SURGICAL INSTRUMENT

Abstract

An operation device for operating a tool of a surgical instrument. The operation device has an operation element that is pivotably supported between an initial position and a working position. The operation element is movably coupled with the tool by means of a coupling device comprising a coupling link or consisting of a coupling link. The coupling link is elastically deformable and effectuates a resetting torque due to the elastic deformation in case the operation element is deflected out of the initial position, wherein the resetting torque urges the operation element back in the initial position.

Claims

1. A surgical instrument comprising: a tool that is movably supported in a longitudinal direction in a guided manner; an operation element that is pivotably supported in order to be pivoted between an initial position and a working position; and a coupling device that establishes a movement coupling between the operation element and the tool, wherein the coupling device comprises a coupling link that is elastically deformable and that is elastically deformed in the working position of the operation element such that it effectuates a resetting torque in direction toward the initial position (onto the operation element.

2. The surgical instrument according to claim 1, wherein the coupling link forms a connecting rod.

3. The surgical instrument according to claim 1, wherein the coupling link is directly arranged on the operation element with a first end and/or wherein the coupling link is directly arranged on the tool or a connection part immovably arranged on the tool with a second end.

4. The surgical instrument according to claim 1, wherein the coupling link comprises a longitudinal leg and a transverse leg adjoining thereto that extends in a transverse direction orthogonal to the longitudinal direction.

5. The surgical instrument according to claim 1, wherein the coupling link comprises two longitudinal legs arranged with distance to each other that are connected with each other via a transverse leg.

6. The surgical instrument according to claim 5, wherein each longitudinal leg comprises a free leg end that are arranged offset with regard to each other.

7. The surgical instrument according to claim 5, wherein the longitudinal legs have different lengths.

8. The surgical instrument according to claim 5, wherein the longitudinal legs and the transverse leg are arranged in a common plane in the initial position of the operation element.

9. The surgical instrument according to claim 5, wherein the longitudinal legs include an angle different to zero in the working position of the operation element.

10. The surgical instrument according to claim 4, wherein the at least one longitudinal leg is elastically undeformed in the working position of the operation element compared with the initial position.

11. The surgical instrument according to claim 4, wherein the transverse leg is twisted around its extension direction in the working position of the operation element.

12. The surgical instrument according to claim 1, wherein the coupling link extends along a straight line between its both ends in the initial position of the operation element.

13. The surgical instrument according to claim 1, wherein the coupling link extends in a curved manner between its both ends in the working position of the operation element.

14. The surgical instrument according to claim 1, wherein in the working position of the operation element, the elastically deformed coupling link applies a force on at least one of the tool and a connection part connected with the tool in a direction orthogonal to the longitudinal direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Preferred embodiments of the inventive surgical instruments are derived from the dependent claims, the description and the drawings. In the following, preferred embodiments are explained in detail with reference to the attached drawings. The figures of the drawings show:

[0031] FIGS. 1 and 2 show a schematic side view of a surgical instrument, particularly an electrosurgical instrument respectively,

[0032] FIG. 3 shows an embodiment of an operation device of the surgical instrument in a schematic side view, wherein the operation element of the operation device is in an initial position and the coupling link of a coupling device is in a first condition,

[0033] FIG. 4 shows the operation device of FIG. 3 in a schematic side view, wherein the operation element is in a working position and a coupling link of a coupling device is in a second condition,

[0034] FIG. 5 shows an embodiment of a coupling link of the operation device of FIGS. 3 and 4 in a top view,

[0035] FIG. 6 shows a further embodiment of an operation device for the surgical instrument in a schematic side view, wherein the operation element of the operation device is in an initial position and the coupling link of a coupling device is in a first condition,

[0036] FIG. 7 shows the embodiment of the operation device of FIG. 6 in a schematic side view, wherein the operation element is in a working position and the coupling link of the coupling device is in a second condition,

[0037] FIG. 8 shows a perspective illustration of an embodiment of a coupling link of the operation device according to FIGS. 6 and 7,

[0038] FIG. 9 shows a further embodiment of the operation device for the surgical instrument in a schematic side view, wherein an operation element of the operation device is in an initial position and a coupling link of a coupling device is in a first condition,

[0039] FIG. 10 shows the operation element, a coupling link and a connection part of the operation device of FIG. 9 in a schematic individual illustration,

