EP2284340B1 - Magnetic catch for closure of an opening - Google Patents

Description

The invention relates to a magnetic catch for closing an opening according to the preamble of claim 1.

Out WO 97/03912 A1 is a generic magnetic catch known.

Out DE 1 802 116 U For example, a magnetic closure for furniture and room doors, flaps and the like closure organs is known.

For small, labile doors and flaps, e.g. in the packaging industry, magnetic closures or magnetic catches are required with which the door or flap can be held in the closed position.

Depending on the material and dimensions of the doors and flaps, it is advantageous if the magnetic catch can be adjusted or adjusted in terms of their locking force.

The object of the invention is therefore to provide a magnetic catch for closing an opening, the clamping force is adjustable.

This object is solved by the features of claim 1.

This creates a magnetic catch for closing an opening including a movable part and a fixed part. The movable part is the door or the flap o. Ä., And the fixed part of a wall or wall. The magnetic catch comprises a magnetic circuit. The magnetic circuit has a yoke and a lockable with the yoke magnet, wherein the magnetic effect of the magnet is changeable to the yoke. The yoke is attached to the movable part and the magnet is attachable to the fixed part. The magnet which can be closed with the yoke has at least two pole shoes on which the magnetic field lines can emerge in a defined shape. In addition, at least one switching magnet connecting the pole shoes is provided. The "connection" of the pole pieces via the switching magnet is such that the switching magnet has a magnetization direction along the connection of the two pole pieces, wherein the orientation can be changed by 180 °. The direction of the magnetic field remains the same when the orientation changes. Illustrated in a vector represented by an arrow, in this illustration, the position of the arrowhead indicates the orientation of the vector and the arrow shaft indicates its direction. Since the magnetic field, the orientation of the field lines is defined by the position in which the north pole of a compass needle points, pivots an imaginary compass needle for displaying the magnetic field of the switching magnet in a Ummagnetisierung same by 180 °. By the switching magnet, it is possible to change the course of the magnetic field lines in the pole pieces and in particular at the ends facing the yoke. In one of the two magnetization orientations of the switching magnet, magnetic field lines essentially do not emerge from the pole shoes, but the magnetic flux is "short-circuited" by the switching magnet in the magnet.

By means of the switching magnets, the magnetic flux defined can be "switched off" and "switched off" from the pole shoes, so that the magnetic effect of the magnet can be switched "on" and "off". The closable by the yoke magnet acts as a magnet system with permanent magnet and solenoid, which can exert a high clamping force on the yoke, which is time-independent, whereby the magnetic force of the magnet system can be switched on and off by the at least one switching magnet. For a change between a locking by the magnetic catch and the canceling of the locking only a remagnetization of the switching magnet or is required.

The magnetization of the magnet system can be measured by means of a sensor, so that a reliable statement can be made with sufficient certainty as to which clamping force is exerted between the moving part and the stationary part. There is a feedback capability whereby an input signal may be applied to a controller as a result of the determination of the magnetization, which is configured as a function value, to inform the controller with the input signal whether and which clamping force is achieved.

The advantage achieved with the magnetic catch according to the invention lies in the fact that a desired holding force is adjustable so that even in unstable doors they are not uncontrollably opened by vibrations during operation, but on the other hand at the intended opening it does not lead to such tension that the material of the doors or flaps can be damaged by the applied forces to open, with no further power is required to maintain the Schnäpperkraft, since the magnetic catch is outwardly resembles a permanent magnet.

The sensor is designed as a coil which surrounds the magnet at least in one section. Through such a coil, the magnetization of the magnet via the saturation as a measure of the magnetic flux is measurable, adding a frequency of the coil, the saturation of the portion of the magnet as the core the coil is varied, is detected. The frequency measurement of the coil surrounding the section of the magnet makes a reliable statement with sufficient certainty as to what clamping force is exerted between the moving part and the stationary part. The coil whose frequency is measured is preferably designed as a frequency-determining component of an oscillator. By changing the saturation in the iron, the inductance of the coil and thus the frequency of the resonant circuit is changed. As a coil, which is provided for the detection of the saturation via the frequency measurement, the winding of the switching magnet is used, whereby the structure of the magnetic force adjustable magnetic latch is simplified and as few components are present, and also a wiring thereof is reduced. However, it can also preferably be provided that the sensor is arranged as a coil for detecting the saturation of the magnet in the region of the yoke facing the end of a pole piece. Thus, a further coil is provided in addition to the winding for the switching magnet, which makes the detection of saturation alternatively or in addition to a detection of saturation via the winding of a solenoid.

