GB2427621A

GB2427621A - A method and apparatus for controlling yarn tension

Info

Publication number: GB2427621A
Application number: GB0512884A
Authority: GB
Inventors: John Dalton Griffith
Original assignee: Griffith Textile Machines Ltd
Current assignee: Griffith Textile Machines Ltd
Priority date: 2005-06-24
Filing date: 2005-06-24
Publication date: 2007-01-03
Also published as: BE1017314A3; GB0512884D0

Abstract

A method and apparatus of controlling yarn pull-off tension in yarn 14 being drawn from a cheese having a carrier tube 12 rotatably mounted on a spindle 16, involve providing the carrier tube 12 with braking means 38 which is engagable with the spindle 16 so as to apply a desired braking force of a predetermined value eg. 0.5N to said carrier tube, the braking force being independent of the mass of yarn on the cheese, whereby the braking force FR1 is able to compensate for a reduction in a first yarn pull-off tension component T1 which is dependent on the mass of yarn on the cheese by generating a second, independent, yarn pull-off tension component, thereby providing a total yarn pull-off tension which is a combination of the first and second tension components, the desired braking force being chosen such that the total yarn pull-off tension is constrained within a smaller range of values than the yarn pull-off tension generated by the first yarn pull-off tension component alone.

Description

A METHOD AND APPARATUS

FOR CONTROLLING XARN TENSION

This invention relates to in particular. but not exclusively, a method and apparatus s for controlling yarn tension when drawing yarn from a rotatably mounted yarn cheese; a removable bearing fur use between a carrier tube of a cheese and a spindle of a creel frame; and a cheese including a said removable bearing.

In weaving, particularly Axminster weaving, yarn is supplied to a loom by a plurality of cheeses on a creel frame. Each cheese comprises a cheese or yam carrier tube around which yarn is wrapped. Typically the creel frame includes a large number of static spindles arranged in rows. A cheese is rotatably mounted on each spindle and the yarns being drawn from the cheeses in a given row pass along paths closely spaced to one another.

During weaving the yarn on a given cheese is pulled off from one side of the cheese causing each cheese to rotate about a rotational axis defined by the spindle on which it is carried.

When a cheese is full of yarn the mass of yarn thereon is high. As a result the frictional resistive force between the earner tube and the spindle is also relatively high. This means that the resulting tension in the yarn pulled from the cheese, i.e. the so-called "pull-off tension" is also relatively high, thereby maintaining the yarn in a desired tight condition.

Typically, the carrier tubes freely rotate on their spindles and so the pull-off tension in the yarn being drawn off decreases by a considerable amount as the diameter and weight of the cheese decreases. When the cheese is about depleted the yarn pull-off tension is usually relatively low causing the yarn to be slack and thereby causing snagging and tangling problems along the running paths of the yarn.

For example. a typical full cheese 1 0. as shown in Figure 1, has a mass of about 1.5kg The cheese 10 includes a carner tube 12 on which yarn 14 is wound The carner tube 12 is supported on a spindle 16 about which ills rotatable.

The outer radius R1 of the full cheese 10 is about 80mm. A typical spindle 12 has a radius r of 4mm.

A first frictional resistance force F11 between the carrier tube 12 and the spindle 16 is given by F, =pN where i is the coefficient of friction between the carrier tube 12 and the spmdle 16. Typically this is about 0.25N.

Resolving forces vertically, the Normal reaction force N1 between the carrier tube 12 and spindle 16 is given by N1 =nlfg where mj is the mass of the full cheese. i.e. 1.5kg, and g is the acceleration due to gravity. i.e. 9.81 rns2. So,

N1 =1.5(9.98) =14.751V 15N This gives a first frictional reaction force FRI of FRI = 0.25(15) =3.75 N Equating moments about a centre 1 8 of the spindle 1 6 gives 7RJ =Fr where T1 is a maximum pull-off tension in the yarn 14. Accordmgly (80) = 3.75(4) T = 3.75(4) 7 =0.1875 N In the condiflon when a cheese 20 is almost empty, as shown in Figure 2, the mass me of the cheese 20 is only about SOg (i.e. 0.050kg) .