[0040] FIG. 11 shows the coupling link of the operation device according to FIGS. 9 and 10 in a schematic side view, wherein the coupling link is elastically deformed and is in its second condition,

[0041] FIG. 12 shows a further embodiment of an operation device for the surgical instrument in a schematic side view, wherein the operation element of the operation device is in an initial position and a coupling link of a coupling device is in a first condition,

[0042] FIG. 13 shows the embodiment of the operation device of FIG. 12 in a schematic side view, wherein the operation element is in a working position and a coupling link of a coupling device is in a second condition,

[0043] FIGS. 14 and 15 show a schematic basic illustration of a coupling link of the operation device according to FIGS. 12 and 13 in a top view respectively,

[0044] FIG. 16 shows a further embodiment of an operation device for the surgical instrument in a schematic side view, wherein an operation element of the operation device is in an initial position and a coupling link of a coupling device is in a first condition and

[0045] FIG. 17 shows the embodiment of the operation device of FIG. 16 and a schematic side view, wherein the operation element is in a working position and the coupling link of a coupling device is in a second condition.

DETAILED DESCRIPTION

[0046] Different embodiments of a surgical instrument 20 are illustrated schematically in FIGS. 1 and 2. As illustrated, the surgical instrument 20 can be configured as electrosurgical instrument. It can be a monopolar or bipolar electrosurgical instrument. The surgical instrument is particularly a reusable instrument. It has to be cleaned and sterilized after each use.

[0047] In the illustrated embodiments the surgical instrument 20 has two jaws 21, 22 that are pivotably supported at one another. Each jaw 21, 22 has a tissue contact surface 21a or 22a. The jaws 21, 22 can be pivoted toward or away from each other to clamp or release a biological tissue between the tissue contact surfaces 21a, 22a.

[0048] The surgical instrument 20 further comprises a tool 24. The tool 24 is movably supported in longitudinal direction L in a tool channel 23. For example, the tool 24 can be formed by a knife 25. The tool channel 23 can extend in a shank 26 adjoining the jaws 21, 22 (FIG. 1) and/or can extend in one of the jaws 21, 22 (FIG. 2).

[0049] The instrument 20 comprises a handling unit 27. By means of the handling unit 27 the jaws 21, 22 can be pivoted relative to each other and the tool 24 can be moved in longitudinal direction L. In electrosurgical instruments an electric voltage can be applied to the tissue contact surfaces 21a, 22a by means of the handling unit 27.

[0050] The tool 24 and according to the example, the knife 25 can be moved in longitudinal direction L between a retracted position E and an extended position A. For this the instrument 20 comprises an operation device 30. Different embodiments of the operation device 30 or components thereof are schematically illustrated in FIGS. 3-17.

[0051] The operation device 30 comprises an operation element 31 that is part of the handling unit 27 for operating the instrument 20. The operation element 31 can be configured as separate operation element of the handling unit 27 (FIG. 2) or can alternatively be formed by an operation element that also comprises one or more additional functions (FIG. 1).

[0052] The operation element 31 is pivotably supported around a pivot axis. In the embodiment the pivot axis extends in a transverse direction Q that is orientated orthogonal to the longitudinal direction L. The pivot axis is defined by a pivot joint 32 by means of which the operation element 31 is pivotably supported on a stationary or with regard to the housing of the instrument 20 immovably arranged part. The operation element 31 has two arms 33, 34 that extend originating from the pivot joint 32. The arms 33, 34 can extend in different and particularly opposite directions, as illustrated in the embodiment.

[0053] A first arm 33 serves for manual operation. A second arm 34 is movably coupled with the tool 24 via a coupling device 35.

[0054] The coupling device 35 comprises an elastically deformable coupling link 36. In the embodiment the coupling device 35 is formed by the coupling link 36. Additional parts for movement transmission can be omitted. According to the example, the coupling link 36 is arranged with a first end 37 on the operation element 31 and particularly the second arm 34. From the first end 37 the coupling link 36 extends to a second end 38 that is assigned to the tool 24 or a connection part 39 that is preferably immovably connected with the tool 24. In the embodiments illustrated here the second end 38 is arranged on the connection part 39. In modification thereto it could also be directly arranged on the tool 24.

