Plant for the continuous or discontinuous single or dual dyeing, with indigo and other reduction DYES and in two different operating modes, of warp yarn chains, of rope-type, for denim textiles

Abstract

A plant for dyeing yarn ropes is disclosed, which comprises at least one dyeing machine provided with an openable and / or removable upper lid, at least one device for squeezing the yarn ropes and at least one oxidation pathway in an atmospheric environment of the yarn ropes. Between a point for the entry of the yarn ropes in the at least one dyeing machine and a point for the exit of the yarn ropes from the at least one oxidation pathway there is obtained a first dyeing / oxidation pathway. Between the point for the exit of the yarn ropes from the at least one oxidation pathway and the point for the entry of the yarn ropes in the at least one dyeing machine there is instead obtained a pathway for the return of the yarn ropes, which overlies both the at least one dyeing machine and the at least one oxidation pathway at a predefined height from the ground. Between the point for the entry of the yarn ropes into the at least one dyeing machine and the point for the exit of the yarn ropes from the at least one oxidation pathway there is therefore obtained at least one second pathway for dyeing / oxidising the yarn ropes, which is parallel and coplanar with respect to the first pathway for dyeing / oxidising the yarn ropes, so as to avoid any overlapping of the yarn ropes both inside the at least dyeing machine and at the at least one oxidation pathway.

Description

[0001] PLANT FOR THE CONTINUOUS OR DISCONTINUOUS SINGLE OR DUAL DYEING, WITH INDIGO AND OTHER REDUCTION DYES AND IN TWO DIFFERENT OPERATING MODES, OF WARP YARN CHAINS, OF ROPE-TYPE, FOR DENIM TEXTILES

[0002] The present invention generally relates to a plant for dyeing yarns and, in particular, a plant for the continuous or discontinuous single or dual dyeing, with indigo and other reduction dyes and in two different operating modes, conventionally in air and ecologically in inert environment, of warp yarn chains, in ropes, for denim textiles. The present invention is of great interest for almost all world’s manufacturers of denim, that is those who for the dyeing of the warp use the conventional system in ropes.

[0003] Denim is the textile used for making jeans and “casual” articles in general which, produced in more than five billion clothing items per year, make it the world’s most used textile. The conventional denim textile is obtained with the warp threads dyed with indigo and with the raw weft strand. The success of the denim-blue jeans combination specifically lies in dyeing the warp of this textile with indigo.

[0004] Indigo is one of the most ancient dyes, that is not easy to apply to cotton with which it has low affinity, but it also has a unique characteristic which confers to the textile, and as a result the clothing item made, an appearance that is shiny and pleasant to sight over time. As a matter of fact, blue jeans are appreciated for their typical marine blue tone which gradually, due to repeated washing, take an increasingly lighter tone until they reach a shiny light-blue colour. As far as known, no other dye has revealed similar properties. After many washing cycles, other classes of dyes turn to a dirty grey colour or stain the weft raw yarn with an unappealing blue / greyish colour. The peculiarity mentioned above, together with the impression of worn clothing item, which is highlighted with abrasion in the most exposed areas, and which creates a plastic effect on the body of the wearer, represents the charm of blue jeans, which made and treated in several ways are and remain the world’s most sold clothing item.

[0005] One of the characteristics of the indigo dye, which makes it unique, lies in the particular dyeing method required for the application thereof on the cotton yarn. This dyeing method has remained almost intact since the times of vegetable dyeing up to date, more than one hundred years since its synthesis. Due to its relatively small molecule and the low affinity with the cellulosic fibre, in order to be applied not only does the indigo dye need to be reduced into alkaline solution (leuco), but it also has to be subjected to a plurality of impregnations alternated by squeezing and successive air oxidations. Basically, a medium or dark colour tone is only obtained by subjecting the yarn to a first dyeing (impregnation, squeezing, oxidation) immediately followed by several over-dyeing operations, whose number increases proportionally to the greater darkness of the tones and as the required colour strength increases.

[0006] This particular dyeing method, typical of the indigo dye, greatly shows the importance of complying with determined basic parameters regarding the yarn submersion and oxidation times. This so as to allow the dye to impregnate and be uniformly distributed in the cortical or superficial layer of the yarn (“ring dyeing”) and, after a perfect squeezing, to be fully oxidised before entering into the subsequent tank, so as to be able to “re-fix”, that is intensify the colour tone. The most important and qualifying operation of the entire denim textile production cycle therefore lies in the continuous dyeing, with the indigo dye, of the warp yarn chain, before the latter are placed in a loom for the production of the textile.

[0007] The continuous dyeing with the warp chains for denim textiles is carried out according to three systems, that is the conventional system, so-called “rope-dyeing”, which is the most common one, the so-called “slasher” or “open-width” system and the “loop” system, slasher, but with superimposed layers. “Loop” dyeing systems are shown, for example, in documents GB 1430154 A and FR 8027071 A, as well as in the Italian patent application n° 68953A / 80, filed in 1980.

[0008] Another dyeing system according to the prior art is disclosed, for example, in document US 2021 / 0189622 A in the name of the same applicant. Document US 2021 / 0189622 A discloses a dyeing plant according to the preamble of claim 1 .

