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Title:
SYSTEMS FOR COUPLING A SUSPENSION AND/OR TRACTION MEDIUM TO A LOAD CARRYING STRUCTURE, ELEVATOR INSTALLATION AND METHODS FOR MOVING A LOAD
Document Type and Number:
WIPO Patent Application WO/2019/121219
Kind Code:
A1
Abstract:
The invention concerns systems (1, 1') for coupling a suspension and/or traction medium (11) to a load carrying structure (2), an elevator installation (100) and methods for moving a load (101). A system (1) for coupling a suspension and/or traction medium (11) to a load carrying structure (2) of an elevator installation (100) comprises at least one pulley (13) with a pulley axis (14) arranged in a pulley frame (3). The pulley frame (3) is mountable or mounted to the load carrying structure (2), such that the pulley frame (3) is translationally moveable relative to the load carrying structure (2) in a plane perpendicular to a take-off direction (20) of the suspension and/or traction medium (11), in particular in a direction (16) parallel to the pulley axis (14). Alternatively pulley frame (3) is mountable or mounted to the load carrying structure (2), such that the pulley frame (3) is rotatable around an axis (12) perpendicular to a take-off direction (20) of the suspension and/or traction medium (11).

Inventors:
FERNANDO DEMATTIO JOHANSEN CARLOS (BR)
MARTINS DE MORAIS BUENO RICARDO (BR)
Application Number:
PCT/EP2018/084524
Publication Date:
June 27, 2019
Filing Date:
December 12, 2018
Export Citation:
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Assignee:
INVENTIO AG (CH)
International Classes:
B66B11/02; B66B7/08; B66B15/04
Domestic Patent References:
WO2012084519A12012-06-28
Foreign References:
US20170297869A12017-10-19
JPH01147369U1989-10-12
CN204454184U2015-07-08
JPS5980363U1984-05-30
JPS60154652U1985-10-15
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Claims:
Claims

1. System (1) for coupling a suspension and/or traction medium (11) to a load carrying structure (2) of an elevator installation (100), comprising at least one pulley (13) with a pulley axis (14) arranged in a pulley frame (3), which pulley frame (3) is mountable or mounted to the load carrying structure (2), such that the pulley frame (3) is translationally moveable relative to the load carrying structure (2), particularly the pulley frame is movable in a plane perpendicular to a take-off direction (20) of the suspension and/or traction medium (11), in particular in a direction (16) parallel to the pulley axis (14), wherein a pulley frame support (4) is mountable or mounted to the load carrying structure (2), and the pulley frame (3) is translationally moveable relative to the pulley frame support (4).

2. System according to claim 1, wherein the pulley frame support (4) comprises at least one rail (10) and the pulley frame (3) comprises at least one wheel (5), which is designed for rolling along the rail (10).

3. System according to claim 1, wherein the pulley frame (3) comprises at least one rail (10) and the pul ley frame support (4) comprises at least one wheel (5), which rail (10) is designed for resting or rests on the wheel (5).

4. System according to any of the preceding claims, wherein the system (1) comprises at least one first stopper (7) and at least one second stopper (8) for limiting the translational motion of the pulley frame (3) with respect to the load carrying structure (2), in particular such that the movement of a pulley frame (3) is limited by moving up the first stopper (7) or the second stopper (8) against a wheel (5).

5. System according to one of the preceding claims, wherein the pulley frame (3) is mounted or mounta ble to a pulley frame base (29) such that pulley frame (3) is rotatable with respect to the pulley frame base (29) around an axis (9) parallel to a take-off direction of the suspension and/or traction medium (11).

6. System according to claim 5, wherein the pulley frame (3) is rotatable within a limited angle, in partic ular the rotation is limited by at least one stopper (7’) arranged on or arrangeable on the load carrying structure (2).

