WO2011072725A1

WO2011072725A1 - Identification of a car position of an elevator

Info

Publication number: WO2011072725A1
Application number: PCT/EP2009/067213
Authority: WO
Inventors: Tapani Talonen; Tony Loftus
Original assignee: Kone Corporation
Priority date: 2009-12-15
Filing date: 2009-12-15
Publication date: 2011-06-23

Abstract

The present invention relates to a method for determining the position of a car (14) and/or counterweight of an elevator, in which method a cable (16) is suspended at the car and /or counterweight, the weight (Fs, Fc) of the cable is measured, and from the measured weight the position of the car and/or counterweight is determined. The invention also relates to an elevator implementing this car position identification. The invention allows particularly an easy replacement of existing old car position arrangements during modernization of elevators.

Description

IDENTIFICATION OF A CAR POSITION OF AN ELEVATOR

Field of the invention

The present invention relates to a method for determining the position of a car and/ or counterweight of an elevator and an elevator comprising an arrangement for determining the position of a car and/ or counterweight. Prior art

Currently, the position of the elevator car and/ or counterweight is identified via encoders mounted at the elevator car which are co-acting with counter elements located at the different floors on the elevator shaft. These counter- elements usually are provided as vanes or switches in each floor to provide mechanical interfaces for the encoder.

The disadvantage of these position identifying devices is the fact that they require installations of the counter elements in the elevator shaft which are to be adjusted along the path of the encoder travelling together with the elevator car. These counter elements require additional space in the elevator shaft, are expensive and their installation is time consuming and requires maintenance. Therefore, the known devices for determining the car position cause a permanent cost factor as these arrangements have to be monitored during the normal maintenance cycles of the elevator.

Object of the invention It is object of the present invention to provide a reliable and cheap method and arrangement to identify the position of a car and/ or counterweight in an elevator. Summary of the invention

According to the present invention this object is solved with a method according to claim 1 and with an elevator according to claim 10. Advantageous embodiments are a subject matter of the corresponding sub-claims.

The base idea of the present invention is the use of a cable which is suspended at the car and/ or counterweight as basis for the determination of the car and/ or counterweight position. The invention makes use of the fact that the weight portion of such a cable acting on its suspension points on the elevator car or counterweight or shaft wall changes according to the position of the elevator car in the elevator shaft, as it is apparent from figs, la and lb. These figures show the change of the weight portions F_c and F_s of the cable acting on its suspension points at the car and shaft wall depending on the car position.

This surprising and simple idea of identifying the position of any vertically movable component of the elevator, e.g. car and counterweight, can easily be installed, requires little or no maintenance and can preferably be used to substitute old position identifying arrangements in course of elevator moderniza- tions. The invention further doesn't hamper the access to any components in the shaft and doesn't need any adjustment work. Moreover, cables suspended at the car are regularly already existing in elevators e.g. as supply cables for establishing data transfer and supplying electricity to the elevator car. Other types of already existing cables are available as compensation ropes or -chains which are suspended between the car and the counterweight, particularly in elevator shafts of higher buildings to compensate the load imbalance caused by the very long and heavy hoisting ropes. These supply cables or compensation ropes are per se known and therefore not further described hereinafter. The advantageous use of these already existing cables as means to determine the car position reduces the effort for the implementation of the invention. In this case only a load sensor has to be provided in connection with the already existing cable, particularly in connection with the structure, which takes up the cable weight at the shaft wall and/ or the car/ counterweight and connecting that load sensor with an elevator control. No additional cable has to be provided in this case. Advantageously the load sensor is provided in connection with a hanger for the cable,

Of course, the invention can also be realised in cases where such cables are not existing in an (e.g. old and to be modernized) elevator. In this case also a cable particularly for the function of car position determination can be provided.

