GB2068422A - Weft patterning - Google Patents

Abstract

A weft pattern mechanism comprises a bank of plates B with bores P for the passage of weft yarns Y, the yarns being normally maintained against a wall OH by a main jet of fluid through a bore JM, and being deflected into a selected position, by the Coanda effect of a supplementary jet JS, in which they are engaged by a weft inserter N. <IMAGE>

Description

SPECIFICATION Improvements in manufacture of fabric This invention relates to fabric manufacture such as weaving and knitting and more particularly to the selection of yarns for patterned fabric weaving of tapes, ribbons, webs, belts, elastics, labels and the like.

One loom of known form can weave plain tapes and the like at high speeds, typically 3000 weft yarn cycle (or picks) per minute. However the weft yarn is of one colour only while the warp shed is of fixed layout.

To achieve patterned weaving on a high speed narrow fabric loom several problems must be overcome.

The fabric is typically some 65 mm wide having up to about 400 yarns to the warp. The weft is inserted at about 3000 cycles (picks) per minute.

This allows some 20 milliseconds for weft yarn selection and positioning.

Weft selection systems are known but these require a mechanical control, such as a Jacquard card system acting. on heddles each of which carries one of the weft yarns, selection of a heddle by the mechanical control lifts the heddle and its yarn for weft insertion by the weft needle. The Jacquard system is of limited speed although if the warp is also Jacquard controlled no faster speed could be used anyway. However, another limitation is the need for mechanical linkages from the Jacquard, or other control, to the heddles and the inertia of these parts. Mechanical linkages require careful adjustments and maintenance and are not easily altered or moved to optimise the needle stroke for different fabric widths and also cannot operate at higher speeds.

It is an object of the invention to provide an improved weft yarn selector.

According to the present invention there is provided a weft yarn selector for a plurality of weft yarns to determine which of the plurality of yarns is to be inserted along a weft insertion path as a weft in a fabric, the selector including a fluid jet yarn presentation arrangement for said plurality of yarns to present the yarns at a position clear of said path and fluid jet yarn deflection means effective in operation to selectively deflect a yarn from the presentation position to a weft supply position in the weft insertion path for take-up by a weft insertion means.

The presentation arrangement may include a fluid-pressure feed for each yarn operable to support the yarn in the presentation position. The yarn may be fed along a bore through which the fluid flows from said feed to emerge with the fluid jet at a bore exit. The. deflection means may be a control fluid jet adjacent to the bore exit and operable to deflect the main fluid jet and the yarn entrained within it at the bore exit. The selector may use the Coanda fluid flow attachment phenomenon. Preferably the selector has for the presentation arrangement an adjacent surface extending from over the bore exit in an upward slope to which surface the presentation fluid jet attaches in operation to support emerging yarn in an initially rising curve as the presentation position.The deflection means may be effective to detach the presentation fluid jet from said surface and bring about the deflection of a yarn to the weft supply position.

According to a particular aspect of the invention there is provided a weft yarn selector including a single weft carrier having a yarn catcher and movable in a weft yarn insertion path, together with a plurality of weft yarn supply and positioning devices having for each yarn a main yarn-fed jet operable to hold the yarn in the jet clear of the yarn catcher and an auxiliary air jet yarn positioner operable to deflect the main air jet, and held yarn, into the weft yarn catcher path.

According to a further aspect of the invention there is provided a weft yarn selector for a plurality of yarns including a multiple fluid pressure jet block having for each yarn a main air jet path derived from a common supply path and feeding an individual bore which is also yarn-fed to enable the main jet emerging in operation from the bore exit to support the yarn clear of a weft insertion path, the block also having an individual auxiliary jet path for each yarn including an individual control element operable to selectively deflect or not deflect a main air jet and its entrained yarn emerging from a respective bore exit into the weft insertion path for take-up by a weft insertion means.

The control elements may be electrically operable fluid pressure control valves. The weft insertion means may be a needle having a yarn take-up eye or fork which is not permanently closed. The jet-block may be of laminate construction, each laminate having through it a connection for the common main fluid pressure jet supply and an individual connection for the auxiliary jet supply while providing a through path for other auxiliary jet supplies.

