SETTING A RESCUE TIME PERIOD

Abstract

A method of learning a rescue time period by an elevator system (101). The elevator system (101) includes an elevator car (103) moved by a machine (111) and a machine brake (120), arranged such that braking of the machine (111) by the machine brake (120) brakes motion of the elevator car (103). The method includes releasing the machine brake (120) for at least one test time period, at the end of which the machine brake (120) is engaged, detecting a corresponding at least one maximum travel speed of the elevator car (103) reached as a result of releasing the machine brake (120) for each at least one test time period, checking whether each at least one maximum travel speed is an acceptable speed, and setting the rescue time period based upon said checking.

Claims

1. A method of learning a rescue time period by an elevator system (101), the elevator system (101) comprising an elevator car (103) moved by a machine (111), and a machine brake (120) arranged such that braking of the machine (111) by the machine brake (120) brakes motion of the elevator car (103), the method comprising: releasing the machine brake (120) for at least one test time period, at the end of which the machine brake (120) is engaged; detecting a corresponding at least one maximum travel speed of the elevator car (103) reached as a result of releasing the machine brake (120) for each at least one test time period; checking whether each at least one maximum travel speed is an acceptable speed; and setting the rescue time period based upon said checking.

2. The method as claimed in claim 1, wherein an acceptable speed comprises a speed that is greater than or equal to a minimum speed threshold; optionally, wherein the minimum speed threshold is 0.1 m/s.

3. The method as claimed in claim 1, wherein an acceptable speed comprises a speed that is less than or equal to a maximum speed threshold; optionally wherein the maximum speed threshold is 0.3 m/s.

4. The method as claimed in claim 1, wherein each at least one test time period is greater than or equal to a minimum threshold time period; optionally wherein the minimum threshold time period is at least 500 ms.

5. The method as claimed in claim 1, wherein each at least one test time period is less than or equal to a maximum threshold time period, the method further comprising: if no test time period results in a maximum travel speed that is an acceptable speed, setting the maximum threshold time period as the rescue time period; optionally wherein the maximum threshold time period is no more than 2000 ms.

6. The method as claimed in claim 1, comprising setting as the rescue time period the first test time period that results in a maximum travel speed of the elevator car (103) that is an acceptable speed.

7. The method as claimed in claim 1, comprising first releasing the machine brake (120) for a first test time period, and if the maximum travel speed reached by the elevator car (103) in the first time period is not an acceptable speed, subsequently releasing the machine brake (120) for one or more additional test time periods, wherein each additional test time period is different compared to the preceding time period.

8. The method as claimed in claim 1, wherein the method is carried out during installation of the elevator system (101), or after replacement of the machine (111) or the machine brake (120).

9. The method as claimed in claim 1, wherein the elevator system (101) further comprises an elevator controller (115), and wherein the method is carried out automatically by the elevator controller (115).

10. The method as claimed in claim 1, wherein the releasing the machine brake (120) for at least one test time period is carried out when the elevator car (103) is empty of passengers and additional loads or when the elevator car contains passengers and additional loads having a mass equal to a maximum load limit of the elevator car (103).

11. A method of operating an elevator system (101), comprising, during a learning phase learning a rescue time period using the method of claim 1; and subsequently, during a rescue operation and in response to receipt of a rescue operation trigger, releasing the machine brake (120) for the rescue time period.

12. The method as claimed in claim 11, wherein the rescue operation trigger is input by a maintenance person, and wherein the releasing the machine brake (120) for the rescue time period is carried out automatically by the elevator system (101).

13. The method as claimed in claim 11, wherein the elevator system (101) comprises a motion detection device (113), arranged to detect motion of the elevator car (103), the method comprising during releasing the machine brake for the rescue time period, monitoring for a signal from the motion detection device (113) indicating motion of the elevator car (103); the method further comprising: if the signal indicating motion of the elevator car (103) is received, continuing to release the machine brake (120) beyond the end of the rescue time period; and if the signal indicating motion of the elevator car (103) is not received, engaging the machine brake (120) if the rescue time period has expired.

