# Patent

## Title
Iron-type golf club

## Abstract

Disclosed herein is a golf club including a club head having a muscle back shell or a lightweight muscle back.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser. No. 11/854,689, filed Sep. 13, 2007, now U.S. Pat. No. 8,062,150 which is incorporated herein by reference in its entirety.


FIELD OF THE INVENTION
This invention generally relates to golf clubs, and more specifically to iron-type golf club having an enclosed lower hollow cavity behind the hitting face.
BACKGROUND OF THE INVENTION
Typical iron club heads are solid with a flat hitting face and generally either muscle back and cavity back clubs. Traditionally all irons were muscle back, which are smooth at the back with low offset, thin topline and thin sole. Cavity back irons have a hollowed out back and the club head mass is redistributed to the sole and the perimeter of the club head, which moves the center of gravity lower to the ground and rearward making the iron launch the ball higher, and increases rotational moment of inertia thereby lowering its tendency to rotate on mis-hits and enlarging the sweet spot.
Some muscle back irons have an interior hollow section, such that the club resembles a muscle back on the outside but the interior hollow section alters the club's mass characteristics. One example is U.S. Pat. No. 4,645,207 to Teramoto et al. The Teramoto patent discloses a set of iron golf clubs in which the iron club is cast by the lost wax method, and the back member is welded at the back of the face member to form a hollow section between the back and face members. As the club changes from a longer iron to a shorter iron, the hollow section is gradually decreased to zero and the sole width is gradually decreased. No support is provided to the hitting face.
Another example is U.S. Pat. No. 4,754,969 to Kobayashi. The Kobayashi patent discloses a set of golf clubs wherein each one-piece club head includes a hollow section behind the striking face. Each of the club heads is made of a stainless steel by, for example, a lost wax casting process. The material of each of the face portions of the club heads is then annealed to increase its elasticity. The striking face is thinner for long irons, but no support is provided to the hitting face.
Another example is U.S. Pat. No. 7,126,339 to Nagai et al., which discloses utility golf clubs, which generally include a hollow interior.
There remains a need in the art for an improved iron-type golf club.
SUMMARY OF THE INVENTION
The present invention is directed to iron-type golf club. The inventive iron-type golf club provides a club head that provides the aesthetics of a muscle back iron while improving club head center of gravity disposition, increasing moment of inertia and sweet spot size.



BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:
FIG. 1 is a rear view of a hollow iron-type golf club in accordance with the present invention; FIG. 1A is a perspective rear view of the club head main body without a muscle back shell;
FIG. 2 is a perspective bottom view of club head main body of FIG. 1 without the muscle back shell;
FIG. 3 is a perspective back view of muscle back shell of FIG. 1;
FIG. 4 is a cross-sectional view along line 4-4 of FIG. 1;
FIG. 5 is an exploded rear view of another inventive club head, optional toe dampener, muscle back shell, and optional cosmetic decal;
FIG. 6 is an exploded cross-sectional view along line A-A of FIG. 5;
FIG. 7 is an enlarged view of the circled portion of FIG. 6;
FIG. 8 is a perspective view of the toe dampener using a thinned area; FIG. 8A is a perspective view of the toe dampener using a slot;
FIG. 9 is an exploded cross-sectional view of another embodiment of the hollow iron-type golf club;
FIG. 10 is an enlarged cross-sectional view of another embodiment of the hollow iron-type golf club;
FIG. 11 is an enlarged cross-sectional view of another embodiment of the hollow iron-type golf club; FIG. 11A is a perspective rear view of the club head main body.
FIG. 12 is an enlarged cross-sectional view of another embodiment of the hollow iron-type golf club;
FIG. 13 is a cross-sectional exploded view of another embodiment of the hollow iron-type golf club; and FIG. 13A is a perspective rear view of the club head main body.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to hollow iron-type golf clubs and can also be used with utility golf clubs. The inventive iron-type golf club provides the aesthetics of a muscle back iron while moving the center of gravity lower and further back, increasing moment of inertia, and enlarging sweet spot similar to a cavity back club. The inventive club can accomplish this goal by incorporating a hollow interior cavity in the muscle portion of the club, supporting a thin hitting face with a supporting member, and adding a high density rear sole portion. Additionally, weight from the upper toe can be redistributed to other portions of the club head to improve mass characteristics, and can be advantageously replaced by a vibration and sound dampener. The end result of the present invention is a club that resembles a muscle back iron that low handicap players use, but the club plays like the forgiving cavity back irons that high handicap players prefer. Several embodiments of the present invention are described below.
Referring to FIGS. 1, 2, 3 and 4, a hollow iron-type golf head 10 comprises club head main body 12 including support 14, and muscle back shell 16. Support 14 and partial sole 18 of club head main body 12 are sized and dimensioned to fit flush with muscle back shell 16.
Club head main body 12 is preferably made from a lower density material than muscle back shell 16 to move club head center of gravity lower and further back to increase moment of inertia and sweet spot size to improve the golfer's chances for effective ball-striking. Preferably, main body 12 has a density in the range of about 4 g/cm3 to about 8 g/cm3 and muscle back shell 16 has a density in the range of about 9 g/cm3 to about 19 g/cm3. Suitable materials for club head main body 12 include, but are not limited to, aluminum, stainless steel or titanium and alloys thereof. Preferably, club head main body 12 is made from titanium alloy. Suitable materials for muscle back shell 16 include, but are not limited to, lead, tungsten, gold, or silver. Preferably, muscle back shell 16 is made from tungsten or tungsten nickel alloy. These material alternatives are applicable to all of the embodiments described herein. Preferably, materials with higher density, such as stainless steel and tungsten are located below and away from the center of gravity or the geometric center to enhance mass properties, e.g., larger rotational moment of inertia and lower center of gravity.
As discussed above, it is desirable to have a relatively thin hitting face so that extra mass can be redistributed. However, golf club and golf ball impacts can create a force of up to 2,000 lbs. Repeated impacts may adversely affect the structural integrity of hitting face 20. In accordance with an aspect of the present invention, support 14 is provided behind hitting face 20 to improve its mechanical integrity. While any number of supports can be deployed and the supports can be arranged in any orientation, it is preferred that a single support 14 is used and is positioned in the toe-to-heel direction. Furthermore, as best shown in FIG. 4 support 14 has an I-beam profile, which is known to have high structural integrity and resistance to bending forces while being relatively light weight. Alternatively, support 14 can have any profile including, but not limited to, square, triangular, rectangular, “X”, “Y,” circular, semi-circular, elliptical, etc.
To assemble club head 10, muscle back shell 16 is attached to support 14 and partial sole 18 of club head main body 12 at attachment lines 22. Preferably, attachments 22 of muscle back shell 16 to club head main body 12 are made permanent by welding or force fitting with or without adhesive. Alternatively, shell 16 can be attached via fasteners 112, such as screws and rivets, and holes 98 as shown in FIG. 1A. An advantage of disposing attachments 22 away from hitting face 20 is that the high force of the golf club and golf ball impacts are less likely to cause mechanical failure of attachments 22. This advantage is applicable to all of the embodiments described herein. Preferably, plasma welding is used to attach the heel to main body 12 and laser welding is used to attach support 14 to hitting face 20 of main body 12.
