US3567142A - Device for adjusting the tension of yarn fed to a yarn comsuming machine - Google Patents

Abstract

A device for feeding a high-stretch yarn to a yarn-consuming machine at a constant speed and tension in which a delivery yarn guide supplies the yarn at an uncontrolled tension to a pair of rollers driven at different speeds over which the yarn is looped, which rollers impart to the yarn a constant speed and a tension which is higher than the decrimping tension and subsequently ease the imparted tension so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by the application of the imparted tension so as to achieve a delivery tension but which may be varied without the production of appreciable variation in length of the yarn.

Description

United States Patent [72] lnventors Bernard-Francois Helfl'er Division of Ser. No. 550,715, May 17, 1966,

Pat. No. 3,451,603

Mar. 2 l 97 1 Institut Textile De France Boulogne S, Seine, France 45] Patented [73] Assignee [54] DEVICE FOR ADJUSTING THE TENSION 0F YARN FED TO A YARN COMSUMING MACHINE 5 Claims, 5 Drawing Figs.

[52] US. Cl 242/47.08 [51] Int. Cl B65h51/08 [50] Field of Search 242/47.08,

Primary Examiner-Nathan L. Mintz Attorney-Mason, Fenwick and Lawrence ABSTRACT: A device for feeding a high-stretch yarn to a yarn-consuming machine at a constant speed and tension in which a delivery yarn guide supplies the yarn at an uncontrolled tension to a pair of rollers driven at different speeds over which the yarn is looped, which rollers impart to the yarn a constant speed and a tension which is higher than the decrimping tension and subsequently ease the imparted tension so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by the application of the imparted tension so as to achieve a delivery tension but which may be varied without the production ofappreciable variation in length of the yarn.

PATENTEU MAR 2197! SHEET 1 BF 3 will I HIHII Hlllllll lllllllllllllllllmllllllllll BERNARD-FRANCOIS HELFF'EE,

A T TOE/VEVS DEVICE FOR ADJUSTING THE TENSION F YARN FED TO A YARN COMSUMING MACHINE This application is a division of application Ser. No. 550,7l5 of the same inventors filed May 17, 1966 now U.S. Pat. No. 3,451,603.

The present invention relates to a thread feed device intended to be used primarily for feeding hosiery knitting or other yarn consuming machines.

On a knitting machine, the yarn, while passing through a certain number of straddling devices such as yarn guides, yarn breakers, throwers and the like, is fed from the bobbin to the needles without being controlled at any point in its path, by a device for checking its unwinding speed. Experience shows that the unwinding of the yarn is not uniform, either as between-one yarn and another, or as between one portion and another of the same yarn. This is mainly due to the frictional forces to which the yarn is subjected at various points before it reaches the needles. While the yarn is leaving the spool, moreover, the latter is frequently jerked, which also contributes to the creation of undesirable irregularities.

To remedy these difficulties, it has already been proposed that there should be interposed, between the bobbin and the needles of a knitting machine, a yarn feed device with which either the tension or the speed of the thread might be regulated. One such yarn feed device with which the speed of the yarn can be kept constant, consists of a frustoconical drum, mounted to rotate about its longitudinal axis, and a yarn guide fixed rigidly to a lever, to the other end of which is fitted a restoring spring that causes the lever to swing, to a certain extent, so that the yarn passing through the guide is wound once or several times around the frustoconical drum and rises towards the top or falls towards the base of the drum, in order to keep the thread under constant tension. Obviously, with the drum rotating at a particular speed, the speed of the yarn as it leaves the drum varies with the changes in the drum diameter where the the yarn is wound onto it.

Another previously suggested yarn feed, which consists likewise of a frustoconical drum and a yarn guide movable on an axis parallel to one position of the line generating the inclined face of the frustoconical drum, enables the speed at which the yarn leaves the drum to be kept constant. In this device, the yarn is wound once around the drum, to the face of which it adheres strongly, this face generally being made of a material possessing a high coefficient .of friction, such as rubber. For any given diameter at which the yarn is wound about the drum, the yarn will leave the drum at a constant speed, that is to say, giving a constant feed but, with this device, one cannot closely control the thread tension in the case of a textured yarn.

