Steel strand and belt reinforced with steel strand

Abstract

The invention relates to a steel strand and a belt reinforced with a steel strand. A steel strand and a belt comprising a steel strand, the belt being particularly designed for use as an elevator belt. Such a belt is very long and must withstand multiple cycles. The problem addressed by the invention is that when a steel strand is incorporated into the belt, the belt cannot run well on the crown pulley and is undulating after the load is removed. This problem is solved by a steel strand having a core, a first layer of steel filaments and a second layer of steel filaments, wherein the total angle spanned by the second layer of filaments with an apex at the center of the strand is less than 270 DEG. In this manner, the contact surface between the polymer and the steel strand is greatly increased compared to the prior art steel strand, resulting in better mechanical anchoring, and the adhesive force is greatly increased when using an adhesive.

Description

Technical Field

[0001] The present invention relates to a steel strand and a belt reinforced by such a steel strand.The steel strand is designed to reinforce a belt used in an elevator. Background Art

[0002] It wasn't until the turn of the century that the use of polymer belts in elevators used to transport people or freight increased. These 'elevator belts' offered many advantages over the traditional steel ropes used to drive the elevator up and down the elevator shaft. Elevator belts have a predictable lifespan that greatly exceeds that of steel ropes. For the same strength, they are much lighter than steel ropes. Furthermore, because they are polymer-based, they provide excellent traction to the operating pulleys. One of the main advantages of using belts is that they allow for smaller diameter drive pulleys compared to conventional steel ropes. The smaller diameter of the drive pulley allows for a compact direct drive unit that can be mounted at the top of the elevator shaft, eliminating the need for a rooftop machine room.

[0003] Many of the aforementioned advantages, particularly strength, predictable fatigue life, and small diameter drive pulleys, are made possible by using cords made from high-strength, fine-diameter steel monofilaments as the strength member of the polymer. Other advantages of using steel cords are their fire resistance and creep resistance compared to organic fibers (such as polyaromatic, carbon, or high-density polyethylene fibers). In particular, steel cords made from multiple strands twisted together (the strands themselves consisting of twisted steel monofilaments) are highly preferred due to their favorable elongation properties and good anchoring into the sheathing polymer. A typical construction is the 7×7 construction, which includes a main strand around which six outer strands are twisted. The main strand and outer strands consist of a main wire around which six sheath wires are twisted. Another construction is the 19+8×7, in which the main strand consists of a main wire around which the first six monofilaments are twisted, followed by the twelve filaments in a subsequent operation. Obviously, the production of such a steel cord having many different steel filament diameters is complex and labor-intensive.

[0004] Considerable attempts have been made (for a review see WO 2019 / 002162 A1 of the present applicant) to replace steel cords with steel strands. Such steel strands will have significantly fewer filaments and therefore the steel filaments will be thicker to achieve the same strength, but this is acceptable from a fatigue point of view. Although the problem of core migration is adequately addressed in WO 2019 / 002162 A1, other problems arise during implementation. More particularly, the higher modulus and Hookian properties of steel strands make the use of strands in belts challenging. In particular, the higher modulus of the strands is reflected in the fact that the elongation at low loads is less than that of steel cords. Now when a crown pulley is used, the tracking of the belt is due to the elongation of the steel cords in the belt: when forced off the crown pulley, the belt bends in a plane and thereby climbs back to the top of the crown pulley. Therefore, the elongation properties are crucial to making the steel strands in the belt work.

[0005] Due to the low elongation, the belt's properties become more sensitive to slight differences in strand properties. If some strands, or even certain lengths within a single strand, are stretched during use, the elongation can become permanent. When the load is removed from the belt, this resulting elongation results in an uneven, irregularly wavy, and sometimes curled belt: the problem of belt wrinkling. When the belt is removed from the elevator, the used belt, while remaining generally straight, no longer lies flat on a surface. After much effort, the inventors have developed a solution, now described in detail, to address this belt wrinkling problem. Summary of the Invention

[0006] The main purpose of the present invention is to solve the problem of 'belt wrinkling'. Since the origin of the problem is related to the tension members in the belt, a steel cord configuration is also proposed that solves this problem.

[0007] According to a first aspect of the present invention, a steel wire strand is provided.

[0008] The steel strand comprises a core and a number 'N' of first layer steel filaments twisted around the core with a lay length and twist direction. The first layer filaments have a diameter designated as 'd1' and the core has a diameter designated 'd0' hereinafter.