An elevator necessitates for the realization of the advantageous car position identification of invention following components:

- a cable being suspended at the car and/ or counterweight,

- a load sensor which is located in connection with the cable or its suspension structure for measuring the cable weight, - an elevator control to which the load sensor is connected, which elevator control is designed to derive a signal indicating the position of the car and/ or counterweight from the signal of the load sensor. General understanding of terms in the claims

In the claims and the description the term "cable" is used for any flexible longitudinal member which can be suspended from a car or counterweight of an elevator. This term therefore also comprises ropes, chains, belts and corre- sponding elements.

The invention is described hereinafter at the uppermost part by referring to a cable hanging from a car. It should be understood that the cable can also be suspended on the counterweight or any other elevator component moving vertically in an elevator shaft. Usually the car position is related to the counterweight position via the hoisting ropes. It should anyway be clear, that the position of both components can be identified with the invention even if they travel independent of each other. The term "elevator control" is hereinafter referred to as any kind of centralized or decentralized control means for at least one function of the elevator. This also includes sub-systems of the elevator control. The control unit also may comprise sub-components located in different parts of the elevator, e.g. in the elevator car or the elevator shaft, so they can be operated or integrated with any kind of centralised or decentralized elevator control unit. In case the elevator is arranged in connection with an elevator group the elevator control also be implemented in an elevator group control which takes over the control function for several elevators.

The functions of the elevator control described hereinafter, as e.g. comparator and memory may be implemented as hardware modules which can be connected to/ are already existent in an existing control means or as additional software-implemented functionality of an existing control means. Advantageously the elevator control is based on a microprocessor system with per se known 1/ O-ports. The above-mentioned functions of the elevator control re- garding the determination of the car position from the sensor signals can be provided on a printed circuit board.

Advantageous implementations of the invention These cables are generally fixed on one hand to the elevator car, usually at the lower side, particularly at the bottom thereof whereas the other end of the cable is regularly fixed to the other moving elevator component (counterweight or car) or to the shaft wall. Although a suspension at the bottom of the car is preferred because this requires only little space in the shaft and does not ham- per the access of components beside the car or counterweight, the cable can also be suspended at any point of the car or counterweight.

The other end of the cable should be fixed to the other component of the elevator moving in opposite direction (i.e. if the first end of the cable is fixed to the elevator car the second end of the cable is fixed to the counterweight and vice versa) or to a point connected with the shaft wall, i.e. the shaft wall itself or any structure which is connected to the shaft wall in a fixed manner. By this means the cable is not disturbing the overall layout of the elevator and does not hamper access to any parts of the elevator in the shaft pit.

Anyway, for realization of the invention it is already sufficient that the other end of the cable hangs loose from the car into the shaft pit. In this case the cable should have a length that it touches the ground when the car is at its highest position in the shaft. This means that the weight of the cable at the suspension point at the car (hanger) changes according to the vertical car position, because according to the vertical position of the car a larger or smaller portion of the cable is suspended at the car whereas the other portion lies on the ground.

Anyway for safety reasons it is to be preferred that a first end of the cable is suspended at the car or counterweight and a second end is suspended at the component moving in opposite direction, i.e. counterweight or car or at a point fixed to the shaft wall. In this case the load sensor providing the cable weight data is preferably located in connection with the first and/ or second end of the cable. The location at one end of the cable, usually in connection with the hanger at the car bottom, provides an comfortable possibility to con- nect the load sensor to existing data lines, as e.g. a serial data bus. On the other hand by locating the sensor at a cable end the weight change of the complete cable during the travel of the car is determined.

In this connection it should be mentioned that he term "end" of the cable re- lates to the cable part which is connected to a suspension point. Of course this must not be the real end of the cable. Supply cables are usually running from the car to a suspension point at the shaft wall from where they run further to the elevator control. In this case the term "end" relates to the cable part which is fixed to the suspension point, which takes up a portion of the weight of the cable hanging between this suspension point and the car. Preferably the position of the car and /or counterweight is obtained by comparing the measured weight from the load sensor with stored data comprising information about the relationship between the cable weight and the car /counterweight position. The stored data can easily be obtained by driving the elevator car along its path and measuring the cable weight portion acting on a load sensor at different car positions and storing these values as reference values. By this comparison the position of the car /counterweight can be obtained exactly, reliably and without much effort, as the corresponding functionality can easily added as hard- and/ or software implementation to an existing elevator control system.

