The present invention relates to an elevator as de¬ fined in the preamble of claim 1 and to a method as defined in the preamble of claim 10 and to a use as defined in the preamble of claim 13.

One of the objectives in elevator development work is to achieve an efficient and economical utilization of building space. In recent years, this development work has produced various elevator solutions without ma¬ chine room, among other things. Good examples of ele¬ vators without machine room are disclosed in specifi¬ cations EP 0 631 967 (Al) and EP 0 631 968. The eleva¬ tors described in these specifications are fairly ef¬ ficient in respect of space utilization as they have made it possible to eliminate the space required by the elevator machine room in the building without a need to enlarge the elevator shaft. In the elevators disclosed in these specifications, the machine is com¬ pact at least in one direction, but in other direc¬ tions it may have much larger dimensions than a con¬ ventional elevator machine.

In these basically good elevator solutions, the space required by and placement of the hoisting machine lim¬ its the freedom of choice in elevator lay-out solu¬ tions. Some space is needed to provide for the passage of the hoisting ropes. It is difficult to reduce the space required by the elevator car itself on its track and likewise the space required by the counterweight, at least at a reasonable cost and without impairing the performance and operational quality of the eleva¬ tor. In the case of a traction sheave elevator without machine, room, mounting the hoisting machine in the elevator shaft is difficult, especially in a solution with machine above, because the hoisting machine is an object of fairly large size and weight. Especially in the case of larger loads, speeds and/or hoisting heights, the size and weight of the machine are a problem regarding installation, even so much so that the required machine size and weight have in practice limited the sphere of application of the concept of elevator without machine room or at least retarded the introduction of said concept in larger elevators. In modernization of elevators, the space available in the elevator shaft has often limited the sphere of appli- cation of the concept of elevator without machine room. Often, especially when hydraulic elevators have had to be modernized or replaced, it has not been practical to apply a roped elevator solution without machine room due to insufficient space in the elevator shaft, particularly when no counterweight has been used in the hydraulic elevator solution to be modern¬ ized/replaced. The drawbacks of elevators with coun¬ terweight are the cost of the counterweight and the space required for the counterweight in the elevator shaft. Drum driven elevators, which are nowadays rather seldom installed, have the drawbacks of heavy and complicated hoisting machines and their large power and/or torque requirement. Prior-art elevators without counterweight are exotic. So far it has not been technically or economically reasonable to make elevators without counterweight. One solution like this is disclosed in specification WO9806655. A recent international patent application discloses a feasible solution. In prior-art elevator solutions without counterweight, the tensioning of the hoisting rope is implemented using a weight or spring, and that is not an attractive approach to implementing the tensioning of the hoisting rope. Another problem with elevators without counterweight, when long ropes are used e.g. due to a large hoisting height or large suspension ra¬ tios used, is the compensation of rope elongations, and a further problem is how to maintain a sufficient friction between the traction sheave and the hoisting ropes. An additional problem is how to ensure the com¬ pensation and/or equalization of rope elongations and/or rope tensions, and/or how to ensure the reli¬ ability of the compensating device used. In an eleva¬ tor, especially an elevator without counterweight, a further problem is uncontrolled slackening of the hoisting ropes and the risk of the ropes getting tan- gled in a disturbance situation.

The aim of the invention is to achieve at least one the following objectives. On the one hand, it is an objective of the invention to develop the elevator without machine room so as to achieve more efficient space utilization in the building and in the elevator shaft than before. This means that the elevator should permit of being installed in a relatively narrow ele¬ vator shaft if necessary. On the other hand, it is an objective of the invention to eliminate dangerously large rope elongation. Another objective is to prevent uncontrolled slackening of the elevator hoisting ropes in a disturbance situation, such as e.g. in situations where the elevator car is driven onto the buffer or when the elevator car is stopped by the safety gear. An additional objective is to improve the reliability of the compensating device acting on the hoisting ropes and at the same time the reliability of opera¬ tion of the elevator.

The elevator of the invention is characterized by what is disclosed in the characterization part of claim 1, the method of the invention is characterized by what is disclosed in the characterization part of claim 10, and the use according to the invention is character¬ ized by what is disclosed in claim 13. Other embodi- ments of the invention are characterized by what is disclosed in the other claims. Inventive embodiments are also presented in the description part of the pre¬ sent 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 in respect of advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be super¬ fluous from the point of view of separate inventive concepts.

