Friction false twist apparatus

A yarn false twisting apparatus is disclosed which comprises a pair of circular discs which are mounted for rotation about 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 the operative position, one disc is resiliently deflected from its normal plane of rotation at the twisting zone by its engagement with the friction surface of the other disc, or a yarn passing therebetween, to thereby effectively engage and impart twist to the yarn. The bearing housings for the supporting shafts of the discs are held against movement with respect to each other during the twisting operation, and means are provided for automatically separating the housings and thus the discs in the event of a yarn breakage, to thereby avoid wear of the opposing disc surfaces.

The above copending application Ser. No. 168,734 discloses a friction false 
twist apparatus for false twisting synthetic filaments in texturing 
machines, in which the yarn is twisted by nipping it between the front 
face of a rotating, flexible disc and an opposing surface on a second 
rotating disc or the like. The flexible disc is deflected by a pressure 
applying member acting directly upon the rear surface of the flexible 
disc, and such that the disc is locally biased in a direction toward the 
opposing surface and the yarn is nipped between an annular friction 
surface and the opposing surface in the area of the threadline. 
The above friction false twist apparatus has opened new areas of 
application in false twist texturing, in particular for higher-denier 
yarns, and has made it possible to further increase texturing speeds at 
the same or increased crimp. 
In copending application Ser. No. 272,936, there is disclosed an embodiment 
wherein a disc supported in a gimbal-type mount is utilized, and the 
pressure applying member acts upon the entire bearing assembly of the 
disc, rather than directly upon the disc (see also German Gebrauchsmuster 
No. 80 16 896). 
In accordance with one aspect of the present invention, a further technical 
simplification is provided in that a flexible disc, including its bearing, 
can be firmly positioned in an operating position in such a manner that 
the annular yarn engaging friction surface of the flexible disc is 
resiliently biased against the yarn engaging friction surface of the 
opposing member. A pressure applying member resiliently operating on the 
back side of the disc, or a pressure applying member resiliently operating 
on the bearing housing thus need not be utilized. Also, the adjustment of 
the frictional forces acting on the yarn is simplified and made possible 
by the adjustability of a stop within wide ranges. As in the friction 
false twist apparatus disclosed in the parent applications, the present 
embodiment likewise has the advantage that the resiliently moved mass of 
the disc and, therefore, the forces of the moved mass, are so small that 
eccentricities of the friction surfaces, i.e. of the flexible disc or of 
the opposing member, can be balanced so quickly that they do not result in 
pulsations. 
With the present invention, flexible discs may be used which are, in 
particular, springy and supported in a gimbal-type mount. In this 
connection, reference is made to the German application P No. 31 40 261.5. 
It is also possible to mount a flexible or even a rigid disc on its 
supporting shaft in rotational engagement with the shaft, while permitting 
relative movement in the axial direction and against spring force, and to 
thereby produce a resilient mobility of the disc relative to its shaft. 
As a further embodiment of the present invention, the bearing of the 
opposing twist imparting member may be guided for movement in a direction 
essentially perpendicular to the front face of the flexible disc and such 
that it is held in its operating position, either rigidly or by a spring 
force. Special conditions of installation can make this embodiment 
preferable. 
The present invention preferably also provides means whereby the bearing 
housing and/or the disc is disengageable from its operating position, 
especially when a yarn end is down. This serves to avoid having the two 
frictional surfaces rub against each other when a yarn is not present.

Referring more particularly to the drawings, in all illustrated 
embodiments, the friction false twist apparatus comprises a disc 1, which 
is resiliently movable relative to its shaft 8, and has an annular 
friction surface or ring 3. Disc 1 is mounted to rotate with the shaft 8 
in a bearing housing 10, and it is driven in a non-illustrated manner in 
the direction indicated by an arrow in FIG. 1a. Further, the friction 
false twist apparatus includes an opposing member 2, which in the 
exemplified embodiments, is formed by the front face of rigid disc 2. Disc 
2 is mounted on shaft 9 and rotates in the direction indicated by the 
arrow, which is opposite to that of disc 1. The friction surface 4 of this 
rigid disc 2 forms with the friction surface 3 of flexible disc 1 a 
nipping area or twisting zone 6, through which the yarn 5 is guided. In 
the illustrated embodiments according to FIGS. 1-11, the bearing (not 
shown) of disk 2 is stationary. 
