Method, tool, and tool assembly for introducing an electrical conductor into a foam cladding of a steering wheel frame, and vehicle steering wheel

Abstract

A method of introducing an electric conductor (22), especially a heating wire, into foam padding (20) of a steering wheel skeleton (18) includes introducing at least one cut (26) into the foam padding (20) by means of a cutting tool (34). At the same time the conductor is introduced into the produced cut (26). Moreover a tool as well as a tool assembly for implementing the method and a vehicle steering wheel are provided.

Claims

1. A method of introducing an electric conductor (22) into foam padding (20) of a steering wheel skeleton (18) comprising the following steps of: introducing cut (26) into the foam padding (20) by means of a cutting tool (34) during a first method step, the foam padding (20) having an initial shape, and simultaneously introducing the electric conductor (22) into the cut (26) during a second method step at a location that is offset from a point where the cut is being introduced, the offset of the location being a distance where the electrical conductor is introduced into the cut before the cut foam padding returns to the initial shape.

2. The method according to claim 1 wherein the cut (26) automatically closes, is closed, and/or covered after inserting the conductor (22).

3. The method according to claim 1, wherein after introducing the conductor (22) the foam padding (20) is covered by further foam padding or wrapping.

4. The method according to claim 1, wherein after being introduced into the cut (26), the conductor (22) is integrally connected to the foam padding (20).

5. The method according to claim 1, wherein the cut (26) substantially extends in the circumferential direction around the steering wheel hub (12) along the steering wheel rim (14).

6. The method according to claim 1, wherein the cut (26) has a depth of at least 0.1 mm.

7. The method according to claim 1, wherein the cut (26) is guided along the steering wheel rim (14) in plural revolutions about the steering wheel hub (12) so that a substantially spiraled cut (26) is produced and the conductor (22) extends in plural windings and/or that in the case of intersecting cuts the cutting depths are different in the point of intersection.

8. The method according to claim 1, wherein the cut (26) and the introduction of the conductor (22) are implemented by means of a tool (32) being mounted on a programmable industrial robot that can move the tool (32) three-dimensionally in space.

9. The method according to claim 8, wherein the steering wheel skeleton (18) is held on a second programmable industrial robot that can move the steering wheel skeleton (18) three-dimensionally in space.

10. The method according to claim 1, wherein a tool (32) implements the steps of introducing cut and simultaneously introducing the electric conductor, the tool including a cutting tool (34) having a cutting means (36) which includes a cutting edge (38) pointing to the cutting direction (S) as well as an inserting tool (40) for the conductor (22), wherein the cutting tool (34) and the inserting tool (40) are coupled to each other.

11. The method according to claim 10, wherein the width (b) of the inserting tool (40) perpendicularly to the cutting direction (S) is smaller than or equal to the width (B) of the cutting means (36).

12. The method according to claim 10 wherein the inserting tool (40) includes an inserting passage (42) through which the conductor (22) can be guided, the inserting passage (42) ending in the cutting direction (S) behind the cutting means (36) of the cutting tool (34).

13. The method according to claim 10, wherein the cutting tool (34) protrudes perpendicularly to the cutting direction (S) at a precutting depth from the inserting tool (40), the precutting depth ranging from 0.1 mm to 2 mm.

14. The method according to claim 10, wherein the inserting tool (40) includes a conically tapering guide within an inserting aid (58) of the electric conductor (22).

15. The method according to claim 10, wherein the cutting means (36) is a blade and/or an ultrasonic cutting tool.

16. The method according to claim 10, wherein a pressing device (62) is provided which is adapted to load the tool (32) with a defined force against the steering wheel skeleton (18), the pressing device being configured to compensate for tolerances in the steering wheel skeleton.

17. The method according to claim 10, wherein the cutting tool (34) comprises a separate guide means (64) for adjusting the cutting depth.

18. The method according to claim 17, wherein the guide means (64) comprises a guide shoe adapted to contact the steering wheel skeleton (18), wherein the cutting means (36) protrudes from said guide shoe (65) into the steering wheel skeleton.

19. The method according to claim 18, wherein the guide means (64) comprises an actuating mechanism (67) which is adapted to move the guide shoe (65) relative to the cutting means (36).

