EP1652203B1 - Protector suitable for cascade connections and corresponding method for safety-conditioned switching - Google Patents

Description

The present invention relates to a protective device for safety-related switching of an electrical unit having a first input for receiving a switch-off signal, a second input for receiving a switch-on signal in the form of a switch-on pulse and an output for driving the electrical unit. Moreover, the present invention relates to a corresponding method for safety-related switching of an electrical unit.

In safety-relevant systems and facilities, an emergency stop button for switching the system or device may be provided. Shutdown is carried out by a safety or protective device. In FIG 1, such a system is shown as a block diagram. The protection device 1, which can also be referred to as an emergency stop device, has a multi-channel input via which it receives an emergency stop signal from an emergency stop button 2. In addition, the protective device 1 has a second input, via which a switch-on signal can be received by an on-push button 3. This button 3 is designed as a normal open button. The protection device 1 controls an actuator 4, e.g. a contactor. The actuator 4 in turn switches a load contact 5 and at the same time a monitoring contact 6. In the non-active state of the actuator 4, the load contact 5 is open and the monitoring contact 6 is closed.

According to the European safety standard EN 954, category 4 after an emergency stop on a safety device must not be automatically restarted after the emergency stop cause has been eliminated. This means that after pressing an emergency stop button, it must first be locked again for restarting. The device does not start up yet. First when a On button is pressed, the output (s) are enabled and the device starts up. In addition, a monitoring of the actuators must be given for category 4 of this safety standard EN 954, ie monitoring contacts 6 of the emergency stop device 1 or of the connected actuator 4 must be introduced into the on-button circuit. As a result, errors of the actuator 4 can be detected. If, for example, the load contact 5 of a contactor is welded due to an overload, then the monitoring contact 6 is open, even if the contactor is not activated. This means that the on-button circuit is interrupted and a restart is prevented.

For category 4 of the safety standard EN 954, it is also stipulated that the evaluation of the one-button circuit must be edge-sensitive. Specifically, the falling or both edges of a switch-on pulse must be detected. As a result, for example, an unwanted restart of an electrical device can be prevented by a cross-circuit at the inputs or outputs of the emergency stop device 1.

In a larger systems, such as a conveyor belt, several emergency stop buttons may be provided. In this case, the associated protection devices are cascaded, as shown in FIG 2. The essential structure of each circuit group corresponds to that of FIG. 1. For the sake of clarity, only two stages of a cascade, each with a protective or emergency stop device or an emergency stop button, are shown in FIG. The first emergency stop device 11 is connected to a two-channel emergency stop button 12, 12 '. This, in turn, controls two actuators or contact multipliers 14 and 14 'in accordance with category 4 of the safety standard EN 954. The actuators 14 and 14 'actuate monitoring contacts 16 and 16', which are connected in series and with an on-button 13 form a one-button circuit, for example, from an external supply voltage source (24 V) to the emergency stop device 11.

With the help of the actuators 14 and 14 'further two load double contacts 15 and 15' are also actuated. These form together with a dual-channel emergency stop button 22, 22 'an emergency stop circuit on the second emergency stop device 21. This also controls two actuators or contact multipliers 24 and 24', which in turn monitoring contacts 26th and 26 'and load double contacts 25 and 25' actuate. The monitoring contacts 26 and 26 'form the on-button circuit of the emergency-stop device 21 with an on-button 23. The cascading can be continued at the load-double contacts 25 and 25' as desired.

The operation of this cascade circuit can be described as follows. If the emergency stop button 12, 12 'is actuated on the first emergency stop device 11, the actuators 14, 14' of the emergency stop device 11 are deactivated. Thus, the load contacts 15, 15 'of these actuators 14, 14', which are installed in the emergency stop circuit of the emergency stop device 21, are opened. This leads, as in the emergency stop circuit of the emergency stop device 11, to an interruption in the emergency stop circuit of the emergency stop device 21. This also causes the actuators 24 and 24 'of the emergency stop device 21 switched off. Consequently, all load circuits of the cascade are turned off.

If only the emergency stop button 22, 22 'is actuated, only the actuators 24, 24' are deactivated by the emergency stop device 21. Thus, the load monitoring contacts 26, 26 'and the load double contacts 25, 25' are also deactivated. Consequently, all subsequent load circuits of the cascade are turned off. The actuators 14, 14 'of the emergency stop device 11 remain active.

