EP3739091B1 - Friction disc for false twisting device - Google Patents

Description

The invention relates to a friction disk for a false twist device with an annular hub on which a circular raceway formed by a PU layer with a minimum wall thickness necessary for a secure form fit can be fixed, wherein the hub has a circumferential support ring and a central bore via which the friction disk can be fixed on one of the shafts of the false twist device.

In connection with the production of crimped textile threads, it is known to create a false twist in the threads by friction, which is then fixed, for example, in a texturing zone by thermal treatment of the threads.

False twisting devices have proven to be effective in generating the false twist, in which the thread is guided along the circumferential surfaces of several rotating, overlapping friction disks during the twisting process.

In such cases, for example in the EP 0 943 022 B1 In the false twist devices described, the friction disks are usually arranged on three shafts, which in turn are supported in a bearing block so that they can rotate. The shafts are arranged at a distance from one another in a triangle such that the friction disks overlap in the center of the triangle. In addition, the shafts are driven by a drive such that the friction disks rotate at a constant peripheral speed.

During the twisting process, the thread, subjected to frictional engagement at a relatively high transport speed, runs over the cooperating friction disks, which rotate at circumferential speeds of >2000 m/min. The frictional force between the thread and the friction disks rotating in a plane transverse to the direction of thread travel continuously generates the desired false twist.

However, the frictional stress leads to wear on the friction disks, which is further exacerbated by the heating of the friction disks. In order to guarantee consistently good working quality on a texturing machine equipped with false twist devices, it should be ensured that the average deviation of the thread tension from position to position in the texturing machine is minimized. This means that after a certain, often relatively short, downtime, the friction disks of the false twist devices must be removed and replaced with new ones.

In order to keep the costs incurred in such overhaul work as low as possible or to make the time period between such overhaul work as long as possible, various proposals have already been made in the past.

In the US Patent 4 718 226 and the US Patent 5 400 507 For example, friction disks for false twisting devices are described, where the costs of overhaul work are to be kept as low as possible by designing the race and the hub as separate components. This means that, if necessary, the race on these known friction disks, which is in frictional contact with the thread during the twisting process and is subject to wear, can be replaced with a new race, while the hub of the friction disk can continue to be used. However, the amount of work required to change the race has proven to be impractical, so that these friction disks have not been able to prevail in practice.

Through the EN 35 00 208 A1 Friction discs are also known in which the wear of the bearing rings is to be reduced by adding a fine powder substance to the rubber-elastic material of the bearing rings.

A comparable friction disc is also available in the EN 10 2005 050 068 A1 described. According to this publication, the friction discs each have a so-called bushing carrier, which is surrounded by a ring made of friction material. The friction material is formed by a composite of a polyurethane and a ceramic material. This means that ceramic nanoparticles are embedded in a base material made of polyurethane.

However, in the case of these known friction discs, the service life of the friction discs has been improved at the expense of the friction value, which means that the friction values of these known friction discs can be greatly improved.

EP 1 082 475 B1 discloses friction discs whose manufacturing process is optimized by the fact that both the hub and the race are manufactured using injection molding technology. This means that a hub is first manufactured from a hard thermoplastic using an injection molding process and then a race is created on the hub, also using an injection molding process. Further information can be found in the documents DE 198 15 578 C1 and DE 100 46 525 A1 .

The race is formed by a layer of aramid-filled thermoplastic polyurethane, which is mechanically fixed to the hub after the injection molding process and has an almost uniform, relatively thin layer thickness. Friction discs manufactured in this way are Although they are relatively advantageous in terms of their production costs, further improvements are possible with regard to their service life and running characteristics.

Based on the above-mentioned prior art, the invention is based on the object of improving the known friction disks of false twisting devices in such a way that they are not only inexpensive to manufacture and have a relatively long service life, but that they are also very advantageous in terms of their running behavior. In particular, the heat development that is unavoidable during the false twisting process should be minimized in the friction disks according to the invention.

This object is achieved according to the invention in an alternative or combined manner in that the race is ground according to a predeterminable profile such that the flanks of the race have a predeterminable width after the grinding process and/or the hub has a circumferential shoulder at a distance from the support ring for the attachment for the fixable PU layer, wherein a cross-sectional width of the shoulder is smaller than a cross-sectional width of the support ring.

