Abstract:
A grip for cylindrical or elongated elements, such as an umbilical cable. The system includes a mesh fabric that is created by interwoven lines that are initially laid out in a flat rectangular or trapezoidal shape. The mesh fabric is wrapped around the object to be gripped. A lifting eye is integrated into one end of the mesh. The grip is closed by a series of interlocking loops that create a sort of daisy-chain closure.

Description:
BACKGROUND INFORMATION 
     Field of the Invention 
     The invention relates to the field of grips that are used for lifting, pulling, stopping and deployment of objects, particularly heavy objects that are cylindrical in shape, such as umbilical cable, drill pipe, production pipe, power cables etc. More particularly, the invention relates to grips used for such objects in the offshore oil industry. 
     Discussion of the Prior Art 
     Umbilical cable, referred to simply as “umbilicals” in the industry, are used in oil and gas operations to provide the necessary control systems, electrical and/or hydraulic power, etc., to the various operations. An umbilical in this type of operation is typically a large cable that encases a plurality of cables or lines, such as flow lines for providing hydraulic fluids and/or chemicals, electrical cables that provide power and controls, and telecommunications cables. The various types of lines and cables may be integrated into a single umbilical or may be provided as separate umbilicals. 
     The umbilicals reach from the surface, i.e., from a ship or a platform, down to the operation and, thus, may be kilometers long, depending on the depth of the operation. Accordingly, an umbilical being placed into operation weighs many thousands of pounds, which provides a challenge. Conventional gripping systems for an umbilical include a Chinese-finger type grip, such as the grip sold under the band name YALE GRIP. This type of grip includes a plurality of very high tensile rope tails or braids that are integral to a lifting eye at one end and that are individually and contra helically wrapped around the umbilical, such that a grip is formed around the cable. The grip functions as a Chinese finger: when tension is applied to the eye of the grip in the axial direction, the grip extends in length and narrows in the radial direction, thereby creating a firm grip on the umbilical over the length of the applied grip. This type of extended textile grip does not scar or permanently deform the object being lifted. 
     Often, the size or diameter of an umbilical or pipe may be large and many tons of lifting capacity may be required. One of the drawbacks of the conventional grip is that the rope tails have to be very long (50 to 100 feet or more) to wrap the object, and this requires a significant amount of time, often a number of hours, physical space, and man power to apply the grip and subsequently remove it. 
     What is needed, therefore, is a grip that can be quickly and easily assembled on the object and subsequently easily removed while also being a grip that is safe and that provides the necessary lifting strength. 
     BRIEF SUMMARY 
     The grip according to the invention may be used to grab many different types of cylindrical or longitudinal elements such as conduit, large ropes, cable, conductor, hose, or pipe, but was developed to grip umbilical cable that is typically used in the oil industry. Reference is made in the description of the inventive grip to an “umbilical cable” and to a “cable grip”, but these terms are used for ease of explanation. It is understood that the use of the term “umbilical” is not limiting and that the grip according to the invention may be used to grab other types of elements. 
     The grip according to the invention is a mesh fabric. The fabric is initially a flat rectangular and/or trapezoidal shape that is wrapped around the umbilical. The two edges that extend in the axial direction of the umbilical are then closed to form a grip around the cable. The mesh fabric has a weave that allows the grip to function like a “Chinese finger,” i.e., when tension is applied to the lifting eye of the grip in the axial direction, the mesh fabric of the grip narrows in the radial direction, thereby providing a secure grip on the umbilical. The closure is a daisy-chain type closure that is simple in its construction, yet strong and secure and that is quickly created on an umbilical and is also quickly removed. A preferred embodiment of the grip is constructed of various synthetic materials, but may be fabricated from a wide variety or combination of materials, including, but not limited to, metals, organic material, or any material possessing tensile strength for either the mesh fabric or closure material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale. 
         FIG. 1A  shows the grip according to the invention, assembled on a cable and shown from the lifting end. 
         FIG. 1B  shows the grip of  FIG. 1A , from the tail end. 
         FIG. 2A  is a perspective view of one embodiment of the grip, laid out flat on the frame that is used to fabricate the grip, looking from the lifting end toward the tail end, and showing particularly the weave, the lifting eyes, independent closure loops, and the geometry stabilizing element. 
         FIG. 2B  is a perspective view of the grip shown in  FIG. 2A , looking from the tail end and showing an optional tail closing treatment. 
         FIG. 3  illustrates the grip being wrapped on a simulated umbilical, with the daisy-chain closure being created. 
         FIG. 4  illustrates closure loops being interlocked to a daisy-chain closure. 
         FIG. 5  is a first embodiment of the daisy-chain closure, with the closure loops as an integral part of the weave material of the grip. 
         FIG. 6  is a second embodiment of the daisy-chain closure, wherein the closure device is a component separate from the weave material of the grip. 
         FIG. 7  is a third embodiment of the daisy-chain closure comprising a series of separate closure loops. 
