US3710460A

US3710460A - Yarn treating jet having a guide fastened to its outlet end

Info

Publication number: US3710460A
Application number: US00125229A
Authority: US
Inventors: W Segraves
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1971-03-17
Filing date: 1971-03-17
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16

Abstract

A yarn treating jet includes a yarn guide fastened over the outlet end of the jet. The guide is in the form of a plate having a slot through it coaxial with the yarn passage of the jet. The slot defines parallel walls and has a particular dimensional relationship with the yarn passage in the jet with at least one of the parallel walls and the outer face of the guide serving as guiding surfaces for the yarn passing from the jet.

Description

United States Patent [1 91 Segraves [75] Inventor: William Benjamin Segraves, Martinsville, Va.

[73] Assignee: E. I. du Pont de Nemours and Com pany, Wilmington, Del.

'[ 51 Jan. 16, 1973 Primary Examiner-Louis K. Rimrodt Attorney-Howard P. West, Jr.

57 ABSTRACT [22] Filed: March 17, 1971 A yarn treating jet includes a yarn guide fastened over l v the outlet end of the jet. The guide is in the form of a [21] p plate having a slot through it coaxial with the yarn passage of the jet. The slot defines parallel walls and [52] US. Cl. ..28/1.4 a particular dimensional relationship with the yarn [51] Int. Cl. ..D02ql/l6 passage in the jet with at least one of the parallel walls [58] Field of Search ..28/ 1.4, 72.12; 57/34 B and the outer face of the guide serving as guiding surl faces for the yarn passing from the jet. [5 6] References Cited i 4 Claims, 5 Drawing Figures UNITED STATES PATENTS l 2,584,043 1 1952 v Oberly.. ..28/l.4 x

2 3 A r 2 /l V PAIENTEBJAII I s 1975 F I G- 3 I Ii T W 43 I-L/IO FIG-4 FIG-5 INVENTOR WILLIAM BENJAMIN SEGRAVES awe W I.

ATTORNEY YARN TREATING JET HAVING A GUIDE FASTENED TO ITS OUTLET END BACKGROUND OF THE INVENTION This invention relates to a jet-device in which the yarn is heated and forwarded at minimum tension by a a I It is known to heat-treat a running yarn by passing it 1 along a jet of heated gas. Very high heat-transfer rates are obtained in this fashion. Such hot-gas jets are particularly effective for developing maximum shrinkage or shrinkage-forces in a running yarn because the yarn makes no frictional contact with solid surfaces within the heating zone and minimum-yarn-tension may, therefore, be achieved during heating. Jet-devices suitable for minimum tension heat-treatment of yarns are disclosed, for example, by Clendening et al., U. S. Pat. No. 3,26l,07l,issued July 19, 1966.

A specific instance where heating a yarn at vanishingly low yarn-tension is desirable is that of precrimping two-component filaments wherein each component is continuous along the length of each filament and eccentrically disposed in the cross section of each filament. When the two components exhibit quite different shrinkages on exposure to heat, the resultant shrinkage causes the filaments to coil helically. This provides stretchability for fabrics prepared from yarns of such filaments.

Olson, in U. S. Pat. No. 3,399,108, issued Aug. 27, 1968, discloses a process by which yarns of such helically crimpable filaments may be prepared. The composite yarns (and filaments) are first drawn to develop differential shrinkage potential between the two 'components and then heat-treated under little or notension to generate thediffering shrinkages. This latter step is referred to as precrimping. The precrimped yarns may be wound into packages under sufficient tension to straighten them. In subsequent fabric-form, the crimp is redeveloped or enhanced by another heat-treatment.

The stretchability of fabrics so prepared increases in proportion to the degree of completion of shrinkage during precrimping. Sinceonly small shrinkage-forces are available, it is essential that a yarn be under a 7 minimum operable tension during precrimping in order to maximize ultimate stretch properties. For this purpose, hot-gas jets for heating yarns during precrimping are particularly effective;

On exit from a precrimping jet-device, a yarn, still under the minimum tension, ordinarily undergoes a change in direction at a conventional yarn guide, e.g., a wire hook, V-guide, grooved roller or the like. The low tension and the turbulence created by jet-exhaust combine to promote jumping of the yarn out of such conventional guides, particularly as the yarn-velocity is desirably increased. Each such occurrence causes costly interruption of the process. Using conventional guides, threadline-instability permits frequent random yarn-to-wall contacts inside the jet-device, and the guides tend to hold all filaments in a multifilament yarn in close contact. Both of these effects promote nonuniform along-the-length precrimping'in individual filaments.

SUMMARY-OF THE INVENTION The invention involves a yarn treating apparatus including a jet having inlet and outletfends connected by a passage through which yarn passes for treatment. The jet includes a plate fastened over the outlet end of the jet. The plate has an outer face and a slot through it defining parallel walls each terminating at the outer face. The slot is coaxial with the passage and has a loo- 0 gitudinal cross-sectional dimension no greater than and preferably equal to the corresponding cross-sectional dimension of the passage. The cross-sectional width dimension of the slot is less than its longitudinal dimension and less than the corresponding cross-sectional dimension of the passage. At least one of the parallel slot walls and the outer face of the guide plate serve as guiding surfaces for yarn passing out from the jet.

