Electromagnetic Actuator For A Display With Improved Spring Arrangement And Output Device with Said Actuator

Abstract

The invention relates to an electromagnetic actuator, which is designed to be connected to a backside of a plate like structure and which comprises an annular coil arrangement and a magnet system being designed to generate a magnetic field transverse to the annular coil arrangement. The annular coil arrangement and the magnet system are connected to each other by a plurality of springs, which are arranged inside of the annular coil arrangement. Furthermore, the invention relates to an output device, comprising a plate like structure and an electromagnetic actuator of the above kind connected to a backside of the plate like structure.

Claims

1. An electromagnetic actuator, configured to be connected to a backside of a plate-like structure opposite to a sound emanating surface of the plate like structure, the electromagnetic actuator comprising an annular coil arrangement and a magnet system configured to generate a magnetic field transverse to a longitudinal direction of a wire of the annular coil arrangement wound around an actuator axis, wherein the annular coil arrangement and the magnet system are connected to each other by a plurality of springs, the plurality of springs being arranged inside of the annular coil arrangement.

2. The electromagnetic actuator according to claim 1, further comprising a spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder, wherein the plurality of springs is arranged between the annular outer holder and the center holder.

3. The electromagnetic actuator according to claim 2, wherein the annular outer holder and the center holder are arranged in different planes in an idle position of a movable part of the electromagnetic actuator.

4. The electromagnetic actuator according to claim 2, wherein the spring arrangement is one piece.

5. The electromagnetic actuator according to claim 2, wherein the annular outer holder of the spring arrangement is fixedly arranged relative to the plate-like structure and the center holder of the spring arrangement is fixedly arranged relative to a movable part of the magnet system.

6. The electromagnetic actuator according to claim 2, wherein the center holder of the spring arrangement is fixedly arranged relative to the plate-like structure and the annular outer holder of the spring arrangement is fixedly arranged relative to a movable part of the magnet system.

7. The electromagnetic actuator according to claim 1, further comprising at least one spring arrangement comprising a combined holder with an annular section and an additional center section, wherein the plurality of springs extend from the center section and have a connecting section at their extending ends inside of the annular section.

8. The electromagnetic actuator according to claim 7, wherein the annular section of the combined holder and the connecting sections of the springs are arranged in different planes in an idle position of a movable part of the electromagnetic actuator.

9. The electromagnetic actuator according to claim 7, wherein the annular section of the combined holder is fixedly arranged relative to the plate-like structure and the connecting sections of the springs are fixedly arranged relative to a movable part of the magnet system.

10. The electromagnetic actuator according to claim 7, wherein the connecting sections of the springs are fixedly arranged relative to the plate-like structure and the annular section of the combined holder is fixedly arranged relative to a movable part of the magnet system.

11. The electromagnetic actuator according claim 1, wherein the plurality of springs is preloaded in an idle position of a movable part of the electromagnetic actuator.

12. The electromagnetic actuator according to claim 1, wherein the springs are symmetrically shaped only around the actuator axis in case of circular coil arrangement.

13. The electromagnetic actuator according to claim 1, wherein the springs are symmetrically shaped around an axis perpendicular to the actuator axis in case of a non-circular coil arrangement.

14. The electromagnetic actuator according to claim 1, wherein the springs are spirally and/or arc shaped.

15. The electromagnetic actuator according to claim 1, wherein the springs are shaped like a meander.

16. The electromagnetic actuator according to claim 1, wherein the annular coil arrangement is fixedly arranged relative to the plate-like structure and at least a movable part of the magnet system is movably arranged relative to the plate-like structure.

17. The electromagnetic actuator according to claim 16 wherein the movable part of the magnet system comprises: a top plate from soft iron; a bottom plate from soft iron; and a center magnet mounted to the top plate and to the bottom plate.

18. The electromagnetic actuator according to claim 17, wherein the coil arrangement comprises only a single voice coil, the top plate is disc shaped and the bottom plate is pot shaped, wherein the annular part of the pot shaped bottom plate is arranged outside of the annular coil arrangement.

