US3842578A

US3842578A - Method and apparatus for threading yarn into a stretch and false twist crimping machine

Info

Publication number: US3842578A
Application number: US00303086A
Authority: US
Inventors: H Schippers
Original assignee: Barmag Barmer Maschinenfabrik AG
Current assignee: Oerlikon Barmag AG
Priority date: 1971-11-09
Filing date: 1972-11-02
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22
Also published as: DE2155514B2; JPS4875813A; CH543612A; DE2155514A1; FR2160102A5; GB1394263A

Abstract

A method and apparatus for threading a combination stretch and false-twist crimping machine having feed and draw rolls which continuously draw the yarn over an elongated heated plate and through a rotatable false-twist spindle, at least one movable guide means operating to place the running yarn in contact with the heated plate only after the false-twist spindle has first been adjusted to a speed substantially smaller than its normal operating speed, the movement of the guide means being such as to maintain a substantially constant yarn length between the feed and draw rolls and thereafter adjusting the false-twist spindle to its normal operating speed.

Description

Unite 11.

States Patent 1191 Schippers 1 Oct. 22, 1974 METHOD AND APPARATUS FOR 3,336,738 8/1967 Mattingly C181 57/34 115 YARN [NT A STRETCH AND 3,541,775 11/1970 Fisher. Jr.

CRIMPINg MACHINE 3,559,255 2/l97l Cockroft 57/34 HS X 3,636,697 1/1972 Treptow et a1. 57/106 [75] Inventor; Heinz Schippers, Rcmschcid, 3,724,191 4/1973 Hooper ct a1 57/34 HS Germany LUSk Cl 3,733,801 5/1971 Jones [73] Assignee: Barmag Barm r M hin nf k 3,747,227 7/1973 22mg et a] 57/106 x Aktiengesellschaft, Wuppertal, Germany Primary Examiner lohn Petrakes 22 Filed; 2 1972 Attorney, Agent, or FirmJohnston, Keil, Thompson & Shurtleff 1211 Appl. No.: 303,086

[57] ABSTRACT [30] Forelgn Apphcatmn Pnomy Data A method and apparatus for threading a combination Nov. 9. 1971 Germany 2155514 Stretch and false twist crimping machine having feed and draw rolls which continuously draw the yarn over [52) US. Cl 57/34 HS, 28/62, 57/106, an elongated heated plate and through a rotatable 57/157 TS false-twist spindle, at least one movable guide means 1 it. p ti g t pl th i g y i t t th [58] Fleld of Search 57/34 5565 157 T5, heated plate only after the false-twist spindle has first 57/157 90, 106; 28/62 been adjusted to a speed substantially smaller than its normal operating speed, the movement of the guide 1 1 References Cited means being such as to maintain a substantially con- UNITED STATES PATENTS stant yarn length between the feed and draw rolls and 2,780,047 2 1957 Vandamme C1111 57/34 HS thereafter adjusting the false-twist Spindle to its 2,918,778 12 1959 Wormser 57/34 HS mal operating speed. 3.041.813 7/1962 Enneking.... 57/34 HS 3,289,400 12/1966 Scragg 57/34 HS 11 Clam, 8 Drawmg PATENTED 2 21974 mi 11: a

FIGI

METHOD AND APPARATUS FOR THREADHNG YARN INTO A STRETCH AND FALSE TWIST CRIMPING MACHINE False-twist crimping machines consist essentially of a feed means for the continuous delivery of a yarn taken off a supply spool and a heating device as well as a false-twist assembly and a draw means to at least maintain the yarn under a certain tension. After the draw means, the yarn may be subjected to a second heat treatment and/or wound into a durably crimped product on a take-up spool or the like. The application of heat to the yarn has been carried out with contact heating devices and also with convection heating apparatus. The false twisting is accomplished by means of a rapidly spinning false-twist spindle or by means of friction between the running thread and rotating wheels, drums or similar elements. The initial yarn being delivered is most usually already in the form of a stretched yarn. The servicing of false twist machines occurs randomly, i.e. each operating position of a multi-unit machine is serviced as needed while the other positions continue to function.

