EP1655258A2 - Friction element - Google Patents

Abstract

The friction unit has a ring (10), which fits on a winding shaft in a mounted condition, and a clamping unit (12) pressed against a hub (30) by a rotary motion relative to the ring (10) by a clamping surface. The clamping unit has a ring shaped, radially expandable holder, which fits on an outer circumferential surface of the ring. The holder presides with a projection radially over an inner diameter of the hub in a relaxed condition.

Description

The invention relates to a friction element for transmitting a certain torque to a winding core for Aufwikkeln strip-shaped materials, for. As adhesive tape, with a friction element which is rotatably driven with a limited friction by sliding torque, and one of the friction element mitnehmbaren in the circumferential direction clamping member by a rotational movement relative to the friction by means of at least one extending obliquely to the circumferential direction clamping surface radially outward, non-rotatably clamping is pressed against the winding core.

Such friction elements are z. In US-A-4,551,010 and Japanese Patent Application 2-132043 (A). The clamping element consists of a plurality of relatively small clamping bodies, which sit in individual pockets of the friction element and are each pressed by an inclined surface or eccentric bearing radially outwardly against the winding core. The construction becomes particularly complicated if the clamping elements are not mounted on the friction element but on a guide ring arranged between the latter and the winding core and pressed against the winding core by relative movement between friction element and guide ring by means of an oblique clamping surface.

Also, the friction element described in EP 0 863 101 B1 is due to the division of its functions on different components, eg. B. multi-part friction elements and separate return elements for retracting the clamping elements of the winding core, relatively complicated and expensive. In addition, condition the known friction elements a relatively large minimum width.

In contrast, the present invention seeks to provide a friction element of the type mentioned above, which consists of a few easy-to-clean items, is suitable for very narrow versions and can be realized inexpensively.

The above object is achieved in that the clamping element has the form of an annular, radially elastically expandable bracket, which sits on a non-circular outer peripheral surface of the friction element and projects with at least one projection already in the relaxed state radially over the inner diameter of the winding core.

The new friction element basically only needs to consist of two simple parts, namely an elastic, ring-shaped bracket, z. B. wire, and serving as a friction ring, z. B. plastic, with a circumferential groove for receiving the bracket. Since this ring does not need to be much wider than the wire diameter, friction elements with a width of about 5 mm can easily be produced.

The simplification achieved by the invention is based essentially on the fact that the inherent elasticity of a one-piece bow-shaped clamping element is utilized to withdraw this from the expanded clamping position radially inwardly into the relaxed, non-clamping position. In the relaxed position of the bracket can then be wound Pull the hubs axially from the friction elements easily.

In the preferred embodiment of the invention, the mentioned projection in the axial view sharp or rough, but with a view in the circumferential direction bevelled or rounded and arranged at the end of the bracket, which points in the winding direction. The projection presses a little into the inner circumferential surface of the winding core and brakes in this way the entrainment of the bracket when the friction element begins to rotate in the winding direction. This results in a relative rotation between the annular friction element and the substantially annular clamping element, wherein at least one obliquely extending to the circumferential direction clamping surface on the friction and / or clamping element latter presses so strongly against the winding core that it comes to the rotationally fixed clamping of the parts.

In a further preferred embodiment of the invention, the non-circular outer circumferential surface of the friction element has a plurality of circumferentially distributed cams, which cooperate with a plurality of distributed over the inner circumference of the clamping element, extending obliquely to the circumferential direction clamping surfaces. The cams can have many forms, because they only auflieaufen on a relative rotation on the inclined surfaces on the inner circumference of the clamping element and thereby have to press radially outward against the winding core. If z. B. eight evenly distributed over the circumference cams on the annular friction element are present, can be pressed by one of the cams provided with the sharp-edged or rough projection end of the open annular clamping element radially outward against the winding core while the seven remaining cams, distributed over the circumference, press against the annular clamping element and ensure a fairly uniform expansion and thus centering of the winding core.

