Steel wire rope and assembly comprising said steel wire rope

Abstract

A wire rope for use in a backhoe or dragline, the wire rope comprising: a core formed of a plurality of core strands; a plurality of outer layer strands twisted over the core; a plurality of spacer strands located in interstices between the core strands and the outer layer strands; a plastic sheath surrounding the plurality of outer layer strands, the plurality of spacer strands, and the core strands, wherein the plurality of spacer strands extend from the core strands and are located between each pair of the plurality of outer layer strands so as to form and maintain a gap between the each pair of the plurality of outer layer strands; the core strands are compacted, the gap between the core strands is less than 0.4% of the diameter of the core strands.

Description

Technical Field

[0001] The present invention relates to wire ropes, in particular high performance wire ropes for use in face shovels and draglines, and assemblies comprising a drum and such wire ropes. Background Art

[0002] Plastic dipped wire ropes are recommended for use in harsh mining applications where the rope is subject to high levels of wear and fatigue, especially where abrasive dust, dirt or corrosive materials have the potential to penetrate the rope during normal operation.

[0003] The steel wire rope is impregnated through a special process whereby each interstices in the steel wire rope are filled with a thermoplastic sealing material, forming a protective layer around the core of the steel wire rope between each strand.

[0004] Plastic impregnation protects the wire rope from dust, dirt, and other corrosive substances, and prevents internal wear caused by friction between the strands. Consequently, the service life of the wire rope is significantly extended. Plastic-impregnated wire ropes also offer several advantages. Because the thermoplastic fills the voids in the wire rope, plastic-impregnated wire ropes have significantly lower stretch than standard wire ropes, reducing their pull-down capacity. This is particularly beneficial for wire ropes subjected to high torques, as it prevents the rope from twisting and unraveling. Another advantage relates to fatigue performance: the plastic filler reduces bending stresses at the wire contacts, thereby reducing stress concentrations at the contact points between the strands and the core. Plastic impregnation creates a more stable wire rope because the components are locked in place by the plastic. The resulting rope is more resistant to shock loads, significantly increasing its service life.

[0005] Plastic-coated wire ropes are suitable for use in more extreme conditions (e.g. dust, dirt or chemical environments). Plastic-coated wire ropes are also often used in the coal or mining industry, in pile driving operations and excavator cranes, as well as in applications with very high abrasion levels.

[0006] The traditional plastic dipping process for steel wire ropes is not well controlled due to the difficulty in controlling how the wire rope is impregnated. Typically, the plastic simply randomly fills the voids within the wire rope. This process makes it difficult to avoid situations where, when the wire rope bends during use, two or more outer strands come into contact with each other, or with the outer strands of the core. Over the course of the rope's life, these contact points become steel-to-steel wear points, leading to eventual failure of the rope.

[0007] Maintaining separation between strands and the core of plastic-coated steel wire ropes is quite difficult. U.S. Patents No. 5,386,683 and No. 7,389,633 disclose methods in which specially designed plastic or fiber rods are used as inserts to prevent contact between outer strands. Furthermore, U.S. Patent No. 4,534,162 and International Patent Application WO 2016 / 120237 disclose the use of metal spacers to maintain distance between outer strands.

[0008] On the other hand, during transportation or use, wire ropes are wound / bent around the drum. Poor support of the wire rope on the drum can lead to rope tumbling and internal shearing of the plastic. This becomes particularly challenging in critical applications such as face shovels and draglines, where the ratio of the rope drum to the rope diameter is highly unfavorable. Therefore, there is a need to improve the stability and service life of the wire rope. Summary of the Invention

[0009] The object of the present invention is to provide a steel wire rope having high fatigue life and wear resistance.

[0010] Another object of the present invention is to provide a steel wire rope having a stable plastic sheath and an extended service life.

[0011] Yet another object of the present invention is to provide a wire rope suitable for use in severe wear and critical applications such as for use in face shovels and draglines.

[0012] According to a first aspect of the present invention, there is provided a steel wire rope for a face shovel and a dragline. The steel wire rope comprises: a core composed of a plurality of core strands; a plurality of outer strands twisted onto the core; a plurality of separator strands located in gaps between the core strands and the outer strands; and a plastic sheath surrounding the plurality of outer strands, the plurality of separator strands, and the core strands. The plurality of separator strands extend from the core strands and are located between each pair of outer strands in the plurality of outer strands, thereby forming and maintaining a gap between each pair of outer strands in the plurality of outer strands. The core strands are compacted, and the gap s between the core strands is less than 0.4% of the diameter of the core strands.

