Abstract:
A synthetic roundsling which has an endless load-bearing core with a plurality of loops of synthetic fibers for use in harsh environments. A tubular cover is provided for loosely containing the load-bearing core so that the fibers in the core are movable relative to each other and to the cover. The cover is waterproof to prevent the core from absorbing liquid. The core is prevented from increasing in weight and decreasing in flexibility due to liquid being absorbed by the core, thereby insuring that the roundsling will stay light and flexible even in harsh environmental conditions. A second, outer cover may provide additional protection to the core to protect the core from physical damage.

Description:
FIELD OF THE INVENTION 
       [0001]    The present embodiment is directed to industrial slings used in heavy load handling and control applications. In particular, the embodiment is directed to synthetic slings which maintain their lightweight and flexible characteristics even in harsh environments. 
       BACKGROUND OF THE INVENTION 
       [0002]    Wire rope slings made of a plurality of metal strands twisted together and secured by large metal sleeves or collars are common in the industry. During the past thirty years, industrial metal slings have seen improvements in flexibility and strength. However, compared to non-metal or synthetic fiber slings, metal slings are relatively stiff and inflexible. 
         [0003]    Synthetic fiber slings have gained popularity over the last fifteen years and are replacing metal slings in many circumstances. Synthetic slings are usually comprised of a core made of twisted strands of synthetic fiber and an outer cover that protects the core from physical damage. One of the more popular designs of synthetic slings is a roundsling in which the core forms a continuous loop and the sling has a circular or oval-shaped appearance. These synthetic slings have a very high strength-to-weight ratio which provides for lighter, more flexible and even stronger slings than their heavier and bulkier metal counterparts. 
         [0004]    As thousands of roundslings are being used on a daily basis in a broad variety of heavy load lifting applications and safety applications, the slings are subjected to harsh environmental conditions in which the slings are subjected to extreme temperature and moisture conditions. In such conditions, the synthetic slings can absorb water or other liquids, making the saturated slings much heavier for an operator to effectively lift and maneuver. In addition, saturated slings exposed to cold temperatures can freeze, thereby eliminating the flexibility of the slings. 
         [0005]    Therefore, there exists the need to provide a synthetic sling which can be effectively used in all conditions. It would, therefore, be beneficial to provide a synthetic sling which maintains its lightweight and flexible characteristics in harsh environments in which the sling is exposed to extreme moisture conditions. 
       SUMMARY OF THE INVENTION 
       [0006]    One aspect of the disclosure is directed to a synthetic sling which has an endless load-bearing core with a plurality of loops of synthetic fibers. A tubular cover is provided for loosely containing the load-bearing core so that the fibers in the core are movable relative to each other and to the cover. The cover is waterproof to prevent the core from absorbing liquid. Due to the configuration of the cover, the core is prevented from increasing in weight and decreasing in flexibility due to liquid being absorbed by the core. The use of a waterproof cover insures that the roundsling will stay light and flexible even in harsh environmental conditions in which the sling is exposed to extreme moisture conditions. 
         [0007]    Another aspect of the disclosure is directed to a synthetic sling which has an endless load-bearing core with a plurality of loops of synthetic fibers. A tubular cover is provided for loosely containing the load-bearing core so that the fibers in the core are movable relative to each other and to the cover. The cover is constructed to prevent the core from absorbing chemical liquids. This insures that the load-bearing core will not be exposed to non-compatible chemicals. The use of the cover also improves the rinsing characteristics of the sling, as the amount of water or rinsing or buffering liquids that are required to remove the chemical liquids from the sling is reduced, thereby reducing the drying time of the sling. 
         [0008]    Another aspect of the disclosure is directed to a synthetic sling for use in harsh environments. The sling has a load-bearing core with a plurality of loops of synthetic fibers. A cover is provided for containing the load-bearing core loosely so that the fibers in the core are movable relative to each other and to the cover. The cover has a first end and a second end, with the second end extending over the first end and forming a seal therewith to enclose the core within the cover. The cover and the seal form a waterproof barrier which prevents the core from absorbing liquid and thereby prevents the core from increasing in weight and decreasing in flexibility due to such liquid absorption. This insures that the sling will stay light and flexible even in harsh environmental conditions. 
