THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

A RING WITH IMPROVED COATING FOR USE IN A TEXTILE MACHINE

FIELD OF THE INVENTION

[0001] This invention relates to generally to, a ring for spinning
and/or twisting for use in a textile machine, and more particularly to, a spinning and/or twisting ring with an improved coating and method thereof, for use in a textile machine.

PRIOR ART

[0002] In general, in a textile machine, a spinning and/or twisting
ring (hereinafter referred to as a ring or spinning ring) is used to support a traveler that moves rapidly around the circumference of the spinning ring. The ring generally includes a flange portion that makes up a track for running of the traveler in sliding contact condition. During operation, the traveler engages the ring and guides the delivery of a yarn from a drafting zone as the yarn gets twisted and wound onto a tube mounted on a spindle.

[0003] In the above-mentioned set-up of operation, an increase in the spinning speed increases the speed at which the traveler revolves around the surface of the spinning ring thereby, increasing the centrifugal force generated between the traveler and the ring. Greater the centrifugal force, greater is the functional heating of the ring and the traveler and greater is the abrasion of the ring relative to the traveler. In the event of frequent high speed operation, fine vibrations are likely to be generated on the ring flange portion which may cause abnormal wear and reduce the service life of both the ring and traveler. As a result, surface of the ring gets peeled off, chipped, or otherwise become roughened. As the spinning speed increases, the resulting increase in frictional or abrasion between the ring and the traveler may cause breakage of the yarn being spun or twisted. Yarn breakages are particularly undesirable because they lead to downtime in the spinning operation and thus lead to a reduction in manufacturing efficiency. For this reason, the construction of the ring and the traveler has a significant impact on the efficiency of the ring spinning and twisting operations.

[0004] US4677817 issued to Kanai discloses a traveler for spinning made of hard drawn steel wire or alloy steel wire, having at least at the surface of a part which makes contact with a ring a ceramic coated layer. The ceramic coated layer consists of one or plural layers selected from a layer of carbide, nitride, oxide, boride or the like. The traveler with a ceramic coated layer has high wear resistance, runs stably for many hours, prevents frequent yarn breakage and has longer service life.

[0005] International Patent Application Publication No. WO2006134066 titled "Coated spinning ring" discloses 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 the outer surface of the layered structure.

[0006] In the conventional rings disclosed above, the rings are coated with hard chrome plating having higher coefficient of friction and lesser hardness. Further the hard chrome plated rings do not provide higher machine efficiencies at higher speeds of the spindle rotation. The main drawback in the hard chrome plating is substantial rejections of ring at the manufacturing stage itself due to the inherent problems associated with the manufacturing process (i.e. peel off, rough surface finish, etc). It also pollutes the environment. Further, after assembling the rings in the machine, the spindle speed has to be maintained at lower levels for few days in order to provide proper running-in for the rings. During running-in period, the production efficiency is very low.

[0007] Thus there is a need in the art for a ring that overcomes the disadvantages of the prior art.

OBJECTS OF THE INVENTION

[0008] An object of the present invention is to provide a ring with an improved coating, for spinning and twisting in textile machines, wherein the ring provides for zero running-in period after assembling of the ring on to the textile machine frame, and has smooth surface and higher resistance to wear and tear.

[0009] It is another object of the present invention to provide a ring for textile spinning and twisting, wherein the ring provides for enhanced efficiency of textile spinning and twisting.
[0010] It is yet another object of the present invention to increase the life of the ring as well as the traveler in textile spinning and twisting machines.

[0011] It is still another object of the invention to provide a pollution-free coating process for the rings of textile spinning and twisting machines.

[0012] It is yet another object of me invention to provide zero rejection of the rings at the manufacturing stage.

SUMMARY OF THE INVENTION
[0013] A ring for spinning and/or twisting in a textile machine includes a ring main body. A first coating layer is provided on the ring mainbody. The first coating layer includes at least one of molybdenum, chromium and titanium. A second coating layer is provided on the first coating layer characterized in that said second coating layer includes tungsten carbide co-deposited with carbon.

