A METHOD FOR A RESCUE OPERATION AND AN ELEVATOR SYSTEM
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] This invention relates to solution for facilitating a rescue operation in an elevator system during power failure in an electric network, for instance.
DESCRIPTION OF PRIOR ART
[0002] Sometimes an operational anomaly, such as a power failure interrupts elevator travel causing stopping of an elevator car between landing floors. In that case the elevator car needs to be relocated to a rescue floor to release passengers from the car. This operation is referred to as rescue operation. [0003] Traditionally, a field technician goes to the elevator site and opens hoisting machinery brakes with a manual brake lever, allowing drifting of the elevator car to a rescue floor by means of gravity. This solution will of course work only with imbalanced load where gravity can be used to move the elevator car in a desired direction.
[0004] However, in case the load is balanced or imbalanced in a wrong direction preventing movement of the elevator car to a rescue position by gravity, a separate manually operated hoist is needed. In that case the position of the elevator car can be changed with this hoist. Such a rescue operation is slow and labor-intensive.
SUMMARY OF THE INVENTION
[0005] An object of the present invention is to solve the above-mentioned drawback and to provide a solution facilitating a simple and rapid rescue operation without a need for additional expensive devices in the elevator system. This object is achieved with a method according to independent claim 1 and an elevator system according to independent claim 9.
[0006] By launching a regenerative operation with a first elevator it becomes possible to energize a drive system of a second elevator having a second elevator car requiring a rescue operation with electric power from the first elevator, if the obtained load information indicates a balance condition of the second elevator car or an imbalance condition in a direction preventing the second elevator car from

drifting towards a rescue position. Term "drifting" refers herein to movement of second elevator car in an uncontrolled manner with brakes open by means of gravity, i.e. without supplying electrical power from an external power source to the drive system of the second elevator car. With such a solution the electric power needed for driving the second elevator car to a rescue position can be generated without a need for expensive additional equipment.
[0007] Preferred embodiments of the invention are disclosed in the dependent claims.
BRIEF DESCRIPTION OF DRAWINGS
[0008] In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which [0009] Figure 1 is a flow diagram illustrating a method, and [0010] Figure 2 illustrates an elevator system where the method of Figure 1 can be implemented.
DESCRIPTION OF AT LEAST ONE EMBODIMENT
[0011] Figure 1 is a flow diagram illustrating a method and Figure 2 illustrates an elevator system 1 where the method of Figure 1 can be implemented. [0012] The elevator system 1 comprises a first elevator 3, with a first elevator car 8, a first counterweight 4 and a first drive system 5. The first drive system 5 includes a first hoisting machine 6 with an electric motor and a brake 23 and a first control cabinet 7 with a motor drive, such as frequency converter, for instance. The first drive system 5 moves the first elevator car 8 and the first counterweight 4 in a first elevator shaft 10 by means of ropes 11 between landing floors 9 of the building. In the illustrated example it is by way of example assumed that the first elevator is also provided with compensation ropes 12 between the elevator car 8 and the counterweight 4.
[0013] Additionally, the elevator system 1 comprises at least one additional elevator. In Figure 2, the second elevator 13 comprises a second elevator car 18, a second counterweight 14 and a second drive system 15. The second drive system 15 includes a second hoisting machine 16 with an electric motor, a brake 23 and a second control cabinet 17 with a motor drive, such as frequency converter, for instance. The second drive system 15 moves the second elevator car 18 and the second counterweight 14 in a second elevator shaft 20 by means of ropes 11 and by utilizing compensation ropes 12 between landing floors 9 of the building.

[0014] In the illustrated example it has by way of example been assumed that the fist 7 and second 17 control cabinets are implemented as separate control cabinets located at a distance from each other. In some implementations, the first and second control cabinets may be located side by side, as illustrated, or alternatively as integrated into one single control cabinet only. In that case the single control cabinet includes the necessary parts for both the first 3 and second elevator 13.
[0015] In case one of the first and second elevator car gets stuck between landing floors 9 of the building due to a power failure in the mains electrical network supplying electricity to the building in question, a rescue operation to move the stuck elevator car to a landing floor where passengers can leave the second elevator car may be implemented as illustrated in Figure 1. In the following it is by way of example assumed that it is specifically the second elevator car which is stuck and requires a rescue operation.
[0016] In step A load information of the second elevator car 18 is obtained. This
load information may be obtained from a load sensor 2 if such a load sensor is
provided. In the illustrated example, it is by way of example assumed that both the
first elevator car 8 and the second elevator car 18 are provided with a load sensor
at the interface from where the elevator car in question is suspended to the ropes
11. In that way the load of the elevator car, in other words weight of elevator car
with passengers and cargo, can be determined based on the indication from the
load sensor 2 of the second elevator car 18. This reading in combination with prior
information about what the load should be when a balance condition exists for the
second elevator car is used to determine the load information.
[0017] An alternative way of obtaining the load information of the second
elevator car 18 is to open the brakes of the second elevator car 18 for a short period of time and monitor any movement and movement direction of the second elevator car 18 while the brakes are open. The brakes which are opened may include hoisting machinery brakes 23 of the second drive system 16, for instance. This opening of brakes and monitoring of movement can be manually made by service personal on site. With this alternative approach, no load sensor is needed to obtain the load information.
[0018] If in step B an imbalance condition in a correct direction is determined, in other words the second elevator car 18 drifts by gravity towards a rescue position when the brakes 23 are opened, it is sufficient to launch in step C the second elevator car 18 to drift to the rescue position by opening the brakes in the

