Fiber composite and process of manufacture

What is this patent about?

'666 is related to the field of manufacturing composite structures, specifically sports racquets like tennis and badminton racquets, golf club shafts, and bicycle frames. Traditional methods involve manual labor, molds, and air injection to form graphite composite frames. These frames are typically hollow, which presents limitations in achieving thinner, stronger designs and can contribute to vibration-related injuries.

The underlying idea behind '666 is to use a foamable plastic material within a closed layup to apply pressure during the curing process, eliminating the need for air injection. This is achieved by incorporating a microencapsulated foaming agent into the layup. When heated, the agent expands, pressing the fiber layers against the mold walls and fusing them together. This results in a solid, rather than hollow, frame.

The claims of '666 focus on a resin and fiber composite racquet comprising two tubular members: one extending around the head, and another extending from the handle, around the head, and back to the handle. Each tubular member has an outer shell of fiber layers secured by a resin, and a second resinous material inside the cavity defining voids containing a gaseous material under pressure exceeding 30 psi.

In practice, the process involves wrapping layers of fiber (e.g., graphite) permeated with resin around a mandrel. A powdered, microencapsulated foaming agent is then placed inside the wrapped layers, and the ends are sealed to form a closed bladder. This bladder is placed in a mold and heated. The heat causes the foaming agent to expand, creating pressure that forces the fiber layers against the mold, resulting in a solid, cured composite structure. The closed-cell foam also dampens vibrations.

This method differs from traditional air injection techniques in several key ways. It eliminates the need for manual attachment of air nozzles, enabling a more automated and consistent manufacturing process. The resulting solid frame can be made thinner and stronger than conventional hollow frames, improving swing speed and feel. Furthermore, the solid core reduces vibration and shock, potentially minimizing injuries. The use of microencapsulated foaming agents allows for precise control over the expansion process, ensuring optimal pressure and fiber alignment during curing.