WO2007048528A1

WO2007048528A1 - Apparatus for fully-automatized control of the length of a yarn

Info

Publication number: WO2007048528A1
Application number: PCT/EP2006/010022
Authority: WO
Inventors: Kurt Arne Gunnar Jacobsson
Original assignee: Memminger-Iro Gmbh
Priority date: 2005-10-27
Filing date: 2006-10-17
Publication date: 2007-05-03

Abstract

An apparatus for automized controlling of the length of a yarn Y supplied to a knitting system (1) in a knitting machine (2) comprises a yarn storing device YSD with a stationary drum SD, a yarn length measuring detector YLD for measuring a value (YLActual) of the actual length of the yarn Y as withdrawn and supplied to the knitting system (1), and a controllable yarn tensioning element YTE which is actuable by an electronic drive unit EDU for varying the position of force of the yarn tensioning element YTE against a withdrawal end WE of the stationary drum in order to controllably adjust the tension in the yarn as withdrawn in dependence from the value of an error signal ES, the value of which is the result of a comparison between the value of the actual yarn length and the value of a desired yarn length (YLDesired).

Description

DESCRIPTION

The present invention relates to an apparatus according to the preamble of claim 1 , in particular to an apparatus for fully-automatized controlling of the length of a yarn supplied to a knitting system in a knitting machine for ensuring a uniform, perfect quality of each knitted fabric article of a production series over time.

Such an apparatus is known from US-4199965 A. Therein, actual rotation signals originating from the feeding devices are evaluated to measure the yarn length and to carry out comparisons with the respective yarn length of a masterpiece knitted beforehand.

The main object of the present invention is to achieve an apparatus of this kind but which represents a further break-through-development which has essential, decisive advantages in technical performance over the known apparatus.

Another important object is to achieve an apparatus which, despite requiring several function-wise different types of components, yet results in an extremely compact, space- saving accessory unit which can be easily fitted, even in big numbers, at a knitting machine, e.g. at multi-system circular knitting machines, having a great number of knitting systems.

The apparatus according to the invention is applicable to practically any kind of kitting machine, but is particularly suitable for implementation in connection with circular or flat knitting machines.

The above-mentioned objects are achieved by the features of claim 1.

One of the essential advantages of an apparatus according to the present invention, as compared with the above-mentioned prior art solution, is that the yarn Y coming from the yarn store YS, just before entering the controllable tensioning element YTE, already has a desirable low and uniform basic tension after having been respooled in the yarn storing device YSD, which influence of the yarn storing device YSD will efficiently prevent too high or even sudden peak tension values before the yarn enters the tensioning element. Such peak tension values could sometimes occur due to problems in or at the yarn supply, e.g. yarn snatches, and then, in absence of a properly operating yarn storage device, could come through to the core of the closed loop yarn tension regulation process, i.e. to a location in the yarn path where the yarn is to be controllably adjusted, i.e. is adjusted to its desired value of the yarn tension.

Also essential for a successful performance of this knitting quality increasing and maintaining apparatus is the fact that, from the running yarn point of view, the yam tensioning element YTE follows downstream of the yarn storing device YSD, or rather at the withdrawal end WE thereof, i.e. upstream of the point in the yarn path where then the yarn length measurement is carried out. This means that the yarn length measurement is carried out on the yarn after it has been adjusted to the desired tension value by the upstream, and preferably closely positioned, controllable yarn tensioning element YTE. This results in the fact and advantage that the yarn tension regulation will always be carried out based upon a true value of the measured yarn length, i.e. upon a yarn length which is truly drawn into the knitting system , since there is no other yarn influencing component in the yarn path between the yarn length measuring detector and the knitting system.

The combination of the yarn storing device YSD, the controllable yarn tensioning element YTE and the yarn length measuring detector YLD into one single unit, results in an extremely compact and space-saving knitting machine accessory device, which can be easily fitted even on multi-system circular knitting machines.

The yarn length measuring detector YLD can be of any type but it is preferably a yarn passage detector of an optical type, e.g. a so-called beam sensor, comprising at least one pair of light emitter and light receiver, the beam between which is crossed e.g. twice by the yarn when being withdrawn in an orbiting- or pointer-wise movement from the storing drum SD. The detector does not add any additional tension to the adjusted tension of the yarn on its way from the controllable yarn tensioning element YTE to the knitting system in the knitting machine if it is integrated into the output eyelet OE. The yarn length measuring detector YLD is preferably built into the conventional output eyelet OE of the yarn storing device YSD. This also strongly contributes to gaining the desirable compact and space-saving benefits in the apparatus according to the invention.