Referring to FIG. 1A, an alternative embodiment comprises a bore 104 with internal threads in the heel below hosel 106 of club head main body 92, a bore 108 with internal threads in toe 110 of club head main body 92, or both. Internal threads of bores 104 and 108 fastenably mate with a fastener 112, such as a screw 112. The embodiment provides decorative aesthetics compatible with other embodiments discussed herein.
Referring to FIGS. 5 to 8A, another embodiment of golf head 10 comprises club head main body 32 including support 34 and optional toe dampener 46, and muscle back shell 36. Support 34 and partial sole 38 of club head main body 32 are sized and dimensioned to fit with muscle back shell 36. Toe dampener 46 is made from a viscoelastic material, such as urethane or other polymers, and provides weight redistribution in addition to vibration and sound attention when the golf club strikes a ball.
Club head main body 32 comprises upper back cavity 48, support 34 with first interlocking structure 60, recessed flange 50, partial sole 38 with second interlocking structure 62, and optional toe dampener 46 and cosmetic badge 76. In addition, club head main body 32 may have recess 52 in support 34 providing support 34 with an I-beam profile for weight redistribution to move lower and further back club head center of gravity. Support 34 can be cast integral with hitting face 20, or can be manufactured separately as a different material or same material, such as stainless steel or carbon fiber reinforced plastics, and later attached to hitting face 20 via welding or by interference fit with tension.
Muscle back shell 36 comprises back flange 54 with third interlocking structure 64 and sole section 56 with fourth interlocking structure 66. In addition, muscle back shell 36 may have recess 58 in back flange 54 for weight redistribution to move lower and further back club head center of gravity.
First interlocking structure 60 of support 34 and second interlocking structure 62 of partial sole 38, of club head main body 32, are sized and dimensioned to mate with third interlocking structure 64 of back flange 54 and fourth interlocking structure 66 of sole section 56, of muscle back shell 36, respectively. While any number of interlocking structures can be deployed and the interlocking structures can be arranged in any orientation, it is preferred that a single notch is disposed in support 34 and partial sole 38 and is positioned in the toe-to-heel direction to mate with corresponding interlocking structures 64 and 66, as shown in FIGS. 5 and 7. Alternatively, interlocking structures 60, 62, 64, and 66 can have any profile including, but not limited to, square, triangular, rectangular, curvilinear, sine wave, serrated, etc. Depending on the shape, and in particular the profile in cross section, of the interlocking structures, both increased surface area contact and increased mechanical binding is achieved between club head main body 32 and muscle back 36 when fit together. An advantage of this embodiment is that the shape of interlocking structures 60, 62, 64, and 66 can be matched to other club decorative aesthetics, such as the hosel.
Referring to FIGS. 8-9, by removing mass, in the form of titanium alloy or other suitable material as discussed above, from toe 68 of club head main body 32 and replacing the material, as toe dampener 46, with a lower density material club head center of gravity is moved lower and further back, while also providing vibration and sound attenuation when the golf ball is mis-hit on toe 68 of the golf club. Preferably, toe dampener 46 is made from a soft viscoelastic material such as thermoplastic elastomer, rubber, or polyurethane that has a density in the range of about 0.8 g/cm3 to about 1.5 g/cm3 and Shore A40-A90 hardness rating. Preferably, toe dampener 46 is created by thinning an area 70 in toe 68 on the back of club head main body 32, as shown in FIG. 8. Alternatively, thinned area 70 is in upper back cavity 48. In either case, thinned area 70 is replaced with viscoelastic toe dampener 46. An alternative embodiment comprises a lightweight member 72 made of viscoelastic material that is inserted into a slot 74 created in toe 68 of club head main body 32, as shown in FIG. 8A. Slot 74 can also be formed in the middle of the topline of the club head. Alternatively, a combination of thinned areas and slots may be used to add viscoelastic material to club head main body 12.
Toe dampener 46 viscoelastic material provides vibration attenuation that reduces the distance and off-line penalties, and unpleasant sensation radiating up the shaft into the hands and arms of the golfer when a ball is mis-hit on toe 68 of club head main body 32. Furthermore, golf balls mis-hit on high toe 68 cause a low frequency (“bass”), high amplitude (“loud”) noise. The viscoelastic material in toe dampener 46 provides sound attenuation that generates an esthetically pleasing sound when a golf club strikes a ball. Additionally, the number of high toe mis-hits is statistically low therefore less metal is required at that location and the metal can be replaced with lower density polymers.
Finally, optional cosmetic badge 76 adheres to the upper back cavity 48 of the club head main body 32. If toe dampener 46 is produced by thinning an area 70 as shown in FIG. 8, then cosmetic badge 76 holds toe dampener 46 captive against back of club head main body 32. In addition to the current embodiment, toe dampener 46 and cosmetic badge 76 are applicable to all the embodiments discussed herein.