By applying the invention, one or more of the follow¬ ing advantages, among others, can be achieved: - control of the motion of the compensating device can be implemented in an easy and reliable manner by us¬ ing the invention — the friction characteristics of the elevator, espe¬ cially those of the traction sheave of the elevator are improved because the ratio Tχ/T2 between the rope tensions Ti and T2 acting over the traction sheave can be held constant more easily and accu¬ rately by means of the compensating device used in the elevator of the invention, especially in dynamic situations, and the ratio Ti/T2 can be adjusted by varying the weight of a diverting pulley/diverting pulleys - the dead load of the diverting pulley/diverting pul¬ leys of the compensating device together with possi- ble auxiliary weights and their suspension always tend to keep the rope force T2 acting on the hoist¬ ing rope portion below the elevator car at a high tension, which leads to an improved friction between the hoisting ropes and the traction sheave, espe- cially in a situation where the elevator starts mov¬ ing after the car has been driven onto the buffer — the propensity to slippage between the traction sheave and the hoisting ropes of the elevator of the invention is substantially reduced due to the im¬ proved friction characteristics achieve by means of the compensating device, — when the elevator starts moving, the dynamic proper¬ ties of the compensating device are better due to the force of inertia caused by the mass of the di¬ verting pulley of the compensating device and its possible auxiliary weights and suspensions, with the result that e.g. the hoisting rope portion below the elevator car behaves in a more stable manner when the elevator starts moving — the use of an additional force acting in the direc- tion of the first rope tension T1 used in the com¬ pensating device means that the additional force produced by the diverting pulley/diverting pulleys of the compensating device and their suspensions and possible auxiliary weights increases the second rope tension T2 in relation to the first rope tension Ti, so the ratio Tχ/T2 is more advantageous for the op¬ eration of the elevator — due to the dynamically better and more stable opera¬ tion of the compensating device, an impact of the compensating device's diverting pulley of a reduced force and speed against the buffer used as a slack- rope prevention means is achieved because the impact takes place in a direction against gravity — in the elevator and compensating device of the in- vention, the mass of the diverting pulleys of the compensating device as well as that of the possible auxiliary weights and suspensions are utilized to keep the ratio between the rope forces T1 and T2 better at a constant value - in the elevator of the invention, creeping of the elevator car in the starting and/or stopping situa¬ tion can be better prevented - the use of the compensating device in the elevator reduces the risk of the hoisting ropes getting tan¬ gled with other shaft equipment in situations where uncontrolled slackening of the hoisting ropes oc¬ curs, such as situations where the elevator car is driven onto the buffer or the safety gear of the elevator is activated - the service life of the elevator hoisting ropes is increased and the risk of failure is reduced as the motion of the hoisting ropes is kept better under control by the compensating device of the invention and its use - the reliability of the elevator is better in the elevator of the invention and the invention makes it easy to' ensure that the compensating device works in the desired manner.

The primary area of application of the invention is elevators designed for transporting people and/or freight. A normal area of application of the invention is in elevators whose speed range is about or below 1.0 m/s but may also be higher. For example, an eleva¬ tor traveling at a speed of 0.6 m/s is easy to imple¬ ment according to the invention.

In the elevator of the invention, normal elevator ropes, such as generally used steel wire ropes, are applicable. The elevator may use ropes of synthetic material and rope structures with a synthetic-fiber load-bearing part, such as e.g. so-called "aramid" ropes, which have recently been proposed for use in elevators. Applicable solutions are also steel- reinforced flat belts, especially because of the small deflection radius they permit. Particularly advanta- geously applicable for use in the elevator of the in¬ vention are elevator hoisting ropes twisted from e.g. round and strong wires. Using round wires, the rope can be twisted in many ways using wires of the same or different thicknesses. In ropes well applicable with the invention, the wire thickness is below 0.4 mm on an average. Well-suited ropes made from strong wires are those in which the average wire thickness is under 0.3 mm or even under 0.2 mm. For example, thin-wired and strong 4-mm ropes can be twisted relatively advan¬ tageously from wires such that the average wire thick¬ ness in the finished ropes is between 0.15 ...0.25 mm, the thinnest wires having a thickness even as small as 0.1 mm. Thin rope wires can easily be made quite strong. In the invention it is possible to use rope wires having a strength e.g. as high as about 2000 N/mm2. Appropriate rope wire strengths are 2100-2700 N/mm2. In principle, it is possible to use rope wires of a strength of about 3000 N/mm2 or even more.