The controllable yam tensioning element YTE can be part of any type of yarn tensioner. The part is held in contact with the withdrawal end WE of the drum with a force or pressure which can be controlled by active and controllable axial force-generating means.

One example of such a yarn tensioner can be a further developed, controlled version of one of Applicant's own, known, not-controlled yarn tensioners for a yarn storing device, for example the so-called MFLEX, which was shown fitted on Applicant's new yarn storage feeder with a stationary drum for knitting machines, the so-called MSF, exhibited at the FAST Knitting Machine Exhibition in Verona, Italy, in May, 2005. This known, not- controlled yarn tensioner consists mainly of a truncated-cone-shaped, radially flexible, axially stiff brake body, i.e. the yarn tensioning element, which is held in contact under an adjustable force or pressure against the withdrawal end of the yarn storing drum by means of an arrangement of repelling permanent magnets, co-actingly positioned in a stationary part of the yarn storing device and in a brake body carrying part.

In one embodiment of this invention, this known passive yarn tensioner, for example, is modified to become a controllable yarn tensioner, constituting the yarn tensioning element YTE in the apparatus. The force-generating means (preferably, however not necessarily, being an arrangement of repelling permanent magnets generating a steady contact pressure for accomplishing a certain desirable basic yarn tension), comprises at least one solenoid coil SC as a supplemental controllable force generator. The solenoid coil is supplied wit a controllable current, the momentary value of which is representative of the error or difference between the desired value (YL_Desired) and the actual value (YL_Actuai) of the measured yarn length. The solenoid coil is arranged in a stationary part SP of the yarn storing device and co-acts with at least one permanent magnet or even a soft-iron part fixed to a brake body carrying part, in order to controllably adjust the force or pressure of the brake body against the withdrawal end of the drum and the yarn therebetween. One embodiment of the apparatus of the present invention is schematically shown in Fig. 1.

An apparatus for fully-automized controlling the length of a yarn Y supplied to a knitting system 1 of a knitting machine 2 comprises a yarn storing device YSD in a yarn path between a yarn supply YS and the knitting system 1. The knitting machine 2 may be any type of powered knitting machine, preferably is, however, a multi-systems, circular knitting machine.

The yarn storing device YSD has a housing 3 containing an electronically controlled electric drive motor 4 for rotatably driving a winding element 5 in relation to a stationary drum SD. On the periphery of the stationary drum SD, by rotation of the winding element 5, a temporary yam store, consisting of several yarn windings YW, is wound between the winding-on element 5 and a downstream yarn withdrawal zone YWZ, which is separated from the yarn windings YW by a withdrawal end WE or a withdrawal rim of the stationary drum SD.

The yarn withdrawal zone YWZ is occupied by a controllable yarn tensioner T, which, for example, is mounted onto a stationary housing part 7 ending in a stationary part SP, the axial position of which can be adjusted manually in the direction of an arrow 12, in order to, for example, adjust a basic contact pressure of the yarn tensioner T.

The controlled yarn tensioner T may be of any type, allowing a variation of the contact pressure and the braking effect on the yarn Y, while the yarn Y is withdrawn from the yarn windings YN of the yarn storing device YSD into the knitting system 1.

A preferably used type of a controllable yarn tensioner T, in Fig. 1 , contains a yam tensioning element YTE consisting of a frustoconical brake body 13 which is, for example, made of plastic material such that it is radially flexible but axially relatively stiff. The brake body 13, for example, is shaped with a cylindrical extension at the small diameter end of the frustocone.

The cylindrical extension at the small diameter end carries a ring part 6 equipped with either a permanent magnet ring or a plurality of circumferentially distributed permanent magnets PM which are surrounded, with distance, by another either permanent magnet ring or a plurality of circumferentially distributed, repelling, permanent magnets PM, secured to the stationary part SP such that the permanent magnet PM, at the stationary part SP, generates a plurality of axial and oblique force vectors in the permanent magnet PM on the ring part 6, and in order to hold the brake body 13 with a certain axial force in axial contact with the withdrawal end WE of the stationary drum SD.

