EP0168058B1 - Safety relay - Google Patents

Description

The invention relates to a safety relay of the type specified in the first part of claim 1. Such a relay is known from DE-U-7 512 499.

Safety relays have the task of safely disconnecting the circuit to be switched, for example the supply circuit of presses, machine tools, combustion systems or medical devices. In conventional arrangements, two independent contacts are connected in series in the circuit, which are normally open contacts of two monostable relays. If one of the two contacts does not open, for example as a result of contact welding, the circuit is interrupted by the other contact of the second relay, which is connected in series. It is assumed that the same error does not occur on both contacts at the same time. Safety can be increased by connecting more than two contacts in series.

To detect an error, each of the known safety relays has, in addition to the main contact in the circuit to be switched, a monitoring contact which is positively actuated with the main contact and therefore indicates the position of the main contact regardless of the energized state of the relay. These two monitoring contacts are included in an evaluation or control circuit for the two safety relays in such a way that the circuit to be switched is not closed again when the contacts are welded. In the case of simpler control circuits, the position of these monitoring contacts is evaluated via a capacitor which is charged in the rest position of the safety relay via the monitoring contact which is designed as a normally closed contact and whose charge is required to switch the other safety relay into its working position. With more complex control circuits there is an increasing tendency to evaluate the position of the monitoring contacts via a microprocessor.

Safety relays also have further contacts which serve as holding contacts and as contacts in a signal circuit for checking the function of the system. With conventional safety relays, all these contacts (main, monitoring, holding and signal circuit contacts) are jointly positively driven by the relay armature or an actuator actuated by it.

From EP-A-0 013 991 an electromagnetic relay with several contacts is known, the contact spring of all contacts being moved by a common actuator. The actuator acts on each contact spring on opposite sides at different distances from the contact point in such a way that the contact closure takes place with a relatively large and the contact opening with a relatively small flexibility. Because of the low flexibility in the contact opening, welded contacts, for example, should be torn open.

The invention has for its object to provide a safety relay of the type mentioned, which can be used as the only relay instead of the previously required two in the circuit to be secured and thus leads to a reduction in circuitry and space requirements with the same security of the circuit break and fault detection.

The inventive solution to this problem is specified in claim 1. This solution is based on the knowledge that the only thing that is important for the safety of the circuit interruption and fault detection is that the additional contact used as the monitoring contact is positively guided with the main contact assigned to it, not that both the main and additional contact are positively actuated by the actuator of the relay. By using the movable contact elements of a main contact and an additional contact with each other coupling drivers, which can be moved independently of one another at least during their return movement, it is possible according to the invention to provide the main contact provided in the prior art in a second relay within the same relay with the same one Actuator too control, an additional contact is also assigned to this second main contact. If one of the two main contacts, which are preferably in the form of work contacts, does not open as a result of contact welding, the additional contact which is forcibly guided with this main contact via the driver is also held in this working position, while the actuator, which is independent of the driver, remains movable and allows the other main contact to be opened.

The adjustment of the movable contact elements of the main contacts by the actuator can take place directly, as is the case in the developments of the invention according to claims 2 to 6. The actuator can rest directly on the movable contact elements of the main contacts and take them with it when it moves in its one direction, the additional contacts being actuated via the drivers which are completely separate from the actuator. This design has the advantage that not only the welding of a contact can be ascertained and a later re-activation of the circuit switched by the relay is prevented, but that contact breakage can also be ascertained, for example by the associated additional contact actively opening when a main contact breaks.

In the development of the invention according to claims 7 and 8, on the other hand, the main contacts are adjusted indirectly in that the actuator engages the respective driver when moving in its one direction and the latter takes along the two movable contact elements of the relevant contact pair coupled with it.

The development of the invention according to claim 9 is advantageous in that the additional contacts can be switched directly into the charging circuit of a capacitor contained in a control circuit of the relay, the charge for the excitation of the relay coil to convert the actuator from the resting position the working situation can be used.

Claim 10 relates to an advantageous embodiment to achieve the flexibility and elasticity required for the contact movements.

The development of the invention according to claims 11 and 12 serves the advantage that further contacts can be provided in the same relay as holding contacts, signal circuit contacts or as additional safety contacts. In principle, any two contacts can be used as main contacts in the circuit to be switched, as long as they do not belong to the two positively driven contacts via a common driver and insofar as they are arranged with respect to the actuator so that they open both when moving in one direction and when moving in the other direction, both close.