14. A rescue time period learning system (116) for an elevator system (101), the rescue time period learning system (116) configured to carry out a method as claimed in claim 1.

15. An elevator system (101) comprising: an elevator car (103); a machine (111), arranged to move the elevator car (103); a machine brake (120), arranged to brake the machine (111), wherein braking of the machine (111) by the machine brake (120) brakes motion of the elevator car (103); and a rescue time period learning system (116) as claimed in claim 14.

Description

DRAWING DESCRIPTION

[0046] Certain preferred examples of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0047] FIG. 1 is a schematic illustration of an elevator system according to an aspect of the present disclosure;

[0048] FIG. 2 is a schematic illustration of the machine and machine brake of the elevator system of FIG. 1;

[0049] FIGS. 3-5 are graphs representing lifting of the machine brake for different time periods, and the resulting maximum travel speeds achieved by the elevator car;

[0050] FIG. 6 is a flow chart illustrating a method of learning a rescue time period by an elevator system according to an aspect of the present disclosure; and

[0051] FIG. 7 is a flow chart illustrating a method of operating an elevator system according to an aspect of the present disclosure.

DETAILED DESCRIPTION

[0052] FIG. 1 is a perspective view of an elevator system 101 including an elevator car 103, a counterweight 105, a tension member 107, a guide rail 109, a machine 111, a motion detection device 113, and an elevator controller 115. The elevator car 103 and counterweight 105 are connected to each other by the tension member 107. The tension member 107 may include or be configured as, for example, ropes, steel cables, and/or coated-steel belts. The counterweight 105 is configured to balance a load of the elevator car 103 and is configured to facilitate movement of the elevator car 103 concurrently and in an opposite direction with respect to the counterweight 105 within an elevator hoistway 117 and along the guide rail 109. In particular, the mass of the counterweight 105 is equal to the mass of the elevator car plus half of the maximum load permitted in the elevator car 103. Thus, the counterweight 105 exactly balances the elevator car 103 when the elevator car 103 contains a load having a mass equal to half of the maximum load permitted for the elevator car 103.

[0053] The tension member 107 engages the machine 111, which is part of an overhead structure of the elevator system 101. The machine 111 is configured to control movement between the elevator car 103 and the counterweight 105. The motion detection device 113 may be mounted on a fixed part at the top of the elevator hoistway 117, such as on a support or guide rail, and may be configured to provide position signals related to a position of the elevator car 103 within the elevator hoistway 117, and thereby indicating whether the elevator car 103 is moving, by indicating whether or not the position of the elevator car 103 is changing. In other embodiments, the motion detection device 113 may be directly mounted to a moving component of the machine 111, or may be located in other positions and/or configurations as known in the art. The motion detection device 113 can be any device or mechanism for monitoring a position of an elevator car and/or counterweight, and therefore their movement, as known in the art. For example, without limitation, the motion detection device 113 can be an encoder, sensor, or other system and can include velocity sensing, absolute position sensing, etc., as will be appreciated by those of skill in the art.

[0054] The elevator controller 115 is located, as shown, in a controller room 121 of the elevator hoistway 117 and is configured to control the operation of the elevator system 101, and particularly the elevator car 103. For example, the elevator controller 115 may provide drive signals to the machine 111 to control the acceleration, deceleration, leveling, stopping, etc. of the elevator car 103. The elevator controller 115 may also be configured to receive position and/or motion signals from the motion detection device 113. When moving up or down within the elevator hoistway 117 along guide rail 109, the elevator car 103 may stop at one or more landings 125 as controlled by the elevator controller 115. Although shown in a controller room 121, those of skill in the art will appreciate that the elevator controller 115 can be located and/or configured in other locations or positions within the elevator system 101. In one embodiment, the elevator controller may be located remotely or in the cloud. The elevator controller 115 includes a rescue time period learning system 116, the operation of which is described below with reference to FIG. 6. Although shown as part of the elevator controller 115, it will be understood that the rescue time period learning system 116 may be provided as a separate component.

