ELEVATOR COUNTERWEIGHT

Abstract

An elevator counterweight (2) includes a first part (4). The first part (4) is configured to be connected, in use, to a suspension member (8) of an elevator system (1). The first part (4) is arranged to receive an additional mass (6) when the first part (4) is connected to the suspension member (8), such that a mass of the elevator counterweight (2) can be varied. A controller (14) may be arranged to control a mass variation system (12) to vary the mass of the elevator counterweight (2) according to a schedule. The controller (14) may determine the schedule in a learning process.

Claims

1. An elevator counterweight (2, 2′, 2″, 2′″, 202, 202′), comprising: a first part (4, 4′, 4″, 4′″, 204, 204′) configured to be connected, in use, to a suspension member (8, 8′, 208, 208′) of an elevator system (1, 1′, 201, 201′), wherein the first part (4, 4′, 4″, 4′″, 204, 204′) is arranged to receive an additional mass (6, 6′, 6″, 6′″, 206, 206′) when the first part (4, 4′, 4″, 4′″, 204, 204′) is connected to the suspension member (8, 8′, 208, 208′), such that a mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) can be varied.

2. The elevator counterweight (2, 2′, 2″, 2′″) of claim 1, wherein the additional mass is a second part (6, 6′, 6″, 6′″), which is attachable to and detachable from the first part (4, 4′, 4″, 4′″).

3. The elevator counterweight (2″, 2′″) as claimed in claim 2, wherein the elevator counterweight (2″, 2′″) further comprises a third part (7″, 7′″), which is attachable to and detachable from the first part (4″, 4′″) when the first part (4″, 4′″) is connected to the suspension member (8, 8′).

4. The elevator counterweight (202, 202′) of claim 1, wherein the first part comprises a container (204, 204′), and the additional mass is a fluid or fluid-like material (206, 206′).

5. An elevator system (1, 1′, 201, 201′), comprising: an elevator car (10, 10′, 210, 210′); an elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) as claimed in claim 1; and a mass variation system (12, 12′, 212, 212′), wherein the mass variation system (12, 12′, 212, 212′) is arranged to add additional mass (6, 6′, 6″, 6′″, 206, 206′) to the first part (4, 4′, 4″, 4′″, 204, 204′) and/or remove additional mass (6, 6′, 6″, 6′″, 206, 206′) from the first part (4, 4′, 4″, 4′″, 204, 204′), so that a mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) can be varied.

6. An elevator system (1, 1′, 201, 201′), comprising: an elevator car (10, 10′, 210, 210′); an elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) including a first part (4, 4′, 4″, 4′″, 204, 204′) configured to be connected, in use, to a suspension member (8, 8′, 208, 208′) of an elevator system (1, 1′, 201, 201′), wherein the first part (4, 4′, 4″, 4′″, 204, 204′) is arranged to receive an additional mass (6, 6′, 6″, 6′″, 206, 206′) when the first part (4, 4′, 4″, 4′″, 204, 204′) is connected to the suspension member (8, 8′, 208, 208′), such that a mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) can be varied; and a mass variation system (12, 12′, 212, 212′), wherein the mass variation system (12, 12′, 212, 212′) is arranged to add additional mass (6, 6′, 6″, 6′″, 206, 206′) to the first part (4, 4′, 4″, 4′″, 204, 204′) and/or remove additional mass (6, 6′, 6″, 6′″, 206, 206′) from the first part (4, 4′, 4″, 4′″, 204, 204′), so that a mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) can be varied; further comprising a controller (14, 14′, 214, 214′), wherein the controller (14, 14′, 214, 214′) is arranged to control the mass variation system (12, 12′, 212, 212′) to add or remove the additional mass (6, 6′, 6″, 6′″, 206, 206′) from the first part (4, 4′, 4″, 4′″, 204, 204′) of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′).

