CA1245432A - Method and apparatus for drying tubular knitted fabric - Google Patents

Abstract

P2486.01 METHOD AND APPARATUS FOR DRYING TUBULAR KNITTED FABRIC
ABSTRACT OF THE DISCLOSURE
The disclosure relates to techniques for high efficiency drying of wet-processed tubular knitted fabric. The wet tubular fabric is initially spread to flat form and then guided in a controlled manner over a so-called Mach nozzle, at which high velocity gaseous medium, usually steam, at speeds approaching the speed of sound and above, is discharged directly through the fabric, which is maintained in tension as it passes over the nozzle outlet. The thus treated tubular knitted fabric, now with a greatly reduced liquid content, is then immediately directed over a second spreader device, which distends the fabric widthwise to a predetermined, uniform width, to restore the fabric width lost during wet processing and during the relatively high tension nozzle treating operation. In this damp, geometrically stabilized condition, the fabric may be directed immediately into an otherwise conventional tensionless dryer for tubular knitted fabric, where the necessary final drying operations are completed. More typically, the fabric is loosely folded and then dried later. Significant production economies are realized pursuant to the invention, both in energy savings and labor savings, as well as reduction in capital equipment costs. The process also makes wet-on-wet foam processing relatively attractive for certain tubular knitted farics.

Description

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M13THOD AND APPARATU~ ~FOR DRnE~G TUBI~LA:R KNIrl~D ~ABRIC
Tubul~r knitted fabric typically is manufactured on circular knitting machines in semi~ontinuous lengths of tubular fabric. In most cases, the tubular fabric is processed through finishing and even cutting while retained in tubular form. Typically, such processing includes a number of wet processing stages, such as washing, bleaching~ sometimes dyeing, etc. At the end of this wet processing stage, the fabric is dried and prepared for finishing.
In a typical conventional wet processing line for tubular knitted fabric, the semi-continuous tubular fabric, at the end of the wet processing stage, is directed over an internal spreader device, which is designed to restore the fabric 10 width to some desirable and appropriate dimension. In this respect, it will be understood that knitted fabric is inherently unstable geometrically (as distinguished from woven fabric, which is rather stable), and typically becomes substantially elongated in length and reduced in width, by reason of the lengthwise tensions applied to the fabric during wet processing. After passing over the spreader, the fabric conventionally goes through extractor rolls, in the form of one or more opposed sets of resilient nip rollers. These serve to physically displace water from the fabric, typically reducing the percentage of water to, say, 85% (meaning 85 pounds of water per 100 pounds of dry fabric). Typicallyg the fabric is then treated in a tensionless dryer, which usually is either steam heated or direct 20 fired with gas. A typical dryer apparatus for this purpose is shown in the Frezza U.S. Patent No. 3,496,647.
With conventional practices, in a two drum dryer of the type shown in the before mentioned patent No. 3,496,647, there may be a maximum drying capacity of approximately 350 pounds of water per hour. In the more economical dryer units, particularly the direct fired units, the drying costs at current energy cost levels typically are on the order of 1.5 cents per pound of water removed.
Pursuant to the present invention, significant economies are realized by utilizing in advance of the conventional dryer apparatus a so-called Mach nozzle, particularly of the type described and claimed in the Brugman U.SO Patent 30 No. 4,137,045. The nozzle is arranged to act on the tubular knitted fabric in advance of the dryer and serves to remove a substantial portion of the liquid content of the fabric before the fabric enters the dryer. The nozzle treatment serves to reduce the liquid content of the fabric well below the 85% level, achievable with conventional roller extraction, typically9 to under 50%, thus greatly reducing the workload on the dryer for a given amount of fabric. With the nozzle treatment according to the invention, energy costs per pound of water removed are significantly less than with conventional drying arrangements.
Accordingly, significant overall production cost s~vings are achieved. In addition, since a given amount of fabric has significantly less water to be removed by the 10 dryer, the operating rate of the entire processing line, which tends to be limited by the dryer capacity, can be greatly increased.
The theoretical advantages of the so-called Mach nozzle system are well known from the disclosure Oe the Brugman U.S. Patent No. 4,137,045, which even suggests its app]icability to knitted fabrics. Nevertheless, it has been conventional wisdom that the Mach nozzle procedures could not be employed with knitted fabrics, at least tubular knitted fabrics, because of the high distortability of such fabrics and the need for maintaining the fabric under significant tension during pene$ration of the fabric by the high velocity steam jet. Thus, while the patent itself states that the processing of knit wear can be accomplished, the 20 wisdom of people skilled in the art, has been that such processing could not in fact be carried out, at least on a basis that would enable a commercially acceptable product to be realized at a commercially acceptable cost basis.
In accordance with the present inYention, a novel procedure and apparatus is provided, which indeed does enable tubular knitted fabric to be effectively processed and dried, using a Mach nozzle treatment stage in advance of a tensionless dryer.
Pursuant to one aspect of the invention7 wet processed fabric may be taken directly from a truck or similar container and is spread to flat form and predetermined width while still in wet form. The wet, spread fabric is then 30 discharged directly into a resilient control nip, comprising a pair of opposed resilient rollers. From this roller pair, sometimes referred to as entry-side rollers, ~L2~ 3~

