DE3937122A1 - Fail=safe switching circuitry using relays - having closing contacts coupled in series in release current circuit - Google Patents

Abstract

The circuitry, with a safety feature, has at least two forcibly driven relays with closing contacts arranged in a current loop. One closing contact of one of the relays is in series with a contact of the other relay in each loop. One opening contact (K12,K22) of each relay is respectively connected at one end to an ON-push button (6) connected in series with an OFF-push button (5) and an emergency button (4) at one terminal (1) of a drive voltage source, and at the other end to an input (E1,E2) of a fail-safe AND-gate (7) whose output (8) is connected to the coils (K15,K25) of both relays. The coils are also connected via series connected contacts (K11,K21) of the relays to the OFF-push button (5) in a self contained loop. ADVANTAGE - Very high efficiency with as few relays as possible. compact and reliable. @(6pp Dwg.No.1/2)

Description

The invention relates to a circuit arrangement Safety function, the at least two positively driven relays contains the normally open contact arranged in release circuits have clocks, each having a make contact of the one Relay with a normally open contact of the other relay in the respective Release circuit is placed in series.

A circuit arrangement of the type described above is from the company publication "SRB - basic building block for security electric circuits ", pages 6 and 7 of ELAN. This Circuit arrangement contains three positively driven relays or Auxiliary contactors. The first relay with its coil is in series with each an NC contact, an on-button switch, an off button switch and an emergency stop switch to a control voltage source connected. The series connection of a normally open contact with the parallel connection of one NO contact two each Another relay is a self-holding circuit between the coil of the first relay and the off button switch arranged. The second Relay is one with its coil via the parallel connection Normally open contact of the first and second relay with the Pushbutton connected. The third relay is across the parallel switching of a normally open contact of the first relay and one Normally open contact of the third relay to the off button switch  connected. In the known circuit positively driven relays used with which an improvement security is achieved. Are the compo nenten of the circuit in perfect condition, then pulls first the first relay turns on and goes latching when the others Relays have still dropped out. Then the other relays pick up, causing the first relay to drop out. At a Failure in one of the three auxiliary contactors will result in the enabling circuit either not closed if there is an error when turning on already exists or is interrupted if the error occurs during operation.

The invention has for its object a circuit arrangement tion of the genus described above develop that with as few relays as possible a very high reliability casualness is achieved.

The object is achieved in that a NC contact of each relay on the one hand with a one-button switch, in line with an off button and an emergency stop Switch connected to a pole of a control voltage source and on the other hand with an input of a fail-safe AND gate is connected, the output side with the coils of the two relays are connected, and that the coils over together the series connection of one normally open contact of the first relay connected to the off pushbutton switch in a self-holding branch are. With this circuit arrangement there is no need for a relay, if the circuit works properly after switching on the other two relays turn on and then drop out again. The The arrangement works with only two positively driven relays who are guaranteed that the break contacts are open, before the normally open contacts are closed. The fail-safe AND gate, which is also referred to as a "fail-safe" circuit, changes to the safe state in the event of an internal error which no output signal occurs. In the event of an error in the fail safe The AND gate cannot therefore switch the arrangement on will.  

The circuit described above works according to the rules VDE 0113, Section 5.7.1b and e, advantageously also electronic components are used. A special is seen in the fact that positively driven relays with a "Fail-Safe" AND linked in a way that has resulted in a new safe emergency stop. The "Fail-safe" AND element has both a memory in this circuit cher- as well as a control function. For one thing, it takes over AND operation of the two positively driven relays, i.e. the electromechanical parts of this circuit, on the other hand it serves the control and storage of the correct functioning one of the components of this circuit. If one of these com components, be they electronic or electromechanical, one If the circuit is defective, the circuit reacts with an operation inhibition, whereby the required "safe state" is reached becomes.

In a preferred embodiment it is provided that the Relays are delayed. A slight delay in waste is sufficient tion that prevents relay flutter from occurring. In particular, the dropout delay is a few milliseconds.

Preferably, a relay with its second connection is immediate bar connected to the second pole of the control voltage source, while the other relay with its second connection over Another contact of the emergency stop switch to the second pole the control voltage source is laid. The advantage of this arrangement voltage is that there is security against cross-circuits is achieved.

In a further expedient embodiment there are two further positively driven relays with their coils each in parallel the coils of the other relays are arranged, normally closed contacts the other relays in series between the on-button switch and the parallel break contacts of the other relays are and with NO contacts of the other relays in series with the normally open contacts of the other relays in the latching branch are arranged. This arrangement is used when  the normally open contacts of the first two relays are not for the the desired number of enabling circuits is sufficient. Through the additional relays become additional NO contacts for Freiga current circuits made available, whereby for all release current circles the same reliability exists.

Further details, advantages and features of the invention, the relate essentially to safety circuits such as emergency stop Circles, follow-up circuits for safety gate protection, approval operation or other movements that relate to people protective functions should not only result from the Claims, the features to be extracted from them for themselves and / or in combination - but also from the following Description of exemplary embodiment shown in the drawing play.

