1. Technical Field
The present application is directed to a web section, a round sling constructed from the web section, and methods of making the same and, more particularly, to a web section including elasticized weft strands, a round sling constructed from the web section, and methods of making the same.
2. Related Art
Round slings (also known in the art sometimes as endless or circular slings, or endless spools) are used in a variety of industries for lifting and/or protecting objects, for example, for lifting and protecting nuclear fuel rods during transfer from one location to another.
Simple round slings may be constructed by sewing the ends of a length of material together to form a loop.
More complex round slings may be formed from tubular web sections, the ends of which have been attached, typically by sewing. The tubular webs may be woven as a tube, or may be formed from a planar webbing that is sewn together longitudinally to form a tubular web, as disclosed in U.S. Pat. No. 1,373,457 to Smith. The web sections from which the round slings are formed are typically stiff and inflexible in order to meet the strength requirements of the round slings and to prevent stretching in the axial direction.
Round slings that are used for lifting or weight bearing sometimes may include a load bearing material inside a tubular web. The load bearing material is typically a material that increases the ability of the sling to withstand greater loads.
During use, round slings may be rubbed against other objects, which may cause wear to the web and in some instances may tear the web and/or load bearing material, thereby reducing the strength of the sling as well as its longevity. In such instances, ‘jackets’ have been added to the round slings. Such jackets are simply a second tubular web into which the first tubular web and/or load bearing material is inserted or woven together. If desired, the outer tubular web may be made more abrasion resistant by using a particular weave or yarn or by coating a portion of or the entire outer surface of the outer tubular web to make the outer surface rougher.
A typical construction technique for forming double-jacketed round slings involves inserting the inner tubular web section into the outer tubular web followed by inserting a load bearing material into the inner tubular web. The ends of the inner tubular web and outer tubular web are then attached together in succession, preferably by sewing. This type of construction causes concern with regard to the rupture of the seams or stitches when they engage or are bearing against the sling.
U.S. Pat. No. 4,210,089 to Lindahl discloses a lifting sling that includes a single inner core which is divided or spaced apart from itself inside of a protective cover which has its edges connected by a seam which penetrates diametrically through the sling core material. This sling suffers in practical usefulness because it is only a single core and has no safety backup core in case there is damage to or a defect in the single core which reduces the load lifting capacity of the sling, or indeed, which renders it totally useless.
In order to attach or sew the components of the round sling together, it is necessary to expose the underlying load bearing material or web by pushing or folding back the ends of the web sections. In practice, this is very difficult because the tubular webs are generally quite thick and/or stiff. When outer jackets are used, the difficulties are exacerbated, especially if the weave used is less flexible than the inner tubular web, or if it includes an abrasion resistant coating. Thus, the lack of pliability of the webs makes pushing and folding or unfolding the webs particularly difficult, thereby increasing manufacturing time. In addition, the narrower the tubular web, the less pliable the tubular web.
The patent literature provides many examples of attempts to improve the construction of round slings. For example, U.S. Pat. No. 4,843,807 to von Danwitz discloses a method of producing an endless spool that involves using two tubular linked sections as the outer jacket of the sling, which maybe overlapped to expose the underlying section for attachment. U.S. Pat. No. 4,850,629 to St. Germain discloses a sling that includes multiple discrete sling cores which are each contained inside separate cover material to prevent contact between the sling cores. The core material comprises a length of high tensile material that is in an endless loop within each core. U.S. Pat. No. 5,402,832 to Kämper et al. discloses an endless sling in which a plurality of binding elements are positioned between two webs to connect them through a variety of chambers.
A need exists in the art for an improved web section that facilitates an improved method of making a round sling, without sacrificing tensile strength.