False twist roll

Details False twist roll False twist roll

1989-05-11

1990-09-18

Petrakes, John

Textiles: spinning, twisting, and twining

Apparatus and processes

False twist device

57331, 57348, D02G 108

Patent

active

049569708

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a false twisting roll of the type used in a false twist crimping machine to impart false twist to a manmade, continuously advancing endless yarn. A false twisting roll of this general type is disclosed in German OS 24 60 031.
The false twisting roll as disclosed in German OS 24 60 031 is arranged so that the angle of lead of the yarn (epsilon) at the beginning of the line of contact with the false twist roll is approximately equal to half the acute angle of the cone of contact (gamma Epsilon) at the point of entry. In order to meet this condition, yarn guides precede the false twist roll. Optimal twist imparting conditions are preset by these yarn guides thus associated to the roll. A change of the twist level while maintaining the optimal twist imparting conditions is not possible
It is the object of the present invention to design and construct a false twisting roll, which permits the desired twist level to be adjusted, while maintaining the optimal twist imparting conditions.


SUMMARY OF THE INVENTION

The above and other objects and advantages of the present invention are achieved in the embodiments illustrated herein by the provision of a false twisting roll which has a concave yarn contacting surface portion, and which defines a central roll axis. The twisting roll is mounted for rotation about the roll axis and for pivotal movement about a pivot axis which is perpendicular to the roll axis, and the roll may be set in a selected pivotal position. Yarn guide means is provided for guiding an advancing yarn along a predetermined yarn path leading into contact with the yarn contacting surface portion, and the concave yarn contacting surface portion is configured, and the pivotal axis is located, so that in all pivotal positions of the roll the angle alpha is equal to the angle gamma, with the angle alpha being defined as the angle between the predetermined yarn path and a circumferential tangent to the roll at the point of contact of the yarn path to the roll, and with the angle gamma being defined as the angle between the roll axis and a tangent to the concave surface portion at the point of contact of the yarn path to the surface portion and which intersects the roll axis.
The present invention is based upon the discovery that the angle condition, according to which the angle of lead of the yarn at the beginning of the line of contact with the body of rotation, i.e. the angle alpha as defined above, is approximately equal to the half the acute angle of the contact cone at the point of entry, i.e. the angle gamma, is not the cause for an optimal operation of the false twist roll, but is a consequence occurring independently in the operation of the false twist roll. Resulting therefrom is the further discovery that the aforesaid angle condition is maintained when changing the inclination of the roll, but that the looping conditions change on the preceding yarn guide. This disadvantage of the known false twist roll is eliminated by the present invention.
More particularly, in the present invention, the position of the pivotal axis is adapted to the contour of the roll, so that in the predetermined path of the yarn the angle alpha between the contacting yarn and the circumferential tangent of the roll in the point of first contact is always equal to the angle gamma between the roll axis and the tangent of the contour line at the point of first yarn contact, irrespective of the inclination of the roll axis. To this end, the position of the pivotal axis is determined by geometric construction, calculation and/or test, with the contour and yarn path being given. Conversely, with the yarn path and axis of rotation being given, the contour is determined by geometric construction, calculation and/or test. Thereafter, the ideal surface line (contour line) extending in an axial plane of the roll can be approximated by a circular, parabolic, hyperbolic or any mathematically determinable function.
In order to make the yarn path independent of the inclina

REFERENCES:
patent: 3559391 (1971-02-01), Rice
patent: 3680302 (1972-08-01), Hess et al.
patent: 3735575 (1973-05-01), Hattori
patent: 3998041 (1976-12-01), Graf et al.
patent: 4204394 (1980-05-01), Luthi
patent: 4237686 (1980-12-01), Fluck et al.
patent: 4562694 (1986-01-01), Sumar

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