EP2546401B1

EP2546401B1 - Method of and device for controlling fabric take-up in electronic pattern knitting machine

Info

Publication number: EP2546401B1
Application number: EP12175937.7A
Authority: EP
Inventors: Yoshihiro Aramaki; Ken Shimosakoda
Original assignee: Precision Fukuhara Works Ltd
Current assignee: Precision Fukuhara Works Ltd
Priority date: 2011-07-13
Filing date: 2012-07-11
Publication date: 2016-03-09
Anticipated expiration: 2032-07-11
Also published as: TW201319348A; TWI604099B; CN102877208B; CN102877208A; EP2546401A1; JP2013019082A

Description

BACKGROUND OF THE INVENTION

(Field of the Invention)

The present invention relates to a method of and a device for controlling the take-up of a knitted fabric in an electronic pattern knitting machine such as, for example, a circular knitting machine of a kind having an electronic needle selecting function, both of which are used for controlling the take-up of a tubular knitted fabric having been knitted in accordance with the knitting condition including a pattern setting in the knitted fabric.

(Description of Related Art)

The circular knitting machine of the kind having the electronic needle selecting function generally includes a knitting unit for knitting a tubular fabric by a revolving cylinder having needle grooves in which knitting needles are accommodated, by means of the drive of a motor in accordance with the knitting condition including a pattern setting in the knitted fabric, and then supplying a yarn to each of the knitting needles, and a take-up mechanism for take-up the tubular fabric so knitted by the knitting unit. In recent years, however, consequent upon the diversification of yarns and patterns to be formed in the fabric and the sophistication of the quality level, a servo motor of a kind capable of being controlled accurately and at high speed is frequently employed for driving take-up rollers employed in the take-up mechanism. In such case, a take-up control unit performs a control of take-up of the fabric by applying a command, synchronized with the operating speed of the knitting machine and is known to make use of a speed control mode, a position control mode and a torque control mode of the servo motor.
In take-up of the knitted fabric in the circular knitting machine, unless the take-up tension is constant, an uneven take-up will occur, which leads to a defective product. Also, in the case of a large take-up in which the take-up diameter of a roll of cloth tends to become large, the take-up tension acting on the fabric tends to vary because the weight of the roll of cloth at the start of take-up of the roll of cloth and that at the end of the roll of cloth differ considerably from each other.
It has been known that in the conventional take-up control, where the torque control of the torque (servo) motor is utilized in the take-up of the knitted fabric in the knitting machine, an automatic torque adjustment is carried out by setting an output torque of the motor to a certain value so that, even when the amount of production of the knitted fabrics changes the torque motor can be controlled so as to maintain the take-up tension at the certain value.
On the other hand, it has been also known that where the position control of the servo motor is utilized in controlling the take-up, the take-up of the knitted fabric is performed under a constant take-up tension by applying beforehand the amount of production of the knitted fabrics, which is the angle of rotation of the servo motor per one complete rotation of the knitting machine, that is, the movement amount data (position control data) per 1 pulse in the number of command pulses to be applied to the servo motor, to a servo motor driver each time the pattern of the knitted fabric is changed.
It has yet been known that in the conventional take-up control, a series of works of measuring the amount of production is measured while the take-up of the knitted fabric is performed under the take-up tension set by the utilization of the torque control mode at first and then switching over to the position control mode that is set to such amount of production. In this respect, see the patent document 1 listed below. In the event of the change in pattern of the knitted fabric, this mode switching is manually carried out to acquire the movement amount data under a proper take-up tension.

[Prior Art Literature]

[Patent Document 1] JP Laid-open Patent Publication No. 2010-285700 (Family member: EP 2261407 )
[Patent Document 2] Japanese Patent No. 2733760

