SUSPENSION ARRANGEMENT FOR A TRACTION SHEAVE ELEVATOR AND METHOD FOR REDUCING THE NEED FOR COMPENSATING ROPES

The present invention relates to a suspension arrangement for a traction elevator as defined in the preamble of claim 1 and to a method as defined in the preamble of claim 15 for reducing the compensating ropes of an elevator.

In counterweighted traction elevators, the weight of the compensating ropes produces an imbalance between the elevator car and counterweight when there is a large height difference between the elevator car and the counterweight . The imbalance is at a maximum when the elevator car is in the top part of the elevator shaft and the counterweight in the bottom part of the shaft or vice versa. In the case of elevators having a large hoisting height, this is a problem because these elevators have long and heavy hoisting ropes. Due to heavy ropes and a large height difference between the elevator car and counterweight, the imbalance may become so great that the friction between the hoisting ropes and the rope grooves of the traction sheave is not sufficient, with the result that the hoisting ropes start slipping on the traction sheave. In elevators with a smaller hoisting height, the imbalance caused by the hoisting ropes has no essential importance as it is relatively small, so it can be disregarded, but the imbalance appearing in the case of greater hoisting heights must be compensated in some way. The aforesaid imbalance generally needs to be compensated in the case of elevators having a hoisting height exceeding a certain limit, which typically is about 30-40 meters.

In prior art, the imbalance between elevator car and coun- terweight has been compensated by using so-called compen-

sating ropes, which are attached by their first ends to the lower part of the elevator car and by their second ends to the lower part of the counterweight . When the elevator car is in the lower part of the elevator shaft, the counter- weight is in the upper part of the shaft and the portion of the hoisting ropes between the elevator car and the traction sheave, which is located in the upper part of the shaft, is long and heavy. In this situation, however, the compensating ropes hanging from the lower part of the coun- terweight are likewise long and heavy, so they compensate the imbalance between the rope forces on the traction sheave caused by the hoisting ropes. However, the use of compensating ropes involves the problem that the compensating ropes increase the costs and the ropes may also be a hindrance is some cases, such as e.g. in maintenance situations. Moreover, the compensating ropes increase the total weight of the elevator, which may necessitate stronger elevator structures, which again increases the costs.

In EP publication EP1724229 Al, Fig. 9 represents an elevator suspension arrangement wherein the angle of the hoisting rope going from the traction sheave to the counterweight relative to the vertical direction changes as the height position of the counterweight changes. However, the aforesaid publication is not concerned with solving the same problem as the arrangement according to the present invention, nor does the description make any mention of the change in the angle . The change in the angle results from placing the hoisting machine at a position as suitable as possible in respect of lay-out relative to the elevator car. This has made it necessary to position the traction sheave at a greater lateral distance from the diverting pulley of the counterweight, whereby the said angle has been produced.

The object of the present invention is to overcome the above-mentioned drawbacks and achieve a simple and advantageous suspension arrangement for a counterweighted elevator that can be used to reduce the imbalance of the rope forces, i.e. the difference between the rope forces on either side of the traction sheave. A concurrent aim is to build elevators having a greater hoisting height than before without the use of compensating ropes. A further object of the invention is that, in elevators with a hoisting height so large that compensating ropes are required in any case, the amount of ropes needed will be smaller than in previously known solutions . The arrangement of the invention is characterized by what is disclosed in the characterizing part of claim 1. The method of the invention is characterized by what is disclosed in the characterizing part of claim 15. Correspondingly, other embodiments of the invention are characterized by what is disclosed in the other claims .

Inventive embodiments are also presented in the description part of the present application. The inventive content disclosed in the application can also be defined in other ways than is done in the claims below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or with respect to advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts. Similarly, different details described in connection with each embodiment of different embodiments of the invention may be applied in connection with other embodiments. In addition, obviously at least some of the sub-claims can at least in appropriate situations be regarded as being inventive in themse1ves .

