Patent Publication Number: US-7914590-B2

Title: Apparatus and method for carrying out optical readings on textile materials submitted to dyeing

Description:
The present invention relates to an apparatus and a method for carrying out optical readings on textile materials submitted to dyeing. 
     More particularly, the apparatus and method of the present invention relate to the control of depletion, that is to say of the absorption, of single colouring agents in a dyeing bath. 
     Optical systems and processes based on transmittance spectrophotometry are well-known in this field. By means of these systems, the concentrations of the single colouring agents present in the solution, that is to say in the dyeing bath, are measured by emitting a light beam having known properties through the solution. Part of the emitted light is absorbed by the substances present in the fluid, whereas the remaining part is transmitted to the spectrophotometer which detects its amount and its properties. This information is used to determine the residual quantities of the single colouring agents present in the solution according to the well-known Beer-Lambert law. 
     It is also known that, whatever the specific algorithm used to process the above information, the exact determination of the residual quantities of the single colouring agents present in a dying bath is still an unsolved problem from a practical viewpoint, considering the innumerable chemical and dyeing types of the various colouring agents used in textile industry. 
     The use of known optical systems for transmittance readings leads to practical difficulties in determining the concentration of the single colouring agents present in a dyeing bath with sufficient exactness, especially when concentrations are very small or higher than a given value. In practice, the known optical systems are ineffective in the control of solutions containing colouring agents whose concentrations are external to a given range. In other words, the optical control systems currently available on the market are basically unusable for practical purposes when the concentrations concerned assume values which are not within a given range, that is to say when solutions are too diluted or too concentrated. 
     Further inconveniences caused by the use of known optical systems are due to the remarkable lack of precision in the results obtained by carrying out readings on solutions containing heterogeneous colouring agents, that is of different chemical classes. Inconveniences also derive from a substantial inability of these known systems in distinguishing two different colours of the same kind (two reds, two yellows or two blues present in the same solution). 
     Other inconveniences are caused by the state changes, that is by the colour changes of the single colouring agents when the pH, the salinity or the temperature of the solution vary, as normally happens during the dyeing cycle: in fact, in this case the transmittance optical control does not guarantee correct and homogeneous readings, since chromatic changes may occur or the dyeing bath may become torpid. 
     Moreover, the control carried out on dispersions and on opalescent baths are very difficult as the light transmission through the liquid is altered, because part of the light is deviated by the dispersed particles within the liquid. This leads to erroneous evaluations, that is, the spectrophotometer evaluations can be wrong. 
     Examples of apparatuses for carrying out controls by transmittance readings on dyeing baths are described in EP325529, FR2399066, FR2307074, FR2443524, GB2050002, JP1006164, W099/66117, JP5098557 and JP61105432. 
     The main object of the present invention is to eliminate or at least drastically reduce said drawbacks. 
     According to the present invention, these results have been achieved thanks to the apparatus and the method having the features described in the independent claims. Further features of the present invention are the subject of the dependent claims. 
