The present invention generally relates to a method for manufacturing an endless loop, such as a tether, a sling, etc., and, more particularly, to a method of cabling an endless loop.
Various methods of manufacturing an endless loop, such as tethers and slings, are known. Factors to consider in the manufacturing methods include the cost, weight, and cross-sectional diameter of the endless loop while providing adequate operational characteristics (e.g., strength and flexibility) for a particular application. The breaking tenacity, or force to break with respect to linear density, of the endless loop is generally desired to be high. Also, having a low utilization variance between slings manufactured with the same processes is desirable.
Traditional manufacturing methods of slings and tethers include selecting a strand material, a number of strands, and a cover material to target the operational characteristics (e.g., the strength and flexibility needs) of a given application. However, in some applications, simply selecting a certain combination of these criteria are not enough to meet the desired mechanical properties of the sling or tether. These slings or tethers may break before reaching the desired breaking strength and are susceptible to utilization variance.
In one independent aspect, a method of manufacturing an endless loop (e.g., a tether, a sling, etc.) may be provided. The method may generally include providing, around a first roller and a second roller, a loop including a plurality of twisted strands; and feeding a plurality of body strands onto the loop, feeding including, with the plurality body strands connected to the loop, moving the loop about the first roller and the second roller to cause the body strands to lay and be twisted on the plurality of twisted strands.
In another independent aspect, a method of manufacturing an endless loop may generally include forming, around a first roller and a second roller, a loop including a plurality of loops strands, forming including applying a twist to the plurality of loop strands to provide a plurality of twisted strands; and feeding a plurality of body strands onto the loop, feeding including, with the plurality body strands connected to the loop, moving the loop about the first roller and the second roller to cause the body strands to lay and be twisted on the plurality of twisted strands.
In yet another independent aspect, a method of manufacturing an endless loop may generally include positioning, around a first roller and a second roller, a plurality of twisted strands; and, with the plurality of twisted strands formed in a loop, feeding a plurality of body strands onto the loop, feeding including, with the plurality body strands connected to the loop, moving the loop about the first roller and the second roller to cause the body strands to lay and be twisted on the plurality of twisted strands.
Other independent aspects of the disclosure may become apparent by consideration of the detailed description, claims and accompanying drawings.
Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.
Relative terminology, such as, for example, “about”, “approximately”, “substantially”, etc., used in connection with a quantity or condition would be understood by those of ordinary skill to be inclusive of the stated value and has the meaning dictated by the context (for example, the term includes at least the degree of error associated with the measurement of, tolerances (e.g., manufacturing, assembly, use, etc.) associated with the particular value, etc.). Such terminology should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4”. The relative terminology may refer to plus or minus a percentage (e.g., 1%, 5%, 10% or more) of an indicated value.
Also, the functionality described herein as being performed by one component may be performed by multiple components in a distributed manner. Likewise, functionality performed by multiple components may be consolidated and performed by a single component. Similarly, a component described as performing particular functionality may also perform additional functionality not described herein. For example, a device or structure that is “configured” in a certain way is configured in at least that way but may also be configured in ways that are not listed.
A method for cabling an endless loop, such as a tether, a sling, etc., is illustrated in the figures. Generally, a base including a plurality of base strands with a selected twist rate is provided on a winding machine and arranged in a loop extending about spaced apart rollers. The base loop may be formed on the machine with the base strands being fed onto the machine and secured in a loop and with a twist being applied to the strands on the machine. Alternatively, a pre-formed base with twisted strands may be positioned on the machine (e.g., as an elongated member secured in a loop around the rollers or as a pre-formed loop positioned around the rollers).
In another alternative, the base strands and twisted strands may be formed as braided strands. In yet another alternative, the pre-formed base with twisted strands may be formed of braided subcomponents.
With the loop with twisted strands on the machine, additional rope material is laid on the loop. Body strands (e.g., strands formed continuously with the base strands, separate strands connected to the base loop, combinations thereof) are drawn into the machine by driving the base loop around the rollers (e.g., with a drive roller). The body strands lay on the underlying twisted strands (e.g., the base strands or previously-laid body strands), and, as the body strands are added, the twist is applied to this subsequently-added, following rope material. As the structure of laid twisted strands rotates about the rollers, the laid twisted structure also spins about its axis, causing the following body strands to follow a helical path onto the laid structure so that the twist is applied.
