Device for tensioning warp threads in a loom

Details Device for tensioning warp threads in a loom Device for tensioning warp threads in a loom

2000-03-15

2001-05-15

Falik, Andy (Department: 3741)

Textiles: weaving

Warp manipulation

Feeding

C139S110000

Reexamination Certificate

active

06230757

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a warp thread tensioning apparatus used in a weaving machine and comprises a rotatably supported carrier beam acting a distance from its axis of rotation on a warp thread-tensioning device and loaded preferably with a prestressed torsion spring.
2. Description of the Related Art
Apparatus of the above kind is known from U.S. Pat. No. 4,534,386. This patent discloses that the warp tension can be determined by the angular position of the carrier beam and optionally may be used to regulate or control the warp thread letting off speed. In this patent, the angular position of the carrier beam is determined not only by the warp tension, thus the determination of warp tension is fairly inaccurate.
It is known from U.S. Pat. No. 5,029,619 to determine the warp tension from the force that is exerted by parts of the warp threads via a sensor. The measured force depends on the number of warp thread threads acting on the sensor. Therefore care must be made that the number of warp threads remain constant. Moreover this design includes the danger of the sensor damaging the warp threads.
SUMMARY OF THE INVENTION
The objective of the invention is to design an apparatus related to the initially cited type of art wherein the warp tension may be accurately determined, in particular for the purpose of adjusting the warp tension and/or to regulate or control the warp thread letting-off speed as a function of the warp tension, while being free of the danger of damage to the warp thread threads.
This problem is resolved by using sensors measuring the torques of the torsion spring.
The invention offers the advantage that the warp tension can be ascertained in a simple manner from the torques exerted by the torsion spring.
In a preferred embodiment of the invention, the end of the torsion spring is mounted inside the carrier beam and is supported in the beam by means of a bearing and further is connected to a device that cooperates essentially in the radial plane of the bearing with a stationary stop, and sensors for the torques of the torsion spring which may be integrated in the torsion spring.
This design offers the advantage that torques can be sensed which substantially correspond to the torques exerted by the warp threads through the tensioning device on the carrier beam. The torsion-spring torque differs from the torque exerted by the warp threads only by the amount of torque generated by the friction of the bearing between the carrier beam and the torsion spring. In the preferred embodiment wherein the stop is mounted in the region of the bearing, resulting friction is low because the bearing is practically free of bending torque. Furthermore the friction inside the bearing is low because the carrier beam and the torsion spring rotate relative to each other during weaving operations and accordingly the friction inside the bearing is a so-called dynamic friction that is relatively low.
In one embodiment of the invention the bearing is mounted in the carrier beam and the device according the invention is mounted around said carrier beam and is situated in a radial plane running perpendicularly to the carrier-beam axis in the region of the bearing.
Preferably the bearing diameter is small. This feature offers the advantage that, because of the small diameter, bearing friction forces will apply only a slight torque on the torsion spring and as a result the sensed torque present within the torsion spring will practically be the torque exerted by the warp threads on the carrier beam.
In a preferred embodiment the bearing is a needle bearing. Such a needle bearing has low friction. Because the carrier beam and the torsion spring rotate relative to each other during weaving operations, there is little danger that such a needle bearing will wear.
In another preferred embodiment, the device of the invention comprises a non-rotating element connected to the torsion spring and linked by an adjusting element to a transmission element resting against a stationary stop. This configuration, wherein the bearing is between the carrier beam and the torsion spring is free of a bending torque due to prestressing the torsion spring, allowing the friction to be kept low in this bearing.
In another preferred embodiment of the invention, the torsion springs are composed of several segments which are non-rotationally connected to each other and are mutually displaceable in the axial direction. Preferably the springs are connected to the carrier beam selectively in a non-rotational manner. This torsion spring composed of segments offers the advantage that no axial forces caused by torsion will arise. Furthermore the spring rigidity can be set by selecting the segments connected to the carrier beam.


REFERENCES:
patent: 4240471 (1980-12-01), Rotrekl et al.
patent: 4262706 (1981-04-01), Popp et al.
patent: 4534386 (1985-08-01), Pfarrwaller
patent: 4722368 (1988-02-01), Pezzoli
patent: 5090453 (1992-02-01), Stacher et al.
patent: 5305802 (1994-04-01), Fehrenbach
patent: 5755268 (1998-05-01), Arndt et al.

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