     Thanks to the present invention, it is possible to carry out a depletion test of the single colours (red, yellow, blue) in a dyeing bath whatever the class or nature of the colouring agents used, even in case of very low or of high concentrations, and even in case of opalescent baths or in the presence of dispersed particles. In particular, thanks to the present invention, it is possible to use the detections carried out by two different devices for testing the absorption of single colours with different modalities, in order to basically eliminate the possibility of reading mistakes; in particular, depending on the bath temperature, it is possible to use the most suitable device for carrying out a detection as properly and as much precisely as possible. Moreover, the present apparatus and method allow said testing directly on the material of the specimen or sample or “witness” immersed in the dyeing bath, So that the results obtained with the test take into account the specific nature of the material submitted to dyeing. A further advantage is the possibility of carrying out repetitive readings with sufficiently high frequency so that they can be considered as “dynamic readings”, or, in other words, continuous readings. Moreover, an apparatus according to the present invention is easy to be made, economical and reliable, even after long operating periods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other advantages and characteristics of the invention will be best understood by anyone skilled in the art from a reading of the following description in conjunction with the attached drawings given as a practical exemplification of the invention, but not to be considered in a limitative sense, wherein: 
         FIG. 1  shows a simplified scheme illustrating the application of a device ( 1 ) used in an apparatus according to the present invention; 
         FIG. 2  shows a schematic plan view of the support for the specimen or samples of the textile materials submitted to dyeing; 
         FIG. 3  shows a schematic plan view of the support of  FIG. 2 , on which a specimen or sample of textile material is placed; 
         FIG. 4  shows a schematic longitudinal section view of a device according to the invention; 
         FIG. 5  shows a top plan view of the specimen chamber of the device shown in  FIG. 4 , with the support of  FIG. 3  inserted in it; 
         FIG. 6  shows a top plan view of the device shown in  FIG. 4 ; 
         FIGS. 7-10  show a sequence of operating steps related with the use of the device shown in  FIG. 4 ; 
         FIG. 11  is an enlarged detail of the device shown in  FIG. 4 ; 
         FIG. 12  is a further enlarged detail of the device shown in  FIG. 4 ; 
         FIG. 13  shows an enlarged detail of  FIG. 9 ; 
         FIG. 14  shows an enlarged detail of  FIG. 10 , in this figure the upper base ( 13 ) being not shown to better illustrate the arrangement of the elements inside chamber ( 10 ); 
         FIG. 15  schematically shows a possible embodiment of an apparatus according to the present invention; 
         FIGS. 16-19  are similar to  FIGS. 11-14  but they refer to a further possible embodiment of device ( 1 ). 
     
    
    
     An apparatus according to the present invention can be used to carry out optical readings on textile materials to be dyed and it comprises optical detecting means connected to corresponding processing means. The optical detecting means comprise two devices: a first device ( 1 ) by means of which it is possible to carry out a reflectance detection and a second device ( 101 ) by means of which it is possible to carry out a transmittance detection, connected to processing means ( 20 ), the latter being shown in  FIGS. 1 and 15  by a schematic block which represents a two-channel spectrometer. 
     In practice, the first and the second device ( 1 ,  101 ) provide output signals related to detections respectively executed by reflectance and by transmittance, and corresponding optic cables connections ( 23 ,  230 ) are used to convey said signals to said processing means. ( 20 ). 
     The transmittance reading device ( 101 ) is per se known, so it will not be described in detail. As already mentioned in the preamble of the present description, the device ( 101 ) emits a luminous radiation towards the fluid to be tested: part of the light is absorbed by the substances present in the fluid, whereas the remaining part is transmitted to the spectrometer/spectrophotometer ( 20 ) which detects its amount and properties. In a conventional manner, the device ( 101 ) comprises a reading chamber within which the liquid to be tested flows and an optical sensor associated with a lighter apt to emit a luminous radiation. Optical readings are carried out by device ( 101 ) by transmittance and concern the fluid flowing in its reading chamber. 
     With reference to  FIG. 15 , said device ( 101 ) is connected to a duct (C 3 ) in which the dyeing bath to be tested flows, by means of corresponding input ( 102 ) and output ( 103 ) ducts. In particular, as shown in  FIG. 15 , said device ( 101 ) acts on a secondary circuit which is connected to said duct (C 3 ) and is provided with a heat exchanger ( 105 ) keeping the liquid at a predetermined temperature and with a pump ( 104 ) allowing the circulation of the liquid within the secondary circuit. The liquid to be tested enters the heat exchanger ( 105 ) and the device ( 101 ) trough the duct ( 102 ) which is connected to duct (C 3 ). The liquid exiting the device ( 101 ) is conveyed to said duct (C 3 ) by means of the duct ( 103 ). As further described below, said duct (C 3 ) is connected, on one end, to a dyeing tank or dyeing machine (T) inside which there is the liquid, i.e. the dyeing bath, to be tested and, on the other end, the duct (C 3 ) is connected to a pump (P) allowing re-circulation of the liquid within a main circuit (C 1 , C 2 , C 3 ). 
