DE9010320U1 - Device for securing control circuits, in particular PLC controls, as a safety terminal - Google Patents

Description

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"Device for securing control circuits, in particular PLC controls, as a safety terminal"

The invention is directed to a device for securing control circuits as a safety terminal, which interrupts the control circuit in the event of a wire break or short circuit.

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So-called monitoring modules or coupling switches are known in very complex designs. Such modules are used in unearthed networks to monitor the protective conductor for interruptions and/or short circuits between the protective conductor and the monitoring conductor. They are also used to transmit control commands in systems at risk of explosion. These are usually modules that can weigh up to 2 kg depending on the design, such as the universal coupling switch from Fern-

^; '' sprech- und Signalbau KG with the designation sB 21122 or

the Siemens protective conductor module 8 SG 1150.

&phgr; A safety electronic is known from DE 20 15 413 - Al-

its components including the shutdown device

The switching contacts cannot be accommodated in a standard terminal housing, and this circuit is also not suitable for operating a standard inductive DC proximity switch. The switch contacts of Ta are not included in the short-circuit monitoring.

The same applies to the monitoring device according to DE 29 22 782 - C2, here two different voltages are also required, the evaluation is carried out via relay clocks and logic modules. The monitoring is only directed at the A-B line to the consumer, in the event of a short circuit in the switch line (reference number 4 there) the error would not be detected and a perfect function would be simulated.

The object of the invention is to create a solution with which, in addition to the possibility of monitoring control circuits in electrical systems for wire breaks and short circuits at the same time and suppressing faulty switching in both cases, it is also possible to make such devices so small and universally applicable that conventional terminal blocks are suitable for accommodating such devices.

This object is achieved according to the invention in that the device body is designed in the size and shape of a conventional series terminal and that, in addition to the terminal bodies for the electrical conductors, an electronic circuit is provided which takes over the function of the safety terminal, that a control circuit with a peripheral switch is provided and that in functional connection at least one of a resistor and a &Kgr;&ogr;&eegr;&aacgr;&ogr;&eegr;-

sator consisting of an RC element in conjunction with a Zener diode is provided.

The invention has the particular advantage that, thanks to its identical design in the manner of a conventional intermediate terminal, the device can be used as the sole terminal block between a peripheral switch and, for example, a PLC control. The line monitoring significantly increases the level of safety of conventional control and monitoring circuits.

The RC element in the device body in conjunction with the Zener diode ensures that the capacitor is periodically charged and discharged when an alternating voltage is applied, whereby the ^voltage of the ^capacitor does not reach the breakdown voltage of the Zener diode, so that the downstream input, for example of the PLC control, remains blocked. However, if the diode connected in parallel on the peripheral switch is activated by opening this switch, only the positive half-wave of the applied alternating voltage acts on the capacitor of the RC element. The capacitor is charged in a few periods and the downstream PLC input is controlled. If a fault now occurs, for example due to a short circuit in the peripheral line, this leads to the capacitor in the RC element being discharged and the control circuit is blocked.

The subclaims provide further advantages:

For example, the oscillator in the terminal body switches off the applied DC voltage in a pulse-like manner at a certain frequency and the

^ switched side short-circuited, the shutdown phase is so

chosen so that an inductive DC proximity switch still works perfectly and, when activated and the peripheral line is intact, charges the capacitor via the resistance to above the breakdown voltage of the Zener diode, the Zener diode becomes conductive and activates the output. If the peripheral line is short-circuited, the capacitor

Phases are each discharged and the output remains blocked.

f The same function is also achieved according to the invention with a

This is achieved by connecting the peripheral line to the terminal points with an opener and a parallel diode. If the opener is not activated or the 2-pole peripheral line is short-circuited, the capacitor is discharged in the switched-off and short-circuited phases and the charging voltage of the capacitor does not reach the breakdown voltage of the Zener diode, so that the output remains blocked. However, if the diode is activated by activating the opener contact, the discharge pulse is blocked.

the capacitor is charged above the breakdown voltage of the Zener diode and the output is activated.

In addition to the pure security function of the device, these additional tasks can also be taken on. According to the invention, an optocoupler in the terminal provides galvanic isolation between the input and output.

output circuit.

It can also be advantageous if, in addition to the RC element, an additional PTC resistor is provided in series with the first resistor.

In order to make the switching state at the terminal visible, the invention also provides for indicator lights to be provided.

A particular advantage of the present invention is directed

on the possibility of not only having a positive effect in alternating current circuits, but also in direct current circuits.

Here, the invention provides that in the security

terminal, e.g. an oscillator is provided to generate an alternating voltage for the operating circuit.

Another embodiment provides that the built-in oscillator generates positive, -? direct current pulses. Commercially available contactless

DC switches can be operated without special diode circuitry.

It can also be advantageous if a PTC resistor is integrated into the circuit in such a way that it monitors the components via heat and current coupling.

As already mentioned, the device is designed in the form of an intermediate terminal; it is particularly suitable and designed for combining several identical terminals in, for example, blocks of 8, as the invention also provides.

The invention is described below with reference to the drawing.

Fig. 1 is a schematic diagram of the device according to the invention and in the

Fig. 2, 3 and 4 embodiments of the device according to the invention .

