Winding – tensioning – or guiding – Unidirectional winding and unwinding – Fixed number of windings on winding surface
Patent
1998-04-02
2000-06-27
Walsh, Donald P.
Winding, tensioning, or guiding
Unidirectional winding and unwinding
Fixed number of windings on winding surface
242366, 2423664, 242418, 276 44, 66132R, B65H 5102
Patent
active
060796561
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to yarn supply apparatus, and more particularly to a yarn supply apparatus which serves to supply elastic yarns, ribbons, strands and the like when demand fluctuates abruptly over time.
BACKGROUND INFORMATION
In knitting machines, yarn supply apparatuses have the task of supplying the appropriate knitting stations with yarn at the correct time, at the requisite tension, and in the desired amount. This is especially true for elastomeric yarns or other kinds of elastic yarns, which are predominantly processed in combination with hard or in other words essentially inelastic yarns (basic yarns) to make more or less elastic knitted goods. The tension of the elastomeric yarn substantially determines the feel and dimensional rigidity of the resultant knitted goods. Fluctuations in the tension of the elastomeric yarn supplied, especially when they recur systematically from one row of loops to another, can lead to a substantial impairment in quality of the knitted goods produced.
Because of the high expansion of often-used elastomeric yarns, which is up to 600% of the basic length, keeping the yarn tension constant requires an appropriate yarn supply apparatus, which furnishes the correct yarn quantity at a given time regardless of the yarn consumption at the time and regardless of the initial tension of the yarn paid out from a yarn bobbin.
This is true especially for knitting machines with an abruptly changing and at least sometimes very high yarn consumption, such as flatbed knitting machines or other knitting machines, in which a single yarn supply apparatus by itself supplies one row of needles. In flatbed knitting machines, the loop-forming needles arranged in one or more rows are supplied with one or more yarns to be knitted by means of a yarn guide moving back and forth in translational motion along the row of needles. Yarn supply is effected by means of a yarn supply apparatus which is located laterally next to the yarn guide in such a way that the yarn guide in its operating motion moves toward and away from the yarn supply apparatus. It will be appreciated that the requisite yarn supply quantity varies considerably in the two phases of operation. A further factor is that at the turning points between the two operating phases, zero yarn consumption occurs, and at the transition from the operating phase moving away from the yarn supply apparatus to the operating phase moving toward it, a brief interval of operation occurs in which the yarn travels backward.
For applications with yarn consumption that fluctuates greatly over time, the yarn supply apparatus known from German Patent DE 36 27 731 C1 was developed; it has a yarn wheel driven by a stepping motor. The yarn wheel carries the yarn, drawn from a yarn bobbin, to the applicable knitting station via a yarn brake.
The yarn supplied by the yarn wheel travels through a terminal eyelet of a lever supported pivotably on its other end; the eyelet represents a turning point, at which the yarn is rerouted at an acute angle. To adjust a constant yarn tension, the pivot lever is acted upon by a constant torque by means of a direct current motor. The pivot lever is also connected to a position transducer, which detects its pivoted position and readjusts the stepping motor accordingly. The pivot lever thus acts as a yarn store, for temporary storage of yarn that has not been drawn off by the knitting stations, yet has continued to be supplied because of the moment of inertia and the control characteristics of the stepping motor. It also serves to adjust the yarn tension and, in cooperation with the sensor device, to detect the existing yarn supply.
This yarn supply apparatus is only limitedly suitable for supplying elastic yarns, and the pivot lever proves to be overly insensitive for tension monitoring. Because of the intrinsic elasticity of the yarn, the pivot lever during operation reaches its extreme positions (stops), where the yarn tension is then not under control.
As a further development, the yarn supply ap
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Park Gerhard
Schmodde Hermann
Memminger-Iro GmbH
Pham Minh-Chau
Walsh Donald P.
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