With another previously suggested yarn feed device it is possible to eliminate the variations in yarn tension due to variations in the speed of unwind from the bobbin. This feed device comprises a drum to which rotary motion is imparted and which consists of two truncated cones following each other along the axis of the drum and joined by a'frustoconical bevel, associated yarn guides being so placed in relation to the drum that the yarn, during the first part of its path from bobbin to needle, makes contact with the first truncated cone along an arc of a circle and then, during the second part of its path, firstly with the same truncated cone along a helical path diametrically opposite the circular arc and then with the frustoconical bevel, the yarn finally making contact, during a third part of its path, with the second truncated cone along a circular are equal to that defined on the first truncated cone by the first part of the path of the yarn. By reason of the particular path followed, the yarn is subjected to a given tension during the first part of this path, to a higher tension during the second part of its path and, finally, in the third part of its path to a tension equal to the first. In general terms, this yarn feed preventsthe thread from slipping on the drum.

These previously proposed yarn feed devices, and the methods that can be used with their aid, are more or less well suited to feeding hosiery knitting machines with nontextured, that is to say, low-stretch, threads. However, when yarns likely to stretch considerably, such as textured threads (crimped yarns) are to be used, the previously proposed feed devices and the feeding methods made possible by their use do not enable the yarn tension and speed to be kept constant, because sudden changes in tension beyond the feed device may cause the yarn to slip thereon.

High-stretch yarns, such as crimped yarns, elastometers and the like, are known to be characterized by very high variations in stretch for very small changes in loading force. If we look at the load/stretch curve for such a thread, we find that, in an initial zone which we may call the uncurling, uncrimping, or curl elongation zone, the variations in stretch for small changes in the load are very large. Beyond this zone the variations with load in the stretch of the yarn is very small, even for considerable changes in tension or loading. The length (in other. words, the speed) of a high-stretch yarn could therefore be controlled if the tension applied to it lay beyond the uncurling zone. This means that the tension should be higher than 0.1 gram/denier, or 0.9 g./tex. Even for ZOO-denier thread, however, this would make a tension equivalent to a load of 20 g.; and in the case of a textured yarn used in a knitting machine, one cannot knit at such high tensions without running into trouble.

The object 'of the present invention is to provide a feed device whereby yarn consuming machines, and knitting machines in particular, can be fed with high-stretch yarn at substantially constant speed and under substantially constant tension. 7

The present invention is directed to a yarn feed device for feeding a high-stretch yarn to a yarn consuming machine at a constant speed and tension, said device comprising means for supplying the yarn at a high but uncontrolled tension over a first part of its path, means for imparting to the yarn a constant speed and a high tension over a second part of its path, the said high tension being beyond the decrimping tension of the load/stretch curve of the yarn, and means for easing in the yarn said high tension over a third part of its path so as to achieve a relatively lower delivery tension, the value of which lower tension lies below the decrimping tension of the said curve. The term decrimping tension when used herein means the tension required to remove substantially all of the crimping from a given yarn.

The subject invention is also directed to a device in which the yarn feed enables a knitting machine with which it is associated to expeditiously change from continuous to noncontinuous knitting with complete control of tension. This result is effected by the employment of a yarn feed device in which two conical drums are rotating at constant revolutions per minute with different portions along the surface of each drum having different peripheral speeds. A guide member is provided at the delivery drum of the yarn feed device for positioning and holding the yarn against the periphery of the delivery drum with yarn in engagement with the other drum being engaged with a portion of the drum surface moving at a speed less than the speed of the portion of the delivery drum engaged by the yarn.

In other embodiments the yarn is fed over a delivery and an infeed cylinder with the delivery cylinder being driven faster than the infeed cylinder and with a pressure member being provided to urge the yarn against at least the delivery drum.

