EP3326956A1

EP3326956A1 - Locally magnetic pulley for an elevator and elevator with such pulley

Info

Publication number: EP3326956A1
Application number: EP16200569.8A
Authority: EP
Inventors: Ajay NARENDAR; Rohit RAJ
Original assignee: Inventio AG
Current assignee: Inventio AG
Priority date: 2016-11-24
Filing date: 2016-11-24
Publication date: 2018-05-30

Abstract

A pulley (15) for cooperating with a suspension traction member (7) in an elevator (1) is proposed. Therein, the pulley (15) comprises a magnetic field generator (35) for generating a magnetic field such as to induce attractive forces upon a magnetisable portion of the suspension traction member (7) in a direction (27) orthogonal and/or towards a middle line (29) along a circumferential surface (21) of the pulley (15). Due to the forces induced by the generated magnetic field, the suspension traction member (7), typically including cords comprising a magnetisable material such as steel, is attracted towards the circumferential surface (21) of the pulley (15), particularly towards the middle line (29) such as to be centred and aligned with the circumferential surface (21) of the pulley (15). Furthermore, in case the circumferential surface (21) of the pulley (15) and a traction surface of the suspension traction member (7) are profiled with complementary profiles, the induced magnetic forces avoid any detachment of the suspension traction member (7) from the pulley (15), and therefore avoid any disengagement of the profiles, even in cases of temporarily slacking of the suspension traction member (7). Accordingly, any jumping or even jumping-off of the suspension traction member (7) may be avoided.

