EP3137664B1

EP3137664B1 - Method to control feeding a yarn and yarn feeder

Info

Publication number: EP3137664B1
Application number: EP14734025.1A
Authority: EP
Inventors: Filippo Oneda
Original assignee: Memminger IRO GmbH
Current assignee: Memminger IRO GmbH
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2018-04-18
Anticipated expiration: 2034-06-13
Also published as: TW201615912A; TWI568903B; WO2015188883A1; EP3137664A1

Description

The invention concerns a method to control feeding a yarn from a yarn feeder to a textile machine and a corresponding yarn feeder according to the preamble of the independent claims.
In particular, the invention concerns a tension-controlled feeding of a yarn to a textile machine. The yarn tension is measured by a yarn tension sensor and controlled in relation to a reference tension.
In operation, the zero offset level of the measured tension of known yarn tension sensors is not constant in time. The tension sensors show a positive or negative drift of its zero offset values. The drift may cause from intrinsic physical characteristics or the mechanical construction process of the yarn sensor, mechanical stress on the sensor during operation or temperature effects.
The EP 0 943 713 B1 describes a yarn or thread tension sensor and a method for calibrating the thread sensor, in particular for zero balancing of the thread tension sensor. The method comprises detecting a possible calibrating state, separating the thread from the thread feeler element, detecting the signal emitted by the thread tension sensor when the thread is raised and re-threading the thread onto the thread feeler element by moving the feeler element in the measuring position. The measured value, which is determined when the thread is raised, is taken as zero value. The thread sensor is provided with a feeler element which is movable between a calibration position and a measuring position. The thread is separated from the feeler element by moving the feeler element in the calibration position and re-threaded by moving back the feeler element in the measuring position. The thread tension sensor is e.g. used for a feeder for feeding elastic threads to knitting machines.
The EP 0 406 735 B1 discloses a method for measuring the tension of an advancing yarn which is subject to interruptions in its path. The yarn is e.g. being wound on a package. The method provides the ability to correct for any errors in the zero point output signal of the tension sensor as follows. The tension of the advancing yarn is continuously monitored wherein a sensor produces an output signal representative of the tension. The output signal of the sensor is monitored and whenever the yarn path is interrupted a zero point output signal is produced and stored. The indicated output is inputted as the zero point signal for the subsequent yarn advancing cycle.
The IT MI2007 A 001557 describes a method for resetting a tension sensor of a yarn feeder for a textile machine. The feeder comprises a rotating element which is driven by its own actuator wherein the yarn cooperates with the rotating element before reaching the tension sensor and the textile machine. During a decrease of the tension indicated by the tension sensor, wherein the yarn is in contact with the tension sensor, the tension is monitored until the tension reaches a certain e.g. low value. The decrease of the tension is executed by forward rotating the rotating element about a predetermined angle. Subsequently, the sensor is reset and possibly the rotating element backward rotated. The resetting procedure is interrupted when a tension controlling start is requested.
A purpose of the invention is to improve a method and a yarn feeder with a tension sensor with respect to a determination of a new value of a zero offset of the yarn tension wherein the yarn is present at the tension sensor. Especially, a less time consuming resetting procedure should be developed.
The problem is solved according to the independent claims.
A method of the invention controls feeding a yarn from a yarn feeder to a textile machine. The yarn is delivered from a delivering wheel of the yarn feeder which is driven by driving means. A yarn tension is measured by a tension sensor which is arranged between the yarn feeder and the textile machine. The yarn tension is controlled by a control device controlling the driving means depending on the measured tension and a reference tension. A new value of a zero offset of the yarn tension is determined wherein the yarn is present at the tension sensor.
The determination of the new value of the zero offset is executed in a stop situation at the beginning of a start-up procedure.
When the resetting procedure is implemented as a first phase of a start-up procedure it only needs a negligible additional time. The procedure is not interrupted caused by an operation start request, as it is itself the first short part of the start-up procedure.
The determination of a new value of the zero offset is executed in two phases:

At first, a potential new value of the zero offset is determined. Then, the new value is verified by analysing the values of the measured tension during slowly moving back the yarn delivering wheel.