[0009] After initial good reviews, the “loop” dyeing system over time revealed several operational and quality drawbacks, mainly due to the different tension of the various yarn layers, their imperfect superimposition, the difference in squeezing between the centre and the sides, etc. These drawbacks basically contributed to their decline, and therefore the production stop of the various plants.

[0010] It should be observed that the rope-dyeing system according to the present invention, which will be described hereinafter, has nothing in common with the “loop” dyeing system from all points of view, just like it does not reveal any of its drawbacks. As a matter of fact, the “loop” dyeing system operates in a slasher fashion with a mat of various yarn layers, with only one dyeing tank and with only one long loop, which incorporates the dyeing tank, the pretreatment tanks and the beams of raw yarn. Besides the function of overlapping various yarn layers, this long loop also carries out the function of air oxidiser for the dyed yarn.

[0011] The dyeing plant according to the present invention instead operates with the rope yarn, with one or more dyeing machines, preferably four, each complete with the relevant assembly of cylinders for the air oxidation of the dyed yarn. Furthermore, the dyed yarn ropes exiting from the latter dyeing machine, by means of a very short half-loop which overlies the dyeing machines alone, are returned back, to the inlet of the first dyeing machine, and they are not overlapped, but conveniently arranged adjacent to each other with the same number on the two sides (see figure 2) and / or at the centre of the incoming raw yarn ropes (see figure 3), so that they can be dyed again. Basically, with only four dyeing machines there can be obtained the eight classic dyeing operations like it happens in almost all dyeing lines currently in use.

[0012] Furthermore, it should be observed that this new, unprecedented, simple and brilliant operating concept, subject of the present patent application, as well as implemented as mentioned above, with appropriate adaptations, can also be applied to each single dyeing machine and / or particular treatment. Lastly, it should be observed that the three operating systems mentioned above, although differing substantially, however share the common trait of using the same dyeing method, essentially consisting of three operating steps which are repeated several times: impregnation of the yarn with the dye, squeezing to remove the excess dyeing bath and oxidation of the dye by exposing the dyed yarn to air.

[0013] Typically, and conventionally, in all the various systems, the dyeing of the warp chains for denim textiles with indigo is carried out continuously on lines consisting of dyeing machines with open tanks and at low temperature.

[0014] In detail, with regard to the dyeing system carried out by the plant according to the present invention, that is the rope-dyeing one, the conventional lines for the continuous dyeing with indigo sequentially normally consist of four pretreatment tanks, eight dyeing tanks and further four final treatment tanks. All these tanks are provided, at the exit of the yarn, with a squeezing assembly to remove excess dyeing bath, while the dyeing machines are also provided with cylinder assemblies exposed to air for the oxidation of the yarn.

[0015] It should be observed that in order to meet the new needs of the denim market, which requires production eco-sustainability and maximum operating flexibility, as well as to meet the increasingly changing and unpredictable fashion needs, the applicant designed a new machine for dyeing with indigo with two use methods, conventionally exposed to air and ecologically in inert environment, preferably under nitrogen. This new machine, shown in the document WO 2023 / 148587 A1 , can be used both in conventional “slasher” dyeing lines, and in “rope-dyeing” lines. In the indigo dyeing lines, the use of this new machine enables them to operate, not only conventionally exposed to air, but also innovatively ecologically, in inert environment, preferably under nitrogen, with several economic and ecological advantages. In inert environment, the indigo is fully and perfectly reduced chemically, and leuco is disintegrated into nanometric-sized particles, a condition which enables to fix indigo to the fibre more efficiently compared to the conventional system exposed to air. Therefore, this a machine which enables to obtain eco- friendly and cost-effective dyeing.

[0016] It should be observed that most of the rope-dyeing lines currently in use required a significant investment, given that these dyeing lines are large in size, with several planes, maximally structured and used for standardised large productions. As a matter of fact, these dyeing lines, designed for operating with twelve yarn ropes, increased to twenty-four, thirty-six or forty-eight yarn ropes, that is by two times, three times and four times the warp threads required to produce the denim textile, and therefore large and ultra-large in size, while the market increasingly requires widely diversified medium and small-size productions.

[0017] In the light of the of the problems mentioned above, it is clear that to all producers of denim who use the rope-dyeing system it would be extremely useful and beneficial to have a dyeing plant that is simple, economic and versatile which can confer greater operating flexibility thereto, so as to fully meet these new needs. Obviously, this new dyeing plant according to the present invention, both in the sampling version, for small-scale productions and / or medium-scale productions, should have maximum operating flexibility, that is to be able to dye conventionally exposed to air, as well as ecologically and cost-effectively, preferably under nitrogen, so as to be able to add to normal products several new, unique and inimitable items obtained cost-effectively and sustainably.