For economical and technical reasons, it has become especially desirable to also undertake a stretching of a multifilament yarn on the same machine used for imparting a durable false-twist or so-called torque crimp. In this case, the machine is used for processing an unstretched synthetic thermoplastic yarn, e.g. such as polyethylene terephthalate yarn. in one version of this combined apparatus for stretching and false-twist crimping, an additional feed mechanism is introduced prior to the feed rolls leading into the heating device. The relative speeds of these two feed means are then adjusted in such a manner that the yarn is stretched by a predetermined amount before being conducted to the heating device. (For example, see German Patent No. 1,807,687.)

The present invention is particularly concerned with yet another version of such a combined stretching and false-twist crimping machine wherein the stretching occurs simultaneously with the crimping. This is accomplished by adjusting the relative speed as between the draw rolls or similar transporting means following the false-twist assembly and the feed roll or similar feed means preceding the heating device so that a stretching occurs simultaneously in the same step or stage as the false-twist and heat treatment of the yarn. (For example, see British Patent No. 777,625.)

It is especially difficult to achieve a satisfactory threading of the yarn into the individual working positions of this last mentioned combination stretch and false-twist crimping machine. The threading occurs while the many other working positions are in operation. For this reason, it is not possible to shut off the heating device, which is centrally controlled and regulated, when threading a single position. This means that the stationary or only slowly running unstretched yarn material comes into direct contact with the heating device while it is still at the high operating temperature. Depending upon the yarn material, this in turn leads to yarn breakage, embrittlement or melting of the unstretched thermoplastic filaments. Polyester yarns or threads are especially sensitive to heat in their unstretched state.

It is a primary object of the present invention to provide a method and certain apparatus which will avoid prior problems in the threading and operation of a combination stretch and false-twist crimping machine. More particularly, it is an object of the invention to thread a heat-sensitive but initially cold and unstretched polyester yam into a combination stretch and false-twist crimping device in a rapid and controlled manner without any substantial damage to the yarn or excessive loss of production time.

It has now been found in accordance with the invention that these and other objects can be achieved in threading an apparatus for the simultaneous stretching and false-twist crimping of a yarn composed of synthetic thermoplastic filaments wherein the yarn is continuously conducted for stretching in a normal operating path between a stretch feed point and a stretch draw point while simultaneously being subjected to a heat treatment by direct contact with an elongated heating surface in said normal operating path and also imparting a false twist to the heat treated yarn by means of a rotating false-twist spindle before the yarn reaches said stretch draw point, provided that the process includes the steps of first threading the yarn from the stretch feed point to the stretch draw point through the false-twist spindle and also through a movable guide point adjacent one end of the elongated heating surface, this guide point being initially maintained in a position such that the yarn runs in a preliminary operating path which is free of contact with the heating surface, then conducting the yarn through said preliminary path while adjusting the speed of the false-twist spindle to a speed substantially smaller than its normal operating speed, thereafter moving this guide point to bring the yarn into its normal operating path in contact with the heating surface, the movement of the guide point being such that the yarn length between said stretch feed point and said stretch draw point remains substantially constant and subsequently adjusting the false-twist spindle to its normal operating speed. This improved method according to the invention is especially applicable to the proper treatment of unstretched polyethylene terephthalate filaments or yarns as the initial material being treated.

The known combination of apparatus essentially includes spatially separated feed roll means and draw roll means for stretching a length of yarn therebetween, an elongated curved heating plate for contact with the yarn being stretched and positioned to receive the yarn from said feed roll means during normal operation and a false-twist spindle following said heating plate for imparting a temporary twist to the yarn at a point preceding said draw roll means. The improvement of this apparatus in its broadest context accordingto the invention includes at least one yarn guide means adjacent one end of the elongated heating plate for movement substantially perpendicular to the plate from an open position in which the yarn is maintained free of contact with the plate to a closed position in which the yarn is maintained in running contact with the plate, the movement of the guide means between said open and closed positions being such that the yarn length between the feed roll means and the draw roll means remains substantially constant.