In particular, a potential new value of the zero offset is determined while the yarn delivering wheel of the yarn feeder is stopped, e.g. in a break situation.
Following, the yarn delivering wheel is slowly moved back, while the values of the measured tension are monitored and approved. The potential new value of the zero offset is verified or not depending on the values of the measured tension.
It is not necessary to forward rotate the delivering wheel. An overfeeding and rewinding of the excessive yarn is avoided. The resetting procedure is performed in a very short time. There is no significant loss of time for the operator for this integrated resetting procedure.
For determining the potential new value of the zero offset a current value of the measured tension is determined. It is verified that the current value is around a last used value of the zero offset. The potential new value of the zero offset is calculated.
For verifying the potential new value of the zero offset, at each of n steps, the yarn delivering wheel is moved in a backward movement for an angle, such as a total of 2 to 120° or more. The value of the yarn tension is measured and verified that it is around the potential new value of the zero offset, at each step. At a last step, the potential new value is determined as new value of zero offset.
For verifying that the value of the measured tension is around the potential new value of the zero offset, it is verified that the value of the measured tension is below a product of a factor X and the potential new value of the zero offset where the factor X is bigger than 1. If the value of the measured tension is bigger than the product of the factor X and the potential new value of the zero offset, an original value of the zero offset is determined as the value of the zero offset.
For verifying that the value of the measured tension is around the potential new value of the zero offset, it is verified that the value of the measured tension is bigger as a product of a factor Y and the potential new value of the zero offset where the factor Y is below 1. If the value of the measured tension is below the product of the factor Y and the potential new value of the zero offset, an alarm signal is created.
A yarn feeder for feeding a yarn to a textile machine comprises a yarn delivering wheel for delivering the yarn, driving means for driving the yarn delivering wheel, a tension sensor for measuring the yarn tension which is arranged between the yarn delivering wheel and the textile machine and a control device for controlling the yarn tension by controlling the driving means depending on the measured tension and a reference tension.
A resetting unit for determining a new value of a zero offset of the yarn tension, is integrated in a start-up unit of the control device. The resetting unit is designed for determining a new value of the zero offset in a stop situation at the beginning of a start-up procedure. The resetting unit comprises a determination item for determining a potential new value of the zero offset and an verification item for verification the potential new value of the zero offset by analysing the values T of the measured tension during slowly moving back the yarn delivering wheel.
The verification item comprises, for n steps, a motor control partition for moving the yarn delivering wheel in a backward movement for an angle, and an analysis partition for verifying that the value of the measured tension is around the potential new value of the zero offset and for a last step, a determination partition for determining the potential new value of the zero offset as the new value of the zero offset.
Further details of the invention will emerge from the ensuing description of one embodiment of the invention. The embodiment is shown in the schematic drawings in which:

Figure 1 shows a schematic perspective view of a yarn feeder of the embodiment wherein some housing parts are omitted;
Figure 2 shows a block diagram of the yarn feeder;
Figure 3 shows a flow diagram; and
Figure 4a to 4f show curves of values of the yarn tension depending on time.
Figures 1 and 2 show a yarn feeder 1 for feeding a yarn 2, e. g. from a bobbin 3 to a textile machine 4. The textile machine 4 is e.g. a knitting machine. The yarn feeder 1 is provided with housings with a front plate 5 and a back shell 6. The yarn feeder 1 comprises a yarn delivering wheel 7 for delivering the yarn 2 and driving means, namely an electric motor 8, for driving the yarn delivering wheel 7.