[0009] A second layer of steel monofilaments is provided around the first layer with the same twist direction and lay length. Thus, the strands are 'constant lay' strands, having a single lay length and twist direction. The second layer of monofilaments has a second diameter, hereinafter referred to as 'd2'. The second diameter d2 is equal to or greater than d1 (d2 ≥ d1).

[0010] When considering a vertical section of the steel strand, each of the monofilaments of the second layer will subtend, spanning an angle when considered from the center of the steel strand (which is also the center of the core), wherein the sides of this angle are tangential to the section of the monofilament. The sum of these angles for all the monofilaments of the second layer is less than or equal to 270°.

[0011] The sum of all angles spanned by the second layer of monofilaments with their apex at the center of the strand may also be less than 260°, or even less than 250°. In any case, the sum of the angles must be greater than 200°, otherwise the second layer will hardly increase the breaking load of the strand. The breaking load of a strand is the tension (in N) at which the strand fails catastrophically.

[0012] When the second layer of steel monofilaments covers less than 270° of the circle, the second layer is open 90° and the first layer of monofilaments is present within it. This has many advantages:

[0013] Since the monofilaments of the first layer can now come into contact with the polymer of the belt (see below), the monofilaments of the first layer are also held by the polymer.

[0014] - Due to the very large open spaces between the filaments of the second layer, the steel strands are better mechanically anchored in the polymer.

[0015] - Compared to a semi-Warrington cord such as proposed in WO 2019 / 002162 A1, the contact surface per unit length between the steel monofilaments and the polymer is also increased.

[0016] When adhesive is used, this results in a more adherent surface and, therefore, a higher bond between the steel strands and the polymer. Since the steel strands carry all the forces in the belt when the torque of the drive sheave or pulley interacts with the polymer, good force transmission between the steel strands and the polymer is essential. This invention increases both mechanical anchoring and chemical bonding.

[0017] - Since the second steel monofilament layer is very open, the contact pressure of the belt when running on the elevator sheave is also transferred to the first layer of steel wires. In this way, the core is better maintained.

[0018] The total angle spanned by the second layer's filaments is proportional to the number of filaments in the second layer, proportional to the diameter d2 of the second layer's filaments, and inversely proportional to their distance from the center of the core. Furthermore, strand lay length has an impact, as the angle formed by the filaments with the strand axis increases as the lay length decreases. Thus, in a vertical cross-section, a circular strand will appear elliptical. Therefore, the sides of the angle spanned by the filaments must be tangential to this ellipse.

[0019] The number of filaments in the second layer is equal to or greater than the number of filaments in the first layer, 'N', but not greater than '2N – 1'. When there are '2N' filaments, the second layer is considered 'saturated,' meaning no more filaments can be added to the layer. In this case, a compact cord type is obtained, which is a single-twist cord in which all filaments are identical. Therefore, the second layer can be called 'unsaturated.'

[0020] However, in order to allow all the second layer filaments to be accommodated as well as possible in a configuration with the lowest potential energy (i.e., a stable configuration), it is most preferred that the filaments of the second layer be nested in the cracks, recesses, or valleys formed by the twisted first layer filaments. This means that the number of second layer filaments is preferably 'N'. A special case of this configuration is known as the Seale configuration, in which the number of second layer filaments is equal to the number of first layer filaments, and the second layer steel filaments have a diameter such that the second layer is completely closed, or in other words, the total span angle of the second layer steel filaments is 360°, or at least very close to 360°.

[0021] The number 'N' can be equal to 5, 6, 7, 8, or 9. Particularly preferred are 6, 7, and 9, as they result in sufficiently small filament diameters while keeping the number of filaments in a strand limited. The diameter of the filaments has a significant impact on their fatigue life expectancy. For strands themselves or in a band with the same bending diameter, smaller diameters result in less bending stress.

[0022] The diameter of the second layer of monofilaments can be equal to that of the first layer. Alternatively, the diameter of the second layer of monofilaments can be greater than that of the first layer, for example, greater than 5%, greater than 10%, or even greater than 20% of the diameter of the first layer of steel monofilaments. Thus, d2 is greater than 1.05×d1, 1.10×d1, or 1.20×d1. Preferably, diameter d2 is kept below 2.00×d1, or below 1.75×d1, and even more preferably below 1.50×d1. This in turn improves fatigue life.

