Washing system for washing fabric WEBS and related washing method

Abstract

Washing system (100) for washing fabric webs in continuous, open, or tubular mode including active ultrasonic generators (114, 115) arranged in a washing tank (111) so as to be at least partially submerged by the washing liquid and so as to generate ultrasonic sound waves directed in a consistent direction within the washing tank (111) against opposite sides of the fabric web as it passes through the washing liquid contained in the washing tank (111). The application also concerns a method for washing fabric webs in continuous, open, or tubular mode, implementable with the washing system (100) described above.

Description

[0001] WASHING SYSTEM FOR WASHING FABRIC WEBS AND RELATED

[0002] WASHING METHOD

[0003] TECHNICAL FIELD

[0004] The present invention relates to the washing of fabrics following their industrial

[0005] 5 weaving and printing processes, and more specifically to a system and a related method for washing fabrics in the manner known in the industry as "continuous", "open", or tubular, which respectively mean that fabric webs pass through a washing system from inlet to outlet completely stretched in the width direction.

[0006] BACKGROUND

[0007] 10 In industrial weaving processes, washing is necessary to remove impurities from raw or semi-finished fabrics, such as weaving residues, as well as chemicals such as caustic soda, and bleach. When removing weaving oils, the washing process is more intense and requires specific solvents, which is why it is generally referred to as "scouring".

[0008] Washing and scouring are generally performed before heat-setting treatments to prevent

[0009] 15 the oxidation of oil present on the fabric fibers and their consequent yellowing.

[0010] Prior art fabric washing systems comprise one or more washing units comprising tanks for washing and rinsing liquids. Rotating rollers or cylinders are mounted inside the washing units, defining a washing path for a web of fabric from an inlet to an outlet of the washing unit.

[0011] 20 Washing is performed with liquids such as mixtures of water with detergents, soaps, and / or solvents, such as limonene, or with water alone at temperatures between 20°C and 99°C. Fabric washing can be performed by immersion in washing liquids, typically first, in tanks containing mixtures of water with detergents, soaps, and / or solvents and then in tanks containing only water for rinsing, or by spraying using jets delivered by

[0012] 25 slotted spray bars and / or nozzles arranged along the washing path. Washing systems that, use combinations of immersion tanks and spray bars are also known.

[0013] The Italian patent 102013902142642 discloses a machine for continuously purging a fabric web, comprising a. washing tank for containing a. washing liquid and means for heating the liquid. The machine also comprises a plurality of rollers that define a

[0014] 30 washing path along which a fabric web is transported, and spraying means arranged along the washing path. The spraying means comprise first nozzles configured to emit 2 respective fan-shaped jets that cover a first face of the fabric web along its entire width without overlapping, as well as second nozzles arranged on the opposite side of the first nozzles with respect to the washing path, so as to emit, respective fan-shaped jets on a second face of the fabric web opposite the first face. Like the first nozzles, the second

[0015] 5 nozzles are also configured to emit fan-shaped jets that cover the second face of the fabric web along its entire width without overlapping.

[0016] The first and second nozzles are arranged to direct their respective fan jets onto the same area of the fabric web in transit, thus canceling the resultant of the forces directed perpendicularly to it without the use of support rollers.

[0017] 10 The Italian patent 102013902188808 describes a continuous and open-mode fabricwashing system comprising at least one treatment unit in which a plurality of cylinders are arranged that define a washing path from an inlet to an outlet. The treatment unit comprises first and second perforated handling surfaces configured to sandwich a fabric web to be treated between them. The handling surfaces are supported by a set of

[0018] 15 cylinders, forming a closed loop.

[0019] Similar to the Italian patent 102013902142642, the treatment unit also includes a plurality of first and second nozzles arranged along the entire washing path and facing the perforated conveyor surfaces to deliver washing fluids to the opposite sides of the sandwich-like fabric they transport. The washing fluids are delivered at pressures

[0020] 20 between 0.5 and 3 bar with flow rates between 20,000 and 40,000 liters / hour per linear meter of fabric in the width direction.

[0021] Thanks to the nozzle arrangement and the high pressures and flow rates of the washing fluids, it is possible to minimize the problems of stretching and creasing of the fabric along its washing path.

[0022] 25 Despite the availability of machines and methods for washing and scouring fabrics in continuous and open modes, there is still a need to improve washing processes and related equipment, both in terms of impurity removal efficiency and treatment speed. There is also a strong need to minimize the risk of fabric damage caused by the forces exerted by the relatively high-pressure washing fluids sprayed from the nozzles, while

[0023] 30 maintaining the same washing efficiency, as well as the need to further reduce the energy consumed to heat the washing fluid to a suitable temperature to effectively 3 remove oils and chemicals from the fabric webs to be washed.

