Friction false twisting apparatus

A yarn false twisting apparatus is disclosed which comprises a pair of circular discs which are mounted for rotation about generally parallel spaced apart axes, and such that portions of the surfaces are disposed in opposing face to face relation and define a twisting zone therebetween. In one embodiment, one of the discs is relatively thin and flexible, and such disc is resiliently biased toward the other disc only at the twisting zone. In other embodiments, both discs are relatively inflexible or rigid, and one disc is mounted to its supporting shaft by a gimbal-like interconnection and such disc is resiliently biased toward the other disc only at the twisting zone.

Yarn false twisting apparatus for the false twist texturing of synthetic 
filaments are known, and which consist of two circular discs which are 
rotated in opposite directions. Typically, the axes of rotation are 
inclined toward each other and the peripheral edges of the discs contact 
each other at the twisting zone. In one apparatus of this type, note 
German Patent Publication No. 1,192,779 and U.S. Pat. No. 4,145,871, the 
rotary discs are movable in the axial direction toward and away from each 
other and the discs are mechanically pressed against each other by spring 
pressure. The yarn is advanced along a path of travel which extends in a 
direction essentially perpendicular to the common plane of the two axes of 
rotation. 
The above known friction false twist apparatus have not proved entirely 
successful in the industry however, since unavoidable inaccuracies in the 
manufacture, such as non-uniform bearing clearances, have led to slightly 
pulsating movements, of one or both discs. As a result, the vary is nipped 
with a pulsating or fluttering force, and is non-uniformly twisted and 
crimped. 
It is an object of the present invention to avoid the above limitations of 
the known false twisting apparatus. These and other objects and advantages 
of the present invention are achieved in the illustrated embodiments by 
the provision of a false twisting apparatus of the described type, and 
which includes means for resiliently biasing one of the rotating discs 
toward the other disc or twist imparting member only at the twisting zone. 
In one embodiment, the disc is relatively thin and flexible, and its 
supporting shaft is mounted for pivotal movement about an axis extending 
in a direction transverse to the axis of the shaft. Spring biasing means 
is provided for urging the shaft about the transverse axis, in such a way 
that the disc is biased toward the other member only at the twisting zone. 
In another embodiment, the disc is relatively rigid, and it is mounted to 
its supporting shaft by a gimbal-like interconnection which permits the 
disc to freely incline with respect to the axis of the shaft. A pressure 
applying member is mounted adjacent the circular disc on the side opposite 
the friction surface and in alignment with the twisting zone, to bias the 
disc toward the other member at the twisting zone. In still another 
embodiment, the disc is relatively rigid and similarly mounted in a 
gimbal-like interconnection to its supporting shaft, and the shaft is 
pivotally mounted for movement about a tranverse axis. Means are also 
provided for resiliently urging the shaft for movement about such 
transverse axis. 
An advantage of the present invention resides in the fact that even in the 
event the disc is somewhat out of true run, it does not perform any 
transitory movements, i.e., movements effecting the nipping force and thus 
a constant nipping force can be provided by the pressure applying means. 
The pressure applying member which acts upon the back side of the disc may 
be in the form of a roll or plunger, which is connected to a resilient 
supply of force, such as a pneumatic cylinder-piston assembly, spring, 
magnet, or the like. Where the pressure applying member is used to pivot 
the shaft about a transverse axis, it may also be connected to any desired 
known supply of force, as described above. However, in certain instances, 
a nonresilient force may be acceptable as the pivoting mechanism, such as 
an adjustable screw spindle. 
In the present case, it is also advantageous that the pressure applying 
means insures a proper frictional engagement, in that the nipping gap is 
automatically adjusted to the particular yarn size or diameter.

