US2400276A - Opposite-twist woven fabric and method - Google Patents

Description

, y 1946- R. c. WHITMAN 2,400,276

OPPOSITE-TWIST WOVEN FABRIC AND METHOD Filed March 9, I94? 2 Sheets-Sheet 1 v a w/Z%M fnvenfizt p1 A! a May 14, 1946. I R. c. WHITMAN 2,400,276

OPPOSITE-TWIST WOVEN FABRIC Al lD METHOD Filed March 9, 1944 2 Sheets-Sheet 2 sm- A i .4 4 I a.

Patented May 14, 1946 Ross C. Whitman, Walpole, Mass, asslgnor to The Kendall Company, Boston, Mass.,

tion of Massachusetts 7 Application March 9, 1944, Serial No. 525,719 12 Claims. (01. 28-74) This invention relates to woven textile fabrics and methods of making the same, and the object of the invention is to provide fabrics having substantially no tendency to curl which are woven using yarns twisted in opposite directions. The principal commercial applications of the invention are found in the field of stiffened woven fabrics to which the invention is particularly di-: rected, though it is also useful in some unstiifened fabrics, principally narrow fabrics. v

There are numerous uses for fabrics having little or no curling tendency,'for instance, in dress goods, yard goods, and curtain fabrics (e. g.. organdies, lawns, voiles, marquisettes, fine muslins, uniform, and print cloths); in narrow fabrics including slit goods, tapes, ribbons and the like; and in various mechanical and industrial fabrics, both wide and narrow- (e. g. muslins, drills, twills,sheetings) such as those used for radio spiders, condenser and insulating cloths, shoe linings, etc. Though most fabrics do not curl objectionably in the absence of a stiffening treatment, this is by no means universally true, particularly with respect to narrow and "s1it fabimproved materially were it possible to determine and eliminate therefrom objectionable curling and so provide, as the present invention does, a satisfactory and certain basis for substantially eliminating such objectionable curling during not only cuttin and fabrication into various articles of manufacture (which is suflicient for many purposes) but also during the utilization thereof-the latter particularl with respect to stiffened fabllCS.

It has long been known in the textile art that many fabrics exhibit an undesirable degree of curl. For example, if a typical piece of a commercial light-weight stiff fabric, such as ordinary organdy, say about a foot square, is laid upon a flat surface, it willexhibit a.curl such that diagonally opposite corners, for example, the top left-hand corner and lower right-hand corner, will lift from the flat surface and curl back over'the-central portion of the square of fabric so as to form a scroll. .This tendency of certain farics to curl and roll up has been particularly troublesome to manufacturersand proca corporachemical and mechanical finishing treatments of the yarns employed and/ or of the body of the fabries; special weaving or treatment of selvages; and special weaving of the body of the fabrics, such as weaving a fabric with right-hand (Z) and lefthand (S) twisted yarns arranged in alternate pairs in the warp and with unidirectionally twisted yarns in the filling, as in Schiinholzer;

U. S. Patent No. 2,215,938 (Fig. 2), or to use yarns in pairs of alternate twists both in the warp and in the filling (Fig. 3), only the latter of which can possibly achieve-by a mode of operation differing from the present invention and at very considerable manufacturing expense because of requiring box looms- -a non-curling stiffened fabric. However, all of these methods have proven incapable of solving the problem, except one which is very expensive, if not prohibitively so (as f in Schonholzer Fig. 3) because it involves the use of specialized equipment and extra operations.

The many conflicting proposals for the solution of the long-standing problem of fabric curl, particularly in stiffened fabrics, many of which proposals involve the use of opposing directions of twist of component yarns, evidence both a failure to understand the significance of yarn twist to the phenomena of curl in fabrics and a complete failure to appreciate the presence and importance of' vide textile fabrics both wide and narrow which exhibit substantially no tendency to curl. A particular object is to provide a fabric of such novel characteristics that it will not curl materially or objectionably upon being subjected to a fusing or other stiffening treatment. Further particular objects are to ,provide non-curling stiffened fabrics and a method of making the same.

The present invention was made only after very considerable study and experimental investigation in the course of which, in accomplishing the above objects, there were made several as-' tonishing and unpredictable discoveries relating to the factors which influence fabric curl, namely, the discovery that yam size of component yarns is the major factor though but one factor involved in the curl of fabrics and that yarn twist and the number of yarn ends per inch of fabric component yarns.

in the warp and filling directions have an important effect as hereinafter appears. Fundamentally, it was discovered that the sets of warp and filling yarns have a profound relationship and eifect inter se and that the fabric curling r torque efiect exerted by a given warp yarn can be and is neutralized or offset. by the curling effect of a filling yarn of the same size and the same twist (same number of turns per inch'and same direction of twist), and, further, it was discovered that the curling effect of one set of yarns (warp or filling) can be neutralized by the other set of yarns including yarns of both directions of twist, and though said other set also differs from the first set in yarn size, in twist multiple, and in number of yarns per inch of fabric, the difference occurring in one or more of the factors. The method of practising the invention by applying these discoveries in the manufacture of fabrics having substantially no tendencyto cur1 is fully set forth hereinafter.