To assemble club head 10, muscle back shell 36 is attached to support 34 and partial sole 38 of club head main body 32. Preferably, attachments 42 of muscle back 36 to club head main body 32 are made permanent by welding, fasteners or force fitting with or without adhesive, as discussed above.
Referring to FIG. 9, another embodiment of club head 10 comprises separate face plate 84 that is welded to club head main body 82 rather than being made integral. An advantage of this embodiment is that the style and/or density of face plate 84 can be changed without modifying the rest of club head 10.
Referring to FIG. 10, another embodiment of golf head 10 comprises holes or openings 98 on top surface 100 of support 94 of club head main body 92. Internal cavity 102 formed by club head main body 92 and muscle back shell 96 can be filled with material including, but not limited to, foamed or un-foamed polyurethane, or other substance, to prevent water, or other material, from entering otherwise hollow cavity 102. The material can be transparent or translucent, clear or colored, and may have multiple colors exposed through openings 98. Hollow cavity 102 can be filled through openings 98. While any number of holes can be deployed and the holes can be arranged in any orientation, it is preferred that three holes 98 are used and are positioned in the toe-to-heel direction. Alternatively, holes can have any arrangement including, but not limited to, diamond, oval, etc. An advantage of using filling material is to increase the dampening effect and to provide additional aesthetics to the club head, allowing the user to look into the muscle back. Hollow cavity 102 may not be filled completely. Instead, a material can be added into hollow cavity 102 to bring the club head to any desired weight during manufacturing. For example, up to 6 grams of mass can be added to bring the weight of the club head to regulation weight. Suitable added mass includes, but is not limited to an adhesive commonly known in the art as rat glue.
Top surface 100 can be a recessed surface, as illustrated in FIG. 10. The recess can be filled with a three-dimensional insert, which can be a filler or can serve as a badge carrying marketing indicia or a bridge. The insert can have any shape and can have an L-shape. The insert can also be functional, e.g., to dampen vibration from impacts with golf balls. Suitable dampening materials include, but are not limited to, soft polymers having hardness value from Shore A-30 to Shore A-90, preferably from Shore A-35 to Shore A-60. The functional insert can carry sensors and or electronics to measure location of impacts on the hitting face. In one embodiment, the sensors are located on or proximate to the hitting face and the electronics including memory, such as EEPROM and other memory storage devices, is located proximate to the grip of the club to minimize vibration to the sensitive electronics.
Referring to FIGS. 11-11A, another embodiment of club head 10 comprises posts 130 projecting from back 136 of club head main body 122. Posts 130 comprise enlarged heads 132 that provide mounting attachments, or anchors, for muscle back solid 126 disposed on top of posts 130 and support 124 projecting from back 136 of main body 122. Suitable materials for posts 130 include, but are not limited to, lead, tungsten, gold, or silver. Preferably, posts 130 are made from tungsten nickel alloy. Posts 130 are custom milled, as needed, for weight distribution, to move the center of gravity lower and further back. Preferably, enlarged heads 132 have a disk shape as shown in FIGS. 11-13A, or any other suitable shape, such as cube, octahedron, sickle, boat anchor, etc. Whereas suitable material for making translucent overcast of muscle back solid 126 may include, but is not limited to, polyurethane, or similar substance, made into any color, design, logo, etc.
To assemble club head 10, posts 130 are attached to back 136 of club head main body 122 at attachment lines 134. Preferably, attachments 134 of posts 130 to club head main body 122 are made permanent by welding, fasteners or adhesive. Then, the mold for making muscle back solid 126 is created with club head main body 122 forming a part of the mold. Main body 122 connects with a half-mold that would create muscle back 126. While any number of posts can be deployed and the posts can be arranged in any orientation, it is preferred that three posts 130 are used and are positioned in the toe-to-heel direction to move the center of gravity low to the ground. Alternatively, posts can have any arrangement including, but not limited to, square, triangular, rectangular, curvilinear, diamond, oval, etc. An alternative embodiment comprises no support as shown in FIG. 12.
Referring to FIGS. 13-13A, another alternative embodiment comprises a honeycomb system 158 of many interconnected anchors 160 and enlarged heads 162 attached to support 154 and back of club head main body 152. Muscle back solid 156 is a translucent overcast disposed on top of honeycomb system 158. In manufacturing club head 10, honeycomb system 158 of club head main body 152 is part of the mold, as discussed above.
All the main bodies of the golf head 10 embodiments, discussed above, may be constructed from a cast or forged stainless steel 431.
While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives stated above, it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments, which would come within the spirit and scope of the present invention.