7. The elevator system (1, 1′, 201, 201′) of claim 6, wherein the controller (14, 14′, 214, 214′) is arranged to carry out a learning process, comprising the controller (14, 14′, 214, 214′) receiving measurements, over a first time period, representative of a load (16, 16′, 216, 216′) within the elevator car (10, 10′, 210, 210′), and then, after the first time period ends, either: the controller (14, 14′, 214, 214′) determining a predicted schedule (100) of the maximum load in the elevator car (10, 10′, 210, 210′) over time; or the controller sending the measurements representative of a load (16, 16′, 216, 216′) within the elevator car (10, 10′, 210, 210′) over the first time period to a cloud service (15), wherein the cloud service (15) is configured to determine the predicted schedule (100) of the maximum load in the elevator car (10, 10′, 210, 210′) over time, and send this predetermined schedule (100) to the controller (14, 14′, 214, 214′); wherein the controller (14, 14′, 214, 214′) is arranged to control the mass variation system (12, 12′, 212, 212′) to vary the mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) according to the predicted schedule (100).

8. The elevator system (1, 1′, 201, 201′) of claim 7, wherein after the first time period ends, the controller (14, 14′, 214, 214′) continues to receive measurements representative of the load (16, 16′, 216, 216′) within the elevator car (10, 10′, 210, 210′), and updates the predicted schedule (100) based on these measurements received after the end of the first time period.

9. The elevator system (1, 1′, 201, 201′) of claim 6, wherein the controller (14, 14′, 214, 214′) is arranged to control the mass variation system (12, 12′, 212, 212′) to vary the mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) in response to a trigger from the elevator system (1, 1′, 201, 201′).

10. The elevator system (1, 1′, 201, 201′) as claimed in claim 6, further comprising an elevator system controller (18, 18′, 218, 218′) arranged to control operation of the elevator system (1, 1′, 201, 201′), wherein the control of the operation of the elevator system is adapted in correspondence with variations in the mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′).

11. The elevator system (1, 1′, 201, 201′) as claimed in claim 6, wherein the elevator car (10, 10′, 210, 210′) further comprises a dynamic display (20, 20′, 220, 220′), and wherein the dynamic display (20, 20′, 220, 220′) is arranged to display a current duty load, wherein the current duty load varies in correspondence with variation in the mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′).

12. The elevator system (1, 1′, 201, 201′) as claimed in claim 6, further comprising at least one operation-mode display (20, 20′, 22′), wherein the operation-mode display (20, 20′, 22′) is arranged to display an indication of an elevator mode of operation, wherein the mode of operation corresponds to a variation in the mass of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′).

13. The elevator system (1, 1′, 201, 201′) of claim 6, further comprising a hoistway (24, 24′, 224, 224′), within which the elevator car (10, 10′, 210, 210′) is configured to travel, the hoistway (24, 24′, 240, 240′) comprising a parking location (26, 26′, 226′) and wherein the elevator system (1, 1′, 210, 210′) is configured so that the additional mass (6, 6′, 6″, 6′″, 206, 206′) is stored in the parking location (26, 26′, 226′) when it has been removed from the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′) by the mass variation system (12, 12′, 212, 212′).

14. The elevator system (1, 1′, 201′) of claim 13, wherein the parking location (26′, 226′) is located on the hoistway wall (36′), wherein the parking location (26′, 226′) is at a height in the hoistway (24′, 224′) which corresponds to a height of the elevator counterweight (2′, 202′) when the elevator car (10′, 210′) is positioned at a main floor (28b′) of the elevator system (1′, 201′), wherein the main floor (28b′) of the elevator system is the floor of the elevator system (1′, 201′) at which the majority of incoming passengers arrive at the elevator system (1′, 201′).

15. A method of operating an elevator system (1, 1′, 201, 201′), comprising: operating the elevator system (1, 1′, 201, 201′) to transport one or more loads (16, 16′, 216, 216′); then, removing a mass (6, 6′, 6″, 6′″, 206, 206′) from an elevator counterweight (2, 2′, 2″, 2′″, 202, 202′); and operating the elevator system (1, 1′, 201, 201′) using the elevator counterweight (2, 2′, 2″, 2′, 202, 202′) having a reduced mass as a result of removal of the mass (6, 6′, 6″, 6′″, 206, 206′) of the elevator counterweight (2, 2′, 2″, 2′″, 202, 202′).

