EP1308976A1 - Relay - Google Patents

Abstract

The monitoring device (21, 23, 25, 27) operates without contacts and has a sensor (23) in the casing near the slide (17). The slide includes a sensor actuation device (27).

Description

The invention relates to a relay with a number of load contacts each a movable contact spring, a slide that is connected to the movable Contact springs of the load contacts is engaged and a driving the slide Drive for switching the load contacts with the slide, and one non-contact monitoring device in the housing of the relay for Monitor the switching of the load contacts.

From US-A-3,821,771 a contactor is known which has a base plate thereon Housing and in the housing has an actuating structure. This Actuating structure has a U-shaped yoke with one on each leg of the U. Coil winding of a coil. The U-shaped yoke works with a U-shaped anchor together. The contactor has a number of stationary contact pairs, and to each stationary contact pair on a movable contact bridge. The contact bridges are arranged on a movable contact carrier. The stationary contacts are arranged on the housing of the contactor. The contact carrier and the contact bridges are moved together with the anchor relative to the housing when the Coil is activated or deactivated. When the coil is activated, the Contacts closed by the electromagnet. When the coil is deactivated the contacts are opened by the spring force of two spiral springs. Such a Schütz only has a number of NO contacts as load contacts, but none NC contact as control contact.

An additional contact device for such a contactor is known from US-A-4,309,683. This additional contact device has a second housing that is connected to the first housing of the Contactors can be attached. In this second case there is a fixed and a movable contact arranged on a second contact carrier. The first Contact carrier of the contactor and the second contact carrier of the additional contact device are mechanically coupled, so that the second contact carrier prevents the movements of the must be involved in the first contact carrier. The contact of the Additional contact device closed or opened. For the connection of the two Contact carriers are provided in the first contact carrier slots, while on there are second contact carrier projections which engage in these slots. This connection of the contact carrier of the additional contact device with the Contact carrier of the contactor allows the spring means in the additional contact device dispense.

US-A-5,198,789 proposes a logical contactor according to US-A-3,821,771 Safety switch in front of the type of additional contact device according to US-A-4,309,683 can be attached to a contactor. This safety switch has a plunger protruding from a housing of the safety switch, the taps the movement of the armature and therefore between the open position and the closed position of the contacts is moved back and forth. Are in the housing logical sensors are arranged around the plunger and an activator is arranged on the plunger. The Depending on the position of the armature, the activator selectively activates the logic sensors, which sensors therefore have a logic corresponding to the position of the contact bridges Generate signal. The following are proposed as activators and sensors: Permanent magnet and reed switch, an optical conductor on the plunger and an optical transmitter and receiver around the plunger, a magnet and inductive sensors. In a preferred embodiment, the tappet has its own Spring means that press the plunger against the anchor, making the safety switch the coil springs of the contactor are not loaded.

WO 92/00599 A1 describes an additional electronic contact to a contactor known. The additional contact has at least one switching element that is "ON" and can have an "OFF" state to the position of a contact bridge in the Contactor. The additional contact also has an actuating element that is mechanically connected to the contact bridge and actuate the switching element can. The actuating element has an activator for activating the Switching element that has no mechanical connection to the switching element. The additional contact is in a housing block on the outside of a contactor arranged. The actuating element reaches into the inside of the contactor with a pin and is attached to the contact carrier there. A carriage connected to the pen will together with the pin by moving the contact carrier around the same Distance moved like the contact carrier in the housing block. The position of the Sled is detected by sensors. The following sensors are proposed: Hall sensors, inductive or capacitive proximity sensors and optical Distance sensors.

In such shooters, the drives are designed so strong and the movement the contact bridges are so spacious that there is no adjustment effort to adjust of contacts is required. The drive takes a correspondingly considerable Control current. The contact bridges are so that the contact over a long Period can be reliably produced and interrupted, spring-loaded. However, this also requires long switching distances. These shooters don't have one Control contact. By adding an electronic one, for example Additional contact can monitor the switching position of the contactor. adversely on these shooters, however, is their size, which for example does not allow the Attach contactor to a circuit board of an electronic control.