7. System ( ) for coupling a suspension and/or traction medium (11) to a load carrying structure (2) of an elevator installation (100), wherein the system (G) comprises at least one pulley (13) with a pulley axis (14) arranged in a pulley frame (3), which pulley frame (3) is mountable or mounted to the load carrying structure (2), such that the pulley frame is rotatable around an axis (12) perpendicular to a take-off direc- tion (20) of the suspension and/or traction medium (11), wherein a pulley frame support (4) is mountable or mounted to the load carrying structure (2), and the pulley frame (3) is translationally moveable relative to the pulley frame support (4).

8. System according to claim 7, wherein the system (G) comprises a pivot axle (21) rotatable around the axis (12) perpendicular to a take-off direction (20) of the suspension and/or traction medium (11), which pivot axle (21) is connected or connectable to a yoke (15) of a load carrying structure (2).

9. Elevator installation (100) comprising at least one system (1 ; G) for coupling a suspension and/or trac tion medium (11) to a load carrying structure (2) according to claims 1 to 8.

10. Elevator installation according to claim 9, wherein the elevator installation (100) comprises at least one load carrier structure (2) with a plurality of systems (1 ; G).

11. Elevator installation according to one of claims 9 and 10, wherein the load carrier structure (2) is con nected to a load (101) and the load (101) comprises a counter weight (103).

12. Method for moving a load (101) with a load carrying structure (2) in an elevator installation (100), comprising a system (1 ; G) for coupling a suspension and/or traction medium (11) to the load carrying structure (2), the system comprising a pulley (13) arranged in a pulley frame (3), which pulley frame (3) is connected to the load carrying structure (2), wherein the pulley frame (3) moves translationally with respect to the load carrying structure (2) in a plane perpendicular to a take-off direction (20) of the sus pension and/or traction medium (11) when the load (101) moves along the hoistway (104), in particular the pulley frame (3) moves in a direction (16) parallel to the pulley axis (14), wherein a pulley frame sup port (4) is mountable or mounted to the load carrying structure (2), and the pulley frame (3) moves trans lationally relative to the pulley frame support (4).

13. Method according to claim 12 wherein the pulley frame (3) rotates around an axis (9) parallel to a take-off direction (20) of the suspension and/or traction medium (11) when the load (101) moves along the hoistway (104).

14. Method for moving a load (101) with a load carrying structure (2) in an elevator installation (100), comprising a system (1 ; G) for coupling a suspension and/or traction medium (11) to the load carrying structure (2), the system comprising a pulley (13) arranged in a pulley frame (3), which pulley frame (3) is connected to the load carrying structure (2), wherein the pulley frame (3) rotates around an axis (12) perpendicular to a take-off direction (20) of the suspension and/or traction medium (11) when the load (101) moves along the hoistway (104).

Description:
Systems for coupling a suspension and/or traction medium to a load carrying structure, elevator installation and methods for moving a load

The invention concerns systems for coupling a suspension and/or traction medium to a load carrying structure, an elevator installation and methods for moving a load.

In a known elevator installation, a suspension medium - such as a rope or flat belt-type rope - typically interconnects a counterweight and a cabin. A drive motor causes the suspension medium to move in order to thereby move the counterweight and the cabin up and down along a hoistway. A drive sheave may be coupled to the drive and may act upon the suspension medium by means of traction between the drive sheave and the suspension medium. In such an embodiment, the suspension medium serves as a suspen sion and traction medium.

The suspension medium loops around at least one sheave system, for example a pulley, which may be mounted to a load, that is the cabin or the counterweight, or both. The sheave system is, for example, mounted to a load carrying structure of the cabin or the counterweight.

The drive motor and the drive sheave are typically disposed in a machine room above the elevator hoist way.

The drive sheave and the pulley being mounted to the load must be precisely aligned. Otherwise the sus pension and/or traction medium may suffer a strain or may even jump out of the pulley, which may cause a premature wear or serious accidents.

