Method of and apparatus for dyeing yarn

Abstract

 A method of continuously dyeing a moving yarn is characterized by applying at least one dye liquid to the yarn in a series of discrete quanta of variable volume and at variable frequency. Apparatus for performing the method includes dye-apptying means (2,3,4 or 11, 12, 13) and means - (8,9,10) for varying the volume and rate of application of the quanta of dye liquid.

Description

[0001] The subject of this invention is a method of and apparatus for dyeing yarn and particularly for the continuous dyeing of yam.

[0002] The method of dyeing yam usually performed heretofore has been a batch dyeing method, i.e. a package containing a considerable length of yam is immersed in a vat containing a mixture of dyes in proportions to give the required dye shade to the yam on the package. The batch process presents several important difficulties and drawbacks. For example a considerable time is usually required for the dye liquid to penetrate to the innermost layers of the yam on the package and further time is required for the dyeing reaction to be completed. As dye pigment is continually removed from the dye liquid on its passage through the yam _package the dye liquid becomes progressively weaker, i.e. it contains a continually diminishing proportion of dyestuff to liquid as it moves to the interior of the package so that the shade changes. In addition some of the dyestuffs making up the mixture have a greater affinity for the yam material than others so the proportions of the pigments to one another change and thus the colour changes as well as the shade.

[0003] Another trouble is that often the yam shrinks on the package and this causes the inner layers to be compressed giving rise to difficulties in unwinding the package as well as hindering dye penetration.

[0004] The wet packages must be dried thoroughly and this requires a considerable amount of time and space.

[0005] Also when fresh batches of undyed yam are to be dyed a different colour all the handling equipment and the vats must be thoroughly cleaned so that no vestige of the original dye remains. This operation is time consuming and labour intensive.

[0006] It is also difficult to ensure that successive batches of the dye mixture provide exactly the same colour. If any mismatch occurs which may not be seen until the dyed packages are dried the whole length of yam on the package is the wrong colour.

[0007] There is also normally left an effluent containing unused and expensive dyestuff which presents costly pollution problems. Apart from the difficulties of performing the process the apparatus required is bulky and expensive.

[0008] To eliminate the difficulties associated with batch dyeing attempts have been made to dye yam continuously, i.e. a single strand of undyed yam is moved continuously forward and as the yam passses a particular position a dye mixture is applied to it. All the known continuous processes require the premixing of the dye constituents in a reservoir of dye liquid or a stream of dye liquid through which the yarn is passed. Examples of such known devices are disclosed in the following patent specifications US 2 310 764, US 3 620 662 and GB 2 111 091. A continuous yam dyeing process of a somewhat different type is described in patent specification EP 0 079 213. Some of the known devices make provision for changing the colour of the yarn by providing several reservoirs containing different dyes or streams of different coloured dyes, the yam being transferred from one reservoir or one dye stream to another when the colour is to be changed.

[0009] All the known processes and apparatus are complicated or time consuming in one way or another. For example these processes employing several reservoirs or several streams of dye liquid require more or less complicated apparatus for transferring the yam from one reservoir or stream to another. Combining of several dye mixes to provide accurate colours is time consuming and requiires a great deal of skill and care. They are also wasteful of dye liquid in that an excess of dye liquid is applied to the yam.

[0010] It is an object of the present invention to provide a method of and apparatus for continuous yam dyeing which eliminates complicated mechanical devices and the need for separately mixing dyes and filling separate reservoirs with dye mixtures while still making it possible to control with great accuracy the shade and colour of dye being applied to a continuously moving yam and to change the shade and/or colour instantly.

[0011] According to the invention a method of continuously dyeing a yam by applying a dye liquid to the yam while the yarn is in motion is characterized by applying at least one dye liquid to the yam in a series of discrete quanta, the volume of each quantum and the number of quanta applied per unit length of the yam being predetermined to provide a dyed yarn of the desired visual appearance.

[0012] Where it is desired to dye a yam a nonprimary colour several different dye liquids may be applied simultaneously in discrete quanta against the moving yam, the volume of each quantum of each dye liquid and the number of quanta of each dye liquid applied per unit length of the yam being predetermined to provide that the dyed yam is of the desired colour and shade.

[0013] For certain purposes one of the dye liquids may be a diluent such as water.

[0014] The colour and shade of the dyed yam may be automatically controlled by passing the dyed yam through a colour analyser, e.g. a spectrophotometer, which can detect variations in the spectrum of the colour of the dyed yam from that desired, the analyser being operative on occurrence of any undesired change in the spectrum to detect the change and send a correcting signal arranged to initiate a change in the volume of each quantum and/or the number of quanta applied per unit length of one or more of the dye liquids being applied whereby to restore the desired spectrum.