the fabric is guided downward and around the high velocity nozzle and then upwardly to an exit-side pair of resilient ro~lers. According to one aspect of the invention, the respective pairs of roIlers make very light contact with the fabric, so as not to crease the fabric edges, but sufficient, nevertheless~ together with the clegree OI wrap-around of the fabric about the lower rollers, to provide relatively positive control over the movement of the fabric.
In typical mill practice, pre-drying extraction operations are usually carried out on an off-line basis from the dryer proper, because such operations can be performed at much greater rates of speed than the rate of operation of 10 a typical dryer. Thus, the extraction equipment may service more than one dryer, and9 in many cases multiple strings of tubular knitted fabric Qre run side by side through the dryer. Nevertheless, it is contemplated by the invention that the fabric may be processed by the Mach nozzle section on an in-line basis with the dryer, perhaps with a plurality of nozzle sections feedin~ two or more webs to a single dryer.
The procedures and apparatus of the invention make it possible, contrary to conventional wisdom, to process highly distortable tubular knitted fabric by means of the Mach noz21e system, and enable very significant economies in energy costs to be realized, as well as significant increases in processing speed with 20 concomitant reduction in labor costs per production urlit.
The procedures of the invention are additionally advantageous with respect to the application of wet-on-wet foam processing. In general, the use of foam-based chemicals in the processing of fabrics is advantageous because the lower liquid content of the foam-based chemicals reduces subsequent drying costs.
However, the application of foam-based chemicals to wet processed fabric has not, under conveRtional practices, enabled consequential savings to be realized because OI the high residual content of the incoming fabric. Pursuant to the present invention, however, the liquid level of the incoming fabric is sufficiently low that the low moisture content of the foam-based chemicals results in a 30 meaningfully low total liquid content after foam processing.
For a better understanding of the above and other features and s~