In an advantageous embodiment of the invention a load sensor is located at both cable ends and the mutual relationship of the weight signals of the load sensors are used for determining the position of the car and/or counterweight. Hereby the dependence of obtained signal strength from the car posi- tion is boosted because the increase of one sensor signal is correlated with the decrease of the other sensor signal (See figs, la and lb). This already holds true, if the second end is fixed to the shaft wall. But is effect is further boosted when the cable is suspended between two elevator components moving in opposite direction (generally car and counterweight). If the signals are sub- tracted the use of the relationship of both sensor signals allows the compensation of a weight change of the cable based e.g. on dirt displacing on the cable over the time. Further, this embodiment with sensors at both cable ends al- lows a simple reliability test to monitor the correct function of each sensor by generating an alarm action if the mutual relationship between the sensor signals exceeds an allowed predetermined value range. Advantageously the invention allows a simple monitoring of the position identification arrangement. Thus, the value of the load sensor signal at a predetermined position of the car and/or counterweight can monitored over time. By this means the actual signal value at a predetermined position , e.g. the uppermost floor, can be monitored from time to time and be compared with at least one earlier value or reference value. By this comparison changes of the sensor behaviour, of the cable weight etc. can be determined. An alarm or maintenance action can then be initiated if the deviation of measured weight value from the earlier or reference value exceeds a predetermined range.

The monitoring or alarm function can advantageously be implemented by providing an alarm circuit in connection with the elevator control, which circuit provides an alarm action, e.g. to operate a switch in a safety circuit of the elevator, if a predetermined value range stored in a memory of the elevator control is exceeded by the weight signal of the load sensor or by the mutual relationship of the signals of at least two load sensors, or if a predetermined deviation of the measured signal(s) from a reference value is exceeded.

The position of the car and/ or counterweight can advantageously and easily be derived from the load sensor signal if the elevator control comprises a memory in which relationship data between the car/ counterweight position and the cable weight is stored and a comparator to derive the actual car /counterweight position from a comparison between the weight signal of the load sensor and the relationship data. The relationship data can be implemented as a calculation factor or as a reference table between cable weights and car positions which table may be established as reference table for a cer- tain elevator type or via test runs during or after set-up of the elevator.

A very reliable embodiment of the invention is provided for an elevator with counterweight. In this embodiment a first cable is located between the car and the elevator shaft and a second cable is located between the car and counter- weight. The load sensor can established in this embodiment in connection with either the first or second cable. Advantageously a load sensor is provided in connection with both cables, particularly one sensor in connection with the cable hanger at the counterweight. Via this measure redundant information about the position of the car as well as the position of the counter- weight is obtained.

The invention can easily be implemented with means to check up or correct the measured signal which is always affected by vibrations, acceleration or deceleration of the car etc. On this behalf advantageously a processing circuit is provided to generate a position signal from the sensor signal, which processing circuit has a filter means to eliminate dynamic load changes from the sensor signals. By this means vibrations can be filtered so as to obtain a smooth reliable signal allowing a more reliable and exact position determination.

Further the elevator control comprises advantageously a memory for correction data based on acceleration/ deceleration of the car and a subtracting means to add/ subtract that correction data to/ from the weight signal. The correction data can be determined in connection with test runs or in connection with the start up of the elevator system. The signal portion based on acceleration or deceleration is then stored as correction data, which is

added/ subtracted from the measured signal of the load sensor, thereby deriv- ing a very exact position signal almost unaffected of the car acceleration or deceleration.

Electric components to obtain a position signal from the signals of the load sensors are very cheap as only a small memory for reference data and a com- parator are used to compare the actual or signal value with the reference data to obtain a position signal.