Typically the selector selected from 6 weft yarns at up to 3000 weft cycle per minute in a narrow fabric loom, but it could be applied to any number of weft yarns from 2 upwards.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a six-fold weft-yarn jet block and air supply connections, Figure 2 shows the yarn feed and general arrangement of the selective weft supply for the six-fold block of Figure 1, Figure 3 shows the operation of one element of the six-fold block of Figure 1, Figure 4 shows a side and plan view of a weft needle for selective weft insertion, and Figure 5 shows a portion of fabric woven using the described weft selection.

In order to obtain a woven patterned textile fabric, which has fine and accurate detail and includes many different coloured yarns, it is necessary to have the ability to choose one yarn from several weft yarns for each pick (cycle of the loom). The existing high picking speeds obtainable by the narrow fabric, single weft loom intended for plain fabrics are in part due to the system of weft insertion employed. A needle with an eye near one end, through which the single weft yarn is passed, is mounted on a pivoted arm so that the eyed end can pass through the shed formed in the warp threads. The weft thus forms a loop across the fabric width, the end of which is caught to form the selvedge.In one known arrangement used with this embodiment the loop is caught on the hook of a latch needle so that. as the insertion needle retracts, the loop of the weft yarn is retained in the warp shed which is then closed.

This typical arrangement is described only as an example of the many techniques that are usable in circumstances apparent to those skilled in the art.

An important requirement for good quality fabric is to feed the same length of weft yarn into the fabric during each cycle. This is achieved on the standard machine by a positive yarn feeding device driven from the main shaft of the machine.

An embodiment of the invention described below provides for selection of the weft from several different weft yarns at each pick.

To achieve selection of one of several coloured weft yarns for each pick it has been found necessary to keep the mass of any parts selected to a minimum. A single constantly reciprocating needle is still used but in one embodiment the eye has been opened out into a very carefully shaped fork, Figure 4. In other embodiments a more closed eye is used. Preferably an eye closed by bearding or latching is used to reduce risk of shed damage.

The coloured yarn to be incorporated into the fabric is placed and held to be in the path of the oncoming needle whilst this is still outside the shed; the time available to so-position the yarn, at 3,000 cycles per minute, is 1 to 5 milliseconds depending on the width of fabric being woven, and the selected stroke of the weft insertion needle.

The weft positioning system must therefore have a very fast response time. In one embodiment, illustrated in Figures 1, 2 and 3 this is achieved by the use of fluid-pressure jets. Six weft yarns can be used in the illustrated embodiment as a six-fold fluid-pressure (air) jet block B is provided. (For clarity Figure 2 shows only one yarn emerging from jet block B.) An element BE of the jet block for one yarn is shown in Figure 3. Each element BE is typically a plate about 1.5 mm thick and is provided with a yarn path of a 1 x 1 mm bore P through which a weft yarn YE can pass to an outlet 0. A cover plate BC is also provided.A main air jet JM typically 1 x 1 mm cross-section and an auxiliary or secondary air jet J5 typically 1 x 1 mm cross-section are arranged to be supplied with air from a suitable source, that to the auxiliary jet being selectively supplied, and to apply the supplied air to the yarn in the yarn path.

In Figure 1 the selective supply is indicated by valves in connection to each secondary jet. A valve is included in the common manifold main jet connection. These valves could be operated in any suitable manner, e.g. electrically or by fluidpressure, as described below. The elements are stacked as shown in Figure 1 and the air connections made in suitable manner producing a compact, economically manufactured assembly.

In the embodiments described the fluid used is air. Clearly other gaseous fluids as well as liquid fluids could be used with appropriate modifications and all are included in the term "fluid".