The guide plate may also include opposed parallel surfaces on its outer periphery which, in turn, are parallel to the parallel walls of the slot.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED, I EMBODIMENT With reference to the drawings, FIG; 1 represents a I process for minimum-tension heating of running yarn, wherein a continuous-filament yarn 10, composed of filaments each of which comprises two continuous adherent polymeric components eccentrically disposed in transverse cross section, is drawn between feed-rolls' (not shown) and draw-rolls l2 and! 12'; Draw-roll 12 is driven at a peripheral velocity higher than that of the feed-roll to effect drawing. Drawn yarn l0, advancing as indicated by arrow A, makes several wraps about draw-roll 12 and its associated idler-roll 12. Departing draw-roll 12, yarn 10 passes through hotgas jet-device 11, through .a change of direction at yarn-guide 15, through snubbing devices 16, in several wraps around driven letdown-roll 14 and its associated idler-roll 14' and thence to packaging as indicated by arrow B. I

In a prior art process, represented in FIG. 1 by dashed lines for the yarn path, a conventional V-guide 13, is positioned downstream of jet-device 11 so as to guide yarn 10 along the axis of symmetry of device 11. To avoidhaving exhaust gas from device 11 blow yarn 10 out of guide 13, the distance between the outlet of device 11 and guide 13 is preferably large. Long unsup ported lengths between device 11 and guide 13 result in threadline instability, particularly when tension on yarn 10 in this region is minimized. In operation, both these considerations are optimized. As yarn velocity is desirably increased, however, no position canbe found which reliably prevents jumping of yarn 10 out of V- guide 13.

The improvement of this invention is in the addition of yarn-guide 15, fastened over theoutlet-end of jetdevice 11.. This guide permits a change of about in the direction of advance of yarn 10; In this fashion,

yarn is immediately led away from the zone of exhaust gases from device 11 and the unsupported length of yarn 10 within and beyond device 11 is reduced to an absolute minimum. Moreover, as discussed in detail, hereinafter, guide 15 keeps the threadline within jetdevice 11 near the center of symmetry and also splays the individual filaments of a multi-filament yarn to provide improved along-the-length uniformity of precrimping.

FIGS. 2-5 show essential features of improved yarn guide 15, FIGS. 3-5 being alternative forms of guide 15. In FIG. 2, which is a cross section along the axis of symmetry ofjet device 11, guide 15 completely covers the exit-end of device 11. It has a single opening 26 centered on the axis of symmetry of the jet.

Yarn 10 enters the inlet end 34 of device 11 via guide 22 which is conically tapered on its downstream surfaces 28 to match a conical taper of surfaces 30 leading to circular passage 36 of device 11.

Surfaces

28 and 30 are separated to provide a conical duct communicating with passage 36 and encircling plenum 20. Hot gas (e.g., air) fed under pressure through duct 24 into plenum 20 forms a symmetrical jet stream along passage 36 to outlet 38 of jet 11. The passage 36 is circular in cross section.

Yarn-guide 15 is plate-like, preferably disc-shaped, and has a cross-sectional shape (FIG. 2) or other provision for attachment to the outlet-end of jet-device 11. The thickness of guide 15, at least in the region of outlet-opening 36 of device 1 1, is preferably the minimum consistent with requisite strength and rigidity of guide 15. Minimizing this thickness also minimizes its effect on resistance to flow of hot gas through device 11.

The shape of opening 26 is important to satisfactory operation. As seen in FIGS. 35, it should be symmetrical and centered on the axis of symmetry of jet-device 11. In addition to being coaxial with the passage 36, slot-like opening 26 defines parallel walls 40 terminating at the outer face 45 of guide 15. The slot has a longitudinal cross-sectional dimension L no greater than and preferably equal to the corresponding cross-sectional dimension of the passage 36 at its outlet 38. The cross-sectional width dimension W of the slot is less than the corresponding cross-sectional dimension of the passage 36 at outlet 38 and less than its longitudinal dimension L. Consistent with the above dimensional requirements, the area of outlet opening 38 left exposed with guide 15 in position is as large as possible while providing a planar wall-portion 40 as near as possible to the axis of symmetry of device 11. In this way, yarn 10 is supported for travel near the axis of symmetry of device 1 l, but increased resistance to flow of hot gas through device 11 is minimized.