     The detections carried out by device ( 101 ) originate signals which are transmitted to processing means ( 20 ) by means of an optical cable. ( 230 ). 
     In order to determine the residual amounts of the single colouring agents present in the tested solution, the processing means ( 20 ) can use the information coming from transmittance processing means ( 101 ) as an alternative to the information obtained from reflectance detecting means ( 1 ), as further described below. 
     Through experimental tests, the applicant verified that up to a given temperature, approximately 80° C., the transmittance detection provides reliable readings. Beyond this value, instead, transmittance detection means cannot be considered as reliable, due to a tonality variation on the dispersed colouring agents. Moreover, through experimental tests the applicant verified that said tonality variation does not occur on the textile material submitted to dyeing. 
     Then, the applicant got the idea of combining two different methods of analysis in a same apparatus and invented the apparatus according to the present invention, which is capable of acting both on the dyeing bath (by means of the transmittance detecting device) and on a dyeing specimen or sample of the textile material submitted to dyeing (by means of the reflectance detecting device). 
     In practice, up to a given temperature value (for example 80° C.) the apparatus according to the present invention uses device ( 101 ) which acts on the dyeing bath by transmittance; beyond said value, that is to say whenever said temperature value is reached and the tonality variation of the colouring agents dispersed in the dyeing bath takes place, the apparatus uses device ( 1 ) which acts on the fabric sample that, on the contrary, is not subjected to the tonality variation of the colouring agents. The results provided by the present apparatus during experimental tests are considered reliable for each temperature value normally reached in a textile dyeing process, the optical readings thus carried out being reliable over the whole temperature range, that is below 80° C. as well as at higher temperatures. 
       FIGS. 1 and 15  show a temperature sensor designed by (ST) which is capable of providing a corresponding signal relative to the temperature of the dyeing bath. The detections of sensor (ST) are used to determine which of the two optical detecting devices ( 1 ) or ( 101 ) is to be used, i.e. which of the optical readings executed by devices ( 1 ) and ( 101 ) is to be accepted. In particular, device ( 101 ) will be used for dyeing bath temperatures below a given threshold value (preferably 80° C.) whereas device ( 1 ) will be used for higher dyeing bath temperatures. 
     As more clearly shown in  FIGS. 1-14 , device ( 1 ) advantageously comprises a chamber ( 10 ), delimited by a fixed lower base ( 11 ) having corresponding fixed side walls ( 12 ), and by a mobile upper base ( 13 ). An input section (I) and an output section (U) associated with corresponding pipe unions ( 14 ,  15 ) are provided on two opposite side walls of fixed base ( 11 ). 
     Said fixed base ( 11 ) features a central opening in which an optical detector or probe ( 2 ), which is connected to spectrophotometer or colorimeter ( 20 ), is inserted. 
     Probe ( 2 ) can consist of any optical detector or sensor available on the market which can be connected to a spectrophotometer or colorimeter. 
     Four fixed columns ( 16 ) are mounted on the internal bottom of said fixed base ( 11 ) and a fixed conical tip ( 17 ) is mounted on each of said columns. A bushing ( 18 ) is provided each column ( 16 ) between the bottom of fixed base ( 11 ) and the corresponding tip ( 17 ). The bushing is provided with an annular projection or ring whose lower side ( 18 L) is mounted on the upper base of a spring ( 19 ). The lower base of said spring ( 19 ) is placed on the internal bottom of fixed base ( 11 ). 
     Said columns ( 16 ) are orthogonally oriented towards the bottom of fixed base ( 11 ) which is preferably in a horizontal position when the device is used. As a consequence, bushings ( 18 ) are orthogonal to the bottom of base ( 11 ). 
     Due to the presence of springs ( 19 ), each bushing ( 18 ) can be pushed down towards base ( 11 ) and, once exhausted the thrust which overcomes the resistance of the respective spring ( 19 ), it can return to its lifted starting position. This allows a correct circulation of the dyeing bath inside chamber ( 10 ) and a consequent more uniform dyeing of the specimen or sample as mentioned below. 
     Moreover, device ( 1 ) comprises a support element for a specimen or sample of the textile material submitted to dyeing. 
