In the archery industry, there is a consistent drive to manufacture arrows having decreased weight and increased durability. Traditionally, arrow shafts were made from lightweight wood, bamboo, and reeds. To decrease their weight and produce arrows that are easier to shoot and that can fly farther, modern arrows are made from aluminum and fiber reinforced plastic. Carbon fiber, a type of fiber reinforced plastic, has been used since the 1990s as a lightweight material used to make arrows. While modern materials are lighter in weight than traditional materials, modern materials are not as durable. Moreover, while modern materials are lighter, there is a consistent pursuit to decrease arrow weight.
Modern arrows are typically made from a carbon fiber arrow shaft that is hollow, and include an arrow tip in the front of the arrow shaft, a nock in the rear of the arrow shaft, and fletching along the surface of the arrow shaft adjacent the nock. In flight, the hollow arrow shaft flexes slightly along its length in an oscillatory motion. Specifically, the action of shooting the arrow from the bow creates a deflection along the length of the arrow, which oscillates as the arrow travels. As a result, archers generally choose the arrow shaft and its components to match their equipment and to meet their shooting requirements. This includes choosing an arrow shaft having the correct length, weight, and stiffness. Archers chose an arrow shaft with a defined static spine, which is the stiffness of the arrow shaft and its resistance to bending. Based on their chosen arrow shaft and corresponding static spine, they then add tips, fletching, and nocks to tune the dynamic spine, which is the deflection of the arrow when fired from a bow. The physical properties of the arrow shaft, including the overall weight and the center of gravity of the arrow, affects the arrow performance.
For a specific arrow shaft having a particular length and static spine, the change in weight will adversely affect the static spine of the arrow shaft. The static spine of an arrow shaft is generally determined by the material of the arrow shaft, the thickness of the arrow shaft walls, and the length of the arrow shaft. Changing weight between arrow shafts made of the same carbon fiber material with the same length requires changing the wall thickness of the arrow shaft. The thinner walled arrows shafts will be lighter, but will have a lower static spine because the stiffness of the arrow shaft would decrease. Altering any one of the properties of the arrow shaft will affect the other. This limits the ability of the archer to choose a particular carbon fiber arrow shaft having a specific weight, length, and diameter with a specific static spine.
In light of the above, it would be advantageous to provide a lightweight arrow shaft having an overall stiffness comparable to the stiffness of a heavier arrow shaft. It would further be advantageous to provide a thin walled arrow shaft having an overall stiffness comparable to a thicker walled arrow shaft. It would further be advantageous to provide an arrow shaft with internal bracing with stiffness comparable to heavier weighted arrow shafts.
USPTO Backgrounds
USPTO Backgrounds