Description

DETAILED DESCRIPTION

[0064] Certain preferred examples of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0065] FIG. 1 is a schematic drawing showing an elevator system according to a first example of the present disclosure;

[0066] FIG. 2 is a graph showing a predicted schedule as can be used in accordance with an example of the present disclosure;

[0067] FIG. 3 is a schematic drawing showing an elevator system according to a second example of the present disclosure;

[0068] FIG. 4 is a schematic drawing showing the elevator system of FIG. 3 in which the elevator car is attached to the elevator counterweight, and positioned adjacent the parking location;

[0069] FIG. 5 is a schematic drawing showing an elevator system of FIG. 3 in which the second part of the elevator counterweight is stored at the parking location;

[0070] FIG. 6 is a view from above showing the elevator counterweight of FIGS. 3 to 6, according to a second example of the present disclosure;

[0071] FIG. 7 is a view from above showing an elevator counterweight according to a third example of the present disclosure;

[0072] FIG. 8 is a view from above showing an elevator counterweight according to a fourth example of the present disclosure;

[0073] FIG. 9 is a schematic drawing showing an elevator system according to a third example of the present disclosure including an elevator counterweight according to a fifth example of the present disclosure; and

[0074] FIG. 10 is a schematic drawing showing an elevator system according to a fourth example of the present disclosure including an elevator counterweight according to the fifth example of the present disclosure.

DETAILED DESCRIPTION

[0075] FIG. 1 shows an elevator system 1 according to a first example of the present disclosure. The elevator system 1 includes a motor 30, which drives movement of a suspension member 8. The suspension member 8 suspends an elevator counterweight 2, on one side of the motor 30, applying a torque T.sub.CWT in a first direction of rotation, and suspends an elevator car 10 on the other side of the motor 30, applying the torque T.sub.CAR in a second direction of rotation. These components are located in a hoistway 24, the walls of which are not shown in FIG. 1. The arrangement of sheaves, and end-hitches which is used to suspend the elevator car 10 and the elevator counterweight 2 is not important to the present disclosure, and the various possible arrangements are well known in the art and will therefore not be described in detail here. For example, a 2:1 roping arrangement is shown in FIG. 1, but a 1:1 or other roping arrangement is equally viable.

[0076] The torque T.sub.CAR applied to the motor 30 in the clockwise direction is proportional to the mass of the elevator car 10, added to the mass of a load 16 which is transported within the elevator car 10. The torque T.sub.CWT applied to the motor 30 is proportional to the mass of the elevator counterweight 2. For the most efficient operation of the elevator system 1, requiring the lowest torque output from the motor 30, it is desirable that the mass of the elevator counterweight 2 matches as closely as possible the sum of the mass of the elevator car 10 and the mass of the load 16 within the elevator car 10.

[0077] In order that the mass of the elevator counterweight 2 might continue to match this value more closely throughout operation of the elevator system 1, the elevator counterweight 2 is arranged so that its mass is variable. In particular, the elevator counterweight 2 includes a first part 4 and a second part 6. The first part 4 is connected to the suspension member 8 (in FIG. 1 it is shown connected via a pulley, but in other examples it could be connected by an end hitch). The second part 6 is attachable to and detachable from the first part 4 when the first part 4 is connected to the suspension member 8, so that the mass of the elevator counterweight 2 is variable. In this example the elevator counterweight 2 includes just one detachable part, i.e., the second part 6. The elevator counterweight 2 can therefore either have a low-mass configuration, or a full mass configuration (i.e., 100%), depending on whether or not the second part 6 is attached to the elevator counterweight 2. In this particular example the attachment and detachment (i.e., the mass variation system) is achieved by a detachment system 12, which in this example is a hook, represented schematically in FIG. 1.

[0078] When the detachment system 12 detaches the second part 6, i.e., unhooks it so that the second part 6 is no longer connected to the first part 4, the second part 6 is stored at a parking location 26, which is at the bottom of the hoistway 24 (i.e., the pit), where clearly this is not represented to scale in FIG. 1. The storage of the second part 6 at the parking location 26 allows the second part 6 to be conveniently reattached when it is required again.

[0079] The operation of the elevator system 1 is controlled by an elevator system controller 18, as represented by a dashed line connecting the elevator system controller 18 to the elevator car 10. This elevator system controller 18 is connected to a controller 14 (as shown with a dashed line) which in turn controls the detachment system 12 (as explained below with reference to FIG. 2) as represented by a dashed line from the controller 14 to the detachment system 12. The controller 14 is optionally connected to a cloud service 15, which is remote from the elevator system 1.