DISCLOSURE OF THE INVENTION

In the meantime, it often occurs that in the practice of the conventional position control of the servo motor, after a fabric having a predetermined pattern for production purpose has been manufactured by the use of the position control of the take-up servo motor, a fabric having a different pattern in place of the predetermined pattern is manufactured. In such case, nothing can be comprehended unless measurement is made after the pattern has been actually knitted if it be a change to a new pattern. Also, it also often occurs that in the event of occurrence of any trouble in the machine in connection with the pattern being produced such pattern has to be changed to a pattern for test purpose that is suited for a machine adjustment required to remove the trouble. In such case, since the amount of production of knitted fabrics differs for each pattern in the knitted fabric, there has been such a problem that a secondary trouble occurs, in which due to the problem that the take-up tension of the knitted fabric increases or decreases abnormally the knitted fabric may be torn or knocked up. In order to alleviate such problem, it is necessary to find out and set the movement amount data per one pulse of the command pulse number to be applied to the servo motor so as to realize a proper take-up tension each time the pattern is changed, but this setting is complicated and, therefore, automation of the take-up control has been difficult to achieve.
Also, since the torque control of the servo motor takes advantage of the proportional relation between the output torque of the servo motor and the take-up tension although when the servo motor is driven with a certain force the take-up tension within a certain range can be obtained, the proportional relation between the output torque and the take-up tension may change by the effect of a mechanical change in a load such as, for example, gears and/or rollers in the take-up mechanism and/or in roll diameter of the cloth to such an extent that the take-up tension will eventually change even for the same output torque, and, accordingly, the torque control referred to above cannot be necessarily regarded as a take-up control under a stabilized take-up tension. In such case, a method is known, in which a change in weight of the roll is detected during the take-up process and the torque motor is controlled so as to gradually increase the torque according to such change to thereby accomplish an automatic torque control. In this respect, see the patent document 2 listed below. It has, however, been found that such known method requires an addition of a detecting circuit for detecting the change in roll weight.
In view of the foregoing, the present invention has been devised to substantially eliminate the problems and inconveniences inherent in the above discussed prior art counterparts and is intended to provide a take-up control method and a take-up control device both for use in an electronic pattern knitting machine, which are effective to perform an automatic take-up of the knitted fabric under a proper, and stabilized take-up tension even though the pattern of the knitted fabric is changed.
In order to accomplish the foregoing object of the present invention, there is provided a take-up control method and a take-up control device in an electronic pattern knitting machine, in which by means of a take-up mechanism including take-up rollers and a take-up servo motor for roller driving purpose, a tubular fabric knitted by a knitting unit in accordance with the knitting condition including a pattern setting for the knitted fabric; the take-up mechanism referred to above is controlled by a take-up control unit; the take-up control unit is so designed as to set a control mode of the take-up servo motor to one of a plurality of modes including a torque control mode, in which the take-up servo motor is driven so that the take-up tension of the fabric attains a certain value, and a position control mode in which the take-up servo motor is driven at a certain angle of rotation relative to the rotation of the knitting unit, namely at a certain rotation amount relative to, or in conformity with, the rotation amount of the knitting unit; the position control mode is automatically shifted to the torque control mode, when after the knitted fabric having a first pattern has been produced under the position control mode the first pattern is changed to a second pattern, to allow the knitted fabric having the second pattern then changed under the torque control mode to be automatically performed.
According to the present invention, since after the knitted fabric having the first pattern has been produced under the position control mode, at the time of change to the second pattern, the position control mode is automatically switched over to the torque control mode, since the take-up tension of the knitted fabric under the torque control mode becomes constant, the take-up of the knitted fabric can be automatically performed under the proper and stabilized take-up tension even though the production amount of the knitted fabric changes consequent upon the change of the pattern of the knitted fabric.
In a preferred embodiment of the present invention, by means of the take-up control unit, in the event that the pattern of the knitted fabric once changed from the first pattern to the second pattern is returned to the initial first pattern, the torque control mode at the time the change has been made to the second pattern is switched over to the position control mode at the time the first pattern is being produced, so that the take-up of the knitted fabric having the initial first pattern so changed is performed under the position control mode. Accordingly, when the change is made to the initial first pattern after the pattern of the knitted fabric has been changed to the second pattern, the take-up of the knitted fabric can be automatically performed under the proper and stabilized take-up tension under the position control mode when the change is made to the first pattern after the pattern of the knitted fabric has been changed to the second pattern.
In another preferred embodiment of the present invention, the first pattern is a pattern for production purpose and the second pattern is a pattern for test purpose or a different pattern for production purpose. Accordingly, not only in the case where the pattern of the knitted fabric is changed between the patterns for production purpose, but also in the case where it is changed to the pattern for test purpose for the purpose of resolving a trouble, the take-up of the knitted fabric can be automatically performed under the proper and stabilized take-up tension.
In a further preferred embodiment of the present invention, an automatic mode is set by means of the take-up control unit, when the pattern of the knitted fabric is switched from the first pattern over to the second pattern and, as a result of the setting of the automatic mode, a change is made from the position control mode at the time of production of the first pattern to the torque control mode at the time the change is made to the second pattern, while the take-up of the knitted fabric having the second pattern is performed until a take-up state become stabilized under the torque control mode, position control data, which is the production amount of the knitted fabric under the torque control mode in such stabilized state are measured, and the knitted fabric having the second pattern so changed is would up by changing to the position control mode utilizing the measured position control data. Accordingly, even though in addition to the change of the pattern of the knitted fabric the change occurs in roll diameter of the cloth and/or in mechanical load, the constant take-up tension can be automatically maintained and the take-up of the knitted fabric can be performed further stably.
In a still further preferred embodiment of the present invention, the torque control mode set by the take-up control unit is set to the measured output torque value when the change is made from the first pattern to the second pattern, with an output torque under the position control mode at the time the first pattern being produced measured. Accordingly, even when the state, in which the relation between the output torque and the take-up tension changes, occurs at the time of change of the pattern of the knitted fabric, the take-up of the knitted fabric can be properly performed under the torque control mode by the utilization of the output torque required to realize the required take-up tension.
Any combination of at least two constructions, disclosed in the appended claims in combination with the specification and/or the accompanying drawings should be construed as included within the scope of the present invention. In particular, any combination of two or more of the appended claims should be equally construed as included within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will -become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:

Fig. 1 is a schematic front elevational view of the whole of an electronic pattern knitting machine such as, for example, a circular knitting machine equipped with a take-up control device, designed in accordance with the present invention, and having an electronic needle selecting function;
Fig. 2 is a block diagram showing the take-up control device in the electronic pattern knitting machine according to a preferred embodiment of the present invention;
Fig. 3 is a flowchart showing one example of the sequence of operation of the take-up control device in the electronic pattern knitting machine shown in Fig. 2;
Fig. 4 is a flowchart showing another example of the sequence of operation of the take-up control device in the electronic pattern knitting machine shown in Fig. 2;
Fig. 5 is a flowchart showing a third example of the sequence of operation of the take-up control device in the electronic pattern knitting machine shown in Fig. 2; and
Fig. 6 is a flowchart showing a fourth example of the sequence of operation of the take-up control device in the electronic pattern knitting machine shown in Fig. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will be described in detail with particular reference to the accompanying drawings. Fig. 1 illustrates, in a schematic front elevational view, an electronic pattern knitting machine such as, for example, a circular knitting machine.
As shown in Fig. 1, the circular knitting machine 1 includes a knitting unit 2 for knitting a tubular knitted fabric and a take-up mechanism 3 for take-up of a tubular knitted fabric, which has been knitted, and a take-up control unit 6 for controlling the take-up mechanism 3. A knitting machine control panel 20 for performing data input to the circular knitting machine 1 and various displays is provided on a circular knitting machine side inclusive of the knitting unit 2.
Referring to Fig. 1, the knitting unit 2 is disposed above a machine bed 22 supported by a plurality of support legs 21. The machine bed 22 has a plurality of support posts 24 mounted thereon so as to extend substantially vertically, and a horizontal member 25 is fixed to tops of those support posts by means of respective connecting members. A plurality of yarn feed units 9 are supported by the horizontal member 25. The take-up mechanism 3 including take-up rollers 4 for take-up of a knitted fabric, which has been knitted, and a take-up servo motor 5 for roller driving purpose is disposed beneath the bed 22.
The knitting machine control panel 20 and an entire control unit 8 for controlling the circular knitting machine 1 in its entirety is provided at a location on a lower left side of the bed 22. The entire control unit 8 includes a knitting condition setting unit 16 for setting a knitting condition of the knitting machine (cylinder) and the knitting condition setting unit 16 includes a pattern setting unit 17 for setting a pattern to be formed in the knitted fabric as shown in Fig. 2. Change of the pattern of the knitted fabric is generally carried out by manually providing the pattern setting unit 17 with an input.
The knitting unit 2 best shown in Fig. 1 is operable according to a knitting condition, including a pattern setting for a knitted fabric, to cause the knitting machine (cylinder), having a plurality of knitting needles slidably accommodated in respective needle grooves, which is not shown, to be driven by means of a main motor 7, to pile up knitted loops helically by supplying yarns from the yarn feed units 9 to the knitting needles and to form a tubular knitted fabric. The main motor 7 for rotating the knitting machine (cylinder) is controlled by the entire control unit 8 so as to be driven at a predetermined number of rotations by means of the frequency control by, for example, an inverter.
Fig. 2 illustrates a block diagram showing the sequence of operation of the take-up control unit 6. The take-up control unit 6 includes a take-up servo driver 10 provided in the take-up mechanism 3 shown in Fig. 1, a control mode setting unit 11 included in a data processing and setting unit 13 provided in the entire control unit 8, and a machine rotation detecting unit (rotary encoder) 12 provided in the take-up mechanism 3, shown in Fig. 1 (the cylinder and the take-up mechanism 3 being connected together), and operable to detect the number of rotations of the cylinder by the main motor 7.
The take-up servo driver 10 performs a PWM control by providing the take-up servo motor 5 with, for example, a PWM control output (shown by c) and controls the angle of rotation of the take-up servo motor 5 by applying an output pulse number of a command pulse synchronized with the angle of rotations of the cylinder (a machine rotation detection signal shown by g) caused by the main motor 7 inputted from the machine rotation detecting unit 12. Although not shown, the take-up servo driver 10 includes, in addition to a motor control and PWM control output unit and a machine rotation detection signal input unit, a serial communication unit with the data processing and setting unit 13, a feed-back current detecting unit between take-up servo drivers 5 as will be detailed later, and a motor rotation angle input unit.
The control mode setting unit 11 shown in Fig. 2 is operable to set the control mode of the take-up servo motor 5 to one of a torque control mode, a position control mode and an automatic mode (shown by e), based on the change of the pattern of the knitted fabric from the pattern setting unit 17 of the knitting condition setting unit 16. The change of the pattern of the knitted fabric includes a change from a pattern for production purpose, which is a first pattern, to a second pattern, a pattern for test purpose, which is a second pattern, or a different pattern for production purpose, and a change from the pattern for test purpose or the different pattern for production purpose to the initial pattern for production purpose. The pattern for test purpose is used as a pattern appropriate for machine adjustment in order to resolve a trouble in the event that any machine trouble occurs in connection with the pattern being produced.
