US3343207A - Novelty yarn apparatus - Google Patents

Description

"J.w. MOTTERN ETAL,

NOVELTY YARN APPARATUS Sept. 26, 1967 Original Filed Oct. 14. 1963 INVENTORS JOHN w. MOTTERN BRUCE v v HIS B i ATTORNEY United States Patent 3,343,207 NOVELTY YARN APPARATUS John W. Mottern, Cary, and Bruce Van Voorhis, Raleigh,

N.C., assignors to Monsanto Company, a corporation of Delaware Original application Oct. 14, 1963, Ser. No. 316,026.

Divided and this application Apr. 20, 1966, Ser.

3 Claims. (Cl. 181) ABSTRACT OF THE DISCLOSURE An apparatus for spinning variable denier filaments wherein a source of radiant heat energy is periodically focused upon yarn being subjected to a uniform drawing tension. In a preferred embodiment, radiant energy is focused by a pair of optically aligned parabolic reflectors, the yarn being passed through the focus of one of the reflectors; a revolving shutter configuration is employed to effect an interruption of the desired periodicity of the optical path extending between the pair of reflectors to thereby effect a timed application of radiant heat upon the threadline.

This application constitutes a divisional of our copending application Ser. No. 316,026, filed Oct. 14, 1963.

This invention relates to an apparatus for producing thick-thin yarns from synthetic thermoplastic material. More particularly, it relates to an improved apparatus for producing thick-thin yarns from thermoplastic continuous filaments by selective drawing or elongation. It will be understood that, where the context permits, the term yarn is to be understood as denoting both continuous filament yarns and spun yarns comprised of staple fiber.

It is well known, in the utilization of synthetic organic polymers for the preparation of filamentary structures, to introduce non-uniformities of'diameter or denier at intervals along the length of such structures. Products prepared in this way can be made into fabrics for textile and other end uses having a pleasing hand and attractive surface variations. Also, a fabric constructed of such yarns may be caused to exhibit a pleasing color variegation due to the fact that the substantially undrawn, thick segments possess different dyeing characteristics relative to the drawn, thin segments, the thick segments normally being the deeper dyeing. By virtue of this phenomenon, it is possible to produce color variegated fabrics by the single application of one dye, a proposition of obvious economic advantage. Also, such fibers or filaments may be caused to simulate natural fibers having a slub content, such as, for example, linen and dupioni silk.

One process by which such thick-thin or nubby yarns have been made is to introduce variations in the feed rate at which the polymeric material is supplied during the spinning operation. The variations can be regular or random in nature and, for many purposes, it is desirable that they be as random as possible. A great deal of ingenuity is displayed in the prior art in the employment of various mechanical or electronic devices productive of a true random or non-uniform distribution of feed variations. Frequently, such variations are introduced by altering the speed of operation of a positive displacement spinning pump.

Another way of producing thick-thin filaments is by varying the rate of draw-down of the filaments in the course of their production from the spinning jet through which they are extruded. This can be done by drawing the filaments along a path Whose length is caused to vary periodically or randomly, the filaments being passed over a deflecting surface, e.g. a cam, cam-operated guide or the like, which moves transversely of the filament path so as to deflect the filaments from their normal, shortest route. The filaments are drawn away from the spinning jet at a higher linear rate while the path is lengthening, to thereby produce thin segments in the filaments, and at a lower rate while the path is shortening so as to produce relatively thick or undrawn segments or .slubs in the filaments. It has been found that in order to produce definite and pronounced thick segments of reasonably sharp demarcation between the thin segments, it is desirable that the movement of the deflecting surface to a position corresponding to the shorten-ed path of the filament should be as sudden and abrupt as possible. However, the speed with which the deflecting surface can be moved for this purpose is limited by considerations of inertia of the filaments and mechanical limitations inherent in the design of the apparatus used for the purpose.