Typically the load is guided by guide rails along the hoistway. A misalignment of the guide rails may lead to a deviation of a strictly vertical movement of the load and to a misalignment of the pulley with respect to the driving machine, when the load ascends or descends along the hoistway. The guide rails may get misaligned due to manufacturing issues or due to movements of the whole building, which is usually the case in high buildings.

WO2012084519 and documents cited therein disclose systems for coupling a suspension and/or traction medium to a load carrying structure, wherein a pulley system is rotatable and adjustable about an axis parallel to a take-off direction of a respective suspension and/or traction medium. However, the rotatabil- ity around a vertical axis only allows a limited liberty of action. Especially when the guiding rails are deflected from a vertical axis, a vertical rotation of the pulley may not be able to provide an alignment between the pulley and the driving sheave.

It is the object of the present invention to provide systems for coupling a suspension and/or traction me dium to a load carrying structure, an elevator installation and methods for moving a load in an elevation installation, which prevent the disadvantages of the known solutions and which allow a compensation of a misalignment of hoistway structures.

According to a first aspect of the present invention a system for coupling a suspension and/or traction medium to a load carrying structure of an elevator installation comprises a pulley with a pulley axis ar ranged in a pulley frame.

The pulley axis corresponds to the axle, around which the pulley rotates.

The load carrying structure may be part of a load.

The pulley frame may comprise two spaced apart side walls holding a pulley axis for supporting a pulley. The pulley frame may also contain more than one pulley for guiding more than one suspension and/or traction medium. Usually all pulleys arranged in a common pulley frame have parallel pulley axis, in particular coincident pulley axis.

The pulley frame is mountable or mounted to the load carrying structure, such that the pulley frame is translationally moveable relative to the load carrying structure in a plane perpendicular to a take-off direc tion of the suspension and/or traction medium.

The take-off direction of the suspension and/or traction medium is perpendicular to the pulley axis and generally corresponds to the vertical direction, since the gravity force which causes the pulley frame to move translationally causes the suspension and/or traction medium to generally extend vertically from the pulley axis after its translational movement due to the gravity force. It is therefore obvious that the take off direction of the suspension and/or traction medium is perpendicular to the pulley axis and generally corresponds to the vertical direction, when the system is installed within the elevator installation. Regu larly a pulley arranged in a frame is designed for specific take-off directions, in particular for on specific take-off direction. The take-off direction may be defined by the arrangement of the pulley axis in the pul ley frame. The take-off direction For example the pulley frame may provide openings or guides for threading and unthreading the suspension and/or traction medium. Hence if the movement of the load carrying structure deviates from a pure vertical movement during transportation, for example because the guide rails no longer follow a vertical direction, there will be a lateral force component on the suspension and/or traction medium which causes the pulley to move hori- zontally, such that the pulley still keeps aligned, especially aligned in a vertical direction, with the upper sheave or the driving machine. The planes defined by the circumferences of the sheaves of the pulley may remain parallel to the vertical axis.

In particular the pulley frame is translationally moveable in a direction primarily parallel to the pulley axis. The stress on the suspension and/or traction medium is especially significant and the risk of jumping off the pulley is great, when the traction direction of the suspension and/or traction medium deviates from the vertical axis in a direction parallel to the pulley axis.

In an advantageous embodiment of the invention, the pulley frame is in contact with a pulley frame sup- port, and the pulley frame support is mountable or mounted to the load carrying structure, such that the pulley frame is translationally moveable relative to the pulley frame support and thus to the load carrying structure.

Advantageously the pulley frame comprises at least one wheel and the pulley frame support comprises at least one rail, wherein the wheel is designed and arranged for rolling along the rail. The rail is mounted or mountable to the load carrying structure.

The wheel is rotatable around an axis which is also arranged perpendicularly to the take-off direction of the suspension and/or traction medium. Thus the wheel axis is arranged horizontally when the system is installed in an elevator installation.