Description

The present invention relates to the technical field of elevators. Particularly, the present invention relates to a pulley which may cooperate with a suspension traction member in an elevator.
In elevators, an elevator car may typically be displaced within an elevator shaft. Therein, the elevator car is typically suspended by one or typically more suspension traction members such as for example belts or ropes. On the one hand, such suspension traction members shall carry the load of the elevator car and, in most cases, a counterweight also being attached to the suspension traction member. On the other hand, the suspension traction member may be displaced using a drive engine rotating a traction sheave thereby displacing the elevator car within the elevator shaft.
Typically, the elevator car is suspended to the suspension traction member via one or more pulleys. Similarly, the counterweight may be held by the suspension traction members via one or more pulleys attached thereto in a rotatable manner.
Generally, a pulley is a rotatable component with a circumferential surface around which the suspension traction member may be wound. In most cases, the pulley has a substantially cylindrical shape. An axial length of the pulley is at least same or longer than a width of for example the one or more belts forming the suspension traction member. Accordingly, the belt may contact the circumferential surface of the pulley with one of its major surfaces (also being referred to as traction surface) and may run along the circumferential surface of the pulley upon being displaced in its longitudinal direction.
In contrast to the traction sheave which is to be actively driven into rotation by for example an electromotor of the drive engine, pulleys are generally not driven themselves but passively rotate only upon the suspension traction member which cooperates with them is displaced along its longitudinal direction.
While the suspension traction member should be capable of running along the circumferential surface of the pulley in its circumferential direction, substantial motion of the suspension traction member in an axial direction of the pulley (i.e. orthogonal to the circumferential direction) should generally be prevented. Otherwise, such axial motion of the suspension traction member would result in an inhomogeneous load distribution throughout the suspension traction member or, in worst cases, the suspension traction member may even jump-off the pulley.
Accordingly, means are generally provided for avoiding excessive axial motion of the suspension traction member with respect to the pulley. For example, the pulley may have flanges or other portions with an extended diameter at or close to its opposite axial ends. Accordingly, the suspension traction member may be guided between these flanges but normally should not be able to jump over these flanges.
However, providing a pulley with lateral flanges requires additional efforts in manufacturing the pulley.
Furthermore, it has been observed that particularly as the pulleys typically attached to the elevator car or the counterweight, situations may occur in which flanges may not reliably prevent a jumping-off of the suspension traction member. For example, upon rapidly accelerating or decelerating a motion of the suspension traction member, situations may occur in which the suspension traction member temporarily becomes loose or slacking. Such loose or slacking suspension traction member may temporarily detach from the circumferential surface of the pulley in a radial direction. Accordingly, the loose or slacking suspension traction member may jump over an edge of one of the flanges and eventually may even jump-off the entire pulley.
Furthermore, the provision of lateral flanges at opposite axial ends of the circumferential surface of a pulley may require that the suspension traction member is very precisely aligned with the pulley. Otherwise, upon continued longitudinal motion of the suspension traction member, for example side portions of the suspension traction member may permanently contact an adjacent side wall of a flange or may even attempt to overlap the flange, thereby provoking excessive wear or even damages to the suspension traction member. Typically, an alignment within tolerances of less than a few degrees in orientation and/or less than a few millimetres in position has to be fulfilled in order to avoid any negative interference between the suspension traction member and the lateral flanges.
Accordingly, there may be a need for a pulley in an elevator at least partially overcoming some of the above-mentioned deficiencies of conventional pulleys. Particularly, there may be a need for a pulley for cooperating with a suspension traction member in an elevator which pulley may be manufactured easily and/or at low costs, may reliable prevent excessive displacements of the suspension traction member with respect to the pulley or even jumping-off of the suspension traction member from the pulley and/or which allows for relaxed alignment tolerances between the suspension traction member and the pulley. Furthermore, there may be a need for an elevator comprising such pulley.
Such needs may be met with the subject-matter of the independent claims. Advantageous embodiments are defined in the dependent claims and the following specification.
According to a first aspect of the present invention, a pulley for cooperating with a suspension traction member in an elevator is proposed, wherein the pulley comprises a magnetic field generator for generating a magnetic field such as to induce attractive forces upon a magnetisable portion of the suspension traction member in a direction towards a circumferential surface of the pulley.
According to a second aspect of the invention, an elevator assembly is proposed to comprise an elevator car being displaceable within an elevator shaft, a suspension traction member suspending the elevator car and a pulley cooperating with the suspension traction member, wherein the pulley is embodied in accordance with the above first aspect of the invention.
Ideas underlying embodiments of the present invention may be interpreted as being based, inter alia, on the following observations and recognitions.
