WO2000017085A9 - Lifting sling system having multiple strap components - Google Patents

Abstract

A flexible sling system (10) constructed of a multiplicity of flexible loops (12a-12j) linked together to form a chain of individual loop slings. Each individual sling component comprises a length of flexible woven material which overlaps on itself and is sewn closed to form a circular loop of woven material. Each component is linked to the next in a manner that provides flexibility and movement of one link with respect to the others. The resultant chain of sling components functions as a long sling section comprised of operable portions of the chain of sling components as the load conditions might require. For smaller diameter loads, fewer links of the chain may be utilized for lifting, while for larger diameter loads, more links of the chain may be used. In addition, where the load may require it, the chain of sling components can operate to tighten around the load by passing the one end of the flexible chain through one of the sling loops in a manner that permits the sling loop to slip along the length of the chain and tighten against the load. Under either such described use of the sling system, multiple attachment points are provided by securing lift line hooks (24, 28, 30, 34) or the like to any of the multiplicity of circular sling components that make up the lifting sling system.

Description

Lifting Sling System Having Multiple Strap Components

BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION

The present invention relates generally to flexible slings used for lifting, pulling, or otherwise moving heavy loads. The present invention relates more specifically to a flexible fabric sling constructed of individual link components that permit the use of a single sling in a variety of conditions where slings of different lengths might otherwise be warranted. 2. DESCRIPTION OF THE RELATED ART

In both the construction and transportation industry, it is common to use slings of various types to lift and move heavy loads from one place to another on a construction site or from a loading dock onto a vehicle for transport. The slings so utilized take a number of different forms, depending to some extent upon the nature of the load being lifted. It is typical for all such slings, however, to be flexible to some degree and to be capable of suspending significant weight during the loading and lifting process .

It is known in the art to use a strap of flexible woven material with loops formed at each end of the strap as the basic component for a lifting sling. Strong polymer-based fibers are woven to form flat webbing material that can be looped and sewn back on itself to form very strong lift lines with attachment loops positioned where necessary. Examples of such woven strap slings include those described in U.S. Patent No. 3,592,502 issued to Bolliger on July 13, 1969, and U.S. Patent No. 4,239,271 issued to Beasley et al. on December 16, 1980.

It is not uncommon for construction sites to have on hand a large number of different slings constructed in this manner, each sling of varying length appropriate for use in different situations. Because it is sometimes preferable for a sling to fit snugly (as well as compressively when required) around a particular load being lifted, it is often desirable to utilize a sling just long enough to surround the load and prevent any significant unstable movement of the load during the lifting process. For this reason a single long sling is simply not suitable for use in all situations. Long slings might be used for very large diameter loads, whereas a short sling would be more appropriate in situations where a small diameter load is involved.

Various efforts have been made in the past to accommodate the need for slings of a variety of lengths within a single device. Typically such devices are overly complicated and often fail to provide the versatility desired. Examples of efforts in the past include U.S. Patent No. 4,834,439 issued to Van de Camp on May 30, 1989, which includes four lifting loops formed by slots at spaced locations along the length of the sling. U.S. Patent No. 4,856,836 issued to Delphin on August 15, 1989 uses two straps with variable diameter end loops that include choker sleeves that slip up or down to close the effective diameters of the loops. U.S. Patent No. 3,840,262 issued to Foster et al. on October 8, 1974 describes a pipe sling having spaced end members and fabric belting material wrapped back and forth between the end members . U.S. Patent No. 5,688,011 issued to Gulley on November 18, 1997 describes a single sling having spaced in-line eye loops sewn at a variety of attachment points along the length of the sling. One significant disadvantage to the Gulley structure involves the weakness experienced when a loop is pulled against the direction it is sewn onto the primary sling strap.

Various other types of heavy duty sling construction are disclosed in a series of patents issued to St. Germain as exemplified by U.S. Patent No. 4,043,581 issued August 23, 1977; U.S. Patent No. 4,240,659 issued December 23 , 1980; and U.S. Patent No. 5,561,973 issued October 8, 1996. Each of the St. Germain patents describe combinations of sub-slings that are woven from single cables in such a manner that they have an eye at each end of a sling length. The St. Germain patents disclose the use of multiple slings in parallel to form a single sling of greater strength.