Preferably the pulley frame comprises two wheels.

The wheel may be seated on a radial bearing such that the wheel may turn with low friction and the pulley may move immediately.

When the system is installed, the wheel is in contact with a rail of a pulley frame support which is fixedly mounted to the load carrying structure. Alternatively the pulley frame support comprises at least one rotatable roller and the pulley frame is de signed for resting or rests on the rotatable roller, which is fixable or fixed to the load carrying structure. The pulley frame may comprise rails, which are in contact with the roller when the system is installed. In an advantageous embodiment of the invention the system comprises at least one first stopper and at least one second stopper for limiting the translational motion of the pulley frame with respect to the load carrying structure.

In particular the movement of a pulley frame support is limited by moving up the first stopper or the sec- ond stopper against a wheel.

The first and second stopper may form respective end parts of a rail, along which a wheel rolls.

Preferably the pulley frame is mounted or mountable to a pulley frame base such that the pulley frame is rotatable with respect to the pulley frame base around an axis parallel to a take-off direction of the sus pension and/or traction medium.

Preferably the axis corresponds to a symmetry axis of the pulley frame and crosses the pulley axis. The combination of lateral movement and rotation provides an additional degree of freedom for aligning the pulley with the driving sheave. The pulley frame may carry out a short movement in reaction to force components deviating from the vertical direction, hence the alignment may be established very quickly.

Preferably the wheels are mounted to the pulley frame base.

Usually the direction deviations of the guiding rail fluctuate and alternate with respect to the vertical di rection. Hence the pulley has to perform a forth and back movement. To ensure, that the returning move ment does not take too long or that the movement leads to a twisting of the medium, the pulley frame preferably is rotatable within a limited angel. In particular the rotation is limited by at least one stopper arranged on or arrangeable on the load carrying structure.

According to a second aspect of the present invention a system for coupling a suspension and/or traction medium to a load carrying structure of an elevator installation comprises at least one pulley with a pulley axis arranged in a pulley frame. The pulley frame is mountable or mounted to the load carrying structure, such that the pulley frame is rotatable around an axis perpendicular to a take-off direction of the suspen sion and/or traction medium.

When the pulley frame is installed in an elevator installation the pulley frame is rotatable around a basi cally horizontal axle, which preferably is mounted to the load carrying structure.

In a favoured embodiment the system comprises a pivot axle, which is fixed or fixable onto a yoke of a load carrying structure. The pivot axle defines the axis around which the pulley is rotatable. Preferably the pivot axle is fixedly mounted to the pulley frame. In the installed position the pivot axle is seated in a slide bush arranged in the load carrying structure.

The rotatability of the pully frame allows to keep the suspension and/or traction medium in the take-off direction also when the yoke of the load carrying structure deviates from an originally adjusted orientia- tion, which usually is a horizontal orientation.

According to the present invention an elevator installation comprises at least one system for coupling a suspension and/or traction medium to a load carrying structure as described above.

The elevator installation may further comprise at least one load, e.g. a cabin or a counterweight, with a load carrying structure, a suspension and/or traction medium arranged in a hoistway and a driving sheave or a driving machine, arranged in or above a hoistway.

Independent of any particular roping configuration or structure of the elevator installation, the suspension and/or traction medium may have one of several configurations. In one embodiment, the suspension me dium has a belt-type configuration in which several cords of metallic material are fully or partially em bedded in an elastomeric coating. That configuration has a cross-section having a width that is longer than its height. The surface of such a suspension medium may be flat or have longitudinal grooves. In another embodiment of a suspension and/or traction medium with such a cross-section, cords of non-metallic material, such as aramid fibers, are fully or partially embedded in an elastomeric material. In yet another embodiment, the suspension and/or traction medium may have a round configuration in which individual cords of metallic or non-metallic material are twisted to a rope. Such a round suspension and/or traction medium may be uncoated or coated with an elastomeric material.