The permanent magnet and the switching magnet of the magnet or the magnet system are preferably substantially longitudinal in a first exemplary embodiment staggered to each other, and the pole pieces are configured as transversely extending body made of soft magnetic material.

In a further embodiment, the pole pieces may be arranged between a permanent magnet and a switching magnet, so that they connect a permanent magnet and a switching magnet, wherein adjacent permanent magnets in the arrangement or sequence each have a different magnetization orientation, and the permanent magnets are arranged on a soft magnetic material for a magnetic return on the pole shoes opposite side, so that a simple magnetic field line is formed. The "switching off" of the magnetic flux is, for example in the further embodiment, the case when the solenoid is magnetized so that it has a magnetic north pole at the connected via the pole piece permanent magnet having a magnetic south pole at its end, and a magnetic South pole has on the permanent magnet connected via the pole piece, which has at its end a magnetic north pole. The magnetic field then substantially does not emerge from the pole pieces, that is, when the switching magnet is magnetized so that it has an opposite polarity at the ends to the permanent magnets. The situation is different if the switching magnet with the same polarity at the ends is magnetized to the permanent magnets connected via the pole shoes. Then, the switching magnet has a magnetic south pole on the permanent magnet, the end of which forms a magnetic south pole and a magnetic north pole on the permanent magnet, whose end forms a magnetic north pole. In the latter case, the magnetic field lines are "pushed out of the switching magnet" and exit through the pole shoes. A yoke present can be attracted by the pole pieces in the opposite polarity.

An electrical energy store, for example a capacitor, is preferably provided for the remagnetization. Further preferred is the electrical Energy storage disposed in a housing in which the Umzumagnetisierenden switching magnets are located. As a result, a compact and simple design with simple components can be achieved, which can also switch in the event of a power failure between "on" and "off" of the magnet system

Preferably, the permanent magnets on a rare earth or neodymium magnetic material. Thereby, it is possible to use a hard magnetic material which has excellent properties as a permanent magnet. The magnetic material neodymium-iron-boron is used to generate strong magnetic fields in a small volume. The magnetic material has high coercivities of 870 to 2750 kA / m at room temperature and is relatively inexpensive.

Preferably, the switching magnet comprises an AlNiCo magnetic material, which is surrounded by a current-carrying winding. By using an AlNiCo magnet material, it is possible to use a magnetizable magnetizable material, which does not depend on the generation of very high magnetic fields. Furthermore, given by the AlNiCo magnetic material in the longitudinal direction surrounding current-carrying winding a simple way of remagnetization, which is structurally simple, compact and low maintenance.

It may also be preferable to provide a Hall or GMR sensor which also allows the detection of a stray field. The Hall or GMR sensor is preferably adjacent to the (exposed) pole piece of the

Magnet system arranged. When the magnet system is open, the Hall or GMR sensor detects the entire field and can thus also be used to detect a disturbing residual magnetization as well as to set a field for a defined holding force of the magnetic latch. When the activated magnet system is closed, a leakage flux can be measured by the Hall effect sensor or GMR sensor arranged on the pole piece, which also supplies information about the potential closing force of the magnet system.

It is also possible to use a strain gauge which detects a deformation of the end of the magnet facing away from the yoke due to the polarity of the pole pieces. For this purpose, the strain gauge can be attached to the yoke remote from the end of the magnet or magnet system. For example, it is possible that the strain gauge is attached to the soft magnetic material that is present for the magnetic return of the magnet. There will be a bending moment, i. causes a deformation, from which it is possible to determine how the pole pieces are "poled" and how strong the flow through the adjacent yoke is. If there is a strong magnetic flux through the pole pieces to the outside, so that the magnetic catch stops, acts a force that wants to drive the two outer pole pieces apart. By contrast, if the magnetic catch is "switched off", it is pulled together by the magnetic field now flowing inside the magnet. A strain gauge provides an example, not disturbed by an external magnetic field, structurally compact way to determine the locking force of Magnetschnäppers.

It is preferred if the control of a machine which can be accessed by means of the opening, the signal of the measurement of the sensor - prepared or in its original form - is supplied, and with the control for the machine itself, the locking force of the magnetic latch is adjustable , It can Furthermore, it may be preferred that the controller and the magnetic catch are coupled via an AS-Interface.

