US3304593A

US3304593A - Yarn bulking method and apparatus

Info

Publication number: US3304593A
Application number: US427021A
Authority: US
Inventors: Glenn A Burklund
Original assignee: BURKLUND LAB Inc
Current assignee: BURKLUND LAB Inc; BURKLUND LABORATORIES Inc
Priority date: 1965-01-21
Filing date: 1965-01-21
Publication date: 1967-02-21
Anticipated expiration: 1984-02-21
Also published as: FR1467312A; ES322402A1; DE1660216B1; BE674986A; GB1126673A; CH441607A

Description

Feb. 21, 1967 G. A. BURKLUND YARN BULKING METHOD AND APPARATUS Filed Jan. 21, 1965 ULTRASON IC GENERATOR R mD m WL K R U B A N N E L G v Q ATTORNEYJ- United States Patent 3,304,593 YARN BULKING METHOD AND APPARATUS Glenn A. Burklund, Fairfax, Va., assignor to Burklund Laboratories, Inc., a corporation of Virginia Filed Jan. 21, 1965, Ser. No. 427,021 19 Claims. (Cl. 28-1) This invention relates to an improved process and apparatus for bulking and/or texturing synthetic yarn, and more particularly relates to a method and apparatus for producing crimps in each filament of a continuous running strand by applying mechanical shock to the fibers as they pass over a vibrating head at a high linear rate.

It is known in the prior art to bulk drawn yarns of thermo-plastic filaments for the purpose of providing serpentine stretch yarn from which stretch garments can be manufactured. The prior art teaches several different ways of accomplishing such bulking, as follows:

A first process teaches the idea of subjecting the yarn to air jets which cause the filaments within the yarn to be blown apart and to become mutually entwined so that a certain amount of crimping or kinking occurs.

A sec-0nd process known as the false-twist process subjects linear increments of the yarn to torsional twisting about the yarns longitudinal axis, and the process further employs subsequent heating of the twisted yarn so as to substantially set the twist.

A third process includes the steps of passing the yarn over a heating element to raise its temperature to a point where the yarn becomes plastic but short of its melting point; and then stuffing the yarn into a stuffing box or else drawing the yarn over an acute-angle knife edge so as to distort its normal cross-sectional distribution of plastic, whereby when the yarn cools each filament will have a tendency to form a series of loops somewhat resembling the convolutions of a coil spring.

A fourth process has been suggested wherein the yarn is passed between electrodes to which a difference of potential is periodically applied at a relatively high repetition rate, the yarn having been heat-softened when it is introduced between the electrodes to permit it to distort under the potential stresses,

The present invention represents a novel approach employing the application of physical shock to the yarn as it is drawn over a crimping head which is vibrated at a relatively high mechanical rate, driven for instance by a signal recurring at at least a sonic rate, which signal is applied to a crystal transducer mechanically connected to the head. In the working embodiment of the invention illustrated in the present application yarn ends are drawn over the edges of crimping heads which are vibrated in such a direction as to pulse the yarn transversely of its linear axis, thereby distorting each of the fibers by relatively violent mechanical shock so that the fibers develop adjacent cusps or kinks, the separation between which depends upon the vibration rate of the head and the linear rate of travel of the yarn thereover.

It is a principal object of this invention to mechanically shock the fibers by repeated-1y applying mechanical pulsations having extremely high rates of acceleration, but having amplitudes which are small enough that the fibers are not broken despite the violence of the impact. In the present working embodiment of the invention, the acceleration is of the order of magnitude of 1000 to 150,000 Gs, but the amplitude of the mechanical shock is only a few thousandths of an inch, perhaps 3 to thousandths.

Another object of the invention is to provide a bulking method and apparatus in which the yarn, while passing over the crimping head, changes direction at right angles or at obtuse angles so that the molecules in the fiber are transversely shocked at spaced points along their lengths. In the working embodiment of the present invention, the head comprises a small block against which the yarn is distorted by feeding the yarn up one side of the block, across the top of the block, and down the other side of the block with the block vibrating back and forth in a direction parallel to its sides. The block is supported upon a crystal transducer which is connected to a signal generator capable of driving the transducer with a power oscillation, in the present embodiment of up to watts, at an ultrasonic rate of about 20 kilocycles.