While the above discoveries 'are novel contributions to the art, there were also made other discoveries relating to the mechanism of curl of stiffened fabrics which are equally astonishing. My conception as to the true mechanism of fabric curl has beenconflrmed by study and dissection of numerous test specimens which show that soft unstiffened fabrics that tend to curl are caused so to do by the untwisting of certain dominant Study of certain stiffened fabrics, however, resulted in the paradoxical discovery that in such fabrics the curl is caused by an increase in the twist (i. e. a twisting tighter) of the dominant component yarns-these yarns imparting a net curling effect even though the same set of yarns include stiffened yarns of opposite twist. For example, when a foot square piece of a certain commercial broadcloth was laid upon a fiat surface, it was observed to curl in that two of the diagonal corners lifted up somewhat from the flat surface and the other two diagonal cor ners attempted to curl downwardly. The curl here was caused by an untwisting of certain component yarns. However, upon subjecting said piece of fabric to the usual starch stiffening treatment and again laying it upon the table, it was observed that the diagonal corners which tended to curl upwardly before, then tended to curl strongly in the opposite direction, or downwardly, and that those corners which had curled downwardly before curled strongly in an upward direction. This was caused by the component yarns twisting tighter as the result of such stiffening treatment. This phenomena of reversal of direction of curl upon such stiffening has not been known and appreciated heretofore.

By properly applying these discoveries in yarn manufacture and selection, in weave layout and weaving of textile fabrics, one can produce a wide range of novel fabrics having at least one set of yarns with opposite twists and which are characterized by a substantial absence of curl even though stiffened, or by a curl which is controlled to any desired small degree. Furthermore, one can produce the required yarns and such fabrics on standard textile equipment and at no substantial increase in cost over the cost of otherwise similar common textile fabrics of equivalent weight.

In the drawinzs- Figs. 1 and 2 are perspective views representing fabrics, much enlarged, and illustrate the modus operandi of curling, Fig. 1 being an unstifiened fabric with warp and filling of opposite twists,

respectively, and Fig. 2 being a stiffened fabric with warp of right-hand (Z) and, left-hand (S) twisted-yarns arranged alternately and with filling of unidirectional twist;

Fig. 2a is a perspective view representing typical curl of a small square of the fabrics of Figs. 1 and 2' when wholly unrestrained;

Fig. 3 is a perspective view illustrating one preferred type of a non-curling fabric, much enlarged, of the present invention; and

Fig. 4 is an enlarged diagrammati plan view illustrating another preferred type of fabric of my invention.

Referring to the drawings, and particulary to Figs. 1 and 2, there are illustrated two portions of different fabrics resting on flat horizontal surfaces (indicated by dashed lines). Fig. 1 represents a conventional unstiffened fabric with warp yarns 2 and filling yarns 3 of opposite twists, respectively, the warp yarns 2 being of S-twist and the filling yarns 3 being of Z-twist., In Fig. l the warp yarns 2 tend to untwist (as indicated by the arrows) and, in turn, to lift the lower and diagonally oppositeupper corners (as shown) of the fabric from the supporting surface, the two remaining diagonally opposite comers tending to bend in the opposite or downward direction, and

the filling yarns 3 tend to untwist in the opposite direction (as indicated by the arrows) ,-and also lift said comers so that the curlingtendencies of the'two sets of yarns augment each other in lifting said lower and upper corners, and try to bend the other two corners downwardly. If the fabric of Fig. 1 were stiffened, the diagonally opposite left and right corners would strongly curl upwardly, and the other corners downwardly.

Fig. 2 represents a stiffened fabric of unidirectional twist having warp yarns of right-hand (Z) and left-hand (S) twisted yarns, 4S and 4Z respectively, arranged alternately, and filling yarns 5 of unidirectional (S) twist and of the same size as the warp yarns 4 in which the yarns of both sets seek to twist tighter (as indicated by the arrows), the tendency of the yarns of each pair of warp yarns 4 being to oflset each other and the wholly unopposed tendency of the filling yarns 5 being to lift the lower and diagonally opposite upper corners from the supporting surface. In order better to show the mechanism of curl, Fig. 2 illustrates it as more nearly fiat rather than in the strongly curled position which it would normally assume, as indicated by the dot and dash lines. f

Fig. 2a shows a curl typical of either of the fabrics of Fig. 1 or Fig. 2 when a piece of such fabric is wholly unrestrained and illustrates how such a fabric, if the curl continues, tends to form.

a scroll. In accordance with the earlier explanation, then, the curl of a textile fabric isdue to the net curling effect of the two sets of yarns on each other. V f

Fig. 3 illustrates a non-curling stiffened fabric of this invention resting on a flat horizontal support, with warp yarns 62 and GS of opposing twists, there being five yarns 62 for each yarn is as shown. These warp yarns are of larger size than the unidirectional Z-twist filling yarns l. with the latter equal in number of ends but of the required degree of twist (not shown) in which both sets of yarns tend to twist tighter; the net tendency of the warp yarns 3 to lift the lower and upper corners being neutralized by the set of fillfabric does not curl.

