EP1442189B1 - Device for opening and closing a mobile element - Google Patents

Abstract

A device for opening and closing an opening ( 11 ), in particular in a motor vehicle, by means of a motor-driven, movable part ( 10 ), with a control unit ( 26 ) and a pinch prevention sensor ( 14 ), which is disposed essentially along an edge ( 20 ) of the part ( 10 ) and/or of a frame profile ( 12 ) bordering the opening ( 11 ) and which, during the closing of the part ( 10 ), detects an obstacle ( 24 ) that is in the movement path of the part ( 10 ) and sends a signal to the control unit ( 26 ) in order to stop or reverse the movement of the part ( 10 ), wherein the pinch prevention sensor ( 14 ) has a highly elastic, electroactive polymer (EAP) material ( 30 ), in particular polyurethane, fluoroelastomer, polybutadiene, fluorosilicone, or silicone, disposed between electrodes ( 28, 34, 36 ), which produces a voltage change in the electrodes ( 28, 34, 36 ) in the event of a deformation.

Description

State of the art

The invention relates to a device for opening and closing a movable part according to the preamble of the independent claim.

With DE 199 13 106 C1 a anti-trap with a hollow profile for a power-operated locking device is known, in which a molded as a hollow profile terminal strip along a frame, such as a sunroof opening, is arranged. The hollow profile has two spaced-apart, electrically conductive regions whose contact triggers a switching operation for driving the motor of the closure device. In this case, the production of such a profile is quite complicated and in use, such a system is susceptible to false triggering, caused by a permanent deformation of the electrically conductive areas.

With the US 4,943,757 an anti-pinch system for a window of a motor vehicle has become known. In this case, a window is moved by a motor against the stop of the window frame. In the sealing lip of the window frame in this case a piezoelectric cable is integrated, which serves as anti-pinch sensor. In this case, an electrical pulse is generated as soon as an insulating polymer is compressed between two electrical conductors. As soon as a trapping case is detected, the closing window pane is reversed in its direction of movement.

Advantages of the invention

The device according to the invention with the features of claim 1 has the advantage that the highly elastic, electroactive polymer (EAP) material already reliably exerts a slight pressure on it when applying a lower pressure measurable voltage change on the electrodes applied to the EAP material. The construction of the anti-pinch sensor is very simple and insensitive to interference since the system is based on the electroactive material properties of the EAP material. In addition, EAP materials are favorable in the production and processing, so that according to the invention an extremely cost-effective and reliable anti-jamming protection with various geometric sensor shapes is possible.

The features listed in the dependent claims advantageous developments of the device according to the invention are possible. The electroactive properties of the EAP material are based on an effective extension or alignment of the polymer chains by a corresponding external deformation of the EAP material. Depending on the force acting on the EAP material and the arrangement of the electrodes on the EAP material then a voltage increase or a decrease in voltage is caused.

It is particularly advantageous to form the EAP material into thin layers having a thickness of, for example, 1-100 microns, since here, especially with a vertical force acting on the same even at low external force, an elongation of the EAP material by up to 300%, and so that a correspondingly high voltage change is generated. The thinly-formed layers can also be particularly easily arranged along the edge of the part or of the frame profile, for example on or within a sealing lip.

Characteristic of EAP materials is a voltage change according to the formula $$\mathrm{U}=\mathrm{t}*•(\mathrm{p}/\mathrm{.epsilon..sub.R}*\mathrm{\epsilon }0).\mathrm{,}$$

The magnitude of the voltage change can be quite advantageously determined by the choice of the thickness t of the EAP material.

If a plurality of EAP layers, each equipped with electrodes, are arranged one above the other and connected in quasi-series, the individual voltage changes add up, whereby a simpler signal evaluation is made possible due to the higher measuring signal.

It is advantageous to arrange the at least one EAP layer approximately perpendicular to the expected clamping force, since this achieves the greatest possible deformation of the material, and thus a maximum voltage change.

Alternatively, however, arrangements are conceivable in which a plurality of EAP layers are arranged approximately parallel to the adjustment plane of the part. The pinching force then acts approximately parallel to the EAP layers and changes their surface area, which is correlated with a change in the thickness of the layers. In this case, the electrodes can be arranged both between the EAP layers and on the front sides of the EAP layers.

