Patent Application
20060281593
The following references are considered relevant prior art.
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Shafts used in the construction of arrows for archery have undergone substantial technological development starting from the historical known construction using solid wooden stakes to light-weight, extruded metal tubes to present composite, tubular, roll-wrapped construction. Each newly developed construction method included new advantages and restrictions caused by the constraints of each new technology. The shafts of the present invention teach a unique wall construction designed to overcome restrictions of previous teachings and a construction method designed to simplify the manufacturing process of high-strength shafts.
It is therefore a purpose of the invention to teach a simplified method of producing arrow shafts, while another purpose of the invention is to produce unitary shafts with functionality that required expensive assembly of several components in previous shaft construction techniques. A further purpose of the invention is to teach unitary shaft design with function possibilities not easily available with earlier construction methods.
While the teachings of this invention are primarily described for the construction of arrow shafts, it will be obvious to those with knowledge of the art that the design and construction method taught may apply with equal advantage to a wide range of substantially long and narrow products.
Modern tubular arrow shafts are generally produced using two main methods of manufacture. These methods are (1) extruding metal into shafts, typically using an aluminum alloy for the extruded metal, and (2) roll-wrapping shafts typically using carbon composite fabric or other sheet material as the rolled substance. There is also a combination of these two main methods sometimes used to make shafts in which fabric material is rolled over and bonded to an extruded aluminum shaft to make a unitary shaft construction.
Metal shafts are typically extruded of a single alloy and rely almost exclusively on the chemical and mechanical characteristics of the metal alloy to determine the strength, flex and other characteristics of the finished shaft. Because the metal shafts are extruded, the shape considerations of the shafts are understood to be the same as those applied to all extruded products. The metals chosen to extrude shafts are typically expensive alloys, but the extrusion process is well known and generally lends itself to known automated manufacturing processes.
Because they have a number of layers, roll-wrapped shafts can have their characteristics adjusted by selecting different fabric materials and deciding the order of materials as they are layered or wrapped around a substantially bar-shaped forming tool called a mandrel. Further, the shape and dimensional cuts of fabric patterns can be adjusted to produce special shaft characteristics.
Producing shafts by wrapping and bonding fabric over extruded metal shafts can combine the benefits and final shaft characteristics of both methods but tends to be very costly since the expenses of both systems must be added together.
The arrow of
In known methods of producing arrow shafts, forming tools are required to produce the shape of the shafts, and the forming tools, while essential to the formation of the shafts, are removed during the production process and are not a part of the finished product. The forming tool for extruded metal shafts is typically a hardened-metal bushing through which metal is forced under very high pressure to form a continuous metal tube which is then cut to length to become the final shaft.
The forming tool for roll wrapped shafts is typically a bar of hardened steel named a mandrel which is shaped to establish the inside diameter and shape of the arrow shaft. Cut fabric patterns of a chosen material are wrapped around the mandrel by a known rolling method and then processed into the finished arrow shaft, during which process, the mandrel is removed and recycled to be used again for another shaft. The roll wrapping method involves a substantial number of steps and a large amount of labor and time and is illustrated in
Specialized fabric usually comprising a matrix of high-strength fibers and thermoset resin is cut into patterns that are roll-wrapped around solid steel mandrels.
A polymer tape is spiral-wrapped over the wrapped fabric to both hold the fabric in place and to squeeze the fabric into tight compaction.
The assembly of mandrel, fabric and tape is baked in an oven for a prescribed period of time during which the fiber/resin matrix solidifies into a single-characteristic tube which forms the base characteristics of the arrow shaft.
After baking, the mandrel is removed from the inside of the shaft and recycled, following which the polymer tape is removed from the outside of the shaft.
The shaft is sanded smooth, cut to length, cleaned and the insert is fixed into one end of the tube. The shaft is then processed for final assembly and packaging.
The shaft of the invention is produced in a much simplified process using known processes and in which the Forming Tool remains an integral part of the finished shaft. The forming tool of the invention is clad with material that provides an Exoskeleton 8 as shown in
The simplified process of the invention is illustrated in
Forming Tool 20 is precisely formed by known processes such as injection molding, extrusion, machining or the like.
Forming Tool 20 is Clad 21 with an exoskeleton of substantially rigid material by a choice of know processes such as plating, dipping, physical vapor deposition or the like. The desired final shaft characteristics determine which known cladding process will be used and which material will be used to form the Exoskeleton. Since known processes can precisely control the cladding thickness, the Forming Tool 20 is dimensionally shaped so that the cladding builds to the final dimension of the shaft, and after cladding the shaft can go directly to Final Assembly and Packaging 23.
While the invention proposes the use of known cladding process to apply an Exoskeleton over a Forming Tool, it anticipates the development of improved materials to be used in those known processes so that improved Exoskeletons will develop as the materials used in conventional cladding processes become available.
Since the cladding process provides a substantial portion of the final shaft strength, Forming Tool 20 has limited requirements concerning strength and material content. Forming Tool 20 requires primarily that its shape remain stable during all stages of processing and that it be of a material compatible with proper cladding of the Exoskeleton material.
The liberty to shape the Forming Tool by conventional means permits features to be included in the Forming Tool to reduce parts assembly and to add features that might be difficult or prohibitively expensive to include with existing production methods. The sectioned view of
U.S. Pat. Nos. 6,179,736 B1 and 6,821,219 B2 teach a tapered shaft construction.
U.S. Pat. No. 6,595,880 B2 teaches a method of fluting an arrow shaft.
U.S. Pat. No. 6,129,642 teaches a grooved arrow shaft
U.S. Pat. No. 6,017,284 teaches a reduced diameter portion arrow shaft.
U.S. Pat. No. 5,273,293 teaches a variety of fluted shapes for arrow shafts.
All the taught features such as tapers, flutes, grooves, varied diameters and the like can be far more easily formed with the use of a Forming Tool and the rigid Exoskeleton structure of the invention. Even logos and names can be shaped into the Forming Tool to become integral features of the final shaft. Any shape into which the Forming Die can be formed determines the basis of the final Exoskeleton shape.
It is understood that known methods of controlling cladding processes can also vary the thickness and therefore the characteristics of the Exoskeleton even when using a standard Forming Tool. For example the Exoskeleton thickness can be adjusted during processing along the axial length of the shaft to produce differing axial weight distribution or provide extra strength at chosen shaft positions or other similar considerations.
While the description of the invention is directed at shaft manufacture and specifically at arrow shaft construction, it will be understood by those with knowledge of the art that the techniques described may apply with equal advantage to a wide variety of parts that share the common feature of a substantially long, thin shape. Such a variety of parts may include but are not restricted to fishing rods, golf shafts, helicopter blades, boat propellers, oars, hockey sticks, tennis rackets, pool cues, ski poles, boat tillers, bicycle parts, and control linkage for motorcycles, automobiles, and aircraft.