To restart the load circuits, the emergency stop button 12, 12 'of the emergency stop device 11 is locked again, ie the emergency stop circuit is in a closed state. At this point, however, the load circuits are not yet closed. For this purpose, the ON button 13 and 23 must also be pressed become. If the ON button 23 on the emergency stop device 21 is first actuated, then the emergency stop device 21 does not switch its actuators 24, 24 'on, since the actuators 14, 14' of the emergency stop device 11 switch on Stop the emergency stop circuit of the emergency stop device 21. To restart the load circuits so the on-button 13 of the emergency stop device 11 must first be pressed. Thereafter, the actuators 14, 14 'of the emergency stop device 11 are activated and the emergency stop circuit of the emergency stop device 21 is closed. Only now, the emergency stop device 21 can be started by pressing its on-button 23. This means that a prescribed order must be observed for the operation of the ON button. However, such uncomfortable operation of systems are unsuitable for the practice.

A similar safety switching device system is known from the document DE 100 11 211 A1. This safety relay system comprises two safety relays whose construction and function correspond to each other. The two devices are connected in series with the interposition of an emergency stop switch. In addition, a start switch is provided on both devices.

The object of the present invention is thus to propose a protective device or protective system and a corresponding method for the safety-related shutdown of an electrical unit, with which the operation of complex systems is more comfortable.

According to the invention, this object is achieved by a protective device for safety-related switching off an electrical unit having a first input for receiving a switch-off signal to a second input for receiving a switch-on signal in the form of a switch-on and an output for driving the electrical unit, and a pulse processing device for moving the protection device in an activation state in which it is in the absence of the Switch-off is switched on, for a predetermined period of time from the start of the switch-on.

Further, the invention provides a method for safety-related switching of an electrical unit by receiving a turn-off, turning off the electrical unit, receiving a turn-on signal in the form of a turn-on and turning on the electrical unit, wherein turning on the electrical unit after recording the switch-on pulse is only possible for a predefinable period of time.

Preferably, the turn-on signal comes from an on-button. This gives the protection device a simple switch-on, which has the binary form L-H-L in the rule.

The switch-off signal usually comes from a lockable emergency stop button. The closing of the emergency stop button can not be done unconsciously, which is of the utmost importance for safety technology.

The electrical unit that is switched by the protection device may be an actuator and in particular a contactor. As a result, load circuits with higher currents can be switched easily.

The inputs and outputs of the protection device should be multi-channel. This is mandatory for category 4 of the EN 954 standard and increases the safety standard.

Advantageously, the falling or both edges of the switch-on pulse for displacing the protective device into the activation state can be evaluated by the pulse processing device. This edge sensitivity is also prescribed by the named safety standard, so that a cross-circuit does not cause an involuntary restart of the emergency stop device or protective device.

To realize the temporary activation state, the pulse processing device may comprise a timer which, after the switch-on pulse, provides an acknowledgment command for maintaining the activation state for a predetermined time. Thus, the protection device can be turned on as desired a certain time after the switch-on. In accordance with the invention, reaction times of the individual devices with one another can thereby be taken into account.

Preferably, the activation state for the period of time is set to correspond to the activation time of at least one electrical unit and / or at least one further switching device.

The connection of protective devices according to the invention to a cascaded protection system is particularly advantageous. In this case, the first input of a second of the multiple protection devices is driven by the output of one of the multiple protection devices. This applies mutatis mutandis to the other cascade stages. The above-mentioned duration for the activation state is to be dimensioned for this purpose so that it is greater than the sum of the reaction times of all protection devices. This protection system can then be switched on with a common on-button, if the inputs of the several protection devices are connected accordingly. Thus, the units or systems connected by the protective devices can be switched on again comfortably after an emergency stop operation.

FIG 1

ein Blockschaltdiagramm einer Sicherheitskombination gemäß dem Stand der Technik;

FIG 2

ein Blockschaltdiagramm mehrerer kaskadierter Sicherheitskombinationen entsprechend dem Stand der Technik;

FIG 3

ein Blockschaltbild kaskadierter Sicherheitskombinationen gemäß der vorliegenden Erfindung und

FIG 4

ein Blockschaltbild zur erfindungsgemäßen EinTaster-Impulsauswertung.

