GB1577313A - Feed apparatus for yarn and like filamentary and other elongate materials - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO FEED APPARATUS FOR YARN AND LIKE FILAMENTARY AND OTHER ELONGATE MATERIALS (71) We, NATIONAL RESEARCH DEVELOPMENT CORPORATION, a British Corporation established by Statute, of Kingsgate House, 66 - 74 Victoria Street, London, S.W.1, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an apparatus for feeding yarn and like filamentary and other elongate materials.

The invention is pertinent to textile machinery for warp knitting, weaving, tufting and stitch bonding processes and has particular relevance in relation to machines demanding yarn at an uneven rate, for example carpet machines, some knitting machines and looms.

Generally speaking however it will usually only be suitable for creel fed machines as opposed to beam fed ones.

Up to now, two solutions have been proposed to deal with the problem of uneven yarn feed. The first of these solutions is to feed the yarn by means of a so-called "negative feed" system i.e. one in which the force pulling the yarn off the package is provided at the needles of the machine to which the yarn is being fed. The drawbacks of this system are first that the yarn fed to the machine is necessarily under significant tension and secondly that this yarn tension will vary unpredictably - principally because the force needed to pull the yarn off the package at any given instant will depend on the amount of yarn left on the package and on the operation currently being carried out by the needle concerned. Varying yarn tension will in all cases lead to a corresponding variation in the performance of the machine using the yarn, reflected for example in variations in stitch size.

The second solution commonly adopted for uneven yarn feed situations is a programmed system incorporating what is in effect a yarn "reservoir". In this case, a predetermined amount of yarn is periodically pulled off the package by some means other than the machine needles to which the yarn is to be fed, and this amount is held in reserve ready for use by the machine when it next requires it. The drawback with this second system is that if it is to be used with a machine in which local variations in the working programme mean a wide and complex variation in yarn demand, the system must be correspondingly complex and comprehensive. A second factor of course is that no matter how carefully the feed system is programmed, the expected yarn demands on the basis of which programming is carried out, may not exactly correspond to what occurs in practice.In other words, the amount of yarn pulled off the package each time takes no account of the amount actually used by he machine in its previous yarn-demanding operations. Where too much yarn is being supplied, errors due to the unpredictable difference between theoretical and actual yarn demands will be cumulative.

The disadvantages outlined above for the "negative tension" and programmed feed systems may be acceptable in some instances but not in others. Machines for producing "Locstitch" fabrics (as described in U.K. Patent 1268201) which are sculptured in accordance with the method described in U.K. Patent 1541431 present a special problem on the one hand, it would be prohibitively expensive to provide a programmed feed system that could deal with the many local variations occurring in the fabric, and on the other hand the "negative tension" method could not be used because apart from anything else, in Locstitch, the stitch is preferably made at substantially zero yarn tension.

According to the present invention there is provided for use with a machine to be fed with one or more continuous lengths of yarn or like filamentary or other elongate material, a feed apparatus comprising a store for storing when full a predetermined amount of the material for use in a subsequent material-demanding operation by the machine, and supply means adapted to replace in the store any of the material taken from the store in said material-demanding operation, the apparatus comprising means for engaging the material with the supply means in a manner which depends on the degree of fullness of the store.

Preferably the predetermined amount of material of the or each length held in the store is in excess of the demand in the subsequent machine operation so that sufficient material is available to the machine for any given operation.

In contrast with conventional feed systems the present invention embraces systems especially suitable for feeding yarn to a sculptured Locstitch machine.

According to a preferred feature, the feed apparatus of the present invention comprises a single store and/or a single supply means adapted to operate simultaneously with two or more lengths of the material.

In preferred embodiments, the supply means comprise one or more elements mounted for rotation about an axis with the surface of the or each element adapted to be engaged by one or more lengths of the material, and the store comprises one or more members mounted for movement relative to said axis with the surface of the or each member adapted to be engaged by one or more lengths of the material.