advantages of the invention, reference should be made to the fol-lowing detailed description of a preferred embodiment of the in-vention and to the accompanying drawings.
Fig. 1 is a simplified, partially schematic side eleva-tional view illustrating a processing system for tubular knitted fabric, including a Mach nozzle system for preliminary extrac-tion, to be followed by folding and subsequent off-line drying or immediately by in-line drying.
Fig. 2 (shown out of sequence on sheet two of the draw-ing) is a simplified, partially schematic top plan view of the system of Fig. 1.
Fig. 3 is a fragmentary illustration of a fabric spread-er apparatus as utilized in the system of the invention.
Figs. q and 5 are end elevational and longitudinal cross-sectional YieWs respectively of a high velocity steam dis-charge nozzle as used in the process of the invention.
Referring now to the drawings, and initially to Fig. 1, the reference numeral 10 designates a truck or other container, usually on wheels, for containing a length of wet processed tubu-lar knitted fabric, which is ready for detwisting, wet spreading and extractiny, in preparation for drying. The fabric 11 typi-cally is drawn upwardly, through an eye guide 12 and onto the forward end of an adjustable width spreader 13 which may, by way of example only, be of the type shown in the S. Cohn et al. U.S.
Patent No. 3,207,616, the Frezza U.S. Patent No. 3,875,62q, or the Frezza U.S. Patent No. 4,103,402, all owned by Samcoe Hold-ing Corporation of Woodside, New York. In accordance with known practices, the spreader, generally designated by the numeral 13, is comprised of opposed, spaced belt frames 14, 15, connected by an adjustable length bar 16. As reflected in Fig. 3, the illus~
trated form of belt f:rames contain entry side and exit side ~L24~9~32 belts 17, 18 respectively. Adjacent drive sheaves 19, 20 for the respective belts are engaged, supported and driven by rotat-able edge drlve rolls 21, 22 at opposite sides of the machine.
The edge drive rolls are mounted on carriages 23 which are mov-able toward and away from the center line of the processing equipment, in accordance with known practices, in order -4a-5~3~

to support and drive the fabric spreaders oE various predeter-mined width settings.
Immediately downstream of the spreader 13, in the direc-tion of fabric travel, is a water (liquid) removal apparatus which, in part, comprises a so-called Mach nozzle 24, substan-tially as described and claimed in the Brugman U.S. Patent No.
4,137,0~5. On each side of the nozzle, upstream and downstream thereof, is a pair of fabric driving and control rolls. Rolls 25, 26 are located on the entry side of the nozzle and rolls 27, 28 are located on the exit or discharge side of the nozzle.
Pursuant to the invention, the upper rolls 25, 27 of each of the roll pairs straddling the Mach nozzle are not load-ed, in the sense of being urged downward toward the correspond-ing lower rolls by springs, airloading devices, weights, or the like. To the contrary, the upper rolls are desirably relatively light in weight, and are loosely supported above their respec-tive lower rolls, as for example by means of loose vertical guide slots or the like (not shown).
As illustrated in Fig 2, the first stage spreading de-vice 13 discharges the spread, wet fabric directly into the first roll pair 25, 26. Uncharacteristically, although the fab-ric at this stage is thoroughly wet from the prior wet process-ing operations, the roll pair 25, 26 is not required to perform any significant liquid extracting function. In this respect, while there is no advantage in continued retention of liquid past the first roll ~stage, there is, on the ot~er hand, no advan-tage in removing any of it at that stage, because the operation of the Mach nozzle 2~ is not significantly affected by the presence or absence of the amount of liquid that could be ex-pressed by the first roll pair. On the other hand, the loading forces necessary to achieve expression of significant liquid at the first roll pair would result in increased power consumption, reduced roll life, and possibly some fabric distortion resulting from the squeezing action of the rolls. It has been found that, by providing the rolls with resilient coverings, which have good gripping action on the fabric, the roll pairs 25, 26 and 27, 28 can serve their principal function of controllably and adjust-ably advancing the forward movement of the fabric, using rela-tively lightweight upper rolls without any external loading.