During operation of the yarn storing device YSD, the yarn Y is pulled off from the yam supply YS. The yarn supply YS sometimes contains snatches or knots or other irregularities which may cause sharply varying yarn tension in the pulled off yarn Y. However, these sharp variations of the yarn tension are compensated for by the yarn storing device YSD before the yarn Y reaches the controllable yarn tensioning element YTE. In other words, by respooling the yarn Y, which first was spooled in the yarn supply YS, into the for example separated yarn windings YW on the storage body SD, it is avoided that such too high or even sudden peak yarn tension values can reach the yarn tensioning element YTE. The main task of the yarn tensioning element YTE is to adjust or regulate the yarn tension to a desired value, which desired value will no longer be influenced by such upstream peak tension values. It is of utmost importance that this desired value of the yarn tension is assured when, downstream of the yarn tensioning element YTE of the controllable yarn tensioner T, a yarn length measurement is carried out for precisely monitoring the yarn length consumed in the knitting system 1.

The controllable yarn tensioner T is positioned in yarn running direction upstream of a downstream yarn length measuring detector YLD where the yarn length measurement is carried out after the yarn has been given the desired value of the yam tension, such that there will not be any further influences of sudden peak tension values originating from pulling off the yarn Y from the yam supply YS.

The yarn tensioning element YTE and the yarn length measuring detector YLD, ought to be positioned, preferably, as close as possible to one another. As no other yarn influencing component exists in the yarn path between the yarn length measuring detector YLD and the knitting system 1 of the knitting machine 2, the yarn tension regulation, which then is carried out on the basis of the measured yarn length by the controlled yarn tensioner T₁ will always be carried out based on a true value of the measured yarn length. In this connection it is also of importance that the yarn Y, in the yarn windings YW on the stationary drum SD, does have a desirable low and uniform basic tension just before entering the braking zone between the yarn tensioning element YTE and the withdrawal end WE.

The structural combination of the yarn storing device YSD, the controllable yarn tensioning element YTE of the controllable yarn tensioner T and the yarn length measuring detector YLD, form a single unit, i.e. an extremely compact and space-saving knitting machine accessory device.

The yam length measuring detector YLD can be of any type, but, preferably, is a yarn passage detector of an opto-electronic type, for example, a so-called beam sensor, comprising at least one pair of a light emitter 9 and a light receiver 10 between which a beam 11 is created. The yarn length measuring detector YLD preferably is integrated into a conventional output eyelet OE, as provided in the stationary part SP. The task of the output eyelet OE is to guide and deflect the yam exiting the yarn withdrawal zone YWZ in an axial direction to the knitting system 1. While passing through the braking zone in the yarn withdrawal zone YWZ, the yarn orbits pointer-wise or like the hand of a clock while it is deflected from an inclined direction into the axial direction. While passing through the output eyelet OE, the yarn Y crosses the beam 11 twice when one full yarn winding YW is withdrawn. This generates two passing signals which can be used as a value for the withdrawn yarn length.

In the controllable yarn tensioner T, at least one solenoid coil SC is arranged as a variable force generator of the controllable yarn tensioner T. The solenoid coil SC, when supplied with a variable current, either varies the force generated between the co-acting permanent magnets PM or magnetically influences a soft iron part, for example, the ring part 6, such that the braking effect on the withdrawn yarn Y is varied, according to a command given to the solenoid coil SC.

The controlled current for varying the braking effect of the controlled yarn tensioner T is supplied, for example, to the solenoid coil SC by an electronic drive unit EDU for varying the position of force or pressure of the yarn tensioning element YTE against the withdrawal end WE, in order to controllably adjust the tension in the yarn Y in dependence on a value of an error signal ES supplied to the electronic drive unit EDU from an electronic yarn lengths-values storing and processing unit SPU. The value of the error signal ES is the result of a comparison which is carried out in an electronic comparator COMP. In the comparison, as carried out, a value YL_Desired is compared with a value YL_Actuai. The value YL_Desired is supplied by the electronic yarn length-values storing and processing unit SPU, while the value YL_Actuai is supplied to the comparator COMP from the yarn length measuring detector YLD.

The value YL_Desired preferably is a stored value which is obtained by an early signal or value YL_Master, during a master cycle, from the yarn length measuring detector YLD, at a corresponding moment in the working or production cycle of the knitting machine 2 during an initial and preparatory knitting of a masterpiece of the same knitted fabric as is produced in the knitting machine 2 while the yarn tension regulating process is carried out, as mentioned above.