The supply means may for example comprise a number of wheels mounted for rotation about a common axis or it might comprise a rotatable drum.

Conveniently, the supply means is driven by a variable speed drive unit.

Means may be provided for operating the supp:y means intermittently.

The apparatus may include means for varying the angle of wrap of the material about the supply means.

The store may comprise one or more arms mounted for oscillatory movement between two fixed positions.

Conveniently, the stroke of the arm or arms can be varied.

The timing of the arm or arms may be variable in relation to some operational function of the machine.

Conveniently, the rate of stroke of the arm or arms can be varied.

The apparatus may include means for varying the angle of wrap of the material around the arm or arms.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 shows a perspective view of an apparatus according to the present invention in use in a yarn feed system for a sculptured Locstitch machine and Figure 2 illustrates the performance details associated with the apparatus shown in Figure 1.

Thus referring first to Figure 1. reference numeral 10 indicates an apparatus according to the present invention for feeding a plurality of yarns 12 to the yarn feed system 38, 39, 41, 42 sculptured Locstitch machine (not shown).

The supply means in apparatus 10 is provided by a drum 16 rotatable about a shaft 18 lying on the axis of symmetry of the drum. The surface of the drum is provided by a rubber sleeve 20. Other high friction materials could be used instead of rubber of course.

The store is provided by a so called "dancing bar" 22 which extends the length of the drum 16. The bar is carried by a first end of a bell crank lever 24 rotatably mounted on shaft 18. In operation lever 24 is oscillated between two fixed positions by the action of a drive member 26 carried by an eccentric 28. The eccentric is mounted on a drive shaft 30.

Reference numeral 32 indicates a connecting rod joining the bearing sleeve of member 26 with a pivotal connection 34 at the second end of lever 24. In the situation illustrated, the eccentric has driven bar 22 to the lower of its two fixed positions.

Upstream of apparatus 10, a fixed guide bar 36 ensures that the yarns are correctly positioned for their approach to drum 16 whilst downstream of the apparatus the yarns pass through disc tensioners 38. 39 and a double bar tension compensator 41, 42 on their way to the needle bar of the Locstitch machine.

In operation, the drum is rotated at, say, 200 r.p.m. and the dancing bar 22. oscillates, as already described, between two fixed positions, typically completing 35 cycles for each revolution of the drum. In moving from its lower to its upper fixed position the bar will release for use in the Locstitch machine a sufficient amount of each yarn for use in any operational step that the machine has to perform. In moving back to its lower position the bar will pull the yarns used into contact with the high friction surface of the rotating drum 16.The consequent frictional grip of the drum surface on the yarns concerned will result in the drum feeding yarn to the store until the tension in these yarn drops sufficiently for slip again to occur between the yarns and the drum surface, at which stage the yarn amounts used in the previous operational step will have been replenished in the store. This will happen of course when the bar 22 has finished its downward travel i.e. in the bar position illustrated.

Clearly the less material a particular yarn has supplied to the Locstitch machine, the lower will be the dancing bar 22 before it begins to pull that yarn into yarn-feeding engagement with drum 16 since in the initial part of its downward movement the bar will be doing no more than taking up slack in the yarn. If none of a particular yarn has been used by the Locstitch machine in the preceding machine operation, then obviously that yarn will not then be brought into yarn-feeding engagement with the drum by dancing bar 22. In such a case, the downward movement of the bar will do no more than take up the slack in the yarn created by the previous upward movement of the bar.

It will be appreciated from the above explanation that in each oscillatory cycle of the bar 22, a specific and unvarying amount of slack will be guaranteed for use in the Locstitch machine if, and as, desired. The amount of slack yarn made available will be entirely independent of previous events in the machine's operation. Moreover because the reservoirs of yarn periodically created by upward movement of the bar 22 are at substantially zero yarn tension, these fixed amounts of yarn are available to the machine either at this substantially zero tension or, if desired, at some other tension superimposed on the yarn by a conventional tensioners positioned downstream of the apparatus.