Relays of the type mentioned are, however, much smaller and the balance of power between spring force and drive is very balanced. Therefore, a considerable adjustment effort for adjusting the spring elements operated. Such relays have so far at least one control contact is constructed similarly or identically to the load contacts, and that with the same slide how the load contacts are operated. The control contact must be in this relay Be opener if the work contact is a make contact, or a make contact if the Make contact is a break contact. This can ensure that the Control contact cannot be closed when the load or work contact welded or otherwise does not open when it should open.

A disadvantage of this conventional monitoring of the switch position A relay's load contacts through a control contact is either the drive very powerful or the control contact must be adjusted. Has both Influence on the price of the relay. Choosing a powerful drive in favor of reduced adjustment effort also has an impact on the size of the relay. Conversely, the choice of a minimal drive has an increased adjustment effort result, which causes relatively high costs.

An electromechanical switching device is known from DE 199 60 399. This is in particular a safety relay module intended for a safety shutdown. The switching device has at least one mechanical switching contact. in the Switching device, an optical sensor is provided which detects the switching position of the Switching contact monitored, so that a common positive control of the Switching contact with a control contact is omitted and still a high degree Security can be achieved. The sensor is an optical sensor, the one Transmitter for emitting a light beam and a light-sensitive receiver includes. The light beam lies in a plane in which the contact surfaces of the Bump the switch contact when the switch contact is closed. The Light beam can also lie in a plane in which a switch contact pin of the Switch contact is in the closed or open state. Alternatively, you can the sensor can be designed as a reflection light barrier. On the contact pin is for this purpose, a reflective surface is formed.

This design is only suitable for monitoring a single contact. However, around several contacts of a safety relay module arranged side by side This document proposes to monitor, a fork light barrier to provide, the light beam emanating from the transmitter side by side arranged normally open contacts in the area of the contact surfaces.

Such monitoring is not suitable for relays with both make contacts also openers in a row. Nor can this monitoring indicate that one of the make contacts next to each other is still open, though only one is closed. Above all, this monitoring requires one Align the contacts along a line that is transverse to the direction of movement Switch contact pins runs. It is therefore not possible to monitor one of these Relay normally closed and normally open contacts with a common slide actuate. Moreover, such monitoring is only possible optically. At a Monitoring of a contact in the area of the contact surfaces with an optical Sensor is also only through a dynamic way of monitoring rule out that a voltage spark of a contact is not a wrong signal triggers. Furthermore, an optical sensor arranged in the region of the contacts is the Exposed to pollution. To requirements regarding electrical isolation between a sensor in the area of the load current carrying parts and these parts are also not a small design effort or spatial dimensions required. Furthermore, with such an arrangement, all contact surfaces be arranged exactly in a line, so that the opto-sensor technology can also be half a millimeter distance between the contact areas indicates that the contacts are separated. To achieve this, an increased adjustment effort is to be expected.

The object of the invention is therefore to a relay of the type mentioned create a plurality of each other via a common slide actuable contacts regardless of whether they are NO or NC contacts with are monitored by a common monitoring device. With this relay the costs for both the drive and the adjustment effort should be low can be held. It should be possible without reinforcing the drive to reduce the adjustment effort, or without increasing the adjustment effort Reduce drive. Drive and adjustment effort can even be advantageously reduced become.

According to the invention, this object is achieved by the features of patent claim 1 solved. The monitoring device is therefore a contactlessly operated Monitoring device and has at least one arranged in the housing Sensor in the vicinity of the slide and the contacts which force the contacts at least one activator of the sensor arranged on the slide. A with Mechanical control contact actuated by the same slide is therefore eliminated. The The contact spring of this control contact does not have to be moved accordingly, so that the power of the drive can be reduced. In addition, at least one Contact spring can be adjusted less. Monitoring the position of the slide has the advantage that the non-contact monitoring device does not must be arranged in the polluting area of the contact chambers. This also allows optimal separation of the load and control circuit in the relay.

Since the contacts are positively guided together with the slide, the position allows of the sensor in the vicinity of the slide and the arrangement or training of the activator on, on or in the slide all with the common slide to monitor switched contacts simultaneously. A single contact remains in one position, the slide also stays in place and with it all other contacts this position.

The monitoring device of the relay according to the invention switches, generates or changes a current via one of the phenomena light, magnetism or capacitance or its tension. The signal generated in this way can now be used to the position or movement of the slide and thus the contact monitor.