[0013] In the context of the present invention, "separator strands" refer to inserts, spacers or dividers used to maintain a gap between each pair of outer strands in the outer layer. In the prior art, separator strands or inserts are different from fillers. The position and function of inserts are different from fillers. Separator strands or inserts are located between each pair of outer strands in the outer layer, while fillers fill the gap between two adjacent layers of strands. Separator strands or inserts are used to maintain a gap between each pair of strands, while fillers are generally used to fill in gaps in the wire rope to make the wire rope more round. The lay length of the separator strand or insert is the same as the lay length of the layer with which it is associated, while the lay length of the filler is the same as the lay length of the steel wire with which it is in contact.

[0014] In the context of this invention, a "strand" may also be referred to as a "strand rope." It is typically composed of several monofilaments. In the context of this invention, a "monofilament" refers to a single, uninterrupted length of steel wire. The individual uninterrupted wires do not necessarily have to be the same length. The wires or filaments are twisted together at a predetermined lay length to form a strand or rope.

[0015] The plurality of outer strands and the plurality of separator strands may be made of a metal or metal alloy, such as copper, aluminum, or steel. Preferably, the plurality of separator strands of the steel wire rope have a lower hardness than the plurality of outer strands. Preferably, the core, the plurality of outer strands, and the plurality of separator strands are all made of steel. For example, the core and the plurality of outer strands may be made of high-carbon steel having a carbon content of 0.5% to 1.5% by weight, and the plurality of separator strands may be made of low-carbon steel having a carbon content of 0.2% to 0.5% by weight. For example, the high-carbon steel may have the following composition by weight: a carbon content of 0.5% to 0.8%, a manganese content of 0.3% to 0.80%, a silicon content of 0.10% to 0.50%, a maximum sulfur content of 0.05%, a maximum phosphorus content of 0.05%, and the remainder being iron and possibly trace amounts of copper, chromium, nickel, vanadium, molybdenum, or boron. Alternatively, the outer strands may have a composition by weight of 0.8% to 1.0% carbon, 0.5% to 0.8% manganese, 0.1% to 5.0% silicon, 0.1% to 0.5% chromium, 0.02% to 0.2% vanadium, with the remainder being iron and possible trace elements. For example, the outer strands may have a composition by weight of 0.84% ​​carbon, 0.67% manganese, 0.23% silicon, 0.24% chromium, 0.075% vanadium, with the remainder being iron and possible trace elements. A low-carbon steel composition is one in which the content of all elements, possibly with the exception of silicon and manganese, is less than 0.50% by weight, for example, less than 0.20%, such as less than 0.10%. For example, the silicon content may be up to 1.0% by weight, for example, up to 0.50%, such as 0.30% or 0.15%. For example, the manganese content can be up to 2.0% by weight, such as up to 1.0%, for example 0.50% or 0.30%. For the example of a low carbon separator strand, the carbon content can be up to 0.5% by weight, such as up to 0.06%. The minimum carbon content can be about 0.02% by weight.

[0016] Alternatively, the core and the outer strands may be made of steel (high-carbon or low-carbon steel), and the separator strands may be made of copper. Using copper or low-carbon steel as the separator strand material, but high-carbon steel as the outer strand material, has the advantage that the separator strands, being relatively soft, act as "weak points" during wear. This prevents the outer strands from experiencing significant wear due to the metal separator strands.

[0017] According to the present invention, the separators between the outer strands of the steel wire rope are in the form of strands that allow the plastic to bypass the separators without being blocked by the separators or inserts. The plastic sheath can penetrate the plurality of separator strands. This is an advantage over fiber inserts, which have little or no space for plastic to penetrate.

[0018] The plastic sheath on the steel wire rope can be made of a material selected from polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyurethane (PU), polysulfone (PES), and ethylene tetrafluoroethylene (ETFE). The plastic sheath is formed to extend over the entire circumference of the steel wire rope and preferably has a thickness of 1.0 mm to 2.0 mm. The plastic sheath can be formed by any suitable method, preferably by extrusion.

