Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Patent
1995-12-18
1997-07-15
Falik, Andy
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
B65H 5122, D03D 4734
Patent
active
056474040
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns devices to feed yarn to machines making use thereof, and particularly a weft yarn feeder for gripper or projectile loons having improved characteristics.
BACKGROUND OF THE INVENTION
It is well known to feed yarn to machines making use thereof, particularly the weft yarn to looms, by means of feeding devices or yarn feeders. Such devices are positioned between the spool and the loom and are meant to temporarily store the weft yarn. They also facilitate its unwinding from the spool, and subsequently feed it to the loom insertion members with optimal and preset yarn tension values.
The type of structure universally adopted at present for such feeding devices involves winding the yarn into successive turns around a winding unit or drum, kept motionless, by means of a winding arm moved by an electric motor. Means for detecting the amount or reserve of yarn present on the winding drum are provided to control the running and rotation speed of the motor of the feeding device according to the amount of yarn drawn by the loom; so as to make the yarn unwinding speed from the spool as uniform as possible.
When yarn feeders are used on gripper or projectile looms, they comprise at their outlet end yarn braking means, positioned downstream of the yarn winding drum and meant to feed the weft yarn to the loom with a specific desired tension. Many of the known yarn braking devices act directly on the outlet end of the drum and are positioned upstream of an outlet yarn guide of the feeder, meant to ensure a correct unwinding of the weft yarn.
Most yarn feeders make use of brake devices consisting of a plurality of natural or synthetic bristles, fixed to a support in the form of a closed ring carried by a bracket movable along the main axis of the yarn feeder. The plurality of bristles bear--with a variable pressure adapted to be preset by adjusting the axial position of the bracket--onto the outer periphery of the yarn reserve winding drum of the feeder.
Other yarn braking devices have been conceived, as an alternative to the ones with bristles: and their use has proved advantageous to overcome the drawback of the rapid wear of the bristles. The braking element in these devices comprises a plurality of thin sheet-metal strips, positioned side-by-side onto a frustoconical surface and pressing onto the outlet end of the feeder drum. To guarantee--by a self-adjustment of the strips--an efficient and continuous-contact of the strips with the winding drum, the said braking element is preferably mounted onto a cup-shaped support with open bottom, carried by a bracket of the yarn feeder the position of which is adjustable along the drum axis. A yarn braking device with sheet-metal strips of this type, which has proved satisfactory and has found a widespread use, is disclosed in EP-B1-49897 filed by the same Applicant. In this brake device, the sheet-metal strips are in the form of thin blades and the cup-shaped support is mounted on the movable bracket of the yarn feeder by way of a double articulation, so as to be able to perform limited oscillations about two axes perpendicular to each other and to the axis of the feeder drum.
More recently, brake devices for yarn feeders having still different characteristics have been conceived. These devices comprise a continuous braking band carried by a plurality of tongues with varying flexibility. The tongues are self-adjustable in that they are mounted movable into a fixed support. Examples of such brake devices are described in PCT/EP93/03086 and PCT/EP93/03262, both filed by the same Applicant. Due to the particular configuration of these devices and, above all, to their mounting--which allows the braking element to be widely deformed and to perform short movements in every direction in the support (thus acting like a universal joint, adapted to guarantee all degrees of freedom)--a perfect adjustment of the braking element in respect of the drum is obtained in the tangent area of contact, particularly taking into account the def
REFERENCES:
patent: 4429723 (1984-02-01), Maroino
patent: 5123455 (1992-06-01), Maina
Bertolone Roberto
Maina Bruno
Falik Andy
Nuova Roj Electrotex S.r.1.
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