Technical field: This invention relates to a retrofit attachment for modem multi feeder circular knitting yarn for knitting short staple yarns using tube feed creels.
Background and prior art: Modern Multi feeder circular knitting machines 23 as seen in FIG I use multiple yarn feeds. Depending upon knitting machine 23 construction up to ninety six or more yam ends / feeds are common in today's industrial environment. Yam is wound on large conical or cylindrical packages 22. To feed multiple yarns ends to a circular knitting machine 23, Vertical floor standing creels 21 are employed, in which yam packages 22 are stacked vertically and these creels are placed around the knitting machine 23. As seen in a conventional circular knitting machine shown in FIG II, each end of yarn from its package 22 passes through the enclosed tube 27,28, 29 & 30, ceramic guides/eyelets 31, 32 & 33 before the yam is wound on the positive drive storage yam feed wheel system called "IRO" 26. Each set of yam feeding tube consists of four independent tubes 27,28,29 & 30 connected by two sets of elbows 34 & 35. Each elbow 34 & 35 is a small tube which is bent at 90° at its centre and it has a ceramic eyelet placed within. The purpose of the elbows 34 & 35 is to allow connecting the tubes 27,28,29 & 30 and to allow the yam to flow and change flow direction at the ceramic eyelet.Tubel 27 is used to carry the yam from the package 22 to the top of the vertical creel 21. Tube 2 28 is used to carry the yam from the top of the vertical creel 21 to the top of the knitting machine 23. Tube 3 29 is used to slide in Tube 2 28 and this arrangement is necessary for adjusting the variable distance between the creel 21 and the knitting machine 23. Tube 4 30 is used to carry the yam from the top of the knitting machine 23 into the IRO 26, to the yam storage wheel system of the knitting machine 23. Normally three yam guides (ceramic eyelets 31, 32 & 33) placed within the four tubes carrying the yam from the package 22 to the knitting machine 23. These ceramic eyelets 31, 32 & 33 are highly polished and are shaped like a cylinder with a bore with rounded edges. A high level of surface finish is provided to these ceramic eyelets 31, 32 & 33 to reduce friction coefficient as far as possible.
There are three purposes of these ceramic eyelets 31, 32 & 33. First is to provide for yam to easily pass through these guides with the lowest possible friction. Second purpose of the ceramic eyelets 31, 32 & 33 is to facilitate the change in flow direction of yam by 90°. The yam path from the creel 21 to the knitting machine 23 changes direction thrice by 90°. Third
purpose is to reduce tension by preventing the yam from touching the internal surface of the tubes.
A problem of a particular concern to the knitting industry is the problem of yarn breakages in the short staple yams. The yam breakage rate accounts for a substantial loss in productivity of circular knitting machines-representing as much as 30% losses in productivity. A knitting machine is halted by stop motions as and when yam breaks. The yam break has to be mended manually by inserting a knot in the two broken ends of the yam by the machine operator. Each inserted knot has two tails. "When this knot is knitted in the fabric, the tails of the knots are knitted in as well and this causes yam thickness to double, at location of the knot causing a localized fabric defect called a knitted-in-thick-place.
Knitting machine builders and knitted fabric producers have traditionally considered the problem of yam breakages to be a specific problem of the yam and depending exclusively upon the quality of yam and consequendy yam spinners have been held responsible. Over the last few decades, much effort and improved capability of newer spinning machineries has improved the breaking strength of short staple yarns. However, in spite of increase in breaking strength of yams, the problem of yam breakages on the knitting machine during knitting has not been resolved. The yam continues to break to the disadvantage of the knitters. The knitters have no option but to face all the problems caused by yam breaks and have to bear the substantial loss in production and fabric defects. Further to reduce yam breakage rate, Knitters have to reduce machine RPM (rotation per minute) which causes a further loss in productivity.
