Winding – tensioning – or guiding – Coil holder or support – Spool or core
Patent
1995-07-03
1997-10-21
Mansen, Michael
Winding, tensioning, or guiding
Coil holder or support
Spool or core
242149, 139452, B65H 5100, B65H 5922, D03D 4736
Patent
active
056787790
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a yarn feeding device with a self adjusting braking mechanism.
BACKGROUND OF THE INVENTION
In a yarn feeding device as known from U.S. Pat. No. 4,068,807, the conical yarn braking surface is defined by the inner circumference of an elastic synthetic rubber ring, fixed to the base of a rigid frustoconical brake carrier. A yarn guide eyelet, fixed to the small diameter end section of the brake carrier, acts as counterdeflection surface. The brake carrier is fixed with its small end section into a bearing, mounted axially slidable--essentially in a direction of the drum axis--into the stationary part of the feeder. A spring acts as pre-loading element and presses the braking surface in an axial direction against the inclined deflection surface. A detection device detects yarn tension and adjusts the brake carrier so as to oppose the pre-loading force and thus reduce the braking effect between the braking surface and the deflection surface, as yarn tension increases. During unwinding of the yarn, its tension increases in proportion to the unwinding speed, and the braking surface thus reduces its braking effect on the yarn so as to compensate for the yarn tension increase resulting from the unwinding speed.
The same principle--i.e. to reduce the braking effect between the braking surface and the deflection surface, as yarn tension increases--is adopted in a yarn feeding device known from the publication "TWM", INFORMA 92, of L.G.L. ELECTRONICS S.p.A., Gandino, Italy. In this case, the braking surface is defined by the inner circumference of a conical metal plate ring, fixed to the inner side of the wide diameter end section of a carbon fiber cone. The counterdeflection surface is defined by the conical lining inside the small diameter end section of the cone. The cone is mounted with its small end into an annular ring membrane, fixed to the stationary part of the feeder and forming the pre-loading element. The yarn slides between the braking surface and the deflection surface, and then inwardly and around the counterdeflection surface, transmitting the axial components of its tension, while the cone is simultaneously kept balanced by the membrane. In this way, the axial component of yarn tension shifts the braking surface against the action of the membrane, as soon as yarn tension increases on rising of the unwinding speed, in order to reduce the braking action.
The prior art on the subject includes also FR-A-2.422.577, EP-A-49.897 and EP-A-330.951, which foresee the use of braking means formed by a plurality of metal laminae cooperating with the drum of the weft feeder, as well as the possibility to adjust the pre-loading force with which the braking means are pressed upon the drum.
SUMMARY OF THE INVENTION
In view of the ever increasing yarn unwinding speeds of modern projectile or gripper looms, the object of the present invention is to supply a yarn feeding device of the aforementioned type, wherein yarn tension is detected with high sensitiveness, and the braking action is exactly adapted to the force vectors of the sliding yarn and efficiently adjusted, without perceptibly disturbing yarn movement.
According to the invention, this object is reached with a yarn feeding device for projectile and gripper looms, comprising a storage drum for storing turns of a yarn which is tangentially wound thereon into turns, and is unwound from the turns in an essentially axial unwinding direction over an inclined annular and rounded deflection surface provided at a free front end of the storage drum and under a conical braking surface provided at a wider end of a hollow conical brake carrier. The brake carrier also has a smaller end and is arranged essentially coaxial of the storage drum, with the wider end overlapping the annular and rounded deflection surface. The brake carrier is provided with openings defining separate spring tongues ending in correspondence of the braking surface. The tongues extend up to the smaller end of the brake carrier. The braking surface is pressed in contact wit
REFERENCES:
patent: 3411548 (1968-11-01), Pfarrwaller
patent: 4068807 (1978-01-01), Jacobsson
patent: 4261526 (1981-04-01), Roj
patent: 4429723 (1984-02-01), Maroino
patent: 4926912 (1990-05-01), Zenoni
patent: 5046536 (1991-09-01), Zenoni
patent: 5316051 (1994-05-01), Zenoni et al.
patent: 5343899 (1994-09-01), Jacobsson et al.
Mansen Michael
Nuova Roj Electrotex S.r.l.
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