DYEING APPARATUS AND METHOD THEREFOR

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a continuous fabric-dyeing apparatus and

a method therefor, and, more particularly, to a continuous fabric-dyeing

apparatus for, and method of, dyeing bulky, three-dimensional fabrics and

narrow fabrics having a plurality of hard protrusions such as a trim tape, zip tape,

hook-and-loop fastener tape, and braided cords.

Various known machines for continuous dyeing of narrow fabrics rely on

a dip trough and roller squeezing mechanism, commonly referred to as a padding

machine, to control the amount of dye liquor deposited on the fabric (United

States Patent Nos. 5,050,258, 5,205,008, 4,878,365, and 3,995,457). The

padding machine may include single or multiple baths (United States Patent No.

4,997,453). Alternatives to squeeze rollers such as absorbent fiber webs, have

been taught (United States Patent 4,046,506). The impregnated fabric is then

subjected to dry or steam heating to fix the dye in the fibers of the fabric (United

States Patent 6,364,189). Alternative heating media have been taught such as

high boiling-point fluorocarbon liquids (United States Patent 3,958,934). The

fabric is then washed off to remove excess unfixed dyestuff. Various continuous

dyeing methods of impregnating-dipping, squeezing and thermally fixing are

also known.

When the fabric for dyeing is a three-dimensional fabric, a narrow fabric

having a plurality of hard protrusions, and the like, the above-referenced

machines for continuous dyeing are prone to producing an unevenly dyed

product, due to uneven pressure from the squeeze rollers. Additionally, such

machines may be subject to frequent deformation of the squeezing rollers, guides

and feed rollers because the protrusions on the fabric continuously gouge these

elements as the fabric traverses the machine.

There is therefore a recognized need for, and it would be highly

advantageous to have, a continuous fabric-dyeing apparatus for, and method of,

dyeing bulky, three-dimensional fabrics and narrow fabrics having a plurality of

hard protrusions, that produce an evenly dyed product. It would be of further

advantage if the apparatus and method would be simple, robust, and economical,

with respect to the known art.

SUMMARY OF THE INVENTION

The present invention is a continuous dyeing apparatus and method

therefor.

According to the teachings of the present invention there is provided a

dyeing apparatus for continuous dyeing of a fabric article with dye, the apparatus

including: (a) a dyeing vessel for containing therein a high-density liquid; (b) a

heating mechanism, thermally associated with the dyeing vessel, for heating a

dye fixation zone within the vessel to a temperature above 70 ⁰ C; (c) a continuous

transport mechanism for continuously transporting the fabric article, through a

dye impregnation chamber, and through the dye fixation zone of the dyeing

vessel, and (d) a dye-dispensing mechanism for delivering a dye liquor within

the dye impregnation chamber, so as to impregnate with the dye, the fabric

article passing through the chamber, wherein the dyeing vessel is dimensioned

and configured such that a height of the high-density liquid, when disposed in

the vessel, delivers a hydrostatic pressure of at least 0.1 bar gauge to the dye

fixation zone, so as to effect fixation of the dye in the fabric article.

According to further features in the described preferred embodiments, the

dyeing vessel includes at least a first upwardly directed member and a second

upwardly directed member for containing therein the high-density liquid, the first

upwardly directed member for allowing the transporting of the fabric article

downwards into the dye fixation zone, and the second upwardly directed member

for allowing the transporting of the fabric article upwards out of the dye fixation

zone.

According to still further features in the described preferred embodiments,

the dyeing vessel is further configured so as to fluidly communicate with an

ambient environment.

According to still further features in the described preferred embodiments,

the first upwardly directed member and second upwardly directed member are

associated so as to form a first U-tube.

According to still further features in the described preferred embodiments,

the U-tube is further configured so as to fluidly communicate with an ambient

environment.

According to still further features in the described preferred embodiments,

the dyeing vessel includes the first U-tube and at least a second U-tube, the first

and second U-tubes connected in series, the second U-tube having upwardly

directed members.

According to still further features in the described preferred embodiments,

the first and second U-tubes connected in the series are fluidly connected by an

inverted U-tube disposed therebetween.

According to still further features in the described preferred embodiments,

the dyeing vessel at least partially contains the dye impregnation chamber, such

that the dye liquor for the dye impregnation chamber is disposed above the high-

density liquid when disposed in the dyeing vessel.

