EP0483560B1 - Two-channel forked light barrier in Failsafe-design - Google Patents

Abstract

A two-channel forked fail-safe light barrier generates shaft position information in the region of the floors for the premature opening of the doors on arrival of an elevator car and includes a cyclical dynamic self-monitoring circuit by means of which a prophylactic fault recognition is possible. The self-monitoring circuit is responsive to the arrival and standstill of the car at a floor and periodically simulates genuine operational sequences as a brief emergence of the switching vane by an optical short-circuit of the fail-safe light barrier. The simulation effects interruption of the light barrier relay power which is, however, shorter than the release time of the relays so that the relays do not release when the circuit is intact. A sequence of timing signals controls the sequence of the self-monitoring functions and, in the case of any kind of component faults, this sequence is disturbed and a corresponding reaction in the safety circuits of the elevator control takes place by way of the relay contacts. A cyclically appearing test signal is generated as the primary control signal for the simulated interruptions.

Description

The present invention relates to a two-channel fork light barrier in "failsafe" design, which is attached to an elevator car and which generates a corresponding shaft information when a switch flag attached to the elevator shaft, which defines the door zone, is inserted into the slot of the fork light barrier in order to initiate the premature opening and bridging of the door door contacts that open before the end of the journey.

The premature initiation of the door opening when entering an elevator car into a target floor places high demands on devices and circuits which bridge the door and lock contacts within the door phase at the stops in the final phase of the entering elevator car. There are regulations and norms which prescribe the function and partly the execution of such devices, respectively. recommend.

Assemblies that meet these relevant safety regulations are known as failsafe assemblies. In general, such apparatus circuits are designed to be fail-safe in that an error or a combination of errors for the device to be controlled, in this case an elevator, cannot cause a dangerous state.

European patent application No. 0 357 888 describes a method and a device for generating shaft information for elevators by means of a safety light barrier. Circuit-internal test circuits monitor statically in the idle position and dynamically while the elevator is moving when the light barrier is inserted and removed into the bezw. from the actuating lugs in the shaft their correct function and in the event of an error emit appropriate error signals.

U.S. Patent No. 3,743,056 describes a failsafe detector which has a fail-safe circuit and is in particular protected against extraneous light and reflections.

Both circuits have the disadvantage that an error is only discovered when the corresponding function is needed, and the latter is also not redundant.

The present invention has for its object to provide a failsafe light barrier whose operational safety and readiness is known before each trip of the elevator.

This object is achieved by the invention characterized in the claims.

The advantages achieved by the invention are essentially to be seen in the fact that a possible fault in the light barrier is recognized before the elevator leaves, and for this reason the journey and thus an emergency stop due to an open safety circuit between two floors is prevented.

Fig.1

ein Blockschaltbild der Einrichtung,

Fig.2

die Anordnung der Sender und Empfänger in der Gabel-Lichtschranke,

Fig.3

ein Signaldiagramm bei ein- und austauchender Schaltfahne,

Fig.4

ein Signaldiagramm der zyklisch dynamischen Selbstüberwachung,

Fig.5

ein Signaldiagramm der Ueberbrückung Stockwerkfahne,

Fig.6

eine Relaisschaltstufe mit Ansteuerung,

Fig.7

ein Blockschaltbild der zyklisch dynamischen Selbstüberwachung und

Fig.8

ein Signaldiagramm mit Einzelheiten der zyklisch dynamischen Selbstüberwachung.

An exemplary embodiment of the invention is shown in the drawings and shows it

Fig. 1

a block diagram of the device,

Fig. 2

the arrangement of the transmitters and receivers in the fork light barrier,

Fig. 3

a signal diagram with switching flag in and out,

Fig. 4

a signal diagram of the cyclically dynamic self-monitoring,

Fig. 5

a signal diagram of the bridging storey flag,

Fig. 6

a relay switching stage with control,

Fig. 7

a block diagram of the cyclically dynamic self-monitoring and

Fig. 8

a signal diagram with details of the cyclically dynamic self-monitoring.

In Fig.1 all parts of the device and their relationships to each other are shown in a block diagram. 1 with the slot of the fork light barrier is designated, in which the switching flags, not shown, dip in and out while the elevator is moving and thereby interrupt a light beam 11. When the elevator stops on one floor, the light beam 11 is continuously interrupted by the switching flag present there. 7 denotes an oscillator which controls an IR transmitter diode SDA operated in terms of pulses.

