Drive sheave for elevator

Abstract

An elevator drive sheave for use with a coated steel cord includes a metal body and a divider. The metal body has a shallow circumferential groove having a groove depth. The grooves are separated from each other by a divider extending out of the metal body substantially greater than the depth of the grooves. The separator is made of or provided with a low friction cover layer. A coefficient of friction between the separator and the covering layer of the coated steel cord is much lower than a coefficient of friction between the metal body and the covering layer of the steel cord. The metal body may be assembled from discs each having a single groove. And the width of the groove is smaller than the diameter of the coated steel cord, so that the friction force of the coated steel cord can be further influenced. An elevator comprising a coated steel cord extending over a sheave is also claimed.

Description

Technical Field

[0001] The invention relates to a drive sheave for an elevator. The drive sheave transmits force and torque between a transmission system and a tension member. The drive sheave is suitable for elevator ropes coated with a polymer. Background Art

[0002] Since the turn of the century, elevator builders have been striving to eliminate the rooftop machine room above the elevator shaft. A key element in facilitating this has been the introduction of tension members consisting of high tensile strength fine-filament steel cords, replacing thick-wire, low tensile strength steel ropes. While in the old technology elevator ropes were 8mm or thicker, in the new technology the diameter of the steel cord is less than or equal to 5mm in the case of a single steel cord, or even less than 2mm when multiple steel cords are wrapped in parallel in the polymer sheath of the belt.

[0003] In the following, 'steel rope' refers to older technology steel wire assemblies with a total rope diameter greater than 8 mm, where the steel wires are thicker than 0.30 mm, with a load lower than 2000 N / mm 2 The term "steel cord" refers to a steel wire assembly made of thin wires thinner than 0.30 mm, with a tensile stress of more than 2000 N / mm 2 The tensile strength of a steel wire (expressed in Newtons per square millimeter) is the force required to break the wire (called the 'breaking load' (in Newtons)) divided by the metal surface area in a vertical section (in mm2). 2 count).

[0004] In fact, this high tensile strength filament allows the diameter of the tension member from which the car and counterweight are suspended to be reduced. This in turn allows the use of a smaller diameter drive sheave that moves the tension member. The smaller drive sheave can be driven by a direct drive motor, thereby eliminating the bulky gearbox that would be required if a larger sheave had to be used. All of this makes it possible to design a smaller drive system that can be installed at the top or bottom of the shaft. A machine room on top of the roof above the shaft is no longer required.

[0005] However, the use of high tensile steel filaments brings with it special problems that are not present in older technology steel ropes. When thinner filaments bend under load, they generate higher transverse stresses between the filaments, called Hertzian stresses, due to their smaller diameter. In addition to this, high tensile steel filaments are less ductile and break more easily under transverse forces.

[0006] This problem is usually solved by wrapping one or more steel cords in a polymer sheath or outer cover. In particular, thermoplastic polyurethane is preferred because it has good wear resistance and because it is a thermoplastic material, no heat treatment is required to cure it. In the following, a single steel cord wrapped in a polymer sheath is referred to as a 'coated steel cord'. Multiple steel cords arranged in parallel, kept together and wrapped in a polymer sheath, are referred to as 'coated elevator belts'. 'Tension member' refers to a 'coated steel cord' or a 'coated elevator belt'.

[0007] The introduction of polymer jackets brings additional difficulties, because the friction coefficient between polymer and drive sheave behaves differently than the friction coefficient of the known steel rope / cast steel drive sheave. Not only are the materials different (polymer vs. steel), but also the geometry is different: the contact surface is larger in the case of the coated elevator belt, and smaller in the case of the coated steel cord. In general, the friction between polymer and steel sheave is higher than in the known steel rope / steel sheave combinations.

[0008] Furthermore, the use of thin steel wires results in steel cords not being able to resist torque as well as conventional steel ropes, since steel cords have a much lower 'torsional stiffness' than steel ropes. Torsional stiffness is the product of the shear modulus G (a material constant in MPa) and the torsional constant 'J' which (for thin wires with a circular cross section of diameter 'd') is equal to πd 4 / 32, the second polar moment of a round filament. Therefore, the thin steel wires in a steel cord will resist a much smaller torque applied to them than a steel rope made of thick steel wire, even when multiple wires are combined. Therefore, a coated steel cord is easier to twist about its axis than a conventional steel rope. One rotation of the cord about its axis is called 'twist'. Torsion can be applied when a torque turns the steel cord, or it can be elastic torsion, that is, torsion that is released when the torque on the cord is removed. The applied or released torsion is usually calculated per unit length of cord.

