METHOD AND APPARATUS FOR DETECTING THE POSITION OF AN ELEVATOR

Abstract

An elevator system (1) includes a load sensor (4, 24, 34, 44), a flexible member (2, 18, 22) and an elevator unit (10, 20, 28) arranged to move vertically in a hoistway. The system is arranged such that the load sensor (4, 24, 34, 44) detects a load from at least a fraction of the flexible member (2, 18, 22) and the fraction of the flexible member (2, 18, 22) that applies load to the load sensor (4, 24, 34, 44) changes as the elevator unit (10, 20, 28) moves vertically in the hoistway. The system further includes a non-volatile memory, arranged to store load conversion information for converting the detected load into an elevator unit position.

Claims

1. An elevator system (1) comprising: a load sensor (4, 24, 34, 44); a flexible member (2, 18, 22); an elevator unit (10, 20, 28) arranged to move vertically in a hoistway; the load sensor, flexible member and elevator unit being arranged such that the load sensor (4, 24, 34, 44) detects a load from at least a fraction of the flexible member (2, 18, 22); and arranged such that the fraction of the flexible member (2, 18, 22) that applies load to the load sensor (4, 24, 34, 44) changes as the elevator unit (10, 20, 28) moves vertically in the hoistway; and further comprising a non-volatile memory, arranged to store load conversion information for converting the detected load into an elevator unit position.

2. The elevator system (1) of claim 1, wherein the flexible member comprises a suspension element (18), arranged to suspend the elevator unit (10, 20, 28).

3. The elevator system (1) of claim 1, wherein the flexible member has a first end attached to the elevator unit (10, 20) such that as the elevator unit (10, 20) travels vertically in the hoistway (8) the length of the flexible member (12, 22) hanging from the elevator unit (10, 20) varies.

4. The elevator system (1) of claim 1, wherein the load detected by the load sensor (4, 24, 34, 44) has a substantially linear relationship with the length of the flexible member (12, 22).

5. The elevator system (1) of claim 1, wherein the flexible member comprises a flexible member that has a first end attached to the elevator unit (10, 20) such that as the elevator unit (10, 20) travels vertically in the hoistway (8) the length of the flexible member (12, 22) hanging from the elevator unit (10, 20) varies, and wherein the load detected by the load sensor (4, 24, 34, 44) has a positive relationship with the length of the flexible member (12, 22) hanging from the elevator unit (10, 20).

6. The elevator system (1) of claim 1, wherein the load comprises the weight of the flexible member (12, 22) hanging from the elevator unit (10, 20).

7. The elevator system (1) of claim 1, wherein the load comprises the weight of the elevator unit (10, 20) and the weight of any passengers and/or cargo, and wherein the elevator system (1) is arranged to measure, in use, the load of passengers and/or cargo within the elevator unit (10, 20), and to store the load of the passengers and/or cargo in the non-volatile memory.

8. The elevator system (1) of claim 1, wherein a compensation flexible member (27) is attached to the elevator unit (10, 20, 28), and the load includes the weight of the compensation flexible member (27) hanging from the elevator unit (10, 20, 28).

9. The elevator system (1) of claim 1, wherein the conversion information comprises load calibration values which represent the load, detected by the load sensor (4, 24, 34, 44) in at least two elevator positions, and wherein the non-volatile memory is arranged to store the load calibration values and the corresponding elevator unit position information.

10. A method of sensing the position of an elevator unit (10, 20, 28) arranged to move vertically in a hoistway, comprising: detecting, by a load sensor (4, 24, 34, 44), a load which depends on at least a fraction of a flexible member (12, 18, 22), wherein the fraction of the flexible member (12, 18, 22) that applies load to the load sensor (4, 24, 34, 44) changes as the elevator unit (10, 20, 28) moves vertically in the hoistway; reading from a non-volatile memory conversion information for converting the detected load into an elevator unit position and thereby determining the elevator unit position.

11. The method of claim 10, wherein the flexible member (12, 22) has a first end attached to the elevator unit (10, 20) such that as the elevator unit (10, 20) travels vertically in the hoistway (8) the length of the flexible member (12, 22) hanging from the elevator unit (10, 20) varies and the load depends on the length of the flexible member (12, 22) hanging from the elevator unit (10, 20, 28).

12. The method of claim 10, wherein the load detected by the load sensor (4, 24, 34, 44) has a substantially linear relationship with the length of the flexible member (12, 22).

13. The method of claim 10, wherein the flexible member comprises a flexible member that has a first end attached to the elevator unit (10, 20) such that as the elevator unit (10, 20) travels vertically in the hoistway (8) the length of the flexible member (12, 22) hanging from the elevator unit (10, 20) varies, and wherein the load detected by the load sensor (4, 24, 34, 44) has a positive relationship with the length of flexible member (12, 22) hanging from the elevator unit (10, 20).

