Textiles: weaving – Stopping – Weft
Reexamination Certificate
2000-09-25
2001-09-11
Falik, Andy (Department: 3765)
Textiles: weaving
Stopping
Weft
C242S419300, C139S450000, C139S452000, C335S257000
Reexamination Certificate
active
06286562
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a weft brake, particularly for weaving looms and the like.
As it is known, weft thread is fed to weaving looms by unwinding the weft thread from a spool which is arranged ahead of a weft thread feeder, from which the thread is then sent to the weaving loom or other textile machine.
Electrically-actuated weft brakes are typically inserted between the spool and the feeder and between the feeder and the loom and are meant to modulate the mechanical tension of the thread in order to adapt it to the weaving requirements.
Modulation of the braking action is achieved in several conventional manners and in particular by passing the thread between two laminar elements, respectively a fixed one and a movable one, and by varying the mechanical pressure with which the movable element is pressed against the cooperating fixed element.
As an alternative, both the fixed element and the movable element are comb-shaped, with tines ending with transverse bars which mutually interpenetrate, varying the degree of mutual penetration of the two combs, which accordingly deflect to a greater or smaller extent the path of the thread, correspondingly braking its sliding.
In both cases, the movable element of the weft brake is moved by an electric actuator which is supplied with a current modulated according to the modulation of the intended braking action.
As it is also known, the movable element of weft brakes is actuated by means of linear electric motors, particularly with three-pole motors having very high intervention speeds and requiring very low excitation currents.
Conventional weft brakes of the specified type, while providing excellent performance in terms of braking action, suffer drawbacks and in particular are not entirely satisfactory as regards the possibility to modulate the braking action.
Moreover, the weft brakes can break the thread rather easily, especially in the presence of uneven portions, e.g. in the presence of knots or weaker portions of the thread.
SUMMARY OF THE INVENTION
The aim of the present invention is to eliminate the above noted drawbacks and to provide a weft brake which not only can apply a powerful and rapid braking action when required but also can apply an action which can be easily modulated and most of all is gradual, in order to facilitate the passage of knots or other uneven portions, where the term “gradual” designates a braking action which is not only modulated but variable from the inlet to the outlet of the weft brake.
Another important object of the invention is to provide a weft brake which has a simplified and sturdy structure and is very reliable in operation.
Another important object of the invention is to provide a weft brake which is capable of containing the moving thread and of preventing the thread from disengaging from the fixed and movable elements and escaping the modulated braking action of the weft brake.
In order to achieve this aim, these and other objects which will become better apparent from the following detailed description, the present invention provides for a weft brake for weaving looms having the specific characteristics stated in the appended claims.
Substantially, the invention is based on the concept of making the weft thread slide between a rigid and flat fixed plate made of non-magnetic material (e.g. aluminum) and a flexible lamina made of magnetic material (e.g. steel) in which only one end is rigidly coupled to the rigid support; and of magnetically actuating the lamina against the fixed and rigid plate by means of a movable yoke provided with a plurality of permanent magnets and subjected to an electric actuator which is energized by a current modulated according to the modulation required for the braking action, and which moves the yoke with respect to the lamina so as to move the magnets towards or away from the lamina in order to correspondingly vary the attraction applied by the magnets to the lamina and accordingly vary the pressure that the lamina applies to the thread to brake it.
REFERENCES:
patent: 4875506 (1989-10-01), Gacscay et al.
patent: 5398731 (1995-03-01), Schuster
patent: 5398732 (1995-03-01), Zenoni et al.
patent: 5492286 (1996-02-01), Motta
Castelli Rosario
Pedrini Giovanni
Zenoni Pietro
Falik Andy
Josif Albert
L.G.L. Electronics S.p.A.
Modiano Guido
O'Byrne Daniel
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