US 4,438,931 · Granted 1984-03-27
The Hollow Golf Club Head That Changed How Clubs Are Built
Instead of carving golf club heads from solid metal, this patent describes gluing together thin shells and filling the cavity with foam to make clubs lighter and more forgiving. It's the reason modern drivers feel almost like you're swinging air.
The plain-English version
What it protects
The claim covers a golf club head made by joining multiple thin shell sections (front and rear, or face, top, and body sections) along their edges to create a sealed hollow space, with a shaft integrated during assembly and the interior cavity filled with foam or rubber filler material. What's protected is this specific construction method—the hollow multi-shell architecture and the integrated filling process that gives the club its structure and performance characteristics.
Why it matters
Before this approach, golf clubs were mostly solid forgings, which limited design flexibility and made them heavier. This hollow shell-and-foam construction became the foundation for modern club design, allowing manufacturers to redistribute weight, adjust center of gravity, and improve impact performance—innovations that define premium golf clubs today. Kabushiki Kaisha Endo Seisakusho's patent laid the groundwork for how virtually all contemporary metal woods and irons are engineered.
Real-world use
Every time a golfer swings a modern driver or fairway wood, they're benefiting from a hollow head filled with foam designed to absorb impact and launch the ball farther than a solid club ever could.
Original USPTO abstract
A golf club head comprising two or more thin shell sections, for instance a front shell section and a rear shell section, or a face shell section, a top shell section and a body shell section including a bottom section and a side section, are secured together along their edges to form a one-piece shell having a sealed space. A shaft is also secured together with the shell sections when securing these sections. The sealed space is filled with a filler material such as foamed urethane and rubber.
Patent details
- Publication number
- US 4,438,931
- Filing date
- 1982-09-16
- Grant date
- 1984-03-27
- Assignee
- Kabushiki Kaisha Endo Seisakusho
- Inventor(s)
- MOTOMIYA; TETSUO
- CPC class
- A63B53/04
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