         [0009]    Another aspect of the disclosure is directed to a synthetic sling which has two covers for use in harsh environments. The sling has a load-bearing core with a plurality of loops of synthetic fibers. An inner cover is provided for containing the load-bearing core loosely so that the fibers in the core are movable relative to each other and to the inner cover. The inner cover has a first end and a second end; the second end extends over the first end and forms a seal therewith to enclose the core within the inner cover. An outer cover is positioned over the inner cover. The outer cover is larger than the core and the inner cover and is generally spaced from the inner cover. The outer cover can move with respect to the inner cover. The outer cover protects the core from physical damage, and the inner cover and the seal form a barrier which prevents the core from absorbing liquid and thereby prevents the core from increasing in weight and decreasing in flexibility due to such liquid absorption. This insures that the sling will stay light and flexible even in harsh environmental conditions. 
         [0010]    Another aspect of the disclosure is directed to a synthetic sling in which the function of the two covers is reversed. The sling has a load-bearing core with a plurality of loops of synthetic fibers. An inner cover is provided for containing the load-bearing core loosely so that the fibers in the core are movable relative to each other and to the inner cover. The inner cover protects the core from physical damage. An outer cover is positioned over the inner cover. The outer cover is larger than the core and the inner cover and is generally spaced from the inner cover. The outer cover can move with respect to the inner cover. The outer cover has a first end and a second end; the second end extends over the first end and forms a seal therewith to enclose the core and the inner cover within the outer cover. The outer cover and the seal form a barrier which prevents the core and the inner cover from absorbing liquid and thereby prevents the core and the inner cover from increasing in weight and decreasing in flexibility due to such liquid absorption. This insures that the sling will stay light and flexible even in harsh environmental conditions. 
         [0011]    Other features and advantages will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a single-walled roundsling in accordance with the present embodiment. 
           [0013]      FIG. 2  is an enlarged cross-sectional view of the roundsling illustrated in  FIG. 1  taken along line  2 - 2 . 
           [0014]      FIG. 3  is an enlarged perspective view of the seal provided on the roundsling illustrated in  FIG. 1 . 
           [0015]      FIG. 4  is an enlarged perspective view of an alternate seal which may be used with the roundsling illustrated in  FIG. 1 . 
           [0016]      FIG. 5  is a perspective view of a double-walled roundsling in accordance with the present embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    In describing the representative embodiments, specific terminology will be selected for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0018]      FIG. 1  illustrates a perspective view of a roundsling  10  in accordance with the present disclosure, however other types of slings may be substituted for the roundsling shown.  FIG. 1  specifically shows a single-path roundsling, but the principles disclosed herein may be applied to other slings, whether single or multiple-path, which have a cover or sleeve which surrounds the core. Generally, such slings are constructed to have a high lifting and break strength, lighter weight, high temperature resistance and high durability, compared to wire rope or metal chain slings. 
         [0019]    As best shown in  FIG. 2 , the roundsling  10  comprises an inner core  20  encased within a protective tubular cover  30 . The inner core  20  is designed to bear the entire weight of the load to be lifted, secured or absorbed. The cover  30 , shown in  FIG. 2 , is larger than the load-bearing core  20  and is maintained in close proximity to the load-bearing core  20 . Alternatively, the cover  30  may be configured to be spaced from the core. In either configuration, the cover  30  can move relatively freely with respect to the load-bearing core  20 . The cover  30  may have various different configurations without departing from the scope of the invention. Regardless of the particular configuration of the cover  30 , the cover  30  is configured to allow strands  22  of the core  20  to move relative to each other and relative to the cover  30 . 
         [0020]    The core  20  is preferably made of a single or multiple fibers or strands  22  configured in a plurality of endless parallel loops of strands to form a single core or multiple cores, all of which are contained inside the protective cover  30 . The use of a single strand or multiple strands in this configuration is typical in the construction of roundslings. 
         [0021]    The core  20  of the roundslings  10  may be derived from one or more natural or synthetic materials, such as polyester, polyethylene, polypropylene, nylon, HMPE, LCP, para-aramid or other types of synthetics. The material chosen for the core  20  primarily depends on the maximum weight the sling is designed to lift or the maximum force the sling is designed to withstand and the environment in which the sling  10  will be used. 
