# Patent

## Title
Golf club head

## Abstract

A cavity back iron type club head includes a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween. The rear surface defines a striking plate rear cavity region. A perimeter support is coupled to a peripheral portion of the striking plate. The surface area of the striking surface is related to the club head loft angle by the equation SSA≧14.4(L)+2875, where SSA is the surface area of the striking surface in units of square-millimeters and L is the club head loft angle in units of degrees.

## Background
TECHNICAL FIELD
The disclosure pertains to iron type golf clubs.
BACKGROUND
The performance of golf equipment is continuously advancing due to the introduction of advanced materials to both golf clubs (irons, woods, and putters) and balls, as well as the development of innovative clubs and club designs such as high loft woods and oversize drivers. While all clubs in the golfer's bag are important, both scratch and novice golfers rely on the performance and feel of their irons for many commonly encountered playing situations.
Irons are generally configured in a set that includes clubs of varying loft, with shaft lengths and clubhead weights selected to maintain an approximately constant “swing weight” so that the golfer perceives a common “feel” or “balance” in swinging both the low irons and high irons in a set. The size of an iron's “sweet spot” is generally related to the size (i.e., surface area) of the iron's striking face, and iron sets are available with oversize club heads to provide a large sweet spot that is desirable to many golfers.
Conventional “blade” type irons have been largely displaced (especially for novice golfers) by so-called “perimeter weighted” irons, which include “cavity-back” and “hollow” iron designs. Cavity-back irons have a cavity directly behind the striking plate, which permits club head mass to be distributed about the perimeter of the striking plate, and such clubs tend to be more forgiving to off-center hits. Hollow irons have features similar to cavity-back irons, but the cavity is enclosed by a rear wall to form a hollow region behind the striking plate. Perimeter weighted, cavity back, and hollow iron designs permit club designers to redistribute club head mass to achieve intended playing characteristics associated with, for example, placement of club head center of mass or a moment of inertia.
While perimeter-weighted designs offer more design possibilities than blade type designs, perimeter weighting can result in clubs with an undesirable “feel.” In addition, even with perimeter weighting, significant portions of club head mass, such as the mass associated with the striking plate, are unavailable for redistribution. Additional design flexibility is needed for improved club heads and clubs.
SUMMARY
A cavity back iron type club head includes a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween. The rear surface defines a striking plate rear cavity region. A perimeter support is coupled to a peripheral portion of the striking plate. The surface area of the striking surface is related to the club head loft angle by the equation SSA≧14.4(L)+2875, where SSA is the surface area of the striking surface in units of square-millimeters and L is a club head loft angle in units of degrees.
In alternative examples, the cavity back iron type club head may include an unsupported striking plate area defined as the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa. An unsupported area ratio defined as a ratio of the unsupported striking plate area and the surface area of the striking surface may be used to characterize the club head. In some examples, the unsupported area ratio is greater than or equal to 80%.
In yet other alternative examples, the striking plate thickness and the unsupported striking plate area may be associated with a characteristic thickness ratio defined as a ratio of the average striking plate thickness within the striking plate rear cavity region and a square root of the unsupported striking plate area. In some examples, the characteristic thickness ratio is less than about 5%.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded view of a representative club head for an iron type golf club.
FIG. 2 is an elevational view of the representative club head of FIG. 1.
FIG. 3 is a partial sectional view of the golf club head of FIG. 1 illustrating a cartridge insert in contact with a rear surface of a striking plate.
FIG. 4 is an additional sectional view of the golf club head of FIG. 1 illustrating contact of the cartridge insert with a rear surface of a striking plate.
FIGS. 5A-5B are views of rear surfaces of representative striking plates.
FIG. 5C is a sectional view of the striking plate of FIG. 5A illustrating a control feature defined on the rear surface of the striking plate.
FIG. 6 illustrates an additional example of a cartridge configured for placement in a head body of an iron type golf club.
FIGS. 7A-7B illustrate a variable thickness striking plate that includes a thinned circular striking zone.
FIGS. 8A-8C illustrate a club head that includes a variable thickness striking plate having an oval striking area.



