Flexible cable with extended life and method for manufacturing the same - Patents.com

Abstract

The flexible cable 1 is manufactured by endlessly winding at least one thread 6 around two thimbles 2,4. The thread 6 comprises aramid or similar fiber. Each thimble 2,4 holds a stack 9 of multiple layers 10 of turns of thread 6. The cable 1 comprises a resin 12 provided on at least one of the first and second thimbles only to interconnect the layers of turns of thread and to maintain the tangential orientation of the respective thread layers 10 relative to each other when the flexible endlessly wound cable is subjected to a load. The cable has optional carbon fiber sheets 18,20 between preselected layers of thread in the thimbles.

Description

Detailed Description of the Invention

[0001] The invention relates to a flexible cable according to the preamble of claim 1 and to a method for manufacturing a flexible cable according to the preamble of claim 13. This type of cable can be used in various types of industries, including but not limited to offshore mining and heavy lifting, and construction. Offshore, this type of cable can be used as mooring lines for floating oil exploration or production installations, or for floating wind turbines. In particular, this type of cable can be used as so-called tendons or tethers to anchor (semi-submersible) floating objects under tension to the bottom of the sea or ocean, to form Tension Leg Platforms (TLPs) as foundations for wind turbines or other installations. In mining and heavy lifting, such cables can be used to suspend cranes. In construction, such cables can be used as tension members in bridges or as roof suspension cables.

[0002] The concept of an endlessly wound cable or rope is explained on the English Wikipedia page on ropes: "An endlessly wound rope is produced by wrapping a single strand of high performance yarn around its two extreme ends until the desired breaking strength or stiffness is reached. This type of rope (often identified as a cable to distinguish it from braided or twisted structures) has the advantage, as in the case of the constructions mentioned above, of no structural elongation."

[0003] An endless wound cable is known from WO2017 / 086778 (WO'778). This document discloses a cable manufactured by winding a main thread around two thimbles which form two end fittings in the final cable. In order to reduce wear of the cable, WO'778 proposes providing, on the support surface of the thimbles, a stack of layers of a second type of fibre. The stack of the second type of fibre avoids direct contact between the main thread and the support surface. As a result, the main thread is not worn by the movement of the main thread relative to the support surface. The properties of the second type of fibre are selected such that their wear is less than that of the main thread.

[0004] While the solution of WO2017 / 086778 (WO'778) represents an improvement over the then known prior art, further improvements in cable strength and lifespan continue to be sought.

[0005] The present invention aims to provide a cable with greater strength and / or longer life than the cables of WO '778, or at least to provide an alternative. This object is achieved by a cable according to claim 1.

[0006] The flexible cable is manufactured by endlessly winding at least one thread around two thimbles, and comprises a first thimble, a second thimble, and at least one thread. The thread comprises a highly elastic synthetic or natural fiber having a Young's modulus of at least 55 GPa as specified by ASTM D7269, specifically at least 100 GPa, preferably at least 110 GPa, more preferably at least 120 GPa, and selected from the list including aramid fibers, polyarylate fibers, PBO fibers, and basalt fibers. The first thimble and the second thimble are provided at both ends of the cable. The at least one thread extends from the first thimble to the second thimble, wraps around the second thimble, and extends from the second thimble to the first thimble, wraps around the first thimble, such that the thread forms a wrap around the first and second thimbles, each thimble carrying a stack of multiple layers of wraps of the thread. The adhesive is provided on at least one of the first and second thimbles only and interconnects at least two of the multiple layers of yarn windings within each stack of the first or second thimbles to maintain the tangential orientation of each yarn layer relative to one another when the flexible endless wound cable is subjected to a load.

[0007] The invention is based on the discovery that a failure mechanism occurs when a flexible endlessly wound cable is wound for transport. In the wound state, the cable is loaded such that the fibers on the radially inner side of the roll are compressed while the fibers on the radially outer side of the roll are stressed. This local difference in load causes a slight misalignment of the layers of yarns in the stack of one or both thimbles relative to each other. This misalignment may remain at least partially after the cable is unwound, resulting in uneven lengths and thus uneven loading of the fibers when the cable is loaded during use. Since the claimed fiber type has a relatively high Young's modulus, the difference in length causes some parts of the yarns to be loaded less than designed and other parts to be loaded more than designed, resulting in premature failure of the parts that are loaded more highly.

[0008] Connecting at least two layers together with adhesive prevents relative movement of the layers when the cable is wound or otherwise placed in a curved configuration, thus preventing uneven loading of the threads on one side of the cable relative to the threads on the other side. It is sufficient to apply adhesive to only a portion of the circumference of the thimble that supports the threads, which prevents slippage caused by winding the cable.

