HK1021554B - Method for producing a knitted article on a flat knitting machine and flat knitting machine for implementing the method - Google Patents

Description

Method for producing knitted fabric on flat knitting machine and flat knitting machine for carrying out said method

Technical Field

The invention relates to a method for producing knitted fabrics by simultaneously inputting two different elastic yarns to a knitting needle of a flat knitting machine on one flat knitting machine and the flat knitting machine for implementing the method.

Background

A series of knitted fabrics are made of yarns with different elasticity. Such as leg-protecting stockings or stretch women's stockings, the wearing comfort is achieved by a textile bottom thread having a low elasticity, and the definite supporting force or compression force is obtained by the elasticity of an elastic thread. The elastic yarn may be made of different materials, such as an elastomer yarn or an elastic wrapped yarn, or may be made of other yarns to form a core spun yarn. When the yarn is subjected to the yarn tension by the yarn guide of the knitting machine, the elasticity of the yarn is differentiated according to the material and structure of the yarn. In order to obtain a uniform knitted fabric appearance, care must be taken in the looping process when feeding different elastic yarns to the needles of a knitting machine, so that the more elastic yarns are inserted into the hooks with a tension which is lower and uniform over the entire width of the knit. In addition, it must be noted that two yarns of different elasticity constitute a loop of the same shape and size. For circular weft knitting machines, devices have been developed which introduce the higher elastic yarn into the guide at a particular tension at which the fabric is knitted. The device has two parallel shafts driven in the same direction, and elastic yarn bobbin with circumference is set on the shafts. The two shafts are directly connected with a transmission mechanism of the knitting machine by a gear belt. The number of revolutions of the shaft and its peripheral speed are always in a fixed proportion to the number of revolutions of the knitting machine. At high weaving speeds, more yarn is unwound from the bobbin, and at lower weaving speeds, the bobbin unwinding is correspondingly less. However, this device cannot be used in a flat knitting machine because different sizes of stitches may be formed in a knitting course and the width of each course may be different. Here, it is not possible to feed a highly elastic yarn depending only on the knitting speed.

Disclosure of Invention

The aim of the invention is to propose a method for simultaneously feeding two yarns of different elasticity into a knitting needle for producing a knitted article, which is carried out on a flat knitting machine and which allows to obtain a perfectly uniform stitch structure.

This object is solved according to the invention by a method of the type mentioned above, in which for each respective loop to be formed, the length of the higher elastic thread to be fed to a knitting needle is calculated from the lower elastic thread length already supplied and the material property data relating to the higher elastic thread, and a feed device for the higher elastic thread is controlled on the basis of the calculated length of the thread to be fed. In this way, the length of the elastic thread to be fed is determined for each loop, depending on the thread material properties and the lower elastic thread length which has already been fed. In this way, an optimum yarn feed is always achieved for the entire pattern and yarn type. A preferred option of the method is to calculate a reduction factor from the performance data of the higher elastic yarn material, and multiply the length of the lower elastic yarn by this factor to obtain the length of the higher elastic yarn to be fed. The higher elastic yarn must be inserted into the hook at a significantly lower tension than the lower elastic yarn. The tension is composed of the fact that a smaller yarn quantity is fed for the looping process, according to the reduction factor, than the yarn quantity of the lower elastic yarn. Furthermore, the knitting direction may also be considered, with more higher elastic yarn being fed when the knitting direction is moved away from the conveyor of higher elastic yarn and less higher elastic yarn being fed when the knitting direction is moved towards the conveyor. In this way it is ensured that the optimum tension of the higher elastic yarn is not dependent on the weaving direction. The information about the length of the lower elastic thread that has already been fed, which is required for calculating the length of the higher elastic thread that is to be fed, can be determined, for example, by a measuring device. The entered length of the lower elastic yarn can also be calculated from the stitch size data provided by a machine control unit in respect of each lower elastic yarn, the stitch sequence and the number of stitches in each weaving train. One measuring device can be omitted thereafter. Two yarns with different elasticity can be fed to a common yarn guide or to separate yarn guides without the need for minor modifications to the process.

The invention also relates to a flat knitting machine with at least one needle bed for carrying out the inventive method, comprising a bobbin with a lower elasticity, a feed device for a higher elasticity thread, at least one thread guide for two different elasticity threads, a machine control unit and a computer and control unit for determining the length of the higher elasticity thread to be fed and for controlling the feed device for the higher elasticity thread. The conveying device is somewhat similar to an elastic yarn conveying device of a circular weft knitting machine, and can be provided with two parallel conveying rollers which are driven in the same direction and have the same diameter, and a high-elasticity yarn bobbin with a circumferential surface is arranged on the conveying rollers. The feed device can be provided with an electric motor connected to the calculation and control unit, so that the peripheral speed of the feed roller can be adjusted according to the calculated length of the higher elastic thread to be fed. In a known manner, a thread tensioner can be arranged between the bobbin with lower elasticity and the thread guide, which maintains tension balance when the thread guide is intermittently changed. In addition, a yarn break sensor may also be provided for the higher elastic yarn.

Drawings

Two preferred embodiments of the thread delivery device for a flat knitting machine for carrying out the method according to the invention are explained in detail below with the aid of the figures. Wherein:

FIG. 1 is a side view of a first yarn delivery device;

fig. 2 is a side view of a second yarn feeding device.

