Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Patent
1997-06-18
1999-07-06
Falik, Andy
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
2423654, 335257, D03D 4736
Patent
active
059186461
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns improvements in measuring weft feeders for fluid jet looms i.e. those special feeders wherein the weft yarn, wound so as to form a reserve around a drum kept motionless, is drawn by the loom through a main nozzle and is measured, while being unwound from said drum, with a system counting the yarn turns which have been drawn.
In such feeders, the unwinding of the weft yarn is normally stopped by means of an electromagnetic unit, a rod connected to its movable core being apt to engage the outlet end of the weft feeder drum by penetrating with slack into a hole, generally slotted, formed in said drum
The present invention proposes to improve in said measuring weft feeders the performances of said electromagnetic weft yarn stopping unit, so as to block--more efficiently than done so far with the known units--the weft yarn soon after it has stopped and, particularly, upon cutting thereof by the cutting devices provided on the loom.
FIELD OF THE INVENTION
In the last years various improvements have already been introduced by the Applicant in the electromagnetic yarn stopping units of measuring weft feeders for fluid jet looms, so as to improve their performances and make them more suited to the increasingly hard conditions of use to which they are subjected.
BACKGROUND OF THE INVENTION
Such improvements are described in IT-U-9044, in IT-U-209674 and above all, in the more recent EP-363.938 wherein, to allow eliminating dangerous rebounds and make the operating times more uniform, the electromagnetic unit has two coils, so that the movable core to stop the weft yarn is controlled both to take up its working position and to take up its position of rest.
Though the performances of the electromagnetic stopping unit have thus been improved, the situation is still critical when the weft yarn is being cut by the loom cutting device positioned at the outlet of the main nozzle feeding the weft yarn into the loom shed.
In fact, in this step there is a sudden change of weft yarn tension causing oscillations along the tensioned yarn, which return from its cut end up to the point in which the yarn has been blocked by the rod of the electromagnetic stopping unit, and which may continue up to reaching the turns wound on the weft feeder drum.
Such oscillations, which produce on the yarn strong transversal and longitudinal waves, can cause said yarn to wedge under the rod of the electromagnetic stopping unit--in a working position into the drum hole--even after the yarn has stopped against said rod; they can also cause ruffling of the yarn turns wound in the area of its outlet from the feeder drum, close to said electromagnetic stopping unit.
This behavior obviously determines an incorrect measuring of the weft yarn length being inserted into the loom, producing faults which may have different consequences, but which always involve damages.
In fact, a general consequence is that a yarn turn may end up by sliding under the rod of the electromagnetic stopping unit (in particular cases it could even be more than one turn) after the weft yarn has been inserted into the loom, and this could lead to a successive weft yarn insertion including a yarn length which is longer than one turn--in case of a single-colored weave--or else it could lead to the simultaneous insertion of a one color turn with a different color turn, in case of a many-colored weave.
This drawback is particularly felt in the case of a many-colored weave, in that it can show up when changing of the color takes place, in the form of an insertion corresponding to one or more turns, together with the next color and in the same shed, with no possibility of being detected by the weft yarn control systems used at present on fluid jet looms.
To overcome this drawback the EP-239.055, filed by the Applicant, supplied a device to be applied at the outlet of measuring weft feeders, apt to greatly dampen the oscillating and vibratory motion of the weft yarn at the outlet of said feeder, particularly upon cutting of the
REFERENCES:
patent: 4632155 (1986-12-01), Maina
patent: 4811762 (1989-03-01), Bucher et al.
patent: 5271435 (1993-12-01), Maina
patent: 5462096 (1995-10-01), Svanstroem et al.
Falik Andy
Nuova Roj Electrotex S.r.l.
LandOfFree
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