Generally, the number of cables suspended at the bottom of the elevator car is not relevant with respect to their usage as a means for position indication. Therefore, it is also possible to use a fixing for several cables to which fixing the load sensor may be connected. It shall be further clear for the skilled person that the cables must not be connected to the bottom of the car or counterweight but can also be connected to another point e.g. a side wall or even the roof of the elevator car on the upper side or side wall of the counterweight. The cables must furthermore not be fixed with their ends to the car, counterweight or shaft wall.

It shall be further clear that the position identifying means according to the present invention can be used for any type of elevator as e.g. traction sheave elevator, winch type elevator, hydraulic elevator, linear motor elevator etc. For the skilled person it should be obvious that instead one load sensor several sensors or at least one sensor array can be used in connection with the cable or fixings of the cable at the car, counterweight and/ or shaft wall. A larger number of sensors may improve the redundancy of the system thereby improving the reliability.

The sensor signal of the load sensor can of course be used in different and per se known ways. For example, the signal of the load sensor may be used by the elevator control for the floor display in the lobby and/ or car.

Advantageously, the measured weight the position of the car is determined, e.g. by the elevator control, and communicated to the passenger. Thus the elevator car position, preferably the nearest floor of the car, at each moment can be determined and this information can be given to the passengers expressed in floor numbers. This solution provides easy add-on feature to be added in older elevators where previously no floor data has been informed to the passenger.

The car position is advantageously communicated to the passenger via a dis- play in the elevator car and/ or landing(s). This further refinement makes it possible that a floor-determining/informing device can be built as an independent add-on device, which does not require communication with / complicated connections to the old elevator main control. It only needs a power input or source. All said components can thus be installed immovably with respect to each other, e.g in unity of the car or in unity of the building (e.g. in sensors and control are fixed to shaft structures and the display fixed to a structure at the landing area). No communications via travelling cable is necessary (even though possible).

The measured weight signal of the load sensor or a position signal derived therefrom may be fed to an elevator group control to assist handling and/ or monitoring of elevators in an elevator group, in which case the wieght data can advantageously used for the control of an elevator group, e.g. for the call allocation. A load sensor to take up forces is per se known. This sensor may be an analogue or digital sensor which fits to the overall system of the elevator control. Preferably the sensor is able to provide digital a digital signal which can be transferred via a serial data bus. The load signals can be current signal data or voltage signal data which is converted in the elevator control into discrete floor data or distance data from a predetermined origin position.

Preferably, if via the elevator control discrete floor data shall be obtained from the load sensor signals a certain hysteresis of the allocation of the load sensor signal to discrete floor data values can be provided so when the system is switching to the next floor and returns to the previous floor there is a certain time limit before the floor number is changed back to the previous floor. This is eliminating impact of fluctuation in input coming from the load sensors due to any movement of the cable or the flexibility of the cable. The invention can be preferably used in any kind of modernization overlay group control for easily getting the floor level position information from an existing old elevator construction for a modern elevator control or group controller. The invention can also be used as a repair or modernizing kit for an old elevator construction where the old position identifying means is not working any longer.

The position data of the elevator can also be used in any kind of elevator group supervision system for getting position information about existing lifts. The invention can finally be used for fine tuning elevator starts by giving a signal comprising the cable weight information of the load sensors to the drive control to compensate for dynamic impact of the acceleration during the elevator start to the travelling cable weight. Finally the load sensor can also be provided in connection with the cable whereby sensor elements can be located at one point or at several points in the cable.

Particularly it shall be clear for the skilled person that the above mentioned advantageous implementations of the invention can be combined with the base idea of the invention as mentioned before or in the independent claims as well as with each other as long as these combinations are technically compatible, i.e. they are able to be realized together in connection with a base idea of the invention.

Brief description of the drawings The invention will hereinafter be described in examples by the aid of the enclosed schematic drawings. In these drawings show:

Figure la a side view of an elevator having a car identification arrangement comprising a cable suspended between the car bottom and the shaft wall showing the weight forces acting on the suspension points of the cable when the elevator car is in a lower part of the elevator shaft, and

Figure lb a side view according to figure la when the elevator car is in the top part of the elevator shaft.

