US 5,482,285 · Granted 1996-01-09
The Three-Layer Golf Ball That Changed How Pros Play
Golf balls used to be one solid piece, but this patent describes a smarter design with three layers—a hard inner core, a softer outer core, and a tough ionomer cover. The specific sizes and weights of each layer let the ball fly farther and spin differently depending on how you hit it.
The plain-English version
What it protects
The claim covers a golf ball design with a precisely engineered three-piece structure: an inner core between 10–38 mm in diameter, a low-density outer core (specific gravity 0.2–0.79) with a diameter of 37–40 mm, and an ionomer resin cover. What's protected here is this exact layering strategy and the weight ranges—any golf ball manufacturer copying this core-within-core geometry and material specification would infringe.
Why it matters
Golf ball design is a high-stakes competitive arena where performance gains translate directly into tournament wins and equipment sales. By engineering the inner and outer cores to different densities and sizes, manufacturers can tune how the ball behaves—controlling compression, spin rate, and distance in ways a single-piece or two-piece ball cannot match. This patent gave Sumitomo Rubber a protected formula for a generation of performance golf balls.
Real-world use
When a golfer at any course on earth pulls a three-piece Sumitomo golf ball from their bag and drives it down the fairway, they're benefiting from the precise layer thicknesses and material choices locked in by this patent.
Original USPTO abstract
A three-piece solid golf ball comprising an inner core 1a, an outer core 1b, and a cover formed principally of an ionomer resin, wherein said inner core 1a has a diameter of 10 to 38 mm, said outer core 1b has a specific gravity of 0.2 to 0.79 and has a diameter of 37 to 40 mm and a total weight of the inner core 1a and the outer core 1b is within the range of 32.0 to 39.0 g.
Patent details
- Publication number
- US 5,482,285
- Filing date
- 1994-01-26
- Grant date
- 1996-01-09
- Assignee
- Sumitomo Rubber Industries, Ltd.
- Inventor(s)
- YABUKI; YOSHIKAZU, HIRAOKA; HIDENORI, KOIZUMI; YOSHIMASA
- CPC class
- A63B37/0003
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