[0015] The quanta of dye liquids may be brought together on the yam itself or may be brought together in a continuous mixing operation at the yam.

[0016] Apparatus for performing the method comprises yam feed means for feeding yam to be dyed forwardly, means for holding the dye liquid to be applied to the yam and means for applying dye liquid to the yarn and is characterized in that the means for applying the dye liquid to the yarn incorporates means arranged to feed the dye liquid to the yarn in individual quanta and means is provided for varying the volume of each quantum and for varying the rate at which the quanta are applied to the yam.

[0017] Means operatively linked to the yarn feed means may be arranged to control the volume of each quantum of dye liquid applied to the yarn and/or the time interval between which successive quanta are applied to the yam in accordance with the rate at which the yarn is being fed forwardly by the yam feed means.

[0018] The dye applying means may incorporate valve means controlled by individual pulses of a pulsed signal the frequency of the pulses of which is controllable.

[0019] Where several dye liquids are to be applied simulta- neousty to the yam several dye applying devices may be arranged angularly spaced from one another around the yam, each dye applying device having its own control means capable of controlling the volume of each quantum of dye liquid and the frequency with which the quanta are applied.

[0020] Each dye applying means may incorporate a pump arranged to feed dye liquid in pulses to a dye-applying device. One type of pump which is suitable is a pump of the type known as a peristaltic pump in which a flexible tube is stroked successively by pressure devices each of which in succession comes against the tube, flattens it, moves some distance forward and then releases the tube so that quanta of liquid in the tube are trapped and propelled forwardly in pulses. Another type of pump suitable for performing the method is a pump of the Le Blanc type which incorporates a bladed wheel working within a casing which has a tangential opening, liquid being fed from the interior of the wheel to the blades and on rotation of the wheel the liquid is expelled by centrifugal action into the tangential discharge passage in a series of quanta. Pumps of the types described may be connected to synchronous electric motors fed from sources of controllable frequency.

[0021] Alternatively pumps of the diaphragm type may be used, the diaphragms being connected to vibrator type mechanism arranged to be fed from sources of pulsed electric current.

[0022] Where a spectrophotometer is used to monitor the colour of the dyed yam light sensitive devices may be so arranged that each receives the light from a part of the spectrum particular to that light sensitive device and provides a control signal which is in accordance with the intensity of the light from the particular part of the spectrum and which is applied to the corresponding dye liquid applying device to vary the volume of each quantum and/or the frequency of delivery of successive quanta of dye liquid to the yam in accordance with said control signal.

[0023] Practical embodiments of the invention are illustrated in the accompanying diagrammatic drawings in which Fig. 1 illustrates apparatus in its most basic form, Fig. 2 indicates an apparatus employing pumps each of which is connected to an individual synchronous motor and Fig. 3 shows an apparatus providing automatic colour control by means of a spectrophotometer.

[0024] In the drawings and referring first to Fig. 1, 1 denotes a yam to be dyed, 2, 3 and 4 denote dye liquid projecting devices arranged to project dye liquid in discrete quanta against the yam 1, the dye liquid projecting devices being connected to dye supply tanks 5, 6 and 7 respectrvely. The dye projecting devices are connected to variable frequency sources 8, 9 and 10 respectively. Referring now to Fig. 2 the dye liquid projecting devices incorporate pumps 11, 12 and 13 discharging into a chamber 14 through which the yam 1 is arranged to pass, the dyes being mixed at the same instant as they are brought into contact with the yam 1. The pumps ₁1, ₁2 and 13 are connected to synchronous motors arranged to be controlled by the variable frequency sources 8, 9 and 10. In Fig. 3, a spectrophotometer provides a spectrum 16 of the colour of the yam 1 after it is dyed. Light sensitive devices 17, 18 and 19 are arranged to detect the respective light values of different portions of the spectrum 16 and to issue corresponding control signals which are fed to the variable frequency sources 8, 9 and 10 as frequency control signals. In Figs. 2 and 3, 20 denotes means for feeding forwardly the yam 1.