The yarn delivering wheel 7 is arranged on the front plate 5. The electric motor 8 is arranged in the back shell 6 wherein its axles 9 projects through the front plate 5. The yarn delivering wheel 7 is fixed to that axle 9 of the electric motor 8. In figure 1, a part of the back shell 6 is omitted in order to show the electric motor 8.
The yarn feeder 1 comprises a yarn tension sensor 10 for measuring the yarn tension which is arranged between the yarn delivering wheel 7 and the textile machine 4.
The yarn tension sensor 10 comprises, arranged in the direction A of the yarn course in normal operation, an inlet guide element 11, a feeler element 12 and an outlet guide eye 13. It also comprises measuring means, e.g. a measuring circuit on a sensor circuit board 14, for providing values T of the measured yarn tension. Figure 1 only shows a small part of a support element 15 of the yarn tension sensor 10. The main part of the support element 15 is omitted in order to show the elements 11, 12, 13.
The yarn feeder 1 comprises a control device 20 for controlling the yarn tension by controlling the driving means depending on the measured tension and a reference tension. The value of the reference tension is named as Tref.
The control device 20 is, at least in parts, incorporated e.g. in circuits on at least one main circuit board 21 which is arranged under the front plate 5. The axle 9 of the electric motor 8 also projects through the main circuit board 21.
The control device 20 comprises a tension control unit 22 and a motor activation unit 23. The tension control unit 22 is designed for determining a signal S depending on the measured tension and a reference tension. The motor activation unit 23 is designed for controlling the driving elements, i.e. the electric motor 8, in accordance with that signal S by determining a motor signal M.
The control device 20 comprises a start-up unit 24.The start-up unit 24 is designed for a start-up procedure of the yarn feeder 1.
The control device 20 comprises at least one microprocessor as a part of its circuits. The units of the control device 20, i.e. the tension control unit 22, the motor activation unit 23 and the start-up unit 24, are developed as circuits or as software (computer programs) or as combination of circuits and software.
The start-up unit 24 comprises a resetting unit for determining a new value of a zero offset of the yarn tension at the beginning of the start-up procedure.
Figure 3 show a flow diagram of one example of a method for determining a new value of the zero offset using the exemplary resetting unit.
The resetting unit comprises a determination item for determining a potential new value T*(B) of the zero offset and a verification item for verifying the potential new value T*(B) by analysing the measured values during slowly moving back the yarn delivering wheel 7.
The determination item comprises a start partition 30, a reset partition 31 for resetting a number n of steps to zero: n = 0 and a determination partition 32 for determining the value T(0) of the measured tension.
The verification item comprises a loop start partition 40 for counting steps: n = n+1, a motor control partition 41 for stepwise moving back the yarn delivering wheel 7, a measuring partition 42 for measuring the value T(n) of the yarn tension, an analysis partition with an upper limit section 43 and a lower limit section 44 for verifying that the value T(n) of the measured tension is around the potential new value T*(B), a loop end partition 45 for recognising the last step n-max, a determination partition 46 for determining the potential new value T*(B) as a new value T(B) of the zero offset and an end partition 47.
The verification further comprises an exit partition 48 for the case that the value T(n) exceeds the upper limit, followed be an end partition 49, and a stop partition 50 for the case that the value T(n) decreases the lower limit followed by an end partition 51.
Figure 4a to 4f show curves of values T or filtered values of the tension depending on the time t.
Figure 4a shows a curve of values T of the measured tension while controlling to a value Tref of a reference tension and Figure 4b a curve of values T which are filtered from the values T of figure 4a.
Figure 4c shows a curve of increasing values T of the measured tension e.g. due to a drift and Figure 4d a curve of values T which are filtered from the values of figure 4c.