The manner in which the objects of this invention are accomplished by the following described embodiments will be better understood with reference to the accompanying drawings in which:

FIG. 1 is a plan view showing a first embodiment of a thread feed device in accordance with the invention;

FIG. 2 is an end elevation of the feed device of FIG. 1;

FIG. 3 is an end elevation of a second embodiment of the feed device;

FIG. 4 is an end elevation of a third embodiment feed device; and

FIG. 5 is a graph of the load/stretch curve illustrating hysteresis of a textured thread for example HELANCA-IOO-d (Registered Trademark).

In the graph of FIG. 5, the abscissae represent the loading in grams applied to a textured thread (crimped yarn) of given initial length 0.50 m., the ordinates representing the stretch L in centimeters corresponding to a given loading. High-stretch yarns such as crimped yarn, elastometer filaments and the like are known to be characterized by very high variations in stretch for small changes in loading. If the load/stretch curve R of such a yarn is considered, it will be observed for a zone lying between the origin and the point H, which may be called the uncrimping or crimping elongation curve, that the variations in the stretch of the yarn are clearly larger than for equal changes in the loading to which it is subjected beyond this zone, that is to say, above the point H, where an increase in the yarn loading results in only slight further elongation. In fact, from curve R, it willbe seen that, for one end and the same load variation, AC, the stretch variation AL obtained in uncrimping zone OH is far larger than the stretch variation AL: obtained in that part of the curve which lies beyond point H. This means that it is possible to control the length of yarn taken only when the tension applied to it is equal to or greater than the value H, which is approximately 0.1 g./denier. It must be recognized, however, that this represents, for a ZOO-denier yarn, a load of 20 grams, and that one cannot knit at such high tension without encountering difficulties. If the load on the yarn be first increased to a value K and then reduced, the resulting curve S lies above the curve R and shows a given hysteresis, so that one can reduce the yarn tension to values substantially lower than value H without thereby affecting the length of yarn delivered, that is to say, without the yarn undergoing any considerable reduction in length.

The yarn feed devices in accordance with the invention serve to apply the results of this experiment.

In one advantageous form, the device comprises two frustoconical drums A and B (FIG. 1), of suitable dimensions for covering the entire range of tightness of the knitting or other yarn consuming machines. These two drums may be identical to or differently shaped from each other. In one such pair of drums A and B (as illustrated), they are situated side by side with their axes parallel and are covered with a facing having a high coefficient of friction to prevent the yarn from slipping. This facing may, for example, be made of rubber. On the base of each of the frustoconical drums is mounted a pinion, the pinion spindles being journaled in suitable bearings (not shown). Gearwheel mounted between the two drums meshes with each of the drum pinions. These two drums are mechanically driven from a motor (not shown) through the said gearwheel and may each rotate at the same speed and in the same direction. It would be equally possible to drive the drums in opposite directions and at different speeds. Each driving drum A and B is associated with a takeup yarn guide 1 and 3 respectively, and a delivery yarn guide 2 and 4 respectively. Takeup yarn guides 1 and 3 and delivery yarn guides 2 and 4 are rigidly attached to runners 5 and 6 respectively, mounted on a worm thread 7 and 8 respectively, along which they can move axially. A separate guide rod (not shown) passes through each runner 5 and 6 in order to prevent its rotation about thread 7 or 8. Each worm thread lies near the corresponding frustoconical drum and parallel to a line generating then sloping face thereof or to the axis thereof. By

rotating the thread 7 or 8, it is possible to obtain the desired independent positioning of each runner, with its takeup yarn guide and delivery yarn guide, in relation to the frustum height of the corresponding drum A or B. Yarn F arriving at an uncontrolled speed and tension from a supply bobbin (not shown), passes through the takeup yarn guide 1 of the first drum A, passes once completely around this drum and through the delivery thread guide 2 and is then led to the takeup yarn guide 3 of the second drum B. The yarn then passes once completely around the drum B and on through the delivery yarn guide 4, before being taken to the knockingdown cam and from there to the needles.