• Ein Licht abstrahlendes Element (Sender) und ein lichtempfindliches Element (Sensor) diesseits und jenseits eines sich mit dem Schieber in den Lichtstrahl verschiebenden Unterbrechungsteils (Aktivator in Form eines Reflektors oder Fensters),
• ein Elektromagnet (Sender), welches ein wechselndes Magnetfeld erzeugt und ein zweites Elektromagnet (Sensor), in welchem mit dem Wechselmagnetfeld über eine mit dem Schieber in das Magnetfeld verschieblichen Metallbrücke (Aktivator) ein Strom induziert wird;
• eine Induktionsschlaufe (Sensor), welche ein Magnetfeld bildet und eine Bewegung eines sich mit dem Schieber verschiebenden Metallteils (Aktivator) überwacht;
• eine passive Induktionsschlaufe (Sensor), welche eine Bewegung eines sich mit dem Schieber verschiebenden Permanentmagneten (Aktivator) überwacht;
• ein Reedkontakt (Sensor), der auf einen mit dem Schieber verschieblichen Magneten (Aktivator) reagiert; ein Reedschalter kann in bekannter Betriebsweise als Öffner, Schliesser oder Wechsler eingesetzt werden;
• ein magnetfeldabhängiger Widerstand (Sensor), der auf einen mit dem Schieber verschieblichen Permanentmagneten (Aktivator) anspricht;
• ein Hallgenerator (Sensor) im Einflussbereich eines mit dem Schieber verschieblichen Magneten (Aktivator).

Such monitoring devices are, for example:

• A light-emitting element (transmitter) and a light-sensitive element (sensor) on either side and beyond an interruption part (activator in the form of a reflector or window) that moves into the light beam with the slide,
• an electromagnet (transmitter) which generates an alternating magnetic field and a second electromagnet (sensor) in which a current is induced with the alternating magnetic field via a metal bridge (activator) which can be moved into the magnetic field by the slide;
• an induction loop (sensor), which forms a magnetic field and monitors a movement of a metal part (activator) that moves with the slide;
• a passive induction loop (sensor) which monitors the movement of a permanent magnet (activator) which moves with the slide;
• a reed contact (sensor) that reacts to a magnet that can be moved with the slide (activator); a reed switch can be used in a known mode of operation as a break contact, make contact or changeover contact;
• a magnetic field-dependent resistor (sensor) which responds to a permanent magnet (activator) displaceable with the slide;
• a Hall generator (sensor) in the area of influence of a magnet that can be moved with the slide (activator).

A relay with monitoring the switching of the load contacts can Monitoring device for monitoring the position or movement of the Have slide. With the monitoring device, an electrical current can generated or a predetermined electrical signal can be changed.

• Ein Piezokristall, der in der einen Endstellung des Schiebers unter Druck steht, und
• ein Schiebewiderstand, dessen Widerstand durch die Verschiebung des Schiebers verändert wird.

Monitoring devices of this type are, in addition to the above-mentioned contactless exemplary embodiments, also the following exemplary embodiments working with contact:

• A piezo crystal that is under pressure in one end position of the slide, and
• a sliding resistance, the resistance of which is changed by the displacement of the slide.

• Erzeugen einer Spannung, z.B. durch Druck auf einen Piezokristall oder durch das einem Magnetfeld Aussetzen eines Hallgenerators,
• Auslösen eines Stromflusses, z.B. durch Belichten einer Fotozelle oder eines Fototransistors, oder Betätigen eines Reedschalters durch Annähern eines Magneten an die Schaltlamellen des Reedschalters,
• Verändern eines Stromflusses, z.B. durch Belichten eines Fotowiderstandes oder eines Fototransistors,
• Verändern einer Spannung, z.B. durch Belichten eines Fotoelements oder einer Fotodiode,
• Verändern der Kapazität eines Kondensators durch Veränderung der relativen Lage der beiden statisch aufgeladenen Metallschichten,
• Verändern eines induzierten Stromes durch Bewegen eines Magnetfeldes oder eines Metallteils im Magnetfeld.
• Induzieren eines Stromes in einer Induktionsschlaufe durch Bewegen eines Magnetfeldes relativ zur Induktionsschlaufe,
• Induzieren eines Stromes in einer Induktionsspule durch Übertragen eines Wechselmagnetfeldes auf den Kern der Spule.
• Verändern eines Widerstandes in einem magnetfeldabhängigen Widerstand durch Verändern der Lage eines Magnetfeldes bezüglich des Widerstand-Bauteils.

