US3255983A - Yarn tensioning apparatus - Google Patents

Description

June 14, 1966 Y 3,255,983

YARN TENSIONING APPARATUS Filed Feb. 12, 1964 4 Sheets-Sheet 1 O v? 6 7 x/ '2 0 i I g Fl G. 40

2| FIG. 4 [R A Tl Q 9 FIG. 4b

T2 INVENTOR RICHARD YOUNG HAYS ATTORNEY June 14, 1966 R. Y. HAYS YARN TENS IONING APPARATUS Filed Feb. 12, 1964 4 Sheets-Sheet 2 w F G. 2 E31 23 ,23.

a; Ill!!! 23 24pm 27 24 QYiEiif l 28-\ 26 27 29 F G. 9 Tl in grams T2 In grams IO 2p 3p 4p 89 IQO 12p I CI) (b) O) E i:

INVENTOR RICHARD YOUNG HAYS BY $4w- ATTORNEY June 14, 1966 R. Y. HAYS YARN TENSIONING APPARATUS 4 Sheet Sheet 5 Filed Feb. 12, L964 INVENTOR RICHARD YOUNG HAYS ee/V lez w 0 a J w v O m H K f \m P 0 S ATTORNEY June 14, 1966 R. Y. HAYS 3,255,983

YARN TENSIONING APPARATUS Filed Feb. 12, 1964 4 Sheets-Sheet 4 FIG-H INVENTOR RICHARD YOUNG HAYS ATTORNEY yarn between the initial supply and final package.

United States Patent 3,255,983 YARN TENSIQNENG APPARATUS Richard Young Hays, Kinston, N.C., assignor to E. l. du Pont de Nernours and Company, Wilmington, Del., a corporation of lfielaware Filed Feb. 12, 1964, Ser. No. 344,356 8 Claims. (Cl. 242155) This invention relates to a compensating tensioner for yarns and more specifically to a tension-regulator in which delivery tension is substantially completely independent of variations in input tension.

In apparatus wherein textile yarn is fed from a continuous supply and is being wound onto a package (such as a spool, pirn or beam), it is generally desirable to effect said winding with uniform tension. For this purpose, a large variety of yarn tensioning devices have been proposed or actually used, for interposing in the path of the Not all of these devices, however, achieve the desired result to a high degree of satisfaction. In particular, no tensioner has, to my knowledge, been devised heretofore which will make the delivery tension of the yarn essentially independent from variations in the tension of the input yarn. Thus It has been recognized in the art that yarn tensioners of the snubbing type tend to magnify in the delivery the input variations in tension. This effect has been expressed by the belt equation T =T e wherein T is delivery tension, T is input tension, at is the angle of wrap on the snubbing, stationary pin and f is the coefiicient of friction of the yarn over the snubbing surface at the speed of yarn travel employed (Marks, Mechanical Engineers Handbook, th edition, page 228).

Variations in the tension of the input yarn may arise from various factors, a typical illustration being the pirn 11 illustrated in FIG. 1 of the accompanying drawing (discussed more fully hereinbelow). For instance, when the yarn is unwound from the lower half of the pirn 11, it has to bend around the midline bulge of the pirn, and the resulting friction compels an increase in the tension T required to unwind the yarn. Accordingly, any tensioner which employs a snubbing action to any substantial degree has inherently undesirable characteristics for use as a tension regulator. The magnification of input tension is avoided by use of braked-roller tensioners, wherein a chosen increase in tension may be accomplished by applying a variable braking force on a roller around which the yarn travels. (US. Patent 2,519,882.). provement is disclosed in US. Patent 2,738,144, for example, wherein the braking force applied to the roller is balanced against the yarn delivery tension. In no instance, however, has, to my knowledge, complete independence of delivery tension on yarn input tension been achieved to date.

Accordingly, it is an object of this invention to provide a novel tensioner for yarn by the aid of which the delivery tension can be made essentially independent of any variations in the input tension. Another object is to provide a device of the nature above set forth wherein there is no sliding friction between the yarn and the tensioner elements, and which is generally free of any snubbing points or snubbing action. A still further object is to provide a device for the purpose aforesaid which is simple in construction and easy to set initially for various values of required delivery tension. Other objects and achievements of this invention will become apparent as the description proceeds.