According to still further features in the described preferred embodiments,

the transport mechanism includes at least one guide disposed within the dyeing

vessel, the guide being configured for guiding the fabric article within the dyeing

vessel.

According to still further features in the described preferred embodiments,

the guide is a rotating guide, the rotating guide being configured for guiding the

fabric article within the dye fixation zone within the dyeing vessel.

According to still further features in the described preferred embodiments,

the transport mechanism includes at least one rotating guide being configured for

guiding the fabric article around a curve in a bottom section of the first U-tube.

According to still further features in the described preferred embodiments,

the dye-dispensing mechanism includes a reservoir.

According to still further features in the described preferred embodiments,

the dyeing apparatus further includes: (e) at least one air jet, disposed with

respect to the dyeing vessel so as to deliver an air stream on the fabric article

after the article has been conveyed out of the dye fixation zone by the continuous

transport mechanism.

According to still further features in the described preferred embodiments,

the dyeing apparatus further includes: (e) at least one brushing mechanism

including a brush, disposed with respect to the dyeing vessel such that the brush

impinges on the fabric article after the article has been conveyed out of the dye

fixation zone by the continuous transport mechanism.

According to still further features in the described preferred embodiments,

the apparatus further includes the high-density liquid.

According to still further features in the described preferred embodiments,

the high-density liquid includes at least one molten metal.

According to another aspect of the present invention there is provided a

continuous method of dyeing a fabric article with dye, the method including the

steps of: (a) providing a dyeing apparatus including: (i) a dyeing vessel for

containing therein a high-density liquid; (ii) a heating mechanism, thermally

associated with the dyeing vessel, and (iii) a continuous transport mechanism for

continuously transporting the fabric article, through a dye impregnation chamber,

and through a dye fixation zone of the dyeing vessel; (b) impregnating the fabric

article with the dye in the dye impregnation chamber; (c) maintaining, within the

dye fixation zone, a hydrostatic pressure of at least 0.1 bar gauge using the high-

density liquid, and a temperature of at least 7O ⁰ C, using the heating mechanism,

and (d) passing the fabric article through the high-density liquid and into the dye

fixation zone so as to fixate the dye on the fabric article.

According to still further features in the described preferred embodiments,

the high-density liquid has a specific gravity above 6.

According to still further features in the described preferred embodiments,

the high-density liquid includes at least one liquid selected from the group

consisting of high molecular-weight polymer liquids and salt brines.

According to still further features in the described preferred embodiments,

the high-density liquid includes at least one molten metal.

According to still further features in the described preferred embodiments,

the fabric article is a tape.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference

to the accompanying drawings. With specific reference now to the drawings in

detail, it is stressed that the particulars shown are by way of example and for

purposes of illustrative discussion of the preferred embodiments of the present

invention only, and are presented in the cause of providing what is believed to be

the most useful and readily understood description of the principles and

conceptual aspects of the invention. In this regard, no attempt is made to show

structural details of the invention in more detail than is necessary for a

fundamental understanding of the invention, the description taken with the

drawings making apparent to those skilled in the art how the several forms of the

invention may be embodied in practice. Throughout the drawings, like-

referenced characters are used to designate like elements.

In the drawings:

FIG. 1 is a schematic cross-sectional representation of a continuous

dyeing apparatus according to a first embodiment of the present invention, and

FIG. 2 is a schematic cross-sectional representation of a continuous

dyeing apparatus according to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a continuous dyeing apparatus and method

therefor.

The principles and operation of the continuous dyeing apparatus and

method according to the present invention may be better understood with

reference to the drawings and the accompanying description.

Before explaining at least one embodiment of the invention in detail, it is

to be understood that the invention is not limited in its application to the details

of construction and the arrangement of the components set forth in the following

description or illustrated in the drawing. The invention is capable of other

embodiments or of being practiced or carried out in various ways. Also, it is to

be understood that the phraseology and terminology employed herein is for the

purpose of description and should not be regarded as limiting.

An object of the present invention is to provide a continuous dyeing

apparatus for controllably dyeing articles such as bulky and uneven narrow

fabric without entailing problems such as uneven dyeing of fabric and

deformation of the dyeing machine squeezing rollers and guide rollers.