Particular yarn guide means in a number of combinations with the stretch and false-twist crimping apparatus are illustrated by the embodiments shown in the accompanying drawing wherein:

FIG. 1 is a schematic side elevational view of one embodiment of the invention in which a feed godet or set of feed rolls is itself movable to act as the essential yarn guide means for threading the combination stretch and false-twist crimping machine;

FIG. 2 is a schematic side elevational view of another embodiment of the invention in which the movable yarn guide means is positioned above a curved heating plate traversed twice by the running thread;

FIG. 3 is a front plan view of the same embodiment shown in FIG. 2;

FIG. 4 is another schematic front plan view of a contact heating plate adapted to receive a plurality of running yarns with several traversing runs each across the plate and with reversal elements above and below the plate as the movable yarn guide means;

FIG. 5 is a schematic perspective view of yet another embodiment of a stretch and false-twist crimping machine with a curved and slotted heating plate for a doubly traversing yarn path and at least one movable reversing element as the essential yarn guide means for threading the apparatus; and

FIGS. 6, 7 and 8 illustrate schematic cross-sections of suitably enclosed heating zones where the contact heating plate is arranged near the upper end of the stretch and false-twist machine so as to require specially adapted movable yarn guide means for threading the machine at a point which is normally out of reach of the person tending the machine.

In all of the illustrated embodiments of the apparatus or combination of the invention, there is at least one yarn guide element or assembly which is movable in a path substantially perpendicular to the vertical plane of the heating plate while the yarn is fully engaged and running in the stretch and false-twist apparatus first out of contact with the heating plate and then in running contact with this plate. Most importantly, this perpendicular movement, which is subject to slight variation for obvious reasons, must occur while essentially maintaining a constant yarn length between the feed and draw means used for stretching the yarn.

Referring to the first embodiment of the invention as shown in FIG. 1, the stretch and false-twist crimping machine generally requires a spool holder to carry the supply spool l of unstretched polyester yarn Y which is cold" in the sense that it is provided at room temperature and without any special heat treatment as it is fed into the machine. Each processing position or unit of the machine also includes a feed mechanism 2 and a pair of draw rollers 3 or the like which can be controlled or regulated at different feed and draw speeds by any conventional control system 4 to stretch the yarn over the length between the nip points, i.e. so as to adjust the speed ratio between the feed point and draw point where the yarn is clamped or engaged in running contact with the feed and draw means, respectively.

Two fixed guide eyelets 5 and 6 direct the yarn Y in a normal operating path for contact with the slightly curved surface of heating plate 7 having an inlet 7a and outlet 7b for circulation of a heating medium. The feed mechanism 2 itself is movable in a slightly curved path on a suitable track or guide rail as indicated by the double headed arrow so that it can be placed in a closed position 8 for normal operation of the machine or in an open position 9 for initial threading of the unit in accordance with the invention.

Thus, while the feed means 2 is in its open position 9, the yarn is taken from the supply spool 1, through eyelet 5 and engaged in the feed means 2 at its outermost or open position 9 opposite the bottom end of contact heating plate 7 and then taken through eyelet 6 adjacent the top of the plate 7 to be engaged with the false-twist spindle ll operated by drive belt 12. The draw rolls 3 finally engage the yarn Y above the spindle 11 so that the yarn is continuously conducted through the apparatus and taken up onto a conventional winding package (not shown).

The threading of the yarn thus occurs while the feed mechanism as a movable guide means keeps the yarn out of contact with heater 7 without otherwise interfering with the essential threading and engagement of all other yarn-conducting or yarn-twisting elements of the apparatus. Once the spindle 11 is brought to a speed substantially smaller than its normal operating speed, the feed and guide means 2 is moved back into its closed position 8 to quickly engage the running yarn Y with the curved heated surface of plate 7. Only then is the false twist spindle ll brought up to its normal operating speed.

Thus, the contact heating plate 7 can be maintained at the normal operating temperature to receive a number of yarns in a corresponding number of stretch and false-twist crimping units of a single machine. The initially threaded yarn of any given unit being placed in operation is preferably continuously drawn or stretched between the feed and draw points but with the false-twist spindle 11 only lightly engaged, i.e. in relatively loose frictional contact with drive belt 12, so that the initial revolutions of this spindle take place at a rate far below normal operating speed, eg more than about 20 percent and preferably 20-50 percent smaller than this normal operating speed. Then, the speed of the spindle can be increased up to full normal operating speed after the yarn is brought into contact over the entire length of the plate heating surface.