The present invention will be explained in more detail with reference to the accompanying drawings, in which:

FIG. 1

a block diagram of a safety combination according to the prior art;

FIG. 2

a block diagram of several cascaded security combinations according to the prior art;

FIG. 3

a block diagram of cascaded security combinations according to the present invention and

FIG. 4

a block diagram for EinTaster pulse evaluation according to the invention.

The embodiments described below represent preferred embodiments of the present invention.

The purpose of the following embodiment is, as mentioned, for example, a conveyor belt, on which several emergency stop button are mounted. The switching on of the conveyor belt after an emergency stop operation, however, should only be performed by an authorized person. For example, there is a central on-button on a control unit, eg a control cabinet. In Figure 3, a suitable security system with multiple emergency stop devices in cascade with a common on-button as a block diagram is shown. The construction is substantially similar to that of FIG. 2, so that reference is made to the description of FIG. 2 with regard to the same elements. It is different from the embodiment of FIG. 2 that in the exemplary embodiment according to FIG. 3 only a single on-pushbutton 33 is used, which supplies an on-pulse for all protective or emergency-off devices. So there are both the monitoring contacts 16 and 16 'and the monitoring contacts 26 and 26' in the one-button circuit.

If the emergency stop devices 11 and 21 are configured in a known manner, a system realization according to category 4 (monitored start / restart) is not possible. The reason for this is that the one-button impulse arrives at the subordinate device 21 before the release (unlocking) of the emergency stop circuit 15, 22 or 15 ', 22' or the one-button circuit 26 'arrives. , 26, 16, 16 ', 33 is interrupted. Namely, the emergency stop button 12, 12 'is locked again to turn on the system, i. closed, and the common on-button 33 is actuated (L-H-L pulse), so while the first emergency stop device 11 turns on, the second emergency stop device 21 can not turn on. This is due to the fact that, at the time of the one-button pulse, the emergency stop circuit is still interrupted by the second emergency stop device 21, since the actuators of the emergency stop device 11 are only activated after a certain reaction time. Button impulse react.

A very simple solution for this would be to release the multiple emergency stop devices with multiple presses of the common on-button. For two emergency stop devices in cascade you would have to press the on button twice to turn the system back on. However, if the emergency stop assemblies become more complex, it is also possible to work with small controls which generate appropriate release pulses for the emergency stop devices. However, this is associated with very high costs, in particular in safety technology, and in some cases also not permitted.

According to the invention, it is now provided to modify both emergency stop devices 11 and 21 simultaneously by modifying the device-internal evaluation of the one-button pulse, with a single release command by the on-button 33 and thereby the required safety conditions for the emergency stop circuits observed.

FIG. 4 shows a block diagram of the one-button evaluation according to the invention. Accordingly, a one-key signal is subjected to edge evaluation 40. In this case, the falling or both edges of the switch-on pulse is evaluated in accordance with the required safety standard. A corresponding binary signal 401 is provided to a pulse processing device 41. This extends the switch-on pulse to a predetermined acknowledgment time by starting a timer. This results in an internal acknowledgment command 411 for the further safety logic, which for a certain time, e.g. 500 ms, is provided. This evaluation of the one-button pulse is carried out continuously, even if an emergency stop is present. If the emergency stop circuit is then closed within this acknowledgment time, the output is controlled via the safety logic and the device to be switched is switched on again.

With this impulse processing according to the invention, the following functional sequence results for the circuit of FIG. 3: both emergency stop buttons 12, 12 'and 22, 22' are already closed to restart the device or the system. The on-button 33 is actuated, whereby the known from FIG 4 LHL pulse 401 is generated. The emergency stop device 11 switches on. At the same time, the acknowledgment time is also started in the emergency stop device 21. After the emergency stop device 11 has closed both actuators 14, 14 'after a certain reaction time, the emergency stop device 21 detects a closed emergency stop circuit 22, 22', 15, 15 'and switches on the basis of the still present acknowledgment command also its actuators 24, 24 'on. If the emergency stop device 11 does not switch its actuators 14, 14 'due to an error, then the emergency stop device 21 does not switch its actuators 24, 24' on, since then the emergency stop circuit 22, 22 ', 15, 15' of the second emergency stop device 21 is open. The internal acknowledgment command in the two emergency stop devices 11 and 21 is then cleared after the end of the acknowledgment time.

