Field of the Invention

The present invention relates to yarn delivery systems and, in particular, to those including yarn accumulators. In this specification the term "yarn" includes fibres, tapes and other filamentary materials or strips.

Background to the Invention

A weaving, weft insertion knitting or fibre laying machine requires a feed of yarn to its weft insertion mechanism. It will be appreciated that this feed is required to be intermittent as the weft insertion device traverses the apparatus. This causes a variable force to be exerted on the yarn package from which yarn for the weft is drawn and hence variable tension in the yarn, both of which can be problematic.

If a stationary yarn package is used, the variation of force is not a significant problem as only the removed yarn from such a package is moving. However, in the case of a rotating yarn package, the whole package rotates and builds up momentum accordingly.

A rotating yarn package holder for use in a yarn delivery system is disclosed in published International Patent Application no. W094/26646 which solves many of the problems encountered with prior systems. The yarn package holder disclosed in W094/26646 is of a rotating type (that is it enables yarn to be withdrawn from a yarn package t carries by the rotation of the yarn package) and includes a braking and tensioning control mechanism. Typically, to

pull yarn from the yarn package on this yarn package holder a force is required corresponding to a yarn tension of about 150g or more, and even about 250g or more in the case of glass fibre yarn. This tension is too high to be compatible with an intermittent feed for weft insertion mechanisms, which typically require lowest possible tension typically of no more than about 50g.

In order to avoid insertion of twist into yarn unwinding from a yarn package, it is necessary to rotate the package and draw the yarn off tangentially. Any rotating package unwinding spindle of non-motorised design incorporating the necessary means for both yarn tension and package overrun breaking control must necessarily operate at a higher tension than may be demanded by subsequent processes because the unwinding yarn tension has to be high enough to provide the motive power to pull the package round. Low tension delivery from a rotating package system especially when combined with the need for intermittent yarn feed is, therefore, a significant problem.

By way of example, intermittent feed is required in the weft insertion of multi-axial or warp knitting machines.

It is an aim of preferred embodiments of the present invention to obviate or overcome disadvantages encountered in the prior art, whether referred to herein or otherwise.

Summary of the Invention

According to the present invention there is provide. a yarn delivery system comprising:

a yarn package holder of a rotating type,

a yarn accumulator comprising means for defining a volume in which a length of yarn can accumulate, and

means for urging yarn into the accumulation volume from the yarn package holder.

This system enables the delivery to a subsequent processing step of yarn under low tension and without introduction of substantial twist. In particular, the yarn tension at its exit from the accumulator is lower than that required for unwinding of the yarn from the yarn package .

Suitably, means are provided for guiding yarn from the yarn package holder to the accumulator.

Suitably, the means defining the accumulation volume comprises a chamber. Suitably the chamber includes a first hole through which yarn can enter the chamber and a second hole through which yarn can exit the chamber.

Suitably, the means for urging the yarn into the accumulation volume encourages the yarn to hang towards the base of the accumulation volume. The base of the accumulation volume is not necessarily the lowest point .

Suitably, the urging means comprises a weight on or of the yarn in the accumulator.

Suitably, the means for urging the yarn into the accumulation volume comprises air flow means applied to the accumulation volume.

Suitably, means are provided for varying the flow of air caused by the air flow means. Suitably, the varying means comprises means for moving the air flow means relative to the accumulation volume. Suitably, the varying means is adapted only to reduce the air flow when, in use, yarn is being drawn from the accumulation volume. Suitably, the air flow means comprises air suction means which comprises a hollow tube which draws air from the accumulation volume. Suitably, the varying means moves the tube relative to the accumulation volume longitudinally or about the longitudinal axis of the tube.

Suitably, the air flow means comprises an air blower.

Suitably, the air blower generates a substantially laminar air flow from its output.

Suitably, the air blower is located substantially outside the range of movement of the yarn loop.

Suitably, the air blower comprises a fan.

Suitably, there are a plurality of accumulators which preferably are in a side-by-side relationship.

Suitably, the urging means comprises a positive drive unit between the yarn package holder and the accumulator. Suitably, the positive drive unit comprises a plurality of rollers, at least one of which is driven. Suitably, all of the rollers are driven. Alternatively or additionally, the positive drive unit may comprise at least one nip roller system, which expression includes arrangements such as endless belts.

Suitably, the positive drive unit comprises a driven roller and an endless belt assembly.

Suitably, the creel comprises a plurality of yarn package holders. Suitably, there are at least as many accumulators as yarn package holders. Suitably, the yarn package holders are arranged on the creel in generally vertical columns above which a guide acts to divert yarn to the accumulator. Suitably, means are provided between the yarn package holders and the accumulators to keep the yarn from the yarn package holders separate.