This procedure of the invention offers the advantage that only the running and stretched yarn, which is thus temperature sensitive, is applied onto the contact heating plate. On the other hand, however, the movement of the yarn from its preliminary threading path into its normal operating path on the heating plate can lead to an excessive tension with yarn breakage or to a reduction in stretching with a melting of the yarn on the heating plate. Also, the low speed of the false-twist assembly during the initial threading stages causes a very favorable frictional relationship for the running yarn and tends to avoid excessive tension on the yarn. The method of the invention permits a more certain and rapid threading of the yarn within an optimally short time and with a minimum of yarn breakage.

In referring to a substantially perpendicular movement of the essential yarn guide means of the invention, it should be understood that this is taken with reference to a substantially flat surface of the elongated heating plate. In fact, this plate preferably has a slight curvature and the movement of the yarn guide means in and out of the normal operating position preferably occurs in a path which represents an involute to the curved surface of the heating plate.

Thus, the path of the feed and guide means 2 represented by the double-headed arrow in FIG. 1 is essentially perpendicular to but preferably an involute of the curved contacting surface of the heating plate 7. Then,

in moving between the

positions

8 and 9, any change in the length of the yarn path between the feed means 2 and draw means 3 is substantially prevented. Thereby, variations of yarn tension are avoided which can cause breakage through excessively high tension or a melting of the yarn on the heating plate when tension becomes too low.

The particular stretch and false-twist crimping machine shown schematically in FIGS. 2 and 3 has a stretching zone formed between the speed regulated feed rolls 2 and draw rolls 3 which in this instance are placed below the heating plate 7 with its gilft 7a and outlet 717 for the fluid heating medium This permits the yarn Y to pass twice over the heated curved surface of the plate 7, e.g. somewhat at an angle as indicated in FIG. 3. In this overall stretching zone, one can further provide another heating device such as the stretch pin 13, preferably between the feed rolls 2 and the heating plate 7'.

In this instance, the yarn Y is conducted from the feed rolls 2 upwardly over the heated surface 7', preferably with preheating by wrapping about once around the fixed heating pin 13, and is then reversed to travel back downwardly again over the heated surface 7 by means of the guide or deflecting member 14 arranged close to the upper end of the contact heating plate. The yarn Y then is taken off through the fixed eyelet guide 10 and the false-twist assembly 11 to the draw rolls 3'. By sliding the deflecting member 14 back and forth on the guide rail 15 between the open position 8' and the closed position 9', the yarn y is maintained out of contact or placed in contact with the curved surface of the heated plate 7. The rail or track 15 is placed in such a manner as to be approximately perpendicular to the plate 7', i.e. so that the movement of the deflecting member 14 changes the yarn length between the draw and feed rolls only very slightly. Again, the perpendicular movement of the member 14 as a yarn guide means is essentially with reference to a plane tangential to the curved surface of the heating plate 7'. Also, while the guide rail 15 is shown to be straight, it can also be formed as an involute to the surface of the contact heating plate or as an arc of relatively large radius. Other minor variations in this structure or the arrangement of the movable yarn guide means are quite acceptable, provided they meet the requirement of maintaining the yarn length in the stretching zone between the feed and draw points.

In FIG. 4, the yarn guide means are selected and arranged in such a manner that the yarns Y and Y" are conducted three times over the contact heating plate 7 which is substantially the same as the plate in FIGS. 2 and 3. Thus, each deflecting

member

14a, 14b, 140" or 14b is constructed and mounted on a guide rail in the same manner as the member 14 in FIG. 2 so that every run of yarn across the face of the plate 7' can be moved into or away from contact with the heated surface of this plate. Again, the stretching carried out simultaneously with the false twist imparted by the spindle means 11 or 11" can be accomplished by means of adjusting the relative speeds of the paired feed and draw rolls 2'3 and 2",3". As illustrated in this example, one can further carry out a preliminary stretch between a prior set of feed rolls l6,l6 and the corresponding subsequent feed rolls 2',2". Each pair of rolls l6',2 and 16",2" has a heated stretch pin 17' and 17" respectively associated therewith to provide sufficient heating of the yarn in this preliminary stretching zone. All such paired rollers for the stretching of the yarn are easily regulated for adjustment of the amount of stretch by any suitable control means such as that indicated by the numeral 4 in FIG. 1.