DETAILED DESCRIPTION
Referring to FIGS. 1-4, an iron-type club head 100 includes a head body 110, a cartridge assembly 120, and a striking plate 130. The head body 110 includes a heel 112, a toe 113, a top line 114, a sole 116, and a hose/140 configured to attach the club head 100 to a shaft (not shown in FIGS. 1-4). The head body 110 defines a front opening 121 configured to receive the striking plate 130 at a front rim 119 formed around a periphery of the front opening 121. Club head mass may be distributed about the perimeter of the club body 110 based on a particular mass distribution for the club head 100 selected by a club head designer. Perimeter weighting can take various forms. Typical designs include a sole bar or other mass at or near the club head sole 116 to provide a center of gravity that is situated low in the club head 100 and behind the striking plate 130 as viewed from a striking surface 132 of the club head.
As shown in FIG. 1, the striking plate 130 and the head body 110 may be formed separately. In such a design, the completed club head 100 is made by placing the striking plate 130 in the front opening 121 and in contact with the front rim 119. The striking plate 130 is then welded or otherwise secured to the heady body 110, thereby forming a cavity 118 behind a rear surface 134 of the striking plate 130. When secured to the head body 110, the striking plate 130 is supported at or by the front rim 119. As defined herein, the striking surface 132 is a substantially planar surface configured to strike a golf ball. As shown in FIG. 3, where the striking plate 130 and the head body 110 are formed separately, the striking surface 132 may be defined by both the striking plate and at least a portion of the front rim 119 of the head body if the substantially planar striking surface extends beyond the periphery of the striking plate.
Grinding and/or polishing operations can be used to remove any excess material or irregularities introduced in the welding process, or to provide a selected club head appearance such as, for example, a specularly reflective polished appearance, or other appearance. The striking plate 130 may also include a set of scorelines, such as exemplary scorelines 135, 136 formed in the striking surface 132.
The head body 110 includes a sole cavity 126 formed in proximity to a sole portion of the head body 110 and configured to receive a cartridge assembly 120. The sole cavity 126 is defined in part by a sole-facing surface 127 and a rear cavity surface 128. The sole cavity 126 is configured so that at least a portion of a surface of the cartridge assembly 120 contacts the rear surface 134 of the striking plate 130 when a cartridge assembly 120 is inserted into the sole cavity 126. Typically, the cartridge assembly 120 contacts at least some portions of the sole-facing surface 127 and the rear cavity surface 128, and is secured to the sole-facing surface 127.
As described above, the striking plate 130 and the head body 110 may be formed separately. However, alternative manufacturing processes can also be used. For example, the head body 110 and the striking plate 130 can be formed as one piece using various forging, casting, and molding processes as are commonly practiced by golf club head manufacturers. Where the head body 110 and the striking plate 130 are formed as one piece, the substantially planar striking surface 132 is defined by the one piece club head.
In one embodiment, the cartridge assembly 120 includes a cartridge body 122 that is configured to receive one or more cartridge inserts 124. Typically the cartridge body 122 is provided with one or more cylindrical bores or other cavities that retain the cartridge inserts 124. Generally the cartridge body 122 has a modulus of elasticity that is lower than that of the cartridge inserts 124.
Some examples of materials that can be used to form the cartridge body 122 include, without limitation, viscoelastic elastomers; vinyl copolymers with or without inorganic fillers; polyvinyl acetate with or without mineral fillers such as barium sulfate; acrylics; polyesters; polyurethanes; polyethers; polyamides; polybutadienes; polystyrenes; polyisoprenes; polyethylenes; polyolefins; styrene/isoprene block copolymers; metallized polyesters; metallized acrylics; epoxies; epoxy and graphite composites; natural and synthetic rubbers; piezoelectric ceramics; thermoset and thermoplastic rubbers; foamed polymers; ionomers; low-density fiber glass; bitumen; silicone; and mixtures thereof. The metallized polyesters and acrylics can comprise aluminum as the metal. Commercially available materials include resilient polymeric materials such as ScotchdampTM from 3M, Sorbothane® from Sorbothane, Inc., DYAD® and GP® from Soundcoat Company Inc., Dynamat® from Dynamat Control of North America, Inc., NoViFlexTM Sylomer® from Pole Star Maritime Group, LLC, Isoplast® from The Dow Chemical Company, and LegetolexTM from Piqua Technologies, Inc. In one embodiment the cartridge body 122 may be formed from a material having a modulus of elasticity ranging from about 0.001 GPa to about 25 GPa, and a durometer ranging from about 10 to about 30 on a Shore D scale. In a preferred embodiment the cartridge body 122 may be formed from a material having a modulus of elasticity ranging from about 0.001 GPa to about 10 GPa, and a durometer ranging from about 15 to about 25 on a Shore D scale. In a most preferred embodiment the cartridge body 122 may be formed from a material having a modulus of elasticity ranging from about 0.001 GPa to about 5 GPa, and a durometer ranging from about 18 to about 22 on a Shore D scale. In some examples, a material providing vibration damping is preferred.
As shown in FIGS. 1-4, the cartridge inserts 124 are typically formed of relatively dense materials that permit a center of gravity of a club head to be low and rearward of the striking surface 132. Some examples of materials that can be used to form the cartridge inserts 124 include, without limitation, steel alloys, tungsten and tungsten alloys, other metals and metal alloys, or other materials. Typical densities of such materials are preferably greater than about 2.5 g/cm3 or 5.0 g/cm3. In some preferred examples, insert densities are at least about 15 g/cm3.