[0018] Due to the fact that it uses dual-purpose dyeing machines (operating both exposed to air, and in inert environment, preferably under nitrogen) like the ones shown in document WO 2023 / 148587 A1 mentioned above, the dyeing plant according to the present invention not only allows everything described above, with the relevant advantages, but also adds other advantages, determined by the simultaneous use of the unprecedented, simple and brilliant dual drawing-in, and therefore dual dyeing, operating system. Basically, the dyed yarn ropes, exiting from the latter dyeing machine, are returned back, to the inlet of the first dyeing machine, and preferably arranged adjacent to each other with the same number on the two sides (see figure 2) and / or in the middle (see figure 3) of the incoming raw yarn ropes, so as to be dyed a second time. Therefore, the dyeing machines and the relevant air oxidisers are wider than the pretreatment and post-treatment tanks.

[0019] This particular combination, that is combining the possibility of operating both exposed to air and in inert environment (preferably under nitrogen), together with the option of dyeing the yarn ropes twice, confers an unprecedented and extraordinary operating flexibility to this new dyeing plant. The latter is extrinsic due to the fact that, besides the classic eight air-dyeing operations and the relevant variables, normally carried out with low-concentration and low-temperature dyeing baths, there is also the option of carrying them out even innovatively and exclusively in inert environment, under the same conditions and even using dyeing baths with higher concentrations as well as at high temperature, or in just four dyeing machines with dyeing bath at higher concentration, both at low temperature and at high temperature. Compared to the conventional dyeing lines, the greater advantages of this unique combination, which can be obtained with various embodiments, can be summarised by way of example as follows: a) operating conventionally exposed to air:

[0020] - halving the number of dyeing tanks and the relevant oxidisers;

[0021] - halving the volume of the dyeing baths, chemicals, steam, etc.;

[0022] - halving the volume of the containers for preparing, recovering and storing the dyeing baths; b) operating innovatively in inert environment;

[0023] - further halving the volume of the dyeing baths, with drastic decrease in chemicals;

[0024] - eco-sustainable dyeing;

[0025] - significant decrease in production costs;

[0026] - eliminating the need for vaporisation to fix the reduction dyes, such as sulphurs, etc.;

[0027] - doubling the production range, with the possibility to provide, besides the classic ones, also new, unique and unprecedented items, which cannot be obtained and are inimitable on conventional dyeing lines; c) ergonomic, simple and cost-effective construction with the whole plant positioned on the ground; d) drastic decrease in the investment.

[0028] The dyeing parameters of the dyeing plant according to the present invention are wholly identical to those of the dyeing lines according to the prior art, while the method for constructing the same differs significantly. As a matter of fact, this dyeing plant uses half of the dyeing machines (usually four instead of eight), and it is obtained cost-effectively, simply and ergonomically with all components positioned on the ground.

[0029] In the light of the above, it is clear that being the only system that combines the operating dual purpose and dual dyeing, that is tradition and the future, the dyeing plant according to the present invention can be considered as the state-of- the-art of continuous dyeing with indigo for warp chains for denim, in the rope-dyeing system. The dyeing plant according to the present invention is the answer to the new creative, eco-friendly and cost-effective production needs, maximum flexibility, versatility as well as management cost-effectiveness and environmental sustainability.

[0030] Therefore, an object of the present invention is to provide a dual operating mode plant and dual rope-dyeing of yarns that is capable of overcoming the prior art drawbacks mentioned above in an extremely simple, cost-effective and particularly functional manner.

[0031] In detail, an object of the present invention is to provide an indigo dyeing plant provided with one or more dyeing machines which, without changing the drawing-in of the yarn, can operate in dual mode of use, that is conventional exposed to air and ecological in inert environment, as well as for dual dyeing with indigo, with the conventional multi-step method, it also being potentially used as a component of the dyeing systems operating discontinuously and / or in the continuous lines in the rope system.

[0032] Another object of the present invention is to provide a dyeing plant provided with one or more dyeing machines which can be used in continuous indigo dyeing methods, with the conventional multi-step method, so that these dyeing methods can be carried out with full dyeing bath volume according to the conventional method, that is in contact with air, and also alternatively, with reduced dyeing bath volume, in inert environment.

[0033] Another object of the present invention is to provide a dyeing plant provided with one or more dyeing machines that is capable of operating in inert environment, therefore enabling to significantly reduce the indigo dyeing bath volume and as a result the consumption of sodium hydrosulphites and caustic soda.

[0034] Another object of the present invention is to provide a dyeing plant provided with one or more dyeing machines which, for dyeing with indigo and reduction dyes for warp chains for denim textiles, can use in cost-effective and advantageous conditions both a system for cooling the dyeing bath, whose maximum affinity stands at about 15°C, and one or more ultrasonic generators so as to further increase the colour yield.

[0035] Another object of the present invention is to provide a dyeing plant provided with one or more dyeing machines that can operate so as to increase the current potential operating variables.

[0036] A further object of the present invention is to provide a dyeing plant provided with one or more dyeing machines which, for dyeing with indigo and other reduction dyes, enables to increase the degree of fixation of the dye to the fibre, reducing the consumption of washing water, so as to contribute to environmental sustainability.

[0037] Still another object of the present invention is to provide a dyeing plant provided with one or more dyeing machines which allows indigo dyeing in technologically more excellent conditions, and which allows to increase the diffusion and fixation of the dye to the fibre.

[0038] These objects according to the present invention are achieved by providing a dyeing plant provided with one or more dyeing machines, with two operating modes and for the dual dyeing of the yarns, as disclosed in claim 1 .