The stretch and false-twist crimping arrangement shown in FIG. 5 is especially advantageous in providing two parallel passes of the yarn over and in contact with the preferably grooved surface of the heating plate 18. In this instance, a single fixed deflection member 19 is located below the heating plate 18 while another fixed guide 20 is situated directly after the feed means 2 such that the incoming yarn Y is placed in parallel alignment with the outgoing yarn Y being conducted to the false-twist assembly 11 and draw means 3. One or two movable

yarn guide members

21 and 22 are positioned above the plate 18, for example to provide a means of changing the yarn path by moving guide rod 21 in a track 23 from the normal operating position 8 to a position 9" where the yarn is maintained free of contact with the heated plate 18. The use of two

guide rods

21 and 22 is of particular value in this embodiment because both rods can be jointly manipulated through predetermined paths which keep the total yarn length substantially constant for the stretching zone between the feed means 2 and draw means 3. Such paths of movement of

rods

21 and 22 can be straight, an arc with a large radius or an involute to the grooved and curved yarn contacting surfaces of the heated plate 18. At least one of these guide rods 21 must follow a path which is approximately perpendicular to the plate while the other guide rod 22 may follow a parallel path or one extending in the same direction to maintain a constant yarn length or it may follow a path extending in a different direction. For example, rod 22 can travel upwardly while rod 21 is moved outwardly from position 8 to position 9". This is most advantageous in providing a definite parallel arrangement of the ingoing and outgoing yarns Y and Y within a relatively compact space.

The embodiments shown in FIGS. 68 are particularly preferred if the contact heating plate is to be located in the upper portion of the machine such that it is out of normal reach of anyone tending the machine. Stretching occurs in the yarn path extending from the feed rolls 2 to the draw rolls 3, the yarn passing twice over the heated plate 7 as in FIGS. 2 and 3.

The apparatus of FIGS. 6-8 is also characterized by the fact that the heating plate 7 is maintained in an at least partly enclosed box or casing to provide heat insulation and a certain degree of protection for the transported yarn. Therefore, it is essential under these conditions to provide a means of positioning the thread at a remote and relatively inaccessible location, for example near the upper end of the at least partly enclosed heating plate. This positioning means essentially takes the form of an extension rod 24 with a suitable handle 25 for manipulative movement of the thread upwardly mounted in a holder 29 (FIG. 8) but is generally introduced so as to slide upwardly in a position which is essentially parallel to the thread contacting surface of the heated plate 7'. At its upper end, the rod 24 carries a yarn guide element 30 which serves to receive the incoming yarn from the stretch feed means 2 as the yarn extends past or in contact with the heating plate 7' and then directs the yarn back again over the plate to the false-twist spindle l1 and then to the stretch draw means 3.

The rod 24 can be placed in a lowered position 24' so that the person tending the machine can reach the guide element 30' near the bottom end of the heating plate 7 for initial insertion of the yarn. The rod is also capable of being fastened in a second position 24" where the guide element 30 retains the yarn ina path free of contact with the heating plate 7.

In FIGS. 6 and 7, the yarn guide element 30 is connected to a

lever

31 or 32 which pivots on the axis-33. In threading the yarn and sliding the rod 24 into the second position 24", the lever 31 is located approximately parallel to the rod, i.e. in a retracted or withdrawn position. However, when further sliding the rod 24 from position 24 into an immediately adjacent third position 34, the

lever

31 or 32 is actuated by a boss or projection 35 or 35' extending from the casing 27 or 27' so as to pivot the lever and its guide element 30 into an extended or expanded position 36. This extended position is maintained by locking the arm 24 in its third position by any suitable clamping or locking mechanism (not shown) so as to provide a firm support for the guide 30 and its

lever

31 or 32. Any number of variations in the construction of this lever are feasible, for example using a two-armed lever 31 as in FIG. 6 or a single-armed lever 32 as in FIG. 7. When using this latter single-armed lever, it is preferable to maintain or resiliently urge the lever 32 into its parallel position by means of a torsion spring 37. Then, when the rod 24 is lowered to disengage the lever 32 from the boss 35', the lever automatically returns to its retracted position parallel to the rod.

