EP2085349B1 - Magnetic grabber - Google Patents

Description

The invention relates to a magnetic gripper for gripping and handling of ferromagnetic workpieces, comprising a housing, on which a housing bottom is provided which has an end face facing the workpiece to be gripped and with at least one magnetic piston arranged in the housing, the at least one connection for a working fluid is assigned for moving the magnetic piston, so that the magnetic piston is transferred to a working position at a first working pressure, in which the working piston is positioned at or close to the housing bottom and is transferred with a further working pressure in a rest position, in which the magnetic piston removed to the housing bottom is positioned.

Such a magnetic gripper is from the DE 199 51 703 A1 known. For gripping and transporting workpieces, the magnetic piston is acted upon by a working pressure, so that it bears against the housing bottom. This results in a magnetization of the ferromagnetic workpiece, which is fixed to the end face of the housing by the magnetic holding force. After transport, a pressure pulse acts on the magnetic piston, so that it moves to a remote position to the housing bottom, whereby the magnetic field is weakened and the workpiece can be stored or released.

Such magnetic grippers are preferably used in workpieces which, due to their requirement or already performed machining, have a variety of holes, penetrations, transformations and / or complicated geometric shapes, such as lattice structures. Due to the fact that the movement of the magnetic piston takes place in a closed space and the holding of the workpiece is carried out by the magnetic force, single pressure pulses or pressure surges are sufficient to allow gripping or depositing of the workpiece. As a result, such magnetic grippers can work with low energy. The disadvantage with such magnetic grippers, however, is that an automatic detection of whether a workpiece was picked up or not taken, or whether it has been lost during transport, can not be detected. As automation progresses, however, it is desirable and necessary to monitor such work situations as well.

From the GB 2 000 870 A A permanent magnet gripper with its safety device emerges, which compares the magnetic force between the magnetic gripper and the workpiece with the load. This safety device determines if the magnetic force is sufficient to lift the load. For this purpose, a coil fixedly arranged in the magnetic gripper is used. This arrangement requires a complex electrical control and monitoring.

The invention is therefore based on the object, a magnetic gripper of the type mentioned in such a way that while retaining the previous functional principle is an independent state recognition is made possible to determine whether a workpiece on the magnetic gripper exists or does not exist.

This object is achieved by the features of claim 1. The at least one detection device associated with a magnetic gripper, which is provided in or on the housing in order to detect the holding of the workpiece or the absence of the workpiece, has the advantage that active process monitoring is possible with such magnetic grippers. This can improve process reliability. This at least one detection device in or on the magnetic gripper thus makes it possible to detect whether a magnetizable workpiece has been gripped and held by the magnetic gripper and whether such a workpiece has been lost during transport or handling movement. Thus, a magnetic gripper is provided which allows a state recognition with respect to the workpiece to be handled.

By the at least one detection device, a working pressure of the working fluid is determined depending on their own active or inactive working position. This has the advantage that the respective working pressure or a change in the working pressure of the working fluid is determined and the previous operation and the previous structure of the magnetic gripper can be maintained. The applied and constantly maintained working pressure, which is preferably given in the detection device in an active working position or the changing working pressure, which is preferably given in the detection device in a non-active working position, is evaluated for detecting and monitoring the prevailing conditions. As a result, the previously created arrangement and the structure of a handling device with one or more magnetic grippers can be maintained.

According to an advantageous embodiment of the invention it is provided that for transferring the magnetic piston in a working position, a working pressure, in particular a negative pressure or a vacuum, is applied and the detection device maintains the applied working pressure when gripping or handling the workpiece. Thus, over the actual prevailing working pressure of the working fluid for controlling a lifting movement of the magnetic piston in a working position simultaneously or after taking the working position allows detection with respect to the presence of a ferromagnetic workpiece be. The same applies if an overpressure is provided as working pressure.