in this condition a second frictional resistive fbrce F,2 generated at the interface between the carrier tube 12 and the spindle 16 is lower than the first frictional resistive force FR!, i.e. "2 = mg = 0.050(9.81) = 0.4905 0.5N and so, using R2 _11j'T2 gives F1,, = 0.25(0. 5) = 0.125 N Equating moments about the centre 1 8 of the spindle 16 gives TR2 =FR,r n where T2 is a minimum pull-off tension in the yam 14. and R2 is the outer radius of the almost empty cheese 20. R2 is approximately 12.5mm.

Accordingly T. (12.5) = 0.125(4) = 0.125(4) 12.5 T, =0.040N The maximum pull-off tension T1 is over 4.5 times greater than the minimum pull- off tension T2. In other words the minimum pull-off tension T2 is only about 21% of the maximum pull-of tension T1.

The variation in yam pull-off tension due to the mass of yarn on the cheese, as the cheese empties of yarn 14, is shown by plot line A of the graph in Figure 6. The yarn pull-off tension is high initially and falls away as the cheese empties.

At 0.040N the minimum pull-off tension T2 is relatively low and so gives rise to a slack yarn between the creel frame and the loom. Such slack yarns are liable to become entangled with one another as they move towards the loom. This is undesirable as it effects product quality and can interrupt production.

A general aim of the invention to maintain the yarn pull-off tension within a range of values such that the minimum yarn pull-off tension is sufficient to avoid the aforementioned entanglement problems.

According to a first aspect of the invention there is provided a method of controlling yarn pull-off tension in yarn being drawn from a cheese having a earner tube rotatably mounted on a spindle, the method including providing the carrier tube with braking means which is engagable with the spindle so as to apply a desired braking force of a predetermined value to said earner tube, the braking force being independent of the mass of yarn on the cheese, whereby the braking force is able to compensate for a reduction in a first yarn pull-off tension component which is dependent on the mass of yarn on the cheese by generating a second, independent, yarn pull-off tension component, thereby providing a total yarn pull-off tension which is a combination of the first and second tension components, the desired braking force being chosen such that the total yarn pull- off tension is constrained within a smaller range of values than the yarn pull-off tension generated by the first yarn pull-off tension component alone.

Constraining the total yarn pull-off tension in this way helps to ensure that the minimum pull-off tension is sufficient to reduce the likelihood of the yarn becoming tangled with another yarn as it is pulled off of the cheese.

The method of the invention further provides a simple solution which automatically compensates for a reduction in the mass of yarn on the carrier tube without the need for complicated variable mechanisms.

Preferably the method includes applying the braking force such that a minimum total yarn pull-off tension is at least 60% of a maximum total yarn pull-off tension.

A preferred method of the invention includes applying the braking force via at least one removable bearing lying between the earner tube and the spindle.

Optionally the method includes applying the braking force via at least one flexible portion of the or each removable bearing, and further includes spacing the or each flexible portion from the earner tube and biasing the or each flexible portion into frictional contact with the spindle.

The foregoing method steps provide a convenient way of applying a desired braking force of predetermined value to the carrier tube.

According to a second aspect of the invention there is provided an apparatus for controlling yarn pull-off tension in yarn being drawn from a cheese having a carrier tube rotatablv mounted on a spmdle. the apparatus including a braking means engagable with the spindle so as to apply a desired braking force of a predetermined value to the said carrier tube, the braking force being independent of the mass of yarn on the cheese, whereby the braking force is able to compensate for a reduction in a first yarn pull-off' tension component which is dependent on the mass of yarn on the cheese by generating a second, independent, yarn pull-off tension component, thereby providing a total yarn pull-off tension which is a comhmation of the first and second tension components, the desired braking force being chosen such that the total yarn pull-off tension is constrained within a smaller range of values than the yarn pull-off tension generated by the first yarn pull-off tension component a] one.

Preferably the braking means includes at least one removable bearing lying between the carrier tube and the spindle.

