A golf club head and a method of making a golf club head includes a framework that is applied to the rear portion of the club head. A heat shrinkable membrane is mounted to the framework, by either mechanical means or by application of a bonding agent, creating a hollow golf club wherein the membrane material at the center of the rear portion is taut and exposed. The membrane is made from a conformable heat shrinkable fabric having a high tensile strength and negligible compressive strength. The fabric comprises thin, relative flexible, long interwoven fibers such as Kevlar, canvas, sailcloth and fabrics used in the skins of airplanes.
1. A hollow golf club head comprising:
a body formed from a material having a density, the body having a rear surface formed by an upper portion and a sole portion, the upper and sole portions defining a cavity therein;
the rear surface having a substantially oval shaped perimeter opening defined therein;
a framework supporting a conformable heat shrinkable membrane of density less than the body, the framework having a perimeter edge of a size and configuration for attaching about the perimeter opening;
means for attaching the framework to the rear surface; and
the membrane being in a tensioned condition but having virtually no compressive strength,
wherein the membrane is exposed through the rear portion and maintains a tensioned condition for varying temperatures and environmental exposures.
2. The golf club head according to claim 1 , wherein the heat shrinkable membrane comprises thin, relatively flexible, long interwoven fibers being strong in tensile strength.
3. The golf club head according to claim 1 , wherein the framework is constructed of aluminum.
4. The golf club head according to claim 1 , wherein the framework is constructed of plastic.
5. The golf club head according to claim 1 , wherein the membrane is securely captured and stretched in the framework by an injection molding process.
6. The club head of claim 1 , wherein the membrane has a shrink rate of about
0 to 35% at a temperature range between about 200° F. to 450° F.
7. The club head of claim 1 , wherein the membrane has a woven strength between 50 to 1100 pounds per inch.
8. The club head of claim 1 , wherein the membrane has a woven flexural strength of about 20 to about 450 MPa.
9. The club head of claim 1 , wherein the membrane has a woven flexural modulus of about 2 to 45 GPa.
10. The club head of claim 1 , wherein the membrane has a density between
0.1 g/cc to 2.5 g/cc.
11. The club head of claim 1 , wherein the membrane has a yarn tenacity of 2 to 40 g/d.
12. The club head of claim 1 , wherein the membrane has a yarn modulus between about 20 to about 1600 g/d.
13. The club head of claim 1 , wherein a decorative medallion is attached directly to the membrane, the membrane having a first specific gravity and the medallion having a second specific gravity greater than the first, wherein upon impact of the club head and a golf ball, a vibration dampening is created that will dampen unwanted vibrations.
14. The golf club head according to claim 1 , wherein the attaching means comprises:
a ledge disposed about and in close proximity to the perimeter opening;
a loom ring assembly attached to the ledge and held in place with an epoxy;
the membrane secured within the framework and attached to the loom ring assembly; and
a stop bead located at the perimeter edge of the membrane to prevent slippage out of the loom ring assembly.
15. A method of forming a hollow golf club head comprising the steps of:
providing a body having a cavity defined therein, and a substantially oval shaped perimeter opening defined in a rear surface;
providing a ledge about and in close proximity to the oval shaped perimeter opening;
providing a framework made from a lightweight material;
attaching a membrane to the framework;
heating the membrane causing it to be taut within the framework; and
attaching the framework to the oval shaped perimeter opening to seal the cavity,
wherein the membrane is visible on the rear surface and has a tensile strength but virtually no compressive strength.
16. The method of claim 15 , wherein the framework comprises a lightweight material such as aluminum or plastic.
17. The golf club head according to claim 15 , wherein the attaching means comprises:
a ledge disposed about and in close proximity to the perimeter opening;
a loom ring assembly attached to the ledge and held in place with an epoxy;
the membrane secured within the framework and attached to the loom ring assembly; and
a stop bead located at the perimeter edge of the membrane to prevent slippage out of the loom ring assembly.
18. The method of claim 15 , wherein heating the membrane includes heating a membrane material selected from a fabric that is thin, relatively flexible, and having long interwoven fibers which are very strong in tension.
19. The method of claim 18 , wherein the attaching of the membrane to the framework is by an injection molding process.
20. The method of claim 18 , wherein the membrane has a shrink rate of about 0 to 35% at a temperature range between about 200° F. to about 350° F.
21. The method of claim 18 , wherein the membrane has a woven strength between 50 to 1100 pounds per inch.
22. The method of claim 18 , wherein the membrane has a woven flexural strength of about 20 to about 450 MPa.
23. The method of claim 18 , wherein the membrane has a woven flexural modulus of about 2 to 45 GPa.
24. The method of claim 18 , wherein the membrane has a density between 0.1 g/cc to 2.5 g/cc.
25. The method of claim 18 , wherein the membrane has a yarn tenacity of 2 to 40 g/d.
26. The method of claim 18 , wherein the membrane has a yarn modulus between about 20 to about 1600 g/d.