WO2007075225A1

WO2007075225A1 - Calibration and adjustment method for elevation weighing device

Info

Publication number: WO2007075225A1
Application number: PCT/US2006/043971
Authority: WO
Inventors: Mitsuru Kato; Kensaku Yamane; Mitsuhiro Ichihara
Original assignee: Otis Elevator Company
Priority date: 2005-12-20
Filing date: 2006-11-13
Publication date: 2007-07-05
Also published as: JP2007168938A

Abstract

A method of adjusting an elevator weighing device (12) is provided to improve the operability of the elevator, while reducing costs. After a car (7) is fixed to a pit floor (14) via an adjustment load cell (15a), a braking force is released. Due to the weight on a side of a counterweight (8), a pulling force pulls the car (7) upward; this upward pulling force is pre-measured with the adjustment load cell. When the weighing device is adjusted, the car is fixed to the pit floor with a connecting chain and the braking force of brake (3) is released. As a result, the upward pulling force is applied to the load cell (10) of the weighing device. A gain coefficient and an offset value of the load cell are determined based on the output value of the load cell. The output characteristics of the weighing device are stored in an output characteristics storage part (11a).

Description

CALIBRATION AND ADJUSTMENT METHOD FOR ELEVATION WEIGHING DEVICE

BACKGROUND

[0001] The present invention relates to a method of adjusting an elevator weighing device. In particular, the present invention pertains to a method of adjusting a weighing device for a traction type rope elevator.

[0002] An elevator weighing device has a load cell that generates an output corresponding to the load applied to the car. The device stores the output characteristics of the load cell and computes the load from the value output by the load cell. Because of variation over years, however, there may be changes in the output characteristics of the load cell. As a result, to maintain the performance of the weighing device, the load cell must be appropriately adjusted. The weighing device is adjusted by applying a prescribed load to the load cell and reading the output value of the load cell so that the output characteristics of the load cell can be measured and compared to the value associated with the prescribed load. These output characteristics are stored in the weighing device.

[0003] In the prior art, a test weight has been loaded in the car as the means for loading the load cell. This method, however, requires much time and labor for carrying the test weight in and out of the car. The techniques described in Japanese Patent Application Nos. 2005-145620 and 2004-99303 take this problem into consideration.

[0004] According to the techniques described in Japanese Patent Application No. 2005-145620, the car and the pit floor are connected via an adjustment load cell such that the car is fixed, and the output of the adjustment load cell is monitored while the hoist motor is used to pull the car upward, so that a prescribed load is applied to the load cell of the weighing device. With the technique described in Japanese Patent Application No. 2005-145620, however, to measure the load applied to the load cell with the hoist, the adjustment load cell has to be carried in/out of the pit each time the weighing device is adjusted, thereby creating a complicated transporting operation. Further, as the adjustment load cell is expensive and as it is necessary to perform regular calibration to maintain the measurement precision, the costs associated with this approach are heightened.

[0005] According to the technology described in Japanese Patent Application No. 2004-99303, the car is fixed on the guide rail at the middle of the lift process such that the inherent weight of the principal rope from the hoist to the car and the inherent weight of the principal rope from the hoist to the counterweight are equal to each other. Then, the braking force of the brake is released so that the car is pulled upward by the counterweight and a load is applied to the load cell. As the weight of the counterweight is set to be equal to the weight of the car with a prescribed ballast load applied, after the release of the braking force, the same load as that when the ballast load is applied to the car is applied to the load cell. The output characteristics of the load cell are computed based on the balance load that is preset. Consequently, it is necessary to fix the car at the guide rail middle during the lift process such that the inherent weight of the principal rope from the hoist to the car is in balance with the inherent weight of the principal rope from the hoist to the counterweight. This operation, however, must be performed at an elevated location at which there is no place for the worker to stand. As a result, the operation is dangerous and cannot actually be adopted.