19. The electromagnetic actuator according to claim 17, further comprising a first and a second spring arrangement, each spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder, wherein the plurality of springs is arranged between the annular outer holder and the center holder, and wherein the center holder of the first spring arrangement is mounted to the top plate and the center holder of the second spring arrangement is mounted to the bottom plate.

20. The electromagnetic actuator according to claim 19, wherein first spring arrangement and the second spring arrangement are of identical shape, but turned by 90 to one another around the actuator axis.

21. The electromagnetic actuator according to claim 17, further comprising: a first and a second spring arrangement, each spring arrangement comprising a combined holder with an annular section and an additional center section, wherein the plurality of springs extend from the center section and have a connecting section at their extending ends inside of the annular section, wherein the connecting sections of the springs of the first spring arrangement are mounted to the top plate and the connecting sections of the springs of the second spring arrangement are mounted to the bottom plate.

22. The electromagnetic actuator according to claim 17, wherein: the coil arrangement comprises a first voice coil and a second voice coil arranged above another; both the top plate and the bottom plate are disc shaped; the top plate is arranged vis-a-vis the first voice coil and the bottom plate is arranged vis-a-vis the second voice coil; and a fixed part of the magnet system comprises an outer ring from soft iron arranged around the annular coil arrangement vis-a-vis both the first voice coil and the second voice coil.

23. The electromagnetic actuator according to claim 17, further comprising: a spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder, wherein the plurality of springs is arranged between the annular outer holder and the center holder; and a center connector fixedly arranged relative to the plate-like structure, wherein center holder of the spring arrangement is mounted to the center connector, and the top plate or the bottom plate of the movable part of the magnet system is mounted to an annular outer holder of the spring arrangement.

24. The electromagnetic actuator according to claim 23, wherein a fixed part of the magnet system is mounted to the center connector.

25. The electromagnetic actuator according to claim 23, wherein an air gap between the movable part of the magnet system and the center connector or between the movable part of the magnet system and a fixed part of the magnet system is smaller than an air gap between the movable part of the magnet system and the annular coil arrangement, each measured in a direction perpendicular to the actuator axis.

26. The electromagnetic actuator according to claim 17, further comprising: a first and a second spring arrangement, each spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder; and a center connector fixedly arranged relative to the plate-like structure, wherein the center holder of the first spring arrangement is mounted to the center connector, the center holder of the second spring arrangement is mounted to the center connector at a distance away from the center holder of the first spring arrangement, the movable part of the magnet system is arranged between the annular outer holder of the first spring arrangement and the annular outer holder of the second spring arrangement, the top plate is mounted to the annular outer holder of the first spring arrangement, and the bottom plate is mounted to the annular outer holder of the second spring arrangement.

27. The electromagnetic actuator according to claim 17, further comprising: a spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder, wherein the plurality of springs is arranged between the annular outer holder and the center holder; and a center connector movably arranged relative to the plate-like structure, wherein a center holder of the spring arrangement is mounted to the center connector, and the top plate, the bottom plate and the center magnet of the movable part of the magnet system are all mounted to the center connector.

28. The electromagnetic actuator according to claim 27, wherein a fixed part of the magnet system is mounted to the annular outer holder.

29. The electromagnetic actuator according to claim 17, further comprising: a first and a second spring arrangement, each spring arrangement comprising an annular outer holder and a center holder inside of the annular outer holder; and a center connector movably arranged relative to the plate-like structure, wherein a center holder of a first spring arrangement is mounted to the center connector, a center holder of a second spring arrangement is mounted to the center connector at a distance away from the center holder of the first spring arrangement, and the top plate, the bottom plate and the center magnet of the movable part of the magnet system are mounted to the center connector.

30. The electromagnetic actuator according to claim 1, wherein the coil arrangement comprises a first voice coil and a second voice coil arranged above another, wherein the magnetic field passes the first voice coil from the inner side of the annular coil arrangement to the outer side of the annular coil arrangement, and the magnetic field passes the second voice coil from the outer side of the annular coil arrangement to the inner side of the annular coil arrangement.

31. The electromagnetic actuator according to claim 1, wherein a fixed part of the magnet system comprises an outer ring from soft iron arranged around the annular coil arrangement, and the coil arrangement touches said outer ring or is connected thereto.

