Patent Application
20200087856
The present invention relates to rope systems, more specifically to a rope comprising a splice. Rope splicing refers to the formation of a joint between two ropes or two parts of the same rope by partly disassembling and reassembling strands of the rope or ropes by interweaving.
Many splice technologies have been described in literature amongst which splices that can retain a very high percentage of the strength of the original rope, or even splices with strength superior to the strength of the rope itself such as disclosed in WO2016059261. Nevertheless, especially when exposed to dynamic applications such as cyclic bending over sheave, the rope or ropes connected by the splice may dislocate and start to slip causing lengthening of the rope system and shortening of the splice, and thus resulting in a reduction of splice strength, finally resulting in a failure of the splice as a whole. Currently splices are subjected to a regular monitoring by use of for example markers, which provides a certain assurance. Nevertheless it is expected that especially in dynamic applications a periodic inspection might prove insufficient since a not yet visible dislocation might mature into a failure between inspection intervals.
For safety related applications the current detection systems are inadequate and not an acceptable tool for risk mitigation. There is hence a need for an improved monitoring of the state of the splice in a spliced rope.
Accordingly the aim of the present invention is to provide a rope system comprising a splice structure not showing above disadvantages. Especially a rope system comprising a splice structure that enables a save use without the need for frequent inspection. Hence the present invention relates to a particular form of rope splicing herein referred to as a reliable splice. A reliable splice minimizes the number of inspections needed for a safe usage of the splice in static as well as dynamic rope applications.
Surprisingly, the aim of the invention was achieved by a rope system comprising a first rope section, a second rope section and a splice structure, wherein the first and the second rope section comprise each at least three rope strands, wherein said splice structure is between the first rope section and the second rope section and connects said first to said second rope section, wherein the rope system further comprises at least one conductive element extending from within the first rope section through the splice structure into the second rope section whereby at least a portion of the conductive element is immobilized in both, the first and second rope section.
It was observed by the inventors that such a rope system provides a substantial increase of the safety of a spliced rope while being used under load. It was further observed that a rope system according to the invention can be employed for splicing a safety relevant rope that had been damaged, whereas normally the damaged rope would have been discarded.
The present invention is of particular significance in the context of forming a splice as an end-to-end connection of two rope sections. However, the present invention also covers application of splices, other than end-to-end splices, like eye-splices or splices to form circular grommets or round slings. The present inventive rope structure may be especially relevant for applications where monitoring of the splice is difficult, for example in case of a covered splice, or critical, for example if desirable for safety reasons.
In one embodiment of the invention the first rope section and the second rope section are sections of a single rope whereby the rope system is an eye-splice or a round sling. In an alternative embodiment of the invention the first rope section and the second rope section are sections of distinct ropes whereby the rope system is a spliced rope.
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A rope system according to the invention comprises at least a first rope. In the case of an eye-splice, the rope system comprises one rope, said rope comprising a first rope section and a second rope section, whereby the first and second rope sections are joined together by the splice forming an eye in said rope. Preferably the first rope section is a section close to one end of the rope and the second rope section is more distant from said end, whereby said end of the rope is spliced to the second rope section. In the case of an end-to-end splice the first and the second rope section may be close to the 2 ends of a single rope whereby the splice results in a loop or the first and the second rope section may be close to the ends of 2 distinct ropes whereby the splice results in a connection between said 2 ropes.
The rope or ropes of the rope system of the invention may have various constructions amongst which a laid or braided rope construction. The various constructions, in particular the braided or laid ropes, may comprise primary strands (herein also referred to as rope strands or strands) that in turn may comprise sub-strands of bundles of parallel or twisted yarns, typically multifilament yarns. The nature of rope will substantially depend on the properties and use of the rope. For heavy-duty applications braided ropes are preferred, providing a rope construction with increased robustness.
Splice structures that may be employed for the present invention will be well known to the skilled person and are amongst others know from for example Chapter 7 of the Handbook of fibre rope technology (eds McKenna, Hearle and O'Hear, Woodhead Publishing Ltd, ISBN 1 85573 606 3) or WO16059261. The length of a splice may strongly depend upon the type of splice construction and end use of the rope system. By introducing a splice in a rope system the skilled person will attempt to strike a balance between the reliability of the splice and the length of the splice. For economical but also manufacturing reasons the splice should be as short as possible but long enough to avoid slippage of the splice. The present invention hence allows an additional safety factor in the splice, allowing to build as short as possible splices while safety is guaranteed by the slip detection according to the present invention. Typically the length of the splice is at most 100 times the diameter of the rope or ropes, preferably at most 80, more preferably at most 50 times the diameter of the rope or ropes.