[0009] The combination of the increased coefficient of friction between the polymer and the sheave surface and the much lower torsional stiffness of the coated steel cord results in increased torsion of the coated steel cord during use. In fact, when the coated steel cord entering the drive sheave is not in the plane of the drive sheave, the coated steel cord will roll in the sheave as the sheave turns due to the increased friction and reduced torsional stiffness between the sheave and the polymer jacket. The plane of the drive sheave is the plane perpendicular to the sheave axis and passing through the middle of the sheave. Unfortunately, few elevators are completely free of misalignment of tension members.

[0010] The repeated increase and decrease of torsion during each run causes the filaments in the steel cord to move relative to each other, which is a source of erosive wear of the filaments relative to each other. The erosive wear between the filaments leads to early failure of the coated steel cord due to 'torsion fatigue'.

[0011] Since the total load on the rope during acceleration is different when traveling upwards (the acceleration of the sheave is added to the acceleration of gravity) and when traveling downwards (the acceleration of the sheave is subtracted from the acceleration of gravity), there may be a tendency for torsions to increase, accumulate, or for torsions to decrease in the coated steel cord and be removed from the cord between the sheave and the anchor point of the coated steel cord. In general, when these induced torsions are in the 'closing' direction of the steel cord, the inventors have found that this is less harmful than when these torsions are in the 'opening' direction of the steel cord. The 'closing' direction of the steel cord is the direction that shortens the lay length of the outer strands in the steel cord. The 'opening' direction of the steel cord is the direction of rotation that increases the lay length of the outer strands in the steel cord.

[0012] Another complication is that the covered steel cords in elevators are used with smaller drive sheave diameters, sometimes even below the generally accepted D ≥ 40 × d, where ‘D’ is the minimum diameter of the drive sheave and ‘d’ is the diameter of the steel cord. This means that in one travel of the car, the covered steel cord hits the sides of the groove many more times than in prior art elevators using large diameter steel wire ropes. This, therefore, also exacerbates the torsion accumulation or torsion reduction problem.

[0013] To overcome this 'torsion fatigue' problem, US 2004 / 0256180 A1 suggests coating the sides of the grooves in which the coated cords run with a friction reducing coating having a lower coefficient of friction with the coated cords than with the bottom of the grooves.

[0014] However, it has proven to be very difficult to do this in a consistent and lasting manner. Therefore, the inventors have proposed the following solution which will be described in detail below. Summary of the invention

[0015] The main object of the present invention is to provide a drive sheave for an elevator which prevents torsional fatigue in the coated steel cords. Another object of the present invention is to provide an elevator arrangement which reduces the torsional fatigue problem.

[0016] According to a first aspect of the invention, there is provided a drive sheave for an elevator. The drive sheave is used to transmit the torque of the drive motor of the elevator to a linearly moving coated steel cord that lifts or lowers the car and counterweight. The drive sheave comprises a metal body. In the metal body, there is a circumferential groove for receiving the coated steel cord.

[0017] The groove has the shape of an arc of a circle or an arc of an ellipse, with its major axis parallel to the drive sheave axis. The groove has a bottom, a valley at the minimum radial distance and a circumferential ridge at the maximum radial distance. The depth of the groove ('groove depth') is the radial distance from the bottom of the groove to the ridge and is equal to the difference between the maximum radial distance and the minimum radial distance on the metal body. Note that the cross-section of the groove is always concave, never convex.

[0018] The drive sheave further comprises separators that circumferentially separate the grooves from each other. The separators are not part of the metal body. The separators protrude radially above the circumferential ridges of the grooves by a separator height. The separator height is greater than the groove depth. The number of separators is equal to the number of grooves or the number of grooves plus one.

[0019] The surface of the separator, at least the surface of the separator that can contact the covering layer of the wrapped steel cord, has a first friction coefficient between the separator surface and the covering layer of the wrapped steel cord. The groove in the metal body and the covering layer of the wrapped steel cord slide over each other with a second friction coefficient. The first friction coefficient is lower than the second friction coefficient. 'Friction coefficient' refers to the static friction coefficient, which is a dimensionless constant.