[0006] In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict conventional elevator weighing methods and devices. Specifically, the present invention aims to provide a method of adjusting an elevator weighing device that reduces the costs associated with the use of a test weight, adjustment load cell, and/or other special devices.

SUMMARY

[0007] An embodiment of the invention addresses a method of adjusting an elevator weighing device of an elevator car that is positioned in a hoistway and that is connected to a counterweight by a rope that is provided on a hoist that includes a brake for stopping the car, wherein the car includes a load cell that generates an output that corresponds to a load carried in the car. This method includes, among other possible steps: (a) performing a pre-measurement for the weighing device using a first connecting member that includes an adjustment load cell, wherein the first connecting member is connected to the car and to the hoistway, said step of performing a pre-measurement for the weighing device yielding an initial offset and an initial gain; (b) performing an adjustment for the weighing device using a second connecting member that is connected to the car and to the hoistway, said step of performing an adjustment for the weighing device yielding a revised offset and a revised gain; and (c) overwriting the stored initial offset and initial gain with the revised offset and revised gain. _

[0008] In a further embodiment of this method, the step of performing a pre-measurement for the weighing device may include the steps of: (i) obtaining a first output of the car load cell; (ii) stopping the car, using the brake, with the car suspended on one end of the rope and with the counterweight suspended on the other end of the rope; (iii) connecting the car and the hoistway using the first connecting member; (iv) obtaining a second output of the car load cell; (v) obtaining a first output of the adjustment load cell; (vi) releasing the brake; (vii) obtaining a third output of the car load cell; (viii) obtaining a second output of the adjustment load cell; (ix) determining and storing the initial offset for the weighing device; and (x) determining and storing the initial gain for the weighing device from the second and third outputs of the car load cell and the first and second outputs of the adjustment load cell.

[0009] hi another further embodiment of this method, the step of performing an adjustment for the weighing device may include the steps of: (xi) obtaining a fourth output of the load cell; (xii) stopping the car, using the brake, with the car suspended on one end of the rope and with the counterweight suspended on the other end of the rope; (xiii) connecting the car and the hoistway using the second connecting member; (xiv) obtaining a fifth output of the car load cell; (xv) releasing the brake; (xvi) obtaining a sixth output of the car load cell; (xvii) determining the revised offset for the weighing device; and (xviii) determining the revised gain for the weighing device from the fifth and sixth outputs of the car load cell and the first and second outputs of the adjustment load cell.

[0010] hi another further embodiment of this method, the initial offset may be determined to be the first output of the car load cell.

[0011] hi another further embodiment of this method, the initial gain may be determined by dividing the difference between the second and third outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

[0012] hi another further embodiment of this method, the revised offset may be determined to be the fourth output of the car load cell.

[0013] hi another further embodiment of this method, the revised gain may be determined by dividing the difference between the fifth and sixth outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

[0014] In another further embodiment of this method, the first connecting member may be connected to a lower portion of the car and to a pit floor of the hoistway. Similarly, the second ,

connecting member may be connected to a lower portion of the car and to a pit floor of the hoistway.

[0015] In another further embodiment of this method, the step of obtaining a first output of the car load cell may be performed while the car is unloaded. Similarly, the step of obtaining a fourth output of the car load cell may be performed while the car is unloaded.

[0016] hi another further embodiment of this method, the step of obtaining a first output of the car load cell may be performed while the car is located at a lower end of the hoistway. Similarly, the step of obtaining a fourth output of the car load cell may be performed while the car is located at a lower end of the hoistway.

[0017] hi another further embodiment of this method, the step of performing a pre-measurement may be performed during initial adjustment of the weighing device.

[0018] hi light of this method, when the car and the building structure are connected by the second connecting member and the braking force of the brake is released, the weight of the counterweight upwardly pulls the car with a predetermined pulling force that is applied to the load cell. Therefore, no special equipment is needed in the adjustment step, hi addition, as the car is fixed to the building structure near the bottom of the hoistway, the operator can operate in the pit safely.