Show it:

Fig. 1 is a circuit diagram of an arrangement with a safety function and

Fig. 2 is a circuit diagram of another arrangement with a safety function.

A used for switching on and off industrial machines circuit arrangement with safety function contains two positively driven relays (K 1 ), (K 2 ), the coils of which are designated in Fig. 1 and 2 with (K 1 S) and (K 2 S) . A fuse ( 2 ) is connected to a pole ( 1 ) of a control voltage source, followed by an NC contact ( 3 ) of an emergency stop switch ( 4 ). The contact of an off pushbutton ( 5 ) is arranged in series with the break contact ( 3 ). The off key switch ( 5 ) is connected at its one connection point on the one hand with an on key switch ( 6 ) and on the other hand with a normally open contact (K 11 ) of the relay (K 1 ), which is in series with a normally open contact (K 21 ) Relay (K 2 ) is arranged.

An opening contact (K 12 ) of the first relay (K 1 ) and an opening contact (K 22 ) of the second relay (K 2 ) are connected in parallel to the on-button switch ( 6 ). An input (E 1 ) of a fail-safe AND gate ( 7 ) is connected to the break contact (K 12 ), the second input (E 2 ) of which is connected to the break contact (K 22 ) of the second relay. The fail-safe AND gate gives only if it works properly and when both inputs are loaded with z. B. high signals, ie signals to which a certain binary value is assigned, a corresponding signal at its output ( 8 ). Fail-safe AND gates, which are also referred to as "fail-safe" AND gates, are known per se.

The coils (K 1 S) and (K 2 S) are each connected to the output of the AND gate ( 7 ) with one connection. The second connection of the coil (K 1 S) is connected to the second pole ( 9 ) of the control voltage source, which is connected to ground. Parallel to the coil (K 1 S) is a consisting of a capacitor ( 10 ) and an opposing ( 11 ) existing RC element, through which a drop delay of the relay (K 1 ) is achieved. The second connection of the coil (K 2 S) is connected to the pole ( 9 ) via a second break contact ( 12 ) of the emergency stop switch ( 4 ). The series connection of a capacitor ( 13 ) and a resistor ( 14 ) is arranged parallel to the coil (K 2 S). The RC circuit consisting of these two components causes a delay in the fall of the relay (K 2 ).

Each of the relays (K 1 ) and (K 2 ) has further make contacts. For example, the relays (K 1 ) and (K 2 ) each contain four make contacts (K 13 ), (K 14 ), (K 15 ), (K 16 ) and (K 23 ), (K 24 ), (K 25 ) and (K 26 ). Two NO contacts (K 14 ), (K 24 ) and (K 15 ), (K 25 ) and (K 13 ), (K 23 ) and (K 16 ), (K 26 ) are in series in an enabling circuit ( 15 ), ( 16 ), ( 17 ), ( 18 ) are arranged. One normally closed contact (K 17 ) of the first relay (K 1 ) and one normally closed contact (K 27 ) of the second relay (K 2 ) are arranged in parallel in a display circuit. The series connection of the normally open contacts (K 21 ) and (K 11 ) is connected as a self-holding circuit with the coils (K 1 S) and (K 2 S).

Fig. 1 shows numbers arranged in circles which correspond to the accordingly marked contact connections of commercially available relays emergency stop switches, on-key switches or off-key switches.

After applying the supply voltage and pressing the on-button switch ( 6 ), the two inputs (E 1 ) and (E 2 ) of the AND gate ( 7 ) are supplied with voltages via the normally closed contacts.

The AND gate ( 7 ) controls and the relays (K 1 ) and (K 2 ) pick up. Thereafter, the relays (K 1 ), (K 2 ) go into latching via the normally open contacts (K 11 ) and (K 22 ). So that no relay flutter occurs, the relays are connected with a delayed dropout. Delay times of a few milliseconds are sufficient. When the relays (K 1 ) and (K 2 ) have picked up, the enabling circuits ( 15 ) to ( 18 ) switch through. The circuit is designed according to the criteria of VDE 0113 section 5.7, ie it is single-fault-proof.

Occurs z. B. an error on one of the contacts (welding), then this error will occur on the next cycle, i.e. at the next Most switched on detected, and there is an inhibition responds.

Fig. 2 shows a circuit arrangement with Sicherheitsfunkti on, which has more contacts for release circuits at a predetermined number of circuits available for the release circuits on a relay contacts. The same elements in FIGS . 1 and 2 are provided with the same reference numbers.

The arrangement shown in Fig. 1 can be formed in the form of a construction group, the connector connections ( 19 ), ( 20 ), ( 21 ), ( 22 ), ( 23 ), ( 24 ), ( 25 ) and ( 26 ) .