The acknowledgment time must be selected in such a way that, for a desired cascading depth, the internal acknowledgment command still stands for the individual reaction or activation times of the actuators and emergency stop devices. This is easy to implement, especially in electrical emergency-stop devices, since their reaction times are low and thus the acknowledgment time can be small. On the other hand, if the acknowledgment time is specified in the emergency stop devices, only a certain cascading depth can be achieved, depending on the reaction times of the individual devices. Cascading depths that are too high are to be avoided, however, since the response time when switching off via the emergency stop button causes considerable delay due to cascading.

Another advantage results from the fact that all monitoring contacts 16, 16 ', 26, 26' are connected in series. If there is an error in the subordinate emergency stop device 21 or its actuator 24, 24 ', then the higher-level emergency stop device 11 can not be switched on again.

Claims (19)

1. Protective device (11, 21) for the safety-related shutdown of an electrical unit having

   - a first input for the purpose of receiving a switch-off signal,

   - a second input for the purpose of receiving a switch-on signal in the form of a switch-on pulse (401), and

   - an output for the purpose of driving the electrical unit (14, 14', 24, 24'),

   characterized by
   a pulse processing device (41) for the purpose of setting the protective device (11, 21) for a predetermined period of time from reception of the switch-on pulse to an activation state, in which it is switched on when the switch-off signal is not applied.
2. Protective device according to Claim 1, the switch-on signal originating from an on pushbutton (33).
3. Protective device according to Claim 1 or 2, the switch-off signal originating from a latchable emergency-stop pushbutton (12, 12', 22, 22').
4. Protective device according to one of the preceding claims, the electrical unit (14, 14', 24, 24') being an actuator and, in particular, a contactor.
5. Protective device according to one of the preceding claims, the inputs and outputs having a plurality of channels.
6. Protective device according to one of the preceding claims, it being possible for the falling edge or both edges of the switch-on pulse (401) to be evaluated by the pulse processing device (41) for the purpose of setting the protective device to the activation state.
7. Protective device according to one of the preceding claims, the pulse processing device (41) having a timing element which provides an acknowledgment command for the purpose of maintaining the activation state for a predetermined time after the switch-on pulse (401).
8. Protective device according to one of the preceding claims, the predetermined period of time for the activation state corresponding at least to the activation time of the electrical unit (14, 14', 24, 24') and/or a further protective device.
9. Protective system having a plurality of protective devices (11, 21) connected in cascade fashion according to one of the preceding claims, the first input of a second of the plurality of protective devices (21) being driven by the output of a first of the plurality of protective devices (11).
10. Protective system according to Claim 9, the inputs of the plurality of protective devices (11, 21) being connected to a common on pushbutton (33).
11. Method for safety-related switching of an electrical unit (14, 14', 24, 24') by means of

    - receiving a switch-off signal,

    - switching the electrical unit (14, 14', 24, 24') off,

    - receiving a switch-on signal in the form of a switch-on pulse (401), and

    - switching the electrical unit (14, 14', 24, 24') on,

    characterized in that

    - it is possible to switch the electrical unit (14, 14', 24, 24') on for a predeterminable period of time after reception of the switch-on pulse (401), and this is carried out when the switch-off signal is not applied.
12. Method according to Claim 11, the switch-on signal originating from an on pushbutton (33).
13. Method according to Claim 11 or 12, the switch-off signal originating from a latchable emergency-stop pushbutton (12, 12', 22, 22').
14. Method according to one of Claims 11 to 13, the electrical unit (14, 14', 24, 24') being an actuator and, in particular, a contactor.
15. Method according to one of Claims 11 to 14, the switch-on and switch-off signals being received on a plurality of channels.
16. Method according to one of Claims 11 to 15, the falling edge or both edges of the switch-on pulse (401) being evaluated in order to start the predeterminable period of time in which the electrical unit (14, 14', 24, 24') can be switched on.
17. Method according to one of Claims 11 to 16, the predeterminable period of time for switching on the electrical unit (14, 14', 24, 24') corresponding at least to the activation time of the electrical unit (14, 14', 24, 24') and/or a further protective device.
18. Method for safety-related switching of a plurality of protective devices (11, 21) connected in cascade fashion, a second of the plurality of protective devices (21) being connected with the aid of a first of the plurality of protective devices (11) in accordance with the method according to one of Claims 11 to 17.
19. Method according to Claim 18, the switch-on signal making all of the plurality of protective devices (11, 21) available simultaneously.

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