32. An output device, comprising a plate-like structure and an electromagnetic actuator connected to a backside of the plate-like structure, with a sound emanating surface and a backside opposite the sound emanating surface, wherein the electromagnetic actuator is designed according to claim 1.

33. The output device as claimed in claim 32, wherein an average sound pressure level of the output device measured in an orthogonal distance of 10 cm from the sound emanating surface is at least 50 dB_SPL in a frequency range from 100 Hz to 15 kHz.

34. An output device as claimed in claim 32, wherein the plate like structure is embodied as a display and that the electrodynamic actuator is connected to the backside of the display.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] These and other aspects, features, details, utilities, and advantages of the invention will become more fully apparent from the following detailed description, appended claims, and accompanying drawings, wherein the drawings illustrate features in accordance with exemplary embodiments of the invention, and wherein:

[0058] FIG. 1 shows a first embodiment of an electromagnetic actuator with two spring arrangements and the movable part of the magnet system in-between in exploded view.

[0059] FIG. 2 shows the electromagnetic actuator of FIG. 1 in sectional view.

[0060] FIG. 3 shows a second embodiment of an electromagnetic actuator with a single spring arrangement in sectional view.

[0061] FIG. 4 shows a third embodiment of an electromagnetic actuator with a single coil in sectional view.

[0062] FIG. 5 shows a fourth embodiment of an electromagnetic actuator with a movable center connector in sectional view.

[0063] FIG. 6 shows an embodiment of an electromagnetic actuator with a different spring arrangement in sectional view.

[0064] FIG. 7 shows a top view of the spring arrangement with spiral springs, which is used in the embodiment of FIG. 1.

[0065] FIG. 8 shows a top view of another spring arrangement with spiral springs.

[0066] FIG. 9 shows a top view of a spring arrangement with springs shaped like meanders.

[0067] FIG. 10 shows a top view of a spring arrangement with springs shaped like meanders which are symmetrical about an axis perpendicular to the actuator axis.

[0068] FIG. 11 shows a top view of another spring arrangement with springs shaped like meanders which are symmetrical about an axis perpendicular to the actuator axis.

[0069] FIG. 12 shows a top view of a spring arrangement with distinct outer holders.

[0070] FIG. 13 shows a top view of a spring arrangement with a combined holder with an annular section and an additional center section and

[0071] FIG. 14 shows the spring arrangement of FIG. 13 turned by 90.

[0072] Like reference numbers refer to like or equivalent parts in the several views.

DETAILED DESCRIPTION OF EMBODIMENTS

[0073] Various embodiments are described herein to various apparatuses. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims

[0074] Reference throughout the specification to various embodiments, some embodiments, one embodiment, or an embodiment, or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases in various embodiments, in some embodiments, in one embodiment, or in an embodiment, or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional.

[0075] It must be noted that, as used in this specification and the appended claims, the singular forms a, an and the include plural referents unless the content clearly dictates otherwise.

[0076] The terms first, second, and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms include, have, and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0077] All directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, front, rear, top, bottom, over, under, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the any aspect of the disclosure. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0078] As used herein, the phrased configured to, configured for, and similar phrases indicate that the subject device, apparatus, or system is designed and/or constructed (e.g., through appropriate hardware, software, and/or components) to fulfill one or more specific object purposes, not that the subject device, apparatus, or system is merely capable of performing the object purpose.

[0079] Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims

[0080] All numbers expressing measurements and so forth used in the specification and claims are to be understood as being modified in all instances by the term about or substantially, which particularly means a deviation of 10% from a reference value.

[0081] A first example of an electromagnetic actuator 1a is disclosed by use of the FIGS. 1, 2 and 7. FIG. 1 shows an exploded view of the electromagnetic actuator 1a, FIG. 2 shows a cross sectional view of the electromagnetic actuator 1a and FIG. 7 shows a top view of a spring arrangement used in the electromagnetic actuator 1a.