The device according to Fig. 1, generally designated 1, has a device body 2 in the form of an intermediate clamp.

The connection of the intermediate terminal 1 marked 3 is supplied with a control alternating voltage, whereby a connection marked 4 leads to a PLC input not shown in detail, while 5 designates a peripheral line with a peripheral switch 6, whereby this peripheral switch 6 is equipped with a parallel diode 7.

In addition to the designated components, the device 1 has a resistor 8, a capacitor 9 and a Zener diode designated 10, as can be seen from Fig. 1.

The way this device works is described above.

In Figs. 2 to 4, modified embodiments of the device 1 are shown, wherein all the same or ( Identical components bear the same reference symbol.

In Fig. 2, the additional design consists in the provision of an optocoupler 11 as well as an additional PTC resistor 12 and a light-emitting diode 13, which is suitable for the optical display of the respective switch state.

The same function is achieved with a peripheral line 5 connected to terminal points 5.1 and 5.2 with a break contact 6 and a parallel diode 7. If not

If the break contact 6 is actuated or the 2-pole peripheral line 5 is short-circuited, the capacitor 9 is discharged from the switched-off and short-circuited phases and the charging voltage of the capacitor 9 does not reach the breakdown voltage of the Zener diode 10, so that the output 4 remains blocked. However, if the diode 7 is activated by actuating the break contact 6, the discharge pulse ■;· ^τ is blocked, the capacitor 9 is charged above the breakdown voltage of the Zener diode and the output 4 is activated.

Fig. 3 shows the possibility of providing an oscillator 14 for generating a control alternating voltage, while in a further embodiment according to Fig. 4 the possibility is given of providing an oscillator 15 for generating positive direct current pulses as well as a contactless limit switch, i.e. here an inductive direct current contact switch as a peripheral switch.

The oscillator 15 in the terminal body switches off the applied direct voltage 3+ in a pulse-like manner at a certain frequency and the switched-off side 5.1 is short-circuited with 5.3. The switch-off phase is selected in such a way that an inductive direct voltage proximity switch 16 still works properly and, when actuated and the peripheral line 5 is intact, the capacitor 9 is switched off via the resistor 8 to above the breakdown voltage of the Zener-

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diode 10 is charged, the Zener diode becomes conductive and activates the output 4. If the Perl^-iörle line 5 is short-circuited, the capacitor 9 is discharged in the switched-off and short-circuited phases and the output bS^ib-. is blocked.

Of course, the description can be modified in many different ways in the embodiments of the invention , for example by adding or removing electrical components or diodes (not shown in detail) for internal protective circuitry or rapid discharge, without departing from the basic idea of the invention. In addition to the designs shown, other module shapes can also be provided, the one shown here being particularly useful for combining the device into blocks in the manner of a series terminal, which is not shown in detail in the figures.

Claims (9)

Expectations: 1. Device for protecting circuits, i of PLC controls, as a safety terminal, characterized by - that the device body (2) is designed in size and shape like a conventional terminal block, - that in addition to the clamping bodies for the electrical conductors (3-5), an electronic circuit is provided which takes over the function of the safety clamp, - that a control circuit with a P-peripheral switch (6) is provided and - that at least one RC element consisting of a resistor (8) and a capacitor (9) is provided in functional connection in connection with an ".enon code (10). 2. Device according to claim 1,
characterized, that an inductive DC proximity switch (16) or an opening contact (6/ with a parallel diode (7) is provided as a peripheral switch, such that when the peripheral switch is not actuated or the peripheral line (5) is short-circuited, the charge of the capacitor (9) remains below the breakdown voltage of the Zener diode (10) and that the output (4) thus remains blocked or, when intact, With the peripheral line (5) and the peripheral switch (16) or (6) activated, the capacitor (9) is charged above the breakdown voltage of the Zener diode (10) in such a way that the Zener diode is conductive and the output (4) is activated. 3. Device according to claim 1 or 2, ^ characterized in that an oscillator (15) is provided to switch off the applied DC voltage (3+ Fig. 4) in a pulse-like manner at a certain frequency and to short-circuit the switched-off side (5.1) with (5.3), whereby the RC element consisting of the resistor (8) and the capacitor (9) in connection with the Zener diode (10) is provided for evaluation. 4. Device according to one of the preceding claims, characterized in that an integrated optocoupler (11) with galvanic isolation between the input and output circuits is provided in the device body (2). 5. Device according to one of the preceding claims, characterized in that in addition to the RC element, an additional PTC resistor (12) is provided in series with the first resistor (8). 6. Device according to one of the preceding claims, characterized in that a light-emitting diode (13) or the like is provided in the device body (2) to indicate the respective switching state. 7. Device according to one of the preceding claims, characterized in that an oscillator (14) for generating an alternating voltage for the actuating circuit or an oscillator (15) for generating an alternating voltage in order to operate a peripheral switch with alternating current excitation and semiconductor output is provided. 8. Device according to one of the preceding claims, characterized in that a PCT resistor (12) is integrated via heat and current coupling to monitor the components in order to limit the short-circuit current. 9. Device according to one of the preceding claims, characterized in that it is formed from the combination of several identical internal circuits to form a multiple block, e.g. a block of 8 or the like.