GB2128643A

GB2128643A - Open-end spinning thread guides

Info

Publication number: GB2128643A
Application number: GB08229924A
Authority: GB
Inventors: Vaclav Maixner; Emil Pelinka; Frantisek Pesek; Jiri Sefl
Original assignee: Elitex Zavody Textilniho; Elitex Koncern Textilniho Strojirenstvi
Current assignee: Elitex Zavody Textilniho; Elitex Koncern Textilniho Strojirenstvi
Priority date: 1982-10-23
Filing date: 1982-10-20
Publication date: 1984-05-02
Also published as: DE3239289C2; CH661059A5; DE3239289A1; GB2128643B; FR2535740A1; FR2535740B1; JPS5988933A

Abstract

The subject matter of the present invention consists namely in that the effect of frictional forces acting upon the yarn at the first contact point in the withdrawing path behind the collecting surface of the spinning rotor is reduced by shortening the contact path of the withdrawn yarn, such that the axial force of the withdrawn yarn in the area behind the outlet of the funnel does not exceed a 2.5 multiple of the axial force <IMAGE> where: Fo=the axial force in the withdrawn yarn in the area between the collecting surface of the spinning rotor and the inlet into the withdrawing funnel (mN/tex> R=the radius of the spinning rotor (mm), n=the number of revolutions of the spinning rotor (min<-1>). The working surface of the funnel of the yarn exit guide is formed by an inlet edge 4 and the section, defined by said inlet edge and the last point of contact of the yarn on the working surface. The contact path of the yarn at a given radius of curvature r of the exit guide is reduced by truncating the upper surface at a height h. <IMAGE>

Description

SPECIFICATION Method of rotor spinning fibres with specific properties and device for performing said method The present invention relates to rotor spinning of fibres, of which the properties do not make it possible to perform an acceptable processing by rotor spinning by the equipment hitherto known, as the resultant of those properties excessively enhances the axial forces in the yarn withdrawn from the spinning rotor, which is an important difference of those fibres, particularly relative to cotton. The socalled "specific" properties are the coefficients of friction (particularly dynamic friction) of the fibre surface, the adhesion of the fibres to other surfaces, the deformability of the fibre cross section, including reduced hardness of its surface, resistance of the fibres against bending and its specific surface.Particularly cotton-processed fibres are provided already upon their manufacturing with a surface dressing film (lubricator) for securing processability without further modification of surface properties during further processing. It is not usual in the cotton processing technology to finish or refinish the fibre surface before processing, as is done in the wool processing technology. Therefore, it is obvious that the said specific properties relate to the whole complex fibre/surface dressing film. It also follows therefrom, that fibres, although made of the same macromolecular material (even from the viewpoint of morphology) might differ very substantially in the mentioned surface properties, just due to a different surface dressing.

Rotor spinning of fibres with specific properties is secured by the present invention by reducing the excessive axial force of the withdrawn yarn to a predetermined optimum value by modifying the point of first contact of the yarn within the withdrawing path behind the collecting surface of the rotor, at the entry of the yarn into the so-called yarn withdrawing funnel, i.e. by modifying the inlet working surface of the yarn withdrawing funnel.

The rotor spinning methods hitherto known are practised in the most successful manner with natural fibres (cotton, wool at the initial state), man-made fibres (viscose staple fibres) and synthetics (polyester fibres), or possibly their blendings. The resultant of the effect of specific properties of the said man-made and synthetic fibres on friction and, in consequence thereof the axial tension of the yarn spun therefrom and withdrawn about the metallic surfaces from the rotor does not make them different from cotton in an important manner. For those fibres, the rotor spinning is nowadays optimized, and the development of fibres endeavours to adapt above all the surface properties of new fibres to that optimation.The contemporary development of the yarn withdrawing funnels for the fibres hitherto rotor spun, i.e. fibres not too different from cotton, aims at constituting at the funnel such friction conditions, which would make possible a better control and a certain localization of the twist in the area back from the funnel to the collecting surface of the rotor. This endeavour requires higher friction at the inlet working surface of the funnel and, as its limiting factor is represented by the axial force of the withdrawn yarn, the constructions hitherto known from patents make use of various combinations of smooth and rough inlet working surfaces of the funnel (e.g. alternation of smooth and rough segments on the funnel during one revolution of the rotor), radial and concentric grooves on the inlet working surface of the funnel, and similar.However, those constructions cannot be applied for rotor spinning of fibres with specific properties, as their friction on a usual smooth inlet working surface of the funnel is already of such extent, that it is impossible to increase it further, e.g. by using a rougher segment.