If, after winding, the winding shaft is stopped and the roll for loosening in the winding direction is further rotated or alternatively stopped and the winding shaft is rotated counter to the winding direction, a plurality of cams and clamping surfaces after an initial relaxation of the clamping element in another relative position of the friction element Expansion and clamping take place. To prevent this, is provided in a preferred embodiment of the invention that when releasing the relative movement between the friction element and the clamping element is limited by stop in a relative angular position in which the clamping element is in the relaxed state.

Upon rotation of the winding shaft in the winding direction, the relative movement between the friction element and the clamping element can be limited simply by its radial tension between the friction element and the winding core. For this it may be sufficient, a single point on the circumference of the clamping element, z. B. the not provided with the sharp-edged or rough projection end to bend radially outward and so long and rigid to measure that it comes at this point by one of the cams for fixed contact with the winding core, if at the other of the cams radially to Pressed outside, elastic peripheral regions of the clamping element which is required for the necessary static friction clamping voltage is reached.

Alternatively, there is the possibility that even with rotation of the friction element in the winding direction, the relative movement between the friction element and the clamping element is limited by a stop which limits the radial strain of the clamping element between the friction element and the winding core. The stop may be formed by a cooperating with a cam on the friction element end of the open-ring clamping element.

The above basic idea allows numerous other practical embodiments. So z. B. the clamping element is a polygonal curved, open wire ring or wire hanger, while the outer peripheral surface of the friction element in cross-section corresponding polygonal, z. B. octagonal, is shaped. The aforementioned cams are formed in this case by the possibly rounded corners of the polygonal peripheral surface of the friction element. This may further be modified in that it is formed with recesses. Since the uniform polygonal design of the wire bracket bearing peripheral surface of the friction element is neutral, while the wire bracket is to be inserted so that its the sharp-edged or rough projection forming end in the winding direction, needs to be reversed when changing the winding direction only the wire hanger so that his for the first friction on the winding end end of turn again in the winding direction.

In addition, when the polygonal peripheral surface of the friction member is recessed, the other end of the wire bracket may be bent radially inward and engage with one of the recesses. In this way, a stop win, both a relative rotation between Friction element and clamping element in the clamping direction and restricts the return movement in the relaxed position.

In a further alternative embodiment, the clamping member is a sawtooth curved, open wire ring or wire bow, one end of which projects radially outward and forms the projection, while the outer peripheral surface of the friction element is formed with or without recesses corresponding sawtooth. The winding direction is determined in this case by the fact that the weaker inclined flank of each sawtooth leads the steep flank. In this variant, the steep flank of the sawtooth-shaped cam can serve as a stop for the completion of the return movement in the relaxed position. When changing the winding direction, the friction element is to turn over a total.

In further embodiments of the friction element according to the invention is used instead of a wire hanger at a point open plastic or metal ring use, which has a substantially circular, the inner diameter of the winding core adapted outer circumference and a polygonal inner circumference. The friction element is formed with a number of outer cams which sit in the relaxed state of the plastic or metal ring in its inner corners. Such a friction element may also be in the form of a cage in which the cams are formed by recessed, axially extending pins. In all such cases, the relative rotational movement between the clamping element and the friction element by striking a cam or against at least one of the ends of the metal or plastic ring or by abutment of at least one cam or pin against limit at least one arranged between two inner corners of the metal or plastic ring stop.

In a particularly simple and reliable manner, the wire clip or open metal or plastic ring forming the clamping element is guided and held in that the outer peripheral surface of the friction element on which the clamping element is seated forms the bottom of a groove in the friction element which holds the clamping element axially. In this case, the outer diameter of the friction element next to the groove is only slightly smaller than the inner diameter of the winding core.

Regardless of the shape of the clamping element and the shape of this supporting outer peripheral surface of the friction element whose acted upon by the sliding friction of the drive torque surface may be either the radially inner peripheral surface or at least one end face.

