Patent Publication Number: US-7913524-B2

Title: Apparatus for dyeing textile substrates with foamed dye

Description:
This application is a continuation-in-part of pending U.S. patent application Ser. No. 11/805,893, filed May 25, 2007, published Nov. 22, 2007, as Publication No. 2007-0266505-A1, which is a continuation-in-part of U.S. patent application Ser. No. 10/833,450, filed Apr. 28, 2004, published Nov. 3, 2005, as Publication No. 2005-0241078-A1, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for dyeing textile substrates with a foamed dye. In one form, the present invention relates to an apparatus for dyeing textile substrates containing cellulosic fibers with a reduced leuco-state dye foamed with an inert gas and applied in the leuco foamed state in an inert atmosphere to the textile substrate and subsequently oxidized thereon to affix the indigo dye to the cellulosic fibers of the textile substrate. In another form, the present invention relates to dyeing a textile fabric substrate with foamed dye applied incrementally by a plurality of spaced applicators. 
     Dyeing cellulosic textile material, such as cotton yarn or fabric, with a leuco-state dye, such as indigo dye, has a large market, particularly for cotton denim clothing items, such as blue jeans. The fastness of the indigo dye on cotton and the deep color or shade that can be obtained make indigo dyed fabric a very popular product. However, dyeing cellulosic textile material with indigo dye is a complicated, complex and expensive procedure, because indigo in its natural state will not affix to cellulosic fibers. To render the indigo dye capable of affixing to cellulosic fibers, it is necessary to reduce the indigo by removing oxygen as by mixing with hydro (hydrosulfite) or other reducing agents to render the indigo a colorless leuco-state material. It then must be handled to remain in a substantially leuco-state until it is applied to the cellulosic textile material. To be capable of being applied, the leuco-state indigo dye must be sufficiently dilute to penetrate into the interstices of the cellulosic material. Typically, indigo dye is obtained from a supplier in a paste form that is, for example, in a 40% solution. It then must be further diluted to, for example, a 2% solution with a non-oxidizing liquid, such as hydro and caustic soda, to maintain the leuco-state to be capable of penetration into a traveling textile substrate that is immersed through a vat of the diluted indigo dye. Because of this dilution, it is necessary to pass the textile substrate through a series of sequential indigo dye vats with intermediate exposure to the atmosphere or other oxidizing agents to set the indigo applied during the preceding immersion. To obtain a desired deep color or shade, it is common to utilize a dyeing range having anywhere from four to eight, dye vats in series with arrangements of guide rolls between vats to assure proper oxidation of the indigo between vats. In addition, the dye in the vats must be continuously and rapidly recirculated in a tank or tanks into which reduced water or other similar material is added and regulated to remove oxygen taken up in the dye vats and to return any oxidized indigo dye to the reduced leuco-state. 
     A significant problem with prior art indigo dyeing ranges is that of waste dye and water disposal. Because of the numerous vats and the amount of dye liquor that must be provided, there is a significant quantity of dye liquor that must be disposed of at the end of every dyeing operation. This creates an undesirable substantial expense and environmental problem. 
     Another prior art dyeing system is disclosed in U.S. Pat. No. 4,613,335, issued Sep. 23, 1986, to Hans-Ulrich Berendt, et al. This patent discloses a process for dyeing or printing cellulosic-containing textile material with a reduced leuco-state dye in a foam carrier. While mentioning dyeing, the disclosure is primarily directed to printing, and there is no disclosure of the substrate being in a sealed, inert atmosphere. Rather, the substrate is exposed to the atmosphere as it approaches the applicator, as it passes across the applicator, and as it leaves the applicator. Therefore, there is no control of the condition of the substrate as it approaches and passes under the applicator and no control of the oxidation of the dye after it is applied to the substrate. 
     In contrast, the present invention, in one form, provides for the applicator face and substrate to be in a controlled inert atmosphere so that the foam can be applied without oxidation or controlled oxidation of the leuco-state dye and the foam can at least partially collapse in the inert atmosphere allowing the dye in its leuco-state to disperse on the substrate without oxidation or with controlled limited oxidation before it is fully oxidized as the substrate leaves the inert atmosphere, assuring that desirable affixing of the dye on the substrate occurs when the substrate is exposed to the atmosphere. 
     In another form of the present invention, the apparatus is not limited to dyeing of any particular textile fabric substrate, which dye can be in the leuco-state or any other form that is foamed for application to the traveling substrate. Also, it is not limited to a dyeing chamber sealed from ambient air, but can be utilized with a sealed chamber or a chamber that is open to ambient air. This form of the apparatus utilizes a plurality of spaced foam applicators applying dye in foam form onto the surface of the substrate in increments and being spaced apart to permit at least partial collapse of the foam between applicators. 
