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 portion 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.

1 . A golf club head comprising:
 a hollow body defining an enclosed internal cavity, the hollow body comprising:   a strikeface;   a heel portion;   a toe portion opposite the heel portion;   a sole;   a top rail;   a rear portion extending between the top rail and the sole, and separated from the strikeface by the internal cavity;   a solid ballast within the internal cavity extending substantially between the heel portion and the toe portion;   wherein the solid ballast extends upward from the sole and forward from the rear portion;   wherein the solid ballast comprises a ballast top surface, a ballast forward surface, and a ballast juncture between the ballast top surface and the ballast forward surface;   a ballast forward plane tangent to the ballast juncture and parallel to the strikeface;   wherein a ballast angle is defined between the ballast forward surface and an interior surface of the sole;   wherein the ballast angle is between 30 and 80 degrees;   an undercut formed between the ballast forward surface and the interior surface of the sole;   wherein the undercut comprises:
 an undercut bottom edge formed by the interior surface of the sole; 
 an undercut top edge formed by the ballast forward surface; 
 an undercut juncture located at a transition between the interior surface of the sole and the ballast forward surface; 
   an undercut height measured as a vertical distance between the undercut bottom edge and the undercut top edge; and   wherein the undercut height measured at the ballast forward plane is greater than 0.250 inch.   
     
     
         2 . The golf club head of  claim 1 , further comprising:
 a cascading region defining an internal transition region from the strikeface to the sole, the cascading region comprising;   a first tier comprising a first thickness;   a second tier comprising a second thickness different than the first thickness; and   a tier transition region between the first tier and the second tier.   
     
     
         3 . The golf club head of  claim 2 , further comprising a cascading region perimeter defining a boundary between the cascading region and the sole; and
 wherein the cascading region perimeter comprises a cascade front edge proximate a leading edge of the strikeface and a cascade rear edge spaced rearwardly from the strikeface.   
     
     
         4 . The golf club head of  claim 3 , wherein the cascade rear edge is arcuate and bows rearward relative to the cascade front edge;
 wherein the cascading region comprises a depth measured as a front-to-rear distance between the cascade front edge and the cascade rear edge; and   wherein the depth of the cascading region is greater proximate a center of the club head than the depth of the cascading region near the toe portion and the heel portion.   
     
     
         5 . The golf club head of  claim 3 , wherein a width of the cascading region is greater proximate the cascade front edge than near the cascade rear edge. 
     
     
         6 . The golf club head of  claim 1 , further comprising an undercut depth measured as a perpendicular distance between the ballast forward plane and the undercut juncture; wherein the undercut depth is greater than 0.100 inch. 
     
     
         7 . The golf club head of  claim 1 , wherein the ballast angle is between 60 degrees and 80 degrees. 
     
     
         8 . The golf club head of  claim 1 , wherein the ballast forward surface comprises a concave curvature relative to the strikeface. 
     
     
         9 . The golf club head of  claim 1 , further comprising a top rail-to-sole moment of inertia ranging from 95 g·in 2  to 130 g·in 2  and a heel-to-toe moment of inertia ranging from 350 g·in 2  to 420 g·in 2 . 
     
     
         10 . A golf club head comprising:
 a hollow body defining an enclosed internal cavity, the hollow body comprising:   a strikeface;   a heel portion;   a toe portion opposite the heel portion;   a sole;   a top rail;   a rear portion extending between the top rail and the sole, and separated from the strikeface by the internal cavity;   a solid ballast within the internal cavity extending substantially between the heel portion and the toe portion;   wherein the solid ballast extends upward from the sole and forward from the rear portion;   wherein the solid ballast comprises a ballast top surface, a ballast forward surface, and a ballast juncture between the ballast top surface and the ballast forward surface;   a ballast forward plane tangent to the ballast juncture and parallel to the strikeface;   wherein a ballast angle is defined between the ballast forward surface and an interior surface of the sole;   wherein the ballast angle is between 30 and 80 degrees;   an undercut formed between the ballast forward surface and the interior surface of the sole;   wherein the undercut comprises:
 an undercut bottom edge formed by the interior surface of the sole; 
 an undercut top edge formed by the ballast forward surface; 
 an undercut juncture located at a transition between the interior surface of the sole and the ballast forward surface; 
   a cascading region defining an internal transition region from the strikeface to the sole, the cascading region comprising;
 a first tier comprising a first thickness; 
 a second tier comprising a second thickness different than the first thickness; 
 a tier transition region between the first tier and the second tier; 
 wherein the cascading region comprises a perimeter boundary comprising a cascade front edge proximate a leading edge of the strikeface, a cascade rear edge spaced rearwardly from the strikeface, a cascade heel edge extending between the cascade front edge and the cascade rear edge proximate the heel portion, and a cascade toe edge extending between the cascade front edge and the cascade rear edge proximate the heel portion; 
 wherein the cascading region comprises a depth measured as a front-to-rear distance between the cascade front edge and the cascade rear edge; 
 wherein the depth of the cascading region is greater proximate a center of the club head than the depth of the cascading region near the toe portion and the heel portion; and 
 wherein the depth of the cascading region at the cascade heel edge is between 50% and 90% of the depth of the cascading region at the center of the club head. 
   
     
     
         11 . The golf club head of  claim 10 , wherein the cascading region further comprises a cascading region depth measured between the cascade heel edge and the cascade toe edge in a heel to toe direction; wherein the cascading region depth is greater near the cascade front edge than near the cascade rear edge. 
     
     
         12 . The golf club head of  claim 10 , wherein the cascade rear edge is arcuate and bows rearward relative to the cascade front edge. 
     
     
         13 . The golf club head of  claim 10 , wherein the cascading region further comprises a third tier. 
     
     
         14 . The golf club head of  claim 10 , wherein the tier transition region linearly declines at an angle less than 45 degrees. 
     
     
         15 . The golf club head of  claim 10 , wherein the ballast forward surface comprises a concave curvature relative to the strikeface. 
     
     
         16 . The golf club head of  claim 10 , wherein the ballast angle is between 60 degrees and 80 degrees.