are approximate values, the numerical values set forth in the specific examples are set forth as precisely as possible. Any numerical value, however, inherently inherently contains certain errors resulting from the standard deviation found in their respective testing measurements. Also, when numerical ranges of variable ranges are recited herein, it is contemplated that any combination of such values, inclusive of the recited values, may be employed.

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

Claims (20)

The iron golf club head is:
A frontal portion having a striking face defining a face height H _Face , comprising:
wherein the striking face further comprises a substantially planar front surface and a non-planar rear surface;
the non-planar back surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transitional portion, and a thin perimeter portion;
The thin peripheral portion forms a face thickness (T _Face ),
wherein the thick central portion forms a VFT height (H _VFT ) and a VFT thickness (T _VFT );
a body portion attached to the rear portion of the front portion;
The iron golf club head forms a boundary height (H _Boundary ) and boundary thickness (T _Boundary ),
wherein the iron golf club head has an ESA ratio of about 4.5 to 5.5, wherein the ESA ratio is defined as:

, And
The golf club head is the following relation

An iron golf club head, having a COR defined by According to claim 1,
The iron golf club head has an ESA _Face of about 14 mm ² to about 25 mm ² , wherein the ESA _Face is

Defined as an iron golf club head. 3. The method of claim 2,
wherein the ESA _Face is from about 16 mm ² to about 23 mm ² . 4. The method of claim 3,
An iron golf club head, wherein the ESA _Face is about 19 mm ² . 3. The method of claim 2,
The iron golf club head has an ESA _Boundary of about 380 mm ² to about 420 mm ² , wherein the ESA _Boundary has

Defined as an iron golf club head. 6. The method of claim 5,
wherein the ESA _Boundary is from about 390 mm ² to about 410 mm ² . 7. The method of claim 6,
wherein the ESA _Boundary is about 400 mm ² . According to claim 1,
The thick central portion has a VFT thickness (T _VFT ) of about 1.9 mm to about 2.3 mm, a VFT height (H _VFT ) of about 10 mm to about 27 mm, and a VFT width (W) of about 15 mm to about 35 mm. _VFT ), an iron golf club head. 9. The method of claim 8,
wherein the VFT thickness (T _VFT ) is from about 2.0 mm to about 2.2 mm, the VFT height (H _VFT ) is from about 15 mm to about 22 mm, and the VFT width (W _VFT ) is from about 20 mm to about 30 mm; , iron golf club head. 10. The method of claim 9,
wherein the VFT thickness (T _VFT ) is about 2.1 mm, the VFT height (H _VFT ) is about 18 mm, and the VFT width (W _VFT ) is about 26 mm. The iron golf club head is:
A frontal portion having a striking face defining a face height H _Face , comprising:
wherein the striking face further comprises a substantially planar front surface and a non-planar rear surface;
the non-planar back surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transition portion, and a thin perimeter portion;
The thin peripheral portion forms a face thickness (T _Face ),
wherein the thick central portion defines a VFT height (H _VFT ) and a VFT thickness (T _VFT );
a body portion attached to the rear portion of the front portion;
wherein the iron golf club head defines 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;
wherein the iron golf club head has an ESA ratio of about 4.5 to 5.5, wherein the ESA ratio is defined as:

, And
The golf club head is the following relation

An iron golf club head, having a COR defined by 12. The method of claim 11,
wherein the boundary height (H _Boundary ) is from about 36 mm to about 39 mm, and the boundary thickness (T _Boundary ) is from about 19 mm to about 23 mm. 13. The method of claim 12,
wherein the boundary height (H _Boundary ) is from about 37 mm to about 38 mm, and the boundary thickness (T _Boundary ) is from about 20 mm to about 22 mm. 14. The method of claim 13,
wherein the iron golf club head has an ESA _Boundary of from about 380 mm ² to about 420 mm ² , wherein the ESA _Boundary comprises:

Defined as an iron golf club head. 15. The method of claim 14,
wherein the ESA _Boundary is from about 390 mm ² to about 410 mm ² . 16. The method of claim 15,
wherein the ESA _Boundary is about 400 mm ² . The iron golf club head is:
A frontal portion having a striking face defining a face height H _Face , comprising:
wherein the striking face further comprises a substantially planar front surface and a non-planar rear surface;
the non-planar back surface of the striking face defines a VFT profile, the VFT profile further comprising a thick central portion, a transitional portion, and a thin perimeter portion;
The thin peripheral portion forms a face thickness (T _Face ),
wherein the thick central portion forms a VFT height (H _VFT ) and a VFT thickness (T _VFT );
a body portion attached to the rear portion of the front portion;
The iron golf club head defines 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,
wherein the iron golf club head has an ESA _Boundary of from about 380 mm ² to about 420 mm ² , wherein the ESA _Boundary comprises:

Defined as an iron golf club head. 18. The method of claim 17,
wherein the ESA _Boundary is from about 390 mm ² to about 410 mm ² . 19. The method of claim 18,
wherein the ESA _Boundary is about 400 mm ² . 20. The method of claim 19,
The thick central portion has a VFT thickness (T _VFT ) of about 1.9 mm to about 2.3 mm, a VFT height (H _VFT ) of about 10 mm to about 27 mm, and a VFT width (W) of about 15 mm to about 35 mm. _VFT ), an iron golf club head.

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