Iron-type golf club head

Abstract

Disclosed herein is an iron-type golf club head that comprises a strike plate, an enclosed internal cavity, and a rear aperture formed in a rear wall. The iron-type golf club head also comprises a stiffening plug, within the internal cavity and compressed between the back surface of the strike plate and the rear wall. The stiffening plug is insertable, through a rear aperture, into the internal cavity. The iron-type golf club head further comprises a rear fascia covering the rear aperture and at least a portion of the rear wall. A characteristic time (CT) at a geometric center of the strike face is at least 250 microseconds. A maximum thickness of the strike plate, at the strike face, is less than 3.5 millimeters, inclusive. The strike plate, excluding grooves, has a minimum thickness between 1.1 millimeters and 2.2 millimeters.

1 . An iron-type golf club head, comprising:
 a body, comprising a heel portion, a sole portion, a toe portion, a top-line portion, a front portion, and a rear portion;   a strike plate, coupled to the front portion of the body and comprising a strike face and a back surface opposite the strike face;   an internal cavity, defined between the back surface of the strike plate and the body; and   at least one stiffener comprising a discrete mass of polymeric material within the internal cavity and directly coupled to the back surface of the strike plate, wherein the polymeric material of the at least one discrete mass has a hardness equal to or greater than Shore 5.95D; and   wherein the iron-type golf club head has coefficient of restitution (COR) change value between 0.000 and +0.008, the COR change value being defined as a difference between a measured COR value of the iron-type golf club head and a calibration plate COR value.   
     
     
         2 . The iron-type golf club head according to  claim 1 , wherein the iron-type golf club head, without the at least one stiffener, has a COR change value no less than +0.009. 
     
     
         3 . The iron-type golf club head according to  claim 1 , wherein the internal cavity is enclosed. 
     
     
         4 . The iron-type golf club head according to  claim 3 , wherein the front portion of the body comprises an aperture extending through the front portion at a location corresponding with the discrete mass of polymeric material. 
     
     
         5 . The iron-type golf club head according to  claim 4 , further comprising a plug covering the aperture of the strike plate. 
     
     
         6 . The iron-type golf club head according to  claim 3 , further comprising a filler material surrounding the discrete mass of polymeric material and filling at least a portion of the internal cavity. 
     
     
         7 . The iron-type golf club head according to  claim 6 , wherein the filler material surrounds a portion of the polymeric material and occupies about 50% to about 99% of the internal cavity of the golf club head. 
     
     
         8 . The iron-type golf club head according to  claim 7 , wherein the filler material reduces a coefficient of restitution (COR) of the golf club head no more than 0.025. 
     
     
         9 . The iron-type golf club head according to  claim 8 , wherein the filler material reduces the COR of the golf club head no more than 0.010. 
     
     
         10 . The iron-type golf club head according to  claim 6 , wherein the filler material has a density greater than 0.21 g/cc and no more than 0.71 g/cc. 
     
     
         11 . The iron-type golf club head according to  claim 10 , wherein the filler material has an overall mass greater than 5 grams. 
     
     
         12 . The iron-type golf club head according to  claim 11 , wherein the density of the filler material is no less than 0.30 g/cc and no more than 0.60 g/cc. 
     
     
         13 . The iron-type golf club head according to  claim 12 , wherein the overall mass of the filler material is no less than 5.4 grams. 
     
     
         14 . The iron-type golf club head according to  claim 13 , wherein the overall mass of the filler material is less than 11 grams. 
     
     
         15 . The iron-type golf club head according to  claim 6 , wherein a total combined mass of the filler material and the at least one stiffener is greater than 5 grams. 
     
     
         16 . The iron-type golf club head according to  claim 15 , wherein the total combined mass of the filler material and the at least one stiffener is greater than 5.5 grams. 
     
     
         17 . The iron-type golf club head according to  claim 6 , wherein the at least one stiffener further comprises an enclosure within the internal cavity and defining a cavity isolated from the internal cavity of the golf club head, and wherein the discrete mass of polymeric material is retained within the cavity of the enclosure. 
     
     
         18 . The iron-type golf club head according to  claim 1 , wherein the polymeric material has an overall mass less than 5 grams and more than 0.25 grams. 
     
     
         19 . The iron-type golf club head according to  claim 1 , wherein the polymeric material has an overall mass no more than 3 grams and more than 0.25 grams. 
     
     
         20 . The iron-type golf club head according to  claim 3 , wherein:
 the toe portion comprises an aperture extending through the toe portion and providing access to the back surface of the strike face; and   the discrete mass of polymeric material is insertable, through the aperture in the toe portion, into the internal cavity against the back surface of the strike plate.   
     
     
         21 - 106 . (canceled)