An evaluable signal can therefore be achieved by:

• Generating a voltage, for example by pressure on a piezo crystal or by exposing a Hall generator to a magnetic field,
• Triggering a current flow, for example by exposing a photocell or a phototransistor, or actuating a reed switch by bringing a magnet closer to the switch blades of the reed switch,
• Changing a current flow, for example by exposing a photo resistor or a photo transistor,
• Changing a voltage, for example by exposing a photo element or a photo diode,
• Changing the capacitance of a capacitor by changing the relative position of the two statically charged metal layers,
• Changing an induced current by moving a magnetic field or a metal part in the magnetic field.
• Inducing a current in an induction loop by moving a magnetic field relative to the induction loop,
• Inducing a current in an induction coil by transferring an alternating magnetic field to the core of the coil.
• Changing a resistance in a magnetic field-dependent resistor by changing the position of a magnetic field with respect to the resistance component.

These lists are not exhaustive.

With many of these monitoring devices, their adjustment, if such is necessary at all, electronically, e.g. in one in the relay existing component or outside of the relay, and so on the output signal of the monitoring device to a selectable value can be set. The production-related occurring within a range Signal value can also, e.g. by setting one accordingly User program, when using the relay individually to the respective Position of the relay can be read.

The location of the monitoring device can be chosen relatively freely in the relay. It can one, two or more monitoring devices can be provided in the relay. The Signals from such monitoring devices can be user specific used differently.

Brief description of the figures:

Fig. 1

ein Relais mit zwei geschlossenen Schliessern als Lastkontakte und einer optoelektrischen Überwachungsvorrichtung,

Fig. 2

das Relais gemäss Figur 1 mit geöffneten Lastkontakten,

Fig. 3

ein Relais mit einem Schliesser und einem Öffner und zwei optoelektrischen Überwachungsvorrichtungen,

Fig. 4

eine induktive Überwachungsvorrichtung mit zwei elektromagnetischen Spulen und zwei beweglichen Eisenbrücken,

Fig. 5

die Überwachungsvorrichtung gemäss Figur 4 mit verschobenen Eisenbrücken,

Fig. 6

zwei Reedschalter mit einem beide gleichzeitig aktivierenden Permanentmagneten,

Fig. 7

zwei Reedschalter mit einem entweder den einen oder den anderen Reedschalter aktivierenden Permanentmagneten,

Fig. 8

ein Schieber mit einer Kondensatorfläche, welche zusammen relativ zur anderen Kondensatorfläche verschiebbar ist,

Fig. 9

der Schieber gemäss Figur 8, jedoch in verschobener Position,

Fig. 10

eine passive Induktionsschlaufe mit einem relativ zur Schlaufe verschieblichen Permanentmagneten,

Fig. 11

eine ein Wechselmagnetfeld erregende Induktionsschlaufe mit einem relativ dazu verschieblichen Eisenteil,

Fig. 12

eine Induktionsspulenanordnung mit mehreren getrennten Induktionsschlaufen und einem gegenüber diesen verschieblichen Magneten,

Fig. 13

eine zweite Induktionsspulenanordnung mit mehreren getrennten, aktiven Induktionsschlaufen und einem gegenüber diesen verschieblichen Eisenstab.

Individual exemplary embodiments are described below using schematic representations. It shows:

Fig. 1

a relay with two closed make contacts as load contacts and an optoelectric monitoring device,

Fig. 2

the relay according to Figure 1 with open load contacts,

Fig. 3

a relay with a closer and an opener and two optoelectric monitoring devices,

Fig. 4

an inductive monitoring device with two electromagnetic coils and two movable iron bridges,

Fig. 5

the monitoring device according to Figure 4 with shifted iron bridges,

Fig. 6

two reed switches with a permanent magnet that activates both at the same time,

Fig. 7

two reed switches with a permanent magnet that activates either one or the other reed switch,

Fig. 8

a slide with a capacitor surface which can be moved together relative to the other capacitor surface,

Fig. 9

the slide according to Figure 8, but in a shifted position,

Fig. 10

a passive induction loop with a permanent magnet that can be moved relative to the loop,

Fig. 11

an induction loop which excites an alternating magnetic field with an iron part which is displaceable relative thereto,

Fig. 12

an induction coil arrangement with a plurality of separate induction loops and a magnet which is displaceable relative to these,

Fig. 13

a second induction coil arrangement with a plurality of separate, active induction loops and an iron rod which can be displaced relative to them.