When the desired amount of rope material has been added to the laid twisted structure, the endless loop with twisted strands is formed. For a sling, the free end of each body strand is secured to a free end of a base strand (e.g., by a knot or other securing method or device). For a tether, the free end of each body strand is also secured to a free end of a base strand (e.g., by a knot or other securing method or device), and eyes or other connection points are provided through whipping applied to the endless loop.
A cover may be provided over the endless loop, and, for an endless loop with a discontinuity in the rope strands (e.g., a connection between the ends of the body and base strands, a connection of the body strands to the loop, etc.), an indicator to identify the discontinuity is provided on the cover. The indicator may also indicate other mechanical properties of the endless loop.
Each strand 14, 18 is stored on a bobbin 30, and each bobbin 30 engages a pin 34 mounted on a supply stand 36. The bobbins 30 are rotatable to allow the strand 14, 18 to be pulled from the bobbin 30 when tension is applied to an end of the strand 14, 18.
Each strand 14, 18 extends from a bobbin 30 through a loophole 38 without interfering with the strands 14, 18 on the other bobbins 30. After passing through the loopholes 38, the ends of the strands 14, 18 may be secured by an end securing mechanism 42 (e.g., a knot, a zip tie, a splice, etc.).
Each strand 14, 18 is formed of fiber material such as, without limitation, a gel-spun ultra-high-molecular-weight polyethylene (UHMWPE) (for example, Dyneema® available from DSM Dyneema B.V., the Netherlands), a recrystallized high modulus polyethylene (for example, Plasma®), a liquid crystal polyester (LCP; for example, Vectran® available from Kuraray Co., Japan), a gel-spun polyethylene (for example, Spectra® available from Honeywell International, Inc., New Jersey, U.S.A.), a para-aramid (for example, Kevlar® available from DuPont, Delaware, U.S.A. or Twaron® available from Teijin Aramid B.V., The Netherlands), a para-aramid copolymer (for example, Technora® available from Teijin Aramid B.V.), a polyamide (nylon), a polyester, or the like or combinations thereof. The fibers of the strands 14, 18 may have a polyurethane finish, although other finishes may alternatively be used.
The supply assembly 10 also includes a “fish ladder” 50 including two offset stationary rods 54 which contact, tension, and reduce bunching of the strands 14, 18. As shown in
The strands 14 initially placed on the machine 22 (at least two strands 14) are base strands 14 of the endless loop 144 to be formed, as shown in
As described below in more detail, the strands 18 provide additional rope material laid on the loop. The body strands 18 may be formed continuously with the base strands 14 (as shown in the illustrated embodiment), separate strands 18 connected to the base loop, and combinations thereof. The body strands 18 will be laid on the underlying twisted strands (e.g., the base strands 14 or previously-laid body strands 18).
In another embodiment (not shown), the base strands 14 and the body strands 18 may also be braided structures that are fed into the machine 22. In this embodiment, a plurality of braided ropes act as subcomponents to allow the body strands 18 to lay on the braids of the base strands 14.
As shown in
As shown in
The twist rate applied to the base strands 14 (and, eventually the body strands 18) depends on the desired application and the desired mechanical properties of the sling 26 such as, for example, sling strength and utilization variance, and may also influence other mechanical properties of the sling 26. In general, a twist rate of about 0.8 to about 1.5 twists per meter may be desired for the endless loop 144. In the illustrated embodiment, a twist rate of about 1.0 twist per meter (e.g., a right hand twist) is applied (e.g., by hand) to the base strands 14. In other embodiments (not shown), the twist rate may be lower or higher than the range 0.8 to 1.5 twists per meter.
In applying the twists to the base strands 14 for the endless loop 144, the distance between the supply assembly 10 and the drive roller 58 is also taken into account. For example, to manufacture a ten meter long sling 26, with a twist rate of 1.0 twist per meter, and with two meters between the fish ladder 50 and the drive roller 58, twelve twists 82 are applied to the base strands 18.
As shown in
The base strands 14 engage and extend around the driven roller 74 and extend towards the drive roller 58. Alignment rods 98 are provided adjacent to each roller 58, 74 to align the base strands 14 and later-supplied strands 18 within the machine 22.