[0039] Further features of the invention are outlined by the dependent claims, which are an integral part of the present description.

[0040] As a matter of fact, the dyeing plant according to the present invention, with dual operating mode and dual continuous and / or discontinuous dyeing enables to operate, besides with conventional multi-step indigo dyeing technology carried out in contact with air, also in a simple and rational manner with the new ecological dyeing in inert environment, with all the relative benefits and advantages, described in document WO 2023 / 148587 A1 . Depending on the needs, this dual operating dyeing and dual-dye plant, without change in the drawing-in of the yarn, may alternatively operate with the air technology or with the inert environment technology, cost-effective and ecological method, thus combining the different flexibilities of the two operating systems and enabling to obtain a new wide range of different, particular and unprecedented inimitable clothing items, on conventional dyeing lines.

[0041] The dyeing plant according to the present invention, is unique, original and brilliant in its simplicity. Its construction, with all the components positioned on the ground, also makes it not only ergonomic, but also significantly cost-effective. It can also be used in a particular and unprecedented manner, besides for conventional dyeing exposed to air, also for dyeing in inert environment (preferably under nitrogen), that is with the ecological and cost-effective dyeing system of the future. Its dual-purpose operating mode also adds the unique and unprecedented dyeing in inert environment (preferably under nitrogen) to the almost hundred-year tradition of multi-step rope-dyeing, with indigo, exposed to air.

[0042] The features and advantages of the dyeing plant according to the present invention will be more apparent from the following exemplifying and non-limiting description, with reference to the attached schematic drawings, wherein: figure 1 is a lateral raised view of a preferred embodiment of the dyeing plant according to the present invention; figure 2 is a top schematic view of the dyeing plant of figure 1 , shown in the operative configuration with twelve yarn ropes entering into the plant, which are arranged adjacent to each other with the same number on the two sides of these twelve yarn ropes after their return pathway; figure 3 is another top schematic view of the dyeing plant of figure 1 , still shown in the operative configuration with twelve yarn ropes entering into the plant, but which are arranged at the centre of these twelve yarn ropes after their return pathway; figure 4 is a perspective schematic view which shows the drawing-in of the yarn ropes, there are six of them in this case, only in the delivery pathway of the dyeing plant of figure 1 ; and figure 5 is another perspective schematic view which shows the drawing-in of the yarn ropes, still six of them, both in the delivery pathway and in the return pathway of the dyeing plant of figure 1 , in an operative configuration similar to that of figure 2.

[0043] It should be observed that the description below and the attached drawings do not show, given that they are well-known to a person skilled in the art, numerous components, accessories and instruments with which most dyeing plants are normally provided, such as for example dyeing bath lever regulators, thermoregulation assemblies, containers for preparing, recovering dyeing baths and supplying auxiliary products, automated metering systems, command and control instruments, etc.

[0044] With reference to the figures, there is shown a preferred embodiment of the dual operating mode plant and dual rope-dyeing of yarns according to the present invention. The dyeing plant is indicated in its entirety with the reference numeral 10.

[0045] The dyeing plant 10 is designed to carry out the dyeing of a plurality of yarn ropes 100 that are continuous and in motion. The dyeing plant 10 comprises at least one dyeing machine 12A, 12B, 12C, 12D which in turn comprises at least one side wall 14, which is substantially vertical, and which fully surrounds each dyeing machine 12A, 12B, 12C, 12D, so as to at least partially enclose a dyeing tank 16 of each dyeing machine 12A, 12B, 12C, 12D.

[0046] Each dyeing tank 16 is at least partially filled with a dyeing bath for the yarn ropes 100. This dyeing bath for the yarn ropes 100 preferably consists of a dyeing bath based on indigo and / or other reduction dyes.

[0047] The dyeing tank 16 of each dyeing machine 12A, 12B, 12C, 12D further comprises at least one bottom wall 18, which has a preferably convex outer surface, and at least one upper lid 20, which is movably and / or removably fitted above the side wall 14 of the respective dyeing machine 12A, 12B, 12C, 12D. Each upper lid 20 forms a perimeter system for the water-tight sealing of the respective dyeing tank 16 so that, when the dyeing tank 16 is water-tight sealed, this dyeing tank 16 may be at least partially filled with at least one process fluid additionally to the dyeing bath. This process fluid preferably consists of an inert gas which is designed to generate an inert environment in the dyeing tank 16. Even more preferably, this inert gas is nitrogen.

[0048] The presence of a respective movable and / or removable upper lid 20 on each dyeing machine 12A, 12B, 12C, 12D therefore allows such dyeing machine 12A, 12B, 12C, 12D to operate according to two operating modes. When the upper lid 20 is open or removed, the conventional dyeing mode exposed to air can be carried out in the dyeing tank 16. It should be observed that the dyeing exposed to air may also be carried out with the upper lid 20 closed, but without using inert gas. On the other hand, instead, when the upper lid 20 is sealed in a water-tight manner, the dyeing mode in inert environment, preferably under nitrogen, can be carried out in the dyeing tank 16.

