Patent Description:
In flat knitting machines, a large number of top tension devices (upper tensioning biasing devices) are equipped to apply tension to yarns from yarn packages and to supply the yarns to side tension devices, to positive yarn feeding devices, or directly to carriers (see Patent document <NUM>: <CIT>). A flat knitting machine has, for example, about twenty top tension devices, and therefore, a knitting shop having a large number of flat knitting machines has a considerably large number of top tension devices.

When an electrically controllable disc, rollers, or the like is provided in a top tension device, tension can be applied to a yarn controllably. For example, when a disc cramps a yarn and when the pressure from the disc to the yarn is controlled, the tension is controlled. Similarly, when rollers of a yarn are driven by a motor and when the torque applied to the rollers is controlled, the tension can be controlled. However, even if the pressure from the disc or the torque to the rollers is made constant, different yarns make the applied tension change.

The suitable tension to be applied by a top tension device is dependent upon and changes according to a yarn feeding route to a carrier for the yarn. Further, the yarn feeding routes change according to respective top tension devices. Therefore, it is troublesome to set tension for a large number of top tension devices.

Prior art document <CIT> discloses a yarn feeder system which includes a plurality of yarn feeders combined into one group. In the trial mode, the yarn feeders operate in an individually tension-controlled manner on the basis of a specified yarn tension value. The yarn feed quantities or yarn speeds that result from this at the various yarn feeders are reported to a central unit. From the reported yarn speeds, the central unit calculates a group average and sends this to the yarn feeders as a specified value for subsequent operation.

From document <CIT>a method and a system is known for managing and controlling the feeding of at least one thread to a textile machine as a function of the operating step of the latter in the production of a product or in the processing of such thread, such production or processing providing for a succession of said steps corresponding to the obtainment of various parts of the same product or different treatments of such thread, the latter being fed to said machine by a corresponding feeder device at a constant tension and/or speed and/or controlled by a sensor which monitors the sliding or any of the inherent characteristics thereof such as tension, speed, diameter, quantity and color, said sensor and/or feeder being controlled by setting and control means which set the operation thereof, said setting and control means receiving synchronization signals from the machine and detecting - according to the latter - the aforementioned operating steps and thus the processing progress status of a product or production process, said setting of the operation being programmed as a function of said operating steps.

The object of the invention is to set tension automatically for top tension devices that apply electrically controllably tension to yarns.

This and other objects are met by set-up methods stated in claims <NUM> to <NUM>. A preferred embodiment of the set-up methods is defined in claim <NUM>.

The mentioned object and other objects are also solved by a set-up system having the features of claim <NUM>.

According to the invention, when the species of yarn is changed, for the top tension devices that apply electrically adjustable tension to yarns, the setup of the torque is automatically changed. The invention is particularly efficient when a large number of the top tension devices are used. In addition, yarns of the same species may be regarded as the same yarn, however, there are cases where the same species of yarns have different characteristics due to changes in the temperature, humidity, and the production lot. In such cases, when temperature, humidity, or the production lot changes, it is preferable to measure the input value to the adjusting member once more.

Preferably, in said setup step, said input value is corrected based on a species of a yarn feeding object to which said each yarn is fed by the top tension device at an upper stream position of the carrier along a direction of yarn feeding, the number of eyelets (yarn guide) which said each yarn passes through in said each yarn feeding route, and the degree of bending of said each yarn in said each yarn feeding route. The tension to be applied by the top tension device is dependent upon the yarn feeding route. However, according to the above construction, the input value is corrected according to the elements in the yarn feeding route and may be transformed to the setup value.

Preferably, said input value is measured for each of plural yarn feeding speeds, and the controller of the flat knitting machine corrects the setup value during knitting, based upon the yarn feeding speed from the top tension device. As a result, adequate tension is applied according to the knitting speed, and disturbance in the fabric sizes is prevented.

Preferably, in the measuring step, said each yarn is fed through the adjusting member and a tension sensor to a drawing member, the adjusting member applies tension to said each yarn, the drawing member draws said each yarn, and the input value to the adjusting member is measured when the tension applied to said each yarn, measured by the tension sensor, is a desired value. If a dedicated measuring device having the above construction is used, the input value can be measured without using a flat knitting machine, as defined in claim <NUM>. And therefore, knitting machines have not to be halted during the measurement. Therefore, knitted fabrics are produced more efficiently. If without using the dedicated measuring device, the tension sensor is provided between the top tension device and a side tension device, a positive yarn feeding device, or the like, the drawing member is provided at a downstream position of the carrier, and then, the input value to the adjusting member can be measured on a flat knitting machine and without actual knitting, as defined in claim <NUM>.