The mechanism of yam breakage on knitting machine
Short staple yarns can have integral spun-in slubs (FIG III) and thick places. Thick yam and slubs (FIG III) can not be permitted to travel to the knitting zone 24. Thick places and slubs in the knitting zone can cause disastrous fabric press offs causing the fabric to fall from the needles or the needles can break causing holes in the fabric or needles can get bent causing needle lines in the fabric or numerous other defects such as drop stitches causing laddering.
In knitting, yam breaks occur mainly at the slub catcher 17 on the IRCs 26 or at the yam feeders 25. These two devices are intentionally deployed in the knitting machine 23 to
prevent slubs to pass into the knitting zone 24. Since majority of yarn breakages are happening at these two points on the knitting machine 23, hence it becomes obvious that the yam is intentionally being broken by the two yarn diameter restricting devices on the knitting machine 23. Yam diameter restricting devices 17 & 25 will break the yam only if objectionable slubs are present in the yam. Surprisingly, the linear speed of yam has the most influence on the number of breaks in yam during knitting.
Since the total number of yam breaks can be reduced or increased by changing the linear speed of yam, that is, by changing the RPM of the knitting machine 23, therefore, there is a need to determine how increasing linear speed of yam, creates more slubs, which are caught by the slub catchers 17 & 25 causing more yam breakages during knitting. Investigations reveal that slubs are always responsible for breaking the yam at the slub catcher 17 & 25. "When these slubs are investigated, it is found that these slubs can be manipulated to slide on the yam, confirming that these slubs were not spun into the yam and were therefore not present in the yam package 22. If these slubs were an integral part of the yarn, then these slubs will not be able to slide or move on the yam. Therefore this is conclusive evidence that these yam breaking slubs have been produced in the knitting machine 23, some where between the IRO 26 and the yam package 22, that is, in the yam feeding tube system of the knitting machine 23.
The mechanism of lint accumulation and slub formation at the ceramic eyelets within the elbows of the tube feed system
The unwinding process causes ballooning 20 of yam, from the package 22 to the point of
entry of yam 16 into the yam feeding tube. Centrifugal forces during ballooning 20 cause
individual fibers to be flung out of the yam body. Some fibers are completely ejected from
the yam body as lint, others fibers get partially ejected from the yam body (one end of the
fiber still caught within the yam body) but not completely and these fibers only increase their
protrusion from the yam body causing a higher level of hairiness on the yam.
The higher the linear speed of yam, the higher is ballooning 20 angle A°, higher is the
centrifugal force and higher is the lint generation (complete fiber ejection) and higher is the
hairiness increase (part fiber ejection) of the yam.
Tension builds-up during the passage of yam from the package 22 to the storage feed wheel
of the IRO 26. As the yam is moving forward in the tubes, the tension in the yam ensures
that the yarn is positively held in contact with the ceramic eyelets 31, 32 & 33 in the yarn path and the yam is constandy rubbing with these eyelets 31,32 & 33. The yam has hairiness or protruding fibers. Some of these protruding fibers strike the ceramic eyelets 31, 32 & 33 at speeds up to 100 meters per minute. This impact force causes the fibers to break and broken fibers are shed from the yam, as lint, on the ceramic eyelets 31, 32 & 33. Some of these broken fibers get caught between the yam and the ceramic eyelets 31, 32 & 33 and start to collect at this point 37. A slub starts to build-up at the point of contact of the yam and the ceramic eyelets 37. Soon this slub builds up all over and around the yam. A ball type slub is eventually formed. The yam is sliding through this lint ball and this lint ball is held in place by the ceramic eyelet 31,32 & 33. The slub thus formed permits yam to slide through this lint build-up.
The broken fibers shed from the yam, are caught between the ceramic eyelets 31, 32 & 33 and the yam, lint accumulation keeps building until such time that the lint accumulation forms a large enough slub/ball, which is eventually able to restrict yam movement due to sufficient friction.