Fig. 1

einen Querschnitt durch eine erste Ausführungsform des erfindungsgemäßen Friktionselements im entspannten Zustand;

Fig. 2

einen Teil-Längsschnitt durch drei axial nebeneinander angeordnete Friktionselemente gemäß Fig. 1;

Fig. 3

einen Querschnitt des Friktionselements nach Fig. 1 in Klemmstellung während des Aufwickelns eines bandförmigen Materials auf einen Wickelkern, wobei der Antrieb des Friktionselements durch Gleitreibung an seiner radial inneren Umfangsfläche erfolgt;

Fig. 4

einen axialen Teil-Längsschnitt durch mehrere nebeneinander angeordnete Friktionselemente nach Fig. 1 während des Aufwickelns von bandförmigem Material, wobei die Stirnflächen mit der Gleitreibung des Antriebsmoments beaufschlagt werden;

Fig. 5

einen Querschnitt durch ein Friktionselement mit nur einem auf einen Drahtbügel wirkenden Nocken;

Fig. 6

das Friktionselement nach Fig. 5 in Klemmstellung während des Aufwickelns eines bandförmigen Materials auf einen Wickelkern;

Fig. 7

ein Friktionselement ähnlich dem nach Fig. 1 im Querschnitt, wobei jedoch die polygonale Umfangsfläche des Reibelements, auf welcher der Drahtbügel sitzt, mit Aussparungen versehen ist;

Fig. 8

das Friktionselement nach Fig. 7 im Querschnitt in Klemmstellung während des Aufwickelns eines bandförmigen Materials auf einen Wickelkern;

Fig. 9

ein Friktionselement im Querschnitt, bei dem ein mehrfach sägezahnförmig gebogener Drahtring im entspannten Zustand auf einem Reibelement mit einer entsprechend sägezahnförmig gestalteten Umfangsfläche sitzt, die im Beispielsfall mit Ausnehmungen geformt ist;

Fig. 10

einen Querschnitt des Friktionselements nach Fig. 9 im geklemmten Zustand während des Aufwickelns von bandförmigem Material auf einen Wickelkern;

Fig. 11

einen Querschnitt eines Friktionselements, bei dem das Klemmelement ein offener, außen kreisrunder und innen polygonaler Kunststoffring ist, während die ihn tragende Umfangsfläche des Bremselements mit Nocken geformt ist, die im entspannten Zustand in den Innenecken des Klemmelements sitzen;

Fig. 12

einen Teil-Längsschnitt durch das Friktionselement nach Fig. 11;

Fig. 13

einen Querschnitt des Friktionselements nach Fig. 11 im geklemmten Zustand während des Aufwickelns von bandförmigem Material auf einen Wickelkern;

Some embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

Fig. 1

a cross section through a first embodiment of the friction element according to the invention in the relaxed state;

Fig. 2

a partial longitudinal section through three axially juxtaposed friction elements of FIG. 1;

Fig. 3

a cross section of the friction element of FIG. 1 in the clamping position during the winding of a band-shaped material onto a winding core, the drive of the friction element being effected by sliding friction on its radially inner peripheral surface;

Fig. 4

an axial partial longitudinal section through a plurality of juxtaposed friction elements of Figure 1 during the winding of band-shaped material, wherein the end faces are subjected to the sliding friction of the drive torque.

Fig. 5

a cross section through a friction element with only one acting on a wire hanger cam;

Fig. 6

the friction element of Figure 5 in the clamping position during the winding of a strip-shaped material on a winding core.

Fig. 7

a friction element similar to that of Figure 1 in cross section, but wherein the polygonal peripheral surface of the friction element, on which the wire hanger sits, is provided with recesses.

Fig. 8

the friction element of FIG. 7 in cross-section in the clamping position during the winding of a band-shaped material onto a winding core;

Fig. 9

a friction element in cross section, in which a multi-sawtooth curved wire ring sits in the relaxed state on a friction element with a corresponding sawtooth-shaped peripheral surface, which is formed in the example with recesses;

Fig. 10

a cross section of the friction element of Figure 9 in the clamped state during the winding of tape-shaped material on a winding core.

