Corrugated-core flanges for spools and reels
A flange design providing improved strength, fracture resistance, and the like using corrugations extending substantially radially from an arbor aperture toward a rim portion. A spool or reel may include a tubular member to receive a stranded material wrapped therearound. A first flange comprising a core portion and an outer portion may secure to one end of the first flange engaging the tubular member.
A second flange may secure to the other end of the tubular member. The core portion of a flange may comprise an arbor wall defining the perimeter of an arbor aperture. The arbor wall may be directly contacted and supported by a plurality of corrugations extending radially therefrom. The outer portion of a flange may contact the core portion and extending radially away therefrom to an outer edge to restrain the stranded material in an axial direction.
The first flange further comprising corrugations substantially rectangular in radial cross section and extending radially from proximate the core radius to proximate the outer radius, the corrugations comprising a plurality of webs, each web of the plurality of webs being offset axially from and dimensionally of the same order of magnitude am adjacent webs of the plurality of webs, and a plurality of connecting walls, each connecting wall of the plurality of connecting walls extending between two adjacent webs of the plurality of webs, the connecting walls and webs being molded of a homogeneous material.
Spools and reels have suffered from a lack of intelligent application of technology for many years. Spools date back hundreds if not thousands of years. Wooden spools and reels have been used in the textile industry as well as various electrical industries for many years with almost no innovation in their structures. Some use of plastic materials began a few decades ago. Nevertheless, manufacturing techniques continue to fall short of implementing all of the principles of engineering that are available.
Manufacturing techniques tend to focus on the simplicity of manufacture, and the simplicity of design, rather than the optimization of strength, weight, stiffness, non-catastrophic failure modes, and the like. Some of these latter considerations have been found to be significant in the manufacture and use of plastic spools and reels. Accordingly, developments by Applicant have provided improved methods for providing spools and reels having substantially reduced weight with improved stiffness and cost. Moreover, failure modes are available to provide "graceful degradation" of performance rather than catastrophic failure of spools and reels in situations such as the dropping of loaded reels or spools.
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 the conventional shapes of central tubes (hubs, cores, etc.), the 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 a spool or reel 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.
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.
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. 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.
The reels have an additional difficulty when they are dropped during use. The flange do not stay secured. The flange and tube are often precarious wooden assemblies held together by three or more axial bolts compressing the flanges together. The tube is prone to slip with respect to the flanges, breaking, tilting or otherwise losing its integrity under excessive loads. Such loads result from the impact of dropping onto a floor from a bench height or less. For the largest reels, rolling over or into obstacles or from decks during handling is more likely to be the cause of damage.
