EP3233702B1

EP3233702B1 - Elevator rope and method of manufacturing said elevator rope

Info

Publication number: EP3233702B1
Application number: EP15802107.1A
Authority: EP
Inventors: Veerle Van Wassenhove; Hendrik Rommel
Original assignee: Bekaert Advanced Cords Aalter NV
Current assignee: Bekaert Advanced Cords Aalter NV
Priority date: 2014-12-19
Filing date: 2015-12-01
Publication date: 2023-06-07
Anticipated expiration: 2035-12-01
Also published as: WO2016096395A1; FI3233702T3; CN107109786A; CN107109786B; EP3233702A1; ES2954911T3

Description

Technical Field

The invention relates to an elevator rope for use in an elevator for persons, goods, warehousing and any other appliance similar to that. Furthermore a method to produce such elevator ropes is disclosed.

Background Art

When the 'European Parliament and Council Directive 95/16/EC on the approximation of the laws of the Member States relating to lifts' of June 1995 came into force on 01/07/1997 this spurred a series of innovations in the field of elevators within the European Union. As now the ban on fine, high tensile wires as enshrined in EN 81-1 was lifted, other different tension members could be evaluated with these kinds of wires.
Basically there emerged two development tracks. In the first track steel ropes were replaced with thin belts comprising several fine steel cords built from fine and high tensile wires and encased in a polymer jacket ( WO 99/43589 ). In the second track, steel ropes of smaller diameters were used, either with or without a polymer coating ( EP 1213250 ). Both enabled the use of smaller drive rolls and sheaves and hence the use of 'direct drive' motors which on their turn made the whole lifting machine compact and light and thereby enabled to install a lift without machine room on top of the building. The invention relates to this second track of development with the variant of a steel rope having a polymer jacket.
As the decrease in diameter of sheave and rope results in an increased pressure between rope and sheave - as the load forces remain invariant and the contact surface diminishes - lateral pressures in the steel rope increase. As fine, high tensile wires are more prone to breakage when under lateral pressure, the use of an elastomer jacket is now widespread in order to alleviate this lateral pressure by spreading it throughout the elevator rope.
Furthermore, as the contact surface between elastomer jacket and sheave is smaller than when using a thick steel rope on large diameter sheave, the friction coefficient between sheave and coated steel rope must be increased to generate enough grip force. The presence of an elastomer jacket has a profound influence on the friction between the coated steel rope and the sheave. Compared to the prior-art friction coefficient between steel rope and steel sheave that is about 0.1, friction coefficients between sheave and elastomer jacket tend more to 1.0 and even higher.
However, a too high friction leads to other problems in that:

When a cabin is in its upward flight and the counterweight is blocked in its movement or arrives on its buffers, the cabin could be further lifted by the drive sheave, while the rope at the counterweight side slackens, possibly pushing the cabin against the top of the shaft;
When a cabin with passengers is in its downward flight and an emergency stop occurs (e.g. due to a power interruption), passengers could experience an unpleasant downward acceleration as the elevator rope grips too much into the sheave.

Furthermore, as friction occurs between the surfaces of two different parts

the sheave and the elevator rope - both surfaces have to be adapted, tuned to one another in order to obtain the most appropriate friction behaviour. There is therefore a need to be able to adapt at least one of the surfaces to the optimal friction value with the other surface. As the total surface of the elevator rope is larger than the surface of the sheave that is repeatedly contacted with the rope, it is best that the surface of the rope is adaptable, while the surface of the sheave is kept wear resistant.

Different solutions have been proposed in order to adapt the friction of the elastomer jacket to the sheave:

JP2004131897 describes a wire rope with a resin coating layer, wherein the coating layer has a cross sectional contour deviating from a true circle on at least a part along the longitudinal direction of the rope. For example a plurality of grooves or ridges can extend along the length of the rope.
DE 10 2012 015 580 describes a rope with an elastomer jacket having at least two areas at the outer surface that have a different coefficient of friction. By varying the area ratio or the friction difference between the two areas, it becomes possible to modulate the coefficient of friction of the rope.
US 2011/0192131 is about an elevator rope with a main rope body covered with a jacket. The jacket mainly comprises a thermoplastic polyurethane elastomer to which one or more of the following has been admixed:
- An isocyanate compound having two or more isocyanate groups per molecule or;
- A thermoplastic resin other than the thermoplastic polyurethane and an isocyanate compound having two or more isocyanate groups per molecule or;
- Inorganic fillers in fibrous or platelike form.
WO 2013/053621 describes a load bearing assembly for use in an elevator system comprising at least one steel rope surrounded by a thermoplastic elastomer that comprises polymer particles with a molecular weight that is larger than 500 000 g/mol.
US 2014/0008154A1 describes in paragraph [0037] a belt of non-circular cross section comprising cords wherein the jacket could be a woven fabric that engages and/or integrates the cords or the jacket could be a polymer or elastomer applied to the cords via extrusion or the jacket could be a single material, multiple materials, two or more layers of the same or dissimilar materials, and/or a film or any one or more of the previously mentioned alternatives in combination.

Another problem that sometimes occurs with high tensile ropes with an elastomer jacket is that due to the compression of the jacket and/or the relative movement of the strands during use, the shear forces in the elastomer rise above the tear force and cracks occur in the coating.
The inventors therefore sought other ways to solve the friction problem and cracking problem.