[0055] Due to the movement coupling between the tool 24 and the operation element 31 by means of the coupling device 35, the pivot movement of the operation element 31 around the pivot axis or the pivot joint 32 can be transmitted in a movement of the tool 24 in longitudinal direction L, particularly in order to move the tool 24 between the retracted position E and the extended position A. If the tool 24 is in the retracted position E, the operation element 31 is in a initial position I (FIGS. 3, 6, 9, 12, 16). If the tool 24 is in the extended position A, the operation element 31 is in a working position W (FIGS. 4, 7, 13, 17).

[0056] In order to pivot the operation element 31 out of the initial position I in the working position W, an operator can apply an operating force FB on the first arm 33.

[0057] According to embodiments of the invention, the coupling link 36 is configured in an elastically deformable manner. In the preferred embodiments described here the coupling link 36 is integrally formed and thus does not comprise seams or joints. It can form a separate part from the operation element 31 (FIGS. 3-15) or can alternatively be integrally formed with the operation element 31. In addition or as an alternative, the coupling link 36 can be integrally formed with the connection part 39 (FIGS. 16 and 17). In modification to the embodiment illustrated in FIGS. 16 and 17, the coupling link 36 can also be integrally formed either only with the operation element 31 or only with the connection part 39 and apart therefrom arranged or attached as illustrated or explained with regard to the other embodiments.

[0058] In the preferred embodiments described here the coupling link 36 forms a connecting rod 42. The connecting rod 42 is configured to transmit the pivot movement of the second arm 34 in a linear movement in longitudinal direction L of the tool 24 or the connection part 39. According to the example, the first end 37 is thus arranged on the second arm 34 and thus pivotably supported around the pivot axis S or the pivot joint 32. The first end 37 of the coupling link 36 is arranged with distance to the pivot axis or the pivot joint 32. The second end 38 of the coupling link 36 is shiftably arranged in longitudinal direction L together with the tool 24 or the connection part 39. Thus, the coupling link 36 can also be denoted as connecting rod 42.

[0059] In the embodiment of the operation device 30 illustrated in FIGS. 3-5 the coupling link 36 comprises a first longitudinal leg 43 and a second longitudinal leg 44. The two longitudinal legs 43, 44 are arranged with distance in transverse direction Q relative to each other. On the second end 38 the two longitudinal legs 43, 44 are connected with each other by a transverse leg 45 extending in transverse direction Q and are, according to the example, integrally formed.

[0060] On the second end 37 the first longitudinal leg 43 comprises a first free leg end 46 and the second longitudinal leg 44 comprises a second free leg end 47. The free leg ends 46, 47 are bent or angled relative to the longitudinal legs 43, 44 and extend, according to the embodiment, substantially parallel to the transverse leg 45, i.e. in transverse direction Q. The first free leg end 46 and the second free leg end 47 are, according to the example, shorter than the transverse leg 45.

[0061] As particularly apparent from FIGS. 4 and 5, the free leg ends 46, 47 are arranged offset or with distance to each other in a projection plane that is orientated orthogonal to the transverse direction Q. In the embodiment this is achieved in that the first longitudinal leg 43 has a longer length from the transverse leg 45 to the first free leg end 46 than the second longitudinal leg 44 from the transverse leg 45 to the second free leg end 47.

[0062] The transverse leg 45 can extend in transverse direction Q through a through-hole extending through the connection part 39. Alternatively, the transverse leg 45 can also engage or can be latched in a groove on the connection part 39 and/or on the tool 24 that is open toward the top such that a releasable connection is established between the tool 24 and the coupling device 35. This can facilitate the assembly and/or replacement of the tool independent from the coupling device 35.

[0063] The two free leg ends 46, 47 can extend into a holding hole in the second arm 34. According to the example, the coupling link 36 is supported rotatably or in a hinged manner on the connection part 39 as well as on the second arm 34.

[0064] In the initial position I of the operation element 31 the coupling link 36 is in a first condition. In the first condition the coupling link can be elastically undeformed. In the working position W of the operation element 31 the coupling link 36 is in a second condition being elastically deformed compared with the first condition.