Each drum A and B enables yarn to be delivered at a given constant speed for a given speed of rotation, which is the same for each drum, the speed of delivery of the yarn from each drum being determined by the diameter of that section of the drum around which the yarn is wound. Three cases can arise: the yarn delivery speed of the drum A is lower than the yarn delivery speed of the drum B; or the delivery speed from drum A is equal to that from the drum B; or the delivery speed from the drum A is higher than that from the drum B. It is only the first of these cases with which this embodiment is concerned. If the position of the yarn guides 3 and 4 at the drum B is so adjusted that the yarn is delivered from the drum A at a lower speed than from the drum B, stretching of that part of the yarn which lies between the two drums will take place, i.e. a first part of its path, so that the tension on this part of the yarn will be increased. This yarn tension between the two drums will be termed the intermediate tension T Preferably, the intermediate tension is up to 10 times higher than the tension at delivery.

The positioning of the runner 6', with its yarn guides 3 and 4, makes it possible, after passing partly around the drum B which constitutes a second part of its path, to obtain from the second drum the yarn delivery speed at a third part of its path requisite for the desired length of stitch. The positioning of the runner 5, with its yarn guides 1 and 2, enables the speed of delivery of the yarn from the first drum A, to be so determined as to produce the correct intermediate tension T between the drums A and B. The takeup tension T of the yarn F prior to its admission to the feed device at the yarn guide 1 may vary and may be of any value. The delivery tension T of the yarn F after its passage through the feed device and between this and the yarn consuming machine (that is to say, in the case of a knitting machine, the needles), is regulated to the desired value by suitable positioning of the knocking-down cam of the knitting machine (not shown).

Thus, with the aid of a feed device hereinbefore particularly described, it is possible to use a method of feeding high-stretch yarn to a hosiery knitting or other yarn consuming machine at constant speed and tension, the tension at which the yarn reaches the machine remaining low, this method comprising, the steps of subjecting the yarn to tension which is higher than the decrimping tension, such as to bring it into a load/stretch zone in which variations in the loading applied to the yarn do not result in appreciable stretching, and then in reducing the tension in accordance with the hysteresis characteristic, whereby a considerable reduction in loading does not produce appreciable variation in the length of the yarn; so that the yarn delivery and the low tension on the yarn reaching the yarn consuming machine (and, more particularly, the needles of a knitting machine) remain strictly constant, irrespective of the speed and tension at which the yarn is taken up by the feed device. 4

Instead of frustoconical drum rotating at equal peripheral speeds and winding the same yarn, of which the loop round the first drum is smaller in diameter than the loop round the second drum, it is possible to employ cylindrical drums, the first rotating at a lower peripheral speed than the second. The feed device can be used not only with a hosiery knitting machine, but can also be applied to any machine or mechanism which requires yarn at a strictly controlled speed and tension.

A yarn feed device shown in FIGS. 3 and 4 has two cylindrical driving drums 11 and 12 spaced apart from each other.

In general terms, the takeup drum 11 turns at a lower peripheral speed than the delivery drum 12. The drums 11 and 12 may be driven by a single motor, a variable speed gearbox (not shown) being interposed between the two drums to provide any desired differences in peripheral speeds.

In the second embodiment shown in FIG. 3, the delivery drum 12 is provided with a device 13 for holding other yarn with part of the surface of the drum 12. This device 13 consists of two rollers 14 and 15, spaced apart from each other and mounted on one end and the same support (not shown). This support is adjustable and enables the rollers 14 and 15 to be brought towards or moved away from the drum 12. The two rollers 14 and carry an endless belt 16, which, like the drum 12, has a high coefficient of friction. The endless belt is driven either by one of the rollers 14 and 15 or by the drum l2.