In a favourable embodiment the elevator installation comprises a load carrying structure with at least one guide device for guiding the load along a guide rail. The guide devices may comprise guidance rollers. The guidance rollers contact and roll on the guide rail which is typically mounted to a wall or along a wall of the hoistway. For long hoistways the guide rails may deviate from the vertical alignment. The system according to the invention compensates a horizontal or rotational movement of the load to keep the verti cal alignment of the suspension and/or traction medium.

Typically an elevator installation comprises at least two guide devices for two respective guide rails ar ranged on both sides of the load.

In some cases it is appropriate to use more than one suspension and/or traction medium for manoeuvring a load. Favourably the elevator installation comprises a plurality of systems, for example a pair of sys tems, which are mounted to a load carrier structure and which are parallelly moveable. Preferably the systems are mounted such that respective pulleys may translate and/or rotate independently.

In a beneficial embodiment of the elevator installation the load carrier structure is connected to a load and the load comprises a counter weight.

A further aspect of the present invention concerns a method of moving a load with a load carrying struc ture in an elevator installation. The elevator installation comprises a system for coupling a suspension and/or traction medium to the load carrying structure. The system comprises a pulley arranged in a pulley frame, which pulley frame is connected to the load carrying structure. According the invention the pulley frame moves translationally with respect to the load carrying structure in a plane perpendicular to a take off direction of the suspension and/or traction medium when the load moves along the hoistway. The movement of the system may compensate a potential deviation of the ascending or descending load from a strict vertical movement and may hence prevent a misalignment of the suspension and/or traction medi um.

In a beneficial embodiment of the method the pulley frame additionally rotates around an axis parallel to a take-off direction of the suspension and/or traction medium when the load moves along the hoistway. Preferably the axis corresponds to a symmetry axis of the pulley frame and crosses the pulley axis.

A further aspect of the present invention concerns a method of moving a load with a load carrying struc ture in an elevator installation. The elevator installation comprises a system for coupling a suspension and/or traction medium to the load carrying structure. The system comprises a pulley arranged in a pulley frame, which pulley frame is connected to the load carrying structure, wherein the pulley frame rotates around an axis perpendicular to a take-off direction of the suspension and/or traction medium when the load moves along the hoistway. Preferably the pulley frame rotates around a horizontal axis with respect to the load carrying structure.

The invention is explained in more detail in the following in exemplary embodiments and with the aid of drawings.

The figures show:

Figure 1 a schematic illustration of one embodiment of an elevator installation;

Figure 2 a first example of a system for coupling the suspension and/or traction medium to a load carrying structure in a perspective view;

Figure 3 a second example of systems for coupling the suspension and/or traction medium to a load carrying structure in a perspective view;

Figure 4 a third example of systems for coupling the suspension and/or traction medium to a load carrying structure in a perspective view;

Figure 5 a detail of the system according to Figure 4 in an exploded view;

Figure 6 a system according to Figures 1 and 2 in a side view;

Figure 7a a schematic illustration of a movement of a load carrying structure according to the state of the art;

Figure 7b a schematic illustration of a movement of a load carrying structure according to a first embodiment of the invention.

Figure 1 shows a schematic illustration of one embodiment of an elevator installation 100 typically in stalled in a multi-story building. The elevator installation 100 includes a cabin 102 connected by a sus pension and/or traction medium 11 with a counterweight 103, wherein the cabin 102 and the counter weight 103 are movable up and down in opposite directions in a vertically extending hoistway 104. A drive 105 is provided to move the loads 101 and is arranged near the upper part of the hoistway 104 to a structure 106. Depending on whether the elevator installation 100 is provided with or without a machine room, the structure 106 may be a floor of a separate machine room, which houses the drive 105, or a sup port structure provided below the hoistway roof. In the latter situation, the structure 106 could be mount ed to a shaft wall to support the drive 105 in proximity of the shaft wall.