Still another way in which non-uniformities of yarn diameter have been obtained is by taking advantage of a characteristic of synthetic or organic polymers known as cold-drawability. Synthetic fibers in general are improved in strength, durability, and dimensional stability by orienting the molecules or crystalline-like sub-structures which constitute the filament by subjecting the filament to a cold-drawing procedure, that is, by elongating the filament after its formation in an irreversible manner, generally to approximately 2 to 6 times its original length. Under some circumstances, particularly in cases where the filament can be plasticized or softened by heat, an increase in length of 2.0 or more times its original length can be obtained without molecular or crystallographic orientation. Naturally, since the amount of material present in the fiber is constant, when a fiber is increased in length it necessarily experiences a decrease in its diameter.

If the drawing process is applied to a fiber in a sporadic or non-uniform fashion, variation in yarn diameter will be achieved due to the fact that less than the full length of the fiber will be drawn the same amount. Thus, it is possible to obtain fibers of non-uniform diameter in which the sections of greater diameter are substantially undrawn and unoriented, or at most partially drawn and partially oriented. There are, in addition, other ways by which it is possible to introduce variation in diameter of fibers produced from synthetic organic polymers. For example, it is known to include, at intervals along the length of a filament, quantities of an inert material, such as sand or the like, which will not decrease in diameter during the drawing process, but this results in a weakening of the filament structure so that breakage of the filament at the point of increased diameter is apt to occur; another method is to apply to a uniform filament a non-uniform surface coating of some adherent material, but this approach suffers from the tendency of such non-uniform coatings to snag, if they are permanent, while, otherwise, they are apt to rub off during processing.

In the production of thick-thin yarns, the needs is therefore apparent for an improved and simplified apparatus which would avoid the above elated difiiculties.

It is, therefore, an object of the present invention to provide an improved apparatus for producing thick-thin filamentary structures.

- A further object of this invention is the production of thick-thin filamentary structures by subjecting such struc tures to selective elongations.

Still another object of ourinvention is an improved apparatus for use in producing thick-thin filamentary structures, which apparatus is designed to accomplish intermittent radiant heating of such structures while they are subjected to a draw ratio below their natural draw ratio.

In accordance with our invention, the above and still other objects are achieved by providing an apparatus for producing variable denier filamentary structures, which apparatus Comprises means to propel the yarn under a uniform drawing tension and means to focus a remote source of radiant heat energy upon the yarn being drawn and means to periodically obstruct the optical path between the heat source and the yarn path. In a specific structural embodiment, this is accomplished by mounting a pair of optically aligned parabolic reflectors so that a source of radiant heat is disposed at the focus of one of said reflectors to be transmitted to the focus of the other reflector, through which latter focus the yarn being processed is caused to pass. A shutter device is employed to cause a timed interruption of the optical path extending between the pair of reflectors to thereby effect a timed application of the radiant heat being focused upon the thread line.

The invention will be more clearly understood by reference to the following detailed description and accompanying drawing, which shows a simplified embodiment of one form of apparatus which may be employed in the practice thereof.

In the drawing, there is depicted a perspective view of one possible arrangement embodying the essential elements of the subject apparatus.

As previously mentioned, one aspect of our invention contemplates the intermittent application of radiant heat energy to a yarn being drawn at a ratio less than its natural draw ratio. By the phrase natural draw ratio is meant a draw ratio at which a certain degree of permanent, non-reversible extension is imparted to the polymeric material which is just sufficient to change it from its undrawn state to a uniformly drawn and highly oriented state without straining the polymeric material to the point of introducing surface cracks or failure. In general, when any material is drawn in the conventional sense used in processing synthetic fibers, one or both of two phenomenon will normally be observed. There can be plastic flow and there can be orientation of the material. The plastic flow mode of drawing is used to elongate a polymeric material 10 to more than 100 times its original length. However, in the plastic flow process, only slight orientation of the material occurs. Plastic flow drawing is normally carried out under conditions of either high temperature or moisture, or in the presence of other plasticizing agents, or both. There is no natural draw ratio, in the sense here employed, for plastic flow elongation. When a synthetic, thermoplastic polymer is not in a plastic condition, it will, under normal conditions, tend to draw at its natural draw ratio and, in the process, become highly oriented. If, for example, an undrawn filament can be drawn to 5 times its original length to produce a highly oriented, uniformly drawn material, it is not possible, in general, to draw it completely at either 4 or 6 times its original length under the same conditions. If one attempts to draw to 6 times the original length, the filament will break; if one chooses a lower ratio of, for example, four times, one will find that some sections of the yarn will draw at the natural draw ratio while other sections will not draw at all or only partially.