The device which according to this invention achieves the aforegoing objects and purposes is characterized by consisting of a stationary support (preferably, a platelike member) containing a pivot on which another plate A further int-- is rotatably supported. The latter supports on stationary pivots, properly spaced from each other, a pair of separator rollers around which the yarn can travel with a rolling contact, thereby excluding the existence of or need for sliding contacts, pinching or any other form of snubbing action. Affixed to the stationary support but rising into a plane slightly above the rotatable plate is a brake shoe device, set to bear against one of the separator rollers, contacting it near the base thereof, that is in the region which will not normally be contacted by the travelling yarn, so that no pinching action on the yarn will result. Finally, near the end of the rotatable plate which is opposite the location of the braked roller, an adjustable spring device is present which is so aflixed to the two plates as to tend to impart rotation to the rotatable plate, whereby the brake shoe can be made to bear against said one separator roller with an optionally adjustable pressure.

For a clearer understanding of this invention, reference is now made to the accompanying drawings, in which FIG. 1 is a diagram of the general apparatus layout for winding yarn packages by the aid of this invention.

FIG. 2 is a front view of a vertically mounted tension regulator according to this invention.

FIG. 3 is a side view of the same (looking from the left of FIG. 2).

FIG. 4 is a diagram of the forces and distances involved in the design and use of the tension regulator.

FIG. 4a is a vector diagram clarifying a certain detail with respect to FIG. 4.

FIG. 4b is a diagram clarifying another detail with respect to FIG. 4.

FIGS. 5, 6, 7 and 8 are diagrams like FIG. 4, showing alternative designs and alternative modes of using this invention.

FIG. 9 constitutes a reproduction of tension diagrams obtained by recording tensiometers in one experiment on both the input yarn tension a and the delivery yarn tension [1.

FIGS. 10 and 11 are front views like FIG. 2 but showing two additional modifications of the tension regulator of this invention.

Turning now to FIG. 1, yarn 1 from any continuous source (such as bobbin 11 or directly from a spinning machine) passes over wire pigtail 12, through pre-ten-- sioner 13, and then through a tension regulator of this invention (indicated generally as 2) and over an idling roller 40, and is finally wound on a spool, pirn, cop, cheese or beam indicated generally at 4 1. In FIG. 1, the input yarn is being fed to the left, while the delivery yarn moves to the right; The tensions follow the direction of movement and are indicated at T and T respectively.

Turning now to FIG. 2, a stationary back plate 20 has projecting therefrom a pivot 21 which supports swingable plate 22. The latter supports two separator rollers 23 and 24, which rotate freely on ball bearings mounted on shafts 231 and 241, respectively. The shafts of the two rollers are canted slightly toward each other at their outer extremities, as a result of which the input yarn 1, when wound several times around the two rollers, spreads out slightly lengthwise of the rollers, as shown at 14 in FIG. 3. The yarn finally parts with roller 24 and travels to the right to be wound upon the package 41 shown in FIG. 1.

Pigtail 12 and pre-tensioner 13 of FIG. 1 are aflixed to some stationary part of the general apparatus layout of FIG. 1, in such a manner that the input yarn 1 passes in front of pivot 21 as nearly as possible opposite its center 211.

Opposite roller 23, a brake shoe 25 is fastened to the edge of stationary plate 20. Its curved contact surface 251 projects forward, however, into a plane slightly in 23 front of swingable plate 22, and contacts roller 23 in the region 232 near the base thereof, so that the windings 14 of the yarn stay clear of the braking area and do not become snubbed thereby.

Near the lower edge of plate 22, a spring 26 attached to a rod 27 tends to urge plate 22 in a direction opposite (or predominantly opposite) to that of the delivery tension T Rod 27 is slideable within a groove 28 i in plate 20, but is adjusted to the desired position and fastened there by means of set-screw 29. In this fashion, any degree of tension. can be applied to the spring to counteract the delivery tension T whereby the net pres sure of brake shoe 25 against roller 23 can be controlled.