Fig. 11

a cross section of a friction element, wherein the clamping element is an open, outside circular and inside polygonal plastic ring, while the circumferential surface of the brake member carrying it is formed with cams which sit in the relaxed state in the inner corners of the clamping element;

Fig. 12

a partial longitudinal section through the friction element of FIG. 11;

Fig. 13

a cross section of the friction element of Figure 11 in the clamped state during the winding of strip-shaped material on a winding core.

The friction element 10 shown in FIGS. 1 to 4 consists of a friction element 10 and a clamping element 12. The friction element 10 is a preferably made of plastic or other material with good sliding properties ring in the mounted state on a matching to its inner diameter winding shaft 14th sitting, that he can turn on it with little friction. In the peripheral surface of the winding shaft 14, however, brake body 16 are radially movably inserted, which by brake cylinder 18, z. B. in a simple design in the form of flexible hoses, with a certain pressure force against the inner peripheral surface of the ring 10 can be pressed. Thus, the ring 10 can be driven by the winding shaft 14 with a limited torque, which is determined by the sliding friction against the brake bodies 16, according to the adjustable contact pressure.

If, as shown in FIG. 2, three or more rings 10 are seated axially next to each other on the winding shaft 14, they can be frictionally driven by sufficiently long brake bodies 16 and brake cylinders 18 in the manner described.

Another type of drive is shown in Fig. 4. In this case sits on the outside of each of the outermost rings 10 and between two adjacent rings 10 each have a drive plate 20 which engages with a radially inner projection 22 in a matching longitudinal groove 24 in the winding shaft 14. By an in Fig. 4 indicated by arrows axial pressure force the drive plates 20 are pressed against the side surfaces of the rings 10. In this way, also here by the adjustable axial contact pressure, the sliding friction between the positively connected to the winding shaft 14 driver disks 20 and the rings 10 and thus the maximum transmittable drive torque can be determined.

The ring 10 has a cylindrical outer peripheral surface with a molded or machined central circumferential groove 26 in which the clamping element 12 is seated. The outer diameter of the ring 10 is slightly smaller than the inner diameter of a sleeve-shaped, with a strip of material 28, z. As adhesive tape to be wound hub 30, so that it can be pushed easily axially on a ring 10 and at a larger axial length on several rings 10.

For winding the band-shaped material 28 onto the winding core 30, this is to be taken without slippage from the ring 10 according to arrow 32 in Fig. 3 in the winding, so that no abrasion on the inner peripheral surface of the winding core 30 is formed. Therefore, the clamping member 12 must on the one hand unimpeded sliding of the winding core 30 on the ring 10 and the decrease allow, on the other hand at the beginning of the winding a rotationally fixed clamping connection between the ring 10 and the winding core 30 produce. To achieve this, in the embodiment of FIGS. 1 to 4, the bottom of the annular groove 26 has a polygonal, z. B. octagonal, contour, the corners are rounded. The seated in the annular clamping element 12 is in this construction, a polygonal contour of the annular groove 26 adapted, made by bending spring wire spring clip, which is designed as a polygonal open ring and loose in the relaxed state shown in FIG. 1 in the annular groove 26th sitting, that the corners of the polygonal base are radially aligned with the corners of the spring clip 12. The one end 34 of the spring clip 12 is located approximately at a corner of the annular groove 26, while the other end 36 of the spring clip 12 assumes a position in the central region of one of the straight portions of the outer peripheral surface of the ring 10 in the annular groove 26. As is apparent from Fig. 1, the end 34 of the spring clip 12 forms a projection which protrudes beyond the inner diameter of the winding core 30 already in the relaxed state of the spring clip 12. Also, one or more corners or projections of the spring clip may protrude beyond the outer diameter of the ring 10 as shown in FIG. 1 and attack the winding core 30 instead of the strap end 34 or together with it already in the relaxed state. In any case, the radially outwardly bent other end 36 of the spring clip 12 in its relaxed state should not attack the winding core 30, so lie within the annular groove 26 to be able to shift in the circumferential direction when the spring clip 12 is radially stretched. The spreading of the spring clip 12 takes place at the beginning of the winding, when the ring 10 is frictionally entrained by the winding shaft 14 in the winding 32, while the required for winding traction in the band-shaped material 28, the winding core 30 and the end 34 with a little in it pressed depressed spring clip 12 is anxious. This results in a rotational movement of the ring 10 relative to the spring clip 12 from the position of FIG. 1 in the position of FIG. 3. The corners of the polygonal groove bottom of the annular groove 26 run on the straight portions of the spring clip 12 and thereby press its outer Corners radially outward against the winding core 30. The same thing happens with the already already engaged end 34, which digs even deeper into the winding core 30. In order to promote the anchoring of the end 34 of the spring clip 12 in the winding core 30, it may, for. B. sharp-edged, pointed or roughened. Because the polygonal, annular spring clip 12 is pressed with its outer corners and ends around the circumference against the winding core 30, the clamping causes a centering of the winding core 30th