[0009] In one embodiment, the adhesive is spread over only a portion of the circumference, specifically the portion is centered about the longitudinal axis of the cable. This embodiment reduces the cost of applying adhesive to a portion, specifically the center, compared to applying adhesive to the entire circumference, not only in terms of materials but also in terms of labor.

[0010] For example, the adhesive extends over less than 50% of the circumference, such as less than 25% of the circumference, specifically less than 10% of the circumference. The adhesive extends over more than 1% of the circumference, specifically more than 2% of the circumference, more specifically more than 5% of the circumference. Preferably, the adhesive extends over one-third to one-quarter of the circumference.

[0011] In another embodiment, the adhesive spreads over the entire circumference of the thimble that supports the thread. The present invention is based on the discovery that prior art cables fail prematurely due to micro-wear between the layers of thread at the end fittings. This is caused by one or more of the following mechanisms: The length of the thread at the thimble is longer in the outer layers of thread turns than in the inner layers of turns. While this difference in length is small in an absolute sense from one layer to the next, it results in different thread elongations under load, since the amount of elongation corresponds to the thread length for a given Young's modulus and cross-sectional area of ​​the thread, as well as the tension in the thread. When the cable is subjected to a load cycle with repeated increasing and decreasing tensile loads on the thimble, the difference in elongation results in a back and forth movement of each layer of thread turns relative to the adjacent layers. This movement causes micro-wear of the thread. A further failure mechanism caused by the load cycle is that the yarn layer stack is slightly compressed as the longitudinal stress in each of the yarn layers is transferred to the thimble as radially inward pressure through the middle yarn layers. The inward pressure results in slight compression of the middle layers. An uncompressed yarn winding stack may contain 50% air, which may be compressed to a minimum of 35% air. Compression results in a reciprocating movement of the outer yarn layers relative to the inner yarn layers, thus resulting in microwear.

[0012] According to the invention, at least two of the layers of yarn windings in the yarn stack of at least one of the thimbles are adhesively connected to each other such that the layers remain tangential to each other when the flexible endless wound cable is subjected to the maximum design load of the flexible endless wound cable, which prevents relative movement of the layers and thus wear of the yarns of the layers in the stack.

[0013] The present invention provides a solution for reducing microwear in endlessly wound cables made with threads comprising highly elastic synthetic or natural fibers with a Young's modulus of at least 55 GPa. In filing this application, the applicant has used and / or tested threads comprising aramid, polyarylate, PBO or basalt fibers for such endlessly wound cables. All tested endless cables using such threads show an extension of life or a life span of more than 10 to 20 times that of similar cables without the application of the present invention. The present application is intended to provide additional protection, at least by comparable means, to endlessly wound cables using threads made of fibers having comparable properties to the above-mentioned fibers in terms of strength, Young's modulus and fiber surface roughness, and thus subject to the same or similar failure mechanisms.

[0014] The additional layers of yarn may also include an adhesive to connect the yarns of such layers together within their respective stacks, in particular, substantially all of the layers in at least one of the thimbles are connected by adhesive.

[0015] Adhesive is applied and cured on each layer of threads in only one, or all, of the thimbles, and not between the threads along the entire length of the cable. Applying and curing adhesive between the threads over the entire length of the cable would result in a stiff rod instead of a flexible cable. The expression that adhesive is applied only to at least one of the first and second thimbles is to be interpreted accordingly within the context of this specification.

[0016] Preferred embodiments are defined in the dependent claims. In one embodiment, the adhesive comprises a resin, specifically an epoxy resin. The resin provides another beneficial effect of maintaining the layers of yarn turns in the stacked structure in their radial position relative to the center of the thimble. Each layer transmits a portion of the load on the cable to the associated thimble. In the cable described in WO'778, this load is transmitted as pressure to the underlying layer of yarn, the layer between the associated layer and the support surface of the thimble. This pressure can result in a reduction in the load capacity of the yarn fibers, since high performance fibers, such as aramid fibers, release part of their load capacity when the fibers are subjected to a lateral load. By applying the resin, at least a portion of the load is transmitted through the resin instead of the underlying yarn, resulting in less pressure, and therefore less wear, or even completely eliminated. The resin specifically acts as a matrix. Another beneficial effect of the resin is that the local transmitted load on the yarn is reduced, since the surface of the yarn is rough at a micro level and the transmitted load is transmitted to adjacent yarns mainly through the resin and not through the protrusions of the rough yarn surface.

