EP0631961B1 - Yarn guiding component with an improved outer surface - Google Patents

Description

The present invention relates to thread-guiding components of a plant for the production, treatment and processing of fiber materials with a surface which comes into contact with the fiber materials or their raw materials, the properties of which change little over a long period of time during operation, and which therefore compared to corresponding conventional components have a significantly improved service life.

Numerous components are used in the production of synthetic fibers, which come into close contact with the spun, fast-running threads and have to perform various tasks. Examples of such components are bundling and deflecting elements which are intended to combine filament coulters or to change the running direction of filament bundles, drawing pins which have to determine the drawing point of filament webs, take-off godets, i.e. rolls which pull the filament sheets from the spinneret, drawing godets, between which the filament bundles are stretched and thus oriented and consolidated, swirling nozzles, in which the continuous filament bundles are swirled by blown compressed air in order to improve the textile effect of the threads and the cohesion of the individual filaments of the threads (thread closure).
Depending on the type of task, the filaments come into sliding contact with the components, such as, for example, in the case of deflection elements or swirling nozzles, or they should come into more or less positive or at least non-positive contact with the components, such as in the case of take-off or drawing godets or in sliding contact, but with which defined forces are to be transferred, such as for example with stretching pins.

It has long been shown that the quality of the threads obtained depends to a large extent on the flawless nature of the surfaces of these components and that changes in the surface during operation after a certain period of operation ("service life") lead to a sharp increase in defects in the generated Lead fiber material, which makes it necessary to replace the component. The replacement of the component causes considerable costs, since not only the costs for a new or reconditioned building have to be spent, but also the production has to be interrupted for a certain time, which causes additional costs at a considerable amount.

It is therefore customary to manufacture such thread-guiding components from wear-resistant materials that retain a defined surface over a long period of operation in order to ensure the longest possible service life.
The godets, which serve to convey the fiber materials, are a source of particularly frequent disturbances. On the one hand, they must be able to exert a high tensile force on the fiber materials wrapping around them, which requires positive, or at least non-positive, contact, but they must not tend to bind the individual filaments too tightly, as they would otherwise be torn out of the fiber bundle and disruptive windings form the godet. Such godets are therefore required to have the most favorable "grip-release" behavior. However, filament breaks not only impair the production process but also represent quality defects which can lead to serious difficulties in the further processing of the threads.

Widely used godets are made the surface of a ceramic material, preferably of a ceramic mixture of Al ₂ O ₃ 3 to 20 wt .-% of TiO _2, in particular approximately 13 wt.% TiO _2.
These standard godets can be used in both delivery and fume cupboards and allow at least practical continuous operation of a spinning system. However, the service life of these godets still leaves something to be desired, in particular the service life is spread statistically from godet to godet and, in addition, this fluctuation is increased by different loads on the godets, depending on the task at hand.
The person skilled in the art recognizes the increasing wear of the godet from the increase in defects (filament breaks) and the additional problem then arises the large number of godets installed in a spinning system to find the one that causes these defects.

There has been no shortage of attempts to improve the service life of thread-carrying components of spinning systems, especially godets.
From German patent specification DE-B-32 18 402 it is known, for example, to thread-guiding components, such as godets or stretching pins, with a coating of a metal-ceramic mixture with 50-90% by weight chromium carbide as the ceramic component and 50-10% by weight % of a nickel-chromium alloy as metal content.
This surface proves to be clearly superior to conventional surfaces made from Al ₂ O ₃ / TiO ₂ . Nevertheless, wishes remain open; in particular, the state of wear is not readily recognizable even on this surface.

From European patent EP-A-0 230 633 it is known to provide the surface of thread-carrying components with a ceramic or metal carbide coating, whereby tungsten carbide, but also titanium carbide, tungsten / titanium carbide and chromium carbide, possibly in combination with Cobalt, nickel, chrome or iron, but also pure ceramic materials made of aluminum, aluminum / titanium, chrome, chrome / aluminum or zirconium / magnesium oxides are particularly emphasized. To produce a defined surface finish, these layers are first treated with an epoxy resin that closes the pores of the layer, then ground to a low roughness of Ra = 0.2 to 0.76 μm and finally by laser engraving with a large number, for example 2032 to 13970 (80 to 550), recesses per mm (inch), which have a depth of a few microns to over 140 microns.

It has also been proposed to overcome the disadvantages of the prior art by using components in devices for the production, treatment and processing of fiber materials which are characterized in that the surface of the fiber material or raw material which comes into contact with the Component consists of a first 0.1 to 10.0 microns, preferably 1 to 5 microns thick layer of nitrides and / or carbides of titanium or chromium, which on a component or a second layer of a material with a specific electrical resistance of at most 25, preferably 20 to about 1.5 µΩ · cm is deposited. Although this measure leads to a valuable application-related improvement of the components, the long-term constancy of the surface properties still leaves something to be desired.

