A method for bobbin classification according to the stiffness of a yarn package arranged on a tube for dyeing provided with a plurality of radial through holes.
An apparatus for detecting the permeability of a yarn package on a tube provided with a plurality of radial through holes for classification of bobbins according to the stiffness of a yarn package determined by permeability of the package.
Dyeing yarns and similar linear textile formations is generally carried out on a wound bobbin by forcing dye liquor through a layer of yarn.
A dyeing apparatus comprises a vessel connected to the supply of dye liquor from a storage reservoir and for discharging the dye back to the reservoir. Wound bobbins in the vessel are mounted on shanks which are composed of perforated pipes and are closed at one end, whereby the inlets to these perforated pipes are connected to the dye supply. The tubes of the bobbins are also perforated and so the dye supplied under pressure enters through the cylindrical surface of the tube into the volume of the yarn package and, having passed through the package, it returns to the storage reservoir. Such an apparatus is known, for example, from the document
The aim of the dyeing process of the yarn package is achieving uniform colour shade of all the wound yarn for all the bobbins of the entire dyed batch. Owing to the fact that the stiffness of individual yarn packages may vary, which may be caused, for example, by the yarn being unevenly tightened during winding, the yarn may be dyed unevenly. Naturally, this also unfavourably influences the appearance of the textile product, for example a knitted textile, a fabric and others, which are produced from such yarn.
There are several methods known from the background art that are used for detecting the stiffness of the yarn package. The known solutions are based, for example, on measuring the resistance to the deformation of the package. This is performed by measuring the resistance forces acting during the penetration of a needle into a layer of the package, or during turning a flat needle in a layer of the package. Other solutions derive benefit from measuring the reflection of testing weight falling on the package surface.
However, such measurements do not evaluate the package as a whole. The package is only assessed at certain points and, therefore, the outcome of the evaluation is not only influenced by an objective error of the measuring device caused by manufacturing tolerances and wear of the device, but also by subjective errors resulting from the measurement method, which is limited by the capabilities of the device used. The accuracy of the measurement is determined by the number of point measurements made at a particular package. A prerequisite for the applicability of the results is a relatively long time needed for the measurements and for the statistical evaluation, since it is known that there are significant variances in the obtained set of measured values.
The goal of the invention is to shorten the time which is necessary for determining the stiffness of the yarn package and increase considerably the objectivity of the evaluation of the measured data.
The aim of the invention has been achieved by a method for classification of bobbins according to the stiffness of a yarn package arranged on a tube for dyeing, whose principle consists in that the bobbins are sorted into groups according to the permeability of the package. This criterion is very close to the actual process of dyeing packages.
The permeability is determined by measuring the hydraulic gradient on a layer of a package at a specific constant air flow rate, or the permeability is determined by measuring air flow rate through a layer of the package at a specified constant hydraulic gradient on the layer of the package. From the point of view of the results of testing, both methods are virtually equal and selecting one method depends on the availability of the testing means and/or possible unique features of the packages being dyed, the type of dye or the testing frequency.
In order to determine the hydraulic gradient on a layer of a package, the overpressure of the air supplied into the inner space of the tube with close ends in comparison with the ambient atmospheric pressure is measured. Thus it is possible to obtain also the direction of the hydraulic gradient which corresponds to the passage of the dye through the package during the process of dyeing.
The goal of the invention has also been achieved by an apparatus for detecting the permeability of a yarn package, which is arranged on a tube provided with a plurality of radial through holes, whose principle consists in that the ends of the tube are closed and the inner space is interconnected with a source of compressed air, whereby a flow meter is arranged in the inlet piping leading into the inner space and a pressure gauge is connected to the outlet piping of compressed air.
The advantage of the solution according to the invention is relative simplicity of its implementation, obtaining reproducible and reliable results, availability of the means which constitute the testing apparatus, as well as the fact that it is possible to store the measured values so that they can be retrieved for the purpose of finding the reason of altered stiffness of the package or its colouring.
The apparatus for measuring the stiffness of a yarn package according to the invention is schematically represented in the drawing, where
The apparatus for detecting the permeability of the yarn package according to the invention is based on a principle which physically corresponds to a method of dyeing yarn carried out during its production.
The permeability of the package is determined by its stiffness resulting from the tightening of separate turns during winding the bobbin. During dyeing the dyeing liquor is forced through a layer of the package so as to achieve uniform colour shade of the yarn. Measuring the package stiffness and, accordingly, its permeability is therefore carried out by forcing the liquor through analogically with the actual process of dyeing. For practical reasons, which particularly include the price of the device, the elaborateness of measurements and the necessity to maintain the yarn package in a dry state, the testing medium is gas, preferably air.