[0065] In the first condition of the coupling link 36 the two longitudinal legs 43, 44 and the transverse leg 45 extend in a common plane (FIG. 3). If the operation element 31 is pivoted out of its initial position I, the two longitudinal legs 43, 44 are inclined relative to each other with view in a projection plane that is orientated orthogonal to the transverse direction Q. This can be traced to the fact that the support locations of the two free leg ends 46, 47 outside the initial position I are no longer located in a common plane together with the transverse leg 45. The inclination of the two longitudinal legs 43, 44 relative to one another outside of the initial position I results in that the transverse leg 45 is twisted and thus a twisting torque MT in circumferential direction around the transverse leg 45 is created that urges the too longitudinal legs 43, 44 to take the position in the common plane with the transverse leg 45. In doing so, concurrently a resetting torque MR is applied on the operation element 31 that urges the operation element 31 back into its initial position I.

[0066] According to the example, in the working position W of the operation element 31 the two free leg ends 46, 47 are arranged on the same side relative to a reference plane B that extends orthogonal to the longitudinal direction L along the pivot axis of the operation element 31 (FIG. 4). Particularly, the two free leg ends 46, 47 are arranged on the one side and the second end 38 of the coupling link 36 is arranged on the other side of the reference plane B in the working position W of the operation element 31.

[0067] Thus, the coupling link 36 does not only form a mechanical element by means of which the movement coupling between the operation element 31 and the tool 24 is established, but concurrently also a resetting device, whereby the operation element 31 is urged back in its initial position I. Without application of an operating force FB on the operation element 31 it takes the initial position I and the tool 24, according to the example the knife 25, is pulled back in the retracted position E. Additional elastically deformable resetting components, particularly helical springs, can be omitted. In doing so, the construction of the coupling device 35 is very simple. The number of required components in the coupling device 35 or the operation device 30 is reduced. The simple construction also facilitates the cleaning. Particularly by avoiding helical springs in which the windings can tightly abut against each other, the cleaning or sterilization is remarkably simplified.

[0068] A further optional configuration possibility of the operation device 30 is highly schematically illustrated in FIGS. 3 and 4. According to the example, the coupling link 36 creates a force component in a direction orthogonal to the longitudinal direction L and orthogonal to the transverse direction Q that is denoted as pressing force FA. This force component is created, if in the embodiment according to FIGS. 3 and 4 the transverse leg 45 is twisted, i.e. at least outside of the initial position I. The pressing force FA can be used in order to press a latch projection 48 on the tool 24 and/or on the connection part 39 in an assigned latch recess 49 adjacent to the tool channel 23. It is also possible that multiple latch projections 48 and/or multiple latch recesses 49 are provided. In doing so, the tool 24 can be latched during the movement in longitudinal direction L in at least one position. A feedback about the actually achieved position of the tool 24 relative to the tool channel 23 or relative to the jaws 21, 22 can be provided to an operator, due to the latching. In FIG. 4 the latching is illustrated in the extended position A of the tool 24, wherein the latched position can also be predefined in at least one other arbitrarily defined position of the tool 24 relative to the tool channel 23.

[0069] In FIGS. 6-8 a further embodiment of the operation device 30 or the coupling link 36 is illustrated. Apart from the embodiment of the coupling link 36, this embodiment of the operation device 30 can correspond to the embodiment described based on FIGS. 3-5 above. Thus, reference is made to the above description.

[0070] The modified coupling link 36 is particularly apparent from FIG. 8. Analog to the embodiment according to FIG. 5, the coupling link 36 comprises a bracket-shaped form having a first longitudinal leg 43, a second longitudinal leg 44 and a transverse leg 45 at the second end 38. The opposite first end 37 of the coupling link 36 is configured differently than in the embodiment according to FIG. 5. Both longitudinal legs 43, 44 have preferably the same length and the free leg ends 46, 47 extending in transverse direction Q are preferably aligned along a common straight line in transverse direction Q. Each longitudinal leg 43, 44 has a leg section 43a, 44a extending along a straight line originating from the transverse leg 45 and a curved leg section 43b, 44b directly adjoining the straight leg section 43a, 44a. In a rest condition that is not subject to a force, the curved leg section 43b, 44b comprises an arc-shaped and particularly a circular arc-shaped extension. In the embodiment illustrated in FIG. 8, the curved leg section 43b, 44b comprises at least one complete winding and according to the example multiple windings. The wound or curved leg section 43b, 44b establishes a connection between the respective straight leg section 43a, 44a and the respective leg end 46, 47. According to FIG. 8, the coupling link 36 is integrally formed and can be, for example made by bending a wire. As apparent from FIG. 8, the free leg ends 46, 47 are arranged closer to the transverse leg 45 than the wound or curved leg sections 43b, 44b.

