Patent Description:
It is object of the present invention to improve the aforementioned drive device and elevator such that the general safety level is improved as to allow the omission of main contactors with the elevator drive.

The object is solved with a drive device according to claim <NUM> as well as with an elevator according to claim <NUM>. Preferred embodiments of the invention are subject-matter of the corresponding dependent claims. Advantageous embodiments are also described in the description as well as in the drawings.

According to the invention, the drive prevention circuit comprises two separate safety input circuits each configured to be connected to the elevator safety circuit to receive a safety signal, respectively. Furthermore, each of the safety input circuits is configured to interrupt the connection between the control circuit and the motor bridge. The interruption occurs preferably by the safety input circuit itself, but could also performed via a separate circuit. As the main contactors of the elevator drive as hardware elements improving the safety of the drive are to be left away, the invention seeks to compensate a corresponding high safety level by providing redundant safety signalling and redundant input safety circuits which each are able to interrupt the connection between the control circuit and the motor bridge as to shut the elevator motor off. This arrangement ensures that even in case of breakdown of one signal line and/or one safety input circuit, the other safety input circuit and the other signal line are still able to interrupt the transmission of control signals from the control circuit to the motor bridge in case of any operation anomalies.

Preferably, the two safety input circuits are connected to a shut-down circuit of the drive prevention circuit which is configured to monitor the safety input circuits and preferably also to interrupt the connection between the control circuit and the motor bridge. The advantage of the shut-down circuit is that this additional circuit can be used to monitor the function of the two separate safety input circuits as to gather information regarding the reliability of the redundant signal transmission. On this behalf, the shut-down circuit preferably has a fault memory for storing safety shut-down events in the operation history of the elevator. Preferably, this shut-down circuit is itself able to interrupt the connection between the control circuit and the motor bridge as to initiate the disconnection of the control circuit from the motor bridge if the operating history of the safety input circuits indicate a certain safety problem in the signal transmission or in the occurrence of safety shut-downs. Preferably, the shut-down circuit does not only comprise a fault memory but also comprises a diagnosis circuit for the monitoring and function evaluation of the safety input circuits or brake safety input circuits. The fault-memory of the shut-down circuit may be read e.g. by a maintenance tool or by a remote maintenance center. Further, the diagnosis circuit may preferably be configure to issue a maintenance signal to a remote maintenance center, e.g. via telephone network or internet.

Preferably, two separate signal communication channels are arranged to be connected to separate outputs of the elevator safety circuit and to be connected with the two safety circuits, whereby one of both channels is connected to one of said safety input circuits, respectively. The basic redundancy idea is here extended to the signal transmission line from the elevator safety circuit to the safety input circuits. Preferably, in the inventive elevator the elevator safety circuit has two parallel safety switches or modules for one safety function, so that not only the safety input circuits and the signal transmission but also the safety signal generation is redundant.

In a preferred embodiment of the invention, the drive device comprises a brake drive configured to be connected to at least one elevator motor brake, which brake drive is connected to a brake controller via a brake drop-out circuit, which is per se known from <CIT>. According to the invention, the brake drop-out circuit has two (brake) safety input circuits configured to be connected to the elevator safety circuit and each of the brake safety input circuits is configured to interrupt the connection between the brake control circuit and the brake drive. The safety input circuits for the motor drive and the brake drive could preferably be identical. Usually, the brake drive comprises like the motor bridge at least one semiconductor switch to shut-down or to initiate the feeding of current to the elevator motor brake. Usually, the feeding of current to the motor brake means the releasing, i.e. opening of the brake, whereas the shut-down of current to the brake initiates immediate closing of the brake whereby the elevator motor brake usually grips a rotating part of the motor or of a traction sheave connected to the motor. The brake drive normally gets its energy from a brake energy supply circuit which is normally a DC converter to be connected with a public AC supply network. This advantageous embodiment of the invention raises the safety regarding the operation of the motor brake to the same safety level as the stopping of the elevator motor in any case of operation anomaly as now two independent safety input circuits are located in the connection between the brake controller and the brake drive as to initiate braking an any case of unclear safety situation of the elevator. Therefore, this embodiment of the invention provides a high safety level.

Preferably, the two brake safety circuits are connected to a shut-down circuit of the brake drop-out circuit which shut-down circuit is configured to monitor the (brake) safety input circuits and preferably also to disconnect the connection between the brake controller and the brake drive. Accordingly, the operation of the elevator brake in any case of operational anomaly of the elevator is essentially improved. Also in this case, the shut-down circuit opens (as already mentioned in connection with the motor bridge) the possibility to monitor the (brake) safety input switches and to initiate the operation of the elevator motor brake if the operation history of the brake safety input circuits indicates any kind of loss of safety level. Therefore, the safety of the overall device is not only improved by the redundant safety signal processing but also by the monitoring of the two independent brake safety input circuits as to check the operation history of these circuits to any kind of operational defects. For the advantages regarding the safety input circuit monitoring reference is made to the statements in connection with the motor drive. Thus the shut-down circuit may have a fault-memory and a diagnosis circuit.