The drive 105 is configured to drive the suspension and/or traction medium 11 to move the loads, in this case the cabin 102 and the counterweight 106. The suspension and/or traction medium 11 is hereinafter also referred to as medium 11.

The elevator installation 100 includes further a load carrying structure 2 that carries the counterweight 103. The elevator installation 100 may also include a further load carrying structure 2 that carries the cabin 102.

The load carrying structure 2 may include a yoke 15 (see figures 2-5), a crosshead and/or a frame that at least partially surrounds the counterwight 103 or the cabin 102. The counterweight 103, as well as the cabin 102, empty or loaded with goods or passengers, constitutes a load 101 to be carried by the load carrying structure 2. ft is contemplated that the cabin 102 includes at least one door on one side of the cabin 102; however, for ease of illustration, Fig. 1 does not show a door or any other component of the cabin 102.

A system 1 for coupling the medium 11 to the load carrying structure 2 interfaces the load carrying struc ture 2 and the medium 11.

This system is hereinafter also referred to as coupling system 1. ft is contemplated that the coupling system 1 may be provided at the counterweight 103 or at the cabin 102 to interface the counterweight 106 or the cabin 102 and the medium 11.

The elevator installation 100, therefore, may have the coupling system 1 at the cabin 102 or the counter- weight 103, or both. ln the illustrated elevator installation 100 of Fig. 1 , terminal ends of the medium 11 are fixed at fix points 107, 108 to the structure 106. Starting at the fix point 108, the medium 11 extends downwards, loops around a pulley 13 of the system 1 mounted to the cabin 102 and extends upwards towards the drive 105. There, the suspension medium 11 loops around a drive sheave 109 of the drive 105 and extends towards a deflection roller 110 positioned next to the drive 105 above the structure 106. The deflection roller 110 guides the medium 11 sideways so that the up and down movement of the coun terweight 103 does not interfere with the up and down movement of the cabin 102. At the deflection roller 110, the medium 11 extends downwards, loops around a pulley 13 at the counterweight 103 and extends upwards towards the fix point 107.

This configuration of the medium 11 is typically called a 2:1 configuration ft is contemplated that in other embodiments of the elevator installation 100 other configurations, e.g., 2:1, 4:1 or 6:1, may be used; the number of sheaves, rollers and fix points may then vary depending on a particular embodiment. ft is contemplated that the elevator installation 100 may in certain embodiments include more than one medium 11. The number of media 11 used in the elevator installation 1 depends, for example, on the load capacity of the cabin 102. ln the embodiments described with respect to Fig. 2 - 4, the respective elevator installations 100 include at least two media 11. The number of suspension media 11 affects the number of pulleys, sheaves and rollers used in the elevator installation 100.

To provide a stable actuation of the loads 102, 103, it is important that the take-off direction 20 of the medium 11 remains vertical, such that the fix points 107, 108, the drive sheave 109 and deflection roller 110 remain aligned with the pulleys 13.

Figure 2 shows a first example of a system 1 for coupling the medium 11 (not disclosed in the figure) to a load carrying structure 2 in a perspective view. The system 1 comprises two pulleys 13, each having a pulley axis 14 arranged in a respective pulley frame 3. The pulley frames 3 are mounted to the load carry ing structure 2, such that the pulley frame 3 is translationally moveable relative to the load carrying struc ture 2 in a plane perpendicular to a take-off direction 20 of the medium 11. ln the shown example the pulley frame 3 is translationally in a direction 16 primarily parallel to the pulley axis 14.