20. The method according to claim 1 wherein a positioning means (66) for the electric conductor (22) is provided which may be positioned on the steering wheel skeleton (18) and includes a seat (78) for an electric connection (24) arranged on the steering wheel skeleton (18) for the electric conductor (22) as well as retaining elements (72a, 72b) for the start (22a) and the end (22c) of the electric conductor (22).

21. The method according to claim 20, wherein the positioning means (66) includes guide elements (74, 76) for the electric conductor (22).

22. The method according to claim 20 wherein the positioning means (66) includes a fastening device (68) and positioning aids (70) for fixing the positioning means (66) to the steering wheel skeleton (18).

23. The method according to claim 1, wherein the steering wheel skeleton (18) includes a steering wheel rim (14) foam-padded by the foam padding (20) the electric conductor (22) being located in the cut that is introduced to the foam padding (20).

24. The method according to claim 23, wherein the conductor is permanently fixed in the foam padding (20).

25. The method according to claim 23 wherein the cut (26) extends substantially in the circumferential direction around the steering wheel hub (12) along the steering wheel rim.

26. The method according to claim 23, wherein a first layer of windings of the electric conductor (22) is laid at a first depth (t.sub.1) and a second layer of windings of the electric conductor (22) is laid at a second depth (t.sub.2).

27. The method according to claim 23, wherein the cut (26) includes points of intersection of portions of the cut, wherein in the area of the points of intersection one of the intersecting portions of the cut (26) has a larger depth (t) and in this portion of the cut (26) the electric conductor is inserted more deeply than in the overlying portion.

28. The method according to claim 23, wherein the foam padding (20) is covered at least in the area of the cut (26) by further foam padding or wrapping.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features are found in the following description in connection with the enclosed drawings in which:

(2) FIG. 1 shows a perspective view of a vehicle steering wheel according to the invention manufactured according to the method of the invention including an electric conductor introduced to the foam padding,

(3) FIGS. 2a and 2b show detailed views of the vehicle steering wheel of FIG. 1 in the area of a steering wheel spoke,

(4) FIGS. 3a and b show further detailed views of the vehicle steering wheel of FIG. 1 in the area of a recess for receiving a steering wheel wrapping,

(5) FIG. 4 shows a radial section across the steering wheel rim of the vehicle steering wheel of FIG. 1,

(6) FIG. 5 shows a radial section across a second embodiment of a steering wheel rim of a vehicle steering wheel,

(7) FIG. 6 shows a detailed view of the vehicle steering wheel of FIG. 5 in a section.

(8) FIGS. 7a and 7b shows a side view as well as a sectional view across a tool according to the invention for introducing an electric conductor to the vehicle steering wheel of FIG. 1,

(9) FIGS. 8a to 8c show different views and orientations of a second embodiment of a tool according to the invention for introducing an electric conductor,

(10) FIGS. 9a to 9c show different views and orientations of a third embodiment of a tool according to the invention for introducing an electric conductor,

(11) FIGS. 10a to 10c show different views and orientations of a fourth embodiment of a tool according to the invention for introducing an electric conductor,

(12) FIGS. 11a to 11c show different views and orientations of a fifth embodiment of a tool according to the invention for introducing an electric conductor,

(13) FIGS. 12a to 12c show different views and orientations of a sixth embodiment of a tool according to the invention for introducing an electric conductor,

(14) FIGS. 13a to 13c show different views and orientations of a seventh embodiment of a tool according to the invention for introducing an electric conductor,

(15) FIGS. 14a to 14c show different views and orientations of an eighth embodiment of a tool according to the invention for introducing an electric conductor,

(16) FIG. 15 shows a detailed view of an inserting aid for a tool according to the invention,

(17) FIGS. 16a to 16b show different views of a positioning assembly for a tool assembly according to the invention for introducing an electric conductor to the vehicle steering wheel of FIG. 1 according to the method of the invention,

(18) FIG. 17 shows a view of a tool assembly according to the invention, and

(19) FIG. 18 shows a view of a positioning means of a tool assembly according to the invention.

DESCRIPTION

(20) FIG. 1 illustrates a vehicle steering wheel 10 comprising a steering wheel hub 12, a steering wheel rim 14 and plural spokes 16 interconnecting the steering wheel hub 12 and the steering wheel rim 14. As is evident from FIGS. 2a and 2b as well as 3a and 3b, the vehicle steering wheel 10 includes a steering wheel skeleton 18 made of hard material (preferably a light metal alloy) as well as foam padding 20 which is made of soft elastic material and completely encloses the steering wheel skeleton 18 least in the area of the steering wheel rim 14 on the outside.