Advantageous embodiments of the invention are the subject of the subclaims.

The embodiment of a friction disk according to the invention has the particular advantage that the friction disk is optimized in terms of its geometry and use of material, whereby a significantly lower surface temperature can be generated during the texturing process as a result of the improved flow situation, which has a positive effect on both the running behavior and the service life of the friction disks. Furthermore, the reduced temperature, viewed across the number of friction disks on a spinning machine, promotes energy savings.

With the friction disk designed and ground to measure according to the invention, a significantly more stable machine cV% can be achieved, whereby machine cV% is understood to be the average deviation of the thread tension from position to position of the texturing machine. This means that the lower and more uniform the machine cV% of a texturing machine is, the better the quality of the yarn that can be produced on this textile machine, especially with regard to later dyeing results of the yarn.

The defined design of the rotating attachment ensures that advantageous flow conditions can be achieved in the area of the rotating friction disk, which also has a positive effect on the machine cV% during the texturing process. Such a new hub shape, which is improved compared to the hubs of previously known friction discs, can ensure greater rigidity and strength, which also has a positive effect on the grinding process of the flanks of the race.

Furthermore, the new geometry of the hub of the friction disk leads to a larger surface area, which results in a lower disk temperature during the texturing process, which has a positive effect on the running behavior and service life of the friction disk, or can be used to increase the production of the texturing machine by increasing the speed of the friction disks.

In an advantageous embodiment, the width of the flanks of the race is equal to, and preferably smaller than, the maximum cross-sectional width of the hub. By providing a relatively thin wall thickness for the race, it can be ensured, for example, that the swelling of the PU layer can be kept to a minimum during the texturing process, which leads to better dimensional and shape stability over the entire service life of the friction disk and thus to less influence on the texturing process.

According to one embodiment, it is particularly preferred that the wall thickness of the PU layer of the race is minimized to the minimum wall thickness required for secure positive locking. The optimal minimization of the minimum wall thickness of the race that can be achieved in this way not only allows the wear layer designed as a PU layer to adhere securely to the carrier designed as a hub, but also advantageously causes a further reduction in the swelling of the PU layer and the surface temperature during the texturing process.

According to a further preferred embodiment, the hub is made of a plastic, preferably PBT 40% GK natural. PBT (polybutylene terephthalate) 40% GK natural is a thermoplastic that contains 40% glass fibers and is very suitable for the production of machine components using the injection molding process due to its favorable cooling and processing behavior. PBT is also characterized by high strength and rigidity, very high dimensional stability and good friction and wear resistance.

According to a further preferred embodiment, the PU layer of the friction disc race has a hardness of at least or equal to 85 Shore A. Such a Shore hardness not only ensures a relatively high wear resistance of the race, but also ensures that there is sufficient frictional resistance between the running ring and the yarn to be processed, thus ensuring that the yarn is properly twisted at all times during the texturing process.

The friction disk preferred according to one of the embodiments described above also enables an improved air exchange of the ambient air prevailing between the adjacent friction disks during operation, which heats up during operation of the friction disks, with the cooler ambient air outside the friction disks.

According to a further preferred embodiment, the cooling effect of the friction disk can be improved in that the hub has at least one passage which passes through the hub for the predetermined conduction of the air flowing through the passage when the friction disk is rotating. Both surface sides of the hub are therefore connected to one another via the passage. The passage enables the predetermined conduction of an air flow generated as a result of the rotation of the friction disk, the ambient air surrounding the hub, which is entrained along with it, whereby the hub can be suitably cooled not only on the surface side, but also along the profile thickness running in the axial direction of the friction disk.

Preferably, the at least one passage is designed in such a way that the air flowing through the passage during rotation of the friction disk is directed in the direction of another friction disk of the false twist device arranged adjacent to the friction disk. This enables cooling not only of the friction disk itself, but also of the adjacent friction disk. Thus, different friction disks can be used with a false twist device, some with a cooling effect and some without a cooling effect, whereby these can be arranged alternately along a shaft in a particularly preferred manner in order to achieve an improved cooling effect.

