FIELD OF THE INVENTION

The invention relates elevators and particu ^¬ larly to braking systems used in elevators.

BACKGROUND OF THE INVENTION

Elevator systems are regulated all over the world. Regulations typically relate to the security of an elevator. Each elevator must fulfill the regula- tions and these requirements are sometimes verified regularly. Typically elevators are inspected regularly and parts not filling the requirements must be changed. As elevators are typically used for trans ^¬ porting passengers the security is an essential as- pect. Thus, all aspects that can have a negative im ^¬ pact on the security should be eliminated. Sometimes a small failure in a part of the elevator may lead into security issues.

One of the important issues is that the ele- vator is operating without additional forces restrict ^¬ ing the movement of the elevator car. One possible cause is a defected brake that is not completely re ^¬ leased and causes friction. The problem associated with this is the fact that the brake wears very fast and will not have the required braking power when it is needed. The wearing may be very fast and the dan ^¬ gerous technical condition occurs so that the conven ^¬ tional inspection frequency is not able to notice the wearing in time.

The problem mentioned above is regulated by many authorities and it is also desirable without reg ^¬ ulation to prevent the movement of the elevator car when the brake is not completely released so that pos ^¬ sibly dangerous situation is avoided.

Conventionally displacement sensors have been used for detecting the release of a brake. These sen- sors are additional components that are not always re ^¬ liable because the mechanical movement of a brake is very small. Furthermore, sometimes the brake does not open completely but the sensor indicates that the brake has been opened but it still has a contact which will cause friction and leads into undesired wearing as discussed above. A further drawback of additional sensor is that in general, using additional components causes expenses because of additional components and additional design needed. Thus, there is a need for reliable and cost efficient arrangement for brake re ^¬ lease monitoring.

SUMMARY

The invention discloses an arrangement, wherein brake release sensors for an elevator can be replaced by an arrangement wherein the brake release is determined from the force caused by the brake. This is achieved by providing measuring device for measur- ing the weight of an elevator car between the brake and the motor body so that the weight of the elevator car is measured only when the brake is on.

An example of an elevator where a weight measuring device is arranged between the brake and the motor body is disclosed in WO2013/183742 Al, wherein the measurement device is used for measuring the weight of an elevator car in order provide smooth start for an elevator and, for example, detecting overweight situations. In the embodiment disclosed in the publication mentioned above the weight of an ele ^¬ vator car is measured from a rotating shaft part of traction sheave when the break is on. This is a pre ^¬ ferred way of measuring the weight as it will measure the load actually caused to the traction sheave. Be- cause of this arrangement the measurement result should be zero when the brake is released the elevator is operated. However, if the brake is not opened com ^¬ pletely and the brake drags, the weighing device will indicate a value that deviates from the value of com ^¬ pletely released brake.

An embodiment is implemented as a method for de ^¬ tecting release of a brake of an elevator. In the method a measuring device for measuring weigh of an elevator car from a rotating shaft of part a traction sheave of the elevator when the brake of the elevator is closed is used. Then, when the brake is about to be released a brake release signal is generated. After the brake release signal values a value from the meas ^¬ uring device generating the brake release signal are still received. Received values are compared with a reference value. A brake failure is detected when the received value deviates from the reference value.

In an embodiment the method described above is implemented as a computer program embodied on a computer readable medium. The computer program is con- figured to cause the method described above when exe ^¬ cuted in a computing device. In a further embodiment an apparatus is used to cause the method described above. In a further embodiment the above described method, computer program or apparatus is implemented in an elevator.

The benefit of the invention is that it pro ^¬ vides a reliable way of replacing conventional switch ^¬ es for detecting the brake release. Furthermore, as the arrangement suggested by the present invention is more accurate it will fulfill the increased require ^¬ ments by different regulations around the world. A further benefit of the present invention is that it provides cost savings compared to traditional switches by providing reliable brake monitoring by weighing de- vice of the elevator. Thus, no additional components are needed, which causes cost savings in manufacturing and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illus ^¬ trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

Fig. 1 is a block diagram of an example embodiment of the present invention,

Fig. 2 is a flow chart of a method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

In figure 1 a block diagram of an arrangement according to the present invention. In the embodiment of figure 1 an elevator car 10 is operated by using a hoisting rope 11 which is arranged to a traction sheave 12, which is operated by the hoisting machine 13. The elevator car 10 transports passengers accord- ing to given calls. The hoisting machine of the embod ^¬ iment is controlled by a controller 16 that is con ^¬ nected to the hoisting machine 13. For example, when the controller receives a call, directly or indirect ^¬ ly, from the elevator car, it will instruct the hoist- ing machine to move the elevator to the called floor. When the elevator is not moving it will be kept in its position by a break 14. The break is typically magnet ^¬ ic so that an electromagnetic force is used to keep the brake released during the movement of the elevator car. When the elevator car stops the brake closes when the electromagnetic force is turned off. In the embod- iment of figure a weighing device 15 is arranged be ^¬ tween the brake 14 and traction sheave 12 so that the weighing device 15 is able to measure the weight of the elevator car when the brake 14 is in closed posi- tion. The present invention is not limited to any brake or hoisting machine type but any hoisting ma ^¬ chine and brake type can be used, provided that they can be configured in a manner that the weight of the elevator car is measured only when the brake is in closed position. Examples of suitable brake, measuring device and hoisting machine are given, for example, in WO2013/183742 Al mentioned above.

