GB2181752A - Spinning-in yarn in open-end rotor spinning machines - Google Patents

Abstract

The invention solves the problem of yarn spinning-in in open-end spinning machines with high-speed rotors, and particularly eliminates deformations of yarn end, due to impacts thereof onto opposite rotor walls while being returned into the rotor. Such deformations reduce the strength of splicings. According to the invention, the yarn end (29) is moved back and stopped for a short time in an intermediate position between the inlet (17) of the take-off duct (15) and a collecting groove (12) and then it is conveyed by another backward motion to a fibrous ribbon in said groove (12). <IMAGE>

Description

SPECIFICATION Spinning-in yarn in open-end rotor spinning machines The invention relates to spinning-in yarn in an openend rotor spinning machine.

The yarn spinning-in process in conventional open-end rotor spinning machines, such as according to the Czechoslovak Patent Specifications Nos.

122,618 and 152,063, is effected in such a manner that a duly re-shaped yarn end, after cleaning and preparing the spinning unit and after setting the spinning rotor in rotation, is supplied by backward motion to a fibrous ribbon in a collecting groove of the rotor and spun-in, whereupon the yarn is withdrawn from the rotor. Prior to said backward motion, yarn is reintroduced into the take-off duct up to an initial position, or remains in said position after a preceding take-off stop. Yarn is moved at first back through the take-off duct to the inletthereof whereupon after having been discharged therefrom, it has to be bent in radial direction to said collecting groove.Whileescapingthetake-offductinlet,the yarn backward motion, especially in high-speed rotors with more than 60,000 rpm, has a speed of up to 3 metres per second.At such a linear speed, the yarn tends, dueto inertia, to continue its linear course so that it impinges sometimes against an op positewallofthespinning rotor,oraseparatorbe- fore being bent atthetake-offduct inlet edge inthe radial direction to the collecting groove. Owing to such an impact, the yarn end rebounds againstthe opposite wall of the spinning rotor where it gets doubled in loop form, or otherwise deformed so that it is unable to be spun into the fibrous ribbon in the collecting groove. This manifests itself in the final yarn products in that the strength of splicing spots varies within relatively broad limits.This results in that even at a sufficiently high average strength of splicing spots, some of them have a minimum strength so that they tend to break during the further yarn processing.

It is an object of the present invention to eliminate the drawbacks of prior art as herein before set forth and to provide a method of spinning yarn in openend spinning machines, which warrants standard conditionsforfaultless supply of yarn tothe collect inggrooveofthespinning rotoraswell as uniform splicing spots in the final yarn product, and part icularlywith regard to tensile strength, in all of the spinning units ofthe machine.

According to one aspect ofthe invention,there is provided a yarn spinning-in method in an open-end rotorspinning machine,wherein yarn end is returned by backward motion from an initial position in a take-offduct into the spinning rotor, and led to a fibrous ribbon in a collecting groove, and wherein yarn, after being spun-in, is withdrawn and wound on a bobbin, and wherein,the yarn end is discharged by backward motion out of the take-off duct into the spinning rotor whereupon it is stopped for a short time in an intermediate position between the inlet of said duct and the collecting groove, and then conveyed by another backward motion to said fibrous ribbon.

According to another aspect ofthe invention, there is provided an apparatus for carrying out the above method, comprising yarn taking-off means, yarn taking-up means and meansforspinning-in yarn by moving it backward from an initial position in the take-off duct to the collecting groove, wherein means fortheyarn backward motion are interconnected in a ciruitwith a control device for stopping the yarn backward motion for a short time in a position between the inlet of the take-off duct and the collecting groove ofthe spinning rotor.

An advantage ofthe method of the invention consists in thattheyarn end suppliedto an intermediate position in the interior of the spinning rotor, i.e. between the inlet ofthe take-off duct and the collecting groove, is exposed to an airwhirl inthespinning rotorfor a shorttime, say e.g. two seconds, while stopping the yarn backward motion, whereby the twist in the yarn portion designed for being spun-in is stabilized.After feeding the yarn to said intermediate position in the rotor,theyarn end is captured bysaid airwhirl and takes a characteristicthree-dimensional curvilinear course in a radial direction whereby a correct contact between said yarn end and the fibrous ribbon in the collecting groove is warranted. In this way the reliability of spinning process rises and the range of qualitative values of splicing spots becomes narrower.

