WO2006134066A1

WO2006134066A1 - Coated spinning ring

Info

Publication number: WO2006134066A1
Application number: PCT/EP2006/063020
Authority: WO
Inventors: Peter Osselaer; Marc Sercu
Original assignee: Nv Bekaert Sa
Priority date: 2005-06-13
Filing date: 2006-06-08
Publication date: 2006-12-21

Abstract

The invention relates to a spinning ring having a low friction, high durability bearing surface for supporting a traveler. At least the bearing surface of the spinning ring is coated with a layered structure. The layered structure comprises at least a diamond-like carbon layer and a diamond-like nanocomposite layer. The diamond- like nanocomposite layer is located at outer surface of the layered structure.

Description

Coated spinning ring

Field of the invention.

The invention relates to a spinning ring and more particularly to a spinning ring having a low friction, high durability bearing surface for supporting a traveler.

Background of the invention.

In a conventional spinning operation, spinning rings are used to support a traveler moving rapidly around the circumference of the spinning ring.

The traveler engages and guides a loose yarn as it is being twisted and wound onto a twisting spindle.

As textile industry is moving to higher spinning speeds, traveler speeds also increases. However, the increase in spinning speeds is limited. As spinning speeds increase, both tension, which is the force exerted by the yarn on the traveler, and friction, which is the force that opposes relative motion between the yarn and the traveler and between the traveler and the ring, increase.

Furthermore, as spinning speed increase, the bearing surface of the ring become roughened and the life time of a spinning ring will be limited.

Therefore, there is a need for spinning rings having simultaneously a high surface durability and low frictional characteristics.

Combining high durability and a low friction surface is however contradictory as high durability surface requires a high hardness and surfaces having a high hardness apply a significant force to the traveler.

Spinning ring coated with a diamond like carbon coating are described in EP 861922.

However, this type of spinning rings has a high running-in period. During this running-in period the spinning equipment is operated at a low spinning speed, resulting in a loss of productivity. Summary of the invention.

It is an object of the present invention to provide a spinning ring avoiding the problems of the prior art.

It is another object of the invention to provide a spinning ring combining a high durability, a high hardness and a low friction.

It is a further object of the invention to provide a spinning ring that avoids long running-in periods.

It is still a further object of the invention to provide a spinning ring having self-lubricating properties so that the use of liquid lubricants is no longer required.

According to a first aspect of the present invention, a spinning ring is provided. The spinning ring has a bearing surface for supporting a traveler. The bearing surface is coated with a layered structure. The layered structure comprises at least a diamond-like carbon layer and a diamond-like nanocomposite layer. The diamond-like nanocomposite layer is thereby located at the outer surface of said layered structure. The diamond-like nanocomposite layer is making contact with the traveler.

Possibly, the layered structure comprises a number of periods, each period comprising a diamond-like carbon layer and a diamond-like nanocomposite layer. The number of periods ranges preferably between 2 and 100 as for example between 5 and 30.

Diamond-like carbon layer

The diamond-like carbon layer comprises preferably amorphous hydrogenated carbon (a-C:H).

Preferably, a diamond-like carbon layer comprises a mixture of sp² and sp³ bonded carbon with a hydrogen concentration between 0 and 60 at%. More preferably, the hydrogen concentration is between 20 and 30 at%. The diamond-like carbon layer may be metal doped, for example to influence the electrical conductivity of the coating. Preferred doping elements are transition metals, such as the transition metals of Group IVB to VIIB of the periodic table. W, Zr and Ti are for example well suited as doping element.

The thickness of the DLC layer is preferably between 0.1 and 10 μm, as for example between 0.5 and 3 μm.

The hardness of a DLC coating is preferably between 18 -25 GPa.

The hardness is measured by nanoindentation.

A DLC coating is characterized by a coefficient of friction ranging between 0.1 and 0.2. The coefficient of friction is measured by means of a steel-ball-on disc test in dry circumstances (10 Newton, 0.17 m/s,

25 ⁰C, 50 % relative humidity, 100 000 cycles).

The DLC layer may be deposited by any technique known in the art. A preferred technique comprises chemical vapor deposition (CVD), such as plasma assisted chemical vapor deposition (PACVD).