Although the Locstitch machine has not be described, reference may be made to the patents quoted above for details of the basic machine and of how this can be adapted for producing sculptured Locstitch fabrics. Basically, any such machine so adapted will require yarn to be fed to it in differing amounts depending on whether the next stitch is to form part of the low loop pile or the high loop pile which together will give the fabric its sculptured appearance. In a typicl case where the fabric is being produced at a stitching pitch setting of fourteen stitches per inch, the yarn demand per stitch may vary from about eleven millimetres (for a three millimetre high "low-pile" loop) to about seventeen millimetres (for a six millimetre high "high-pile" loop).

The tension requirements in such cases can probably be most easily explained by a simplified mathematical treatment and with this in mind reference letters A, B, C, D have been included in the Figure to show positions in the yarn path at which will occur the yarn tenions TA, TB, Te and TD referred to below. In this discussion the symbols "0" and "F" will be used to indicate the included angle (0) subtended at the axis of the drum by the yarns wrapped around the drum and the coefficient of static friction (u) between the yarns and the material of the drum surface. The pressure exerted on the yarns at disc tensioners 38, 39 (normal to the yarn axis) is represented by the letter "P" and, as usual "e" represents the exponential function.

Using these symbols it can be shown mathematically that, to a first approximation, (1) TB = TC + 2uP and (2) Tn = TCeMO Looking now at the operation of the apparatus in more detail, it will be seen that when Tc is zero no yarn feed will occur becaue TD = TCeRE = O. As the dancing bar 22 moves downwards however, Tc begins to increase until TD = Toe40 = 1 to 3 gf (i.e. the tension needed to pull the yarn off its creel). At this stage the yarn will grip the drum 16 and rotation of the drum will pull the yarn off the creel. This movement of yarn has the effect of reducing Tc until TD = Tce0 = 0 again, and the yarn feed ceases.

When the bar 22 is then raised, slack yarn is created and the needle stitching action may use as much of this slack yarn as it requires for that particular stitch.

Thus when the bar 22 again moves downwards some yarns will receive a "Tc" value and commence feeding before others, but the complete downwards movement of the bar will lead to the same quantity of slack being produced in each yarn irrespective of whether and to what extent that yarn has provided material to replenish that consumed in the previous stitching action of the Locstitch machine.

It may be observed from the relationship TD = Tcelte that Tc will be a relatively small value compared with Tn and therefore the disc tensioners 38. 39 can be preset to give a substantially constant yarn tension TB to the needles with little effect from Tc since TB = Tc + 2yP where Tco - The importance of the dancing bar 22 may not immediately be apparent because it would seem at first sight that as the needles of the Locstitch machine move towards the base fabric, yarn is demanded which would result in an increase in TA, TB and Tc that would cause the yarn to feed automatically over the drum 16 without the bar 22 having to be present.However it should be borne in mind that it is at a stage when the yarn is following a tortuous path through the base fabric and the needle eye and then out of the base fabric and over the loopers that the needles are demanding yarn. In order to allow the yarn to slide easily by the flank of the needle and through the eye at this stage, TA must be zero. This can be achieved by movement of the bar 41 relative to the fixed bar 42 of the double bar compensator 41, 42 when, at this point in the cycle, Tc is substantially zero. This latter condition, as will be clear from the foregoing description, can be obtained by the provision of the dancing bar to ensure that yarn is only fed by the drum at some other point in the cycle when it is not in demand by the needless of the Locstitch machine.

A suitable point in the needle cycle for applying a tension Tc, and thus yarn feed, is as the needle of the Locstitch machine reaches full penetration depth through the base fabric. At this point no yarn is demanded from the yarn supply and an increase in TA can be used to assist the spring returned loopers in the machine to reach their pile height setting thereby relieving the work done by the springs in the loopers, especially when low pile heights are selected. In practice this increase is best achieved by supplementing TA with a pulse tension at this point to overcome the drag from the base fabric which has been found to affect the tension control on the looper.