     SUMMARY OF THE INVENTION 
     Briefly described, in one form the present invention provides an apparatus for dyeing textile substrates containing cellulosic fibers with a foamed reduced leuco-state dye. The apparatus includes a housing having an interior chamber sealed from atmospheric air and through which the substrate travels from an entrance having a seal through which the substrate enters the chamber to an exit having a seal through which the substrate exits the chamber. A supply of inert gas communicates with the chamber to provide an inert environment therein. At least one foam applicator has an applicator face in said chamber and extending across the width of the substrate for applying foam containing the dye in leuco-state to the substrate in the chamber. A foam generator generates foam containing the leuco-state dye in the absence of oxygen with the generator communicating with the applicator for supplying the foamed leuco-state dye to the applicator. Thus, oxidation occurs primarily only after the substrate exits the chamber. However, there may be a minimal amount of oxygen in the otherwise inert gas and some small controlled amount of oxygen may purposely be included in the inert gas for desired controlled partial oxidization of the dye before it exits the chamber. Preferably, the supply of inert gas is under pressure to provide a pressurized inert environment in the chamber and minimize the entry of any atmospheric air through the entrance and exit. Also, preferably, the at least one applicator is spaced from the entrance to provide a free reach of the substrate in which air trapped in the interstices of the substrate is allowed to escape, and the at least one applicator is spaced from the exit to allow foam on the substrate to collapse and deposit and distribute the leuco-state dye on the substrate before the substrate exits the chamber and the dye is oxidized. 
     In a preferred embodiment of this form of the present invention there is a plurality of applicators with application faces in the chamber and disposed with spaces therebetween to allow foam to at least partially collapse and the leuco-state dye to at least partially deposit on the substrate before having foam applied by the following applicator. Holddown elements, which may be in the form of rollers, may be disposed between the applicators for engaging the substrate to displace the substrate between the applicators to maintain the substrate in foam receiving engagement with the applicator faces. The applicators are preferably parabolically shaped for uniform distribution of foam across the width of the substrate. 
     In this preferred embodiment, the inert gas is nitrogen and the foam generator generates a foam of nitrogen containing the leuco-state dye. One advantage of nitrogen being in the foam is that when the foam collapses in the chamber, the nitrogen increases the amount of inert nitrogen in the chamber environment. 
     This form of the present invention has special application to dyeing woven denim fabric with indigo dye, which may be applied at a weight of approximately 5% to 20% of the weight of the fabric and preferably 10% to 15%. 
     To allow access into the chamber, the housing may have an openable cover sealingly mounted thereon and the holddown elements may be mounted on a frame that is moveable to move the holddown elements away from the spaces between applicators when the cover is open. 
     In another form of the present invention, the apparatus is directed to dyeing a traveling textile fabric substrate in a housing having an interior chamber through which the substrate travels. An entry roller assembly feeds the substrate into the chamber and an exit roller assembly draws the substrate from the chamber. A plurality of spaced foam applicators are disposed in the chamber and have applicator faces extending transversely of the traveling substrate for applying dye in foam form onto the surface of the substrate in increments, with the space between applicators permitting at least partial collapse of foam between applicators to facilitate dye application by the subsequent applicator. To maintain the traveling substrate in contact with the foam delivery faces of the applicators, holddown elements, which may be in the form of rollers, extend between applicators below the level of the applicator faces. The holddown elements are preferably idler rollers and to minimize an increase in the tension in the traveling substrate as it progresses over successive applicators, the depth of the holddown elements between the applicators gradually decreases in the direction of travel of the substrate to reduce the angle of inclination and thereby reduce tension causing friction. This decrease in depth can be obtained by providing the housing with a cover to which the holddown elements are attached with spacer blocks therebetween with the number of spacer blocks decreasing with successive holddown elements in the direction of travel of the substrate. The chamber may be sealed from atmospheric air in the manner of the previously described form of the present invention, or the chamber may be open to the atmosphere when dyeing with non-leuco-state dye. The entry roller assembly and the exit roller assembly are driven synchronously to maintain substantially uniform tension in the substrate as it travels through the apparatus to facilitate uniform incremental application of foam. A first holddown element or roller is mounted in advance of the first of the applicators and a last holddown element or roller is mounted after the last of the applicators, with the first and last holddown elements guiding the substrate at the same level as the entry and exit roller assemblies. 