According to a further preferred embodiment of the invention, it is provided that for transferring the magnetic piston in a working position, a negative pressure or vacuum is applied as working pressure and the working pressure degrades in the absence, release or placement of the workpiece. As a result, a further state detection or change of the state detection can in turn be detected via the working pressure of the working fluid for controlling the magnetic piston. The same applies if an overpressure is provided as working pressure.

According to an advantageous embodiment of the invention, it is provided that the detection device is arranged in the housing of the magnetic gripper and associated with a closed space formed between the magnetic piston and the housing. As a result, the arrangement of handling devices with a plurality of magnetic grippers in their previous arrangement or their grid dimension arrangement due to the uniform size of the housing of the magnetic gripper can be maintained. The at least one detection device in each magnetic gripper makes it possible to monitor the required minimum holding force by interrogating the sum of the active magnetic grippers and the position of the active magnetic checkers in the case of a handling device with, for example, a plurality of magnetic grippers. As soon as a minimum number of detection devices, which distribute in a corresponding arrangement, in particular uniformly over the workpiece, have given a corresponding signal on the respective working pressure, it is ensured that the required minimum holding force for transporting the workpiece by the magnetic gripper exists.

A preferred further embodiment of the invention provides that the at least one detection device is integrated in the movable magnetic piston. Thus, the detection device is always used only when the magnetic piston is actually transferred to a working position to perform a handling.

According to a further advantageous embodiment of the invention, it is provided that the detection device is designed as a magnetically controllable valve arrangement, which controls a passage in the magnetic piston between a piston space which can be acted upon by the working fluid with a working pressure and an opposite movement space which can be acted upon by a further working pressure. This makes it possible that such magnetic gripper with a working pressure of a working fluid, such as vacuum or compressed air, are controlled, wherein the holding force of the workpiece is effected by a magnetic force and also the control of the detection device is provided by a magnetic force independent of the working pressure of the working fluid.

The advantageously designed as a magnetically controllable valve assembly detection device comprises a valve carrier with a valve seat and a slidably disposed therein control valve having a valve seat surface. In an active working position of the valve assembly, the valve seat surface abuts the valve seat and closes the passage between the movement space and the piston chamber in the housing of the magnetic gripper. As a result, an easily controllable valve arrangement can be provided, which can be converted into an active and a non-active working position due to a lifting movement.

According to a further advantageous embodiment of the valve arrangement is provided that the control valve has at least one permanent magnet at an end facing the housing bottom. This makes it possible that when gripping a workpiece and the positioning of the magnetic piston in its working position, the control valve due to the build-up magnetic force closes the passage. As a result, a working pressure in the piston chamber, in particular a applied negative pressure or an applied vacuum in the piston chamber, kept constant. This state is preferably detected and evaluated by at least one sensor. This fulfills a safety criterion during handling. A changing state due to the loosening of the workpiece during transport can be recognized due to the change of the working step, so that immediately afterwards following corresponding further steps, such as a stop of the movement of the handling device, can be initiated.

According to a further preferred embodiment of the invention, it is provided that the control valve of the detection device is held by a force storage element in an inactive working position and lifted relative to the valve seat. This inactive working position enables a vacuum or negative pressure can not be maintained, unless in the region of the detection device no workpiece is assigned to the end face of the housing. The energy storage element, which is preferably designed as a spiral or compression springs, has a spring force which is smaller than a resulting on the at least one permanent magnet on the control valve Magnethaltekraft as soon as a workpiece is assigned to the end face of the housing.

According to a further preferred embodiment of the invention, at least one guide section is provided between the control valve and the valve carrier. This can be given an immediate guidance of the control valve in the valve carrier. Thus, a structurally simple and tilt-free recording is given in the valve carrier.

Furthermore, a guide section is preferably provided between the valve seat and the permanent magnet on the control valve, which has at least one channel-shaped recess and forms a portion of the passage between the movement space and the piston chamber. This arrangement results in a small-sized and compact arrangement with a small number of component. This ensures trouble-free operation.