## Claims

1. A golf club head, comprising:
a club head main body constructed of a first material, wherein the club head main body comprises a support projecting rearward from a rear surface of a hitting face of the main body, the support extending across a central portion of the rear surface in a generally heel to toe orientation;
a muscle back solid constructed of a second material, wherein the second material has a lower density than the first material; and
a sole weight constructed of a third material having a higher density than the first material, wherein the sole weight is disposed within the muscle back solid and proximate a sole of the club head.

2. The golf club head of claim 1, wherein the sole weight comprises a plurality of posts.

3. The golf club head of claim 2, wherein the plurality of posts extend from the rear surface of the hitting face at a location between the support and the sole.

4. The golf club head of claim 2, wherein at least one of the plurality of posts comprises an enlarged head disposed at a rearward end of the post.

5. The golf club head of claim 2, wherein the plurality of posts comprises at least three posts.

6. The golf club head of claim 5, wherein each of the plurality of posts comprises an enlarged head.

7. The golf club head of claim 5, wherein the at least three posts that are distributed across the main body in a heel to toe direction.

8. The golf club head of claim 1, wherein the second material of the muscle back solid comprises a thermoplastic over-molded on the sole weight.

9. The golf club head of claim 8, wherein the sole weight comprises an enlarged head to anchor the over-molded thermoplastic.

10. A golf club head, comprising:
a club head main body constructed of a first material, the club head main body comprising a hitting face;
a muscle back solid constructed of a second material, wherein the second material has a lower density than the first material; and
a sole weight constructed of a third material having a higher density than the first material, wherein the sole weight is disposed within the muscle back solid and proximate a sole of the club head,
wherein the second material comprise a thermoplastic over-molded on the sole weight.

11. The golf club head of claim 10, wherein the club head main body comprises a support that supports the hitting face to maintain the mechanical integrity of the hitting face, the support extending across a central portion of a rear surface of the hitting face in a generally heel to toe orientation.

12. The golf club head of claim 10, wherein the sole weight comprises a plurality of posts.

13. The golf club head of claim 12, wherein the plurality of posts comprises at least three posts that are distributed across the main body in a heel to toe direction.

14. The golf club head of claim 10, wherein the sole weight comprises an enlarged head to anchor the over-molded thermoplastic.

15. A golf club head, comprising:
a club head main body constructed of a first material, wherein the club head main body comprises a support projecting rearward from a rear surface of a hitting face of the main body, the support extending across a central portion of the rear surface in a generally heel to toe orientation;
a muscle back solid constructed of a second material, wherein the second material has a lower density than the first material; and
a plurality of posts constructed of a third material having a higher density than the first material, wherein the plurality of posts are disposed within the muscle back solid and proximate a sole of the club head, and wherein the muscle back solid comprises an over-molded thermoplastic and each of the plurality of posts comprises an enlarged head to anchor the over-molded plastic.

16. The golf club head of claim 15, wherein the plurality of posts extend from the rear surface of the hitting face at a location closer to the sole than the support.

17. The golf club head of claim 15, wherein the plurality of posts comprises at least three posts.

18. The golf club head of claim 17, wherein the plurality of posts comprises at least three posts that are distributed across the main body in a heel to toe direction.

19. The golf club head of claim 15, wherein each of the plurality of posts comprises an enlarged head.