In order to provide selected mass, mass distribution, and/or vibration dampening characteristics, in some examples the cartridge body 122 can be provided with an additional loading material as spheres, rods, fibers or other particles that are distributed throughout the cartridge body 122. In other examples, the cartridge body 122 may comprise two or more sections of different materials that are configured to provide such benefits. In yet other examples, the cartridge assembly 120 may be formed without cartridge inserts 124, and fiber or particulate loading material may be distributed throughout the cartridge body 122 to achieve desirable mass distribution and/or vibration dampening characteristics. The fiber or particulate loading material may be formed from materials such as those listed above with respect to the cartridge inserts 124. Other cartridge body 122 configurations may include a laminar structure comprising alternating layers of materials having varying modulus of elasticity values.
The cartridge assembly 120 can be conveniently secured to the sole cavity 126 in the club head 100 with a tape strip 129, other adhesive, or otherwise secured or retained in the sole cavity 126. Cartridge inserts 124 can be cylindrical or other shapes, or can be omitted based on the dimensions and density of the cartridge body 122. A badge 125 can be applied to the head body 110, to control mass distribution, for ornamentation, club identification, or other purposes. As shown in FIGS. 3-4, the cartridge body 122, as retained by the head body 110, is configured to contact the rear surface 134 of the striking plate 130 in a cartridge contact area.
Referring to FIG. 3, the rear surface 134 of the striking plate 130 is opposite the striking surface 132 and faces the cavity 118. For an iron manufactured using pull face construction, a perimeter portion 138 of striking plate 130 contacts the head body 110 at the front rim 119. A striking plate rear cavity region is defined as the portion of the striking plate rear surface 134 that is exposed to the cavity 118. Consequently, for an iron manufactured using pull face construction, the portions of the striking plate rear surface 134 supported by the front rim 119 are not included within the striking plate rear cavity region.
The surface area of the striking surface 132 (i.e., the surface area of the substantially planar surface defined by the striking plate 130 and the perimeter portion 138) can be selected based on, for example, club type, striking surface shape, and whether or not the club is to be a so-called “oversized” club. The thickness of the striking plate 130 is defined as the distance between a selected point on the striking face 132 and the rear surface 134 along an axis perpendicular to the striking face 132. The striking plate thickness can be selected to reduce mass associated with the striking plate 130, so that additional mass can be distributed to other parts of the club head 100 to achieve intended club design goals. Typically, striking plate thickness is selected consistent with long term club use to avoid premature striking plate failure due to fatigue cracking and other such failure modes. Typically, redistributed mass is situated low on the club head 100 and rearward of the striking plate 130.
Some examples of materials that can be used to form the striking plate and the head body include, without limitation, carbon steels (e.g., 1020 or 8620 carbon steel), stainless steels (e.g., 304, 410, or 431 stainless steel), PH (precipitation-hardenable) alloys (e.g., 17-4, C450, or C455 alloys), titanium alloys (e.g., 3-2.5, 6-4, SP700, 15-3-3-3, 10-2-3, or other alpha/near alpha, alpha-beta, and beta/near beta titanium alloys), aluminum/aluminum alloys (e.g., 3000 series alloys, 5000 series alloys, 6000 series alloys, such as 6061-T6, and 7000 series alloys, such as 7075), magnesium alloys, copper alloys, nickel alloys, glass fiber reinforced polymers (GFRP), carbon fiber reinforced polymers (CFRP), metal matrix composites (MMC), ceramic matrix composites (CMC), and natural composites (e.g., wood composites). High strength materials having a relatively high modulus of elasticity (typically greater than about 50 GPa, 100 GPa, 150 GPa, 200 GPa, or 250 GPa) are generally preferred. In use, the striking plate 130 is subject to numerous high speed impacts with a golf ball, and should resist cracking and permanent deformation. Different types of irons (e.g., long irons and short irons) can experience different forces in golf ball impacts, and striking plate thickness can be adjusted accordingly, if desired.
FIGS. 5A-5B illustrate control features 152, 154 situated on rear surfaces (i.e., surfaces opposite a striking surface) of representative striking plates 150, 151. Referring to FIG. 5C, the control feature 154 is defined by a recess 155 in the rear surface that is provided with a plurality of grooves such as a representative groove 158. Control features can be adjusted to provide a selected club playing characteristic, typically to provide an intended sound when striking a golf ball. FIGS. 5A-5B also illustrate representative striking plate areas in which a cartridge assembly such as the cartridge assembly 120 or other cartridges or cartridge assemblies contacts a rear surface of a striking plate. For example, as shown in FIG. 5A, the striking plate 150 contacts a cartridge assembly in a cartridge contact area 157 situated on the rear surface of the striking plate 150. In another representative example shown in FIG. 5B, the striking plate 151 contacts a cartridge assembly in surface area portions 159A, 159B, 159C.
Striking plate dimensions can vary based on striking plate composition and preferred club head dimensions. Larger or smaller striking surfaces can be provided for “short” or “long” irons, if desired. Typically, cavity-back club head designs such as the example of FIGS. 1-4 include a thin striking plate so that striking plate mass is reduced and redistributed to the club head perimeter. All or a portion of the rear surface 134 of the striking plate 130 within the striking plate rear cavity region may be unsupported by the clubhead body such that the striking plate deforms upon impact with a golf ball.