Referring to Figures 3A and 3B these shown the effect of the secondary jet J5. In Figure 3A air is supplied only to the main jet JM and the yarn substantially follows the streamline air flow in path P. At outlet 0 the air stream attaches to the lowly diverging upper wall (typically 1 50 to path P), as viewed in the drawing, as the lower wall diverges much more rapidly (typically at 450) from the line of the air stream. The yarn remains in the air stream, as shown, and emerges on the high side, OH, of outlet 0. Referring to Figure 2 it will be seen that the weft insertion path of the needle N through the shed S will not touch the yarn blown from outlet side OH.The yarn is held to the line of the slowing rising outlet wall by the Coanda effect attachment of the air stream to the wallline, which lifts the yarn emerging at OH to maintain clearance from the needle. The momentum of the air stream also aids in the lifting of the yarn beyond outlet OH, as does air flow induced in direction A', through a low pressure area at the lower wall corner into the weft presentation path WP. (The Coanda or wallattachment phenomenon is the tendency of a fluid jet to adhere to an adjacent surface.) If jet J5 is applied, Figure 3B, the Coanda attachment is destroyed and the air flow of the main jet deflected towards the more rapidly divergent lower wall and outlet OL. The yarn YE in path P is deflected with the combined air flow as shown in Figure 3B.It is seen from Figure 2 that the deflected yarn will be picked up in the needle fork and carried through the shed SH. The weft yarn loop inserted in this way can be retained in the shed in any suitable manner, for example the conventional weft knitted edge of catch thread knitted edge.

The air supply is filtered and regulated to a constant pressure. The main air jet supply is nominally at 1 5 psi but pressure drops in the available conduit sizes reduce this to about 10 psi at bores P. The auxiliary jet supply is nominally at 50 psi. Again conduit and control element pressure drops reduce this to about 10 psi at the effective point, i.e. adjacent to the exit from bore P. The supply to individual auxiliary or secondary jets J5 is through respective control elements in the form of valves, V1to V6, for example the Clippard Minimatic EV03M valve which is electrically operated. This is a small valve affording a high response speed with low power drive (0.65 watt) and such performance is most suitable permitting yarn selections at the jet exit at the rate of 100 per second to be achieved, i.e. a potential selection rate of 6000 picks per minute.

Additionally the low output power permits the valve to be driven via a simple amplifier from the output of a microprocessor which output is used to control the pattern woven by selection of wefts.

The arrangement described in this specification can be operated in association with a warp selection arrangement for example that described in the same Appiicants' Application "IMPROVEMENTS IN FABRIC MANUFACTURE".

The microprocessor could then control warp and weft selection.

Desirably the timing and form of the valve drive are adjusted for optimum response. One suitable drive waveform has a high voltage initial kick (circa twice normal voltage) falling to the normal, hold voltage. The drive starts 900 of machine main shaft revolution after the fully retracted needle position (00) and is maintained for the whole weft insertion weaving cycle (circa 3600).

The initial kick is some 1 mS in durection. The valve drive is most useful at higher speeds.

The weft yarns are fed along respective main jets which have a constant air flow through them, the yarn tending to follow very closely the streamline of the air flow. In the "non-select" state the air flow passes along the upper wall of the jet, which holds the air stream, and the yarn with it, by Coanda effect in the upper position. An appropriate number of jets are assembled in sandwich construction and supplied with air and threaded with different yarns. To select the yarn passing through a jet a second smaller jet is used to deflect the main air flow and position the yarn in the path of the fork of the weft insertion needle.

Thus one of several yarns is selected when the appropriate secondary jet is pressurised. The unselected yarns, even when attached to the fabric at an earlier insertion, remain lifted clear of the weft insertion path.

The advantages of this arrangement are that: a) a jet assembly to control say 6 yarns occupies a small space, approximately 40 X 25 x 15 mm; b) there are no moving mechanical connections required to the unit, thus permitting adjustment of selector position of optimum performance unit e.g.

needlestroke and c) the air flows which have to be switched are very small and if required can be carried in flexible tubes, thus permitting a small and fast solenoid operated valve to be used which can be driven from the output of a microprocessor through a single stage transistor amplifier controlled by the TTL output of the microprocessor.

Clearly other fluid-pressure arrangements may be used. Two control jets are possible one to move the yarn into the weft path the other to move the yarn away, as in a fluidic flipflop (bistable).

Reference has been made to the Coanda phenomenon which is used to improve the separation of the yarn positions. However, in other embodiments the Coanda effect can be applied differently or not used at all.

The yarn feeding system, as with other forms of weft selection, must allow for the intermittent feeding of any one yarn.