[0020] The invention eliminates the difficulties of applying the friction-reducing coverings of the prior art: the transition from the high-friction surface to the low-friction surface of the covering contacting the coated steel cord is clear and well-defined. There is no gradual transition in friction when the coated steel cord climbs up the sides of the groove. Furthermore, a larger difference between the second friction coefficient and the first friction coefficient on the separator is possible. By means of the invention, the torsion increase of the coated steel cord in a misaligned installation is reduced and can even be prevented.

[0021] Preferably, the separator height is greater than twice the groove depth, or even three times the groove depth, or greater. The separator height is defined by the diameter of the coated steel cord running therein. There is little benefit in making the separator height greater than twice the diameter of the coated steel cord.

[0022] The metal of the metal body is steel, cast iron or non-ferrous metals and alloys (e.g. copper, brass, bronze or other copper-containing alloys). For this purpose, for example, high tensile strength steel grades S690QL, S355JR, S960QL, Q355A, A514 grade F, A514 grade P, A517 grade F according to EN 10025-6 are preferred steels. Typically, the metal body is milled out of a steel cylinder. Alternatively, the metal body can be milled from a carbon steel cylinder, the steel grades being as follows: S235JR, Q235A, A283 grade C, A36, St37-2, A537 grade 70, Q345, SS400, SM400A (according to EN 10025). Stainless steels such as X5CrNi18.9, Werkstoffnummer 1.4301, X5CrNiMo18.10, Werkstoffnummer 1.4401, X2CrNiMo18.10, Werkstoffnummer 1.4404, 42CrMo4-V Werkstoffnummer 1.7225 may also be used. The surface of the groove may be treated by etching, sanding, polishing, laser texturing or similar operations to increase the coefficient of friction.

[0023] The groove width is defined as the axial distance between the facing edges of the circumferential ridges of the groove in the metal body. The separator spacing is the widest axial distance between the two facing surfaces of a pair of separators. Preferably, the ratio of the groove width to the separator width is between 0.4 and less than 1.0, preferably between 0.45 and 0.95, even more preferably between 0.50 and 0.95, for example between 0.55 and 0.90. This ratio allows fine-tuning the force transmitted from the drive sheave to the coated steel cord: if the ratio is low, less force can be transmitted, while when the ratio is 1.0, the transmitted force is maximum. This is also important in the case of an emergency stop for regulating the deceleration experienced by the passengers: due to too high a deceleration, the passengers may be injured during an emergency stop. If the deceleration is too low, the car may hit the bottom of the elevator shaft.

[0024] The shape of the groove is preferably an arc of an ellipse with a minor axis in the radial direction of the drive sheave and a major axis in the axial direction of the drive sheave. The ratio of the major axis to the minor axis is between 1 and 1.5. Obviously, a ratio of 1 corresponds to a circular groove. More preferably, the ratio of the major axis to the minor axis is between 1.05 and 1.1. Using an arc of an ellipse groove shape takes into account the flatness of the covering layer of the steel cord being coated. Since the covering layer is usually soft, it will yield and flatten.

[0025] The separator is an annular body mounted between the grooves. The annular body includes a first flank and a second flank facing the grooves. In a preferred embodiment, the annular body is made of metal, and the first flank and the second flank of the annular body are coated with a friction reducing coating. Alternatively, the first flank and the second flank of the annular body are subjected to a friction reducing treatment.

[0026] For example, the friction reducing coating is an amorphous carbon coating (diamond-like carbon coating, DLC), a polytetrafluoroethylene (PTFE, Teflon(R)) coating, an ethylene-tetrafluoroethylene copolymer (ETFE, Tefzel(R)) coating, or a ceramic coating.

[0027] In another preferred embodiment, the annular body is made of a polymer material, preferably a hard polymer material. The polymer may be one of the group consisting of polyamide (nylon), polyoxymethylene (POM), polytetrafluoroethylene (PTFE, Teflon(R)), ethylene-tetrafluoroethylene copolymer (ETFE, Tefzel(R)), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polyimide (PI), polyetherimide (PEM), polyetheretherketone (PEEK), ultra-high molecular weight polyethylene (UHMPE). It is generally considered that the use of polymers is cheaper than having to use a metal annular body, which must also be coated with an anti-friction covering layer.