Optionally the or each removable bearing includes at least one flexible portion spaced from the carrier tube and biased into frictional contact with the spindle.

The foregoing features of the apparatus of the invention share the corresponding advantages of the aforementioned method steps.

According to a third aspect of the invention there is provided a removable bearing, for use between a carrier tube of a cheese and a spindle, comprising a body portion including at least one flexible portion spaced from one of the carrier tube or the spindle and biased into frictional contact with the other of the spindle or the carrier tube, so as to apply a desired braking force of a predetermined value to the carrier tube, the braking force being independent of the mass of yarn on the cheese.

Spacing the flexible portion from one of the earner tube or the spindle ensures that braking force generated thereby is independeni of the mass of arn on the earner tube s This allows for a constraining of the total yarn pull-off tension such that the minimum yarn pull -off tension us sufficient to reduce entanglement problems.

In addition, the provision of a removable hearing allows an operator to use the bearing with the carrier tube of another cheese, as desired.

Preferrably the body portion includes two flexible portions arranged opposite one another. This provides for an even distribution of the braking force.

Optionally the or each flexible portion includes a flexible finger protruding from a first end of the bod3 portion. This arrangement allows for economical moulding of the removable bearing in, e.g. a plastics material, with simple tooling.

Conveniently the body portion further includes one or more sleeves protruding from the first end thereof, the or each sleeve extending adjacent to respective edges of the or each flexible finger. The or each sleeve helps to protect the or each finger from mechanical damage when not inserted into a yarn carrier tube.

In another preiérred embodiment of the invention the or each flexible portion includes a pad of frictional material. This provides a convenient way of increasing the surface area of the flexible portion that is in frictional contact with the spindle or earner tube, thereby generating a desired amount of braking force.

Preferably the body portion has a substantially square cross-sectional profile.

Respective corners of the cross-sectional profile are engagable with an inner surface of the earner tube, thereby ensuring that in this embodiment the bearing rotates with the earner tube.

in addition, each semenl of the camer tube rntenor between the body portion and the carner tube provides space for a respective flexible portion to expand into when biased into contact with the spindle. This allows the or each flexible portion to remain spaced from the camer tube, thereby ensuring thai the braking force is independent of the mass ofyarn on the cheese.

Conveniently the body portion includes a shoulder at a second end thereof opposite the first end. The shoulder portion prevents insertion of the removable bearing too far within a carner tube, thereby permitting the easy removal of the hearing from the carrier tube following exhaustion of the yarn wrapped thereon.

According to a fburth aspect of the invention there is provided a cheese, for use in weaving, comprising a carrier tube for wrapping yarn thereon, at least one end of the carrier tube having inserted therein a removable bearing as described hereinabove.

Such a cheese shares the aforementioned advantages outlined in connection with the removable bearing of the invention.

There now follows a brief description of a preferred embodiment of the invention, by way of non-limiting example, with reference being made to the accompanying drawings, in which: Figure 1 is a front elevational view of a conventional arrangement of a cheese and creel frame in a first condition; Figure 2 is a front elevational view of the arrangement shown in Figure 1 in a second condition; Figure 3 is an clevational, partially sectioned, view from a first side of a cheese and creel frame arrangement incorporating a removable bearing according to one embodiment of the invention; Figure 4 is an elevational, cross-sectioned, view from the first side of the removable bearing shown in Figure 3: Figure 5 is a front elevational vie' of the removable hearing shown in Figure 3; and Figure 6 is a graph showing how various yarn pull-off tension components vary as a cheese empties of yarn.

A removable bearing according to the invention is designated generally by the reference numeral 30 The hearing 30 comprises a body portion 32. In the embodiment shown, the body portion 32 is slidably engagable with a spindle 16 so as to rotate thereabout. The spindle 1 6 forms part of a creel frame 22, only part of which is shown The body portion 32 shown is also insertable into one end of a yarn carrier tube 12 so as to rotate therewith. Another end of the carrier tube 12 includes a conventional, plain bearing 34 which is rotatable about the spindle 16.