As shown in
As shown in
In other embodiments (not shown), the core 110 may be on a different machine or in accordance with a different process. For example, the core 110 may include pre-twisted base strands (not shown) positioned on the machine 22. In some constructions (not shown), the core 110 may include an inner core that is not twisted and an outer core twisted about the inner core. These pre-twisted strands may be formed into a loop on the machine 22 or may be pre-formed in a loop and then positioned on the machine 22.
As also shown in
As shown in
In operation, the drive roller 58 is driven to rotate the core 110 about the drive roller 58 and the driven roller 74. Rotation of the core 110 along with the securing knot 42 force the body strands 18 to follow the rotation of the core 110 and be drawn into the machine 22.
As the drive roller 58 is driven, the core 110 (along with the added body strand 18) also spins about the axis of the core 110 (see the change in position between
With this rotational and spinning motion of the core 110, the following body strands 18 mesh with the structure of the core 110 (the spaces/grooves between adjacent strands 14). The body strands 18 are added to the core 110 in a helical path. After introduction, the added body strands 18 become twisted strands onto which additional following rope material is laid.
The process continues until the necessary rope material has been to obtain the selected endless loop 144 and its characteristics. Sufficient material of the body strands 18 may be added to fully cover the core 110. The material of the body strands 18 may form an additional layer 138 over the core 110 such that the endless loop 144 includes a core 110, and any number of additional layers 138.
For a sling 26 or a tether 24, as shown in
As shown in
For a tether 24, after forming the endless loop 144, the endless loop 144 is folded at least once such that multiple portions of the endless loop 144 bear the loads applied to the tether 24. Once the endless loop 144 is folded in the desired configuration, a whipping 174 is applied to the folded sling 24 to secure the sling 24 in the desired configuration.
Liners 154, 158 and a mud filter 178 are applied to either the endless loop 144 or the multi-looped (e.g., doubled, tripled) endless loop 144. Layers providing abrasion protection 162, 182 are applied. The connection point 176 is covered with a wear pad 177 which provides additional wear resistance to the abrasion protection layers 162, 182. Wear pads 177 may also be applied to the eyes 175.
A cover 166 may be applied to portions of the tether 24. The cover 166 may be fluorescent to promote visibility of the tether 24. Handles 186 are formed or otherwise attached to either the cover 166 or the outermost abrasion protection layer 182. The handles 186 provide contact points to allow remote operated vehicles (ROV) or other structures (e.g., a user or a hook) to handle the tethers 24.
The “twisted” sling 26 or the “twisted” tether 24 resulting from the manufacturing method may be capable of higher breaking strength when compared to comparable slings and tethers of the same strand material, number of strands, and cover material with the strands laid parallel rather than being twisted. Additionally, the sling 26 and the tether 24 are less susceptible to manufacturing variance (the difference between the lengths of the various strands 14, 18) when compared to comparable parallel-laid slings and tethers. Thus, without the need to use more expensive strand and/or cover material or using additional strands (leading to a higher cross-sectional diameter/weight of the sling), the desired mechanical properties can be achieved.
For example, an increase (e.g., at least about 20% or more (about 22%)) of breaking tenacity was observed in comparing the “twisted” sling 26 with comparable parallel-laid slings. When multiple slings 26 were compared to multiple comparable parallel-laid slings, the utilization variance of the slings 26 was less than (e.g., at least about 20% less than) the utilization variance of the comparable parallel-laid slings. A similar increase in breaking tenacity and decrease in utilization variance of the “twisted” or “cabled” tether 24 is projected when compared with comparable parallel-laid tethers. When comparing parallel slings 26 to cabled slings 26 with similar properties, the cabled slings 26 had increased average breaking strength of at least about 10% and as much as about 36%. Numerous advantages of cabling may be exemplified in the below test results table. One such advantage may be that, in the case of both Winyarn and S1000 strands with a design minimum breaking load of 98 Te, the average breaking strength was below the minimum breaking load for the parallel slings 26, but above the minimum breaking load for the cabled slings 26.
The embodiment(s) described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present disclosure. As such, it will be appreciated that variations and modifications to the elements and their configuration and/or arrangement exist within the spirit and scope of one or more independent aspects as described.
One or more independent features and/or independent advantages of the invention may be set forth in the following claims:
The present application claims the benefit of U.S. Provisional Patent Application No. 62/873,041, filed Jul. 11, 2019, the entire contents of which are hereby incorporated by reference.
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