[0082] The electromagnetic actuator 1a is designed to be connected to a backside of a plate like structure, which is assumed to be embodied as display 2 in this example (see FIG. 2). Nevertheless, in principle, the plate like structure may be any plate like structure, which is able to output sound when it is excited. The electromagnetic actuator 1a has an annular coil arrangement 3a, which in this example comprises a first voice coil 4a and a second voice coil 4b stacked above another and connected to each other by means of a glue layer 5 for example.

[0083] The electromagnetic actuator 1a furthermore has a magnet system 6a, which in this example comprises a top plate 7a from soft iron, a bottom plate 8a from soft iron, a center magnet 9a, which is mounted to the top plate 7a and to the bottom plate 8a, and an outer ring 10a from soft iron. The top plate 7a, the bottom plate 8a and the center magnet 9a are comprised of the movable part 11a of the magnet system 6a or these parts may even form the movable part 11a of the magnet system 6a. The outer ring 10a is comprised of the fixed part of the magnet system 6a or it may even form the fixed part of the magnet system 6a. Accordingly, the fixed part of the magnet system 6a may be denoted with the reference sign of the outer ring 10a as the case may be. Both the top plate 7a and the bottom plate 8a are disc shaped, wherein the top plate 7a is arranged vis-a-vis of the first voice coil 4a and the bottom plate 8a is arranged vis-a-vis of the second voice coil 4b. The fixed part of the magnet system 6a, which is the outer ring 10a in this example, is arranged around the annular coil arrangement 3a vis-a-vis of both the first voice coil 4a and the second voice coil 4b.

[0084] The magnet system 6a generally is designed to generate a magnetic field B1, B2 transverse to a longitudinal direction of a wire of the annular coil arrangement 3a wound around an actuator axis A. In detail, the magnetic field B1 passes the first voice coil 4a from the inner side of the annular coil arrangement 3a to the outer side of the annular coil arrangement 3a, and the magnetic field B2 passes the second voice coil 4b from the outer side of the annular coil arrangement 3a to the inner side of the annular coil arrangement 3a.

[0085] The annular coil arrangement 3a and the movable part 11a of the magnet system 6a are connected to each other by a plurality of springs 12a, which are arranged inside of the annular coil arrangement 3a. In detail, the springs 12a are part of a spring arrangement 13a, 13a, 13a, which additionally comprises an annular outer holder 14a and a center holder 15a inside of the annular outer holder 14a. The plurality of springs 12a is arranged between the annular outer holder 14a and the center holder 15a and fixed thereto (one end of each spring 12a is connected to the annular outer holder 14a, and the other end of each spring 12a is connected to the center holder 15). In particular, the spring arrangement 13a, 13a, 13a is one piece like this is the case in the example of FIG. 7. By the aforementioned measures, the springs 12a can be held in position, and assembly of the electromagnetic actuator 1a is simplified.

[0086] The electromagnetic actuator 1a of this example furthermore comprises a center connector 16a fixedly arranged relative to the display 2. In more detail, a center holder 15a of a first spring arrangement 13a is mounted to the center connector 16a, and a center holder 15a of a second spring arrangement 13a is mounted to the center connector 16a at a distance from the center holder 15a of the first spring arrangement 13a.

[0087] The movable part 11a of the magnet system 6a is arranged between an annular outer holder 14a of the first spring arrangement 13a and an annular outer holder 14a of the second spring arrangement 13a, wherein the top plate 7a is mounted to the annular outer holder 14a of the first spring arrangement 13a, and the bottom plate 8a is mounted to the annular outer holder 14a of the second spring arrangement 13a. Moreover, the fixed part 10a of the magnet system 6a is mounted to the center connector 16a, in particular outside of the first spring arrangement 13a and the second spring arrangement 13a. By these measures, a rocking movement of the movable part 11a of the magnet system 6a is avoided or at least kept low because the mounting points of the movable parts 11a of the magnet system 6a are located at an axial distance.

[0088] Finally, the electromagnetic actuator 1a comprises a top mounting plate 17 on the upper end of the center connector 16a and a bottom mounting plate 18 on the lower end of the center connector 16a. The top mounting plate 17 connects the center connector 16a and the annular coil arrangement 3a, and the bottom mounting plate 18 connects the center connector 16a and the outer ring 10a of the magnet system 6a. Moreover, an adhesive sheet 19 is arranged on the upper side of the top mounting plate 17, by means of which the electromagnetic actuator 1a is mounted to the backside of the display 2. However, a glue layer may be used for this reason as well. Beneficially, the connecting area between the display 2 and the annular outer holder 14a is comparably large in this embodiment.