The torque control mode referred to above is a mode in which a control is made to drive the take-up servo motor 5, best shown in Fig. 2, so that an output torque is constant. Since under this torque control, the torque control takes advantage of the proportional relation between the output torque of the motor and the take-up tension as hereinbefore described, the take-up tension within a certain range can be obtained. However, it may occur that the proportional relation referred to above may change under the influence of a change in roll diameter of the cloth and/or a change in mechanical load of the gears and/or rollers of the take-up mechanism with the take-up tension consequently changed even for the same output torque.
The position control mode referred to above is a mode in which a control is made to drive the take-up servo motor 5, best shown in Fig. 2, at a certain angle of rotation (a motor rotation signal shown by b) relative to the knitting machine. Since under this position control a highly accurate rotational angle control of the take-up servo motor 5 is carried out while the constant take-up tension is maintained, nothing is affected by the change in mechanical load such as, for example, the gears and/or rollers of the take-up mechanism 3 in contrast to the torque control discussed above and, therefore, the take-up of the same amount of production of the knitted fabric can be performed at all times and the take-up can be accomplished at a stabilized take-up tension. However, no follow-up take-up such as the torque control cannot be performed in the event - that the amount of production of the knitted fabric changes during the operation of the device as hereinbefore described. In the present invention, in changing the pattern of the knitted fabric, attention has been focused on advantages of the position control mode and the torque control mode so that the take-up control for automatically take-up of the knitted fabric at a proper and stabilized take-up tension can be achieved.
The control mode setting unit 11 referred to above is switched over from the position control mode when the knitted fabric having the pattern for production purpose is being produced and, in the event of the setting of the torque control mode when the change is made to the pattern for test purpose or the different pattern for production purpose, the torque control mode, for example, in which a predefined torque value is set with respect to the pattern for test purpose or the different pattern for production purpose is utilized. Alternatively, the output torque during the position control mode when the knitted pattern having the pattern for production purpose is being produced is measured and, at the time of the switching over to the torque mode, the torque control mode which is set to the output torque value so measured is utilized.
In the event of the setting of the position control mode having been switched over from the torque control mode, while the take-up of the knitted fabric having the second pattern is performed until the take-up state is stabilized, for example, under the position control mode set to the production amount (position control data) of the knitted fabric having, the initial pattern or under the torque control mode, the position control data, which is the production amount of the knitted fabric under the torque control mode in that stabilized state is measured and the position control mode set to the position control data so measured is utilized.
In the event of the setting of the automatic mode having been switched over from the position control mode, this automatic mode is the one including the torque control mode and the position control mode and, when the position control mode when the knitted fabric having the pattern for production purpose is being produced is switched over to the torque control mode consequent upon the change of the pattern for test purpose to the different pattern for production purpose, while the take-up of the knitted fabric having the pattern for test purpose or the different pattern for production purpose of the production purpose is performed until the take-up state under the torque control mode is stabilized, the position control data, which is the knitted fabric production amount under the torque control mode in that stabilized condition is measured and is shifted to the position control mode utilizing the measured position control data. The data processing and setting unit 13 shown in Fig. 2 is operable to process and set data on the knitting machine and the entire take-up unit and includes, in addition to the control mode setting unit 11, a data acquiring unit 14 and a stabilization determining unit 15.
The data acquiring unit 14 is operable to acquire the angle of rotation (the motor rotational angle shown by d) per one rotation of the knitting machine of the take-up servo motor 5 from the take-up servo driver 10 to thereby perform a process of acquiring a predetermined number of the production amount data, which is the rotational angle of the take-up servo motor 5 per one rotation of the knitting machine in the knitted fabric. This production amount data is represented by the movement amount data (position control data) per one pulse in the output pulse number of the command pulse to the take-up servo motor 5 synchronized with the angle of rotation of the cylinder by the main motor 7 referred to previously.