[0017] It should be noted that US 2013 / 0000087 (US'087) discloses a cable end connection for a cable constructed from a plurality of twisted filaments. The cable end connection comprises an end piece for installing or supporting the cable. The end piece is fastened to one end of the cable, is manufactured from a castable, hardenable material, such as a synthetic resin, and is connected only to the filaments in a conformal manner, without additional mechanical connection elements, by being cast around or molded onto them. The filaments are unwound from the original twisted assembly in the area of ​​the end piece and are essentially uniformly distributed. The end piece is manufactured by injection molding of synthetic fibers in a mold, the filaments being embedded and cast in a conformal manner around the material of the end piece under prestress. The synthetic resin of US'087 thus forms the cable end fitting. If the synthetic resin were to break or if the embedded filaments were to break away from the resin, the entire end fitting would fail. In contrast, the end fittings of the present invention are made of thimbles having an uninterrupted winding of thread, and the resin or any other adhesive serves only to prevent relative movement between the layers of thread. If the adhesive were to fail, the end fittings of the present invention would still function like the end fittings in WO '778, and although they would suffer from long term wear, they would not fail immediately like the cable end fittings of US '087.

[0018] In one embodiment, the layers of thread in both thimbles are provided with adhesive. In one embodiment having more than two thimbles, all thimbles are provided with adhesive. In another embodiment, all of the layers of yarn in at least one of the thimbles are provided with adhesive.

[0019] In one embodiment, a stack of different types of fibers of the yarn, in particular a sheet of such fibers, is provided on a support surface of at least one thimble prior to winding the yarn, as disclosed in more detail in WO2017 / 086778.

[0020] In one embodiment, the aramid fibers are para-aramid fibers. This fiber type is very strong compared to metals and most other types of synthetic fibers. In one embodiment, the cable comprises at least a first sheet disposed in the stack of layers of thread windings between two layers of one of the stacks of the first and second thimbles. The addition of the first sheet between adjacent layers of thread windings of the thimbles increases the stiffness of the stack of layers, thus minimizing the relative movement between the layers of thread windings of the thimbles.

[0021] In one embodiment, the at least first sheet is one of a plurality of sheets, each sheet being separately disposed between two layers of one of the stacks of the first and second thimbles in the stack of layers of yarn windings. This configuration with multiple sheets distributes the stresses required to make the stack of layers of yarn with the sandwiched sheets sufficiently stiff across the multiple sheets.

[0022] In one embodiment, each of the thread stacks of both thimbles is provided with at least one sheet between the two layers of thread. In one embodiment, at least the first sheet comprises a unidirectional fabric, which provides maximum strength and stiffness in the direction of the fibers of the fabric, specifically, the fibers in the unidirectional fabric are generally parallel to the yarn direction.

[0023] In one embodiment, the stiffness of at least the first sheet is greater than the stiffness of the threads, which improves the effect of binding the sheet on the threads. In one embodiment, at least the first sheet comprises sheet fibers, the Young's modulus of the sheet fibers being higher, specifically at least twice as high, than the Young's modulus of the highly elastic synthetic fibers of the yarn.

[0024] In one embodiment, at least the first sheet comprises fibers selected from the list consisting of carbon fibers, PBO (polybenzobisoxazole) fibers, and high modulus aramid fibers. In one embodiment, at least the first sheet comprises more than one type of fiber, and at least one of the fiber types is selected from the list consisting of carbon fiber, PBO fiber, and high modulus aramid fiber.

[0025] In another aspect, the present invention relates to a method for manufacturing a flexible endless wound cable as claimed in claim 13, in particular a method for manufacturing a flexible endless wound cable as claimed in any one of claims 1 to 12 or an inventive flexible endless wound cable as defined in the preceding paragraphs.

[0026] At least two layers of yarn windings in each thimble are interconnected by applying adhesive at least once to at least one of the thimbles. As a result, the method according to the invention provides an endless wound cable with the beneficial properties described above. Adhesive is not applied and / or cured on the endless wound cable extending between the first and second thimbles, so that the flexible endless wound cable remains pliable between the first and second thimbles.

[0027] Specifically, one step of applying adhesive results in connecting two or more layers of yarn turns. Due to tension in the yarn during winding, excess adhesive is pressed from the layer of yarn turns first applied to the additional layer. Adding more adhesive than is needed to connect two layers of yarn turns results in connecting more layers of yarn turns than the step of adding adhesive.

[0028] Preferred method steps are defined in the dependent claims. In one embodiment, the method includes placing at least a first sheet on one of the layers of wound thread on one of the first and second thimbles after providing at least one layer of wound thread and before providing a next layer of wound thread.