In the elevator of the invention, which preferably is an elevator without machine room, the elevator car is at least partially supported by a set of hoisting ropes. The set of hoisting ropes comprises one rope or a number of parallel ropes. The elevator has a trac- tion sheave which moves the elevator car by means of the hoisting ropes. The elevator has hoisting rope portions going upwards and downwards from the elevator car, and the rope portions going upwards from the ele¬ vator car are under a first rope tension (Ti) and the rope portions going downwards from the elevator car are under a second rope tension (T2) . The elevator has a compensating device acting on the hoisting ropes to equalize and/or compensate the rope tension and/or rope elongation and/or to render the ratio of the first and the second rope tensions (Tχ/T2) substan¬ tially constant. Arranged in the compensating device is an auxiliary force acting in substantially the same direction with the first rope tension (T1) . The auxil¬ iary force is used to increase the second rope tension T2 in relation to the first rope tension Ti.

In the method of the invention, the elevator car is at least partially supported by means of a set of hoist¬ ing ropes comprising one rope or a number of parallel ropes. The elevator has a traction sheave which moves the elevator car by means of the hoisting ropes, and which elevator has hoisting rope portions going up¬ wards and downwards from the elevator car and the rope portions going upwards from the elevator car are under a first rope tension (Ti) and the rope portions going downwards from the elevator car are under a second rope tension (T2) - The elevator has a compensating de¬ vice acting on the hoisting ropes to equalize and/or compensate the rope tension and/or rope elongation and/or to render the ratio of the first and the second rope tensions (Ti/T2) substantially constant. In the method of the invention, an auxiliary force acting in substantially the same direction with the first rope tension Ti is produced by gravity.

By increasing the contact angle using a rope pulley that functions as a diverting pulley, the grip between the traction sheave and the hoisting ropes can be im¬ proved. This makes it possible to reduce the weight of the car and also to increase its size, thereby in¬ creasing the space saving potential of the elevator. A contact angle of over 180° between the traction sheave and the hoisting rope is achieved by using a diverting pulley or diverting pulleys. The compensating device, which compensates the rope elongation, maintains a suitable Ti/T2 ratio to ensure a grip between the hoisting rope and the traction sheave that is suffi- cient for the operation and safety of the elevator. On the other hand, it is essential for the operation and safety of the elevator that the rope below the eleva¬ tor car in an elevator solution without counterweight be kept at a sufficient tension. This can not neces- sarily be achieved using a spring or a simple lever, due to the motion or creeping of the elevator car as a result of elongation of the hoisting ropes.

In the following, the invention will be described in detail with reference to a few embodiment examples and the attached drawings, wherein

Fig. 1 is a diagram representing a traction sheave elevator without counterweight according to the invention and a compensating device ac¬ cording to the invention, and Fig. 2 is a diagram representing another traction sheave elevator without counterweight accord¬ ing to the invention and another compensating device according to the invention.

Fig. 1 presents a general illustration of a traction sheave elevator without counterweight according to the invention, provided with a compensating device accord¬ ing to the invention. The elevator is preferably an elevator without machine room and with the drive ma¬ chine 4 placed in the elevator shaft. The elevator presented in the figure is a traction sheave elevator with machine above and without counterweight, with an elevator car 1 moving along guide rails 2. In eleva¬ tors with a large hoisting height, the elongation of the hoisting rope involves a need to compensate the rope elongation, which has to be done reliably within certain allowed limit values. In respect of operation and safety of the elevator, it is essential that the hoisting rope portion below the elevator car be kept at a sufficient tension. In the rope elongation com- pensating device 24 presented in Fig. 1, a very long movement for compensating the rope elongation is achieved. This allows even very large rope elongations to be compensated, which is often not possible by us- ing simple lever or spring solutions. The compensating device 24 according to the invention presented in Fig. 1 maintains a constant ratio Ti/T2 between the rope tensions Ti and T2 acting over the traction sheave. In the case illustrated in Fig. 1, the Ti/T2 ratio is 2/1. With even suspension ratios above and below the eleva¬ tor car, the compensating- device 24 is fitted in the elevator shaft or in some other- corresponding appro¬ priate place not in conjunction with the elevator car, and with odd suspension ratios above and below the elevator car the compensating device 24 is fitted in conjunction with the elevator car.