No heat is intentionally introduced for the purpose of softening the fibers either before or during the mechanical agitation, although it is believed that the fibers may be warmed to a certain extent at the precise points of contact with the crimping edges of the head. If the vibrating head is touched to an object which is relatively heavy as compared with the slight mass of yarn fibers, consider-able heat is generated by the mechanical agitation. On the other hand, if the yarn is held in one spot against the head while tensioning it in the same manner as it would be tensioned for the purpose of crimping, the yarn does not appear to soften or weaken at the point of contact even though its forward motion be completely stopped. It therefore appears that any heating which does result may be incidental to the present process, and may even help the crimping somewhat, although experiments with the deliberate application of heat from an external source to the yarn as it passes over the vibrating head have indicated that the ultrasonic process is degraded somewhat by such heating. In view of the stretchiness of the yarn, and the small amplitude of vibration of the head, and the rapid transit of the yarn over the head, the heating effect is probably not very significant.

As suggested above, the closeness together of the kinks in the filaments depends on the linear rate of movement of the yarn over the crimping head and upon the rate of vibration of the crystal transducer. Within limits, the displacements during vibration of the transducer affects the tightness or looseness of the kinks in the filaments, although once a sufiicient amplitude of displacement is reached to provide optimum kinking, further increase in amplitude does not appear to be beneficial and in some instances has even proven harmful.

It is another object of the invention to provide crimping heads having advantageous shapes. For example, it is found that standing waves can be sustained in the yarn as it passes across the top of the crimping head between the paths of delivery to and retreat from the head, said paths extending down the sides of the head. At 20,000 cycles one or two standing waves will be created across the top of the crimping head when it is about one-half inch wide. If the head is fiat on top, there is a strong tendency of the top surface to damp the standing wave. On the other hand, if the head is recessed, the yarn will be free to vibrate in a standing wave mode having an amplitude which is much greater than the displacement of the head itself, and it appears that this standing wave vibration assists the crimping action by adding a jerking motion to the yarn at the same rate of occurrence as the vibrations of the head, and the amplitude of the standing wave being augmented greatly by resonance. Experiments have also been run on the idea of placing a follower member opposite the head member itself so that the yarn passes between the two members. Because of the tremendous accelerations and low amplitudes involved, the follower member does not seem to touch the main vibrating head, but there appears tobe a pulsating cushion of air trapped between the heads. The mechanism by which the presence of the follower mass helps the crimping action appears to be different from the resonance theory of the standing waves, perhaps based upon periodic clamping of the yarn to the main vibrating head so as to reduce the ability of the yarn to retreat as the vibrating head approaches its maximum advance against the yarn.

It is another object of the invention to provide means for placing a drag upon the yarn just before it runs up the side of the vibrating head toward the top, and then providing power-driven pinch roll means for pulling the yarn across the head and down the other side, prior to delivery of the bulked yarn to a storage spool. It has been found that the tensioning device and the pinch rolls should be located only a short distance down the sides of the head from its top surface, perhaps an inch from the top thereof, in order to provide optimum crimping of the yarn. It may be that the distance of the drag means and of the pinch rolls from the top surface of the head is a function of the longitudinal stretch characteristics of the yarn as determined by its denier and by its composition, and that by moving the pinch rolls and the drag means further from the top surface of the head, too much stretch of the fibers may be permitted, such stretch allowing them to retreat from the advance of the head to such an extent that optimum crimping does not occur.

There is another reason for having the pinch rolls close to the crimping head. Experiments show that it is desirable to permit the yarn to relax longitudinally as soon as possible after it leaves the crimping edge. The degree of the crimp in the yarn seems to increase gradually for a short period of time after it leaves the crimping edge if the yarn is untensioned right away. By putting the pinch rolls near the edge, the tension required to pull the yarn over the edge can be relaxed almost immediately, thereby permitting the crimp to increase somewhat. The crimping which takes place as a result of the ultrasonic vibration is permanent to a large degree, but the ultimate degree of the crimp can be increased by briefly heating the bulked yarn in untensioned condition after it leaves the pinch roll and before it is stored on a spindle. It is therefore desirable to provide a small heater through which the yarn passes in relaxed condition on its way from the pinch rolls to the storage spool.

One advantage of the present invention is that a very versatile bulking method is provided by which novel effects can be obtained. For instance, a yarn can be provided having alternate bulked and non-bulked longitudinal portions by keying the crystal transducer on and off. Besides producing a stretch fabric more economically, in view of the fact that the extent to which the yarn is bulked is proportional to the extent to which the yarn is foreshortened. If, for example, a three foot length of yarn is subjected to the present process, it may be shortened to about one foot of bulked length. However, by grasping the ends of the one-foot length and pulling it out until it appears unkinked again, it will be found that the yarn under the latter circumstance is still approximately three feet in length. It thus appears that the present process does not stretch the fibers, it mere provides them with a sawtooth shape amounting to a permanent set to which the fibers return when longitudinal tension is released.