Preferably, an elevator comprises two parallel elevator motor brakes. In this case, of course, two (solid state) brake drives are provided which are each connected to a corresponding separate brake controller via a separate brake drop-out circuit. Via this measure, the increase of the safety level is achieved for each of the two elevator motor brakes independently.

Preferably, the safety signals in the signal transmission are 24V signals which are the common voltage levels in an elevator safety logic/circuit. Therefore, the output signals of the elevator safety circuit can be used without any further processing which would induce possible failure sources in the signal processing.

Preferably, the safety input circuit or the brake safety input circuit is embodied as a digital isolator or optical isolator arranged in a control line (between control circuit/brake controller and motor bridge/brake drive) of the solid state switches of the motor bridge or brake drive. Via this embodiment, a reliable disconnection of the signal line to the control contactors of the solid-state switches of the motor bridge and brake drive is obtained.

Of course, it is also possible that the safety input circuit disconnects different signal or supply lines of the motor bridge or brake drive. Thus, one of the safety input circuits can for example disconnect the control line for the control gate of the semiconductor switches of the motor bridge/brake drive whereas the other safety input circuit may disconnect the energy supply line of the motor bridge/brake drive. Via this way, the shut-down of the corresponding drive is even realized via different disconnection lines.

Preferably, the fault memory or the diagnosis circuit of the shut-down circuit could also be read out for example by remote access or via service technicians on site. Thus, the shut-down circuit may comprise a safety logic SSD, which is used for diagnosis operation of the safety input circuits and the signal channels from the elevator safety circuit to the safety input circuits. One SSD may read logic states of the first and the second safety lines and safety input circuits and may interrupt the connection of the control circuit to the motor bridge or of the brake controller to the brake drive in which case the logic states of both safety channels differ from each other at least for a given period. This may be also memorized in the fault memory of the shut-down circuit. Preferably, to resume normal operation, e.g. to restart supplying control pulses from the control circuit to the motor bridge via the control line, the fault memory hardware must be resetted, i.e. via a service technician. The memory function can be implemented in the fault memory of a PWM generating DSP processor, e.g. in the control circuit or alternatively with a separate logic hardware. With the fault memory function implemented in a separate hardware, a higher reliability can be used as when this memory function is provided in the DSP processor of the control circuit.

The invention further relates to an elevator comprising an elevator motor for moving an elevator car, at least one, preferably two elevator motor brakes, at least one drive device of the aforementioned kind, preferably one drive device for the motor bridge and one drive device for each of the two motor brakes. Furthermore, the elevator further comprises at least one elevator safety circuit, for example an elevator safety logic issuing a safety signal indicative of the current safety situation of the elevator. This kind of elevator provides a very high safety level, as e.g. SIL3 safety level which enables the omission of hardware contactors in connection with the elevator drive.

Preferably, the elevator safety circuit/controller has for each safety function two independent safety switches or safety modules which are connected via separate safety channels or safety lines to the two (brake) safety input circuits of the drive prevention circuit or brake drop-out circuit. Via this embodiment, the redundancy level is kept up into the function of the elevator safety circuit itself. Therefore, this embodiment of an elevator provides a very high safety standard.

Preferably the two safety input circuits are series connected in the connection between control circuit/brake controller and motor bridge/brake drive. The shut-down circuit is preferably connected with an own interruption circuit located in the control line of the motor bridge/brake drive to interrupt the control signals and stop the elevator motor/start the brake operation.

Following terms are used as synonyms: elevator safety logic - elevator safety controller - elevator safety circuit;.

The invention is hereinafter described with respect to the appended schematic drawing. This drawing shows a schematic diagram of an elevator with a high safety standard.

