Weft yarn insertion system having deactivatable slip conveyor an

Details Weft yarn insertion system having deactivatable slip conveyor an Weft yarn insertion system having deactivatable slip conveyor an

1996-04-23

1997-08-26

Falik, Andy

Textiles: weaving

Weft manipulation

Weaving with stationary weft supply

139450, 242 4701, D03D 4730, D03D 4734

Patent

active

056602138

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an insertion system of a jet loom.


BACKGROUND OF THE RELATED ART

In an insertion system known from EP-A1-04 77 877, a positive feed mechanism is provided downstream of a measuring feeder comprising an engageable stopper in the yarn path towards the jet insertion device of the jet loom. The feed mechanism consists either of a pair of conveyor rollers with a stationary drivable conveyor roller and a freewheeling roller and a counter-roller which can be pressed against the driven conveyor roller during part of an insertion process, or of a stationarily supported drivable conveyor roller and an actuator which presses the weft yarn onto the conveyor roller only for some time of an insertion process. The weft yarn is positively supplied for the time of the insertion process, during which the drive is activated, exactly with the speed profile of the drive and exactly at the respective circumferential speed of the conveyor roller to the jet insertion device. The drive of the driven conveyor roller is controlled according to a predetermined speed profile to relieve the jet insertion device upon withdrawal of the weft yarn. The control of the conveyor roller drive is complicated. It is difficult to adapt the engagement of the positive supply mechanism to the insertion process and to the engagement and disengagement of the stopper.
In a friction-type yarn feed device which is known from EP-B1-03 87 546 and, for instance, used for a water or air jet loom, there are provided at least two spaced-apart drums which are partly surrounded by the weft yarn and have arranged thereinbetween partition walls offset on the lateral drum surfaces. A yarn brake which is independent of the weaving cycle and fixedly set is respectively provided upstream and downstream of the friction-type yarn feed device. The friction-type yarn feed device withdraws the weft yarn from a yarn coil and supplies it with a slip to the jet loom as soon as the tension produced in the jet loom and prevailing in the weft yarn overcomes the braking effect of the yarn brake arranged downstream of the friction and yarn feed device.
It is the object of the present invention to reduce the number of yarn breaks caused by extreme changes in tension in the weft yarn during operation of a jet loom and to decrease the amount of energy spent on the medium transporting the weft yarn into the shed and to increase the insertion rate without any risk of yarn breaks.
This object is achieved with the insertion system wherein a yarn brake is provided with a slip conveyor downstream of a measuring feeder or device and a yarn brake allows the slip conveyor to be deactivated.


SUMMARY OF THE INVENTION

An exact dimensioning of the weft yarn length takes place in the weft-yarn storage, supply and measuring device. The tension produced by the jet insertion device in the weft yarn is used for requesting the slip conveyor force which supports withdrawal and acceleration and relieves the jet insertion device. The slip conveyor is not of the positively working type, but works with a slip depending, inter alia, on the weft-yarn tension, which is gentle on the weft yarn. The energy consumed by the jet insertion device can be reduced considerably to produce a specific insertion rate. Since the slip conveyor and the jet insertion device share the job, the weft yarn is gently treated. The number of yarn breaks are reduced considerably because the slip conveyor has a compensating effect and because the slip conveyor force is built up gently. The insertion rate can even be increased considerably because of job sharing, i.e., an increased insertion rate can be implemented without any risk for the weft yarn. As soon as the mass of the inserted weft yarn has to be delayed towards the end of the insertion process because of the engagement of the weft-yarn stopping and releasing device, with the jet insertion device possibly still pulling on the weft yarn, the slip conveyor force would considerably increase the yarn tension between the

REFERENCES:
patent: 4875506 (1989-10-01), Gacsay et al.
patent: 4953597 (1990-09-01), Van Bogaert et al.
patent: 5123455 (1992-06-01), Maina
patent: 5141170 (1992-08-01), Sarfati
patent: 5154209 (1992-10-01), Takegawa
patent: 5190231 (1993-03-01), Sarfati
patent: 5417251 (1995-05-01), Josefsson et al.

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