[0089] Advantageously, an air gap a between the movable part 11a of the magnet system 6a and the center connector 16a is smaller than an air gap b between the movable part 11a of the magnet system 6a and the annular coil arrangement 3a in this example, wherein the gaps a and b are each measured in a direction perpendicular to the actuator axis A. In particular the smallest gap a and the smallest gap b is taken for the above considerations. By the proposed measures, a lateral acceleration of the electromagnetic actuator 1a transverse to a direction of the actuator axis A cannot cause a collision of the movable part 11a of the magnet system 6a with the coil arrangement 3a and in turn cannot cause damage of the coil arrangement 3a. Instead, the movable part 11a of the magnet system 6a can just collide with the center connector 16a. Generally, a lateral acceleration of the aforementioned kind may be caused, when a device with the electromagnetic actuator 1a (e.g. a mobile phone) falls down and hits the floor.

[0090] The electromagnetic actuator 1a together with the display 2 forms an output device 20a for both audio and video data.

[0091] When an input signal is applied to the voice coils 4a, 4b of the coil arrangement 3a, the movable part 11a of the magnet system 6a is pushed in the direction of the actuator axis A, that means up or down. Because of the inertia of said movable part 11a, a reaction force is caused, which pushes the coil arrangement 3a in the contrary direction. That is why the display 2 is deflected and sound according to the input signal is generated. It should be noted, that the current flows through the voice coils 4a, 4b in opposite directions so that the electromagnetic forces generated by the voice coils 4a, 4b are summed. The voice coils 4a, 4b are beneficially wired in parallel or in series so that the inductance is reduced by the opposite direction of the induced magnetic fields of both voice coils 4a, 4b.

[0092] In the example shown in FIGS. 1 and 2, the center holder 15a of the spring arrangement 13a, 13a is fixedly arranged relative to the display 2, and the annular outer holder 14a of the spring arrangement 13a, 13a is fixedly arranged relative to the movable part 11a of the magnet system 6a. Although this is advantageous, this is not the only possibility. It is also imaginable that the annular outer holder 14a of the spring arrangement 13a is fixedly arranged relative to the display 2 and the center holder 15a of the spring arrangement 13a is fixedly arranged relative to the movable part 11b of the magnet system 6b like this is the case for the electromagnetic actuator 1b shown in FIG. 3. By these measures, the spring arrangement 13a can extend beyond the coil arrangement 3a and a comparably large connecting area between the annular outer holder 14b and the display 2 is provided.

[0093] The electromagnetic actuator 1b is similar to the electromagnetic actuator 1a, but it is built without a center connector 16a. Instead, the magnet system 6b, which is movable as a whole in this case and which comprises a top plate 7b, a bottom plate 8b and a center magnet 9b, is directly connected to the spring arrangement 13a. In detail, the annular outer holder 14a is connected to the display 2 by means of the adhesive sheet 19 or the glue layer, and the center holder 15a is connected to the top plate 7b. The electromagnetic actuator 1b together with the display 2 forms an output device 20b for both audio and video data.

[0094] FIG. 4 shows a further example of an electromagnetic actuator 1c, which has a coil arrangement 3b with a single coil 4. The movable part 11c of the magnet system 6c again comprises a top plate 7c from soft iron, a bottom plate 8c from soft iron and a center magnet 9c mounted to the top plate 7c and to the bottom plate 8c. The top plate 7c is disc shaped and the bottom plate 8c is pot shaped, wherein the annular part of the pot shaped bottom plate 8c is arranged outside of the annular coil arrangement 3b. Again, a center connector 16b is fixedly arranged relative to the display 2. A center holder 15a of a spring arrangement 13a is mounted to the center connector 16b and the bottom plate 8c of the movable part 11c of the magnet system 6c is mounted to an annular outer holder 14a of the spring arrangement 13a. Beneficially, the connecting area between the bottom plate 8c and the annular outer holder 14a is comparably large in this embodiment because the annular outer holder 14a extends beyond the coil arrangement 3b.