Figure 2 a side view of an elevator car and counterweight comprising a car position identification arrangement with a first cable between the car and the elevator shaft wall and a second cable between the car and the counterweight, and

Figure 3 a schematic circuit of an elevator control comprising a processing circuit with a filter means and a subtraction unit.

Detailed description of the drawings

Figure la and lb are schematic diagrams of an elevator 10 with an elevator shaft 12 in which an elevator car 14 moves along a vertical path between an upper most and a lower most position. Figure la shows the elevator car 14 in its lower most position in the shaft 12, whereas Fig. lb shows the car in its up- permost position . At the bottom of the elevator car 14 a supply cable 16 is connected via a hanger 20 comprising a first load sensor 15 for measuring the load portion of the cable 16 which is supported by the car. The second end of the supply cable 16 is fixed to a mounting 18 connected to the elevator shaft 12, e.g. the shaft wall or any structure fixed thereto. In the mounting 18 a second load sensor 17 is provided which subjected to the weight portion of the suspended cable supported by the wall. The weight force F_c acting on the hanger 20 as well as the weight force F_s acting on the mounting 18 are shown with black arrows, the length thereof indicating the force intensity.

Figures la and lb show how the weight portions of the cable are shared between the hanger 20 and the mounting 18 in different positions of the car. Thus, when the car 14 is at its lower most position the weight portion Fc acting on the first sensor 15 in the hanger 20 of the elevator car 14 is low whereas the weight portion F_s acting on the second load sensor 17 in the mounting 18 is comparably high. The situation is vice versa when the elevator car is in its upper most position as shown in Fig. lb. In this case the weight impact Fs on the second load sensor 17 in the mounting 18 is comparably low whereas the weight impact Fc on the first load sensor 15 in connection with the hanger 20 on the 13 bottom of the elevator car 14 is comparably high.

For the realization of the invention it is sufficient that only one of those load sensors 15, 17 is provided, either the first load sensor 15 in connection with the hanger 20 under the elevator car 14 or the second load sensor 17 arranged in connection with the mounting 18 of the supply cable 16 at the shaft wall 12. Anyway, the inverse correlation between the signals of both sensors 15, 17 dependent on the car position can be used to obtain a signal which is stronger related to the car position than only one sensor signal. As a possible relation- ship the signals of both sensors 15, 17 can be subtracted or divided to boost the position dependence of the resulting signal.

Of course, for the determination of the position of the elevator and/ or counterweight the signal of only one of both sensors 15, 17 is sufficient as both sig- nals depend on the car and counterweight position.

From the sensor signal the car positions can be easily obtained by comparing the measured signal value with reference data comprising a relationship between a cable weight value and a car position.

It is apparent that instead of the position of the elevator car also the position of the elevator counterweight can be determined in the same manner. In elevators where a fixed correlation exists between the position of the elevator car and of the counterweight the position of the corresponding other component is automatically obtained if the position of one of both components is known. This is the fact for example in a traction sheave elevator as shown in figure 2.

Figure 2 shows a traction sheave elevator 30 wherein an elevator car 32 and a counterweight 34 are suspended via a hoisting rope 36 on a traction sheave 38 which is driven by an elevator motor (not shown). This elevator 30 is designed particularly for large hoisting heights. On that behalf a compensation cable 40 is connected via a first hanger 42 comprising a first sensor 44 to the elevator car 32 and via a second hanger 46 comprising a second load sensor 48 to the lower end of the counterweight 34. A supply cable 50 is fixed via a third hanger 52 comprising a third load sensor 54 to the elevator car and via a mounting 56 comprising a load sensor 58 to a shaft wall or a structure con- nected therewith.