The arrangement of the invention has the advantage that the imbalance due to the height difference between the elevator car and counterweight is not so great as in traditional suspension solutions, which makes it possible to omit the compensating ropes in the case of greater hoisting heights than before. This permits a reduction in the costs. A further advantage is that the arrangement is simple and economical to implement. Moreover, the energy efficiency of the elevator may be improved.

According to the invention, in the suspension arrangement for a traction elevator, the elevator comprises at least a hoisting machine and an elevator car suspended on and sup- ported by a set of hoisting ropes preferably by means of at least rope sheaves serving as diverting pulleys, which elevator car has been fitted to travel in a substantially vertical direction along guide rails, and a substantially vertically movable counterweight provided with a rope sheave and fitted to move along guide rails, said elevator additionally comprising at least one fixed rope sheave rotating in place. The rope force of the ropes in the rope portion between a rope sheave moving substantially vertically in the elevator shaft and the fixed rope sheave rotating in place has been adapted to vary as a function of the vertical distance between the vertically movable rope sheave and the rope sheave fixedly mounted in place.

In an embodiment of the invention, the aforesaid rope force has been adapted to be increased when the movable rope sheave is vertically approaching the rope sheave fixedly mounted in place and, correspondingly, the said rope force has been adapted to be decreased when the movable rope sheave is moving vertically farther away from the rope sheave fixedly mounted in place.

In an embodiment of the invention, the variation of the aforesaid rope force has been arranged by varying the angle of the hoisting ropes in the hoisting rope portion between the movable rope sheave and the rope sheave fixedly mounted in place relative to the vertical direction as the movable rope sheave is moving vertically.

In an embodiment of the invention, the aforesaid rope force has been adapted to be increased by increasing the said angle and, correspondingly, the aforesaid rope force has been adapted to be decreased by decreasing the said angle.

In an embodiment of the invention, the vertically movable rope sheave is a diverting pulley mounted on the counterweight, and the rope sheave fixedly mounted in place is the traction sheave of the hoisting machine.

In an embodiment of the invention, the vertically movable rope sheave is a diverting pulley mounted on the elevator car, and the rope sheave fixedly mounted in place is the traction sheave of the hoisting machine.

In an embodiment of the invention, the vertically movable rope sheave is both a diverting pulley on the counterweight and a diverting pulley on the elevator car, and the rope sheave fixedly mounted in place is the traction sheave of the hoisting machine.

In an embodiment of the invention, the rope sheave fixedly mounted in place is a diverting pulley disposed in the elevator shaft or in the machine room.

In an embodiment of the invention, the variable angle of the rope portion between the vertically movable rope sheave

and the rope sheave fixedly mounted in place has been formed by disposing the movable rope sheave on its path of movement at a horizontal distance from the rope sheave fixedly mounted in place .

In an embodiment of the invention, the variable angle has been formed by disposing the movable rope sheave on its path of movement at a horizontal distance from the rope sheave fixedly mounted in place and arranging for the hoisting ropes coming to the rope sheave from above and those going up from the rope sheave to cross each other above the rope sheave. In this way, a roping arrangement advantageous in respect of space utilization is achieved.

In an embodiment of the invention, the hoisting ropes coming to the rope sheave from above and those going up from the rope sheave have been arranged to cross each other by one of the following methods:

- the rope sheave has been rotated sideways relative to the rope sheave fixedly mounted in place by an angle such that the rope set consisting of the hoisting ropes (3b) going upwards from the rope sheave passes in its entirety at the crossing point the rope set coming downwards to the rope sheave,

- the rope set passed obliquely downwards to the rope sheave from the rope sheave fixedly mounted in place has been twisted as an entire bundle preferably through 90-180°, most preferably even approximately 180°, about the center line of the rope set before passing the hoisting ropes into the rope grooves of the rope sheave ,

- each hoisting rope going obliquely upwards from the rope sheave has been arranged to pass by the obliquely

downwards going portion of the same hoisting rope, so that each hoisting rope runs crosswise relative to itself.