It can also be provided that a non-safety-related path of a safety-related sensor for controlling the locking force of the magnetic latch can be used. The safety-related sensor can be designed, for example, as a mechanical switch or electronic sensor for determining whether the opening is closed with the door or flaps. The use of a non-safety-related path of a safety-related sensor is advantageous because the non-safety-related path of a safety component can be used, which is already in the area of the opening in many applications in the industry for implementing human-machine safety in the form of safety switches , And thus the magnetic catch exploits existing hardware.

• Fig. 1 zeigt schematisch ein Ausführungsbeispiel eines Magnetschnäppers, bei dem zwischen Magnet und Joch keine Kraft ausgeübt wird;
• Fig. 2 zeigt schematisch das Ausführungsbeispiel von Fig. 1 bei Ausübung einer Kraft des Magneten auf das Joch;
• Fig. 3 zeigt schematisch ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Magnetschnäppers, bei dem keine Kraft von dem Magneten auf das Joch ausgeübt wird;
• Fig. 4 zeigt schematisch das weitere Ausführungsbeispiel von Fig. 3, bei dem der Magnet eine Kraft auf das Joch ausübt.

The invention will be explained in more detail below with reference to the embodiments illustrated in the accompanying drawings.

• Fig. 1 shows schematically an embodiment of a magnetic latch, in which no force is exerted between the magnet and the yoke;
• Fig. 2 schematically shows the embodiment of Fig. 1 upon application of a force of the magnet to the yoke;
• Fig. 3 shows schematically a further embodiment of a magnetic latch according to the invention, in which no force is exerted by the magnet on the yoke;
• Fig. 4 schematically shows the further embodiment of Fig. 3 in which the magnet exerts a force on the yoke.

Fig. 1 shows an embodiment of a magnetic latch according to the invention. It is a section of a movable part 1 shown schematically, with which an opening is closed. Part 1 can be a flap, Door, lid or the like, which is relative to a likewise schematically illustrated fixed part 2 is relatively movable. The relative movement may be pivoting and / or shifting.

On the movable part 1, a yoke 3 made of soft magnetic material is attached, which abuts when the opening is closed to a magnet 4 and this closes. The magnet 4 has a permanent magnet 5, which is elongated and pole pieces 6 of the magnet 4 connects, from which can escape magnetic field lines shown in dashed lines, which extend through the yoke 3 with the opening closed and can enter through a pole piece 6 in the magnet 4 again (please refer Fig. 2 ). The permanent magnet 5 is magnetized in the longitudinal direction in the connecting direction of the pole pieces 6. The permanent magnet 5 preferably has a magnetic material neodymium-iron-boron. The pole pieces 6 are formed of soft magnetic material.

Between the pole pieces 6, a solenoid 7 is arranged. The arrangement of permanent magnet 5 and solenoid 7 between the pole pieces 6 is such that adjacent to one end of the pole piece 6 of the permanent magnet 5, the pole pieces connects, and adjacent to the other end of the pole pieces 6 of the solenoid 7, the pole pieces 6 connects. The switching magnet 7 is an easily magnetizable permanent magnet which is magnetized in the direction of connection of the pole pieces 6, wherein the orientation of the magnetic field is variable, however. The switching magnet 7 has an AlNiCo magnetic material.

Im in Fig. 1 In the case illustrated, it can be seen from the magnetic field lines shown in dashed lines that the permanent magnet 5 has a magnetic south pole "S" at the top and has a north magnetic pole "N" at the bottom. Together with the orientation of the magnetic field of the switching magnet 7, which has a magnetic north pole "N" above and a south magnetic pole "S" below, the magnetic field lines within the magnet 4 run in a kind of "short circuit". Essentially, no magnetic field lines occur on the pole shoes adjacent to the yoke 3 from the magnet 4. Due to the parallel magnetization of the permanent magnet 5 and the switching magnet 7 with different orientation, the magnetic field lines run inside the magnet 4, in the illustrated case in Fig. 1 clockwise to.

The magnetization orientation of the switching magnet 7 is variable via a surrounding the magnetic material of the switching magnet 7 winding 8, by the switching magnet 7 can be reversed in its magnetic orientation by an external current pulse. The winding 8 is designed as a coil whose longitudinal axis with the longitudinal axis of the hard magnetic material of the switching magnet 7 runs side by side or coincides. A reversal or loading of the winding 8 with a current pulse is caused by the transition of Fig. 1 on Fig. 2 shown. After the brief application of a current pulse, there is no current or voltage from the outside at the winding 8 for exerting the clamping force. The magnetic field of the switching magnet 7 is in its magnetic orientation between the Fig. 1 and 2 been reversed.