Disclosure of Invention

The object of the invention is to provide an elevator rope of which the friction with a sheave can be tuned at will. It is a further object of the invention to provide an elevator rope with a particular coefficient of friction with the sheave of an elevator. Another object of the invention is to provide a reinforced elastomer jacket that reduces cracking of the polymer. Also the method to produce such an elevator rope is the subject of the invention. The invention is set out in the appended set of claims.
According a first aspect of the invention an elevator rope comprising a steel cord and an elastomer jacket surrounding the steel cord is provided. Specific about the elevator rope is that it further comprises one or more yarns wrapped, braided or knitted around the steel cord. These one or more yarns are integrated into the elastomer jacket. The one or more yarns wrapped, braided or knitted around the steel cord form a pattern on said steel cord that comes through, progresses, emerges, imprints or reaches through the polymer jacket to the surface of the elevator rope.
The load bearing member of the elevator rope is a steel cord i.e. a cord comprising multiple steel filaments. For the purpose of this application a steel rope - generally considered to be of larger size e.g. larger than 8 mm - is also considered to be a steel cord. Further the use of non-metal fibers in the steel cord is not excluded per sé. The steel cord may comprise other fibers than steel filaments. In any case the largest part of the load on the steel cord must be carried by the steel filaments. Alternatively the steel cord may consist only out of steel filaments. The elevator rope preferably comprises one single steel cord. The elevator rope has a substantial circular cross section as opposed to the belt tension members of WO99/43589 that have a thickness that is smaller than the width of the tension member.
In order to limit the diameter of the elevator rope, the filaments have a high tensile strength. The tensile strength 'Rm' (in N/mm² or MPa) of a steel filament is its breaking load (in N) divided by its cross sectional area (in mm²). For the purpose of this application the tensile strength expressed in N/mm² is larger than 3000 - 2000×δ wherein 'δ' is the equivalent diameter of the steel filament in mm, i.e. the diameter of a round filament having the same cross sectional area as the filament. Currently, even higher tensile strengths such as higher than 3500 - 2000×δ are considered. The diameters of the filaments envisaged for the steel cord are between 0.15 mm and 0.50 mm, or more preferably between 0.20 to 0.40 mm. Hence, tensile strengths of the filaments are above 2000 N/mm². Generally within the steel cord of the invention different filament diameters are used in order to geometrically fit together the filaments and strands in the steel cord.
In order to reach these high tensile levels plain carbon steel is used that is sufficiently far cold deformed by means of wire drawing. A typical steel composition has a minimum carbon content of 0.65%, a manganese content ranging from 0.40% to 0.70%, a silicon content ranging from 0.15% to 0.30%, a maximum sulphur content of 0.03%, a maximum phosphorus content of 0.30%, all percentages being percentages by weight. There are only traces of copper, nickel and/or chromium.
By preference the outer surface of the filaments are coated with a functional coating to promote adhesion and/or to retard corrosion and/or to improve fatigue wear. An adhesive coating is e.g. brass plated steel filaments that can adhere well to rubber in case a rubber elastomer jacket is envisaged. Alternatively organo functional silanes, titanates or zirconates can be used to improve adhesion with polyurethanes. The latter can be conveniently combined with a zinc coating that brings and improved corrosion resistance as well. Alternatively mineral or synthetic oils - preferably compatible with the elastomer of the jacket - can be used that reduce fretting between filaments and at the same time inhibit corrosion.
By preference the steel cord is a multi-strand steel cord that is built up of strands of steel filaments. A preferred embodiment has a core strand made of two, three or more strands. Another preferred embodiment is one wherein the cord comprises a central steel core strand surrounded by a layer of inner layer steel strands forming an inner strand. On this inner strand layer an outer layer of outer layer steel strands is cabled. The lay length and direction of inner layer steel strands and outer layer steel strands are preferably differing from one another and/or opposite to one another. Typically the lay length of inner layer of strands is chosen between 5 to 12 times the diameter of the inner strand and the lay length of the outer layer strands between 5 to 15 times the diameter of the steel cord. The lay length of the outer layer strands is the cord lay length.
The number of inner layer strands is from 5 to 8, while the number of outer layer strands is from 6 to 12. In a preferred embodiment there is no common divisor between the number of inner layer strands and the number of outer layer strands. This results in less interlayer pressure between strands.
Strands are steel filaments that are twisted together. The twisting can be done in a single step wherein all steel filaments of the strand obtain the same lay length and direction. Simple constructions with equal diameters such as three filaments twisted together (3×1) or six filaments around a single core wire (1+6) are preferred for the core and inner strands. The lay length of the filaments in the strands is from 10 to 20 times the diameter of the strand. Strands with a high metallic fill factor are more preferred for the outer strands, as they are highest in number and must take most of the load. Most preferred is then that filament diameters are chosen according a Warrington, Seale, filler, or Warrington-Seale configuration. Exemplary configurations are 1+6-6-6 Warrington, 1+6+6F+12 filler, 1+9-9 Seale. These configuration have metallic fill factors of 75 % and higher.
Alternatively, strands can be of the multilayer type. In a multilayer type of strand a core strand or filament is covered with a layer of filaments having a different lay length and/or direction compared to the underlaying layer. Multilayer strands are somewhat less preferred due to their point contacts between filaments and lower metallic fill factor.
