Technical field
[0001] A method for bobbin classification according to the stiffness of the yarn package
arranged on a tube for dyeing.
[0002] An apparatus for detecting the permeability of a yarn package which is arranged on
a tube provided with a plurality of radial through holes.
Background art
[0003] Dyeing yarns and similar linear textile formations is generally carried out on a
wound bobbin by forcing dye liquor through a layer of yarn.
[0004] 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
US 5351351.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
Principle of the invention
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
Description of drawings
[0014] The apparatus for measuring the stiffness of a yarn package according to the invention
is schematically represented in the drawing, where Fig.1 shows a flow chart of a pneumatic
circuit, Fig. 2 shows the course of mutual dependence of the air flow (Q) through
the package (axis y) and the hydraulic gradient (P) of the air in the package being
measured (axis x) and Fig. 3 shows the development of the flow lines in the longitudinal
section of the package volume.
Specific description
[0015] 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.
[0016] 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.
[0017] 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.
[0018] An example of embodiment of the apparatus according to the invention is illustrated
in Fig. 1. For detecting the permeability by the air a source
1 of compressed air is used with a flow meter
2 preferably arranged in the outlet branch pipe of the source
1 of compressed air. Behind the flow meter
2, to this branch pipe is connected a flow meter
3 measuring the pressure
P0 of the air before the bobbin
4 with the package
41 of yarn being measured, which constitutes in principle overpressure in relation to
the ambient atmospheric pressure. The package
41 is arranged on a tube
42, which is for the purpose of dyeing yarn provided along its length by a plurality
of regularly divided radial through holes
421. At one end
43 the tube
42 is closed for the measurement purpose. At the other end
44 an inlet orifice
45 of the compressed air supply is arranged for the measurement purpose.
[0019] 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.
[0020] 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.
[0021] 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).
[0022] Fig. 2 shows a diagram of mutual dependence of the air flow
Q in m
3/h through the layer of the package
41 and the hydraulic gradient
P in kPa.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
List of references
[0031]
- 1
- source of compressed air
- 2
- flow meter
- 3
- pressure gauge
- 4
- bobbin (with yarn package)
- 41
- yarn package
- 411
- side of package
- 42
- tube
- 421
- through holes in the tube
- 422
- transition (from the side of the package to the cylindrical surface of the package
- "corner")
- 43
- tube end (closed)
- 431
- flow line (in the area of the closed end of the tube)
- 44
- the tube end (with air supply)
- 441
- flow line (in the area of the tube end with air supply)
- 45
- inlet orifice of air supply
- K1
- curve of the dependence of the pressure on the flow of less stiff package
- K2
- curve of the dependence of the pressure on the flow of stiffer package
- P
- hydraulic gradient on a layer of the yarn package
- P0
- overpressure of the air before the inlet tube area (in comparison with ambient atmospheric
pressure)
- P1
- hydraulic gradient of the air (= pressure of the air in the inlet tube area - specific
- of softer package)
- P2
- hydraulic gradient of the air (= pressure of the air in the inlet tube area - (specific
- of stiffer package)
- Q
- air flow
- Q1
- air flow (specific - of softer package)
- Q2
- air flow (specific - of stiffer package)
1. A method for classification of bobbins (4) according to the stiffness of a yarn package
(41) arranged on a tube (42) for dyeing, characterized in that the bobbins (4) are sorted into groups according to the permeability of the package
(41).
2. The method according to Claim 1, characterized in that the permeability is determined by measuring the hydraulic gradient (P) on a layer
of the package (41) at a specified constant flow rate (Q) of the air.
3. The method according to Claim 1, characterized in that the permeability is determined by measuring the flow (Q) of the air through a layer
of the package (41) at a specified constant hydraulic gradient (P) of the air on a
layer of the package.
4. The method according to Claim 2 or 3, characterized in that in order to determine the hydraulic gradient (P) on a layer of the package (41),
overpressure (P0) of the air supplied into the inner space of the tube (42) with closed ends (43,
44) in comparison with the ambient atmospheric pressure is measured.
5. An apparatus for detecting the permeability of a yarn package (41) of yarn, which
is arranged on a tube (42) provided with a plurality of radial through holes (421),
characterized in that the ends (43, 44) of the tube (42) are closed and the inner space of the tube (42)
is interconnected with a source (1) of compressed air, whereby a flow meter (2) is
arranged in the supply piping leading into the inner space of the tube (42) and a
pressure gauge (3) is connected to the outlet piping of the source (1) of compressed
air (3).