Fig. 1

eine Ansicht des Betätiger- und Kontaktsystems eines Sicherheitsrelais;

Fig. 2

einen Schnitt durch das Relais nach Fig. 1 längs der Linie II-II;

Fig. 3

eine der Fig. 1 ähnliche Darstellung einer anderen Ausführungsform des Sicherheitsrelais;

Fig. 4

eine perspektivische Darstellung einer Variante des einen Hauptkontakt mit einem Überwachungskontakt koppelnden Mitnehmers;

Fig. 5

eine Steuerschaltung unter Verwendung des hier beschriebenen Sicherheitsrelais;

Fig. 6

einen Teil einer weiteren Ausführungsform des Sicherheitsrelais in der Ruhestellung; und

Fig. 7

das Ausführungsbeispiel der Fig. 6 in einem anderen Betriebszustand.

Embodiments of the invention are explained below with reference to the drawings. Show in the drawings

Fig. 1

a view of the actuator and contact system of a safety relay;

Fig. 2

a section through the relay of Figure 1 along the line II-II.

Fig. 3

a representation similar to Figure 1 of another embodiment of the safety relay.

Fig. 4

a perspective view of a variant of the driver coupling a main contact with a monitoring contact;

Fig. 5

a control circuit using the safety relay described here;

Fig. 6

part of a further embodiment of the safety relay in the rest position; and

Fig. 7

the embodiment of FIG. 6 in a different operating state.

The safety relay shown in FIGS. 1 and 2 has a base plate 10, from which coil connections 11 and contact connections 12 protrude downward. A coil former 13 with a coil 14 is mounted on the base plate 10. A yoke 15 made of soft magnetic material runs through the core of the coil body and is provided with yoke legs 16 at its two ends projecting from the coil body 13.

The coil 14 is closed at the top by a base body 17 which carries a central bearing pin 18. An actuator 19 is pivotally mounted around the bearing pin 18 and has two armature rails 21, 22, which are held in a generally H-shaped plastic part 20 and run parallel to one another, and permanent magnets 23 arranged between them. In Fig. 1, the two permanent magnets are visible through oval recesses in the plastic part 20.

The anchor rails 21, 22 are of different lengths at the two ends of the actuator 19 such that in the rest position of the relay shown in FIG. 1 the left longer part of the lower anchor rail 22 and the right longer part of the upper anchor rail 21 on the respective yoke leg 16 concerns. Because of the differently sized, opposing surfaces of the anchor rails and yoke legs, an asymmetry is obtained in the permanent magnetic attraction, so that the actuator 19 is held stable in the position shown. If the coil 14 is now excited so that the yoke legs 16 are reversed, the actuator 19 is pivoted into its working position in which the left shorter end of the upper anchor rail 21 and the right shorter end of the lower anchor rail 22 abut the yoke legs 16. After the spool 14 has dropped, the actuator 19 returns to the rest position shown in FIG. 1.

1, the contact system of the safety relay contains a total of four pairs of contacts, each of which can be switched over by an actuating lug 24 formed near the end and on the outer sides of the actuator 19. The pair of contacts shown in Fig. 1 in the upper left part comprises a normally open contact 25 which is formed by a fixed contact element 26 and a contact spring 27 cooperating therewith, and a normally closed contact 28 which is formed by a fixed contact element 29 and a cooperating with this Contact spring 30 is formed. The fixed contact elements 26 and 29 and the contact springs 27 and 30 are connected to the contact connections shown in FIG. 2. The two contact springs 27 and 30 run essentially parallel to one another and are positively guided near their outer ends by a driver 31 attached there. The driver 31 represents a separate component which can be moved independently of the actuator 19. Between the two contact springs 27 and 30 there runs a plastic web 32 which is molded onto a cap 33 surrounding the coil 14 and the contact system together with the base, and for Extensive separation of the contact spaces from work contact 25 and normally closed contact 28 is used.

In the rest position of the monostable safety relay shown in FIG. 1, the left upper actuating lug 24 acts on the contact spring 27 in such a way that the normally open contact 25 is interrupted, and in this position the contact spring 30 of the normally closed contact 28 is moved via the driver 31 by the contact spring 27 of the normally closed contact 25 acted on such that the normally closed contact 28 is closed. When the coil 14 is excited and the actuator 19 is pivoted into its working position, the normally open contact 25 is closed and the normally closed contact 28 is inevitably opened via the driver 31. To carry out this switching movement, the contact springs 27 and / or 30 are biased accordingly.