[0028] In a preferred embodiment, the polymer contains a friction reducing agent or a slip additive selected from the group consisting of polyethylene glycol, natural or synthetic wax, silicone oil-based, erucamide-based, silicone compounds (such as polydimethylsiloxane), soaps (such as metal soaps), or fine silica (0.5 μm to 5 μm). This embodiment has the advantage of having a very low coefficient of friction when in contact with the covering layer of the coated steel cord.

[0029] A preferred way of realizing the metal body is to machine it from a metal cylinder. According to regulations, an elevator should have at least two tension members and the minimum number of grooves is two. Therefore, the drive sheave will include between two and ten grooves, depending on the load requirements of the elevator.

[0030] Typically, the diameter of such a drive sheave is between 70 mm and 210 mm, for example between 800 mm and 120 mm. A high tensile strength filament (greater than 2500 N / mm) made of a thin diameter (less than 0.30 mm) is used. 2) allows the diameter of the steel cord to be reduced to between 4 mm and 8 mm. As a rule of thumb, the sheave should be at least 40 times the cord diameter (40×d), which results in a drive sheave diameter of between 160 mm and 320 mm. However, for such coated steel cords, the 40×d rule no longer holds, and drive sheave diameters of typically between 80 mm and 130 mm are currently used. Such small diameter sheaves allow the use of direct drive motors, eliminating the need for a gearbox between the motor and the drive sheave.

[0031] Possibly, the surface of the groove is machined, polished, ground, sanded or shot peened to give it the desired roughness. Increasing the roughness will increase the friction coefficient between the metal body and the coated steel cord. The desired roughness Ra is between 0.1 and 2 micrometers, such as between 0.5 and 4 micrometers (μm), such as 0.5 to 2 μm, or 1 to 3 μm, or 2 to 4 μm.

[0032] In a preferred embodiment, the separator is held in the slot between the grooves. Possibly, the slot locks, holds, engages the separator to the metal body.

[0033] In a preferred embodiment, the metal body is constructed of individual pieces or disks assembled from individual pieces or disks in which a groove is machined. The separators are mounted between these individual grooved disks. End pieces are provided at either end of the drive sheave: one for connection to the shaft of the direct drive motor and one as an end cap to hold the nearest separator away from the motor.

[0034] In a further development of this embodiment, the individual grooved discs and the separator are held together by bolting, axial and circumferential interlocking, or a combination thereof. 'Axial and circumferential interlocking' means that the facing parts of the individual grooved discs have projections and recesses that fit axially with each other and prevent the grooved discs from being displaced circumferentially with each other. The parts are 'form fit' ('Formschlussig' in German). Possibly, the individual discs could be welded to each other, but this is less preferred because it no longer allows the discs to be separated without damaging them.

[0035] In another embodiment, the separator is rotatable relative to the single grooved disc, for example, by means of a friction bearing, possibly with the aid of a lubricant such as mineral oil, silicone oil, graphite, molybdenum sulfate or the like.

[0036] According to a second aspect of the invention, an elevator is claimed, more particularly a traction type elevator. Typically, an elevator comprises a car running on car tracks and a counterweight running on its own track. The counterweight and car are mechanically connected by two, three or more separate tension members. 'Mechanical connection' means that if the car moves, the counterweight also moves.

[0037] The counterweight and the track are connected in a 1 to 1, 2 to 1, 3 to 1 or 4 to 1 roping or wire winding by introducing a diverting pulley that bears the load but does not transfer the torque to the tension member. Only the drive sheave transfers the torque received from the drive motor (preferably a direct drive motor) to the tension member. In all cases, there is one drive sheave on which the tension member (e.g. a coated steel cord) runs in the groove of the drive sheave. The drive sheave is according to the previously described embodiments.