As indicated in the introductory portion, excessive axial motion of the suspension traction member along the circumferential surface of the pulley should be reliably prevented. Based on the observations that the conventional provision of lateral flanges at opposing edges of the pulley's circumferential surface may result in disadvantages as indicated in the introductory portion, it is proposed to support an alignment between the pulley and the suspension traction member using alternative means. Particularly, it is proposed to provide the pulley with a specific magnetic field generator which may be one or more permanent magnets or electromagnets and which is specifically configured for generating a specific magnetic field. Therein, the magnetic field should be adapted with respect to its field strength as well as with respect to its direction or orientation such as to induce attractive forces upon a magnetisable portion of the suspension traction member. These attractive forces should be directed towards the circumferential surface of the pulley.
The magnetic field generator may be configured for generating the magnetic field such as to induce attractive forces upon the magnetisable portion of the suspension traction member in a direction orthogonal to the circumferential surface of the pulley. Accordingly, the suspension traction member is attracted orthogonally towards the circumferential surface of the pulley thereby avoiding that it may detach from the pulley e.g. upon the suspension traction member becoming temporarily loose or slacking.
Alternatively or preferably additionally, the magnetic field generator may be configured for generating the magnetic field such as to induce attractive forces upon the magnetisable portion of the suspension traction member in a direction towards a middle line along the circumferential surface of the pulley. Such attractive forces may draw the suspension traction member in a direction parallel to the circumferential surface of the pulley towards the middle line of this circumferential surface.
In other words, the forces induced by the interaction of the magnetic field with the magnetisable portion of the suspension traction member should attract the suspension traction member orthogonally towards the circumferential surface and/or towards a middle portion of the circumferential surface of the pulley. Such middle portion or middle line is to be located somewhere between the opposing axial edges of the circumferential surface of the pulley and should be sufficiently spaced from these edges in an axial direction towards the centre of the circumferential surface of the pulley.
Due to the forces induced by the magnetic field generator, the suspension traction member is continuously or repeatedly attracted towards the circumferential surface and/or towards the middle line along the circumferential surface of the pulley and is therefore prevented from moving in an axial direction towards or even over the axial edges of the circumferential surface. Accordingly, the attractive forces due to the generated magnetic field help aligning the suspension traction member with respect to the circumferential surface of the pulley.
According to an embodiment, at least portions of the circumferential surface of the pulley are profiled with grooves extending in the circumferential direction.
In other words, the circumferential surface of the pulley may not be even but preferably parallel grooves and intermediate ridges may extend along the circumferential direction of this surface of the pulley. The grooves may have e.g. a V-shape or U-shape. Such profile may support guidance and/or alignment of the suspension traction member with respect to the pulley's circumferential surface. This is particularly true in case also the suspension traction member comprises a profiled traction surface which preferably mates with the profile of the pulley, i.e. the profile of the pulley and the profile of the suspension traction member are substantially complementary to each other.
However, it has been observed that, while such profiles may in most cases support guidance and/or alignment of the suspension traction member with the pulley, in some cases where the suspension traction member is slacking and not sufficiently pressed against the surface of the pulley, ridges of the profile of the suspension traction member may jump out of adjacent grooves of the pulley and, upon the suspension traction member being tensioned again, may be pressed into a neighbouring groove of the pulley. Accordingly, a lateral displacement of the suspension traction member with respect to the pulley may even be increased when traction surfaces of the pulley and the suspension traction member are profiled.
Therefore, specifically for pulleys with a profiled circumferential surface, the proposed generation of a magnetic field may be beneficial as on the one hand, it helps avoiding any detachment of the suspension traction member from the circumferential surface of the pulley even in cases of temporary slack and, on the other hand, it supports suitable alignment between the suspension traction member and the pulley.
Particularly, the magnetic field generated by the magnetic field generator generally attracts the suspension traction member not only in a direction towards the middle line along the circumferential surface of the pulley but also attracts the suspension traction member in a direction towards a hub of the pulley, i.e. in a direction orthogonal to the circumferential surface of the pulley. Accordingly, the attracted suspension traction member may no more easily detach from the pulley and jump with its profile out of the complementary profile of the pulley, even upon the suspension traction becoming temporarily slacking.
According to an embodiment, the magnetic field generator comprises at least four partial magnetic field generators. These partial magnetic field generators may be arranged at different positions on the pulley. Therein, these different positions should be offset to each other by at most 90°.
In other words, the pulley's magnetic field generator may be comprised of four or more separate units referred to herein as partial magnetic field generators. Each of the partial magnetic field generators may generate its own magnetic field. The partial magnetic field generators should be arranged at different positions spaced from each other such that a position of one partial magnetic field generator is offset from the position of a closest neighbouring other partial magnetic field generator by 90° or less (with respect to the 360° circumferential surface of the pulley).
