US3901011A

US3901011A - False twisting apparatus

Info

Publication number: US3901011A
Application number: US441209A
Authority: US
Inventors: Friedrich Schuster
Original assignee: Kugelfischer Georg Schaefer and Co
Current assignee: IHO Holding GmbH and Co KG
Priority date: 1973-02-12
Filing date: 1974-02-11
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26
Also published as: IT1008814B; FR2217446B3; CH564619A5; GB1457944A; FR2217446A1; JPS49134962A

Abstract

Apparatus for false twisting thread has a rotary twisting member with a composite thread contacting surface which includes separate annular portions having relatively high and relatively low coefficients of friction. Thread is guided by the low friction annular portions of the twisting member with respect to the high friction annular portions where twisting forces are imparted to the thread. Multiple twisting members are arranged in sequence along the direction of movement of the thread to provide predetermined twist characteristics to the thread.

Description

U United States Patent l 1 [111 3,901,01 1

Schuster Aug. 26, 1975 [54] FALSE TWISTING APPARATUS 3.537.250 11/1970 MacKintosh 57/774 3,656.290 4 1972 K z i. 57 77.4 [75] Inventor: Friedrich Schuster, Hammelburg, 3 762 149 51973 57274 Germany 3,777,467 12/1973 Enncking 57/77.4

[73} Assignee: Kugelfischer Georg Schafer & C0.,

Schweinfurt. Germany Primary Examiner-Donald E. Watkins Filed: Feb 1 1974 Attorney. Agent, or Fzrm-Edward R. Wemgram 21 A l. No.: 441,209 I 1 pp 57 ABSTRACT [30] Foreign Application Priority Data Apparatus for false twisting thread has a rotary twistmg member with a composite thread contacting sur- 7 Germany 306853 face which includes separate annular portions having 1973 3359788 relatively high and relatively low coefficients 0f fric- 1974 Germany 400239 tion. Thread is guided by the low friction annular por- Cl 7 77 tions of the twisting member with respect to the high [52] i friction annular portions where twisting forces are im- [511 'f 7 l parted to the thread. Multiple twisting members are [58] new 0 5 5 arranged in sequence along the direction of movement of the thread to provide predetermined twist charac- [56] References Cited teristics t0 the thread.

UNITED STATES PATENTS 2,939,269 6/1960 Dobson 57/774 20 qalms, 18 Drawmg Flgures L7 K T a/ H 49 A 5 PATENTED AUG 2 6 I975 Ix" SiiL ETBUFG FALSE TWISTING APPARATUS BACKGROUND OF THE INVENTION:

1. Field of the Invention This invention relates to apparatus for twisting threads and, more particularly, to apparatus for false twisting threads by passing the threads in frictional contact over rotating frictional surfaces.

2. Description of the Prior Art In friction-type false-twisting apparatus, the thread to be false-twisted is guided past one or more rotary twisting members, such as rotating friction discs, so as to be rolled around on them. The peripheral surface of each friction disc which engages the thread to be falsetwisted is made of resilient material having a suitably high coefficient of friction as a rule polyurethane of predetermined known hardness. The contact surface is as a rule cylindrical or formed with an arcuate cross section.

Devices with friction discs for friction false-twisting synthetic threads for crimping or texturing them are known in various forms. The friction discs are arranged in spaced relation on a rotatably mounted spindle or on two or three substantially mutually parallel rotatably mounted spindles. (See, for example, US. Pat. No. 3,327,463, French Pat. No. 1,261,747, British Pat. No. 854,781, or West German Ausslegerschrift (DAS) 1,222,826).

In the devices having two or three spindles, the friction discs on each spindle generally overlap the friction discs on the other spindle or the other two spindles. All the spindles are driven in the same direction of rota tion. In devices having two spindles, the thread to be false-twisted can be guided to pass in the plane containing the axes of the two spindles between the two axially oppositely mutually offset pairs of discs of the two spinclles (see French Pat. No. 1,261,747) or, alternatively, to run in the wedge-shaped gap between the two sets of friction discs on the two spindles (see British Pat. No. 854,781).

In devices having three spindles, it is known to arrange them so that they form, in plan view, the corners of a substantially equilateral triangle, so that the thread to be false-twisted passes between the mutually overlapping friction discs in a zig-zag path (see West German DAS 1,222,826).