[0019] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are hereafter briefly described. [0021] Figure 1 is a schematic diagram illustrating an embodiment of an elevator, which includes a load cell, according to the present invention;

[0022] Figure 2 is a graph illustrating the output characteristics of the load cell shown in Figure 1;

[0023] Figure 3 is a flow chart illustrating an embodiment of an initial adjustment procedure for the weighing device shown in Figure 1 ; .

[0024] Figure 4 is a schematic diagram illustrating the elevator of Figure 1, when the weighing device is initially being adjusted;

[0025] Figure 5 is a flow chart illustrating an embodiment of a subsequent adjustment procedure for the weighing device shown in Figure 1; and

[0026] Figure 6 is a schematic diagram illustrating the elevator of Figure 1, with the weighing device being subsequently adjusted.

DETAILED DESCRIPTION

[0027] Efforts have been made throughout the drawings to use the same or similar reference numerals for the same or like components.

[0028] Figure 1 is a schematic diagram illustrating an embodiment of an elevator, which includes a load cell, according to the present invention. The elevator is a traction rope type elevator. As shown in Figure 1, a hoist 1 has a hoist motor 2, a brake 3, a driving sheave 4, and a driving shaft 9. A principal rope 6 runs over the driving sheave 4 and a deflector wheel 5 that is arranged near the driving sheave 4. One end of the principal rope 6 is connected to a car 7 (which is suspended on the rope 6) and the other end of the principal rope 6 is connected to a counterweight 8 (which is also suspended on the rope 6). The power of the hoist motor 2 is transferred via the driving shaft 9 to the driving sheave 4. As the car 7 and the counterweight 8 are lifted, the brake 3 can apply a braking force to stop the rotation of the driving shaft 9 so that the car 7 and the counterweight 8 are stopped.

[0029] Here, the weight of the counterweight 8 is selected such that when a prescribed load is applied to car 7, the counterweight 8 has the same weight as that of the loaded car 7. In other words, the weight of the counterweight 8 is greater than the unloaded weight of the car 7. Consequently, when the car 7 is unloaded and is stopped by the braking force of the brake 3, to prevent an upward movement of the car 7, the brake 3 stops the driving shaft 9 from being rotated towards the side of the counterweight 8.

[0030] A load cell 10 is included between the principal rope 6 and the car 7. The load placed on the car 7 is applied to the load cell 10. The load cell 10 generates a voltage output nearly proportional to the load placed on the car 7; this output is sent to a weighing control part 11. A weighing device 12 is composed of the load cell 10 and the weighing control part 11. [0031] Figure 2 is a graph illustrating the output characteristics of the load cell shown in Figure 1. More specifically, the output voltage of the load cell 10 linearly increases along an ,

output characteristics line (a) as the load applied to the load cell 10 is increased. In other words, the slope of the output characteristics line (a) represents a gain coefficient G. When the car 7 is unloaded (i.e., when only the weight of the car 7 itself is applied to the load cell 10), the output voltage Vo of the load cell 10 has an offset value O. Consequently, the weighing control part 11 has a gain coefficient G and an offset value O, both of which are stored as the output characteristics of the load cell 10.

[0032] The gain coefficient G and the offset value O are stored in an output characteristics storage part 11a, which is part of the weighing control part 11. Based on the output voltage of the load cell 10, the load applied to the car 7 is computed by a load computing part 1 Ib, which is also part of the weighing control part 11. The load computing part 1 Ib performs the prescribed control and outputs the computed load applied to the car 7 to a principal control part 13. The principal control part 13 controls the operation of the driving motor 2 and the brake 3. Based on the computed load applied to the car 7, the control part 13 drives and stops the car 7 smoothly. Further, when the load exceeds a maximum load, the control part 13 may generate an alarm and/or stop operation. The output characteristics storage part lla stores the gain coefficient G and the offset value O after an initial adjustment is performed when the elevator is installed. The initial adjustment is performed as follows with reference to Figures 3 and 4. [0033] Figures 3 and 4 illustrate an embodiment of a method of initial adjustment of the weighing device shown in Figure 1. Figure 3 is a flow chart illustrating an embodiment of an initial adjustment procedure for the weighing device shown in Figure 1. Figure 4 is a schematic diagram illustrating the elevator of Figure 1, when the weighing device is initially being adjusted.