If one or more EAP layers-optionally also with intervening insulating layers-are wound up as a roll, then this arrangement can detect all forces in the plane perpendicular to the roll in the same way. Such a role can therefore be arranged particularly favorable along the seal of a frame.

With such an arrangement of the roller approximately parallel to the edge of the part or frame, the electrodes are desirably formed as layers between the wound EAP layers. Alternatively, however, the electrodes may also be on the end faces of such Roll or tube can be arranged, this is particularly advantageous for a subdivision of the anti-pinch sensor along the edge or the frame profile in order to detect an obstacle spatially resolved can.

The arrangement of the at least one EAP layer directly above or below a perforated belt matrix is advantageous. With this matrix spatially fixed support points are created, whereby the EAP layer bulges due to an applied ground voltage through the holes of the perforated tape matrix. This ensures that a sufficient deformation of the EAP layer occurs even when relatively small obstacles occur, since in this arrangement a local force can not be compensated for over a large area of the EAP layer.

In order to create a spatially flexible and thus also locally sensitive anti-pinch sensor, at least one of the electrodes is spatially structured. In this case, it is particularly favorable when the electrode has a high degree of flexibility along the edge of the part or the frame, because in this way even smaller obstacles are reliably detected.

If the at least one electrode of the at least one EAP layer is subdivided into a plurality of mutually insulated electrodes, a sensor with spatial resolution, in particular along the edge of the part or the frame, can thus be realized in a simple manner.
It is advantageous if two polymer films are coated in such a way that the structured electrodes are enclosed in the middle. This ensures that the effective electrode surfaces are directly above each other without adjustment. When integrating the typically very narrow strip conductors in the sensor, these are additionally mechanically protected.

In order to ensure complete detection of an obstacle, the different independent sensors, in particular along the edge or the frame, can spatially overlap. If each independent sensor area has its own electrode, the sensitivity of the sensor can be individually set locally via a suitably specified, applied basic voltage.

Particularly favorable is the arrangement of the anti-pinch sensor between the sealing profile and the frame profile of an opening. In this case, the sensor can be glued, or merely clamped, without a structural change of the existing sealing or frame profiles is necessary.

The spatially subdivided electrodes can be realized particularly advantageously by means of a printed circuit board technology, wherein the individual electrodes are arranged with their leading to the voltage tap traces as a thin layer on a thin, flexible printed circuit board film.
The mutual use of sensor top and bottom side to the track guidance allows a particularly space-saving design of the sensor.

From a manufacturing point of view, it is advantageous to fasten the anti-pinch sensor to the frame or sealing profile with a film, wherein the conductor tracks for the terminals of the electrodes are preferably arranged on the foil. This method allows a spatially fine subdivision of the sensor into areas with independent electrode pairs.

Since the EAP materials have very similar properties to the materials of a sealing profile, the EAP layers can be integrated particularly favorably into the sealing profile and in one operation with the same, for example by coextrusion or multi-component injection molding.

The application of the EAP layer on the sealing profile in the form of a paint or by gluing is also a cost effective alternative. Also anti-pinch sensors made in this way are due to the rubber-like properties of EAP materials very durable against mechanical stress, even over a wide temperature range from -50 ° C to 200 ° C.

By arranging the at least one EAP layer semicircularly around the one end of the frame profile, clamping forces that act on the sealing profile outside the plane of movement of the part can also be reliably sensed.

Due to the spatial resolution of the anti-pinch sensor along the edge or frame, it is easy to specify regions of different sensitivity that are adapted to particular edge portions of the part. In this case, the geometric shape of the part and of the corresponding frame can be taken into account, which causes different clamping force components than the closing direction.

The sensitivity of the individual sensor regions can advantageously be realized by applying an individually adapted working voltage to the electrodes of the corresponding regions.

Since the voltages applied to EAP materials are typically in the kV range, the signals of the electrodes are fed to a DC / DC converter, which is part of an evaluation device in a control unit of the anti-pinch sensor.

drawing

• Figur 1 eine Anordnung eines Einklemmschutzsensors an einem Kraftfahrzeugseitenfenster,
• Figur 2a bis 2c das Funktionsprinzip der erfindungsgemäßen Vorrichtung,
• Figur 3 und Figur 4a bis 4c verschiedene Ausführungsbeispiele eines erfindungsgemäßen Einklemmschutzsensors,
• Figur 5 ein weiteres Ausführungsbeispiel mit einer Lochbandmatrix,
• Figur 6 und 7 verschiedene Ausführungsformen von Elektroden einer erfindungsgemäßen Vorrichtung und
• Figur 8 und Figur 9 weitere Anordnungsmöglichkeiten des Einklemmschutzsensors an einem Rahmenprofil gemäß Figur 1.