The benefits realized by the present apparatus and method include a reduction in size and a greater simplification in the mechanical complexity of the apparatus required to perform the present process. Although a transducer-driving generator is required, such electronic equipment needs very little maintenance, and therefore is believed to be an improvement over the mechanical apparatus performing other texturizing or bulking processes. Moreover, it is believed that the present system produces tighter and more uniform kinks in the filaments, and these kinks being closer together, the invention provides a finer ultimate texture having smaller tighter coils which when woven in a stretch material will permit the material to stretch and/or relax more smoothly. Moreover, since crystal transducers can easily and conveniently produce extremely high rates of vibration, the process itself imposes almost no limit on the speed at which the yarn can be passed over the head, thereby providing a process and apparatus capable of bulking at much higher linear rates without sacrificing the tightness of the individual kinks or coils resulting in the fibers. Of course it is also expected that a larger number of strands or ends of yarn will be passed over the same bulking head in side-by-side relationship in a production embodiment of the apparatus.

Essentially, the present process is anon-torque process of the general type referred to in Patents 2,919,653, 2,931,089, 3,028,653 and 3,028,654, as distinguished from a high-torque process such as the one mentioned above and shown in Patent 3,108,430 in which the yarn is twisted about its longitudinal axis. The present type of nontorque yarn is believed to be more satisfactory since there is no tendency for it to twist while being woven or knitted, and since there is no tendency for the present yarn to distort a fabric due to strand rotation. In hightorque yarns, there is such a tendency to distort a fabric woven therefrom that sometimes weavers find it necessary to ply two or more such yarns together, the yarns having opposite twists so as to cancel out fabric distortions after they are woven. Moreover, since the fibers are individually kinked, there is no tendency in the yarn bulked according to the present process to go into a type of kinking in which all of the filaments in the yarn participate in unison. In other words, yarn made according to the present process when released to a relaxed condition is stable and will not itself go into larger unwanted kinks.

Other objects and advantages of the invention will become apparent during the following discussion of the drawings, wherein:

FIG. 1 is a diagrammatic view showing yarn passing from a spindle over a crimping head, and to a storage spool, and showing a diagram of suitable electrical wiring;

FIG. 2 is a perspective view showing multiple strands or ends of yarn being simultaneously bulked by the same head;

FIG. 3 is an elevation view of a modified form of crimping head showing the yarn passing thereover and developing standing waves across the upper surface of the head;

FIG. 4 shows a second modification of the head, and illustrates how a different mode of standing waves can be set up where the head is vibrated at a different frequency;

FIG. 5 shows a third modified form of the head having a serpentine upper surface located opposite a spring loaded follower member whose lower surface is shaped in the form of a substantially complementary serpentine contour; and

FIG. 6 is a greatly magnified view of a length of yarn in which the fibers are bulked in one longitudinal portion, and unbulked in adjacent portions.

Referring now to the drawings, FIG. 1 shows a practical illustrative embodiment using an ultrasonic generator 1 capable of delivering ultrasonic undulating electrical output at a high power level, the generator being connected to drive a crystal transducer 2 which supports and drives a mechanical motion transforming column 3 which in turn supports a crimping head 4 in the form of a rectangular block of metal, which can also be seen at 4 in FIG. 2. The generator 1, the crystal transducer 2, and the support column 3 are purchased items manufactured by Branson Instruments, Model LS-75.

The electrical circuit of FIG. 1 also includes a rotary drum switch 5 which is capable of alternately making and breaking the circuit between the generator 1 and the transducer 2 when the drum 5 is rotated by a motor 6, thereby modulating the amplitude of the head vibrations at a rate which is slow as compared with the greater-thansonic vibration rate. For illustrative purposes, the drum 5 may also be considered as comprising an ON-OFF switch when it is manually positioned to either continuously make or break the circuit. It is also to be understood that the drum 5 can be replaced with other modulating means which would operate to increase and decrease the vibration amplitude rather than to key it ion, ifl'7,