The hub preferably forms a fan shape with a plurality of passages which are separated from one another by a partition wall which has a predetermined blade geometry for the defined guidance of the air flowing through. A respective partition wall which separates two adjacent passages from one another forms a fan blade for the defined guidance of the air flow generated from the entrained ambient air during the rotation of the friction disk through the respective passage. The respective partition wall is preferably fixed to the end face arranged in the radial direction of the friction disk near the central bore of the friction disk with which the central bore forming the frame of the base body and on the opposite end face in the radial direction, which is close to the support ring, with the section of the base body carrying the support ring or alternatively with the extension running around at a distance from the support ring. The respective fan blade preferably has an aerodynamic profile, more preferably with an inflow edge bent in the radial and/or axial direction of the friction disk and/or an outflow edge bent in the radial and/or axial direction of the friction disk. Furthermore, the number of partition walls provided is preferably odd, with particularly preferably five or seven partition walls being provided, which are preferably evenly distributed around the central bore. Particularly preferably, the fan shape with the blade geometry is selected such that the fan shape forms an axial or diagonal fan, which takes the ambient air from one side of the friction disk and blows it out on the other side of the friction disk in the axial direction of the friction disk or in a diagonal direction.

The fan shape according to one of the preferred embodiments has proven to be particularly advantageous for the cooling and consequently the service life of the false twist device equipped with such a friction disk. This is because the improved cooling effect reduces the wear of the friction disk, since the temperature-dependent chemical load on the friction disk during the spin preparation can be reduced. This is because the higher the temperature of the friction disk, the faster the chemical reactions on the friction disk associated with the spin preparation take place, which cause increased wear on the friction disk. Furthermore, by providing friction disks that provide cooling, an external cooling air supply that would otherwise be required, for example by providing separate, space-consuming fans or similar, can be dispensed with.

According to a further preferred embodiment, the friction disk has a PU layer with a thermally conductive material, such as aluminum. This can also achieve a cooling effect. In conjunction with the fan shape, the cooling effect can be further improved.

According to a further aspect of the present invention, a false twisting device is proposed which comprises a bearing block which has at least one rotatably mounted shaft which has at least two friction disks arranged along the shaft at a distance from one another, wherein one of the friction disks, in particular the friction disk arranged furthest from the bearing block, is a friction disk with cooling effect according to one of the above preferred embodiments. Particularly preferably, the False twist device has three shafts, each of which is rotatably supported and driven in the bearing block. The shafts are further preferably arranged at a distance from one another in a triangle such that the friction disks arranged on the shafts overlap in the center of the triangle. This makes it possible to provide a self-cooling false twist device with an increased service life.

Further details of the invention can be taken from an embodiment illustrated below with reference to the figures.

Fig. 1

schematisch in perspektivischer Ansicht eine Falschdrallvorrichtung, die mehrere rotatorisch gelagerte Wellen aufweist, auf denen jeweils drei Friktionsscheiben nach einem Ausführungsbeispiel festgelegt sind,

Fig. 2

die Nabe einer Friktionsscheibe nach einem Ausführungsbeispiel in Draufsicht,

Fig. 3

die Nabe einer Friktionsscheibe, gemäß Schnitt B - B der Fig.2,

Fig. 4

die Nabe der Friktionsscheibe, gemäß Schnitt A - A der Fig.2,

Fig. 5

eine Friktionsscheibe nach einem Ausführungsbeispiel im Schnitt, mit einer Nabe, deren Stützring von einem durch eine PU-Schicht gebildeten Laufring umgeben ist,

Fig. 6

in perspektivischer Ansicht eine Friktionsscheibe nach einem Ausführungsbeispiel annähernd im Originalmaßstab,

Fig. 7

eine Friktionsscheibe nach einem Ausführungsbeispiel im Schnitt, mit einer in Ventilatorform ausgebildeten Nabe, und

Fig. 8

eine schematische Teilschnittansicht einer Ventilatorschaufel der in Fig. 7 gezeigten Friktionsscheibe.

It shows:

Fig.1

schematically in perspective view a false twist device which has several rotationally mounted shafts on each of which three friction disks are fixed according to an embodiment,

Fig.2

the hub of a friction disc according to an embodiment in plan view,

Fig.3

the hub of a friction disc, according to section B - B of the Fig.2 ,

Fig.4

the hub of the friction disc, according to section A - A of the Fig.2 ,

Fig.5

a friction disc according to an embodiment in section, with a hub whose support ring is surrounded by a race formed by a PU layer,

Fig.6

in perspective view a friction disc according to an embodiment approximately in original scale,

Fig.7

a friction disc according to an embodiment in section, with a hub designed in fan shape, and

Fig.8

a schematic partial sectional view of a fan blade of the Fig.7 shown friction disc.