     In both of the forms of the present invention described above the holddown elements between the applicators are preferably either idler rollers or inverted applicators with their faces engaging and holding down the top surface of the applicators. In using inverted applicators, dye foam is applied to the top surface of the substrate, which could be the same color as, a different color than, the same dye as, or a different dye than the dye applied by the lower applicators. Additionally, whether using only the lower applicators or both lower and upper applicators, the different applicators can be used to apply different colors and/or different dyes in the same apparatus, whether it be with an inert atmosphere or ambient air. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a dyeing range in which the apparatus of one form of the preferred embodiment of the present invention is incorporated; 
         FIG. 2  is a plane view of the dyeing range of  FIG. 1 ; 
         FIG. 3  is an end elevation of the entrance end of the dyeing apparatus included in the dyeing range of  FIGS. 1 and 2 ; 
         FIG. 4  is a plane view of the apparatus of  FIG. 3  with a portion of the cover removed; 
         FIG. 5  is a side elevation of the apparatus of  FIG. 3 ; 
         FIG. 6  is a side elevation of the apparatus of  FIG. 3  with the side panel removed; 
         FIG. 7  is similar to  FIG. 6  with the cover and roller frame open; 
         FIG. 8  is a view similar to  FIG. 6  and illustrating alternative exit seals and drains; 
         FIG. 9  is a view similar to  FIG. 6  showing the apparatus modified to have a plurality of holddown elements in the form of inverted applicators; 
         FIG. 10  is a side elevation of the apparatus of another form of the preferred embodiment of the dyeing apparatus of the present invention with the side panel removed; 
         FIG. 11  is an end elevation of the apparatus of  FIG. 10 ; 
         FIG. 12  is a side elevation of the entry roller assembly of the apparatus of  FIG. 10 ; 
         FIG. 13  is a side elevation of the exit roller assembly of  FIG. 10 ; 
         FIG. 14  is an enlarged view of one of the applicators of the apparatus of  FIG. 10 ; 
         FIGS. 15 ,  16  and  17  illustrate the manipulation of the cover of the apparatus of  FIG. 10  from a closed position ( FIG. 15 ) to an initial vertically raised position ( FIG. 16 ) to a pivoted open position ( FIG. 17 ); and 
         FIG. 18  is a plan view of the cover of the apparatus of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The dyeing apparatus  10  of one form of the preferred embodiment of the present invention is illustrated in  FIGS. 1-8 , of which  FIGS. 1 and 2  illustrate the apparatus incorporated in a dyeing range  12 . A sheet of textile substrate S is fed to the range  12  from a supply roll  14  or a supply of plaited material in a supply box  16 . The substrate S is then relaxed in a J-box  18  from which it is withdrawn by a feed roll assembly  20  from which the substrate travels under a crosswalk grid  48  on which an observer O stands to monitor the dyeing operation in the dyeing apparatus  10 . The substrate is drawn through the dyeing apparatus  10  by a driven pull roll assembly  22 . The drive of the feed roll assembly  20  and pull roll assembly  22  are controlled so that a desired tension is being maintained in the substrate S as it travels through the apparatus  10 . From the pull roll assembly  22  the substrate may be subjected to a supplemental treatment at a supplemental dye application station  24 , at which a foam applicator  26  applies a surface treatment, such as the same or different dye as applied in the dyeing apparatus  10 , or any other desired surface treatment material, which surface treatment can be applied to either surface of the substrate. The treated substrate then passes through an infrared dryer  28  to reduce the moisture content to a desired level. Any other type of dryer could be substituted. From the dryer  28 , the substrate S passes under a crosswalk grid  50  over a series of guide rolls  30 , and is wound on a driven takeup roll  32  to form a roll  34  of the dyed substrate S. 
     As illustrated schematically in  FIG. 2 , an inert gas is fed to the dyeing apparatus  10  from a source  36 , which can be a supply tank containing the inert gas or a generator of the inert gas, such as a nitrogen generator. The gas is fed through a supply line  40  to the interior of the apparatus  10  to provide an inert environment. 
     The inert gas is also fed, from the source through a second supply line  38  to a foam generator  42 , which also receives a reduced, leuco-state dye from a dye supply tank  44 . The dye supply tank  44  is maintained under seal that prevents air from entering the supply tank  44  as dye is fed therefrom to the foam generator  42  so as to prevent oxidation of the leuco-state dye. The foam generator is of any conventional type that can create a foam using the nitrogen and having the dye dispersed therein, which foam is then fed through a feed line  46  into the dyeing apparatus  10 . 
     The dyeing apparatus  10  is illustrated in detail in  FIGS. 3-8 . A front guide roll  52 , under which the substrate travels, directs the substrate S from a horizontal direction to a vertical direction. The front guide roll  52  is mounted on the housing  54  of the dyeing apparatus  10 . 
     As the substrate S travels vertically from the front guide roll  52 , its edges E pass through a pair of opposed sensing forks  56 , illustrated in  FIGS. 3 and 4 , that sense the location of the edges E. In response to sensing of the position of the edges E of the substrate S, servo motors  58  adjust end seals  60  to limit foam application to the lateral extent of the substrate without significant escape of foam from the applicators beyond the position of the lateral edges E of the substrate S. 
     The housing  54  is formed with opposite side panels  64  and corner support legs  66 . The upper portion of the housing  54  is formed as a chamber  68  formed by front and rear walls  70 ,  71 , the side panels  64  of the housing, a bottom wall  72 , L-shaped walls  73  extending from the bottom wall  72  to entrance and exit seals  92  and  126 , and a pivotable cover  74  that sealingly seats on the upper edges of the walls  70  and panels  64  with sealing material, such as resiliently compressible foam material, disposed therebetween, or the seal could be provided by a trough containing water formed at the top of the walls  70  and panels  64  with the bottom edges  76  of the cover seated within the water in the trough (not illustrated). The cover  74  is opened and closed by a pair of laterally spaced piston cylinder mechanisms  78  that have ends  80  attached centrally to the cover  74  and other ends  78  attach to upstanding support posts  84  that extend upwardly from the top of the housing  54 . To accommodate this pivoting of the cover  74 , it is mounted on a pivot shaft  86 , on which are also mounted support bars  88  adjacent the piston cylinder mechanisms  78  and centrally of the cover  74 . These support bars  88  stabilize the cover  74  during pivoting. 