In other embodiments of the invention the bearing 32 may be engagahie with the spmdle 16 so as to remain static therewith, the carrier tube 12 being rotatable about the hearing 32 once inserted therein The body portion 32 includes two flexible portions 36 in the form of flexible fingers 38 arranged opposite one another. Each flexible finger 38 protrudes from a first end 40 of the body portion 32. In the embodiment shown, each flexible finger 38 is spaced from the carrier tube 12 and biased into frictional contact with the spindle 16.

In other embodiments of the invention in which the carrier tube 12 is rotatable about a removable bearing statically engaged with the spindle 16, each flexible finger 38 may be spaced flom the spindle 16 and biased into frictional contact with the carrier tube 12.

The body portion 32 includes a pair of sleeves 39, each of which extends from the first end 40 of the body portion 32 between respective edges of the flexible fingers s Each flexible finger 38 includes a pad 42 of frictional material. Each pad 42 may be or include the same material as the body portion 32 and each flexible finger 38, or a different material, e.g. rubber.

In addition, the cross-sectional profile of each pad 42 may correspond to the circular cross-sectional profile of the spindle 16, as shown in Figure 5. This helps to ensure uniform contact between the pad 42 and the spindle 1 6.

The body portion 32 has a substantially square cross-sectional profile, as shown in Figure 5. Such a profile provides a desired degree of engagement with the inner surface of the earner tube 12 while defining four cavity segments 44, two of which are able to accommodate, in use, a respective flexible finger 38.

The body portion also includes a shoulder 48 at a second end 50 thereof.

In use, a removable bearing 30 according to the invention is inserted into one or both ends of a carrier tube 12.

The pair of flexible fingers 38 impart a braking force, between the carrier tube and the spmdle by way of frictional contact between each finger 38 and the spindle 1 6.

The braking force is independent of the mass of yarn on the earner tube.

An example of a desirable braking force, in connection with the examples shown in Figures 1 and 2, is 0.5N.

So, in a first condition where a cheese is full (i.e. the yarn wound thereon defines a maximum diameter) and the carrier tube 12 and creel frame 22 arrangement includes a bearing 30 according to the invention, we have T, R = r where T1 is a second, independent yarn pull-off tension component in the yarn 14 and FRI is the constant braking force. This gives T (80) = (0.5)(4) = (0.5)(4) T'1 = 0.0250 N Similarly, with the same arrangement in a second condition where the cheese is almost empty (i.e. the yarn wound thereon defines a minimum diameter) we have T'2 R, = F'1, r where T'2 is a modified, second yarn, pull-off tension component, and F' is the constant braking force, i.e. F'R2 = F'1. This gives 2 (12.5)=(0.5)(4) T' (0.5)(4) - 12.5 T', =0.1600N Plot line B of the graph in Figure 6 shows how the second yarn pull-off tension component B varies as the cheese empties.

The second yarn pull-off tension component B (which is due to the applied braking force) is low initially but increases as the cheese empties due to the reduction in radius of the cheese. This increase in the second yarn pull-off tension component B acts to compensate for the reduction in the first, mass-dependent, yarn pull-off tension component A. Consequently the combined effect of the first and second pull-off tension components A, B acting together gives a total yarn pull-off tension which varies within acceptable limits. a shown by plot line C in the graph of Figure 6. This maintams a minimum yarn pull-off tension. i.e the bottom of the curve of plot line C, which is sufficient to reduce the likelihood of yarns 1 4 becoming tangled with one another as they pass between the creel frame 22 and the loom.

Constraining the total yarn pull-off tension in this way is achieved without significantly increasing the maximum total yarn pull-off tension, thereby niinimising the risk of a yarn 14 snapping as ii is pulled from a full cheese.

It is possible to alter the braking force imparted on the carrier tube 12, according to the size of carrier tube 12 and mass of yarn thereon, in order to achieve the aforementioned constraining of the total yarn pulloff tension. The braking force may be altered by adjustmg the degree of biasing within the or each flexible portion 36 and/or by altering the size of surface area of the or each flexible portion 36 that is in contact with one of the spmdle 16 or earner tube 12.