The action of the tension regulator of this invention is best explained by the aid of FIG. 4, in which capital letters represent forces while lever arm lengths are designated by lower case letters. All lever arm lengths are measured with respect to point 211, which is the center of pivot 21, and is designated by A in the diagrams of FIGS. 4 to 8.

More particularly- P is the force exerted by brake 25 upon the surface of roller 23; p is its lever arm.

Q is the frictional force under the brake, which resists rotation of cylinder 23; q is its lever arm. An an elementary law of physics, Q is directed at right angles to P and counter to the direction of rotation. Furthermore, Q is related to P by the equation where f is the coefficient of friction between the two materials involved in the brake shoe and cylinder 23. (The value of f for any two materials may frequently be found in the literature or may be determined experimentally.)

T is the yarn tension at the point where the outgoing yarn breaks contact with cylinder 24; its lever arm is designated by t.

Finally S expresses the tension in spring 26, while s designates its lever arm.

Best results with this invention are obtained if the center 231 of roller 23 is placed so with respect to pivot 21 that the resultant R of the two forces P and Q indicated in FIG. 4, if produced as in FIG. 4a, will pass just about through the center 211 of pivot 21. This is the same as saying that the moment of P about point 211 is just equal and opposite to the moment of Q about the same point. Taking into account the moment arms, the above condition can be expressed mathematically by the relation P =Q But by Equation 1, Q=fP; therefore,

p=fq r P q=f It is thus possible to design the required apparatus as soon as the materials for the brake-shoe facing 251 and the surface of roller 23 have been selected, i.e. without any need for knowing (or estimating) the value of the braking force P.

Another way of expressing the same idea is to say that if we designate by C the midpoint of the are along which the brake-shoe is in contact with the periphery of roller 23; if We designate by B the center of said roller, by A the center 211 of the pivot 21, and by 0 the angle ACB (FIG. 4), then tan 0 should equal 1, wherein f is the coeflicient of friction as explained above.

If the aforesaid, triply expressed condition has been satisfied, the interrelations of the moments acting on plate 22 are as follows:

Clockwise moments: Q +S counterclockwise moments: P +T L Since plate 22 is in equilibrium,

Qq+ s p+ 2 It will be noted that T does not get into the equation, because the input yarn passes in front of the center of pivot 21; therefore, its moment arm is zero. Accordingly variations in the value of T; can have no effect on any of the quantities involved in Equation 3. Of particular interest is the fact that variations in T can have no effect on the value of T Now, Q=fP; therefore, by substitution and rearrangement, we get: T z=S +P(fq-p). But if the layout satisfies Equation 2, fqp=0; therefore, finally,

It follows from Equation 4 that the delivery tension T is dependent solely on the spring tension S, it being noted that the values of s and t will not change in a given instrument once it has been built and adjusted.

To illustrate by a specific example, assume p=0.5" and consider a brake of oak operating on cast iron, in which case f:0.49 (Marks, Mechanical Engineers Handbook, 5th ed, page 2l8). Then q=0.5/O.49=1.02. The radius of roller 23 must be equal to p; therefore the center of roller 23 must be located at a distance (q-p) from point 211 (center of pivot 21), measured along the line CB of FIG. 4. With the figures assumed above, then, the center B of roller 23 is set at coordinates (x, y)=(O.52'-', O.5") with respect to the center of the pivot.

In actual tests with this example of the device of this invention, it has been found that control of delivered yarn tension is entirely determined by tension of spring 6.. Variations in input tension are wholly without effect on the delivery tension. It has also been observed that control of tension with yarn containing extreme variations in denier along its length (such as novelty slub-yarn wherein denier may increase several-fold in the short slubs spaced yards apart) is just as good as the control with yarns having uniform denier. Such performance has heretofore been unattainable.