While each partial magnetic field generator generates a magnetic field the extension of which is (in theory) infinite, the generated magnetic field may be locally restricted such that substantial forces onto the suspension traction member are only induced in close neighbourhood to the partial magnetic field generator. However, although each single partial magnetic field generator may attract the suspension traction member only in its close neighbourhood, the fact that the pulley comprises at least four partial magnetic field generators offset from each other by at most 90°, i.e. at least one partial magnetic field generator being present in each of the quarters of the circumferential surface of the pulley, results in the suspension traction member being sufficiently attracted towards the middle line along the circumferential surface of the pulley in each of the quarters of this circumferential surface.
Accordingly, even in cases where the suspension traction member is wound around the circumferential surface of the pulley only along a 90° portion, i.e. along a quarter, of this circumferential surface, it will still be sufficiently attracted towards the middle line along the circumferential surface of the pulley and will therefore be sufficiently aligned with the pulley.
According to an embodiment, the magnetic field generator comprises one or more electromagnets.
An electromagnet is a device which, upon being energized with electricity, generates a magnetic field while, without being energized, remaining substantially non-magnetic. Such electromagnet may be established for example using an electric coil.
An electromagnet may be relatively easily included into a pulley. Accordingly, a pulley in which an electromagnet serves as a magnetic field generator may be easily manufactured. For example, an electromagnet may be included in a chamber or cavity underneath the circumferential surface of the pulley. The strength of the magnetic field generated by the electromagnet may be easily regulated by regulating the electricity supplied to the electromagnet. Accordingly, a magnitude of the attractive forces induced by the magnetic field may be regulated and may for example be adjusted to temporarily varying requirements.
It may be noted that the magnetic field generator may alternatively or additionally comprise permanent magnets.
According to a specific embodiment, the pulley further comprises a slip ring. Therein, the electromagnet comprised in the magnetic field generator is adapted to be energized via the slip ring. Therein, the slip ring may be configured such that such energizing is accomplished in a way such that the electromagnet generates the magnet field depending on a current rotation position of the pulley and that the magnetic field is generated only in a partial area along the circumferential surface of the pulley.
In other words, using the slip ring upon energizing the electromagnet, the electromagnet may not be energized steadily, i.e. may not generate a temporarily static magnetic field. To the contrary, using the slip ring, energy supply to the electromagnet may be temporarily varied, i.e. for example switched on and switched off, depending on the current rotation position of the pulley.
For example, the slip ring may be adapted such that the electromagnet is only energized when it is at a position at which adjacent portions of the circumferential surface of the pulley come into contact with the suspension traction member, whereas, when the pulley is for example turned into a position where this electromagnet is relatively far away from any portion of the pulley's surface contacting the suspension traction member, it may be de-energized. In other words, the electromagnet is only energized when it comes close to the suspension traction member such as to support aligning of the suspension traction member on the circumferential surface of the pulley whereas it remains de-energized as long as it may not support any such alignment.
This may not only save energy but also may avoid generating magnetic fields where they do not support any alignment of the suspension traction member.
It may be noted that, while the provision of a slip ring offers a technically simple manner of implementing the described orientation-depending variation of the generation of the magnetic field, other technical implementations are also possible. For example, a rotation position of the pulley may be monitored using e.g. sensors and an electricity supply to the electromagnets may be controlled based on signals from such sensors.
According to an embodiment, the magnetic field generator is arranged at the middle line along the circumferential surface of the pulley.
In other words, not only the magnetic field generated by the magnetic field generator should attract the magnetisable portion of the suspension traction member towards the middle line but the magnetic field generator itself may be arranged at such middle line along the circumferential surface of the pulley. Such positional arrangement of the magnetic field generator may simplify generating and orienting the desired magnetic field.
It may be noted that the term "middle line along the circumferential surface of the pulley" may be interpreted in a broad sense as a line extending along the circumference of the pulley with a substantial axial distance to each of the axial edges of the circumferential surface of the pulley. In other words, the middle line should run along the circumference of the pulley in an area which is at least closer to an axial geometric centre of the circumferential surface than to one of the axial edges of this circumferential surface of the pulley.
Specifically, according to an embodiment, the middle line may be arranged at an axial geometric centre of the circumferential surface of the pulley.
In other words, it may be beneficial that the mentioned middle line is not only somewhere close to the axial geometric centre but is arranged at this axial geometric centre of the circumferential surface of the pulley. In such case, the magnetic field generator induces attractive forces which attract the suspension traction member always in a direction towards this axial geometric centre. Thereby, an undesired misalignment of the suspension traction member may be effectively avoided.
Specifically in case that the pulley is profiled at its circumferential surface, according to an embodiment, the magnetic field generator may be arranged at a ridge between two of the grooves of the profile extending along the axial geometric centre of the circumferential surface of the pulley.