Suitably, the at least one accumulator is or are mounted on the creel.

Suitably, the at least one yarn package holder comprise or comprises means for braking the yarn package holder according to a tension of the yarn drawn from the at least one yarn package holder.

Brief Description of the Drawings

The invention will now be described, by way of example only, with reference to the drawings that follo ; in which:

Figure 1 is a schematic isometric illustration of a bank of accumulators according to the present invention.

Figure 2 is a schematic side elevation of the accumulator of Figure 1 attached to a mul i-yarn package holder creel for feeding yarn thereto.

Figure 3 is a schematic plan view of the accumulator and creel shown in Figure 2.

Figure 4 is a schematic isometric illustration of one of the yarn package holders shown in Figures 2 and 3.

Figure 5 is a schematic enlarged perspective elevation of a second embodiment of an accumulator for use with the present invention.

Description of the Preferred Embodiments

Referring to Figure 1 of the drawings that follow, there is shown a bank of yarn accumulators 2 arranged side-by-side. The following description refers only to one accumulator 2, except where the context indicates otherwise, the others being similar.

Each accumulator 2 comprises a chamber 4 defining an accumulation volume therein. The chamber 4 is formed from opposed substantially parallel side pieces 6, 8 spaced apart by edge pieces 10, 12 and 14. Edge pieces 10, 12 extend along the long edges of the chamber 4. Edge piece 14 in the upper face of the chamber 4 includes an entry hole 16 and an exit hole 18. In the area of the base 19 of chamber 4, opposite upper edge piece 14, is a circular hole 20 through side pieces 6,8 which extends through the bank of accumulators 2.

A length of yarn 22 is shown entering entry hole 16 and exiting exit hole 18. Dashed lines in Figure 1 show two of the many alternative positions of the yarn 22 within the accumulator chamber 4.

Extending through the hole 20 is an air extraction manifold 24 comprising a circular cylindrical hollow tube spaced along the length of which are a plurality of aligned extraction holes 26, the spacing of which

corresponds to that of the spacing of the accumulators, ie there is one extraction hole 26 for each accumulator 2 and aligned therewith.

The air extraction manifold 24 is in fluid communication with a suction pump (not shown) and is capable of rotational and/or longitudinal movement relative to the accumulator 2.

In operation, yarn 22 is fed by a positive feed unit (see below) through entry hole 26 at a constant speed to accumulate a loop 28 of yarn 22 in the accumulator 2. Suction is applied to the air extraction manifold 24 to encourage and urge the yarn 22 into the accumulator 2 and help ensure it does not become twisted or knotted because it hangs free. Further, the suction helps to maintain the loop within the accumulator 2.

Yarn 22 can, therefore, be drawn intermittently from the accumulator 2 through exit hole 18 without affecting substantially the tension of the yarn 22 before it enters the accumulator 2. The only tension in the yarn 22 exiting the accumulator 2 is that from its own weight and the suction through air extraction manifold 24. Typically, this tension is about 50g.

The air extraction has the additional advantage that it draws from the yarn and its vicinity loose glass and/or carbon in the case of glass fibre. This helps keep ^' the environment around the system cleaner.

Referring now additionally to Figures 2 and 3 of the drawings that follow, there is shown a vertical creel 30 on either side of which are mounted a plurality of yarn package holders 32 carrying yarn packages 34.

The yarn package holder 32 and yarn package 34 arrangement is shown in Figure 4 of the drawings that follow. This is substantially similar to that described in published International Patent Application No. W094/26646, the content of which is incorporated herein by reference .

Briefly, the yarn package holder 32 and yarn package 34 arrangement has a mechanism for controlling the yarn package 34 during its acceleration, running and stopping phases. It includes a mechanism for rapidly arresting the yarn package 34 (by acting on the yarn package holder 32) once yarn is no longer being drawn therefrom. The mechanism comprises a pivoted member 36, one end of which carries a transverse control roller 38 which overlies the yarn 22, and the other end of which is secured to an end of a tensioning cord 40 wrapped around a pulley on the yarn package holder 32. Typically yarn will be drawn off at a tension of about 150g or more, or about 250g or more for glass fibre yarn. When yarn 22 is being drawn the control roller 38 is lifted and thus has the effect of loosening the cord 40 around the pulley, so that the braking effect is small . When yarn is no longer drawn the control roller 38 drops. This has the effect of tightening cord 40 around the pulley, and rapidly arresting the yarn package holder 32.

Also extending from a mounting bracket 42 for the pivoted member 36 is a guide roller 44 which underlies the yarn 22 before it reaches the braking control roller 38.