     The cover  74  is formed with observation windows  90  through which the observer O can monitor the operation of the dyeing apparatus  10  as the substrate S travels therethrough. At the front of the chamber  68  the entrance seal  92  is located through which the substrate S passes into the chamber  68 . This entrance seal  92  is formed by two pairs of spaced inflatable bladders  93  that prevent the entry of air into the inert environment within the chamber  68 . Above the entrance seal  92  an entrance guide roll  94  directs the substrate S to a plurality of longitudinally spaced foam applicators  96 ,  98 ,  100 ,  102  and  104 . The guide roll  94  is located below the level of the face  106  of the first foam applicator  96  to ensure positive engagement of the substrate S with the applicator face  106 . 
     The applicators  96 ,  98 ,  100 ,  102  and  104  are mounted on the bottom wall  72  by flanges  103  on the applicators secured on the bottom wall  72 . 
     A holddown roller mounting frame  108  is mounted above the foam applicators  96 . This frame  108  has mounted on its underside four holddown rollers  110 ,  112 ,  114  and  116 . These holddown rollers  110 ,  112 ,  114  and  116  are disposed between the foam applicators and project downwardly below the level of the faces of the applicators to force the substrate S to be deflected downwardly between applicators to assure positive engagement of the substrate S with the applicator faces  106 . 
     The frame  108  carrying the holddown rollers  110 ,  112 ,  114  and  116  is pivoted on a pivot shaft  178  spaced rearwardly and upwardly from the last foam applicator  104 . The frame is retained in operating position by wingnuts  180  attachable to upstanding brackets  122  forwardly of the first foam applicator  96 . A coil spring  121  secured to the rear wall  71  of the chamber  68  and a rearward extension  140  of the frame  108  biases the frame  108  to an open position so that when the wingnuts  120  are released, the frame  108  will pivot upwardly into an open position. 
     Beyond the last foam applicator  104 , an exit guide roll  124  is mounted below the level of the foam applicators for guiding the substrate S away from the foam applicators and downwardly through the exit seal  126  having pairs of spaced inflated sealing bladders, with the exit seal  126  and bladders  128  being identical to the entrance seal  92  and bladders  93 , to prevent entrance of atmospheric air into the chamber  68 . 
     Spaced below the exit seal  126  is a guide roll  130  that guides the substrate vertically downward and then horizontally outward to the pull roll assembly  22 . 
     The entrance seal  92  and the entrance guide roll  94  are spaced from the first foam applicator  96  to provide a free reach of the traveling substrate during which air that may have been entrapped in the interstices of the substrate S and thereby entered the chamber  68  will have an opportunity to escape from the substrate interstices, thereby substantially avoiding any undesirable oxidation of the reduced, leuco-state dye when it is applied to the substrate. 
     The foam applicators  96 ,  98 ,  100 ,  102  and  104  are spaced from each other so that, as the substrate travels from one to the next, it is deflected by the intermediate guide rolls  110 ,  112 ,  114  and  116  to provide a free time between applicators for the foam to collapse and the dye disperse before dye is applied by the next applicator. Similarly, the exit guide roll  124  and exit seal  126  are spaced from the last foam applicator  104  to allow collapse of the foam and dispersion of the dye before the substrate leaves the inert atmosphere within the chamber  68  and the dye exposed to oxygen in the atmosphere beyond the exit seal  126 . 
     Each of the foam applicators  96 ,  98 ,  100 ,  102  and  104  are, in the preferred embodiment of  FIGS. 1-8 , parabolically shaped applicators of the type disclosed in U.S. Pat. No. 4,655,056, issued Apr. 7, 1987, to Dieter F. Zeiffer. This type of applicator is particularly useful in that the parabolic shape distributes foam equally and over equal distances from the input to the full extent of the applicator face. Other types of applicators can also be used with varying results. 
     The applicator in the supplemental dye applying station  24  may also be of the parabolic shape, particularly if it is applying a foam, but any other type of dye or other surface treatment may be applied as well in other types of applicators. 
     As seen in  FIGS. 6 and 7 , gutters  131  at each side of the chamber  68  outwardly of the applicators decline centrally toward drain pipes  132  that collect any excess dye or other liquid and have closures  134  that are openable at the end of a dye run to allow flushing of the chamber  68 . The closures  134  also are open at the startup when nitrogen or other inert gas is fed from the inert gas source  36  under pressure into the chamber  68 . As atmospheric air is heavier than nitrogen, the introduction of nitrogen under pressure will cause atmospheric air to exit the closure  134 . When all or substantially all of the atmospheric air has exited the chamber  68 , the closures  134  are sealed and the substrate S is threaded by a lead sheet or other means to begin operation. Alternatively, the substrate may be threaded before air is evacuated from the chamber  68 , which will result in a short length of substrate being imperfectly dyed. 