(21) In the foam padding 20 one or more electric conductors 22 are provided which are connected to the power network of the vehicle by a connection 24 arranged at a spoke. The electric conductors 22 form heating wires which are heated by current supply and heat the vehicle steering wheel 10, especially the steering wheel rim 14.

(22) As is evident in FIG. 1, the outs 26 are circularly guided around the steering wheel hub 12 along the steering wheel rim 14. There may be provided plural circular cuts 26 extending substantially in parallel to each other or one or more of said cuts can also be guided in plural revolutions around the steering wheel hub 12 along the steering wheel rim at a small distance from each other so that a substantially spiraled cut 26 is produced. When the conductor 22 is inserted into said spiraled cut 26, it extends in a plurality of winding. As a matter of course, it is advantageous when cuts are closer to each other at the positions where a higher thermal output is required, it is possible by the method described in more detail hereinafter to adapt the thermal output very flexibly to the circumstances by quite easily producing closer and more cuts or closer revolutions of a spiraled cut. The corresponding tool itself only has to be reprogrammed so as to carry out a different cut.

(23) The conductors 22 are laid substantially at a constant depth t of about 0.1 mm to 3 mm in the foam padding 20 (cf. also FIG. 4).

(24) As is evident in FIGS. 3a and 3b, the conductors 22 are inserted slightly deeper merely in the area of recesses 25 for a wrapping (for example a decorating member) of the vehicle steering wheel 10.

(25) As can be seen from FIG. 4, one or more cuts 28 guided substantially radially inwardly from the surface 28 of the foam padding 20 are introduced to the foam padding 20. The conductors 22 are inserted in said cuts 26.

(26) The material of the foam padding 20 is elastic so that, after inserting the conductors 22 and, resp., introducing the cut 26, the cut edges 30 of the cut 26 spring back into a home position in which the out edges 30 are adjacent to each other. The conductors 22 are thus reliably retained in the position within the foam padding 20 and are protected against falling out.

(27) In FIG. 5 a radial cut is shown in a second embodiment of a vehicle steering wheel 10. In this embodiment cuts 26 having two different depths t.sub.1 and t.sub.2 are provided. The electric conductor 22 thus is laid at two different depths within the foam padding in the steering wheel skeleton 18. In this embodiment initially ail windings of a first layer having the depth t.sub.1 can be laid and subsequently the windings of a second layer having the depth t.sub.2 or else alternately in sections of different depths can be laid.

(28) In FIG. 6, the laying of the electric conductor 22 in the area of the connection 24 is illustrated for an embodiment comprising one conductor 22. The conductor is fixed to the connection 24 by a first end 22a. Subsequently, the windings of the first layer are laid until the electric conductor 22 including an intermediate portion 22b is deflected in loop shape in the area of the connection 24 and the windings of the second layer are laid. Subsequently, the end 22c of the electric conductor 22 is connected to the connection 24 after laying the windings of the second layer.

(29) As an alternative, also two conductors 22 may be provided, a first conductor 28 being laid in the cuts having the first depth t.sub.1 and a second conductor 26 being laid in the cuts having the second depth t.sub.2.

(30) FIGS. 7a and 7b Illustrate a tool 32 according to the invention for facilitating introduction of such conductor 22 into foam padding 20 of a steering wheel skeleton 18.

(31) The tool 32 includes a cutting tool 34 having a cutting means 38 which is formed by a blade in this embodiment. The cutting means 36 includes a cutting edge 38 pointing to the cutting direction S which is V-shaped having a wedge angle y of approx. 30, as can be inferred from FIG. 6b. The outing means 36 broadens starting from the cutting edge 38 against the cutting direction S up to a width B.

(32) Directly adjacent to the rear side of the cutting edge 38 is provided an inserting tool 40 having an inserting passage 42 defined by a small tube 41. The inserting passage 42 is formed so that a conductor 22 can be pushed through the same. A first end 44 of the inserting passage 42 is arranged so that it is located outside the foam padding 20 when a cut 26 is introduced to the foam padding 20. The second opposite end 46 opens in the cutting direction S just behind the cutting means 38.