In the friction discs known up to now, the whole surface which is to be in contact with the thread to be false-twisted is made from a material having a suitably high coefficient of friction with respect to the thread. The thread is urged against the contact surface and rolls upon it. In order to be able to false-twist the thread satisfactorily without subjecting the thread to unacceptably high tension loads which could lead to breakage of the thread, the thread must exactly follow the right path past the friction discs which impart the false twist, and the friction disc must rotate at the same peripheral speed at all points of contact with the thread. These requirements contradict one another.

In the known friction discs, in order to achieve satisfactory imparting of the false twist, in particular to avoid breakage of the thread, very high standards have been set with regard to accuracy of manufacture and assembly, and adjustment of the equipment, with consideration given to the characteristics of the particular thread to be false-twisted. In the case of devices having mutually overlapping friction discs, the tolerances, es-

pecially those for the mutual overlap, disc thickness and disc diameter and for the axial spacing between each adjacent pair of discs are extremely small and, therefore, difficult to maintain in large-scale production of this apparatus. Further, operation of these devices has shown them to be largely incapable of maintaining the tolerances necessary for separate machines to provide satisfactory uniform quality of false twist for similar threads, while keeping thread breakage within practical limits.

In friction false twisting, rotary twisting members other than friction discs are also used. Frequently, friction sleeves are used through which the thread to be false-twisted is guided so as to be in rolling contact with either the whole inner surface of the sleeve bore or simply in the region of the two mouths of the sleeve bore, the overall contact surface being made of a material having a high coefficient of friction for imparting the false twist, as shown in West German (DSA) 1,205,652, and West German offenlegungsschrift (DT- OS) 2,104,255.

SUMMARY OF THE INVENTION To overcome the problems set forth above, the present invention provides apparatus for false twisting thread including a rotary twisting member having separate annular portions with relatively high and relatively low coefficients of friction. The separate annular portions form a composite thread contacting surface with the low friction annular portion guiding the thread with respect to the high friction portion where twisting of the thread occurs. Relative position and shape of the high and low friction annular portions of the thread contacting surface comprises uniform relative velocity at all points of contact between the high friction annular portion and the thread.

In view of the above, it is an object of the present invention to provide apparatus for false twisting thread, which has a composite thread contacting surface with separate portions for twisitng the thread and for guiding the thread.

Another object of the present invention is to provide apparatus for false twisting thread which produces constant relative speed between the thread twisting surface and the thread along all points of contact between-the friction surface and the thread.

It is a further object of the present invention to provide apparatus for false twisting thread, in which guide portions of the thread contacting surfaces are made of relatively low friction material.

Still another object of the' present invention is to provide apparatus for false twisting thread which avoids putting unacceptably high stresses on the threads.

It is yet another object of the present invention to provide apparatus for false twisting thread which can be manufactured, assembled, and operated with relatively large dimensional tolerances and still provide satisfactory performance.

Another object of the present invention is to provide apparatus for false twisting thread which will provide constant and uniform twisting characteristics on the thread processed by the apparatus.

It is still another object of the present invention to provide apparatus for false twisting thread which has a composite thread contacting surface with a separate thread twisting portion that rotates at a relatively constant peripheral speed, regardless of the overall shape of the thread contacting surface.

A further object of the present invention is to provide apparatus for false twisting thread which minimizes breakage of threads processed by the apparatus.

Yet another object of the present invention is to provide apparatus for false twisting thread which allows the thread to exactly follow the proper path past the rotary twist members.

Still another object of the present invention is to provide apparatus for false twisting thread which requires relatively large dimensional tolerances that can easily be maintained during operation of the equipment.

It is another object of the present invention to provide apparatus for false twisting thread which can operate with a minimum of maintenance and adjustment.

Other objects and advantages will be apparent from the following description of embodiments of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a side view of a conventional friction disc for friction false twisting synthetic threads.

FIG. 2 is a view from above looking at a friction false twisting device with at least three mutually overlapping friction discs. I

FIG. 3 is a cross section through the rim of the friction disc of FIG. 1.

FIG. 4 shows diagrammatically the construction of the shape of the cross section of the convex contact surface of a friction disc according to the invention for the device of FIG. 2.

FIG. 5 is a longitudinal section along the line VV in FIG. 2 through a set of friction discs of a device according to FIG. 2.