Figure 4e shows a curve of values T of the measured tension during determining a new value T (B) of the zero offset wherein during the time t, the yarn delivering wheel 7 is slowly moved back and Figure 4f a curve of values T which are filtered from the values T of figure 4e. In Figure 4f the angle n-max x α of n-max steps is marked. It shows that the values T of the measured tension increase when the yarn delivering wheel 7 is further moved back. In an alternative, this feature is used to determine the position of the zero offset of the yarn delivering wheel 7.
In operation, feeding the yarn 2 from the yarn feeder 1 to the textile machine 4 is controlled. The yarn 2 is delivered from the yarn delivering wheel 7 of the yarn feeder 1. The yarn delivering wheel 7 is driven by driving means, i.e. the electric motor 8. The yarn tension is measured by the yarn tension sensor 10 which is arranged between the yarn delivering wheel 7 and the textile machine 8. The yarn tension is controlled by the control device 20 controlling the driving means, i.e. the electric motor 8, depending on the measured tension and a reference tension. A new value T(B) of a zero offset of the yarn tension is determined wherein the yarn 2 is present at the tension sensor 10.
In particular, the new value T(B) of a zero offset of the yarn tension is determined in a stop situation at the beginning of a start-up procedure. At first, a potential new value T*(B) of the zero offset is determined. Then, the potential new value T*(B) is verified by analysing the measured values during slowly moving back the yarn delivering wheel (7).
For determining the potential new value T*(B) of the zero offset, a current value T(0) of measured yarn tension is determined.
At the reset partition 31, a counting number n is reset to zero: n = 0. If applicable, an original value T(A) of the zero offset and a last used value T(B) of the zero offset are provided, e.g. read from an internal memory of the control device 20.
At the determination partition 32, values T of the measured tension are read. A current value T(0) is identified, e. g. as an average value of the last e.g. 128 values T of the measured tension. The current value T(0) is verified that it is around the last used value T(B), i.e. that it is in a range about the this value T(B). If the actual value T(0) is not in such a range the yarn may be already tensioned. As a consequence, a determination of the value of the zero offset is not possible. In this case, the control device 20 switches to normal operation. If the actual value T(0) is approved a potential new value T*(B) is calculated. E.g. T(0) is used as the potential new value T*(B).
Verification of the potential new value T*(B) is executed in a loop with n steps. At the loop start partition 40, the n steps are counted from 1 to n-max. At the motor control partition 41, the yarn delivering wheel (7) is moved in a slow backward movement for an angle α in each step. The sum of all angles α, i.e. n-max x α, amounts 2 to 120°, depending on the quality of the yarn, where the diameter of the yarn delivering wheel is about 6 cm.
At the measuring partition 42, the value T(n) of the measured tension is read.
At the analysis partition, it is verified that the value T(n) is around the potential new value T*(B).
At the upper limit section 43, it is verified that the value T(n) is below a product of a factor X and the potential new value T*(B) where the factor X is bigger than 1. The factor X amounts 1,1 to 1,8, preferably 1,2 to 1,4.
If that the value T(n) exceeds the a.m. product, i.e. if $T (n) > X \times T * (B),$
the yarn is pre-tensioned and the potential new value T*(B) is not a valid value of a zero offset. The exit partition 48 is executed. In the exit partition 48, the original value T(A) of the zero offset is determined as value T(B) of the zero offset. The resetting procedure ends at the end partition 49.
At the lower limit section 44, it is verified that the value T(n) is bigger as a product of a factor Y and the potential new value T*(B) where the factor Y is below 1. The factor Y amounts 0,5 to 0.9, preferably 0,6 to 0,8.
If that the value T(n) falls below the a.m. product, i.e. if $T (n) < Y \times T * (B),$
the yarn tension drop after back movement for yarn brake reason. The resetting procedure and the whole start-up procedure must be stopped. The stop partition 50 is executed. In the stop partition 50, an alarm signal, e.g. a stop signal, is created. The stop signal is sent e.g. to the textile machine 4. The resetting procedure ends at end partition 51.
At the loop end partition 45, a last step n-max is recognised.
At the final determining partition 46, the potential new value T*(B) is determined as new zero offset value T(B). At the end partition 47, the resetting procedure ends.

