Textiles: knitting – Feeding – Positive
Patent
1994-03-15
1995-06-13
Calvert, John J.
Textiles: knitting
Feeding
Positive
66125R, 242 4701, 242 4706, B65H 5122, D04B 1548
Patent
active
054231973
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a yarn-delivery device as a yarn feeder for textile machines including a bobbin for a yarn, a storage drum, and a drive motor having a rotor. The motor draws the yarn off from the bobbin. A yarn-tension sensor is provided that is mechanically deflected by the yarn running off the storage drum. Further, means for electronically evaluating and converting the mechanical deflection of the yarn-tension sensor are provided for regulating a drive of the drive motor.
STATE OF THE ART
Yarn-delivery devices, also called storage feedwheels, as yarn feeders for textile machines are already known, having a storage drum which is fastened to the shaft end of an electric motor and on the circumference of which a plurality of turns of the yarn to be conveyed lie in a slip-free manner (German Offenlegungsschrift P 34 29 207.1-26). The rotational speed of the storage drum is transmitted directly to the electric motor of the storage drum via control electronics by suitable pulse transmitters on the circular knitting machine. A so-called autosyn is thereby obtained between the machine and yarn-delivery device. Further sensors which sense the yarn readjust the set desired value.
Furthermore, a yarn-delivery device, the storage drum of which is likewise attached to the shaft end of an electric motor, has become known (German Offenlegungsschrift P 38 30 381 C1; P 38 20 618 A1). However, here, the signal transmission to the motor takes place via a sensor lever on the yarn which is held magnetically in a variable position. The adjustable return force on the lever then corresponds to the variable desired value for the yarn tension required.
In textile machines, a specific yarn quantity of the appropriate desired value becomes necessary immediately when the knitting machine is switched on directly. The commercially conventional motors required for this and having an appropriately sufficient starting torque and the necessary run-up time are of a constructional size such that they cannot be installed in the housing sizes currently used. In known devices, therefore, there has been a sensor lever which provides a variable yarn reserve between the storage drum and yarn consumer. During the reduction of this reserve, the motor can then be brought to the necessary rotational speed which corresponds to the desired delivery quantity. This yarn reserve is obtained by a multiple deflection of the yarn, for example by means of eyes. However, extreme frictional losses and especially the formation of fluff occur as a result. Furthermore, elastomeric yarns can hardly be regulated in this way or, at most, only very slow rotational speeds are possible.
For a satisfactory lap formation on the storage drum, the known yarn-delivery devices have a preceding permanently set or variable yarn brake. For this, either the yarn is guided through an eye which is weighted, for example by means of a ball, or it is drawn through a disc brake. Here too, depending on the material used, annoying quantities of fluff are obtained. Under high braking forces, the yarn turns on the storage drum will naturally lie on it firmly and be drawn together, most types of yarn being stretched. The yarn then relaxes at the measuring point, for example at a sensor lever, and the sensor lever itself can be set in vibration. The lever must therefore in turn be steadied mechanically.
The known devices therefore altogether still have some weak points which have to be considered as an unsatisfactory overall solution involving too high a technical outlay.
SUMMARY OF THE INVENTION
The object on which the invention is based is to provide a yarn-delivery device, in which the individual subassemblies can be coordinated with one another as exactly as possible, thereby providing an optimum overall system. The object of the invention is, furthermore, also to improve or optimise individual subassemblies of the yarn-delivery device for particular special uses.
This object is achieved by connecting the storage drum to the rotor to form a si
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patent: 5050405 (1991-09-01), Jacobsson
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