[0095] Finally, the electromagnetic actuator 1c comprises a ring cover 21 protecting the inner parts of the electromagnetic actuator 1c. Again, an air gap a between the movable part 11c of the magnet system 6c and the center connector 16b is smaller than an air gap b between the movable part 11c of the magnet system 6c and the annular coil arrangement 3b, wherein the gaps a and b are each measured in a direction perpendicular to the actuator axis A. The advantages disclosed in the context of the electromagnetic actuator 1a apply equally.

[0096] The electromagnetic actuator 1c together with the display 2 forms an output device 20c for both audio and video data again.

[0097] Although it is advantageous if the annular coil arrangement 3a, 3b is fixedly arranged relative to the display 2 and the magnet system 6a . . . 6c partly or as a whole is movably arranged relative to the display 2, it is also imaginable that the magnet system 6a . . . 6c is fixedly arranged relative to the display 2 and the coil arrangement 3a, 3b is movably arranged relative to the display 2.

[0098] FIG. 5 shows another example of an electromagnetic actuator 1d, which is similar to the electromagnetic actuator 1a of FIG. 2. In contrast, the top plate 7d, the bottom plate 8d and the center magnet 9d, which form the movable part 11d of the magnet system 6d, are connected to the center connector 16b. In detail, a center holder 15a of a first spring arrangement 13a is mounted to the center connector 16b at a first position, and a center holder 15a of a second spring arrangement 13a is mounted to the center connector 16b at a second position at a distance from the center holder 15a of the first spring arrangement 13a. Thus, the center connector 16b is movably arranged relative to the display 2. The electromagnetic actuator 1d together with the display 2 forms an output device 20d for both audio and video data again.

[0099] In this example, the fixed part of the magnet system 6d, which is the outer ring 10d here, is connected to the annular outer holders 14a of the first spring arrangement 13a and the second spring arrangement 13a.

[0100] Although the use of a first spring arrangement 13a and a second spring arrangement 13a is beneficial, the center connector 16b can be connected only to a single spring arrangement 13a, 13a, too. In this case, either the first spring arrangement 13a or the second spring arrangement 13a may be used to hang up the center connector 16b. The same counts for the annular outer holders 14a. In case that just a single spring arrangement 13a, 13a is used, the outer ring 10d is either connected to the first spring arrangement 13a or to the second spring arrangement 13a.

[0101] In the embodiment of FIG. 5, the coil arrangement 3c touches the outer ring 10d or is connected thereto. In this way, a collision of the movable part 11d of the magnet system 6d does not cause a substantial damage of the coil arrangement 3c, which is supported by the outer ring 10d in lateral direction. In principle, it is sufficient if the coil arrangement 3c touches the outer ring 10d for the aforementioned supporting function. Also, a small (and unavoidable) gap between the coil arrangement 3c and the outer ring 10d does not substantially deteriorate said supporting function. However, to avoid any air gap between the coil arrangement 3c and the outer ring 10d, the coil arrangement 3c can be connected to the outer ring 10d, e.g. by means of an adhesive. Another advantage of this embodiment is that the magnetic gap between the coil arrangement 3c and the outer ring 10d is zero or almost zero. Thus, in total there is just a single magnetic gap between a coil 4a, 4b and the magnet system 6d. In that, the electromagnetic actuator 1d is very efficient. Another advantage of connecting the coil arrangement 3c to said outer ring 10d is the improved heat dissipation and temperature averaging. Heat generated within the coil arrangement 3c caused by the current flowing through the same can flow into the outer ring 10d thus improving heat dissipation because of the enlarged (outer) surface on the one hand and also averaging the temperature within the coil arrangement 3c because of the higher thermal mass on the other hand. The embodiment of FIG. 5 moreover benefits from the voice coils 4a, 4b being spaced from one another because the enlarged surface of the coil arrangement 3c in comparison to connected voice coils 4a, 4b improves heat dissipation as well.