The pair of contacts shown in Fig. 1 in the lower right part of the safety relay is identical to the one just described, so that its further description is unnecessary. Here, too, the contact spring acted upon by the lower right actuating lug 24 forms the movable contact element of a normally open contact, while the other contact spring forms the movable contact element of a normally closed contact. The two other pairs of contacts provided in the upper right and lower left areas of the relay are also constructed identically to the pair of contacts present in the upper left part, only the switching functions being reversed such that the contact on the outside is a normally open contact and the contact located further inside makes a break contact. 1 and 2, some parts of the top right pair of contacts are given the same reference numerals as the corresponding parts of the top left pair of contacts, but additionally provided with an apostrophe.

If, in the working position of the actuator 19, for example in the case of the working contact 25, there is contact welding between the contact pieces provided on the contact spring 27 and on the fixed contact element 26, this working contact 25 can be caused by the return of the actuator 19 to the rest position shown in FIG. 1 no longer open. As a result of the forced guidance by the driver 31, the normally closed contact 28 remains open in this case. Sufficient flexibility of the contact spring 27 and the dimensioning and arrangement of the four actuating lugs 24 ensure, however, that despite the welded working contact 25, the actuator 19 can pivot back so far in the direction of its rest position that the lower right pair of contacts through the lower right actuating lug 24 is returned to its rest position and the other two Pairs of contacts in the lower left and upper right part of the relay are released by the respective actuating lugs 24 so far that they can also return to their rest position due to the spring preloads.

In the relay described so far, the normally open contact 25 in the upper left part of the relay and the diametrically opposite normally open contact in the lower right part of the relay can be connected in series as two main contacts in a circuit to be switched, for example in the supply circuit of a machine tool. Assuming that two contacts do not weld at the same time within a relay, safety of the switching off of this circuit is guaranteed, since the actuator 19 still opens the right lower working contact when the left upper working contact is welded, for example.

The above-mentioned flexibility of the action of the contact spring 27 of the working contact 25 by the associated actuating lug 24 can be increased in that, as illustrated in FIG. 2 for the contact spring 27 'of the upper right pair of contacts, this contact spring 27' in that area in which the actuating lug 24 engages on it is reduced in width by a recess 34 '. Another possibility, not shown in the drawings, of achieving sufficient flexibility is that the contact lug 24 is not rigidly formed on the actuator 19 but is connected to it via a resilient arm. Such an actuating lug flexibly attached to the actuator 19 could act on the end face of the driver 31 facing the actuator 19 instead of on the contact spring 27.

The exemplary embodiment shown in FIG. 3 differs from that according to FIG. 1 only by a different design of the driver 31. According to FIG. 3 the driver 31 is generally E-shaped and has two incisions 35 into which the ends of the two contact springs 27 and 30 are inserted at the end. Furthermore, in this case, a guide rail 36 is formed on the relay body, which slidably guides the driver 31 in the direction of the contact spring movement. This increases the accuracy of the forced coupling of work and break contacts 25, 28.

Another variant of the driver 31 is illustrated in FIG. 4. This driver 31 consists of a generally U-shaped plastic part, the two legs of which are provided with slots 37, with which it is pushed onto the ends of the contact springs 27 and 30.

5, the safety relay, generally designated 40, is used in a two-hand circuit, for example for a press control. Compared to the arrangement according to FIG. 1, the relay 40 in FIG. 5 is shown rotated by 90 ^° , so that the upper left pair of contacts in FIG. 5 appears at the top right in FIG. The relay 40 is again shown in its rest position in FIG. 5, although only the contacts and not the actuator are illustrated. The four pairs of contacts of the relay are designated in Fig. 5 with I to IV, wherein for the contact pairs I and III the working contact faces the inside of the relay and the normally closed contact is arranged on the outside of the relay, while in the case of contact pairs II and IV the make contact is on the outside of the relay and the normally closed contact is further inside.

The supply circuit of the press runs from the terminal 41 via the fixed contact element 26 and the contact spring 27 of the normally open contact I and the contact spring and the fixed contact element of the normally open contact III to the terminal 42. To the right of these terminals 41 and 42, the series connection of two working contacts thus formed is symbolically represented in FIG. It can be advantageous if the connection of these two make contacts is made internally in the relay.

A capacitor 43 is connected to a monitoring circuit, which leads from a ground line 44 via the movable contact 45 of a control relay 46, the fixed contact element 29 and the contact spring 30 of the normally closed contact I and the contact spring and the fixed contact element of the normally closed contact III to a control voltage line 47 (for example 24V) leads. In the rest position of the safety relay 40 shown, the monitoring circuit is closed, so that the capacitor 43 is charged.