FIG. 1 schematically shows a relay 11 with two switch contacts 13, 15. These are in Engagement with a common slide 17 and positively guided by this. The Slider is controlled by an electromagnetic drive 12. The Forced operation ensures that either all or no contacts 13, 15 connect Join the switching movement. It can therefore be read from the position of the slide 17 whether the contacts 13, 15 are open or closed. The information of the position of the Slider 17 must be able to be recognized electrically or electronically.

So far, at least one of the contacts of the relay has been used for this. With this it can be determined whether the load contacts are open or closed. He must be closed when the load contacts are open and open when these are closed.

This is usually done by hand by practicing a die Contact spring bending force on a contact spring of the control contact.

In Figure 1, the position of the slide 17 is monitored with a optoelectric component. This comprises a light emitting diode 21, a light sensitive one and signaling part 23 due to the action of light and an interrupter 25. The interrupter is formed here by the slide 17 itself. In the slide 17 is a light opening 27 is present. In Figure 1, the signal is the triggering light beam interrupted by the slide 17, since the contacts 13, 15 are closed. The In contrast, light opening 27 is located in FIG. 2 between the light-emitting ones LED and the signaling part 23, since the contacts 13, 15 are open.

The light beam can also be deflected by the interrupter. He can in this case can be directed to different signaling parts 23.

Is the signaling part 23 sensitive to the amount of light that can Intermediate positions of the slide are detected. Such Threshold monitoring is electronically adjustable and adjustable. This adjustment can be done internally in the relay or by the user outside the relay. can signaling part 23, however, only the presence or absence of light, only one end position, namely the Open position are recorded. Any differences in signal strength can be corrected electronically.

FIG. 3 shows an activated relay 11 with a make contact 13 and a break contact 16 shown. To monitor the closer 13 is a first optoelectric Component 21, 23 with the light opening 27 in the slide and a first interrupter 25 available. For the opener 16 is a second optoelectric component 22, 24 with the same light opening 27 in the slide and a second interrupter 26 available.

The monitoring can also be done the other way round, namely so that the interruption of the light beam triggers a signal. Then there are 23.24 for two signaling parts two light openings and in between one via one or the other signaling Part 23.24 sliding breaker available. For security reasons However, the version shown is preferable because there is a loss of light emission, e.g. caused by a defect in the power supply, the signal for closed contacts. This position is in security applications from positively driven relay the relevant position.

All that is needed to adjust the monitoring device is the location of the light emission and light-receiving component can be adjusted. Or it the location of the light opening can be adjusted. These adjustments are made by local movement of the part achieved what compared to the conventional Bending a contact spring is much easier.

Instead of the optoelectric component, a component can also be used that works with induction. In Figures 4 and 5 is a variant with an inductive Detection of the position of the slide shown. The induction component according to the figure 4 and 5 have a first coil 31 with a core and a second coil 32 with a Core, which coils 31, 32 are arranged parallel to one another and next to one another are. The first coil 31 is supplied with an alternating current during operation. The resulting alternating magnetic field is generated by the adjacent second coil 32 partially detected so that an alternating current is induced in their windings, which is weaker than that fed into the first coil 31. By the move an iron bridge 33 in the area of the corresponding core ends of the two coils 31, 32 the magnetic field is deflected. Therefore, depending on Position of the bridge 33 is a stronger (Figure 4) or weaker alternating current (Figure 5) induced in the second coil 32. 4 and 5 are two bridges 33 and 34 are provided, one of which has the magnetic field at one pole and the other attracts at the other pole.

The bridge 33 is therefore expediently moved with the slide 17. The induced current can now be measured and from this the position of the slide can be calculated. By taking suitable measures in the area of relay 11 connected software can adjust the bridge 33 and the coils 31,32 entirely in electronics, e.g. the measured values to the Position of the contacts 13,15,16 are related. This advantage is with everyone Versions that can be used with the sliding position of the slide 17th generate changing signals.