[0019] By using separator strands, on the one hand, it provides better wear resistance than plastic or fiber rod separators, and on the other hand, it ensures minimum gaps between the outer strands, making it easier for the plastic to flow through the separator strands during the sheathing process, thus forming a complete plastic penetration. Therefore, the performance of the wire rope is improved because the plastic sheath is completely permeable.

[0020] On the other hand, the strands can create stress concentrations at the points of contact between the strands. This can cause shearing of the plastic of the wire rope. While separated strands help provide resistance to plastic peeling, separated strands alone are not sufficient. It has been found that non-compacted strands create significant stress concentrations at the points of contact between the strands compared to compacted strands, which can cause shearing of the plastic earlier. According to the present invention, in order to improve resistance to plastic peeling, the outer strands of the wire rope are compacted. This provides a much smoother surface at the points of contact between the strands, which are the points of origin of failure for plastic failure. For example, the strands of the wire rope according to the present invention have a central wire, a first layer of wires surrounding the central wire, and a second or more layers of wires surrounding the first layer.

[0021] The core can be made as compression-resistant as possible. To this end, in the wire rope design, the gaps between the core strands are set to zero, and the strands are compacted to prevent further pulldown during use. However, it should be noted that because the strand helix angle is not perfectly circular or the strand radius varies along its length, the gaps between the strands in the core of the wire rope are not always zero, but can be slightly greater than zero. The gaps between the strands in the core of the wire rope are preferably less than 0.4% of the core strand diameter, for example less than 0.2% of the core strand diameter, preferably less than 0.1% of the core strand diameter, more preferably less than 0.05% of the core strand diameter, and most preferably almost zero. This design is uncommon, as most wire rope designers leave some gap between the core strands to allow them to move and avoid rubbing against each other. It has been found that the plastic impregnation surrounding the core strands can keep the strands sufficiently separated so that when the core strand gap is set to zero, no wire breakage or internal wear occurs. These features make the wire rope compression-resistant, and this solution also provides a very positive improvement in the integrity of the plastic sheath.

[0022] According to the present invention, the lay length of the core is preferably shorter than the lay length of the outer strands. Wire ropes elongate when loaded. For an excavator or dragline wire rope, the elongation is about 2% when loaded to 30-40% of its breaking force. There are three main elements in a wire rope: the core, which has a lay length shorter than that of the outer strands; the separator strands, which are located in the gap below the main strands and have a lay length equal to that of the outer strands; and the main outer strands. The elongation is caused by the elongation of the individual wires, the extension of the lay length, and the pull-down of the wire rope, which reduces the helix diameter and extends the length of the wire rope. The shorter lay length of the core allows the wires in the core to maintain an elongation similar to that of the wires in the outer strands.

[0023] The spacing between the outer strands can be 4% to 8% of the outer strand diameter. Due to the bending and loading properties of the wire rope, the strand spacing must be large enough to allow the strands to close under load, but not to allow the strands to touch. If the strands touch, the plastic film between the strands will be cut and the outer sheath will peel off.

[0024] The plurality of outer strands and the plurality of separator strands may each have a substantially circular cross-section. Preferably, the plurality of outer strands may be identical, and the plurality of separator strands may be identical. The ratio of the diameter of the plurality of outer strands to the diameter of the plurality of separator strands may be 3 to 10, for example 6 to 10, or 5 to 8. This ratio serves to control the size of the gaps between the outer strands and the metal filling ratio in the wire rope.

[0025] For example, the diameter of the plurality of outer strands is 2 to 40 mm, for example 10 to 30 mm, or 15 to 25 mm. The diameter of the steel rope is 5 to 200 mm, for example 10 to 100 mm, or 30 to 50 mm. Metal or steel reinforced separator strands can be used, in particular for large diameter steel ropes, where the gap between the separator strand and the steel rope is relatively large (for example about 1 mm, about 2 mm or more), so that the plastic can flow more easily around the separator. This is also very important for medium to small diameter steel ropes when the sheath needs to be formed in a full impregnation manner. In order for the plastic to flow well during the formation of the sheath, a minimum gap is required. If the gap is too small, then very high pressure is required. By using separator strands, the gap between the outer strands is maintained so that the plastic can still pass through. This is an important advantage even for steel ropes with coated core strands.