[0023] The diameter of the first layer steel monofilaments is selected in conjunction with the strand twist to provide gaps between at least the first layer steel monofilaments. The total gap angle, measured from the center of the core, i.e., the total angular gap span, is at least 20 degrees and at most 50 degrees. The angular gaps between adjacent first layer steel monofilaments need not be equal for all gaps, but are preferred. The presence of gaps between the first layer steel monofilaments prevents the first layer monofilaments from blocking each other if the core is extended. The total angular gap should not be greater than 50 degrees, as this makes cord production difficult.

[0024] The core may be a single steel wire or may even be an organic fiber such as aramid, nylon, polyethylene or even high molecular weight polyethylene. However, these are less preferred as they result in an unacceptable increase in elongation and creep.

[0025] It is more preferred that the core be made of twisted steel monofilaments, i.e., the core itself is a steel strand. Even more preferred is a core of isotwist construction with filaments having non-zero-degree helical deformation, i.e., there are no straight, undeformed filaments in the entire core. Instead, the core comprises all steel monofilaments having a helical shape ('first-degree helical deformation'). Zero-degree helices or straight monofilaments cannot absorb compression. Consequently, they can be wicked out of the steel strand under repeated loading and unloading during use and should therefore be avoided.

[0026] At least the core lay length is different from the strand lay length. The twist directions of the core and strands may be the same or opposite. Preferably, the core lay length is less than the strand lay length. Preferably, the core lay length is less than one-third, one-quarter, one-fifth, or even one-tenth of the strand lay length.

[0027] Alternatively, the core lay length is less than ten, eight, five or even three times the diameter 'd0' of the core. Compared to the helically deformed first and second layers of steel monofilaments, the core has the shortest length in the strand and must be able to stretch and extend elastically, so the short lay length of the core is important.

[0028] The core may simply be two, three, four or five steel monofilaments twisted together. Three are most preferred as this creates a stable configuration.

[0029] Alternatively, a 12-wire semi-Warrington construction can be envisioned, comprising a core-core consisting of three monofilaments twisted together. 'Core-core' should be interpreted as 'core of core strands.' Three larger outer monofilaments are nested in the recesses formed by the monofilaments. A pair of smaller monofilaments is provided between each pair of the three larger outer monofilaments. An example is given in US Pat. No. 4,829,760, which is incorporated herein by reference in its entirety. Another equally preferred embodiment is a 9-wire semi-Warrington construction comprising a core-core consisting of three thin wires and a sheath consisting of six wires of alternating medium and large sizes. Such a cord is described in US Pat. No. 3,358,435.

[0030] To impart greater elongation to the core, it is helpful to use coiled steel monofilaments. Coiled steel wire exhibits curved sections with straight sections in between. "Straight" means that the radius of curvature of the curved section is greater than 100 times the diameter of the wire. Having a coiled steel monofilament can affect the elongation properties of the core. It is more preferable for all core steel monofilaments to be coiled.

[0031] In another preferred embodiment, the core is pre-coated with a polymer. Preferably, this polymer is the same as the polymer of the belt's sheath. Furthermore, during the production of the steel strands, the core polymer is introduced into the gaps between the steel filaments of the first layer. The polymer forms a resilient cushion between the steel monofilaments of the first layer. The core polymer also helps prevent movement of the steel monofilaments of the first layer by securing them in place.

[0032] In another preferred embodiment, the steel strands are coated with an organic primer that promotes adhesion between the steel filaments and the polymer.

[0033] The primer is selected to improve adhesion to the polymer in which the reinforcing strands are intended to be used. Typical organic primers are phenolic, epoxy, cyanoacrylate or acrylic based (e.g. under the trade name Primer sold).

[0034] However, these coatings are relatively thick (greater than 1 micron) and may require considerable processing time. Therefore, nanoscale organic coatings are preferred, which are selected from the group consisting of organofunctional silanes, organofunctional zirconates and organofunctional titanates. Preferably, but not exclusively, the organofunctional silane primer is selected from the compounds of the following formula:

[0035] Y-(CH2) n -SiX3

[0036] in:

[0037] Y represents an organic functional group selected from -NH2, CH2=CH-, CH2=C(CH3)COO-, 2,3-epoxypropoxy, HS- and Cl-;

[0038] X represents a silicon functional group selected from -OR, -OC(=O)R', -Cl, wherein R and R' are independently selected from C1 to C4 alkyl, preferably -CH3 and -C2H5; and

[0039] n is an integer between 0 and 10, preferably 0 to 10, most preferably 0 to 3.