[0029] In one embodiment, the method includes placing a further sheet onto another one of the layers of yarn windings on one of the first and second thimbles. In one embodiment, the step of adding adhesive to the layer of yarn windings in at least one of the thimbles is repeated at least twice during the manufacture of the flexible endless wound cable.

[0030] In one embodiment, the step of applying adhesive to the layer of yarn windings on at least one of the thimbles is repeated after at least one of the thimbles has been provided with n layers of yarn windings, where n is an integer less than 15, particularly less than 10, particularly less than 5, more particularly less than 2. This allows for accurate dosing of the amount of adhesive required. In one embodiment, n is greater than 2. Preferably, n is selected from the range of 5 to 10.

[0031] The invention, its effects and advantages are explained in more detail on the basis of schematic drawings. [Brief description of the drawings]

[0032] [Figure 1] 1 shows an end of a cable according to the invention. [Diagram 2] 5 shows a partially exploded cross section II-II of FIG. 4. [Diagram 3] 3 shows an enlarged detail of FIG. 2. [Figure 4] 2 shows a top view of the cable of FIG. 1. [Diagram 5] 4. Section VV of FIG. [Figure 6] 6 shows a cross section VI-VI of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] 1-6 show a flexible cable according to the present invention, which is generally designated by the reference numeral 1. The cable 1 has a first end fitting 3 with a first thimble 2, a second end fitting 5 with a second thimble 4, and a plurality of threads 6. The first thimble 2 and the second thimble 4 are made of stainless steel and are provided at either end of the cable 1, each having a center 7. The plurality of threads 6 are, in this embodiment, ten (10) threads 6, all of which extend from the first thimble to the second thimble and around the second thimble 4, and from the second thimble 4 to the first thimble 2 and around the first thimble 2. In this way, each of the plurality of threads 6 forms a semi-continuous loop around the first and second thimbles. This loop is repeated a plurality of times, 950 times in this embodiment. Thus, each of the threads 6 forms 950 turns, resulting in a total of 9,500 turns of the thread 6. A cable thus produced is generally referred to as an endless hoisting rope. It should be noted that the figure is only schematic and the actual (relative) dimensions of the cable will in fact differ from those shown. In particular, the cable according to the invention can be of the order of several hundred meters long, or even exceed 1000 meters, so that the length of the cable is much longer than that suggested by FIG. 4.

[0034] The yarns 6 in this embodiment are made of aramid fibers, in this embodiment para-aramid fibers having a density of 3220 dtex and a Young's modulus of 112 GPa. These yarns are sold by Teijin Aramid under the name Twaron® D2200.

[0035] Figure 2 shows in cross section that the thimble 2 has a support surface 8. The thimble 2 holds a stack 9 having a number of layers 10 of windings of thread 6. This is shown in more detail in Figure 3, which is a much enlarged schematic diagram of five (5) layers 10 of windings of thread 6. In the upper part of Figure 2, for the sake of clarity, the stack 9 is shown in an exploded view. In fact, the entire stack 9 is held within the first thimble 2, as shown in the lower part of Figure 2. The second thimble 4 holds the same number of layers of windings 6 of thread in a similar manner and is therefore not shown in detail.

[0036] The multiple yarn layers 10 in one or both of the end fittings 3,5 of the cable 1 are connected to one another by an adhesive, in this embodiment an epoxy resin 12. In this embodiment, an epoxy resin 12 is provided in each end fitting 3,5 to interconnect all of the layers 10 of turns of yarn 6 in each stack of thimbles 2,4 and to maintain the tangential orientation of the respective yarn layers 10 relative to one another when the flexible endless hoisting line is loaded.

[0037] The cable 1 of this embodiment comprises a plurality of sheets 14, 16, 18, 20 in the end fittings 3, 5. The first sheet 14 and the second sheet 16 are provided in the stack 9 of layers 10 of windings of thread 6 in the first thimble 2. The third sheet 18 and the fourth sheet 20 are provided in the stack 9 of layers 10 of windings of thread 6 in the second thimble 4. Each of the plurality of sheets 14, 16, 18, 20 is provided separately between two layers of the associated stack 9. The sheets 14, 16, 18, 20 of this embodiment are made of unidirectional carbon fiber fabric.

[0038] Epoxy resin 12 interconnects layers 10 of turns of yarn 6 with sheets 14, 16, 18, 20. The sheets increase the stiffness of the stack 9 of each thimble 2, 4, resulting in less movement of the stack as a whole and less movement of layers 10 of turns of yarn 9 relative to one another.