[0026] Preferably, the elastic modulus of the separator strand is lower than that of the outer strand, and the elastic limit of the separator strand is higher than that of the outer strand. The separator strand has the same lay length as the outer strand, but due to its smaller helical diameter, it has less resistance to wire rope stretching. They still experience the same amount of stretch, so more of the stretch is converted into wire elongation. If the wire rope elongates too much when subjected to impact loads, the wires in the separator strand will yield and permanently stretch. This can cause the separator strand to move outside the wire rope. The elastic limit is the stress value above which a material ceases to behave elastically and becomes permanently deformed. Preferably, based on the size of the wire rope, the elastic limit of the steel wires in the separator strand is at least 10% higher than that of the steel wires in the core and outer strands. More preferably, the elastic limit of the steel wires in the separator strand is 30% higher than that of the steel wires in the core and outer strands.

[0027] According to the present invention, the outer strands preferably have a Warington-Silo structure. For the Warington structure, the number of steel wires in each layer is represented by 1+n+(n+n), and the steel wires in the second outermost layer have two sizes, one large and the other small. The number of steel wires in the second outermost layer is twice the number of steel wires in the inner layer, and the space between the steel wires is kept very small by combining large-size steel wires and small-size steel wires. For the Silo structure, the number of steel wires in each layer is represented by 1+n+n, and the number of steel wires in the inner and outer layers is the same. The steel wires in the outer layer fit perfectly into the grooves formed by the steel wires in the inner layer. Compared with other parallel-twisted steel wires, the outer layer steel wires of the Silo wire rope are thicker, so its performance is superior, especially in terms of wear resistance. The Warington-Silo structure is a combination of the Warington and Silo structures, in which the second outermost layer includes one large-diameter steel wire and one small-diameter steel wire, and the number of steel wires in the second outermost layer is twice the number of steel wires in the inner layer. This structure has excellent fatigue resistance. It is also very flexible and has excellent wear resistance, which has led to its widespread use. For example, the outer layer strand has a 36-wire structure (1, 7, 7+7, 14), a 31-wire structure (1, 6, 6+6, 12), or a 49-wire structure (1, 8, 8, 8+8, 16).

[0028] When subjected to heavy loads (such as in surface mining applications), the Warrington-Seroux structure offers advantages over other structures, such as the Seeroux structure. The strands of the Seeroux infill structure approach their yield point under heavy loads. When the wire diameters vary widely, as in the Seeroux infill structure (disclosed in U.S. Patent No. 4,534,162), the smaller diameter filler wires tend to yield and stretch. These smaller diameter filler wires then spring out of the strands and cease to contribute to the rope's tension.

[0029] Generally speaking, the more strands a wire rope has, the more flexible it is. The fewer strands a wire rope has, the stronger it is. As a preferred embodiment, the wire rope has eight outer strands. More preferably, the outer strands are compacted.

[0030] According to a second aspect of the present invention, a drum and wire rope assembly for a face shovel or dragline excavator is provided. In this assembly, the wire rope according to the present invention, as described above, is bent or wound around a drum. The drum has a diameter D, the wire rope has a diameter d, and the ratio D / d is 20:1 to 40:1, for example, 20:1 to 30:1. For example, the diameter of the excavator wire rope drum is 1700 mm, and the diameter of the corresponding excavator wire rope bent on the wire rope drum is 72 mm. The ratio D / d is 24. The wire rope of a face shovel or dragline excavator is subject to very high impact loads. The working stress in the wire rope can be as high as 35% of the minimum breaking force. In addition, the bearing groove on the drum can be very shallow. These conditions lead to unique failure modes not seen in other wire rope applications. These specific failure modes are: high internal contact stresses within the wire rope; poor support of the wire rope by the drum, resulting in rope folding and internal shearing of the plastic; and high pressure stresses between the wire rope and the drum, causing plastic deformation. Although the plastic sheath surrounding the outer strands, separator strands, and core strand may deform, the wire rope according to the present invention exhibits a long service life under these conditions. The drum and wire rope assembly demonstrates excellent performance when used in face shovels or draglines. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention may be better understood by reading the following detailed description in conjunction with the non-limiting examples and accompanying drawings, in which:

[0032] Figure 1 An example of a steel rope according to the invention is schematically shown. DETAILED DESCRIPTION

[0033] Figure 1 The structure of the steel wire rope of the present invention is shown. The diameter of the steel wire rope is 72 mm, and its configuration is EP8xK36WS+IWRC (1,6,8+8). Here, EP refers to a steel wire rope covered with a polymer. The steel wire rope has 8 compacted outer strands, each of which has 36 steel wires laid in a combined parallel twist, represented by 8xK36WS. The core is an independent steel wire rope (IWRC). The overall structure of the steel wire rope is represented by 1+6+(8+8), and the outer layer has two types of strands, one with a large diameter and the other with a small diameter, that is, this is a parallel twist structure, and the outer layer is composed of alternating large-diameter strands and small-diameter strands.