FIG. 6 is a plan view of a friction disc according to the present invention, made of a material having a low coefficient of friction, into which portion made from a material of high coefficient of friction is incorporated.

FIGS. 7 to 12 each show the portion A of FIG. 5, with a different construction for the friction discs.

FIG. 13 is a side view, partially sectioned, of one embodiment of the false twisting device built in accordance with the present invention.

FIG. 14 is a side view, to a larger scale, partially sectioned, of a friction disc used in the device of FIG. 13.

FIG. 15 is a plan view of the embodiment of the invention shown in FIG. 13.

FIGS. 16 and 17 each show a side view of another embodiment of the invention, only the friction discs being shown in the mutually overlapping region.

FIG. 18 is a side view, partially sectioned, of another embodiemnt of the invention, having a friction cylinder.

In FIG. 1, there is illustrated by way of example the engagement of a thread 1 to be false-twisted with a friction disc 2 of a device for friction false twisting of synthetic threads according to FIG. 2. Such a device comprises three

sets

3, 4 and 5, of friction discs of which the axes of rotation are substantially parallel to one another and, in plan view, form the corners of an approximately equilateral triangle. The friction discs of each

set

3, 4 and 5 overlap the friction discs of the other two.

sets 4 and 5 or 3 and 5 or 3 and 4. The thread 1 to be false-twisted is in contact with the friction discs of all three

sets

3, 4 and 5.

The thread 1 is pressed against each friction disc 2 and in fact against a contact surface 6 of each disc so as to roll on that surface. The thread 1 forms an angle alpha with the plane of rotation of the friction disc 2. The point of the contact surface 6 of the disc 2 having the greatest outside diameter moves at a peripheral speed of V By virtue of the tension T in the thread, dependent chiefly on the take-up equipment, the thread 1 is pressed against the contact surface 6 of the disc 2 with a certain force, not shown in FIG. 1, directed perpendicular to the plane of the drawing, resulting in a force F,, directed tangentially with respect of the contact surface 6. This can be resolved into two components, namely a force F perpendicular to the longitudinal axis of the thread 1 and a force F,, in the direction of this longitudinal axis. The force F has a twistimparting action on the thread 1, i.e. it rotates the thread 1 about its longitudinal axis. The force F depends chiefly on the peripheral speed V The force F A pulls the thread 1 past the disc 2 in the direction of the arrow P, i.e. it assists the action of the take-up equipment.

If the angle alpha is suitable, it is in fact possible for the thread tension T. to be smaller than the thread tension T which can never be the case under normal conditions, as with the disc 2 stationary, when the thread tension T is always greater than the thread tension T,. This means that the thread tension ratio T /T can be controlled very accurately with the aid of the angle alpha and the peripheral speed V In this way, it is possible, with sensitive threads 1, to keep the thread tension and therefore also the number of thread breakages within acceptable limits. From this theoretical reasoning, it follows that the angle alpha and the peripheral speed V of each friction disc 2 or other rotary twisting member are the deciding factors for economically false-twisting threads to crimp them. By means of the invention, these two important controlling factors can be controlled as accurately as possible and in fact can be maintained without narrow tolerances, so that despite the friction discs being easier to manufacture, the imparting of a false twist and accordingly the crimping are achieved with a uniformly high quality.

In order to maintain the angle alpha as accurately as possible it is best for the thread 1, in its passage through a friction false twisting device according to FIG. 2, to move along a helical line having a substantially constant angle, i.e. it runs helically over the imaginary cylinder 7 in FIG. 2. Tolerances on the diameter of the discs or in the spacing between each adjacent pair of discs 2 have a smaller influence on the angle alpha than when the thread 1 passes over sharp edges between the overlapping discs 2, because these tolerances and thereby also the angle alpha change very markedly, and, since the variation of the thread tension follows an exponential function, this exerts a much greater influence on the thread 1.

In particular, in the example described with overlapping discs, where the thread 1 to be false twisted passes over sharp edges, this thread is very heavily loaded, so that many breakages arise and in practice really fine yarn cannot be handled at all with such friction discs.

In order to acheive a passage of the thread between the discs 2 along a helical path, the path extending along an imaginary cylinder 7 (FIG. 2) the form of the cross section of the contact surfaces 6 which is shown in FIG. 4 is necessary.

