Dec. 24, 1946. A. M. SAW 2,413,073" STRETCHING ROLLS Filed July 26, 1945 INVEN TOR. Aytlzar jlfgLeamz. "z?/Zk!» A TTORNE Y Patented Dec. 24, 1946 UNITED \‘STATESQPATENT. OFFICE ' STRETCHING ROLLS Arthur M. Saum, Wilmington, Dei., assignor to E. I. du Pont de Nemours & Company, Wil mlngton, Del., a corporation of Delaware ' Application J nly 26, 1945, Serial No. 607,234 4 Claims. ' 1 (c1. 28-713) n This invention relates to the manufacture of lation with the feed roll in a manner .hereinaiter fully described, whereby yarn passed over and. between the feed and pinch rolls will cause the arti?cial ?laments, yarns, threads, ribbons, etc., and more particularly to an improved arrange ment to prevent slippage of arti?cial ?laments, yarns, threads, ribbons and ‘the like under ten-' sion on positively driven advancing rolls. . Heretofore, much diiiiculty has been experi enced in the stretching or drawing of yarns and pinch roll to be iorced against the teed roll and 0 pinch the yarn therebetween with a force sum cient to prevent slippage oi’ the yarn on the feed roll. , . ' - Referring now to the drawing wherein like the like by means of two or more sets of positively reference numerals designate like parts. refer driven rolls turning at different peripheral speeds ' 10 ence numeral i (Fig. 1) indicates a freely rotat due to inconstant slippage of the yarn thereon. able pinch roll l, aligned parallel to the usual Various arrangements have been proposed ‘and positively driven feed roll 2, and mounted for used, such asa plurality of turns of the yarn swing on one end of a swing arm 3 which is piv about the advancing roll and about a suitable oted at the opposite end to the frame of the spin auxiliary roller for displacing the yarn in its ning machine or any other suitable support. The‘ several passes about the advancing roll, pressure swing arm and attached pinch roll may be dis ' rolls bearing on the ‘yarn passing around the yarn posed at any point about the feed roll so long as advancing roll, etc. These prior arrangements the pull on the yarn passing over and between ' work quite satisfactorily when the tension diiier the rolls will tend to done the rolls into con ential between the oncoming and o?going yarn 20 tact, and the length of‘ the swing arm and the is not too great. However, where the tension radius of the pinch roll are such that the pinch di?erences are large, yarn slippage on the ad- ' roll cannot be swung past the feed roll. It is vanclng roll occurs and the stretching ratio be further required that'the pivot point of the-swing comes variable. This culty is especially acute in the drawing of heavy denier yarns or ?la 25 arm be so located that the obtuse angle a formed by the intersection of the straight line passing ments of nylon which require an unusually large through and connecting the ‘centers of the two force to attenuate the structure to approximately four times its original length. ' rolls andthe straight line passing through and connecting the center of the pinch roll and pivot It is, therefore, an object of this invention to provide an improved yarn advancing roll arrange 30 point of the swing arm is within the range of from 165° to just short of 180". In the arrange ment that is simple to make and install, easily “strung up,” and, in operation, capable or pre venting slippage oi the yarn on the advancing roll even though the tensions on the yarn thereto and therefrom di?er widely. Other objects will be apparent from the description that follows which is to be read in connection with the ac companying drawing wherein: Figure l is a diagrammatic illustration of one arrangement of yarn advancing rolls embog the principles of my invention; Figure 2 is a diagrammatic representation of an alternate arrangement of rolls according to my invention; and ment shown in Fig. i, the distance between the axes of rotation of the swing arm 3 and of the feed roll 2 is slightly less than the sum of the ‘length'of the swing arm (distance between the 35 axis of rotaticnof the swing arm and axis of rotation of roll 3) and the radii of the pinch roll i and the feed roll 2. in order that the pinch roll cannot quite swing past the feed roll. More 40 over, the center points oi’ the two rolls and the pivot point or theswing arm are almost in a straight line, i. e., the angle a is almost 180". ‘With this arrangement a force which tends to push the pinch roll pat the feed roll develops a Figure 3 illustrates a med form of the 45 muchlgreater compressive force between the two pinch roll. ‘ ' roll surfaces than can be obtained if the pinch These objects are accomplished by my inven- ' ’ vroll is supported in vertical guideways directly over the feed roll or if‘the swing of a swing? tion'. which, brie. stated,‘ comprises associating with the usual driven iced or yarn advancing ably mounted‘ pinch roll is so pivoted that the roll of a conventional system of rolls arranged 50 angle or isless, than about 165°. When the yarn for the stretching of arti?cial yarn and the like, ‘ strung around the rolls disposed in accordance with the principles of this invention and in such a freely rotatable, swinghbly mounted roll (here a way that the tension on the yarn as it is with inafter termed f‘pinchv roll") having its axis of drawn tends to pull, the pinch roll past the iced rotation parallel to the axis of rotation of the mil, and further disposed in contacting re 55 roll, then the pinching action between the rolls / ‘ 2,418,078' 3 . . t 4 ‘ grips the yarn more ?rmly as the yarn tension ful, too, to improve twist uniformity in difiicultly increases and slippage cannot occur. In the modi?cation shown in Fig. 2, the dis tance between the axes of rotation of the swing handled structures such as