Golf club heads with internal undercuts

Abstract

Described herein is a hollow body iron-type golf club head having a sole and ballast configured to relieve stress within a forward region of the sole. In a first configuration, the golf club head comprises a ballast undercut for relieving stress. In other configurations, the ballast undercut is combined with additional stress relief features, such as a cascading sole near the face sole juncture, for further reductions to face thickness. In further configurations, the ballast defines a recess for receiving a ballast weight having a density greater than the body, thereby improving mass properties of the golf club head.

1 . A golf club head, comprising:
 a hollow body defining an enclosed internal cavity, the hollow body comprising:   a front, a heel, a toe opposite the heel, a sole, a top rail, a rear extending between the top rail and the sole, and separated from the strike face by the internal cavity;   a front perimeter edge defining a front opening configured to receive a strike face insert;   a lap joint edge extending around a perimeter of the rear defining a rear opening;   a ballast located in the interior cavity at the junction of the sole and the rear and extending in a heel toe direction, wherein the ballast comprises a bottom surface, rear surface, toe surface, and heel surface defining a ballast recess configured to receive a ballast weight, wherein the ballast weight is seated within the recess to form a continuous and uninterrupted ballast wall and is exposed to the interior cavity.   
     
     
         2 . The golf club head of  claim 1 , wherein the ballast weight comprises a front surface that is contoured towards the towards the rearward region to define an undercut. 
     
     
         3 . The golf club head of  claim 1 , wherein the ballast weight is formed of a tungsten material. 
     
     
         4 . The golf club head of  claim 3 , wherein the ballast weight comprises a mass between 5 and 60 grams. 
     
     
         5 . The golf club head of  claim 4 , wherein the ballast weight comprises a mass between 13 and 35 grams. 
     
     
         6 . The golf club head of  claim 2 , wherein the ballast weight has a top surface that is curved such that a heel end and a toe end of the ballast weight extend further from the sole than a middle of the ballast weight. 
     
     
         7 . The golf club head of  claim 1 , wherein the ballast weight is welded to the weighted ballast. 
     
     
         8 . The golf club head of  claim 1 , wherein the hollow body comprises a first material with a first density and the ballast weight comprises a second material with a second density, wherein the second density is greater than the first density. 
     
     
         9 . The golf club head of  claim 1 , further comprising a support member extending across the rear opening, wherein the support member connects at least two portions of the lap joint edge. 
     
     
         10 . The golf club head of  claim 9 , wherein the golf club head comprises an insert comprising a channel, wherein the insert is configured to cover the rear opening such that the channel receives the support member. 
     
     
         11 . A golf club head comprising:
 a hollow body defining an enclosed internal cavity, the hollow body comprising:   a front portion, a heel portion, a toe portion opposite the heel portion, a sole, a top rail, a rear extending between the top rail and the sole, and separated from the strike face by the internal cavity;   a front perimeter edge defining a front opening configured to receive a strike face insert;   a lap joint edge extending around a perimeter of the rear defining a rear opening;   a weighted ballast located in the interior cavity at the junction of the sole and the rear and extending in a heel toe direction, wherein the weighted ballast comprises a heel recess and a toe recess configured to receive a heel ballast weight and a toe ballast weight, respectively; wherein the toe ballast weight comprises a toe top surface and a toe front surface that are exposed to the interior cavity; wherein the heel ballast weight comprises a heel top surface and a heel front surface that are exposed to the interior cavity.   
     
     
         12 . The golf club head of  claim 11 , wherein the weighted ballast comprises a front surface that is contoured towards the towards the rearward region to define an undercut. 
     
     
         13 . The golf club head of  claim 11 , wherein the toe ballast weight and the heel ballast weight are formed of a tungsten material. 
     
     
         14 . The golf club head of  claim 13 , wherein the toe ballast weight comprises a mass between 5 and 60 grams and the heel ballast weight comprises a mass between 5 and 60 grams. 
     
     
         15 . The golf club head of  claim 14 , wherein the heel ballast weight comprises a mass between 13 and 35 grams and the toe ballast weight comprises a mass between 13 and 35 grams. 
     
     
         16 . The golf club head of  claim 12 , wherein the weighted ballast has a top surface that is curved such that a heel end and a toe end of the weighted ballast extend further from the sole than a middle of the weighted ballast. 
     
     
         17 . The golf club head of  claim 11 , wherein the toe ballast weight and heel ballast weight are welded to the weighted ballast. 
     
     
         18 . The golf club head of  claim 11 , wherein the hollow body comprises a first material with a first density and the toe ballast weight and the heel ballast weight comprise a second material with a second density, wherein the second density is greater than the first density. 
     
     
         19 . The golf club head of  claim 11 , further comprising a support member extending across the rear opening, wherein the support member connects at least two portions of the lap joint edge. 
     
     
         20 . A golf club head comprising:
 a strike face;   a body coupled to the strike face to define an internal cavity, the body comprising:
 a front have a front perimeter configured to receive the strike face; 
 a heel, a toe opposite the heel, a sole, a top rail opposite the sole, a rear opposite the front and extending between the top rail and the sole, the rear defining a rear opening and a lap joint bordering the rear opening; and 
 a ballast located in the interior cavity at a junction of the sole and the rear extending in a heel toe direction, wherein the ballast comprises a ballast bottom surface, a ballast rear surface, a ballast toe surface, and a ballast heel surface, wherein the ballast defines a ballast recess; and 
 a ballast weight disposed in the ballast recess, wherein the ballast weight is formed of a ballast weight material that is more dense than a remainder of the body, wherein the ballast weight comprises a ballast weight bottom surface configured to abut the ballast bottom surface, a ballast weight rear surface configured to abut the ballast rear surface, a ballast weight toe surface configured to abut the ballast toe surface, and a ballast weight heel surface configured to abut the ballast heel surface.