     The purging of oxygen bearing air from the interstices of the fiber structure provided by the spacing of the entrance seal  92  and entrance guide roll  94  from the first applicator  96  prevents the dye liquor from oxidizing prematurely and rather allows subsurface liquor migration that would be restricted were the dye to oxidize, making it immobile resulting in a loss of control over distribution of the dye molecules. 
     However, as commercially supplied inert gas, such as nitrogen, contains some small amount of oxygen and as commercial inert gas generators do not produce totally pure inert gas, there may be a minimal amount of oxygen in the inert atmosphere, resulting in some unintentional slight oxidization of the dye on the substrate before the substrate leaves the chamber. An advantage of the present invention is that, if desired, some small controlled amount of oxygen may purposely be included, in any conventional manner, to provide partial oxidization of the dye on the substrate between and/or after dye application before the substrate leaves the chamber and the dye is substantially oxidized in the ambient atmosphere. 
     If acceptable, only one foam applicator can be incorporated in the apparatus with all of the foam being supplied through that one applicator, but preferably a plurality of foam applicators are used with each applicator applying a fraction, either equally distributed or selectively distributed, depending on preferences, and a much deeper shade can be obtained with the same amount of dye by applying multiple foam applications. With a plurality of foam applicators, with each applicator supplying a relatively small limited amount of dye-containing foam, the migration of the dye into the fiber surface can be a controlled process. Subsequent relatively small amounts of foam put onto the same fiber surface area, in a superimposed fashion, will allow for a dye enrichment to be achieved. Sequential dye applications are accomplished without any dye ever being allowed to oxidize until the final application is made. The substrate surface fibers are unable to satisfactorily absorb large foam volumes that are applied at one, rather than a plurality of, applicators as a large volume single application will disperse dye to a greater extent into the interior of the substrate rather than concentrating on the surface fibers. This allows dyeing with less moisture pickup and, therefore, less required drying and generation of less waste water. 
     With the spaces of the dye liquor delivery system filled with reduced dye, the liquor itself, which can be formulated at a low viscosity, incrementally applied to the fiber surface will provide a controlled specific infusion rate. The lowest viscosity of the foam can be maintained during the foam application, with the foam being in only a temporary delivery state. The foam collapses almost immediately upon fiber contact and does not hinder the dye infusion process. The super-imposition of incrementally small amounts of liquor with time intervals, or infusion stages, between each subsequent foam application takes place with the dye being in a non-oxidized state, in striking contrast to the prior art. 
     In this form of the preferred embodiment, indigo dye in its reduced, leuco-state can be run at normal finishing range speeds, such as about sixty meters per minute. A typical fabric weight would be 400 grams per square meter, and a typical amount of indigo dye to be applied to one side of the fabric may be, for example, about 5% to about 30% of the weight of the fabric, which can be divided in any fashion between the five applicators. For example, each applicator could apply 2% of the dye liquor for a 10% total or 3% for a total of 15% total or unequal amounts or any combination can be distributed by the different applicators. 
       FIG. 8  illustrates a modification of the location of the exit seal and drain pipe. In this arrangement, the exit seal  136  is located in a horizontal disposition for exit of the substrate horizontally and an exit guide roll  138  similarly located in the manner of the guide rolls  110 ,  112 ,  114  and  116  mounted similarly on the frame  108  as in the form of  FIGS. 1-7 , deflects the substrate downwardly following the last applicator  104 , for guiding to the horizontal exit seal  136 . 
     In this variation the drain pipes  142  are located at the rear of the housing  54 , and the gutters  141  slant downwardly rearwardly to drain liquid from the chamber  146  into the gutters  141  and drain pipes  142  to exit from the drain pipes  142  when the drain pipe closures  148  are opened. 
     Variables, such as liquor flows, substrates speed, chemical formulations, purity of the nitrogen, degree of fabric preparation and fiber origin can have distinct effects upon the resulting shades. Also, while the substrate is primarily cellulosic for dyeing with indigo in the leuco-state, the substrate may contain some small amounts of synthetic fibers to obtain any desired results. Shade variations can easily be achieved by varying the number of applicators engaged in the liquor application, even though the total flow would be the same. For example, it is possible to find that the liquor has penetrated to the back of the fabric substrate at a 15% wet pickup level through one applicator, while there will not be any evidence of liquor on the back of the fabric substrate if the same total wet pickup of 15% is applied in fractionated succession through five applicators. When the fabric exits the chamber  68  the reduced, leuco-state dye is almost instantly oxidized as it is exposed to ambient air. 