In Fig. 2 the switching magnet 7 is still magnetized transversely to the pole pieces 6 in the connecting direction between them, but the magnetization has rotated by 180 °. Unlike in the case in Fig. 1 in which the permanent magnet 5 and the switching magnet 7 were oriented opposite to each other, the permanent magnet 5 and the switching magnet 7 have the same magnetic orientation Fig. 2 on.

The in Fig. 2 shown magnetic line course shows how the magnetic field lines from the pole pieces 6 of the magnet 4 escape; the magnetic field lines enter the yoke 3, extend in the yoke 3; and reenter the magnet 4 in the next pole piece 6. On the yoke 3, the magnet 4 acts with a force F. At a pole piece 6, the magnetization of the magnet 4 or magnet system can be measured with its effect on the yoke 3 via the saturation as a measure of the magnetic flux. For this purpose, a winding or coil 9 is provided on a pole piece 6, whose frequency is detected. The frequency is a function of the saturation of the pole piece 6 as the core of the coil 9. The frequency is thus varied depending on the saturation of the pole piece 6. The frequency measurement of the pole piece 6 surrounding the coil 9 makes a reliable statement with reasonable certainty about whether the locking force of the magnetic latch is sufficient. The coil is used as a frequency-determining component of an oscillator. Due to the saturation in the iron, the inductance of the coil 9 and thus the frequency of the resonant circuit is varied. The frequency changes so much in the region of saturation that even a gap between pole piece 6 and yoke 3 of 10 μm can be clearly detected. The potential locking force is still far above the guaranteed locking force. If one sets a maximum current of 300 mA for the coil 9 and would like to have a clamping force of 500 N, the cut-off point is at a gap of approximately 50 μm.

In the Fig. 1 and 2 Also shown is a magnetically sensitive sensor 11 in the region adjacent to a pole piece 6, which may be present as an alternative or in addition to the coil 9. The sensor 11 is designed as a Hall or GMR sensor 11. When the magnet system is open, ie when the yoke 3 is not in contact with the magnet 4, the sensor 11 detects the entire field and can also be used to detect a disturbing residual magnetization, as well as to set a field for a defined locking force of the magnetic latch.

Fig. 3 shows a further embodiment of the magnetic latch according to the invention. For the sake of clarity, the movable part 1 and the fixed part 2 are not shown, however, the arrangement of the magnet 4 and the yoke 3 in the movable part and the fixed part is the same as in FIG Fig. 1 and 2 ,

In the further embodiment, the pole pieces 6 of the magnet 4 are formed by soft magnetic material. The pole pieces 6 connect permanent magnets 5 and permanent magnets made of a hard magnetic magnetic material with switching magnets 7. The permanent magnets 5 are magnetized in the longitudinal direction or in the extension of the pole pieces 6. The permanent magnets 5 have as magnetic material neodymium-iron-boron.

Adjacent permanent magnets 5 are magnetized in different orientations. While in the Fig. 3 5, the magnetic field lines run from left to right, ie that a magnetic north pole is formed at the end facing the pole shoe 6, a magnetic south pole is formed on the end of the adjacent middle permanent magnet 5 facing the pole shoe 6; the magnetic field lines through the middle permanent magnet 5 run from right to left. The lowermost permanent magnet 5 has again a magnetic north pole at the end facing the pole shoe 6.

The permanent magnets 5 of the further embodiment are arranged on a plate-shaped soft magnetic material, which is formed by a steel plate 10 in the illustrated further embodiment. The three in Fig. 3 Accordingly, permanent magnets 5 are magnetized and arranged on the steel plate 10 such that the upper and the lower of the three permanent magnets 5 have the same orientation and direction. The middle permanent magnet 5 has a rotated by 180 ° orientation; the mean permanent magnet 5 is opposite to the lower and the upper permanent magnet 5 magnetized opposite.

Between the pole pieces 6, the switching magnets 7 are arranged, which connect the pole pieces 6 in the region of the yoke facing ends. As in the first embodiment, the switching magnets 7 are easily ummagnetisierbare Permanent magnets which are magnetized in the direction of connection of the pole pieces 6, whose orientation is variable, however. The magnetization of the switching magnets 7 extends transversely to the magnetization of the permanent magnets 5. The switching magnets 7 have an AlNiCo magnetic material.