[0071] Analog to the embodiment according to FIGS. 3-5, the transverse leg 45 extends through a through-hole in the connection part 39 or alternatively in the tool 24. The free leg ends 46, 47 respectively engage a recess or depression on the second arm 34.

[0072] If now the operation element is moved out of the initial position I by application of an operating force FB, the tension in the respective wound or curved leg section 43b, 44b is changed and the coupling link 36 tends to take the condition that it has in the initial position I. In this manner a resetting torque MR around the pivot axis or the pivot joint 32 is created.

[0073] In the embodiment according to FIGS. 3-5 as well as in the embodiment according to FIGS. 6-8, the longitudinal legs 43, 44 or the straight leg sections 43a, 44a are bending-resistant against a bending transverse to their extension direction. In doing so, a force applied externally on the tool 24 is very well supported via the coupling link 36 on the operation element 31.

[0074] Another embodiment of the operation device 30 is apparent from FIGS. 9-11 that is similar to the embodiment according to FIGS. 3-5 such that reference can be made to the description of these figures. The substantial difference in this embodiment is that only one longitudinal leg 43 is provided that connects the transverse leg 45 on the second end 38 with the first end 37. The second longitudinal leg 44 only extends originating from the transverse leg 45 in an area of the second end 38 and serves there to arrange the coupling link 36 on the tool 24 and according to the example on the connection part 39 in a torque-proof manner relative to the transverse leg 45. For this the short second longitudinal leg 44 can be arranged in a groove 54 adjoining a through-hole 53 for the transverse leg 45, as an example. The transverse leg 45 remains twistable around an extension direction, if the first longitudinal leg 43 is moved or pivoted relative to the second longitudinal leg 44 that is arranged in a torque-proof manner, due to the operation of the operation element 31.

[0075] The first end 37 of the coupling link 36 is fixed on the operation element 31. For example, the coupling link 36 can be bent multiple times on the first end 37 such that two holding legs 55 are formed that extend in transverse direction Q and that are connected by means of a connecting leg 56. In the area between the two holding legs 55 an interstice 57 is limited in which the second arm 34 may extend. The holding legs 55 and the connecting leg 56 embrace the second arm 34 of the operation element 31 so to speak. For the attachment a holding groove 58 can be provided in the second arm 34 in which at least the holding legs 55 and/or the connecting leg 56 is/are arranged.

[0076] In FIG. 11 the force and torque application of the coupling link 36 is highly schematically illustrated, if the operation element 31 is deflected from its initial position I. Due to the pivot movement of the two longitudinal legs 43, 44 relative to each other around the transverse leg 45, a twisting torque MT is created at the transverse leg 45. In addition, the first longitudinal leg 43 can be bent out of its straight extension. Due to these forces and torques, a resetting torque MR is created around the pivot axis S or the pivot joint 32 that urges the operation element 31 back in its initial position I.

[0077] In the embodiment of the operation device 30 illustrated in FIGS. 12 and 13 the configuration corresponds to the embodiments described above apart from the configuration of the coupling link 36. The coupling link 36 is configured in this embodiment such that it is bent out of its initial extension in the initial position I of the operation element 31 and thereby creates the resetting torque MR.

[0078] In FIGS. 14 and 15 embodiments for the coupling link 36 are illustrated. The coupling link 36 can have a form of a leaf spring, as schematically illustrated in FIG. 14. The coupling link 36 is attached at the first end 37 on the second arm 34 and at the second end 38 on the tool 24 or on the connection part 39 in an orientation that it takes in the initial position I. In doing so, a bending of the coupling link 36 is created during pivot movement of the operation element 31. The coupling link 36 tends to take its initial position and in this manner creates the resetting torque MR.

[0079] For attachment of the coupling link 36 it can have at least one through-opening and/or at least one recess that is open in an outward direction at the first end 37 or at the second end 38. The portions limiting the recess can be arranged in grooves or recesses, e.g. on the second arm 34. By means of the through-opening the coupling link 36 can be overmolded with the material of the connection part 39 at the second end 38, for example. The connection at the first end 37 and at the second end 38 can be form-fit and/or force-fit and/or a substance bond and/or an adhesive bond. Overmolding of the coupling link 36 is preferably possible on one of the two ends 37 or 38 or alternatively also on both ends 37 and 38.