In order to limit the jamming of the parts, which must be reversed at the end of the winding operation, and to prevent slippage of the ring 10 within the spring clip 12, as shown in FIG. 3 with increasing clamping one of the rounded corners of the bottom surface of the annular groove 26 approaches While the straight portions of the polygonally bent spring clip may flex elastically radially outward when one of the corners of the ring 10 is inwardly pressed, the end 36 of the spring clip 12 may extend slightly into the winding core 30 but is in itself rigid and thereby forms a stop which limits the rotation of the ring 10 relative to the spring clip 12 in the winding 32.

When the winding process for the winding material 28 is completed and the winding shaft 14 is stopped, the clamping between the winding core 30 and the ring 10 by means of the spring clip 12 can be canceled by turning the wound roll in the winding. The spring clip 12 resumes its relaxed shape and position of FIG. 1, and the finished wound roll can be withdrawn axially from the ring 10. When turning the finished wound roll or the empty Wikkelkerns 30 on the fixed ring 10, the projecting end 34 of the spring clip 12 can not press into the winding core 30 so that a deadlock can not come about.

To change the winding direction of the spring clip can be removed and rotated again used. If a side edge of the winding core 30 coincidentally lies in the plane of the spring clip 12 when placing a winding core 30 on a plurality of juxtaposed rings 10, this can also be removed. The friction element is thereby "switched off". The friction effect can thus be adapted in a simple manner from the outside to the needs, without the placement of the winding shaft must be changed. So z. B. in the embodiment of FIG. 4 to the seven friction elements shown there instead of four narrow winding cores 30, a wide winding core are placed, which is about as wide as six or seven juxtaposed rings 10th

In Fig. 5 and Fig. 6, a very simple embodiment is shown. The friction member 10 has in the annular groove 26 on the largest part of its circumference a cylindrical groove bottom, which forms a radially outwardly rising clamping or cam surface 38 only at a single point of the circumference, which ends at a stop groove 40 interrupting the annular groove 26. The clamping element 12 is simply just an annular bent spring wire clip with an opening. Its one end 42 is hook-shaped outwardly and rearwardly, bent in the winding direction and forms, as the strap end 34 in Fig. 1 an outer projection which engages already in the relaxed state of the spring clip on the winding core 30. The spring clip 12 is arranged in the annular groove 26 so that it at the beginning of the winding by the relatively rotating in its direction of winding 32 ring 10 with its hook-shaped end 42 by the clamping or cam surface 38 radially outward in rotationally fixed clamping engagement with the winding core 30 pushed is until the end 42 of FIG. 6 abuts against the stop 40. When releasing the jamming by relative rotation of the winding core 30 and the clamping member 12 relative to the ring 10 in the winding direction of the same stopper 40 cooperates with the other end of the spring clip and thereby limits the relative rotation between the parts 10 and 12th

As can be seen, in this case, the clamping element 12 has no centering effect. The outer peripheral surface of the friction element 10 in the region of the annular groove 26 acts only in one direction of rotation by clamping on the spring clip 12 and the winding core 30. Therefore, in this embodiment, the entire friction element on the winding shaft 14 must be rotated to reverse the direction of rotation.