It may now be seen that the yarn tension and feed requirements for the locked loop process of the Locstitch machine are directly dependent on each other, but the yarn tension requires cyclic control with the slack generator yarn feed system. The cyclic yarn tension requirements are illustrated in relation to the needle cycle in the plot shown in Figure 2.

The vertical axis of the plot represents TA (in gf) and the horizontal axis represents time.

The numerals 1-1(, shown on the time axis indicate different positions of the needles during the stitching cycle (as defined in U.K. Patent 1541431).

Between positions 15 to 5, TA should be a zero, and as above explained this can be achieved by the double bar compensator 41, 42. Between positions 8 to 14, TA should be at a nominal value of 5 to 10 gf achieved by the disc tensioners 38, 39. The increased tension between positions 10 and 12 is not really required but, as excess yarn is removed from the cycle by the retracting double bar compensator 41, 42, the tension may rise slightly over this part of the cycle.

The pulse of 20 gf applied between positions 6 and 8 (required for the looper yarn tension previously discussed) can be achieved by means of the dancing bar 22. As the bell crank lever 24 is driven by an eccentric 28, the dancing bar has a sinusoidal velocity function. Thus at the beginning of the downward stroke of the bar 22, the velocity of the bar is matched approximately with the peripheral velocity of drum 16 creating the relationship TD = TCCR{3 = 1-3 gf. However as the velocity of the bar increases at mid-stroke of the bar, the bar will begin to move faster than the peripheral velocity of the drum 16.This causes the yarn to slip over the drum in advance of the drum rotation and this effect changes the Tc, TD relationship to TC = TD eMH and with values of 0 = z radians, TD = 1-3 gf, and F = 0.57 (found experimentally for yarn on rubber). a value of approximately 15 gf can momentarily be produced for Tc until the velocity of the bar decreases and the Tc, TD relationship reverts back to TD = TCOPH = 1-3 gf. The 15 gf pulse tension in Tc gives rise to a 20 gf in TB as will be clear from the relationship TB = TC + 2tiP.

Having described. by way of example. one particular situation, it ought to be understood that the system may be provided with many variable setting features which can be included to cope with different yarn types, different cone winding tensions and different seam stitching pitches etc. Thus (1) the speed of the drum 16 can be adjusted by driving the shaft 18 from a variable speed drive unit; (2) the drum can be rotated intermittently e.g. to avoid scuffing when the yarn is stationary and this feature could also be used if desired to give additional yarn tension; (3) the stroke of the dancing bar 22 can be varied by means of a slotted arrangement (shown in Figure 1 at 44) in the bell crank lever 24; (4) the timing of the dancing bar 22 can be varied in relation to the cyclic position of the needles to give a 'pull back' of yarn at a discrete position in the stitching cycle; (5) the rate of stroke of the dancing bar can be varied and for example the bar could be made to move faster than the yarn feed in order to tension yarn to the Locstich machine e.g. to "lock" the stitch or to tension yarn in the needle or to cause slip over the looper: (6) the angle of wrap of the yarns around the drum 16 can be varied e.g. by changing the preset position of the guide bar 36. The amount of yarn wrap around the dancing bar could of course also be varied.