     An interesting advantage of the present invention is that when the foam collapses, the nitrogen used to create the foam is released into the environment within the chamber  68 , thereby enhancing the nitrogen content in the chamber  68  in replenishing any nitrogen that has escaped from the chamber. This reduces the amount of nitrogen that must be supplied to the chamber  68 . 
     The number of applicators used in an apparatus according to the present invention may be varied from one to as many as six or more, depending on the application flexibility desired. Further, the application of the liquor can be done at ambient temperature, but, if desired, elevated temperatures could be utilized to provide some advantage on certain fabrics and procedures. 
     While the drawings illustrate and the detailed description describes an apparatus having four applicators, it should be understood that the apparatus can be operated with all or less than all applicators, including with only one applicator, actively applying foamed dye, and that the invention may be practiced with apparatus made with only one applicator therein or any desired number of applicators, all of which may be active or some of which may be inactive. 
     The pressure of nitrogen within the chamber  68  need be only slightly more than atmospheric pressure. It needs to be sufficiently higher than atmospheric pressure to prevent ambient oxygen-containing atmosphere from entering the chamber  68  and causing oxidation of the applied dye. 
     Instead of using idler rollers as the holddown elements, inverted applicators can be used, as illustrated in  FIG. 9 . In this illustration, the apparatus  200  is similar to that of  FIGS. 6 and 8  in that it includes a housing  202 , a first guide roll  204  an entry seal  206 , an entrance guide roll  208 , a plurality of upwardly facing applicators  210  mounted on a platform  212 , followed by an exit seal  216 . 
     The apparatus  200  has an openable cover  220  similar to the cover of  FIGS. 6 and 8 . However, it does not include a separate frame. Rather, the cover  220  has an interior downwardly offset platform  222  on which are mounted holddown elements in the same locations and for the same purposes as the idler roller holddown elements of  FIGS. 6 and 8 . In this variation the holddown elements are inverted applicators  224  identical to, but inverted, in comparison with, the lower applicators  210 . These inverted applicators  224  serve the same holddown purpose as the rollers of  FIGS. 6 and 8  and additionally serve to apply foamed dye to the top surface of the substrate S as the top surface of the substrate passes under the applicator faces  226  of the inverted applicators  224 . 
     With these inverted applicator holddown elements, the same or different dyes can be applied to the upper surface than the under surface of the substrate and various different dyes can be applied through each applicator, including leuco-type dyes and standard dyes, with the apparatus  200  operating either with a sealed inert atmosphere or unsealed ambient atmospheric air contained in the apparatus  200 . 
     Another form of the preferred embodiment of the present invention is illustrated in  FIGS. 10-18 . It comprises a dyeing apparatus  300  similar to the apparatus  10  and  200  of the previously described forms, and capable of being incorporated in an overall dyeing range similar to the dyeing range  12  of the previously described embodiment. With reference to the range as illustrated in  FIG. 2 , the apparatus  300  of the embodiment of  FIGS. 10-18  would use a similar inert gas source, foam generator and dye supply tank when the apparatus  300  is being used with an inert atmosphere in the manner of the apparatus  10  and  200  described above. The apparatus  300  of this form of the present embodiment may also be used with ambient air, in which case the source of inert gas would not be included and only the foam generator and source of dye would be used, with the source of dye and foam generator not requiring an inert condition. 
     The apparatus  300  includes a housing  302  supported on legs  304  and having end walls  306 , side walls  308 , a bottom wall  310  and a cover  312 . These walls  306 ,  308 ,  310  and the cover  312  form an interior chamber  314 . To use the apparatus  300  for dyeing with leuco-state dye, as in the previously described embodiment, the chamber  314  can be air tight with the cover  312  sealed on top of the walls in the same manner as the sealing of the cover  74  of the previously described embodiment. 
     A traveling textile fabric substrate S is fed to the chamber  314  by an entry roller assembly  316  having three rollers, two of which  318  are vertically spaced, and a third roller  320  is offset therebetween. The rollers are driven by a motor  322 , (illustrated in  FIG. 12 ). After passing through the entry roller assembly  316 , the substrate S travels around a tension detection roller  324  that is mounted on a load cell  326 , from which the substrate S travels into the chamber  314  through an entry end seal  328 . The substrate exits the chamber  314  at the other end thereof through an exit end seal  330 , which is identical to the entry end seal  328 , and through an exit roller assembly  332  having an arrangement of two spaced rollers  334  and an offset roller  336  similar to the rollers  318  and  320  of the entry roller assembly  316 . A motor similar to and synchronized with the entry roller assembly drive motor  322  drives the rollers  334  and  336 . 
       FIG. 13  illustrates the exit roller assembly  332 . As seen in  FIG. 13 , a drive belt  338  passes around the offset roller  336  and spaced rollers  334  and two guide pulleys  340 . Belt tensioning elements  342  are adjustably mounted in contact with the drive belt  338  to maintain the belt in driving tension. 
     Mounted in the housing  312  and extending into the chamber  314  are five foam applicators  344 . These foam applicators  344  extend across the apparatus and are spaced from each other and extend parallel with each other for sequential travel of the substrate S over the applicators. 