[0080] The elevator system controller 18 varies certain system parameters based on whether or not the second part 6 is connected to the first part 4 of the elevator counterweight 2, i.e., whether the second part 6 is contributing to the mass of the elevator counterweight 2. For example, the threshold load which is used by the elevator system controller 18 to determine an overload condition of the elevator car 10 is varied based on variations in the mass of the elevator counterweight 2. The elevator car 10 further includes a dynamic display 20 which displays the current threshold load, i.e., the current duty load.

[0081] FIG. 2 is a graph showing a predicted schedule 100 which has been derived by the controller 14. This example schedule 100 shows one of the ways in which the elevator system can operate to control the detachment system 12. The horizontal axis 102 of the graph represents time, in units of a one-hour period, whilst the vertical axis 104 represents the mass of the load 16 as a percentage of the maximum duty load of the elevator car 10. The maximum duty load is achieved when the second part 6 of the elevator counterweight 2 is attached to the first part 4 of the elevator counterweight 2 such that the elevator counterweight has its largest possible mass. A lower duty load (in this example 50%) is achieved when the second part 6 is detached from the first part 4 so that the elevator counterweight 2 has a lower mass. Each dot 106 represents a data point, which is the maximum measured mass value (as a percentage of duty load) of the load 16, transported by the elevator car 10 within that particular hour time slot. In order to obtain the data points 106, the controller 14 carries out a learning process, during which the controller 14 receives measurements of load, over a first time period. The controller 14 can then send these measurements of load, over a first time period to the remote cloud service 15. The cloud service 15 then determines the predicted schedule of the maximum load in the elevator car over time, and sends this predetermined schedule to the controller 14. Alternatively, the predetermined schedule may be calculated on the controller 14 itself without using the cloud service 15. The first time period may be a single 24-hour period, i.e., 1 day, or it may extend over several days with the data for each hour slot being accumulated over multiple days. It will also be appreciated that the measurements may be associated with a day of the week, or a day of the month or year so that weekly, monthly or seasonal variations in use can be captured. It will also be appreciated that data may be captured at higher or lower resolution than hourly intervals. For example, it may be captured at a minute level or at a 3-hourly level, or at a day level. Purely by way of example, in the latter case, with data points at day level, the system can establish e.g., whether the elevator counterweight can be detached for particular days, such as weekend days or holidays.

[0082] Based on these data points 106, the cloud service 15 (or the controller 14) carries out machine learning (or any other suitable computational process or algorithm) and determines a predicted schedule 100 of the times 108 at which the mass of the load 16 in the elevator car 10 is not expected to exceed 50% of the duty load, and the times 110 at which it is expected to exceed 50% of the duty load. Again, it will be appreciated that 50% is purely one example of the lower duty load. This figure will depend on the ratio of the masses of the first part and the second part and can be selected appropriately for the system, or indeed it can be selected or adjusted based on the data acquired during the learning period.

[0083] The controller 14 then controls the detachment system 12 according to this schedule 100, so that at the beginning of each low-mass time period 108, the second part 6 of the elevator counterweight 2 is detached, and then at the end of each of these low-mass time periods 108, i.e., at the beginning of each high-mass time period 110, the second part 6 is reattached to the elevator counterweight 2, i.e., to the first part 4. Since the total mass of the elevator counterweight 2 (the first part+the second part) is optimised for when the load 16 is half of the maximum duty load, it is excessive in those periods 108 in which the load is expected to stay well below that maximum load value. By reducing the total mass of the elevator counterweight 2 in those time periods by detaching the second part 6, the efficiency of the elevator system is improved by temporarily reducing the duty load to less than the maximum duty load.

[0084] The controller 14 continues to receive the load values after the initial learning process, and either the controller 14 or the cloud service 15 adjusts the predicted schedule 100 based on this further data. For example, if the load value in a low-mass time period 108 exceeds half the duty load more than a threshold number of times, the schedule 100 can be updated to make this time period, or part of it, a high-mass time period 110. The threshold number of times might be increased over time, e.g., early on when the controller 14 has not collected much data a single error might result in a change in the schedule 100, but once a large quantity of data has been collected over an extended period, it might be better to require several exceptions to occur before the controller 14 or the cloud service 15 updates the predicted schedule 100.