The diameter of the steel cord 'd' is in principle not limiting the invention. The invention can be used with steel cords with diameter from 1 to 20 mm or even larger. Preferably the diameter of the steel cord 'd' is less than 8 mm, even more preferably lower than 7 mm as for example 4.5, 5, 5.5 or 6 mm. The invention can be advantageously used from diameters 2 mm and higher thereby not excluding its use below that limit.
In order to spread and reduce the pressure on the high tensile steel filaments, the elevator rope is provided with an elastomer jacket that completely surrounds and encases the steel cord. The elastomer can e.g. be a thermohardening elastomer like rubber. Rubber has some particular advantages in that it is wear resistant and enables very good adhesion with brass coated filaments. However, it generates a lot of friction with other objects making it less preferred for the coating of an elevator rope. Also the vulcanisation requires a lot of energy and is an additional step to extrusion.
More preferred are therefore thermoplastic elastomers that can readily be extruded around the steel cord and do not need an additional vulcanisation step. Moreover, the friction coefficient with a steel sheave is lower than that of rubber.
Typical thermoplastic elastomer can be selected from the group consisting of styrenic block copolymers, polyether-ester block copolymers, thermoplastic polyolefin elastomers, thermoplastic polyurethanes and polyether polyamide block copolymers. Examples of thermoplastic polyurethanes comprise ether-based polyurethanes, ester-based polyurethanes, ester-ether based polyurethanes, carbonate-based polyurethane or any combination thereof. Preferred polyurethanes are polyurethanes having a good hydrolysis resistance and low temperature flexibility such as ether-based polyurethanes.
The friction coefficient (static or dynamic) of the elastomer jacket can also be altered by adding fillers to the elastomer compound. Particular noteworthy fillers are high molecular weight polymer particles of spherical or non-spherical shape with a size between 5 to 500 µm, or 20 to 250 µm or most preferred between 50 to 100 µm. High molecular weight polymers are - for the sake of this application - polymers with a molecular weight higher than 0.5•10⁶ g/mol, for example between 1•10⁶ and 15•10⁶ g/mol, or more preferred between 2•10⁶ and 9•10⁶ g/mol. Particularly preferred particles are ultra-high molecular weight polyethylene (UHMW-PE) particles or ultra-high molecular weight poly dimethyl siloxane particles.
As mentioned the elevator rope comprises yarns that are wrapped, braided or knitted around the steel cord.
Within the scope of this application with 'yarn' is meant any type or kind of non-metal wire i.e. a slender, strong monofilament, strand or cord purposively designed to be used in weaving, sewing or other textile work. They can be made of a single filament or of multiple filaments or fibres that are spun together (spun yarn) or laid together without intended twist (zero-twist yarn). Yarns can also be in the form of a narrow strip or tape of material.
Yarns are made of synthetic material selected from the group consisting of glass fibres, poly-aramide fibres, poly(p-phenylene-2,6-benzobisoxazole) fibres, polyurethane fibres, carbon fibres, polyolefin fibres, polyamide fibres, polyester fibres, poly ethylene terephthalate fibres, polycarbonate fibres, polyacetal fibres, polysulfone fibres, poly phenylene sulphide fibre, polyether ketone fibres , polyimide fibres, polyether imide fibres or mixtures thereof.
Alternatively the yarns are natural or semi-synthetic fibres selected from the group consisting of sisal, flax, cotton, hemp, silk, basalt, cellulose based fibres or mixtures thereof. Rayon is a specific example of semi-synthetic regenerated cellulose fibre.
Alternatively combinations of the named synthetic, semi-synthetic and natural yarns are of course also possible e.g. wherein one yarn is synthetic and a second yarns is natural fibre based.
Possibly the yarns are provided with an adhesive size, a coating that improves adhesion with the elastomer of the jacket. In the case of rubber an RFL (resorcinol formaldehyde latex) dip is suggested. In the case of thermoplastic elastomers aqueous size solutions based on starch, acrylic polymer, polyvinyl alcohol or others, dissolved in hot water together with a wax, such as polyolefin wax are recommended. After dipping and drying a layer forms on the yarn. Non-aqueous sizes comprising a heat meltable polymer and a wax such as a polyolefin wax can also be considered. Examples of heat meltable polymer sizings are acrylate ester or methacrylate esters. Best is if the yarn material adheres to the polyurethane without a need for a size for example when the yarn as well as the jacket elastomer is polyurethane based.
Yarns are wrapped around the steel cord by encircling, by winding, by spiralling the yarns around the steel cord. The wrapping can be done in the direction of the cord lay or opposite to the direction of the cord lay. Possibly more than one yarn can be wound around at the same yarn lay length, or the yarns may have a different yarn lay lengths and/or may be wound in opposite direction. Wrapped yarns can be easily unwound from the steel cord by unwinding them in reverse order and in opposite direction: they will not entangle.
Alternatively the yarns can be braided around the steel cord. In a braiding operation two or more yarns are wound around the steel cord of which at least one yarn winds opposite to the others. Again the yarns have a yarn lay length that is equal to the axial distance needed by the yarn to make one turn around the steel cord. The at least one yarn alternatingly crosses under and over one or more of the remaining yarns. This results in a weaving pattern on the surface of the steel cord. Preferably the number of yarns evolving in the one winding direction is equal to the number of yarns running in the opposite direction. All kinds of weaves like plain weave, twill weave or satin weave are possible. Single yarns will not easily disentangle from the resulting braid.
In a third alternative the yarns are knitted or stitched around the steel cord. Preferably this is done in a warp knit or stitch process. Single knitted or stitched yarns do not completely circumscribe the steel cord. However, a yarn lay length can still be defined as being the distance between two contacts of the same pair of yarns. One, two or more yarns can be knitted or stitched around the steel cord. Removal of a single yarn results in the other yarns coming loose.