[0038] It is preferred that the coated steel rope has a circular cross section. That is, the steel cord is extruded together with the polymer sheath and the polymer sheath is substantially circular. The fine diameter and high tensile strength steel filaments in the steel cord in combination with the polymer sheath allow the diameter 'D' of the drive sheave to be reduced to below the generally accepted 40×d, where 'd' is the diameter of the steel cord without the covering layer, which diameter 'D' is taken at its minimum, i.e. at the bottom of the groove. The diameter 'd' of the steel cord is the diameter of the smallest circle surrounding the steel cord in a vertical section of the coated steel cord. The sheave diameter currently being tested by the applicant is 20×d. Therefore, drive sheave diameters below 25×d seem very possible.

[0039] In absolute terms, smaller drive sheave diameters 'D' allow for faster running motors which in turn allow for better control of the acceleration and deceleration of the elevator car. This improves the passenger experience in the elevator. However, this also exacerbates the problem of increased or eliminated twisting of the coated steel cords: as the diameter of the sheave decreases, the number of times the coated steel cords hit the sides of the grooves increases. The number of such sidewall contacts is much greater compared to prior art steel wire ropes because:

[0040] First, the outer diameter of the drive sheave and the covered steel cord is reduced, and

[0041] Second, apply a lower D / d ratio to further reduce the sheave diameter, while

[0042] The distance travelled by the car is not reduced accordingly.

[0043] By the present invention, the problem of torsion increase or elimination is greatly reduced as the low friction separator surface prevents the introduction of torque into the coated steel cords.

[0044] By varying the groove width of the grooves in the metal body and / or adjusting the roughness of the metal body in the grooves, the absolute friction between the coated steel cord and the drive sheave can be fine-tuned so that the friction does not become too high and cause a risk of the car lifting without movement of the counterweight, or so that the friction does not become too low and cause the car not to lift. Likewise, in the event of a downward emergency stop, the coated steel cord should not stick, as this would result in a large deceleration that would be uncomfortable for the passengers. A ratio of the groove width to the coated steel cord diameter 'd0' between 0.4 and 1.0 is preferred. 'd0' is the diameter of the coated steel cord comprising the polymer cover. Even better, the groove width is less than d0, i.e. the ratio is less than 1.0, for example less than 0.95 or even 0.90.

[0045] Additionally or alternatively, the radius of the groove at the bottom of the groove may be chosen to be slightly larger than the semi-diameter of the coated steel cord, for example, the radius of the groove may be 1 to 1.5 times the semi-diameter (i.e. radius) of the coated steel cord. 'At the bottom of the groove' means that the radius of curvature is determined locally in the groove at the location where the coated steel cord contacts the drive sheave. More preferably, the radius of the groove is between 1.05 and 1.1 times the radius of the coated steel cord. Most preferably, the radius of the groove is between 1.06 and 1.1.

[0046] When the covered elevator rope is pulled during use, the radius of curvature at the bottom of the groove, which is higher than the semi-diameter of the covered elevator cord, accommodates the flattening of the covering layer (polymer jacket). However, when the radius of curvature of the groove becomes too large compared to the semi-diameter of the covered steel cord, the covered steel cord starts to drift to the left or right in the groove, which is undesirable. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A known drive sheave for a coated elevator rope is shown.

[0048] Figure 2 A first embodiment of the invention is shown and the various geometric parameters involved are shown.

[0049] Figure 3 A second embodiment of the present invention is shown.

[0050] Figure 4 A third embodiment of the present invention is shown.

[0051] Figure 5 A schematic diagram of an elevator is shown, showing the drive sheave.

[0052] In the reference numerals, the ones and tens digits designate equivalent components in the drawings, and the hundreds digit indicates the number of the drawing. DETAILED DESCRIPTION

[0053] Figure 1 A drive sheave 100 as known in the art is shown. The drive sheave is used with coated steel cords in elevators. The drive sheave is made of one metal piece 110 of hot rolled 42CrMo4-V1.7225 steel. The three grooves 102, 102', 102" have a radius of curvature of 3.5 mm at the bottom of the grooves. The total depth of the grooves from the top of the ridge is 5.5 mm. The spacing of the grooves is 9.5 mm. The grooves are polished to a roughness 'Ra' of 1.6 μm. The narrow slot 104 is used to lock the drive sheave to the axis of the drive motor. The hole 106 is used to receive a bolt to ensure correct attachment to the drive motor.