According to an embodiment, a correction amount for each element in the yarn feeding route is retrieved and added. However, a correction amount for the entire yarn feeding route may be measured. This correction is also a correction corresponding to elements in the yarn feeding route. For example, the drawing speed of the yarn and the tension in the vicinity of the outlet of the top tension device are made constant, and the necessary input value to the adjusting member is measured for each yarn feeding route. Then, the difference from an input value to a standard top tension device is stored as a correction amount for each yarn feeding route. Even when the species of the yarn is changed, this correction amount for each yarn feeding route is usable, for example, without alteration.

The best embodiment for carrying out the invention will be described.

<FIG> indicate an embodiment. <FIG> indicates an example of the top tension device <NUM>; indicated by <NUM> are a pair of dies that cramp a yarn and apply pressure. Indicated by <NUM> is a driver for driving the dies <NUM> so as to adjust the pressure, and indicated by <NUM> is an input port for inputting an electrical input to the driver <NUM>. The whole from the dies <NUM> to the port <NUM> are referred to as an adjusting member <NUM>. Instead of the dies <NUM>, the yarn <NUM> may be braked by rollers in contact with the yarn, and the mechanism for the tension adjustment is arbitrary. Further, indicated by <NUM> is an eyelet for guiding the yarn. In addition, when a tension sensor <NUM> is provided in the top tension device <NUM>, input values to an adjusting member shown in <FIG> can be measured. However, if all top tension devices <NUM> are provided with the tension sensors <NUM>, the present invention reduces practical utility. Therefore, the tension sensors may be provided in a part of the top tension devices <NUM>, when the sensors are provided. When a top tension device <NUM> is used to measure the tension on a flat knitting machine <NUM>, the correction amounts corresponding to elements in the yarn feeding route used in the measurement are subtracted, and correction amounts corresponding to the elements in the yarn feeding route for each top tension device <NUM> are added.

<FIG> indicates the measurement of input values to the adjusting member. A yarn <NUM> is supplied from a yarn source such as an yarn package <NUM> or the like, to a drawing member <NUM>, through an adjusting member <NUM> and the tension sensor <NUM>. The adjusting member <NUM> may be the same as the adjusting member <NUM> in the top tension device <NUM> or a similar one, such as a version having a higher precision. The tension sensor <NUM> measures the tension applied to the yarn <NUM>. The drawing member <NUM> has a pair of rollers for cramping the yarn and draws the yarn by driving the rollers. The adjusting member <NUM>, the tension sensor <NUM>, and the drawing member <NUM> are an example of a dedicated measuring means. Further, the top tension device <NUM> in <FIG> in combination with the tension sensor <NUM> is an example of the measuring means that functions as a top tension device on a flat knitting machine. For each drawing speed of the yarn by the drawing member <NUM>, an input value to the adjusting device <NUM> is measured when the tension measured by the tension sensor <NUM> becomes a desired value, and the measured value is stored in a memory not shown. As a result, data for tables <NUM> shown in <FIG> are obtained. One table is provided for one drawing speed of a yarn, and preferably, input values for respective desired tensions are stored for respective drawing speeds. Instead of tables <NUM> for respective drawing speeds, the yarn may be drawn with a slight speed and the input value to the adjusting member <NUM> is measured when a desired tension is achieved.

<FIG> indicates setup of the top tension devices <NUM> on the flat knitting machine <NUM> according to the embodiment. Indicated by <NUM> are, for example, a pair of needle beds, and <NUM> is a carriage manipulating needles on the needle beds <NUM>. Indicated by <NUM> is a stand over the needle beds <NUM> and supports the top tension devices <NUM> and yarn packages not shown. At both side ends of the needle beds <NUM>, for example, there are provided positive yarn feeding devices <NUM> and side tension devices <NUM>. The top tension devices <NUM> draw yarns from the yarn packages, apply tension to the yarns, and supply them to the positive yarn feeding devices <NUM> or the side tension devices <NUM>. Further, the positive yarn feeding devices <NUM> and the side tension devices <NUM> supply the yarns to carriers <NUM>, and the carriers <NUM> supply the yarns to needles on the needle beds <NUM>. In the yarn feeding routes, there are eyelets for changing the directions of the yarns, and therefore, the eyelets apply friction to the yarns.