     The applicators  344  are similar to the applicators  96 - 104  illustrated above and described in relation to the embodiment of  FIGS. 1-8  and  210  of  FIG. 9  and as disclosed in U.S. Pat. No. 4,655,056 issued Apr. 7, 1987 to Dieter F. Zeiffer. As seen in the enlargement of  FIG. 14 , each applicator  344  has an L-shaped conduit  346  through which foamed dye is supplied from a foam supply. The L-shaped conduit  346  opens into the top of the parabolic applicator  344  and is displaced therein to the slot  348  of the applicator face  350  over which the substrate travels and receives foam from the applicator. The applicator face  350  is rounded convexly to allow the substrate S to cover the slot  348  without appreciable leakage of foam therefrom. 
     At the bottom of the parabolic applicators  344  a pneumatically operable ball valve  352  is operated to allow draining of the applicators at the end of an application or to otherwise purge or empty the applicators into a drain manifold  354 . 
     The substrate is held down against the applicator faces  350  to assure proper application of foam to the surface of the substrate without significant leakage. This is accomplished by four holddown rollers  356 , each intermediate two applicators  344 , and a first holddown roller  358  in advance of the first of the applicators and a last holddown roller  360  following the last applicator. Each of the intermediate, first and last holddown rollers  356 ,  358  and  360  extend downwardly below the level of the applicator faces  350  so as to cause the engaged substrate S to travel upwardly to and downwardly from the applicator faces  350 . The first holddown roller engages  358  the substrate at the level at which it enters through the entry end seal  388 , and the last holddown roller  360  positions the substrate to travel therefrom at the level of the exit end seal  330 . 
     To avoid the complication of a drive mechanism and the necessity of a seal for an exterior drive or power source, particularly when the interior chamber  314  is to be sealed from ambient air, the holddown rollers  356 ,  358  and  360  are idler rollers, but, not being driven, they cannot drive the substrate S at a uniform tension. For this reason all of the holddown rollers  356 ,  358  and  360  are attached to the underside of the cover  312  with spacer blocks  362  that determine the downward extent of each of the holddown rollers, and the number of spacer blocks  362  mounted with the intermediate holddown rollers  356  decreases with successive rollers in the downstream direction of travel of the substrate S, thereby decreasing the depth of the successive holddown rollers, resulting in a decrease in the angle of inclination of the substrate as it progresses over successive applicator faces, thereby reducing the amount of friction being developed that causes increased tension. Uniform tension is advantageous as it results in the amount of foam applied at each applicator being as close as possible to a uniform amount. Variations in tension in the substrate will result in variations in the amount of foam applied to the surface of the substrate by the applicators. The amount of tension in the substrate is controlled by the relative drive speeds of the rollers of the entry roller assembly  316  and rollers of the exit roller assembly  332 , and by the decreasing number of spacer blocks  362  in the sequence of holddown rollers. In this regard, it is desirable that the increase in tension in the substrate as it travels through the apparatus be limited to approximately the range of 1 to 2½ times the tension in the substrate entering the apparatus. The spacer blocks  362  may be of any size and number that provides optimum results. For example, spacer blocks  362  of ⅛, 3/16 or ¼ of an inch thickness decreasing in number from about 6 to about 3 may be used to provide satisfactory results depending on the circumstances. 
     It is desirable that the spacing between applicators  344  be sufficient to permit at least partial collapse of the foam between applicators so that the dye will effectively be absorbed in the surface fibers of the fabric substrate before foam is applied by the next applicator. This, in combination with the decreasing depth of the intermediate holddown rollers  356  results in relatively uniform application of foam from each applicator without significant moisture being absorbed into the fabric. With the apparatus of the present invention, the quantity of dye foam that is normally applied when using one applicator can now be divided and applied in a fraction at each applicator. For example, in the apparatus as illustrated, the foamed dye is applied one-fifth through each applicator, with each application being applied only to the surface of the substrate rather than the foamed dye penetrating significantly into the fabric when all of the foamed dye is applied at one applicator. In a typical operation, the moisture pick up with the apparatus of the present invention may be 15% of the weight of the fabric in comparison with 90% to 100% moisture pick up in a conventional dyeing operation. As a result, time consuming drying can be significantly reduced or eliminated and waste water can be minimized. 
     To limit the discharge of foam to the width of the substrate S, side seals  364  and  366  are provided similar to the side seals  60  of the embodiment of  FIGS. 3 and 4 . The edge of the traveling substrate can be sensed by sensing forks, such as described in the preceding embodiment, which sensing forks are identified by the numeral  56  in  FIG. 3 , or electronic sensors of various sorts may be used. 
     When the apparatus  300  is used to apply leuco-state dye, requiring an inert atmosphere, the bottom wall  310  is located close to the upper extent of the applicators  344  to minimize the volume of the chamber  314  and thereby minimize the amount of inert gas needed to be maintained in the chamber. Also, when using a leuco-state dye, the space between the entry end seal  328  and the first applicator  344  is significant as it allows the dissipation of at least some of the oxygen that may be entrapped in the entering substrate. Similarly, the space between the last applicator and the exit end seal  330  is significant as it allows at least partial collapse of the foam with the dye fastening to the substrate before being exposed to the atmosphere. 