At that very point of time, where the lint slub/ball on yam restricts yam movement, there are only two available options, either the yam breaks because the slub will not permit movement of yarn or the slub is totally entangled with the yam and is carried along with the yam to the yam storage wheel of the IRO 26 on the knitting machine 23. Normally the yam does not break at this point and the slub formed is carried forward to the yam storage wheel on the IRO 26.
Prior to entering the storage wheel, the yarn passes through a user adjustable slub catcher 17. It is the function of this device to prevent slubs on yarn to pass to the knitting zone 24. "When a substantial slub, larger than permitted by the settings of the slub catcher 17, is present, the slub catcher 17 acts and causes the yam to break, to prevent this slub from moving into the knitting zone 24. A secondary slub catching device is deployed in the form of the narrow eyelet at the yam feeder 25 before the knitting zone 24 to prevent slubs from entering the knitting zone. Slubs in knitting zone can cause disastrous fabric press offs causing the fabric to fall from the needles or the needles can break causing holes in the fabric or needles can get bent causing needle lines in the fabric or numerous other defects such as drop stitches causing laddering. Therefore, there is a need for a mechanism to prevent the formation of the slubs by eliminating the accumulation of lint which causes slub
formation.
Thus it is the object of the invention to provide for a mechanism whereby slub formation is prevented. It is another object of the present invention to provide for a mechanism which removes lint being accumulated at critical lint accumulating points in the yarn path. It is yet another object of the present invention to provide for a mechanism to remove lint, without interfering with the knitting process or the circular knitting machine. Last but not the least; it is object of the present invention to provide for a mechanism which is not tedious or cumbersome but simple and easy to employ in the existing circular knitting yarns without any modification.
Summary of the invention: The present invention describes a retrofit attachment employed in yarn feeding tubes of a circular knitting machine for prevention of accumulation of lint within the elbows. The said attachment discharges compressed air into the elbows of the yarn feeding tubes thereby eliminating the accumulation of lint there within and obviating slub formation. Slubs cause yarn breakages, causing the knitting machine to stop, thereby reducing the production efficiency of the said circular knitting machine.
Detailed Description of the Drawings:
FIG I: Elevation and Plan view of Multi Feeder Circular knitting machine.
FIG II: Diagrammatic representation of existing circular knitting machine (Prior art)
FIG III: Photographic representations of the slubs
FIG IV: Exploded view of the slub buster elbow
FIG V: Diagrammatic representation of circular knitting machine
FIG VI: Schematic representation of air sequencing system.
Description of the preferred embodiment:
To minimise confusion only one Lint Buster Elbow 36 and the associated yam feed system are shown in FIG V. It being understood that the other tubes for other yam feeders are similariy constructed and that suitable numbers of Lint Buster Elbows 36 are provided depending on the number of feeders of the knitting machine 23 involved.
The retrofit attachment of the present invention is a tube at Lint Buster Elbow for discharging compressed air to the point of contact 37 of the yarn and the ceramic eyelet 33 in Lint Buster Elbow 36.
Each Lint Buster Elbow 36 consists of a an aluminum or plastic block of a suitable size for example a block measuring 38mm X 38mm X 25mm or any other suitable size with two bores at right angles and a ceramic eyelet placed in the centre of the interconnecting bores. The two bores are suitably sized to achieve push fit of the two yarn feeding tubes, through which the yam is fed from the creel 21 to the knitting machine 23. A suitably sized third bore is provided for injecting compressed air and directing discharged air to the point of first contact between the yam and the ceramic eyelet. (FIG IV and V)
Each Lint Buster Elbows 36 is fed compressed air through an air sequencing system. The Air Sequencing system as seen in FIG VI is designed to provide compressed air to the large number of Lint Buster Elbows 36 in the multi feeds of the knitting machine 23 in a sequential manner thereby reducing the cumulative consumption of expensive compressed air. The compressed air is routed through a solenoid valve 40, which is controlled by a programmable timing device 41 which controls both the frequency and duration of the opening and closing of the solenoid valve feeding compressed air to the Lint Buster Elbows 36.