(33) In this embodiment the cutting angle at which the cutting edge 38 is inclined relative to the cutting direction S is about 60. The angle at which the inserting passage 42 extends relative to the cutting direction S amounts to approx. 70.

(34) For introducing a conductor 22 to the foam padding 20 of a steering wheel skeleton 18 the tool 32 is attached to the surface 28 of the foam padding 20 and the cutting edge 38 is pressed into the foam padding 20 until the desired cutting depth t of 0.1 mm to 3 mm is reached.

(35) After that, the tool 32 is moved in the cutting direction S through the foam padding 20, thus causing a cut 26 to be introduced to the foam padding 20. At the same time, the conductor 22 is introduced through the inserting passage 42 into the out 26 by an active feeding system 48 provided on the tool 32. Preferably the conductor 22 is wound off a supply roller.

(36) Hence introducing the cut 26 and introducing or, resp., inserting the conductor 22 are carried out simultaneously so that the conductor 22 is inserted before the cutting edges 30 of the cut 26 can join each other again.

(37) Since the cut 26 closes directly behind the tool 32, viz. after inserting the conductor 22, the conductor 22 is safely retained within the cut 26.

(38) In addition, the cut 26 may also be closed after introducing the conductor 22, for example by gluing the cutting edges 30 and/or by additional covering. The cut 28 be covered, for example, by further foam padding or wrapping, e.g. made of leather or artificial leather or a decorating element.

(39) Since the conductor 22 is guided via the inserting passage 42 into the out 26, it does not contact the cutting edges 30 so that, on the one band, low-resistance introduction of the conductor 22 is performed and, on the other hand, damage of the cutting edges 30 or the foam padding 20 by the conductor 22 is excluded.

(40) In the embodiment as described herein the width b of the inserting tool 40 to the cutting direction S has been chosen to be smaller than the width B of the cutting means 36 so that no additional resistance is caused by the inserting tool 40 upon introducing the cut 28.

(41) The introduction in the longitudinal direction of the steering wheel rim 18 offers the advantage that the cut(s) 26 can be carried out by an at least three-axle freely programmable industrial robot on which the tool 32 is mounted, without having to stop the tool 32.

(42) The depth of said outs may be monitored, for example, by an appropriate control of the industrial robot or, resp., a tool assembly comprising a tool 32 to the invention and an assembly for pivoting the tool 32.

(43) However, it is also possible that such tool assembly additionally includes a positioning tool 50 shown in FIGS. 16a and 16b by which the cut depth is automatically adjusted.

(44) In the embodiment described here the positioning tool 50 includes a guide roller 52 adapted to be adjacent to the surface 28 of the foam padding 20. As afore-mentioned, (alternatively or additionally) also a tactile or sensor-based control may be provided.

(45) The cutting tool 34 is mounted on the positioning tool 50 so that the cutting means 36 exhibits a defined cut depth t when the guide roller 52 contacts the surface 28. For this purpose, the positioning tool 52 includes a tool holder 54 being resiliency supported by means of plural spring elements 56 so that it may yield in the case of increased pressure. This may prevent the tool 32 and, resp., the cutting tool 34 from immersing too deeply into the foam padding 20. Hence it is ensured that the cut 28 is carried out at a constant depth t in the foam padding 20.

(46) The cutting tool 34 and the inserting tool 40 may have any design to introduce the cut 28 into the foam padding 20 and at the same time lay the conductor 22. Furthermore, the blade may also be made to move at ultrasonic speed so as to increase the cutting quality. Instead of a blade, the cutting tool 34 may also include other suitable cutting means 36.

(47) Preferably, the cut 26 is carried out without any material removal of the foam padding 20 so as to ensure that after being introduced into the foam padding 20 and insertion of the conductor 22 the cut 26 may close completely.

(48) Different embodiments of a tool according to the invention are shown in FIGS. 8a to 8c through 14a to 14c. Each of the tools 32 illustrated in said embodiments includes a cutting means 36 having a blade on the rear side of which an inserting passage 42 of an inserting tool 40 is arranged.

(49) The inserting passage 42 is laid in portions on the rear side of the cutting means 36, wherein the second end 46 arranged behind the cutting means 36 is bent away from the cutting tool 34 against the cutting direction S in each case.