In the drawings, embodiments of a device according to the invention are shown. Show it

• 1 shows an arrangement of an anti-pinch sensor on a motor vehicle side window,
• 2a to 2c, the operating principle of the device according to the invention,
• FIG. 3 and FIGS. 4 a to 4 c show various embodiments of an anti-pinch sensor according to the invention,
• FIG. 5 shows a further exemplary embodiment with a perforated band matrix,
• Figures 6 and 7 different embodiments of electrodes of a device according to the invention and
• FIG. 8 and FIG. 9 show further possible arrangements of the pinch protection sensor on a frame profile according to FIG. 1.

Description of the embodiments

In Figure 1, a side window of a motor vehicle is shown, wherein between a window pane 10 as a movable part 10 and a window opening 11 enclosing the frame profile 12 over the entire length of a pinch protection sensor 14 is arranged. The anti-jamming sensor 14 is integrated, for example, in a sealing profile 16 and divided into different regions 18, corresponding to the shape of the disc 10. The disc 10 has an edge 20 which substantially runs parallel to the frame profile 12. When closing the part 10, a closing force 22 occurs, the component of which can vary in size perpendicular to the edge 20 of the part 10 in the different regions 18. If an obstacle 24 is located in the adjustment path between the part 10 and the frame profile 12, a pressure is exerted on the anti-pinch sensor 14 when closing and a signal is transmitted to a control unit 26 of the closing device. If a preset threshold value of the closing force 22 is exceeded, the motor 21 receives a control command to stop the part 10 or reverse its direction of movement.

FIGS. 2a to 2c show a schematic cross-section of a pinch protection sensor 14 which has a plurality of electroactive polymer (EAP) layers. For example, polyuretan PT6100S, fluoroelastomer LaurenL143HC, polybutadiene Aldrich PBD, fluorosilicone 730 or silicone Sylgard 186 are used as EAP material. EAP materials have the special property that, due to their electrostriction, an external deformation changes the effective length of the electroactive polymer chains. This change in length brings about a change in voltage at the electrodes 28 arranged on the EAP layers. In FIG. 2 a, a first EAP layer 30 is arranged between two electrode layers 28 on a rubber of a sealing profile 16. Separated by an insulating layer 32, a further layer sequence of electrode, EAP layer, electrode is arranged above this first electrode / EAP packet. The two electrodes 34 are grounded and applied to the other two electrodes 36 each have a positive voltage. The thickness 38 of the EAP layer 30 is for example between 1 and 100 micrometers. The thinner this layer is formed, the more it can be stretched, whereby the sensitivity of the anti-jamming protection is increased.

wobei die hervorgerufene Spannungsänderung direkt proportional zu t, der Dicke 38 der EAP-Schicht 30 ist. Der durch die Einklemmkraft 22 eines Hindernisses 24 generierte Druck P und die dielektrischen Materialeigenschaften ε_r und ε₀ beeinflussen die Spannungsänderung lediglich als Faktor unter der Wurzel.Figure 2b shows the deformation of the EAP layers 30 due to a pinched obstacle 24. The pinching force 22 causes the EAP layers 30 to elongate along the sealing profile 16. The EAP layers 30 undergo transverse contraction, thereby reducing their thickness 38. This leads to a voltage change between the two electrode pairs 34, 36, which corresponds to a specific force on the anti-pinch sensor 14. The voltage change is measured in the control unit 26 and compared with a limit, is exceeded or under which the motor 21 is stopped or reversed. The voltage change takes place according to the formula $$\mathrm{U}\mathrm{=}\mathrm{t}\mathrm{*}\mathrm{\surd }\left(\mathrm{p}\mathrm{/}\mathrm{.epsilon..sub.R}\mathrm{*}\mathrm{\epsilon }\mathrm{0}\right)\mathrm{.}$$

wherein the induced voltage change is directly proportional to t, the thickness 38 of the EAP layer 30. The pressure P generated by the pinching force 22 of an obstacle 24 and the dielectric material properties ε _r and ε ₀ influence the voltage change only as a factor under the root.