The yarn F, in this case, passes around the first drum 11,- without the friction force necessarily being the same between the starting up and the normal running of the feed device. After passing once completely around the first or braking drum 11, yarn F is applied against part ,of the face of the drum 12 by the endless belt of the device 13. Hence, the yarn F moves at the same speed at any point on the periphery of the drum 12. Since the peripheral speed of the drum 12 is higher than that of the drum 11, yarn F undergoes stretching while passing between these two drums, accompanied by the intermediate tension hereinbefore referredto.

For the knitting of adjoining edges or-heel reinforcements, I

the device 13 is moved clear of the drum 12. By reason of its being wound around the drum 11, the yarn F is still well controlled as regards tension.

In the third embodiment shown in FIG. 4, the takeup drum 11 in the yarn feed device is likewise provided with a device' thus firmly held against both drumsll and 12 and is bound to move at speeds equal to the peripheral speeds of the two i drums. Because of the difference in speed between the first drum and the second, the yarn F is subjected to tension between drums 11 and 12. To free the yarn F, all that is required is to move devices 13 and 13 away from drums 11 and 12. It is equally possible, of course, for these devices 13 and 13' to be stationary and for drums 11 and 1,2 to be adjustable in relation to them.

We claim:

1. A yarn feed device for feeding a high-stretch yarn to a yarn consuming machine at a contact speed and tension, said device comprising: means for supplying the yarn to the device at an uncontrolled tension; means for imparting to the yarn, over a first part of its path a constant speed and a tension which is higher than the decrimping tension; and means for casing in the yarn the said imparted tension over a second part of its path so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by application of the high tension such that over a third part of its path a delivery tension is achieved which is lower than the decrimping tension whilst permitting a variation of tension to be tolerated without the production of appreciable variation in length of the yarn.

2. A yarn feed device according to claim 1 wherein the constant speed and tension imparting means comprises two rotatably mounted frustoconical drums, the peripheral surface of each of which has a high coefficient of friction, and yarn guide means arranged to lead yarn initially onto the surface of the first drum, thence onto the surface of the second drum and finally away from the latter, said yarn guide means serving further so to direct the yarn that the speed of that part of the yarn which is in contact with the surface of the first drum is lower than the part of the yarn in contact with the second drum. 1

3. A yarn feed device according to claim it wherein the constant speed and tension imparting means comprises two rotatably mounted cylindrical drums, the peripheral surface of holding device comprises two spaced rollers and an endless belt passes around both said rollers and 19 arranged so as to be capable of being brought into contact with said part of the surface of the second drum.

Claims (5)

1. A yarn feed device for feeding a high-stretch yarn to a yarn consuming machine at a contact speed and tension, said device comprising: means for supplying the yarn to the device at an uncontrolled tension; means for imparting to the yarn, over a first part of its path a constant speed and a tension which is higher than the decrimping tension; and means for easing in the yarn the said imparted tension over a second part of its path so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by application of the high tension such that over a third part of its path a delivery tension is achieved which is lower than the decrimping tension whilst permitting a variation of tension to be tolerated without the production of appreciable variation in length of the yarn.

2. A yarn feed device according to claim 1 wherein the constant speed and tension imparting means comprises two rotatably mounted frustoconical drums, the peripheral surface of each of which has a high coefficient of friction, and yarn guide means arranged to lead yarn initially onto the surface of the first drum, thence onto the surface of the second drum and finally away from the latter, said yarn guide means serving further so to direct the yarn that the speed of that part of the yarn which is in contact with the surface of the first drum is lower than the part of the yarn in contact with the second drum.

3. A yarn feed device according to claim 1 wherein the constant speed and tension imparting means comprises two rotatably mounted cylindrical drums, the peripheral surface of each of which has a high friction coefficient and each of which is capable of being rotated at different speeds.

4. A device according to claim 3, comprising an adjustable device arranged to hold the yarn in engagement with part of the surface of the second drum, thereby preventing slippage of the yarn.

5. A device according to claim 4, wherein said adjustable holding device comprises two spaced rollers and an endless belt passes around both said rollers and is arranged so as to be capable of being brought into contact with said part of the surface of the second drum.

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