The sequencer provides compressed air from a remote compressed air supply to all the deployed Lint Buster Elbows 36 in a predetermined sequence and at the same time controls both the duration and the frequency of air discharge within the Lint Buster Elbows 36. "With the timing device, the duration of air discharge can be a precisely controlled, thereby controlling the volume of air to be discharged on the ceramic eyelet 33 within the Lint Buster Elbow 36. Adequate volume of air is discharged only to provide a minor lift of the yam and to dislodge the accumulated lint. Further with the timing device, frequency of the compressed air discharge within the Lint Buster Elbows 36 can be precisely regulated to control the number of air discharges per unit of time. The Air Sequencing System also includes an air pressure regulating device 42 which regulates the pressure of the air that is supplied at the Lint Buster Elbows 36 and the pressure of the compressed air is displayed by the pressure display device 44. It is desired to maintain optimum pressure that blows away the broken lint fibers and at the same time does not upset the normal yarn passing at the same time. The primary objective is to prevent built up of lint, the frequency or duration of
air discharge will depend on the nature of yarn. Yarns with higher content of short fibers (carded cotton yarns) would shed more fibers and would require a higher frequency and duration of air discharges, whereas combed cotton or long staple yarns with lesser short fiber content will require lesser frequency and duration of air discharge. Furthermore, care is taken to supply clean compressed air. For this purpose, the compressed air that is discharged in the Lint Buster Elbows 36 is filtered through a filtering unit 45.
Thus, suitable volume of compressed air is passed at suitable intervals through the Lint Buster Elbows 36. This discharge of pressurized or compressed air to the point of contact 37 of the yarn and the ceramic eyelet 33 causes the yam to lift; this yarn lift and compressed air flow dislodges any accumulated lint. This tiny amount of accumulated lint is now free to move along with the yam to the knitting zone 24, where it poses no problems. Frequent enough compressed air discharges at this point will ensure that no lint is ever allowed to accumulate at this lint trapping point 37 thereby eliminating the possibility of slub/ ball formation. Therefore, if lint is not allowed to accumulate then slubs can not be formed. If no slubs are formed then no slubs will be passed on to the yarn, to be caught by the slub catchers 17 & 25, if no sufficiently large slubs are presented to the slub catcher 17 & 25, then yam will not be broken by slub catcher 17 & 25 and if yarn does not break then knitting machine 23 will operate without interruptions. If knitting machine 23 runs continuously without machine stops caused by yarn breakages, then knitting efficiency will increase dramatically. If yam does not break, then no knots need to be inserted to mend broken ends of yam. If there are no knots, then there are no knot tails and hence no knitted-in-thick-place defects will be created in fabric by knot tails.
Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

We claim,
1. An attachment for a circular knitting yarn, said attachment being employed at the yarn feeding tubes and discharging compressed air in a sequential manner to blow away lint/fibers shed by yam thereby preventing accumulation of lint and consequendy obviating slub formation .
2. The said yam feeding tubes as claimed in claim 1, comprises of the yarn carrying tubes connected to each other by lint buster elbows, within this elbow is the point of contact of yam and the ceramic eyelet.
3. The said attachment as claimed in claim 1, being a circular opening at the lint buster elbow of the yarm feeding apparatus, through which compressed air is discharged in a sequential manner.
4. The said circular opening as claimed in claim 3, leading to a tubular passageway further connected to a solenoid valve through which the compressed air is introduced into the lint buster elbow via the said tubular passageway.
5. The said solenoid valve as claimed in claim 4, being further connected to pressure controlling apparatus comprising of pressure regulating device, pressure display device and air filtering unit regulating and filtering the compressed air to be introduced into the said lint buster elbow.
6. The said attachment as claimed in any of the preceding claims, wherein each said lint buster elbow is associated with its own corresponding said attachment.
7. The said circular knitting yam as claimed in claim 1 being a short staple yarn.