The natural draw ratio of most-thermoplastic filaments is primarily controlled by the yarn temperature immediately prior to the point of draw (hereafter referred to as the drawing temperature), moisture (both that of the material being drawn and that of the ambient atmosphere attending the drawing operation), the as-spun birefrengence and the drawing speed. At given conditions of moisture and drawing temperature, there will be a corresponding natural draw ratio for a given specimen at which it will preferentially elongate to the highly oriented, uniformly drawn state. Therefore, when the drawing temperature is selected for given moisture conditions, the natural draw ratio is primarily determined by these conditions for a given specimen. Alternatively it is possible The natural draw ratio is also effected by the drawing speed. As the drawing speed is increased and the yarn is held at given conditions of temperature and moisture, the natural draw ratio will normally be found to increase, i.e. to obtain uniform drawing at such conditions, the draw ratio must be increased.

Moisture content of either or both the material being drawn and the ambient conditions attending the drawing is still another parameter affecting the natural draw ratio. In general, for many materials, as the moisture content of the material and/ or ambient atmosphere is increased, there will be reached a point above which uniform d-rawing will be observed to take place. Conversely, for certain thermoplastic polymeric materials, the moisture conditions may be reduced to a point below which drawing, even of the non-uniform variety, is impossible, nylon being one example. As-spun birefringence has been recognized as still another parameter affecting natural draw ratio.

In summary, then, it is recognized that the natural draw ratio for a given thermoplastic, filamentary material is primarily a function of moisture content of the material, relative humidity of the ambient atmosphere attending the drawing operation, the as-spun birefringence of the filamentary structure, the temperature of the material at the point of draw, the draw ratio and the drawing speed. The complementary manipulation of these parameters is largely a matter of art involving trial and error by observation, it being possible to obtain natural drawing, as above defined, under innumberable combinations of these various parameters. It is to be understood that the quantitative aspects of the various factors, already referred to, recognized as affecting the drawing behavior of a molecularly orientatable structure are not considered part of the present invention, nor is a precise understanding of the interplay, quantitatively, of such factors essential to its practice. It need only be recognized that the phenomenon of natural draw, as above defined, does exist and that it is primarily a function of previously enumerated factors which are susceptible to manipulation on a trial and error basis to intermittently obtain the conditions requisite to natural, uniform drawing.

In its broadest terms, the essence of the present invention contemplates the concept of drawing a given yarn specimen at a draw ratio less than its natural draw ratio under the prevailing conditions of moisture, as-spun birefringence, draw speed, etc., while equalling or exceeding, at timed intervals, of predetermined and variable occurrence and duration, the minimum conditions requisite to natural, uniform drawing, specifically by the time-controlled application of radiant heat energy to thereby elevate chosen segments of the yarn to a temperature exceeding that necessary to effect uniform drawing, i.e., equalling or exceeding the conditions which, in concert with the prevailing, possibly controlled, conditions affecting draw, result in natural, uniform drawing of the particular yarn being processed.

As a practical matter, the only essential to an understanding and practice of the present invention is the recognition of the necessity of subjecting the yarn to a draw ratio which, under the given conditions, is less than the natural draw ratio while intermittently varying one of the conditions effecting natural draw ratio, preferably yarn temperature at the point of draw, to effect natural drawing of spaced segments of the yarn. When the temperature is below that necessary to effect natural, uniform drawing, the draw ratio should be such as will effect, under the prevailing conditions, random or non-uniform drawing, which is uncontrolled and to be avoided. By introducing periodic applications of heat to raise the yarn temperature at the point of draw, such random, uncontrolled drawing is prevented by virtue of the fact that any drawing which takes place is highly preferential to the point or zone of heat application.