In some embodiments, a cartridge or cartridge assembly may be configured to contact a portion of the rear surface 134 of the striking plate 130 in a secondary support area, or cartridge contact area. In this way, the cartridge allows for a thinner striking plate because of the additional support the cartridge provides to the striking plate. As used herein, portions of a striking plate or other striking member of a golf club that lack a backing support structure (e.g., a cartridge or cartridge assembly) having a modulus of elasticity greater than about 25 GPa are referred to as unsupported. Consequently, an unsupported striking plate area may be defined as the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa, or equivalently the surface area of the striking plate rear cavity region minus the cartridge contact area. Striking plate dimensions, surface area of the striking plate rear cavity region, unsupported striking plate surface area, striking plate thickness, and cartridge contact area can be selected based on a desired mass distribution, club durability, striking plate materials, and other design goals.
As used herein, a contact area of an elastomeric portion of a cartridge with a rear surface of a striking plate is referred to as a secondary support area, or cartridge contact area. As noted above, the cartridge body may be formed from an elastomeric material having a modulus of elasticity ranging from about 0.001 to about 25 GPa. Providing such a secondary support area with elastomeric materials permits mass reduction in the striking plate with no decrease in striking plate durability. In order to maintain a large striking surface, such mass reduction can be conveniently associated with a relatively thin striking plate. In a typical example, a stainless steel striking plate (modulus of about 200 GPa) having an unsupported striking plate area of about 2000 mm2 has an average thickness of about 1.9 mm and a cartridge contact area of about 400 mm2. Details for several representative examples are set forth in the table below.
While FIGS. 1-4 illustrate a representative cavity back iron of pull face construction, in other examples cavity back irons are configured based on one piece (i.e., unitary) construction using manufacturing methodologies such as forging or casting. In one piece construction, a striking plate portion can be formed integrally with a club body, and defines a front striking surface and a rear surface opposite the front striking surface of the striking plate portion. In one piece construction, a striking plate thickness is defined as the distance between a selected point on the striking surface 132 and the rear surface 134 along an axis perpendicular to the striking surface 132. Generally in the case of a cavity back iron of unitary construction, the rear surface 134 of the striking plate 130 may gradually or abruptly transition from a relatively thin striking face thickness to a much thicker perimeter weighting region. In this case the striking plate rear cavity region is delineated by and includes a peripheral region having a striking plate thickness less than or equal to about 2.2 mm, which is bounded by a thicker perimeter weighting region having a thickness greater than about 2.2 mm. Typically, the maximum thickness of the perimeter weighting region is at least as thick as about 4.5 or 6 times the thickness of the thinnest portion of the striking plate rear cavity region.
An additional cartridge example is illustrated in FIG. 6. Referring to FIG. 6, a cartridge 162 includes alternating elastomeric sections 164 and insert sections 166. The elastomeric sections are selected from materials having a relatively low modulus of elasticity, typically less than about 25 GPa, less than about 10 GPa, less than about 5 GPa, or less than about 1 GPa. The insert sections 166 are generally formed of stiffer, denser materials than the elastomeric sections. The modulus of elasticity for such sections is typically greater than about 10 GPa, 50 GPa, or 100 GPa. The cartridge 162 includes a contact surface configured to contact a striking plate rear surface 134, where the contact surface is defined by surfaces 170-174 of the insert sections. While the cartridge of FIG. 6 illustrates sections alternating horizontally, in other examples, the sections can alternate vertically and fewer or more sections can be provided. In addition, the insert and elastomeric section alternation can be periodic in some examples, but generally need not be. In other examples, the elastomeric sections can be denser and/or stiffer than the insert sections, and the insert sections configured to contact a striking plate rear surface. Sections can have rectangular, square, or other cross sections.
Striking plates of pull face construction irons or striking plate portions of one piece cast or forged irons can be conveniently described based on a characteristic thickness ratio that is defined as a ratio of the average striking plate thickness within the striking plate rear cavity region and a square root of the unsupported striking plate area (i.e., the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa). In addition, a portion of an unsupported striking plate area in contact with the cartridge can be described by a relative cartridge contact area ratio defined as a ratio of the cartridge contact area and unsupported striking plate area.
In typical examples, unsupported striking plate areas range from about 1500 mm2 to about 3000 mm2, average striking plate thickness within the striking plate rear cavity region range from about 1.5 mm to about 2.2 mm, and cartridge contact areas range from about 300 mm2 to about 400 mm2. Consequently, characteristic thickness ratios may range from about 2% to about 4.8% and relative cartridge contact area ratios may range from about 10% to about 25%, or preferably from about 10% to about 18%. Such club head parameters can vary depending on club head geometry as affected by material properties such as, for example, a modulus of elasticity of striking plate material. Parameters can also be selected based on whether a particular club head is to be a short iron, a mid iron, or a long iron.
Club head geometries for three representative club set configurations A, B, and C are described in Table 1 below. For each of the three sets, representative values for a 3 iron, a 6 iron, and a 9 iron are listed. Tabulated values are unsupported striking plate area (USPA), average striking plate thickness (ASPT), cartridge contact area (CCA), characteristic thickness ratio (CTR), and relative cartridge contact area ratio (RCAR).
The representative club set heads may be manufactured from discrete components using, for example, pull face construction methods, or the representative club set heads may be manufactured as unitary components using, for example, various casting or forging techniques.