[0085] The controller 14 may have a reset function, which, when activated, causes the predicted schedule 100 to be forgotten, e.g., deleted or overridden, and then causes the learning process to be carried out again, to derive an entirely new predicted schedule 100 from a new set of collected data.

[0086] FIGS. 3, 4 and 5 are schematic drawings showing an elevator system 1′ according to a second example of the present disclosure. Like components of the elevator system have been labelled with the same labels as used above with reference to FIG. 1, but denoted with an additional apostrophe, e.g., 1′ rather than 1.

[0087] As with the example of FIG. 1, the elevator system 1′ includes a motor 30′, which drives movement of a suspension member 8′. The suspension member 8′ suspends an elevator counterweight 2′ on one side of the motor 30′ and an elevator car 10′ on the other side of the motor 30′. These components are located in a hoistway 24′. The hoistway 24′ connects to four different floors of a building (not shown) in which the elevator system 1′ is located. The floors include a basement, or underground landing 28a′, also referred to as a −1 landing, a ground floor landing 28b′, a first floor landing 28c′ and a second floor landing 28d′. The ground floor is referred to as the ground floor since it is the floor which corresponds to the entry floor of the building in which the elevator system 1′ is installed. In this example the ground floor is also the main floor of the elevator system 1′, since it is the floor of the elevator system at which the majority of incoming passengers arrive at the elevator system 1′, and possibly also or alternatively the floor at which the majority of outgoing passengers leave from the elevator system 1′.

[0088] The elevator counterweight 2′ includes a first part 4′ and a second part 6′. The first part 4′ is connected to the suspension member 8′. The second part 6′ is attachable to and detachable from the first part 4′ when the first part 4′ is connected to the suspension member 8′, so that the mass of the elevator counterweight 2′ is variable.

[0089] The operation of the elevator system 1′ is controlled by an elevator system controller 18′, in the same manner as the elevator system controller 18 described above, and the elevator car 10′ similarly includes a dynamic display 20′ which displays the current threshold load.

[0090] The elevator system controller 18′ is connected to a controller 14′, which controls detachment and reattachment of the second part 6′. The controller 14′ is capable of carrying out the same functionality as the controller 14, as described above with reference to FIG. 2, and this therefore will not be described again. Furthermore, in this example, there is no cloud service, and instead the controller 14′ itself is able to provide the functionality described above with reference to the cloud service, for example determining and updating the predicted schedule. Additionally, the controller 14′ is also able to detach or reattach the second part 6′ in a manner which is not in accordance with the predicted schedule 100, i.e., to override the predicted schedule 100, based on a trigger received from the elevator system 1′.

[0091] In this example the ground floor landing 28b′ includes a camera 32′ which is arranged to detect the number of passengers approaching the ground floor landing 28b′. Where it is deemed that the current duty load of the elevator car 10′ is insufficient for the elevator car 10′ to accommodate all of the passengers approaching the ground floor landing 28b′ due to the second part 6′ of the elevator counterweight 2′ being in a detached state, the camera 32′ signals the controller 14′, which then controls the detachment system 12′ to reattach the second part 6′ to the elevator counterweight 2′, even if this is not in accordance with the predicted schedule 100, thus restoring the elevator car 10′ to its maximum load capacity. As described above, the ground floor 28b′ of this particular exemplary building is the main floor, and therefore the floor where most passengers arrive, and it is therefore the landing at which the number of waiting passengers is most likely to exceed the current duty load. It is therefore advantageous that the camera 32′ is located at this particular floor. It will of course be appreciated that cameras may be positioned at any or all of the others floors and also that sensors other than cameras may be used, e.g., depth-sensing sensors, infrared detectors, etc.