In the embodiment of FIG. 1, the disc 1 is relatively thin and readily 
flexible, and may be formed of a suitable elastomeric material. The 
bearing housing 10 for the flexible disc 1 pivots about axis 11, which 
extends in a direction transverse to the axis of shaft 8. The housing 10 
is pressed by spring 20 against stop 21, so that the bearing is 
stationarily positioned in the operative position of disc 1. In the 
operative position, the peripheral portion of the disc 1 is resiliently 
deflected from its normal or free plane of rotation at the twisting zone 
by its engagement with the friction surface of the disc 2 or the yarn 5 
passing therebetween. The force of spring 20 is adequate to resiliently 
maintain the disc 1 in such operative position. Any eccentricities in the 
discs 1 and 2, or their mountings, and which would result in non-uniform 
texturing of the yarn, are thereby quickly and sensitively balanced by the 
low-mass resilient mobility of friction ring 3, so that they do not affect 
the texturing result. 
A yarn detector 17 is provided which emits an electric signal which is 
transformed to pneumatic pressure in the electropneumatic converter 18. 
When an end is down, this pressure acts via the cylinder-piston assembly 
19, to pivot the bearing housing 10 about axis 11 and withdraw it from 
stop 21. Thereby, the frictional contact between friction rings 3 and 4 is 
discontinued or reduced, and damage to the friction rings is avoided. 
It should be noted that the avoidance of damage to the friction rings can 
also be accomplished in a different manner, for example, by terminating 
the drive of the friction false twist apparatus. The advantage in such 
case would be that housing 10 need not be movable, and thus the need for 
the cylinder-piston assembly 19 and spring 20 could be avoided. Provided 
each friction false twist apparatus is operated by its own drive, housing 
10 for flexible disc 1 could then be stationary and immobile, and the 
drive would be disconnected when an end is down. However, if a common 
drive for a plurality of friction false twist apparatus is provided, it is 
preferable, when a yarn breaks, to interrupt the frictional contact 
between friction rings 3 and 4 by the movement of bearing housing 10 as 
described above. 
The embodiment shown in FIG. 2 differs from that in FIG. 1 only in the 
design of the disc 1 and its mounting to the shaft 8. Here, disk 1 is 
relatively rigid and is mounted to the shaft by a gimbal-like 
interconnection which permits the disc to freely incline with respect to 
the shaft. The interconnection includes a gear tooth system 13 and 14 on 
the shaft and disc respectively. A resilient support is provided by a 
support plate 15 which is fixed to the shaft, and the tension springs 16 
which are interposed between the plate 15 and disc. Thus the tension 
springs 16 axially bias the disc 1 against disc 2. Otherwise, the mode of 
operation is identical to that described above with respect to FIG. 1. 
It should be noted that, in the illustrated operating position, bearing 
housing 10 is stationarily positioned by resting against a stop, but it 
can also be positioned in a different manner. For example, an identation 
could be provided in which the bearing housing engages in its operating 
position, and from which it disengages when an end is down. 
It should further be noted that in all illustrated embodiments, the axes of 
rotation of shafts 8 and 9 of discs 1 and 2 are spaced apart but appear to 
slightly intersect each other when viewed in side elevation, i.e., they 
are somewhat inclined with respect to each other and they cross in space. 
Therefore, the axis of rotation of shaft 8 of the disc 1 is not exactly 
perpendicular to, but slightly inclines toward, the opposing face of disc 
2. Also, the friction surfaces of the discs define respective planes which 
are somewhat inclined with respect to each other. 
The embodiment shown in FIG. 3 differs from the previously described 
embodiments in that disc 1 is relatively rigid and is attached to a 
rubber-elastic hub 22 on shaft 8. In this case, the friction ring 3 is 
resiliently deflected from its normal or free plane of rotation relative 
to shaft 8 by its operative contact with the friction ring 4 of rigid disc 
2 or yarn 5. 