         [0022]    The jacket, sleeve or cover  30  is applied to the core  20  using any known method. The cover  30  generally carries no load. The cover  30  may be have one or more layers and is formed from flexible polyester, nylon woven fabric, extruded material, or other yarn/fiber material which exhibits high tenacity or high abrasion characteristics, or high modulus to improve durability, abrasion and/or cut resistance, such as, but not limited to, ultra high molecular weight polyethylene (UHMWPE), aramid, and liquid crystal polymers, or other materials having similar characteristics. The cover  30  may be made in a seamless manner or may be formed by adjoining the long edges of an elongated strip of material to produce a watertight joint by known means, such as, but not limited to, stitching, seaming, adhesive and the like. If the material used for the cover  30  is not waterproof, the cover may be impregnated with materials with water resistant characteristics, such as, but not limited to, vinyl, polyurethane, rubber, latex, polyethylene, polyolefin, other polymeric or elastomeric compounds or a combination thereof, in order to make the cover  30  water-resistant and/or waterproof. 
         [0023]    The cover  30  is configured to be waterproof (which includes water-resistant), thereby preventing water or other liquid, including liquid chemicals, from penetrating the cover  30  and saturating the core  20 . If the sling  10  is used around chemicals, the cover  30  prevents the core  20  from being exposed to non-compatible chemicals. The use of the cover also improves the rinsing characteristics of the sling, as the amount of water or rinsing or buffering liquids that are required to remove the chemical liquids form the sling is reduced, thereby reducing the drying time of the sling. 
         [0024]    In addition, another purpose of the cover  30  is to prevent physical damage to the core  20  from abrasion, sharp edges on the load, etc. The cover  30  will also help to reduce damage to the sling when it is used in an environment that will subject it to harsh elements such as heat, ultraviolet light, corrosive chemicals, gaseous materials, or other environmental pollutants. Protecting the core  20  is important as the roundslings can be used for many applications relating, but not limited, to construction, plant and equipment operations, ship building, oil drilling and the like. 
         [0025]    Referring to  FIG. 3 , the cover  30  has a first end  32  and a second end  34 . The cover  30  is inserted onto the core  20  such that the second end  34  extends over the first end  32 , thereby insuring that the entire core  20  is encased in the cover  30 . The portion of the second end  34  that overlaps the portion of the first end  32  is sealed to the portion of the first end  32 . A sleeve  36  which uses heat shrink technology can be used to create the seal. Alternatively, adhesives may be applied to perfect the seal. Other known methods, such as applying a single or double sided adhesive lined film or tubular film  35  between the overlapping portion of the first end  32  and the second end  34  (as shown in  FIG. 4 ), can also be used in addition to or in lieu of the seal described with respect to  FIG. 3  to seal the second end  34  to the first end  32 . 
         [0026]    Referring to  FIG. 4 , a flexible sealing member  38  may be applied over the second end  34  such that respective ends of the sealing member  38  are positioned on either side of the second end  34  of the cover  30 . The flexible sealing member  38  may be made from elastomeric material or other materials having the flexibility and waterproof characteristics required. The sealing member  38  may be secured to the cover  30  using adhesive, tape  39  or other known materials applied proximate the ends of the sealing member  38 . As the second end  34  is positioned between the sealed ends of the sealing member  38 , the second end  34  and the cover  30  are sealed. The sealing member  38  can be used in combination with the sleeve  36  described above. No matter how the sealing is accomplished, the area of the seal must remain flexible, as the roundsling  10  must be able to be twisted along its entire length. Therefore, the seal must be able to accommodate twisting motion without failure. 
         [0027]    Referring to  FIG. 5 , an alternate embodiment is shown. In this embodiment, the roundsling  10  has the core  20 , the sleeve or cover  30 , and a tubular outer cover  40 . The outer cover  40  is larger than the load-bearing core  20  and the cover  30  and is generally spaced from the cover  30 , such that the outer cover  40  can move relatively freely with respect to the cover  30 . The outer cover  40  may have one or more layer and may have various different configurations without departing from the scope of the invention. 
