Winding – tensioning – or guiding – Coil holder or support – Spool or core
Reexamination Certificate
1999-11-05
2001-01-30
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Coil holder or support
Spool or core
Reexamination Certificate
active
06179245
ABSTRACT:
BACKGROUND
1. The Field of the Invention
This invention relates to spools and reels for receiving stranded materials, and, more particularly, to novel systems and methods for producing plastic flanges for reels and spools as take-up of electrical wire during manufacture.
2. The Background Art
Spools and reels are used in many industries. However, in the wire and cable industry, the comparative weight of stranded material on a reel or spoon is greater than others of similar size in other industries. Fracture of flanges near an outer diameter thereof is common if dropped. Likewise, due to certain conventional shapes, central tubes (hubs, cores, etc.) and their junctions with flanges are not inherently resistant to fracture from impact loads caused by dropping. Dropping from a working bench is common for reels and spools. Manufacturing processes for manufacturing reels and spools, as well as manufacturing processes for wire and other stranded materials, typically compels smooth circumferential edges at the outermost diameter of a flange. Accordingly, a spool not retained on an arbor during use (using the wire, rather than manufacturing and taking up the wire) may roll easily across any flat surface. Thus, while a spool or reel is considered tare weight in shipping wire and cable, and a disposable item whose cost is to be minimized, it must function reliably and durably during its entire useful life.
Otherwise, a substantial length of stranded material may be damaged beyond use the material held on a spool or reel having a value of a few dollars may itself have a value of one thousand times the cost of a spool. A value two orders of magnitude greater than that of the spool is routine for wire of common usage.
3. State of the Art
Stranded materials, upon manufacture, are typically taken up directly onto a reel or spool. The take-up spool or reel receives the strand directly from the last step in the manufacturing process. Thereafter, the filled spool is effective for storage and handling purposes. Upon sale or distribution, the spool is often placed on an arbor, either alone or with other spools, for convenient dispensing of the linear or stranded material. Linear or stranded materials include electrical wire whether in single or multiple strands and cable (comprised of multiple wires), rope, wire rope, hose, tubing, chain and plastic and rubber profile material (generally any polymeric or elastomeric extruded flexible material).
In general, a host of elongate materials as diverse as pharmaceutical unit dose packages, fiberoptic line and log chains are stored on spools. Likewise, ribbon, thread and other stranded materials are wrapped on spools.
The requirement for a spool in the manufacture and handling of wire is substantially different than spools in the textile industry. For example, the weight of wire is several times the weight of thread or rope. The bulk of wire, which translates to the inverse of density, is substantially lower for wire than for hose, tubing or even chain.
Meanwhile, most spools are typically launched on a one way trip. The collection and recycling of spools is hardly worth the effort, considering that their materials are not easily recyclable.
In the art, a typical spool has a tube portion extending between two flange portions positioned at either end of the tube portion. A spool may have a rounded rim or rolled edge at the outermost diameter. This rim serves structural as well as aesthetic and safety purposes. Spools may be manufactured in a variety of tube lengths. Each flange is fitted by some fixturing to one end of the tube and there retained. Details of spools are contained in the U.S. Pat. No. 5,464,171 directed to a mating spool assembly for relieving stress concentrations, incorporated herein by reference.
The impact load of a spool of wire dropping from a bench or other work surface to a floor in a manufacturing environment is sufficient to fracture the spool in any of several places. Fracture may damage wire, preclude removal, or release the wire in a tangled, useless mass.
Spools may break at the corner where the tube portion meets the flange portion or may fracture at an engagement portion along the tube portion. Spools may break near the corner between the flange and the tube portion where a joint bonds or otherwise connects the tube portion to the flange portion.
Spools and reels experience significant breakage during drop tests when manufactured in styrene or styrene-based plastics such as ABS. Polyolefins are very tough materials. Tough means that a material can tolerate a relatively large amount of straining or stretching before rupture. By contrast, a material which is not tough will usually fracture rather than stretch extensively. As a result, when a reel of wire is dropped, the energy of impact breaks the spool.
Polyolefins, by contrast, may actually be drawn past yielding into their plastic elongation region on a stress-strain chart. Polyolefins thus elongate a substantial distance. The result is that olefinic plastics will absorb a tremendous amount of energy locally without rupture. Thus, the wire on a spool which has been dropped does not become a tangled mat of loops.
Given their toughness, olefinic parts will bend, strain, distort, but usually not break. Nevertheless, olefinic plastics are not typical in the art of wire spools. Polyolefin parts are not bonded into multi-piece spools. However. Lack of a solvent is one problem, lack of a durable adhesive is another. Therefore, any spool would have to be manufactured as unit of a specific size. The inventory management problem created by unique spools of various sizes is untenable, although the cost of some olefinic resins is lower than that of styrene-based resins.
Moreover, the cycle time of molds directly related to material properties is usually much faster for styrene-based resins. The designs available use wall thicknesses which result in warpage as well. All these factors and more combine to leave olefinic resins largely unused in the spool industry, as is the design of bonded parts for spools from olefinic resins.
In drop tests, a spool may be dropped axially, radially, or canted off-axis. In a radial drop, spools that break typically fail near the middle of the length of the tube, or tubes may shear at a flange. In axial drops, flanges may separate from tubes in failed spools. In an off-axis drop, flanges typically fracture, and may separate from tubes, releasing wire.
Large spools are typically called reels in the wire industry. Heavy-duty reels of 12 inches in diameter and greater (6 feet and 8 feet are common) are often made of wood or metal. Plastic spools of 12-inch diameter and greater are rare and tend to be very complex. The rationale is simple. Inexpensive plastics are not sufficiently strong or tough to tolerate even ordinary use with such a large mass of wire or cable wrapped around the spool.
Moreover, large flanges for reels are very difficult to manufacture. Likewise, the additional manufacturing cost of large spools is problematic. High speed molding requires quick removal after a short cycle time. Flanges are typically manufactured to have very thick walls. Increased thicknesses directly lengthen cycle times. Thus designs do not scale up. Therefore, the flanges have very slow cooling times and molding machines have low productivity in producing them.
Styrene plastic is degraded by recycling. That is, once styrene has been injection molded, the mechanical properties of the resulting plastic are degraded. Thus, if a spool is recycled, ground up into chunks or beads and re-extruded as part of another batch, the degradation in quality can be substantial. Olefinic plastics improve over styrene-based plastics in that olefinic plastics can be completely recyclable. The mechanical properties of an olefinic plastic are virtually identical for reground stock as for virgin stock.
In reels, a 12-inch diameter unit is instructive. Such a spool is usually manufactured of wood. Nevertheless, a plastic spool in 12-inch diameter may also be manufactured with a pair of plas
Jillions John M.
Pate & Pierce & Baird
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