FIG. 4 shows how the shape of the cross section of the contact surface 6, i.e. the profile 8, can be built up point by point where the diameter D of the mutually overlapping friction discs 2, the spacing A and thereby the overlap B between three adjacent discs 2, and the disc thickness H and the axial spacing AH between each adjacent pair of friction discs 2 are known. The procedure is as follows first a circle is drawn having a diameter D and then within this there is drawn a circle having a radius B, so that the two circles touch one another tangentially. Then the outer one-third arc of the circle having the radius B is divided uniformly and through each of the resulting points X1, X2 there is struck a respective circle which is concentric with the circle of diameter D. Two

lines

8 and 9 are drawn in, H AH apart, these lines being parallel to a common radius of the circle of diameter D. On the line 9 the portion C (21rTTB)/3 is cut off and divided into the same number of portions as the outer one-third arc of the circle of radius B. Through the resulting points X1, X2 perpendicular lines are drawn. The uppermost point of the line 9 in FIG. 4 and the lowermost point on the line 8 are connected by an inclined line 10. Through the points of intersection of this line 10 with the above mentioned perpendicular lines parallel straight lines 11 are drawn. Each such line 11 cuts the associated circle around the center M at a predetermined point X1" or X2" by connecting up these last-mentioned points we obtain the profile 8.

The ideal cross section of the contact surface 6 in accordance with the profile 8 can be closely approximated by a cross section which is easier to produce, for example by an arcuately curved cross section in accor dance with FIG. 3.

It follows from what has been said above that for a predetermined angle alpha the contact surface 6 of the friction disc 2 must have a predetermined cross section shape which does not depart significantly from the theoretical shape set out above. Otherwise the thread 1 is overloaded by the sharp change in direction in the thread path.

As shown in FIG. 3, in known friction discs a material having a suitably high coefficient of friction is present over the entire contact surface 6 that engages the thread I. The surface 6 has a radius R, which varies over the thickness H of the disc, and consequently produces a varying peripheral speed V This speed variation conflicts with the exact imparting of a false twist since for this purpose the peripheral speed V of the contact surface 6 should be of uniform magnitude over the whole region of the twist-imparting contact surface 6, as explained above.

According to the invention in particular in friction discs 2 for friction false twisting devices according to FIG. 2 the contact surface 6, which preferably has a cross sectional shape according to FIGS. 4 or 3, is divided into regions of different coefficient of friction, which are mutually adjacent in the direction of the thickness H of the disc and extend around the entire periphery of the disc. The region of higher coefficient of friction serves to impart the false twist, and the other region of lower coefficient of friction serves to guide the thread. In the region of higher coefficient of friction the peripheral speed is substantially uniform so that exact imparting of the false twist is achieved.

In devices like those shown in FIG. 2, the shapes of friction disc according to the invention shown in FIGS. 7 to 9 are particularly suitable, the embodiment of FIG. 9 being the preferred one. In the embodiment shown in FIG. 7, the disc 2 is made of material of low coefficient of friction. An annular groove 13 is machined to receive a ring 14 of material of high coefficient of friction. In the embodiment shown in FIG. 8, the disc is made of material of lower coefficient of friction, and

has an outer annular flange 15. A ring 14 of higher coefficient of friction is positioned between flange l5 and a ring 16 of material of lower coefficient friction. The ring 16 can be made of the same material as the disc 2. The embodiment shown in FIG. 9 differs from that of FIG. 7 in that the disc 2 has, in addition to the annular groove 13, a ring of axial holes 17, as shown in FIG. 6. These communicate with the groove 13 and are likewise filled with material of higher coefficient of friction, for example, by the material which was cast in place, and then machined to obtain the desired shape for the contact surface 6.

FIGS. 10 and 11 show embodiments of the friction discs accordingto the invention with asymmetrical distribution in the contact surface 6 of the regions of different coefficient of friction. The overall shape of the cross section in the embodiment of FIG. 10 is symmetrical, while being asymmetrical in the embodiment shown in FIG. 11. In the embodiment of FIG. 10 the disc 2 is made of material of lower coefficient of friction and has a side annular flange 15 and a second annular flange 18 with an inwardly directed annular shoulder 19 and a ring of axial holes 17 through flange 18. The flange 18 is embedded, by casting, in material of higher coefficient of friction. The cross sectional shape of the contact surface 6 is obtained by subsequent machining.