In Fig. I1 the hoisting ropes run as follows: One end of the hoisting ropes 3 is fixed to a diverting pulley 26 and/or its possible suspension arrangement, said diverting pulley 26 being fitted to hang on a rope portion coming downwards from a diverting pulley 25, which . hoisting rope portion passes around diverting pulley 26 and goes further to the fixing point 29 of the second end of the hoisting rope 3 in the elevator shaft. The compensating device 24 is fitted in place in the elevator shaft. From diverting pulley 26, the hoisting ropes 3 go downwards and meet a diverting pulley 27 placed in the elevator shaft, preferably in the lower part of the elevator shaft below the eleva- tor car, passing around it along rope grooves provided on the diverting pulley 27. These rope grooves may be coated or uncoated, the coating used may be e.g. a friction-increasing material, such as polyurethane or some other appropriate material. All or some of the diverting pulleys of the elevator and/or its traction sheave may be coated with such material. From divert- ing pulley 27, the ropes go further upwards to a di¬ verting pulley 16 fitted in place in the upper part of the elevator shaft, and having passed around this pul¬ ley the ropes go further downwards to a diverting pul- ley 15 fitted in place on the elevator car. Having passed around this diverting pulley 15, the ropes come again upwards to a diverting pulley 14 fitted in place in the upper part of the elevator shaft, pass around it and go further downwards to a diverting pulley 13 fitted in place on the elevator car. Having passed around this diverting pulley 13, the hoisting ropes 3 go further upwards to a diverting pulley 12 fitted in place in the elevator shaft, and having passed around it the ropes 3 go further downwards to diverting pul- ley 11 on the elevator car, pass around it an go fur¬ ther upwards to a diverting pulley 10 fitted in place in the upper part of the elevator shaft. Having passed around diverting pulley 10, the hoisting ropes go fur¬ ther downwards to a diverting pulley 9 fitted in place on the elevator car, pass around it and go further up¬ wards in tangential contact with diverting pulley 7 to the traction sheave 5. Diverting pulley 7 is prefera¬ bly fitted near and/or in conjunction with the hoist¬ ing machine 4. Between diverting pulley 7 and the traction sheave 5, the figure shows Double Wrap (DW) roping, in which roping the hoisting ropes 3 go in tangential contact with diverting pulley 7 upwards to diverting pulley 5 and, having passed around the trac¬ tion sheave 5, the hoisting ropes return to diverting pulley 7, pass around it and go back to the traction sheave 5. In Double Wrap roping, when diverting pulley 7 is substantially the same size with the traction sheave 5, diverting pulley 7 may also function as a damping pulley. In this case, the ropes going from the traction sheave 5 to the elevator car 1 pass via the rope grooves of the diverting pulley 7 and the deflec- tion of the rope caused by the diverting pulley is very small. It could be stated that the ropes going from the traction sheave 5 to the elevator car and the ropes coming to it only run in "tangential contact" with diverting pulley 7. Such "tangential contact" functions as a solution for damping vibrations of the outgoing ropes and it can also be applied in other roping solutions. An example of other roping solutions is Single Wrap (SW) roping, wherein the diverting pul- ley is substantially the same size with the traction sheave and the diverting pulley is used as a "tangen¬ tial contact sheave" as described above. In the SW roping mentioned above, the ropes are passed only once around the traction sheave, so the contact angle of the rope on the traction sheave is about 180° and the diverting pulley is only used as an auxiliary wheel for "tangential contact" of the rope as described above and wherein the diverting pulley functions as a rope guide and a damping pulley suppressing vibrations or no diverting pulley 7 is provided at all. Diverting pulleys 16,15,14,13,12,11,10,9,7 together with the traction sheave 5 of the hoisting machine 4 form the suspension above the elevator car, which has the same suspension ratio as the suspension below the elevator car, which suspension ratio in Fig. 1 is 8:1. The first rope tension T1 acts on the hoisting rope por¬ tion above the elevator car. (T1)From the traction sheave 5, the ropes go further in tangential contact with diverting pulley 7 to diverting pulley 8, which is preferably fitted in place in the lower part of the elevator shaft. Having passed around diverting pulley 8, the ropes 3 go further upwards to a diverting pul¬ ley 18 fitted in place on the elevator car, and having passed around said diverting pulley 18 the ropes go further downwards to a diverting pulley 19 in the lower part of the elevator shaft and, having passed around this pulley, return to a diverting pulley 20 fitted in place on the elevator car. Having passed around diverting pulley 20, the hoisting ropes 3 go further downwards to a diverting pulley 21 fitted in place in the lower part of the elevator shaft, pass around it and go further upwards to a diverting pulley 22 on the elevator car. Having passed around diverting pulley 22, the hoisting ropes 3 go further downwards to a diverting pulley 23 fitted in place in the lower part of the elevator shaft, pass around it go further upwards to a diverting pulley 25 fitted in place on the elevator car, and having passed around it the hoisting ropes go further to the diverting pulley 26 of compensating device, and having passed around it the hoisting ropes go further to the fixing point 29 of their second end, which is located in a suitable place in the elevator shaft. Diverting pulleys 8,18,19,20,21,22,23,25,26 form the suspension and rope portion below the elevator car. The second rope ten- sion T2 of the hoisting rope acts on this hoisting rope portion below the elevator car. The hoisting ma¬ chine 4 and traction sheave 5 of the elevator and/or the diverting pulleys 7,10,12,14,16 in the upper part of the elevator shaft may be mounted in place on a frame structure formed by the guide rails 2 or on a beam structure at the upper end of the elevator shaft or separately in the elevator shaft or on some other appropriate mounting arrangement. The diverting pul¬ leys in the lower part of the elevator shaft may be mounted in place on a frame structure formed by the guide rails or to a beam structure placed at the lower end of the elevator shaft or separately in the lower part of the elevator shaft or on some other appropri¬ ate mounting arrangement. The diverting pulleys on the elevator car may be mounted in place on the frame structure of the elevator car 1 or to a beam structure or beam structures in the elevator car or separately on the elevator car or some other appropriate mounting arrangement. The diverting pulleys may also be of a modular construction, e.g. such that they are separate modular structures, such as e.g. cassette-type struc¬ tures, which are fitted in place on the shaft struc¬ ture of the elevator, on the structures of the eleva¬ tor car and/or car frame or in some other appropriate place in the elevator shaft or in its vicinity or in conjunction with the elevator car. The diverting pul¬ leys placed in the elevator shaft and the hoisting ma¬ chine equipment and/or the diverting pulleys fitted in place in conjunction with the elevator car may be placed either all on one side of the elevator car in the space between the elevator car and the elevator shaft or in a desired manner on different sides of the elevator car.

