GB2324541A - Textile machines : yarn feed : dyeing - Google Patents

Abstract

In an apparatus for the dynamic dyeing and colour control of yarns being fed to a textile machine, such as a knitting, weaving, sewing or embroidery machine, dyes are sprayed onto the yarn passing a dyeing head from four or more spray nozzles which are preferably piezoelectric spray nozzles. The movement of the yarn along an operative yarn path past the dyeing head is carefully monitored, for example by a rotary encoder, and the amount of dye or colouring agent dispensed by each nozzle is automatically controlled by a central control unit to dye the yam from an infinitely variable colour palette and to create a multi-coloured yarn which when used by the textile machine generates a predetermined pattern in the fabric being created or processed.

Description

TITLE The Dynamic Dyeing and Colour Control of Yarns.

Field of the Invention The invention relates to a dynamic colour dyeing system for dyeing a yarn as it travels from a yarn package to a textile machine, such as a knitting or weaving machine or a sewing or embroidery machine.

Background Art The dynamic dyeing of yarns is the subject of a number of existing patent specifications. GB-A-1482946 discloses a process for dyeing weft yarns prior to the weaving of fabrics. In this process the yarn is saturated with dye prior to the weaving process. US-A-3978695 describes a special dyeing nozzle which ensures clean dyeing with maximum dye take up by the yarn. GB-A-2111091 also uses a saturation technique to dye the yarn on a sewing machine. The invention of GB-A-2111091 consists of a computer controlled attachment for switching between a number of coloured dye pots through which the yarn is passed prior to sewing.

All of the above processes have a limited colour range determined by the number of dyes used, with only one coloured shade and intensity available for any single dye or colouring agent. It is an object of this invention to allow a vastly wider range of different shades and intensities of colour. It is also an object of this invention that the resulting dyed or coloured yarn can be multi-coloured along its length to an extent that when used by the textile machine it generates a predetermined pattern in the fabric being created or processed.

THE INVENTION The invention provides an apparatus for dyeing a yarn as it travels from a yarn package to or within a textile machine, comprising: a dyeing head comprising one or more spray nozzles for spraying one or more dyes or colouring agents onto the yarn as it travels past the dyeing head; means defining an operative yarn path taking the yarn past the dyeing head; a yarn monitoring device for accurately sensing the movement of the yarn along the operative yarn path; and a central control unit responsive to yarn usage at the textile machine and to the output of the yarn monitoring device, for independently controlling the one or more spray nozzles to spray the one or more dyes or colouring agents onto yarn following the operative yarn path in amounts to create a multi-coloured or multi-toned yarn which when used by the textile machine generates a predetermined pattern in the fabric being created or processed.

When the apparatus comprises only one spray nozzle it may be usèd to create continuously variable tone or shade variations on a white yarn travelling from the yarn package to the textile machine. If the original yarn at the yarn package is a self-coloured yarn, then the dye or colouring agent sprayed onto the yarn as it passes the dyeing head can create continuously variable tone or shade variations in the yarn resulting from the colour combination of the original yarn colour plus the colour of the dye or colouring agent.

When the apparatus comprises two or more spray nozzles, the nozzles preferably spray dyes or colouring agents of different colours onto the yarn as it passes the dyeing head. By varying the amounts and combinations of those dyes or colouring agents, a greater variety of colours and colour combinations as well as single tone variations can be created using either white or self-coloured yarn stock on the supply yarn package. Preferably three or more nozzles are used, spraying different primary colours to generate the predetermined pattern.

The term 'pattern' in this context is used to include continuous areas of uniformly coloured yarn, abrupt changes in the colour of the yarn to build up pattern shapes as the yarn is used by the textile machine, and gradual variations in the colour of the yarn being used by the textile machine to create gradually varying zones of colour in the fabric being created or processed.

The textile machine may be any knitting, weaving, sewing or embroidery machine. Common to all is the characteristic that yarn demand by the textile machine is variable. The invention will be further described, by way of example only, with reference to sewing or embroidery machines in which the yarn is formed into stitches in a piece of fabric. In that case the pattern is the coloured lines or areas created by those stitches.

The apparatus may be provided physically between the yarn package and the textile machine, or may be incorporated within the textile machine. In the latter case all that is important is that the yarn is dyed by the apparatus of the invention before it is formed into stitches or loops or otherwise used by the textile machine.

