Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Patent
1994-06-06
1995-05-23
Falik, Andrew M.
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
139194, 1394352, D03D 4734
Patent
active
054172519
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a loom with a programmable insertion brake.
DESCRIPTION OF THE PRIOR ART
An air-jet loom according to EP-A1-03 56 380 includes a driving motor of the controlled insertion brake (e.g. a solenoid plunger for displacing a braking element) which, in its braking position, deflects the weft yarn and reroutes it at two stationary rerouting elements. For damping tension peaks in the weft yarn, the deflection is at least partially eliminated, with the amount of elimination of the deflection being adjusted or controlled. For adjusting and controlling the elimination of the yarn deflection in the insertion brake, which is controlled such that it occupies the braking position until the insertion process has been finished, an elastically yielding energy accumulator is utilized. The energy accumulator is constructed such that it yields with a certain delay to the force exerted due to the rerouting of the weft yarn. The said energy accumulator may be a magnet or a spring whose excitation is controlled so that it will be stronger for initial braking and weaker for the subsequent damping when the deflection is being eliminated. For damping the tension peaks, the force in the deflected weft yarn, which increases when the tension increases, is used for deforming the energy accumulator, which dissipates energy and reduces tension peaks in a reciprocal action. Even if the insertion brake acts on the weft yarn only for the period of time actually required for braking and damping, the elastic energy accumulator will, after the reduction of a tension peak, generate a countermovement with a new tension peak in the weft yarn and with a retraction movement of the weft yarn into the shed. It follows that, in the case of this elastic damping, an additional interference is induced at the end of the insertion process because of the active participation of the weft yarn. Moreover, a jolt perceptible in the weft yarn as well as noticeable mechanical wear in the insertion brake are caused due to the fact that the insertion brake is moved so that it strikes a stop means.
In an air-jet loom according to EP-A1-01 55 431, a cam-controlled insertion brake is provided. A deflection lever of the insertion brake is pivoted relative to stationary rerouting elements by a cam drive in accordance with a program which is identical for all insertion processes and which has to be carried out completely during each insertion process. The insertion brake occupies a braking position at the beginning of the insertion process and is gradually moved to its position of rest when the weft yarn is starts to move for the purpose of insertion. Towards the end of the insertion process, the insertion brake is readjusted to a braking position where it will remain with increasing deflection of the weft yarn until the next insertion process takes place. However, a mechanically controlled insertion brake is not precise enough for being used with modern jet looms having high insertion speeds and a high insertion frequency.
EP-A1-01 55 431, which has a prior time rank, discloses the measures of pressing a brake pap, which is arranged on a bent lever and which is controlled via a lever mechanism, onto a countersurface and of decelerating by means of clamping the yarn passing through. The lever mechanism is driven via a stepper motor with a resolver, in accordance with the gripper movement, thus generating a specific braking force curve for the yarn. The stepper motor is controlled by programmed instructions outputted by a logic circuit.
EP-A1-04 67 059, which has a prior time rank, discloses a yarn tension regulating device also adapted for use with jet looms. It is provided with a two-armed oscillating lever whose one end deflects the yarn guided across two stationary abutments, whereas the other end thereof carries a magnet coil which is in alignment with two spaced permanent magnets of a linear electric motor. In a normal position of the lever, in which the yarn is deflected, the two permanent magnets produce an
REFERENCES:
patent: 2202323 (1940-05-01), Sullivan
patent: 3408832 (1968-11-01), Abe et al.
patent: 3633711 (1972-01-01), Pfarrwaller
patent: 5050648 (1991-09-01), Pezzoli
patent: 5179980 (1993-01-01), Hubner et al.
Jacobsson Kurt A. G.
Josefsson Paer
Tholander Lars H. G.
Falik Andrew M.
Iro AB
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