WO1997013902A1

WO1997013902A1 - Method for the automatic extraction of faulty weft yarns from the shed of a gripper loom

Info

Publication number: WO1997013902A1
Application number: PCT/EP1996/004333
Authority: WO
Inventors: Egidio Tasca
Original assignee: Somet Societa' Meccanica Tessile S.P.A.
Priority date: 1995-10-06
Filing date: 1996-10-04
Publication date: 1997-04-17
Also published as: DE69607973D1; DE69607973T2; EP0853693B1; ITMI952038A1; IT1276828B1; EP0853693A1; ITMI952038A0

Abstract

A method for the automatic extraction of a short weft yarn from the shed of a gripper loom comprises, upon detection of the error, the following stages: deactivating the cutting means (M) and the weft feeding devices (F) stopping the loom, moving the loom backwards into the position where the faulty weft (A) was inserted; selecting the weft feeding device (F) on the same faulty weft and inserting across the shed with the new weft grippers (C, R) a new weft (A') connected to the faulty weft; recovering the new weft launched and hence the faulty weft (A) on the weft insertion side; moving the loom backwards so as to bring it back into the position where the faulty weft (A) was inserted.

Description

METHOD FOR THE AUTOMATIC EXTRACTION OF FAULTY WEFT YARNS FROM THE SHED OF A GRIPPER LOOM

*0*O*O* The present invention relates to a method for performing the automatic extraction of faulty weft yarns from the shed of a gripper weaving loom. In particular the method has been devised to allow the automatic extraction of weft yarns which have become detached from the grippers during carrying or during exchange of the weft yarn between the carrying gripper and the drawing gripper. In other words, the method according to the present invention can be applied to all those cases of a faulty yarn where there has been no interruption in the continuity of the weft yarn itself.

Hitherto various methods and devices based on mechanical or pneumatic operation or a combination thereof have been proposed for performing the automatic extraction of faulty yarns from the shed of the loom, but only in the sector of air looms. Among the most improved methods of this type there are those which allow extraction of the faulty weft from the weft receiving side of the loom with a "peeling" effect (in the manner of adhesive tape) so as to avoid undesirable over-tensioning of the weft yarn itself and warp yarns which - particularly in the case of natural yarns - already adhere tightly thereto as a result of beating-up of the reed. It must be remembered, in fact, that when the loom monitoring devices detect that the weft has failed to arrive on the weft receiving side and therefore send a stop signal to the loom, said loom - on account of the inertia of its moving parts - cannot be stopped immediately, but only after at least one stroke. During this braking stroke, the weft insertion device is immediately stopped, and for this reason said stroke is referred to as an "idle stroke", but obviously it is not possible to prevent movement of the reed which therefore performs in the normal manner beating-up of the faulty weft on the fabric being formed. When, immediately after stopping, the loom performs an idle stroke backwards so as to reveal the faulty weft, the latter obviously - except in the case of very shiny synthetic fibres - is already tightly pressed against the warp yarns, thus requiring extraction by means of peeling, i.e. from the weft insertion side of the loom, but with the direction of extraction towards the weft receiving side of the loom. An improved device of this type is described in the patent EP-A-

534541 in the name of same Applicant, the contents of which are understood as being incorporated here for the sake of reference, as far as it is useful or necessary for better understanding of the present invention. For some time the Applicant has been attempting to solve the problem of transferring, also to gripper looms, a system for automatic extraction of the faulty wefts which is similar, in terms of operating principle, to that developed for air looms. The difficulties in achieving this transfer, however, have been numerous and consist in particular in the need to avoid the loom becoming burdened with an excessive amount of additional equipment, compared to that required for normal weaving operations, both owing to obvious considerations of an economic nature and owing to the space occupied by this additional equipment which is not always compatible with the space available on the loom.

Consequently, the arrangement used by the Applicant in the aforementioned patent for extraction of the faulty weft in air looms - which involves the formation of a loop of weft yarn connected to the faulty weft and the extraction of said loop and then the defective weft from the weft receiving side of the loom - was not feasible at all in gripper looms because obviously they do not have, in that position, the pneumatic device for tensioning the weft which is present in air looms (with which device, therefore, in said looms, the extraction device could be associated). Finally, this operation would require a further exchange of weft, in addition to that normally performed between carrying gripper and drawing gripper, i.e. an exchange of weft between the carrying gripper and the aforementioned hypothetical extraction device, an exchange which would certainly require modification in the operation of the drawing gripper since the latter, as is well known, is normally controlled so as to release the weft yarn as soon as it leaves the shed. Another important difference between air looms and gripper looms concerns, on the weft yarn insertion side, the positioning of the waiting weft yarns. While, in fact, in the case of air looms, said yarns are always in the launching position inside a nozzle gun, in gripper looms they must instead be brought on each occasion in front of the entry path of the carrying gripper and this operation would certainly be impossible or in any case more complicated in the case where the weft feeding yarn terminating in the faulty weft were extracted from the weft receiving side, as instead occurs advantageously in air looms.