The friction is a result of the mutual action of two surfaces, the rubbed surface and the rubbing surface. The contemporary technical practice has a relatively very limited possibility of compensating too high friction coefficients of certain fibres by reducing the friction coefficients of working surfaces of withdrawing paths. In the same manner are limited possibilities for an analogous procedure with fibres, i.e. reducing the friction coefficients of fibres by using a dressing applied to the fibre surface during its manufacture.

In the devices for rotor spinning hitherto known, comprising a spinning unit with a rotor and a yarn withdrawing funnel, it is not presumed that the embodiment of the yarn withdrawing funnel would become principally adapted to the resultant of influence of the said specific properties of certain fibres.

The path and the way of contact at the given angle of contact of the withdrawn yarn on funnels hitherto known, which are given by the radius of curvature "r" (see the accompanying drawing) of the inlet surface of the funnel contacted by the yarn, are too unsuitable for spinning fibres with specific properties. It is, however, known that a reduction of a radius of curvature of the inlet working surface of the funnel can reduce the axial force in the withdrawn yarn, but within a rather inadequate extent, so that this step cannot be and also is not systematically applied for the purpose of compensation of an undesired resultant of the influence of specific properties of their friction at the inlet working surface of the funnel, and thus an excessive increase of the axial force in the withdrawn yarn.

An excessive increase of the axial force has the following consequences: diminishing productivity (the axial force, which is proportional to the square of number of revolutions of the rotor, enforces their diminishing and thus also the diminishing of the yarn withdrawing speed), an excessive abrasion of the dressing from the fibre surface or even the abrasion of the fibre mass, consequently thereto an increased formation of dust which is sucked back into the rotor, thus requiring a more frequent rotor cleaning, but mainly a diminishing yarn quality.

a high breakage rate of yarn, which is in correlation with the higher probability of breakage due to tension surpassing yarn strength.

The above mentioned disadvantages are removed by the present invention in accordance with one aspect of which there is provided a method of rotor spinning of fibres with properties, exerting by the resultant of their influence an increase of axial force in the withdrawn yarn, wherein the effect of frictional forces acting upon the yarn at the first contact point in the withdrawing path behind the collecting surface of the spinning rotor, i.e. on the inlet working surface of the yarn withdrawing funnel, is reduced by shortening the contact path of the withdrawn yarn, thus attained an optimum axial force of the withdrawn yarn in the area behind the outlet from the funnel, which does not exceed a 2.5 multiple of the axial force Fro=5*45 10-12.R2 . n2 where =the axial force in the withdrawn yarn in the area between the collecting surface of the spinning rotor and the inlet into the withdrawing funnel,/mN/texl, R=the radius of the spinning rotor (mm), n=the number of revolutions of the spinning rotor (in').

The shortening of the yarn contact path on the inlet working surface of the funnel is obtained by lowering the height of the funnel head of a given radius of curvature, at which it is not possible to perform acceptably rotor spinning of fibres with specific properties. By lowering the height of the funnel head is formed, besides shortening the contact path of the yarn on the inlet working surface of the originally unsuitable withdrawing funnel, a qualitatively new working surface, formed by the inlet edge and the rest of the original inlet working surface.

By the mentioned method, and an easily applicable device for performing said method, it is possible to compensate the resultant to influence of specific properties, which is different with various fibres, on their friction in the decisive part of the withdrawing path, and the excessive axial force in the withdrawn yarnfollowing therefrom, to the final effect of gaining high quality yarns, which are to be spun at outstanding productivity factors.

An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawing wherein an outlet working surface of a withdrawing funnel is shown together with the principle of the present invention, residing in the changed yarn contact of the withdrawn yarn with the spinning rotor at the inlet working surface of the funnel.

A withdrawing funnel 1 with an inner diameter "D" of its aperture is represented in section through a plane laid through the axis 2 of the funnel, which is simultaneously the axis of rotation of the spinning rotor. Yarn 3 is withdrawn from the collecting surface of the spinning rotor via a circular edge 4, and further via an inlet working surface 5 of the funnel, said surface being determined by edge 4 and the last point of contact 6 on the inlet working surface, which has a radius of curvature "r". Edge 4 is a circular intersection line of the surface formed by rotation of one fourth of the circular arch of radius "r" about axis 2 at a distance D/2 (a rotary surface, forming the inlet working surface 5) and a plane defining the height "h" of the funnel headpiece, said plane being normal to axis 2.