TABLE 1







Representative club head geometries.














Set and 
USPA
ASPT
CCA
CTR
RCAR



Club
(mm2)
(mm)
(mm2)
(%)
(%)







A-3
2062
1.8
304
4.0
14.7



A-6
2062
1.8
304
4.0
14.7



A-9
1898
1.8
304
4.1
16.0



B-3
1701
1.9
387
4.6
22.8



B-6
1714
1.9
387
4.6
22.6



B-9
1898
1.9
387
4.4
20.4



C-3
2112
2.1
393
4.6
18.6



C-6
2310
2.1
393
4.4
17.0



C-9
2211
2.1
393
4.5
17.8










The tabulated values are representative, and other configurations can be provided as described above. Cartridges can be configured to provide secondary support areas of various shapes and sizes, and situated at club locations based on, for example, an intended mass distribution. Unsupported striking plate surfaces may be of constant thickness, continuously variable thickness, stepped thickness, or combinations thereof. In some examples, only portions of an elastomeric surface of a cartridge contacts the rear surface of a striking plate or other striking portion.
Striking plates of pull face construction cavity back irons or striking plate portions of one piece cast or forged cavity back irons may also be described based on an unsupported area ratio that is defined as a ratio of the unsupported striking plate area and the area of the substantially planar striking surface 132. Club head geometries for two representative club set configurations D and E are described in Table 2 below. For club set configuration D, representative values for 4, 5, 6, 7, 8, and 9 irons are listed. For club set configuration E, representative values for 5, 6, 7, 8, and 9 irons are listed. Tabulated values are loft angle (L), striking surface area (SSA), unsupported striking plate area (USPA), and unsupported area ratio (UAR). As above, the representative iron heads may be manufactured from discrete components using, for example, pull face construction methods, or the representative club set heads may be manufactured as unitary components using, for example, various casting or forging techniques.







TABLE 2







Representative club head geometries.











Set and
L
SSA
USPA
UAR


Club
(degrees)
(mm2)
(mm2)
(%)





D-4
20
3167
2599
82.1


D-5
23
3207
2613
81.5


D-6
26
3264
2671
81.8


D-7
30
3314
2697
81.4


D-8
34
3366
2730
81.1


D-9
39
3442
2805
81.3


E-5
22
3214
2572
80.0


E-6
25
3265
2628
80.4


E-7
28
3318
2653
80.0


E-8
32
3366
2743
81.5


E-9
37
3447
2796
81.5









For each of the exemplary club heads listed in Table 2, the striking surface area SSA is related to the loft angle L by the following equation:

SSA≧14.4(L)+2875,

wherein SSA is the striking surface area measured in square-millimeters and L is the loft angle measured in degrees. In other examples, areas and angles can be expressed in different units with corresponding changes in any numerical constants in the equation. This relationship provides for increased striking face surface area for a given loft angle compared to traditional cavity back iron club heads. Additionally, the unsupported area ratio for each of the club heads listed in Table 2 is greater than or equal to 80%. In alternative embodiments of the invention, the unsupported area ratio may range from about 80% to about 88%, and in preferred embodiments of the invention, the unsupported area ratio may range from about 83% to about 88%.