There was therefore still a need to design the surface of the godets in such a way that a surface structure with a favorable "grip-release" behavior is maintained during operation for as long as possible.
It has now been shown that the long-term durability of the godet surfaces can be decisively improved if one takes care from the outset to create a certain topography of the surface.
The present invention thus relates to thread-carrying components, in particular godets, with a defined surface topography.

• a) der aus 5 Messungen ermittelte Mittelwert $\overline{{\text{R}}_{\text{max}}}$
  
  ihrer maximalem Rauhtiefe R_max zwischen 20 und 30 µm liegt, mit einer Streubreite von 3 bis 8 µm, und
• b) der aus 5 Messungen ermittelte Mittelwert $\overline{{\text{R}}_{\text{Z}}}$
  
  ihrer gemittelten Rauhtiefe R_Z zwischen 15 und 25 µm liegt, mit einer Streubreite von 2 bis 5 µm.

Unter der "Streubreite" ist die Standardabweichung (Siehe "Ullmanns Encyklopädie der technischen Chemie", 4.Auflage, (1972), Bd.1, Seite 296) zu verstehen.The thread-guiding components according to the invention have, at least in the areas that come into contact with the fiber material, a surface made of a material with a specific electrical resistance of at most 25, preferably 20 to about 1.5 μΩ · cm, which is characterized in that
that

• a) the mean value determined from 5 measurements $\overline{{\text{R}}_{\text{Max}}}$
  
  their maximum roughness R _max between 20 and 30 microns, with a spread of 3 to 8 microns, and
• b) the mean value determined from 5 measurements $\overline{{\text{R}}_{\text{Z}}}$
  
  their average roughness depth R _{Z is} between 15 and 25 µm, with a spread of 2 to 5 µm.

The "deviation" is to be understood as the standard deviation (see "Ullmanns Encyklopadie der Technische Chemie", 4th edition, (1972), Vol. 1, page 296).

• c) sich ein Traganteil von 10 % sich in einer Ebene von 6 bis 12 µm Schnittiefe und ein Traganteil von 90 % sich in einer Ebene von 18 bis 25 µm Schnittiefe errechnet, und
• d) die Steigung der Schnittiefen/Traganteil-Funktion im Bereich zwischen 30 und 70 % Traganteil bei 0,11 bis 0,16 µm/% liegt.

Preferably, the surface coming into contact with the fiber material is designed in such a way that

• c) there is a load share of 10% in a plane of 6 to 12 µm Depth of cut and a load share of 90% is calculated in a plane of 18 to 25 µm depth of cut, and
• d) the slope of the depth of cut / bearing component function in the range between 30 and 70% bearing component is 0.11 to 0.16 µm /%.

The components according to the invention, especially if they have smaller dimensions, such as are given, for example, in swirling nozzles, can consist entirely of the material with a specific electrical resistance of at most 25, preferably 20 to about 1.5 μΩ · cm.
Larger components, such as godets, on the other hand, expediently consist, as usual, of suitable steels and are provided, at least in the regions of their surface which come into contact with the fiber materials, with a “thick layer” of such a metal-ceramic material.
Such a “thick layer” applied as a coating usually has a layer thickness of 100 to 400 μm, preferably 150 to 300 μm.

The surface topography is measured with a device that scans the contour of the surface along a measurement line of usually 5 mm in length with a stylus, the tip of which expediently has a rounding radius of approximately 5 μm.
The specified topography values relate to such a scan. A suitable device for determining the surface topography is, for example, a Perthometer M4P from Feinprüf-Perthen, equipped with a TKX 300 stylus with a rounding of 5 µm.

The deflections of the needle are stored digitally and the course of the surface profile thus obtained is evaluated mathematically.
At the same time, a graphical representation of the surface profile along the measuring line can take place.
1 shows a schematic representation of such a surface profile to explain the terms "maximum roughness depth" and "average roughness depth".

FIG. 2 serves to explain the term “load share”.