Diamond-like nanocomposite layer

The diamond-like nanocomposite (DLN) layer comprises an amorphous structure of C, H, Si and O. Preferably the diamond-like nanocomposite layer comprises in proportion ot the sum of C, Si and O : 40 to 90 % C, 5 to 40 % Si, and 5 to 25 % O (expressed in at%).

Preferably, the diamond-like nanocomposite layer comprises two interpenetrating networks of a-C:H and a-Si:O.

The diamond-like nanocomposite coating may further be doped with a metal, such as a transition metal. Preferred transition metals are the metal of Group IVB to VIIB of the periodic table. The coating can be doped to influence the conductivity of the coating. W, Zr and Ti are for example well suited as doping element.

The diamond-like nanocomposite layer has preferably a thickness ranging between 0.01 and 5 μm. More preferably, the thickness is beween 0.1 and 1 μm, as for example 0.2 or 0.5 μm.

The hardness of a DLN coating is preferably between 8 - 18 GPa. The hardness is measured by nanoindentation.

A DLN coating is characterized by a coefficient of friction ranging between 0.05 and 0.1. The coefficient of friction is measured by means of a steel-ball-on disc test in dry circumstances (10 Newton, 0.17 m/s, 25 ⁰C, 50 % relative humidity, 100 000 cycles).

The diamond-like nanocomposite layer may be deposited by any technique known in the art. A preferred technique comprises chemical vapor deposition (CVD), such as plasma assisted chemical vapor deposition (PACVD).

Compared to diamond-like carbon layers, diamond-like nanocomposite layers have a lower hardness.

As high durability and high hardness are the first requirements of a spinning ring, a person skilled in the art will choose a diamond-like carbon coating and will not be inclined to choose a diamond-like nanocomposite coating.

Surprisingly, it has been found that a layered structure comprising a diamond-like carbon layer and a diamond-like nanocomposite layer with the diamond-like nanocomposite layer being located outermost.

The layered structure according to the present invention is combining the advantages of a diamond-like carbon layer and a diamond-like nanocomposite layer : a high hardness, a low coefficient of friction and a good adhesion to the substrate.

The application of a layered structure according to the present invention results in an improved spinning ring. First of all, a spinning ring according to the present invention has a bearing surface for a traveler having a low friction and a high durability.

The spinning ring according to the present invention has self-lubricating properties so that liquid lubricants are not needed.

As a spinning ring according to the present invention does not require a running-in period, a significant increase in the production yield can be realized.

The extreme wear resistance and self-lubricating properties of the coating yield a higher lifetime of both the spinning ring and the traveler.

Furthermore the quality of the yarn is improved and remains stable for a longer period.

Adhesion promoting layer

To further increase the adhesion of the layered structure to the spinning ring, it can be preferred to deposit an adhesion promoting layer on the spinning ring before the deposition of the layered structure.

As adhesion promoting layer, any layer increasing the adhesion of the layered structure to the spinning ring can be considered. Preferably, the adhesion promoting layer comprises at least one element of the group consisting of silicon and the elements of group IVB, the elements of group VB, the elements of Group VIB of the periodic table. Preferred adhesion promoting layers comprise Ti and/or Cr.

Possibly, the adhesion promoting layer comprises more than one layer, for example two or more metal layers, each layer comprising a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group VB and the elements of group VIB of the periodic table, as for example a Ti or Cr layer. Alternatively, the adhesion promoting layer may comprise one or more layers of a carbide, a nitride, a carbonitride, an oxycarbide, an oxynitride, an oxycarbonitride of a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group

VB and the elements of group VIB of the periodic table. Some examples are TiN, CrN, TiC, Cr₂C₃, TiCN and CrCN.

Furthermore, the adhesion promoting layer may comprise any combination of one or metal layers of a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group VB and the elements of group VIB of the periodic table and one or more layers of a carbide, a nitride, a carbonitride, an oxycarbide, an oxynitride, an oxycarbonitride of a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group

VB and the elements of group VIB of the periodic table. Some examples of adhesion promoting layers comprise the combination of a metal layer and a metal carbide, the combination of a metal layer and a metal nitride, the combination of a metal layer and a metal carbonitride, the combination of a metal layer, a metal carbide layer and a metal layer and the combination of a metal layer, a metal nitride layer and a metal layer.

The thickness of the adhesion promoting layer is preferably between 10 nm and 5 μm. More preferably, the thickness of the adhesion promoting layer is between 100 nm and 1 μm.