In a preferred embodiment of the invention the rope system comprises one or two laid ropes, preferably said laid rope or ropes comprises 3, 4, 6, or 6+1 primary strands wherein the splice structure is a tucked splices between the ends of the rope or ropes, the advantage being very little slip in the spliced connection.
In another preferred embodiment of the invention the rope system comprises one or two braided ropes, preferably said braided rope or ropes comprises 6, 8, or 12 primary strands. Preferably the splice structure comprises a tucked splice or an insert splice (also called buried splice) between the ends of the rope or ropes. The advantage of such braided rope splices is a robust and stable connection.
The rope system according to the invention wherein each of the first and/or second rope section is braided and/or laid each from at least 4 rope strands, more preferably each from at least 6 rope strands and most preferably each from at least 8 rope strands.
The strands of the rope or ropes of the rope system of the invention preferably comprise polymeric elongated elements with a tenacity of at least 1.0 N/Tex. This can be an elongated element, preferably a yarn, of any high performance fibre material, like polyester, polyamide, aromatic polyamide (aramid), poly(p-phenylene-2,6-benzobisoxazole), or polyethylene yarns. Preferably the elongated element is a high modulus polyethylene (HMPE) yarn, also referred to as UHMWPE yarns. HMPE yarn comprises highly-drawn fibres of high-molecular weight linear polyethylene. High molecular weight (or molar mass) here means a weight average molecular weight of at least 400,000 g/mol. Linear polyethylene here means polyethylene having fewer than 1 side chain per 100 C atoms, preferably fewer than 1 side chain per 300 C atoms, a side chain or branch generally containing more than 10 C atoms. The polyethylene may also contain up to 5 mol % of one or more other alkenes which are copolymerisable therewith, such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene or 1-octene.
In a yet preferred embodiment, the polymeric material of choice for the elongated element of the rope or ropes is ultrahigh molecular weight polyethylene (UHMWPE). UHMWPE in the context of the present invention has an intrinsic viscosity (IV) of preferably between 3 and 40 dl/g, more preferably between 8 and 30 dl/g. UHMWPE yarns are preferably manufactured according to a gel spinning process as described in numerous publications, including for example WO2005066401 and WO2012139934. This process essentially comprises the preparation of a solution of a polyethylene of high intrinsic viscosity, spinning the solution into solutions filaments at a temperature above the dissolving temperature, cooling the solution filaments to below the gelling temperature to form solvent-containing gel filaments and drawing the filaments before, during or after at least partial removal of the solvent.
Advantages of a rope structure comprising HMPE yarn include high abrasion resistance, good resistance against fatigue under flexural loads, a low elongation resulting in an easier positioning, an excellent chemical and UV resistance and a high cut resistance.
The elongated element is preferably a fiber, a yarn, and especially a multifilament yarn. By fiber is herein understood an elongate body, the length dimension of which is much greater than the transverse dimensions of width and thickness. Accordingly, the term fiber includes filament, ribbon, strip, band, tape, and the like having regular or irregular cross-sections. The fiber may have continuous length, known in the art as filament, or discontinuous length, known in the art as staple fiber. Staple fibers are commonly obtained by cutting or stretch-breaking filaments. A yarn for the purpose of the invention is an elongated element containing many fibers. A multifilament yarn for the purpose of the invention is an elongated element containing many filaments.
The elongated elements, preferably the yarns, of the rope or ropes are of high strength, sometimes also referred to as high modulus. In the context of the present invention, the elongated element has a tenacity of at least 1.0 N/Tex, preferably of at least 1.2 N/Tex, more preferably at least 1.5 N/Tex, even more preferably at least 2.0 N/Tex, yet more preferably at least 2.2 N/Tex and most preferably at least 2.5 N/tex. When the polymeric elongated element is a UHMWPE yarn, said UHMWPE yarn preferably has a tenacity of at least 1.8 N/Tex, more preferably of at least 2.5 N/Tex, most preferably at least 3.5 N/Tex. Preferably the polymeric elongated element has a modulus of at least 30 N/Tex, more preferably of at least 50 N/Tex, most preferably of at least 60 N/Tex. Preferably the UHMWPE yarn have a tensile modulus of at least 50 N/Tex, more preferably of at least 80 N/Tex, most preferably of at least 100 N/Tex.