[0102] One should also note that the voice coils 4a and 4b of the coil arrangement 3c are located at an axial distance from one another what provides more design freedom in terms of the height of the top plate 7d, the bottom plate 8d and the center magnet 9d in relation to the height of the voice coils 4a and 4b. Nevertheless, also stacked (interconnected) voice coils 4a and 4b can be used in the electromagnetic actuator 1d shown in FIG. 5.

[0103] FIG. 6 shows another embodiment of an electromagnetic actuator 1e, which is similar to the electromagnetic actuator 1d of FIG. 5. In contrast, no center connector 16b is used. Instead, the connecting sections 26 of the springs 12g of a first spring arrangement 13g are mounted to the top plate 7e, and the connecting sections 26 of the springs 12g of a second spring arrangement 13g are mounted to the bottom plate 8e. Again, the top plate 7e, the bottom plate 8e and the center magnet 9e form the movable part 11e of the magnet system 6e, and the outer ring 10e forms the fixed part of the magnet system 6e. The electromagnetic actuator 1e together with the display 2 forms an output device 20e for both audio and video data again.

[0104] Like the electromagnetic actuator 1c of FIG. 4, the coil arrangement 3b of the electromagnetic actuator 1e comprises just a single voice coil 4, which touches the outer ring 10e or is connected thereto for the same reasons presented in context with the electromagnetic actuator 1d of FIG. 5. For improved safety, an air gap a between the movable part 11e of the magnet system 6e and the fixed part of the magnet system 6e, which is the outer ring 10e here, is smaller than an air gap b between the movable part 11e of the magnet system 6e and the annular coil arrangement 3b, each measured in a direction perpendicular to the actuator axis A. So, the movable part 11e of the magnet system 6e usually cannot collide with the coil arrangement 3b. But even if it does, the coil arrangement 3b is supported by the outer ring 10e.

[0105] The use of both measures is beneficial. However, it is also possible only to use either the supporting function of the outer ring 10e or the aforementioned condition for the gaps a and b.

[0106] Moving now to the example of FIG. 7, the springs 12a are symmetrically shaped around the actuator axis A, and the springs 12a are spirally and arc shaped there. In particular, the springs 12a in the example of FIG. 7 are symmetrically shaped only around the actuator axis A (and not about an axis, which is perpendicular to the actuator axis A). By these measures, a comparably large spring length in a relatively small radial room can be obtained.

[0107] FIG. 8 shows another spring arrangement 13b with springs 12b, which are arranged between an annular outer holder 14b and a center holder 15b. The springs 12b are symmetrically shaped only around the actuator axis A and are spirally shaped, too.

[0108] FIG. 9 shows an alternative embodiment of a spring arrangement 13c with springs 12c, which are arranged between an annular outer holder 14c and a center holder 15c. The springs 12c are symmetrically shaped only around the actuator axis A, too, but are shaped like a meander and thus can be made very long and very soft within a small radial room, too.

[0109] FIGS. 10 to 11 show spring arrangements 13d . . . 13f with springs 12d . . . 12f, which are shaped like a meander, but which are symmetrically shaped around an axis perpendicular to the actuator axis A. In detail, the springs 12d . . . 12f are symmetrical around a vertical axis and around a horizontal axis crossing the actuator axis A. By these measures, a rotation between the annular coil arrangement 3a . . . 3c and the magnet system 6a . . . 6e is hindered so that they do not collide when the electromagnetic actuator 1a . . . 1e is excursed.

[0110] FIGS. 10 and 11 show embodiments with center holders 15d, 15e and annular outer holders 14d, 14e, whereas FIG. 12 shows an embodiment with a center holder 15f and distinct outer holders 22 at the end of the springs 12f.

[0111] FIGS. 13 and 14 show embodiments of spring arrangements 13g and 13g, which are a bit different to those used for the other examples. In detail, the spring arrangements 13g and 13g each comprise a combined holder 23 with an annular section 24 and an additional center section 25 and the plurality of springs 12g, which extend from the center section 25 and have a connecting section 26 at their extending ends inside of the annular section 24.