second elevator and allowing the second elevator car 18 to drift by gravity to the rescue position while applying motor braking to keep the speed suitable. Depending on the implementation, the drifting may require that also other brakes are opened in addition to the hoisting machinery brake. Motor braking may be affected by modulating motor inverter transistors actively to generate a rotation magnetic field, for instance. Alternatively, motor braking may be affected by passively shorting motor windings of a permanent magnet elevator motor to enable passive dynamic braking. In any case, no electricity is needed to drive the second elevator car 18 to the rescue position. A suitable rescue position is in that case the closest landing floor 9 located below the position where the second elevator car 18 is stuck in the second elevator shaft 14 where passengers and cargo may be taken out of the second elevator car 18.
[0019] However, in case a balance condition or an imbalance condition in a wrong direction is detected in step B, additional measures are needed for the rescue operation. If a balance condition is determined, this means that the second elevator car 18 and counterweight 14 with the ropes 11 and compensation ropes 12 are in balance, due to which the second elevator car 18 remains stationary in the elevator shaft 14 when the brakes 23 are released. On the other hand, if an imbalance condition in a wrong direction is determined, this means that the imbalance is in a direction preventing the second elevator car from drifting towards a rescue position. This may occur in case the second elevator car 18 is heavily loaded and located below the lowest landing floor 9 such that the drifting direction due to gravity would be downwards in the wrong direction, for instance. [0020] Consequently, if a balance condition or an imbalance condition in a wrong direction is determined for the second elevator car 18 in step B, then in step D a regenerative operation is launched in the first elevator 3 to provide electric power to the second drive system 15 of the second elevator 13. [0021] In step E the second drive system 15 of the second elevator 13 is energized to drive the second elevator car 18 to a rescue position with the electric power provided from the first elevator 3.
[0022] In order to provide electric power from the first elevator 3 to the second elevator 13, a power distribution system of the building will be utilized. According to an exemplary embodiment, an electricity distribution network of the building may be utilized. Alternatively, a supply conductor 21 (such as a cable) may be utilized, which may be connected between regenerative operation interfaces 22 in the first 3 and second 13 elevators, such as between the first and second control

cabinets 7 and 17. This supply conductor may be permanently attached between these interfaces, in which case a service technician may take it into via use by turning one or more switches in a rescue operation control of the elevator system, for instance. Alternatively, the supply conductor 21 may be a separate cable which is mounted and connected in a separate method step prior to launching the regenerative operation with the first elevator 3. With the supply conductor 21, the drive systems of the first and second elevator may be connected to provide a common electricity distribution network of the elevator system, which enables power sharing between the elevators. Alternatively, DC links of the power converters of the drive systems may be interconnected via one or more power cables or busbars.
[0023] The regenerative operation may be implemented to utilize potential energy of the first elevator car 8, or alternatively, of the counter first weight 4 depending on the balance in the first elevator at the moment, which is allowed to ascend or descend by gravity in the first elevator shaft 10. In that case regenerative operation of the first hoisting machinery 6 of the first elevator may be utilized to produce the electric power.
[0024] In some implementations, the power consumption of the second elevator 13 is monitored during the energizing. This monitoring may be carried out by the motor drive in the second control cabinet 17, for instance, from where the information about the power consumption is passed on to the first control cabinet 7. The first control cabinet 7 utilizes the received information to control the electric power provided to the second elevator 13 to match the power consumption of the second elevator 13 during the energizing. This matching may be implemented by consuming extra regenerative power into heat in the drive system of the first elevator 3 by utilizing resistors, such as braking resistors of the first elevator or the motor of the first hoisting machine 6, for instance. Such active control of the regenerated power eliminates the risk that an UPS (Uninterruptible Power Supply) provided to the elevator system or to each separate elevator of the elevator system breaks due to the provided regenerated power.
[0025] An advantage obtained by the above described solution is that it is not necessary to provide the elevator system 1 with a power backup, such as an UPS, having sufficient power to drive an elevator car during a rescue operation necessitated by a power failure in a mains network, for instance. The elevator system 1 may instead be provided with a much smaller battery backup, for instance, which provides sufficient power only to emergency lighting, control