In an embodiment of the invention, the variable angle of the rope portion between the vertically movable rope sheave and the rope sheave fixedly mounted in place has been formed by disposing the movable rope sheave on its path of movement at a horizontal distance from the rope sheave fix- edly mounted in place.

In an embodiment of the invention, the variable angle has been formed by arranging for the hoisting ropes coming from above to the rope sheaves servings as diverting pulleys on the elevator car and the hoisting ropes going upwards from the rope sheaves to run crosswise relative to each other above the rope sheaves .

In an embodiment of the invention, the hoisting ropes have been arranged to run crosswise relative to themselves above the rope sheaves in such manner that, from the rope sheave fixedly mounted in place, the hoisting ropes are first passed obliquely downwards around a rope sheave disposed at a larger horizontal distance from the rope sheave and after this around a rope sheave disposed at a shorter horizontal distance from the rope sheave and, having passed under and around it, the hoisting ropes are passed obliquely upwards so that they run crosswise relative to each other and continue up to their point of anchorage.

In an embodiment of the invention, the elevator has no compensating ropes .

A method for reducing the need for compensating ropes in an elevator comprising a hoisting machine and an elevator car

and counterweight suspended on a set of hoisting ropes, which elevator car and counterweight have been fitted to move in a substantially vertical direction along guide rails, and which elevator further comprises at least one fixed rope sheave rotating in place, and in which method the counterweight and/or elevator car are/is suspended to be supported by a rope sheave / rope sheaves moving together with it/ them in the elevator shaft. In the method, the elevator suspension is so arranged that the rope force of the ropes in the rope portion between a rope sheave moving substantially vertically in the elevator shaft and the fixed rope sheave rotating in place varies as a function of the vertical distance between the vertically movable rope sheave and the rope sheave fixedly mounted in place.

In an embodiment of the method of the invention, the suspension is so arranged that the aforesaid movable rope sheave is the rope sheave of the counterweight. One of the advantages is that the need for a compensating rope can be reduced without necessarily altering the suspension of the elevator car and/or the suspension ratio of the elevator car can be freely selected as desirable. In this way, the ropes of the hoisting rope set going upwards from the elevator car can also be arranged to go directly upwards if desirable. When the aforesaid movable rope sheave is the counterweight rope sheave, a further advantage is that the suspension of the elevator car can be arranged in different ways if desirable, for example with a 1:1 hoisting ratio by securing the end of the hoisting rope set to the elevator car or with a 2:1 hoisting ratio by having the elevator car supported by a rope sheave mounted in conjunction with the elevator car. Thus the advantage is achieved that one and the same counterweight suspension arrangement is suited for use in conjunction with several different elevator types as regards the hoisting ratio. This also allows the counter-

weight to be so fitted in the elevator shaft that its range of back-and-forth travel is shorter than that of the elevator car, which means that the length of counterweight travel does not limit the length of travel of the elevator car.

In an embodiment of the method of the invention, the suspension is so arranged that the movable rope sheave is on its path of movement at a horizontal distance from the rope sheave fixedly mounted in place and that the hoisting ropes coming to the rope sheave from above and those going up from the rope sheave run crosswise relative to each other above the rope sheave. This results in an advantageous roping arrangement as regards space utilization.

In an embodiment of the method of the invention, the need for a compensating rope is reduced by implementing the suspension according to the above-described suspension arrangement of the invention for a traction elevator.

In an embodiment of the method of the invention, the elevator is implemented without the use of compensating ropes.

In an embodiment of the method of the invention, the need for compensating ropes in an existing elevator is reduced by arranging the suspension of the elevator in the manner described above. In this way, an elevator that has already been in use for a long time can be modernized by this method, thereby improving its energy efficiency, inter alia.

In an embodiment of the method of the invention, the method is a modernization method for an elevator that has already been in use .

In an embodiment of the method of the invention, the weight of the compensating ropes of an existing elevator is reduced or the compensating ropes are even removed altogether. This can be done by arranging the elevator suspen- sion in the manner described above. Thus, the method can be used to modify an existing elevator, e.g. an old elevator that has long been in use, and to improve its energy efficiency, inter alia.