This sends its light through an exit window 1.2 via the space in slot 1 into an entry window 1.3, behind which a phototransistor T1 converts the light pulses into current pulses, which are then in a receiver and signal amplifier 3 be processed into a strong signal. At the output of the receiver and amplifier, a measuring point is designated P1A. The signal pulses, clocked with the oscillator signal, are subsequently integrated in an integrator 4 to form a continuous signal which can then be tapped at a measuring point P2A. In this way, non-conforming to the oscillator frequency and any other interference signals are blanked out and eliminated. A subsequent Schmitt trigger 5 is provided in a known manner for a clean switching edge, which can be tracked at a measuring point P3A. The next switching stage with a transistor T2 controls a relay switching stage with a transistor T3 via a cyclically dynamic self-monitoring 6 (hereinafter referred to as ZDU 6). A measuring point P4A is also located on the connection between the transistor and a relay coil A. The relay coil A is connected in the usual way with a back diode and actuates four normally open contacts and two normally closed contacts a1 to a6. On the positive side, the relay coil A is connected via a resistor R1A and a normally closed contact b2 to a supply voltage which comes from a voltage converter and interference filter 9. The relay contacts b1 to b2 are part of relay B in the analog channel B of the failsafe light barrier. The contact combinations a4 / b4, a5 / b5 and a3 / b3 partly present status information and partly parts of the contact safety circuit in the elevator control. With the contact a6, an LED 10 is controlled as an optical status control via a resistor R3A. From measuring point P4A, a connection leads back to ZDU 6. From ZDU 6 itself, an output with a periodic test signal TSA leads to a bridging storey flag 8, which in turn has an input blocking signal SPS and a further input with the oscillator sequence originating from a photodiode HDA. Depending on the input signals, an auxiliary transmitter HSA is operated from the bridging storey flag 8. The light pulses emitted by the transmitter diode SDA also act on the photodiode HDA, the pulse signals of which are continuously applied to the corresponding input of the bridging storey flag 8 and from this when a test pulse TSA arrives or a blocking signal PLC can be passed on to the auxiliary transmitter HSA. Its light pulses then act on the phototransistor T1 (FIG. 1), which completes the process referred to as an optical short circuit.

2 shows the mutual arrangement of the transmitters SA and SB and the receivers EA and EB in the fork arms 12 and 13 of a fork sensor housing 14. The light beams 11 of the two transmitters SA and SB are directed in opposite directions to one another, so that no stray light from a transmitter in can reach a receiver of the neighboring channel.

The functions of the failsafe light barrier with its ZDU 6 are described below with reference to FIGS. 3 to 7.

The signal diagram in FIG. 3 shows the normal function of the failsafe light barrier (hereinafter referred to as the FS light barrier). The first vertical line marked with "in" represents the point in time at which a switching flag in the shaft just interrupts the light beam 11 in the FS light barrier.

The second vertical line marked with "off" represents the point in time at which the switching flag in the shaft just emerges from the FS light barrier and releases the light beam 11. Before the switch flag is dipped to the left of the "in" line, the pulsating signal from the transmitter diode SDA is present at measuring point P1A. When the switch flag is immersed, the signal suddenly disappears and the integrator 4 (FIG. 1) discharges, which can be seen at the measuring point P2A. After falling below the lower trigger threshold value, P3A becomes zero and subsequently also P4A, whereby relay A is energized and relay A can pick up after a time t. The same thing naturally also happens in channel B with relay B. If the two relays A and B have picked up within a predetermined time, the function has run correctly and, if the elevator is entering a destination, the control commands for the premature opening of the door will be given. The principle of simultaneity checking when the relays are activated is described in the application document mentioned for the prior art. The relays A and B remain energized as long as the elevator is on one floor and the light beam 11 through one Switch flag remains interrupted. When the elevator moves away from a floor and the associated flag emerges from the FS light barrier, the pulsating signal at P1A reappears immediately, the integrator 4 charges up, P3A switches to one at the threshold value, P4A also switches and relay A (and B) falls off after a time t. When the elevator drives past the floors without a stop, it is not desirable for various reasons that relays A and B then pick up each time and drop out when the switching lugs in and out of the FS light barrier. For this reason, a blocking signal PLC is formed, for example by the control computer, which brings about the optical short-circuit already described (FIG. 1) and thus makes the switching flags for the FS light barrier that are not yet used for a control function virtually invisible. The effect of PLC can be seen in the signal diagram in Fig. 5. At the moment when the PLC becomes active, the auxiliary transmitter HSA is switched on by bridging the floor flag 8 and the photo transistor T1 is fired with it. Since the light pulses originate from the SDA transmitter diode and are returned via the HDA photodiode to bypass the floor flag 8, it means no difference to the original signal for the subsequent switching and the relays A and B remain dropped or do not react to a switch flag as long as the blocking signal PLC is active. These additional opto-elements are the basis for the implementation of the ZDU (cyclical dynamic self-monitoring) for error detection. The term dynamic is used to address the functioning of the monitoring, which is carried out in the same way as an operating function, and the term cyclical is an indication of the periodic repetition of the monitoring function every second. It is about recognizing faulty elements and errors in function at any time. The diagram of FIG. 4 shows the test signals TSA of channel A and TSB of channel B coming from the ZDU 6. The test signals TSA and TSB have a pulse length tp which is, for example, half shorter than the relay dropout time t (FIG. 3). Furthermore, the test signals TSA and TSB are offset in time from one another at a time tpv (Fig. 8). The time shift serves to ensure that the monitoring functions run completely separately for each channel in order to avoid mutual interference. The test signals TSA and TSB simulate a brief escape from the switch flag during which the elevator is at rest on the floor. The functions correspond in principle to those as shown in the diagram in FIG. 3, with the difference that they run inversely and are much shorter in time. With the ZDU 6, all elements involved in the operational function are checked during each function cycle. In the event of a fault, the monitoring cycle is interrupted, whereupon at least one relay A or B drops out and the safety circuit of the elevator thus responds. The ZDU 6 essentially consists of a number of interdependent time signal circuits. The time signals and circuits are called t1A, t2A, t3A and t4A for channel A and t1B, t2B, t3B, t4B and tVB for channel B (FIG. 7). 6 shows the details of the relay switching stage with the switching transistor T3 and its control with an OR gate. The inputs of the OR gate form the time signals t1A and t3A.