[0014] A process for coating a ring for spinning and/or twisting in a textile machine includes forming a first coating layer on the ring. The first coating layer includes at least one of molybdenum, chromium and titanium. A second coating layer is formed on the first coating layer characterized in that said second coating layer includes tungsten carbide co-deposited with carbon.

DETAILED DESCRIPTION OF INVENTION

[0015] Various embodiments of this invention provide a ring with an improved coating for spinning and/or twisting in a textile machine. The embodiments of this invention are not limited to ring, and may be implemented in connection with other parts of the textile machine, which may be operated under severe wear and tear conditions, for example, gears, rollers, etc.

[0016] The ring according to an embodiment of this invention includes a mainbody. A first coating layer is provided on the mainbody. A second coating layer is provided on the first coating layer. The first coating layer is provided for binding the second coating layer on to the mainbody. Examples of the constituents of the first coating layer include one or more selected from the group consisting of molybdenum, chromium and titanium. The second coating layer is provided for giving wear and abrasion resistance to the ring. An example of the constituents of the second coating layer includes tungsten carbide co-deposited with carbon.

[0017] It should be noted that molybdenum, chromium and titanium are well known constituents in the art that may be used in the first coating layer for firmly binding the second coating layer on the first coating layer. Examples of such constituents include cobalt, tin and copper.

[0018] In an embodiment, the second coating layer includes tungsten carbide co-deposited with hydrogenated amorphous form of carbon. The amount of tungsten carbide in the second coating layer is preferably in range of about 30 to 70 volume percent. More preferably the amount of tungsten carbide in the second coating layer is in the range of about 50 to 60 volume percent. The amount of hydrogenated amorphous carbon in the second coating layer is preferably in range of about 30 to 70 volume percent. More preferably the amount of hydrogenated amorphous carbon in the second coating layer is in the range of about 40 to 50 volume percent.

[0019] It should be noted that the tungsten carbide is preferred as a constituent in the second coating layer because of the nature of tungsten carbide to provide a very high resistance to wear and tear. However, other constituent materials known in the art for providing such wear and tear resistance may also be used as a constituent in the second coating layer. Examples of such constituent materials include chromium nitride, titanium nitride, vanadium carbide, etc.

[0020] It should also be noted that the carbon, especially, hydrogenated amorphous form of carbon co-deposited with tungsten carbide produces modified nuclei growth of tungsten carbide at the surface of the second coating layer. The co-deposited carbon reduces the effect of epitaxial crystal growth thereby providing a smooth surface to the ring mainbody.

[0021] In an example, the surface roughness of second coating layer is less than 0.1 Ra.

[0022] In an example, the coefficient of friction of the second coating layer is up to 0.1.

[0023] In an example, the hardness of the second coating layer is at least 1000 VHN.

[0024] The process for coating the ring used for spinning and/or twisting in a textile machine, according to an embodiment of this invention is described in detail in the following description.

[0025] In an embodiment, the ring mainbody chosen to form a coating according to this invention, is made from a material known in the art such as, for example, carbon steel and alloy steel. The manufacturing process for the ring mainbody may be the one known to a person skilled in the art. An example of a preferred method of manufacturing the ring includes machining on multi-spindle automat. The ring mainbody after manufacturing by the above-discussed method is hardened and smooth finished to a surface finish of less than 0.2 Ra by any known method. An example of a preferred method of hardening includes heating and quenching and an example of a preferred method of smooth finishing includes mechanical polishing.

[0026] In an embodiment, prior to applying the first coating layer, the surface of the ring mainbody is cleaned to remove any foreign particles that are adhering on to the surface. In one example, cleaning is carried out by alkaline cleaning followed by organic solvent cleaning. However, other cleaning methods that may be obvious to a person skilled in the art may also be used.