[0034] like Figure 1As shown, the wire rope 10 has an independent wire rope core (IWRC) 12. The independent wire rope core 12 is a wire rope made of seven core strands 14 of the same rope structure. Each core strand 14 is compacted. In addition, the gap between the core strands is less than 0.03 of the core strand radius, but in the wire rope design, the gap between the core strands 14 is set to zero.

[0035] There are eight spacer strands 16 and eight compacted outer strands 18 made of steel and twisted onto the independent steel cord core 12. The spacer strands 16 are disposed between the compacted outer strands 18 to form a gap between each pair of compacted outer strands 18.

[0036] The steel wire rope 10 is surrounded by a plastic sheath 19. Preferably, the plastic sheath 19 is made of polypropylene and is preferably manufactured by extrusion. The plastic sheath 19 is extruded to extend over the entire circumference of the steel wire rope and has a thickness of 1 to 2 mm, for example 1.50 mm.

[0037] This wire rope can be wound onto a wire rope drum with a diameter as low as 1700 mm. This wire rope for face shovels or draglines has a very long service life.

Claims

1. A steel wire rope for a face shovel or a dragline, the steel wire rope comprising: a core formed of a plurality of core strands, a plurality of outer strands twisted onto the core, A plurality of separator strands located in the spaces between the core strands and the outer strands, a plastic sheath surrounding the plurality of outer strands, the plurality of spacer strands, and the core strand, wherein the plurality of separator strands extend from the core strand and are positioned between each pair of outer strands in the plurality of outer strands so as to form and maintain a gap between each pair of outer strands in the plurality of outer strands; wherein the core strands are compacted, The gaps between the core strands are less than 0.4% of the diameter of the core strands, and The elastic modulus of the separating strands is lower than the elastic modulus of the outer strands, and the elastic limit of the separating strands is higher than the elastic limit of the outer strands.

2. The wire rope for a face shovel or a dragline according to claim 1, wherein The core, the plurality of outer strands, and the plurality of spacer strands are all made of steel.

3. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The core and / or the outer strands have a central steel wire, a first layer of steel wires surrounding the central steel wire, and a second or more layers of steel wires surrounding the first layer of steel wires.

4. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The gaps between the outer strands are 4% to 8% of the diameter of the outer strands.

5. The steel wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The lay length of the core is shorter than the lay length of the outer strands.

6. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The elastic limit of the steel wires of the separator strands is at least 10% higher than the elastic limit of the steel wires of the core and the outer strands.

7. The steel wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The wire rope has 8 outer strands.

8. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The outer strands are compacted.

9. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The outer strands have a Warington-Seloux structure.

10. The wire rope for a face shovel or a dragline according to claim 1 or 2, wherein The outer strands have a structure of 36 steel wires, wherein the structure of the 36 steel wires is 1, 7, 7+7, 14; a structure of 31 steel wires, wherein the structure of the 31 steel wires is 1, 6, 6+6, 12; or a structure of 49 steel wires, wherein the structure of the 49 steel wires is 1, 8, 8, 8+8, 16.

11. An assembly comprising a drum and a wire rope for a face shovel or dragline, the wire rope being wound around the drum, the wire rope being a wire rope according to any one of the preceding claims, wherein The diameter of the reel is D, The diameter of the steel wire rope is d, The ratio D / d is 20:1 to 40:

1.

12. The assembly comprising a drum and a wire rope for a face shovel or a dragline according to claim 11, wherein The ratio D / d is 24:

1.

13. An assembly comprising a drum and a wire rope for a face shovel or a dragline according to claim 11 or 12, wherein The plastic sheath surrounding the plurality of outer strands, the plurality of spacer strands, and the core strand is deformable.

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