[0054] Figure 2 A first embodiment of the invention is shown. Here, the driving sheave also comprises a metal body 210 in which different grooves 202, 202', 202", . . . are provided. However, the groove depth 'δ' is relatively shallow compared to the grooves of the prior art. The groove depth is from the radial bottom of the groove to the circumferential ridge of the groove in the metal body. The radius of curvature R of the groove bottom is 1 It is approximately 1.05 times the semi-diameter "d0" of the coated steel cord. The drive sheave 200 is characterized in that the grooves 202, 202', 202", 202"',.. are also provided with separators 212, 212', 212",.. between adjacent grooves. The separators 212, 212', 212",.. protrude from the metal body, wherein the separator height from the top of the metal body ridge is 'Δ'. In addition, the separator height 'Δ' is 5 times the groove depth 'δ'. In addition, the groove width represented by 'w' is smaller than the separator width represented by 'W'. An end cap 216 is provided to support the end separator. The drive sheave diameter is represented by 'D'.

[0055] In this embodiment, the separators are made of polyamide, nylon 6 / 6. Nylon 6 / 6 itself already has a very low coefficient of friction for many materials. The coefficient of friction can be further reduced by introducing a slip additive. The separators 212, 212', 212", .. are held in circumferential slots 214 machined into the metal body 210. The separators are made by subtractive manufacturing:

[0056] First, a metal body is prepared according to given appropriate dimensions. A slot 214 is also machined into the metal body. The slot 214 has a dovetail-shaped cross section.

[0057] In a cylindrical container, the metal body is coaxially mounted and fixed to the cylindrical container. The container has a diameter twice the height of the divider.

[0058] A vacuum is drawn from the space between the container and the metal body.

[0059] The molten nylon 6 / 6 is drawn and pressed into a vacuum chamber to solidify the nylon.

[0060] The cylindrical container is opened and the intermediate elevator casing is further allowed to cool and harden.

[0061] The nylon sleeve is machined so that only the divider remains: the remaining material is chiseled away.

[0062] At the end away from the drive motor, the drive sheave is provided with an end cap 216 which is held by screws (not shown) to the nearest separator. In this way, the separator is well held between the grooves by the circumferential slot 214 through a dovetail connection.

[0063] exist Figure 3 In the second embodiment shown, the metal body of the drive sheave 300 is composed of a series of individual grooved disks 311, 311', 311", 311'", each having a groove. The individual grooved disks 311, 311', 311", 311' have a protruding square portion 320 inserted into a recess having the same shape and depth. By bolts 322, the individual grooved disks are securely bolted to end blocks 324, which are connected to the motor sheave (not shown). Spacers 312, 312', 312", 312'" are installed between the individual grooved disks. These are bronze disks covered with a diamond-like coating, such as CeraTough applied by IBC coating technology. TM This diamond-like coating is strong and exhibits a very low coefficient of friction. The end cap 326 ensures that the nearest divider is well retained on the nearest single grooved disc 311"'. The drive sheave diameter 'D' is shown.

[0064] exist Figure 4 In the third embodiment 400 shown, the ratio between the groove width 'w' and the separator spacing 'W' is greatly reduced. The coated steel cord 430 contacts the single grooved disc 411 only over a narrow area. Most of the coated elevator cord is in contact with the separator discs 412, 412'. As a result, the friction between the coated steel cord and the drive sheave is reduced. In this case, these separator discs 412, 412' are machined annular bodies made of steel coated with a Teflon (R) covering. It must be noted that the transition from the separator to the single grooved disc is very smooth and there are no edges that could damage the covering.

[0065] Figure 5An elevator 550 is depicted with a car 552 running on car tracks 554. The weight of the car is balanced by a counterweight 556 running on counterweight tracks 558. The car 552 is mechanically connected to the counterweight 556 by three coated steel cords 560 running in parallel. The coated steel cords 560 have a substantially circular cross-section. One end of the coated steel cord 560 is connected to the ceiling of the elevator shaft above the counterweight 556 by a clamp 568', extends down the shaft toward the diverting pulley 566" on the counterweight 556, and continues upward to the drive sheave 500. The drive sheave 500 is driven by a motor 562. Continuing after the drive sheave, the coated steel cord is guided through the diverting pulleys 566', 566 under the car 552, and finally the coated steel cord is connected to the top of the shaft by a clamp 568. This type of tension member path is generally called 2-to-1 winding. As described above, the elevator is driven by the drive sheave 500.