[0024] SLMMARY

[0025] These objectives are at least partially achieved with a washing system for washing fabric webs in continuous, open, or tubular mode, as defined in the appended claims.

[0026] 5 The system allows for effective washing of fabric webs even by spraying washing liquid at reduced pressure and maintained at lower temperatures because it includes two active ultrasonic generators arranged in the washing tank so as to be at least partially submerged by the ^washing liquid and so as to generate ultrasonic waves directed in a. concordant direction within the washing tank against opposite sides of the fabric web as

[0027] 10 it passes through the washing liquid contained in the washing tank.

[0028] This disclosure also provides a method for washing fabric webs in continuous and open mode, implementable with the system described above, which involves washing or scouring fabric webs through the following operations:

[0029] Filling the washing tank with wash liquid so as to at least partially submerge the active

[0030] 15 ultrasonic generators of the system;

[0031] Dispensing jets of wash liquid toward opposite faces of a fabric web moving along the washing path of the system;

[0032] Generating ultrasonic sound waves directed in a concordant direction in the washing tank against both opposite faces of the fabric web moving while immersed in the wash

[0033] 20 liquid, contained in the washing tank.

[0034] Further embodiments are defined in the appended claims.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a side sectional view schematically showing a washing unit of the washing system according to the present disclosure.

[0037] 25 DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0038] With reference to the figure, a continuous and open-mode textile ^washing system is collectively designated by the reference numeral 100.

[0039] The washing system 100 comprises, in a known manner, at least one washing unit 110 containing two tanks arranged in sseernieess i inn a longitudinal working direction

[0040] 30 schematically indicated by an arrow L.

[0041] These tanks are, respectively, a washing tank 111 intended to contain a washing liquid, 4 such as a water and limonene solution, and a rinsing tank 1 12, intended to contain a rinsing liquid, such as water.

[0042] Figure 1 schematically shows the liquid levels in each tank in broken lines.

[0043] Inside the washing unit 110 there are also housed a plurality of cylinders 113 which

[0044] 5 rotate around their own axis and which together define a washing path for a fabric web F, which extends from an inlet 116 to an outlet 117 of the washing unit 110 itself.

[0045] In the illustrated embodiment, two sets of cylinders are shown, specifically four cylinders 113 arranged in correspondence with the washing tank 111 and four cylinders 113 arranged in correspondence with the rinsing tank 112.

[0046] 10 To allow the fabric web F to pass through the washing unit 110, at least some of the cylinders are motorized. Preferably, all the cylinders are motorized to minimize any rubbing problems with the fabric web in transit, which could cause unwanted stretching. As shown in Figure 1, with respect to a vertical direction V perpendicular to the longitudinal direction L, one cylinder of each set is arranged near the bottom of the

[0047] 15 respective tank. Therefore, in an operating condition of the system 100, it operates immersed, in the washing or rinsing liquid, while the other cylinders are spaced from it and are located outside the washing and rinsing liquid bath in an operating condition of the system. It will be understood that this configuration of the washing unit 110 allows, in a known manner, the washing of a fabric web by immersion in the tanks 111, 112. In

[0048] 20 other words, the arrangement of the cylinders is such that the washing path, shown schematically in broken lines, develops partly outside the tanks 111, 112 and partly inside them.

[0049] In the embodiment illustrated in the figures, two cylinders 113 are immersed in the washing liquid and designed to operate in the washing tank 111, allowing the path of the

[0050] 25 fabric web in immersion to be extended, leaving a space between the portion of fabric entering the washing tank 1 1 and the portion exiting therefrom.

[0051] The washing liquids fed into the tanks 111 and 112 are maintained at the desired temperature by means of special heating devices, such as coiled pipes 118 and 1 19. More generally, the temperature of the washing and rinsing liquids is determined by the

[0052] 30 type of detergents, soaps, and / or solvents used and the type of impurities to be removed. The washing and rinsing liquids are recirculated in the tanks 11 1 and 112 after 5 purification.

[0053] The system 100 also comprises a plurality of spraying means 120 arranged along the washing path in the sections above the tanks 111, 112, so that a fabric web F can be treated both by spraying and by immersion. The spraying means 120 comprise, in a

[0054] 5 known manner, a plurality of spray bars connected to the washing unit 110 transversely to the washing path, therefore having respective axes substantially parallel to those of the cylinders, and comprising respective nozzles, or alternatively slits, configured to direct the jets of liquid against the opposite faces of the fabric web.