[0034] As shown in Figure 3, at step Sl, the unloaded car 7 is stopped. In step S2, the output voltage Vo of load cell 10 in this state is read. Then, in step S3, a lower portion of the car 7 and the pit floor 14 of the building itself are connected to each other by a connecting chain 15, as shown in Figure 4. The connecting chain 15 serves as a first connecting member with an adjustment load cell 15a included in the middle thereof.

[0035] The car 7 is fixed to the pit floor 14 at a prescribed position near the lower end of the hoistway such that upward movement of the car 7 is restricted. To connect the lower portion of the car 7 to the pit floor 14 with the connecting chain 15, for example, eyebolts may be screwed into the lower portion of the car 7 and the pit floor 14, respectively. Hooks may then be attached .

to the two ends of connecting chain 15, so that the eyebolts and the hooks may engage each other. Also, when the car 7 and the pit floor 14 are connected to each other, the connecting chain 15 may have a chain lock or other tension applying means included in it, so that a tension equal to the tension in the principal rope 6 maybe applied to connecting chain 15. [0036] While the car 7 is fixed to the pit floor 14, the output voltage Vl of load cell 10 is read in step S4. At the same time, in step S5, a load Pl applied to the adjustment load cell 15a is measured and the adjustment load cell 15a is pre-calibrated. Then, in step S6, the braking force of brake 3 is released. After the release of the braking force, the output voltage V2 of the load cell 10 is read is in step S7. At the same time, the load P2 applied to the adjustment load cell 15a is also measured in step S8.

[0037] As the brake 3 prevents the car 7 from upwardly moving in response to an otherwise downward movement of the heavier, counterweight 8, when the braking force of the brake 3 is released, the counterweight 8 upwardly pulls the car 7. At the same time, however, the upward movement of the car 7 is restricted by the connecting chain 15. Consequently, when the braking force of the brake 3 is released and the car 7 is upwardly pulled, the same load is applied to both the load cell 10 and the adjustment load cell 15 a. The offset value O and the gain coefficient G of the load cell 10 are then determined in steps S9, SlO. Subsequently, in step SI l, the determined offset value O and the gain coefficient G are written and stored in the output characteristics storage part 11a.

[0038] As shown in Figures 2 and 4, when the braking force of the brake 3 is released in process step S6, a pulling force ΔP is created that upwardly pulls the car 7. The pulling force is ΔP determined using the following formula:

Δ P = P 2 - P I

Under the load of the pulling force ΔP, the change in the output voltage ΔV of the load cell 10 is determined as follows: ώ v * V 2 — V 1 Consequently, the gain coefficient G of the load cell 10 is computed as follows:

G = i V/ i- P

The output voltage Vo becomes the offset value O of the load cell 10 plus the gain G multiplied by the load. As the gain coefficient G and the offset value O, as previously determined, are stored in the output characteristics storage part 11a, the load computing part 1 Ib can compute the ,

load applied to the car 7 based on the output voltage Vo, the gain coefficient G, and the offset value O.

[0039] As previously explained, the weighing device 12 performs the initial adjustment. However, long-term changes in gain coefficient G and the offset value O of the load cell 10 may lead to errors when the load computing part 1 Ib computes the load on the car 7. For example, when the car starts to move or is stopped, a jerk may occur, thereby leading to passenger unease and/or other problems. Correspondingly, it is desirable to monitor the weighing device 12 periodically and to adjust it, if necessary. Figures 5 and 6 illustrate an embodiment of a method of adjusting the weighing device 12. Figure 5 is a flow chart illustrating an embodiment of a subsequent adjustment procedure for the weighing device shown in Figure 1. Figure 6 is a schematic diagram illustrating the elevator of Figure 1, with the weighing device being subsequently adjusted.