In the embodiment shown in FIG. 11 the friction disc 2, made of material having a lower coefficient of friction, has a central annular flange 18 with respective inwardly directed annular shoulders 19 on both sides and with a ring of axial holes 17. The flange 18 is embedded, by casting, in material of higher coefficient of friction, which also passes through the holes 17. The high friction material is shaped asymmetrically at the periphery of the disc. On the side of the disc 2 where the surface 6, which is of relatively small radius meets the flat face of the disc 2, there is provided a ring 20 of material of low coefficient of friction.

The friction discs 2 according to FIGS. 7 to 11 each have a hub 21 as shown in FIG. 5, by which they are secured on a spindle 22. As shown in FIG. 5 three discs 2 form the friction disc sets 3, 4 or 5 in the device according to FIG. 2. The discs 2 are arranged one above the other on the spindle 22, a predetermined spacing 23 being provided between each adjacent pair of discs 2 in order to prevent undesired deformation of the spindle 22.

The friction discs of the type shown in FIGS. 10 and 11, when mounted in a friction false twisting device, such as the type shown in FIG. 2, are preferably mounted so that the thread to be false-twisted first comes into contact with the surface 6 in the region of higher frictional value and leaves from the region of lower coefficient of friction.

The invention also provides advantages if used in friction discs having the shape shown in FIG. 12, where a substantially cylindrical contact surface 6 meets the two faces of the disc at small radii of curvature.

The material of lower coefficient of friction can be a metal, for example brass, steel or aluminum, or a synthetic resin, for example a resin based on a polyoxymethylene, polymer, known under the Trade Mark Hostaform or manufactured by polymerization from water-free CH O, known under the Trade Name Delrin. The material of higher coefficient of friction can for example be a polyurethane or a special synthetic rubber known under the Trade Mark Perbunan.

The friction discs according to the present invention are particularly advantageous in that the thread to be false-twisted is subjected to significantly lower loads during the false twisting. In the known friction discs, the entire contact surface has a frictional action on the thread. Since the contact surface, as shown in FIG. 3, has a radius R1 which varies over the thickness H of the disc, the peripheral speed V will vary over the thickness H and, accordingly, the forces on the thread will differ at different points of the contact surface because the thread can only travel at a single speed. All the other peripheral speeds which differ from the spped of the thread only cause additional friction of the disc on the thread and subject it to loads. Moreover it is difficult to achieve an exact well defined false twist.

In addition, the friction disc according to the present invention is distinguished by the feature that it is easier and cheaper to produce in view of the greater tolerances that are permitted on its dimensions. Further, in view of the greater permitted tolerances, the friction disc is easier and cheaper to assemble and adjust with regard to its position relative to the adjacent disc or discs. This ease of assembly and adjustment is particularly significant when replacement of friction discs in friction false twisting apparatus is necessary in the course of repairs.

FIG. 13 shows a three-spindle, multi-friction disc false twisting device. Three spindles 32 are mounted in a baseplate 31. These are arranged parallel to each other and form in plan view the corners of an equilateral triangle, as shown in FIG. 15. Each spindle 32 is provided with an encapsulated bearing 33 secured to the baseplate 31 by means of a nut 34. On the lower end in FIG. 13 each spindle 32 is in addition provided with an externally toothed gear 35. All three gears 35 are surrounded by a common internally toothed belt 36. Accordingly, in operation, the spindles 32 all run in the same direction of rotation, as shown in FIG. 5.

On each spindle 32 there is mounted a set of three friction discs 37, each having a hub and an annular flange at one end of the hub. The discs 37 of each set are secured next to one another on a common locating sleeve 38. The locating sleeve 38 is fitted onto the associated spindle 32 together with at least one spacing ring 39 and connected to it so as to rotate with it by means of an annular disc 40 and a screw 41. On the opposite side from the disc 40 and the screw 41 the locating sleeve 38 engages against an abutment ring 42 which is provided on the spindle 32.

The mutually identical sets of friction discs are arranged on the respective associated spindle 32 with the discs 37 at different axial positions. This is achieved by the spacing rings 39. On the lefthand spindle 32 in FIG. 13 such a spacing ring 39 is provided above the set of discs, and the same applies to the righthand spindle 32 except that here the set of friction discs is inverted, i.e. standing on its head. On the middle spindle 32 there are provided two spacing rings 39, namely a taller one below and a shallower one above the set of friction discs, which set of discs is itself arranged the same way up as on the lefthand spindle 32.