From Figure 1 it can be seen that the roughness is the distance in microns between the lowest point and the highest point of a profile section. To determine the average roughness depth R _Z , a measuring section l _{m is divided} into 5 equal sections l ₀ and its individual roughness depth R _{Z is} determined for each section l ₀ . The arithmetic mean of the 5 individual values R _Z1 , R _Z2, etc. obtained is the value of the average roughness depth R _Z. $${\text{R}}_{\text{Z}}{\text{= 1/5 · (R}}_{\text{Z1}}{\text{+ R}}_{\text{Z2}}{\text{+ R}}_{\text{Z3}}{\text{+ R}}_{\text{Z4}}{\text{+ R}}_{\text{Z5}}\text{)}$$

The maximum roughness depth R _max is the largest of the five determined individual values of the roughness depth.

und $\overline{{\text{R}}_{\text{Z}}}$

ergeben sich durch arithmetische Mittelwertbildung aus 5 Messungen von R_max bzw. von R_Z. $$\begin{array}{c}\begin{array}{c}\overline{{\text{R}}_{\text{max}}}{\text{= 1/5 · (R}}_{\text{max1}}{\text{+ R}}_{\text{max2}}{\text{+ R}}_{\text{max3}}{\text{+ R}}_{\text{max4}}{\text{+ R}}_{\text{max5}}\text{)}\\ \overline{{\text{R}}_{\text{Z}}}\text{= 1/25 ·}\sum_{=\text{i=1}}^{\text{i=25}} {\text{R}}_{\text{Zi}}\end{array}\end{array}$$

The mean values given under point a) above $\overline{{\text{R}}_{\text{Max}}}$

and $\overline{{\text{R}}_{\text{Z}}}$

arithmetic averaging results from 5 measurements of R _max or R _Z. $$\begin{array}{c}\begin{array}{c}\overline{{\text{R}}_{\text{Max}}}{\text{= 1/5 · (R}}_{\text{max1}}{\text{+ R}}_{\text{max2}}{\text{+ R}}_{\text{max3}}{\text{+ R}}_{\text{max4}}{\text{+ R}}_{\text{max5}}\text{)}\\ \overline{{\text{R}}_{\text{Z}}}\text{= 1/25}\sum_{=\text{i = 1}}^{\text{i = 25}} {\text{R}}_{\text{Room}}\end{array}\end{array}$$

und $\overline{{\text{R}}_{\text{Z}}}$

liegen somit die Meßwerte von 25 Einzelabschnitten l₀ zugrunde.Any given mean $\overline{{\text{R}}_{\text{Max}}}$

and $\overline{{\text{R}}_{\text{Z}}}$

are thus the measured values of 25 individual sections based l _0th

FIG. 2 shows a section of a surface section profile in which the section planes (1) and (2) are shown in dashed lines. The cutting plane (1) cuts the profile in the areas (11), (12) and (13) which are drawn out more strongly, the cutting plane (2) in the areas (21), (22), (23) and (24).

The sum of the length l _{is of} these areas in relation to the total length of the measuring section l _X is the load bearing component TA _S in the depth of cut S. $${\text{TA}}_{\text{S}}\text{[\%] =}\frac{\text{100}\sum_{=\text{i = 1}}^{\text{i = n}} {\text{l}}_{\text{is}}}{{\text{l}}_{\text{X}}}$$

The load factor TA _S is therefore a function of the depth of cut S. $${\text{TA}}_{\text{S}}\text{= f (S)}$$

FIG. 3 shows a graphical representation of such a function in the range from 10 to 90% of the load.

Components according to the invention are particularly preferred, in particular godets, which still have a particularly hard outer layer on the surface of the defined topography described above.

The outer layer, which is to be regarded as a so-called “thin layer” due to its small thickness, preferably consists of titanium nitride (TiN) and / or titanium carbonitride (Ti (C, N)) and / or chromium nitride (CrN), in particular titanium nitride (TiN) , and / or titanium carbonitride (Ti (C, N)).
The thin layers made of these materials have intrinsic colors. Titanium nitride layers have yellow, mixed crystal layers with titanium carbide bronze or brownish shades, titanium carbonitride layers have a blue-gray to violet color and chrome nitride layers are white to brown-gray.

In a particularly preferred embodiment of the present invention, the composition of the material is selected such that outer layers with a golden yellow to bronze shade are obtained.

The superiority of the devices according to the invention results from the interaction of the outer layer with the structure of the surface on which it is applied is deposited.

Godets with the surface structure according to the invention, i.e. with a roughness depth of 15 to 25 µm are preferably used for the non-positive conveying of fiber materials or for guiding and bundling fiber materials, e.g. as high-wrap godets in take-off and drafting units or in swirling nozzles.

The interaction of such a surface of defined topography with the hard outer layer described above results in relatively low dry friction coefficients between the surfaces and the fiber materials.

The components according to the invention can be formed, for example, by pressing and sintering processes known per se from metal-ceramic materials with a specific resistance of at most 25 μΩ · cm. Such components can e.g. B. Swirl nozzles.
Larger components, such as godets, on the other hand, are expediently made as usual from suitable steels and provided, at least in the regions of the surface thereof which come into contact with the fiber material, with a “thick layer” of such a metal-ceramic material.
In the particularly preferred embodiment of the invention, the hard outer layer is located on this “thick layer” of defined surface structure.