The effectiveness of the tension regulator of this invention is further portrayed by FIG. 9 which reproduces an actual set of diagrams a and b obtained by recording tensiometers in one experiment. Diagram a reproduces the record of a tensiometer on the input yarn. The horizontal scale indicates tension in grams. The vertical dimension represents time. Diagram b reproduces the record of a second tensiometer on the delivery yarn during the same time interval. The horizontal scale for diagram b is condensed in the ratio of 2:1 with respect to that of diagram :1. To be readable on the same scale as diaphragm a, the variations in graph b would have to be doubled in the horizontal dimension. It is clear nevertheless from the diagram that the variations are negligible, the tension T maintaining an essentially constant value throughout the time interval, in spite of the wide oscillations at the same time in tension T It will be obvious to one skilled in the art that many alternative arrangements are possiblewhile retaining the essential features of this inventions preferred embodiment provided the following two basic principles are observed: namely, (1) the input yarn or the geometrical extension thereof must pass over the pivot about which the tensioner rotates as it adjusts to the required braking force, and (2) the resultant of the brake-pressure vector and the vector representing the friction due to braking must, if extended pass through the center of the pivot. Practical considerations of available space, required yarn direction in and out, level of tension required in the delivery, and size of yarn being processed, among other things, will dictate specific arrangements of the critical features and the mounting attitude of the tension regulator. Thus, FIGURES 5 and 6 exemplify additional arrangements involving a spring for the applied tension force, but differing from FIG. 4 in that the directions of the entering yarn and emerging yarn are not parallel. In the embodiments of FIGS. 4, 5 and 6, the rotatable plate may be supported in a vertical, horizontal or inclined plane.

FIGURES 7 and 8 show still further alternatives, in which the applied tension-force vector may be gravitational if desired. Thus, in FIG. 7, the swingable plate 22 is mounted in a vertical plane on a horizontal pivot and has one end of it weighted (as by counterweight 221) so that its center of gravity passes above and to the left of pivot 21. Consequently, gravity tends to rotate'the plate and its attachments counterclockwise; this tendency serves to apply pressure in the area of contact between the brake shoe and roller 23. In FIG. 8, plate 22 has its center of gravity below and to the left of the pivot, and the brake is applied to roller 23 (at point P) from below. The action is otherwise essentially the same as in FIG. 7.

The symbols employed in these alternative embodiments parallel those employed in FIG. 4, the description for which is also applicable to FIGS. through 8.

Other variations and modifications will be readily apparent. For instance, the brake does not necessarily have to be applied to the roller which is nearer the pivot, but may be located for application to the remote roller. Nor is its form limited to a brake shoe. For instance, it may take the form of a flexible brake-band (made of fabric, cord, metal, etc.) which runs around the roller selected for braking and has its ends fixed at convenient points in the stationary support 20.

It will be further obvious that the'pigtail 12 shown in FIG. 1, or any other equivalent yarn guide, may be attached directly to the tensioner apparatus 2 (preferably at some point in plate 20), whereby the tensioning apparatus can be manufactured and handled in commerce as a self-complete unit, containing in itself all the elements which are needed for best performance according to this invention.

In conclusion, it may be summarized that the device of this invention is characterized by two basic features, and one preferred feature, namely:

(1) The device is free of parts or features which would cause snubbing or pinching of the yarn at any point.

(2) Either the device itself or the support of the genoral apparatus for feeding and winding the yarn has affixed thereto a stationary yarn guide (for instance a wire pigtail, an orifice in a plate, or a pre-tensioning device) so situated that the straight line defined by the incoming segment of the yarn being fed in from the input supply will pass essentially through the axis of the pivot for the swingable plate.

A third feature, which is preferred, requires that the brake which contacts one of the separator rollers is so disposed on the swingable plate that the moment formed r by the braking force about the pivot for the swingable plate is essentially completely overcome and nullified by the moment, with respect to the same pivot, of the rotational friction which results from said braking action at the surface of said separator roller.

I am aware of US. Patent No. 2,932,077 (issued to F. Honig) wherein an apparatus for stressing strand materials is described. In said apparatus, however, the two rolls 10 and 11 are in contact with each other; one of them is lined on the outside with a resilient tire 12 with the object of enabling the one roll to be pressed tightly against the other one; and the yarn Y is supported to be fed through the contact point P betwen the two rollers and is intended to be pinched or nipped with considerable pressure at said point.