The embodiment according to FIGS. 7 and 8 differs only from the embodiment according to FIGS. 1 to 4 in that the outer peripheral surface of the friction element 10 in the middle region of the straight sections of the polygonal bottom surface in the annular groove 26 with recesses or depressions 44 is shaped. By not the beginning of the winding core 30 engaging end 46 of the spring clip 12 is not bent radially outward, but radially inward and engages in one of the recesses 44, there is a stop, the relative movement between the friction element 10 and the clamping element 12th limited in both directions. Otherwise, this embodiment corresponds to that of FIGS. 1 to 4.

In the embodiment according to FIGS. 9 and 10, both the outer peripheral surface of the friction element 10 in the region of the annular groove 26 and a clamping element 12 bent again from spring wire have a sawtooth-shaped contour. In the relaxed state of It is seen that the steep flanks of the teeth form stops which limit the relative rotational movement of the parts 10 and 12 in the relaxed position.

At the beginning of a winding operation, the weaker inclined flanks of the sawtooth-shaped cams of the ring 10 press wedge-shaped under the weaker inclined flanks of the saw teeth of the spring clip 12. As a result, this is radially expanded and clamped between the ring 10 and the winding core 30. Recesses 50 between the sawtooth-shaped cams 48 of the ring 10 provide the remaining in the annular groove 26, facing in the circumferential direction end 52 of the spring clip 12 a stop which limits the relative movement of the two parts 10 and 12 in the clamping direction.

Since the friction element according to FIGS. 9 and 10 acts in a clamping manner only in one direction of rotation, it has to be turned overall when the direction of rotation is reversed.

In the embodiment of FIG. 11 to 13, the friction element 10 at the bottom of the annular groove 26 has a cylindrical outer peripheral surface with uniformly distributed over the circumference, radially outwardly projecting, rounded cam 54. They correspond in function to the rounded corners of the polygon in the The clamping element 12 is in this case no longer a wire bow, but an open at one point, outside circular ring made of metal or plastic, the radially inner peripheral surface is designed polygonal. In the relaxed state of FIG. 11 sit of the z. B. eight existing cam 54th A cam 54 protrudes into the opening of the annular clamping element 12, the ends of which thus act as stops which limit the relative rotational movement of the parts 10 and 12 in both directions of rotation. One of the two ends of the annular clamping element 12 is provided with a sharp-edged, radially outwardly projecting projection 56 which has the same function as the radially projecting end 34 of the spring clip according to FIGS. 1 and 3.

Because the sharp-edged projection 56 engages a little in the winding core 30 already in the relaxed state, it comes to the beginning of the winding process shown in FIG. 13 to a rotational movement of the ring 10 relative to the clamping element 12, wherein the cam 54 on the straight portions of the inner peripheral surface of the emerge annular clamping element 12 and this radially expand elastically so that it comes to clamping of the annular friction element 10 via the likewise annular clamping element 12 with the winding core 30.

To limit the relative rotational movement between the parts 11 and 12, instead of a cam cooperating with the ends of the annular, open clamping element 12, a projection of the clamping element 12 projecting radially inwardly between two inner corners could serve. The projection is to be dimensioned so that, starting from the relaxed position of the clamping element 12 of FIG. 11, only a relative rotation of the friction element 10 relative to the clamping element 12 in the winding direction and limited to a certain angle of rotation.