[0112] In more detail, the annular section 24 of the combined holder 23 and the connecting sections 26 of the springs 12g are arranged in different planes in an idle position of a movable part 11e of the magnet system 6e (see FIG. 6). In particular, the connecting sections 26 of the springs 12g are connected to the movable part 11e of the magnet system 6e, whereas the annular section 24 of the combined holder 23 is located more outwards. For this reason, basically the complete free space between the annular section 24 of the combined holder 23 and the connecting sections 26 of the springs 12g can be used for a movement of the movable part 11e of the magnet system 6e.

[0113] The plurality of springs 12g can also be preloaded in an idle position of a movable part of the electromagnetic actuator le. In this way, manufacturing of the electromagnetic actuator 1e can be made easier because the springs 12g need not to be bent before assembly of the electromagnetic actuator 1e. Instead, they are moved out of the plane of the annular section 24 of the combined holder 23, when the electromagnetic actuator 1e is assembled and they keep their preloaded state in the idle position of the movable part of the finalized electromagnetic actuator 1e.

[0114] In this example, the first spring arrangement 13g and the second spring arrangement 13g are of identical shape, but turned by 90 to one another around the actuator axis A. In this way, a tilting movement of the movable part 11e of the magnet system 6e can be avoided or at least can be kept low. However, also different designs may be used for the first spring arrangement 13g and the second spring arrangement 13g, or identical designs at the same orientation may be used for the first spring arrangement 13g and the second spring arrangement 13g.

[0115] It should be noted that the above measures are not limited to the embodiment of FIGS. 13 and 14, but may also be applied to the spring arrangements 13a . . . 13f shown in FIGS. 7 to 12. Accordingly, the annular outer holders 14a . . . 14e and the center holders 15a . . . 15f can be arranged in different planes in an idle position of a movable part of the electromagnetic actuator 1a . . . 1d. Moreover, the plurality of springs 12a . . . 12e can be preloaded in an idle position of a movable part of the electromagnetic actuator 1a . . . 1d. In addition, the spring arrangements 13g, 13g can be used for the embodiments shown in FIGS. 1 to 5, and the spring arrangements 13a . . . 13f can be used for the embodiment shown in FIG. 6.

[0116] Furthermore, it should be noted that the examples depicted in the Figs. are not limited to a particular circular or polygonal shape of the electromagnetic actuators 1a . . . 1d and their parts. Instead, the shape of the electromagnetic actuators 1a . . . 1d in top view is interchangeable.

[0117] It should also be noted that the invention is not limited to the above-mentioned embodiments and exemplary working examples. Further developments, modifications and combinations are also within the scope of the patent claims and are placed in the possession of the person skilled in the art from the above disclosure. Accordingly, the techniques and structures described and illustrated herein should be understood to be illustrative and exemplary, and not limiting upon the scope of the present invention. The scope of the present invention is defined by the appended claims, including known equivalents and unforeseeable equivalents at the time of filing of this application. Although numerous embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure.

LIST OF REFERENCES

[0118] 1a . . . 1e electromagnetic actuator [0119] 2 plate like structure (display) [0120] 3a . . . 3c annular coil arrangement [0121] 4, 4a, 4b voice coil [0122] 5 glue layer [0123] 6a . . . 6e magnet system [0124] 7a . . . 7e top plate [0125] 8a . . . 8e bottom plate [0126] 9a . . . 9e center magnet [0127] 10a . . . 10e outer ring (fixed part of the magnet system) [0128] 11a . . . 11e movable part of the magnet system [0129] 12a . . . 12g spring [0130] 13a . . . 13g spring arrangement [0131] 14a . . . 14e annular outer holder [0132] 15a . . . 15f center holder [0133] 16a, 16b center connector [0134] 17 top mounting plate [0135] 18 bottom mounting plate [0136] 19 adhesive sheet/glue layer [0137] 20a . . . 20e output device [0138] 21 ring cover [0139] 22 distinct outer holder [0140] 23 combined holder [0141] 24 annular section of combined holder [0142] 25 center section of combined holder [0143] 26 connecting section of spring [0144] a, a air gap between the movable part of the magnet system and the center connector [0145] a air gap between the movable part of the magnet system and the outer ring [0146] b . . . b air gap between the movable part of the magnet system and the annular coil arrangement

[0147] A actuator axis [0148] B, B1, B2 magnetic field [0149] S sound emanating surface