Also, when the control mode setting unit 11 referred to previously is switched over to the torque control mode at the time of the change of the pattern as a result that, while the knitted fabric having the pattern for production purpose is being produced under the position control mode, the output torque under such position control mode is measured, in the event of setting to the torque control mode of the output torque value so measured, the data acquiring unit 14 is at first in a take-up state under the position control mode and the take-up servo driver 10 acquires and stores the output torque value (output torque value shown by h) for, for example, 1 second from the take-up servo motor 5. Subsequently, when the pattern is changed and, hence, the mode is switched over from the position control mode to the torque control mode, the take-up tension of the knitted fabric can be maintained at the same value as that before the pattern is changed, by setting the average value of the output torque values stored as a torque command value. By way of example, the torque values during t second before the change of the pattern are stored and, when 1 < t/2 < t seconds, a process takes place in which the average value of the output torque values during a period ranging from t/2 to t second before the change of the pattern is set as the torque command value at the time of change of the pattern. The reason that the output torque value immediately before the machine halt (1 to t/2 second before the change of the pattern) is not used is because, in the event of the halt of the machine as a result of the knitted fabric being perforated incident to occurrence of a trouble such as, for example, breakage of the yarns, the tension of the knitted fabric changes in the presence of those perforations, accompanied by the change of the torque value, and, therefore, the output torque value immediately before the machine halt will become a value departing from the tendency that has persisted.
The stabilization determining unit 15 referred to above is operable to perform such a process that when during the take-up state under the torque control mode the production data of a predetermined number of knitted fabrics, that is, the movement amount data per 1 pulse of the command pulse number to the take-up servo motor 5 converges within a predetermined range, the take-up state referred to can be determined as stabilized. For example, when 10 movement amount data for one complete rotation of knitting machine converges within ±1 % of the average value thereof, the take-up state is determined as stabilized.
The data processing and setting unit 13 is operable, for example, to automatically set (as shown by f) the movement amount data, which is the production data of the knitted fabric, and a current data of the take-up servo motor 5, apply it to the take-up servo driver 10 and switch over from the torque control mode to the position control mode.
In this way, the data processing and setting unit 13 performs the automatic setting (shown by f) of the production amount data by accomplishing a mode setting (shown by e) of the torque control mode, the position control mode and the automatic mode to the take-up servo driver 10. The take-up servo driver 10 performs the motor control (shown by c) by means of the electric current of the take-up servo motor 5, which is required to achieve a proper take-up tension under the torque control mode, and the movement amount data (position control data) of the take-up servo motor 5, which is automatically set under the position control mode, and the electric current of the take-up servo motor 5, by performing the PWM control output to the take-up servo motor 5.
Hereinafter, the operation of the take-up control device for the electronic pattern knitting machine 1 of the structure hereinabove described will be described. Fig. 3 illustrates the flowchart showing a first example of the sequence of operation of the take-up control device for the electronic pattern knitting machine 1. At the outset, when at step S1 the knitted fabric having the pattern for production purpose (the first pattern) is being produced under the position control mode, and due to the occurrence of some mechanical trouble, decision is made at step S2 to determine if a change is made from the pattern for production purpose to the pattern for test purpose (the second pattern) that is suited for the machine adjustment. In the event that the pattern for production purpose is switched to the pattern for test purpose as determined at step S2, the operation is caused at step S3 to work under the torque control mode that has been set to the designated torque value with respect to the pattern for test purpose, followed by the return of the program flow to step S2 if no change is made from the pattern for production purpose to the pattern for test purpose. The designated torque value referred to above is a value stipulated beforehand in dependence on the change of the roll diameter of the cloth and/or the change in mechanical load such as gears and/or rollers of the take-up mechanism in the case of the pattern for test purpose. Even when no change occur from the pattern for production purpose to the pattern for test purpose, the program flow goes to step S2.
In this way, when the change is made from the pattern for production purpose to the pattern for test purpose, the take-up tension of the knitted fabric under the torque control mode becomes constant, and, therefore, even though the pattern of the knitted fabric is changed, the take-up of the knitted fabric can be automatically performed under a proper take-up tension in correspondence with the change of the pattern of the knitted fabric. It is to be noted that although in the first example discussed above, the pattern of the knitted fabric has been described as switched over from the pattern for production purpose to the pattern for test purpose, the change may be made from the pattern for production purpose to the different pattern for production purpose.