In the following, the invention will be described in detail by referring to an embodiment example and the attached drawings , wherein

Fig. 1 presents a simplified and diagrammatic side view of a counterweighted traction elevator in which an embodiment of the solution of the invention is used,

Fig. 2 presents a simplified and diagrammatic side view of another counterweighted traction eleva- tor in which another embodiment of the solution of the invention is used,

Figs. 3-5 represent different embodiments of the solution according to Fig. 2 in simplified and diagrammatic top view, Fig. 6 presents a three-dimensional simplified diagram of an implementation of the embodiment represented by Fig. 4, and

Fig. 7 presents a simplified and diagrammatic side view of a third counterweighted traction eleva- tor in which a third embodiment of the solution of the invention is used.

Fig. 1 presents a simplified and diagrammatic side view of an elevator solution in which the invention can be applied. The elevator in the figure is a counterweighted and machin-

eroomless traction elevator, in which the hoisting machine 5, provided with a traction sheave 6 and controlled by a control unit 7, is disposed in the top part of the elevator shaft. The elevator car 1 has been placed inside a car frame 2 and it is supported by a set of hoisting ropes 3 and fitted to move back and forth in the elevator shaft along guide rails 4 in a substantially vertical direction. The elevator obtains its hoisting power from the hoisting machine 5 by friction between the traction sheave 6 and the hoisting ropes 3. The counterweight 8 of the elevator is suspended on the hoisting ropes 3 on the opposite side of the traction sheave 6 relative to the elevator car 1. The counterweight 8 has been fitted to move substantially vertically in the elevator shaft along its own guide rails 9. The suspension ratio of the elevator presented in the figure is 2:1.

The set of hoisting ropes 3 is secured by its first end to a first anchorage 10 in the upper part of the elevator shaft, from where it is passed around the elevator car 1, around and under diverting pulleys 11 and 12 attached to the lower part of the car frame 2, from where the ropes are passed further to the traction sheave 6 mounted in the upper part of the elevator shaft. The set of hoisting ropes 3 has been arranged to pass around and over the traction sheave 6, after which the rope 3 is passed around and under a diverting pulley 13 attached to the upper part of the counterweight 8 and then further to a second anchorage 14 in the upper part of the elevator shaft, to which the sec- ond end of the set of hoisting ropes 3 is secured. In the figure, that portion of the set of hoisting ropes 3 which remains on the side of the elevator car 1 relative to the traction sheave 6 is indicated by number 3a, while the portion remaining on the side of the counterweight 8 is indi- cated by number 3b.

The counterweight 8 is so disposed that the mutually opposite outer edges of the traction sheave 6 and the diverting pulley 13 attached to the upper part of the counterweight 8 are have a horizontal distance "a" between them, so that the portion of the hoisting ropes 3 between the diverting pulley 13 and the traction sheave 6 does not extend vertically but forms a varying angle α relative to the vertical line, the size of said angle depending on the height posi- tion of the elevator car 8 in the elevator shaft. Similarly, the second anchorage 14 of the set of hoisting ropes 3 is disposed at the same horizontal distance "a" from the other outer edge of the diverting pulley 13, so that the portion 3b of the hoisting ropes 3 between the second an- chorage 14 and the diverting pulley 13 likewise forms an angle α relative to the vertical line. Thus, the suspension of the counterweight 8 is symmetrical relative to the vertical line, because the angle of the portion 3b of the hoisting ropes 3 relative to the vertical line is the same on both sides of the counterweight 8. The higher the position of the counterweight 8, the greater is the angle α. Correspondingly, when the counterweight 8 is moving downwards in the elevator shaft, the angle α decreases.