The yarn Y to be processed is taken from one or more spindles 10 through guide means 11 and through friction drag blocks 12 and 13, the block 13 being supported on a rod 13a which can be reciprocated through a sleeve 14, and which is urged toward the block 12 by a spring 15 calibrated to provide a predetermined drag upon the yarn Y. The yarn passes between the

blocks

12 and 13 upwardly over the top surface of the crimping head 4 and down again on the other side of the head. It then passes between

pinch rollers

16 and 17, the latter roller being driven continuously by a motor 18 and serving to draw the yarn over the crimping head 4 against the degree of tension determined by the spring 15. It will be noted that as soon as the yarn has passed beyond the pinch rolls 116 and 17, the tension on it is relaxed so that the yarn hangs in a loose catenary as indicated at K. As soon as the tensioning is relaxed on the yarn it goes into bulked condition as indicated by the reference character B. As stated above, it is desirable that the tension be removed from the yarn very soon after it passes over the crimping head 4, meaning that the pinch rolls l6 and 17 should be near the crimping head.

The bulked yarn B passes over a roller 20 and downwardly to a storage spool 21 which is rotated by suitable means (not shown). Experience with the present working embodiment of the invention has shown that the crimping of the filaments is permanent and that no further treatment of the yarn is necessary. On the other hand, some improvement in the degree of bulking can be bad if the yarn which has been crimped is relieved of tension and then heat-treated somewhat, for example by passing it through an electricheater 22 which can be conveniently connected to a source of power. The warming of the filaments to a temperature below the melting point thereof, as taught in prior art patents such as 3,099,064 permits the coiling and kinking of the filaments to increase noticeably, and appears to set the kinks at this increased amplitude. The heater is therefore considered to be a desirable option.

PEG. 2 shows a modification of FIG. 1 in which multiple ends of yarn are passed over the same crimping head 4- so that they are simultaneously bulked, this being especially advantageous for production purposes, it merely being necessary to lengthen the friction blocks 12 and 13' as well as the pinch rolls l6 and 17' to accommodate plural strands. The present thinking suggests that approximately 40 strands can be drawn over a single crimping head and that the electrical power to drive such a head would be about 75 watts. In any event, the crimping heads are driven so that they reciprocate in the direction of the arrows A, and the yarn passes over the tops of the heads at a predetermined velocity in the direction of the arrows V. This velocity and the rate of vibration of the head are interrelated parameters which together determine how far apart the kinks will be separated in the bulked yarn.

A number of experiments have been run to determine an optimum shape for the crimping head itself, numerous shapes having been tried such as acute knife-edge shapes, rounded edges, and the particular shapes shown in FIGS. 1, 2, 3, 4, and of the present drawing. As long as the crystal transducer is driven to a sufficient amplitude, any edge which will give an abrupt change of direction of the yarn seems to perform in a satisfactory way. In each of the structures shown in the present drawings, the yarn actually is bent through an obtuse angle which for some fibers such as nylon should approach 90, although obtuse angles of about 150 are more desirable for other fibers such as polyester. The rectangular crimping head 4 as shown in FIG. 1 is very simple to make and appears to contribute to accidental breaking of the filaments somewhat less than a single upstanding knife edge,

although the latter when slightly rounded does not break the yarn under normal operating conditions.

Close observation of the rectangular head shown in FIG. 1 when operating indicates that the yarn attempts to set up simple-harmonic-motion standing waves, and therefore experimental heads were made of the types shown in FIGS. 3 and 4 designed to encourage the formation of these standing waves. By adjusting the system until resonance was reached as indicated by the size of the standing waves, improved crimping occurred which contributed to a reduction in the power required to drive the transducer 2. Such a reduction in power is desirable where a large number of strands are simultaneously bulked as shown in FIG. 2. It is intended that the showings in FIGS. 3, 4, and 5 are not limited to single strands of yarn passing over the heads.

The head shown in FIG. 3 comprises a block 24 having two recessed areas extending across the block for its full width in a direction measured normal to the plane of the paper on which the drawing is made. These recesses are separated by a cusp 25 in the center which would be located at a node in the vibratory pattern of the standing waves Y so that the vibration is essentially a full-wave mode. A different mode of vibration is obtained in FIG. 4 by the head 25 which has only a single recess across its full width intended to permit a standing wave Y" to occur, resonance being obtained in FIG. 4 at a different frequency of the vibration head 26, as compared with the resonant frequency in FIG. 3, assuming the same weight of yarn.