[0027] After cleaning, the ring mainbody (herein after referred to as ring) is heated in a chamber to a temperature in the range of about 100 deg C to 300 deg C. An example of a form of chamber used for heating may include low pressure vacuum chamber. The heating is carried out in an inert atmosphere. For example, the inert atmosphere may include non-reactive gases such as, for example, argon and/or hydrogen and the heating method may include either resistive heating or gas bombardment or both. The bombardment for heating may be carried out using argon and/or hydrogen.

[0028] Subsequent to heating, cleaning is carried out within the chamber using any known method such as, ion etching or plasma etching using an inert gas such as, for example, argon or hydrogen or both, under high negative voltage bias and under low pressure. For example, the negative voltage bias is in the range of about 100 to 300 V and the chamber pressure is in the range of about 10-4 to 10-2 mbar.

[0029] In an embodiment, a first coating layer is formed on the ring. A second coating layer is formed on the first coating layer. The first coating layer is provided for binding the second coating layer on to the ring. Examples of the constituents of the first coating layer include one or more selected from the group consisting of molybdenum, chromium and titanium. The second coating layer is provided for giving wear resistance and abrasion resistance to the ring. An example of the constituents of the second coating layer includes tungsten carbide co-deposited with carbon.

[0030] In an example, the fist coating layer is formed by physical vapor deposition technique that is known in the art. The deposition is carried out under a pressure in the range of 1x10-3 to 3x10-3 mbar and a negative voltage potential in the range of 200 to 600 V.

[0031] In an embodiment, the thickness of the first coating layer formed is in the range of about 0.01 to 0.1 microns. The temperature maintained during the physical vapor deposition is optimum, and is set in the range of 100 deg C to 300 deg C so as to enable proper adhesion and growth of the deposition over the ring.

[0032] In an embodiment, the second coating layer includes tungsten carbide co-deposited with hydrogenated amorphous form of carbon. The amount of tungsten carbide included in the second coating layer is preferably in range of about 30 to 70 volume percent. More preferably the amount of tungsten carbide in the second coating layer is in the range of about 50 to 60 volume percent. The amount of hydrogenated amorphous carbon in the second coating layer is preferably included in range of about 30 to 70 volume percent. More preferably the amount of hydrogenated amorphous carbon included in the second coating layer is in the range of about 40 to 50 volume percent.

[0033] It should be noted that the tungsten carbide is preferred as a constituent in the second coating layer because of the nature of tungsten carbide to provide a very high resistance to wear and tear. However, other constituent materials known in the art for providing such wear and tear resistance may also be used as a constituent in the second coating layer. Examples of such constituent materials include chromium nitride, titanium nitride, vanadium carbide, etc.

[0034] In an example, the second coating layer is formed by any known technique such as, for example, plasma vapor deposition or plasma enhanced chemical vapor deposition.

[0035] In an example, in the second coating layer, the carbon constituent deposited along with tungsten carbide is preferably in the form of hydrogenous amorphous carbon. During deposition process, any hydrocarbon such as, for example, acetylene, or a mixture of known hydrocarbons may be used as a source of carbon. Argon or any other inert gas such as, for example, hydrogen may be used for generating plasma that assists in exciting and dissociating the source of carbon.

[0036] In an embodiment, the chamber used for deposition of the second coating layer is maintained at a pressure in the range of about 3x10-3 to 9x10-3 mbar. The negative bias voltage for deposition is maintained in the range of about 200 to 600 V. The temperature of the ring is maintained optimum, in the range of 100 deg C to 300 deg C to facilitate adhesion of the second coating layer over the first coating layer and also the growth of deposition.

[0037] It should be noted that the principles of this invention are directed towards forming a second coating layer containing both tungsten carbide and carbon, said carbon selected preferably in the form of hydrogenated amorphous carbon. The term co-deposition in the claims is used herein to denote deposition of both tungsten carbide and carbon in the second coating layer.