Fig. 4 illustrates the flowchart showing the second example of the sequence of operation of the take-up control device for the electronic pattern knitting machine. At the outset, as is the case with the first example, when the pattern for production purpose is being produced under the position control mode at step T1; decision then is made at step T2 to determine if the pattern for production purpose is changed to the pattern for test purpose; in the event that the pattern for production purpose is changed to the pattern for test purpose as determined at step T2, the operation is caused at step T3 to work under the torque control mode that has been set to the designated torque value with respect to the pattern for test purpose, followed by the return of the program flow to step T2 if no change is made from the pattern for production purpose to the pattern for test purpose. Subsequently, in order to reopen the production after the mechanical trouble has been resolved as a result of the machine adjustment with the pattern for test purpose, decision is made at step T4 to determine if the pattern for test purpose is changed to the initial pattern for production purpose. In the event that the decision at step T4 indicates that the pattern for test purpose has been changed to the initial pattern for production purpose, the operation is caused at step T5 to work under the position control mode with respect to the initial pattern for production purpose, followed by the return of the program flow to step T2. Should the pattern for test purpose have not been changed to the initial pattern for production purpose as determined at step T5, the program flow goes to step T4.
In this way, when the pattern of the knitted fabric, which has been once changed to the pattern for test purpose, is returned to the initial patter for production purpose, the take-up of the knitted fabric can be automatically performed under the position control mode with a proper and stabilized take-up tension. It is to be noted that as is the case with the previously described first example, in place of the change from the pattern for production purpose to the pattern for test purpose, the change may be made from the pattern for production purpose to the different pattern for production.
Fig. 5 illustrates the flowchart showing a third example of the sequence of operation of the take-up control device for the electronic pattern knitting machine. At the outset, when the pattern for production purpose is being produced under the position control mode at step P1; the output torque during the operation of the machine under this position control mode is measured at step P2. This output torque is the one that depends on the change in roll diameter of the cloth or the change in machine load, and, even though the pattern of the knitted fabric is changed, only the production amount of the knitted fabric changes and no output torque itself change after the change of the pattern.
Subsequently, decision is made at step P3 to determine if the pattern for production purpose is changed to the different pattern for production purpose. In the event that the pattern for production purpose is changed to the different pattern for test purpose as determined at step P3, the operation is caused at step P4 to work under the automatic mode, followed by the return of the program flow to P2. Even when no change occur from the pattern for production purpose to the different pattern for production purpose, the program flow goes to step P2.
During the automatic mode at step P4, the operation takes place at first under the torque control mode which has been set by the output torque value measured at step P2 and the take-up of the knitted fabric is performed until the take-up tension becomes stabilized at step P4-1. Here, the stabilization of the take-up tension is determined by whether or not the average value thereof is converged within the predetermined range, after a predetermined number of the production amount per one complete rotation of the knitting machine during the take-up under the torque control mode, that is, the movement amount data (position control data) per one pulse of the command pulse number to the take-up servo motor 5 has been measured. Thereafter, the position control data (the production amount of the knitted fabrics) during the stabilized state is measured at step P4-2. Then, the change is made from the torque control mode to the position control mode utilizing the position control data so measured and the take-up of the same production amount of the knitted fabric can be performed at all times at step P4-3.
In that way as described, even when in addition to the change of the pattern of the knitted fabric, the change occurs in the roll diameter of the cloth and/or the change in mechanical load, the certain take-up tension can be maintained and the take-up of the knitted fabric can be automatically and stably performed. It is to be noted that since the case may occur in which the amount of production of a different normal pattern may be stipulated beforehand, when the change is made to the different normal pattern, under this automatic mode, it is preferred that either the utilization of the position control mode set to the stipulated amount of the knitted fabric or the utilization of the position control mode set to the amount of production measured in the manner described previously can be selected.