Figure 2 also shows the weft yarn feed arrangement. For clarity only one weft yarn feed to a multiyarn jet block B is shown. Clearly a similar arrangement is used for each weft yarn.

Yarn on a supply package SP is drawn off at a constant low tension by suitable device. That commercially available as the IRO type SFS 1 706 is suitable, providing yarn storage and feed by dispensing yarn over the end of the rotating body of the device at an even, low tension. This provides a buffer against the effects of uneven package tension and minor "snags" in the yarn path from the yarn supply package. A conventional spring-loaded cymbal tensioner applies additional tension for weaving. This arrangement permits the ready supply of yarn when a selected yarn is to be inserted into the shed but prevents the supply of excess yarn.While a positive yarn feed to operate selectively at the required feed rate is an alternative the arrangement described is effective and economic and not liable to produce inaccurate yarn feed as could an intermittently operated positive feed.

Various types of yarn are suitable. Included in those tried in experiments and found to be satisfactory are 100 decitex rayon of 50 filaments at 100 twists/metre and 1 50 decitex nylon of 50 filaments and 100 twists/metre and even sewing threads of the type made and sold under the Sylko registered trade mark. The weft selection sequence can be varied while weaving is in progress by adjustement of the pulse rate and timing of the signals to the control valves.

It is also necessary to provide a small initial feed of yarn at low tension at the yarn collection time to enable the yarn at the jet-block outlet to either arch away or towards the needle path. This is provided by a driven back-robber BR. A spring S is attached at one end to a disc U on an oscillating shaft OS. The spring carries at its other, free, end a yarn eye. As the shaft oscillates with machine action the yarn is alternately taken up and allowed to slack by the transmitted disc movement. The main air jet pulls the slack through as it is made available. When a weft has been inserted and the far selvedge formed the take-up draws any surplus from the knitted selvedge providing a tight edge.

The near selvedge is formed by the unselected weft yarns.

The timing of the various operations of the machine is important. Reference has been made above the pulse for weft selection. This can take place immediately the previously selected weft has been taken up by the needle and can continue for up to one machine cycle. The back-robbing spring is timed with regard to the nature of the yarn and selvedge. A suitable position for the yarn used in some trials is for the spring to be fully advanced at 1450 of a machine cycle and fully retracted at 3250 by the oscillation of the shaft carrying the disc to which the spring is attached. If yarns of different types are used in one group of weft yarns the back robbing for each yarn can be made independent.

Synchronisation of the various motions and control valves can be based on an optoelectronic sensor responsive to a timing disc on the machine main or other shaft and connected to suitable control circuits. The back-robbing oscillation can be provided and set by adjustable pulleys driven from the positive yarn feed drive of a conventional machine. In some trials using arrangements described herein a standard Bonas Varitex 2/65 loom was modified by removing the positive yarn feed mechanism, fitting the multiple jet block about 2 mm above the needle path and fitting the forked needle described below. The optimum block position is then set by trial for each fabric width. The yarn feed drive remains for backrobbing drive using a slip-free drive.

Figure 5 shows an example of a fabric woven using these techniques. It is a tape or ribbon about 25 mm wide with a uniform warp of about 130 yarns. Six weft yarns are available (A, B, C, D,E, F) and by manipulating the valve controls during the weaving the fabric woven in a continuous piece can be varied as shown from a portion with a single weft yarn A to a repeated cycle of one weft of each yarn (A-F) then alternations of only two yarns e.g. E and F with a few wefts of each. These variations are woven at a steady speed. Cleady other pattern forms can be generated, these merely showing the versatility and speed of weaving and adjustment.

The cymbal tensioner is set to provide a tension high enough to maintain a neat selvedge without weft yarn damage for the fabric being made. The storage and feed units and cymbal tensioners should be placed as close as possible to the weaving zone as each eye through which the yarn passes increases yarn tension and extension under tension increases with yarn path length. A similar path for each weft yarn is preferable to produce even results. The cymbal tensioners can be adjusted individually to cope with a mixture of yarn types in one group of weft yarns.