The desirable features of a sling versatile enough to use in a variety of situations would include significant strength regardless of the length of the sling being used, flexibility, non- damaging contact with the load, snug encirclement of the load, and a multiplicity of attachment points for lifting the load. It would be desirable to have a sling system comprised of a single device that could replace the multiplicity of slings typically utilized on construction siles and loading docks. Rather than have a multiplicity of slings from the smallest size for lifting small diameter to the largest size required for encircling larger diameter loads, it would be helpful if a single sling device were capable of being used in conjunction with each of the loads described. It would be preferable if such a device did not "choke" the load and exert undue encircling pressure on the load in a manner that might damage the load in the process of lifting. In other words, while the slip loop construction (possible with many single strand slings) would permit their use with loads of a variety of diameters, the tightening of such a slip loop frequently causes damage to the load or makes it difficult to later remove the sling from the load after being lifted. It would be helpful, therefore, if a sling device was capable of encircling loads of a variety of diameters without excessive tightening around the load in the process unless specifically intended. It would also be desirable for such a single sling device to permit attachment to the load at a variety of points and in a variety of directions. It would, for example, be helpful to overcome the drawbacks of such devices as are described in the Gulley patent wherein multiple loops are provided for a variety of attachment points but which multiple loops suffer from operating properly only when lifted from a particular direction.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sling device capable of functioning at a variety of operable lengths for lifting loads having a variety of diameters.

It is a further object of the present invention to provide a flexible sling device capable of appropriately encircling loads of a variety of diameters and providing a multiplicity of attachment points for lifting the load. It is a further object of the present invention to provide a flexible sling device capable of appropriately encircling loads of a variety of diameters without exerting a damaging tightening force against the load while the load is being lifted.

It is a further object of the present invention to provide a flexible sling lifting device capable of encircling loads of a variety of diameters and providing a multiplicity of attachment points for lifting the load where the attachment points are operable by connecting to lift lines directed from any direction.

It is a further object of the present invention to provide a flexible sling lifting device capable of appropriately encircling loads of a variety of diameters and functioning in such a way as to tighten around the load where appropriate or remain loose around the load when appropriate. It is a further object of the present invention to provide a flexible sling lifting device capable of being easily repaired through the replacement of a single link in the sling system rather than the replacement of the entire sling.

It is a further object of the present invention to provide a flexible sling lifting device versatile enough to replace a multiplicity of individual slings of varying lengths as are frequently utilized on construction sites and loading docks.

In fulfillment of these and other objectives, the present invention provides a flexible sling system constructed of a multiplicity of flexible loops linked together to form a chain of individual loop slings. Each individual sling component comprises a length of flexible woven material which overlaps on itself and is sewn closed to form a circular loop of woven material . Each component is linked to the next in a manner that provides flexibility and movement of one link with respect to the others. The resultant chain of sling components functions as a long sling having an eyelet loop at each end thereof or as a shorter sling comprised of operable portions of the chain of sling components as the load conditions might require. For smaller diameter loads, fewer links of the chain may be utilized for lifting, while for larger diameter loads, more links of the chain may be used. In addition, where the load may require it, the chain of sling components can operate to tighten around the load by passing the one end of the flexible chain through one of the sling loops in a manner that permits the sling loop to slip along the length of the chain and tighten against the load. Under either such described use of the sling system, multiple attachment points are provided by securing lift line hooks or the like to any of the multiplicity of circular sling components that make up the lifting sling system. Other objectives of the present invention will be become apparent to those skilled to the art after a reading of the following detailed description and a review of the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the sling system construction of the present invention.

FIG. 2 is a side view of a typical load with the sling system of the present invention shown surrounding the load in a first method of attachment .

FIG. 3 is a side view of the same load disclosed in FIG. 2 showing the sling system of the present invention encircling the load in a second method of attachment . FIG. 4 is a side view of a load encircled by the sling system of the present invention and attached to a multiplicity of lift lines .

FIG. 5 is a side view of the sling system of the present invention utilized in conjunction with a small diameter load, showing a majority of the sling system components unused in the lifting process.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is made first to FIG. 1 for a detailed description of the construction of the sling system of the present invention. Sling system (10) is comprised of a multiplicity of sling loop components (12a) -(12j). Each sling loop component (12a)-(12j) is comprised of a section of flexible woven webbing material formed in a circle and overlapped back on itself. The section of overlap (14) is then sewn with heavy thread material to form a closed loop of sufficient strength for lifting purposes. It is well known in the art to construct loop slings in this single component fashion wherein a closed loop of polymer-based woven fabric material is turned back on itself to overlap and form a loop section of flexible material . What is heretofore unknown in the industry is the combination of components as described herein.