The pulley frame 3 is connected to a pulley frame support 4, and the pulley frame support 4 is mountable or mounted to an upper yoke 15 of the load carrying structure 2, such that the pulley frame 3 is transla tionally moveable relative to pulley frame support 4. The pulley frame support comprises rails 10. Each pulley frame 3 comprises two wheels 5 which are may roll along a respective rail 10. The rails 10 are mounted or to the yoke 15 of the load carrying structure 2. The wheels 5 are rotatable with respect to a horizontal axis 6 when the coupling system 1 is installed. Each rail 10 comprises a first stopper 7 and a second stopper 8 for limiting the translational motion of the pulley frame 3 with respect to the pulley frame support 4 and to the load carrying structure 2. The move ment of a pulley frame 3 is limited by moving up the first stoppers 7 or the second stoppers 8 against the wheels 5.

Additionally each pulley frame 3 is rotatable with respect to a respective pulley frame base 29 around an axis 9 parallel to a take-off direction 20 of the medium 11.

The load carrying structure 2 comprises guide devices 17 for guiding the load 102, 103 along a guide rail (not shown in the figures).

Figure 3 shows a second example of a coupling system 1, which is similar to the example shown in Fig ure 1.

The pulley frames 3 are rotatable with respect pulley frame bases 29 to the only within a limited angel. The rotation is limited by stoppers 7’ arranged on a yoke 15 of the load carrying structure 2.

Figure 4 shows a third example of a system 1’ for coupling the suspension and/or traction medium 11 to a load carrying structure 2 in a perspective view.

The system 1’ comprises four pulleys 13. Two pulleys 13 with a common pulley axis 14 are arranged in a common pulley frame 3, such that in total four media 11 may be coupled to the load carrying structure 2. The pulley frames 3 are mounted to the load carrying structure 2, such that the pulley frame 3 is rotatable around an axis 12 perpendicular to a take-off direction 20 of the media 11. Hence the media 11 stay verti cally aligned even when the main orientation 18 of an upper yoke 15 of the load carrying structure 2 devi ates form a horizontal direction 19.

Figure 5 shows a detail of the coupling system 1’ according to Figure 4 in an exploded view. The cou pling system 1’ comprises a pulley frame 3 with two pulleys 13 and a pivot axle 21 defining an axis 12. The axle 21 and the pulley frame 3 are fixedly coupled. A yoke 15 of a load carrying structure provides a bore 22, wherein a slide bush 23 is arranged. The pivot axle 21 may be introduced into the slide bush 23 and be held by a washer 24 and a retaining ring 25.

Figure 6 shows a coupling system 1 according to Figures 1 and 2 in a side view. The pulley 13 is arranged in a pulley frame 3. The pulley frame 3 is connected to a pulley frame base 29 by a vertical axle 26 which is seated on an axial bearing 27. The pulley frame 3 comprises two wheels 5. The wheels 5 are seated on radial bearings 28 such that they are rotatable with respect to a horizontal axis 6. The wheels 5 are in con tact with a pulley frame support 4 comprising rails 10 which are mounted to a load carrying structure 2 not disclosed in the figure.

Figure 7a shows a schematic illustration of a movement of a load carrying structure 2 according to the state of the art.

In case a hoistway 104 is not perfectly aligned with the take-off direction 20 of the medium 11 , which normally is the vertical direction, the load carrying structure 2 may perform not only a vertical movement but also a horizontal movement when it descends.

When the load carrying structure 2 descends from a first position pi to a second position p2 and further reaches a third position p3 the relative position of the pulley frames 3 and the load carrying structure 2 stays the same. Hence the pulleys 13 carry out a horizontal movement and the angles between the media 11 and the pulley 13 change. There is the risk that a medium 11 jumps off the pulley 13.

Figure 7b is a schematic illustration of a movement of a load carrying structure 2 according to a first em bodiment of the invention. As the load carrying structure 2 descends from a first position pi to a second position p2 and further reaches a third position p3 the load carrying structure 2 carries out a horizontal movement due to the misalignment of the hoistway 104.

However, the pulley frames 3 are translatable in a horizontal direction 16 with respect to the load carrying structure 2. Hence the pulley frames 3 may stay aligned with the machine not disclosed in the figure and the media 11 remain tensioned in vertical direction.