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In accordance with the teachings of the Brugman U.S. Patent P~o.
4,137,0453 liquid removal from the fabric 11 is effected by passing the fabric around and in contact with a wedge-shaped nozzle having a ~edge angle of 60 to 90 and having a somewhat rounded lower edge provided with a transverse slit for the discharge of high velocity gaseous drying medium, typically, in this case, steam. As reflected in Fig. 1, the nozzle 24 is positioned below the plane of the roller pairs, so as to cause the fabric 11 to be diverted downward, around the nozzle, and back up to the exit side roller pair. The fabric thus forms a V-like trough and is in intimate contact with the wedge-like surfaces of the nozzle from which the high velocity steam is ejected.
Figs. 4 and 5 illustrate end elevational and fragmentary cross sectional views respectively of the high veloeity nozzle 24 according to the before mentioned Brugman patent, which is utilized in the process and apparatus of the invention.
TypicaUy, the nozzle consists of two half sections 29, 30, of more or less symmetrical configuration, arranged to be bolted together in the manner reflected in ~ig. 4. An inlet passage 31 is formed in one of the sections 30 and is arranged for connection to Q pipe 32 (~ig. 1) leading to an appropriate source of steam under pressure. The passage 31 discharges into a horizontally elongated manifold cavity 33, which extends over substantially the full width of the nozzle, being 20 closed at each end. A plurality of distribution passages 34 lead downwardly from the manifold cavity and diverge at 35 into a secondary manifold cavity 36, which also extends along substantially the full width of the nozzle. A narrow slot forming recess 37 is machined in one or both of the nozzle sections, to define a transversely extending narrow discharge slot 38. The size and configuration of the slot is, in accordance with the teachings of the Brugman patent, such as to provide for the discharge of the gaseous treating medium, typically steam9 at extremely high velocity, approximating the speed of sound.
The wedge 1ike lower surfaces 39, 40 of the assembled nozzle halves, form an included angle of 6û to 90 and are desirably smoothly polished in order 30 to accommodate the movement thereover of fabric being treated. The lower extremity of the nozzle is rounded, as at 41, to allow for the relatively abrupt ~LZ~ 3~2 change in direction of the fabric without abrasion or damage.
Desirably, a steam recovery chamber 42 is provided under the no~zle 24. The chamber leads to an exhaust duct 43, by which excess steam is vented off.
In accordance with one aspect of the invention, the tubular knitted fabrie being processed by the high velocity steam nozzle 24 is unsupported, that is, it is neither conveyed by nor supported from below by a secondary carrier web. Rather, it is held in tension contact with the high velocity nozzle by reason of lengthwise tension in the fabric itself. Of course, as will be appreciated, the wet fabric being discharged from the first stage spreader 13 is highly dimensionally unstable and, when placed under the tension necessary to maintain working contact with the high velocity nozzle 24, both elongates significantly ~e.g., fifteen percent in a typical case) and correspondingly narrows in width, as reflected at 44 in Fig. 2. To this end, the respective entry side and exit side roll pairs are adjustably synchronized by way of a variable speed clrive 56 (P.I.V.) such that the speed of operation of the exit side rolls can be adjusted to be appropriately higher than the speed of operation of the entry side rolls. This cm be adjusted as a function of visual observations of the machine operator such that proper tension is maintained in the fabric without, on the other hand, excessively distorting it.
This is a rnatter of empirical determination in each case, depending on the specifics of the fabric construction, but is an adjustment easily carried out by an operator of even modest capability.
Fabric leaving the high velocity nozzle 24 and the exit side roll pair 27, ~8, is greatly reduced in liquid content. Typically, the liquid content of the nozzle-processed fabrie may be on the order of 50% (i.e., 50 pounds of water per lOa pounds of clry fabric), whereas fabric subjected to roller expressing according to prior art techniques would more typically have a water content of g5% (i.e., some 70% greater liquid content than after nozzle processing).
In accordarlce with the invention, immediately following liquid removal 30 by nozzle processing, the now-damp fabric is distended to a predetermined uniform width, approximating desired finished width, b~ way of a second stage belt 5~32 spreader device 51 which may, for example, be of the same con-struction as the first stage spreader 13. In a typical case, the second stage spreader 51 may be integrated directly into the nozzle processing unit, and this is of course contemplated by the disclosure. In the specific system illustrated, however, a multipurpose system is provided, in which the second stage spreader forms part of a so-called Tri-Pad unit, such as illustrated in the S. Cohn et al. U.S. Patent No. 3,207,616 ("Tri-Pad" is a trademark of Tubular Textile Machinery Co.) In the illustrated system, the second stage spreader 51 discharges onto a set of rolls of inverted triangular configuration If no further processing of the fabric is desired, it merely travels over the surfaces of synchronously driven processing rolls 52, 53, 54, without nip pressure being applied, but with the fabric being geometrically stabilized by contact with the roller surfaces. Fabric leaving the processing roller 54 may be directed into a tensionless dryer unit 62 of the type illustrated in, for example, the S. Cohn et al. Patent No 3,207,616 or the beforementioned Frezza U.S. Patent No.
3,496,647.
In the illustrated form of the invention, the control-ling drive for the processing line is a variable speed motor 45 which, through a drive mechanism 46, is directly connected to the rollers 52-54 of the Tri-Pad unit. The second stage spread-er unit 51, forming part of the Tri-Pad apparatus, is driven off of the main Tri-Pad drive 46 through a variable speed pulley or the like 47, such that a range of speed adjustment of the spread-er relative to the rolls of the Tri-Pad is possible. Most typi-cally, this is adjusted to provide for a slight degree of overfeeding of the fabric by the spreader 51 to assure tension-less conditions in passing over the Tri-Pad rolls. A drive 48, ,~