FIG. 5 shows still another modified form of the head in which a head block 27 has a serpentine upper surface 27a extending the full width of the head, and a complementary follower block member 28 is mounted on a vertical rod 29 passing through a sleeve 30. A spring 31 biases the follower member 28 downwardly toward the head member 27. A surprising result is obtained with this structure. It appears that the follower member 28 never touches the vibrating head 27 even when the yarn is removed from the space between these members. An air cushion develops between the

members

27 and 28, the air apparently not having sufiicient time to escape when the member 27 and the member 28 approach each other. The result is that an air cushion is formed between the two members so that no wear occurs. When yarn is passed between the serpentine surfaces 27a and 28a, the yarn is apparently alternately clamped and released therebetween, and this alternate clamping and releasing tends to increase the violence of the crimping action, again permitting a reduction in power to the crystal transducer 2 because of the fact that less amplitude of vibration is necessary to accomplish the degree of crimping desired.

FIG. 6 shows a greatly magnified strand of yarn in which the yarn is alternately bulked and unbulked in a novel fashion. This alternate bulking of the yarn is the result of rotation of the drum switch 5 by the motor 6 so that the energy to the crystal from the ultrasonic generator is alternately keyed on and off while the yarn is continuously drawn over the bulking head. By stopping the motor in a position in which the drum switch 5 completes the circuit, the yarn passing over the crimping head can be continuously bulked.

Although this invention is illustrated in terms of yarn crimping, the process has utility in connection with the crimping of a wide variety of other continuous filaments and at frequencies which may be in a sonic range where the filaments are of larger diameter.

The present invention is not to be limited to the exact illustrative forms shown in the drawing, for obviously changes may be made therein within the scope of the following claims.

I claim:

1. The method of bulking a synthetic fiber by crimping, comprising:

(a) continuously passing the fiber through a crimping zone;

( b) applying mechanical shock against the fiber at a rate which is at least sonic, the shock being applied to the fiber in a non-longitudinal direction and comprising recurring pulsations having high acceleration rates but low displacement amplitudes; and

(c) collecting the shocked fiber.

2. The method of bulking a synthetic fiber by crimping, comprising (a) continuously passing the zone;

(13) applying mechanical shock against the fiber at a greater-than-sonic rate, the shock being applied to the fiber in a non-longitudinal direction and comprising recurring pulsations having acceleration rates in the order of 1000 G5 or more, but low amplitudes; and

(c) collecting the shocked fiber in longitudinally relaxed condition.

3. The method of bulking a synthetic fiber by crimping, comprising (a) continuously zone; (b) applying mechanical shock against the fiber at a greater-than-sonic rate, the shock being applied to the fiber in a non-longitudinal direction and comprising recurring pulsations having high acceleration rates but low amplitudes;

(c) subsequently briefly heating the shocked fiber while in longitudinally untensioned condition to a temperature below its melting point; and

(d) collecting the fiber.

4. The method of bulking a synthetic fiber by crimping, comprising (a) continuously passing the fiber through a crimping zone;

(b) applying mechanical shock against the fiber at a rate which is at least sonic, the shock being applied to the fiber in a non-longitudinal direction and comprising recurring pulsations having high acceleration rates but low displacement amplitudes;

(c) modulating the displacement of the applied pulsations at a rate which is slow as compared with said at-least-sonic rate; and

(d) collecting the shocked laxed condition.

5. The method of bulking a synthetic yarn by crimping, comprising (a) continuously passing the yarn over a crimping edge while tensioning the yarn on both sides of the edge to pull it thereagainst;

(b) reciprocating the edge against the tensioned yarn at a rate which is at least sonic to shock the yarn with mechanical vibrations at very high rates of acceleration but low displacements; and

(c) subsequently releasing the tension on yarn and then collecting it.

6. The method of bulking a synthetic yarn by crimping,

comprising l (a) continuously passing the yarn over a crimping edge while tensioning the yarn at points located close to the opposite sides of the edge to pull it thereagainst;

(b) reciprocating the edge against the tensioned yarn at a rate which is at least sonic to shock the yarn with mechanical vibrations at very high rates of acceleration but at displacements of only 3 to 15 thousandths of an inch; and

(c) subsequently releasing the tension on the crimped yarn and then heating it briefiy to a temperature less than its melting temperature.

7. The method of bulking a synthetic yarn by crimping,

comprising fiber through a crimping passing the fiber through a crimping fiber in longitudinally rethe crimped (a) continuously passing the yarn over a crimping head having spaced edges while tensioning the yarn on both sides of the head to pull it against the edges;

(b) reciprocating the head against the tensioned yarn at a high vibration rate to shock the yarn with mechanical vibrations at very high rates of acceleration but low displacements, the vibration rate being selected to set up standing waves in the yarn located between said edges; and

(c) subsequently releasing the tension on the crimped yarn and then collecting it.