The above embodiment provides four sensor signals, e.g. the signals of the first, second, third and forth load sensor 44, 48, 54 and 58 for the elevator control which can determine based on either of the load sensor signal and/ or via the relationship between the at least two sensor signals the position of the elevator car and the counterweight.

It is also possible to provide only two sensors in connection with one of both cables (compensation rope 40 or supply cable 50) to provide a redundant in- formation about the position of the elevator car or counterweight. Because each of the four sensors provides a load signal which is dependent on the position of the elevator car as well as the counterweight in the elevator shaft. The provision of one sensor at each end of a cable 50, 40 provides on the one hand a signal which is stronger depends on the position of the car or counter- weight. If e.g. the car moves upwards the load on the first load sensor 44 for the compensation rope 40 decreases while simultaneously the load on the second load sensor 48 of the counterweight increases. Therefore, the relation between both signals more clearly depends on the position of the car and counterweight. In the end by this means a more accurate determination of the posi- tion is possible. The same holds true with the third and forth load sensors 54 and 58 at both ends of the supply cable 50 although the increase of the sensibility of the reassure the signal sensors of both load sensors is not that high as in case of the load sensors connected to the car and counterweight which are both moving in opposite direction.

With respect to figure 2 it shall be clear that the type of elevator construction is not essential for the invention. Therefore, instead of a traction sheave drive also a winch drive could be used or any other kind of drive. Furthermore, in- stead of a 1:1 ration suspension ratio also other suspension ratios can be used for the car and counterweight. With respect to the compensation cable 40 it is only relevant that this compensation cable is not tightened by any tensioning means to a certain tension level because in this case the load acting on both ends of the compensation cable is no longer dependent on the car position.

Figure 3 shows a schematic structure of a processing circuit 60 as part of the elevator control 61 for determining the car position from a signal of a load sensor. This processing circuit 60 can be provided in connection with the central elevator control 61 or in form of separate modules which are connected and located at different places in the elevator shaft. This processing circuit 60 can also be provided as a module in an elevator group controller which includes the control for a number of several elevators.

The processing circuit 60 comprises two input lines 62, 64 which are connected with load sensors provided at both ends of a cable, e.g. the load sensors 15 and 17 in fig. 1, the first and second load sensor 44 and 48 in figure 2 or the third and forth load sensor 54 and 58 in figure 2. The load signals from these data line 62, 64 are fed to a filter means 66 which eliminates dynamic effects, e.g. vibrations from the load signal. Preferably this filter is a low pass filter. After passing the low pass filter 66 the signals are fed to a subtracting means 68 which is connected to the memory 70 of the processing circuit 60 via a data line 72. In the memory 70 load signal portions are stored which are caused by acceleration and deceleration of the car and these load signal portions are subtracted as correction data in the subtracting means 68 from the signals.

The signals fed to comparators 74 of the elevator control are now free from any signal portions based on dynamic effects like acceleration, deceleration and vibrations. The load signals are now compared in the comparator 74 with correlation in data stored in the memory 70 which provides for each signal value the corresponding position of the elevator car or counterweight from a reference table. The cable can comprise corresponding correlations of the sin- gle signals as well as the correlations for signal ratios of both signals coming via the data line 62, 64.

The position signal 76 thus obtained may be fed to the elevator control and/ or elevator group control for status monitoring of the elevator and/ or for the car and floor display of the car position.

In the embodiment of figure 3 the subtraction unit 68 is optional. The effect of acceleration and deceleration on the sensor signals can also be reduced by dis- regard a certain time period, e.g. one second, after the starting of the elevator car from a floor of the building and/ or with the beginning of deceleration of the car. Figure 3 shows one possibility of the use of the processing unit 60 in the elevator control 61 in connection with two sensor signals but the processing unit can also be used in the same way with only one signal obtained from one load sensor.

Further the filter means 66 is not obligatory to realize the invention but it is advantageous to obtain cleaner signals which are only dependant on the car position.

The invention is not restricted to the above embodiments but may be varied within the scope of the appended claims.