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for the dryer unit 62, is driven of f of the Tri-Pad drive 46 through a P.I.V. or similar variable speed drive 49, such that the speed of the dryer may be adjusted to be slightly less than the operating speed of the Tri-Pad rolls, ayain for the purpose of maintaining tension free conditions for the fabric 11.
The extractor section, consisting of the first stage spreader 13, roll pairs 25, 26 and 27, 28 and the high velocity nozzle 24, advantageously may be independently driven by a sec-ond variable speed motor 50. However, the operation of the ex tractor unit is controlled to follow automatically the operation of the -8a-Tri-Pad unit, by means of a dancer control unit 58. As r0~1ected in Pig. 1, there is positioned between the Tri-Pad unit, generally designated by the reference numeral 63, and the extractor unit, generally designated by the numeral 64, a pair of guide rolls 56, 60 and a vertically movable dancer roll 61, all forming part of the dancer control 58. The speed of the extractor unit motor 50 is controUed by the position of the vertically movable dancer roll 61 in accordancewith known control techniques. Thus, to the extent that the speed of operation of the extractor unit tends to lag that of the Tri-Pad unit, the dancer roll 61 will be elevated by the progressively shortening loop 59 of fabric passing around the dancer roll. In response, the speed of operation of the motor 50 is increased proportionately, such that, on the average, the dancer roll 61 seeks a predetermined average elevation and, in doing so, enables the speed of the extractor unit 64 to closely track that of the Tri-Pad unit.
As reflected in Fig. 2, the extractor unit mot~r operates through an extractor drive 55 to drive directly the lower roll 26 of the entry side roll pair.
The lower roll 28 of the exit side pair is driven off of the extractor drive 55 through a variable speed P.I.V. unit 56, which provides for the exit side pair to be driven at a some-Nhat higher rate of speed than the entry side pair, enabling the fabric to be elongated sufficiently to maintain desired levels of lengthwisetension in the fabric. The first stage spreader unit 13 is also driven off of the extractor drive 55, through a variable speed pulley system 57 or the like3 such that the speed of the spreader unit may be varied slightly with respect to that of the entry side roll pair. Typically, there might be a slight overfeeding of the fabric from the spreader unit 13.
As will be evident in Fig. 29 there is a substantial enlargement of fabric width as the fabric enters the second stage spreader 51. To aecommodate this enlargement in ~ridth, the average speed of advancement of the fabric in the Tri-Pad stage is considerably less than the average speed of advancement of the elongated fabric being discharged from the exit side roll pair 27, 28 of theextractor unit. This? however, presents no problem, inasmuch as the dancer control 58, by maintaining a predetermined average loop 59 of fabric, automatically 3;~