[0040] The aforementioned organofunctional silanes are commercially available. These primers are particularly suitable for achieving adhesion to polyurethanes. The thickness of the organic coating is less than 1 micron, preferably less than 500 nanometers, for example, between 5 nm and 200 nm. Thin coatings of this size are preferred because they conform to the outer surface of the reinforcing strand and, due to their thinness, do not prevent the polymer from filling the valleys between the outer filaments. This is important in the case of the strands of the present invention, as the outer surface of the steel strands exhibits a very curved surface.

[0041] For all embodiments of the strands or tapes of the present invention, whether preferred or not, whether alternatives or additions, the following are valid:

[0042] Whenever 'steel monofilaments' are mentioned in this application, it is meant a substantially round steel wire having a diameter between 0.02 mm and 0.40 mm, more preferably between 0.04 mm and 0.35 mm or between 0.10 mm and 0.30 mm. The high tensile strength of these monofilaments, i.e. the breaking load of the monofilament (in N) divided by its cross-sectional area (in mm) 2 Unit), higher than 2000N / mm 2 , preferably higher than 2350N / mm 2 , for example, higher than 2700N / mm 2 Currently, the upper limit of tensile strength is 4000N / mm 2 , while the tensile strength of ordinary carbon steel is upper bounded (see below).

[0043] 'Steel' refers to any type of steel. Plain carbon steel is preferred. Such steel typically contains a minimum carbon content of 0.40 wt% C or at least 0.70 wt%, but most preferably at least 0.80 wt% C and a maximum of 1.1 wt%. Manganese content ranges from 0.10 wt% to 0.90 wt% Mn. Sulfur and phosphorus levels are each preferably kept below 0.03 wt%. Additional microalloying elements such as chromium (up to 0.2 wt% to 0.4 wt%), boron, cobalt, nickel, and vanadium (not exhaustive) may also be added. Such carbon steel monofilaments can be produced with strengths exceeding 2000 MPa, preferably above 2700 MPa, with strengths exceeding 3000 MPa becoming common, and progress is being made towards strengths exceeding 3500 MPa. Stainless steel is also preferred. Stainless steel contains a minimum of 12 wt% Cr and significant amounts of nickel. Austenitic stainless steel is more preferred, as it is inherently more suitable for cold forming. The most preferred compositions known in the art are AISI (American Iron and Steel Institute) 302, AISI 301, AISI 304 and AISI 316 or duplex stainless steels known under EN 1.4462.

[0044] Preferably, the steel monofilaments have a metal coating or a metal alloy coating. Such alloys can be used to provide corrosion protection for the steel, to allow the monofilaments to adhere to polymers, or to combine both: corrosion protection and adhesion. The corrosion-resistant coating is, for example, zinc or a zinc-aluminum alloy. Most preferred is a low-zinc hot-dip coating as described in EP 1280958. The thickness of such a zinc coating is less than 2 microns, preferably less than 1 micron, for example 0.5 microns. A zinc-iron alloy layer is present between the zinc coating and the steel.

[0045] When steel strands are used to reinforce rubber, other preferred metal bond coatings are, for example, brass coatings (copper-zinc alloys). So-called ternary brasses, such as copper-zinc-nickel (e.g., 64% / 35.5% / 0.5% by weight) and copper-zinc-cobalt (e.g., 64% / 35.7% / 0.3% by weight), or copper-free bond systems, such as zinc-nickel or zinc-cobalt, can also be used.

[0046] According to a second aspect of the present invention, there is provided a belt.

[0047] The belt comprises a polymeric sheath and a plurality of steel strands oriented along the length dimension of the belt and maintained in a parallel relationship by the polymeric sheath.For the purposes of this application, 'parallel relationship' means that the steel strands are arranged in a single surface, such as a planar surface.

[0048] The difference between this belt and the belt of prior art is that the steel strand is the steel strand according to the first aspect of the present invention.By using this steel strand, the polymer fills the openings between the second layer of monofilaments up to the first layer of monofilaments.

[0049] To quantify the extent of contact surface per unit length between the steel strand and the polymer, it can be compared to the surface of an imaginary cylinder surrounding the steel strand. In a vertical cross-section, a minimum circumscribed circle with diameter 'D' can be identified. This circle therefore has a circumference of 'πD', where π is Archimedean constant. Therefore, the surface of the imaginary cylinder is 'πD' times the length of the cylinder.