[0040] As shown in Figure 5, an adjustment of the weighing device 12 may be performed using nearly the same procedure as the initial adjustment. As the pulling force ΔP is established in a pre-measurement step in the initial adjustment, there is no need to use the adjustment load cell 15a. Consequently, as shown in Figure 6, a connecting chain 16 is used without an adjustment load cell. The connecting chain 16 serves as a second connecting member for connecting the car 7 and the pit floor 14. An adjustment of the weighing device 12 is performed as follows. [0041] As shown in Figure 5, in step S21, the unloaded car is stopped in a lower portion of the hoistway. Then, the output voltage Vo of the load cell 10 is read in step S22. Subsequently, in step S23, the car 7 is fixed to pit floor 14 at the prescribed position (possibly in the manner previous described with respect to step S3 in Figure 4 but without an adjustment load cell) by connecting the lower portion of the car 7 to the pit floor 14 with the connecting chain 16. In this state, the output voltage V3 of the load cell 10 is read in step S24. Then, the braking force of the brake 3 is released in step S25 and the output voltage V4 of the load cell 10 is thereafter read in step S26. In steps S27 and S28, a revised offset value O' and a revised gain coefficient G' of the load cell 10 are determined using the pulling force ΔP that was previously measured in the initial adjustment. Further, in step S29 the offset value O and the gain coefficient G that were previously stored in the output characteristics storage part 1 Ia are replaced by the revised values O' and G'. ,

[0042] Consequently, as explained above, by performing an adjustment of the weighing device 12, the load computing part 1 Ib may compute the load applied to the car 7 based on the offset value O and the gain coefficient G of the load cell 10. Also, when the weighing device 12 needs to be adjusted (after the previous adjustment of weighing device 12), an adjustment of weighing device 12 may be performed in the same way as aforementioned.

[0043] With the method of the adjusting weighing device 12 herein described in which the weight on the side of counterweight 8 is used to generate pulling force a ΔP, the braking force of the brake 3 may be released while the car 7 and the pit floor 14 are connected to each other. Consequently, by pre-measuring the pulling force ΔP, there is no need to use a special device to adjust the weighing device 12 and, therefore, adjusting the weighing device 12 advantageously becomes both easier and cheaper.

[0044] The aforementioned method also presents additional advantages. For example, as the weight on the side of the counterweight is used to apply a load to the load cell 10, the reproducibility of the loading condition on the load cell 10 is good. In addition, as the car 7 is connected to the pit floor 14 at the lower end of the hoistway, the connection operation can be performed safely in the pit. hi addition, there is no need to use a specific device after measuring the pulling force and, therefore, the worker can perform the operation safely, more easily and at lower cost.

[0045] This application claims priority to, and hereby incorporates by reference in its entirety, Japanese Priority Application No. JP2005-365701, which was filed on December 20, 2005. [0046] The aforementioned discussion is intended to be merely illustrative of the present invention and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present invention has been described in particular detail with reference to specific exemplary embodiments thereof, it should also be appreciated that numerous modifications and changes may be made thereto without departing from the broader and intended scope of the invention as set forth in the claims that follow. For example, although connecting chains 15, 16 were used in the previously described embodiment as the first and second connecting members, one may also adopt connecting ropes and connecting rods, etc., instead of connecting chains 15, 16.