In a more preferred embodiment each lay length of the one or more yarns is shorter than the cord lay of the steel cord. This ensures that the yarns cross the outer strands of the steel cord under an angle and that the yarns are not oriented parallel to the steel strands.
In another preferred embodiment, at least two yarns are wrapped around the steel cord in opposite directions. When the lay lengths of the opposite running yarns are equal, crossings will always occur diametrically opposite and at the same circumferential position. This results in a repeated pattern of protrusions at the surface of the elastomer. Alternatively when the wrappings are with lay lengths that are co-prime to one another (for example 15 and 14 mm, or 5 and 9 mm,...) crossings will not occur diametrically to one another and are evenly spread around the circumference of the steel cord. It is also possible that the lay length is varied along the length of the steel cord. Wrapping is a preferred method to apply the yarns as it operates at the highest linear speeds.
The wrapping, braiding or knitted yarns should not cover the steel cord completely. On the contrary: it is the intention that sufficient parts of the steel cord remain open for the ingress of the elastomer jacket in order to consolidate, to unite the elevator rope. The yarns are therefore embedded in the elastomer jacket and are an integral part of the elastomer jacket. As such the yarns reinforce the elastomer jacket and prevent it from cracking during extended use.
A further purpose of the yarn is to introduce a controlled unevenness to the outer surface of the elastomer jacket. This controlled unevenness influences the friction coefficient of the elevator rope. At the spots where yarns cross, i.e. the thickness of the yarn doubles, a small bulging at the surface of the elastomer jacket appears. As the amount and place of these crossings can be controlled, the number of bulges at the surface of the elastomer jacket can also be controlled.
An open yarn layer further improves the mechanical anchorage of the jacket to the steel cord. By preference less than 60% of the outer surface of the steel cord is covered with the one or more yarns. If the coverage degree is too high the yarn will isolate the polymer jacket from the steel cord thereby jeopardising the integrity of the elevator rope. A too high coverage degree will also lead to a too smooth surface of the elastomer jacket. At least 5% of the surface must be covered with yarn in order to at least have a beneficial effect. If there is not enough yarn present the jacket surface will remain unaffected and the reinforcement of the jacket will be insufficient. Other possible coverage degrees are between 5 and 50% or between 10 and 50%, or between 15 and 45 %.
Also the yarns must be sufficiently spread from one another hence an individual yarn should not cover too much of the steel cord surface on its own. Therefore the width of the yarn should be less than 30% of the diameter of the steel cord, or even less than 20%. The width of the yarn is the dimension in a direction perpendicular to the yarn as it is in position on the steel cord as during wrapping, braiding or knitting the yarn can be flattened. At the other end of the range, the thickness of the yarn is preferably more than 1%, or even more than 5% of the diameter of the steel cord in order to leave a sufficient imprint at the outer surface of the polymer jacket.
Furthermore the thickness of the wrapped, braided or knitted yarns should neither be too large nor too small compared to the thickness of the elastomer jacket. The thickness of the elastomer jacket is equal to half the difference between the diameter of the elevator rope measured with elastomer jacket and the steel cord diameter. These diameters are to be measured with a micrometer with large anvils. With 'large anvils' is meant circular anvils with a diameter that is larger than at least the cord lay length of the steel cord. As a 'diameter' the average of the minimum and maximum measured value over the circumference of the elevator rope or steel cord is used. Hence the jacket thickness also includes the thickness of the yarn.
The thickness of the elastomer jacket is between 5 to 50% of the diameter of the steel cord with more preferred thicknesses between 5 to 30%, or 5 to 25%.
With the thickness of the yarn is meant the radial size of a single yarn when in position around the steel cord. This thickness of the yarn is less than the thickness of the elastomer jacket. The yarn must be covered by the polymer at least when the elevator rope is in its fresh state. During use, some of the yarns may surface at the elastomer jacket. Preferably the thickness of the yarn is less than 75% of the thickness of the elastomer jacket. The yarns should also have a minimum amount of thickness e.g. 5% of the elastomer jacket. This in order that the imprint of the yarn continues to the surface of the elastomer jacket. Other favourable ranges are: between 10% and 60% between 10% and 50%.
Due to the controlled roughness of the surface not all of the elastomer will come into contact with the surface of the sheave. Part of the polymer jacket where under yarn is present will be more easily contacted by the flat surface than the valleys in the polymer jacket. The pattern of the yarn allows to control this contact surface. By rolling out the elevator rope under a diametrical force of 10 N onto a flat surface over a width of 100 mm, the contact surface of the elastomer jacket to the flat surface can be determined (for example by inking the elastomer surface or by using pressure sensitive paper). By varying the yarn pattern a swing between 10% to 90% of the elastomer jacket contact surface can be obtained. An advantageous range is that between 10% and 60% of the elastomer jacket contacts the flat surface when rolled out. Alternative ranges are between 10% to 50%, 15% to 40% and 20% to 40%.
The elevator rope is intended for use in an elevator of goods and/or persons. Its size and strength as described above are such that it can be used with small drive sheaves enabling the use of direct drive motors without gearbox. The elevator rope can be used with sheaves of diameter 'D' that are equal to or smaller than 40×d, 'd' being the diameter of the steel cord.
According a second aspect of the invention, a process or method to make the above described elevator rope is explained. The process starts with the provision of a steel cord of the sizes and geometry as disclosed above. Around this steel cord yarns are continuously applied in one or more of the following ways:

