Twist tube for false-twisting devices

A twist tube for a false-twisting device for texturing textile yarns has an enlarged end in which the bore has an oblong cross-section with both the major and minor axes substantially longer than the bore of the main portion of the tube. The thread guide pin extends in the direction of the minor axis between flat sides of the bore which are joined at each end by arcuate sides. Two circular, coaxial openings extend from outside the enlarged end to the arcuate sides. The oblong shape and these openings assist the threading of the twist tube. The thread guide pin is displaced laterally with respect to the longitudinal axis of the main portion of the tube by a fraction of the pin diameter. The axis of the openings, which is perpendicular to the pin axis, is displaced from the pin axis by a similar fraction, towards the main portion of the tube.

FIELD OF THE INVENTION 
The present invention relates to a twist tube for false-twisting devices 
for texturing textile yarns. 
DESCRIPTION OF THE PRIOR ART 
The development of false-twisting devices for texturing textile yarns tends 
to achieve higher and higher revolution speeds of the twist tube in order 
to increase in this manner the yarn advance speed and therefore the 
production quantity of textured yarns. 
False-twisting devices are already known which comprise two axially 
parallel rollers and twist tubes in tangential contact therewith, one of 
the rollers being driven and the other idling as a guiding roller and the 
twist tube being pressed against the rollers by means of magnets. 
Furthermore, twist tubes for false-twisting devices of this kind are known 
which comprise, at one end of the twist tube or in the middle thereof, a 
portion of a diameter larger than the diameter of the twist tube, in the 
axial bore of which there is arranged a transverse guide pin of hard 
material, for example of sapphire. In this case, the yarn to be textured, 
which passes through the longitudinal bore of the twist tube, is wrapped 
once around the pin. 
With the above described known false-twisting devices, it is already 
possible to achieve revolution speeds of the twist tube of several hundred 
thousand r.p.m. In order to further increase these revolution speeds, it 
is necessary to produce twist tubes having relatively small dimensions. 
The use of twist tubes having small dimensions has, on the other hand, the 
disadvantage that threading of the textile yarn into the twist tube as 
well as the passage of knots causes considerable difficulties. 
SUMMARY OF THE INVENTION 
It is the purpose of the present invention to eliminate this disadvantage 
and to provide a twist tube which is suitable for extremely high 
revolution speeds of up to 800,000 r.p.m. and more, which at the same time 
renders possible threading of the textile yarn and the passage of knots 
without difficulties. 
According to the present invention, a twist tube comprises a transverse 
thread-guide pin arranged in the axial bore of an enlarged cylindrical 
portion of the twist tube, which is characterized in that the axial bore 
of the enlarged portion has an oblong or ellipsoidal cross-section and in 
that two parallel wall portions of the bore situated opposite each other 
have holes or grooves in which the ends of the thread-guide pin are fitted 
and fixed. 
Advantageously, the axis of the thread-guide pin may be displaced laterally 
with respect to the longitudinal axis of the twist tube by a fraction of 
the thickness of the pin. 
Furthermore, the enlarged cylindrical part may comprise, as a further 
threading help, opposed coaxial openings having an axis crossing the axis 
of the thread-guide pin but displaced in the direction of the main part of 
the twist tube by a fraction of the thickness of the pin. 
The twist tube according to the present invention has the advantage that, 
on the one hand, even when the twist tube has very small dimensions, there 
is sufficient space in the enlarged portion of the twist tube -- because 
of the oblong shaped bore -- to enable the textile yarn to be threaded, 
i.e. to render possible one wrapping around the thread-guide pin and also 
the passage of knots. On the other hand, the bore of oblong shape has also 
the advantage that the parallel portions of the bore situated opposite 
each other and the bores or grooves provided in these wall portions, in 
which the two ends of the pin are supported, lie relatively near each 
other. Thereby, the danger of breakage of the pin because of the high 
centrifugal forces that arise is considerably reduced.

The portion of the twist tube shown in FIGS. 1 and 2 consists of steel tube 
1 and an enlarged cylindrical head 3 of aluminum fitted round the end 
thereof and projecting beyond the end. The steel tube has an outer 
diameter of 2 mm and a longitudinal bore 2 having a diameter of 1 mm. The 
portion of the enlarged head 3 projecting beyond the tube 1 has an outer 
diameter of 4 mm and has a longitudinal bore 4 with an oblong 
cross-section, the minor axis of which is 2 mm and the major axis of which 
is 2.78 mm. The oblong section of the bore 4 has straight parallel sides 
4', 4" and arcuate ends. 
Into bores 6, 6' extending transversely between the sides 4', 4" of the 
bore 4 are fitted the ends 5', 5" of a cylindrical thread-guide pin 5 and 
are fixed there by means of an adhesive. The pin 5 consists of sapphire, 
and its ends 5', 5" have a diameter of 1 mm whereas the diameter of the 
centre of a central, concave portion is 0.7 mm. The axis of the pin 5 lies 
on the minor axis of the bore 4 and bisects the major axis thereof, so 
that the bore 4 facilitates threading of the yarn. 
As shown in FIGS. 2 and 3, the pin 5 is laterally displaced with respect to 
the longitudinal axis of the twist tube by approximately half its 
thickness so that the minimum diameter of the concave portion of the pin 5 
over which the textile yarn passes is only displaced from the longitudinal 
axis of the twist tube by the order of half the yarn thickness. 
As shown in FIGS. 1 and 2, the head 3 furthermore is provided with a 
diametral bore which provides opposed openings 7 having an axis 
perpendicular to the pin axis but displaced towards the end of the tube 1, 
which further facilitates threading of the yarn. The axis of the openings 
7 lies on the major axis of the bore 4. 
In the modified embodiment of the twist tube shown in FIG. 5, the head 3, 
instead of the bores 6, 6', comprises, at each of the oppositely situated, 
parallel wall portions 4' 4" of the bore 4, a groove 8, 8' extending 
axially along the head 3. The two ends 5', 5" of the thread guide pin 5 
are fitted and fixed by means of an adhesive respectively in the grooves 
8, 8'.