         [0028]    The outer cover  40  is applied using any known method. The outer cover  40  generally carries no load and is formed from flexible polyester, nylon woven fabric, extruded material, or other yarn/fiber material which exhibits high tenacity or high abrasion characteristics, or high modulus to improve durability, abrasion and/or cut resistance, such as, but not limited to, ultra high molecular weight polyethylene (UHMWPE), aramid, and liquid crystal polymers, or other materials having similar characteristics. The outer cover  40  may be made in a seamless manner or may be formed by adjoining the long edges of an elongated strip of material to produce a watertight joint by known means, such as, but not limited to, stitching, seaming, adhesive and the like. If the material used for the outer cover  40  is not water-resistant, the cover may be impregnated with materials with water resistant characteristics, such as, but not limited to, vinyl, polyurethane, rubber, latex, polyethylene, polyolefin, other polymeric or elastomeric compounds or a combination thereof, in order to make the outer cover  40  water-resistant. 
         [0029]    As this embodiment has a cover  30  and an outer cover  40 , the functions of the covers can be divided. Generally, one purpose of the outer cover  40  is to prevent physical damage to the core  20  and the cover  30  from abrasion, sharp edges on the load, etc. Both cover  30  and outer cover  40  help to reduce damage to the core  20  when the sling  10  is used in an environment that will subject it to harsh elements such as heat, ultraviolet light, corrosive chemicals, gaseous materials, or other environmental pollutants. While outer cover  40  may be water-resistant, cover  30  is configured to be waterproof, thereby preventing water, chemicals or other liquid from penetrating the cover  30  and saturating the core  20 . In the alternative, the functions of the cover  30  and outer cover  40  may be reversed, with the cover  30  configured to prevent physical damage to the core  20  and the outer cover  40  configured to be waterproof. 
         [0030]    By having the cover  30  and outer cover  40  separated, each of the covers  30 ,  40  can be manufactured to have specific characteristics and perform different functions as described above. This allows each cover  30 ,  40  to be cost-effectively manufactured to perform the desired functions. This also provides better wear-resistance for extra sling life. 
         [0031]    In all of the embodiments shown and described, one or both of the covers prevents water from permeating the core  20 . While the introduction of water to the core  20  does not affect the strength of the core, the absorption of water in the core  20  causes the unwanted result of the core  20  and sling  10  becoming heavier due to the weight of the water absorbed. In various applications, the sling  10  must be handled and manipulated on site. In order for the sling  10  to be handled and manipulated properly, the weight and flexibility of the sling  10  must be maintained essentially the same as when the sling was new. Therefore, in harsh environments or in surroundings in which water is present, if the core  20  is allowed to become saturated, the weight of the sling  10  will increase significantly, making it difficult for a user/operator to transport or manipulate the sling  10 . In addition, in environments where the sling  10  is exposed to extreme cold temperatures, any water absorbed into the core  20  will freeze, making it more difficult for the user/operator to manipulate the sling  10 , as the sling  10  will become rigid due to the formation of ice, rather than flexible. 
         [0032]    In addition, in environments in which the sling  10  is exposed and possibly submerged in chemicals, one or both of the covers prevent the core  20  from absorbing the chemical liquids. This insures that the load-bearing core  20  will not be exposed to non-compatible chemicals. The use of one or both of the covers also improves the rinsing characteristics of the sling  10 , as the amount of water or rinsing or buffering liquids that are required to remove the chemical liquids form the sling  10  is reduced, thereby reducing the drying time of the sling  10 . 
         [0033]    As an example, in oil drilling applications, in which the sling  10  is used as a safety restraint to reduce the area of danger around high-pressure flow line disengagement, the user/operator must be able to move the sling  10  in position around the flow line. Once in position, the sling  10  must be secured to the flow line, by means of bending the sling  10 , in order to be effective. Many of these drilling applications occur in areas such as the North Sea or other areas where water and frigid temperatures are common. If the core  20  of the sling  10  is allowed to absorb water, the sling  10  becomes essentially useless in this environment, as the sling  10  becomes extremely heavy from the water and stiff or rigid from the freezing of the water. It is, therefore, important for the cover  30  to be waterproof to prevent water from being introduced to the core  20  of the sling  10 . 
         [0034]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.