     According to the example shown in the accompanying drawings, said support element comprises a plate ( 3 ) provided with a circular central window ( 30 ) and also provided with four passing holes ( 31 ) which are disposed according to the vertices of a quadrangle. With reference to the example shown in  FIGS. 2 and 3 , said holes ( 31 ) are provided on four corresponding appendixes ( 32 ) of plate ( 3 ). 
     Said holes ( 31 ) allow the positioning of plate ( 3 ) on upper sides ( 18 U) of the rings provided on the external surface of said bushings ( 18 ). 
     In practice, said bushings ( 18 ) constitute elastic positioning and support elements for plate ( 3 ) and allow its guided lowering towards the internal bottom of fixed base ( 11 ) and respectively its guided lifting. 
     The shape of said plate ( 3 ) allows a specimen or sample of the textile material submitted to dyeing to be applied on the plate itself. For example, as illustrated in  FIG. 3 , the specimen or sample or “witness” can consist of a given amount of threads (F) wound on plate ( 3 ) so as to cover its central window ( 30 ). The specimen can also have a different shape, i.e. it may not be in the form of threads; for example, the specimen can consist of fabric. In any case, the specimen is made of the same material submitted to dyeing and it is applied on support plate ( 3 ) so as to be adjacent to window ( 30 ). 
     The upper edge of walls ( 12 ) which laterally delimit said chamber ( 10 ) provide a seat for an annular gasket (G). 
     Upper base ( 13 ) of chamber ( 10 ) features a central opening which allows the stem ( 40 ) of an actuator ( 4 ), whose axis is oriented perpendicularly to base ( 13 ) itself, to pass through it. A pad ( 41 ) is fixed on the free end, that is to say on the lower end of said stem ( 40 ); said pad features a circular and central projecting portion ( 42 ). The diameter of said portion ( 42 ) is inferior to the diameter of the central opening ( 30 ) featured by said plate ( 3 ). 
     The skirt of said actuator ( 4 ) is fixed on the upper side of upper base ( 13 ) by means of a bracket (which is not shown in the drawings). 
     Moreover, the lower side of said upper base ( 13 ) features four cavities ( 130 ), each cavity having the shape and size corresponding to those of the upper ends of said tips ( 17 ). 
     Said upper base ( 13 ) features a series of passing holes ( 131 ) for screw means (not shown) which allow its connection to fixed base ( 11 ), being said base provided with corresponding holes ( 110 ). In this way, it is possible to obtain a hermetic closing of said chamber ( 10 ) which, however, features input (I) and output (U) sections for the dyeing bath. 
     The simplified scheme of  FIG. 1  shows:
         a first duct (C 1 ) which, on one side, is connected to a dyeing tank or dyeing machine (T) and, on the other side, to the exit ( 14 ) of device ( 1 );   a second duct (C 2 ) which, on one side, is connected to exit ( 15 ) of device ( 1 ) and, on the other side, to the entry of a pump (P) which re-conveys the bath into tank or machine (T) by means of a third duct (C 3 ).       

     A pH detecting probe (SP) is inserted on the second duct (C 2 ) whereas the bath temperature is detected by a thermometer associated with tank or machine (T). 
     The same scheme shows the above optical probe ( 2 ) which is connected to a lighter ( 21 ) and to the spectrophotometer or colorimeter ( 20 ) by means of corresponding optical fibres, i.e. optical cables, ( 22 ,  23 ). 
     The tank or dyeing machine (T) as well as probes (ST) and (SP), pump (P), probe ( 2 ) and lighter ( 21 ), spectrophotometer or colorimeter ( 20 ) and optical fibres ( 22 ,  23 ) are per se known. 
     The device ( 1 ) works as follows. 