Relay A is therefore live if one or both inputs are one or is not live if both inputs are zero. The ZDU 6 now causes both inputs t1A and t3A to periodically become zero for a short time without relay A dropping out.

7 shows the time signals t1A to t4A or tVB and t1B to t4B, as well as the two OR gates and a flip-flop QFF as blocks with the corresponding connections to one another. The blocks shown are the essential content of block ZDU 6 in the block diagram of FIG. 1. The upper part of the block diagram shows the elements of the A channel and the lower part those of the B channel. QFF is a common element and has a synchronization task. An additional time signal circuit tVB is present in the B channel and has the task of causing a pulse shift in order to form a QFF start signal.

The timing of the signals mentioned is shown in the diagram in FIG. In addition to the time signals, the Test signals TSA and TSB, the measuring points P4A / B, the relays A / B, and a JK flip-flop output QFF are listed. The time signal t1A is a bridging signal and is approximately twice as long as t1B. The time signals t2A and t2B are short control signals for QFF and the time signals t3A and t3B are the actual cycle-determining signals. t3A and t3B are started together with the falling edge of QFF, but have a length different by tPV, with t3A <t3B. The point in time of the diagram is given when the switch flag is dipped in and defined with the vertical line marked above with "in". First, t1A, which is identical to P3A, becomes one, generates the switching pulse t2A, which in turn makes QFF one. At the same time, relay A is switched on via P4A, which picks up after a time t. The time signal tVB is first started in channel B and only switched through to relay B after it has elapsed, as a result of which it receives voltage, for example, 2 ms later. The end of the time signal tVB generates the switching pulse t2B which then makes QFF zero again. The falling edge of QFF is now the start signal, synchronizing both channels, for the time signals t3A and t3B. The time signals t3A and t3B are of different lengths, with t3A being shorter than t3B. The time difference corresponds to the test signal delay time tPV in the diagram in FIG. 4. After t3A has elapsed, the first test in channel A begins by generating a test signal TSA via t4A and which makes measuring point P4A one during its duration, thus creating a time gap of the same duration for the relay.