[0092] The elevator system 1′ further includes landing displays 22′ at each of the landing floors 28a′, 28b′, 28c′, 28d′. These landing displays 22′ are arranged to display an indication of an elevator mode of operation, where the mode of operation corresponds to a current state (or mass) of the elevator counterweight 2′. Thus, in this example the landing displays 22′ provide operation-mode displays. If the second part 6′ is attached to the first part 4′, thus forming part of the elevator counterweight 2′, then the duty load of the elevator car 10′ is at its maximum and the mode of operation is “normal”. This might be displayed on the landing displays 22′, but also might not be indicated as there is no need to notify passengers of normal operation. If the second part 6′ is detached from the elevator counterweight 2′, then the duty load of the elevator car 10′ is below its maximum duty load and the mode of operation is a “reduced” or “environmentally friendly” or “eco” mode. This is displayed on the landing displays 22′ and possibly also on the dynamic display 20′ within the elevator car 10′, so that passengers are informed of the change in capacity of the elevator car 10′, but also that this change is having a positive impact as a result of reduced energy consumption, so that they might be more understanding or forgiving of any reduced capacity.

[0093] Thus, the mass of the elevator counterweight 2′ is varied during operation according to the expected needs of the elevator system 1′, under the control of the controller 14′, as described above. In the example of FIG. 3-5, this is done using a retractable detachment system 12′, which includes two attachment mechanisms 34′ which are each selectively retractable into the hoistway wall 36′. It will be appreciated that this is just one example detachment system 12′.

[0094] FIG. 3 shows the elevator system 1′ in a configuration in which the elevator car 10′ contains a load 16′ with a large mass, and therefore the second part 6′ is attached to the first part 4′ as part of the elevator counterweight 2′. In FIG. 3, the elevator car 10′ is located at the top of the elevator hoistway 24′, adjacent to the second floor landing 28d′, and correspondingly the elevator counterweight 2′ is located at the bottom of the elevator hoistway 24′, above the pit.

[0095] In FIG. 4, the elevator car 10′ has moved to be at the ground floor landing 28b′. With the elevator car 10′ in this position, the elevator counterweight 2′ is positioned adjacent to the detachment system 12′. In FIG. 4 the attachment mechanisms 34′ are retracted within the hoistway wall 36′. The second part 6′ is still attached to the first part 4′, however the load 16′ in the elevator car 10′ is now only a low mass, therefore the full duty load capacity is not required. Therefore, the controller 14′ can control the detachment system 12′ to detach the second part 6′ from the elevator counterweight 2′. Accordingly, the attachment mechanisms 34′ are controlled to protrude from the hoistway wall 36′, and engage with the second part 6′, e.g., to hook into it, so that the rest of the elevator counterweight 2′ can move away without the second part 6′. The second part 6′ is then stored by the detachment system 12′ whilst the operation of the elevator system 1′ continues without it, as shown in FIG. 5. Therefore, the detachment system 12′ in this example also provides the parking location 26′, which is on the hoistway wall 36′. In FIG. 5 the elevator counterweight 2′ has moved upwards, without the second part 6′, and the elevator car 10′ has moved downwards in the hoistway 24′ to be adjacent to the −1 landing 28a′.

[0096] FIG. 6 is a view from above showing the elevator counterweight 2′ of FIGS. 3 to 5. The elevator counterweight 2′ includes the first part 4′, and the second part 6′. The first part 4′ further includes a pulley 60′, which enables connection of the first part 4′ to the suspension member 8′, shown in FIG. 3. The first part 4′ and the second part 6′ are both symmetrical in a side-side direction, i.e., the left side is symmetrical with the right side as seen in the Figure. This ensures side to side balance regardless of whether the second part 6′ is attached or detached. The elevator counterweight 2′ may run on guiderails which are typically located to the sides (to the left and right in the figure). Ensuring the same balance regardless of whether the second part 6′ is attached or detached means that friction and noise and braking ability are not adversely affected by the state of the elevator counterweight 2′. In addition, it can be seen that both the first part 4′ and the second part 6′ have projections that extend across the mid-line of the elevator counterweight 2′ in a front-back direction. For example the first part 4′ has an ‘M’ shape with a left projection 3′, a mid-projection 5′, and a right projection 9′, while the second part 6′ has a ‘U’ shape nested into the ‘M’ with a left projection 11′ located between the left and mid projections 3′, 5′ of the first part 4′ and a right projection 13′ located between the mid and right projections 5′, 9′ of the first part 4′. These projections ensure that each of the first part 4′ and the second part 6′ have part of their mass on the front side of the centre of mass of the elevator counterweight 2′ and part of their mass on the back side of the centre of mass of the elevator counterweight 2′. The front and back mass distributions can be designed to be evenly distributed either side of a plane joining the two guiderails (i.e., a vertical plane perpendicular to the page of the figure and running horizontally through the elevator counterweight 2′ as shown in the figure). In this way, the centre of mass of the first part 4′ may be vertically aligned with the centre of mass of the second part 6′ (meaning that one lies vertically directly above the other or they are coincident). With such an arrangement, attachment or detachment of the second part 6′ from the first part 4′ will not move the centre of mass of the elevator counterweight 2′ in the horizontal plane and therefore will not adversely affect the friction, noise or braking of the elevator counterweight 2′ during use. It should be appreciated that FIG. 6 is not drawn to scale, but shows the general principle of the mass distribution.