In the embodiment according to figure 1 hoisting machine 13, weighing device 15 and brake 14 are connected to the controller 16. In the figure a separate connection between each of the components is disclosed, however, it is possible that the arrange ^¬ ment comprises a further controller at the vicinity of the hoisting machine or hoisting arrangement and the information is then transmitted further to the controller. Conventionally the weighing device 15 has been used for providing a smooth start for elevator ride by estimating the force needed from the weight of the elevator car. A further use has been to detect possible overload situations when the elevator car is too heavy. When the elevator is overloaded the opera ^¬ tion of the elevator should be prevented for security reasons. In other words, conventionally the weighing device has been used between the rides when the eleva- tor car is stationary in a floor waiting for a next call or having a stop in a floor when the elevator rides have been called to a plurality of destinations.

When the arrangement of figure 1 is operated the controller 16 receives calls and schedules the movement of the elevator car 10. During the operation it may receive indications from and can send instruc ^¬ tions to the elevator car 10, hoisting machine 13, brake 14 and weighing device 15. According to the em ^¬ bodiment of figure 1 the release of the brake 14 can be detected using, for example, a method discussed be ^¬ low with regard figure 2. In the method the controller 16 detects or receives an indication that the brake release signal has been generated and/or the elevator is moving. At the same time it will continue receiving data from weighing device 15. When the brake 14 and weighing device 15 are configured as discussed above, there should not be any load to be measured if the brake 14 is released completely. If the weighing de ^¬ vice, however, indicates a value different to the val ^¬ ue without load it might be an indication of a brake failure. The different value is caused by dragging brake.

The controller 16 further includes at least one processor 17 and at least one memory 18 for storing and executing computer programs and related data. Furthermore, the controller 16 may include other com- ponents that are not shown in the figure, for example, data communications connection if the controller is located at a remote site so that the data can be re ^¬ ceived and instructions transmitted through this data communication connection.

In figure 2 a method according to the present invention is disclosed. The method is initiated by generating brake release signal, step 20. For example, if the controller 16 of figure 1 is responsible for monitoring and instructing the operation of the eleva- tor system, the brake release signal may be an inter ^¬ nal message within the software framework operating the elevator. Thus, when the software component re ^¬ sponsible for instructing brake release sends an in ^¬ struction for brake release it simultaneously sends message to monitoring component that the brake has been released. As a response to the brake release sig- nal the brake is released, or if the brake is defect, at least tried to release.

The monitoring component receives values from the weight measuring device, step 21. When the brake is in closed position the monitoring means receive the weight of the elevator car. When the brake is released the value received should be zero if the weighing de ^¬ vice is calibrated to show zero when there is no load. The received value is compared to a reference value, step 22. It is important to understand that the weigh ^¬ ing device does not necessarily show zero when there is no load but may deviate from zero. This offset val ^¬ ue may be determined by monitoring the values that the weighing device provides and if it is the same value to both elevator operating directions the value can be considered as an offset from zero and used as a refer ^¬ ence value. If the measured value deviates from this reference value, there may be a brake problem and it is detected, step 24. Correspondingly, if the refer- ence value cannot be determined, i.e., the weighing device shows different values to different directions, there may be a brake problem.

After detecting the brake problem different actions may be taken. For example, the elevator may be brought to the next floor and stopped there. The oper ^¬ ation of that elevator may be prevented and a mainte ^¬ nance call may be launched.

The above mentioned method may be implemented as computer software which is executed in a computing device, such as the controller 16 of figure 1. When the software is executed in a computing device it is configured to perform the above described inventive method. The software is embodied on a computer reada ^¬ ble medium so that it can be provided to the computing device, such as the controller 16 of figure 1.

As stated above, the components of the exem ^¬ plary embodiments can include computer readable medium or memories for holding instructions programmed ac ^¬ cording to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein. Computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution. Common forms of computer-readable media can include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other suitable magnetic medi- urn, a CD-ROM, CD±R, CD±RW, DVD, DVD-RAM, DVD1RW, DVD±R, HD DVD, HD DVD-R, HD DVD-RW, HD DVD-RAM, Blu- ray Disc, any other suitable optical medium, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other suitable memory chip or cartridge, or any other suitable medium from which a computer can read.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.