compensates for any width variations in the fabric and resultincJ
differences in the speed of advancement of the fabric.
Important theoretical advantages accrue where the tubu lar knltted fabric, after second stage spreading, can be direct-ed immediately into the dryer for completion of the drying opera-tion. This results in part from the fact that the fabric, imme--diately after nozzle processing, is very hot, virtually at the temperature level for the commencement of drying, such that addi-tional energy savings and increased operating speeds may be real-ized in the dryer. on the other hand, the speed of operation oE
the nozzle processing unit typically is much greater than the maximum operating speed of a typical commercial tensionless dry-er. As a result, many processors find it to be more economical to fold the damp fabric as it emerges from the second stage spreading operation, transport the folded fabric to a dryer at another location, and feed the dryer from the supply of folded fabric. By way of the last described procedure, a noz71e pro-cessing unit, operating at speeds significantly greater than that of the dryer, can supply fabric to several dryers and/or supply several strings or webs of fabric to a given dryer. In this respect, it is quite common for dryers to process multiple webs side by side to increase overall throughput of fabric even though operating at relatively slow linear speeds of advance.
Folders suitable for the purposes hereof are reflected in the Eugene Cohn et al. U.S. Patent No. 2,761,678 and/or the Frezza U.S. Patent No. 4,053,152, for example.
In a practical, commercial-size unit according to the invention, a nozzle unit of about forty-three inches in width was provided for the processing of tubular knitted fabric up to maximum width somewhat less than the nozzle width. Steam was _10-~5~

supplied at a pressure of about 80 psi, corresponding to a steam temperature of about 325F. Under such conditions, the nozzle temperature, in the region of the tip, can be stabilized at about 220F. Steam at the rate of 460 pounds per hour was discharged through a one mill wide (0.001") slot, approximately at sonic velocities. Under the conditions specified, it is possible to remove approximately 1.4 pounds of water from the fabric for each pound of -lOa 5'~

steam cvnsumed, and the fabric processing speed may be controlled accordingly, as a function of the weight of water per pound of dry fabric. By way of comparison, a conventional tensionless dryer, of the type herein described and ir~
common use throughout the industry, utilizes approximately 2.5 pounds of steam to remove a pound of water, as compared to approximately .7 pounds of steam per pound of water removed via the no~æle processing procedure of the invention.
Equally importantly, a typical two drum commercial dryer of known and widely used construction may have a maximum water removal capacity of, say, 350 pounds per hour. Under conventional practices, utilizing roller extraction of the fabric in advance of drying, the incoming fabric to the dryer will contain approximately 85% moisture, such that approximately ~10 pounds of dr~ weight fabric can be processed in an hour's time. By way of comparison, fabric subjected to nozzle processing according to the invention has a liquid content of 50% or less, such that approximately 700 pounds or more of dry weight fabric cnn be processed in an hour's time. Thus, quite in addition to the obvious energy savings, the fact that a given dryer unit may be almost doubled in capacity allows for significant reduction in capital investment, factory floor space and, perhaps more importantly than either of the foregoing, greatly reduced labor expense.
Another significant advantage derivable from the process and apparatus of the invention is the practical improvement of so-called wet-on-wet foam processing to the point of greater economic viability. In this respect, so-called foam processing of tubular knitted fabrics has certain advantages in enabling the application of dyes and other processing ehemicals through a ~oam medium, rflther than more conventional liquid medium, with a resulting reduction in liquid input to the fabric and a concomitant reduction in energy cost in the subsequent (hying and/or curing of the foam-processed fabric. For wet-on-wet processing, however9 wherein foam-based chemicals are applied to wet processed fabric, the enonomies of foam processing are less evident, at least with conventional extraction procedures. For example, with conventional, roller-expressed wet fabric, containing a moisture level of approximately 85%, the addition of foam-based chemicals will raise the moisture content of the fabric to approxima$ely 95%, ~5~