A preferred embodiment of the invention is a rope system wherein the first and/or second rope section comprise elongated elements, preferably synthetic yarns, more preferably high modulus synthetic yarns, most preferably high modulus ultrahigh molecular weight polyethylene (UHMWPE) yarns, most preferably UHMWPE yarns with a tenacity of at least 1.8 N/Tex.
Preferably the rope or ropes of the rope system according to the invention comprises polymeric elongated elements that are at least partially coated with a thermoset or thermoplastic polymer. Any thermoset or thermoplastic polymer able to form a suitable composite with the elongated elements may be used, whereas silicone resins and plastomers are the preferred thermoset or thermoplastic polymers, respectively. A rope system according to this embodiment may form a splice deforming to a lesser extent when the splice is stretched. This is advantageous when objects, such as hooks for instance, are passed through the eye, especially when the rope system is under load. The coating also offers further protection against damage development during dynamic loading conditions for instance and limit the deterioration of properties during long term use. In a preferred embodiment of the invention at least the first or the second rope section comprises a thermoset or thermoplastic coating, preferably the rope or ropes comprise a thermoset or thermoplastic coating.
The rope system of the invention comprises at least one conductive element extending from the first rope section through the splice structure to the second rope section. Herewith is meant that a substantial length of the conductive element is present in the first rope section, the second rope section and in the splice structure.
The rope system is built such that at least a portion of the conductive element is immobilized in both, the first and second rope section, such that upon application of a tension on the rope system at least said portions of the conductive element do not move along the axial direction of the rope structure. Such construction may be achieved by choosing the length of the conductive element to be sufficiently long for transferring the tension from the rope to the conductive element. Optionally, friction modifying additives may be applied to the conductive element or fastening means may be employed. In the inventive construction, upon slippage of the splice structure, the first and the second rope section will be pulled apart from each other, increasing the distance between them. The conductive element being immobilized in each of the first and second rope section is consequently subjected to a tensile force. At a certain slippage of the splice structure and hence a certain displacement of the first and second rope section from each other, the conductive element will split. Splitting of the conductive element may for example occur by cleavage of the conductive element through breakage or a disconnection of two individual conductive sub-elements by separation. In a preferred embodiment of the invention, the conductive element comprised in the splice structure is arranged such that the conductive element splits when the length of the splice structure is reduced to less than 50% of the original length of the splice structure, preferably to less than 75% of the original length of the splice structure, most preferably to less than 90% of the original length of the splice structure. Herein the length of the splice structure is the distance in longitudinal direction of the rope structure where both the first and the second rope section are present. Upon slippage the respective rope sections move apart from each other whereby the overlapping part, the splice, is reduced in length. By conductive element is herein understood an elongated element having the capability to transfer electrons, ions, electro-magnetic waves, acoustic waves or combinations thereof along its longitudinal direction. Accordingly in a preferred embodiment the conductive element of the invention is an optical conductive element and/or an acoustic conductive element and/or an electrical conductive element. Conductive elements will be well-known to the person skilled in the art. An optical conductive element may for example comprise or be optical fibers, like glass fibers or fibers from any other material that has sufficient transparency for the chosen signal. An electrical conductive element may for example comprise or be a metal wire, carbon fibers or fibers coated with an electrical conductive material or assemblies thereof. In a preferred embodiment of the invention the conductive element is an optical fiber, a metal wire or metal cable, a carbon yarn or carbon fiber, or a synthetic yarn or synthetic fiber coated with a conductive layer, preferably the synthetic yarn is a UHMWPE or LCP yarn or UHMWPE or LCP fiber coated with a conductive layer.
A conductive element to monitor strain in a rope is for example described in US2005/0226584, where a direct in situ measurement of large strains on the order of 0 to 15 percent in ropes is reported, allowing the identification of local strains using plastic optical fibers combined with light time-of-flight measurements.