(50) The tools 32 shown in FIGS. 8a to 8c, 9a to 9c and 10a to 10c show the same cutting means 38, but they differ by the respective angle at which the end 46 the inserting passage 42 is bent away from the near side of the cutting means 36. The angle is between 15 and 45, wherein the angle is selected so that the conductor 22 may exit the inserting passage 42 preferably against the cutting direction S, i.e. already at the desired orientation.

(51) Each of the tools 32 illustrated in FIGS. 11a to 11c, 12a to 12c and 13a to 13c has a different shape of the cutting edge 38.

(52) Independently of the shape of the cutting edge 38, the latter may be guided into the foam padding at different angles relative to the cutting direction S. The angle preferably ranges from 45 to 75.

(53) Independently of the shape of the cutting means 36 and, resp., the cutting edge 38, the inserting tool 40 is configured and mechanically tightly coupled to the cutting tool 34 so that the conductor 22 can be introduced to the cut 26 independently of the angle at the same respective depth t.

(54) Further embodiments of a tool according to the invention are shown in FIGS. 14a to 14c, with the inserting passage 42 having a straight design in each of these embodiments.

(55) In ail embodiments the penetration depth of the inserting passage 42 into the foam padding may be adjusted relative to the deepest point of the cutting edge 38. It is possible in this way that both end at the same depth or at a different depth, as this is most clearly evident from FIGS. 14a to 14c.

(56) Preferably the cutting tool 34 and, resp., the cutting edge 38 protrudes from the inserting passage 42 perpendicularly to the cutting direction S by a precutting depth so that behind the cut a larger free space is provided into which the electric conductor may be inserted. Said precutting depth preferably ranges torn 0.1 mm to 2 mm.

(57) It is also imaginable to design the tool 32 so that said precutting depth is individually adjustable, especially also during the cutting and laying operation. This may be performed via tool control.

(58) FIG. 15 illustrates an insertion aid 58 which facilitates threading of the electric conductor 22 into the inserting tool 40. The insertion aid 58 substantially has a conical guide 58f which is connected to the guide passage 42 of the inserting tool 40 and the diameter of which is tapered from an insertion-side diameter D1 to an exit diameter D2 which is larger than or equal to the diameter Df of the guide passage 42. Of preference, there is further provided a Teflon hose 59 having an inner diameter Dt (Dt is larger than or equal to D1) within which the electric conductor 22 is guided with low friction. The insertion aid 58 may be permanently arranged on the tool head 61 (FIG. 17).

(59) The cutting tool 34 may as well include other cutting means 36, for example including a cutting wire.

(60) It has merely to be ensured that the inserting tool 40 is coupled to the cutting tool 34 and the inserting tool 40 is directly adjacent to the cutting means 36 against the cutting direction so as to introduce the conductor 22 simultaneously with the cut 26 into the foam padding 20.

(61) In FIG. 17 a tool head 61 is shown as cutout of a tool assembly 60 in the area of a tool according to the invention.

(62) The tool assembly 60 comprises two at least three-axle industrial robots not shown in detail here. On a first industrial robot the tool 32 is retained in the tool head 61. The tool head is attached to the first industrial robot by means of a retaining flange 61f. On the second industrial robot the foam-padded steering wheel skeleton 18 is retained. The steering wheel skeleton 18 and the tool 32 may be positioned and moved arbitrarily relative to each other so that even complicated cuttings are possible.

(63) A pressing device 62 on which the tool 32 is retained is provided on the tool head 61 held on the first industrial robot. Said pressing device 62 ensures the tool 32 be pressed against the foam-padded steering wheel skeleton at a constant pressure and uniform cutting to be safeguarded.

(64) The pressing device 62 includes a guide means 64 associated with the cutting tool 34 and having a guide shoe 65. The guide means 64 further includes an actuating mechanism 87, in this case a cylinder adapted to adjust the guide shoe 65 relative to the cutting tool so that only the length of the cutting tool 34 required for the respective desired cut depth t protrudes from the guide shoe 65.

(65) The pressing device 62 presses the guide means 64 and, resp., the guide shoe 65 and thus the tool 32, for example in a spring-loaded manner, against the surface of the foam padding 20 of the steering wheel skeleton 18 so that the tool 32 cuts into the foam padding 20 at the desired and adjusted length.