     As seen in  FIG. 11 , any unapplied foam that accumulates as liquid in the chamber  314  drains through side conduits  368  to flaps  370  that are openable manually or automatically as desired. Similarly, a drain valve  374  on the drain manifold  354  ( FIG. 10 ) is operable to discharge accumulated liquid from the drain manifold  354 . 
     Monitoring and control of the operation of the apparatus  300  is conducted by an Operator O using the control panel  378  mounted at the entry side of the apparatus  300 . 
     The embodiment of the apparatus  300  in  FIGS. 10-18  can be used either to apply leuco-state dyes or non-leuco-state dyes to substantially equal advantage. When utilizing the apparatus  300  to dye non-leuco-state dye, it is not necessary that a chamber be formed or that end seals be provided air tight or that the cover be sealed in place. Rather, ambient air is present before and after the lid is closed and can enter through unsealed openings, including the opening resulting from disconnection from the inert gas supply. Also, air is released from the foam as it collapses. 
       FIGS. 15 ,  16  and  17  illustrate the sequence of operation in opening the cover  312 .  FIG. 15  shows the cover closed during operation of the apparatus. The first step in opening is to raise the cover  312  vertically. This is accomplished by extension of short front piston-cylinder mechanisms  380  at the bottom of the front legs  304  of the apparatus  300 . These short piston-cylinder mechanisms  380  are attached to the lower ends of long front piston-cylinder mechanisms  382 . The upper ends  384  of the front piston-cylinder mechanisms  382  are attached to the front corners of the cover  312 , which is raised by the extension of the short front piston-cylinder mechanisms  380  and simultaneously by extensions of short rear piston-cylinder mechanisms  386  mounted on rear corner extensions  388  of the housing  302 . The upper ends of the rear piston-cylinder mechanisms  386  are attached to corner pivots  390  of the cover  312  with the extension of the rear piston-cylinder mechanisms  386  raising the rear of the cover  312  to the same height as the front of the cover is raised by the front piston-cylinder mechanisms  380 . This initial vertical raising of the cover  312  is particularly desirable when the cover  312  is sealed during operation. 
     Subsequent to the initial vertical raising of the cover  312 , the front piston-cylinder mechanisms  382  are extended fully to raise the front of the cover  312 , during which the cover pivots about the rear pivots  390  to swing the cover  312  open to a position as shown in  FIG. 17 . As the cover  312  approaches the upper extent of its pivoting, latch plates  394  secured at an inclination at the sides of the top of the cover  312  engage latches  396  pivotally mounted on a reciprocal cross rod  397  mounted on and extending between upstanding posts  398  until the latch plates  394  displace the latches  396  sufficiently for the latches  396  to engage in openings  400  in the latch plates  394 , thus holding the cover  312  in the open position illustrated in  FIG. 17 . An arm  402  fixed to and extending from one end of the rod  397  has an outer end  404  attached to a spring mechanism  406  having an end  408  fixed to the reciprocal cross rod  397  and its other end  410  attached to a bracket  412  on the post  398 . The spring mechanism  406  normally urges the cross rod  397  to position the latches  396  into downwardly extending positions, as shown in  FIG. 10 . The latches  396  and latch plates  394  connection is disengaged either manually or mechanically when it is desirable to pivot the cover  312  downwardly to its closed position. 
     The spacer blocks  362  described in relation to the form of the present invention illustrated and described with relation to  FIGS. 10-18  can also be used with the forms of  FIGS. 1-8  and  FIG. 9  for the same purpose and to obtain the same advantages. Further, all of the forms of the present invention described herein may be used with leuco-type dyes and also with other dye systems that are not leuco systems, such as sulfur dyes, vat dyes, conventional aqueous textile dyes and any other dye that is capable of application in a foam form, and heating systems can be included for best results with a particular dye selected. Also, the textile fabric substrate may be woven material, knit material or non-woven material of cellulosic, non-cellulosic or blends thereof. Furthermore, the applicators in any of the forms of the present invention can be each supplied individually or in combinations by dedicated individual foam generators to simultaneously supply different dyes and chemicals to the substrate and applying the material in layers. 
     The apparatus of the present invention is particular applicable to dyeing substrate in fabric form, including heavy denim fabric for manufacturing jeans, which can be dyed in any variegated pattern for fashion effects, which is not done with conventional dyeing where yarn, not fabric, is dyed, although light-weight fabrics, not heavy jean fabrics are sometimes dyed in conventional machines. 
     In view of the aforesaid written description of the present invention, it will be readily understood by those skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to preferred embodiments, it is to be understood that this disclosure is only illustrative of examples of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended nor is it to be construed to limit the present invention or otherwise exclude any other embodiment, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.