[0039] A cable cover 28 extends around the cable 1 from the first thimble 2 to the second thimble 4 and bundles all of the spools of thread 6 extending between the first thimble 2 and the second thimble 4 into one compact bundle 30 at the midsection 32 of the cable 1. The midsection 32 in this embodiment is shown to be relatively short compared to the overall length of the cable 1. In most embodiments, the midsection will be the longest portion of the cable. In this embodiment, the cable cover 28 also covers the spools of thread 6 at the end fittings 3,5. The cable cover 28 creates gatherings 33,34 of the spools of thread 6 extending from the respective thimbles 2,4 to the midsection 32.

[0040] FIG. 5 shows that the cable 1 in the middle section 32, i.e. between the end fittings 3, 5, is formed by winding the threads 6 without the presence of epoxy resin 12 or any other adhesive between the threads 6, thereby allowing the cable to remain flexible.

[0041] FIG. 6 is a schematic longitudinal section through the end fitting 5. The longitudinal section through the end fitting 3 is not shown in detail since it is similar in this embodiment. The inner and outer contours 40 and 42 of the convergent portion 34 of the bundle of turns of thread 6 are shown as they engage and go around the thimble 4. As the turns of thread 6 are bundled at the intermediate portion 32, they are divided into two equal parts and diverge towards the thimble 4, so that in this embodiment the turns of thread 6 engage the support surface 8 of the thimble 4 at an angle α of about 220°. The sheets 18, 20 extend around the thimble 4 over at least the same angle α and also over the entire width of the support surface 8. In this embodiment the sheets 18, 20 extend from the thimbles 2, 4 through the convergent portions 33, 34 towards the intermediate portion 32 so as to increase the surface for attaching the sheets 18, 20 to the layer 10 of turns of thread 6 with the epoxy resin 12. Because the sheets 18, 20 do not extend into the intermediate portion 32, the elasticity of the intermediate portion 32 is not affected.

[0042] The area of ​​the support surface 8 supporting the yarns 6 is referred to as the support area 44. The support area 44 subtends an angle α, as illustrated by the dashed line in FIG. 6. Generally, adhesive is applied to a portion 46 of the support area 44, which in a preferred embodiment is substantially the entire support area 44. This causes the yarns 6 to be interconnected throughout the support area 44, eliminating movement of the yarns 6 relative to one another and thus preventing fiber abrasion that would result in premature failure of the respective cables 1.

[0043] In an alternative embodiment, the adhesive is present in further portions of each end fitting, particularly within the entire end fitting. In alternative embodiments, the adhesive covers less than half of the support area 44, for example, ⅓ or ¼ of the support area 44, as illustrated in FIG. 14. The adhesive applied portion 46 is centered about the longitudinal axis 48 of the cable 1.

[0044] The adhesive connects at least two of the multiple layers 10 of the thread 6, and in a preferred embodiment, substantially all layers of the thread are connected by adhesive. Connecting substantially all layers of the thread turns provides a better life extension than connecting only two layers. Within the context of this specification, substantially all layers of the thread turns is understood as at least 80% of the layers, specifically at least 90% of the layers, and more specifically at least 95% of the layers.

[0045] In an embodiment, no adhesive is applied to the non-supported portions of the support surface 8 which do not support the windings of the thread 6, i.e. the non-supported areas covering the remaining angle (360°-α), e.g. the remaining 140° in the example of FIG.

[0046] Flexible cables according to the invention have been tested and have not failed after over 9 million load cycles, and several tests have shown that the invention increases life span, measured in number of load cycles, by 30 to 50 times.

[0047] An embodiment of a method for manufacturing a flexible endless wound cable according to the invention, such as a cable according to one of the embodiments disclosed above, comprises the steps of: positioning the first thimble and the second thimble at a predetermined distance from each other, the distance corresponding to a required cable length; providing 10 para-aramid yarns; winding the ten threads from the first thimble to the second thimble, wrapping them half way around the second thimble, returning them to the first thimble, and wrapping them another half way around the first thimble; applying an adhesive to a layer of yarn windings on the thimble; repeating the step of winding ten lengths of thread around the first and second thimbles until a first predetermined number of layers of windings of thread are provided on both the first and second thimbles; placing a first unidirectional carbon fiber sheet on one of the layers of yarn windings on the first thimble; placing a second unidirectional carbon fiber sheet over one of the layers of yarn windings on the second thimble; applying additional adhesive to the layer of yarn windings on the thimble; repeating the step of winding ten strands of thread around the first and second thimbles on the first and second sheets until a second predetermined number of layers of windings of thread are provided on both the first and second thimbles; placing a further sheet on one of the layers of yarn windings on the first thimble; placing a second additional sheet on one of the layers of yarn windings on the second thimble; applying additional adhesive to the layer of yarn windings on the thimble; repeating the step of winding ten lengths of thread around the first and second thimbles until a third predetermined number of layers of thread windings are provided on both the first and second thimbles, the first, second and third predetermined numbers of layers of thread windings collectively corresponding to a required cable thickness; allowing the adhesive to cure such that the layers of yarn windings remain tangential to one another when the flexible endless wound cable is subjected to a load; Equipped with.