[0097] FIG. 7 is a view from above showing an elevator counterweight 2″ according to a third example of the present disclosure, which can be used in accordance with the example elevator systems described above. The elevator counterweight 2″ again includes a first part 4″, connectable to a suspension member, and a second part 6″, which can be detached from and reattached to the first part 4″. The first part 4″ further includes a pulley 60″, which enables connection of the first part 4″ to a suspension member. The elevator counterweight 2″ further includes a third part 7″ which is also detachable from and reattachable to the first part 4″. This allows the mass of the elevator counterweight 2″ to be varied in smaller degrees, e.g., rather than just having a maximum load and a partial mass, there are multiple degrees of partial mass which the elevator counterweight 2″ can provide. It will be understood that these can correspond to multiple different modes of operation, e.g., varying degrees of “eco-mode”.

[0098] FIG. 8 is a view from above showing an elevator counterweight 2′″ according to a fourth example of the present disclosure, which can be used in accordance with the example elevator systems described above. As with the elevator counterweight 2″ of FIG. 7, the elevator counterweight 2′″ includes a first part 4′″, connectable to a suspension member, a second part 6′″ and a third part 7′″. The first part 4′″ further includes a pulley 60′″, which enables connection of the first part 4′″ to a suspension member. The second part 6′″ is nested within the first part 4′″ and can be detached from and reattached to the first part 4′″. The third part 7′″ is nested within the second part 6′″ and can be detached from and reattached to the second part 6′″ and/or the first part 4′″. This allows the weight of the elevator counterweight 2′″ to be varied in smaller degrees, as with the elevator counterweight 2″ of FIG. 7. In this case the nesting arrangement of the parts 4′″, 6′″, 7′″ advantageously means that each is symmetrical about the centreline (i.e., the left side is symmetrical to the right side as seen in the figure) so that regardless of how many of the parts 4′″, 6′″, 7′″ are attached, the mass distribution in a side-side direction is unaffected, providing a balanced arrangement. The three parts 4′″, 6′″, 7′″ have the same mass distribution properties as are described above in relation to FIG. 6, namely in a side to side direction and a front to back direction such that each of the first part 4′″, the second part 6′″ and the third part 7′″ have centres of mass that are vertically aligned and therefore attachment and detachment of the second and/or third parts 6′″, 7′″ does not cause movement of the centre of mass of the elevator counterweight 2′″ in the horizontal plane.

[0099] FIG. 9 shows a third example of an elevator system 201, which includes a fifth example of an elevator counterweight 202, according to of the present disclosure. The elevator system 201 includes a motor 230, which drives movement of a suspension member 208. The suspension member 208 suspends an elevator counterweight 202, on one side of the motor 230, applying a torque T.sub.CWT in a first direction of rotation, and suspends an elevator car 210 on the other side of the motor 230, applying the torque T.sub.CAR in a second direction of rotation. The torque T.sub.CAR is proportional to the mass of the elevator car 210, added to the mass of a load 216 which is transported within the elevator car 210.

[0100] These components are located in a hoistway 224, the walls of which are not shown in FIG. 9. The arrangement of sheaves, and end-hitches which is used to suspend the elevator car 210 and the elevator counterweight 202 is not important to the present disclosure, and the various possible arrangements are well known in the art and will therefore not be described in detail here. For example, a 2:1 roping arrangement is shown in FIG. 1, but a 1:1 or other roping arrangement is equally viable.