Fig. 6 illustrates the flowchart showing a fourth example of the sequence of operation of the take-up control device for the electronic pattern knitting machine. At the outset, when the pattern for production purpose is being produced under the position control mode at step R1; the output torque during the operation of the machine under this position control mode is measured at step R2. As is the case with the previously described third example, this output torque is the one that depends on the change in roll diameter of the cloth or the change in machine load, and, even though the pattern of the knitted fabric is changed, only the production amount of the knitted fabric changes and no output torque itself change after the change of the pattern. Subsequently, decision is made at step R3 to determine if the pattern for production purpose is changed to the pattern for test purpose or the different pattern for production purpose. In the event that the change is made from the pattern for production purpose as determined at step R3, the output torque value measured at the step R2 is utilized as is the case with that in the previously described third example, the operation takes place at step R4 under the torque control mode, which is one of the case, in which the torque control mode set by the above described output torque value is utilized, or the case in which the automatic mode is utilized. Should the pattern have not been changed from the pattern for production purpose, the program flow goes to step R2.
Subsequently, decision is made at step R5 to determine if the pattern for test purpose or the initial pattern for production purpose has been switched over to the initial pattern for production purpose. If the change has been made to the initial pattern for production purpose as determined at step R5, the operation takes place at step R6 under the position control mode with respect to the initial pattern for production purpose, followed by the flow to the step R2. On the other, if the change to the initial pattern for production purpose has not been made as determined at step R5, the program flow goes to step R5.
The fourth example shown in and described with reference to Fig. 6 is used particularly where the roll weight of the cloth such as, for example, a large take-up is high. In such case, as compared with the case in which the roll weight of the cloth is low, even with the same output torque the take-up amount of the knitted fabric becomes small and the take-up tension correspondingly decreases. For this reason, the relation between the output torque and the take-up tension as hereinbefore described changes. In view of this, the output torque during the position control mode, at which time it is not controlled with the output torque of the motor, is measured in a condition before the change of the pattern and, by setting to the torque control mode at which time the output torque value measured during the change of the pattern taking place, even when the relation between the output torque and the take-up tension changes during the change of the pattern, the take-up of the knitted fabric can be automatically performed properly and stably under the torque control mode during which the output torque necessary to achieve the required take-up tension. In this way, when the change is made from the pattern for production purpose to the pattern for test purpose or the different pattern for production purpose, even when the roll weight of the cloth such as the large take-up is high, the take-up of the knitted fabric can be automatically performed properly and stably.
It is to be noted that the production is to take place with the pattern having been changed after the production of the large take-up has come to end and the large cloth has been withdrawn, the use of the output value measured under the condition in which the roll weight of the cloth is high will result in the increase of the take-up tension and, therefore, there is the possibility of a trouble occurring. For this reason, at the time the pattern is changed, it is preferred to use either the output torque value measured in the manner described above or the output torque value stipulated beforehand in the manner described above. Or, when the number of counts of machine revolutions, which is not shown, is reset, it is preferred to use the output torque value which has been automatically stipulated beforehand. Alternatively, the use of a roll weight sensor may be preferably made so that when the roll weight changes, the output torque value automatically stipulated beforehand can be preferably used.
As hereinbefore described, since in the present invention, when the change is made to the second pattern (the pattern for test purpose or the different pattern for production purpose) while the knitted fabric having the first pattern (the pattern for production purpose) is being produced, the position control mode is automatically switched over to the torque control mode, the take-up tension of the knitted fabric becomes constant under the torque control mode and, therefore, even when the pattern of the knitted fabric is changed, the take-up of the knitted fabric can be automatically performed under the proper and stabilized take-up tension correspondingly and, hence, ACT (Automatic Control Tension) can be realized.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings which are used only for the purpose of illustration, those skilled in the art will readily conceive numerous changes and modifications within the framework of obviousness upon the reading of the specification herein presented of the present invention. Accordingly, such changes and modifications are, unless they depart from the scope of the present invention as delivered from the claims annexed hereto, to be construed as included therein.