Furthermore, no provision is made in Honig for feeding in the yarn along a line which passes through the pivot of the apparatus, and no suggestions to that effect are contained in his disclosure. The apparatus of Honig therefore does not achieve the principal objects of this invention, namely: (1) exclude any friction or snubbing action between the yarn and the tensiometer elements, and (2) prevent variations in incoming tension T from affecting the tension T in the outgoing yarn.

In particular, the device of Honig is incapable of achieving the first one of the aforegoing objects, because of its resort to friction rollers whereas the instant invention calls for separator rollers. Separator rollers are per se known in the art and imply a structure characterized by the following features:

(a) The two rolls are mounted on axles sufficiently spaced apart to enable each roller to roll on its axle independently of the speed or direction of rotation of the other roller. (In a device like Honigs one roller will act as driver for the other and the two therefore are compelled to rotate in opposite directions.)

(b) The two rollers are spaced sufficiently apart not to exert any snubbing action on the yarn, even if the latter were directed to pass between them.

(c) The axles of the two rollers are tilted (canted) toward each other slightly as they rise from their support, so that if a moving yarn is wound several times around the pair of rollers, their individual coils will automatically spread out in helical fashion lengthwise of the axles, whereby no coil can exert any snubbing action on any other coil in the group.

The same effect as in (c) may be obtained also by tilting the axles sideways slightly, one to the right and one to the left of the plane that would otherwise contain their axes. Accordingly, the expression disposed toward each other at a small angle in the claims below, should be construed as including both a cant toward each other or a sideways tilt, as above indicated.

FIGS. 10 and 11 show two more alternative ways of making or using the apparatus of this invention.

In FIG. 10, the apparatus of FIG. 2 is used, except that a pigtain device 212 is attached to the frame 26 at the upper left, which suggests an intent to feed in the yarn from left to right. In this figure, the yarn itself does not pass over the pivot 21, but a continuation of the straight line defined by the incoming segment will pass over the center of the pivot. Also, the position of the brake 25 has been shifted from that shown in FIG. 2, for the purpose of satisfying the third of the basic features hereinabove, namely of making the moments of P and Q about point A equal and opposite to each other.

In FIG. 11 is shown a modification wherein the pivot 21 is located between the two rollers 23 and 24 and on the line joining their axes. But the pigtail 212 is located so as to direct the incoming yarn over the center of the pivot, and the brake 25 is again shifted, whereby the advantages of this invention are realized.

I claim as my invention:

1. In combination with a yarn tensioning device having a pair of separator rollers suppOrted 0n a back plate which is itself swingably supported on a fixed pivot,

(l) a brake device afiixed to a stationary base and projecting therefrom beyond the plane of said rotatable plate whereby to bring a braking surface into frictional contact with one of said separator rollers in a region thereof which is normally not contacted by the yarn passing over said one roller,

' (2) means for pressing said one roller with a controllable force against said braking surface,

(3) means for guiding the entering yarn so that it comes in contact with said one roller along a straight line which passes essentially through the straight line defined by the axis of said pivot, and

(4) means for removing said yarn from the other of said separator rollers.

2. A yarn tensioning device comprising in combination (1) a plate rotatably supported on a pivot fixed on a stationary base,

(2) a pair of separator rollers freely rolling on axles which are aflixed to said rotatable plate in a plane at right angles to the plane of said plate,

(3) a brake device afiixed to said stationary base and projecting therefrom beyond the plane of said rotatable plate whereby to bring a braking surface into frictional contact with one of said separator rollers in a region thereof which is normally not contacted by the yarn passing over said one roller, (4) means for pressing said one roller with a controllable force against said braking surface, and (5) means for guiding the entering yarn so that it comes in contact with said one roller along a straight line which passes essentially through the straight line defined by the axis of said pivot, the axles of said pair of separator rollers being spaced from each other sufficiently to prevent contact between the lateral surfaces of said rollers and being disposed toward each other at a small angle as they rise from the plane of said rotatable plate, to the effect that when yarn is wound several times around the pair of rollers and pulled, (a) the successive coils of the yarn will spread out in helical fashion with respect to the axes of said rollers, (b) snubbing action between any coil and another and between any coil and the rollers will be eliminated,

and (c) each roller can roll freely under the belt-like action of the yarn coils in contact therewith.