The rope forces acting across the traction sheave 6 when the elevator car is stationary can be represented by the following equations:

F _c = (C/2 + h * mr) * g (Equation 1)

where :

F _c = rope force on the side of elevator car C = total mass of elevator car and load

h = hoisting height mr = rope weight per meter g = gravitational acceleration

Few = (CW/2 + b * mr) * SQRT (a ² + b ² ) /b) * g (Equation 2)

where :

Few - rope force on the side of counterweight

CW = mass of counterweight b = vertical distance of midline of counterweight pulley from rope anchorage mr = rope weight per meter g = gravitational acceleration

When the elevator car is moving, the effect of acceleration of the elevator car must be included in the equation so that it either increases or reduces the magnitude of g, de- pending on the direction of travel of the elevator.

In the following, the rope forces are calculated by way of example for the rope portions on either side of the traction sheave in the solution of the invention and, as a ref- erence, in a prior-art construction where the hoisting rope portion between the diverting pulley 13 and the traction sheave 6 extends vertically and consequently angle α = 0 and likewise the aforesaid horizontal distance "a" = 0.

Let us assume that

C = 1300 kg CW = 1000 kg mr = 1.2 kg/m

a = 0 . 33 m h = 30 m g = 9 . 81 m/ s ²

The values used in the case of the prior-art elevator are otherwise the same but the horizontal distance "a" is zero as stated above. The differences in the rope forces are shown in the table below for three different height positions of the elevator car 1, i.e. for the lowest position, a roughly midway position and the highest position. The counterweight 8 is in these cases at the reverse height positions, excepting the mid position.

Elevator according to the Prior-art elevator (a=0) invention

Car at low position h=31, Car at low position h=31, b=l b=l

Fc = 6741 N F _c = 6741 N

Few = 5178 N Few = 4917 N

Fc - Few = 1563 N F ₀ - Few = 1824 N

Car at mid position h=16 , Car at mid position h=16 , b=16 b=16

Fc = 6565 N F _c = 6565 N

Few = 5094 N F _cw = 5093 N

Fc - Few = 1471 N F _c _ Few = 1472 N

Car at low position h=31 , Car at low position h=31 , b=l b=l

Fc = 6388 N F _c = 6388 N

Few = 5270 N Few = 5270 N

Fc - F _cw = 1118 N F _c - F _cw = 1118 N

Difference between the differences in rope forces at the low and high positions of the elevator car, i.e. (F _c - Few) _LOW

POSITION - (Fc - Few) HIGH POSITION :

445 N 706 N

From the above it is clearly to be seen that the solution of the invention significantly increases the rope force of the rope portion 3b on the counterweight 8 side of the traction sheave 6 when the elevator car 1 is at the low po- sition and the counterweight 8 at the high position. Thus, the mutual difference between the rope forces on either side of the traction sheave 6 is reduced, and consequently the imbalance is also reduced. It can be seen from the calculation that the imbalance between the low and high posi- tions of the elevator car 1 is likewise significantly reduced. The suspension arrangement of the invention provides the benefit that the imbalance due to the height difference between the elevator car 1 and the counterweight 8 is not so great as in traditional suspension solutions and the compensating ropes can be omitted from elevators with a greater hoisting height than before.

Fig. 2 presents a simplified and diagrammatic side view of an elevator solution resembling Fig. 1 but using another embodiment of the solution of the invention. This embodiment differs from that represented by Fig. 1 in that the set of hoisting ropes 3 is passed around the diverting pulley 13 attached to the upper part of the counterweight 8 by a different way than in the solution in Fig. 1. The hoist- ing ropes coming from the traction sheave 6 to the diverting pulley 13 are now passed obliquely downwards to the diverting pulley 13 by that edge of the diverting pulley which is farther away from the traction sheave 6. After this, the hoisting ropes pass around and under the divert-

ing pulley 13 and go up by that edge of the diverting pulley which is closer to the traction sheave 6 and, as they go obliquely upwards, cross the downward moving hoisting ropes above the diverting pulley 13.

Figs. 3-5 represent different embodiments of the solution according to Fig. 2 in simplified and diagrammatic top view. In the figures, only one rope in the set of hoisting ropes is indicated by reference number 3b. This hoisting rope 3b is the edgemost hoisting rope on the traction sheave 6, and its passage around the diverting pulley 13 is visualized by marking the same rope 3b on the diverting pulley 13 as well, or on the other side of the diverting pulley.