[0049] Each dyeing machine 12A, 12B, 12C, 12D further comprises a plurality of first return rollers 22 for the yarn ropes 100. These first return rollers 22, which, by way of non-limiting example, are six for each dyeing machine 12A, 12B, 12C, 12D shown in figure 1 , are at least partially positioned in the dyeing tank 16 and they are at least partially submerged in the dyeing bath. These first return rollers 22 are therefore designed to transfer the yarn ropes 100 from an inlet point 24 for the entry of the yarn ropes 100 in the at least one dyeing machine 12A, 12B, 12C, 12D to an outlet edge 26 for the exit of the yarn ropes 100 from such dyeing machine 12A, 12B, 12C, 12D. These first return rollers 22 are also designed to increase the drawing-in of the yarn ropes 100 into the dyeing tank 16.

[0050] Each dyeing tank 12A, 12B, 12C, 12D may lastly comprise other equipment of the known type, such as for example one or more partitioning elements in the dyeing tank 16, one or more hydraulic circuits for supplying and discharging the dyeing bath, one or more hydraulic circuits for supplying and draining the process fluid (inert gas, preferably nitrogen), means for thermoregulating the fluids contained in the dyeing tank 16, one or more ultrasonic generators designed to increase colour yield, etc. All these equipment are shown, for example, in document WO 2023 / 148587 A1 in the name of the same applicant.

[0051] Downstream of the outlet edge 26 of each dyeing machine 12A, 12B, 12C, 12D there is positioned at least one squeezing device 28 for squeezing the yarn ropes 100. This squeezing device 28, preferably of the opposite cylinder type (so- called “foulard”), is configured to remove the excess dyeing bath from the yarn ropes 100.

[0052] Downstream of each squeezing device 28 there is provided for at least one oxidation pathway 30A, 30B, 30C, 30D for oxidizing in an atmospheric environment the yarn ropes 100. The oxidation pathway 30A, 30B, 30C, 30D comprises at least one second return roller 32 which is designed to increase the drawing-in of the yarn ropes 100 in the atmospheric environment. In this manner, between the inlet 24 for the entry of the yarn ropes 100 into the dyeing machine 12A, 12B, 12C, 12D and a first outlet point 34 for the exit of the yarn ropes 100 from the at least one oxidation pathway 30A, 30B, 30C, 30D there is obtained at least one first dyeing / oxidation pathway 36 (figure 2) or 36A, 36B (figure 3) for dyeing / oxidizing the yarn ropes 100, which also comprises the oxidation pathway 30A, 30B, 30C, 30D.

[0053] Between the first outlet point 34 for the exit of the yarn ropes 100 from the at least one oxidation pathway 30A, 30B, 30C, 30D and the inlet point 24 for the entry of the yarn ropes 100 in the at least one dyeing machine 12A, 12B, 12C, 12D there is obtained at least one return pathway 38A, 38B for the return of the yarn ropes 100 towards the aforementioned inlet point 24 for the entry of the yarn ropes 100 in the at least one dyeing machine 12A, 12B, 12C, 12D. This return pathway 38A, 38B for the return of the yarn ropes 100 comprises at least one third return roller 40 for the yarn ropes 100. According to the invention, at least part of this return pathway 38A, 38B for the return of the yarn ropes 100 overlies the at least one dyeing machine 12A, 12B, 12C, 12D and the at least one oxidation pathway 30A, 30B, 30C, 30D at a predefined height H from the ground, which may be only slightly greater than the maximum height from the ground of the at least one dyeing machine 12A, 12B, 12C, 12D and of the at least one oxidation pathway 30A, 30B, 30C.

[0054] Thanks to the return pathway 38A, 38B for the return of the yarn ropes 100, there can be obtained, between the inlet point 24 for the entry of the yarn ropes 100 into the at least one dyeing machine 12A, 12B, 12C, 12D and the first outlet point 34 for the exit of the yarn ropes 100 from the at least one oxidation pathway 30A, 30B, 30C, 30D, a second dyeing / oxidation pathway 42A, 42B for dyeing / oxidising the yarn ropes 100, which also comprises the oxidation pathway 30A, 30B, 30C, 30D. Advantageously, this second dyeing / oxidation pathway 42A, 42B for the yarn ropes 100 is parallel and coplanar to the first dyeing / oxidation pathway 36, 36A, 36B for the yarn ropes 100, so as to avoid any overlapping of the yarn ropes 100 both in the at least one dyeing tank 16 and at the at least one oxidation pathway 30A, 30B, 30C, 30D.

[0055] Preferably, the plurality of yarn ropes 100 entering into the dyeing plant 10 comprises a multiple number of two of yarn ropes 100 or, in other words, an even number of yarn ropes 100. The return pathway 38A, 38B for the return of the yarn ropes 100 may therefore comprise a first return pathway 38A and a second return pathway 38B (see figures 2 e 3) which are parallel and coplanar to each other. The first return pathway 38A and the second return pathway 38B are designed to respectively move a first half and a second half of the multiple number of two of yarn ropes 100.