[0101] In order that the mass of the elevator counterweight 202 might continue to match the sum of the elevator car mass and the elevator car load mass more closely throughout operation of the elevator system 201, the elevator counterweight 202 is arranged so that its mass is variable.

[0102] In particular, the elevator counterweight 202 comprises a first part 204, which comprises a container 204a, e.g., a tank, and a fixed mass 204b. The container 204a is detachable from and attachable to the fixed mass 204b in the same or similar manner as the first and second parts attach and detach in the examples given above. The container 204a is fillable with a fluid or fluid-like material 206, e.g., a large number of particles or granules. The fluid or fluid-like material 206 may be, for example, sand or water or a mixture of sand and water.

[0103] The fluid or fluid-like material 206 may be supplied via a supply system 207 located in the hoistway 224 and added to the container 204a through an inlet 203, and may be removed from the container 204a via an outlet 205. Together these may provide a mass variation system 212. The fluid or fluid-like material which has been output from the outlet 205 is removed from the hoistway 224 by a drain 209. Thus, the outlet 205 together with the drain 209 provide an exhaust system.

[0104] Thus, by adding or removing some of the fluid or fluid-like material 206 the mass of the elevator counterweight 202 can be adjusted.

[0105] The operation of the elevator system 201 is controlled by an elevator system controller 218, as represented by a dashed line connecting the elevator system controller 218 to the elevator car 210. This elevator system controller 218 is connected to a controller 214 (as shown with a dashed line) which in turn controls the mass variation system, which is made up of the supply system 207, the inlet 203 of the container 204, and the outlet 205 of the container 204, and optionally a detachment system (not shown) which attaches and detaches the container 204a from the fixed mass 204b, as represented by a dashed line from the controller 214 to each of these components. The elevator system controller 218 and controller 214 may operate in the same way as the elevator system controller 18, 18′ and controller 14, 14′ described above with respect to either of the first two examples. In particular, the elevator system 201 may use a cloud computing service as discussed in relation to FIG. 1.

[0106] The elevator system controller 218 varies certain system parameters based on the mass of fluid or fluid-like material 206 that is contained within the container 204 of the elevator counterweight 202. For example, the threshold load which is used by the elevator system controller 218 to determine an overload condition of the elevator car 210 is varied based on variations in the mass of the elevator counterweight 202. The elevator car 210 further includes a dynamic display 220 which displays the current threshold load, i.e., the current duty load.

[0107] FIG. 10 is a schematic drawing showing an elevator system 201′ according to a fourth example of the present disclosure. Like components of the elevator system have been labelled with the same labels as used above with reference to FIG. 9, but denoted with an additional apostrophe, e.g., 201′ rather than 201.

[0108] Most components of this elevator system are the same as those shown in FIG. 9, and described above, and they therefore will not be described again. The mass variation system 212′ of this elevator system 201′ differs from that shown in FIG. 10. In particular, instead of including a separate supply system and drain, as shown in FIG. 9, the mass variation system 212′ comprises a reservoir 207′ located at a parking location 226′ on the wall of the hoistway 224′. The reservoir 207′ contains a supply 217′ of fluid or fluid-like material, the reservoir 207′ having a pumped output 213′ and an input 215′. The parking location 211′ is adjacent to the position of the elevator counterweight 202′ when the elevator car 210′ is located at a main floor of the elevator system 201′, as described above with reference to earlier examples. In this position, the pumped output 213′ of the reservoir 207′ is located adjacent to, e.g., in fluid connection with, the inlet 203′ of the container 204′, and the input 215′ to the reservoir 207′ is located adjacent to, e.g., in fluid connection with, the outlet 205′ of the container 204′. The inlet 203′ and outlet 205′ of the tank 204′ and the input 215′ and pumped output 213′ of the reservoir 207′ together are controlled by the controller 214′, and provide a mass variation system 212′. The mass of the elevator counterweight 204′ is varied by moving fluid or fluid-like material between the reservoir 207′ and the container 204′.

[0109] 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.