In the preferred embodiment each loop component (12a)-(12j) is formed by overlapping end sections of a length of flat webbing material and sewing such end sections together as shown. In the preferred embodiment the material is sewn back on itself in a manner that forms a flat loop without twists in the material. In an alternative embodiment and under certain circumstances, it may be preferable to twist the material once in order to encourage the end sections of the loop to orient at right angles when drawn tight. Each of the sling components (12a) -(12j) is linked to the next as in a chain structure as shown in FIG. 1. Contact with the next link in the chain at section (16) in each loop provides both a strong connection and a flexible linkage that permits slippage and rotation of the links one against the other. Sling system (10) thus formed in its most basic structure has eye loops (18) and (20) at each end thereof and may be used as a long sling of a length equal to the overall length of the component system when stretched from each end. Alternatively, the operable length of the sling may be shortened by using, for example, only a portion of the sling, such as links (12a) - (12h) . This would leave link sections (12h) - (12j) inoperable, hanging loosely in association with the sling system.

Reference is now made to FIG. 2 for a brief description of one method for attaching the sling system of the present invention to a load. In FIG. 2, load (22) shown in cross-section is, for example, a section of pipe to be lifted. Sling system (10) is encircled about load (22) and attached to lifting hook (24) . Sling component (12a) is first attached to lifting hook (24) and then the appropriate additional sling component, (12g) in this case, is also attached to lifting hook (24) . The choice of the second sling component to attach to lifting hook (24) is dependent upon the diameter of load (22) and whether or not it is desired for the sling to fit snugly or loosely about load (22) . In the example shown in FIG. 2, it is desired that the sling system fit loosely about load (22) in a manner such that lifting load (22) does not cause too great a tightening force about the load in a manner that might damage it. In the example shown in FIG. 2, sling components (12i) and (12j) hang loosely apart from the sling, being inoperable for the lifting process. In the arrangement shown in FIG. 2 therefore, sling system (10) appropriately encircles load (22) sufficient to keep it from slipping from the lift line but loosely enough to prevent any damage to the load in the lifting process. Reference is now made to FIG. 3 for an alternative means for utilizing the sling system of the present invention to encircle the same load as described in FIG. 2. Load (22) in this case is encircled by sling system (10) and is lifted by lifting hook (24) . While sling component (12a) is again attached to lifting hook (24) , in this case sling component (12g) rather than being attached to lifting hook (24) surrounds sling system (10) in a slip loop fashion. In other words, after encircling load (22) , sling component (12a) is passed through the loop of sling component (12g) before being hooked onto lifting hook (24) . In this manner, sling system (10) may encircle load (22) in a manner that further tightens as the load is lifted. Here again, sling components (12h)-(12j) are not operable and hang loosely away from sling system (10) in the lifting process.

Reference is now made to FIG. 4 for yet another manner in which the sling system of the present invention might be utilized to lift a load under specific conditions. In this example, load (26) is to be lifted by two separate lift lines shown by lifting hook (28) and lifting hook (30) . Load (26) may be the type of load that could easily be damaged by the tightening of a sling about it, and thus it would be desirable to lift the load at a multiplicity of points, pulling slightly apart from each other. In this case, sling system (10) is attached first to lifting hook (30) at sling component (12a) as shown. A portion of sling system (10) encompasses load (26) and is then attached to lifting hook (28) at sling component (12h) . In addition to sling component (12h) being attached to lifting hook (28) , sling component (12i) , as it is attached to sling component (12h) , is also engaged by lifting hook (28). Sling component (12j) is further engaged by lifting hook (30) in a manner that completely encircles load (26) but does not encompass it tightly. In this manner, lifting hooks (28) and (30) are held at a set distance apart by sling components (12i) and (12j), while load (26) is lifted by the remaining components of sling system (10) .

Reference is now made to FIG. 5 for a brief description of the sling system of the present invention used in conjunction with the lifting a smaller diameter load. Load (32) in this case is a plurality of small pipe sections that might be surrounded by at most five sling components of the sling system (10) . In this manner lifting hook (34) engages sling component (12a) and sling component (12e) with sling components (12b) - (12d) , forming the remaining sections that surround load (32) . The remaining components of sling system (10), (12d)-(12j), hang loosely apart from load (32) , or may be used in some cases to draw the load towards the point that it is to be released. It is not uncommon on construction sites for guide lines to be attached to loads being lifted in a manner that facilitates their movement to a specific point on the construction site. The sling system of the present invention lends itself particularly well to the attachment of such guide lines to the "extra" links in the sling system that are not being used for the load lifting process.

As indicated above, the construction of the sling of the present invention lends itself to easy repair where abrasion and sharp edges may have deteriorated the integrity of the sling. Whereas a typical sling constructed of a single length of flexible material must be entirely replaced when its integrity is compromised, the sling system of the present invention can be completely repaired through the replacement of the single compromised link. Since each link is independently sewn, it becomes a simple matter of removing the damaged link and replacing it with a link of new flexible material that is then sewn back on itself as in the original manufacture of the sling. It is also possible, in this same manner, to increase the length of a particular sling after its original manufacture through the addition of one or more links.