[0056] As a result, at the inlet point 24 for the entry of the yarn ropes 100 into the at least one dyeing machine 12A, 12B, 12C, 12D, the first return pathway 38A and the second return pathway 38B are respectively transformed into a first half 42A of the second dyeing / oxidation pathway for the yarn ropes 100 and in a second half 42B of the second dyeing / oxidation pathway for the yarn ropes 100, which are parallel and coplanar to each other and each of which comprise a first half and a second half of the multiple number of two of yarn ropes 100.

[0057] Preferably, in accordance with the conventional dyeing lines which typically operate with twelve, twenty-four, thirty-six or forty-eight yarn ropes, in the dual dyeing plant 10 according to the present invention the multiple number of two of yarn ropes 100 may be selected from the group consisting of:

[0058] - six yarn ropes 100;

[0059] - twelve yarn ropes 100; and

[0060] - twenty-four yarn ropes 100.

[0061] Despite all return rollers 32 of the at least one oxidation pathway 30A, 30B, 30C, 30D having been positioned on the ground where the oxidation of the dyed yarn is carried out, the dual dyeing plant 10 according to the present invention has the same length, measured in the advancement direction of the yarn ropes 100, as the conventional dyeing lines. Obviously, depending on the production needs, the number of yarn ropes 100 entering into the dyeing plant 10 may vary without departing from the scope of protection of the present invention.

[0062] With reference to the operative configuration of figure 2, the dyeing plant 10 may comprise a single first dyeing / oxidation pathway 36 for the yarn ropes 100. As a result, the first return pathway 38A and the second return pathway 38B are respectively arranged, in a parallel and coplanar fashion, on the two outer sides of this single first dyeing / oxidation pathway 36 for the yarn ropes 100.

[0063] On the other hand, with reference to the operative configuration of figure 3, the first dyeing / oxidation pathway of the dyeing plant 10 may comprise a first half 36A of the first dyeing / oxidation pathway for the yarn ropes 100 and a second half 36B of the first dyeing / oxidation pathway for the yarn ropes 100, which are parallel and coplanar to each other and each of which comprises a first half and a second half of the multiple number of two of yarn ropes 100. As a result, the first return pathway 38A and the second return pathway 38B arranged adjacent to each other, in a parallel and coplanar fashion, in the middle between the first half 36A of the dyeing / oxidation pathway for the yarn ropes 100 and the second half 36B of the dyeing / oxidation pathway for the yarn ropes 100.

[0064] Once the yarn ropes 100 have been dual-dyed, these yarn dyed ropes 100 may exit from the dyeing plant 10 through a second outlet point 46 (figure 1 ). The dyeing plant 10 may therefore comprise diverter means 44 which are arranged at the first outlet point 34 for the exit of the yarn ropes 100 from the oxidation pathway 30A, 30B, 30C, 30D. The diverter means 44 are designed to selectively divert:

[0065] - towards the return pathway 38A, 38B for the return of the yarn ropes 100 the yarn ropes 100 that have only traversed only the first dyeing / oxidation pathway 36, 36A, 36B for the yarn ropes 100 (that is the yarn ropes 100 that have been subjected only to one dyeing step); and

[0066] - towards the second outlet point 46 for the exit of the yarn ropes 100 from the dyeing plant 10 the yarn ropes 100 that have sequentially traversed the first dyeing / oxidation pathway 36, 36A, 36B for the yarn ropes 100, the return pathway 38A, 38B for the return of the yarn ropes 100, the second dyeing / oxidation pathway 42A, 42B for the yarn ropes 100 (that is the yarn ropes 100 both of which have been subjected to dyeing steps and are therefore ready to undergo the posttreatment operations subsequent to the dyeing).

[0067] Preferably, the dyeing plant 10 according to the present invention comprises four dyeing assemblies that are arranged sequentially, in which each dyeing assembly comprises a respective dyeing machine 12A, 12B, 12C, 12D and a respective oxidation pathway 30A, 30B, 30C, 30D. The inlet point 24 for the entry of the yarn ropes 100 is therefore arranged upstream of the first dyeing machine 12A, that is the machine part of the first dyeing assembly. As a result, the first outlet point 34 for the exit of the yarn ropes 100 is arranged downstream of the fourth oxidation pathway 30D, that is the oxidation pathway part of the fourth dyeing assembly. In this manner, the first dyeing / oxidation pathway 36, 36A, 36B for the yarn ropes 100, the second dyeing / oxidation pathway 42A, 42B for the yarn ropes 100 fully traverse all four dyeing assemblies. At least part of the return pathway 38A, 38B for the return of the yarn ropes 100 therefore overlies, still at the same predefined height H from the ground, all four dyeing assemblies.

[0068] Downstream of one of the first three dyeing assemblies, but in any case, upstream of the fourth dyeing assembly and thereof of the first outlet point 34 for the exit of the yarn ropes 100 from the fourth oxidation pathway 30D, there is provided for at least one bypass pathway 48 which joins said first dyeing / oxidation pathway 36, 36A, 36B the yarn ropes 100 with the return pathway 38A, 38B for the return of the yarn ropes 100. This bypass pathway 48, which actually shortens the length of the return pathway 38A, 38B for the return of the yarn ropes 100, is provided with at least one own return roller 50 and it is useful even when one intends to over-dye the yarn ropes 100 with black sulphur dye in inert environment. With this operative configuration, using the bypass pathway 48 arranged downstream of the third dyeing assembly, there can be obtained six dyeing operations with the dyeing bath (indigo) plus the dyeing with black sulphur dye.