To accomplish this object, the present invention provides a dyeing

apparatus having a dyeing vessel adapted to contain a high-density liquid heating

medium therein. The dyeing apparatus has a transport mechanism and rollers for

transporting the fabric article through the dyeing vessel. The penetration of the

dye substance into the fabric article is effected by subjecting the article to

superambient pressure and superambient temperature as the article is

continuously conveyed through the dyeing vessel.

A schematic cross-sectional representation of a continuous dyeing

apparatus 100 according to a first embodiment of the present invention is

provided in FIG. 1. Dyeing apparatus 100 preferably includes a dyeing vessel 1,

electrical coil heating members 2, a dye reservoir 5, a let-off device 6, a tape or

fabric 7 to be dyed, an air jet device 19 and/or a brushing device 9, guide rollers

10, a drying device ll,a frame 12, and a motorized transport device 14.

As will be elaborated hereinbelow, dyeing vessel 1 includes a dye liquor

impregnation zone 3, a zone containing a high-density liquid heating medium 4,

and a wash-off zone 8.

In the embodiment schematically provided in Figure 1, dyeing vessel 1 is

a vertically oriented, cylindrical "U"-shaped tube. Typically, dyeing vessel 1 has

a height of 150 centimeters and a diameter of 10 centimeters, and contains a

dense liquid for providing heat at 135°C. The liquid may contain bismuth, tin,

lead, indium or cadmium, or a combination thereof (e.g., Neylo® 158, obtained

from Ney Metals®, N. Y., N.Y.). The tape to be dyed is continuously fed from a

package, box or reel 22 into dye liquor impregnation zone 3. Preferably, dye

liquor impregnation zone 3, is situated within the tube of dyeing vessel 1, above

high-density liquid heating medium 4. Alternatively, dye liquor impregnation

zone 3 may be disposed outside of the U-tube.

Fresh dye liquor stored within dye reservoir 5 is continuously or

intermittently fed to the impregnation zone 3 so as to maintain a substantially

constant amount of dye therein.

When motorized transport device 14 is operated, tape 7, which is engaged

by transport device 14, is conveyed through the tube of dyeing vessel 1. After

being impregnated with dyestuff in impregnation zone 3, tape 7 passes through

high-density liquid heating medium 4. As tape 7 proceeds downwards, the

hydrostatic pressure in the tube of dyeing vessel 1 gradually increases. Electrical

coil heating members 2, disposed around the tube of dyeing vessel 1, supply heat

so as to attain the requisite temperature. Depending on the particular application,

the requisite temperature is at least 60 ⁰ C, and more typically 130 ⁰ C, and up to at

least 200 ⁰ C.

Similarly, for a given high-density liquid, the height of the liquid

determines the hydrostatic pressure in the tube. Thus, the height of the liquid can

be adjusted to attain the requisite pressure for a given application. Preferably,

the requisite pressure is above 0.1 bar, more preferably, above 1 bar, and most

preferably, from 1 bar to 6 bar.

As used herein in the specification and in the claims section that follows,

the term for the units of pressure, "bar" values are gauge values.

The bottom of the tube of dyeing vessel 1 is preferably curved, so as to

facilitate the movement of tape 7 therethrough. The movement of tape 7 is

further facilitated by tape guides disposed within the tube. In an exemplary

embodiment provided in Figure 1, the tape guides (rotating guides or bearings

13) are disposed within the U-tube of dyeing vessel I ₅ near the inner curve of the

U-tube, such that tape 7 passes between rotating guides 13 and the outer curve of

the U-tube. Rotating guides 13 serve, inter alia, to guide tape 7 while reducing

frictional forces and preventing tearing of tape 7 and/or damage to the dyeing

process.

After passing around rotating guides 13, tape 7 proceeds upwards through

high-density liquid heating medium 4, and subsequently, through wash-off zone

8. After emerging from the tube, tape 7 passes through air jet device 19 and

brushing device 9, where the cleaning operation is completed. Subsequently,

tape 7 is dried as it passes through a drying device 11, before tape 7 is collected

in/on a package, box or reel 24.

Dyeing vessel 1 is advantageously disposed in a housing 12, which may

also include drying device 11. Although housing 12 may also contain dye

reservoir 5, it is usually preferable to situate dye reservoir 5 outside of housing

12, so as to facilitate the introduction of additional dye material to reservoir 5.