Furthermore, it is preferably provided that when transferring the magnetic piston into a working position and when magnetizing the workpiece for positioning the workpiece on the end face of the housing bottom, the control valve can be converted by the magnetic force of its permanent magnet in an active working position. As a result, the control valve, in particular the valve seat surface provided on the control valve, lies at the valve seat and closes the passage between the piston and the movement space. Thus, ambient air can not flow via the preferably associated with the environment movement space in the housing or affect the voltage applied in the movement space working in those of the piston chamber, and the applied working pressure in the piston chamber for transferring the magnetic piston in its working position is maintained. Thus, the condition is recognized that a workpiece is present on the front side of the housing bottom.

Furthermore, it is preferably provided that, in the case of a closed valve arrangement or in the case of an active working position of the control valve, an end face of the permanent magnet facing the housing bottom rests. As a result, the largest holding force acting on the control valve to close the valve seat.

According to a further advantageous embodiment of the valve arrangement, a cover is provided for limiting and setting an opening stroke of the control valve, which is fastened to the valve carrier and preferably comprises a throttle point.

According to a further advantageous embodiment of the detection device, it is provided that the valve arrangement, which comprises a valve carrier, a control valve and a force storage element arranged therebetween and a lid, can be inserted as a preassembled module into the housing or into the magnetic piston. As a result, a modular design of the magnetic gripper is possible, so that depending on the respective applications, individual modules may be provided, which may comprise a control valve with different strong permanent magnets and / or a lid with a different sized throttle.

According to a further preferred embodiment of the invention, a connecting line is formed between the detection device and the associated port of the housing for supplying and discharging the working fluid. This allows for multiple in one Magnetic gripper arranged detection devices each detection device is individually controlled.

According to a further preferred embodiment of the invention it is provided that the maintenance of the working pressure or the change of the working pressure can be detected by at least one sensor. This at least one sensor is preferably provided on a valve strip remote from the individual magnetic grippers. The valve bar is connected to a large number of pressure lines which lead to the pneumatic connection of the magnetic grippers and to signal lines of a control and evaluation device. Each pressure line is interrogated and monitored by the sensor at the prevailing working pressure. Such sensors, which are designed in particular as pressure sensors, allow a quick and easy evaluation of this additional information.

According to a further preferred embodiment of the invention, a plurality of detection devices are provided on or in a housing, which allow a sectional detection of the end face of the housing. As a result, individual areas of the front of the housing can be monitored and other areas can not be monitored. This sectional monitoring can provide additional information about the position of the workpiece to the respective magnetic gripper.

Figur 1

eine schematische Seitenansicht eines Magnetgrei- fers,

Figur 2

einen schematischen Vollschnitt des Magnetgreifers entlang der Linie I-I in Figur 1,

Figur 3

eine schematische Schnittdarstellung des Magnet- prüfers entlang der Linie II-II in Figur 1,

Figur 4a

eine schematisch vergrößerte Detailansicht eines Magnetkolbens des Magnetgreifers mit einer darin integrierten Detektionsvorrichtung in einer aktiven Arbeitsposition und

Figur 4b

eine schematisch vergrößerte Detailansicht eines Magnetkolbens des Magnetgreifers mit einer darin integrierten Detektionsvorrichtung in einer nicht ak- tiven Arbeitsposition.

The invention and further advantageous embodiments and developments thereof are described in more detail below with reference to the examples shown in the drawings and explained. The features to be taken from the description and the drawings can be applied individually according to the invention individually or in combination in any combination. Show it:

FIG. 1

a schematic side view of a Magnetgrei- fers,

FIG. 2

a schematic full section of the magnetic gripper along the line II in FIG. 1 .

FIG. 3

a schematic sectional view of the magnetic tester along the line II-II in FIG. 1 .

FIG. 4a

a schematically enlarged detail view of a magnetic piston of the magnetic gripper with a detection device integrated therein in an active working position and

FIG. 4b

a schematically enlarged detail view of a magnetic piston of the magnetic gripper with a detection device integrated therein in a non-active working position.