It should also be appreciated that other changes in the system could be incoporated in order to modify its performance. For example (1) the frictional characteristics of the drum could be varied by using other materials for sleeve 20 and/or the frictional characteristics of the dancing bar could be varied if desired; (2) the bell crank lever 24 does not necessarily have to pivot about the shaft 18 but could pivot about some other independent axle and this would allow the velocity of the dancing bar 22 to be changed relative to the peripheral velocity of the drum 16; (3) a cam drive on the bell crank could be used instead of an eccentric since this would facilitate a very precise control of the cyclic feed and tension changes should this control be required for a particular application; (4) the drum 16 and/or the bar 22 may be grooved to maintain the various yarns separate but this will only be necessary for yarns which are prone to interentanglement; (5) the dancing bar could be split into two or more separate bars (each with its own drive system), for example where it is desired say to have a Locstitch machine producing sculptured Locstitch fabric at some needles and plane Locstitch fabric at others; (6) the dancing bar may be positioned above the axis of the drum rather than below it in which case downward movement of the bar would provide the reservoirs of slack yarn (provided in the illustrated embodiment by the bar's upward movement) and upward movement of the bar (although being in a direction tending to decrease the angle of yarn wrap around the drum) would tension those yarns that had provided material for the machine to draw them into feed engagement with the surface of the drum; (7) the bell crank lever could be replaced by any other functionally equivalent device e.g. a piston; (8) the surface of the drum need not be uniform. For example the frictional grip could be provided by strips of raised material extending, for instance, along the drum surface parallel to the axis of rotation of the drum.

These modifications are referred to in the Claims as modifications of the type hereinbefore described.

Although only Locstitch applications of the invention have been discussed above in any detail, it will of course be clear that the invention will also be applicable to warp knitting, weaving, tufting and stitch bonding processes. Filamentary materials other than textile materials may also be fed with apparatus employing the characteristic features of the present invention. Accordingly, the term "like filamentary and other elongate materials" should be interpreted as including for at least one of the lengths to be supplied any flexible material that can be fed in this way e.g. a woven or knitted fabric, a roll or sheet of plastics material, paper etc. The term also includes within its scope individual filaments such as nylon filaments, metal wires etc. as well as those consisting of a number of single filaments joined together in some fashion.

WHAT WE CLAIM IS: 1. For use with a machine to be fed with one or more continuous lengths of yarn or like filamentary or other elongate material, a feed apparatus comprising a store for storing when full a predetermined amount of the material for use in a subsequent material-demanding operation by the machine, and supply means adapted to replace in the store any of the material taken from the store in said material-demanding operation, the apparatus comprising means for engaging the material with the supply means in a manner which depends on the degree of fullness of the store.

2. An apparatus as claimed in Claim 1 when used with a machine in which the predetermined amount of material of the or each length held in the store is in excess of the demand in the subsequent machine operation so that sufficient material is available to the machine for any given operation.

3. An apparatus as claimed in Claim 1 or Claim 2 in which the apparatus comprises a single store adapted to operate simultaneously with two or more lengths of the material.

4. An apparatus as claimed in any of Claims 1 to 3 in which the apparatus comprises a single supply means adapted to operate simultaneously with two or more lengths of the material.

5. An apparatus as claimed in any preceding claim in which the supply means comprises one or more elements mounted for rotation about an axis with the surface of the or each element adapted to be engaged by one or more lengths of the material, and the store comprises one or more members mounted for movement relative to said axis with the surface of the or each member adapted to be engaged by one of more lengths of the material.

6. An apparatus as claimed in Claim 5 in which the supply means comprises a number of wheels mounted for rotation about a common axis.

7. An apparatus as claimed in Claim 5 in which the supply means comprises a rotatable drum.

8. An apparatus as claimed in any preceding claim in which the supply means is driven by a variable speed drive unit.

9. An apparatus as clairned in any preceding claim including means for operating the supply means intermittently.

10. An apparatus as claimed in any preceding claim including means for varying the angle of wrap of the material around the supply means.