14. The method of claim 10, wherein the load comprises the weight of the elevator unit (10, 20) and the weight of any passengers and/or cargo, and wherein the method further comprises measuring, by the elevator system (1), of the load of any passengers and/or cargo, and storing the load of the passengers and/or cargo in the non-volatile memory.

15. The method of claim 10, wherein the method further comprises detecting the load in at least two elevator unit positions within the hoistway (8) to give load calibration values and storing these load calibration values in association with the corresponding elevator unit position information in the non-volatile memory.

Description

DRAWING DESCRIPTION

[0037] Certain preferred examples of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0038] FIG. 1 shows a first example of an elevator system according to the present disclosure.

[0039] FIG. 2 shows a second example of an elevator system according to the present disclosure, arranged in a 1:1 roping arrangement.

[0040] FIG. 3 shows a third example of an elevator system according to the present disclosure, arranged in a 2:1 roping arrangement.

[0041] FIG. 4 shows a fourth example of an elevator system according to the present disclosure, arranged in a 2:1 roping arrangement.

DETAILED DESCRIPTION

[0042] FIG. 1 shows an elevator system 1 according to the present disclosure. The elevator system includes an elevator car 10, arranged within an elevator hoistway (not shown). A load cell controller 6 is attached to the bottom surface of the elevator car 10, i.e. the surface nearest to the floor of the hoistway. A flexible member (which in this non-limiting example is a travelling cable 2, i.e. a cable that typically carries power and/or communications to/from the elevator car 10) is also attached to the bottom surface of the car 10 by a fixing bracket 12. The other end of the travelling cable 2 is connected to a structure within the hoistway, which is not shown in the Figure. For example, the travelling cable 2 could be connected to an elevator controller which could be fixed at the top of the hoistway. A load sensor 4 is fitted to the travelling cable at the end that is attached to the elevator car 10 so that it measures the load of the travelling cable 2 that hangs below the elevator car 10.

[0043] As the elevator car 10 moves up the hoistway, the length of travelling cable 2 hanging below the elevator car 10 increases, and therefore the load value read by the load sensor 4 will increase. Similarly, as the elevator car 10 descends in the hoistway, more of the cable weight will be suspended from the hoistway structure (not shown) holding up the left hand part of the cable 2 (as shown in the Figure), and therefore a smaller amount of cable 2 will be hanging below the car 10, and hence the reading of the load sensor 4 will decrease.

[0044] The principle of the present disclosure is to convert the detected or measured load from the load sensor and convert that into an elevator position based on stored conversion information. As discussed earlier, this could be via a stored formula or it could be achieved by measuring the load value at a plurality of different elevator car positions, and storing each load value and its corresponding elevator position within a memory. Then, in use, the load sensor 4 can measure the load of the travelling cable 4 hanging below the elevator car 10, compare this to the stored values, and can determine the position of the elevator car 10 to be the position which corresponds to the stored load value which is closest to the load value currently measured by the load sensor 4 or can determine the elevator car position more accurately by interpolating or extrapolating from the stored load values. For example, if the measured load is halfway between the load values measured at two adjacent floors, then the elevator system can establish that the elevator system is positioned halfway between these floors (in cases where the relationship is linear).

[0045] It will be appreciated that the principles described above apply equally to an example where the elevator car 10 is replaced with an elevator counterweight.

[0046] FIG. 2 shows an example of an elevator system according to the present disclosure. The elevator system is arranged in a 1:1 roping arrangement in which the suspension element 18 is connected directly between the elevator car 20 and the counterweight 28. The suspension element 18 could be one or more suspension ropes or cables or could alternatively be one or more belts, e.g. coated steel belts. This Figure shows the elevator car 20 located within the hoistway 8. Similar to FIG. 1, a travelling cable 22 is connected at a first end to the bottom surface of the elevator car 20, i.e. the surface closest to the floor of the hoistway 8. The travelling cable 22 is connected at its second end to an elevator controller 16. The elevator car 20 is suspended by suspension element 18 which connects at one end to the elevator car 20 and at the other end to a counterweight 28. The suspension element passes over a traction sheave 31 and a diverting sheave 33, which, together with the controller 16, are located within a machine room 35. A compensation chain 27 connects the bottom of the counterweight 28 to the bottom of the elevator car 20. A compensation chain 27 is present in many elevator systems, and connects the bottom surface of an elevator car 20 to a counterweight 28. It is arranged to compensate (or partially compensate) for the weight of the suspension element 18 which connects the top of the elevator car 20 and counterweight 28, such that the overall weight on either side of the drive traction 31 does not vary significantly during movement of the elevator car 20. In some elevator systems the compensation chain 27 compensates exactly for the weight of the suspension element 18. Alternatively in some examples the compensation chain 27 only partially compensates for the weight of the suspension element 18. Alternatively the compensation chain may be completely absent from the elevator system, leaving the weight of the suspension element totally uncompensated.