In the elevator presented in Fig. 1, the rope force equalizing sheave assembly 24 compensates rope elonga- tions by the movement of diverting pulley 26. The di¬ verting pulley 26 moves through a limited distance, thereby compensating elongations of the hoisting ropes 3. In addition, this arrangement keeps the rope ten¬ sion over the traction sheave 5 at a constant level, so that the Tl/T2 ratio between the first and the sec¬ ond rope tensions in the situation shown in Fig. 1 is about 2/1. The diverting pulley 26, which in Fig. 1 functions as a compensating wheel, may be guided by guide rails to keep it on its desired track of motion, especially in situations where the compensating device 24 receives a strong impact, such as the impact occur¬ ring when the safety gear of the elevator grips. By means of the guides of the diverting pulley 26, a de¬ sired distance between the elevator car and the com- pensating device and a controlled motion of the com¬ pensating device can be maintained. The guide rails of the compensating device may be almost any type of guide rails applicable for the purpose, such as e.g. guide rails made of metal or some other appropriate material, or e.g. guiding ropes. The compensating de- vice 24 may also comprise a buffer fitted in it to damp impacts against the diverting pulleys of the com¬ pensating device and/or to function as a device pre¬ venting slackening of the compensating device. The buffer 28 used is so fitted in place that the divert- ing pulley 26 remains supported by the buffer 28 be¬ fore the rope elongation of the hoisting ropes has been completely discharged into the ropes, especially into the rope portion above the elevator car. The ele¬ vator of the invention is designed with an aim to en- sure that when the normal compensation range of the compensating device is exceeded, the compensating de¬ vice is prevented from delivering rope from the com¬ pensating device in the direction of the rope portions below the elevator car, thus maintaining a certain tension in the hoisting ropes. In the compensating de¬ vice 24 of the invention, use is made of the mass of the diverting pulley and its suspensions as well as that of possible auxiliary weights and the auxiliary force produced by them, said auxiliary force acting in the same direction with the first rope tension Tx and (Ti)thus tending to increase the tension of the rope portion below the elevator car, in other words, the second rope tension T2 is increased preferably by the amount of the auxiliary force produced. The auxiliary force produced by the arrangement of the invention is preferably less than 15% of the first rope tension Ti, and a more advantageous range in which the best advan¬ tages are achieved is 5-10% of the first rope tension Ti. For example, if the total first rope tension Ti is about 3000 N, then using a diverting pulley weighing about 20 kg together with its suspension and auxiliary weight, which produces an auxiliary force in the di¬ rection of the first rope tension Ti due to gravity, the best possible advantages are achieved, and which arrangement is applicable for use preferably in DW roping of the traction sheave to ensure a frictional grip between the traction sheave and the hoisting ropes when a compensating device is used that main¬ tains a constant T1ZT2 ratio of about 2/1. Positive ef¬ fects on the operation of the elevator and its compen- sating device are already achieved by only slightly increasing the mass of the diverting pulley and the suspension, e.g. by using very light auxiliary weights of even less than 3 kg. However, the auxiliary force produced by the traction sheave, its suspension and auxiliary weights can not be increased too much in re¬ lation to the first rope tension T1 to ensure that the elevator and the compensating device used will work in the desired manner, because by increasing the auxil¬ iary force the friction between the traction sheave and the hoisting ropes is improved all the time while the T3VT2 ratio simultaneously approaches the value 1 but the rope forces are correspondingly increased con¬ tinuously. Besides by using the diverting pulleys of the compensating device and their suspensions, the re- quired auxiliary force can also be produced e.g. by replacing the auxiliary weights with a spring or some other arrangement applicable for the purpose. It is possible to implement the compensating device 24 in other ways besides that described in the example, such as e.g. by using more complex suspension arrangements in the compensating device, such as e.g. by providing different suspension ratios between the diverting pul¬ leys of the compensating device.