[0080] Instead of a leaf-spring-like coupling link 36, as illustrated in FIG. 14, the coupling link 36 can also be formed by a wire element or wire bracket (FIG. 15). It consists particularly of a longitudinal leg 43 that extends between the first end 37 and the second end 38 and that transitions at the first end 37 as well as at the second end 38 in an end leg 59 extending orthogonal to the longitudinal leg 43. The two end legs 59 extend preferably parallel to one another and particularly in a plane that is orientated orthogonal to the transverse direction. The two end legs 59 can be inserted in respective holes or recesses on the second arm 34 or on the tool 24 or the connection part 39 respectively and can be attached there as necessary, e.g. by means of an adhesive bond. During deflection of the operation element 31 out of its initial position I the longitudinal leg 43 is bent out of its initial extension, because the end legs 59 at the two ends 37, 38 are held in place in their orientation relative to the second arm 34 on one side and relative to the tool 24 or the connection part 39 on the other side.

[0081] A further embodiment of the operation device 30 is illustrated in FIGS. 16 and 17. While the coupling link 36 is a separate component in the embodiments described above, the coupling link 36 is formed integrally with the operation element 31 and/or with the connection part 39 in the embodiments according to FIGS. 16 and 17. In the illustrated embodiment the operation element 31, the coupling link 36 and the connection part 39 are one single integral component that consists of plastic, for example, and can be particularly formed as injection mold part. If the coupling link 36 is integrally formed only with the operation element 31 or only with the connection part 39, it can be connected at the respective other end 37 or 38 in a force-fit manner and/or form-fit manner and/or by substance bond and/or by adhesive bond with the operation element 31 or the connection part 39 respectively.

[0082] Analog to the embodiments according to FIGS. 12-15, the coupling link 36 forms a bending spring and can thus have the form of a leaf spring similar to the embodiment according to FIG. 14 or a web-shaped form similar to the straight longitudinal leg 43 according to FIG. 15. The function corresponds to the embodiment according to FIG. 12 or 13.

[0083] FIG. 16 also shows a further optional possibility. In addition to effectuating the resetting torque MR by a deformation of the coupling link 36, the resetting torque MR can also be at least partly created by a deformation of the second arm 34 of the operation element 31. In order to allow this deformation, the second arm 34 can have a respective deformable configuration. In FIG. 16 this is by way of example illustrated by through-opening 60 that extends through the second arm. Adjacent to the through-opening 60 the second arm 34 comprises web-shaped sections 61 that are sufficiently small dimensioned in cross-section. In doing so, a bending or deforming of the web-shaped sections 61 and/or a movement of the web-shaped sections toward each other is allowed. If this area of the second arm 34 is deformed (outside of the initial position I), the second arm 34 tends to take its undeformed initial shape and thus creates at least a component of the resetting torque MR.

[0084] In another modification of the operation device 30 it would be possible to configure the coupling link 36 undeformably stiff with regard to the applied forces and to only configure at least a part of the second arm 34 in a deformable manner in order to create the resetting torque MR.

[0085] In all of the bracket-shaped configurations of the coupling link, particularly in the embodiments according to FIGS. 3-11 and 15, the coupling link 36 can be formed by a wire bent part. The wire can have a circular cross-section. Preferably the wire consists of a metallic alloy.

[0086] The deformability of at least a part of the second arm 34 and/or the latch means 48, 49 explained in connection with FIGS. 3 and 4 can be provided in all of the embodiments.

[0087] In all of the embodiments a releasable connection between the tool 24 and the coupling device 35 can be provided indirectly via the connection part 39 or also directly, e.g. a force-fit and/or form-fit connection, preferably a latch connection.

[0088] Embodiments of the invention include an operation device 30 for operating a tool 24 of a surgical instrument 20. The operation device 30 has an operation element 31 that is pivotably supported between an initial position I and a working position W. The operation element 31 is movably coupled with the tool 24 by means of a coupling device 35 comprising a coupling link 36 or consisting of a coupling link 36. The coupling link 36 is elastically deformable and effectuates a resetting torque MR due to the elastic deformation in case the operation element 31 is deflected out of the initial position I, wherein the resetting torque MR urges the operation element 31 back in the initial position I. Additional spring elastic resetting elements can thus be omitted.