Reference signs:

1: yarn feeder
2: yarn
3: bobbin
4: textile machine
5: front plate
6: back shell
7: yarn delivering wheel
8: electric motor
9: axle
10: yarn tension sensor
11: inlet guide element
12: feeler element
13: guide eye
14: sensor circuit board
15: support element
20: control device
21: main circuit board
22: tension control unit
23: motor activation unit
24: start-up unit
30: start partition
31: reset partition
32: determination partition
40: loop start partition
41: motor control partition
42: measuring partition
43: upper limit section
44: lower limit section
45: loop end partition
46: determination partition
47: end partition
48: exit partition
49: end partition
50: stop partition
51: end partition

Claims

Method to control feeding a yarn (2) from a yarn feeder (1) to a textile machine (4),
wherein the yarn (2) is delivered from a yarn delivering wheel (7) of the yarn feeder (1) which is driven by driving means,

wherein a yarn tension is measured by a yarn tension sensor (10) which is arranged between the yarn delivering wheel (7) and the textile machine (4),

wherein the yarn tension is controlled by a control device (20) controlling the driving means depending on the measured tension and a reference tension, and
wherein the determination of a new value T(B) of zero offset is executed in a stop situation at the beginning of a start-up procedure,
characterized in that,
a new value T(B) of a zero offset of the yarn tension is determined by a resetting unit wherein the yarn (2) is present at the yarn tension sensor (10),

wherein at first, a potential new value T*(B) of the zero offset is determined and then, the potential new value T*(B) is verified as new value T(B) of the zero offset by analysing the values T of the measured tension during slowly moving back the yarn delivering wheel (7).
Method according to claim 1, characterized in that
determining the potential new value T*(B) of the zero offset comprises

determining a current value T(0) of the measured tension,

verifying that the current value T(0) is around a last used value T(B) of the zero offset, and calculating the potential new value T*(B) of the zero offset.
Method according to claim 1 or claim 2, characterized in that
verifying the potential new value T*(B) of the zero offset comprises,

at each of n steps (n),

moving the yarn delivering wheel (7) in a backward movement for an angle (α),

measuring the value T(n) of the yarn tension, and

verifying that the value T(n) is around the potential new value T*(B); and,

at a last step (n-max),

determining the potential new value T*(B) as new value T(B) of the zero offset.
Method according to claim 3 characterized in that
verifying that the value T(n) is around the potential new value T*(B) of the zero offset comprises verifying that the value T(n) is below a product of a factor X and the potential new value T*(B) of the zero offset where the factor X is bigger than 1.
Method according to claim 4 characterized in that,
if the value T(n) is bigger than the product of the factor X and potential new value T*(B) of the zero offset, an original value T(A) of the zero offset is determined as the value T(B) of the zero offset.
Method according to one of the claims 3 to 5 characterized in that
verifying that the value T(n) is around the potential new value T*(B) of the zero offset comprises verifying that the value T(n) is bigger as a product of a factor Y and the potential new value T*(B) of the zero offset where the factor Y is below 1.
Method according to claim 6 characterized in that,
if the value T(n) is below the product of the factor Y and the potential new value T*(B) of the zero offset, an alarm signal is created.
A yarn feeder (1) for feeding a yarn (2) to a textile machine (4), comprising
a yarn delivering wheel (7) for delivering the yarn (2),

driving means for driving the yarn delivering wheel (7),

a yarn tension sensor (10) for measuring the yarn tension which is arranged between the yarn delivering wheel (7) and the textile machine (4) and

a control device (20) for controlling the yarn tension by controlling the driving means depending on the measured tension and a reference tension, and

resetting unit for determining a new value of a zero offset of the yarn tension, wherein the resetting unit is integrated in a start-up unit (24) of the control device (20) wherein the resetting unit is designed for determining a new value T(B) of zero offset in a stop situation at the beginning of a start-up procedure and

wherein the resetting unit comprises a determination item for determining a potential new value T*(B) of the zero offset,
characterized in that
the resetting unit further comprises a verification item for verification the potential new value T*(B) of the zero offset by analysing the measured values T during slowly moving back the yarn delivering wheel (7).
A yarn feeder (1) according to claim 8, characterized in that,
the verification item comprises,

for n steps (n),

a motor control partition (41) for moving the yarn delivering wheel (7) in a backward movement for an angle (α), and

an analysis partition for verifying that the value T(n) of the measured tension is around the potential new value T*(B) of the zero offset and

for a last step (n-max)

a determination partition (46) for determining the potential new value T*(B) as the new value T(B) of the zero offset.