Fig. 2 presents another traction sheave elevator with- out counterweight according to the invention, in which elevator is also presented a second compensating device according to the invention. The elevator is preferably an elevator without machine room with a drive machine 204 placed in an elevator shaft. The elevator presented in the figure is a traction sheave elevator with ma- chine above and without counterweight and comprises an elevator car 201 moving along guide rails 202.

In Fig. 2, the hoisting ropes 203 run as follows: One end of the hoisting ropes is secured to the elevator shaft at point 227. From the fixing point 227 in the elevator shaft, the hoisting ropes 203 go upwards and meet a diverting pulley 228 fitted in the compensating device 224 and forming part of the compensating device 224 of the elevator, and having passed around this di¬ verting pulley 228 the hoisting ropes 203 go further downwards and meet a diverting pulley 223 placed in the elevator shaft, preferably in the lower part of the elevator shaft, below the elevator car, the rope being passed around this diverting pulley 223 along rope grooves provided on it. From diverting pulley 223, the ropes go further upwards to a diverting pulley 213 fit¬ ted in place in the upper part of the elevator shaft above the elevator car, and having passed around this diverting pulley the ropes go further downwards to a diverting pulley 213 on the elevator car, pass around it and go further upwards to a diverting pulley 212 fitted in place in the upper part of the shaft. Having passed around diverting pulley 212, the rope comes again downwards to a diverting pulley 211 fitted in place on the elevator car, and having passed around it the hoisting ropes go further upwards to a diverting pulley 210 fitted in place in the upper part of the shaft, and having passed around diverting pulley 210 the rope comes again downwards to a diverting pulley 209 mounted on the elevator car. Having passed around this diverting pulley the hoisting ropes go further up¬ wards to a diverting pulley 207 which is preferably fitted near the hoisting machine 204 or in conjunction with it. Between diverting pulley 207 and the traction sheave 205, the figure shows X wrap roping, wherein the hoisting rope runs crosswise with the rope portion go- ing from the diverting pulley 207 to the traction sheave 205 and the rope portion coming back from the traction sheave 207 to the diverting pulley 207. Di¬ verting pulleys 214,213,212,211,210,209,2077 together with the traction sheave 205 of the hoisting machine 204 form the' suspension of the rope portion above the elevator car, in which rope portion the suspension ra¬ tio is the same as the suspension of the rope portion below the elevator car, which suspension ratio in Fig. 2 is 6:1. In Fig. 2, the hoisting rope portion above the elevator car is acted on by the first rope tension Ti. From diverting pulley 207, the ropes go further to a diverting pulley 208 preferably fitted in place in the lower part of the elevator shaft e.g. on a car guide rail 202 or on the shaft floor or at some other suitable point. Having passed around diverting pulley 208, the ropes 203 go further upwards to a diverting pulley 218 fitted in place on the elevator car, and having passed around it they go further downwards to a diverting pulley 219 in the lower part of the elevator shaft, pass around it and return to a diverting pulley 220 fitted in place on the elevator car. Having passed around diverting pulley 220, the hoisting ropes 203 go further downwards to a diverting pulley 221 fitted in place in the lower part of the elevator shaft, and hav- ing passed around it the ropes go further upwards to a diverting pulley 222 fitted in place on the elevator car. Having passed around diverting pulley 222, the hoisting ropes go further to a diverting pulley 226 in the compensating device, and having passed around it the ropes 203 go further to a diverting pulley 225 fit¬ ted in place in the elevator shaft. Having passed around this pulley, the ropes come back to diverting pulley 226, to which the second end of the hoisting ropes is secured, the fixing point being preferably on the axle of the diverting pulley 226 at some other suitable point on the diverting pulley 226 or its sus¬ pension. Diverting pulleys 208,218,219,220,221,222 to¬ gether with the diverting pulley 226 fitted in place in the compensating device 224 form the suspension of the rope portion below the elevator car, in which rope por- tion the suspension ratio is the same as in the suspen¬ sion above the elevator car, this suspension ratio in Fig. 2 being 6:1. In Fig. 2, the rope portion below the elevator car is acted on by the second rope tension T2.