The Figure 1 shows schematically in perspective view an embodiment of a false twist device 1, as used for example in texturing machines in connection with the production of crimped textile threads 3.

As is known, such false twist devices 1 each have a bearing block 2 with several rotatably mounted shafts 4, which are connected at the end to a Fig.1 not shown, drive. Such drives for false twist devices are known and are used, for example, in the EP 0 744 480 A1 described in relatively great detail.

As from Fig.1 As can be seen further, the shafts 4, each of which is equipped with friction disks 5, are arranged in such a way that they form a triangle. In the exemplary embodiment, each of the shafts 4 has three friction disks 5 arranged one behind the other at a distance in the running direction F of the thread 3.

The exact design of a friction disk 5 according to an embodiment is explained below with reference to the Figures 2 - 6 explained in more detail.

The Figures 2 - 4 show on a larger scale and in different views a hub 6 made of plastic of a friction disk 5 according to an embodiment.

As from Fig.2 , which shows a hub 6 in plan view, the hubs 6 of such friction disks 5 each have an annular base body 13 made from a plastic by injection molding with a central bore 8. The diameter of this central bore 8 is matched to the diameter of the shafts 4 of the false twist device 1, so that friction disks 5 can be easily positioned on the shafts 4 of a false twist device 1 after their completion.

As can also be seen, such hubs 6 each have an outer, circular support ring 7 and, spaced from this support ring 7, a projection 11 which also runs around the circumference. Between the support ring 7 and the projection 11, a plurality of locking openings 12, eighteen in the exemplary embodiment, are also arranged in the base body 13 of the hub 6. These locking openings 12 serve, as will be explained below, to fix a Figures 5 and 6 shown race ring 9 of the friction disc 5, consisting of a PU layer.

The Figures 3 and 4 show the hub 6 of a friction disk 5 in section. The Fig.3 shows the hub 6 according to section B - B of the Fig.2 , while in Fig.4 the hub 6 according to section A - A of the Fig.2 is shown.

As can be seen from the Figures 3 and 4 As can be seen, the base body 13 of the hub 6 has its maximum cross-sectional width BN in the area of the central bore 8, while the cross-sectional width BS of the outer, circumferential support ring 7 of the hub 6 is slightly below the maximum cross-sectional width BN of the hub 6.

Furthermore, the base body 13 of the hub 6 has a projection 11 which is arranged at a distance from the support ring 7 and also runs all the way around, the cross-sectional width BA of which is slightly less than the cross-sectional width BS of the support ring 7.

As can be seen in particular from the Figures 2 and 4 As can be seen, in the area between the support ring 7 and the projection 11 there are also a number of so-called locking openings 12, in the embodiment eighteen, which ensure proper fixation of a PU-made Figures 2 - 4 not shown race 9.

The Fig.5 shows a section through a finished friction disk 5 according to an embodiment, that is, a friction disk 5 having a hub 6 made of PBT using the injection molding process, which is surrounded by a race 9 also made using the injection molding process.

The race ring 9, which consists of a PU layer, surrounds the support ring 7, rests on the shoulder 11 and is ground according to a predeterminable profile 14, has a substantially uniform, relatively thin profile thickness. In addition, the flanks 10 of the race ring 9 in the area of the support ring 7 are ground to a predefined width dimension BFL. The width dimension BFL of the flanks 10 of the race ring 9 is slightly smaller than the maximum cross-sectional width BN of the hub 6.

In Fig.6 a friction disk 5 according to an embodiment is shown in a perspective view approximately on a scale of 1:1. This friction disk 5 has, as already explained above, a hub 6 made of a plastic with a central bore 8 and a race 9 also made of a plastic. The hub 6, which is manufactured using the injection molding process, advantageously consists of PBT (polybutylene terephthalate) 40% GK natural, while the race 5 consists of a PU layer, which preferably has a hardness of at least or exactly 85 Shore A.

Fig.7 shows a friction disc 5 according to a further preferred embodiment in section, which is approximately equal to the friction disc 5 according to Fig.6 is formed, the only difference being in the design of the hub 6. Regarding the same design, marked with the same reference symbols, reference is therefore made to the above description.