The adhesion promoting layer can be deposited by a number of different techniques as for example by physical vapor deposition such as sputtering or by chemical vapor deposition such as plasma assisted chemical vapor deposition. Spinning ring

The spinning ring can be made of any metal or metal alloy. Preferably, the spinning ring is made of a steel alloy such as low carbon steel (carbon content ranging between 0.08 and 0.25 %).

Possibly, a chromium coating is applied on the spinning ring before the deposition of the layered structure.

In case the spinning ring is made of low carbon steel, it is preferred that the spinning ring is subjected to a carburizing or a carbonitriding treatment before the layered structure according to the present invention is applied.

By such a treatment the carbon content is increased in the outer layer of the spinning ring. With 'outer layer' is meant the layer located at the outer surface of the spinning ring having a thickness ranging between 1 μm and 4 mm, for example between 2 μm and 2 mm.

In carburizing or carbonitriding treatments known in the art, the outer layer has a carbon content between 1 and 1.2 %. Surprisingly, it has been shown that a coated spinning ring according to the present invention has the best performance characteristics if the carbon content in the outer layer is lower than 1.0 %, as for example between 0.6 and 1 % C. More preferably, the carbon content of the outer layer is between 0.6 and 0.9 % as for example 0.8 %. By applying a layered structure according on a low carbon spinning ring having in the outer layer between 0.6 and 1 % C, an optimum in hardness, friction and adhesion of the layered structure to the spinning ring is obtained.

At least the bearing surface that is supporting and guiding the traveler is coated with the layered structure according to present invention. However, it can be preferred that, in addition to the bearing surfaces, other surfaces of the spinning ring are coated with the layered structure for example to give the spinning ring the desired corrosion protection. In some embodiments it is preferred that all surface of the spinning ring are coated with the layered structure.

Brief description of the drawings.

The invention will now be described into more detail with reference to the accompanying drawings wherein

Figure 1 is a partial cross-sectional view of a first embodiment of a spinning ring according to the present invention;

Figure 2 is a partial cross-section view of a second embodiment of a spinning ring according to the present invention.

Description of the preferred embodiments of the invention. Figure 1 is a partial cross-sectional view of a spinning ring 10. The spinning ring 10 has a flange 12 for supporting and guiding a traveler (not shown).

The spinning ring 10 may further comprise a vertical portion 14 and a mounting flange (not shown). The mounting flange 14 is used for mounting the spinning ring to the ring rail of a spinning apparatus and may have various shapes. Also flange 12 can have various shapes for cooperating with a traveler.

At least the surface 16 of the spinning ring 10 bearing a traveler 18 is coated with a layered structure according to the present invention.

In other embodiments, other surfaces of the spinning ring or even all surfaces of the spinning ring can be coated with a layered structure according to the present invention.

Figure 2 shows an alternative embodiment of a spinning ring 20.

At least the surface 26 bearing a traveler 28 is coated with a layered structure according to the present invention.

Some embodiments of coating for the traveler bearing surface of a spinning ring are given below. A first example comprises a coated spinning ring known in the prior art having a diamond-like carbon layer. The diamond-like carbon layer has a thickness ranging between 0.5 and 3 μm.

A second, third and fourth example comprise coated spinning rings according to the present invention.

In the second, third and fourth example, the spinning rings are coated with a layered structure comprising at least one diamond-like carbon layer and at least one diamond-like nanocomposite layer with the diamond-like nanocomposite layer being located outermost.

In the second example the spinning ring is coated with a layered structure comprising a diamond-like carbon layer deposited on the spinning ring and a diamond-like nanocomposite layer deposited on the diamond-like carbon layer.

The diamond like carbon layer has a thickness of between 0.5 and 3 μm and the diamond-like nanocomposite layer has a thickness between 0.5 and 1 μm.

In the third example the spinning ring is coated with a layered structure comprising a first diamond-like nanocomposite layer deposited on the spinning ring, a diamond-like carbon layer deposited on the diamond- like nanocomposite layer and a second diamond-like nanocomposite layer deposited on the diamond-like carbon layer. The thicknesses of the layers are respectively between 0.5 and 1 μm, between 0.5 and 3 μm and between 0.5 and 1 μm.