In the embodiment of FIG. 8, the yarn guide element 30 is rigidly connected to the end of the rod 24 on an axis slightly inclined from a perpendicular to the rod axis. The rod in this case can be pushed to its second position 24" in which the guide element 30" at this position is located in the upper region or above the contact heating plate 7 at a distance sufficiently far away to maintain the guided yarn in a path free of contact with the heating plate. The rod 24 is pivotable with the member 29 so that the guide element can move to the position 36 and the rod and guide assembly clamped or locked in this position for maintaining the yarn in its normal operating path in contact with the heating plate 7.

In all of these embodiments, it is still essential to provide a movement of the upper yarn guide element 30 from its open position 30" to its closed position 36 in a direction approximately perpendicular to the heated yarn contacting surface of plate 7 or preferably in a swinging are which is as close as possible to the involute curve of the slightly curved surface of the heating plate.

The particular embodiments of FIGS. 6-8 are especially advantageous and most useful where it is desirable to locate the heating plate within a chamber 28 which is almost fully enclosed on all sides and provided with heat-insulated walls by the box or casing 27'. The only opening 38 is that required for introducing and withdrawing the yarn, using an opening sufficiently large to also permit a complete withdrawal of the guide element 30 externally of the casing 27' so that the yarn can be inserted thereon.

In special embodiments such as FIGS. 6-8 which require an initial application of the yarn onto the guide element 30, eg at a point below the heated plate 7 and/or externally of the casing 27', it will be apparent that the method of threading according to the invention will require a preliminary step of lifting the movable yarn guide 30 into its upper or second position 30" before the yarn is brought through the false-twist spindle 11 and then to the draw means 3. Thus, the yarn is already in position 30" when the stretching effect of the feed and draw means is placed into operation while the false-twist spindle is operated well below its normal operating speed. Only then is the rod 24 pushed into the third position 34 so thatthe yarn guide element swings on one of the lever arms or pivots on the rod into its normal operating position 36, the spindle ll thereafter being brought to its normal operating speed.

Although some variations of the yarn length between the stretching feed and draw means are permissible, they are preferably limited to something less than 1 percent and preferably less than 0.1 percent of this stretching zone length. It will be apparent that this order of magnitude is attainable within the limitations of structure and position of the essential elements of the new combination. The use of this combination in a stretch and false-twist crimping machine greatly facilitates threading of the yarn so as to reduce the labor and expense of tending such a machine. Also, a continuous supply of a high quality stretched and torque-crimped yarn is obtained with a minimum of waste or poor quality yarn.

The invention is hereby claimed as follows:

1. A method of threading an apparatus for the simultaneous stretching and false-twist crimping of a yarn composed of synthetic thermoplastic filaments wherein the yarn is continuously conducted for stretching in a normal operating path between a stretch feed point and a stretch draw point while simultaneously being subjected to a heat treatment by direct contact with an elongated heating surface in said normal operating path and also imparting a false twist to the heat treated yarn by means of a rotating false-twist spindle before the yarn reaches said stretch draw point, which process comprises:

first threading the yarn from said stretch feed point to said stretch draw point through said false-twist spindle and also through a movable guide point adjacent one end of said elongated heating surface, said guide point being initially maintained in a position such that the yarn runs in a preliminary operating path which is free of contact with said heating surface;

then conducting the yarn through said preliminary path while the speed of the false-twist spindle is substantially smaller than its normal operating speed;

thereafter moving said guide point to bring the yarn into its normal operating path in contact with said heating surface, the movement of said guide point being such that the yarn length between said stretch feed point and said stretch draw point remains substantially constant; and subsequently increasing the speed of the false-twist spindle up to its normal operating speed. 2. A method as claimed in claim 1 wherein the yarn is composed of polyethylene terephthalate filaments.

