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The present invention relates to a traction sheave elevator having an elevator car and a counterweight suspended on elevator ropes which are driven by a traction sheave of a drive machine. The elevator has an elevator controller for the control of the elevator operation and the elevator controller has at least one door controller for operating a car door whereby the door controller is connected to a door status indicator indicating the open or closed status of the car door. Furthermore, the elevator has at least one load weighing device for the load of the elevator car. The elevator controller has a drive control which is connected with an elevator safety device which enables run of the elevator car only if a measured car load of the elevator is within a preset car load limit value.
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Current traction sheave elevators comprise a car load weighing device in connection with the elevator cabin. Generally, this car load weighing device is located between a frame of the elevator car and the elevator cabin which makes it possible to directly measure the load of the elevator car. The problem with this known solution is that in case of oversized elevator cabins, the provision of an efficient car load weighing device is difficult. In this case, multiple load weighing devices would have to be located under the elevator cabin in a quite homogeneous manner. This necessitates a lot of hardware effort and is quite expensive. The present invention intends to provide the elevator control and particularly a safety device of the elevator with a correct car load value so that it is able to immediately recognize an overload condition of the elevator car and can take appropriate measures to avoid an elevator run with an overloaded elevator car.
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The object of the invention is solved with a traction sheave elevator according to claim 1 and with a method accordingto claim 10. Preferred embodiments of the invention are also described in the description as well as in the drawings.
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According to the invention, at least one load weighing device is arranged to measure a force acting on the elevator ropes. Accordingly, the load of the elevator cabin but is measured by measuring the load acting on the elevator ropes. Such load weighing device could therefore be located in the rope anchorage, in a machine bed or bedplate of the drive machine or in a diverting pulley arranged in connection with the elevator car or with the counterweight. Further, the elevator controller has a load determination logic which is configured to calculate the car load from the output signal of the load weighing device considering the car position. The problem of measuring the load acting on the elevator ropes, for example at a rope anchorage, is that with one and the same car load, the force acting on the elevator ropes differs according to the position of the elevator car as the distribution of the rope mass on both sides of the traction sheave changes according to the position of the elevator car in the shaft. Accordingly, the load determination logic is in line with the invention configured to perform a calibration run by measuring the output signal of the load weighing device at at least two specified different height levels of the elevator car in the elevator shaft. By measuring the output signal of the load weighing device at these two different height levels in the calibration run, a sloped straight line is obtained from which it is possible to determine the car load at any location of the elevator car in the elevator shaft, which again makes it possible in normal elevator operation to calculate at any time the car load from the output signal of the load weighing device after the calibration has been performed.
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When measuring the output signals of the load weighing device at these two different height levels of the elevator car it is essential that the load of the elevator car is not changed in between. Accordingly, the load determination logic is configured to monitor the door status indicator as to indicate that the car door is continuously closed during the calibration run. Via this measure it is ensured that the car load is the same between the two measurements. From these two measured output signals, the load determination logic is then able to determine calibration data for the car position dependency of the output signal of the load weighing device for calculating a correct car load value, which is essential for the safety device of the elevator to avoid the run off the elevator car in an overload condition.
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The invention leads to an essential cost saving particularly in elevators which are large sized elevator cars as the hardware effort for performing the inventive car load determination is much less than with the known solutions measuring the load of the elevator cabin with regard to the frame of the elevator car.
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If during the calibration run a known load is loaded into the elevator car - which even can be no load at all - it is possible via the absolute levels of the output signals of the load weighing device as well as the sloped straight line indicating the position dependency of the output signal to get an exact car load value for all elevator positions and all car loads. In this connection it is clear for the skilled person that the elevator control and/or the safety device comprise a memory in which all relevant load data of the elevator is stored, as the net weight of the elevator car, the weight of the counterweight, the nominal load of the elevator, the mass of the elevator ropes etc..
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This is particularly safety-relevant as the safety device of the elevator is able to compare the calculated car load value with a preset car load limit value so as to enable or disable a car run. Via this measure, a run of the elevator car with an overloaded cabin can be effectively avoided. Such a run with overload could harm the elevator construction per se as well as persons in the car as well as in the vicinity of the elevator.
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In a preferred embodiment of the invention, the two height levels are the departure and the arrival floor of an elevator car run whereby the load determination logic is configured to start the calibration run with measuring the output signal of the load weighing device at the departure floor with the door status indicator indicating that the car door is already closed. And the calibration run ends with measuring the output signal of the load weighing device at the arrival floor when the door status indicator indicates that the car door is still closed. Via these measurements, the output signal of the load weighing device is obtained at the departure and arrival floor which makes it possible to determine the position dependency of the output signal of the load weighing device which again enables the calculation of the exact car load.