In FIG. 2 c, the anti-pinch sensor 14 is arranged in a cavity 39 of the sealing profile 16, which extends approximately parallel to the edge 20.

FIG. 3 shows an alternative embodiment of the anti-pinch sensor 14. Here, too, an EAP layer 30 is arranged between two planar electrodes 28, with four EAP layers 30 with intervening electrodes 28 being combined to form a package on the right in the image. However, the closing force 22 does not act perpendicular to the EAP layers 30 and the electrodes 28, but in the layer plane of the EAP layers 30. This force also causes a change in shape of the EAP layers 30, which leads to a thickening of the same.

At the arranged between the EAP layers 30 electrodes 28, in turn, a voltage change is tapped, which is correlated with the closing force 22. In this embodiment, the anti-pinch sensor 14, the EAP layers 30 are arranged between the frame profile 12 and the disc 10 in etea parallel to the direction of movement. The addition of the individual voltage changes leads in a simple manner to an increase in the measurement signal when using a plurality of EAP layers 30.

In a further exemplary embodiment according to FIG. 4, a layer sequence of electrode 28, EAP layer 30, electrode 28, EAP layer 30 is wound around a winding core 40 to form a roller 42, which extends axially approximately parallel to the edge 20. When closing the part 10, the anti-jamming sensor 14 experiences a radial force as soon as an obstacle 24 presses on it. In this case, the EAP layers 30-at least those layers perpendicular to the closing force-are compressed in such a way that the thickness 38 of the EAP layers 30 is reduced. This also leads to a summed voltage change, which is tapped off at the two electrodes 28.

In Figure 4b, an EAP layer 30 is also wound with intervening electrodes 34, 36 analogous to Figure 4a, but in this arrangement, the force in the axial direction to the roller 42. In this case, several rollers 42 with their axis approximately in the disc plane and in arranged approximately perpendicular to the edge 20, wherein an axial change in length of the roller 42 causes a change - in this case, an increase - the thickness 38 of the EAP layers 30.

FIG. 4c shows a further variation in which the EAP layer 30 is formed as a single tube 44, the electrodes 34, 36 being respectively provided at the two axial ends of the tube Tube 44 are arranged. The action of force also takes place axially in accordance with FIG. 4b, whereby the thickness 38 of the EAP layer 30 likewise changes. The electrode arrangement does not measure the voltage change across the thickness 38 of the EAP layer 30, but rather over its axial extent.

FIG. 5 shows a further embodiment of the anti-pinch sensor 14 according to the arrangement in FIG. In this case, an EAP layer 30 embedded between two electrodes 34, 36 is arranged above a perforated belt matrix 46. Between the individual holes 48 of the perforated strip 46, which extends approximately parallel to the edge 20, there are support points 50 on which the EAP layer 30 is suspended. The perforated tape matrix 46 represents a spatially fixed framework through whose holes 48, when applied to the electrodes 34, 36 voltage, the EAP layer 30, together with the electrodes 34, 36 extends therethrough. The perforated tape matrix 46 is integrated together with the electrodes 34, 36 and the EAP layer 30 in a sealing profile 16 or manufactured directly by means of multi-component injection molding in one piece with this. The spatially fixed support points 50 also cause small obstacles 24 a relatively large deformation of the EAP layer 30, since this is pushed back to the plane 52 of the perforated belt matrix 46 through the holes 48. This causes a voltage change between the adjacent electrodes 34, 36, which is evaluated to trigger the anti-trap function.

FIG. 6 shows an anti-pinch protection sensor 14 with one and two EAP layers 30, wherein one electrode 56 each has a structuring. The electrode 56 is divided along the edge 20 or the frame profile 16 into small sections, which are interconnected by flexible connecting pieces 54. The structured electrode 56 is formed as an integrated layer and can have different geometric shapes. Such, arranged on or between EAP layers, electrode 56 is very flexible and extremely elastic even with one-piece design and thus very resistant to wear.

FIG. 7 shows an exemplary embodiment of a sensor 14 with a one-piece, unstructured base electrode 34 and an EAP layer 30 arranged thereon. In turn, a structured electrode 56 is arranged as an integrated layer, the individual electrode sections 58 being insulated from one another. The individual electrode sections 58 have, for contacting, printed conductors 62, which are likewise part of the integrated layer. The electrode sections 58 are preferably subdivided in the direction 20 'of the edge 20 in order to locally increase the sensitivity of the anti-pinch protection sensor 14 or else to realize a division into areas 18 corresponding to the wheel contour according to FIG. If the base electrode 34 is connected to ground, each individual electrode section 58 can be assigned an individual base voltage for the respective electrode section 58 or corresponding to the sensor zones 18. As a result, a different sensitivity of the sensor 14 can be set for each section 58 or area 18. Alternatively, such a local sensitivity can also be set via different threshold values of the voltage change.