After extensive research on the subject, the Applicant has finally managed to devise a method for extracting the faulty wefts which can be applied to gripper looms, according to which the faulty weft is extracted on the weft insertion side of the loom, although with the same weft peeling effect already obtained for air looms and described in the aforementioned European patent. In this way the extraction method may be realized without the need for special additional devices in the loom - except obviously for the actual device for picking up and extracting the broken weft - and without modifying the basic operating parts of the loom and in particular the grippers.

The aforementioned method for the extraction of faulty weft yarns from the shed of a gripper loom is therefore characterized by the following steps: a) deactivating the weft cutting means and the weft feeding devices and at the same time stopping the loom; b) moving the loom backwards, bringing it back into the position where the faulty yarn was inserted; c) selecting the weft feeding device on the same weft where faulty insertion occurred and inserting a new weft across the shed by means of the carrying gripper and the drawing gripper of the loom; d) stopping the loom as soon as the new weft has emerged from the weft receiving side of the loom; e) recovering the new weft launched and hence the faulty weft connected thereto, on the weft insertion side; f) moving the loom backwards, bringing it back into the position where the faulty weft was inserted.

The method for the automatic extraction of faulty weft yarns according to the present invention will in any case now be better illustrated in detail with reference to the accompanying drawings which illustrate schematically some operating steps and in which:

Fig. 1 is a schematic plan view of the loom illustrating insertion of a faulty weft;

Figs. 2 and 3 are views similar to Fig. 1 which illustrate the initial steps of separation of the faulty weft from the warp yarns, with a peeling effect;

Fig. 4 is a view similar to that of Fig. 1 which shows the final step of extraction of the faulty weft into the pneumatic/mechanical winding device; and

Fig. 5 is a schematic side view of the loom, on the weft insertion side, during the final stage of extraction of the faulty weft into the pneumatic/mechanical winding device.

In the drawings, the conventional parts of a gripper loom are shown in a manner which is fairly schematic, although entirely adequate for understanding of the invention by a person skilled in the art and so as to ensure greater simplicity in interpretation of the drawings themselves. The individual devices, known per se, of a gripper loom to which the method of the invention is applicable are denoted by the following reference letters: W for the waiting weft yarns, O for the warp yarns, T for the fabric being formed, P for the reed, S for the device detecting the weft on the weft receiving side, G for the weft guiding device on the weft insertion side, M for the weft cutting means, F for the weft insertion devices or fingers (shown in the drawings simply with the respective yarn threading eyelet), C for the carrying gripper and R for the drawing gripper.

When insertion of a faulty weft A occurs, the sensor S detects the fault and sends a stop signal to the loom, immediately deactivating the weft feeding movement of the fingers F and the cutting means M. The loom therefore performs, as mentioned above, an idle stroke during which the weft A is beat up by the reed against the fabric T being formed. At the same time as deactivation of the fingers, suction of a nozzle 1 , oriented perpendicularly with respect to the weft, is activated, thus ensuring that the weft A is kept tensioned so as to avoid being gripped by mistake during an idle stroke of the loom. At the end of the idle stroke, the loom stops and automatically performs an idle stroke backwards so as to free the faulty weft A from the warp yarns.

As already mentioned, if one attempted at this point to free the faulty weft from the shed, drawing it out towards the weft insertion side of the loom, considerable difficulties would be encountered since the weft has already been inserted and beat up inside the shed and greatly resists direct extraction since it is intertwined both with the warp yarns and with the preceding weft yarn against which it has been beat up. This operation can therefore be performed in very few cases and only when the yarns have a very low mutual adherence factor (e.g. some synthetic yarns). In all other cases, and in particular in the case of natural yarns such as wool and cotton, the pulling force required to free the faulty weft could cause breakage of the weft yarn or one or more of the warp yarns, or at least an unacceptable lateral displacement of the latter.

According to the automatic extraction method of the invention, however, a loop is formed with the weft yarn A' still attached to the faulty weft A, using for this purpose the pair of carrying and drawing grippers C and R, as illustrated in Figs. 2 and 3, during execution of a forwards stroke of the loom performed at very low speed. For this purpose, the same finger F of the weft feeding device where stoppage for the faulty weft occurred - indicated by the reference 3 in Figs. 2 and 3 - is reselected, excluding with suitable control means the cutting means M and raising at the same time the weft guide G from the working position shown in continuous Iines in Fig. 5, into the rest position G' shown in the same figure in broken Iines, and freeing in this manner from the groove 4 the waiting wefts W including the weft A' which is still joined, since the cutting means M have been deactivated, with the faulty weft A.

When the carrying gripper C picks up again this new weft A' and transports it into the shed, said weft, freed from the weft guide G, extends in a rectilinear manner within the shed between the finger 3 and the carrying gripper C and, as can be clearly seen from Figs. 2 and 3, as the new weft is carried through the shed by the carrying gripper C and then by the drawing gripper R, the faulty weft A is separated from the shed with a peeling effect starting precisely from the weft insertion side of the loom. In this way it is possible to achieve a reliable and problem- free extraction even in the case of weft yarns which have a high adherence factor and low mechanical resistance. When the drawing gripper has emerged from the shed, the loom stops, but the faulty weft cannot be completely freed yet (it is freed in fact only if it terminated within the first half of the shed) and its end at this point is freely housed in the hook of the drawing gripper R outside of the shed. As is well-known, in fact, the holding device of the drawing gripper R is structured so as to open when leaving the shed, without however allowing the loop formed by the weft A-A' to come out of the eyelet formed by the hook of the gripper R.