FIG. 1 shows a schematic side view of a magnetic gripper 11, which has a pin 12 with a fastening device 14, for example, to attach this to a robot arm or a handling device. Opposite, a housing bottom 17 is provided on a preferably cup-shaped housing 16, which is bolted to the housing 16, for example. This housing bottom 17 has an end face 18 on which a workpiece 19 to be gripped, which is represented for example as a ferromagnetic plate, rests.

In FIG. 2 is a sectional view taken along the line II in FIG FIG. 1 of the magnetic gripper 11 shown. In the housing 16, a magnetic piston 21 is guided movable up and down. The magnetic piston 21 comprises a guide ring 22, in which a seal 23 is arranged, which separates a present above the magnetic piston 21 movement space 24 and a present between the magnetic piston 21 and the housing bottom 17 piston chamber 26. The size of the two spaces 24, 26 determined in inverse proportion to the position of the magnetic piston 21 in the housing 16. The movement space 24 communicates via a through hole 27 with the environment. For example, a screen 28 may be provided to protect against contamination of the movement space 24 in the through hole 27. The piston chamber 26 communicates with a connection 31, in particular a pneumatic connection Connection to which a pressure line 32 is connected, which leads to a valve bar 33 with a plurality of control valves 30. Via the valve strip 33, the individual pressure lines 32 are acted upon by actuation of the control valves 30 with a working pressure. Each pressure line 32 is preferably associated with a sensor 35 which monitors the working pressure in the pressure line 32. The signals detected by the sensor 35 are forwarded to an evaluation unit for evaluation and also for controlling the magnetic grippers 11.

FIG. 3 shows a schematic sectional view of the magnetic gripper 11 along the line II-II in FIG. 1 , The magnetic piston 21 receives at least one permanent magnet 34 on a front side facing the housing bottom 17. Preferably, a plurality of individual segments existing as permanent magnets 34 are associated with each other.

For positioning the magnetic piston 21 in the in FIG. 2 shown position, a working position 36, a working pressure, in particular a negative pressure or a vacuum, in the piston chamber 26 is applied via the terminal 31. The magnetic piston 21 is sealed via the seal 23 to the housing 16, so that the piston chamber 26, which is preferably in communication with the pressure line 32, forms a closed space. By the applied working pressure of the magnetic piston 21 is transferred to a lower position. In this case, the permanent magnet 34 is preferably held with a small, but defined distance by a spacer element 35, in particular a spacer ring. Alternatively, the at least one permanent magnet 34 may rest on the housing bottom 17. By magnetizing the workpiece 19, a magnetic holding force acts between the at least one permanent magnet 31 and the ferromagnetic workpiece 19, and the workpiece 19 is held exclusively by this magnetic holding force and positioned to the housing bottom 17. In this position of the magnetic piston 21 is in the movement space 24, a further working pressure, in particular the ambient pressure to. For depositing the workpiece 19, the negative pressure or the vacuum is reduced or pressure pulses are introduced into the piston chamber 26, whereby the magnetic piston 19 is pressed into a raised position relative to the housing bottom 17, ie in a rest position 37 (dashed line shown schematically). The movement of the magnetic piston 21 thus takes place in a closed piston chamber 26, that is, no large volume flows of compressed air and vacuum must be made available.

The magnetic gripper 11 has according to the embodiment in FIG. 2 a detection device 41, which is integrated as an example in the magnetic piston 21. A simple embodiment of a magnetic gripper 11 provides the arrangement of a detection device 41. Alternatively, a plurality of detection devices 41 may be provided, wherein the housing 16 advantageously according to the number of detection devices 41 has the partitions, so that in each case a magnetic piston is arranged with at least one detection device 41 in a closed space. This in FIG. 2 shown detection device 41 is in the FIGS. 4a and b shown schematically enlarged in different working positions and is based on this FIGS. 4a and b explained in more detail.