There presently exists no practicable means of effecting such periodic applications of heat to the yarn to eflect selective drawing. The present invention contemplates an apparatus designed to effect a periodic focusing of radiant heat energy to the yarn, which concept particularly recommends itself to high speed operations in view of its inherent ability to be controlled virtually instantaneously.

The drawing illustrates one possible embodiment of the apparatus utilized to carry out the present invention. Such an apparatus, in simplified form, includes a supply of continuous filamentary thermoplastic material in the form of a supply package or bobbin 10, which material may or may not have been previously processed on a drawtwister. The loose end of the yarn, which may be in the form of either a continuous monoor multi-filament, is strung behind snubbing roll 14 and over feed roll 16. Conventionally, the snubbing roll 14 is spring biased against the feed roll 16 to maintain a non-slipping uniform feedrate of the yarn 17 to the draw roll 18. After passing the threadline about draw roll 18 and separator roll 20 a suflicient number of times to prevent slippage, the yarn is passed to a conventional grooved traverse roll 22 which traverses the yarn over take-up bobbin 24 to build a package of the desired configuration. The structure described up to this point is a single stage draw arrangement of conventional arrangement, the various drive rolls and take-up mechanism normally being provided with variable speed drives to effect varying draw ratios and draw speeds.

Intermediate the feed rolls 16 and draw roll 18, there is disposed a pair of parabolic reflectors 26, 28'which are mounted to be in optical alignment, i.e., so that the image of a subject positioned at the focus of one of the parabolic reflectors will be transmitted to the focus of the other reflector. It is a well known characteristic of the geometry of the parabolic reflector that, when a source of radiant energy is placed at its focus, the energy impinging upon the reflector surface will be redirected in par allel beams. A second reflector of a similar geometry mounted to intercept such a collimated beam will redirect such beam to a point located at the focus of the second parabolic reflector.

A source of radiant heat energy, preferably in the form of an electric arc 30 supplied by power leads 32 is positioned so that the gap defined by electrodes 30 occupies the focus position of the parabolic reflector 26 whereby heat radiating from the electric arc impinges upon the interior surface of reflector 28.,as a collimated beam. Reflector 28 is provided with a pair of spaced apertures 34 so arranged that a straight line extending therebetween passes through the focus of the reflector. It is, therefore, apparent that upon passing a threadline through aperture 34 and, therefore, through the focus of reflector 28, such threadline will be subjected to the radiant heat energy transmitted from the electric arc and focused at that point.

In order to provide a timed interruption of the application of radiant heat to the yarn path for periods of predetermined and variable occurrence and duration, it has been found expedient to mount a rotatable shutter 36 having circumferentially spaced cut-out portions 38 formed therein. It will be appreciated that, when the shutter is caused to rotate at a predetermined speed, the optical path between the pair of parabolic reflectors 26, 28 is caused to be interrupted at timed intervals, the duration and occurrence of which are dependent upon the rotative speed of the shutter and the dimensions of the cut-out portions 38 vis-a-vis the solid portions of the shutter. Though only two cut-out portions are illustrated in the drawing it is to be understood that any number of such portions may be formed in the shutter, which portions may be of uniform size and/or configuration, or

may vary in size and configuration, either randomly or periodically.

The power output required of the radiant heat source, an electric arc being illustrated, will of course vary with the mass per unit length of the material being processed, the drawing speed and the slub pattern desired, whether long or short in its variations. One ready means of controlling the power output of the radiant heat source is by varying the voltage drop across the gap as well as the size of the gap, voltage variations being expediently controlled by connecting the power leads 32 through any conventional voltage control, not illustrated, which may take the form of a variable transformer.