Referring again to Figures 2 and 3, for each yarn package holder 32, yarn 22 proceeds from the yarn package 34 over guide roller 44 and under braking control roller 38.

Above each vertical column of yarn package holders 32 is a diversion roller 46 over which the yarn 22 passes towards a positive feed unit 48. The positive feed unit 48 comprises three driven rollers 50, 52 and 54 to draw the yarn 22 from the yarn package 34 at a constant speed. The driven rollers 50, 52 and 54 drive the yarn 22 by frictional contact only.

Between the diversion rollers 46 and the positive drive unit 48 is interposed a comb 56 (which could equally be an eye-bar) to keep separate and untangled the yarns 22.

Thus, a plurality of separate parallel yarns 22 exit from the positive drive unit 48.

The accumulator bank (Figure 1) is mounted on the side of creel 30 underneath the outlet of positive drive unit 48 by mounting brackets 58. There is one accumulator 2 for each yarn package holder 32 and hence each yarn 22.

The yarn 22 enters the chamber 4 through the entry hole 16, forms the loop 28 in the accumulator 2 and leaves through exit hole 18. It then passes over roller 60 before proceeding to its subsequent processing.

The operation of accumulator 2 is as described above in relation to Figure 1. The build up of loop 28 in the chamber 4 ensures that the input to the accumulator 2 can be constant while the output from it is variable (ie intermittent) .

If desired, the suction applied by the air extraction manifold 24 can be reduced when yarn 22 is drawn from the chamber 4 by the subsequent processing apparatus (not

shown) . It is believed that this will assist in the smooth withdrawal of yarn 22 from the accumulator 2. This is achieved by indexing the manifold 24 longitudinally, and/or rotating it about its longitudinal axis as the yarn 22 is withdrawn to provide less direct suction on the yarn 22. The manifold 24 is returned to its operating position while yarn 22 is not being drawn from the accumulator 2.

It will be appreciated that in alternative embodiments of the present invention, the air extraction manifold 24 can be modified to be static and for the suction to be applied only when required. Further, individual extraction manifclds could be provided, one for each accumulator.

Referring to Figure 5 of the drawings that follow there is shown an alternative form of accumulator construction in which similar reference numerals are used for like integers as in Figures 1-4. In the Figure 5 embodiment the yarn is urged towards the base 19 of accumulator 2 by air blown from a blower 62 mounted above the accumulation chamber 4. The blower 62 is mounted outside the range of movement of the yarn loop so that it does not become entangled with yarn 22.

The blower 62 comprises an air impeller unit 64 and an outlet 66. The outlet 66 includes baffles 68 to produce a substantially laminar flow from the output of outlet .66. ^' The laminar air flow urges the loop 28 of the yarn towards the base 19 without it becoming tangled. Arrows 70 indicate generally the air flow path.

The base 19 includes a trash collection box 72 which may include a removable drawer. The box 72 can collect

debris from the yarn 22, particularly relevant in the case of glass yarn.

Air exits the accumulation chamber 4 via an exit hole 74 and enters flexible tubing 76 which conveys the air to a cyclone dust collection unit 78 after which the air is recycled through blower 62 via tubing 80.

Thus there can be provided a closed-loop air flow and cleaning system.

Also shown figuratively in Figure 5 is an alternative positive feed unit indicated generally at 82. The positive feed unit 82 comprises a driven roller 84 and an endless belt assembly comprising two idler rollers 86, 88 and an endless belt 90 which bears against the yarn 22 passing over roller 84. In this arrangement the positive drive unit does not rely solely on friction over the roller 84. Instead the yarn also bears against the belt 90.

The apparatus described above delivers twist free yarn at an intermittent speed and considerably lower tension than is required for unwinding to a subsequent processing apparatus.

An alternative technique for controlling the yarn in the accumulator may be used. For instance, a light diablo roller over the yarn, which roller runs in slots in the accumulator chamber could be used.

It will be appreciated that in a simplified embodiment of the present invention, the hole 20 and air extraction manifold 24 can be omitted.

Clearly, the yarn 22 from the yarn package holders 32 can be drawn horizontally to a vertical edge of the creel 30, instead of vertically to a horizontal edge as shown in the accompanying drawings and as described above. In this case, the guide rollers 44 would be on a vertical side of the creel 30.

The accumulators 2 need not be mounted such that the accumulation volume is vertical as shown, although this is preferable.

Instead of or as part of the positive drive unit, some form of nip roller system arrangement may be required to drive the yarn adequately.

It will also be appreciated that the apparatus described above is substantially independent of the nature of the subsequent processing apparatus.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed m this specification (including any accompanying claims, abstract and

drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.