Fig. 4 illustrates diagrammatically a stiffened fabric in which the warp yarns I2 and US of opposing twists are twice as numerous and are of the same size and degree of twist (not shown) as the unidirectional Z-twist filling yarns 9, the set of warp yarns being neutralized as to'fabric curling tendency by the filling yarns, the excess part of the warp having the same direction of twist as the filling being offset by an equal number of warp yarns of opposite twist direction, providing a fabric having substantially no tendency to number of filling ends per inch exceeds that ofthe warp. Also, forsimilar reasons of economical and practical manufacture on modern spinning and weaving equipment, nearly all fabrics heretofore, particularly industrial fabrics, have larger warp yarns than filling yarns. For the same reasons, warp twist has been ahnost invariably higher than filling twist-in the trade "warp twist is synonymous with high twist, and filling twist is synonymous with low twist. l

. The foregoing principles of the invention afforded a basis for my derivation of a mathematical equation which, as a practical matter, gives a general guide for successful application and use of the invention. in the actual manufacture of non-curling fabrics. follows:

M is twist multiple, N is yarns number (size) E is end count, and w and if refer to warp and filling, respectively.

In the use of the equation for fabric design and manufacture after the general construction as to end count and yarn size has been determined (for example, in a preferred fabric with a set of opposing twists and a set of unidirectional twist) the equation is applied first only to warp and filling yarns of unidirectional twist, that is, to the unidirectional set of yarns (whether such set be filling, as usually preferred, or warp) and to the yarns of the same direction of twist-in the other or second set and the equation is solved so as to determine the number of such latter yarns necessary to neutralize the fabric curling tendency of the first set. The remaining yarns of said second set are then divided equally into yarns of each direction of twist (it being assumed that all the yarns of said second set are of the same size and twist multiple).

Referring to the fabric of Fig. 3, for example, the equation is first applied to filling yarns of unidirectional Z-twist and the required number of warp yarns of the desired size of theme direction of twist necessary to neutralize the fabric curling tendency of said filling yarns is determined-here four warps per six fillings. This leaves two warp yarns for each basic unit of this The basic equation is as fabric construction, which two warp yarns are then divided into l-S and l-Z-all of the warp yarns in this example being of the same size and twist multiple. This gives the square weave fabric 5 as shown in Fig. 3 in which there are six Z-twist filling yarns for six warp yarns made up of five Z-twist yarns and one S-twist yarn.

In Fig. 4 the procedure is similar only there two Z-twist warp yarns are found to equalize the fabric curling tendency of each two of the unidirectional twisted filling yarns, leaving two warp yarns of opposing twist for each basic unit of this fabric construction.

In accordance 'with the teachings of this invention, fabric curl can always be avoided by in- I corporating the correct number of opposite twist 1 yarns (of the required size and twist multiple) in but one set of yarns-the st that would otherwise be dominant from the standpoint of curl-so that the net fabric curlingtendency qf said set just neutralizes the opposite fabric curling tendency of the other set of yarns. Normally, then,

as in the preferred fabrics of this invention. one set of yarns is of unidirectional twist, and in the 'majority, of cases the filling set is of unidirectional twist rather than the warp set for, in such cases, the warp set normallyand conventionally would be the dominant set to be modified in accordance with this invention. If the filling set includes yarns of opposite twist, important economic advantages are lost, particularly where box looms would be required to insert singles yarns of opposite twist. Though both sets may include yarns of opposing twist, it is notnecessary, and, similarly. important advantages are lost in so doing. I

Where each set includes yarns'of opposing twist (as well as where but one set does) the basic equation may be applied to give the net fabric 40 curling effect of each set as follows:

where M equals twist multiple, N equals yarns number, E equals end count, 10 and f refer to warp and. filling respectively, and Z and S refer to the respective directions of twist.

Similarly, if either set of yarns includes yarns differing from each other in size or twist. multiple, it will .be necessary to consider each group of similar yarns separately and add together the results thereof to obtain the total net factor for each set. The twist multiple employed in the equations is the-same as that employed in the textile art and equals twist turns per inch of yarn divided by the square root of the yarn number (cotton system), and for the purpose of the equations and in the specification and 05 claims the size of all yarns is expressed on the cotton system, for example, 350 denier rayon yarns are classified approximately as number 15.2; and the expression "end count is to be taken as meaning the number of yams per inch '7 offabricin the designated direction. In the application and use of the invention it is not necessary'strictly to adhere to absolute equality as variations from the equality represented by the equations are necessarily encountered inpractice, thev ultimate test being whether any given fabric embodies the principles and features of the invention as herein described and claimed.

In the manufacture of stifi'ened fabrics to which this invention is principally directed, there are various means of stiffening which can be conveniently divided into-three general groups. The first and most common involves the application of a water-soluble film or sizing to the surface of the base fabric. This group includes water-solutions of the starches, various common finishing gums, sugars, etc. The stiffening obtained with these products is removed when the fabric is laundered. The second method is to apply a water-carried water-insoluble substance to the base fabric. Various resins such as phenol formaldehyde, urea formaldehyde, casein formaldehyde, the alkyd resins, and the methacrylates are useful for this purpose. icals are water-insoluble when applied, or are rendered insoluble after application (by baking the fabric, usually), the stiffness obtained is not immediately or readily removed when the fabric is washed. Effects obtained with such waterinsoluble materials as these are called permanent finishes, although in a series of, say, 10 to 25 launderings, these resins are gradually dislodged from the fabric and their benefits disappear. The two methods may be applied to plain or mixed fabrics or yarns made of any textile fibres including staple or cut staple, natural or synthetic cellulosic fibres or continuous filaments (later referred to). There also may be included silk, wool or Aralac (casein wool) nylon, or other non-cellulosic synthetic fibres r filaments, such as vinyl acetate and vinyl chloride copolymers, and vinylidene chloride, for example, those sold under the respective names of Vinyon and Saran, or even inorganic fibres such as glass or asbestos.