By wrapping one or more yarns around the steel cord. Wrapping can be done in opposite directions when two or more yarns are present. Preferably the wrapping is done with a lay length that is shorter than the steel cord lay length. Also preferred is that the lay lengths of oppositely running yarns differ. Existing wrapping machinery can be used to this end.
By braiding two or more yarns around the steel cord. In braiding two oppositely running groups of yarns alternatingly cross one another over and under thereby forming a weave pattern. The braid should be open. Typically maypole type or high speed braiders (as for example known in hose manufacturing) can be used to this end.
By knitting. In knitting at least two yarns hold one another at stitches. The yarns do not completely circle the steel cord, but only an angular part of it. Existing round knitting machines can be used to this end.

In this manner an intermediate product of steel cord with an open yarn mantle is obtained. This intermediate product is further extruded with an elastomer jacket whereby the elastomer ingresses between the open yarn mantle and even further penetrates into the steel cord thereby integrating the yarn mantle into the polymer jacket.
The process has some advantages over the prior art. First, the yarn mantle improves the drag of the polymer during extrusion. The surface of the elevator cord thereby gets a substantially round cross section. The centricity of the steel cord in the elevator rope is also improved.
Secondly, the yarn mantle prevents sleeving of the steel cord strands during extrusion. As during extrusion a large pressure is exerted on the steel cord, the outer strands tend to be pushed back at the entrance of the extrusion head. This pushing back results in an accumulation of extra length of the outer strands thereby opening the steel cord. This may even lead to steel cord fracture if two outer strands exchange position. The presence of the yarn mantle prevents the outer strands to accumulate the extra length and therefore the occurrence of sleeving.
In the following sections the invention will be further clarified by examples and embodiments. The examples are not limitative to the invention and are only meant to illustrate how the invention can be reduced to practise.

Brief Description of Figures in the Drawings

Figure 1a shows a first embodiment lengthwise and Figure 1b shows the same embodiment in cross section.
Figure 2a shows a second embodiment lengthwise and Figure 2b shows the same embodiment in cross section.
Figure 3a shows a third embodiment lengthwise and Figure 3b shows the same embodiment in cross section.
Figure 4a, 4b and 4c shows the surface prints of different elevator rope surfaces according the invention.

In the drawings, references with equal units and tens indicate corresponding parts of the invention across figure numbers indicated by the thousands digit.