Im in Fig. 3 illustrated case can be seen in the magnetic field lines shown in dashed lines, that the upper switching magnet 7 has a magnetic south pole above and below a magnetic north pole. The lower switching magnet 7 has a magnetic north pole at the top and a magnetic south pole at the bottom. The magnetic field lines essentially do not emerge from the pole shoes 6. The in Fig. 3 shown magnetic field line course shows that substantially no magnetic field lines emerge from the pole pieces of the magnet 4 as a magnetic system that could exert a clamping force on the yoke 3. The magnetic catch has substantially no magnetic force on the yoke and the door, flap or the like can be opened. The magnetic field lines extend within the pole shoes 6 designed as permanent magnets and the switching magnets 7 with the conclusion about the steel plate 10; there is no force on the yoke 3. In the magnet 4, a magnetic field line closure is generated, which does not penetrate to the outside.

In Fig. 3 adjacent poles of the switching magnet 7 and permanent magnet 5 are oppositely poled, that is, the poles of the switching magnet 7 have different polarity for magnetizing the adjacent ends of the permanent magnets 5.

As in the first embodiment, the magnetization orientation of the solenoids 7 is variable over a surrounding the magnetic material of the switching magnet 7 winding 8, by a (short) outer current pulse of the solenoid 7 can be reversed in its magnetic orientation. The magnetic field of the switching magnet 7 is in its magnetic orientation between the 3 and 4 been reversed.

In Fig. 4 the switching magnets 7 are still magnetized transversely to the permanent magnet 5 in the connecting direction between the pole pieces 6, however, the magnetization has rotated by 180 °. Unlike in the case in Fig. 3 , the adjacent poles of the switching magnets 7 and the permanent magnets 5 are homopolar to each other.

Im in Fig. 4 In the case shown, the field profile of the pole shoes 6 is parallelized at the ends, and the yoke 3 is attracted by the magnet 4 and held with the holding force F from the sum of the force of the permanent magnets 5 and the switching magnets 7.

The magnetic field lines emerge from the pole shoes 6, enter the yoke 3 and enter from the yoke 3 again in the next adjacent pole piece 6 a. The magnet 4 forms a magnet system from which the magnetic field lines can exit into the yoke 3 and reenter. Due to the alternating sequence with oppositely magnetized permanent magnets 5 reinforcing magnetic fluxes are created with different sense of circulation. In a pair of adjacent pole pieces 6 with associated switching magnet 7, there is another direction of circulation of the magnetic flux than in the next adjacent pair of pole shoes 6 and switching magnet 7. In Fig. 4 The magnetic field lines flow in the upper pair of pole pieces 6 and the associated switching magnet 7 in the clockwise direction, while in the lower pair of pole pieces 6 and the associated switching magnet 7, the magnetic field lines flow in a counterclockwise direction.

Also in the further embodiment, the coil 9 is provided on a pole piece 6, whose frequency is detected, so that a reliable statement can be made with sufficient certainty about whether the locking force of the magnetic latch is sufficient. In addition, a Hall or GMR sensor 11 is disposed at an open end of a pole piece 6.

Furthermore, in the 3 and 4 illustrated that a strain gauge 12 for detecting a deformation of the yoke 3 opposite end of the magnet 4 due to the polarity of the pole pieces 6 is present. The strain gauge 12 can be used as a sensor. Im in the 3 and 4 illustrated embodiment, the strain gauge 12 is attached to the steel plate 10 and measures due to the polarity of the pole pieces 6 occurring bending moments of the steel plate 10, which is a measure of the strength of the magnetic flux from the pole pieces 6 to the outside. The illustrated strain gauge 12 represents a possibility of a sensor for detecting the magnetization of the magnet 4, which may be provided in addition to the detection of the change in frequency of the winding 8, the coil 9 or the Hall or GMR sensor 11. It should be noted that the representation of several sensors 8, 9, 11, 12 in the 3 and 4 has only explanatory simplifying character. The presence of only one of the sensors in the form of the winding 8 is possible.

Im in Fig. 1 and 2 illustrated embodiment, the use of a strain gauge 12 is also possible, wherein the strain gauge 12 may be attached to the switching magnet 7. Again, the strain gauge 12 can detect due to the polarity of the pole pieces 6 occurring bending moments, which is a measure of the strength of the magnetic flux from the pole pieces 6 to the outside.