[0055] The illustrated, washing unit is particularly suitable for washing or scouring thin,

[0056] 10 lightweight fabrics that are more easily damaged when high-pressure washing liquid is sprayed against them, because it comprises at least one active ultrasonic generator 114, 1 15, arranged in the washing tank 111 so as to be at least partially submerged by the washing liquid and so as to generate ultrasonic waves directed against at least one face of the fabric w'eb immersed in the washing liquid. As illustrated in the accompanying

[0057] 15 example figure 1 , the washing system comprises two active ultrasonic generators 1 14, 115, arranged in the washing tank 111 so as to be at least partially submerged by the washing liquid and so as to generate ultrasonic waves directed in a. consistent direction within the washing tank 111 against opposite faces of the fabric web immersed in the washing liquid.

[0058] 20 Tests conducted, by the Applicant have shown that when the washing nozzles 120 spray liquid at relatively low pressure, they have a primarily superficial effect, meaning that to thoroughly clean the fabric, it is necessary to increase the pressure of the liquid. In particular, fabrics such as cotton and Lycra, cotton and polyester fabrics, as well as nonwoven fabrics, tend to deeply absorb products that must be removed by washing or

[0059] 25 scouring. Consequently, these fabrics can currently be effectively cleaned, only by spraying the washing liquid at relatively high pressure and maintaining the washing liquid in the washing tank 111 at a temperature of approximately 90°C. Thanks to the washing system of this disclosure, it is possible to reduce the pressure of the jets of washing liquid, limiting their effect to a substantially superficial cleaning action, while

[0060] 30 deep cleaning of the fabric is entrusted to the combined action of the two active ultrasonic generators 114, 1.15, immersed in the washing tank 111 and which generate 6 microbubbles that, when they collapse upon contact with the fabric, remove the dirt. Tests performed by the Applicant have shown that, to maximize the cleaning effect that the microbubbles generated by ultrasounds have on the fabric, it is important that, they are not generated simultaneously on both sides of the same portion of the fabric to be

[0061] 5 cleaned. When an ultrasonically generated microbubble collapses against one side of the fabric surface, a vacuum is created that sucks in any debris perpendicular to the fabric surface. If microbubbles are directed simultaneously at both sides of the fabric in opposite directions, debris attached to the fabric is removed less effectively because the microbubbles, which simultaneously collapse on opposite sides of the same portion of

[0062] 10 the fabric, create vacuums in opposite directions, thus at least partially compensating for each other. The end result is that debris attached to the fabric is subjected to a lower resulting vacuum than would be the case with a single active ultrasonic generator. For this reason, the system of the invention includes two active ultrasonic generators 114, 115 that generate ultrasonic waves in the same direction in the washing tank 11 1, so that

[0063] 15 this problem does not occur. Conversely, even if the ultrasonic waves generated by the active generator 114 were to pass through the fabric F and propagate in the liquid of the washing tank 111 , they would be added to the ultrasonic waves generated by the other active generator 115, further improving the cleaning of the fabric F. It is clear that this arrangement of the two active ultrasonic generators 114, 1 15 cleans both sides of the

[0064] 20 fabric F better than if the two active ultrasonic generators were oriented toward, each other to simultaneously generate ultrasonic waves in opposite directions against the same portion of the fabric.

[0065] An advantage of using this technique in combination with the nozzles 120 that spray wash water at a pressure is that in the system 100 of the present disclosure, the pressure

[0066] 25 of the sprayed wash water can be lowered to protect the fabrics from mechanical damages, while the ultrasonic cleaning, performed by immersion in the washing tank 111, allows for thorough cleaning of the fabric web. This synergistic action results in a clean fabric that, has been subjected to less mechanical stress than in known washing systems 100, in which thorough cleaning of the fabric is performed by relatively high-

[0067] 30 pressure washing water jets.

[0068] For ultrasonic cleaning, it is important to limit the maximum temperature of the washing 7 liquid to no more than 70°C, preferably between 60°C and 65°C, because ultrasound waves must create microbubbles by cavitation when they impact the fabric being cleaned, thus a. higher-temperature washing or scouring bath is not possible. This represents a further advantage because it allows the temperature of the washing liquid to

[0069] 5 be reduced, thus saving energy because it is no longer necessary to heat the washing liquid to a temperature between 85°C and 90°C, as is currently the case for certain fabrics, to effectively remove oil from the fabric web F.