It will be apparent to one skilled in the art that various mechanical

elements, such as a let-off element 6, and guide rollers 10, may be

advantageously employed in conveying tape 7 through continuous dyeing

apparatus 100.

Although high-density liquid heating medium 4 preferably includes

molten metals, as described hereinabove, other high-density liquids may be

suitable, provided that the liquids engender and maintain the requisite pressure

range (and 0.1 bar to 6 bar) and temperature range (60 ⁰ C to 200 ⁰ C) for a

particular dyeing application. Thus, in another preferred embodiment of the

present invention, liquid heating medium 4 includes at least one high-density salt

brine (e.g., zinc bromide, calcium bromide, or potassium formate). In this case,

the lower specific gravity of the salt brine, with respect to the specific gravity of

a molten metal, necessitates a higher fluid level to achieve an identical pressure.

A schematic cross-sectional representation of a continuous dyeing

apparatus 200 according to a second embodiment of the present invention is

provided in FIG. 2. Dyeing apparatus 200 is largely similar to dyeing apparatus

100 of Figure 1, but the dyeing vessel includes two vertically oriented,

cylindrical, U-shaped tubes 201, 202 and an inverted U-shaped cylindrical tube

203 connecting therebetween. Inverted U-tube 203 normally becomes at least

partially filled with water vapor during the course of operation. Hence, inverted

U-tube 203 is advantageously equipped with a controlled pressure release valve

15, for stabilizing the pressure within the system.

Fabric or tape 7 to be dyed is continuously fed from a package, box or reel

22 into the dyeing vessel, and is subsequently removed from the dyeing vessel,

in a substantially identical method to that described with respect to Figure 1.

By controlling the speed of traverse, the temperature and height of the

liquid heating medium and the concentration and amount of dyestuff in the

impregnation zone, consistent and even dyeing is achieved.

Owing to the construction described above, it is possible to dye the article

in a continuous, controlled fashion. The apparatus is designed and operated such

that an even pressure is applied to all parts of the fabric. Consequently, an even

distribution of dyestuff is deposited over the entire fabric article. The pressures

and temperatures in the apparatus are predetermined so as to efficiently fix the

dyestuff to the article.

It must be emphasized that the present dyeing machine requires no

squeeze rollers, and relies on the hydrostatic pressure and thermal energy of the

high-density liquid heating medium to control the amount of the dyeing liquid

for impregnating in the fabric article. Advantageously, excess dyestuff floats to

the top of the high-density liquid so that little or no wash-off is required. The

hot liquid also facilitates dye fixation and drying of the article after the dyestuff

has penetrated the article.

In a preferred method of dyeing polyester tape to dark shades in the

above-described apparatus, disperse dyes (such as Terasil®, Ciba®, Switzerland)

are mixed in water containing up to 5% by weight of a dispersing agent (such as

IFCOSOL-DA LIQUID®, Molchemie®, India), up to 5% by weight leveling

agent (such as ESQUAL T-56 CONC®, Winimex®, Thailand) and up to 5% by

weight organic acid. The resulting dye liquor is introduced into the liquor

impregnation zone. The liquid heating medium is heated to 13O ⁰ C, and the

greige tape is traversed through the apparatus at 15 to 30 meters per minute.

As used herein in the specification and in the claims section that follows,

the term "high-density liquid" refers to a liquid having a specific gravity above 2,

preferably, above 4, more preferably, above 6, and most preferably, above 10.

Although the invention has been described in conjunction with specific

embodiments thereof, it is evident that many alternatives, modifications and

variations will be apparent to those skilled in the art. For example, although the

first embodiment illustrated in FIG. 1 employs a U-shaped vessel, any shape that

can contain the high-density heating medium liquid, allow transport of the

narrow fabrics therethrough, and engender the temperature/pressure regimen

described herein, is included. Moreover, while the U-shaped vessel typically has

a circular cross-section, other cross-sections such as oblong, triangular, square,

rectangular, multilateral or multi-lobed, could be used in the apparatus and

method of the present invention. More generally, the invention is intended to

embrace all such alternatives, modifications and variations that fall within the

spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this

specification are herein incorporated in their entirety by reference into the

specification, to the same extent as if each individual publication, patent or

patent application was specifically and individually indicated to be incorporated

herein by reference. In addition, citation or identification of any reference in this

application shall not be construed as an admission that such reference is available

as prior art to the present invention.