Detailed Description

Fig. 1 shows only one flat knitting machine bed 10, not shown in detail, to which a less elastic yarn 11 and a more elastic yarn 12 are fed by means of a yarn guide FF. The less elastic thread 11 is unwound from the bobbin 13, passes through a thread tensioner 14 and a measuring device 15 and passes over a plurality of thread guide rollers U1 to U7 into a thread guide FF. The measuring device 15 continuously determines the length of the lower elastic thread 11 required for a stitch and transmits this value via the data transmission line 16 to a computing and control unit 17, after which it is connected via the data transmission line 18 to a machine control unit 19 of a flat knitting machine and via the control line 20 to the delivery device 21 of the higher elastic thread 12. In addition to the information on the length of the lower elastic thread 11 which is fed in, the calculation and control unit 17 receives the material property information of the higher elastic thread 12 from the machine control unit 19 and calculates therefrom the length of the higher elastic thread 12 which is to be fed in and controls the motor 22 of a conveyor 21 for the higher elastic thread 12 accordingly. The motor 22 drives two transport rollers 23 of the same diameter, on which a bobbin 24 with a circumferential surface of the relatively highly elastic thread 12 is placed. Depending on the peripheral speed of the delivery roller 23, a more or less high elastic yarn 12 is fed into the yarn guide FF. The higher-elasticity thread 12 is now fed directly from the bobbin 24 to the thread guide FF without further thread tensioning devices or the like. But also a sensor 25 for identifying the yarn breakage in the yarn guide.

The yarn feeding device of fig. 2 differs from the device of fig. 1 in that no measuring device 15 is provided for determining the fed length of the lower elastic yarn 11. Here, the calculation and control unit 17 obtains information of each stitch size, stitch sequence and number of stitches in the knitting course and knitting direction of the lower elastic yarn 11 from the machine control unit 19', in addition to the yarn property data of the higher elastic yarn 12. The calculation and control unit 17 thus calculates the length of the higher elastic thread 12 to be fed in and controls the feed device 21 for the higher elastic thread 12 accordingly. The length of the higher elastic yarn 12 to be fed is then obtained by calculating a reduction factor from the yarn property data of the higher elastic yarn 12 and multiplying this factor by the length of the lower elastic yarn already fed. The calculation and control unit 17 recognizes the knitting direction data as to whether the carrier FF of the high elastic yarn 12 moves out of or toward the conveyor 21, and therefore the yarn amount can be increased when the carrier FF moves away from the conveyor 21 and decreased when it moves toward the conveyor 21. This ensures that the highly elastic yarn 12 always has an optimum tension. The yarn tensioner 14 provides a constant yarn tension to the less elastic yarn 11.

Claims (12)

1. A method for simultaneously feeding two different elastic threads (11, 12) to the needles of a flat knitting machine for producing a knitted fabric, characterized in that for each stitch to be formed, the length of the higher elastic thread (12) to be fed to a needle is calculated from the length of the lower elastic thread (11) already fed and the material property data relating to the higher elastic thread (12), and a feeding device (21) for the higher elastic thread (12) is controlled on the basis of the calculated length of the thread to be fed.

2. Method according to claim 1, characterized in that a reduction factor is calculated from the yarn property data of the higher elastic yarn (12), and the length of the higher elastic yarn (12) to be fed is obtained by multiplying the length of the lower elastic yarn (11) fed by this factor.

3. Method according to claim 2, characterized in that the higher elastic yarn is fed more when the weaving direction is directed away from the feeding device (21) for the high elastic yarn (12) than when the weaving direction is directed towards the feeding device (21).

4. Method according to one of claims 1 to 3, characterized in that the length of the lower elastic thread (11) fed in is determined by a measuring device (15).

5. Method according to one of claims 1 to 3, characterized in that the length of the lower elastic thread (11) fed in is calculated from data of the size of each stitch, the sequence of stitches and the number of stitches in each knitting course of the lower elastic thread (11) supplied by a machine control unit (19').

6. Method according to one of claims 1 to 3, characterized in that two yarns (11, 12) of different elasticity are fed to a common yarn guide (FF).

7. Flat knitting machine with at least one needle bed (10) for carrying out the method according to claim 1, characterized in that it comprises a bobbin (13) of a lower elastic thread (11), a transport device (21) for transporting a higher elastic thread (12), at least one thread guide (FF) for two different elastic threads (11, 12), a machine control unit (19, 19') and a computing and control unit (17) for computing the length of the higher elastic thread (12) to be fed and for controlling the transport device (21) of the higher elastic thread (12).

8. A flat knitting machine according to claim 7 characterized in that the feed device (21) has two parallel feed rollers of the same diameter driven in the same direction, on which rollers a relatively highly elastic bobbin (24) with a circumferential surface is placed.

9. A flat knitting machine according to claim 7 or 8 characterized in that the conveying means (21) has a motor (22) connected to the calculation and control unit (17).

10. A flat knitting machine according to claim 7 or 8 characterized in that a yarn tensioner (14) is arranged between the bobbin (13) of the less elastic yarn (11) and the yarn guide (FF).

11. A flat knitting machine according to claim 7 or 8 characterized in that a yarn length measuring device (15) connected to the calculation and control unit (17) is arranged between the bobbin (13) of the less elastic yarn (11) and the at least one yarn guide (FF).

12. A flat knitting machine according to claim 7 or 8 characterized in that a yarn break sensor (25) is provided for the higher elastic yarn (12).