     A specimen or sample of the material submitted to dyeing in the tank or machine is positioned on plate ( 3 ). For example, as shown in  FIG. 3 , it is possible to use a given amount of yarn (of the same material as that present in tank or machine “T”) wound on plate ( 3 ) so as to cover the window ( 30 ), being intended that the textile material present in the dyeing tank or machine (T) can be in any other form, i.e. not only in the yarn form. Then, the upper base ( 13 ) of the device being detached from lower base ( 11 ), plate ( 3 ) is positioned on the elastic support constituted by bushings ( 18 ) fitted on columns ( 16 ), the extensions ( 32 ) of plate ( 3 ) resting on upper side ( 18 U) of said annular projections as shown in  FIGS. 7 ,  8  and  13 ; in this way, plate ( 3 ) is positioned on an elastic support and window ( 30 ) of plate ( 3 ) faces the probe ( 2 ) and is covered by thread (F), that is to say by the material the specimen is made of. Upper base ( 13 ) is subsequently fixed to lower base ( 11 ) as illustrated in  FIG. 9 . In this way, the chamber ( 10 ) is hermetically closed both superiorly and inferiorly and the bath drawn out of tank or machine (T) can flow inside it. The step of positioning upper base ( 13 ) on lower base ( 11 ) is facilitated by the presence of said tips ( 17 ) which act as guide elements as their shape corresponds to that of cavities ( 130 ) provided on the upper base. The dyeing bath flowing inside chamber ( 10 ) moves relative to the specimen of material (F) on plate ( 3 ) which is thus submitted to dyeing just like the textile material present in the dyeing tank or dyeing machine (T). After closing the device, that is after fixing upper base ( 13 ) to lower base ( 11 ), the device can be operatively used: at given time intervals, actuator ( 4 ) is operated so as to obtain the lowering of pad ( 41 ) to bring the specimen of material (F) into contact with probe ( 2 ) as illustrated in  FIG. 10  and in  FIG. 14 . As shown in detail in  FIG. 14 , the wet material (F) is brought into contact with the optical reading probe ( 2 ) that emits an optical signal to spectrophotometer or colorimeter ( 20 ) which processes it. The presence of projection ( 42 ) on the lower side of pad ( 41 ) allows the perfect pushing of the specimen material on probe ( 2 ) without tearing it. At the end of each reading, the stem of actuator ( 4 ) is retracted, so as to eliminate the thrust on plate ( 3 ) which consequently rises and returns back to the lifted starting position, as said plate rests on the elastic support constituted by bushings ( 18 ) and springs ( 19 ). In this way, the specimen returns to an ideal position for a correct and uniform dyeing. The optical reading is cyclically repeated as long as the material submitted to dyeing remains in tank or machine (T). 
     The processing of the luminous signal transmitted by probe ( 2 ) to spectrophotometer or colorimeter ( 20 ) takes place according to known algorithms which are not described in detail as the technician working in this field already know them. Said algorithms allow the absorption evaluation of the single colouring agents present in the material the specimen is made of (that is to say the material submitted to dyeing in tank or machine T) that is, they allow the evaluation of colouring agents depletion, even when a pH or temperature variation of the dyeing bath take place or a salinity variation occurs, and so on. 
     The reading, that is to say the spectroscopic analysis of the signal sent by probe ( 2 ) to spectrophotometer ( 20 ) directly concerns the dyed material. In other words, as the material of the specimen is brought directly into contact with probe ( 2 ) the typical errors made by devices by means of which the reading is carried out on the dyeing bath are avoided. In fact, during the reading step, the specimen material is pushed and then held on probe ( 2 ) by pad ( 41 ), so as to avoid any interferences of the dyeing bath on the readings themselves. The optical reading is carried out by device ( 1 ) by reflectance instead of by transmittance as provided by conventional systems. 
     The scheme of  FIG. 15  features both detecting devices ( 1 ) and ( 101 ) whereas the flow drawn out of duct ( 106 ) passes though device ( 101 ) by means of ducts ( 102 ) and ( 103 ). Dashed arrows (FL) represent the signals sent to spectroscopy ( 20 ) from devices ( 1 ) and ( 101 ). Full arrows (FT) represent the flows of the dyeing bath in the ducts connecting the circuital units shown in the scheme. 