The friction discs on the three spindles thus mutually overlap, and in operation they rotate in the same direction, for example in the direction of the arrow 43 in FIG. 15. The thread 45 which runs in the direction of the arrow 44, i.e. from above in a downward direction through the device, is therefore provided with a Z twist.

It follows azig-zag path past the friction discs 37, engaging against them, to leave the device through a stationary anti-ballooning tube 46. The anti-ballooning tube 46 extends through the baseplate 311 and is secured to it in the middle of the above-mentioned equilateral triangle of spindles.

The thread 45 is pressed against each of the friction discs, in fact against a contact surface 47 of each disc, in order to roll upon it. The thread 45 makes an angle alpha with the plane of the disc 37. By virtue of the thread tension T, which is dependent chiefly on the take-up arrangements, the thread 45 is urged against the contact surface 47 of the disc 37 with a force which is not shown in FIG. 14 but which acts perpendicular to the plane of the drawing in that figure, so that there results the force F T directed tangentially with respect to the surface 47. This force can be resolved into two components, a force F perpendicular to the lonngitudinal axis of the thread 45, and a force F A in the direction of this longitudinal axis of the thread. The force F has a twisting action on the thread 45, i.e. it turns the thread 45 about its own longitudinal axis. The force F,, draws the thread 45 in the direction of the arrow 44 against the disc 37 in question, i.e. it assists the action of the take-up rollers.

The contact surface 47 is divided along its width H into separate regions having different coefficients of friction. Each of the separate regions extend around the entire periphery of the disc. As discussed above, to provide the separate regions, the disc 37 is made of material of lower coefficient of friction, and an annular groove 48 is machined in the periphery to receive a ring 49 of a material having a higher coefficient of friction. The region of the contact surface 47 having higher coefficient of friction formed by the ring 49 serves to impart the false twist and the two adjoining regions of low coefficient of friction serve to feed the thread. In the region of higher coefficinet of friction the peripheral speed of the contact surface 47 is approximately uniform, so that an exact imparting of the false twist is achieved.

According to the invention the different friction discs 37 in the device of FIG. 13 have different coefficients of friction for imparting the false twist. The coefficient of friction of the rings 49 increases from the thread inlet disc 37 to the thread outlet disc 37". All nine discs 37 have the same mutual spacing A and have the same outside diameter D and the same thickness H.

The embodiment of the device shown in FIG. 16 differs from that of FIG. 13. All of the high coefficient of friction rings 49 have the same coefficient of friction with respect to the thread 45 to be false-twisted, for imparting the false twist, and the friction discs 37 have different thicknesses H which increase from the thread inlet disc 37 to the thread outlet disc 37". Accordingly, in the device shown in FIG. 16, the first three, the three intermediate and the three last discs 37 each have the same thickness I-I, i.e. the three sets of discs on the three spindles 32 are identical.

The embodiment of the device shown in FIG. 17 differs from that of FIG. 13 in that all the rings 49 have the same coefficient of friction with respect to the thread 45 but the discs 37 have different mutual spacings A, and the spacings A increase from the thread inlet disc 37 to the thread outlet disc 37". Again the arrangement can be such that the three sets of friction discs on the three spindles 32 are identical.

The features present in the embodiments of FIGS. l3, l6 and 17 could be combined together.

Another embodiment of a false twisting device uses a rotary twisting device of a friction cylinder instead of a friction disc. This embodiment of a false twisting device is shown in FIG. 18, where there are pivotally or rotatably mounted in a carrier 51 a spindle 52 with two thread guides 53 on its two ends and a friction cylinder 54 parallel to it. The bearing of the cylinder 54 is incorporated in a capsule 55 secured to the carrier 51 by means of a nut 56 screwed onto it.

The cylinder 54 is made up of a tube 57 and two heads 58 mounted on its two ends. Secured to the tube 57 is a sleeve 59 engaged by a driving belt (not shown) to drive the cylinder 54.

Each head has an annular insert 60 with an annular twisting 61 in which is provided a ring of material 62 having a higher coefficient of friction than the material of the insert 60. Thus in the relatively narrow region of the annular groove 61 the convexly curved contact surface 63 of each insert 60 has, with respect to the thread to be false-twisted, a higher coefficient of friction than in the remaining regions.