When both hand switches 48 are depressed, a supply circuit is closed which, on the one hand, runs from the control voltage line 47 through the coil 49 of the control relay 46, the upper contacts of the hand switches 48 to the ground line 44, so that the movable contact 45 of the control relay 46 is switched over, and on the other hand 5 via the upper electrode of the capacitor 43 via the upper contacts of the two manual switches 48, a delay element 50 (with a delay time of, for example, 10 ms) and through the coil 14 of the safety relay 40 to the lower electrode of the capacitor according to FIG. 5 43 runs. As a result, the capacitor 43 is discharged via the coil 14, as a result of which the safety relay 40 is switched over in its working position, delayed by the time constant of the delay element 50 in relation to the control relay 46.

In the working position, a holding circuit is closed, which extends from the control voltage line 47 via the fixed contact element and the contact spring of the working contact IV, the contact spring and the fixed contact element of the normally open contact II, the movable contact 45 of the monostable control relay 46, which is now in its working position, runs through the coil 14 of the safety relay 40, the delay element 50 and the two upper contacts of the hand switch 48 to the ground line 44. The two normally open contacts II and IV of the safety relay 40 thus form holding contacts. In this way, the safety relay 40 is held in its working position even after the capacitor 43 has been discharged until one of the hand switches 48 is opened.

The remaining two normally closed contacts II and IV of the safety relay 40 are connected in parallel in a signal circuit between the two terminals 51 and 52. To the right of these terminals 51 and 52, the parallel connection of these normally closed contacts is again symbolically shown in FIG. 5.

If at least one of the two hand switches 48 is released, the supply circuit is opened, as a result of which both the monostable safety relay 40 and the monostable control relay 46 return to the rest position and the two working contacts of the supply circuit of the press are opened. In this state, the charging circuit for the capacitor 43 is closed again, so that it charges up and enables the safety relay 40 to be switched over to the working position again in the next cycle.

Should one of the working contacts I, III of the safety relay 40 weld in the working position, when one of the hand switches 48 is opened, the other working contact I or III is nevertheless opened, as described above. At the same time, however, the normally closed contact, which is positively coupled to the welded working contact, remains in its open position, so that the charging circuit for the capacitor 43 is now interrupted and the capacitor 43 cannot be charged. Therefore, at a subsequent depression of both hand switches 48, the coil 14 of the safety relay 40 is no longer excited, so that it remains in its rest position and the second non-welded work contact is not closed. This avoids restarting the press, which could otherwise lead to the second working contact now being welded and the press no longer being able to be switched off at all.

The signal circuit between the terminals 51 and 52 is used to check the function of the safety relay 40 Capacitor 43 (the monitoring contacts) are open. This state, which corresponds to an error-free operation of the safety relay 40, can be determined by a logical combination. If one of the contact springs of the safety relay 40 breaks, the condition of this logical combination is no longer met, from which an error display can be derived.

The hand switches 48 are additionally provided with lower contacts which serve to discharge the capacitor 43 to ground via a resistor 53 if only one of the hand switches 48 is depressed. The resistor 53 is dimensioned such that the capacitor 43 is discharged practically exclusively via the coil 14 of the safety relay 40 when the two manual switches 48 are actuated. This measure prevents one of the hand switches 48 from being kept in the permanently closed state and an attempt to actuate the press only via the other hand switch 48.

In the exemplary embodiments of the invention according to FIGS. 1 and 3 described at the outset, it has been assumed that two internal contacts facing the actuator 19, which are designed as lift-off contacts, are used as main contacts 25 and that monitoring or additional contacts 28 are used which are used with these main contacts 25 via the relevant driver 31 positively guided, facing away from the actuator 19, external contacts that work as flexure contacts. As explained, it is important in these exemplary embodiments that the direct action on the contact springs 27 by the actuating lugs 24 of the actuator 19 takes place with sufficient flexibility to ensure that when a main contact 25 is welded, the actuator 19 can return as far in the direction of its rest position that he opens the other main contact.

The full mobility of the actuator 19 is retained when one of the external contacts welds. Therefore, two such external contacts, for example the contact formed by the fixed contact element 29 'and the contact spring 30' cooperating therewith in the upper right quadrant of FIG. 1 and the diametrically opposite contact as main contacts, can be inserted into the circuit to be switched. In this case, the internally positively guided contacts with these main contacts would serve as additional or monitoring contacts.

Furthermore, it would be possible to insert the internal working contact 25 in FIG. 1 on the one hand and the external working contact either in the upper right or lower left quadrant of FIG. 1 as main contacts in series in the circuit.