as compared to perhaps 105% where the fabric is conventionally processed with liquid-based chemicals followed by roller expression of the excess processing liquid. Thus, under conventional practices, thle moisture content of fabric entering the dryer after a wet-on-wet processing operation is a 105% with liquid-based chemical proces~sing versus about 95% with foam-based processing, a difference that frequently does not justify modification of a processing line to utilize foam processing. Where the incoming fabrlc has been processed by high velocity nozzle techniques according to the invention, howe!ver, the incoming moisture level of the fabric is approximately 50% or less, which increases to, say, 60% or less 10 after app]ication of foam-based chernicals. Under these conditions, foam-based application of chemicals in wet-on-wet processing achieves an advantage of 61)%
or less moisture going into $he dryer versus 105% moisture resulting from liquid processing (liquid processing results in 105,6, say, independently of the moisture level of the incoming fabric, as will be understood).
The process according to the inventic~n, for the first time enables knitted fabric to be processed by the so-called Mach nozzle technique of the Brugman U.S. Patent No. 43137,045. Thus, notwithstanc]ing the general observations in the Brugman patent of its applicability to knitted fabrics, experience prior to this invention led to the conventional wisdom that Icnitted fabrlcs could not be 20 effectively processed according to this procedure. Among the innovations of the present invention that make this possible, contrary to conventional wisdom, are the first and second stage spreading of first the wet fabric immediately before and then the damp fabric immediately after, nozzle processing, and the tension control of the wet, geometrically unstable fhbric passing over the high velocity nozzle, by independently variable speed control of entry side and exit side rolls, with the exit side rolls being driven at a sufficiently higher rate of speed than the entry side rolls, to maintain tension on the fabric and accommodate the resulting width reduction and length extension of the unstable, wet fabric. The fabric is passed through entry sicle and exit side roll pairs, without, however, 30 loading either roll pair, and particularly the entry side, f or the purpose of expressing li~uid from the fabric. Rather, the upper rolIs of each pair are relatlvely lightweight, non-loaded rolls whose function i5 mere-ly to assist in the frictional engagement of the fabric with the lower, driven rolls of each palr, so as to provide for the neces sary tension control of the fabric, without on the other hand undesirably creasing the edges of the fabric.
In one advantageous form of the process according to the invention, the fabric, after being nozzle processed and lat-erally distended in damp form to desired width, is gathered, as by being loosely folded, and subsequently delivered in its gathered form to a suitable dryer where the fabric is further processed by being fully dried. In another form of the inven-tion, the damp fabric, at its state of elevated temperature from the high velocity steam nozzle, is conveyed substantially direct-ly and in a continuous manner into the dryer, such that the dry-er can be operated at somewhat increased rates of speed, with a reduction in energy utilization. The last described procedure logically requires, however, a dryer whose nominal speed of oper-ation is consistent with -the rate of throughput of the nozzle processing equipment.
The nozzle processing according to the invention also makes highly attractive, for the first time, foam processing of fabric in a wet-on-wet procedure, in which foam-based chemicals are applied to the fabric in its "wet" form, but after reduction of its liquid content by nozzle processing according to the in-vention. With conventional roll expressing techniques for the reduction of liquid content of the fabric, the advantages of wet-on-wet foam processing are rather minimal, and typically in-sufficient to ~us-tify conversion of the processing line to uti-lized foam techniques. With nozzle processing according to the invention, however, the reduction in liquid content of the fab-ric is sufficiently dramatic that very significant advantages can be realized through wet-on-wet foam processing.

The energy savings realizable through the process and apparatus of the invention are most impressive, such that the recovery of investment in equipment to carry out the new process may be realized in a manner of a fraction of a year. At the same time, since the dryer equipment typically is among the slow-est operating units in a line, the entire sequence of processing operations in a plant may be expedited with consequent savings in equipment costs, factory utlization, labor and the like.

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It should be understood, of course, that the specific forms of the invention herein illustrated and described are intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclasure. Accordingly, reference should be made to the foUowing appended claims in determining the full scope of the invention.