In other words, in case the circumferential surface of the pulley is profiled with grooves, it has been found to be beneficial to position the magnetic field generator at or along a ridge formed by two neighbouring grooves, this ridge extending along the geometrical centre of the circumferential surface of the pulley. At such position, the magnetic field induced by the magnetic field generator may beneficially induce attractive forces onto the suspension traction member thereby suitably aligning and pulling the suspension traction member towards this central ridge.
According to an embodiment, a radius of the pulley at axial edges of the pulley may be same or even smaller than in-between the axial edges of the pulley.
In other words, while conventional pulleys typically have flanges at their axial edges, these flanges being areas with an increased radius, embodiments of the pulley described herein may not need such flanges or the flanges may be at least less pronounced due to the attracting and aligning function of the generated magnetic field. Accordingly, the pulley may have a substantially constant radius throughout its entire axial length (ignoring any minor radius deviations due to a superficial profile at the circumferential surface). Lacking or reducing the need for any lateral flanges, the pulley may be manufactured with less efforts and/or may have a reduced axial length.
In the elevator proposed herein, the pulley may be attached to the elevator car. In other words, the pulley described herein may be a pulley which serves for suspending the elevator car and is therefore rotatably attached at some location to the elevator car. For example, the pulleys may be attached to a lower part or bottom at opposite sides of the elevator car such that the suspension traction member may suspend the elevator car by being wound in 90°-windings around each of both opposing pulleys, thereby supporting the elevator car from underneath. Alternatively, the pulley may be attached to a top or ceiling of the elevator car and the suspension traction member may be wound around the pulley thereby holding the elevator car from above.
Additionally or alternatively, a pulley may be attached to the counterweight of the elevator assembly.
According to an embodiment of the elevator, the suspension traction member suspending the elevator car is a belt.
In other words, the suspension traction member is an elongate member having a cross-section with a width dimensioned being substantially larger than a height dimension. While such elongate belts are commonly applied in modern elevators and may provide for various benefits, aligning such belts with respect to the circumferential surface of a pulley may be more challenging than in case of conventional suspension traction members comprising ropes. Especially for belt-type suspension traction members, the additional alignment functionality of the pulley proposed herein may help increasing safety during operation of the elevator and/or reducing wear of components of the elevator such as the suspension traction member and/or the pulley.
Particularly ,according to an embodiment, the suspension traction member comprises at least one magnetisable cord extending along the length of the suspension traction member.
Typically, suspension traction members comprise cords for providing a necessary load-carrying capacity. While, in principle, these cords may be made from various materials, these cords are typically made from a ferromagnetic material such as steel or other iron-including alloys. Accordingly, these cords may be magnetized upon being brought into an external magnetic field and may therefore be attracted by such magnetic field. Typically, the cords are included in a non-magnetic matrix material such as a polymer protecting the cords and/or providing for sufficient traction upon interaction with e.g. the traction sheave of the elevator.
In principle, it may be sufficient that the suspension traction member comprises only a single magnetisable cord which can then be attracted by the magnetic field generated by the magnetic field generator of the pulley. Such single magnetisable cord should preferably be arranged along a middle line or, more preferably, along a geometric centre line extending along the suspension traction member. However, in many cases, the suspension traction member may have multiple cords all of which being made with a magnetisable material.
According to an embodiment, the suspension traction member has a profiled traction surface with grooves extending along a longitudinal direction of the suspension traction member.
As already indicated above, the alignment-supporting functionality of the pulley proposed herein may be particularly beneficial in case of a profiled suspension traction member.
In accordance to a final embodiment, the suspension traction member may be wound around the circumferential surface of the pulley along at least 90° of the circumference.
In other words, for cooperation between the suspension traction member and the pulley, the suspension traction member may mechanically contact the circumferential surface of the pulley along at least one quarter of the entire circumferential surface.
For example, it is a commonly applied configuration in elevators that the suspension traction member supports the elevator car via two pulleys arranged at opposite sides at a bottom of the elevator car and the suspension traction member is wound around 90° of the circumference of each of these two pulleys. As indicated further above, in such case it may be beneficial to provide the pulley with at least one partial magnetic field generator in each of such 90°-portion of the circumferential surface.
It shall be noted that possible features and advantages of embodiments of the invention are described herein partly with respect to a pulley and partly with respect to an elevator assembly comprising such pulley. One skilled in the art will recognize that the features may be suitably transferred from one embodiment to another and features may be modified, adapted, combined and/or replaced, etc. in order to come to further embodiments of the invention.
In the following, advantageous embodiments of the invention will be described with reference to the enclosed drawings. However, neither the drawings nor the description shall be interpreted as limiting the invention.