The flat knitting machine <NUM> is provided with a controller <NUM>. Indicated by <NUM> is the main controller, <NUM> is a carriage controller, and <NUM> to <NUM> are tables. The table <NUM> stores data shown in <FIG>, the table <NUM> stores elements in the yarn feeding route for each top tension device <NUM>. In addition, the data with respect to the elements in the yarn feeding routes may be generated based upon the knitting data or may be inputted by a user from the controller <NUM>.

The table <NUM> stores a correction amount for each element in the yarn feeding routes. For example, it stores an additional tension amount for an eyelet in the yarn feeding routes, correction amounts on the basis of intermediate yarn feeding objects between the carriers <NUM> and the top tension devices <NUM>, and correction amounts on the basis of bending angles of the yarns in the yarn feeding routes.

As upstream side yarn feeding objects, <FIG> indicates the positive yarn feeding devices <NUM> and the side tension devices <NUM>. The positive yarn feeding devices <NUM> feed yarns through a gap between a pair of rollers and control the rotation number of the rollers so as to feed desired lengths of yarns. The side tension devices <NUM> apply tension to the yarns and further work as buffers of yarns. In addition, the positive yarn feeding devices <NUM> and the side tension devices <NUM> are different in the suitable yarn tension to be applied from the top tension devices <NUM>. Without the positive yarn feeding devices <NUM> nor the side tension devices <NUM>, yarns may be directly supplied to the carriers <NUM> from the top tension devices <NUM>. In this case, the correction amount with respect to the direct yarn feeding is stored in the table <NUM>.

While not shown in the drawings, there are plural eyelets between a top tension device <NUM> and a carrier <NUM>, and the yarn is bent by the eyelets. Since the eyelets apply friction to a yarn, an additional amount of tension per eyelet is stored in the table <NUM>. Further, when a yarn is bent at an eyelet, additional tension is necessary. Since the bending angle of a yarn at an eyelet can be considered from <NUM> degrees (no bending) to <NUM> degrees, additional amounts of tension on the basis of the bending angle are stored. For example, the additional amount is stored at <NUM> stages and increases by <NUM> per <NUM> degrees when approaching <NUM> degrees. Further, since thick yarns increase tension loss by the eyelets and so on, it is preferable to store correction amounts on the basis of the thickness of the yarns (for example, three stages in the thickness of under <NUM>, down to <NUM> and up to <NUM>, and over <NUM>) are further stored.

The main controller <NUM> calculates yarn feeding speed from the top tension devices <NUM> on the basis of knitting information, such as the speed of the carriage, the species of push knitting or pull knitting, and consumed loop length. The main controller <NUM> performs the following processing for each top tension device <NUM> in use. Retrieving elements in the yarn feeding routes from the table <NUM>, and calculates the basic tension with reference to the table <NUM>, according to the species of the yarn feeding object of the positive yarn feeding devices <NUM> or the side tension devices <NUM>. Further with reference to the table <NUM>, retrieving a correction amount for tension for each element, and corrects the basic tension. In addition, with reference to the table <NUM> according to the yarn feeding speed, the main controller retrieves the setup value for the top tension device <NUM> with respect to the desired tension and sets the adjustment member <NUM> for the top tension device <NUM>.

The setup algorithm of the top tension devices according to the embodiment is shown in <FIG>. As a preparation, correction amounts for elements in the yarn feeding routes are determined and are stored in the table <NUM>. Yarns for knitted fabrics change from a season to another season, and a large number of new species of yarns are used in one season. Therefore, data necessary for the table <NUM> for one species of yarn are measured by once and they are implemented to the tables <NUM> in plural flat knitting machines <NUM>. In step S <NUM>, the input values to the adjusting member for applying desired tension to a yarn are measured for respective yarn feeding speeds and are stored. Here, the ambient temperatures and humidities may change the characteristics of yarns and thus, may change the suitable input values. Therefore, it is preferable to coincide the environment where the input values to the adjusting member are measured and the environment where the flat knitting machines work. In addition, the characteristics of a yarn may change according to the production lot of the yarn, it is preferable to measure once more the data in the table <NUM> when the production lot is changed, if necessary.

In step S2, the yarn feeding routes for respective top tension devices <NUM> are stored in the table <NUM>. The order to carry out the steps S <NUM> and S2 is arbitrary. In step S3, with reference to the correction amounts stored in the table <NUM> and the yarn feeding routes stored in the table <NUM>, the setup values for the adjusting members <NUM> in respective top tension devices <NUM> are determined. In addition, it is not necessary to perform the step S3 repeatedly during knitting. Changing amounts corresponding to yarn feeding speeds may be stored in the main controller <NUM> or in a table not shown, and the setup values may be changed on the basis of the changing amount corresponding to yarn feeding speeds.