In the embodiment represented by Fig. 3, the counterweight diverting pulley 13 has been rotated sideways relative to the traction sheave 6 so that the hoisting ropes going obliquely upwards from the diverting pulley 13 will not touch the hoisting ropes coming obliquely downwards at the point of crossing of the hoisting ropes. In this case, the whole hoisting rope set consisting of hoisting ropes 3b and going obliquely upwards from the diverting pulley 13 passes at the crossing point the whole rope set coming obliquely downwards to the diverting pulley 13. The diverting pulley 13 can additionally be tilted so that the axis of the diverting pulley forms an angle relative to the horizontal direction. Tilting the pulley increases the distance between the hoisting ropes at the crossing point, so the an- gle of sideways rotation of the diverting pulley 13 can be reduced by suitably tilting it. In addition, it is possible to rotate and/or tilt the traction sheave 6 in a corresponding manner .

In the embodiment represented by Fig. 4, the rope set passed obliquely downwards to the diverting pulley 13 has been twisted as an entire bundle by approximately 180° about the center line of the rope set before passing the hoisting ropes into the rope grooves of the diverting pulley 13. The rope set has thus been turned about its longitudinal axis and so positioned against the diverting pulley 13 that the edgemost ropes in the rope set have been shifted to the opposite side relative to the midmost ropes or the midmost rope in the case of a rope set comprising a number of ropes. The rope set in this turned position comprises a point where the ropes in the rope set are disposed one over the other. In Fig. 4, this occurs at the crossing point, because the arrangement is depicted as seen from above. In the figure, the individual rope indicated by reference number 3b is the bottommost rope at the crossing point. In other respects, the ropes are passed around and under the diverting pulley 13 in the normal manner along its surface, and they would come up and emerge from the left of the diverting pulley 13, but this is not shown in the figure for the sake of clarity. It would be advantageous to arrange for the ropes coming up from the left to pass by the rope set coming from the traction sheave 6 at the point where the plane formed by the ropes in the rope set coming from the traction sheave is upright or at least close by that point, because that is where the ropes can easily pass each other without touching each other. The diverting pulley 13 is preferably, but not necessarily, positioned in the manner illustrated in the figure in an oblique position relative to the traction sheave 6 so that the ropes depicted in the figure will just narrowly avoid touching each other. If the traction sheave 6 and diverting pulley 13 are positioned in the same orientation, then the ropes will lean against each other. In Fig. 4, the individ- ual ropes depicted in the figure run at a distance from

each other because the pulley is in a turned position. Correspondingly, the ropes going obliquely upwards from the diverting pulley 13 to their anchorage can be passed directly to the points 14 of anchorage or, if necessary, the rope set can be once more twisted about its center line before the hoisting ropes are secured to the anchorage 14. The rope set can thus be twisted by 180 ^e , which would result in the narrowest rope bundle at the crossing point of the ropes over the diverting pulley when the ropes are ar- ranged in the manner illustrated in Fig. 2. Even twisting the rope set by a smaller amount will result in an advantage as referred to above, because, as seen from a lateral direction, the ropes are set the more tightly together the more the rope set is twisted. Due to the twisting, the in- dividual ropes in the twisted rope set are at a distance from each other in the vertical direction. Twisting the set of ropes going up from the diverting pulley to the anchorage by even a slight amount is possible, because they can be secured to the anchorage 14 at any position relative to each other. In this embodiment, too, the diverting pulley 13 and/or the traction sheave 6 can be tilted relative to the horizontal if necessary. The traction sheave 6 and diverting pulley may also be displaced horizontally as compared to the positions shown in the figure.