3. A yarn tensioning device as in claim 2, said means (4) being gravity means.

4. A yarn tensioning device as in claim 2, said means (4) being a tension device including a spring.

5. In combination with apparatus wherein yarn fed from a continuous supply is being wound onto a package and wherein it is desirable to effect said winding under essentially constant tension regardless of variations in the tension of the yarn being fed from the supply,

(A) a yarn tensioning device comprising in combination (1) a plate rotatably supported on a pivot in a stationary base and in turn supporting two separator rollers,

(2) a brake device affixed to said stationary base and projecting therefrom beyond the plane of the rotatable plate, whereby to bring a braking surface into frictional contact with one of said separator rollers, and p (3) means for holding said one separator roller with a controllable pressure against said braking surface,

said brake-contacting separator roller having its center located with respect to said pivot so that the moment, with respect to said pivot, of the rotational friction in the brake-contacted zone on the surface of said separator roller is essentially equal in value tothe opposite moment formed by the total braking pressure about said same pivot,

(B) means for guiding the entering yarn so as to make it pass in front of the center of said pivot in said tensioning device.

6. In combination with apparatus wherein yarn fed from a continuous supply is being wound onto a package and wherein it is desirable to effect said winding under essentially constant tension regardless of variations in the tension of the yarn being fed from the supply (A) a yarn tensioning device comprising in combination (1) a plate rotatably supported on a pivot in a stationary base and in turn supporting two separator rollers,

(2) a brake device ailixed to said stationary base and projecting therefrom beyond the plane of the rotatable plate, whereby to bring a braking surface into frictional contact with one of said separator rollers, and

(3) means for holding said one separator roller with a controllable pressure against said braking surface,

said brake-contacting separator roller having its center located with respect to said pivot so that the moment, with respect to said pivot, of the rotational friction in the brake-contacted zone on the surface of said separator roller is essentially equal in value to the opposite moment formed by the total braking pressure about said same pivot,

(B) means for guiding the entering yarn so that a continuation of the straight line defined by said entering yarn shall pass essentially through the straight line defined by the axis of the pivot in said tensioning device.

7. A combination as in claim 1 said pressing means (2) being gravity means.

8. A combination as in claim 1 said pressing means (2) being a tension device including a spring.

References Cited by the Examiner UNITED STATES PATENTS 2,193,044 3/1940 Sibley 242147 X 2,738,144 3/1956 Honig 242-177 2,797,468 7/1957 Brown.

FOREIGN PATENTS 228,785 12/1943 Switzerland.

MERVIN STEIN, Primary Examiner.

W. S. BURDEN, Assistant Examiner.

Claims (1)

1. IN COMBINATION WITH A YARN TENSIONING DEVICE HAVING A PAIR OF SEPARATOR ROLLERS SUPPORTED ON A BACK PLATE WHICH IS ITSELF SWINGABLY SUPPORTED ON A FIXED PIVOT, (1) A BRAKE DEVICE AFFIXED TO A STATIONARY BASE AND PROJECTING THEREFROM BEYOND THE PLANE OF SAID ROTATABLE PLATE WHEREBY TO BRING A BRAKING SURFACE INTO FRICTIONAL CONTACT WITH ONE OF SAID SEPARATOR ROLLERS IN A REGION THEREOF WHICH IS NORMALLY NOT CONTACTED BY THE YARN PASSING OVER SAID ONE ROLLER, (2) MEANS FOR PRESSING SAID ONE ROLLER WITH A CONTROLLABLE FORCE AGAINST SAID BRAKING SURFACE, (3) MEANS FOR GUIDING THE ENTERING YARN SO THAT IT COMES IN CONTACT WITH SAID ONE ROLLER ALONG A STRAIGHT LINE WHICH PASSES ESSENTIALLY THROUGH THE STRAIGHT LINE DEFINED BY THE AXIS OF SAID PIVOT, AND (4) MEANS FOR REMOVING SAID YARN FROM THE OTHER OF SAID SEPARATOR ROLLERS.

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