Fig. 2 presents an elevator according to the invention, in which elevator are also presented a different sus¬ pension arrangement in the compensating device and a different suspension ratio and at the same time a dif¬ ferent constant rope tension ratio than those presented in connection with Fig. 1. In Fig. 2, the compensating device 224 comprises diverting pulleys 228 and 226 im¬ movably fitted relative to each other and preferably placed in the same suspension arrangement, such as e.g. a box. The motion of the compensating device 224 com¬ pensates rope elongations and maintains a constant ra- tio between the rope tensions Ti and T2 acting over the traction sheave. The compensating device 224 presented in Fig. 2 keeps the Tx/T2 ratio between the first and the second rope tensions at about 3/2, due to the sus¬ pension arrangement presented with the compensating de- vice 224 in the figure. The suspension ratio of the compensating device in Fig. 2 is 3/2, from which also follows the ratio between the rope tensions. By varying the suspension ratio of the compensating device, it is also possible to implement different ratios between the rope tensions. A preferred embodiment of the elevator of the inven¬ tion is an elevator without machine room and with ma¬ chine above, which elevator has a drive machine with a coated traction sheave and thin and strong hoisting ropes of a substantially round cross-section. The con¬ tact angle of the hoisting ropes on the traction sheave of the elevator is greater than 180° and is preferably implemented using DW roping in the hoisting machine, which hoisting machine comprises a traction sheave and a diverting pulley, and in which machine the traction sheave and the diverting pulley are pre- fitted in a correct angle relative to each other. This hoisting machine is fitted in place on the elevator guide rails. The elevator is implemented without coun- terweight with a suspension ratio of 8:1 in such man¬ ner that both the suspension ratio of the ropes below the elevator car and the suspension ratio of the ropes above the elevator car are 8:1, and that the ropes of the elevator run in the space between one of the walls of the elevator car and the wall of the elevator shaft. The elevator has a compensating device that keeps the ratio between the rope tensions Ti/T2 as a constant ratio of about 2:1. The compensation distance required by the compensating device used about equals the distance corresponding to the elongation of the rope. The compensating device of the elevator is pro¬ vided with at least one slackening prevention unit for preventing uncontrolled slackening of the hoisting rope's and/or uncontrolled motion of the compensating device, said slackening prevention unit being prefera¬ bly a buffer. The compensating device utilizes an aux¬ iliary force generated by the masses of the diverting pulley and its suspension and of auxiliary weights connected to the diverting pulley, which auxiliary force acts substantially in the same direction with the first rope tension T1 and which auxiliary force increases rope tension T2, so that a more advantageous Ti/T2 ratio is obtained.

Another preferred embodiment of the' elevator of the invention is an elevator without counterweight in which the suspension ratio above and below the eleva¬ tor car is 10:1. This embodiment uses conventional elevator ropes, which preferably are ropes of a diame¬ ter of 8 mm, and a traction sheave made of cast iron at least in the area of the rope grooves. The traction sheave has undercut rope grooves and the contact' angle on the traction sheave has been fitted by means of a diverting pulley to be 180° or greater. When conven¬ tional 8-mm ropes are used, the traction sheave pref¬ erably has a diameter of 340 mm. The diverting pulleys used are large rope sheaves which, when conventional 8-mm hoisting ropes are used, have a diameter of 320, 330 340 mm or even more. The elevator is provided with a compensating device according to the invention.