[0050] In the same vertical cross-section, a contact profile or contact curve is formed where the polymer contacts the steel monofilaments of the first layer and the steel monofilaments of the second layer. The total length along this curved interface is referred to as 'C'. In the belt of the present invention, the length of the contact profile 'C' is greater than 1.5 times the circumference 'πD' of the circumscribed circle. The ratio C / πD can even be greater than 1.6, 1.7, or even 1.8.

[0051] This means that the contact area between the polymer of the tape and the steel strands is at least 50%, or 60%, or 70%, or even 80% greater than the contact area of a smooth cylindrical surface of the same diameter. Consequently, the adhesion surface is also much larger, and the overall adhesion of the steel strands to the polymer is greatly increased.

[0052] The polymer sheath wraps around, surrounds, and holds the steel strands in place. Practical polymers that can be used are thermosetting polymers (such as rubber) and thermoplastic polymers, the latter being preferred due to their ease of processing and the ability to easily modify the mechanical properties of the polymer. The most preferred thermoplastic materials are thermoplastic polyurethane (TPU) and thermoplastic polyolefin (TPO).

[0053] TPUs derived from polyether polyols resist hydrolysis well but have low mechanical properties. TPUs derived from polyester polyols have good mechanical properties but lower hydrolysis resistance. TPUs derived from polycarbonates have hydrolysis resistance and mechanical properties that fall between the other two types. Most preferred are TPUs based on polyether polyols and TPUs based on polycarbonate polyols. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A first embodiment of a belt according to the invention is shown.

[0055] Figure 2 A first embodiment of a steel wire strand according to the invention is shown.

[0056] Figure 3 A second embodiment of a belt according to the invention is shown.

[0057] In the reference numerals, the hundreds digit refers to the figure number, while the ones and tens digits refer to the equivalent features in the figure. DETAILED DESCRIPTION

[0058] Figure 1 A first embodiment of a belt 100 according to the present invention is shown. The belt comprises parallel steel strands 102. Typically, 5 to 15 steel cords may be arranged in a single belt, but 8 to 10 are generally sufficient to impart sufficient strength to the belt. The sheath 110 is a polycarbonate polyol-based polyurethane. Also shown within the steel strands 102 are a core 108, a first layer of monofilaments 106, and a second layer of monofilaments 104.

[0059] Figure 2 Shown Figure 1 Detailed view of steel wire strand 102. Steel wire strand 202 comprises a core 208 made of three monofilaments with a diameter of 0.28 mm, twisted together in the S direction with a lay length of 5.1 mm. The core's lay length is just less than 10 times the 0.60 mm core diameter. This is the core diameter 'd0'. The core is covered with polyurethane (PU) 216, with a diameter of 0.70 mm. Subsequently, nine first-layer steel monofilaments 206 and nine second-layer steel monofilaments 204 are added to the core in a single operation in the S direction with a lay length of 14 mm. The diameter d1 of the first-layer monofilaments 206 is 0.31 mm, and the diameter d2 of the second-layer monofilaments 204 is 0.33 mm. The total gap angle in the first layer is then 38.3°. In a subsequent operation, an organofunctional silane adhesive is applied, and during drying, the core's polyurethane melts into the gaps shown at 214. The polyurethane thus fills the gaps between the first-layer monofilaments.

[0060] The angle indicated as 'α' has its apex at the centre of the core and its sides tangent to the second layer of monofilaments. By multiplying by N (9 in this case), a total angle of 243° is obtained, which is less than 270°.

[0061] In practice, the sum of the angles spanned by the individual filaments in the second layer of the strand can be determined by forming a vertical cross-section of the wire strand, for example by casting it in epoxy resin, followed by vertical sawing and polishing; determining the center of the core, which is also the center of the strand; and then analyzing the cross-section using an optical microscope (e.g., a Zeiss Axio Imager.A1m), preferably using an image processing program such as ImageJ (available from the Laboratory for Optical and Computational Instrumentation at the University of Wisconsin).

[0062] Subsequently, the production has Figure 2 The tape is made by techniques known in the art, such as extruding parallel arranged steel strands through a single extruder head or by laminating parallel unwound steel strands between two sheets, the former being more preferred than the latter.