It has been found that, where nylon is being processed, it is most expedient to control the relative humidity attending the drawing operation at levels below 30 percent in order to obtain the desired non-uniform drawing in the absence of an application of radiant heat; otherwise, at higher levels of relative humidity, nylon will normally have the tendency to draw uniformly at room temperature, an occurrence destructive of the operability of the present process and apparatus. Polyesters, in general, are not so sensitive as nylon to variations in relative humidity and it has been ascertained that the present process may, in many cases, be carried out at normal room conditions of temperature and moisture. Again, in the case of nylon, the criticality of the ambient relative humidity may be somewhat minimized by reducing the moisture content of the finish, which finish may optionally be supplied prior to the selective operation.

The procedure followed in the practice of the present invention is essentially that used during a standard drawing operation with the snub or draw pin omitted. As shown in the drawing, the electric arc constituting the source of radiant heat is mounted between the feed and draw rolls 16, 18, respectively, and at the focus of parabolic reflector 26. With the shutter maintained stationary and in a position so as not to obstruct the optical path between reflectors 26, 28, the radiant heat emitted from the electric arc is carefully adjusted until uniform drawing is observed for the pre-established drawing conditions of draw ratio, draw speed and ambient conditions. With the conditions adjusted to be just within the realm of those conditions affording natural, uniform drawing and just without the realm of non-uniform drawing conditions, it will be found that, upon causing the shutter to rotate at a speed determinative of the slu-b pattern desired, the yarn will be urged to draw at the point of heat application, i.e., at the focus of parabolic reflector 28. Absence of thick portions along the yarn indicates natural, uniform drawing is taking place and the conditions must, therefore, be adjusted in the above related fashion to accommodate non-uniform cold drawing when the yarn path is not being radiantly heated. Where it is observed that drawing, even of the non-uniform variety, is not occurring, it will be necessary to adjust the drawing conditions in an opposite sense to a state productive of nonuniform cold drawing, as previously discussed, this is most easily accomplished by increasing the ambient relative humidity to a value just below the level necessary for uniform drawing, especially in the case of nylons. A preliminary evaluation' of the presence or absence of the desired slub pattern is easily made by a visual examination of a dyed length of yarn which, because of the variable dye take-up of the thick versus thin (undrawn versus drawn) portions facilitates the measurement of the frequency in length of the slub portions.

The invention is further characterized, but is not intended to be limited, by the following examples.

EXAMPLE 1 A sample of nylon 66 yarn having 34 filaments and a spun denier of 310 was drawn at a ratio of 3.2:1 at a draw speed of 73.6 feet per minute in the absence of a draw pin. The yarn Was heated by placing a carbon arc lamp at the focus of one of a pair of optically aligned parabolic reflectors arranged as shown in the drawing. The yarn was passe-d through the focus of the second parabolic reflector, which was spaced about 18 inches from the first reflector and so situate-d that the intercepted beam from the carbon arc lamp transmitted thereto was directed onto the yarn path. A rotary shutter of the type illustrated, fashioned out of a circular piece of heavy paper having two pie shaped sectors cut therefrom with an included angle of 45 and spaced 180 apart. The shutter was mounted on the shaft of a variable speed motor and rotated at 96 r.p.m.

The yarn was collected on a take-up bobbin and was observed to have uniformly spaced thick sections whose frequency was 2. 61 sections per foot and whose length was 1 inch. The thick section denier was observed as 310 While that of the thin or drawn sections was 100.

EXAMPLE 2 The procedure outlined in Example 1 was followed, save that the circular shutter was exchanged for one having pie shaped sectors of an included angle of 60. The slub frequency of 2.61 per foot was unchanged from that obtained in Example 1, but the length was decreased to 0.9 inch.

EXAMPLE 3 Following the procedure of Example 1, but rotating the shutter at 200 rpm, the frequency of the resulting undrawn sections was observed to increase to 5.4 per foot and the length decreased to 0.52 inch.

EXAMPLE 4 The sample of yarn prepared in Example 1 was knitted and dyed with a dispersed dye. The dyed fabric exhibited the expected novel effect of deep dyed thick sections on a background of a lighter shade of thin sections.