Claims

CLAIMS: I. A method of controfling yarn pull-off tension in yarn being

drawn from a cheese having a carrier tube rotatably mounted on a spindle, the method including providing the carrier tube with braking means which is engagahie with the spindle so as to apply a desired braking force of a predetermined value to said carrier tube, the braking force being independent of' the mass of yarn on the cheese. whereby the braking force is able to compensate for a reduction in a first yarn pull-off tension component which is dependent on the mass of yarn on the cheese by generating a second, independent, yarn pull-off' tension component, thereby providing a total yarn pull-off tension which is a combination of the first and second tension components, the desired braking force being chosen such that the total yarn pull-off tension is constrained within a smaller range of values than the yarn pull-off tension generated by the first yarn pull-off tension component alone.
2. A method according to Claim I including applying the braking force such that a minimum total yarn pull-off tension is at least 60% of a maximum tota] yarn pull-off tension.
3. A method according to Claim I or Claim 2 including applying the braking force via at least one removable bearing lying between the carrier tube and the spindle.
4. A method according to Claim 3 including applying the braking force via at least one flexible portion of the or each removable bearing, further including spacing the or each flexible portion from the carrier tube and biasing the or each flexible portion into frictional contact with the spindle.
5. An apparatus for controlling yarn pull-off tension in yarn being drawn from a cheese having a carrier tube rotatably mounted on a spindle, the apparatus including a braking means engagable with the spmdle so as to apply a desired braking force of a predetermined value to the said catTier tube, the braking force 9 t being independent of the mass of yarn on the cheese, whereby the braking force is able to compensate for a reduction in a first yarn pull-off tension component which is dependent on the mass of yarn on the cheese by generating a second.

independent, yarn pull-off tension component. thereby providing a total yarn pull- off tension which is a combination of the first and second tens]on components. the desired braking force being chosen such that the total yarn pull-off tension is constrained within a smaller range of values than the yarn pull-off tension generated by the first yarn pull-off tension component alone
6. An apparatus according to Claim 5 wherein the braking means includes at least one removable bearing lying between the carrier tube and the spindle.
7. An apparatus according to Claim 6 wherein the or each removable bearing includes at least one flexible portion spaced from the carrier tube and biased into frictional contact with the spindle.
8. A removable hearmg, for use between a earner tube of a cheese and a spindle, comprising a body portion including at least one flexible portion spaced from one of the carrier tube or the spindle and biased into frictional contact with the other of the spindle or the carrier tube, so as to apply a desired braking force of a predetermined value to the earner tube, the braking force being independent of the mass of yarn on the cheese.
9. A removable bearing according to Claim 8 wherein the body portion includes two flexible portions arranged opposite one another.
10. A removable hearing according to Claim 8 or Claim 9 wherein the or each flexible portion includes a flexible finger protruding from a first end of the body portion.
11. A removable bearing according to Claim 1 0 wherein the body portion further includes one or more sleeves protruding from the first end thereof, the or each sleeve extending adjacent to respective edges of the or each flexible finger.

s
12. A removable bearing according to any of Claims 8 to 11 wherein the or each flexible portion includes a pad of frictional material.
13 A removable hearing according to any of Claims 8 to 12 wherein the body portion has a substantially square cross-sectional profile.
14. A removable bearing according to any of Claims 8 to 13 wherein the body portion includes a shoulder at a second end thereof opposite the first end.
1 5 A cheese, for use in weaving, comprising a carrier tube for wrapping yarn thereon, at least one end of the earner tube having inserted therein a removable bearing according to any of Claims 8 to 14.
16. A method of controlling yarn pull-off tension generally as herein described with reference to and/or as illustrated in Figures 3 to 6 of the accompanying drawings.
1 7. An apparatus for controlling yarn pull-off tension generally as herein described with reference to and/or as illustrated in Figures 3 to 6 of the accompanying drawings.
1 8. A removable bearing generally as herein described with reference to and/or as illustrated in the accompanying drawings.
19. A cheese generally as herein described with reference to and/or as illustrated in Figures 3 to 6 of the accompanying drawings.