         FIG. 8  is a fourth embodiment of the daisy-chain closure comprising a plurality of separate closure loops and a long loop that closes a plurality of mating loops of the weave material. 
         FIG. 9  illustrates a frame used to fabricate the grip and illustrates a progressive change in weave angles that is necessary to distribute gripping load over the length of the grip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art. 
       FIGS. 1A and 1B  illustrate an umbilical grip  100  according to the invention that has been wrapped around a long object O that is to be lifted, supported, or held, such as an umbilical cable, so as to form a gripping sleeve.  FIGS. 2A and 2B  show the grip  100  after it has been fabricated on a frame F. The cable grip  100  comprises one or more lifting eye  20 , a closure  30 , and a geometry stabilizing element  40 . The end of the grip  100  with the lifting eye  20  is referred to hereinafter as the lifting end, and the other end the tail end. The grip  100  is formed from lines  12  that are integral to the eye  20  and that are interwoven to form a flat mesh fabric  14  that has a top edge that is at the lifting end, a bottom edge at the tail end, and two closure sides  10 A,  10 B, shown in  FIG. 3 , that extend from the lifting end to the tail end. The closure sides  10 A,  10 B are the edges that extend in the axial direction of the umbilical or object O that is to be lifted, supported, or held. 
     The lines  12  are interwoven to form the mesh fabric, but each line is movable relative to each other. This type of weave creates a fabric that is dimensionally changeable. Thus, when the closure sides  10 A,  10 B are connected, the grip  100  is closed and forms a sleeve around the object O and, in its relaxed state, i.e., without tension applied to it, the grip will have approximately a length that is determined by the length of the geometry stabilizing element  40 . Applying tension to the grip at the lifting end, for example, by lifting the object O by the one or more more lifting eyes  20 , causes the individual lines  12  in the weave to try to align in the axial direction. This, in turn, causes the diameter of the grip to constrict, which results in the grip  100  gripping the object tightly. 
     The cable grip  100  is applied to the object O, i.e., the umbilical, as follows: The grip  100  is placed around the umbilical O in a position for closing around the umbilical. The geometry stabilizing element  40 , best seen in  FIGS. 2A and 2B , is an elastic element that holds the fabric of the grip  100  to a desired length while it is being assembled on the umbilical, so as to enable one to work the daisy-chain or zip closure described below. Optionally, a suitable number of auxiliary fasteners (not shown) may be used to temporarily hold the grip in place to facilitate working the closures  30 . These auxiliary fasteners may simply be strips of hook-and-loop fabric fasteners, which are used to intermittently connect closure edges  10 A,  10 B, thereby temporarily securing the position of the grip  100  on the umbilical. 
       FIGS. 3-8  illustrate details of the closure  30 , which is a daisy-chain or zip-type system that is essentially a series of interlocking loops  32  that are worked along the closure edges  10 A,  10 B of the grip  100 . There are a number of embodiments of the zip closure, but common to all embodiments is lacing the series of closure loops  32  along the closure edges, such that a closure loop is long enough to reach from edge  10 A across to the opposing edge loop on edge  10 B and then longitudinally to the next adjacent edge loop of side  10 B, where the closure loop is then interlocked with the next closure loop from side  10 A. This process is then repeated all the way down the closure edges. In this way, each first loop is securely held in place by the second loop, thereby creating a closure that is secure, but, on the other hand, “unzips” easily when the bottom-most loop is released. 
       FIGS. 3, 4, 7 and 8  illustrate an embodiment, in which the series of closure loops  32  comprises a series of individual flexible rings. Referring particularly to  FIGS. 3 and 4 , one can see that the first and second closure edges  10 A,  10 B, respectively, are formed such that each edge has a series of “grab loops”  33  and looking in the longitudinal direction, one can see that, for each grab loop  33  on the first closure edge  10 A, there is a mating grab loop  33  on the second closure edge  10 B that is at approximately the same distance longitudinally. A closure loop  32  has been looped around each of the grab loops  33  on the first closure edge  10 A. To lace up the closure  30 , a first closure loop  32 A is pulled through the mating grab loop  33  on the second closure edge  10 B and, if the particular loop is not the first loop in the series, through a preceding closure loop, and is then pulled down toward an adjacent, second closure loop  32 B and slipped over that second closure loop. The process is repeated with this second closure loop and so on, down the length of the closure edge.  FIG. 1B  shows cable grip  100  from the tail end and shows that straps or tails  16  are threaded through the last closure loop  32  to complete the closure  30 , thereby securing the closure lacing. 