The detection device 41 according to FIG. 4a , which is opposite to the workpiece 19, is in an active working position 42. The detection device 41 according to FIG FIG. 4b however, is shown in an inactive working position 43. The detection device 41 comprises a magnetically controllable valve arrangement. This is composed of a valve carrier 45, an axially displaceably arranged control valve 46, a force acting between the valve carrier 45 and the control valve 46 power storage element 47 and a lid 48 together. The energy storage element 47 is supported on a shoulder 49 of the valve carrier 45 and causes the control valve 46 is basically held in an inactive working position 43, in which an end face 51 of the control valve 46 rests against the lid 48. In this inactive working position 43, a valve seat surface 52 of the control valve 46 is lifted relative to a valve seat 53 of the valve carrier 45. As a result, the valve assembly is open.

A present in the movement space 24 working fluid can via a throttle point 56 in the lid 48 and a longitudinal channel 57 and from there from flowing over a transverse to the valve seat surface 52 transverse channel 58 and at least one channel-shaped recess 59 in the guide portion 61 with the piston chamber 24. The guide section 61 is designed, for example, as an annular collar 62 and acts on a lateral surface 63 of the valve carrier 45. Preferably, a further guide portion 61 between the cover 48 and the valve seat 53 is provided to allow a tilt-free mounting of the control valve 46. On the annular collar 62, the force storage element 47 may be supported, which is preferably designed as a spiral spring, compression spring or rubber-elastic element to arrange the control valve 46 in the inactive working position 43.

For example, a permanent magnet 66 is provided on an end of the control valve 46 facing the housing bottom 17. Between a housing bottom facing end face 67 of the permanent magnet 66 and the housing bottom 17, a distance is provided which is equal to or smaller than the stroke movement of the control valve 46 for transferring into an active working position 42.

The piston chamber 26 is connected via a schematically illustrated connecting line 69 with the terminal 31 in connection. This connecting line 69 can be formed, for example, by a gap or clearance between two adjacent permanent magnets 34, as shown schematically by the line 71 in FIG FIG. 3 is shown, as well as through a channel portion 70 which leads to the terminal 31.

• Der Magnetgreifer 11 wird zum zuhandhabenden Werkstück 19 positioniert. Gleichzeitig wird ein Unterdruck oder Vakuum in dem Kolbenraum 26 angelegt, so dass der Magnetkolben 21 in eine Arbeitsstellung 36 übergeführt wird. Anschließend findet eine Aufmagnetisierung des Werkstückes 19 statt und wird durch die Magnethaltekraft zur Stirnfläche 18 des Gehäuses 16 gehalten. Gleichzeitig findet eine Aufmagnetisierung des Permanentmagneten 66 des Steuerventils 46 der Detektionsvorrichtung 41 statt. Durch die Magnetkraft, welche größer als die entgegenwirkende Kraft des Kraftspeicherelementes 47 ist, wird die Detektionsvorrichtung 41, insbesondere das Steuerventil 46, in eine aktive Arbeitsposition 42 übergeführt. Dabei liegt die Ventilsitzfläche 52 am Ventilsitz 53 an. Dadurch wird der angelegte Arbeitsdruck im Kolbenraum 26, insbesondere der Unterdruck beziehungsweise das Vakuum, aufrechterhalten. Über einen Sensor 35, der den herrschenden Arbeitsdruck des Arbeitsfluides im Kolbenraum 26 erfasst, kann festgestellt werden, dass kein Druckabfall vorliegt, das heißt, dass ein Werkstück 19 an der Stirnfläche 18 des Gehäuses 16 anhaftet und durch den Magnetgreifer 11 ergriffen ist. Da das Werkstück 19 nur teilweise an der Stirnfläche 18 des Gehäuses 16 anliegt, ist die zweite Detektionsvorrichtung 41 in einer nicht aktiven Arbeitsposition 23. Ein Durchgang zwischen dem Bewegungsraum 24 und Kolbenraum 26, der bei einer Detektionsvorrichtung 41 in einer nicht aktiven Arbeitsposition geöffnet ist, ändert den angelegten Arbeitsdruck des Arbeitsfluides im Kolbenraum 26, also den Unterdruck oder das Vakuum, da Umgebungsdruck über der Durchgangsbohrung 27 im Bewegungsraum 24 anliegt und über den Durchgang, also den Längs- und Querkanal 57, 58 des Steuerventils 46 und dem geöffneten Ventilsitz 53, in den Kolbenraum 26 gelangen kann. Daraus wird abgeleitet, dass kein Werkstück 19 der Stirnfläche 18 des Gehäuses 16 zugeordnet ist beziehungsweise daran anliegt.