[0048] In this embodiment, the adhesive is not applied to every layer, but rather in sufficient quantity each time to spread through adjacent layers and sheets, so that in the final product, adhesive is present between all layers and between the layers and sheets before the adhesive cures.

[0049] In this embodiment, the adhesive is an epoxy resin. In this embodiment, the epoxy resin is a thermosetting polymer that is hardened by baking the first and second thimbles.

[0050] In this embodiment, the first and second thimbles are made of stainless steel. In an alternative embodiment, the adhesive is applied after all layers of yarn turns are fitted into the thimbles, i.e., after a complete stack of layers is formed in each thimble. The adhesive penetrates between the yarn turns of the layers and through the sheet and spreads through the complete stack.

[0051] Apparatus suitable for the method of producing an endless wound cable is described in WO2017 / 099589 and WO2017 / 086778 by the same applicant. Several variations are possible within the scope of the appended claims. Features of the preferred embodiments described above may be replaced with any other features within the scope of the appended claims, such as other embodiments and features described in the following paragraphs. Product features disclosed in connection with the method are preferred features of the flexible cable and vice versa.

[0052] The cable according to the invention may be made with more than 10 threads or with less than 10 threads, for example with 1 thread, 2 threads or with at least 5 threads. In particular, the cable is made with at least 12 threads or with 24 threads. The total number of turns of the thread, i.e. the turns of the thread per layer and the number of layers, depends on the strength of the cable required and the strength of the individual threads as well as the required safety margin. The number of layers depends on the number of turns of the thread required and the available width of the thimble that gives the maximum number of turns of the thread in the width direction. In particular, each thread forms at least 1000 turns, more particularly more than 5000 turns.

[0053] Various types of yarns may also be used within the scope of the present invention, such as PBO (polybenzobisoxazole sold under the name ZYLON by Toyobo Co., Ltd.), polyarylate fibers (sold under the name VECTRAN by Kuraray Co., Ltd.), para-aramid yarns sold under the name Twaron (registered trademark of Teijin Aramid BV) and Kevlar (registered trademark of Eldu Pont de Nemours and Company), with or without coating, with densities of 1610 dtex, 4830 dtex, 6440 dtex, 16100 dtex or 17000 dtex, but also higher, lower and intermediate densities, paracopolyamide yarns sold under the name Technora (registered trademark of Teijin Aramid BV), as well as yarns made of fibers with similar properties. Examples of para-aramid yarns include Twaron 2100, which has a Young's modulus of 65 GPa, and Twaron 3200, which has a Young's modulus of 138 GPa. The fiber types for which the invention provides a solution are relatively abrasive fibers, due to the relatively high surface roughness of the fibers, as compared to fiber types such as UHMWPE or nylon fibers. In particular, threads made of basalt fibers are suitable for the endlessly wound cables according to the invention. An example is a basalt thread of 24.000 dtex. The breaking load, and in particular its high Young's modulus, makes such threads suitable for endlessly wound cables, while the invention solves the problem of abrasion in the end fittings due to the relatively high roughness of the fibers.

[0054] In one embodiment, adhesive is provided to the layer of yarn in only one of the thimbles, specifically one thimble in such an embodiment that is different from the other thimble such that adhesive is less useful, for example, when the load on the fibers is smaller due to the larger radius and / or width of each thimble.

[0055] In one embodiment, adhesive is applied to the flexible endless wound cable between the thimbles such that the flexible endless wound cable between the thimbles remains flexible. An endless wound cable is considered flexible if the endless wound cable can be wound, for example for transport. Such flexibility exists if different layers of thread turns in the endless wound cable between the thimbles can be displaced relative to each other in their longitudinal direction. In particular, adhesive is applied but not cured to the endless wound cable extending between the thimbles and / or adhesive is applied and cured only in a small portion of the endless wound cable in the length and / or width direction so that the endless wound cable remains flexible as a whole.

[0056] In one embodiment, the flexible cable includes more than two thimbles. In such an embodiment, at least two thimbles are present at one end of the flexible cable. The two thimbles in one end fitting form a female end fitting, whereby a connection with a further flexible cable can be established by inserting a male end fitting between the thimbles of the female end fitting.