[0063] On a vertical cross-section of the belt, the profile length and diameter 'D' of the cord can also be measured. Because the gaps between the second-layer steel monofilaments are wider, polyurethane easily flows into the gaps. The total profile length 'C' measured is approximately 10.2 mm, while the diameter 'D' of the steel strands is 1.75 mm. Therefore, the ratio of the profile length to the circumference 'πD' of 5.50 mm is 1.86. Note that for a Seale strand with N=9, this ratio is 1.40, as the second-layer monofilaments are close together in a Seale strand.

[0064] Figure 1 The belt was tested in a test elevator installation for 40 to 600 cycles. The tracking on the crown pulley was observed and found to be consistent with a belt using a 7×7 multi-strand belt. After testing, the load was removed from the belt, and no wrinkling was observed. After the belt was removed and stretched along its length on a clean floor, it remained completely straight without any curbing effect and lay flat on the ground.

[0065] Figure 3Another embodiment of a ribbon 300 having strands 302 is shown, wherein the core 308 is made using a half-Warrington method, wherein three core-core monofilaments of 0.18 mm are surrounded by three sets of monofilaments (0.15|0.22|0.15), resulting in a total core diameter of 0.70 mm. The core is not extruded. The diameter of the first layer of monofilaments 306 and the diameter of the second layer of filaments 304 are set to be equal to 0.31 mm. The total angle spanned by the second layer of filaments is 243°, which is less than 270°. The circumscribed circle is indicated by 312 and has a diameter of 1.77 mm and a circumference of 5.56 mm. The contact contour is indicated by 314 and has a length of 9.74 mm. The ratio C / πD is 1.75.

[0066] Figure 3 The belt is currently in testing.

Claims

1. A steel wire strand comprising a core and a first layer of steel monofilaments, N in number, twisted around the core in a first layer with a strand twist moment and strand twist direction, the first layer of steel monofilaments having a first diameter d1 , the core having a core diameter d0 , in, A second layer of steel monofilaments is provided around the first layer with the same twist direction and twist length, the second layer of steel monofilaments having a second diameter 'd2', the second diameter 'd2' being greater than or equal to 'd1', the second layer of steel monofilaments spanning a total angle less than or equal to 270 degrees measured from the center of the steel wire strand in a vertical cross-section of the steel wire strand.

2. The steel wire strand according to claim 1, wherein The number of the second layer steel monofilaments is equal to or greater than the number 'N' and less than '2N-1'.

3. The steel wire strand according to claim 1 or 2, wherein: The number N is equal to 5, 6, 7, 8 or 9.

4. The steel wire strand according to any one of claims 1 to 3, wherein There are gaps between the first layer of steel monofilaments, the gaps having a total angular gap span of at least 20 degrees and at most 50 degrees.

5. The steel wire strand according to any one of claims 1 to 4, wherein The core is a uniformly twisted strand comprising core steel monofilaments having no zero-order helical deformation and twisted together at a core lay length that is different from the strand lay length.

6. The steel wire strand according to claim 5, wherein The core lay length of the core is shorter than one-third of the strand lay length.

7. The steel wire strand according to any one of claims 1 to 6, wherein The core comprises two, three, four or five core steel monofilaments twisted together.

8. The steel wire strand according to any one of claims 1 to 6, wherein The core includes 9 to 12 core steel monofilaments arranged in a semi-Warrington arrangement.

9. The steel wire strand according to any one of claims 5 to 8, wherein At least one core steel monofilament is coiled, the coiled steel monofilament including bends with segments therebetween.

10. The steel wire strand according to claim 4, wherein The core is coated with a polymer which is present in the interstices between the steel monofilaments of the first layer.

11. The steel wire strand according to any one of claims 1 to 10, wherein The steel strands are coated with an organic primer that promotes adhesion to the polymer.

12. A belt comprising a polymeric jacket and a plurality of steel strands, said steel strands being oriented along a length dimension of said belt and held in a parallel relationship by said polymeric jacket, wherein: The steel strand is a steel strand according to any one of claims 1 to 11, and the polymer fills the openings between the second layer of steel monofilaments up to the first layer of steel monofilaments.

13. The belt according to claim 12, wherein The steel strand has, in a vertical cross-section, a minimum circumscribed circle with a diameter D and a circumference πD, the steel strand having a contact profile where the polymer contacts the filaments of the first layer of steel monofilaments or the filaments of the second layer of steel monofilaments, the contact profile having a length 'C' greater than 1.5 times the circumference πD.

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