It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the examples described above, but that they may be varied within the scope of the claims presented below. For example, the number of times the hoisting ropes are passed between the upper part of the elevator shaft and the elevator car and between the diverting pulleys in the lower part of the elevator shaft and the elevator car may be varied so that a desired sus¬ pension ratio both above and below the elevator car is achieved. Embodiments are generally so implemented that the ropes are passed to the elevator car as many times from above as from below, so that the suspension ratios in the suspension above and below the elevator car are the same. In accordance with the examples de¬ scribed above, the skilled person can vary the embodi- ment of the invention as the traction sheaves and rope pulleys, instead of being coated metal pulleys, may also be uncoated metal pulleys or uncoated pulleys made of some other material suited to the purpose.

It is further obvious to the person skilled in the art that the traction sheaves and rope pulleys made of metal or some other material appropriate for the pur¬ pose which function as diverting pulleys and which are coated with a non-metallic material at least in the area of their grooves may be implemented using a coat- ing material consisting of e.g. rubber, polyurethane or some other material suited to the purpose. In addi¬ tion, it is obvious to the person skilled in the art that during fast movements of the compensating device, which occur e.g. in a situation where the safety gear of the elevator grips, the auxiliary force according to the invention also produces in the rope force an inertia mass term that tends to resist the motion of the compensating device. The greater is the accelera¬ tion of the diverting pulley/diverting pulleys and possible auxiliary weights of the compensating device, the greater is the significance of the inertia mass caused by them and tending to resist the motion of the compensating device and reduce the impact against the buffer of the compensating device, because the motion of the compensating device takes place against the force of gravity.

It is obvious to the skilled person that the elevator of the invention can be implemented using as hoisting ropes almost any flexible hoisting means, e.g. a flexible rope of one or more strands, a flat belt, a cogged belt, a trapezoidal belt or some other type of belt suited to the purpose. It is obvious to the skilled person that, instead of using ropes with a filler, the invention can be implemented using ropes without a filler, which are either lubricated or unlu- bricated. In addition, it is also obvious to the skilled person that the ropes may be twisted in many different ways.

It is also obvious to the person skilled in the art that the elevator of the invention can be implemented using other types of roping between the traction sheave and the diverting pulley/diverting pulleys to increase the contact angle α than the roping arrange¬ ments described above as examples. For example, it is possible to arrange the diverting pulley/diverting pulleys, traction sheave and hoisting ropes in other ways than in the roping examples presented. It is fur¬ ther obvious to the skilled person that the elevator of the invention may also be provided with a counter- weight, in which elevator, for example, the counter¬ weight preferably has a weight below that of the car and is suspended on separate ropes, the elevator car is supported partly by the hoisting ropes and partly by' the counterweight and its roping.

Due to the bearing resistance of the rope sheaves used as diverting pulleys and the friction between the ropes and the rope sheaves and also to possible losses occurring in the compensating device, the ratio of the rope tensions may deviate somewhat from the nominal ratio of the compensating device. Even a 5-% deviation is not a significant detriment because the elevator must in any case have a certain in-built robustness. CLAIMS

1. An elevator, preferably an elevator without machine room, in which elevator the elevator car is at least partially supported by a set of hoisting ropes comprising one rope or a number of parallel ropes, and which elevator has a traction sheave which moves the elevator car by means of the hoist¬ ing ropes, and which elevator comprises rope por¬ tions of hoisting ropes going upwards and downwards from the elevator car, and the rope portions going upwards from the elevator car are under a first rope tension (Ti) and the rope portions going down¬ wards from the elevator car are under a second rope tension (T2), and which elevator has a compensating device acting on the hoisting ropes to equalize and/or compensate rope tension and/or rope elonga¬ tion and/or to render the ratio (Ti/T2) of the first and the second rope tensions substantially constant, characterized in that the compensating device comprises an arrangement producing an auxil¬ iary force acting substantially in the same direc¬ tion with the first rope tension (Ti).

2. An elevator according to claim 1, characterized in that the second rope tension (T2) has been in- creased in relation to the first rope tension (Ti) by utilizing the auxiliary force acting substan¬ tially in the same direction with the first rope tension (Tx).

3. An elevator according to claim 1 or 2, character- ized in that the compensating device of the eleva¬ tor comprises an auxiliary device fitted in it to produce the auxiliary force acting substantially in the same direction with the first rope tension (T1) .