The third method is employed only for stiffening base fabrics woven from or including yarns made up of, or which include mixed with other fibres, cotton or other natural cellulosic fibres such as sisal, ramie, hemp or jute, or synthetic cellulosic fibres such as viscose, cuprammonium and other regenerated cellulosic fibres (either cut staple or continuous filament), or cellulose ester fibres (either cut staple or continuousfilament) such as cellulose acetate, cellulose butyrate, and cellulose propionate, or mixtures or copolymers of the same. This method involves the use of a chemical which swells and gelatinizes the cellulosic fibres themselves. When this chemical is neutralized or leached out, the cellulose is reprecipitated, the yarns or cellulosic fibres thereof are more or less stuck together, and the -whole fabric is markedly stiffened, though not necessarily equally in both directions. Since the stiffening medium is in the cellulose itself, this stiffening method is usually the best so far as wash- 2,4co,27c

and rayon, is well known in the cloth-finishing trade and is referred to in the art as swelling,

fusing, gelatinizing or parchmentizing', though h'erein usually termed -fusin'8." The methods or processes followed in using these various agents 'difler but'the conditions have been thoroughly worked out for each of them and are well known to thoseexperienced in the trade. For example, cellulosic fabricsfused with zinc chloride are exposed to treatment for a, number of hours, whereas goods of 'a' cellulosic composition processed'with Since these chemsulphuric acid are treated for only a few seconds. All three types of treatments in stiffening fabrics including cellulosic fibres and cellulosic yarns produce first a. swelling and th'en cause the fibres to coalesce or adhere somewhat as the swelling is reduced during drying.

In ordinary textile fabrics the individual yarns have a desire to untwist somewhat. If the fabric is wet with water and the yarns are thus swollen, or are swollen by other liquid means, the desire of these yarns to untwist is increased. If the normal .yarns could have their diameters decreased, the desire of these yarns to untwist would likewise be decreased, and might be decreased far enough so that they actually try to twist up tighter. This accounts for the fact that swollen and stiffenedyarns in a textile fabric, upon drying, and. accompanying decrease in diameter, at-

tempt to twist tighter. The fibres of the yarns are stuck together so that they approximate monofilaments. In such coalesced yarns, two or three turns per inch will produce a considerable torsion, whereas in ordinarysoft cotton yarns, two or three turns per inch do not produce any detectable torsion. When a yarn is fused, for example, with zinc chloride, it is swelled by the zinc chloride (strongly increasing its desire to untwist), the zinc chloride is then leached out coalescing and solidifying the yarns in a somewhat swollen state (as the zinc chloride is removed, the swelling in the yarn gradually decreases) and, then, as the yarn is dried, its final diameter is somewhat decreased. It is during this drying process that the tendency of the yarn to untwist disappears and the tendency of the yarn to twist tighter becomes evident, the latter tendency, because of the coalescence, being much stronger than the former. This type of reversal of curl or reversal of twist tendency apparently results whenever a yarn is first swollen (either fastness is concerned; For fusing agents a very considerable number of chemicals which are known and have been used in the textile art as fusing agents are available for this purpose, forexample, in treating a cotton fabric, zinc chloride or fusing agents such as cuprammonium (copper tetramine hydroxide) or sulphuric acid can be by water of solution or water of condensation), then stiffened or coalesced, and, upon drying, finally condensed, by condensed meaning that the diameter of the yarn is decreased, the density of the yarn being increased. The similarity of the foregoing types of stiffening agents from a fabric curl standpoint, and the importanceof swelling and subsequent condensation in the production of curl have not been appreciated or understood heretofore. For the purposes of applying the principles and the mathematical equation-before referred to, the direction of twist in yarns so swollen and stiffened must be taken and regarded asin the direction of twisting more tightly. If stiffening takes place in the absence of swelling, however, yarns so stiffened will untwist in the same way as they did beforebeing stiffened.

Various stiffened fabrics may be made which include a substantial proportion of yarns in the warp, filling, or both, which are not swollen and stiffened so as to produce a reverse curl (yarns twisting tighter), in such fabrics the warp and filling each including 20% or more of swollen and stiflened yarns with their reverse fabric curling trol tension with less precision, generally. Also,

tenden' es oflset in general accordance with the forego disclosure. In such cases the proportion of yarns not so stiffened (as well as their direction of twist) may be safely disregarded as not significant in view of their relatively negligible effect upon curling as compared with that of the pronounced and very much greater curling efiect of the swollen and stifiened warp and filling yarns. Similarly, if but a few soft yarns of opposite twist (than the dominant stiffened warp and filling yarns) be inserted, as, for a pattern effect, for example, they may bedisregarded since they do not significantly unbalance the equation.