Claims

Claims:

1. Method for determining the position of a car (14) and/ or counterweight of an elevator,

in which method

- a cable (16) is suspended at the car and/ or counterweight,

- the weight (Fs, Fc) of the cable is measured, and

- from the measured weight the position of the car and /or counterweight is determined.

2. Method according to claim 1, wherein the position of the car and/or counterweight is obtained by comparing (74) the measured weight with stored data (70) comprising information about the relationship between the cable weight and the car/ counterweight position.

3. Method according to one of the preceding claims, wherein as the cable for the weight measurement a supply cable (16,50) of the car or a compensation rope or -chain (40) is used.

4. Method according to any of the preceding claims, wherein a first end of the cable is suspended at the car or counterweight and a second end is suspended at the counterweight or car or at a point fixed on the shaft wall,

and the weight signal from a load sensor (15, 17) is used, which is located in connection with the first and/ or second end.

5. Method according to claim 4, wherein a load sensor (15, 17) is located at both cable ends and that the mutual relationship of the weight signals of the load sensors are used for determining the position of the car and /or counterweight.

6. Method according to claim 5, wherein an alarm action is generated if the mutual relationship exceeds an allowed predetermined value range.

7. Method according to one of the preceding claims, wherein from the measured weight the position of the car is determined by the elevator control (60) and communicated to the passenger

8. Method according to claim 6 , wherein the car position is communicated to the passenger via a display in the elevator car and/ or landing(s).

9. Method according to one of the preceding claims, wherein the weight value at a predetermined position of the car and/ or counterweight is monitored and that an alarm or maintenance action is initiated if the measured weight value exceeds a predetermined value range.

10. Elevator comprising an arrangement for determining the position of a car (14; 32) and/or counterweight (34), characterised in that the elevator comprises:

- a cable (16; 40, 50) being suspended at the car and/ or counterweight,

- a load sensor (15, 17; 44, 48, 54,58) which is located in connection with the cable or its suspension structure (18, 20; 42, 46, 52, 56) for measuring the cable weight, - an elevator control (61) to which the load sensor is connected (62, 64), which elevator control is designed to derive a signal indicating the position of the car and/ or counterweight from the signal of the load sensor.

11. Elevator according to claim 10, wherein the elevator control (61) comprises a memory (70) with relationship data between the car /counterweight position and the cable weight and a comparator (74) to derive the actual car /counterweight position from a comparison between the weight signal of the load sensor and the relationship data.

12. Elevator according to claim 10 or 11, wherein the cable (16; 40, 50) is fixed at its first end to the car (14; 32) or counterweight (34) and at its second end to the counterweight (34) or car (14; 32) or to a point (18; 56) in connection with an elevator shaft (12).

13. Elevator according to claim 12, wherein a load sensor (15, 17; 44, 48, 54,58) is provided at each end.

14. Elevator according to any of claims 10 to 13, wherein the cable (16; 50) is a supply cable for the car or a compensation rope or - chain (40).

15. Elevator according to any of claims 10 to 14, wherein a first cable (50) is located between the car (32) and the elevator shaft and a second cable (40) is located between the car (32) and counterweight (34).

16. Elevator according to any of claims 10 to 15, wherein the elevator control (61) comprises an alarm circuit to provide an alarm action, e.g. to operate a switch in a safety circuit of the elevator, if a predetermined range of reference values or relationships of sensor values stored in a memory of the elevator control is exceeded by the weight signal or by the mutual relationship of the signals of at least two load sensors.

17. Elevator according to any of claims 10 to 16, wherein the elevator control (61) comprises a processing circuit (60) which is provided to generate a position signal from the sensor signal, which process circuit has a filter means (66) to eliminate dynamic load changes from the sensor signals.

18. Elevator according to any of claims 10 to 17, wherein the elevator control (61) comprises a processing circuit (60) having a memory (70) for correction data based on acceleration/ deceleration of the car and a subtracting means (68) to add /subtract that correction data to /from the signal of the load sensor (15, 17; 44, 48, 54,58).