[0055] The machine 111 may include a motor or similar driving mechanism. In accordance with embodiments of the disclosure, the machine 111 is configured to include an electrically driven motor. The power supply for the motor may be any power source, including a power grid, which, in combination with other components, is supplied to the motor. The machine 111 may include a traction sheave that imparts force to tension member 107 to move the elevator car 103 within elevator hoistway 117. The machine 111 is braked by a machine brake 120, seen in FIG. 2. The machine brake 120 includes two braking pads 122a, 122b. They apply pressure to the machine 111 when braking, in order to brake the machine 111 with friction. When the brake pads 122a, 122b are lifted, by being moved along the brake release directions 124a, 124b, the machine brake 120 is lifted and the machine 111 (and therefore the elevator car 103) is free to move.

[0056] Although the elevator system 101 of FIG. 1 is shown and described with a roping system including a tension member 107, elevator systems that employ other methods and mechanisms of moving an elevator car within an elevator hoistway may employ embodiments of the present disclosure. For example, embodiments may be employed in ropeless elevator systems using a linear motor to impart motion to an elevator car. Embodiments may also be employed in ropeless elevator systems using a hydraulic lift to impart motion to an elevator car.

[0057] When the elevator car 103 undergoes a rescue operation, to allow rescue of passengers who are trapped in the elevator car 103 when the elevator car 103 has been stopped between landings 125, the machine brake 120 is lifted to allow at least a small movement of the elevator car 103. If no movement is detected by sensors of the elevator system 101, e.g., by the motion detection device 113, then the machine brake must be re-engaged. If the sensors of the elevator system 101, e.g., the motion detection device 113, appear to be operating properly then the machine brake 120 can be left open and control of the motion of the elevator car 103 in the standard way by the elevator controller 115 can be resumed.

[0058] It is important that the machine brake 120 is lifted for an appropriate period of time during the rescue operation, as illustrated by FIGS. 3-5.

[0059] FIGS. 3-5 are graphs, showing time along the x-axis 300, and containing two y-axes. The left-hand y-axis 302, with a solid line, represents brake lifting distance, as is presented on the graphs by a solid line. The right-hand y-axis 304, with a dashed line, represents the speed of movement of the elevator car 103.

[0060] FIG. 3 shows the effect when the machine brake 120 is lifted for too long. It can be seen that the speed of movement of the elevator car 103 increases quickly, and the speed will therefore become much too high. This risks both the comfort of passengers being rescued, but also their safety, since the elevator car 103 will undergo a rapid deceleration when the machine brake 120 is reapplied, and the car and its passengers will be jolted sharply.

[0061] In contrast, FIG. 4 shows the effect when the machine brake 120 is not lifted for a long enough period of time. In this case the elevator car 103 does not move at all. Thus, this will make the rescue operation impossible since the lifting of the machine brake 120 does not result in movement of the elevator car 103 and therefore cannot be used to move the elevator car 103 close enough to a landing 125 to enable safe debarkation.

[0062] FIG. 5 shows the speed (dashed line) of an elevator car 103 as the machine brake 120 is lifted for an appropriate amount of time during a rescue operation. The elevator car 103 achieves movement, such that it is successfully moved closer to a landing 125, but the machine brake 120 is applied sufficiently soon after release that the speed of the elevator car 103 does not rise too high.

[0063] It is a goal of the present disclosure to learn, for a given elevator installation, an appropriate lifting time for the machine brake 120 during a rescue operation. This time period is referred to herein as a rescue time period. This is achieved using the method described below with reference to FIG. 6, which is carried out by the rescue time period learning system 116.

[0064] The method starts at step 600. In this step the machine brake 120 is lifted for a first test time period. In this example the first test time period is a minimum threshold time period (i.e., the shortest time period to be tested during the learning phase, where the learning phase is what is illustrated in FIG. 6). In this example the first test time period is 500 ms.

[0065] At step 602 (which may be carried out concurrently with step 600), the rescue time period learning system 116 detects the maximum travel speed that is reached as a result of the machine brake 120 being lifted for the first time period. The maximum travel speed may be reached during the first test time period, but also may be reached after the end of the first time period, e.g., if the elevator car 103 is still accelerating even as the machine brake 120 begins to be re-engaged. At step 604 it is checked whether the maximum travel speed that the elevator car 103 reaches is above a minimum speed threshold.