     An operating method according to the present invention comprises the following steps:
         providing a first optical reading chamber ( 10 ) into which a dyeing bath flows, said dyeing bath being drawn out of a dyeing tank or machine (T) carrying out a dyeing process on a given textile material;   providing a sample made of the same material of which said textile material is made and positioning said sample in said first optical reading chamber ( 10 );   providing a second optical reading chamber into which a dyeing bath coming from said dyeing tank or machine (T) flows;   execution of a reflectance optical reading inside said first chamber and a transmittance optical reading inside the second chamber and transmitting the signals respectively corresponding to the light reflected by the specimen surface in the first chamber and/or corresponding to the light transmitted through the fluid contained in said second chamber, said signals being transmitted to optical processing means ( 20 ).       

     Moreover, with particular reference to the reflectance reading, the method comprises the following operative steps:
         providing a first optical reading chamber ( 10 ) into which a dyeing bath flows, said dyeing bath being drawn out of a dyeing tank or machine (T) carrying out a dyeing process on a given textile material;   providing a sample or specimen (F) made of the same material of which said textile material is made and positioning said sample onto a support inside said first optical reading chamber ( 10 ), said sample being submitted to dyeing by the dyeing bath flowing inside the first optical reading chamber;   cyclically approaching said support to an optical detector ( 2 );   by means of said optical detector ( 2 ) emitting a luminous signal on the specimen surface and transmitting the light reflected by the specimen surface to optical processing means; and   moving said support with the specimen of material (F) away from said optical detector ( 2 ).       

     Advantageously, said specimen (F) is elastically applied onto a mobile support from and towards said optical reading probe. 
     Moreover, said approaching phase of the specimen to the optical reading probe is advantageously carried out by exerting a thrust on the specimen and, when the specimen is moved away from the optical reading probe, said thrust is removed. 
     The reflectance optical reading implies the measurement of the amount of light reflected by the surface of the specimen immersed in the dyeing bath in relation to the amount of light incident upon its surface. 
     Thanks to the present invention, it is possible to carry out a correct and reliable depletion test of the single colours (red, yellow, blue) in the dyeing bath, whatever the chemical class or nature of the colouring agents employed, even in case of very low or very high concentrations, considering the specific nature of the material submitted to dyeing, that is to say considering the real absorption and of the consequent real depletion of the single colours through the textile material. It is also possible to choose, for example on the basis of the dyeing bath temperature as said before, which of the reflectance and transmittance readings are to be considered valid. 
       FIGS. 16-19  relate to an alternative embodiment of the reflectance reading device ( 1 ). Here, said paid ( 41 ) is fixed to the lower side of upper base ( 13 ) and the bottom of lower base ( 11 ) features a central opening within which the probe ( 2 ) is positioned. A tubular gasket ( 2 G) is positioned between the probe ( 2 ) and said opening. The probe ( 2 ) can be lifted and lowered by means of a respective actuator (not shown in the drawings). Said actuator for lifting and lowering the probe ( 2 ) can be of any conventional type. According to this alternative embodiment of the reflectance reading device ( 1 ), the probe ( 2 ) moves towards the sample (F). In practice, the plate ( 3 ) is positioned on bushes ( 18 ) and coil springs ( 190 ) are fitted on the columns ( 16 ) so as their lower basis rest on the upper side ( 18 U) of annular projections ( 18 ). Then, the upper base ( 13 ) is connected to the lower base ( 11 ) as described with reference to first embodiment. Cyclically, the probe ( 2 ) is lifted. Lifting of probe ( 2 ) causes support ( 3 ) to move towards the upper base ( 13 ) and the thus exerted thrust overcome the resistance of springs ( 190 ). At the end of the probe ( 2 ) lifting, the sample (F) is pressed between the same probe and the pad ( 41 ) and the optical reading is executed. According to this embodiment, the probe ( 2 ) is moved towards the sample (F) instead of moving the sample (F) towards the probe ( 2 ). 
     The drawings only show practical embodiments of the invention, which can vary in forms and arrangements without however departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided purely to facilitate reading thereof in the light of the description and accompanying drawings, without limiting the scope of protection in any way.