The detailed process in step S3 is indicated by steps S3a to S3d. In step S3a, the elements in the yarn feeding route are retrieved from the table <NUM>. The elements in the yarn feeding route are, for example, the eyelets and the bending angle of the yarn therein, the species of the first yarn feeding object from the top tension device, such as a positive yarn feeding device or a side tension device, the direction of knitting of push knitting or pull knitting, and so on. In step S3b, correction amounts for respective elements in the yarn feeding route are retrieved from the table <NUM> and are added to a total correction amount. In step S3c, a subtable corresponding to the yarn feeding speed in the table <NUM> for each yarn is referred to, and a setup value for a desired tension is retrieved. For example, the table <NUM> in <FIG> includes three subtables corresponding to three yarn feeding speeds. Here it is preferable to store the retrieved setup value. In step S3d, the setup value retrieved in step S3c and the total correction amount gotten in step S3b are added to the setup value of the top tension device.

Knitting speed is frequently changed during knitting. In this case, steps S3a to S3d may be re-executed. However, it is preferable to re-execute only step S3c to calculate the change in the setup value from that at an old yarn feeding speed before the speed change. And, when the change is added to the old setup value before the change, a new setup value for the new yarn feeding speed is resultant. During knitting, the direction of knitting of push knitting or pull knitting may be changed. In this case, the change in the correction amounts according to the direction of knitting is calculated from the table <NUM>, and the calculated change is added to the setup value before the change in order to get a new setup value after the change.

When using a new species of yarn, the data for the table <NUM> are enough to be measured by once for a large number of top tension devices <NUM>, and therefore, the embodiment is very efficient. By the way, when every top tension device <NUM> is provided with a tension sensor <NUM>, the invention is not needed to be carried out. However, this needs a large number of tension sensors.

The embodiment has the following advantageous effects, in addition to the above:
All top tension devices are uniformly set for a yarn to be used. Therefore, stitch sizes in knitted fabrics are made uniform between different carriers <NUM>. Further, the stitch sizes are made uniform between flat knitting machines <NUM>.

Knitted fabrics with higher quality can be knitted when the setup values for tension are corrected not only on yarn feeding speeds but also on knitting start, knitting stitches at edges of a knitted fabric, the species of push knitting or pull knitting, and so on. These corrections are made by feedforward control based upon the knitting information, and the tension is kept constant without a delay resulting in feedback control.

Claim 1:
A setup method of top tension devices (<NUM>) which have adjusting members (<NUM>,<NUM>) for applying electrically controllable tension to yarns (<NUM>) and are provided on a flat knitting machine (<NUM>), being characterized in that
a measuring step (S1), performed outside a flat knitting machine (<NUM>), for measuring and storing an input value for each yarn (<NUM>) to an adjusting member (<NUM>) for applying a desired tension to said each yarn (<NUM>) is performed,
wherein said each yarn (10is fed to and drawn by a drawing member (<NUM>) through a tension sensor (<NUM>) and the adjusting member (<NUM>), wherein the drawing member (<NUM>), the tension sensor (<NUM>), and the adjusting member (<NUM>) are provided out of the flat knitting machine (<NUM>),
wherein said input value to the adjusting member (<NUM>) is measured with a dedicated measuring device when the tension to said each yarn (<NUM>) is a desired value, and
wherein said input value is stored,
that a step (S2) for storing elements (<NUM>,<NUM>,<NUM>) that contact or influence said each yarn (<NUM>) in each yarn feeding route from a top tension device (<NUM>) to a carrier (<NUM>) of said each yarn (<NUM>) and comprise: species of yarn feeding objects (<NUM>,<NUM>), at an upper stream position of the carrier (<NUM>) along a direction of yarn feeding, to which said each yarn (<NUM>) is fed by the top tension device (<NUM>) ; the number of eyelets (<NUM>) through which said each yarn (<NUM>) passes in each yarn feeding route; and a degree of bending said each yarn (<NUM>) by the eyelets (<NUM>) in said each yarn feeding route is performed, and
that a setup step (S3) for correcting said input value on the basis of the elements (<NUM>,<NUM>,<NUM>) in order to transform said input value to a setup value for the adjusting members (<NUM>) in each yarn feeding route and applying the setup value to the adjusting member (<NUM>) in each yarn feeding route by a controller (<NUM>) in the flat knitting machine (<NUM>) is performed.