Due to the jerky nature in which embroidery or sewing yarn, for example, is drawn from the bobbin or yarn package during stitching it is an important feature of this invention that the central control unit is capable of instantaneously controlling and updating the amount of any particular dye or colouring agent, to match the rate at which the yarn is passing the dyeing head, and of timing all changes in the dye or colouring agent amount in synchronism with the yarn usage at the textile machine to create the predetermined pattern in the fabric being processed or created.

When the textile machine is a sewing or embroidery machine, the very precise control of application of the dye or colouring agent and the rapid and accurate monitoring of the yarn motion makes it possible to control rapid and crisp colour changes to the yarn so that the colour changes occur at the correct position on the embroidered or sewn design when the yarn reaches the stitching needle.

The one or more nozzles are preferably of the piezoelectric type which pump droplets of fluid when electrically excited. Separate excitation circuits for each of the nozzles are employed. The size and frequency of the droplets is proportional to the excitation voltage and the frequency respectively. Operating the nozzles in this manner enables exact mixing of colours thus providing limitless colour shades. Exact monitoring of the yarn flow allows for very fine control of colour shades regardless of yarn flow rate. Currently piezoelectric spray jets are the best way to get the fine control and rapid response required by this invention. The development of miniature and micro engineering may however in future enable other methods of dispensing rapid, finely controlled sprays in minutely variable quantities.

Any jet stream of small droplets of liquid dispensed from a nozzle naturally acquires an electric charge, and preferably the apparatus further comprises a means for imparting an opposite static charge to the moving yarn passing the dyeing head, so that droplets of dye or colouring agents are naturally attracted to the yarn to ensure better all-round dye absorption.

The dye or colouring agent for each nozzle in the dyeing head is preferably supplied from remote reservoirs which may be at atmospheric or super-atmospheric supply pressure. The dye or colouring agent may alternatively be supplieEby a local cartridge containing the liquids to be dispensed.

When more than one nuzzle is used, the array of nozzles in the dyeing head may all be in the same plane or may be spread over a short axial zone. Naturally, all the nozzles in the dyeing head should be facing the yarn. The dyeing head containing the nozzles must also be kept unclogged and clean. The invention therefore further comprises means 'for cleaning the nozzles of the dyeing head. If desired the dyeing head may be moved to a cleaning and parking bay while such cleaning takes place.

To facilitate threading-up, the apparatus preferably comprises means for defining alternassivex yarn paths through the apparatus, namely on straight-through yarn path which by-passes the dyeing head and a diverted yarn path which is the operative yarn path. The straight-through yarn path is used fqr threading-up, and the yarn is moved automatically to its diverted yarn path for dyeing.

The dyeing head preferably comprises four or more nozzles. When four nozzles are used, each of the four would dispense one primary colour, so that the set in total would preferably dispense cyan magenta, yellow and black.

Using the apparatus of the invention, precisely controlled amounts and ratios of differently coloured dyes or colouring agents may simultaneously be applied to the yarn to obtain a repeatable and infinitely variable colour palette from the four nozzles each of which sprays a primary coloured dye or colouring agent. Additional spray nozzles may be provided for spraying non-standard colours other than the four printing primaries. A further set of nozzles could if desired dispense one or more fluids other than dye or colouring agent, such as a wetting agent or a setting agent for the dispensed dyes or colouring agents.

Depending on the type of dyes or colouring agents they may require setting or fixing. This may require general heating, steam, or intense light of a particular wavelength, any of which could be supplied by a laser.

The invention therefore further comprises a dye setting chamber, in the operative yarn path downstream of the dyeing head, and means for setting or fixing the dye or colouring agent on the yarn as the yarn passes through that setting chamber.

Colour transitions in the yarn passing through the mechanism are achieved without the need for cutting the yarn, re-y,arning or changing the needle. Simply by changing the proportions of dyes delivered to the yarn we now effect a colour change, all under computer control. As the colour change point is extremely local, it is easy for the computer control system to compensate for the length of yarn between the dyeing head and the needle.

The novel technical effect provided by the invention consists of the fact that, unlike previous related systems, the colour palette is not limited to a small number of discrete colours each representing saturation of the yarn by a single dyestuff. The invention provides a method of overcoming the associated technical difficulties. The invention uses one or more spray nozzles each supplied with one of a number of primary coloured dyes or colouring agents and each capable of varying the amount of dye or colouring agent applied to the yarn in order to obtain an infinitely variable colour palette. This method of dyeing dynamically an erratically moving yarn has not previously been contemplated due to the difficulty of controlling and calibrating the mixture of the primary coloured dyes. This difficulty is compounded by the fact that in order to obtain a given shade and intensity of colour the rate at which any particular dye mix is applied must vary in proportion to the speed of the passing yarn. The nature of sewing and embroidery is such that yarn line speed is continuously varying and therefore very rapid and accurate yarn speed measurements must be taken and processed. This invention incorporates a method for continuously measuring the yarn line speed and adjusting the application of dye accordingly.