The elevator <NUM> comprises a frequency converter <NUM> consisting of a network rectifier <NUM> to be connected to a public AC supply network <NUM>, a motor bridge <NUM> and a DC intermediate circuit <NUM> located between the network rectifier <NUM> and the motor bridge <NUM>. The motor bridge <NUM> preferably comprises IGBTs as solid state switches and is controlled by a control circuit <NUM> as to drive an elevator motor <NUM> in line with reference values or reference curves. Between the control circuit <NUM> and the motor bridge <NUM>, a drive prevention circuit <NUM> is located comprising two safety input circuits 24a, 24b, a shut-down circuit <NUM> and an interruption circuit <NUM>. The safety input circuits 24a, 24b are series connected whereby each of these safety input circuits 24a, 24b is able to disconnect the control circuit <NUM> from a control input of the motor bridge <NUM>. Each safety input circuit 24a, 24b is configured to be connected via a separate signal channel 26a, 26b to two safety outputs 28a, 28b of an elevator safety circuit <NUM>. The two signal outputs 28a, 28b are the outputs of two independent safety switches or safety modules in the elevator safety circuit <NUM> provided for the same safety function. Thus, for example two parallel door contacts can be provided for a landing door, whereby one of the contacts is connected to one of the signal channels 26a, 26b, respectively. Via this measure, the redundancy of the safety signal transmission to the safety input circuits 24a, 24b can be extended to the safety signal generation. The safety input circuits 24a, 24b are connected to the common shut-down circuit <NUM> which is configured to monitor the function of each of the safety input circuits 24a, 24b and the corresponding signal channels 26a, 26b. On this behalf, the shut-down circuit <NUM> preferably has a diagnosis circuit as well as a fault memory. The shut-down circuit <NUM> has an own interruption circuit <NUM> which is able to interrupt the connection between the control circuit <NUM> and the motor bridge <NUM> even in a case when currently the signal outputs of the safety input circuits 24a, 24b are positive but the operation history of these circuits revealed that there is some ambiguity in the safety level.

The elevator <NUM> furthermore has two brake drives 36a, 36b for two elevator motor brakes 42a,b of the elevator. The brake drives 36a,b are connected with a common power supply <NUM>, usually a DC converter connected with the public AC supply network <NUM>. Each brake drive 36a, 36b is connected with a brake controller 40a, 40b which brake controllers 40a, 40b are configured to initiate the closing or opening of corresponding elevator motor brakes 42a, 42b. In the connection between the brake controllers 40a, 40b and the brake drives 36a, 36b a brake drop-out circuit <NUM> is located comprising the same arrangement of two (brake) safety input circuits 24a, 24b, a drop-out circuit <NUM> and an interruption circuit <NUM> is provided as in the control line of the motor bridge <NUM>. Accordingly, the control devices <NUM>, 40a,b are connected with the motor bridge <NUM> as well as each of the brake drives 36a, 36b via a parallel redundant safety system comprising first and second safety channels 26a, 26b and the corresponding safety input circuits 24a,b as to ensure safe action even if one signal line 26a,b or one safety input circuit 24a,b should fail. This redundant safety system is again improved by the shut-down circuit <NUM> which is capable of monitoring the function of the safety input circuits 24a,b as well as the safety channels 26a,b and to trigger the interruption circuit <NUM> to shut-down the control line if the operation history of these safety relevant components leave any doubt with regard to the safety of the elevator. Via this inventive embodiment, not only a redundancy level for the safety signal processing is obtained but also the reliability of these safety components 24a, 24b, 26a, 26b over the time can be monitored and evaluated via the shut-down circuit <NUM> which additionally can interrupt the connection between the corresponding controllers 40a, 40b and the motor bridge <NUM> or brake drive 36a, 36b.

Accordingly, such a kind of elevator reaches safety integrity level (SIL) <NUM> which is a current safety code requirement for elevator safety control when hardware logic elements should be used to replace mechanical safety contactors.

Claim 1:
Drive device of an elevator (<NUM>), comprising a frequency converter (<NUM>) to be connected to a public AC supply network (<NUM>) and an elevator motor (<NUM>),
the frequency converter (<NUM>) comprising a network rectifier (<NUM>) configured to be connected to the AC supply network (<NUM>), a motor bridge (<NUM>) to be connected to the elevator motor (<NUM>) and a DC intermediate circuit (<NUM>) located between the network rectifier (<NUM>) and the motor bridge (<NUM>),
the motor bridge being controlled by a control circuit (<NUM>) which feeds the motor bridge (<NUM>) with control pulses to regulate the motor speed,
the drive device further comprises at least one drive prevention circuit (<NUM>) connected between the control circuit (<NUM>) and the motor bridge (<NUM>), which drive prevention circuit is configured to obtain a safety signal from an elevator safety circuit (<NUM>),
characterized in that the drive prevention circuit (<NUM>) comprises a series connection of two separate safety input circuits (24a, 24b) each configured to be connected to the elevator safety circuit (<NUM>) to receive a safety signal, and that each of the safety input circuits (24a, 24b) is configured to interrupt the connection between the control circuit (<NUM>) and the motor bridge (<NUM>) in response to the safety signal status.