It is recommended that the annular clamping element 12, at least at the end where the projection 56 is located, so bevelled or rounded, that a slight sliding and removing the hub is possible. In the case of the spring clip consisting of round wire in the embodiments according to FIGS. 1 to 10, the round wire cross-section already ensures easy sliding and removal of the winding core 30. If spring wire with a rectangular cross-section is used for the clamping element 12, the lateral bevel or rounding is also used there mounted radially outwardly projecting end.

Claims (12)

Friction element for transmitting a certain torque to a winding core (30) for winding strip-shaped materials (28), for. B. adhesive tape, with a friction element (10) which is rotatably driven with a limited friction by sliding torque, and one of the friction element (10) circumferentially entnehmbaren clamping element (12) by a rotational movement relative to the friction element (10-) means characterized in that the clamping element (12) has the form of an annular, radially elastically expandable bracket, which on a non-circular outer peripheral surface of the at least one clamping surface extending obliquely to the circumferential direction radially outward, non-rotatably clamping against the winding core (30) Reibelements (10) sits and projects with at least one projection (34, 42, 56) already in the relaxed state radially over the inner diameter of the winding core (30). A friction member according to claim 1, characterized in that the projection (34, 42, 56) is disposed at one end of the bracket (12) pointing in the winding direction. A friction member according to claim 1 or 2, characterized in that the non-circular outer peripheral surface of the friction member (10) has a plurality of circumferentially distributed cams (48, 54) which are slanted with a plurality of circumferentially spaced apart circumferences of the annular clamping member (12) cooperating with the circumferential direction extending clamping surfaces spreading. Friction element according to one of claims 1 to 3, characterized in that, when the friction element (10) is stationary and the clamping element (12) is rotated in the winding-up direction, the relative movement between the two is limited by a stop when a relative angular position is reached, in which the clamping element (12) in relaxed state. Friction element according to one of claims 1 to 4, characterized in that, in its drive in Aufwikkelrichtung the relative movement between the friction element (10) and the clamping element (12) by a stop (36, 40, 46, 50) is limited, the radial Tensioning of the clamping element (12) between the friction element (10) and the winding core (30) limited. Friction element according to one of claims 1 to 5, characterized in that the clamping element (12) is a polygonal curved, open wire ring and the outer peripheral surface of the friction element (10) is polygonally shaped in cross section. A friction element according to claim 6, characterized in that said one end (34) of the wire (12) forms the projection, while the other end (36, 46) of the wire is bent radially outward or inward and the rotational movement of the friction element (10) limited in Aufwikkelrichtung relative to the wire (12). Friction element according to one of claims 1 to 7, characterized in that the clamping element (12) has a sawtooth-shaped bent, open wire ring is one of whose ends (34) projects radially outward and forms the projection, and the outer peripheral surface of the friction element (10) with or without recesses (50) correspondingly sawtooth-shaped, wherein in the winding the weaker inclined flank of each Sawtooth (48) leads the steep flank. A friction element according to any one of claims 1 to 5, characterized in that the clamping element (12) is an open metal or plastic ring having a circular outer periphery and a polygonal inner periphery, and the outer peripheral surface of the friction element (10) is provided with cams (54, 54). 62) is formed or provided, which sit in the relaxed state of the metal or plastic ring (12) in its inner corners. A friction element according to any one of claims 7 to 9, characterized in that the end of the clamping element (12) carrying the projection (34, 42, 56) is held in a radially elastically yielding manner on the friction element (10) in the relaxed state. Friction element according to one of the preceding claims, characterized in that the projection (34, 42, 56) is chamfered or rounded on the axial flanks. Friction element according to one of the preceding claims, characterized in that the outer circumferential surface of the friction element (10) on which the clamping element (12) sits forms the bottom of an annular groove (26) in the friction element (10) which axially urges the clamping element (12) holds, with the outside diameter of the friction element (10) next to the annular groove (26) is only slightly smaller than the inner diameter of the winding core (30).

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