The loft angle of an exemplary cavity back 4-iron may range from about 19 degrees to about 21 degrees, preferably from about 19.5 degrees to about 20.5 degrees; the striking surface area may range from about 3156 mm2 to about 3487 mm2, preferably from about 3322 mm2 to about 3487 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%; The loft angle of an exemplary cavity back 5-iron may range from about 21.5 degrees to about 22.5 degrees, preferably from about 22 degrees to about 23 degrees; the striking surface area may range from about 3185 mm2 to about 3519 mm2, preferably from about 3352 mm2 to about 3519 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%. The loft angle of an exemplary cavity back 6-iron may range from about 24.5 degrees to about 26.5 degrees, preferably from about 25 degrees to about 26 degrees; the striking surface area may range from about 3228 mm2 to about 3582 mm2, preferably from about 3405 mm2 to about 3582 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%. The loft angle of an exemplary cavity back 7-iron may range from about 27.5 degrees to about 30.5 degrees, preferably from about 28 degrees to about 30 degrees; the striking surface area may range from about 3271 mm2 to about 3646 mm2, preferably from about 3458 mm2 to about 3646 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%. The loft angle of an exemplary cavity back 8-iron may range from about 31.5 degrees to about 34.5 degrees, preferably from about 32 degrees to about 34 degrees; the striking surface area may range from about 3329 mm2 to about 3709 mm2, preferably from about 3519 mm2 to about 3709 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%. The loft angle of an exemplary cavity back 9-iron may range from about 36.5 degrees to about 39.5 degrees, preferably from about 36 degrees to about 39 degrees; the striking surface area may range from about 3401 mm2 to about 3788 mm2, preferably from about 3594 mm2 to about 3788 mm2; and the unsupported striking plate ratio is greater than or equal to 80%, preferably about 83% to about 88%.
Striking plates can be thinned substantially uniformly or selected locations on a striking plate can be thinned or otherwise shaped so as to provide a redistribution of mass, a desired “feel” when used, and/or a preferred “sweet spot” size or location. Referring to FIGS. 7A-7B, a striking plate 702 includes a thinned striking region 704 and a relief region 706 that is defined by a perimeter groove 708. The relief region 706 includes a plurality of circumferential grooves 711-718 that are typically defined along circular arcs that are approximately centered about a center 720 of the striking region 704. As shown in FIGS. 7A-7B, the striking plate also includes a face region 724 that has a substantially constant thickness. In some examples, grooves can be defined by elliptical, parabolic, hyperbolic or other curved arcs, or by straight line segments, or combinations thereof and situated about a geometric center of a striking region, a focus of a conic section, or otherwise situated. In the example of FIG. 7A, at least some of the grooves 711-718 include a first segment and a second segment that are disconnected. For example, the grooves 712-714 are discontinuous and include first and second segments that are separated by a portion of the face region 724. In the example of FIG. 7A, the thinned striking region 704 is circular and has a diameter of about 11.7 mm. A central edge 726 of the relief region 706 extends along a portion of a circular arc having a radius of 10.4 mm centered about the striking region 704.
As shown in FIG. 7B, the striking plate 702 has a thickness T=2.2 mm and is relieved by a thickness t=0.5 mm at a thinnest portion corresponding to the center 720 of the striking region 704 to have a central thickness of about 1.7 mm. A surface 730 of the region 704 can be defined as, for example, a portion of a spherical surface. In one example, a radius of a spherical surface associated with a 0.5 mm decrease in thickness at the center 720 of a 11.7 mm diameter striking region 704 is about 34.5 mm. A striking surface 740 is provided with a plurality of scorelines 741-748. The relief region 706 also includes transition segments 760, 762 that couple the relief region 706 and the support region 724. In the example of FIG. 7B, surfaces of the transition regions 760, 762 are situated at about 45 degrees with respect to a surface 764 of the support region 724. As shown in the example of FIGS. 7A-7B, a thickness of the striking plate 702 in the relief region 706 is about 1.6 mm, and the grooves 708, 711-718 extend a distance of about 0.15 mm into the striking plate 702 and have radii of curvature of about 0.5 mm. More or fewer grooves can be provided in the relief zone, and relief zones that have larger areas or depths can be used.
Horizontal (H) and vertical (V) locations of the center of a striking zone for a representative iron set are included in Table 3. For convenience, approximate striking plate mass is provided for each club.