Some preferred embodiments of the invention will be hereinafter described, by way of example, with reference to the accompanying schematic drawings, in which Figure lisa sectional view of an open-end spinning unit comprising a take-offdevice and a spinningin device; Figure2 is a perspective view of a spinning-in arm provided above the outlet ofthe take-off duct; and Figure 3 is a perspective view of an alterntive embodiment of the spinning-in device.

The spinning unit shown in Figure 1 comprises a spinning rotor 1 arranged in a recess3which is provided in a spinning housing 2 and which communicates with an air escape piping 4. The spinning rotor 1 which is provided with ventilation ducts 5 has a shaft 6 mounted in bearings 7 and provided with a pulley 8. In operation,the pulley8 is driven via belt9 from an electric motor 10. The spinning rotor 1 has furtherafrontopening 14 and in its interior 13 a sliding wall 11 and a fibre collecting groove 12. Ayarn take-off duct 15 enters the rotor interior 13 through said front opening 14.Thetake-offduct 15 has an inlet 17 in the interior 13 of the spinning rotor 1 and an outlet 18 which is disposed outside the spinning rotor 1. In the proximity of said outlet 18 there is provided a sensor 19 for monitoring thread breakages in the rotor 1. In this embodiment, the take-off duct 15 passes through a fibre separating housing 20 which is associated with the spinning housing 2, and engages thereinto by a separator 21. Adjacent the sep aratorthere is disposed an outlet of a fibre supply duct 22 designed for supplying discrete fibres from a separating device (not shown in detail) intotheinterior 13 of the spinning rotor 1. Alternatively the take-offduct 15 can pass through the rotor shaft 6, which, however, is irrelevant with regard to the present invention.Down-stream of the outlet 18 of the take-off duct 1 5 there are installed known take-off rollers 23 driven from an electric motor 24 which, optionally, can drive also a take-up roller25forwinding yarn 16 onto a bobbin 26. The driving electric motors 10 and 24 as well as the drives of a sliver supply device and an opening cylinder (not shown in detail) are coupled to a known control unit 27. The unit 27, the take-off rollers 23, the take-up roller 25 as well as their driving means coupled to said motors 24, 10 constitutes, in general, means for withdrawing and winding yarn and means for spinning-in yarn, respectively.These means 27,23 and 25 comprise couplings and brakes (not shown in detail) which are disclosed e.g. in the Czechoslovak Inventor's Certificate No. 122,618. A control device 28 forming a part of said control unit 27 serves for a short-termed interruption ofthe backward motion of end 29 of yard 16.

These control means areshown onlyschematically in the form of block diagrams. The control device 28 consists of switching elements such as relays, thyristors, or the like.

The yarn spinning-in process takes place according to the invention as follows: In operation, discrete fibres are supplied through the supply duct 22 onto the sliding wall 11 ofthe spinning rotor 1 and slide down on this wall 11 into the collecting groove 12 where they are deposited in the form of a fibrous ribbon. The latter is, due to the rotation of the spinning rotor 1, twisted in the known wayto yarn 16. Yarn 16 enters then the inlet 17 ofthe take-off duct 15 and is withdrawn upwardsthere- through by means of the take-off rollers 23, and finally wound onto the bobbin 26 by means ofthetake- up roller 25. The operation of the spinning unit is monitored bythesensor19which releases a signal in case of a thread breakage in the rotor 1.The signal is transmitted to the control unit 27 which stops the spinning process in the known way.

Afterthe spinning rotor 1 has been duly cleaned, the spinning unit is prepared for being spun-in. On command of the operator orfrom automatic means of a known travelling service unit, the take-off rollers 23, or, optionally, also the take-up roller 25 are set in reverse rotation, whereby the end 29 ofyarn 16 is returned from the initial position in the take-off duct 15 to the inelt 17 thereof and then through the interior 13 of the spinning rotor 1 in direction to the collecting groove 12.In a first phase, however, the end 29 of yarn 16 is not continuously conveyed up to said collecting groove 12 but stopped for a short time between the inlet 17 and the collecting groove 12, which meansthattheyarn backward motion is interrupted by the spinning-in elements 23,25 on command of the control device 28. The stop period amounts to about one to three seconds or even less, and its pur- pose is to allowthe end 29 ofyarn 16to bestraightened by airwhirl produced in the interior 13 ofthe spinning rotor 1, if it impacts againstthe opposite wall of rotor bottom 30, and to take the course of a three-dimensional curve in radial direction from the inlet 17 to the collecting groove 12.The end 29 of yarn 16 is stopped at most 5 mm in front of said groove 12 so as to prevent it from contacting the rotor inner wall. However, the yarn end 29 has to always protrude, at least partially, out of the take-off duct inlet 17 into the interior 13 of the spinning rotor 1 in order that it could be bent in radial direction. Afterthis short interruption of its backward motion, the yarn 16 continues this motion and is conveyed to the collecting groove 12, and immediately thereafter returned by reversing the rotation ofthetake-offrollers 23 or, optionally, also the take-up roller 25, and led to the bobbin 26. The end 29 ofyarn 16 can be variously shaped before being spun-in. Thus,forexample, according to Czechoslovak Inventor's Certificate No.