In its operating mode, the conductive element is isolated from the rope structure at positions beyond the first and second rope section. The ends of the conductive element may directly or by means of further conductive elements be connected to instruments. As an example, at one end the conductive element is connected to a signal transmitter and at the other end the conductive element is connected to a signal receiver. The transmitter signal is measured by means of the signal receiver and the intactness of the conductive element is evaluated on the basis of the measured or absent signal. EP 0 731 209 shows an example of a conductive element monitoring by means of electric signals. Accordingly, a preferred embodiment of the invention is a rope system comprising devices suitable to emit and receive a signal through the conductive element.
The length of the conductive element present in the rope structure of the invention may vary widely and will substantially depend upon the rope structure and the positioning of the measuring devices. In one embodiment the conductive element may be of substantially the same length as the total length of the rope structure, i.e. from several meters up to thousands of meters whereby the end of the conductive element will be isolated from the rope structure close to its ends. For example the conductive element may have a length close to the length of the splice structure. Such a construction would be chosen when an existing rope requires modification by a monitored splice structure and a disassembling of the rope is challenging. During the splicing operation a conductive element would be embedded into the inventive rope structure and guided out of the rope structure at convenient positions. An alternative construction may be appropriate where in view of the rope operation a monitoring close to the splice is unpractical, requiring the signal to be measured at a place remote from the actual splice. In such cases the conductive element could already have been included in the rope construction during the rope manufacturing process, and at the position of the splice structure to be made the conductive elements from the individual rope sections could be combined to form the conductive element according to the invention. Accordingly, in a preferred embodiment of the invention the rope system comprises a conductive element, which is one unitary element. In an alternative embodiment, the conductive element is assembled from two or more conductive sub-elements connected with each other to form the conductive element. As mentioned, such a conductive element constructed from at least two sub-elements has the advantage that a rope comprising conductive elements can be repaired by a splice with as little as possible loss of rope length, thereby allowing a permanent monitoring of the condition of the splice. Where a conductive element is constructed from at least 2 conductive sub-elements, said sub-elements are connected to each other in a manner allowing the transfer of the signal from one sub-element to the other. Preferably the two or more conductive elements are connected with each other by twisting, compression wrapping, splicing, knotting, clamping, stitching, gluing or combinations thereof.
In a preferred embodiment of the invention, the rope system comprises at least one further conductive element. There are multiple benefits to such further conductive element, amongst which a further increased safety factor by redundancy, but also the additional freedom to distinguish between different levels of splice lengthening. The later construction would provide 2 or more conductive elements through the splice structure with different levels of slag, such that signals would fail at different displacements of the 2 spliced rope sections. A very early warning could for example indicate a setting of the splice, e.g. at a splice length reduction of maximum 5% whereas a critical splice slippage signal failure would occur at e.g. 10 or 20% of splice length reduction.
The conductive element of the rope structure may be positioned at any cross-sectional place of the rope structure. For example the conductive element may be at the rope periphery, in the axial center of the rope, along an individual rope strand or embedded inside one of the strands forming the ropes of the rope structure. Preferably the conductive element is comprised in an individual rope strand. The advantage of such a construction is that the conductive element is substantially shielded from deteriorating conditions and in contrast to a positioning in the axial center of the rope will have an elongation behavior similar to the rest of the rope. In case at least one further conductive element is present in the rope structure, it is preferred that the conductive elements are embedded in distinct rope strands. In an even further preferred embodiment, in the situation that 2 conductive elements are present in the rope structure, it is preferred that said 2 conductive elements are comprised in 2 distinct rope strands with opposite twist.
In one embodiment of the invention the at least one conductive element forms a loop through the rope structure and passes from the first rope section, through the splice structure into the second rope section and back through the splice structure to the first rope section. In other words the conductive element has the shape of a “U” whereby each end of the U comes from the first rope section, both legs of the
U pass the spliced zone of the rope construction and the 2 legs are linked in the second rope section. Such construction has the advantage that a signal emitter and receiver can be located together on one side of the splice structure, preferably at one end of the rope structure. Preferably said U-shaped conductive element construction provides sufficient length of the conductive element in the second rope section to avoid the dislocation of the conductive element without breakage upon slippage of the splice structure. As mentioned, this can be achieved by a sufficiently long length of the conductive element in the second rope section or alternatively by fastening the conductive element to the second rope section by a connection mean, preferably the connection mean is a knot, a braid or a plug.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16206353.1 | Dec 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/084474 | 12/22/2017 | WO | 00 |