Fig. 6 presents a three-dimensional visualization of the implementation of the embodiment according to Fig. 4, said figure showing how the rope set is twisted arid how the ropes run about the diverting pulley 13. In the figure, both the set of ropes coming downwards to the diverting pulley and the set of ropes going upwards from it have been twisted about their respective axes. In the figure, only one rope in the set of hoisting ropes is indicated by reference number 3b. The passage of this hoisting rope 3b around the diverting pulley 13 has been visualized by mark-

ing the same individual rope 3b at different points along the route of the rope set formed by the ropes around the diverting pulley.

In the embodiment represented by Fig. 5, the crosswise passage of the hoisting ropes has been implemented in such manner that each rope going obliquely upwards from the diverting pulley 13 goes up by a path next to the obliquely downwards going portion of the same rope. Thus, each rope runs crosswise relative to itself, and not as an entire rope set as in Fig. 3. In this embodiment, the distance between the rope grooves is larger than in the two solutions described above. Likewise, at least the diverting pulley 13 and, if necessary, the traction sheave 6 as well, has a greater thickness than in the solution described above. In the figure, the diverting pulley 13 has been positioned in an oblique position relative to the traction sheave. The diverting pulley 13 and the traction sheave 6 would not necessarily have to be rotated horizontally and/or tilted relative to the horizontal plane, but it is possible to do so if necessary.

Fig. 7 presents a simplified and diagrammatic side view of yet another counterweighted traction elevator in which a third the solution of the invention has been applied. In this solution, in addition to the solution according to Fig. 1, also the angle β of the portion 3a of the set of hoisting ropes 3 between the traction sheave 6 and the elevator car 1 relative to the vertical direction is varied as the elevator car 1 is moving in the elevator shaft. In Fig. 7, the elevator car is depicted with solid lines in its low position and with dotted broken lines in its high position. When the elevator car 1 is in its high position, angle β and the rope force F _c acting on rope portion 3a are at a maximum. Correspondingly, when the elevator car 1 is in its

low position, angle β and the rope force F _c acting on rope portion 3a are at a minimum.

The angle β of rope portion 3a shown in Fig. 7 can also be implemented by arranging for hoisting ropes 3a to run crosswise relative to themselves in the manner illustrated in the Figs. 2-6. In this case, the hoisting ropes 3a going obliquely downwards from the traction sheave 6 first pass around the diverting pulley 11 placed on the elevator car 1 horizontally farther away from the traction sheave 6 and only then around the diverting pulley 12 placed horizontally closer to it, from which 12 the hoisting ropes 3a go obliquely upwards to their point of anchorage 10. In the solution with the hoisting ropes running crosswise relative to themselves, the elevator requires a narrower space in the sideways direction than in the solution represented by Fig. 7. In an arrangement according to this embodiment, too, the suspension of rope portion 3b can be implemented in the ways illustrated in Figs. 1-6.

A feature common to all the above-described embodiments of the invention is that the rope force Few of the hoisting ropes in the hoisting rope portion 3b between a rope sheave moving substantially vertically in the elevator shaft, such as the diverting pulley 13 of the counterweight 8, and a fixed rope sheave rotating in place either in the elevator shaft or machine room, such as the traction sheave 6, is varied as a function of the vertical distance between the vertically movable rope sheave 13 and the rope sheave 6 fixedly mounted in place. The said rope force F _C w is increased when the movable rope sheave 13 is moving vertically closer towards the rope sheave 6 fixedly mounted in place and, correspondingly, the said rope force F _C w is decreased when the movable rope sheave 13 is moving verti- cally farther away from the rope sheave 6 fixedly mounted

in place. The variation of the said rope force F _0W has been arranged to take place by varying the angle α of the hoisting ropes in the hoisting rope portion 3b between the movable rope sheave 13 and the rope sheave 6 fixedly mounted in place relative to the perpendicular position when the movable rope sheave 13 is moving vertically. The rope force

Few is increased by increasing the said angle α and, correspondingly, the rope force F _C w is decreased by decreasing the said angle α.

For the rope forces F _c in the portion 3a of the hoisting ropes 3 on the side of the elevator car 1, analogically exactly the same applies as was explained in the preceding paragraph, only in this case the angle concerned is β and the movable rope sheave is the second diverting pulley 12 of the elevator car.