[0057] In one embodiment, other types of resins may be used, such as polyester resins, vinyl ester resins, or polyamides, etc. Specifically, the resin is a thermosetting polymer.

[0058] In one embodiment, adhesive is applied to only one of the thimbles. In one embodiment, adhesive is applied only to one or both thimbles of the end fittings and not to the convergence of the thread turns at the end fittings.

[0059] In an embodiment, adhesive is not applied to the portion of the support surface that does not support the thread windings, i.e., the non-supported area spanning the remaining angle (360°-α). In one embodiment, the adhesive is applied during the yarn winding process, i.e., adhesive is applied to the top surface of each layer of yarn wrap, or to the top surface of every nth layer of yarn wrap, where n is an integer greater than or equal to one (1) and less than the total number of yarn wraps in the stack.

[0060] In one embodiment, the adhesive is cured by adding a curing agent, such as a polyamine curing agent for the resin, in another embodiment, the adhesive is cured by using radiation, such as infrared radiation, ultraviolet radiation, or microwave radiation.

[0061] Unidirectional fabrics are generally considered to be nonwoven fabrics. In practice, the parallel fibers that create the unidirectional fabric need to be stabilized, for example by applying warp threads that form a small portion of the fabric. In the context of this specification, a fabric is considered to be unidirectional when at least 95% of the fabric's weight, specifically at least 99% of the fabric's weight, is parallel fibers. While unidirectional fabrics are preferred as sheets, in other embodiments, the sheets are woven sheets, braided sheets, or knitted sheets. In alternative embodiments, the sheets are made of PBO or high elasticity aramid fibers.

[0062] The present invention achieves its advantageous effect by connecting at least two layers of the yarn windings. However, the lifespan is even better extended by connecting substantially all layers of the yarn windings. Within the context of this specification, substantially all layers of the yarn windings are interpreted as at least 80% of the layers, specifically at least 90% of the layers, more specifically at least 95% of the layers.

[0063] Generally, the thread windings engage an angle α about the circumference of the thimble support surface, where α is greater than 180° and less than 360° of the circumference of the thimble support surface. In one embodiment, α is greater than 200°, specifically greater than 220°, and more specifically greater than 240° of the thimble support surface. In one embodiment, α is less than 340°, specifically less than 320°, and more specifically less than 300° of the thimble support surface.

[0064] The sheet in each end fitting extends over at least the same angle α as the turns of thread that engage the support surface. Specifically, the sheet extends from the thimble to the convergence. Specifically, the sheet extends over at least 20% and up to 100% of the length of the associated convergence. Specifically, the sheet extends over at least 50% and more specifically at least 75% of the length of the associated convergence. Specifically, the sheet extends up to 90% and more specifically up to 80% of the length of the associated convergence.

[0065] In one embodiment, no sheet is provided on one or both of the thimbles. In one embodiment, one sheet is provided on one or both of the thimbles. In one embodiment, a sheet is provided between every nth layer and (n+1)th layer of thread windings, where n is an integer that is at least 1 and less than the number of layers. In one embodiment, n is equal to 10. In another embodiment, n is equal to 6. In yet another embodiment, n is equal to 3.

[0066] In one embodiment, the thimble is made of a plastic material instead of metal, or is made of a metal other than stainless steel, including, but not limited to, various steel alloys, aluminum alloys, magnesium alloys, and titanium.

[0067] It should be noted that in the above specification, British spellings have been applied to terms such as "fibre", "mould" and "centre". These terms may be replaced by the relevant American spellings "fiber", "mold" and "centre" without changing the context of the specification.

Claims

1. A flexible endless winding cable, It comprises a first thimble, a second thimble, and at least one thread, The yarn comprises a highly elastic synthetic or natural fiber having a Young's modulus of at least 55 GPa as specified by ASTM D7269. The first thimble and the second thimble are provided at both ends of the cable. The at least one thread extends from the first thimble to the second thimble, around the second thimble, extends from the second thimble to the first thimble, around the first thimble, such that the thread forms windings around the first and second thimbles, and each thimble holds a stack of multiple layers of the thread windings. A flexible endless winding cable wherein an adhesive is provided on at least one of the first and second thimbles, and connects at least two of the plurality of yarn winding layers in each stack of the first or second thimble to each other in order to maintain the tangential direction of each yarn layer relative to one another when the flexible endless winding cable is subjected to a load.

2. A flexible endless winding cable according to claim 1, The aforementioned highly elastic synthetic fiber is a para-aramid fiber, in a flexible, endlessly wound cable.

3. A flexible endless winding cable according to claim 1, A flexible endless winding cable comprising, in the stack of the winding layers of the thread, at least a first sheet provided between two layers of the stack of one of the first and second thimbles.