A significant advantage of guide 15 over prior-art guides (13 of FIG. 1) is achieved when multifilament yarn is being processed. The general V-shape of priorart guides forces all filaments of a yarn into a tight bun dle which tends to interfere with along-the-length uniformity and crimp of individual filaments within device 11. Guide 15, however, as shown in FIG. 3, causes the individual filaments of yarn 10 to splay (separate), thus, decreasing interfilament interaction within device 11 and improving the resultant along-thelength uniformity of shrinkage and crimp. The splaying action of the yarn-guide 15 of this invention represents a significant improvement. Thus, guide 15 provides improved uniformity while simultaneously providing greatly increased yam-velocity without threadline-instability. FIGS. 3 and 5 show the dimension L of slot 26 equal to the diameter of circular passage 36 at its outlet 38. FIG. 4 shows the dimension L of slot 26 to be somewhat less than the diameter of outlet 38.

It is preferred that, in traversing guide 15, yarn 10 undergoes at least a 90 change in direction, i.e., that yarn 10 remains in contact with the outer face 45 of guide 15 as it proceeds downstream. In a preferred guide 15" (FIG. 5), the outer edge or peripheral surface 43 is provided with opposed parallel portions 44 parallel to walls 40 of slot 26. The provision of portions 44 is found to improve threadline stability when the yarn undergoes a change in direction of at least 90.

It is essential that at least the surface portions of guide 15 which are contacted by running yarn 10 be composed of wear-resistant low-friction material. As is well known to textile experts, ceramics provide both high wear-resistance'and low yarn-friction, particularly when the surface of the ceramic material is microroughened in known manner to even further reduce yarn friction. If guide 15 is constructed essentially completely of metal, it may be coated with suitable ceramic material, or ceramic inserts may be placed in areas contacted by running yarn. Alternatively, guide 15 may be formed completely of ceramic material. Edges over which yarn 10 runs are preferably rounded slightly so as to eliminate knife-edges. Appreciable radii of curvature may be provided, but are not required.

In a specific embodiment, yarn-guide 15 is essentially a disc about 1 inch in diameter with a cross section about as shown in FIG. 3. Thickness of the disc, measured along the axis of the jet within opening 26, is 0.25 inch. The perpendicular distance W between parallel wall-portions 40 is 0.093 inch. Maximum length L of opening 26 is 0.25 inch with the ends of the opening semicircular and of 0.093 inch diameter. Yarn guide 15 is cast from a high-alumina ceramic, all edges being rounded to a 0.01 inch minimum radius and all surfaces contacted by yarn being finished to a surface-roughness of 30 to microinches. The outer peripheral surface 43 of guide 15 is provided with two straight portions 44 diametrically opposite one another and each about 0.3 inch wide.

The jet-device 11- is essentially as shown in FIG. 2, terminating in an exit-opening 38 which is circular and 0.25 inch in inside diameter. Using a process as shown in FIG. 1, incorporating guide 13 and the dashed line yarn path, a 20denier 3-filament bicomponent nylon yarn is satisfactorily precrimped at a draw-roll speed of 584 yd./min. When the draw-roll speed is increased to 1,074 yd./min., 18 percent of yarns, on the average, jump out of guides 13 in the course of each doff.

With yarn-guide 15 in place and operation unchanged except for the modification in the yarn path afiorded by guide 15, operation at 1,074 yd./min. is continuous and trouble-free. Crimp-uniformity as judged in finished sheer hose is at least equivalent to 1. In a yarn treating apparatus including a jet having inlet and outlet ends connected by a passage through which yarn passes for treatment, the improvement comprising: a plate fastened over the outlet end of the jet, said plate having an outer face and a slot therethrough defining parallel walls each terminating at said outer face, said slot being coaxial with the passage and having a longitudinal cross-sectional dimension no greater than the corresponding cross-sectional dimension of the passage, said slot having a cross-sectional width dimension less than the corresponding cross-sectional dimension of the passage and less than said longitudinal cross-sectional dimension, at least one of said parallel walls and said outer face serving as guiding surfaces for yarn passing out from said jet with at least 6 about a change in direction.

2. The apparatus as defined in claim 1, said passage being circular in cross section, said longitudinal dimension of said slot being equal to the diameter of the passage.

3. The apparatus as defined in claim 1, said passage being circular in cross section, said longitudinal dimension of said slot being less than the diameter of the passage.

4. The apparatus as defined in claim 1, said plate having an outer peripheral surface, said surface com

Claims

1. In a yarn treating apparatus including a jet having inlet and outlet ends connected by a passage through which yarn passes for treatment, the improvement comprising: a plate fastened over the outlet end of the jet, said plate having an outer face and a slot therethrough defining parallel walls each terminating at said outer face, said slot being coaxial with the passage and having a longitudinal cross-sectional dimension no greater than the corresponding cross-sectional dimension of the passage, said slot having a cross-sectional width dimension less than the corresponding cross-sectional dimension of the passage and less than said longitudinal cross-sectional dimension, at least one of said parallel walls and said outer face serving as guiding surfaces for yarn passing out from said jet with at least about a 90* change in direction.

4. The apparatus as defined in claim 1, said plate having an outer peripheral surface, said surface comprising opposed parallel portions, said portions being parallel with said walls.