In the method of the invention, the need for elevator compensating ropes is reduced in an elevator, particularly a traction elevator, said elevator comprising at least a hoisting machine 5 and an elevator car 1 suspended on and supported by a set of hoisting ropes 3 by means of at least rope sheaves (11, 12) serving as diverting pulleys, which elevator car 1 has been fitted to travel in a substantially vertical direction along guide rails 4, and a substantially vertically movable counterweight 8 provided with a rope sheave 13 and fitted to move along guide rails 9, said elevator additionally comprising at least one fixed rope sheave 6 rotating in place. In the method, the elevator suspension is so arranged that the rope force (F _c , F _C w) of the hoisting ropes in the hoisting rope portion (3a, 3b) between a rope sheave (12, 13) moving substantially vertically in the elevator shaft and a fixed rope sheave 6 rotating in place is varied as a function of the vertical

distance between the vertically movable rope sheave (12, 13) and the rope sheave 6 fixedly mounted in place. The suspension can be arranged according to one of the alternatives represented by Figs. 1-7. If it is desired that the roping arrangement will be advantageous in respect of space utilization, the suspension can be arranged in such manner that the movable rope sheave is on its path of movement at a horizontal distance from the rope sheave fixedly mounted in place and that the hoisting ropes coming to the rope sheave from above and those going up from the rope sheave cross each other above the rope sheave. By this method, the elevator can be implemented without the use of compensating ropes. The method is applicable for use inter alia in modification of the compensating rope arrangement of an exist- ing elevator. By this method, an elevator that has already been in use for a long time can be modernized and i.a. its energy efficiency improved as the amount of the masses to be accelerated is reduced due to the lighter weight / elimination of the compensating ropes. The electric motor used in modernization is preferably of the so-called regenerative type. Using this method, the weight of the compensating ropes of an elevator to be modernized can be reduced or they can even be removed altogether.

The methods and arrangements described above are designed for use preferably in passenger elevators, e.g. elevators in residential apartment buildings. The elevator preferably has a hoisting height of over 30 meters, because in elevators with a hoisting height of this order compensating ropes have traditionally been required. However, the most preferable hoisting height is 40-60 meters, because, by applying the proposed arrangement/method, an elevator having a hoisting height of 40-60 meters can even be implemented without using compensating ropes at all if desirable.

It is obvious to a person skilled in the art that different embodiments of the invention are not exclusively limited to the examples described above but that they may be varied within the scope of the claims presented below. Thus, for example, the reduction of the differences in the rope forces between the traction sheave and the counterweight by means of the aforesaid angle can also be implemented by variation of the rope angles at the traction sheave and elevator car instead of variation of the rope angles at the counterweight pulley.

It is also obvious to a person skilled in the art that the suspension of the counterweight or elevator car need not necessarily be symmetrical, in other words, the angles α on either side of the counterweight pulley and, correspondingly, the angles β on either side of the elevator car need not be of mutually equal size, but the angles α and β situated farther away from the traction sheave may also have a zero value, in which case the outermost portions of the set of hoisting ropes will be substantially perpendicular.

It is likewise obvious to a person skilled in the art that, instead of the traction sheave, the fixed rope sheave rotating in place may also be an ordinary diverting pulley, in which case the traction sheave is disposed at some other point in the structure.

It is further obvious to a person skilled in the art that it is also possible for the hoisting ropes to be arranged to run crosswise in other ways than those described above.

It is further also obvious to a person skilled in the art that the invention can as well be used with other suspension ratios and in suspensions of other types than those

described in the examples. Thus, for example, the number and disposition of diverting pulleys may vary from those described above. It is likewise obvious that the invention can be applied using an arrangement where the elevator car and counterweight are suspended with different hoisting ratios, for example so that the elevator car is suspended with 1:1 ratio and the counterweight is suspended with 2:1 ratio in one of the ways illustrated in Figs. 1-7.