[0066] If lifting the machine brake 120 for the first test time period does result in a maximum travel speed of the elevator car 103 that is above the minimum speed threshold, then the first test time period is set as the rescue time period, at step 606.

[0067] If lifting the machine brake 120 for the first test time period results in a maximum travel speed of the elevator car 103 that is below the minimum speed threshold, then the method proceeds to step 608, at which the machine brake 120 is released for a second time period. In this example, the second time period is longer than the first time period.

[0068] At step 610 (which may be carried out concurrently with step 608), the rescue time period learning system 116 detects the maximum travel speed that is reached as a result of the machine brake 120 being lifted for the second time period. At step 612 it is checked whether the maximum travel speed that the elevator car 103 reaches is above a minimum speed threshold.

[0069] If lifting the machine brake 120 for the second test time period does result in a maximum travel speed of the elevator car 103 that is above the minimum speed threshold, then the second test time period is set as the rescue time period, at step 614.

[0070] If lifting the machine brake 120 for the second, longer test time period results in a maximum travel speed of the elevator car 103 that is below the minimum speed threshold, then the method proceeds to step 616, at which it is checked whether the second test time period, used in the preceding testing steps, is equal to (or over) a maximum time period threshold. If it is not, then the method returns to step 608 and repeats the method again for another test time period, longer than the second, and keeps repeating this process for incrementally increasing test time periods, until either one produces a maximum travel speed above the minimum speed threshold, and the method moves to step 614, or until the time period has been increased to be equal to, or greater than, the maximum time period threshold. At that point, the method proceeds to step 618, in which the maximum time period threshold is set as the rescue time period. In this example the maximum time period threshold is 2000 ms. Thus, if no time periods between 500 ms and 2000 ms produce a speed that is above the minimum speed threshold then 2000 ms is used as the rescue time period.

[0071] In this example the minimum speed threshold is 0.1 m/s. This is sufficiently fast that reasonable movement of the elevator car 103 is achieved, but sufficiently slow that passenger comfort and safety is achieved, and wear on the brake pads 122a, 122b is not excessive.

[0072] This learning phase represented in FIG. 6 is shown as stage 700 in FIG. 7. FIG. 7 shows how the rescue time period set using the method of FIG. 6 is used during operation of the elevator system 101.

[0073] First a problem with the elevator system 101 causes it to undergo an emergency stop, at step 702. During an emergency stop 702 the elevator car 103 is braked by the machine brake 120 (and optionally also by separate safety brakes, not shown).

[0074] A maintenance person then begins the process of a manual rescue operation. Before this is done the maintenance person may make one or more safety checks (locally or remotely), and may control certain components of the elevator system 101 (e.g., release the safety brakes). Once the elevator system 101 is in a ready state, the maintenance person triggers the rescue operation to begin, at step 704, by inputting a command to the elevator controller 115 (again either locally or remotely).

[0075] In response to the command, the elevator controller 115 lifts the machine brake 120 for at least the length of the rescue time period, as set by the rescue time period learning system 116. If a signal is detected from the motion detection device 113 during the rescue time period, then the elevator controller 115 continues to hold the machine brake 120 open past the end of the rescue time period, at step 708. In this case since the sensors used to monitor motion of the elevator car 103including the motion detection device 113seem to be operating correctly, the elevator car 103 can be moved safely and therefore the machine brake 120 can be held open.

[0076] Alternatively, if no signal is detected from the motion detection device 113, despite motion being expected, then the machine brake 120 is re-engaged at step 710. This can be at the end of the rescue time period, if no motion is detected within the rescue time period, or the machine brake can be re-engaged after the end of the rescue time period where there is initially a signal from the motion detection device 113 (and so the machine brake 120 is held open), but then later the signal from the motion detection device 113 ceases, at which point the machine brake 120 is re-engaged.

[0077] It will be appreciated by those skilled in the art that the disclosure has been illustrated by describing one or more specific aspects thereof, but is not limited to these aspects; many variations and modifications are possible, within the scope of the accompanying claims.