[0066] In a particular embodiment, the groove radius measured locally at the bottom of the groove is 1.5 times the half diameter of the coated steel cord. The half diameter or radius is half the diameter of the coated steel cord, ie d0 / 2.

[0067] Due to the reduced diameter of the drive sheave 500, the motor 562 can be kept smaller, thereby allowing the car 552 to rise to the top 564 of the shaft. No machine room is required.

Claims

1. A drive sheave for an elevator having a coated steel cord, the drive sheave comprising a metal body comprising grooves for receiving the coated steel cord of the elevator, the groove depth of the groove being the radial distance from the bottom of the groove to the circumferential ridge of the groove, the drive sheave further comprising a divider circumferentially dividing the grooves, wherein The separator protrudes above the circumferential ridge of the groove by a separator height, the separator height being equal to or greater than the groove depth, having a first friction coefficient between the surface of the separator and the coated steel cord, and having a second friction coefficient between the surface of the groove and the coated steel cord, the first friction coefficient being lower than the second friction coefficient.

2. The drive sheave according to claim 1, wherein: The groove width is the axial distance between the facing edges of the circumferential ridges of the groove in the metal body, and the separator spacing is the widest axial distance between two facing surfaces of a pair of separators, and wherein the ratio of the groove width to the separator spacing is between 0.40 and less than 1.

0.

3. The drive sheave according to claim 1 or 2, wherein: The separator is an annular body including a first wing and a second wing.

4. The drive sheave according to claim 3, wherein: The annular body is made of metal, and the first flank and / or the second flank of the annular body is coated with a friction-reducing coating layer or has been subjected to a friction-reducing treatment.

5. The drive sheave according to claim 4, wherein: The friction reducing coating is one of the group consisting of an amorphous carbon (DLC) coating, a polytetrafluoroethylene (PTFE, Teflon(R)) coating, an ethylene-tetrafluoroethylene copolymer (ETFE, Tefzel(R)) coating, and a ceramic coating.

6. The drive sheave according to claim 3, wherein: The annular body is made of a polymer, which is one of the group consisting of polyamide (nylon), polytetrafluoroethylene (PTFE, Teflon(R)), ethylene-tetrafluoroethylene copolymer (ETFE, Tefzel(R)), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polyimide (PI), polyetherimide (PEM), polyetheretherketone (PEEK), and ultra-high molecular weight polyethylene (UHMPE).

7. The drive sheave according to claim 6, wherein: The polymer has added thereto a friction reducing agent selected from the group consisting of polyethylene glycol, natural or synthetic waxes, silicone compounds such as polydimethylsiloxane, soaps such as metal soaps.

8. The drive sheave according to any one of claims 1 to 7, wherein: The metal body is made of steel, cast iron or non-ferrous metals and alloys, such as copper, brass, bronze or other copper-containing alloys.

9. The drive sheave according to any one of claims 1 to 8, wherein: The divider is retained in the slot between the grooves.

10. The drive sheave according to any one of claims 1 to 9, wherein: The metal body is composed of separate individual disc-shaped members with grooves, and the separator is installed between the separate individual disc-shaped members with grooves.

11. The drive sheave according to claim 10, wherein: The single grooved disk and the separator are held together by bolting, welding, axial and circumferential interlocking, or a combination thereof.

12. The drive sheave according to claim 10 or 11, wherein: The divider is rotatable relative to the single grooved disk.

13. An elevator comprising a car running on a car track, a counterweight running on a counterweight track, the car being connected to the counterweight by two or more coated steel cords driven by a drive motor, the coated steel cords having a substantially circular cross-section, wherein: The coated steel cord is in contact with a driving sheave according to any one of claims 1 to 12 for driving the coated steel cord.

14. The elevator according to claim 13, wherein: The coated steel cord has a semi-diameter, and the circular groove has a groove radius at the bottom of the groove, and the groove radius is between 1 and 1.5 times the semi-diameter of the coated steel cord.

15. The elevator according to claim 13 or 14, wherein: The coated steel cord has a diameter including the polymer cover, and wherein a ratio of a groove width to the diameter of the coated steel cord is between 0.4 and 1.0.

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