The hub 6 according to this preferred embodiment is formed as an axial fan, wherein the base support section between the central bore 8 and the projection 11 has a plurality of fan blades 15 circumferentially around the central bore 8, in particular evenly distributed, which have an aerodynamic profile for the defined conduction of the ambient air from one side of the friction disk 5 to the other side. Fig.8 shows in this context a schematic partial sectional view of a fan blade 15 of the friction disc 5 according to Fig.7 in a perspective from the central bore 8 in the direction of the support ring 11.

The friction disk 5 according to this preferred embodiment promotes a cooling effect of both the friction disk 5 and the false twist device in which such a friction disk 5 is used. For example, the friction disk 5 according to this embodiment can be used in a Fig.1 shown false twist device 1 can be used. It would be advantageous to arrange the friction disk 5 on the shaft 4 in the thread running direction F in the first place, i.e. at a position of the friction disks 5 to be arranged that is furthest away from the bearing block 2. Such an arrangement allows cooling of the friction disks 5 arranged downstream in the thread running direction F as well as the bearing block 2 in which the drive for the shafts 4 can be housed during rotation of the friction disk 5 equipped with the hub 6 designed as a fan. This has a beneficial effect on both the wear and the service life of the friction disks 5.

List of reference symbols

1

False twist device

2

Bearing block

3

thread

4

Wave

5

Friction disc

6

hub

7

Support ring

8th

Central bore

9

Race

10

flank

11

Approach

12

Locking opening

13

Base body

14

profile

15

Fan blade

F

Thread direction

BS

Cross-sectional width/support ring

BFL

Width/flanks

BN

max. cross-sectional width/hub

BA

Cross-sectional width/approach

Claims (10)

1. A friction disc (5) for a false-twist device (1), comprising an annular hub (6), on which a circular race (9) is fixable that can be formed by a polyurethane (PU) layer and has a minimum wall thickness required for a secure interlocking fit, the hub (6) having a circumferential support ring (7) and a central hole (8), by which the friction disc (5) is fixable on one of the shafts (4) of the false-twist device (1),
   characterized in that

   the formed race (9) fixed on the hub (6) is ground according to a predefinable profile such that the flanks (10) of the race (9) have a predefinable width dimension (BFL) following the grinding process; and/or

   the hub (6) has, at a spacing from the support ring (7), a circumferential shoulder (11) for abutment for the fixable PU layer, a cross-sectional width (BA) of the shoulder (11) being smaller than a cross-sectional width (BS) of the support ring (7).
2. The friction disc (5) according to claim 1, characterized in that the width dimension (BFL) of the flanks (10) of the formed race (9) fixed on the hub (6) is equal to or smaller than the maximum cross-sectional width (BN) of the hub (6).
3. The friction disc (5) according to claim 2, characterized in that the wall thickness of the PU layer of the race (9) is minimized to the minimum wall thickness required for the secure interlocking fit.
4. The friction disc (5) according to claim 1, characterized in that the hub (6) is made of a plastic material.
5. The friction disc (5) according to claim 4, characterized in that the hub (6) is made of polybutylene terephthalate (PBT).
6. The friction disc (5) according to claim 1, characterized in that the PU layer of the formed race (9) fixed on the hub (6) has a hardness of at least 85 Shore A.
7. The friction disc (5) according to claim 1, characterized in that the hub (6) has at least one passage which passes through the hub (6) in order to channel, in a predefined manner, the air flowing through the at least one passage during rotational operation of the friction disc (5).
8. The friction disc (5) according to claim 7, characterized in that the at least one passage is designed such that the air flowing through the at least one passage during rotational operation of the friction disc (5) leads towards an additional friction disc (5) of the false-twist device (1) arranged adjacently to the friction disc (5).
9. The friction disc (5) according to claim 7 or 8, characterized in that the hub (6) forms a fan shape having a plurality of passages, which are separated from one another by a partition having a predetermined blade geometry for the defined channeling of the air flowing therethrough.
10. A false-twist device (1) comprising a bearing block (2) having at least one rotatably mounted shaft (4) comprising at least two friction discs (5) arranged along the shaft (4) at a spacing from each other thereon, characterized in that one of the friction discs (5) is a friction disc (5) according claim 8 or 9.

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