In FIG. 18 there is shown in full lines that pivotal po sition of the spindle 52 in the carrier 51 in which the two aligned thread guides 53 are lined up with the longitudinal bore 64 of the cylinder 54, that is to say of the tube 57. This is the position in which the respective thread to be false-twisted is threaded in. The spindle 52 can be swung from this position into the operative position in which the thread guides 53 take up the positions shown in broken lines. In this position the thread runs through the cylinder 54 along the path 63 shown in broken lines.

The thread thus engages against the contact surfaces 63 of both heads 58. It rolls on these contact surfaces 63 when the cylinder 54 is set in rotation, in order to false-twist the thread. As that region of each surface 63 is kept relatively small, in which there is frictional contact between thread and cylinder 54 necessary for twisting the thread, the thread is not dragged at varying peripheral velocities. Further, the resistance which the contact surfaces 63 offers through friction to oppose the passage of the thread through the cylinder 54 is kept to the minimum possible value.

It will be understood that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims.

What is claimed is:

1. A rotary twisting member for imparting a twisting force to threads in contact with the twisting member when it rotates, comprising:

flange means extending in the plane of rotation of said twisting member;

an annular thread contacting surface having a plurality of annular segments peripherally disposed on said flange means including:

an annular segment formed from material having a relatively high coefficient of friction, adapted to impart twisting forces to thread in contact with said segment;

an annular segment formed from material having a relatively low coefficient of friction adapted for guiding a thread in contact with said segment.

2. A rotary twisting member according to claim 1 wherein the annular segment formed from material having relatively high coefficient of friction is disposed on the thread contacting surface at the point of maximum velocity of said thread contacting surface as it rotates.

3. A rotary twisting member according to claim 2 wherein said annular segments formed from material having relatively low coefficient of friction are disposed on opposite sides of said annular segment formed from material having a relatively high coefficient of friction.

4. A rotary twisting member according to claim 3 wherein said contacting surface is symmetrically shaped with relation to the annular segment formed from material of a relatively high coefficient of material.

5. A rotary twisting member according to claim 2 wherein said contacting surface is convex in cross section.

6. A rotary twisting member according to claim 2 wherein said contacting surface is cylindrical in cross section.

7. A rotary twisting member according to claim 2 wherein said rotary twisting member includes a friction disc comprising:

flange means extending in the plane of rotation of said rotary twisting means;

said contact surface being formed on the peripheral edge of said flange means.

8. A rotary twisting member according to claim 7 wherein said annular segments formed from material having relatively low coefficient of friction are disposed on opposite sides of said annular segment formed from material having a relatively high coefficient of friction.

9. A rotary twisting member according to claim 8 wherein said contacting surface is symmetrically shaped with relation to the annular segment formed from material made of relatively high coefficient of material.

10. A rotary twisting member according to claim 7 wherein said contacting surface is convex and is asymmetrically formed with respect to said annular segment formedfrom material having a relatively high coefficient of friction.

1 l. A rotary twisting member for imparting a twisting force to threads in contact with the twisting member when it rotates comprising:

a tubular section for the passage of thread to be twisted;

a mouth at each end of said tubular section;

an annular thread contacting surface having a plurality of annular segments formed on each of said mouths; said annular thread contacting surface including:

an annular segment formed from material having a relatively high coefficient of friction, adapted to impart twisting forces to thread in contact with said segment; an annular segment formed from material having a relatively low coefficient of friction adapted for guiding a thread in contact with said segment; means rotatably supporting said tubular section; thread guide means disposed adjacent each mouth of said rotary twisting member; said thread guide means connected to said means rotatably supporting said tubular section. 12. A rotary twisting member according to claim 11 wherein said annular segments formed from material having relatively low coefficient of friction are disposed on opposite sides of said annular segment formed from material having a relatively high coefficient of friction.

13. A rotary twisting member according to claim 12 wherein said contacting surface is convex in cross section.

14. A device for false twisting threads comprising:

a plurality of rotary twisting members for imparting a twisting force to threads in contact with the twisting member when it rotates, each of said rotary twisting members comprising: flange means extending in the plane of rotation of said twisting member;

an' annular segment formed from material having a relatively low coefficient of friction adapted for guiding a thread in contact with said segment;

said annular thread contacting surfaces of said plurality of rotary twisitng members having parallel axis of rotation.