By regulating or controlling the tension in the yarn, in dependence on the value of the first generated error signal ES, a perfect quality of each later knitted fabric article can be achieved, i.e. the same perfect quality as intentionally was produced by knitting the masterpiece of the knitted fabric article already earlier. The quality control, in other words, is dictated by the respective yarn length which was consumed in every moment during the production of the masterpiece and which same yarn length is achieved by controlling the yarn tension during the production of each later knitted fabric article, now in dependence of the error signal ES.

The embodiment shown in Fig. 1 is a preferred embodiment only. The yarn storing device YSD could also be a yarn storing device having a rotatable storage drum. The controllable yarn tensioner T could be of another construction, as well as the yarn length measuring detector YLD. The yarn length measuring detector YLD could even be integrated into the controlled yarn tensioner T, provided that the yarn length measuring detector YLD is operating downstream from the location where the yarn Y is given the desired value of the yarn tension.

The core of the invention is to control the yarn tension during the knitting cycle such that, ideally, the same yarn length will be consumed by the knitting system for each later knitted fabric article as it is desired, i.e. had been consumed during the knitting cycle of the high quality masterpiece.

For example, in case of decreasing actual yarn length at a certain moment of the cycle or per time unit, the braking effect is reduced accordingly, and vice versa. In order to achieve a precise regulation, any falsifying peak tension values (too high or too low) are already compensated for in the yarn storing device, before the yarn enters the controlled yarn tensioner. This assures that the actual yam length will be measured accurately, which results from the yarn related cooperation between the controlled tensioner and the knitting system only. This allows to then control or regulate the braking effect or the yarn tension such that the actual measured yarn length will be as close as possible to the desired yarn length, for example as recorded earlier for the masterpiece at the same knitting system.

Claims

1. Apparatus for fully-automized control of the length of a yarn (Y) supplied to a knitting system (1) in a knitting machine (2) for ensuring a uniform, perfect quality of each knitted fabric article of a production series over time, characterized by the following features:

a yarn storing device (YSD) with a stationary drum (SD) onto which the yarn from a yarn supply (YS) is wound for forming a temporary yam store of several yarn windings (YW), said yarn storing device having a yarn withdrawal zone (YWZ) adjacent to a withdrawal end (WE) at its output end which comprises:

a yarn length measuring detector (YLD) for sensing the passage of the yarn (Y) during its axial and pointer-wise withdrawal movement from the stationary drum (SD) in order to measure the actual value (YL_Actuai) of the length of yarn (Y) actually withdrawn by and supplied to the knitting system (1) in the knitting machine (2), and

a controllable yarn tensioning yarn element (YTE) which is positioned closely upstream of said yarn length measuring detector (YLD) and is axially coacting with the withdrawal end (WE) of said stationary drum (SD), the tensioning element (YTE) being actuable by an electronic drive unit (EDU) for varying the position or force of the yarn tensioning element (YTE) against the withdrawal end (WE) and the yarn (Y) withdrawn there-between in order to controllably adjust the tension in the yarn (Y) being withdrawn from the stationary drum (SD) in dependence on the value of an error signal (ES) supplied to the electronic drive unit (EDU) from a yarn length-values storing and processing electronic unit (SPU), the value of said error signal (ES) being the result of a comparison in an electronic comparator (COMP) of the value of the output actual yarn length measurement signal (YLActuai) obtained from said yarn length measuring detector (YLD) and a predetermined, desired yarn length value (YL_Desired) available in said storing and processing electronic unit (SPU).

2. Apparatus as claimed in claim 1 , characterized in that the desired yarn length value (YLo_esir_ed) is a stored value obtained by a signal (YL_Master) from the yarn length measuring detector (YLD) at a corresponding moment in the working cycle of the knitting machine (2) during an initial and preparatory knitting process of a masterpiece of the knitted fabric in question (master cycle).

3. Apparatus as claimed in claim 1 , characterized in that the yarn storage device (YSD), the yarn tensioning element (YTE) and the yarn length measuring detector (YLD) are built into one single, compact accessory unit for the knitting machine (2).

4. Apparatus as claimed in one of claims 1 to 3, characterized in that the yarn length measuring detector (YLD) is an optical type sensor, e.g. a so-called beam sensor, preferably housed in an output eyelet (OE) of the yarn storing device (YSD).

5. Apparatus as claimed in claim 1 , characterized in that the yarn tensioning element (YTE) is axially actuated with respect to the position or force against the withdrawal end (WE) by co-acting permanent magnets (PM), and that the position or force is variable by at least one solenoid coil (SC) which is supplied with a control current from the electronic drive unit (EDU).