It should also be noted that the design of the present invention lends itself to the construction of sling systems comprised of links in an arrangement other than a strictly linear orientation. A sling system could, for example, be comprised of three linear sections of chain joined together at a single common point with a single link of flexible material. Any number of variations on this theme of linking linear sling sections together could be conceived.

While the present invention has been described in conjunction with a preferred embodiment both as to sling structure and the use of the sling, it is anticipated that alternative embodiments that are encompassed by the fundamental concepts of the invention could be implemented. The examples shown utilized a specific number of links but are, of course, not dependent upon the number of links for their function. Sling systems of any number of lengths and links of a variety of sizes are anticipated. It is also anticipated that in some circumstances links in a single sling system might be of different sizes to facilitate a variety of attachment points and useable links. In addition, the preferred embodiment has been described as using a flexible polymer-based fabric material as the basis for the sling construction. It is anticipated that a variety of other strong, yet flexible, materials might be used in place of the woven polymer-based material described. In some instances, it would be practical to utilize flexible metal cable strands as the sling components where the load and lifting requirements might be better served by such structures. Other such materials, applications, structures, and functions of the present invention will be anticipated by those skilled in the art from the reading of the above disclosure.

Claims

I Claim:

1. A sling system capable of lifting and moving a load comprising : a plurality of loop components, each of said loop components comprising a length of flexible material having two ends, wherein said ends overlap and are sewn together to form a loop; wherein each of said loop components is linked to at least one other loop component to form a chain of components .

2. The sling system of Claim 1, wherein said length of flexible material of each of said loop components is a section of flat webbing .

3. The sling system of Claim 1, wherein said length of flexible material of each of said loop components is a section of polymer- based fabric.

4. The sling system of Claim 1, wherein said length of flexible material of each of said loop components is a section of woven metal cable strands .

5. The sling system of Claim 1, wherein said loop formed by said length of flexible material is a cylindrical loop wherein said ends overlap and are sewn together without any twists in said length of flexible material .

6. The sling system of Claim 1, wherein said loop formed by said length of flexible material comprises at least one twist in said length of flexible material.

7. The sling system of Claim 6, wherein said at least one twist in said length of flexible material tends to orient a first apex of said loop orthogonally to a second, opposite apex of said loop.

8. A method of lifting a load with a lifting hook comprising the steps of: providing a multilink sling comprising a plurality of loop components, said plurality of loop components comprising two end links and at least one intermediate link, wherein said loop components are each comprised of flexible material ; attaching a first link of said multilink sling to said lifting hook; encircling said multilink sling around said load; and attaching a second link of said multilink sling to said lifting hook.

9. The method of Claim 8, wherein said step of attaching a first link comprises attaching a first end link of said multilink sling to said lifting hook, and said step of attaching a second link comprises attaching a second end link of said multilink sling to said lifting hook.

10. The method of Claim 8, wherein said step of attaching a first link comprises attaching a first end link of said multilink sling to said lifting hook, and said step of attaching a second link comprises attaching an intermediate link of said multilink sling to said lifting hook.

11. A method of lifting a load with a lifting hook comprising the steps of : providing a multilink sling comprising a plurality of loop components, said plurality of loop components comprising two end links and at least one intermediate link, wherein said loop components are each comprised of flexible material ; encircling said multilink sling around said load; passing a first of said end links through a second link of said multilink sling to form a slip loop arrangement; and attaching said first end link of said multilink sling to said lifting hook.

12. The method of Claim 11 wherein said step of passing a first of said end links through a second link comprises passing a first of said end links through a second of said end links.

13. The method of Claim 11 wherein said step of passing a first of said end links through a second link comprises passing a first of said end links through an intermediate link.

14. A method of lifting a load with two lifting hooks comprising the steps of : providing a multilink sling comprising a plurality of loop components, said plurality of loop components comprising two end links and at least one intermediate link, wherein said loop components are each comprised of flexible material ; attaching a first link of said multilink sling to a first of said two lifting hooks; encircling said multilink sling around said load; attaching two of said intermediate links of said multilink sling to a second of said two lifting hooks, wherein a first of said two intermediate links serves to support said load and a second of said two intermediate links extends from said second lifting hook towards said first lifting hook; and attaching a second link of said multilink sling to said first lifting hook so as to connect said first lifting hook to said second lifting hook.