15. The device for false twisting threads according to claim 14 wherein:

said plurality of friction disc comprise:

at least three mutually overlapping friction discs;

the axis of rotation of said three mutually overlapping friction discs disposed to form the corners of a substantially equilateral triangle;

the contact surfaces of said plurality of friction discs coacting to cause thread passing through said false twisting device to travel on a substantially helical path.

16. The device for false twisting threads according to claim 15 further comprising:

a spindle;

said plurality of rotary twisting members disposed in spaced relation on said spindle; and

means to synchronously drive said plurality of rotary twisting members on said spindle.

17. The device for false twisting threads according to claim 16 wherein said plurality of rotary twisting members are disposed on three spindles positioned to form, in the plan view, a substantially equilateral triangle.

18. The device for false twisting threads according to claim 16 wherein the coefficient of friction of said annular segments formed from material of a relatively high coefficient of friction varies in predetermined relationship for said friction discs spaced along said spindle.

19. The device for false twisting threads according to claim 17 wherein the spacing between said friction discs spaced on said spindle varies in a predetermined relationship.

20. The device for false twisting threads according to claim 17 wherein the thickness of said flange means of said friction discs mounted in spaced relation on said common spindle varies along the spindle in accordance with a predetermined relationship. 1

Claims

1. A rotary twisting member for imparting a twisting force to threads in contact with the twisting member when it rotates, comprising: flange means extending in the plane of rotation of said twisting member; an annular thread contacting surface having a plurality of annular segments peripherally disposed on said flange means including: an annular segment formed from material having a relatively high coefficient of friction, adapted to impart twisting forces to thread in contact with said segment; an annular segment formed from material having a relatively low coefficient of friction adapted for guiding a thread in contact with said segment.

7. A rotary twisting member according to claim 2 wherein said rotary twisting member includes a friction disc comprising: flange means extending in the plane of rotation of said rotary twisting means; said contact surface being formed on the peripheral edge of said flange means.

10. A rotary twisting member according to claim 7 wherein said contacting surface is convex and is asymmetrically formed with respect to said annular segment formed from material having a relatively high coefficient of friction.

11. A rotary twisting member for imparting a twisting force to threads in contact with the twisting member when it rotates comprising: a tubular section for the passage of thread to be twisted; a mouth at each end of said tubular section; an annular thread contacting surface having a plurality of annular segments formed on each of said mouths; said annular thread contacting surface including: an annular segment formed from material having a relatively high coefficient of friction, adapted to impart twisting forces to thread in contact with said segment; an annular segment formed from material having a relatively low coefficient of friction adaptEd for guiding a thread in contact with said segment; means rotatably supporting said tubular section; thread guide means disposed adjacent each mouth of said rotary twisting member; said thread guide means connected to said means rotatably supporting said tubular section.

12. A rotary twisting member according to claim 11 wherein said annular segments formed from material having relatively low coefficient of friction are disposed on opposite sides of said annular segment formed from material having a relatively high coefficient of friction.

14. A device for false twisting threads comprising: a plurality of rotary twisting members for imparting a twisting force to threads in contact with the twisting member when it rotates, each of said rotary twisting members comprising: flange means extending in the plane of rotation of said twisting member; an annular thread contacting surface having a plurality of annular segments peripherally disposed on said flange means including: an annular segment formed from material having a relatively high coefficient of friction, adapted to impart twisting forces to thread in contact with said segment; an annular segment formed from material having a relatively low coefficient of friction adapted for guiding a thread in contact with said segment; said annular thread contacting surfaces of said plurality of rotary twisitng members having parallel axis of rotation.

15. The device for false twisting threads according to claim 14 wherein: said plurality of friction disc comprise: at least three mutually overlapping friction discs; the axis of rotation of said three mutually overlapping friction discs disposed to form the corners of a substantially equilateral triangle; the contact surfaces of said plurality of friction discs coacting to cause thread passing through said false twisting device to travel on a substantially helical path.

16. The device for false twisting threads according to claim 15 further comprising: a spindle; said plurality of rotary twisting members disposed in spaced relation on said spindle; and means to synchronously drive said plurality of rotary twisting members on said spindle.

20. The device for false twisting threads according to claim 17 wherein the thickness of said flange means of said friction discs mounted in spaced relation on said common spindle varies along the spindle in accordance with a predetermined relationship.