The embodiment of Figure 6 differs from that of Figure 1 in that here the two contact springs 27 and 30 are biased such that the external contact, the working contact 25 and the internal contact Contact forms the normally closed contact 28. As shown in FIG. 6, the two contact springs 27 and 30 engage in slots of the actuator 31 from below and pretension them for abutment on an extension 60 of the actuator 19. To reduce the friction, a cutting-shaped projection 61 is provided on the lower side of the actuator 31 according to FIG. 6, which engages in a wedge-shaped recess 62 of the extension 60. Furthermore, it is indicated in FIG. 6 that the leaf springs 27 and 30 are also mounted in a knife-like manner within the actuator 31.

If the actuator 19 pivots counterclockwise from the rest position shown in FIG. 6 around the bearing pin indicated at 18, the actuator 31 is positively pressed outward so that the normally closed contact 28 opens and the normally open contact 25 closes. If the working contact 25 welds in its working position, as indicated in FIG. 7, it holds the driver 31 in this position, while the actuator 19 can return to its rest position. The blade-shaped projection 61 detaches from the wedge-shaped recess 62 of the attachment 60 provided on the actuator 19. The normally closed contact 28 is then also held in its open position via the actuator 31.

When using the safety relay according to the embodiment of Figures 6 and 7, for example, the normally open contact 25 shown here and the diametrically opposite (not shown) normally open contact are inserted as main contacts in the circuit to be switched, while the normally closed contact 28 and its diametrically opposite counterpart serve as monitoring contacts.

Claims (12)

1. A safety relay comprising
      an actuator (90) adapted for reciprocation between a rest position and an operative position in response to energisation of the relay, and
      a first principal contact of the circuit to be switched including a movable contact element (27) and a counter contact element (26), and a first additional contact (28) including a movable contact element (30) and a counter contact element (29), wherein the movable contact elements (27, 30) of the principal contact (25) and of the additional contact (28) are ganged by a first driver (31) and are adapted to be moved by the actuator (19) when the latter moves in one direction, and to be reset by a resilient force when the actuator (19) moves in the other direction,
      characterised in
      that a second principal contact of the circuit to be switched and a second additional contact are provided, wherein the movable contact elements of the second principal contact and of the second additional contact are ganged by a second driver and are adapted to be moved by the same actuator (19) when the latter moves in one direction and to be reset by a resilient force when the actuator (19) moves in the other direction, and
      that each driver (31) when reset by the resilient force is movable independently of the other driver.
2. The relay of claim 1, characterised in that the drivers (31) are movable independently of the actuator (19), and that the movable contact elements (27) of the principal contacts (25) or the portions (24) of the actuator (19) actuating the movable contact elements are so flexible that, upon welding of one principal contact (25), the movability of the actuator (19) is retained for opening the other principal contact. (Figures 1, 3)
3. The relay of claim 1 or 2, characterised in that the principal contacts (25) are formed as lift-off contacts.
4. The relay of any of claims 1 to 3, characterised in that the movable contact elements (27) of each principal contact (25) include a spring, and that the actuator (19) engages the movable contact element (27) at a location spaced from the contact location between this movable contact element (27) and the associated fixed counter contact element (26). (Figures 1, 2)
5. The relay of claim 4, characterised in that each spring has a region (34) of reduced width at the engaging location of the actuator (19). (Figure 2)
6. The relay of any of claims 1 to 5, characterised in that the actuator (19) engages the movable contact element (27) of each principal contact (25) through a flexible portion.
7. The relay of claim 1, characterised in that each driver (31) resiliently engages the actuator (19) in the reset direction of the movable contact elements (27, 30) ganged by the driver. (Figure 6)
8. The relay of claim 7, characterised in that the principal contacts (25) are formed as flexure contacts.
9. The relay of any of claims 1 to 8, characterised in that the principal contacts (25) are formed as normally open contacts and the additional contacts (28) are formed as normally closed contacts.
10. The relay of any of claims 1 to 9, characterised in that the movable contact elements (27, 30) respectively ganged by one driver (21) include essentially parallel springs which have one end fixed to a terminal (12) and are engaged by the driver (21) in the region of their other free end.
11. The relay of any of claims 1 to 10, characterised in that the actuator (19) is pivotal about an axis extending transversely of the direction of contact movement.
12. The relay of claim 11, characterised in that the actuator (19) is symmetric with respect to the pivot axis and that a total of four principal contacts (25) and four additional contacts (28) are disposed on both sides opposite the two ends of the actuator.

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