operation of brakes and control circuitry, for instance, however, without a need to provide power signals from the battery backup for driving a hoisting machine to move an elevator to a rescue position. Such a small and relatively inexpensive battery backup may be provided separately for each elevator in an elevator system or as a single common battery backup for all elevators of the same elevator system. [0026] In the previous explanation it has for simplicity been explained that it is the first elevator that is used for the regenerative operation while the second elevator car is driven to a rescue position. However, in practice the roles can be the other way around such that the first elevator car is driven to a rescue position during a regenerative operation with the first elevator.
[0027] It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.

CLAIMS:
1. A method for a rescue operation in an elevator system having at least
a first elevator (3) with a first elevator car (8), a first counterweight (4) and a first
drive system (5), and a second elevator (13) with a second elevator car (18), a
second counterweight (14) and a second drive system (15), characterized
in that a rescue operation of the second elevator car comprises:
obtaining (A) load information of the second elevator car (18), launching (D) a regenerative operation with the first elevator (3) to provide electric power from the first elevator (3) to the second drive system (15) if the obtained load information indicates a balance condition of the second elevator car (18) or an imbalance condition in a direction preventing the second elevator car from drifting towards a rescue position, and
energizing the second drive system (17) to drive the second elevator car (18) to a rescue position with the electric power provided from the first elevator (3).
2. The method according to claim 1, comprising:
connecting a power distribution system of a building supplying said electric power from the first elevator (3) to the second drive system (15) between the first (3) and second elevator (13) prior to said launching.
3. The method according to claim 1 or 2, comprising:
launching the second elevator car (18) to drift to the rescue position, if the obtained load information indicates an imbalance of the second elevator car (13) in a direction allowing drift of the second elevator (18) car to the rescue position.
4. The method according to one of claims 1 to 3, wherein obtaining load
information of the second elevator car (18) comprises:
opening brakes (23) of the second elevator (13), monitoring movement of the second elevator car (18), and determining the load information of the second elevator car (18) based
on detected movement and a movement direction of the second elevator car while
the brakes (23) are open.
5. The method according to one of claims 1 to 3, comprising obtaining load information of the second elevator car from a load sensor (2).
6. The method according to one of claims 1 to 5, comprising:

monitoring power consumption of the second elevator (13) during said energizing, and
controlling the electric power provided to the second elevator (13) during said energizing to match the power consumption of the second elevator.
7. The method according to claim 6, comprising:
controlling the electric power provided to the second elevator (13) during said energizing to match the power consumption of the second elevator (13) by producing heat with excess regenerative power by resistors of the first elevator (3).
8. The method according to claim 6 comprising:
controlling the electric power provided to the second elevator (13) during said energizing to match the power consumption of the second elevator (13) by producing heat with excess regenerative power by a first hoisting machine (6) of the first elevator (3).
9. An elevator system comprising:
at least a first (3) and a second elevator (13), the first elevator (3) having a first elevator car (8), a first counterweight (4) and a first drive system (5), and the second elevator (13) having a second elevator car (8), a second counterweight (14) and a second drive system (15), characterized in that the elevator system comprises:
a regenerative operation interface (22) in the first elevator (3) to provide electric power from the first elevator (3) to the second elevator (13), and
a regenerative operation interface (22) in the second elevator (13) for receiving electric power from the first elevator (3) and for energizing the second drive system (16) to drive the second elevator car (18) to a rescue position.
10. The elevator system according to claim 9, wherein the elevator system comprises at least one control cabinet (7, 17) monitoring power consumption of the second elevator (13) while the second drive system (16) drives the second elevator car to the rescue position, and adjusting the electric power provided by the regenerative operation from the first elevator (3) via the power distribution system of the building (21) to match the power consumed by the second elevator (13) during the driving.
11. The elevator system according to claim 9 or 10, wherein the electric power is provided from the first elevator (3) via a power distribution system of a building to the second elevator (13).

12. The elevator system according to one of claims 9 to 11, wherein the elevator system comprises a supply conductor (21) which may be connected between the regenerative operation interfaces (22) in the first (3) and second (13) elevators, or one or more switches and a supply conductor (21) permanently attached between the interfaces (22) and which may be taken into use by turning said switches to provide electric power from the first elevator (3) to the second elevator (13), for energizing the second drive system (16) to drive the second elevator car (18) to a rescue position in a rescue operation if a balance condition or an imbalance condition in a wrong direction is determined for the second elevator car (18).