In both embodiments, it is possible that via the windings 8 of the switching magnets 7, a magnetization reversal can take place such that the hard magnetic material of the switching magnet 7 is "magnetized" in such a way that the magnetic field at the pole pieces 6 in the magnetization direction is switched off when Magnetschnäpper , Thus, no force is switched off with the magnetic catch, or "off" magnet 4 on the Yoke 3 exerted, and the pole pieces are also field-free and can not be added by ferromagnetic dirt particles.

On the other hand, if the hard magnetic material of the switching magnet 7 is not completely "magnetized" in the cancellation of the magnetic force of the magnetic latch, a magnet having an adjustable force can be realized. To clean the pole pieces of the magnet 4, once the opening is detected, the hard magnetic material of the switching magnet 8 can be completely "magnetized" again in order to determine the residual magnetization of the magnet To prevent pole shoes,

The magnetization of the switching magnets 7 is controlled by a controller, not shown in the figures, which is coupled, for example, with sensors which detect a standstill of the machine or system located in the room area or the presence of a risk potential for persons from the machine or the system and the switching magnets 7 magnetized accordingly, so that the magnetic catch blocks or releases. In addition, the controller can be transmitted by one or more corresponding detectors, whether the opening is closed. The controller then gives the system or machine a signal as to whether it can be started, or whether the controller does not release it because the opening is still open and the access or access of persons is still possible.

Claims (11)

1. Magnetic catch for locking an opening, which includes a moving part (1) and a stationary part (2), comprising a magnetic circuit which comprises a magnetisable yoke (3) which can be fixed to the moving part (1) and at least one magnet (4) which can be closed by the yoke (3), has pole shoes (6) and can be fixed to the stationary part (2), the magnetic action of the magnet (4) on the yoke (3) being variable, the magnet (4) that can be closed by the yoke (3) comprising at least one permanent magnet (5) in an arrangement in which a magnetic field circuit within the magnet (4) can be generated by a switching magnet (7) that connects the pole shoes (6) and the magnetization orientation of the switching magnet (7) being able to be changed via a winding (8), where the direction of magnetization of the switching magnet (7) extends along the connection of the pole shoes (6), and the magnetization of the switching magnet (7) can be reversed for a change in the magnetic field leakage from the magnet (4) at the pole shoes (6), which change can be measured via a measurement of a sensor, characterized in that the sensor is that winding (8) of the switching magnet (7) to which current can be applied for determining a frequency change in the winding (8), which frequency change is dependent on the magnetic saturation of the magnet (4).
2. Magnetic catch according to Claim 1, characterized in that the at least one switching magnet (7) and the at least one permanent magnet (5) are arranged to be offset longitudinally in relation to each other, and the pole shoes (6) are arranged as bodies extending transversely thereto and made of soft magnetic material.
3. Magnetic catch according to Claim 1, characterized in that the pole shoes (6) made of soft magnetic material connect a permanent magnet (5) and a switching magnet (7), and adjacent permanent magnets (5) have a different orientation of the magnetic field.
4. Magnetic catch according to Claim 3, characterized in that the permanent magnets (5) are arranged on a soft magnetic material for a magnetic short-circuit on the side of the pole shoes (6) facing away from the yoke (3).
5. Magnetic catch according to one of Claims 1 to 4, characterized in that the at least one permanent magnet (5) has a rare-earth or neodymium-iron-boron magnetic material.
6. Magnetic catch according to one of Claims 1 to 5, characterized in that the switching magnet (7) comprises an AlNiCo magnetic material, which is surrounded by the winding (8) to which current can be applied.
7. Magnetic catch according to one of Claims 1 to 6, characterized in that a Hall or GMR sensor (11) is provided for the purpose of detecting the magnetic field and is arranged in a manner adjacent to a pole shoe (6).
8. Magnetic catch according to one of Claims 1 to 7, characterized in that a strain gauge (12) is provided for the purpose of detecting deformation of that end of the magnet (4) which faces away from the yoke (3) on account of the polarity of the pole shoes (6).
9. Magnetic catch according to one of Claims 1 to 8, characterized in that an electrical energy store is provided for the purpose of providing the energy needed to reverse the magnetization.
10. Magnetic catch according to one of Claims 1 to 9, characterized in that the signal from the sensor can be supplied to a controller of a machine, which can be accessed by means of the opening, and the controller can be used to adjust the locking force of the magnetic catch.
11. Magnetic catch according to one of Claims 1 to 10, characterized in that a non-safety-oriented path of a safety-oriented transducer can be used to control the locking force of the magnetic catch.

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