In the fourth example the spinning ring is coated with a layered structure comprising an adhesion promoting layer deposited on the spinning ring, a diamond-like carbon layer deposited on the adhesion promoting layer and a diamond-like nanocomposite layer deposited on the diamond-like carbon layer. The thicknesses of the layers are respectively between 0.1 and 0.5 μm, between 0.5 and 3 μm and between 0.5 and 1 μm.

A person skilled in the art would not be inclined to use a coating for a spinning ring having a diamond-like nanocomposite layer outermost as used in the second, third and fourth example, as one of the requirement of a spinning ring is having a high durability and thus a high hardness. As the hardness of a diamond-like nanocomposite layer is considerably lower than the hardness of a diamond-like carbon layer, the hardness of a layered structure having a diamond-like nanocomposite outermost will be lower than the hardness of a diamond-like carbon layer and a person skilled in the art would choose for the diamond-like carbon layer.

Surprisingly, it has been found that the spinning rings of the second, third and fourth example showed good results.

The running-in period, i.e. the period during which the spinning equipment is operated at a low spinning speed, is considerably decreased mainly due to the lower coefficient of friction.

This is leading to a higher productivity. Although the hardness of the layered structures of the second, third and fourth example is lower compared to the hardness of the coating of the first example, a high durability is maintained.

Claims

1. A spinning ring having a bearing surface for supporting a traveler, said bearing surface being coated with a layered structure, said layered structure comprising at least a diamond-like carbon layer and a diamond-like nanocomposite layer, said diamond-like nanocomposite layer being located at the outer surface of said layered structure.

2. A spinning ring according to claim 1 , whereby said layered structures comprises a number of periods, each period comprising a diamond-like carbon layer and a diamond-like nanocomposite layer.

3. A spinning ring according to claim 1 or 2, whereby said number of periods ranges between 2 and 100.

4. A spinning ring according to any one of the preceding claims, whereby all surfaces of said spinning ring are coated with said layered structure.

5. A spinning ring according to any one of the preceding claims, whereby said diamond-like carbon layer comprises amorphous hydrogenated carbon (a-C:H).

6. A spinning ring according to any one of the preceding claims, whereby said diamond-like nanocomposite layer comprises in proportion to the sum of C, Si, and O in at%, 40 to 90 % C, 5 to 40 % Si, and 5 to 25 % O.

7. A spinning ring according to any one of the preceding claims, whereby said diamond-like carbon layer and/or said diamond-like nanocomposite layer are doped with a metal.

8. A spinning ring according to any one of the preceding claims, whereby said diamond-like carbon layer has a thickness ranging between 0.1 and 10 μm.

9. A spinning ring according to any one of the preceding claims, whereby said diamond-like nanocomposite layer has a thickness ranging between 0.01 and 5 μm.

10. A spinning ring according to any one of the preceding claims, whereby an adhesion promoting layer is deposited on at least said bearing surface of said spinning ring before the deposition of said layered structure.

11. A spinning ring according to claim 10, whereby said adhesion promoting layer comprises at least one element of the group consisting of silicon and of the elements of group IVB, the elements of group VB and the elements of Group VIB of the periodic table.

12. A spinning ring according to claim 10 or 11, whereby said adhesion promoting layer comprises at least one metal layer, said metal layer comprising at least one element of the group consisting of silicon and of the elements of group IVB, the elements of group VB and the elements of Group VIB of the periodic table.

13. A spinning ring according to any one of claims 10 to 12, whereby said adhesion promoting layer comprises at least one layer selected from the group consisting of carbides, nitrides, carbonitrides, oxycarbides, oxynitrides, oxycarbonitrides of at least one element of the group consisting of silicon, the elements of group IVB, the elements of group VB and, the elements of Group VIB of the periodic table.

14. A spinning ring according to any one of claims 10 to 13, whereby said adhesion promoting layer comprises a combination of at least one metal layer of a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group VB and the elements of group VIB of the periodic table and at least one layer of a carbide, a nitride, a carbonitride, an oxycarbide, an oxynitride, an oxycarbonitride of a metal selected from the group consisting of silicon, the elements of group IVB, the elements of group VB and the elements of group VIB of the periodic table

15. A spinning ring according to any one of the preceding claims, whereby said spinning ring comprises low carbon steel having at its outer layer a carbon content ranging between 0.6 and 1%.