tire cord. By means of this invention, heavy denier yarns arm and of the feed roll is slightly more than the length of the swing arm minus the radii of the pinch roll and the feed roll and the obtuse angle a is more than 165°. Here, as in the pre and ?laments of nylon have been produced with more uniform physical properties than has been possible heretofore, by virtue of the elimination vof yarn or ?lament slippage on the draw rolls. Furthermore, the arrangement described can be viously described arrangement (Fig.1), the yarn very quickly “strung up" and is easily restrung as it is withdrawn from the pinch roll tends to 10 whenever a break occurs. ‘ ‘ As many apparently different embodiments c this invention can be made without departing feed roll. from the spirit and scope thereof, it is to be un The yarn must be withdrawn in a direction to cause the pinch roll to be forced against the 1 derstood that said invention is not to be re advancing roll, and the surfaces of the two rolls 15 stricted save as de?ned by the appended claims. I claim: ' should in part at least be such that the coe?i~ 1. In combination, a driven roll positively cient of friction between them is relatively high. driven about a ?xed axis, a pinch roll in contact Preferably the ‘feed roll is a steel-surfaced roll with said driven roll ‘and freely rotatable on an while the pinch roll is rubber-, cork- or leather covered.v While the feed roll could be covered 20 axis parallel to the ?xedaxis of the driven roll, said pinch roll being mounted on the free end of with rubber, or leather, or cork, and the pinch a swing arm which is pivoted at the opposite end, _ roll steel-surfaced, a frictional loss will occur re the pivot point of said swing arm being ?xed and ' ducing the resistance to slippage of the yarn on so located that the obtuse angle formed by the these rolls since the relatively large arc of con tact of the yarn with the pinch roll under high 26 straight line connecting the centers of the two rolls in operative contacting position and the tension becomes less effective than if the two straight line connecting the center of the pinch rolls were surfaced as ?rst described. A satis roll and the pivot point of said arm is within the factory pinch action between steel-surfaced rolls can be obtained by providing one of the rolls with . range of from 165° to Just short of 180°. 2. In apparatus for stretching stretchable ma end bands 4 or i as shown in Fig. 3. These bands 30 terial wherein the material is stretched between are of a diameter slightly larger than that of positively driven rolls, the improvement which the roll and are constructed of rubber or like comprises in combination with the ?rst of said resilient material having a high coe?lcient of driven rolls‘ positively driven about a ?xed axis. friction. ‘a swing arm pivoted at one end. a pinch roll The feed roll assembly above described is es pull the pinch roll past, and hence against,_the .‘pecially useful in feeding large denier undrawn mounted on the free end of said arm and free ly rotatable about an axis parallel to said ?xed axis, said pinch roll being further positioned so that it swings on said arm into contact with. stantially higher peripheral speed to stretch the yarn or ?laments approximately four times their 40 said ?rst driven roll, and the pivot point of said arm being ?xed and so located that the obtuse original length. As disclosed in U. 8. Patent No. angle formed by the intersection of a straight 2,289,232 to D. 1"..Babcock, a draw ‘Din is pref erably positioned between two sets of rolls. Even ‘ line passing through and connecting the axes of the ?rst driven roll and the pinch roll in operative though the force required to stretch the yarn or - ?lament to four times its length is as much as 'contacting position and a straight line passing through and connecting the axis of the pinch‘ roll two or three pounds vor more, experience has and the pivot point of the arm is within the range shown that no slippage results on the feed roll of ‘from 165° to Just short of 180°, whereby ma assembly when constructed as above described terial passing between the ?rst driven and pinch with the pinch roll rubber-covered and the driven feed roll steel-surfaced, whereas prior methods 50 rolls and drawn o? the pinch roll under tension in a direction effective to urge the pinch roll into would involve slippage if the drawing tension contact with the ?rst driven roll is subjected to were greater than about 0.5 pound. nylon yarn or a large denier undrawn nylon ?la ment to another pair of rolls turning at sub While this invention is especially suited to the drawing of very heavy denier nylon yarns such ' as 1000 denier or more, and large diameter nylon 55 ?laments such as may be used for bristles, horse hair substitutes. tennis racket strings, musical in strument strings, ?sh line leaders, surgical su a pinch pressure suf?cient to prevent slippage of said material on said ?rst driven roll. v 3. Apparatus according to claim 2 wherein either one of the two contacting rolls is surfaced with a material having a coe?lcient of friction which is high relative to the cce?lcient of fric tion of the surface of the other roll. 4. Apparatus according to claim 1 wherein the 0.002 to 0.06 inch in diameter, the invention may 60 ?rst driven roll is steel-surfaced and the pinch also be used in connection with the feeding .or roll is surfaced with a material having a sub advancing of yarn tow, or ?laments of any char tures, screening, etc., and ranging in size from acter where a; very high tension differential exists in the yarn in going on and coming 01! the ad vancing roll arrangement. This invention-is use stantially higher coefficient of friction. ARTHUR M. SAUM.