Reference has been made above to the forked form of the weft insertion needle. The form illustrated in plan and side view Figure 4 has proved effective in trials but clearly other forms may be suitable. The illustrated form is designed to fit a standard weft needle holder. The longer front arm of the fork is placed and shaped to lie generally on the arc of motion of the needle. The outer end of this arm is curved, as shown in the side view, out of the needle plane. This enables the needle to separate warp threads which have not separated properiy during shedding. The curvature also provides clearance between the weft needle and selvedge latch needle. The shorter trailing arm of the fork is angled out backwards from the front arm and is curved slightly in the plane of the needle. It is not shown in the side view.The trailing arm sweeps across the block outlet OL and guides the weft into the root of the fork. The root is shaped so that yarn running in the form to form the inserted loop always leaves at the same point ensuring interaction with the selvedge needle to form a good selvedge.

The arrangements and techniques described above permit the manufacture of fabrics patterned by using weft selection at high speed. Although specifically described for a narrow fabric weaving machine the invention is equally applicable to other looms and also to knitting machines for yarn control and selection. For example in a weftknitting machine a weft carrier or needle can be selectively supplied with yarn by directing the yarn to the carrier or needle by the techniques described above.

As mentioned above the weft selection techniques can be used with a uniform or invarying warp yarn shed or with a selectively arranged shed, for example as described in the above Application "IMPROVEMENTS IN FABRIC MANUFACTURE".

The techniques described provide an advance over those in which several yarns are permanently threaded through a shaped needle by reducing yarn wear.

Claims (13)

1. A weft yarn selector for a plurality of weft yarns to determine which of the plurality of yarns is to be inserted along a weft insertion path as a weft in a fabric, the selector including a fluid pressure jet yarn presentation arrangement for said plurality of yarns to present the yarns at a position clear of said path and fluid pressure jet yarn deflection means to selectively deflect a yarn from the presentation position to a weft supply position in the weft insertion path for take-up by a weft insertion means.

2. A selector according to Claim 1 in which the presentation arrangement includes a fluidpressure feed for each yarn operable to support the yarn in the presentation position.

3. A selector according to Claim 2 in which the fluid pressure flow from said feed emerges with the yarn at a bore exit.

A selector according to Claim 1 or Claim 2 or Claim 3 in which the deflection means is a control fluid pressure jet adjacent to the bore exit and operable to deflect the primary fluid jet and the yarn supported by it at the bore exit.

5. A selector according to any one of the preceding claims in which at least one yarn position is determined by the Coanda fluid flow attachment phenomenon.

6. A selector according to any one of the previous claims for a plurality of yarns including a multiple fluid pressure jet block having for each yarn a main air jet path derived from a common supply path and feeding an individual bore which is also yarn-fed to enable the main jet emerging in operation from the bore exit to support the yarn clear of a weft insertion path, the block also having an individual auxiliary air jet path for each yarn including an individual control element operable to selectively deflect or not deflect a yarn emerging from a respective bore exit into the weft insertion path for take-up by a weft insertion means.

7. A selection according to Claim 6 in which the control elements are electrically operable fluid pressure control valves.

8. A selector according to Claim 6 or Claim 7 in which the weft insertion means has a yarn take-up eye or fork which is not permanently closed.

9. A selector according to Claim 6 or Claim 7 or Claim 8 in which the jet block is of laminate construction, each laminate having through it a connection for the common main jet fluid pressure at supply and an individual connection for the respective auxiliary jet fluid pressure supply while providing a through path for other auxiliary jet supplies.

10. A weft insertion arrangement having a weft selector according to any one of the previous claims and including a single weft carrier having a yarn catcher and movable in a weft yarn insertion path, together with a plurality of weft yarn supply and positioning devices having for each yarn a main yarn-feed air jet operable to hold the yarn in the jet clear of the yarn catcher and an auxiliary air jet yarn positioner operable to deflect the main air jet, and held yarn, into the weft yarn catcher path.

11. An arrangement according to Claim 10 to select from 2 or more weft yarns as a weft pattern at up to 300 weft cycles per minute in a pattern controlled loom.

12. A weft selector substantially as herein described with reference to the accompanying drawings.

13. A weft selector according to any one of the preceding claims in combination with a warp yarn selection arrangement as described or described and claimed in co-pending Application Improvements in Fabric Manufacture, Application number 8003493.