[0047] The specification and drawings are accordingly to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims, hi light of the foregoing .

disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the present invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of adjusting an elevator weighing device of an elevator car that is positioned in a hoistway and that is connected to a counterweight by a rope that is provided on a hoist that includes a brake for stopping the car, wherein the car includes a load cell that generates an output that corresponds to a load carried in the car, the method comprising the steps of: performing a pre-measurement for the weighing device using a first connecting member that includes an adjustment load cell, wherein the first connecting member is connected to the car and to the hoistway, said step of performing a pre- measurement for the weighing device yielding an initial offset and an initial gain; performing an adjustment for the weighing device using a second connecting member that is connected to the car and to the hoistway, said step of performing an adjustment for the weighing device yielding a revised offset and a revised gain; and overwriting the stored initial offset and initial gain with the revised offset and revised gain.

2. The method of claim 1, the step of performing a pre-measurement for the weighing device comprising the steps of: obtaining a first output of the car load cell; stopping the car, using the brake, with the car suspended on one end of the rope and with the counterweight suspended on the other end of the rope; connecting the car and the hoistway using the first connecting member; obtaining a second output of the car load cell; obtaining a first output of the adjustment load cell; releasing the brake; obtaining a third output of the car load cell; obtaining a second output of the adjustment load cell; determining and storing the initial offset for the weighing device; and determining and storing the initial gain for the weighing device from the second and third outputs of the car load cell and the first and second outputs of the adjustment load cell.

3. The method according to claim 2, the step of performing an adjustment for the weighing device comprising the steps of: obtaining a fourth output of the load cell; stopping the car, using the brake, with the car suspended on one end of the rope and with the counterweight suspended on the other end of the rope; connecting the car and the hoistway using the second connecting member; obtaining a fifth output of the car load cell; releasing the brake; obtaining a sixth output of the car load cell; determining the revised offset for the weighing device; and determining the revised gain for the weighing device from the fifth and sixth outputs of the car load cell and the first and second outputs of the adjustment load cell.

4. The method of claim 2, wherein the initial offset is determined to be the first output of the car load cell.

5. The method of claim 2, wherein the initial gain is determined by dividing the difference between the second and third outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

6. The method of claim 3, wherein the revised offset is determined to be the fourth output of the car load cell.

7. The method of claim 6, wherein the revised gain is determined by dividing the difference between the fifth and sixth outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

8. The method of claim 3, wherein the revised gain is determined by dividing the difference between the fifth and sixth outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

9. The method of claim 4, wherein the initial gain is determined by dividing the difference between the second and third outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

10. The method of claim 3, wherein the initial offset is determined to be the first output of the car load cell.

11. The method of claim 10, wherein the initial gain is determined by dividing the difference between the second and third outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

12. The method of claim 11, wherein the revised offset is determined to be the fourth output of the car load cell.

13. The method of claim 12, wherein the revised gain is determined by dividing the difference between the fifth and sixth outputs of the car load cell by the difference between the first and second outputs of the adjustment load cell.

14. The method of claim 1, wherein the first connecting member is connected to a lower portion of the car and to a pit floor of the hoistway.

15. The method of claim 1, wherein the second connecting member is connected to a lower portion of the car and to a pit floor of the hoistway.

16. The method of claim 14, wherein the second connecting member is connected to a lower portion of the car and to a pit floor of the hoistway.

17. The method of claim 2, wherein the step of obtaining a first output of the car load cell is performed while the car is unloaded.

18. The method of claim 3, wherein the step of obtaining a fourth output of the car load cell is performed while the car is unloaded.

19. The method of claim 18, wherein the step of obtaining a first output of the car load cell is performed while the car is unloaded.

20. The method of claim 2, wherein the step of obtaining a first output of the car load cell is performed while the car is located at a lower end of the hoistway.

21. The method of claim 3, wherein the step of obtaining a fourth output of the car load cell is performed while the car is located at a lower end of the hoistway.

22. The method of claim 20, wherein the step of obtaining a first output of the car load cell is performed while the car is located at a lower end of the hoistway.

23. The method of claim 1, wherein the step of performing a pre-measurement is performed during initial adjustment of the weighing device.