The path of contact of the yarn is shortened, according to the principle of the present invention at the given "r" by reducing the height of the funnel headpiece by a value (H-h) relative to path of contact on the funnel with a headpiece height H, at which the spun yarn shows an excessive axial force. Behind the inlet working surface 5 of the funnel and point 6, the yarn is withdrawn by a usual withdrawing (winding) device, either directly or at first via the outlet working surface of the funnel, which is made e.g.

the form of a ceramic (sintered corundum) ring, a tube fractioned at different angles, and similar, and then the withdrawing device. The outlet working surface and the winding device are not represented in the drawing.

In the drawing, those funnel parts, of a funnel unsuitable for rotor spinning of fibres with certain (specific) properties, i.e. the funnel with a head-piece height H, of which is most easily possible to form a suitable funnel of a headpiece height h, are represented by an interrupted line.

Examples of the embodiment of the present invention are arranged in the following table. The decisive criteria of the axial force in the withdrawn yarn (read as mean values from the graphic records at the same time intervals of the spinning), together with the quality characteristics of the spun yarn, belonging to the originally used funnal (standard-denoted S) or the new (denoted N) formed by adapting S according to the present invention. One sufficiently representative set of results of spinning the same fibre sample at equal climatic conditions is mentioned. The mutual relation of values of axial force and yarn quality remain retained even for a quite different kind of fibres, as follows from the verification of a great number of sets analogous to the mentioned one. The indication of the fibres used is therefore superfluous for the example. The result upon usage of funnels denoted S applies only for the beginning of the spinning, and thereafter becomes worse. With a funnel N, correctly optimized (see Examples 2 and 4) the result does not change with the time of spinning.

Table Rotor spinning machine BD 200 S Rotor radius (mm) 27 Fed sliver twice drafted, 3.3 ktex Revolutions of combing out 6,000 rollers (min.-1) Spun yarn -- number (tex) 35.5 --twist(m-') 620 Revolutions of rotors (min-1) 46,250 51,200 Yarn withdrawing speed (m/min.-1) 74.6 82.6 Used funnel-example number S/i N/2 S/3 N/4 N/5 radius of curvature rofthe 4 4 4 4 4 inlet working surface (mm) inner diameter of aperture D (mm) 2 2 2 2 2 head height H, or possibly (mm) H3.9 h2.4 H3.9 h3.1 h2.4 inlet working surface smooth, hard chrome outlet working surface sintered corundum ring Axial force (mN/tex) in the withdrawn yarn behind the outlet working surface F 40 1 8 50 31 23 -in front of the working surface F0 8.5 8.5 10.4 10.4 10.4 -ratio F/Fo 4.7 2.1 4.9 3.0 2.2 Quality of spun yarn uneveness USTER (CV %) 19.5 16.2 19.6 17.3 15.0 number of weak points 538 40 468 202 0 -number of thick places 460 83 620 310 56 number of neps 380 54 428 150 36

Claims

1. A method of rotor spinning of fibres with properties, exerting by the resultant of their influence an increase of axial force in the withdrawn yarn, wherein the effect of frictional forces acting upon the yarn at the first contact point in the withdrawing path behind the collecting surface of the spinning rotor, 'i.e. on the inlet working surface of the yarn withdrawing funnel, is reduced by shortening the contact path of the withdrawn yarn, thus attaining an optimum axial force of the withdrawn yarn in the area behind the outlet from the funnel, which does not exceed a 2.5 multiple of the axial force F,=5.45 . 10-'2 R2 n2, where F0=the axial force in the withdrawn yarn in the area between the collecting surface of the spinning rotor and the inlet into the withdrawing funnels, /mN/tex/, R=the radius of the spinning rotor (mm), n=the number of revolutions of the spinning rotor (min-1).

2. A device for performing the method as claimed in Claim 1, comprising a spinning unit with a rotor and a withdrawing funnel with a working surface, wherein the working surface of the funnel is formed by an inlet edge and a section defined by said inlet edge and the last point of contact of the yarn on this working surface, and determines the reduction of the contact path of the yarn at the given radius of curvature r by the height of the funnel head h.

3. A method of rotor spinning of fibres, substantially as hereinbefore described with reference to the accompanying drawing.

4. A device for rotor spinning of fibres, substantially as hereinbefore described with reference to the accompanying drawing.