TABLE 3







Representative Striking Plate Specifications












Club
Mass (g)
H (mm)
V(mm)







3 iron
30.7
37.2
19.6



4 iron
31.2
37.2
19.9



5 iron
31.7
37.2
20.4



6 iron
33.1
37.2
21.6



7 iron
33.3
37.4
22.0



8 iron
34.0
37.4
22.1



9 iron
34.6
37.4
24.3



P wedge
35.3
37.3
26.0



A wedge
35.5
37.3
28.2



S wedge 
36.4
37.0
28.6










An additional exemplary striking plate 802 retained in a head body 804 is illustrated in FIGS. 8A-8C. The striking plate 802 has a thickness TFACE and includes an oval support area 806 having a central oval area 810 of thickness TSTRIKE and a rim 812 of thickness TRIM that are provided on a rear surface 814. The rim 812 defines an oval rim region having interior and exterior lengths LI, LO, respectively and interior and exterior widths WI, WO, respectively. The rim 812 has an annular width of between about 0.9 mm and 1.5 mm at the thickest portion, and dimensions of the rim region are based on locations at which the striking plate thickness is substantially the same as the thicknesses associated with the striking region and the face region. A front surface (a striking surface) 816 of the striking plate 802 includes a plurality of grooves 818. In some examples, the oval support area 806 is elliptical and lengths and widths correspond to major and minor axes of ellipses. A bottom edge 817 of a sole 816 typically extends parallel to the ground (and rests on the ground) when the club is positioned so as to address a ball. Typically a long axis of the oval support area 806 extend approximately parallel to the bottom edge 817. In the example of FIGS. 8A-8C, a striking face area is somewhat thicker than the remainder of the striking plate. Dimensions of representative striking plates and associated oval support areas such as illustrated in FIGS. 8A-8C are listed in Table 4.







TABLE 4







Representative Striking Plate Dimensions













Example 1
Example 2 
Example 3
Example 4
Example 5





TFACE (mm)
1.9-2.2
1.9-2.2
1.9-2.2
1.9-2.2
1.9-2.2


TSTRIKE (mm)
2.7-2.9
2.4-2.6
2.2-2.9
2.4-2.7
2.5-2.6


TRIM (mm)
3.4-3.8
2.9-3.2
2.9-3.6
3.1-3.4
3.2-3.3


Striking Face
2825-3113
2793-3152
2800-3200
2800-3200
2800-3200


Area (mm2)







Oval Area
502-554
370 - 408
390-580
450-550
500-550


(mm2)







LO (mm)
39.9-44.1 
34.2-37.8
32-46
36-44
38-42


WO (mm)
15.2-16.8 
13.1-14.5
11-19
13-17
15.5-16.5


LI (mm)
20.9-23.1 
17.1-18.9
15-25
18-22
19-21


WI (mm)
7.6-8.4
6.5-7.2
6-9
7-8.5
7.75-8.25









The striking plate examples shown in FIGS. 7A-7B and 8A-8C may be provided on a club head using pull face construction or unitary construction techniques. A variety of other striking plates can be similarly arranged to include thinned or thickened striking regions, relief regions, or other features described above.
The representative clubs, components thereof, and related assembly and manufacturing methods presented above are examples only and are not to be taken as limiting. As disclosed above, striking plates used in pull face club construction or other club faces can be thinned or thickened to permit improved mass redistribution. In some examples, portion of a thinned striking plate are supported or contacted by a weight cartridge, while other examples, a central or interior portion of a striking plate is thinner or thicker than a surrounding portion. Thickness changes can be abrupt or gradual, and tapered thinned or thickened face plates can be used. Portions of the striking plate can be grooved or otherwise relieved so that the associated mass can be situated as desired to provide an intended playing characteristic. These examples are presented for convenient explanation, and are not to be taken as limiting the scope of the appended claims. We claim all that is encompassed by the appended claims.

## Claims

1. A cavity back iron type club head having a prescribed loft angle, the club head comprising:
a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween, the rear surface defining a striking plate rear cavity region; and
a perimeter support coupled to a peripheral portion of the striking plate;
wherein the surface area of the striking surface is related to the club head loft angle by the equation SSA≧14.4(L)+2875, wherein SSA is surface area of the striking surface in units of square-millimeters and L is the club head loft angle in units of degrees, and wherein the rear surface is selectively contoured to include a thinned region coinciding with the geometric center of the striking surface, the thinned region being at least about 0.5 mm thinner than the maximum thickness of the striking plate, and a perimeter groove formed proximate to the periphery of the rear surface, the perimeter groove including a portion extending substantially parallel to a club head top line and an arcuate portion extending about the thinned region, the perimeter groove being at least about 0.5 mm thinner than the maximum thickness of the striking plate.