Referring more specifically to the drawings, FIGS. 1 and 1a schematically 
illustrate a friction false twisting apparatus which comprises discs 1 and 
2 which are driven in opposite directions. The disc 1 is relatively thin 
and flexible, while the disc 2 is relatively rigid. The discs are provided 
with frictional surface coatings 3 and 4 respectively, and a yarn 5 is 
adapted to be nipped in the nipping area or twisting zone 6, wherein the 
frictional coatings 3 and 4 overlap. Disc 1 is inclined and biased against 
the disc 2 so that the yarn travels freely without being nipped through 
the lower overlapping area 7 of the friction coatings 3 and 4. 
The discs 1 and 2 are fixedly mounted on the shafts 8 and 9 respectively. 
The bearing of the shaft 8 consists of a bearing housing 10, which is 
mounted to pivot about an axis 11 which extends in a direction transverse 
to the axis of the shaft 8. The transverse axis 11 is also illustrated by 
the dashed line in FIG. 1. By the action of the pressure applying member 
12, the bearing housing 10 is resiliently biased to pivot about the axis 
11, and thus the disc 1 also inclines against the plane of rotation of the 
disc 2, with the disc 1 operatively contacting the disc 2 only at the 
twisting zone 6. 
In the illustrated embodiment as shown in FIGS. 1 and 1a, the pressure 
applying member consists of a spring having an adjustable spring tension. 
It may however consist of a pneumatic cylinder-piston assembly, a magnet, 
or other supply of force. 
The transverse axis 11 is so positioned that the nipping of the yarn 5 is 
facilitated in the area of overlap at the twisting zone 6 at the entry to 
the friction false twisting apparatus, and the gap in the overlying area 7 
is increased. The fact that the disc 1 rests against the yarn in the area 
of zone 6 causes the disc 1, which is made of a resilient material, such 
as spring steel, and which is fixedly mounted on its shaft, to resiliently 
deform or deflect so that it inclines from the plane which is normal to 
its axis of rotation. Thus the yarn is resiliently nipped. The resilience 
of the disc 1 and of the pressure applying member 12 causes the gap 
between the discs 1 and 2 to automatically adjust to the thickness or 
diameter of the yarn. 
In the embodiment of FIGS. 2 and 2a, both discs 1 and 2 are relatively 
rigid, i.e. non-flexible. The disc 2 is fixedly mounted to its supporting 
shaft, while the disc 1 is mounted to its supporting shaft 8 by a 
gimbal-like interconnection which permits the disc to freely incline with 
respect to the axis of the shaft 8. In the illustrated embodiment, the 
gimbal-like interconnection (Cardanic) includes a gear tooth system 13 and 
14 on the shaft and disc respectively. A resiliently support is provided 
by a support plate 15 which is fixedly mounted to the shaft 8 adjacent the 
disc 1, and by the tension springs 16 which are interposed between the 
plate 15 and disc 1 at spaced points circumferentially about the axis of 
the shaft 8. Thus the disc is urged in a direction toward the disc 2 by 
the springs 16. 
A pressure applying member 17 acts upon the back side of the disc 1. The 
member 17 includes a plunger 18 and spring 19, which resiliently presses 
the disc 1 against the yarn in the area 6 where the frictional coatings 
overlap. At the same time, the disc 1 inclines from the plane normal to 
its axis of rotation so that the gap for the thread line in the area of 
overlap 7 widens. 
In the embodiment of FIGS. 3 and 3a, the disc 1 is mounted to its 
supporting shaft 8 in a manner corresponding to that described above with 
respect to FIGS. 2 and 2a. However, in the embodiment of FIGS. 3 and 3a, 
the disc 1 is biased toward the other disc 2 by means of a pressure 
applying member 12, which resiliently acts upon the bearing housing 10 of 
the shaft 8, and thus causes the shaft to pivot about the transverse axis 
11. As a result, the yarn is resiliently nipped in the overlapping area 6, 
and the disc 1 is inclined from the plane normal to its axis of rotation. 
In the embodiment of FIGS. 4 and 4a, both discs are relatively rigid. 
However, at least one disc may be flexible as described above. As 
illustrated, the discs 101 and 102 are mounted on the shafts 108 and 109 
respectively, and they define a twisting zone 106 where the frictional 
coatings 103, 104 overlap. The discs are slightly separated at the lower 
overlapping zone 107, and such that the yarn 105 is nipped at the zone 106 
and passes freely through the zone 107. 
The bearing of the shaft 108 consists of a housing 110, which is mounted to 
pivot about the transverse axis 111. The housing 110 is resiliently biased 
to pivot about the axis 111 by the action of the pressure applying member 
112, which is mounted adjacent the disc 101 so as to operatively contact 
the disc on the side opposite the friction surface and in alignment with 
the twisting zone 106. Thus the disc 101 inclines against the plane of 
rotation of the disc 102, with the disc 101 operatively contacting the 
disc 102 only at the twisting zone 106, and so that the gap in the zone 
107 widens. 
The illustrated constructions of the discs and mounting means therefor, 
with the use of a resilient pressure applying member, makes it possible to 
false twist high denier yarns at very high twists, and to thereby obtain a 
high degree of crimping of such yarns. 
In the drawings and specification, there has been set forth a preferred 
embodiment of the invention and although specific terms are employed, they 
are used in a generic and descriptive sense only and not for purposes of 
limitation.