FIG. 8 shows a cross section through a frame profile 12 with a sealing profile 16. The EAP layer 30 arranged between two electrode layers 28 is arranged in a circle around a free end 60 of the frame profile 12 between the latter and the sealing profile 16. Due to the semicircular shape of the anti-pinch sensor 14 in A plane approximately perpendicular to the edge 20 and pinching forces 22 outside the plane of movement of the part 10 can be detected, especially the inner region 15 of the anti-pinch sensor 14 to the disc 10 for the timely detection of an obstacle 24 is crucial. The anti-pinch sensor 14 is glued in this arrangement on the free end 60 of the sealing profile 12, but can also be inserted only in the sealing profile 16 before its assembly and pressed against the free end 60.

In FIG. 9, the anti-pinch sensor 14 is fixed at a free end 60 of the frame profile 12 by means of a foil 64, which carries the conductor tracks 62 for the individual electrode sections 58. If the entire length of the anti-pinch sensor 14 is divided into many sections 58, a large area is required for the plurality of electrode terminals to supply the tracks 62 along the frame profile 12 of a voltage source. For this purpose, the flexible printed circuit board film 64, which extends over the entire region between the outer side 66 of the sealing profile 12 and the sealing profile 16. The EAP layers 30 and the associated electrodes 28 are preferably an integral part of the printed circuit board film 64. The printed circuit board film 64 with the conductor tracks 62 is either glued to the sealing profile 16 or merely pressed between the sealing profile 16 and the frame profile 12. The contact tracks 62 are preferably fed to a control unit 26, in which the applied voltages in the kV range are transformed by means of a DC / DC converter for further processing in the evaluation electronics. At the electrodes 28 occur currents in the order of 0.5 mA, so that even high voltages pose no threat to people. The local change in length of the EAP layer 30 by up to 300% takes place in accordance with the closing speed of the part 10. The reaction time of the electrostriction, that is generating a voltage change at a applied working voltage, takes place in the range of milliseconds to microseconds. The electrostriction can also be represented with the model of a capacitor, wherein as a dielectric the EAP material is arranged between two planar electrode plates. As a result of the outer deformation, changes in the impedance of the system occur because the effective length of the polymer chains or the orientation of the inner dipoles changes in the applied electric field. The stacked EAP layers can be connected in series, so to speak, in order to increase the measurement signal. The thinner the EAP films can be applied, the lower the power losses due to heat dissipation of the electrodes. By including the patterned electrode 56 between two EAP layers, it is ensured that the effective electrode surfaces are directly above each other without adjustment. When integrating the typically very narrow conductor tracks 62 into the sensor, they are additionally mechanically protected. In the production of the EAP layers 30 is to ensure a homogeneous layer thickness 38 thereof, otherwise no constant, homogeneous electric field can be applied. Since the sensor material has very similar mechanical properties as the material of the sealing profile 16, delaminations between sensor 14 and rubber are minimized. This applies to a temperature range of -50 to 200 ° C, which fully covers the application in the automotive sector. Therefore, the inventive design of the anti-pinch sensor 14 can also be applied in a simple form as a paint on the sealing profile 16.

It is also conceivable that conclusions about the course of the impedance changes, for example, on the size of the clamped object 24 and thus also depending on the object size of the triggering threshold can be set.