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process of treating tubular knitted fabric, which comprises (a) supplying wet processed tubular knitted fab-ric in wet form, (b) laterally distending said wet tubular knit-ted fabric in a first stage to flat smooth form, (c) guiding the laterally distended tubular fabric to pass in a generally V-shaped path around and in contact with a gas discharge nozzle, (d) while said fabric is passing said nozzle, discharging a gas-eous drying medium through the fabric at extremely high veloci-ty, (e) adjustably controlling the speed of advance of the tubu-lar fabric on the entry side of said nozzle, (f) adjustably driv-ing the tubular fabric on the exit side of the nozzle to elon-gate said fabric and maintain it under tension and in contact with said nozzle as the fabric passes over said nozzle, (g) said fabric being elongated and reduced in width in the region immedi-ately in advance of and immediately downstream of said nozzle, (h) substantially immediately thereafter, laterally distending said tubular fabric in a second stage to flat form and predeter-mined width, and (i) thereafter further processing said fabric including further drying said fabric.

2. The process of claim 1, further characterized by (a) said gaseous drying medium being at an elevated temperature, and (b) the further drying of said fabric being completed sub-stantially immediately after treatment of the fabric with said drying medium and while said fabric still retains substantial heat from said drying medium.

3. The process of claim 1, further characterized by (a) said gaseous drying medium being steam.

4. The process of claim 1, further characterized by (a) said gaseous medium being discharged through said fabric at velocities approximating the speed of sound.

5. The process of claim 1, further characterized by (a) said fabric being loosely folded in flat form and damp condition following said second stage of lateral distention, and (b) said loosely folded damp fabric thereafter being further dried.

6. The process of claim 1, further characterized by (a) said fabric being maintained free of significant rolling pressure across its width throughout said process until at least after said second stage of lateral distention.

7. The process of claim 1, further characterized by said further processing including the steps of (a) impreg-nating said fabric with foam-based chemicals prior to the further drying of said fabric.

8. The process of claim 1, further characterized by (a) said tubular knitted fabric being adjustably driven on the exit side of said nozzle at a higher rate of speed than at the entry side, whereby said fabric is elongated and narrowed in width in the region of said nozzle.

9. The process of claim 1, further characterized by (a) the further processing of said fabric comprising further drying of said fabric being carried out while maintaining said fabric free of lengthwise tension.

10. Apparatus for the processing of wet tubular knitted fabric in accordance with the process of claim 1, which comprises (a) first stage internal spreader means for receiving wet-processed tubular knitted fabric and spreading it to flat form, (b) means for controlling the speed of advance of the in-coming wet fabric, (c) said nozzle being disposed transversely of the path of fabric movement and on the downstream side of said first stage spreader means, (d) means to supply said nozzle with gaseous drying medium under pressure, (e) said nozzle and said means to supply being so related as to provide for the discharge of drying medium from the nozzle at approxi-mately sonic velocities, (f) means for guiding the fabric around and in contact with said nozzle whereby said drying medium may be discharged through the fabric, (g) said means for guiding including an exit side drive roll engaging the tubular knitted fabric across its width, (h) controllable drive means for driving said first stage spreader and said exit side drive roll, whereby said fabric is elongated and maintained under tension between said first stage spreader and said exit side drive roll, (i) second stage spreader means located downstream of said exit side drive roll for laterally distending the fabric to predetermined width, and (j) means for further processing said fabric.

11. Apparatus according to claim 10, further character-ized by (a) said means for guiding further including an entry side drive roll, (b) said controllable drive means being con-nected to the respective entry side and exit side drive rolls.

12. Apparatus according to claim 11, further character-ized by (a) said entry side and exit side drive rolls each com-prising the lower rolls of a cooperating roll pair, (b) the re-spective upper rolls of said pairs being of lightweight con-struction and being maintained free of external loading whereby to minimize rolling pressure on said fabric.