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In a preferred embodiment of the invention, the traction sheave elevator comprises two load weighing devices in force connection with the elevator ropes. Via this measure, two different output signals of the two load weighing devices are obtained for which via the invention the position dependency of the output signals can be established. Via comparison of the calibrated position dependency of the output signals of the at least two different load weighing devices, the proper function of the load weighing devices or of the parts of the load determination logic processing these output signals can be verified. This embodiment provides for a redundancy verification of the obtained output signals and the function of the processing circuits of the load determination logic to guarantee a proper calculation of the exact car load.
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Accordingly, the load determination logic is preferably configured to establish via the calibration run a relationship between the signals of both load weighing devices whereby the safety device is configured to disable a car run, if the relationship established by the calibration run is not met in the normal operation of the elevator. Thus, this parameter is an additional safety parameter for the proper function of all related hardware and software components which are involved in the determination of the correct car load via rope forces.
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Preferably, first and second of the at least two load weighing devices are arranged in connection with a rope anchorage of the elevator ropes. According to an alternative, still preferred embodiment, first and second of the at least two load weighing devices are located in connection with a bedplate of the drive machine.
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Alternatively, a first of the at least two load weighing devices is arranged in connection with a rope anchorage of the elevator ropes and a second of the at least two load weighing devices is located in connection with a bedplate of the drive machine. Via this measure, the force acting on one end of the elevator ropes and the rope force acting on the drive are measured which give specific information about the force distribution in the whole elevator rope system. If one end of the elevator ropes is fixed to the elevator car or to the counterweight, then via these two load weighing devices, the complete force acting on the elevator system is obtained so that the load measured by the load weighing device on the rope anchorage plus the rope measured on the bedplate is essentially constant. If both rope ends are anchored at the building, load weighing devices could be placed at both load anchorages and at the bedplate of the drive machine in which case also the whole force acting in the elevator system is obtained which should be constant with an unchanged load of the elevator car. Anyway, as this arrangement increases the hardware effort, this solution might be beneficial where a very high safe requirement prevails.
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Preferably, the signals of the at least one load weighing device are fed to two redundant parts of the load determination logic whereby the data from both parts of the load determination logic are compared to each other, and the safety device is configured to disable a car run if the position dependency of the car load value and/or the calculated car load value obtained from both parts of the load determination logic does or do not match. Via this redundancy measurement, it can be ensured that a failure of the signal processing of the output signals in the load determination logic can be effectively recognized and dangerous situations can be effectively avoided.
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In a preferred embodiment of the invention, the load determination logic is configured to perform at least two calibration runs and the safety device is configured to disable a car run if the position dependency of the car load value and/or the calculated car load value obtained in both calibration runs does or do not match. With this measure it can be ensured that the performed calibration runs are without a failure so that a failure in a calibration run does not have a negative impact on the calculation of a correct car load value.
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As already discussed above, preferably the calibration run is performed with a known car load whereby this known car load is considered by the determination logic in determining the position dependency of the weight signal and in the calculation of a correct car load value. This known car load can be even no load as the elevator system knows the loads prevailing in the elevator system which means the net weight of the elevator car (weight of the elevator car without load) as well as the load of the counterweights and via the position dependency of the output signal of the load weighing device also the rope mass portion of the elevator ropes measured by the load weighing device.
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The invention also refers to a method for obtaining car load data in a traction sheave elevator having an elevator car moving in an elevator shaft by means of elevator ropes driven by the traction sheave of a drive machine. In this method a load determination logic is used to calculate from the output signal of at least one load weighing device arranged in force connection with the elevator ropes calibration data for the position dependency of the output signal of the load weighing device for calculating a correct car load value. In this method, the output signal of the load weighing device is measured in a calibration run at at least two different car positions and the at least two output signals corresponding to the different car positions are used to establish calibration data for the car position dependency of the output signal of the load weighing device in order to calculate a proper car load value. With respect to the features and advantages of this method it is referred to the above description of the inventive traction sheave elevator.