In addition to preparing thick-thin yarns from the materials described in the foregoing examples, this invention may be advantageously employed to prepare such yarns from a variety of other fiber-forming materials, insofar as they are capable of being cold drawn non-uniformly. Such materials may include both natural and synthetic polymers which are capable of being uniformly drawn when sufliciently heated under tension at suitable conditions of temperature and moisture. Although yarns which have not been drawn are preferred, partially drawn yarns which may be further drawn upon heating may as well be processed. Yarns prepared from polyamides, polysulfonamide, polyesters, polyurethanes, polyureas, polyacrylonitrile, polyhydrocarbons, e.g., polyethylene, polypropylene, polyvinylchloride, cellulose esters, cellulose ethers, as well as many others, may be drawn employing the process and apparatus of the present invention.

It may now be appreciated that there has been herewith disclosed a novel apparatus for producing thick-thin yarns, which apparatus makes it possible to exercise a precise control over the slub pattern and which is of high reproducibility, making it possible to merge two or more different runs. The application of radiant heat at controlled intervals of predetermined occurrence and duration to a continuously running length of yarn being processed under conditions otherwise productive of non-uniform cold drawing, i.e. below its natural draw ratio, in the absence of a draw pin has been found to fill these objectives in both a simplified and economical manner.

Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

What is claimed is:

1. An apparatus for producing yarns exhibiting a variation in denier along their lengths, said apparatus comprising means to propel a continuously running length of yarn under substantially uniform tension, a pair of parabolic reflectors mounted in optical alignment, a radiant heat source disposed at the focus of one of said pair of reflectors, said propelling means being arranged to travel a length of yarn through the focus of the other of said pair of reflectors, and shutter means interposed between said pair of reflectors and operative to selectively interrupt the optical path between said pair of reflectors Whereby spaced intervals along a length yarn may be heated at timed intervals of predetermined and variable ocurrence and duration to thereby cause the heated segments of said yarn to be drawn to a reduced denier relative to the unheated segments thereof.

2. An apparatus as defined in claim 1 wherein said shutter means is further characterized by a rotatably mounted disc, said disc having circumferentially spaced perforations formed therein.

3. An apparatus as defined in claim 1 wherein said radiant heat source is an electric arc.

References Cited UNITED STATES PATENTS 2,503,758 4/1950 Murray 264-25 X 2,746,084 5/1956 Kreidl 181 2,953,427 9/1960 Egger 18-8 X 2,975,474 3/1961 Smith 264288 X 3,081,485 3/1963 Steigerwald 18--1 X WILLIAM J. STEPHENSON, Primary Examiner.

Claims (1)

1. AN APPARATUS FOR PRODUCING YARNS EXHIBITING A VARIATION IN DENIER ALONG THEIR LENGTHS, SAID APPARATUS COMPRISING MEANS TO PROPEL A CONTINUOUSLY RUNNING LENGTH OF YARN UNDER SUBSTANTIALLY UNIFORM TENSION, A PAIR OF PARABOLIC REFLECTORS MOUNTED IN OPTICAL ALIGNMENT, A RADIANT HEAT SOURCE DISPOSED AT THE FOCUS OF ONE OF SAID PAIR OF REFLECTORS, SAID PROPELLING MEANS BEING ARRANGED TO TRAVEL A LENGTH OF YARN THROUGH THE FOCUS OF THE OTHER OF SAID PAIR OF REFLECTORS, AND SHUTTER MEANS INTERPOSED BETWEEN SAID PAIR OF REFELCTORS AND OPERATIVE TO SELECTIVELY INTERRUPT THE OPTICAL PATH BETWEEN SAID PAIR OF REFLECTORS WHEREBY SPACED INTERVALS ALONG A LENGTH YARN MAY BE HEATED AT TIME INTERVALS OF PREDETERMINED AND VARIABLE OCURRENCE AND DURATION OF THEREBY CAUSE THE HEATED SEGMENTS OF SAID YARN TO BE DRAWN TO A REDUCED DENIER RELATIVE TO THE UNHEATED SEGMENTS THEREOF.

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