In addition to the two positively driven relays (K 1 ) and (K 2 ), the arrangement shown in FIG. 2 also contains two positively driven relays (K 1 A) and (K 2 A), by means of which the number of contacts for the enabling circuits is increased. The coils of the relays (K 1 A) and (K 2 A) are designated in Fig. 2 with (K 1 AS) and (K 2 AS). The coil (K 1 AS) is connected in parallel to the coil (K 1 S) via the connector connections ( 21 ), ( 22 ). The coil (K 2 AS) is connected in parallel to the coil (K 2 S) via the connector connections ( 23 ), ( 24 ). The relay (K 1 A) contains an NC contact (K 1 A 1 ), which is arranged in series with an NC contact (K 2 A 1 ) of the relay (K 2 A). The two normally closed contacts (K 1 A 1 ) and (K 2 A 1 ) are arranged between the one-touch switch ( 5 ) and the normally closed contacts (K 12 ), (K 22 ), the connection being made via the two plug contact connections ( 19 ) , ( 20 ) is made.

A normally open contact (K 1 A 2 ) of the relay (K 1 A) and a normally open contact (K 2 A 2 ) of the relay (K 2 A) are in series with the normally open contacts (K 11 ), (K 12 ) in the latch the relays (K 1 ), (K 2 ), (K 1 A) and (K 2 A) are arranged. The connection of the normally open contacts (K 1 A 2 ) and (K 2 A 2 ) to the module is made via the connector contacts ( 25 ), ( 26 ).

The relay (K 1 ) contains z in the arrangement shown in FIG . B. still the normally open contacts (K 13 ), (K 14 ) and (K 15 ) and the normally closed contact (K 17 ). The relay (K 2 ) in the arrangement according to FIG. 2 also contains the normally open contacts (K 23 ), (K 24 ) and the normally closed contact (K 27 ). The normally closed contacts (K 14 ) and (K 23 ) as well as (K 15 ) and (K 24 ) are unspecified release circuits connected in series. The normally open contacts (K 17 ) and (K 27 ) are connected in parallel in a signaling circuit. The normally open contact (K 13 ) is freely available. Instead of the make contact (K 13 ), a break contact of the relay (K 1 ) can also be arranged in a circuit shown in dashed lines in the drawing.

The further relays (K 1 A) and (K 2 A) each contain further make contacts (K 1 A 3 ), (K 1 A 4 ), (K 1 A 5 ) and (K 2 A 3 ), (K 2 A 4 ) and (K 2 A 5 ), which are arranged in pairs in series in release circuits. Furthermore, normally closed contacts (K 1 A 6 ) and (K 2 A 6 ) are connected in parallel in a signaling circuit.

The arrangement of the contact ( 12 ) in the connecting line of the relay (K 2 ) or the relay (K 2 ), (K 2 A) to the mass circuit, the circuit according to Fig. 1 or 2 is cross-circuit proof, that is achieved a further improvement in reliability.

The numerals in circles in the arrangement shown in FIG. 2 also denote connections of commercially available relays.

It should also be noted that under relay also auxiliary shooters are to be understood.

The circuits described above avoid the disadvantages of Safety circuits with two non-positively driven relays. Compared to safety circuits with positively driven relays the circuits have the advantage of a simpler structure, which also results in savings in space requirements.

Claims (5)

1.Circuit arrangement with safety function, which contains at least two positively driven relays, which have make contacts arranged in the enabling current circuit, one normally open contact of one relay being connected in series with one normally open contact of the other relay in the respective enabling circuit, characterized in that in each case one break contact (K 12 , K 22 ) each relay on the one hand with an on-button switch ( 6 ) connected in series with an off-button switch ( 5 ) and an emergency-off switch ( 4 ) to a pole ( 1 ) of a control voltage source and, on the other hand, is connected to an input (E 1 , E 2 ) of a fail-safe AND gate ( 7 ) which is connected on the output side to the coils (K 1 S, K 2 S) of the two relays and that the coils ( K 1 S, K 2 S) are connected together via the series connection of one normally open contact (K 11 , K 21 ) of the relays in a latching circuit with the off pushbutton ( 5 ). 2. Circuit arrangement according to claim 1, characterized, that the relays are delayed.   3. Circuit arrangement according to claim 2, characterized, that the relay's dropout delay is a few milliseconds is. 4. Circuit arrangement according to one or more of the preceding claims, characterized in that a relay with its second connection is connected directly to the second pole ( 9 ) of the control voltage source and that the other relay with its second connection via a further contact ( 12 ) of the emergency stop switch ( 4 ) is connected to the second pole of the control voltage source. 5. Circuit arrangement according to one or more of the preceding claims, characterized in that two further positively driven relays with their coils (K 1 AS, K 2 AS) are each arranged in parallel to the coils of the other relays that break contacts (K 1 A 1 , K 2 A 1 ) of the further relays are arranged in series between the on-button switch ( 5 ) and the parallel break contacts (K 12 , K 22 ) of the other relays and that make contacts (K 1 A 2 , K 2 A 2 ) of the further relays are arranged in series with the normally open contacts (K 11 , K 21 ) of the other relays in the latch.