[Reference Numeral]

1: Electronic pattern knitting machine (circular knitting machine)
2: Knitting unit
3: Take-up mechanism
4: Take-up rollers
5: Take-up servo motor
6: Take-up control unit
8: Entire control unit
10: Take-up servo driver
11: Control mode setting unit
12: Machine rotation detecting unit
13: Data processing and setting unit
14: Data acquiring unit
15: Stabilization determining unit
16: Knitting condition setting unit
17: Pattern setting unit

Claims

A take-up control method for use in an electronic pattern knitting machine for controlling a take-up mechanism (3) with a take-up control unit (6), while a tubular knitted fabric is knitted by a knitting unit (2) in accordance with a knitting condition, including a pattern setting of the knitted fabric by means of the take-up mechanism (3) including take-up rollers and a take-up servomotor (5) for roller drive purposes, in which:
by means of the take-up control unit (6) a control mode of the take-up servo motor (5) is settable to one of modes including a torque control mode, in which the take-up servo motor (5) is driven so that a take-up tension of the knitted fabric may be constant, and a position control mode in which the take-up servo motor (5) is driven at a certain angle of rotation relative to rotation of the knitting unit (2);
characterized in that
in the event that a change is made from a first pattern to a second pattern while the knitted fabric having the first pattern is produced under the position control mode, the position control mode is automatically switched over to the torque control mode to enable an automatic take-up of the knitted fabric having the second pattern to be performed under the torque control mode.
The take-up control method for use in the electronic pattern knitting machine as claimed in claim 1, in which by means of the take-up control unit (6), in the event that the pattern of the knitted fabric once changed from the first pattern to the second pattern is returned to the initial first pattern, the torque control mode at the time the change has been made to the second pattern is switched over to the position control mode at the time the first pattern is being produced, so that the take-up of the knitted fabric having the initial first pattern is performed under the position control mode.
The take-up control method for use in the electronic pattern knitting machine as claimed in claim 1 or 2, in which the first pattern is a pattern for production purposes and the second pattern is a pattern for test purposes or a different pattern for production purpose.
The take-up control method for use in the electronic pattern knitting machine as claimed in claim 1, in which:
an automatic mode is set by means of the take-up control unit (6), when the pattern of the knitted fabric is switched from the first pattern over to the second pattern;

as a result of the setting of the automatic mode, a change is made from the position control mode at the time of production of the first pattern to the torque control mode at the time the change is made from the first pattern to the second pattern, while the take-up of the knitted fabric having the second pattern is performed under the torque control mode until a take-up state become stabilized under the torque control mode, position control data, which is the production amount of the knitted fabric under the torque control mode in such stabilized state, are measured, and the take-up of the knitted fabric having the second pattern so changed is then performed by changing to the position control mode utilizing the measured position control data.
The take-up control method for use in the electronic pattern knitting machine as claimed in claim 1 or 4, in which the torque control mode set by the take-up control unit (6) is set to the measured output torque value when the change is made from the first pattern to the second pattern, whereby an output torque under the position control mode at the time the first pattern is being produced is measured.
A take-up control device in an electronic pattern knitting machine comprising a take-up mechanism (3), which comprises take-up rollers for the take-up of a tubular knitted fabric and a take-up servo motor (10) for roller drive purposes, and a take-up control unit (6) for controlling the take-up mechanism;
in which the take-up control unit (6) comprises a control mode setting unit capable of setting a control mode of the take-up servo motor (10) to one of modes including a torque control mode, in which the take-up servo motor (10) is driven so that a take-up tension of the knitted fabric may be constant, and a position control mode in which the take-up servo motor (10) is driven at a certain angle of rotation relative to rotation of the knitting unit; and
in the event that a change is made from a first pattern to a second pattern while the knitted fabric having a first pattern is produced under the position control mode, the position control mode is automatically switched over to the torque control mode to enable an automatic take-up of the knitted fabric having the second pattern to be performed under the torque control mode.