11. An apparatus as claimed in any preceding claim in which the store comprises one or more arms mounted for oscillatory movement between fixed positions.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. would allow the velocity of the dancing bar 22 to be changed relative to the peripheral velocity of the drum 16; (3) a cam drive on the bell crank could be used instead of an eccentric since this would facilitate a very precise control of the cyclic feed and tension changes should this control be required for a particular application; (4) the drum 16 and/or the bar 22 may be grooved to maintain the various yarns separate but this will only be necessary for yarns which are prone to interentanglement; (5) the dancing bar could be split into two or more separate bars (each with its own drive system), for example where it is desired say to have a Locstitch machine producing sculptured Locstitch fabric at some needles and plane Locstitch fabric at others; (6) the dancing bar may be positioned above the axis of the drum rather than below it in which case downward movement of the bar would provide the reservoirs of slack yarn (provided in the illustrated embodiment by the bar's upward movement) and upward movement of the bar (although being in a direction tending to decrease the angle of yarn wrap around the drum) would tension those yarns that had provided material for the machine to draw them into feed engagement with the surface of the drum; (7) the bell crank lever could be replaced by any other functionally equivalent device e.g. a piston; (8) the surface of the drum need not be uniform. For example the frictional grip could be provided by strips of raised material extending, for instance, along the drum surface parallel to the axis of rotation of the drum. These modifications are referred to in the Claims as modifications of the type hereinbefore described. Although only Locstitch applications of the invention have been discussed above in any detail, it will of course be clear that the invention will also be applicable to warp knitting, weaving, tufting and stitch bonding processes. Filamentary materials other than textile materials may also be fed with apparatus employing the characteristic features of the present invention. Accordingly, the term "like filamentary and other elongate materials" should be interpreted as including for at least one of the lengths to be supplied any flexible material that can be fed in this way e.g. a woven or knitted fabric, a roll or sheet of plastics material, paper etc. The term also includes within its scope individual filaments such as nylon filaments, metal wires etc. as well as those consisting of a number of single filaments joined together in some fashion. WHAT WE CLAIM IS:

1. For use with a machine to be fed with one or more continuous lengths of yarn or like filamentary or other elongate material, a feed apparatus comprising a store for storing when full a predetermined amount of the material for use in a subsequent material-demanding operation by the machine, and supply means adapted to replace in the store any of the material taken from the store in said material-demanding operation, the apparatus comprising means for engaging the material with the supply means in a manner which depends on the degree of fullness of the store.

2. An apparatus as claimed in Claim 1 when used with a machine in which the predetermined amount of material of the or each length held in the store is in excess of the demand in the subsequent machine operation so that sufficient material is available to the machine for any given operation.

3. An apparatus as claimed in Claim 1 or Claim 2 in which the apparatus comprises a single store adapted to operate simultaneously with two or more lengths of the material.

4. An apparatus as claimed in any of Claims 1 to 3 in which the apparatus comprises a single supply means adapted to operate simultaneously with two or more lengths of the material.

5. An apparatus as claimed in any preceding claim in which the supply means comprises one or more elements mounted for rotation about an axis with the surface of the or each element adapted to be engaged by one or more lengths of the material, and the store comprises one or more members mounted for movement relative to said axis with the surface of the or each member adapted to be engaged by one of more lengths of the material.

6. An apparatus as claimed in Claim 5 in which the supply means comprises a number of wheels mounted for rotation about a common axis.

7. An apparatus as claimed in Claim 5 in which the supply means comprises a rotatable drum.

8. An apparatus as claimed in any preceding claim in which the supply means is driven by a variable speed drive unit.

9. An apparatus as clairned in any preceding claim including means for operating the supply means intermittently.

10. An apparatus as claimed in any preceding claim including means for varying the angle of wrap of the material around the supply means.

11. An apparatus as claimed in any preceding claim in which the store comprises one or more arms mounted for oscillatory movement between fixed positions.

12. An apparatus as claimed in Claim 11 in which the stroke of the arm of arms can be

varied.

13. An apparatus as claimed in Claim 11 or Claim 12 in which the timing of the arm or arms can be varied in relation to some operational function of the machine.

14. An apparatus as claimed in any of Claims 11 to 13 in which the rate of stroke of the arm or arms can be varied.

15. An apparatus as claimed in any of Claims 11 to 14 including means for varying the angle of wrap of the material around the arm or arms.

16. An apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

17. An apparatus as claimed in Claim 16 incorporating one or more of the modifications hereinbefore described.