US 5,888,148 · Granted 1999-03-30
The Hidden Power Shaft That Made Golf Club Heads Stronger
Imagine a metal rod hidden inside a golf club head that's under constant squeeze, like a spring being compressed. This squeeze makes the whole club stiffer and more powerful when you swing it, and the rod is pressed in so firmly that the manufacturer doesn't need to weld it in place—it just stays put.
The plain-English version
What it protects
The claim covers a golf club head design with an internal metal shaft that runs along the target line and is held under compression (squeezed inward). What's protected here is the specific method of press-fitting this power shaft into the front of the club face, plus the technique of casting the club head in two halves and clamping them together during welding so the shaft gets squeezed into a preloaded state that increases the club's stiffness.
Why it matters
This patent protects a manufacturing innovation that solves real problems in club-head construction. By using an internal compressed shaft instead of relying on welding bonds, manufacturers can make larger club heads from lighter, lower-strength alloys while still achieving the rigidity needed for performance. The preload technique also allows for a product line where different club heads have different compression levels tuned to different swing speeds, creating a semi-customized experience without building each club from scratch.
Real-world use
Every time a golfer swings a driver or wood and feels the club face resist and spring back slightly, some of that response comes from innovations like this internal preloaded shaft that increases the club's structural strength.
Original USPTO abstract
A golf club head with an internal power shaft that extends along the target line. In a high volume club head embodiment above 250 cm. 3 , constructed of a low modulus alloy compared to stainless steel, the power shaft has a preload, or static compression, to increase the modulus of elasticity of the head and ball striking face. This preload technique is expanded in another embodiment into a semi-customized line of golf club woods, where the club head modulus of elasticity increases with the golfer's club head speed by progressively increasing preload in the club head line. The power shaft is press-fitted into the rear of the ball striking face to reduce bonding and welding difficulties in joining the power shaft to the ball striking face. The modulus of the face wall and the power shaft is enhanced by casting or welding the sole plate of the club head along an axial extent directly to the outer surface of the power shaft thereby increasing its columnar strength. This unique club is assembled by casting the club head in two pieces parting along a vertical plane parallel to the club face, one forward and one rear, and assembling the head by clamshelling the power shaft between the forward wall and rear pieces and then welding or otherwise bonding the forward and rear pieces together. By applying opposite axial clamping forces to the two club head pieces during and after welding or other heat bonding, the power shaft is preloaded into a static compression state.
Patent details
- Publication number
- US 5,888,148
- Filing date
- 1997-10-09
- Grant date
- 1999-03-30
- Assignee
- Vardon Golf Company, Inc.
- Inventor(s)
- ALLEN; DILLIS V.
- CPC class
- A63B53/04
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