However, as already mentioned, its duration is only about half as long as the fall time of relay A, so that it cannot fall. After TSA has elapsed, a switching pulse t2A is generated again, which now makes t1A one. t1A has a length that overlaps the function of the subsequent test in channel B. The interruption in time in the relay system is therefore in effect a time gap between the two time signals t1A and t3A (FIG. 6). After a time tPV, t3B now also becomes zero and the same sequence now generates the interruption in the relay hold of channel B. The time signal tBV must now be present in channel B TSB be shorter by the amount to cause the interruption of the same length. The time gap in the channel B relay system is made up of the duration of TSB and tVB. At the end of tVB, the switching pulse t2B QFF becomes zero and the time signals t3A and t3B start again, which starts a new cycle. Now that the test in channel B is over, t1A can run out without effect and is ready for the next same function. If there is any fault in the circuit, the response must be on the safe side, i.e. a relay must drop out and its contacts report the fault to the safety circuits. The periodic inspection of all components records interruptions, short circuits, intermittent failures and drifts. As a first example, assume that the measurement point P3A remains at zero. This could be a short circuit in transistor T2 or an error producing this effect in the preceding circuits. If t3A has now expired, no new t1A is started, measuring point P4A becomes one and relay A drops out because neither t1A nor t3A is present at the OR input in the switching stage. Exactly the same happens if, for the same reasons, for example the measuring point P3A remains permanently at one. Then no t1A and no subsequent time signal is started either, which achieves the same effect. In summary, it can be said that any disturbance in the time signal sequences inevitably leads to a relay A and / or B dropping out. When the elevator is at a standstill, the ZDU 6 produces switching sequences as they occur during operation. This is why it is a prophylactic fault detection, because faults in the circuit are recognized before they have an effect and the consequences are thus mitigated. Because opening the safety circuit while driving results in emergency stops and trapped passengers. If a fault is detected, the start of the elevator is blocked and boarded passengers can leave the cabin again. If the light path in the FS light barrier causes components to fail while the elevator is moving, the light path of channel A, for example, simulates PLC as interrupted despite the presence of a blocking signal relay A picks up and immediately activates the ZDU 6.

Then relay B also picks up. For the time difference in which the two relays pick up one after the other, the antivalence of the outgoing relay contacts is disturbed, with which the error is reported to the control. After a cycle time tz, both relays drop out again because the faulty channel does not carry out the signal change controlled by the ZDU 6. In the exemplary embodiment shown and described, the time signal circuits are implemented by means of RC-connected, generally known monostable CMOS multivibrators, and a likewise known dual J-K flip-flop was used for the flip-flop circuit. The measuring points mentioned in the description only serve to explain the function and in the practical version are not designed as electrical connections. The circuit and mode of operation of the FS light barrier shown can also be used in other areas of technology where fail-safe devices are prescribed, such as for machine tools, trains, alarm and security systems.

The design does not have to be limited to the fork shape; a corresponding sensor can also be designed as a proximity sensor based on the reflex principle.

Claims (9)

1. Two-channel forked light barrier in "fail-safe" construction, which is mounted at a lift cage and which, on entry into the slot of the forked light barrier of a switching vane which is mounted in the lift shaft and defines the door zones, generates a corresponding shaft information for the purpose of initiation of premature opening of the foor and bridging over of the thereby opened door contact before the end of travel, characterised thereby, that the fail-safe light barrier comprises a cyclically dynamic self-monitoring circuit ZDU (6), which detects faults in electronic components (3, 4, 5, T2) in the fail-safe light barrier during halt at a storey by periodic temporary tripping of the light barrier in simulation of the function thereof as in a travel of the lift.
2. Fail-safe light barrier according to claim 1, characterised thereby, that the self-monitoring circuit ZDU (6) displays time signal circuits (t1A to t4A, tVB, t1B to t4B), which are connected one among the other, generate time signals, operate sequentially and which control the simulated operating sequence.
3. Fail-safe light barrier according to the claims 1 and 2, characterised thereby, that the self-monitoring circuit (ZDU) (6) displays a flip-flop circuit (QFF), which is common to both channels and starts a cycle time (tz) by way of time signal circuits (t3A, t3B).
4. Fail-safe light barrier according to the claims 1 and 2, characterised thereby, that the self-monitoring circuit ZDU (6) displays an output delivering a periodic test signal (TSA, TSB) interrupting the feed of the relays (A, B) for a time, which is shorter than their release time (t ab), by operative functional blocks (3, 4, 5).
5. Fail-safe light barrier according to the claims 1 and 2, characterised thereby, that the time signal circuit (tVB) in the self-monitoring circuit ZDU (6) in the channel of the fail-safe light barrier is constructed as a timing circuit producing a pulse displacement time (tPV).
6. Fail-safe barrier according to the claims 1 and 2, characterised thereby, that the time signal circuits (t3A, t3B) are constructed as timing circuits producing time signals differing one from the other by the pulse displacement time (tPV).
7. Fail-safe light barrier according to the claims 1 and 2, characterised thereby, that the time signal circuit (t1A) is constructed as a timing circuit producing a timing signal overlapping the test signal (TSB).
8. Fail-safe light barrier according to claim 1, characterised thereby, that light beams (11) display mutually opposite directions through opposed placement of transmitting diodes (SA, SB).
9. Fail-safe light barrier according to claim 1, characterised thereby, that at least one storey vane (8) is presewnt, which is controlled by signals SPS and TSA/TSB and a photo-diode HDA/HDB, controls an auxiliary transmitter HSA/HSB and which bridges over a circuit effecting an optical short-circuit.

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