However, it is also possible to have a switching signal with only two switching states to reach without contact. 6 and 7 is an example to illustrate this shown, in which a reed switch 41 in a manner known per se with a Permanent magnet 43 is switched. The permanent magnet 43 is put together moved with the slider 17. He comes close to the reed switch 41 and switches this. For safety, two reed switches 41, 42 can be used simultaneously be switched. Two reed switches 41, 45 can also be connected in series become. This can e.g. both an opener and a closer through the Movement of a single magnet 43 are monitored. To adjust a Reed switch 41, this or the magnet 43 can be changed in position. The magnet 43 which is changed with respect to the reed switch can switch the reed switch 41, by having a constantly existing one that goes in the opposite direction Magnetic field closing reed switch superimposed.

FIGS. 8 and 9 show an example in which the position of the slide 17 is capacitively determined. For this purpose, the slide 17 has a capacitor plate 51 which is slidable with respect to a second capacitor plate 52. The change in position also changes the measurable on the capacitor Characteristic value. This value can vary depending on the accuracy of work electronically adjusted or software-related to the position of the contacts become.

In Figure 10, a magnet 43 is shown, the slide 17 opposite one Induction loop 53 is slidable. A metal part 55 is opposite in FIG an activated induction loop 53 slidably. With these arrangements can a movement of the slide can be determined. FIG. 12 shows that several Induction loops 53,54,57,58 on both sides of a magnet 43 (or metal part) in Direction of movement can be arranged side by side, each of the other reach differently in the area of influence of the displaceable magnet 43. This allows not only the movement but also the position of the slide 17 be determined.

In Figure 13 it is shown that the loops 53,63,73 also transversely to the direction of movement can be arranged side by side to the location and movement of a the slider 17 displaceable rod 61 can be seen.

In summary, the following can be said: On, in or on one of the Contacts of a relay common slide is arranged an activator. In the A sensor which can be activated with the activator is arranged in the vicinity of the slide. By the contactless generation of a control signal by means of the activator in the Sensor for monitoring the switching position or the switching movement of the Contacts is an adjustment of the monitoring device electronically and / or possible by locally changing the parts of the monitoring device. This reduces the adjustment effort considerably and enables a reduction of the Drive, because fewer springs have to be moved and therefore the required force for switching the relay is reduced.

Claims (9)

Relay (11) with a housing, and in the housing a number of load contacts (13, 15, 16), each with a movable contact spring, a slide (17) which is in positive engagement with the movable contact springs of the load contacts (13, 15, 16) and a drive (12) driving the slide (17) for switching the load contacts (13, 15, 16) with the slide (17), and a monitoring device (for example 21, 23, 25, 27) in the housing of the relay for monitoring the circuit the load contacts (13, 15, 16), characterized, that the monitoring device (for example 21, 23, 25, 27) can be operated without contact, that the monitoring device (for example 21, 23, 25, 27) at least one sensor (23, 24, 32, 41, 42, 45, 52, 53, 54, 57, 58, 63, 73) arranged in the housing in the vicinity of the Has slide (17), and that the monitoring device (for example 21, 23, 25, 27) at least one activator (25-26-27, 33, 34, 43, 51, 55, 61) of the sensor arranged or formed on, in or on the slide (17) having. Relay (11) according to claim 1, characterized in that at least one monitoring device (for example 43.53) is designed such that movement of the slide (17) in the monitoring device (for example 43.53) triggers a signal. Relay (11) according to one of Claims 1 or 2, characterized in that at least one monitoring device (for example 51, 52) is designed such that, depending on the position of the slide (17) in the monitoring device (for example 51, 52), a distinguishable signal is triggered. Relay according to one of Claims 1 to 3, characterized in that a signal is triggered capacitively in the monitoring device (for example 51, 52). Relay according to one of Claims 1 to 3, characterized in that a signal is triggered optoelectrically in the monitoring device (for example 51, 52). Relay according to Claim 5, characterized in that a reflector is arranged on the slide (17) in order to reflect a light beam emitted by a transmitter onto a receiver in a position of the slide (17). Relay according to Claim 5, characterized in that an interrupter is formed on the slide (17) which interrupts a light beam emitted by a transmitter in one position of the slide (17), but in another position enables the light beam to reach a receiver. Relay according to one of Claims 1 to 3, characterized in that a signal is triggered inductively in the monitoring device (for example 51, 52). Relay according to one of Claims 1 to 3, characterized in that a signal is triggered magnetically in the monitoring device (for example 51, 52).

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