Fig. 1 shows an elevator comprising pulleys.
Fig. 2 shows a perspective view onto a pulley according to an embodiment of the present invention.
Fig. 3 shows a cross section through a pulley according to an embodiment of the present invention.
Fig. 4 shows a longitudinal section through a pulley according to an embodiment of the present invention.

The figures are only schematic representations and not to scale. Same reference signs refer to same or similar features.
Fig. 1 shows basic components of an elevator 1. The elevator 1 comprises a car 3 and a counterweight 5. The car 3 and the counterweight 5 are both held by a suspension traction member 7 typically being formed by a multiplicity of elongate belts. Each belt comprises several load bearing cords or wires made of steel or another iron-containing alloy and being enclosed in a polyurethane cover or sheath. The suspension traction member 7 may be driven by a drive engine 9 in which an electric motor may rotate a traction sheave 11. The suspension traction member 7 holds the car 3 and the counterweight 5 via pulleys 13, 15, respectively. The pulleys 13, 15 may be fixed in a rotatable manner for example to a top and/or to a bottom of the car 3 and/or counterweight 5, respectively (for ease of reference, in the following, only reference numeral 15 will be mentioned with respect to the pulleys).
In a configuration of an elevator 1 in which the traction sheave 11 shall displace the suspension traction member 7, i.e. the traction sheave 11 is actively driven into rotation and then shall displace the suspension traction member 7 via friction between a contact surface of the traction sheave 11 and a contact surface of the suspension traction member 7, the contact surface of the traction sheave 11 should be optimized in order to obtain a sufficiently high friction. Typically, at the traction sheave, the suspension traction member 7 is always sufficiently loaded or tensioned such as to permanently stay in contact with the traction surface of the traction sheave 11.
In contrast hereto, the pulleys 15 are not actively driven, i.e. have no own driving means, but are only passively driven by the moving suspension traction member 7. Accordingly, no high friction between contact surface of the pulleys 15 and the contact surface of the suspension traction member 7 is required. Furthermore, in certain conditions such as upon abruptly decelerating the suspension traction member 7, the suspension traction member 7 may get loose or slacking and may temporarily detach from the surface of the pulley.
Fig. 2 shows a perspective view onto an exemplary pulley 15 according to an embodiment of the present invention being one of the pulleys 15 shown in Fig. 1. The pulley 15 has a generally cylindrical geometry. The pulley 15 comprises a base body 17 made e.g. from steel. Such base body 17 comprises an inner central opening 19. A bearing such as for example a ball-bearing may be arranged within this central opening 19. Accordingly, the pulley 15 may be attached to for example the car 3 via the bearing in a rotatable manner. Furthermore, the base body 17 comprises a surface profile at its circumferential surface 21, the surface profile comprising circumferential grooves 25 having for example a V-shaped or U-shaped cross-section and ridges 23 intermediate to neighbouring grooves 25.
The pulley 15 according to an embodiment of the present invention is provided with a magnetic field generator 35. Such magnetic field generator 35 may be arranged at or close to the circumferential surface 21 of the pulley 15 and may create a magnetic field which, upon the suspension traction member 7 abutting to or coming close to the circumferential surface 21, attracts the magnetisable cords comprised therein.
The magnetic field generator 35 may not be visible from outside the pulley 15 and is visualised in Fig. 2 only schematically with dotted lines.
On the one hand, the generated attractive force may be such that the suspension traction member 15 and its cords are attracted by at least one component of this force in a direction as indicated with the arrows 27 in Fig. 2 towards a middle line 29 along the circumferential surface of the pulley 15. For example, the magnetic field generator 35 may be arranged and adapted such that a centre of the generated magnetic field substantially coincides with a ridge 23 extending along the geometric centre of the circumferential surface 21. In such case, the generated magnetic field attempts to align the suspension traction member 7 along with the centre of the circumferential surface 21, i.e. centred between its opposing axial edges 31, 33. As long as the suspension traction member 7 is correctly aligned at such centre, no net lateral force is applied to it. However, as soon as the suspension traction member 7 attempts to displace in an axial direction towards one of the axial edges 31, 33, more of its magnetisable cords will be arranged on one side of the middle line 29 defining the centre of the magnetic field than on the other side such that a net lateral force is generated which forces the suspension traction member 7 back to its centred aligned position.
On the other hand, the magnetic field generated by the magnetic field generator 35 will attract the suspension traction member 7 by at least one other component of its generated force in a direction orthogonal to the circumferential surface 21 of the pulley 15. Thereby, the suspension traction member 7 is always kept in mechanical contact with this circumferential surface 21 and any temporary detachments are avoided. Accordingly, the profile of the suspension traction member 7 will always be kept in complementary engagement with the profile of the pulley 15.
Fig. 3 shows a cross-section of an embodiment of a pulley 15. A centred one of the ridges 23 is magnetised and thereby forms the magnetic field generator 35.
Fig. 4 shows a longitudinal section through an embodiment of a pulley 15. Therein, the entire magnetic field generator 35 is formed by four partial magnetic field generators 37a-d. These partial magnetic field generators 37a-d are arranged at different positions along the pulley such as to generate partial magnetic fields at different locations on the circumferential surface 21 of the pulley 15. In the example shown, the four partial magnetic field generators 37a-d are provided at positions being offset to each other by 90°. In other words, each quarter of the pulley 15 comprises one partial magnetic field generator 37.
Accordingly, as shown in Fig. 1, in the configuration of the pulley 15 being arranged at a bottom of the elevator car 3 at one of its lateral sides and the suspension traction member 7 being wound around only one quarter of its circumferential surface 21, i.e. in a 90° bending, at least one of the partial magnetic field generators 37a-d is always in close proximity to the portion of the circumferential surface 21 currently contacting the suspension traction member 7 and may therefore sufficiently attract it.
The magnetic field generator 35 or its partial magnetic field generators 37a-d may be formed by electromagnets 39. A strength of a magnetic field generated by such electromagnets 39 may be controlled by suitably energising the electromagnets 39 with electricity.
Optionally, these electromagnets 39 may be energised such that only those of the electromagnets 39 generate a magnetic field which currently come close to the portion of the suspension traction member 7 contacting the circumferential surface 21 of the pulley 15. For example, a slip ring arrangement (not shown) may be provided for such purpose in the pulley 15 through which slip ring arrangement the electromagnets 39 may be supplied with electricity.
Finally, it should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