In the practice of this invention itis essential to provide warp yarns and filling yarns that are spun with precision from uniform card sliver to definite sizes and twist multiples, andso woven that all areas of the 'body of the fabric are strictly uniform in construction since it is these factors, and their relation to each other, that are depended upon in arriving at the desired result. Even with the most modern equipment, and with carefully controlled spinning-room humidity, it is well known that considerable variation in the yarn size occurs as spinning proceeds. A spinning machine balanced and adjusted to produce 30s yarns may, after a week or ten days operation, be found to be delivering as fine'as 35's or 36's, or as heavy as 27s or 26s, the shift toward lighter yams usually proceeding faster and further than the shift towards heavier yarns: These variations are usuallyv explained as resulting from humidity changes, temperature changes, stock changes, and

machine wear, producing maladjustments.

Standard practice in modern textile mills calls for the analysis of yarns approximately every two weeks, and the readjustment of yarns size prescribed is made usually on the first roving frame, usually called the slubber, or the second roving frame, known as the .first-intermediate. This measure of control is satisfactory for ordinary fabric manufacture, but since it would permit drifting of yarn size to the extent mentioned above, it is obvious from the equation underlying this invention that it is entirely inadequate for the practice of the invention. Also, any change in yarn size produces a significant change in twist multiple since the spinning-frame delivers a fixed number of turns per inch to the yarn, rather than a fixed twist multiple. In the manufacture of fabrics of this invention it is recommended that -yarn analyses and equipment adjustment as needed be made daily, usually at the second drawing frame rather than on any of the succeeding roving, frames. In addition, special care should be taken in the control of spinning-room humidities, etc.

In making use of the equation, actual yarn sizes, as determined by analyses in the spinning: room, and actual twist multiples, as determined by well known formulas involving spinning-frame gears, should be used rather than the theoretical or standard values. Similarly, actual end counts as reported by the weave room should be used. It isjound that usually the slight changes in the end counts occasioned by variations in reasonable care should be taken to'avoid any considerable distortion'of the woven neutralized fabric in subsequent finishing processes. With fairly equal tensions thereinso that the end count in the finished fabricis roughly equally higher or equally lower in both the warp and the filling, however, no trouble 'need be anticipatedon this score.

Some examples of the invention are as follows:

Example I A certain prior art lightweight fabric designed a to be stiffened with a hydroxyethyl cellulose finish has an actual end count of 59.4 x51.4, warp yarns 29.95s with a twist multiple of 4.48 and filling yarns 50.06s with a twist multiple of 3.91. This material shows a marked curl after 'being stiffened, since it is out according to the equation by 1.002'units in the warp. The reason for the heavy warp yarns in this fabric is that high warp strength is required, and the reason for the light filling yarns is that the weight of the finished product must not exceed certain definite limits. A direct application of the equation (in accordance with my co-pending application Ser. No. 512,211) teaches only that this curl can be avoided by increasing the filling count (which cannot be done here since it would increase the weight of the fabric) or decreasing the warp count (which cannot be done because it would decrease the warp tensile strength) or heavying up on the filling yarn (which cannot be done because it would increase the weight of the fabric) or' lightening up on the warp yarn (which cannot be done because it would decrease the warp tensile strength). curling characteristics of this product by increasing the tightness of twist in the fillingyams and by decreasing the tightness of twist in the warp yarns. The latter would have to be held at a minimum since any significant decrease would significantly decrease the warp tensile strength. On applying the equation it is found that if the filling twist multiple were increased all the way to 6.00, the fabric would still be out by 0.699 unit in the warp, which would be sufficient to generate a very objectionable curl.

In this case, to satisfy the above conditions, the only satisfactory way to eliminate the curl is to include some reverse twist yarns in the warp. 0n application of the equation, it isfound that the warp value is 1.459, the filling 'value being 0.457. By setting the warp side of the equation equal to this filling value and solving for E, it is found that 18.6 warp yarns per inch will exactly balance the 51.4 filling yarns per inch. Subtracting 18.6 from 59.4, the remainder of 40.8 warp' yarns must be balanced between themselves,

fabric is produced which exactly satisfies the stipulated fabric specifications and that is out in the warp by only 0.029 unit.

Example, II

A fabric foruse as a base cloth which will not curl after being impregnated with phenol form- It would be possible to decrease the aldehyde and the resin then set can be made with a standard count of 80 x 60 using 30s yarns with a twist multiple of.4.18 in the warp and 40's yarns with a twist multiple of 3.29 in the filling. when the equation was applied to this fabric, using an actual end count of 79.8 x593, and actual yam numbers of 30.05s and 40.32s, it is found that the warp has 'a value of. 1.804 units and the filling a value of 0.620 unit, giving a fabric which is out in the warp by 1.184 units. If the filling value of 0.620 is substituted in the warp and that side of the equation is solved for E, it is found that 27.4 warp ends are necessary to balance the curling effect of the filling yarns. The balance of the warp yarns numbering 52.4 must be divided evenly between S and Z and thus balanced against each other in order to produce a fabric which is entirely free from curl. Simplifying, if the filling is woven from 100% Z-twist yarns and; the warp has two Z-twist yarns for every one S=twist yarn the warp pattern being SZZ, SZZ, etc., a non-curling stiifened fabric cloth is produced which, according to the equation, is out by only 0.019 unit in the filling. This example is well suited for the manufacture of radio spiders.