(66) Preferably the maximum cutting depth t adapted to be adjusted amounts to 8 mm, especially to 6 mm.

(67) The depth of cut t preferably may be adjusted during the cutting operation so that also various inserting depths can be realized.

(68) For more complicated cuttings, especially in intersecting areas of the heating wires, it is also possible to lock the pressing device 62.

(69) The tool head 61 includes a tolerance compensating means 68 ahead of the retaining flange 61f so as to compensate for possible steering wheel tolerances in the rim profile.

(70) The tool 32, especially the cutting blade 34, is surrounded by the guide shoe 85 in the form of a sliding shoe being connected to a cylinder-piston system 69. The latter may withdraw the sliding shoe by command and expose a maximum blade length. A blade used in this embodiment then allows for a maximum depth of cut of 6 mm and an inserting depth of 5 mm, for example.

(71) In the primary inserting area (steering wheel rim) the sliding shoe 65 is extended by the cylinder-piston system 69, as shown in FIG. 17, and in this way allows for a small inserting depth of the electric conductor. Preferably the conductor/wire then is located within the foam at a depth of 0.1 mm to 2 mm.

(72) In particular areas (such as leather grooves, design edges, finger recesses, cover transition, crossing points etc.) the wire/conductor deliberately has to be laid more deeply into the foam. This is done by the cylinder-piston system withdrawing the sliding shoe 65 and exposing the maximum blade length 34.

(73) At the same time, the tolerance compensation 68 is frozen (currently by a pneumatic brake) and the robot traces the particular areas by numeric control (CNC) while maintaining the preliminary tolerance offset of the rim profile.

(74) When the particular area has been machined and the primary inserting area is reached again, the cylinder-piston system (69) returns the sliding shoe 65 into the home position and the tolerance compensation is released or, resp., activated again.

(75) The blade 34 is fastened via force and form closure as well as connected to the feed line (e.g. a Teflon hose 59) by an adapter/inserting aid 58. The adapter 58 for easy threading of the electric conductor. The wire feeding system 59 the electric conductor to be fed undisturbed at low friction.

(76) In FIG. 18 further a positioning means 66 is illustrated. The positioning means 66 permits facilitated laying of the electric conductor 22 by fixing within the same the start 22a, the end 22c and/or intermediate portions 22b of the electric conductor 22 (cf. FIG. 6) during the method according to the invention.

(77) The positioning means 66 includes a fastening device 68 as well as a plurality of positioning aids 70 so as to fix the positioning means 66 to the steering wheel skeleton 18.

(78) Moreover, retaining devices 72a, 72b for the start 22a and, resp., the end 22c of the electric conductor 22, plural guide elements 74, 76 as well as a seat 78 for the electric connection 24 are provided on the steering wheel skeleton 18.

(79) At the beginning of the method, the positioning means 66 is fixed and aligned with the fastening device 68 and the positioning aids 70 on the steering wheel skeleton. Subsequently the start 22a of the electric conductor 22 is fixed to the retaining device 72a.

(80) After said steps the cuts of a first layer of windings are introduced to the steering wheel skeleton 18 and the electric conductor 22 is introduced into the same. Subsequently, the electric conductor 22 is guided around the guide element 74 in the form of a deflecting pin and the windings of a second layer are introduced to the steering wheel skeleton.

(81) After introducing the cots 28 and laying the electric conductor 22, the end 22c of the electric conductor 22 is fixed in the second retaining device 72b and is cut off, for example, by a given cutting tool 80.

(82) Finally the electric conductor 22 is connected to the connection 24 retained in the seat 78, wherein the guide element 76 serves as hold-down for preventing the electric conductor 22 from being pulled out of the foam padding 20.

(83) An assembling aid 32 assists the exact orientation of the connection 24 as well as connecting the electric conductor 22.

(84) After implementing the method and connecting the electric conductor 22 the positioning means 66 may be removed from the steering wheel skeleton 18.

(85) After laying and connecting the electric conductor 22, it may be strongly heated so that the adjacent foam is softened and/or liquefied for a short time and after cooling is glued to the electric conductor 22. This causes permanent fixation of the conductor 22 within the foam padding of the steering wheel skeleton.

(86) As an alternative, the electric conductor may include a thin thermoplastic adhesive coating which may be activated by means of current supply/heating. By heating the adhesive the cutting edge can moreover be closed again.