3. In an apparatus for the simultaneous stretching and false-twist crimping of a yarn, said apparatus including spatially separated feed roll means and draw roll means for stretching a length of yarn therebetween, an elongated curved heating plate for contact with the yarn being stretched and positioned to receive the yarn from said feed roll means during normal operation and a false-twist spindle following said heating plate for imparting a temporary twist to the yarn at a point preceding said draw roll means, the improvement for threading said apparatus which comrpises at least one yarn guide means adjacent one end of the elongated heating plate for movement substantially perpendicular to said plate from an open position in which the yarn is maintained free of contact with the plate to a closed position in which the yarn is maintained in running contact with said plate, the movement of said guide means between said open and closed positions being such that the yarn length between said feed roll means and said draw roll means remains substantially constant.

4. An apparatus as claimed in claim 3 including a plurality of yarn guide means to traverse the yarn back and forth at least twice across said heated plate, there being at least one of said movable yarn guide means at a deflection point of the traversing yarn adjacent one end of the heating plate.

5. An apparatus as claimed in claim 4 wherein said heated plate is positioned at the upper end of the stretch and false-twist crimping apparatus, the movable yarn guide means being pivotably mounted on an extension rod means for introduction of the yarn first on a line parallel to the heating plate up to a position at the upper end of the heating plate corresponding to said open position and then in a direction approximately perpendicular to the heating plate through the pivotal movement of the yarn guide means into a position corresponding to said closed position in which the yarn is maintained in running contact with the plate.

6. An apparatus as claimed in claim 5 wherein said movable yarn guide means is connected by one arm of a two-armed lever to said extension rod means, the other arm coacting with a projecting boss of the apparatus casing to move said yarn guide means into its closed position.

7. Apparatus as claimed in claim 5 wherein said movable yarn guide means is fixed at the free end of the extension rod which in turn is pivotally fastened on an axis parallel to the heating plate for moving said yarn guide means through an arc between its open and closed positions adjacent the upper end of the heating plate.

8. Apparatus as claimed in claim 5 wherein said heating plate is maintained within a substantially enclosed heating box having insulated walls provided with a relatively small opening for entry and withdrawal of said extension rod and the movable yarn guide means associated therewith, thereby permitting the yarn to be initially applied to the yarn guide means externally of the heating box.

9. An apparatus as claimed in claim 3 including a plurality of yarn guide means to conduct the yarn back and forth through the Zone of the heating plate around a deflection point at one end of the heating plate such that the back and forth paths of the yarn are substantially parallel to each other, there being provided two movable yarn guide rods at the other end of the heating plate to carry the parallel running yarn paths and to provide a movement by at least one of said guide rods perpendicularly to the heated surface of the heating plate and a combined movement of both rods to maintain said constant yarn length.

10. An apparatus as claimed in claim 3 wherein said at least one movable yarn guide means follows the path of a curve which is approximately the involute of the curved yarn contacting surface of the heated plate.

11. A method as claimed in claim 1 wherein said yarn is conducted through said preliminary path at a falsetwist spindle speed which is more than 20 percent smaller than its normal operating speed.

Claims

1. A method of threading an apparatus for the simultaneous stretching and false-twist crimping of a yarn composed of synthetic thermoplastic filaments wherein the yarn is continuously conducted for stretching in a normal operating path between a stretch feed point and a stretch draw point while simultaneously being subjected to a heat treatment by direct contact with an elongated heating surface in said normal operating path and also imparting a false twist to the heat treated yarn by means of a rotating false-twist spindle before the yarn reaches said stretch draw point, which process comprises: first threading the yarn from said stretch feed point to said stretch draw point through said false-twist spindle and also through a movable guide point adjacent one end of said elongated heating surface, said guide point being initially maintained in a position such that the yarn runs in a preliminary operating path which is free of contact with said heating surface; then conducting the yarn through said preliminary path while the speed of the false-twist spindle is substantially smaller than its normal operating speed; thereafter moving said guide point to bring the yarn into its normal operating path in contact with said heating surface, the movement of said guide point being such that the yarn length between said stretch feed point and said stretch draw point remains substantially constant; and subsequently increasing the speed of the false-twist spindle up to its normal operating speed.

2. A method as claimed in claim 1 wherein the yarn is composed of polyethylene terephthalate filaments.

11. A method as claimed in claim 1 wherein said yarn is conducted through said preliminary path at a false-twist spindle speed which is more than 20 percent smaller than its normal operating speed.