Textiles: weaving – Weft manipulation – Tensions
Patent
1996-05-30
1998-01-13
Falik, Andy
Textiles: weaving
Weft manipulation
Tensions
139450, 242149, 2424193, 2424194, B65H 5922, D03D 4734
Patent
active
057068682
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device of the type which includes a yarn feeder, a yarn receiver and a yarn brake.
BACKGROUND OF THE RELATED ART
In a device of this type, as is known from WO 91-05728, the problem of automatic threading which is almost unavoidable in modern yarn-processing systems is already taken into account to avoid expensive and long standstill times for manually threading the yarn into the yarn brake. However, the yarn which is supplied from the yarn feeder and conveyed by the pneumatic threader is transported along the running path of a normal yarn run through the pinch zone, and either a drive must adjust the braking elements into a threading position where they are separated, or the air flow must be so vigorous that it presses the braking elements apart from each other to release a passage for the yarn. With this principle, expensive technical means are needed for adjusting the braking elements into the threading position. The yarn receiver does not participate in the threading operation. This principle is difficult to put into practice for devices including a disc brake.
A yarn storing and delivering device which is known from EP-0 450 686 A1 is equipped with a pneumatic threader which comprises a slotted tube extending over a considerable portion of the axial length of the storing drum. The tube serves to transport the yarn blown forwardly by means of an air flow and extends externally over a bristle-type brake ring which rests with brake bristles on a withdrawal edge of the storing drum. The bristle-type brake ring has a circumferential interruption.
The slit of the tube is not oriented towards the circumferential interruption of the brake ring, but is offset about 90.degree. relative thereto, so that after threading the yarn is first removed laterally from the tube before it first passes between the brake bristles and then below said bristles. The tube extends in a direction perpendicular to the plane defined by the pinch zone.
A disc brake which is known from DE-34 09 179 A1 is threaded manually, just like a lamella brake known from DE-34 46 567 C1.
It is the object of the present invention to provide a device of the above-mentioned type in which threading of the yarn into the yarn brake is made easier and can be carried out with simpler constructional means.
SUMMARY OF THE INVENTION
This object is achieved according to the invention wherein a channel-like guide element is disposed adjacent to the pinch zone of a yarn brake to permit the yarn to bypass the pinch zone during threading.
In this configuration, the yarn to be threaded is deliberately moved out of the yarn running path during normal (braked) yarn run and forced to obviate or bypass the pinch zone. This has the advantage that the adjustment of the braking elements need not be changed for threading, and that auxiliary means are not needed for adjusting the braking elements for threading purposes. After the yarn has reached the yarn receiver by obviating the pinch zone, the drawing force in the yarn is exploited to introduce the yarn into the pinch zone in a direction transverse to its running direction by way of stretching. This is advantageous because the transverse force of the yarn which surrounds the braking elements without contact, which force has been created under the drawing force, is capable of pressing the braking elements slightly apart from each other, so that the yarn is introduced without any significant mechanical load into the pinch zone only when the free yarn end has already reached the yarn receiver and the yarn is also supported by said receiver. Hence, the yarn is not left alone when being introduced into the pinch zone. The yarn detour which first obviates the pinch zone is deliberately accepted, and the yarn is then transferred via the drawing force between yarn feeder and yarn receiver into the normal yarn running path and the pinch zone. Threading is made simple with the aid of simple constructional means. The ratio of incorrect threadings is virtually reduced
REFERENCES:
patent: 3945184 (1976-03-01), Franzen
patent: 4468920 (1984-09-01), Lorenz
patent: 4641688 (1987-02-01), Gehring
patent: 5368244 (1994-11-01), Melillo et al.
Fritzson Joachim
Hagstroem Staffan
Ohlson Per
Falik Andy
Iro AB
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