A permeable package 41 of yarn puts up a resistance to the passage of the air which is characterized by hydraulic gradient P, i.e. by the difference between the pressure before the entry of the air into the layer of the package 41 and the pressure of the air behind the layer of the package 41. The hydraulic gradient P grows with the stiffness of the package 41 and the flow rate Q of the air being forced through. For the same dimensions of the package 41 of yarn, namely its length, its outer diameter and the outer diameter of the tube 42, the package 41 permeability is a fundamental parameter which defines the stiffness of the package 41. The reason why a gas medium is used is the fact that this measurement allows to compare only relative stiffness, that is the total mean permeability of separate packages 41 being tested, not the absolute value of permeability, and the material is not anyhow damaged by it.
An example of embodiment of the apparatus according to the invention is illustrated in
Owing to the fact that the outer surface of the package is in contact with the ambient atmosphere, the value of the hydraulic gradient P on the package 41 layer is virtually identical to the inlet pressure P0 of the supplied air.
In the first alternative of the apparatus according to the invention, the source 1 of compressed air is provided with a means of adjusting the amount of the flow Q of the supplied air. The source 1 of compressed air can be also a low-pressure blower, or the outlet of an unillustrated central distribution system of compressed air provided with a means for flow rate regulation. If a separate source 1 of compressed air is used, the flow meter can be arranged in its suction system. This, however, has a negative influence on the conditions in the suction of the source 1 of compressed air.
In the second alternative, the source 1 of compressed air delivers a constant amount of the air, or the source 1 of compressed air is coupled to a sufficiently precise known regulator of the pressure (not shown).
In the first variant, the detecting of the stiffness of yarn packages 41 is carried out by measuring the flow rate Q of the air by a flow meter 2 at a constant pre-set hydraulic gradient P1 on a layer of the package measured by a pressure gauge 3. In one bobbin 4 a specified hydraulic gradient P1 is obtained after adjusting the source 1 to flow rate Q1, in another bobbin 4 the same hydraulic gradient P1 is obtained after adjusting the source 1 to flow rate Q2. A soft package 41 is characterized by a higher flow rate Q1, whereas a stiff package 41 is characterized by a lower flow rate Q2.
In the second variant, detecting the stiffness of yarn packages 41 is carried out by measuring the hydraulic gradient P by the pressure gauge 3 at a constant pre-set flow rate Q1 of the air controlled by the flow meter 2. A stiff package 41 is characterized by a higher hydraulic gradient P2, whereas a soft package 41 is characterized by a lower hydraulic gradient P1.
On the basis of the values of the hydraulic gradient P measured for different amounts of flow rate Q it is possible to construct the entire curve of mutual dependence of the hydraulic gradient P and the flow rate Q for laboratory use. The curve K2, which is situated lower, defines a stiffer package 4 than the curve K2, situated above.
Handling bobbins, closing the tubes 42 by means of a sealing stopper at the end 43 and a stopper with the supply of compressed air at the end 44, can be easily automated. By means of appropriate converters it is also possible to store the measured values of the hydraulic gradient P and the flow amount Q of the air so as to retrieve the causes of altered stiffness of the package or the colouring.
Apparently, in the usual arrangement of the package on the bobbin, it is not possible to presume a uniform field of flow lines of the flowing fluid. Especially in areas situated on a small diameter of both ends of the package 411 short-circuit flowing from the tube towards the side annulus of the package occurs.
For the purpose of research and development, it is possible to determine the uniformity of the flow through a layer of the package 41 by means of numerical simulation, to detect the places of short-circuit flow of the air and according to need to propose adjustments leading to a reduction of unevenness of the flow through the package.
On the basis of the confrontation of the results obtained by a method of numerical simulation with the known operational process it is possible to propose using a covering plate to cover the ends of individual packages. In this manner, the dye flow from the radial holes 421 directly to the side of the package 411 is restricted, especially the flow through the portion adjacent immediately to the surface of the tube 42, the flow of the dye towards the area of "the corners", i.e. the transition area 422 from the side of the package 411 to the cylindrical surface is strengthened. Similarly, even a short distance between the sides of the neighbouring bobbins, which are in the dyeing apparatus arranged practically one on top of another in the axis direction, has a positive effect on the uniformity of the colouring of these portions of the package.
The outcome of the numeric simulation is also the fact that even bobbins having identical average permeability detected by the method described above have a different intensity of air flow rate in different sections of the package volume, that is in the side, along the circumference, or in the area transition from the side to the circumference and, therefore, theoretically they also have a different degree of local colouring. During the dyeing process, this drawback can be effectively reduced by diversifying directions of the dye liquor flowing to the mass of the package and vice versa. It is apparent that so as to achieve proper colouring of the entire volume, it is also necessary to maintain a certain minimum period of dyeing so that all the sections in the package could be saturated with dye. If bobbins of one colour batch are sorted into groups according to a particular range of permeability, the period of the dyeing of stiffer bobbins will be longer than that of softer bobbins.
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