Eznample III A base cloth for laminated sheets and tapes may be made from an 88 x 40 actually 87.8 x 39.7) construction, using 25.03s yarns in the warp with a twist'multiple of 4.52 and 39.87s yarns in the filling with a twist multiple of 3.28. The

equation shows that this fabric has a warp value of 2.903 and the filling has a value of 0.422, giving a fabric which is out by 2.481 units in the warp. Solving the equation in accordance with tern in this case is ZSZSZSZ, ZSZSZSZ, etc. Ap-

plying the equation to this fabric using a pick count of 87.8 shows that it is out by only 0.007 unit in the filling.

J I Emamplell? A 68 x 56 non-curling organdie is produced as follows: In this fabric the actual end count is 67.8 x 55.4, the warp yarns being 60.31s with a twist multiple of 6.71 and the filling yarns 80.22s

with a twistmultiple of 6.03. Applying the equation to this fabric indicates that it is out by 0.468 unit in the warp, the filling having a value of 0.371. Solving for the warp yarns as before, we find that 30.0 ends are required to balance the filling, and therefore the balance of 37.8 should be equally split into S and Z-twist yarns. This gives a ratio of almost exactly Z-twist yarns to every two S-twist yarns inthe warp providing that the filling is all Z-twist. Using a warp pattern of SZZZSZZ, SZZZSZZ, etc., therefore, a noncurling organdie fabric can be woven to the desired specifications which is out by only 0.012

unit in the filling according to the equation.

Example V A three-leaf filling twill using novelty yarns in the filling which after fusing is suitable for use as an interlining fabric in heavy clothing is made with an actual end count of 69.5 x 71.3.

The warp will consist of 22.607; yarns with a twist multiple of 4.50. The filling yarns will be combined by putting together as a group or separately alternately weaving by a box loom a 13.91s yarn with a twist multiple of 3.75 carrying with it some other-yarn of opposite twist which is heavy enough and twisted tightly enough to produce a fabric which will not curl. The equation shows that the warp value for this fabric is 2.689, and the filling value contributed'by the 13.91s is 4.864. This means that the additional yarns in the filling must contribute a negative filling value of 2.175 equation units. If I set 2.175 equal to the filling side of the equation, substituting 3.50 as a reasonable twist multiple and solve for the weight of the unknown filling yarns to be used, I find that these should be 22.09s reverse twist in order to produce a fabric which will not curl. Such a fabric would be out in the filling by 0.001 unit.

Example VI A mosquito netting with a leno weave which will not curl after being stiffened with one of the permanent stiifening agents such as are described heretofore in this application, is made up as follows: This fabric will have a theoretical end count of 28 x 14, using 29.93s yarns with a twist multiple of 4.60 in the warp and 31.88s' yarns in the filling with a twist multiple of 3.82. The actual end count of this fabric is 27.7 x 13.5. The warp value according to the equation is,0.701, the filling value being 0.250. This gives a fabric which is out by 0.451 unit and curls significantly. Solving for the warp ends as before,I find that 9.9 warp ends per inch are necessaryv to neutralize the curling effect of the filling yarns. The balance of the warp ends should be equally divided between S and Z-twist. This result suggests a very simple warp pattern in which two Z-twist yarns are tied in for every one S-twist yarn providing that the filling is Z-twist. Applying the equation once more to this over-all result indicates that the fabric will be .out by only 0.016 unit in the filling.

Example VII A warp twill fabric useful as an interlining and in various industrial applications which will not curl after being stiffened is made with an actual end count of 72.0 x 41.7. The warp yarns are 7.75s with a twist multiple of 4.90, the filling yarns being 12.03s.with a twist multiple of 3.52. Applying the equation I find that this fabric is out by 12.66 units in the warp, and that 15.0 warp ends are sufficient to entirely neutralize the curling effect of the filling yarns. If the filling is entirely Z-twist, this calls for drawing in the warp in such a way that 43.5 ends per inch are Z-twist and 28.5 ends per inch are S-twist. There is no simple warp pattern which is apparent around these two figures, so I arbitrarily lift the Z count in the warp to 45.0 and depress the S count to 27.0. This permits a fairly simple warp pattern in which five Zs are drawn in with every three Ss. However, it produces a fabric which is out in the warp by 0.63 unit, which is enough to produce a significant curl after. any thorough stiffening treatment. Accordingly, it is here necessary to make one final adjustment. The warp twist multiple which was originally set at 4.90 is dropped to 4.20 to further reduce this warp value. According to the equation this gives a warp value of 3.414, leaving a fabric which is out by only 0.078 unit in the warp.