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Generally, it is possible to provide at two specified points in the elevator shaft devices which could trigger an automatic measurement of the corresponding output signals of the load measuring device. Anyway, such a solution would necessitate additional hardware in the shaft to perform this measurement. Therefore, in a very simple and economic embodiment of the inventive method, the output signals of the load weighing device are measured during a car run at the departure floor and at the arrival floor of the elevator car whereby the car door is monitored to be continuously closed between the two measurements. The departure floor as well as the arrival floor are correlated to a fixed height level in the elevator shaft. Therefore, without requiring any additional hardware in the elevator, the measurement of the output signal of the load weighing device at two different height levels of the elevator car in the shaft can be easily performed so that even for large cabins this method provides a very economic and feasible way to obtain a correct car load without any load weighing devices between the car frame and the cabin of the elevator car. Consequently, the elevator can be in normal service mode during the calibration run. This means that the calibration run can actually be a normal elevator run wherein passengers are transferred from departure floor to arrival floor in accordance with service requests. Therefore there is no need to take the elevator out of service during the calibration, which decreases elevator downtime.
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Preferably, in normal operation of the elevator following the calibration run the car load value obtained by the invention is compared with a preset car load limit value preferably by the safety device and dependent on the comparison result, an elevator run is enabled or disabled by the safety device. This ensures a high safety level of the elevator system.
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In a preferred embodiment of the invention, a determination logic with two redundant parts is used to independently establish calibration data for the car position dependency of the output signal of the load weighing device and/or for a car load value calculated therefrom. An elevator run is then disabled if these data established by the two redundant parts of the determination logic do not match. Via this measure, the proper data processing of the load determination logic can be ensured and thus a high safety standard can be upheld with the inventive method. The safety can still be enhanced if the two redundant parts obtain the output signals of two different load weighing devices. In this case the two values obtained by the redundant parts are total independent and thus a proper function of the load weighing devices as well as the correlated hard- and software of the load determination logic can be verified. If the data provided by the two redundant parts does not match, a car run is immediately disabled. With this measure, an extremely high safety level can be obtained.
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It is apparent for the skilled person that the above features of the traction sheave elevator as well as for the method can be combined with each other arbitrarily as long as they are not contradicting.
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The invention will hereinafter be described by the schematic drawing in which
- Fig. 1
- shows a schematic drawing of a traction sheave elevator with an elevator car and a counterweight and two load weighing devices at a rope anchorage and at a bedplate of the drive machine,
- Fig. 2
- an operating diagram for the inventive method using a determination logic with two redundant parts, and
- Fig. 3
- a diagram with the output signal of a load weighing device with indication of the two measuring points of the output signals.
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Fig. 1 shows a traction sheave elevator 10 having an elevator car 12 as well as a counterweight 14 suspended on elevator ropes 16 which run over a diverting pulley 18 of a drive machine 20. One end of the elevator rope 16 is fixed to the building by means of a rope anchorage 22 whereby in connection with the rope anchorage 22 at least one, preferably at least two load weighing devices 24 are located.
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Fig. 1 also shows an alternative embodiment, wherein the drive machine 20 is supported on a bedplate 26 whereby in connection with the bedplate 26 at least one, preferably at least two load weighing devices 28 are located.
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The use of the output signals of the two load weighing devices 24, 28 to obtain a proper car load value is explained in Fig. 2.
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Fig. 2 shows a load determination logic 30 which is usually provided in connection with the elevator controller of the traction sheave elevator 10. The load determination logic 30 obtains the output signal of a door status indicator 32 indicating the open or closed status of an elevator car door. The load determination logic 30 is furthermore connected with the first and the second load weighing devices 24, 28.
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The load determination logic 30 has two redundant processing parts 34 and 36 which are each connected to a memory 38, 40 of the load determination logic 30. The outputs of the two redundant parts 34, 36 of the load determination logic 30 are further connected with an evaluation unit 42 to which also both memories 38 and 40 of the load determination logic can be connected. Both memories 38 as well as 40 comprise calibration data as well as elevator system data, for example the weight of the empty elevator car, the load of the counterweight, the length and mass of the hoisting ropes and possibly other parameters. Both processing parts 34, 36 read load weight values from their respective load weighing devices 24, 28 at the beginning and at the end of an elevator run and calculate the change between said values measured at the beginning and at the end of the run. The processing parts 34, 36 compare said change values, and if the change values match, the result can be considered reliable. If not, the elevator is taken out of service. The load weighing devices can then be calibrated by the processing parts 34, 36, by using the change values to compensate the change in the weight caused by car movement to the rope masses.
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Calibrated load weighing device can be used for overload detection with improved accuracy.
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At the beginning of a new elevator run the car is loaded at the departure floor, with the door open. When the door is closed and locked, both processing units 34, 36 read load weight information from their respective load weighing devices 24, 28. Weight information read is calibrated in the way described above, and the calibrated weight information is memorized by the processing units 34, 36. The memorized weight information is compared to an overload threshold by the processing units 34, 36 to monitor an overload situation. If neither unit indicates an overload situation, the mechanical brake can be opened to proceed with the new elevator run.