[0069] It is therefore clear that the indigo dyeing plant according to the present invention, with dyeing machines with dual operating mode and with dual rope-dyeing of yarns, attains the objects outlined above.

[0070] The dyeing plant as conceived is in any case susceptible to various modifications and variants, all falling within the scope of protection of the attached claims; furthermore, all details can be replaced by technically equivalent elements. Basically, the materials used as well as the shapes and dimensions may vary according to the technical needs.

[0071] Therefore, the scope of protection of the invention is defined by the attached claims.

Claims

CLAIMS1. A dyeing plant (10) for dyeing a plurality of yarn ropes (100) that are continuous and in motion, the dyeing plant (10) comprising at least one dyeing machine (12A, 12B, 12C, 12D), wherein each dyeing machine (12A, 12B, 12C, 12D) in turn comprises:- at least one side wall (14), which is vertical and which fully surrounds each dyeing machine (12A, 12B, 12C, 12D), so as to at least partially enclose a dyeing tank (16) of each dyeing machine (12A, 12B, 12C, 12D), wherein said dyeing tank (16) is at least partially filled with a dyeing bath for dyeing yarn ropes (100);- at least one bottom wall (18) of said dyeing tank (16), which has a preferably convex outer surface;- at least one upper lid (20), which is movably and / or removably fitted above said side wall (14), forming a perimeter system for the water-tight sealing of said dyeing tank (16) so that, when said dyeing tank (16) is water-tight sealed, said dyeing tank (16) is at least partially filled with at least one process fluid additionally to the dyeing bath;- a plurality of first return rollers (22) for the yarn ropes (100), wherein said first return rollers (22) are at least partially positioned in said dyeing tank (16) and they are at least partially submerged in the dyeing bath, wherein said first return rollers (22) are designed to transfer the yarn ropes (100) from an inlet point (24) for the entry of the yarn ropes (100) into said at least one dyeing machine (12A, 12B, 12C, 12D) to an outlet edge (26) for the exit of the yarn ropes (100) from said at least one dyeing machine (12A, 12B, 12C, 12D), and wherein said first return rollers (22) are designed to increase the drawing-in of the yarn ropes (100) into said dyeing tank (16); and- at least one squeezing device (28) for squeezing the yarn ropes (100), wherein said squeezing device (28) is positioned downstream of the outlet edge (26) of the yarn ropes (100) from said at least one dyeing machine (12A, 12B, 12C, 12D) and it is configured remove the excess dyeing bath from the yarn ropes (100), the dyeing plant (10) further comprising, downstream of said at least one squeezing device (28), at least one oxidation pathway (30A, 30B, 30C, 30D) for oxidizing in an atmospheric environment the yarn ropes (100), wherein said at least one oxidation pathway (30A, 30B, 30C, 30D) comprises at least one second return roller (32)which is designed to increase the drawing-in of the yarn ropes (100) in the atmospheric environment, so that between the inlet point (24) for the entry of the yarn ropes (100) into said at least one dyeing machine (12A, 12B, 12C, 12D) and a first outlet point (34) for the exit of the yarn ropes (100) from said at least one oxidation pathway (30A, 30B, 30C, 30D) there is obtained at least one first dyeing / oxidation pathway (36; 36A, 36B) for dyeing / oxidizing the yarn ropes (100), which also comprises said at least one oxidation pathway (30A, 30B, 30C, 30D), wherein between said first outlet point (34) for the exit of the yarn ropes (100) from said at least one oxidation pathway (30A, 30B, 30C, 30D) and the inlet point (24) for the entry of the yarn ropes (100) into said at least one dyeing machine (12A, 12B, 12C, 12D) there is obtained at least one return pathway (38A, 38B) for the return of the yarn ropes (100) towards the inlet point (24) for the entry of the yarn ropes (100) into said at least one dyeing machine (12A, 12B, 12C, 12D), and wherein said return pathway (38A, 38B) for the return of the yarn ropes (100) comprises at least one third return roller (40) for the yarn ropes (100), the dyeing plant (10) being characterized in that at least part of said return pathway (38A, 38B) for the return of the yarn ropes (100) overlies said at least one dyeing machine (12A, 12B, 12C, 12D) and said at least one oxidation pathway (30A, 30B, 30C, 30D) at a predefined height (H) from the ground, and in that between the inlet point (24) for the entry of the yarn ropes (100) in said at least one dyeing machine (12A, 12B, 12C, 12D) and said first outlet point (34) for the exit of the yarn ropes (100) from said at least one oxidation pathway (30A, 30B, 30C, 30D) there is obtained at least one second dyeing / oxidation pathway (42A, 42B) for dyeing / oxidising the yarn ropes (100), which also comprises said at least one oxidation pathway (30A, 30B, 30C, 30D), wherein said second dyeing / oxidation pathway (42A, 42B) for the yarn ropes (100) is parallel and coplanar with respect to said first dyeing / oxidation pathway (36; 36A, 36B) for the yarn ropes (100), so as to avoid any overlapping of the yarn ropes (100) both inside said dyeing tank (16), and at said at least one oxidation pathway (30A, 30B, 30C, 30D).