The embodiments shown in FIGS. 4, 5 and 6 correspond to those of FIGS. 1, 2 
and 3 with respect to the design of the disc 1. However, bearing housing 
10 of the disc 1 moves in a straight line on guideway 23. Spring 20 
presses the bearing housing against a stop 24 in such a manner that 
friction ring 3 of the disc is deflected from its normal plane of rotation 
relative to the shaft by its contact with friction ring 4 or yarn 5. The 
stationary rigid position of bearing housing 10 against stop 24 is 
interrupted upon a yarn break, by the yarn detector 17, converter 18, and 
cylinder-piston assembly 19, and thus any frictional contact between 
friction rings 3 and 4 then terminates. 
In the embodiment shown in FIGS. 1-6, the stationary positioning of the 
bearing housing during operation can be produced in other ways than by 
pressing it against a stop. For example, it can be produced by a locking 
engagement or any other means of fixation. Likewise, these embodiments 
make it possible to disengage housing 10 from its stationary operating 
position upon a yarn break by other steps, for example, by shutting down 
the friction false twist apparatus. 
Advantageously, all embodiments preferably provide that the stop 21 or 24 
can be effectively moved in a direction toward the housing and locked in 
different positions. This permits the highly sensitive adjustment of the 
contact pressure of friction ring 3 on yarn 5 or disc 2. As a specific 
example, the stop may include an adjustable spindle or set screw 29, note 
FIGS. 3 and 5. This adjustability of the stop makes it possible to 
sensitively adjust the yarn contact pressure. 
In the embodiments shown in FIGS. 7 and 8, bearing housing 10 is mounted in 
the same way as in the embodiments of FIGS. 1-3 and 4-6 respectively. 
However, the elastic mobility of disc 1 relative to its shaft 8 is 
accomplished in that disc 1, which is relatively rigid, is movable in the 
axial direction by means of a toothed interconnection 25 between shaft 8 
and the hub of the disc, and against a spring 27. When a yarn end is down, 
frictional contact is again discontinued by disengaging housing 10 of the 
movable disc from its operation position by means of the detector 17, 
converter 18, and cylinder-piston assembly 19 as described above. 
In the embodiment shown in FIG. 9, disc 1 moves axially in the manner 
described above, and it is pressed by spring 27 in a direction toward disc 
2. More particularly, the disc is relatively thin and flexible, and it is 
mounted to a rigid hub 26. The hub 26 is in turn slideably mounted to the 
shaft by a toothed interconnection 25, and a spring 27 is provided for 
biasing the hub 26 and disc 1 toward the opposing rigid disc 2. The 
bearing housing can in this embodiment be mounted stationarily and 
immovably, since for disengagement upon a yarn break, hub 26 is provided 
with a circular groove 28, in which a carrier 34 is engaged. This carrier 
makes it possible, when an end is down, to discontinue the frictional 
contact between the friction surfaces by axially withdrawing disc 1 
against the force of spring 27. In FIG. 10, the disc 1 includes a rigid 
hub 35 which is slideably mounted on the shaft, and an intermediate 
rubber-elastic portion 36. Thus the disc 1 is axially movable with respect 
to the shaft, and is biased toward the opposing disc by the spring 27. 
In the embodiment shown in FIG. 11, both the flexible disc 1 and its 
bearing housing (not shown) are stationarily supported. The contact 
pressure of disc 1 against the yarn and disc 2 is produced by guiding 
rigid disc 2 axially on its shaft 9 against the force of spring 30. A 
toothed interconnection 31 serves to transmit the torque to the disc 2. It 
can be seen that carrier 32 engaging in groove 33, is adapted to break the 
frictional contact when an end is down. Also, the bearing housing of disc 
1 or disc 2 can be movably mounted more or less in a way as has been shown 
in the embodiments of FIGS. 1-6. 
In the embodiments shown in FIGS. 12 and 13, the invention is modified to 
the extent that bearing housing 12 of the rigid disc 2 is so movable that 
the frictional contact can be discontinued upon a yarn break. In these 
cases, it is possible to press bearing housing 12 by the force of spring 
20 elastically into its operating position or, to provide an essentially 
rigid stop 21 or 24, which accomplishes a stationary support in the 
operating position. 
It should be emphasized that stationary in the sense of this application is 
not to be equated with rigid. Also, the elasticity and damping properties 
of the arrangements, which provide that the bearing housings of the 
opposing surface or flexible disc are held in their operating position, 
are determined by vibrational necessities. 
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.