The detection and monitoring of a held by the magnetic gripper 11 workpiece 19 by the detection device 41 is carried out as follows:

• The magnetic gripper 11 is positioned to be handled workpiece 19. At the same time, a negative pressure or vacuum is applied in the piston chamber 26, so that the magnetic piston 21 is transferred to a working position 36. Subsequently, a magnetization of the workpiece 19 takes place and is due to the magnetic holding force to the end face 18th the housing 16 is held. At the same time, a magnetization of the permanent magnet 66 of the control valve 46 of the detection device 41 takes place. Due to the magnetic force, which is greater than the counteracting force of the force storage element 47, the detection device 41, in particular the control valve 46, transferred to an active working position 42. In this case, the valve seat surface 52 bears against the valve seat 53. As a result, the applied working pressure in the piston chamber 26, in particular the negative pressure or the vacuum, is maintained. Via a sensor 35, which detects the prevailing working pressure of the working fluid in the piston chamber 26, it can be determined that there is no pressure drop, that is, a workpiece 19 adheres to the end face 18 of the housing 16 and is gripped by the magnetic gripper 11. Since the workpiece 19 abuts only partially on the end face 18 of the housing 16, the second detection device 41 is in a non-active working position 23. A passage between the movement space 24 and the piston chamber 26 which is open in a detection device 41 in a non-active working position, changes the applied working pressure of the working fluid in the piston chamber 26, ie the negative pressure or the vacuum, since ambient pressure over the through hole 27 in the movement space 24 and over the passage, so the longitudinal and transverse channel 57, 58 of the control valve 46 and the open valve seat 53, can get into the piston chamber 26. It is derived from this that no workpiece 19 is assigned to the end face 18 of the housing 16 or bears thereon.

If during the transport of the workpiece 19 with the magnetic gripper 11 the case should occur that the workpiece 19 separates from the end face 18 of the housing 16, the detection device 41 is transferred from the active working position 42 by the force storage element 47 in a non-active working position 43 , and the sensor 35 recognizes again that the working pressure of the working fluid in the piston chamber 26 is not maintained, but changed. This means that the workpiece 19 has been lost.

Thus, this detection device 41 allows state detection by monitoring the working pressure of the working fluid, whether a workpiece 19 is picked up and transported or was not picked up or lost during transport.

Claims (18)

