An iron-type golf club head is disclosed having a heel portion, a sole portion, a toe portion, a top-line portion, a front portion, a rear portion, and a striking face. A back wall is also disclosed in the rear portion enclosing a portion of the rear portion to create an enclosed cavity. The cavity is defined by at least a rear surface of the striking face, an inner back wall surface, and the sole portion. A plug and a filler material is located within the enclosed cavity. The filler material surrounds the plug and is configured to hold the plug in place. The plug is lighter than the filler material.
1. A hollow iron-type golf club head comprising: a heel portion, a sole portion, a toe portion, a top-line portion, a front portion, a rear portion, and a striking face; a back wall in the rear portion enclosing a substantial portion of the rear portion to create a substantially enclosed cavity, the enclosed cavity being defined by at least a rear surface of the striking face, an inner back wall surface, and the sole portion; at least one plug and a filler material located within the enclosed cavity, the filler material substantially surrounding the at least one plug and being configured to hold the at least one plug in place, wherein the filler material occupies about 50% to about 99% of the total club head cavity volume in the enclosed cavity and wherein the filler material and the at least one plug have a combined weight of less than about 10 g.
2. The iron-type golf club head of claim 1 , wherein the enclosed cavity has a volume between about 1 cc and 200 cc.
3. The iron-type golf club head of claim 2 , wherein an unsupported face area is between about 300 mm 2 to about 4,000 mm 2 .
4. The iron-type golf club head of claim 3 , wherein the unsupported face area includes a thickened central region.
5. The iron-type golf club head of claim 4 , wherein the at least one plug is positioned to be in contact with at least a portion of the thickened central region.
6. The iron-type golf club head of claim 5 , wherein the at least one plug contacts the inner back wall surface.
7. The iron-type golf club head of claim 1 , wherein the striking face includes a welded striking plate.
8. The iron-type golf club head of claim 1 , wherein a total striking face area is between about 2,700 mm 2 and about 5,000 mm 2 .
9. The iron-type golf club head of claim 1 , further comprising an aperture into the enclosed cavity, the aperture being configured to allow the cavity to be filled with the filler material.
10. The iron-type golf club head of claim 9 , wherein the filler material is an expanding foam material having a density between about 0.03 g/cc and about 0.19 g/cc.
11. The iron-type golf club head of claim 1 , wherein the filler material occupies about 50% to about 99% of the total club head cavity volume in the enclosed cavity.
12. The iron-type golf club head of claim 1 , wherein the filler material completely fills a remaining cavity volume around the at least one plug.
13. The iron-type golf club head of claim 1 , wherein the filler material contacts an entire first side surface of the at least one plug.
14. The iron-type golf club head of claim 1 , wherein the filler material and the at least one plug have a combined weight of less than about 5 g.
15. The iron-type golf club head of claim 1 , wherein the back wall includes a first aperture.
16. The iron-type golf club head of claim 1 , wherein the back wall includes a first aperture having at least a first diameter and a slot configured to match at least a keying portion of the at least one plug.
17. The iron-type golf club head of claim 1 , wherein the coefficient of restitution of the club is greater than about 0.8.
18. The iron-type golf club head of claim 1 , wherein the striking face includes a striking plate formed of a steel selected from the group consisting of maraging steels, maraging stainless steels, and PH stainless steels.
19. The iron-type golf club head of claim 1 , wherein at least a portion of the at least one plug is in direct contact with a rear surface of the striking face and at least a portion of the filler material is in direct contact with a rear surface of the striking face.
20. The iron-type golf club head of claim 1 , wherein the back wall includes at least a first aperture, the first aperture being configured to allow the at least one plug to be inserted into the first aperture and is configured to allow the at least one plug to move from a first position to a second position.
21. The club head of claim 20 , wherein the back wall includes at least one slot, the at least one slot being connected to the first aperture and is configured to secure the at least one plug.
22. A hollow iron-type golf club head comprising: a heel portion, a sole portion, a toe portion, a top-line portion, a front portion, a rear portion, and a striking face; a back wall in the rear portion enclosing a substantial portion of the rear portion to create a substantially enclosed cavity, the enclosed cavity being defined by at least a rear surface of the striking face, an inner back wall surface, and the sole portion; at least one plug and a filler material located within the enclosed cavity, the filler material substantially surrounding the at least one plug and being configured to hold the at least one plug in place, wherein the filler material occupies about 50% to about 99% of the total club head cavity volume in the enclosed cavity and wherein the filler material and the at least one plug have a combined weight of less than about 20% of the total club head weight.
23. The iron-type golf club head of claim 22 , wherein the filler material and the at least one plug have a combined weight of less than about 5% of the total club head weight.