Mode(s) for Carrying Out the Invention

In a first example of the invention - Figure 1a and 1b - a steel cord of the following type was made: ${\{\begin{array}{l} {[{(0.34 + 6 \times 0.31)}_{12.5 s} + 6 \times {(0.25 + 6 \times 0.25)}_{12.5 z}]}_{25 s} + \\ 7 \times (0.34 + 6 \times {(0.31 |0.33| 0.25)}_{20 s} \end{array}\}}_{50 Z}$
Around a central core wire of diameter 0.34, 6 wires of diameter 0.31 are twisted with lay length 12.5 in 's' direction. On this core strand, 6 inner layer strands - having a core filament of 0.25 around which 6 outer filaments 0.25 at lay 12.5 in z direction are twisted - are cabled in lay 25 s. Seven outer layer strands of parallel lay in Warrington configuration with a 0.34 core filament surrounded with 6 filaments of 0.31 on top of which 6 alternating filaments of 0.33 and 0.25 are twisted at lay 20 's' are finally closed around the core strand at lay 50 Z. Hence 50 is the cord lay length. All sizes are in millimetre. Filaments are made of far drawn plain carbon steel with carbon content in excess of 0.70 wt%C. The tensile strength of the filaments is between 2200 to 2900 N/mm² depending on the size of the filament. The filaments are hot dip galvanised. The cross section of the steel cord is indicated with 110 in Figure 1b. The steel cord has a diameter of 5.1 mm.
Around this steel cord two spun yarns of poly ethylene terephthalate (a thermoplastic polymer of the polyester family) of 90 tex (g/km) are wrapped. First the yarn 122 with a lay of 6.1 mm in `s' direction, immediately followed by yarn 120 with a lay of 5.1 in 'z' direction. After wrapping the diameter of the intermediate product was 5.3 to 5.4 mm. The degree of surface coverage was estimated at 15%, the width of the filaments was 0.35 mm while the thickness of the filaments were 0.15mm. Hence, during wrapping the filaments obtained an oblong cross section;
The intermediate product was led through a dipping tank containing a solution of 1.5 vol. % of N-(2-amino ethyl)-3-amino propyl tri methoxy silane (a functionalized organo silane) dissolved in a mixture of isopropanol and water. Air-drying followed the dipping.
The intermediate product was further processed in an extrusion line and coated with clear polyurethane (Desmopan^® of Bayer). An elastomer jacket 140 is thus formed that follows the underlying texture of the yarn and shows an uneven surface that reflects the underlying yarn mantle. The final outer diameter of the cord was 5.65 mm making the thickness of the elastomer jacket 0.275 mm or 5.4 % of the steel cord diameter.
A `surface print' was made of the outer surface of the elastomer jacket by taking a test piece of 10 cm long from the elevator cord, inking the outer surface and rolling it out over a sheet of paper while exerting a diametrical force of 10 N on the test piece. This surface print is represented in Figure 4b. From the surface print a 1200 dpi digitized image is made and the number of non-white pixels to the total of pixels is counted. In this case 17% of all pictures showed colour i.e. the 17% of the surface of the elastomer jacket contacted the flat surface. Furthermore, the figure 4b shows a distinct; semi-regular pattern that reflects the yarn distribution embedded in the elastomer jacket.
In a second alternative embodiment - depicted in Figure 2a and 2b - a steel cord comprises a core strand of type 1+6 surrounded by 5 inner layer strands also of type 1+6. The outer layer comprises 7 strands of 19 filaments in Warrington configuration. Again the cord has a diameter of 5.1 mm.
In this embodiment 4 yarns 220, 220', 222, 222' are braided around the steel cord. Yarns 220, 220' are twisted in the Z direction, while yarns 222, 222' are twisted in the S direction. The yarns cross each other in a plain weave (one under, one over). Each yarn has a lay length of 10.2 mm but as there are four yarns, the axial distance between two consecutive yarns is only 2.55 mm. The yarns are poly phenylene sulphide (PPS) monofilament yarns of diameter 0.20 mm. The coverage ratio of the steel cord surface is 9.3%.
This intermediate product was again treated with the same adhesive and coated with Desmopan^®. The resulting elevator rope had a diameter of 5.65 mm resulting in an elastomer jacket thickness of 0.275 mm or 5.4% of the steel cord diameter. The ratio of yarn thickness to elastomer jacket thickness is thus 73%.
The resulting fingerprint of the surface of the elastomer jacket is shown in Figure 4a. The ratio of contact surface to circumferential surface of the elastomer jacket is 24%.
The steel cord 310 of the third embodiment 300 as represented in Figure 3a and 3b is made according: ${\{{[{(0.44 + 6 \times 0.37)}_{7 z} + 12 \times 0.34]}_{14 z} + 6 \times {[{(0.34 + 6 \times 0.31)}_{10 s} + 12 \times 0.29]}_{20 s}\}}_{50 Z}$
I.e. the core strands and the outer strands are multilayer strands wherein a core wire is surrounded by six outer wires with a first lay length that are on their turn surrounded by twelve outer wires wound with a second lay length. The filaments have tensile strengths between 2300 N/mm² and 2700 N/mm².
The steel cord 310 is surrounded by a cellulose based rayon fibre, twisted to a single yarn with a linear density of 248 tex. Three yarns 320, 322 and 324 are knitted around the steel cord 310, each of the yarn covering radial segments of about 120° each. The yarns show a lay-length 'L' that is equal to the axial contact distance between pairwise contacts of the yarns.
Again the steel cord with yarn coated with Desmopan^® of Bayer. The cord showed an uneven surface with a regular pattern (Figure 4c).