8. The method of bulking a synthetic yarn by crimping, comprising (a) continuously passing the yarn over a crimping head having a surface located between spaced edges while tensioning the yarn on both sides of the head to pull it thereagainst;

(b) reciprocating the head against the tensioned yarn at a high vibration rate to shock the yarn with mechanical vibrations at very high rates of acceleration but low displacements;

(c) periodically clamping the yarn against said surface between said edges and releasing the clamping effect at said vibration rate; and

(d) subsequently releasing the tension on the crimped yarn and then collecting it.

9. The method of bulking a yarn of synthetic material,

comprising (a) tensioning a yarn by pulling it over a vibratory head from points located on both sides of the head and close thereto;

(0) continuously drawing the tensioned yarn over the head;

(0) reciprocating the head in a direction to alternately increase and decrease the yarn tension at an ultrasonic rate through displacements in the range of about 3 to 15 thousandths of an inch; and

(d) subsequently collecting the yarn.

10. The method of bulking a yarn of synthetic material, comprising (a) tensioning a yarn 'by :pulling it over a vibratory head from points located behind both sides of the head and close thereto;

(b) continuously drawing the tensioned yarn over the head;

(d) subsequently releasing the tension on the yarn and briefiy heating it to a temperature below its melting point.

11. Apparatus for bulking a yarn of synthetic fibers,

comprising (a) a yarn crimping head;

(b) means for continuously passing yarn over said head and for tensioning the yarn thereagainst; and

(c) means for vibrating said head at a rate which is at least sonic and in a direction alternately increasing and decreasing the tension of the yarn passing thereacross.

12. In apparatus as set forth in claim 11, said head comprising at least tWo mutually spaced edges across which the yarn is passed under tension, and the head being recessed between the edges to provide clearance permitting the yarn to sustain standing waves therebetween.

13. In apparatus as set forth in claim 11, said head comprising a block having a surface across which the yarn is passed under tension, a second block having a surface substantially complementary in shape to said surface of the head, and spring means urging the second block theretoward to press the yarn thereagainst.

14. In apparatus as set forth in claim 13, said complementary surfaces being serpentine as viewed across the path of the yarn.

15. Apparatus for bulking a yarn of synthetic fibers, comprising (a) a source of supply of said yarn;

(b) a yarn crimping head;

(c) means for continuously passing said yarn over said head including drive roll means and including yarn drag means respectively located on opposite sides of the head and tensioning the yarn thereagainst;

(d) transducer means coupled to the head for vibrating it in a direction to alternately increase and decrease the yarn tension; and

(e) means for generating an electrical signal having at least a sonic frequency and including a circuit for connecting the signal to drive the transducer.

16. In apparatus as set forth in claim 15, means connected in said circuit for periodically modulating the intensity of said drive signal.

17. In apparatus as set forth in claim 15, said drive roll means and said drag means being located close to the crimping head to reduce the tendency of the yarn to stretch between the head and these means to partially escape the shock of the applied vibrations.

18. In apparatus as set forth in claim 15, means for collecting the yarn after it leaves the drive roll means; and heater means interposed between the drive roll means and the collecting means for heating the crimped yarn to a temperature below its melting point to improve the set of the crimping.

19. In apparatus as set forth in claim 15, said head comprising at least two mutually spaced edges across which the yarn is passed under tension, and the head being recessed between the edges to provide clearance permitting the yarn to sustain standing waves therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,977,661 4/1961 (Evans 611211 2s-1 3,047,932 8/1962 Pittman 61: a1. 2s 1 3,167,847 2/1965 Gonsalves 28-1 FOREIGN PATENTS 1,342, 601 12/1962 France.

M'ERVIN STEIN, Primary Examiner. L. K. RIMRODT, Assistant Examiner.

Claims

11. APPARATUS FOR BULKING A YARN OF SYNTHETIC FIBERS, COMPRISING (A) A YARN CRIMPING HEAD; (B) MEANS FOR CONTINUOUSLY PASSING YARN OVER SAID HEAD AND FOR TENSIONING THE YARN THEREAGAINST; AND (C) MEANS FOR VIBRATING SAID HEAD AT A RATE WHICH IS AT LEAST SONIC AND IN A DIRECTION ALTERNATELY INCREASING AND DECREASING THE TENSION OF THE YARN PASSING THEREACROSS.