       FIG. 5  shows a closure device  30  that is formed from the mesh fabric of the grip  100 , rather than comprising one or more separate components. SIDE A, for example, has a first closure edge in which the grab loops are now much longer than described above with reference to  FIGS. 3, 4, 7 and 8 , and now serve as the closure loops  32 . The process of threading one closure loop through a mating grab loop on the second closure edge and then over an adjacent closure loop remains the same. The weave of the mesh fabric of grip  100  desirably progresses from a low angle relative to the axis of the umbilical at the lifting or eye end to a much higher angle at the tail end. Consequently, the longitudinal distance between edge grab loops  33  decreases progressively from the eye end to the tail end. If the mesh fabric of the grip  100  is constructed as a rectangle, the closure loops  32  of edge side  10 A correspondingly decrease in length to match the decreasing distance between adjacent edge grab loops. Alternatively, the mesh fabric of the grip  100  may be constructed as a trapezoid in such a way that, when wrapped around umbilical O, the distance or gap between closure edges  10 A and  10 B increases in direct proportion to the decrease in longitudinal distance between adjacent edge grab loops, such that the length of the closure loops  32  remains constant from the eye end to the tail end of grip  100 . The final closure loop at the tail end may be longer to accommodate the grip or mesh material tails. 
       FIG. 6  illustrates an embodiment in which the closure device  30  is a separate long component that is laid out along the first closure edge and pulled through each of the mating grab loops on the first closure edge, so as to form a long closure loop, which is then worked the same as the closure loops described above. 
       FIG. 7  illustrates an embodiment in which the closure device  30  comprises separate closure loop components  32  of greater or lesser strength than the mesh material. These closure loop components  32  are laid out along and attached to the first closure edge and are worked the same as the closure loops described above in  FIG. 5 . These separate or independent closure loops may be configured to be replaceable or not. They may also be lengthened or shortened to accommodate a variation in the circumference or girth of the umbilical O or element on which the grip is be used. The weave of the mesh fabric of grip  100  desirably progresses from a low angle relative to the axis of the umbilical at the lifting or eye end to a much higher angle at the tail end. Consequently, the longitudinal distance between each adjacent edge grab loop  33  decreases progressively from the lifting or eye end to the tail end. If the mesh fabric of the grip  100  is constructed as a rectangle, the closure loops  32  of edge side  10 A correspondingly decrease in length to match the decreasing distance between adjacent edge grab loops. Alternatively, the mesh fabric of the grip  100  may be constructed as a trapezoid in such a way that, when wrapped around umbilical O, the distance or gap between closure edges  10 A and  10 B increases in direct proportion to the decrease in longitudinal distance between adjacent edge grab loops, such that the length of the closure loops  32  remains constant from the eye end to the tail end of grip  100 . The final closure loop  32  at the tail end may be longer to accommodate the grip or mesh material tails  16 . 
       FIG. 8  illustrates a closure device  30  that includes a combination of two types of closure devices. The first one is a long closure loop  32 A that is attached to a first grab loop, as described above with reference to  FIG. 7 , and then laced through a series of mating grab loops on  10 A and  10 B closure edges. This type of loop may be advantageous to accommodate a variable diameter of the object being gripped by the grip  100 . Also, greater shear forces are exerted on the first long closure loop  32 A than on the beginning series of mating grab loops and for this reason it may be desirable to construct the long closure loop  32 A of a stronger material to better withstand these greater forces. In order to avoid having to work with a loop that is so long that it becomes cumbersome to handle, a series of second long loops  32 B, such as those described above in  FIG. 7 , may be used. 
       FIG. 9  is a schematic illustration that is used to set up the frame F for weaving the grip  100  with a progressive weave angle. A series of pins P are provided along the frame F. These pins P can also be seen in  FIGS. 2A and 2B . Several representative lines, showing how the lines  12  are laid out, are drawn in on the diagram. Also shown is an axial centerline L. The term “progressive weave angle” refers to an increase in the angle of each subsequent line  12  as it crosses the axial centerline L. For example, the weave angle for the second line from the pull end is a relatively narrow angle of 39.16 degrees and the angle of the last line shown at the tail end is a wider angle of 54.88 degrees. This progressive weave angle enhances the gripping quality of the grip  100 . 
     As mentioned earlier, the interwoven fabric of the grip  100  is changeable in dimension. When tension is applied to the grip  100  in the axial direction, the lines  12  are pulled in the axial direction, which simultaneously extends the length and constricts the diameter of the grip  100 . This effect is what is commonly referred to as a “Chinese finger grip” and it results in the desired gripping effect on the umbilical. 
     The grip  100  is quickly assembled on the object O to be lifted, supported, or held, within a matter of minutes, depending on the length, and provides the strength and safety that is needed to lift and manipulate cables or conduits, even very heavy objects, such as umbilicals. The closure loops  32  are preferably relatively close together so they are relatively easy to lace along the closure. Once all the loops  32  have been interlaced, the straps  16  at each side of the bottom edge  10 A and  10 B, are pulled through the last loop  32  and fastened together or otherwise fastened to the grip to secure the closure. 
     The grip  100  is released from the object O in an extremely short time, a minute or so. The straps  16  are simply unfastened and pulled from last loop  32 . This allows a fast unzipping action of the closure, each loop being freed from the bottom up and releasing the adjacent preceding loop to pull out of its adjacent descendant loop. 
     It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the cable grip may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.