Claims

An elevator rope (100, 200, 300) comprising a steel cord (110, 210, 310) and an elastomer jacket (140, 240, 340) surrounding said steel cord, said elevator rope having a substantially circular cross section,
characterized in that
said elevator rope further comprises one or more yarns (120, 122; 220, 220', 222, 222'; 320, 322, 324), wrapped, braided or knitted around said steel cord, said one or more yarns being integral with said elastomer jacket wherein said yarn is made of synthetic material selected from the group consisting of glass fibres, poly-aramide fibres, poly(p-phenylene-2,6-benzobisoxazole) fibres, polyurethane fibres, carbon fibres, polyolefin fibres, polyamide fibres, polyester fibres, poly ethylene terephthalate fibres, polycarbonate fibres, polyacetal fibres, polysulfone fibres, poly phenylene sulphide, polyether ketone fibres , polyimide fibres, polyether imide fibres or mixtures thereof or

wherein said yarn is natural or semi-synthetic fibre selected from the group consisting of sisal, flax, cotton, hemp, silk, basalt, cellulose based fibres, rayon or mixtures thereof.
The elevator rope according to claim 1 wherein said one or more yarns wrapped, braided or knitted around said steel cord form a pattern on said steel cord that reaches through the polymer jacket to the surface of the elevator rope.
The elevator rope according to any one of claims 1 to 2 wherein said steel cord comprises steel strands twisted around one another with a cord lay length, said yarns being wrapped, braided or knitted around said steel cord with a lay length that is shorter than said cord lay length.
The elevator rope according to any one of claims 1 to 3 wherein at least two yarns are wrapped in opposite directions.
The elevator rope according to any one of claims 1 to 4 wherein said yarn has a width that is less than 30% of the diameter of said steel cord.
The elevator rope according to any one of claims 1 to 5 wherein said yarns cover less than 60% of the outer surface of said steel cord.
The elevator rope according to any one of claims 1 to 6 wherein the thickness of said yarns is less than 75% of the thickness of the elastomer jacket.
The elevator rope according to any one of claims 1 to 7 wherein said elastomer jacket is a thermoplastic elastomer selected from the group consisting of styrenic block copolymers, polyether-ester block copolymers, thermoplastic polyolefin elastomers, thermoplastic polyurethanes and polyether polyamide block copolymers.
The elevator rope according to claim 8 wherein said thermoplastic elastomer further comprises polymer particles with a molecular weight of at least 500 000 g/mol.
The elevator rope according to any one of claims 1 to 9 wherein said steel cord is treated with an adhesive to improve adhesion to said elastomer jacket, said adhesive being selected from the group consisting of organo functional silanes, organo functional titanates or organo functional zirconates.
The elevator rope according to any one of claims 1 to 10 wherein said yarn is provided with a sizing for enhancing adhesion with said polymer jacket.
The elevator rope according to any one of claims 1 to 11 wherein between 10% and 90% of the elastomer jacket surface is in contact with a flat surface when rolled out under a diametrical force of 10 N over a length of 100 mm.
A process to make the elevator rope according to any one of claims 1 to 12 comprising the steps of
- Providing a steel cord;

- Continuously wrapping or braiding or knitting one or more yarns around said steel cord thereby forming an intermediate product;

- Extruding said intermediate product with an elastomer jacket;
characterized in that
said one or more yarns are integrated into said elastomer jacket.