List of reference signs

1: elevator
3: car
5: counterweight
7: suspension traction member
9: driving engine
11: traction sheave
13: pulley of counterweight
15: pulley of elevator car
17: base body
19: central opening
21: circumferential surface
23: circumferential ridges
25: circumferential grooves
27: attraction direction
29: middle line
31: axial edge
33: axial edge
35: magnetic field generator
37: partial magnetic field generators
39: electromagnets

Claims

Pulley (15) for cooperating with a suspension traction member (7) in an elevator (1), wherein the pulley (15) comprises a magnetic field generator (35) for generating a magnetic field such as to induce attractive forces upon a magnetisable portion of the suspension traction member (7) in a direction (27) towards a circumferential surface (21) of the pulley (15).
Pulley of claim 1, wherein the magnetic field generator (35) is configured for generating the magnetic field such as to induce attractive forces upon the magnetisable portion of the suspension traction member (7) in a direction (27) orthogonal to the circumferential surface (21) of the pulley (15).
Pulley of claim 1 or 2, wherein the magnetic field generator (35) is configured for generating the magnetic field such as to induce attractive forces upon the magnetisable portion of the suspension traction member (7) in a direction (27) towards a middle line (29) along the circumferential surface (21) of the pulley (15).
Pulley of one of the preceding claims, wherein at least portions of the circumferential surface (21) of the pulley are profiled with grooves (25) extending in a circumferential direction.
Pulley of one of the preceding claims, wherein the magnetic field generator (35) comprises at least four partial magnetic field generators (37a-d) being arranged at different positions on the pulley (15), the positions being offset to each other by at most 90°.
Pulley of one of the preceding claims, wherein the magnetic field generator (35) comprises an electromagnet (39).
Pulley of claim 6, further comprising a slip ring, wherein the electromagnet (39) is to be energized via the slip ring such that the electromagnet (39) generates the magnet field depending on a current rotation position of the pulley (15) only in a partial area along the circumferential surface (21) of the pulley (15).
Pulley of one of the preceding claims, wherein the magnetic field generator (35) is arranged at a middle line (29) along the circumferential surface (21) of the pulley (15).
Pulley of one of the preceding claims 3 and 8, wherein the middle line (29) is arranged at an axial geometric centre of the circumferential surface (21) of the pulley (15).
Pulley of one of the preceding claims, wherein the magnetic field generator (35) is arranged at a ridge (23) between two grooves (25) extending along the axial geometric centre of the circumferential surface (21) of the pulley (15).
Pulley of one of the preceding claims, wherein a radius of the pulley (15) at axial edges (31, 33) of the pulley (15) is same or smaller than in-between the axial edges (31, 33) of the pulley (15).
Elevator assembly (1) comprising:
an elevator car (3) being displaceable within an elevator shaft;

a suspension traction member (7) suspending the elevator car (3);

a pulley (15) cooperating with the suspension traction member (7);

wherein the pulley (15) is a pulley (15) according to one of claims 1 to 11.
Elevator assembly of claim 12, wherein the suspension traction member (7) is a belt comprising at least one magnetisable cord extending along the length of the suspension traction member (7).
Elevator assembly of one of claims 12 to 13, wherein the suspension traction member (7) has a profiled traction surface with grooves extending along a longitudinal direction of the suspension traction member (7).
Elevator assembly of one of claims 12 to 14, wherein the suspension traction member (7) is wound around the circumferential surface (21) of the pulley (15) along at least 90° of the circumference.