200,910, the yarn end is introduced into a side duct where it is given a sharp appropriateforspinning-in.

Such a new yarn end is then introduced into the spinning rotor 1 as hereinabove referred to.

Theyarnreversing means can also havevarious forms or embodiments. Figure 2 shows one of such embodiments consisting of a spinning-in arm 31 of a known automatic service unit adapted fortravelling along the spinning machine. The end 29 ofyarn 16 seized by this arm 31 is transferred in a known way from the bobbin 26 back into the outlet 18 ofthetake- off duct 15 by means of a known nozzle 32. On the spinning-in arm 31 there are provided spinning-in rollers 33 which make a reverse rotation during the spinning process, since the bobbin 26 is lifted in this time abovethetake-up roller 25, and yarn 16 is led in this phase outside the take-off rollers 23 (not shown).

Then the control unit 27 controls the backward motion of yarn 16 as hereinabove described with reference to Figure 1,which means that it stops the yarn motion for a short time wherein the end 29 of yarn 16 is exposed to the effect of airwhirl in the interior 13 of the spinning rotor 1.

Figure 3 shows an alternative embodiment ofyarn reversing means consisting of a combination of the spinning-in arm 31 ofthetravelling automatic service unit and a system of stationary pegs 34 and a deflecting peg 35. To a web 36 extending from the spinning unit there are fixedly attached two stationary pegs 34, and on a shifting device 37 (not shown in detail) there is provided a movable peg 35for deflecting yarn 16.Afterthe end 29 ofyarn 16 has been introduced into the take-off duct 15 by the spinning-in arm 31, the peg 35 deflects yarn 16 between the stationary pegs34intothe position as indicated in Figure3 whereby a yarn reserve is built, which reserve is necessary, for instance, for returning the end 29 ofyarn 16fromthe intermediate position in the interior 13of the spinning rotor 1 to the collecting groove 12. The supply of the end 29 ofyarn 16 is effected, for example, by reverse rotation of the take-off rollers 23 and the bobbin 26 as hereinabove described with reference to Figure 1. The shifting device 37 for releas- ing the yarn reserve between the stationary pegs 34 by shifting the deflecting peg 35 is set in motion by the operator by means of a control element 28 forming a part of the control unit 27, or by means ofthe travelling automatic service unit.

Claims (4)

1. Ayarn spinning-in method in an open-end rotor spinning machine, wherein yarn end is re turned by backward motion from an initial position in atake-offduct into the spinning rotor, and led to a fibrous ribbon in a collecting groove, and wherein yarn, after being spun-in, is withdrawn and wound on a bobbin, and wherein the yarn end is discharged by backward motion out of the take-off duct into the spinning rotorwhereupon it is stopped for a short time in an intermediate position between the inlet of said duct and the collecting groove, and then conveyed by another backward motion to said fibrous ribbon.

2. An apparatus for carrying out the method as claimed in claim 1, comprising yarn taking-off means, yarn taking-up means and means for spinning-in yarn by moving it backward from an initial postion in the take-off ductto the collecting groove, wherein means forthe yarn backward motionarein- terconnected in a circuit with a control device for stopping the yarn backward motion for a shorttime and in a position between the inlet of the take-off duct and the collecting groove ofthe spinning rotor.

3. Ayarn spinning-in method substantially as hereinbefore described with reference to the accompanying drawings.

4. Apparatusforcarrying out the method as claimed in claim 3, substantially as hereinbefore des cribedwith reference to the accompanying drawings.