[0070] .According to one aspect, the ultrasonic generators 114 and 1 15 are configured to generate ultrasound, waves at a frequency of no less than 20 kHz. Tests conducted by the

[0071] 10 Applicant have shown that excellent cleaning of the fabric web is achieved using ultrasound at a frequency between 30 kHz and 32 kHz.

[0072] According to one aspect, the two rollers or cylinders 113, at least partially submerged in the washing liquid, are arranged so that a first ultrasonic generator 115 is installed between the two immersed rollers or cylinders 113, and a second ultrasonic generator

[0073] 15 114 is installed so that the two immersed rollers or cylinders 113 are on the same side with respect to the second ultrasonic generator 114. As shown in the attached figure 1, the two ultrasonic generators 1 14, 115 are oriented so as to emit ultrasound waves in the same direction and thus impact two opposite faces of the fabric web F immersed in the washing liquid.

[0074] 20 The configuration with the two ultrasonic generators 114, 115 directed towards each other, towards opposite faces of the same portion of fabric F, is not preferred because the two generators could create destructive interference of the ultrasound waves, which would reduce the effectiveness of washing the fabric.

[0075] According to one aspect, the ultrasonic generators 114, 115 can be individually

[0076] 25 activated and deactivated so as to allow the user to configure the washing system 100 as desired, thus being able to carry out both a traditional washing with only the spray nozzles 120, and a washing that benefits from the synergistic action of the nozzles 120 which spray washing liquid at relatively low pressure and ultrasonic generators 1 14, 115 which carry out a deep cleaning of the fabric using washing liquid at a lower

[0077] 30 temperature.

Claims

8CLAIMS1. A washing system (100) for washing fabric webs in continuous, open or tubular mode, said system (100) comprising: i) at least one washing unit (110) inside which are housed a washing tank (111),5 intended to contain a washing liquid, and a rinsing tank (112) intended to contain a rinsing liquid, ii) a plurality of rollers or cylinders (113) arranged inside said washing unit (110) and configured to rotate around their own axis, said rollers or cylinders defining a washing path that goes from an inlet (116) to an outlet (117) of the washing unit (110), in which10 at least some of said rollers or cylinders are motorized, iii) a plurality of nozzles (120), or alternatively slits, suitable for delivering jets of washing liquid towards opposite faces of a fabric belt (F) in transit along the washing path, iv) a heating device (118) of said washing liquid, configured to heat the washing liquid15 in the washing tank (1 1 1); characterized in that said heating device (1 18) is adjustable to heat the washing liquid to an operating temperature established by a user; wherein said washing unit (110) includes two active ultrasound generators (114, 115)20 arranged in the washing tank (111) so as to be at least partially submerged by the washing liquid and so that the two active ultrasound generators generate ultrasound waves directed in a concordant direction inside the washing tank (111) against opposite faces of said fabric belt (F) in transit immersed in said washing liquid in the washing tank (111).25 2. The washing system according to the previous claim, comprising two rollers or cylinders of said plurality of rollers or cylinders (113) positioned in said washing tank (111) so as to be submerged by the washing liquid when the washing tank (111) is fdled, wherein a first active ultrasound generator (115) of said two active ultrasound generators is installed between said two rollers or cylinders (113) and a second active30 ultrasound generator (114) of said two active ultrasound generators is installed so that- said two rollers or cylinders (113) are on a same side with respect to the second active9 ultrasound generator (114).

3. The washing system according to one of the previous claims, wherein said nozzles or slots (120) are directed so as to spray said washing liquid before said fabric belt (F) in transit is immersed in the washing liquid of said washing tank (111).5 4. A method, of washing fabric webs in continuous, open or tubular mode, including: providing and installing a system (100) according to one of claims I to 3; filling said washing tank (111) with washing liquid so as to at least partially submerge said two active ultrasound generators (114, 115) of the system (100); dispensing jets of washing liquid or rinsing liquid towards opposite faces of a10 fabric belt (F) in transit along the washing path of said system (100); generating ultrasound waves directed in a concordant direction inside the washing tank (111) against opposite faces of said washing belt fabric (F) in transit immersed in said washing liquid in the washing tank (111).

5. The method according to claim 4, comprising the operation of generating ultrasound,15 by means of said at least one ultrasound generator (114, 115), at a frequency of not less than 20 kHz, preferably between 30 kHz and 32 kHz.

6. The method according to one of claims 4 to 5, comprising the operation of heating the washing liquid in the washing tank (111) to an operating temperature not exceeding 70°C.20

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