[0025] In practice, the dye liquid either as a single dye or several dyes is applied as a series of quanta to the yam, the volume of each quantum and the rate at which the quanta are applied being adjusted to provide a quantity of dye on the yam such as to provide the required shade and colour. Changes may be made instantly to the colour by adjustment of the quantum volume or quantum frequency of any or all of the dyes applied. Any undesired change in the shade or colour of the yam immediately causes a change in the spectrum 16. This causes an immediate response in the appropriate light sensitive device 17 and/or 18 and/or 19 so that a control signal is issued to the appropriate variable frequency source or sources 9. and/or 10 and/or 11 to cause a change in the quantum volume and/or the frequency with which dye liquid is applied to the yam by the pump 11 and/or 12 and/or 13 until the spectrum 16 returns to that desired indicating that the colour and shade required .have been restored.

[0026] The apparatus and method have the advantage that no excess dye is used. The frequency of quantum deposition may be such that each quantum overlaps the previous quantum deposited or follows immediately on the previous quantum or a gap is left between successive quanta, the gap being small enough to allow dye penetration along the yam to fill the gap. Mottled effects may be achieved by arranging the quanta frequency such that an appreciable gap is left between successive quanta where no dye is deposited on the yam.

[0027] The portion of the device actually discharging dye liquid to the yam may be arranged to contain a minimum quantity of dye liquid so that changes of colour may be effected by switching the dispensing device or devices to different supply tanks containing different dye liquids. Changes to different colours containing the same constituent dyes but mixed in different proportions may be effected immediately by altering the settings of the apparatus controlling the volume of each quantum of dye liquid and the rate at which the quanta are applied to the yam.

[0028] Where totally different colours are to appear succes- sivety on the same yam several groups of dye dispensing devices may be provided, each group being made operative when the particular colour provided by that group is to be applied.

[0029] The present method may be applied to the performance of the method of dyeing which is the subject of the prior patent application EP 0 079 213.

Claims

₁. A method of continuously dyeing a yarn by applying a dye liquid to the yam while the yam is in motion characterized by applying at least one dye liquid to the yam in a series of discrete quanta, the volume of each quantum and the number of quanta applied per unit length of the yarn being predetermined to provide a dyed yarn of the desired visual appearance.

2. A method of continuously dyeing a yam according to claim 1 characterized by applying several different dye liquids simultaneously in discrete quanta against the moving yarn, the volume of each quantum of each dye liquid and the number of quanta of each dye liquid applied per unit length of the yam being predetermined to provide that the dyed yam is of the desired colour and shade.

3. A method of continuously dyeing a yam according to claim 1 characterized by obtaining the spectrum of the colour of the dyed yam and on occurrence of any undesired change in the spectrum of the colour of the dyed yarn from the spectrum of the desired colour changing the volume of each quantum and/or the number of quanta applied per unit length of one or more of the dye liquids whereby to restore the desired spectrum.

4. Apparatus for continuously dyeing a yarn including yam feed means (20) for feeding forwardly yam to be dyed, means (5,6,7) for holding the dye liquid to be applied to the yam and means for applying dye liquid to the yam characterized in that the means for applying the dye liquid to the yarn incorporates means (2,3,4 or 11,12,13) arranged to feed the dye liquid to the yarn in individual quanta and means (8,9,10) is provided for varying the volume of each quantum and for varying the rate at which the quanta are applied to the yam.

5. Apparatus for continuously dyeing yam according to claim 4 characterized by incorporating means (8,9,10) operatively linked to the yam feed means (20) to control the volume of each quantum of dye liquid applied to the yam and/or the time interval between which successive quanta are applied to the yarn in accordance with the rate at which the yarn is being fed forwardly by the yam feed means - (20).

6. Apparatus for continuously dyeing yarn according to claim 4 characterized in that the dye applying means - (2,3,4) incorporates valve means controlled by individual pulses of a pulsed signal the frequency of the pulses of which is controllable.

7. Apparatus for continuously dyeing yam according to claim 4 characterized in that each dye applying means incorporates a pump (11,12,13) arranged to feed dye liquid in pulses to a dye-applying device (2,3,4 or 14).

8. Apparatus for continuously dyeing a yam according to claim 4 characterized by incorporating a spectrophotometer (15) arranged to monitor the colour of the dye yam and thereupon form a spectrum (16) of the colour of the yam and light sensitive devices (17,18,19) so arranged that each light sensitive device receives the light from a part of the spectrum particular to that light sensitive device and thereupon provides a control signal in accordance with the intensity of that particular part of the spectrum and to apply said control signal to a corresponding dye liquid applying device which includes means (8 or 9 or 10) operative under the control of the control signal to vary the volume of each quantum and/or the frequency of delivery of successive quanta of dye liquid to the yam in accordance with the control signal from the particular part of the spectrum.

Drawing