There are many technical aspects to this invention which need to be mastered for the invention to function successfully. These include: Using ink jets on a filament - Current ink jet technology is based around printing on flat sheets in a single plane. Dyeing filaments requires the dye to cover the yarn on all sides (3600) and this invention may therefore incorporate some special treatment eg. multiple jets, dye polarization, or the use of currents of air or a static electric field to direct the dye droplets.

Setting the dye - The yarn is stitched fractions of a second after the dye application and consequently running and smearing of dye is likely to be a problem unless tackled as described above.

Calibrating a good dye mix - A huge range of colours is possible by mixing different combinations of four primary coloured dyes. Knowing which mixtures create which colours and ensuring consistent colour shades is very important.

Predicting stitch lengths - Because the dye is not applied at the point the yarn is stitched, the dyeing unit must begin dyeing the yarn a new colour whilst the previous colour is still being stitched or otherwise incorporated into the fabric. In order that the colour change occurs at the precise point required, the invention calculates the length of each stitch to come and begins the new dye colour in advance of stitching it.

Accounting for stitch speed - The speed at which yarn is metered out varies with different stitch lengths and with stopping and starting. When the yarn is passing through the dyeing unit slowly, a lesser rate of application of dye is needed than at higher speeds. Consequently the instantaneous yarn speed must be measured accurately and the quantity of dye applied controlled accordingly. The yarn monitoring device incorporated into the apparatus of the invention must therefore be capable of very rapid and accurate responses to yarn movement and must not in itself impede or otherwise affect that yarn movement. Rotary encoders are available which achieve that high standard of accuracy.

The very rapid, high accuracy measurement and metering technology used in this invention is new to the area of sewing, embroidery, knitting and weaving.

Claims (8)

1. An apparatus for dyeing a yarn as it travels from a yarn package to or within a textile machine, comprising: a dyeing head comprising one or more spray nozzles for spraying one or more dyes or colouring agents onto the yarn as it travels past the dyeing head; means defining an operative yarn path past the dyeing head; a yarn monitoring device for accurately'sensing the movement of the yarn along at least the operative yarn path; and a central control unit responsive to yarn usage at the textile machine and to the output of the yarn monitoring device, for independently controlling the one or more spray nozzles to spray the one or more dyes or colouring agents onto the yarn in amounts to create a multi-coloured yarn which when used by the textile machine generates a predetermined pattern in the fabric being created or processed.

2. An apparatus according to claim 1, wherein the dyeing head comprises an array of four spray nozzles each spraying a different coloured dye or colouring agent selected from the printing primary colours of cyan, magenta, yellow and black.

3. An apparatus according to claim 2, wherein the dyeing head includes one or more further spray nozzles to dispense one or more non-standard coloured dye or colouring agent other than the four printing primaries.

4. An apparatus according to claim 2 or claim 3, wherein the dyeing head includes one or more further spray nozzles to dispense one or more wetting agent or setting agent for the dyes or colour agents.

5. An apparatus according to any preceding claim, wherein the spray nozzles are piezoelectric spray nozzles,.

6. An apparatus according to any preceding claim, further comprising a dye setting chamber, in the operative yarn path downstream of the dyeing head, and means for setting or fixing the dye or colouring agent on the yarn as the yarn passes through that setting chamber.

7. An apparatus according to any preceding claim, further comprising means for establishing a static electrical charge on the yarn passing the dyeing head to attract droplets of dye or colouring agent from the spray nozzles of the dyeing head onto the yarn.

8. An apparatus according to any preceding claim, wherein the textile machine is a sewing or embroidery machine, and the central control unit is programmed to predict the number of stitches that will be formed from the yarn extending from the dyeing head to the needle of the machine, to enable colour changes in the dyed yarn to be accurately located on the sewn or embroidered fabric created by the textile machine.

1 0. An apparatus according to claim 1, substantially as described herein.

8. An apparatus according to any preceding claim, wherein the yarn monitoring device is a rotary encoder.