[0047] As the elevator car 20 moves within the hoistway, the combined weight of the suspension element 18 and the compensation chain 27 on each side of the traction sheave 31 and diverting sheave 33 remain substantially constant (or at least vary to a lesser extent than they would in the absence of the compensation chain 27), thus reducing risks of slippage.

[0048] In this example a load cell controller 26 is located on the top surface of the elevator car 20, i.e. the surface nearest to the ceiling of the hoistway 8, and a load cell 24 is connected to the suspension element 18, between the point at which the suspension element 18 is joined to the elevator car 20 and the point at which the elevator suspension element contacts the traction sheave 31. It will be appreciated that the load cell 24 should be arranged close enough to the elevator car 20 that it does not interfere with the traction sheave 31 even when the elevator car 20 is near the top of the hoistway 8.

[0049] In this example the load detected by the load cell 24 includes the weight of the travelling cable 22 hanging below the elevator car 20, together with the weight of the elevator car 20, the weight of any passengers within the elevator car 20 and the weight of the compensation chain 27 hanging below the car 20.

[0050] The weight of the elevator car 20 alone is a known value and can be stored in a non-volatile memory of the elevator system. During operation the elevator system can monitor and store the value of the weight of passengers within the elevator car 20. The weight of passengers and/or cargo changes during use of the elevator system, e.g. as passengers enter or exit the elevator car 20 at the various landings. However, the weight of passengers and/or cargo does not change between floors. Further, the elevator system can determine the change in weight that has occurred while it is stopped at a floor by measuring the weight again after the doors have closed (at which point no further changes in weight should occur until the next floor stop). This updated passenger/cargo weight can then be stored in the non-volatile memory before the elevator car 20 departs for the next floor. In the event of a power loss during travel the elevator system can then reload the stored passenger weight from the non-volatile memory when power is restored and use that information together with the data from the load cell 24 to immediately calculate its current position without having to perform a calibration run.

[0051] The weight measured by the load cell 24 therefore changes dependent on both the weight of the travelling cable 22 and the compensation chain 27, hanging below the elevator car 20 and the weight of the passengers and/or cargo. As the elevator car 20 travels up the hoistway 8, the length of both the travelling cable 22 and the compensation chain 27, hanging from the elevator car 20 increase, and therefore the load measured by the load cell 24 increases. The opposite is clearly true as the elevator car 20 descends in the hoistway 8.

[0052] In order to calculate the position of the elevator car 20 within the system, the elevator system first carries out a calibration run, in which the empty elevator car 20 travels to various positions within the hoistway 8, possibly to each floor. In each position the load cell 24 measures a load, preferably while the elevator car 20 is stationary. Optionally the weight of the elevator car 20 can be subtracted from each value. These load calibration values are then stored in a non-volatile memory of the elevator system. In use, the elevator system can determine its position by first taking a load measurement using its load cell 24. The known weight of the elevator car 20, and the load of the passengers and cargo (as stored in the non-volatile memory by the elevator system) are subtracted from the measured weight. The resulting value is then compared to the stored calibration values, and the closest calibration value identified. The position of the elevator car is either taken to be the position corresponding to the closest calibration load value, or can be interpolated or extrapolated from the stored values.

[0053] FIG. 3 shows an example of an elevator system according to the present disclosure. The elevator system is arranged in a 2:1 roping arrangement in which the ends of the suspension element 18 are fixed to the ceiling of the hoistway 8 via dead-end hitches. This Figure shows the elevator car 20 located within the hoistway 8. Similar to FIGS. 1 and 2, a travelling cable 22 is connected to the bottom surface of the elevator car 20, i.e. the surface closest to the floor of the hoistway 8. The travelling cable 22 is connected at its second end to an elevator controller 16. The elevator car 20 is suspended by suspension element 18 which attaches at one end to a dead-end hitch in the machine room 35, passes around a sheave of the elevator car 20, then passes over a traction sheave 31 and a diverting sheave 33, around a sheave of a counterweight 28, and attaches to another dead-end hitch in the floor of machine room 35. The traction sheave 31, the diverting sheave 33 and the controller 16 are located within the machine room 35. A compensation chain 27 connects the bottom of the counterweight 28 to the bottom of the elevator car 20.

[0054] A load cell 34 is arranged to detect the load in the suspension element 18 between the point at which the first end of the suspension element 18, nearest the elevator car 20, is fixed to the floor of the machine room 35, and the point at which the suspension element 18 meets the top of the elevator car 20. The load cell 34 is connected to a load cell controller 36.