The base or unstiifened fabrics made in ac cordance with this invention may conveniently be tested and compared from the standpoint of curl by cutting small five inch squares therefrom, impregnating such squares with a test solution (suitable for the character of the fibres and yarns to be stiffened therein) hot ironing the same, and

then noting their deformation under standard made up as follows:

- Parts Bakelite solution (XR568partially polymerphenol formaldehyde solution, 40% Bakelite, 60% methyl alcohol) 4 Methyl alcohol 1 spam 7 said set of unidirectional twist by means of a part of its yarns of the same direction of twist,

said part of its yarns being so related to said set of unidirectional twist with respect to twist mulwhere M equals twist multiple, N equals yarns number, E equals end count, and w and I refer to warp andfllling, respectively, the remaining Water The pick-up of the solution by the fabric may, for example, be from 125 to 150% by weight (on the weight of base fabric). The sample is then pressed between two heated metallic surfaces (net total pressure lbs.) and a temperature of approximately 150 C., for 60 seconds in order to completely polymerize and set the resin. The sample is then at once removed and placed without restraint on a horizontal surface, such as a table, and promptly observed. 'Since this test is so searching, as a practical matter, fabrics so tested may be regarded as having substantially no tendency to curl if ,the sample remains substantially extended and no corner thereof rises more than 1 to 1 /2 inches above the supporting horizontal surface upon which it was placed.

Fabrics made in accordance with the preferred practice of this invention are well within the amount mentioned. Most of the stiffening or fusing solutions hereinbefore referred to as employed in ordinary commercial applications as practiced in the cloth-finishing trade, will not cause the rise of a corner of a five inch square more than /2 to 1 inch above the supporting horizontal surface.

, It will be clear from the foregoing that this invention provides novel fabrics and novel methods of making such products with equipment and materials commonly available, and that the nature of the invention is such that'these goods can be produced at an entirely reasonable cost. While I have herein disclosed typical fabrics embodying this invention and suitable methods of making them, it will be understood that the invention is susceptible of embodiment in a great variety of forms within its spirit and scope, and that minor departures may be made from the methods above described while still following the essential teachings of the invention.

Having thus described my invention, what .lI desire to claim as new is:

1. A textile material of the class described comprising a stiffened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of uniform-sized warp yarns and a set of filling yarns,

with both sets uniformly dispersed and arranged yarns of said opposing twist set of yarns bein substantially half Z-twist and half S-twist. I

2. A textile material of the class described comprising a stiflened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of uniform-sized warp yarns and a set of filling yarns, one of said sets being lesser in number of ends per inch of fabric than the other of said sets, with both sets uniformly dispersed and arranged throughout the body of the fabric, One of said sets consisting of yarns substantially all of unidirectional twist, the other of said sets having yarns of opposing directions of twist including a substantial number of yarns of each direction of twist but consisting mainly of yarns of the same direction of twist as said set of unidirectional twist, said set with opposing directions of twist neutralizing the fabric curling tendency of said set of unidirectional twist by means of 4 a part of its yarns of the same direction of twist, said part of its-yams being so related to said set of unidirectional twist with respect to twist multiple,

yarn number and end count as to produce substantially the equality represented by the equawhere M equals twist multiple, N equals arns number, E equals end count, and w and 1 refer to warp and filling, respectively, the remaining yarns of said opposing twist set of yarns being substantially half. Z-twist and half S-twist. 3. A textile material of the class described comprising a stiffened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of uniformsized warp yarns and a set of filling yarns, one of said sets being lesser in number of ends per inch of fabric than the other of said sets, withboth sets uniformly dispersed and arranged throughout the body of the fabric, the set of filling yarns consisting of yarns substantially all .of unidirectional twist, the other of said sets having yarns of opposing directions of twist'including of twistbut consisting mainly of yarns of the same direction of twist as said set of unidirectional twist, said set with opposing directions of twist neutralizing the fabric curling tendency of said set of unidirectional twist by means of a part of its yarns of theisame' direction of twist, said part of its yarns being so related to said set of unidirectional twist with respect to twist multiple, yam number and end count as to produce substantially the equality represented by the equawhere M equals twist multiple, N equals yarns number, E equals end count, and' w and ,1 refer to warp-and filling, respectively, the remaining yarns of said opposing twist set of yarns being substantially half Z-twi'st and half S-twist.

4. A textile material of the class described comprising a stiffened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of uniform sized warp yarns and a set of filling yarns, the latter of said sets being lesser in number of ends per inch of fabric than the other of said sets, with both sets uniformly dispersed and arranged throughout the body of the fabric, the set of filling yarns consisting of yarns substantially all of unidirectional twist, the other of said sets having yarns of opposing directions of twist including a substantial number of yarns of each' where M equals twist multiple, N equals yarns number, E'equals end count, and w and 1 refer to warp and filling, respectively, the remaining yarns or" said opposing twist set of yarns being substantially half Z-twist and half S-twist.

5. The method of producing a non-curling, mainly cellulosic woven fabric which comprises spinning, selecting, and weaving a set of uni-3 form warp yarns and a set of uniform filling yarns, one of said sets being of unidirectional twist and the other set including yarns of opposing twist, with the twist multiple, yarn siz and end count in one set, and the twist multiple, yarn ize, end count and same twist direction of a part only of the other set, all determined and the fabric woven in substantial conformity with the equation NW where M equals twist multiple, N equals yarn size, E equals end count, and w and I refer to warp and filling, respectively, the different characteristics of yarn and yarn arrangement specified in the equation being adjusted to produce substantially the equality represented by the question, the balance of the yarns of said other set being substantially half Z-twist and half S-twist, said fabric having its respective warp where M equals twist multiple, N equals yarn size, E equals end count, and w and refer to -warp and filling, respectively, the different characteristics of yarn and yarn arrangement specified in the equation being adjusted to produce substantially the equality represented by the equation, the balance of the yarns of said other set being substantially half Z-twist and half S-twist, said fabric having its respective warp and filling yarns uniformly dispersed and arranged throughout the body of the fabric, and then stiffening at least some of the fibres of at least some of said warp and filling yarns by impregnation with a stiffening agent character izedduring drying and setting by the evolution of water and finally drying the same, thereby materially stiffening saidfabric.