4. A flexible endless winding cable according to claim 3, A flexible endless winding cable in which at least the first sheet is one of a plurality of sheets, each sheet separately provided in the stack of the yarn winding layers between two layers of one of the first and second thimbles in the stack.

5. A flexible endless winding cable according to claim 3, The above-mentioned flexible endless-winding cable comprises at least the first sheet, which is a unidirectional woven fabric.

6. A flexible endless winding cable according to claim 3, A flexible endless-winding cable in which the rigidity of at least the first sheet is greater than the rigidity of the thread.

7. A flexible endless winding cable according to claim 3, A flexible endless-wound cable comprising at least a first sheet, wherein the Young's modulus of the sheet fibers is higher than that of the high-elasticity synthetic fibers of the yarn.

8. A flexible endless winding cable according to claim 3, A flexible endless-winding cable, wherein at least the first sheet comprises fibers selected from a list consisting of carbon fibers, PBO fibers, and high-elasticity aramid fibers.

9. A flexible endless winding cable according to Claim 1, A flexible endless winding cable, wherein the stacks of the plurality of windings of the thread on each thimble engage with each thimble along a portion of the circumference of each thimble, and the adhesive provided on at least one of the first and second thimbles spreads over at least a portion of the circumference of each first or second thimble.

10. A flexible endless winding cable according to claim 9, The adhesive is spread over the entire circumference of the flexible, endlessly wound cable.

11. A flexible endless winding cable according to claim 9, The adhesive is spread only on the aforementioned portion of the circumference of the flexible, endlessly wound cable.

12. The flexible endless winding cable according to claim 11, The portion of the circumferential part of the flexible endless cable is centered on the longitudinal axis of the flexible endless cable.

13. A flexible endless winding cable according to Claim 1, The adhesive is a flexible, endlessly wound cable containing a resin or epoxy resin.

14. A flexible endless winding cable according to Claim 1, The aforementioned highly elastic synthetic or natural fiber is selected from the group consisting of aramid fibers, polyarylate fibers, PBO fibers, and basalt fibers, in a flexible endless-wound cable.

15. A method for manufacturing a flexible endless winding cable, A step of arranging a first thimble and a second thimble at a predetermined distance from each other, wherein the distance corresponds to the required cable length, and A step of supplying at least one yarn, wherein the yarn comprises a highly elastic synthetic or natural fiber having a Young's modulus of at least 55 GPa as specified by ASTM D7269, The process of passing at least one thread from the first thimble to the second thimble, turning it half a turn around the second thimble, returning it to the first thimble, and turning it half a turn around the first thimble to wrap it around, The process described above is repeated until a predetermined number of layers of thread winding corresponding to the required cable thickness are provided on both the first thimble and the second thimble. The steps include applying the adhesive to the layer of the yarn winding in at least one of the first and second thimbles, The process involves curing the adhesive to connect at least two of the layers of the yarn windings so that when the flexible endless winding cable is subjected to a load, the layers of the yarn windings in at least one of the first and second thimbles maintain a tangential orientation to each other, and the flexible endless winding cable remains flexible between the first and second thimbles. A method that includes [the following features].

16. The method according to claim 15, A method comprising the step of placing at least a first sheet on one of the layers of yarn windings in one of the first and second thimbles, after providing at least one layer of yarn windings and before providing the next layer of yarn windings.

17. The method according to claim 16, A method comprising the step of placing a further sheet on another of the layers of the yarn winding in one of the first and second thimbles.

18. The method according to claim 16, A method comprising the steps of applying the adhesive so that it penetrates substantially all layers of the yarn winding and the sheet, and curing the adhesive, which results in the connection of all layers of the yarn winding and the sheet such that substantially all layers of the yarn winding maintain a tangential orientation to each other when the flexible endless winding cable is subjected to load.

19. The method according to claim 15, The method comprising the step of applying the adhesive to the layer of the yarn winding in at least one of the first and second thimbles, wherein the step is repeated after n layers of yarn winding have been provided in at least one of the first and second thimbles, and n is an integer less than 10.

20. The method according to claim 15, A method comprising the steps of applying the adhesive such that it penetrates into almost all layers of the yarn winding, and curing the adhesive, which results in all layers of the yarn winding being connected such that when the flexible endless winding cable is subjected to a load, almost all layers of the yarn winding maintain a tangential orientation to one another.

21. The method according to claim 15, The method comprising the step of applying the adhesive to the layer of the yarn winding in at least one of the first and second thimbles, wherein the step is repeated after n layers of yarn winding have been provided in at least one of the first and second thimbles, where n is an integer less than 5.

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