Claims (23)

1. Device for opening and closing an opening (11), in particular on a vehicle, by means of a motor-driven, movable part (10), comprising a control unit (26) and an anti-trapping sensor (14), which is arranged essentially along an edge (20) of the part (10) and/or a frame profile (12) bounding the opening (11) and, when the part (10) is closing, identifies an obstruction (24) situated in the adjustment path of the part (10), then forwards a signal to the control unit (26) in order to stop or to reverse the movement of the part (10), the anti-trapping sensor (14) having an electroactive polymer (EAP) material (30) arranged between electrodes (28, 34, 36), which material, in the event of a deformation, brings about a voltage change at the electrodes (28, 34, 36), characterized in that the electroactive polymer (EAP) material (30) is embodied in highly extensible fashion, and the anti-trapping sensor (14) along the edge (20) or the frame profile (12) is subdivided into a plurality of independent regions (18, 58) in order to realize a spatial resolution.
2. Device according to Claim 1, characterized in that the effective length of the polymer chains of the EAP material (30) changes in the event of a deformation of said material.
3. Device according to Claim 1, characterized in that the EAP material (30) is shaped in thin layers, in particular having a thickness (38) of 1 to 100 µm.
4. Device according to Claim 1, characterized in that a voltage U is established at the electrodes (28, 34, 36) in accordance with the formula $$\mathrm{U}\mathrm{=}\mathrm{t}\mathrm{*}\left(\mathrm{p}\mathrm{/}\mathrm{ϵr}\mathrm{*}\mathrm{ϵ}\mathrm{0}\right)1/2$$

   

   
   where t represents the thickness (38) of the EAP layer (30), ε_r represents the relative permittivity, ε₀ represents the electric constant and P represents the pressure generated by the obstruction (24) on the EPA layer (30).
5. Device according to one of Claims 1 to 4, characterized in that a plurality of EAP layers (30) with intervening electrodes (28, 34, 36) and/or insulation layers (32) are stacked one above another.
6. Device according to one of Claims 1 to 5, characterized in that the pressure generated by the obstruction (24) acts predominantly perpendicular to the EAP layers.
7. Device according to one of Claims 1 to 5, characterized in that the pressure generated by the obstruction (24) acts predominantly parallel to the EAP layers (30).
8. Device according to one of Claims 1 to 7, characterized in that the at least one EAP layer (30) is shaped as a tube (44) or as a roll (42).
9. Device according to one of Claims 1 to 8, characterized in that the electrodes (28, 34, 36) are arranged at the end sides or at the lateral surfaces of the tube (42) or the roll (44).
10. Device according to one of the preceding claims, characterized in that the at least one EAP layer (30) is arranged above a perforated tape matrix (46) and extends through the holes (48) in the perforated tape matrix (46) when a voltage is applied to the electrodes (28, 34, 36).
11. Device according to one of the preceding claims, characterized in that the at least one of the electrodes (28, 34, 36, 56) is spatially structured, in particular is embodied such that it is easily movable in the direction (20') of the edge (20).
12. Device according to one of the preceding claims, characterized in that the electroactive polymer (EAP) material (30) is embodied as polyurethane, fluoroelastomer, polybutadiene, fluorosilicone or silicone.
13. Device according to one of the preceding claims, characterized in that the regions (18, 58) of the anti-trapping sensor (14) overlap.
14. Device according to one of the preceding claims, characterized in that each sensor region (18, 58) has at least in each case one dedicated electrode (28, 34, 36, 56).
15. Device according to one of the preceding claims, characterized in that the individual electrodes (28, 34, 36, 56) of the sensor regions (18, 58) are embodied in the form of an integrated layer with conductor tracks (62) on the EAP layer (30).
16. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) is arranged between a frame profile (12) enclosing the part (10) and a sealing profile (16) inserted into said frame profile.
17. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) is fixed by means of a film (64) that carries conductor tracks (62) for the driving of the electrodes (28, 34, 36, 56).
18. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) is integrated into the sealing profile (16), in particular is formed integrally with the sealing profile (16) by means of coextrusion or multicomponent injection-moulding.
19. Device according to one of the preceding claims, characterized in that the at least one EAP layer (30) is arranged in the form of a coating or by adhesive bonding on the sealing profile (16).
20. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) is shaped in semicircular fashion around at least one free end (60) of the frame profile (12) facing the part (10).
21. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) along the edge (20) or the frame profile (12) is subdivided into regions (18, 58) of different sensitivity which are assigned a threshold value of the voltage change that is adapted to the geometry of the edge (20), the overshooting or undershooting of which threshold value triggers stopping or reversing of the part (10).
22. Device according to one of the preceding claims, characterized in that different output voltages are applied to the electrodes (28, 34, 36, 58) assigned to the individual EAP layers (30) or sensor regions (18, 58).
23. Device according to one of the preceding claims, characterized in that the anti-trapping sensor (14) has a DC-DC converter (27) for the evaluation of the voltage change in the control unit (26).

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