[0055] In this example the position determination system works similarly to the system described with reference to FIG. 2. However, in this case, the load measured by the load cell 34 will depend on the weight of the travelling cable 22 hanging below the car 20, the weight of the compensation chain 27, the weight of the portion of suspension element 18 hanging below the load cell 34 and above the elevator car 20, the weight of the car 20 and the weight of any passengers and/or cargo within the car 20. As described above the weight of the compensation chain 27 may compensate for the weight of the suspension element 18, or may partially compensate for it. Alternatively the compensation chain may be completely absent in the elevator system leaving the weight of the suspension element totally uncompensated. Where the compensation chain 27 only partially compensates for the changing weight of the suspension element 18 there will still be a difference in weight as the elevator car 20 moves such that the total weight of all flexible members changes with the changing position of the elevator car 20.

[0056] As the elevator car 20 descends in the hoistway 8, less of the travelling cable 22 hangs below the elevator car 20. The compensation chain 27 is lifted by the counterweight 28, which rises, so that less of the compensation chain 27 hangs below the elevator car 20. As the elevator car 20 descends, the length of suspension element 18 hanging below the load cell 34 and above the elevator car 20 increases. If the decrease in the hanging length of compensation chain 27 fully compensates for the increased length of the suspension element 18 then the load measured by the load cell 34 depends only on the length of travelling cable 22 hanging below the elevator car 20. Otherwise, the load measured by the load cell 34 will depend on the travelling cable 22, the compensation chain 27 and the length of suspension element 18 hanging below the load cell 34.

[0057] The load cell 34 will also measure the weight of the elevator car 20 and the weight of any of its passengers and/or cargo, but these values are known to the elevator system (and stored in the non-volatile memory) and can be subtracted from the measured value as previously described. The weight of the empty elevator car 20 is a constant that can be measured once and stored in the system with the expectation that it will not change. The weight of the passengers and/or cargo can be monitored by the elevator system as previously described with reference to FIG. 2.

[0058] FIG. 4 shows another example of an elevator system according to the present disclosure. The elevator system is arranged in a 2:1 roping arrangement like that of FIG. 3. The elevator car 20 is located within a hoistway 8. A travelling cable 22 connects the bottom of the elevator car 20 to a controller 16, located within a machine room 35. A travelling cable 22 is connected to the bottom surface of the elevator car 20, i.e. the surface closest to the floor of the hoistway 8. The travelling cable 22 is connected at its second end to an elevator controller 16. The elevator car 20 is suspended by suspension element 18 which attaches at one end to a dead-end hitch in the machine room 35, passes around a sheave of the elevator car 20, then passes over a traction sheave 31 and a diverting sheave 33, around a sheave of a counterweight 28, and attaches to another dead-end hitch 50 in the floor of machine room 35. The traction sheave 31, the diverting sheave 33 and the controller 16, are located within the machine room 35. A compensation chain 27 connects the bottom of the counterweight 28 to the bottom of the elevator car 20. Alternatively the compensation chain could be completely absent in the elevator system leaving the weight of the suspension element totally uncompensated.

[0059] A load sensor 44 is connected to the suspension element 18, between the point 50, known as the dead-end hitch and the point where the suspension element 18 meets the top of the counterweight 28. The load cell, or load sensor 44, is controlled by load cell controller 46.

[0060] In this example the load measured by the load sensor 44 includes the weight of the counterweight 28, the weight of the compensation chain 27 which hangs below the counterweight 28, and also the weight of the length of suspension element 18 which hangs below the load sensor 44. As the elevator car 20 descends in the hoistway 8, the counterweight 28 rises, hence the length of compensation chain 27 hanging below the elevator car decreases and therefore the length of the compensation chain 27 hanging below the counterweight 28 increases. As the counterweight 28 rises, the length of suspension element 18 hanging below the load sensor 44 decreases. If the increased length of compensation chain 27 were compensated exactly by the decreased length of suspension element 18, then the weight measured by the load sensor 44 would be unchanged as the elevator car 20 travelled in the hoistway 8. Therefore, in this example in order for such an arrangement to successfully allow position determination of the elevator car 20, the compensation chain 27 is arranged so that the weight of the compensation chain 27 does not exactly compensate for the weight of the suspension element 18. Therefore, similarly to the previously described methods, weight of the counterweight 28 can be subtracted from the load measured by the load sensor 44, and the remaining weight will then depend on the position of the elevator car 20 within the hoistway 8 in such a way that the position of the elevator car 20 can be determined using load calibration values previously measured by the load sensor 44 during a calibration procedure and stored in a non-volatile memory as described above.

[0061] It will be appreciated that while certain examples above have been described with reference to a machine room, the principles described here work equally well in machine room-less elevators.

[0062] It will be appreciated by those skilled in the art that the invention has been illustrated by describing one or more specific embodiments thereof, but is not limited to these embodiments; many variations and modifications are possible, within the scope of the accompanying claims.