2. The cavity back iron type club head of claim 1, further comprising:
an unsupported striking plate area defined as the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa; and
an unsupported area ratio defined as a ratio of the unsupported striking plate area and the surface area of the striking surface, wherein the unsupported area ratio is greater than or equal to 80%.

3. The cavity back iron type club head of claim 2, wherein the unsupported area ratio ranges from about 80% to about 88%.

4. The cavity back iron type club head of claim 3, wherein the unsupported area ratio ranges from about 83% to about 88%.

5. The cavity back iron type club head of claim 2, wherein the striking plate thickness and the unsupported striking plate area are associated with a characteristic thickness ratio defined as a ratio of the average striking plate thickness within the striking plate rear cavity region and a square root of the unsupported striking plate area, and the characteristic thickness ratio is less than about 5%.

6. The cavity back iron type club head of claim 5, wherein the characteristic thickness ratio is between about 2% and about 4.8%.

7. The cavity back iron type club head of claim 2, further comprising:
a cavity formed in a sole portion of the perimeter support; and
a cartridge at least partially disposed in the cavity and directly coupled to the rear surface of the face plate, thereby defining a cartridge contact area.

8. The cavity back iron type club head of claim 7, wherein the unsupported striking plate area and the cartridge contact area are associated with a relative cartridge contact area ratio that ranges from about 10% to about 25%.

9. The cavity back iron type club head of claim 8, wherein the cartridge comprises a cartridge body formed from a material having a modulus of elasticity ranging from about 0.001 GPa to about 25 GPa, and a durometer ranging from about 10 to about 30 on a Shore D scale.

10. The cavity back iron type club head of claim 9, wherein the cartridge comprises a cartridge body formed from a material having a modulus of elasticity ranging from about 0.001 to about 10 GPa, and a durometer ranging from about 15 to about 25 on a Shore D scale.

11. The cavity back iron type club head of claim 10, wherein the cartridge comprises a cartridge body formed from a material having a modulus of elasticity ranging from about 0.001 to about 5 GPa, and a durometer ranging from about 18 to about 22 on a Shore D scale.

12. A cavity back iron type club head having a prescribed loft angle, the club head comprising:
a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween, the rear surface defining a striking plate rear cavity region;
an unsupported striking plate area defined as the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa;
an unsupported area ratio defined as a ratio of the unsupported striking plate area and the surface area of the striking surface;
wherein the loft angle ranges from about 19 degrees to about 21 degrees, the striking surface area ranges from about 3156 mm2 to about 3487 mm2, and the unsupported striking plate ratio is greater than or equal to 80%, and wherein the rear surface is selectively contoured to include a thinned region coinciding with the geometric center of the striking surface, the thinned region being at least about 0.5 mm thinner than the maximum thickness of the striking plate, and a perimeter groove formed proximate to the periphery of the rear surface, the perimeter groove including a portion extending substantially parallel to a club head top line and an arcuate portion extending about the thinned region, wherein the perimeter groove is at least about 0.5 mm thinner than the maximum thickness of the striking plate.

13. The cavity back iron type club head of claim 12, wherein the striking surface area ranges from about 3322 mm2 to about 3487 mm2 and the unsupported striking plate ratio ranges from about 83% to about 88%.

14. The cavity back iron type club head of claim 12, wherein the striking surface area ranges from about 3405 mm2 to about 3582 mm2 and the unsupported striking plate ratio ranges from about 83% to about 88%.

15. A cavity back iron type club head having a prescribed loft angle, the club head comprising:
a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween, the rear surface defining a striking plate rear cavity region;
an unsupported striking plate area defined as the portion of the striking plate rear cavity region lacking a backing support structure having a modulus of elasticity greater than about 25 GPa;
an unsupported area ratio defined as a ratio of the unsupported striking plate area and the surface area of the striking surface;
wherein the loft angle ranges from about 24.5 degrees to about 26.5 degrees, the striking surface area ranges from about 3228 mm2 to about 3582 mm2, and the unsupported striking plate ratio is greater than or equal to 80%, and wherein the rear surface is selectively contoured to include a thinned region coinciding with the geometric center of the striking surface, the thinned region being at least about 0.5 mm thinner than the maximum thickness of the striking plate, and a perimeter groove formed proximate to the periphery of the rear surface, the perimeter groove including a portion extending substantially parallel to a club head top line and an arcuate portion extending about the thinned region, wherein the perimeter groove is at least about 0.5 mm thinner than the maximum thickness of the striking plate.