FIG. 4 schematically shows a cross section perpendicular to the center line of a cylindrical godet (41) according to the invention, with the base body (42) made of metal, the thick layer (43) deposited on its surface with a roughness depth as defined above and the outer layer applied thereon ( 44), the dimensions of the godet radius and layer thicknesses shown in the figure not being drawn to scale in order to ensure sufficient clarity.

A preferred metal-ceramic material for the thick layer consists of tungsten carbide (WC) with a carbon content of at least 6.15% by weight with the addition of 10 to 20% by weight of a metal from group 8 of the periodic table, preferably cobalt.
For example, a metal-ceramic material made of 85 to 88% by weight of WC and 15 to 12% by weight of cobalt has proven to be a particularly suitable material for such a thick layer.
Furthermore, the material can also contain up to 5% by weight of other additives customary in hard materials.

The components according to the invention are produced by first producing a corresponding component with a surface which has the topography defined above.
Depending on the size and shape of the device according to the invention, this is done either by producing the desired component, for example by pressing and sintering processes known per se, from the metal-ceramic material described above, the roughness depth R _{Z of} the surface being 15 is set to 25 microns, or the component made of conventional steel is made by known plasma spraying processes, such as, for example, in "Ullmanns Encyklopedia of Technical Chemistry", fourth edition, volume 16, page 546, and volume 2, pages 400-405 and those therein cited primary literature are described, coated with a 100 to 400 µm thick thick film made of the above thick film material. The spray parameters are set so that the topography described above is achieved.

The outer layer made of the materials mentioned above can then be evaporated on the thick layer produced in this way in order to produce the preferred embodiment. The vapor deposition of thin layers is also a known operation and is described, for example, in "Ullmanns Encyklopedia of industrial chemistry", fourth edition, volume 10, pages 257 to 260, and the primary literature cited therein.

It is particularly preferred to design godets according to the invention.

The following table shows the differences in the service life of a godet coated with a conventional surface made of Al ₂ O ₃ with 13% by weight TiO ₂ and a godet designed according to the invention under identical operating conditions and the same production rate.
The end of the service life is defined by the fact that the roughness has dropped below an R _z value of 10 µm and that godet coils form despite suitable scraping devices. table Type of coating Tool life (days) Remarks Al ₂ O ₃ / TiO2 on steel (conventional standard godet; comparison) 100 Degree of wear of the surface not visually recognizable. TiN thin film on WC / Co thick film (according to the invention) > 300 Degree of wear of the surface visually recognizable.

A particular advantage of the preferred galette coated according to the invention with an outer layer is that its surface condition can be recognized by its color and therefore a targeted exchange can be carried out before the quality of the fiber material produced deteriorates.

Claims (6)

1. A thread-guiding component of apparatus for producing, treating and processing fiber materials which has at least in the areas which come into contact with the fiber material a surface composed of a material having a specific electric resistance of not more than 25, preferably from 20 to about 1.5 µΩ·cm, which surface is characterized in that

   a) the 5 measurement average value $\overline{{\text{R}}_{\text{max}}}$

   

   of its maximum roughness depth R_max is between 20 and 30 µm, with a root mean square deviation from 3 to 8 µm, and

   b) the 5 measurement average value $\overline{{\text{R}}_{\text{Z}}}$

   

   of its averaged roughness depth R_z is between 15 and 25 µm, with a root mean square deviation from 2 to 5 µm.
2. The thread-guiding component of claim 1, characterized in that the surface is such that

   c) the loadbearing proportion works out at 10% for a plane at a depth of cut from 6 to 12 µm and at 90% for a plane at a depth of cut from 18 to 25 µm, and

   d) the slope of the depth of cut/loadbearing proportion function is from 0.11 to 0.16 µm/% within the loadbearing proportion range from 30 to 70%.
3. The thread-guiding component of at least one of claims 1 and 2, characterized in that it consists in its entirety of the cermet material having a specific electric resistance of not more than 25, preferably from 20 to about 1.5 µΩ·cm or has a thick layer of such a material at least in the areas which come into contact with the fiber material.
4. The thread-guiding component of at least one of claims 1 to 3, characterized in that it has an outer layer of titanium nitride (TiN) and/or titanium carbonitride (Ti(C,N)) and/or chromium nitride (CrN).
5. The thread-guiding component of at least one of claims 1 to 4, characterized in that the cermet material having a specific electric resistance of not more than 25, preferably from 20 to about 1.5 µΩ·cm consists of tungsten carbide (WC) having a carbon content of at least 6.15% by weight with an addition of from 10 to 20% by weight of a metal of group 8 of the periodic table, preferably of cobalt.
6. The thread-guiding component of at least one of claims 1 to 5, characterized in that it is a godet.

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