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1. Field of the Invention
The present invention relates to rigging, namely slings and grommets that are used during heavy lifting and more particularly to a heavy lifting system that includes a specially configured sling and grommet of improved construction wherein an elongated sling member includes an elongated woven portion having first and second ends and a central passageway surrounded by the woven material, and wherein one or more flexible sleeves can be optionally fitted to the elongated sling member at its loop portions and at its connecting portions. If the tensile material is one large circular loop, it is referred to as a grommet. These elongated sleeves are preferably of a spiral construction that can be easily installed in the field once a sling length is selected, and function to prevent abrasion during use and to prevent slippage at the splice. The grommet has a similar flexible sleeve fitted to splices of the grommet.
2. General Background of the Invention
In the lifting of very heavy items, lifting harnesses are typically employed which comprise an elongated length of tensile material having loops at each end. These slings have commonly taken the form of wire rope having looped ends. In the case of wire rope, the looped ends are often secured using a crimp or band. Once the sling is constructed, its length is “fixed”. A user must plan the lift in advance by selecting slings of a desired fixed length.
Polymeric and plastic material has been used to construct slings and grommets. A grommet is a sling that is circular in shape so that the user simply hooks or grabs the entire sling rather than a looped end portion. New England Ropes publishes a “Splicing Guide” that discloses various rope splicing techniques.
One of the problems with slings and grommets of either metallic or plastic construction is that of field adjusting the sling length. Wire rope slings are not adjustable. Plastic and polymeric slings are typically sewn to form the loops so that they are not easily adjustable on the job site.
One polymeric material that has a high tensile strength is liquid crystal polymer fiber. One brand that is manufactured by Celanese Acetate LLC is sold under the trademark Vectran®. Celanese literature states that Celanese has contracted aerospace and rope manufacturers to conduct pin diameter tests on Vectran® braid and wire rope respectively. The same literature shows a braid test using a braid having two eyes at the ends. However, this type of “test” braid would quickly become disassembled and or slip in routine use as a sling in a construction environment.
When rigging for many different lifts during a day, a rigger desirably wants a sling that is adjustable so that the length can be varied to fit the particular item being lifted. Further, slings should not slip or become disassembled on the job.
The present invention provides an improved lifting system that features a specially configured lifting sling that is comprised of an elongated sling member that includes an elongated woven portion having first and second ends and a central passageway surrounded by woven material.
With the present invention, first and second connections join each end of the woven portion at the central passageway and at spaced apart positions to form eyes or loops (see
The lifting eyes can also be used to be fitted to the woven portion to prevent or discourage slippage after the sling is constructed.
The flexible sleeve can include a spirally configured portion. The flexible sleeve can be a polymeric or polyurethane member, preferably including liquid crystal polymer fibers.
The present invention can be constructed in the form of a grommet or circular sling that does not have loops.
The present invention is easy to fabricate, can be reused at different lengths, and is easy to reuse in a different form (sling, grommet, etc.). The present invention features a sleeve which is preferably in the form of a polyurethane, spiral cut or spring cut tube. This sleeve serves as a grip or compression on the splice to allow for handling in the field without having any concern that the splice will come apart.
The sleeve is preferably removable so it can be reused with different slings of different lengths from day to day.
A polyurethane spring cut sleeve or tube also serves as a flexible thimble at the “bite” or eye of the sling to prevent abrasion and rapid wear at these critical points.
A polyurethane spiral cut or spring-cut clear cover can also be used over the entire length of the sling that is otherwise not covered as a flexible protective cover, minimizing abrasion and keeping the sling intact.
The present invention features an insert that is preferably of straight fiber filler (preferably liquid crystal polymer fiber) for increasing the sling strength at the bite point in a grommet opposite the splice entry point.
This straight insert section of fiber filler increases the sling strength at the bite point in a doubled over eye and eye sling when positioned opposite the two eyes (see
One embodiment of the present invention is a grommet (see
For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:
In
Lifting eye 16 provides an opening 17 that enables it to be attached to hook 65 of a crane and its lifting line 64. Similarly, eye 18 has an opening 19 that enables it to be attached to an object to be lifted such as load 20 or to a shackle 21 that forms an interface between load 20 and eye 18.
The sling member 11 is shown in
In the preferred embodiment, the woven material 27 that comprises sling member 11 is a liquid crystal polymer (LCP) fiber material that is very strong. Such a product is manufactured by Celanese Acetate LLC under the trademark Vectran®.
One of the problems with liquid crystal polymer material is that it typically has a tendency to abraid when used in the hostile environment of a lifting sling in an industrial plant. when spliced, this material can carry a substantial load so long as the splice is loaded and maintained in tension, such as in a controlled setting (eg. lab). However, in an industrial plant or construction environment, slings of this type are handled with little care. They can be, for example, thrown on the ground, rolled over by heavy vehicles, subjected to dragging across dirt, gravel, sand, etc. In such a hostile environment, the splice can easily shift positions or become completely disassembled.
The present invention provides a plurality of spring cut or spiral cut sleeves such as sleeves 22, 23. These spiral cut sleeves 22, 23 include sleeves 22 that are configured to be positioned at the bite area 34 of a lifting eye 16 or 18 as shown in
The spiral cut sleeves 22, 23 are also provided at the area of splices, those sleeves being designated by the numeral 23. For example, in
In
For the grommet 70 of
The woven portion 27 can be comprised of a plurality of for example, twelve (12) plies surrounding a central passageway 33. In
In
With the present invention, the splice that extends between opening 31 and position 32 is covered with spiral cut sleeve 23 as shown in
The construction of a particular spiral cut sleeve 22 or 23 can be seen in
In
In
In
In
In
In
In
In
The cross sectional configuration of the grommet member 68 can be identical to that of the sling member 11 shown in
In
The completed grommet 70 is shown in
The following is a list of parts and materials suitable for use in the present invention:
The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
Priority of U.S. Provisional Patent Application Ser. No. 60/470,695, filed May 15, 2003, incorporated herein by reference, is hereby claimed.
Number | Name | Date | Kind |
---|---|---|---|
2558553 | Hansen et al. | Jun 1951 | A |
2643638 | Villmer | Jun 1953 | A |
2947504 | Ruhlman | Aug 1960 | A |
2981053 | Harrison | Apr 1961 | A |
3007300 | Peterson | Nov 1961 | A |
3067570 | Nischan | Dec 1962 | A |
3120734 | Peterson et al. | Feb 1964 | A |
3338046 | Baur et al. | Aug 1967 | A |
5699657 | Paulson | Dec 1997 | A |
Number | Date | Country | |
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60470695 | May 2003 | US |