[0038] It should be noted that the nuclei growth of tungsten carbide at the surface of the second coating layer is refined by simultaneously coating amorphous hydrogenated carbon, which reduces the effect of epitaxial crystal growth and thereby forms a smooth surface. The amount of tungsten carbide is about 30 to 70 volume % of the second coating layer. The amount of hydrogenated carbon (C: H) is about 30 to 70 volume % of the second coating layer. It should be noted that according to the principles of this invention, the Sp3 bonding content of C: H bonding is 60 to 90% and the Sp2 bonding content of C: H bonding is 10 to 40%.

[0039] It should be noted that the bonding nature of the hydrogenated amorphous carbon in the second coating layer provides significantly improved wear resistant characteristics to the ring surface. The Sp3 bonding nature of the hydrogenated amorphous carbon in the second coating layer provides very less friction between the ring and the traveler due to its low force of attraction towards other materials. The thermal conductivity of the second coating layer is greater than 70 W/mK (Watt / meter. Kelvin) which results in less burning of the traveler and maintenance of smooth surface of less than 0.1 Ra for traveler contact surface of the ring.

[0040] The properties of the second coating layer, obtained according to the principles of this invention includes a hardness of greater than 1100 Vickers hardness number and the coefficient of friction value of less than 0.1. The high hardness on the ring surface and less coefficient of friction provides significantly improved wear resistance due to abrasion of traveler sliding and thus enhances the life of both the ring and the traveler. During normal working condition in production cycle, heat generated on the ring surface due to the sliding of traveler forms graphitization of hydrogenated Carbon. This graphite forms a transfer layer on the traveler and thereby reduces the friction and wear to a large extent.

[0041] The ring with improved coating for spinning and /or twisting in textile machine, made according to the principles of this invention has the following advantages as mentioned herein below:

1. Zero running-in period
2. Smooth surface
3. High wear resistance
4. Low coefficient of friction
5. High bonding strength with substrate or inter layers
6. Enhanced Toughness
7. Good thermal conduction
8. Corrosion resistance
9. Chemical inertness
10. Ability to withstand elevated temperatures
11. Diamagnetic
12. Defect-free surface
13. Retention of prior properties of substrate
14. Low temperature coating process
15. Hazard-free, environmental friendly coating process.

[0042] Thus, various specific embodiments of this invention provide a ring with an improved coating for spinning and/or twisting in a textile machine. Further specific embodiments of this invention provide a method for coating a ring for spinning and/or twisting in a textile machine. Although various modifications which may be obvious to a person skilled in the art are possible, all such modifications will be deemed to be within the scope of the claims claimed herein:

We Claim:

1. A ring for spinning and/or twisting in a textile machine,
comprising;

(i) a ring main body;

(ii) a first coating layer provided on the ring mainbody, said first coating layer including at least one of molybdenum, chromium and titanium; and

(iii) a second coating layer provided on the first coating layer characterized in that said second coating layer includes tungsten carbide co-deposited with carbon .

2. A ring as claimed in claim 1 wherein the carbon is in the form of hydrogenated amorphous carbon.

3. A ring as claimed in claim 2 wherein the amount of hydrogenated amorphous carbon is in range of about 30 to 70 volume percent.

4. A ring as claimed in claim 1 wherein the amount of tungsten carbide in the second coating layer is about 30 to 70 volume percent.

5. A ring as claimed in claim 1 wherein the surface roughness of the second coating layer is less than 0.1 Ra.

6. A ring as claimed in claim 1 wherein the coefficient of friction of the second coating layer is up to 0.1.

7. A ring as claimed in claim 1 wherein the hardness of the second coating layer is at least 1000 VHN.

8. A ring as claimed in claim 1 wherein the second coating layer is a plasma vapour deposition or a plasma enhanced chemical vapour deposition layer.

9. A ring substantially as herein described in the complete specification.

10. A process for coating a ring for spinning and/or twisting in a textile machine, comprising:

(i) forming a first coating layer on the ring, said first coating layer including at least one of molybdenum, chromium and titanium; and

(ii) forming a second coating layer on the first coating layer characterized in that said second coating layer includes tungsten carbide co-deposited with carbon.