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The load determination logic 30 is calibrated in the following manner. Via the two weighing devices 24, 28 at the rope anchorage 22 and/or the bedplate 26, the two parts 34 and 36 of the load determination logic are fed with different output signals of the different load weighing devices 24, 28. In the two redundant parts 34, 36 of the load determination logic 30 the output signals of both load weighing devices 24, 28 is measured at the begin of an elevator run, preferably of an empty elevator car, when the monitored door status indicator 32 shows that the car door is already closed. Now, the calibration run is performed whereby the output signals of the load weighing device 24, 28 are stored in the two independent memories 38, 40 of the load determination logic 30. Accordingly, the signal processing of the output signals of the two load weighing devices 24, 28 is performed completely separated and thus completely redundant. When the elevator car has arrived at the arrival or destination floor, the output signals of the load weighing devices 24, 28 are again measured via the two parts 34, 36 of the load determination logic 30, as long as the door status indicator 32 indicates that the car door(s) is still closed. Again this load data is stored in the corresponding memories 38, 40 of the load determination logic 30. The both redundant parts 34, 36 of the load determination logic 30 are separated data processes on a microprocessor basis. Via these parts 34, 36 the position dependency of the output signals of the load weighing devices 24, 28 is recognized and under consideration of the stored system data in the memories 38 and 40 the correct car load is calculated by the redundant parts 34, 36.
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An evaluation unit 42 compares the output of the two redundant parts 34, 36 of the load determination logic 30 and if the out put data of these two parts 34, 36 match, the determination logic stores these data in its memory 38, 40 for the normal operation of the elevator. Accordingly, before the calibration data is used it is checked beforehand by the redundant parts with reciprocal comparison via the evaluation unit 42 whether the data established by the two parts 34, 36 in the calibration run fits and is thus evaluated as correct. Later on, during normal elevator operation the load determination logic is then able to calculate the correct car load value via the calibration data recorded in the memories 38, 40 during the calibration run.
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Of course, it is possible to provide a system without redundancy which only uses the data of one weight measuring device.
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It has to be added that in the arrangement of Fig. 1 by the output signals of the load weighing devices 24, 28 in the rope anchor and bedplate, the complete force acting on the elevator ropes 16 in the elevator system 10 is obtained so that in this case by adding the values of the two load weighing devices, the car load is directly available considering the net weight of the elevator car, the rope weight and the weight of the counterweight.
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Fig. 3 shows the course of the output signal of a load weighing device 24 during a calibration run. The time t1 designates the time point of departure of the calibration run and the corresponding load value is m1. The elevator moves for example upwards in which case the load m2 at the arrival floor at the time point t2 is lower than at the departure floor, giving information about the rope mass portion of the output signal. Via the slope s of the straight line of the output signal of the load weighing device 24, the exact car load can be calculated at any position in normal elevator operation.
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It is apparent for the skilled person that the described embodiments are not delimiting for the scope of the present invention. The embodiments of the invention may vary within the scope of the dependent patent claims.
List of reference numbers:
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- 10
- traction sheave elevator
- 12
- elevator car
- 14
- counterweight
- 16
- elevator ropes
- 18
- traction sheave
- 20
- drive machine driving the traction sheave
- 22
- rope anchorage at the building
- 24
- first load weighing device at the rope anchorage
- 26
- machine bed of the drive machine
- 28
- second load weighing device at the machine bed
- 30
- load determination logic
- 32
- door status indicator of the car door(s)
- 34
- first of two redundant processing parts of the load determination logic
- 36
- second of two redundant processing parts of the load determination logic
- 38
- first memory of the load determination logic connected to the first redundant part
- 40
- second memory of the load determination logic connected to the second redundant part
- 42
- evaluation unit of the load determination logic comparing the outputs of the two redundant parts of the load determination logic
- 44
- safety device of the traction sheave elevator
- t
- time axis
- t1
- time at the start of the calibration run at the departure floor
- t2
- time at the end of the calibration run at the arrival/destination floor
- m
- weight signal of the load weighing device displaying relative mass = measured car load / load capacity of the elevator
- m1
- weight signal at the start of the calibration run at the departure floor
- m2
- weight signal at the end of the calibration run at the arrival/destination floor
- s
- slope or gradient of the straight line of the weight signal between the two measurement points at t1 and t2