1. Magnetic grab for grabbing and handling ferromagnetic workpieces (19), comprising a housing (16) on which there is provided a housing bottom (17) having an end face (18) facing to the workpiece (19) to be grabbed, and comprising at least one magnetic piston (21) disposed in the housing (16) and at least one connection (31, 27), assigned to the at least one magnetic piston (21), for a drive fluid for moving the magnetic piston (21), so that the magnetic piston (21) is subjected to a first working pressure and is transferred into an operating setting (36), in which the magnetic piston (21) is positioned on or close to the housing bottom (17), and is transferred with a further working pressure into a rest setting (37), in which the magnetic piston (21) is positioned remote from the housing bottom (17), characterized in that at least one detection device (41) is provided in or on the housing (16), which detects the holding or the non-presence of the workpiece (19) on the end side (18) of the housing (16) and determines the working pressure of a working fluid of the detection device (41) in dependence on an active or inactive operating position (42, 43).
2. Magnetic grab according to Claim 1, characterized in that, for the transfer of the magnetic piston (21) into an operating setting (36), an underpressure or a vacuum is applied as the working pressure, and the detection device (41) maintains the applied working pressure during the grabbing and handling of the workpiece (19).
3. Magnetic grab according to Claim 1, characterized in that, for the transfer of the magnetic piston (21) into an operating setting (36), an underpressure or a vacuum is applied as the working pressure, and the working pressure decreases in the event of the non-presence, release or depositing of the workpiece (19).
4. Magnetic grab according to Claim 1, characterized in that the detection device (41) is provided in the housing (16) and is assigned to a closed space formed between the housing (16) and the movable magnetic piston (21).
5. Magnetic grab according to Claim 1, characterized in that the detection device (41) is integrated in the movable magnetic piston (21).
6. Magnetic grab according to Claim 1, characterized in that the detection device (41) is configured as a magnetically actuable valve arrangement, which opens or closes a passage (55) in the magnetic piston (21) between a piston chamber (26), which is subjectable to the working fluid, and an opposite motion chamber (24), which is subjectable to a further working pressure.
7. Magnetic grab according to Claim 6, characterized in that the valve arrangement has a valve support (45) having a valve seat (53), and a control valve (46), arranged displaceably therein, having a valve face (52).
8. Magnetic grab according to Claim 7, characterized in that the control valve (46), on an end facing the housing bottom (17), has at least one permanent magnet (66).
9. Magnetic grab according to Claim 7 or 8, characterized in that the control valve (46) is held by an energy-storing element (47) in an inactive operating position (43) and is raised relative to the valve seat (52).
10. Magnetic grab according to one of Claims 7 to 9, characterized in that at least one guide portion (61) is provided between the control valve (46) and the valve support (45).
11. Magnetic grab according to one of Claims 7 to 10, characterized in that, between the valve seat (53) and the at least one permanent magnet (66) on the control valve (46), a guide portion (61) is provided, which has at least one channel-shaped recess (57) and forms a portion of the passage (55).
12. Magnetic grab according to one of Claims 7 to 11, characterized in that, when the magnetic piston (21) is transferred into an operating setting (36) and the workpiece (19) is magnetized for the positioning of the workpiece (19) on the end face (18) of the housing (16), the control valve (46) is transferrable into an active operating position (42) by the magnetic force of its at least one permanent magnet (66) and the control valve (46) closes the valve seat (53).
13. Magnetic grab according to Claim 8, characterized in that, when the valve arrangement is closed, an end face (67) of the permanent magnet (66), which end face faces the housing bottom (17), bears against the housing bottom (17) with a defined gap, which gap is determined by a spacer ring (69) connected to the magnetic piston (21).
14. Magnetic grab according to Claim 7, characterized in that, for the limitation and adjustment of an opening stroke of the valve face (52), provided on the control valve (46), towards the valve seat (53) of the valve support (45), a cap (48) is provided, which is preferably fastened to the valve support (45).
15. Magnetic grab according to Claim 14, characterized in that the valve arrangement, comprising a valve support (45), a control valve (46) and an intervening energy-storing element (47), as well as a cap (48), is insertable into the magnetic piston (21) or the housing (16) as a pre-assembled unit.
16. Magnetic grab according to Claim 1, characterized in that, between the detection device (41) and the associated connection (31), a connecting line (69) is formed for the supply and evacuation of the working fluid.
17. Magnetic grab according to Claim 1, characterized in that the at least one working pressure for transferring the magnetic piston (21) into an operating setting (36) is detectable by at least one sensor (35).
18. Magnetic grab according to Claim 1, characterized in that a plurality of detection devices (41) are provided on or in a housing (16) and a section-by-section detection of the end face (18) of the housing (16) is provided.

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