7. A textile material of the class described comprising a stiffened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of warp yarns and a set of filling yarns, with .both sets uniformly dispersed and arranged throughout the body of the fabric, at least one of said sets including a substantial number of yarns of each direction of twist and having a net fabric curling tendency opposing the opposite fabric curling tendency of the other set and substantially neutralizing the fabric curling tendency of said other set, the warp yarns being so related to the filling yarns with respect to twist direction and multiple, yarn number and end count sented by the equation:

and filling yarns uniformly dispersed and arranged throughout the body of the fabric.

6. The method of producing a non-curling, stiffened, woven mainly cellulosic fabric which comprises spinning, selecting, and weaving a set of uniform warp yarn and a set of uniform filling yarns, one of said sets being of unidirectional twist and the other set including yarns where. M equals twist multiple, N equals yarns number, E equals end count, w and I refer to warp and filling respectively, and Z and S refer to the respective directions of twist.

8. A textile material of the class described comprising a stiffened mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of warp yarns and a set of filling yarns, with both sets uniformly dispersed and arranged throughout the body of the fabric, at least one of said sets including a substantial number of yarns of each direction of twist but consisting mainly of yarns of one direction of twist and having a net fabric curling tendency opposing the opposite curling tendency of the other set and substantially neutralizing the fabric curling tendency of said other set, the Warp yarn-s being so related to the filling yarns with respect to twist direction and multiple, yarn number and end count as to produce substantially the equality represented by the equation:

where M equals twist multiple," N equals yarns number, E equals end count, and f refer to warp and filling respectively, and Z ands refer to the respective directions of twist.

9. A textile material of the class described com prising astiifened mainly cellulosic woven fabric having substantially no tendency o curl after hot yarns being so related to the filling yarns with respect to twist direction and multiple, yarn number and end count as to produce substantially the equality represented by the equation:

" iis H where M equals twist multiple, N equals yarns out the body of the fabric, each of said sets in-' cluding a substantial number of yarns of each direction of twist but consisting mainly of yarns of one direction of twist, and having a net fabric curling tendency opposing the opposite fabric curling tendency of the other set and substantially neutralizing the fabric curling tendency of the other set, the warp yarns being so related to the filling yarns with respect to twist direction and multiple, yarn number and end count as to produce substantially the equality represented by the equation:

" m s o -s where M equals twist multiple, N equals yarns number, E equals end count, to and I refer to warp and filling respectively, and Z and S refer to the respective directions of twist.

11'. A textile material of the class described comprising a mainly cellulosic woven fabric havin: substantially no tendency to curl after hot ironing, composed essentially of a set of uniformll sized warp yarns and a set of filling yarns, with both sets uniformly dispersed and arranged throughout the body of the fabric, one of said sets consisting 'of yams substantially all of unidirectional twist, the other of said sets having yarns of opposing directions of twist including a substantial number of yarns of each direction of twist but consisting mainly of yarns of the same direction of twist as said set of unidirectional twist, said set with opposing directions of twist neutralizing the fabric curling tendency of said set of unidirectional twist by means of a part of its yarns of the same direction of twist, said part of its yarns being so related to said set of unidirectional twist with respect to twist multiple, yarn number and end count as to produce substantially the equality represented by the equation where M equals twist multiple, N equals yarns number, E equals end count, and w and I refer to warp and filling, respectively, the remaining yarns of said opposing twist set of yarns being substantially half z-twist and half S-twist, whereby the tendency of the sets of yarns to curl the fabric when stiffened by impregnation with a stiffening agent characterized during drying and setting by the evolution of water is neutralized and the fabric when stiffened is substantially non-curling.

12. A textile material of the class described comprising a mainly cellulosic woven fabric having substantially no tendency to curl after hot ironing, composed essentially of a set of warp yarns and a set of filling yams, with both sets uniformly dispersed and arranged throughout the body of the fabric, at least one of said sets including a substantial number of yarns ofeach direction of twist and having a net fabric curling tendency opposing the opposite fabric curlin tendency of the other set and substantially neutralizing'the fabric curling tendency of said other .set, the warp yarns being so related to the filling yarns with respect to twist direction and multiple, yarn number and end count as to produce substantially the equality represented by the equation:

ency of the sets of yarns to curl the fabric when stiffened by impregnation with a stiffening agent characterized during drying and setting b the evaluation of water is neutralized and the fabric when stiffened is substantially non-curling.

ROSS C, WHITMAN.

v Certificate of Correction Patent N 0. 2,400,276. v May 14, 1946.

ROSS o. WHITMAN It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Rage 8, first column, line 59, claim 5, for the word uestion read eguatzon hne 65, clalm 6, for woven mamly cellulosio read mainly cellu osic woventpage 9, second column, lme 63, claim 12, for evoluation read evolution; and that the sald Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 3rd day of September, A. D. 1946.

. v a 1 First Assistant Uommz'asioner of Patents.

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