2. The dyeing plant (10) according to claim 1 , characterized in that said plurality of yarn ropes (100) comprises a multiple number of two of yarn ropes (100), and in that said return pathway (38A, 38B) for the return of the yarn ropes (100) comprises a first return pathway (38A) and a second return pathway (38B) which are paralleland coplanar to each other, wherein said first return pathway (38A) and said second return pathway (38B) are designed to move respectively a first half and a second half of said multiple number of two of yarn ropes (100), and wherein said first return pathway (38A) and said second return pathway (38B) are respectively transformed into a first half (42A) of the second dyeing / oxidation pathway for the yarn ropes (100) and in a second half (42B) of the second dyeing / oxidation pathway for the yarn ropes (100), which are parallel and coplanar to each other and each of which comprise a first half and a second half of said multiple number of two of yarn ropes (100).

3. The dyeing plant (10) according to claim 2, characterized in that said multiple number of two of yarn ropes (100) is selected from the group consisting of:- six yarn ropes (100);- twelve yarn ropes (100); and- twenty-four yarn ropes (100).

4. The dyeing plant (10) according to claim 2 or 3, characterized in that it comprises a single first dyeing / oxidation pathway (36) for the yarn ropes (100), wherein said first return pathway (38A) and said second return pathway (38B) are respectively arranged, in a parallel and coplanar fashion, on the two outer sides of said single first dyeing / oxidation pathway (36) the yarn ropes (100).

5. The dyeing plant (10) according to claim 2 or 3, characterized in that said first dyeing / oxidation pathway comprises a first half (36A) of the first dyeing / oxidation pathway for the yarn ropes (100) and a second half (36B) of the first dyeing / oxidation pathway for the yarn ropes (100), which are parallel and coplanar to each other and each of which comprise a first half and a second half of said multiple number of two of yarn ropes (100), wherein said first return pathway (38A) and said second return pathway (38B) are arranged adjacent to each other, in a parallel and coplanar fashion, in the middle between said first half (36A) of the dyeing / oxidation pathway for the yarn ropes (100) and said second half (36B) of the dyeing / oxidation pathway for the yarn ropes (100).

6. The dyeing plant (10) according to any one of claims 1 to 5, characterized in that it comprises diverter means (44) which are arranged at said first outlet point (34) for the exit of the yarn ropes (100) from said at least one oxidation pathway (30A, 30B, 30C, 30D) and which are designed to selectively divert:- towards said return pathway (38A, 38B) for the return of the yarn ropes (100) the yarn ropes (100) that have only traversed said first dyeing / oxidation pathway (36; 36A, 36B) for the yarn ropes (100); and- towards a second outlet point (46) for the exit of the yarn ropes (100) from the dyeing plant (10) the yarn ropes (100) which have sequentially traversed said first dyeing / oxidation pathway (36; 36A, 36B) for the yarn ropes (100), said return pathway (38A, 38B) for the return of the yarn ropes (100), and said second dyeing / oxidation pathway (42A, 42B) for the yarn ropes (100).

7. The dyeing plant (10) according to any one of claims 1 to 6, characterized in that it comprises four dyeing assemblies arranged sequentially, wherein each dyeing assembly comprises a respective dyeing machine (12A, 12B, 12C, 12D) and a respective oxidation pathway (30A, 30B, 30C, 30D), and wherein said inlet point (24) for the entry of the yarn ropes (100) is arranged upstream of the dyeing machine (12A) of the first dyeing assembly, while said first outlet point (34) for the exit of the yarn ropes (100) is arranged downstream of the oxidation pathway (30D) of the fourth dyeing assembly, so that both said first dyeing / oxidation pathway (36; 36A, 36B) for the yarn ropes (100), said second dyeing / oxidation pathway (42A, 42B) for the yarn ropes (100) fully traverse the four dyeing assemblies, and so that at least part of said return pathway (38A, 38B) for the return of the yarn ropes (100) overlies, always at the same predefined height (H) from the ground, the four dyeing assemblies.

8. The dyeing plant (10) according to claim 7, characterized in that downstream of one of the first three dyeing assemblies, but in any case upstream of the fourth dyeing assembly and thereof of said first outlet point (34) for the exit of the yarn ropes (100), there is provided for at least one bypass pathway (48) which joins said first dyeing / oxidation pathway (36; 36A, 36B) for the yarn ropes (100) with said return pathway (38A, 38B) for the return of the yarn ropes (100).

9. The dyeing plant (10) according to any one of claims 1 to 8, characterized in that said dyeing bath for dyeing the yarn ropes (100) consists of a dyeing bath based on indigo and / or other reduction dyes.

10. The dyeing plant (10) according to any one of claims 1 to 9, characterized in that said process fluid consists of an inert gas which is designed to generate an inert environment inside said dyeing tank (16).11 . The dyeing plant (10) according to claim 10, characterized in that said inert gas is nitrogen.

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