In order to complete extraction of the faulty weft, according to the method of the present invention, at this point use is made of a pneumatic/mechanical extraction device E of a type known per se, schematically illustrated by way of example in Fig. 4. For example, devices of the type described in the abovementioned European patent or in the patent EP-A2-200 168 (Tsudakoma) may be used. In any case the devices in question are ones which combine a sucking function capable of drawing the weft yarn inside a suction mouth of the device itself, where intermittent or continuous mechanical recovery of the weft yarn is performed. Such a suction device, however, in view of its position with respect to the weft yarn A-A', is normally unable to draw directly the yarn inside its own suction mouth 5. For this reason, according to the present invention, the device E is equipped with a hook 6 operated, by a pneumatic cylinder or by other known means, so as to move in a linear path between an extended position where it interferes with the path of the weft yarn A-A' so as to pick up the latter and a position close to the suction mouth 5 into which the weft yarn A-A' may be directly sucked in by the suction air stream inside the pneumatic/mechanical device E. A pair of yarn guides 7 and 8 fixed to the reed P, during this pick-up action by the hook 6 and during the subsequent operation involving extraction of the weft yarn A-A', prevent the yarn itself from being able to interfere with the reed P.

When the weft yarn A-A' is picked up by the drawing or winding device situated inside the pneumatic/mechanical device E, extraction of the faulty yarn A from the shed may be continued owing to the fact that said yarn is guided, in the manner of a pulley, by the hook of the drawing gripper R, said extraction continuing with a peeling effect until all the yarn A has been extracted from the shed and collected inside the pneumatic/mechanical device E, where a special sensor (not shown) detects the absence of the second incoming yarn and issues a consent command to the loom to start the weaving operations again.

The loom, at this point, is in the position shown in Fig. 5, with the warp yarn shed now completely closed (it will be remembered, in fact, that the loom was stopped when the drawing gripper R had already moved outside the shed) but not yet reopened in the opposite direction so as not to hinder recovery of the weft yarn A-A' by the pneumatic/mechanical device E. It is therefore necessary to perform a backward stroke of the loom in order to restore the starting position preceding insertion of the faulty weft A. Performing this operation, the reed P returns into the beating-up zone (shown in broken Iines in Fig. 5) and the yarn guide 7 is thus able to draw the weft yarn A-A' (which is kept taut by the pneumatic/mechanical device) towards the weft guide G which in the meantime has been lowered again into its working position, picking up again the said weft yarn inside the groove 4 thereof.

The loom, at this point, is ready to start again, after performing one of the ordinary automatic restart programs with one or more idle strokes in order to eliminate the signs of stoppage. As soon as the consent command is issued to the weft feeding device, the latter is able to lower the finger 3 so that the carrying gripper C picks up the weft yarn A', carrying it inside the shed. At this point the cutting means proceed to cut, in the usual manner, said weft yarn, the tail end of which is then completely sucked in by the pneumatic/mechanical device E and then discharged in a manner known per se. The pneumatic/mechanical device is then repositioned for a new extraction operation and weaving is resumed in the normal manner.

The description of the method for automatic extraction of the faulty weft according to the present invention has been provided with reference to an embodiment thereof. It must however be clearly understood that, while some steps of the process are to be regarded as essential and hence limiting the invention, as moreover will become clear from the accompanying claims, the remaining steps may be performed also with devices and systems different from those described here, without thereby departing from the scope of the invention itself.

Claims

1 ) Method for the automatic extraction of a faulty weft yarn from the shed of a gripper weaving loom of the type comprising a weft feeding device, a carrying gripper, a drawing gripper, a reed for beating up the weft, weft cutting means on the weft insertion side of the loom and a weft detection device on the weft receiving side of the loom, characterized in that, when a signal indicating that the weft has not arrived is issued by the weft detection device, it comprises the following steps: a) deactivating the weft cutting means and the weft feeding means and at the same time stopping the loom; b) moving the loom backwards, bringing it back into the position where the faulty yarn was inserted; c) selecting the weft feeding device on the same weft where faulty insertion occurred and inserting a new weft across the shed by means of said carrying gripper and drawing gripper; d) stopping the loom as soon as the new weft has emerged from the weft receiving side of the loom; e) recovering the new weft launched and hence the faulty weft connected thereto, on the weft insertion side; f) moving the loom backwards, bringing it back into the position where the faulty weft was inserted.

2) Method as claimed in claim 1 , wherein the loom also comprises a weft guiding device designed to retain in one of its grooves the waiting wefts, characterized in that step b) is followed by the following additional step: b1 ) moving the weft guiding device from a working position where the waiting wefts are retained inside a groove of the device into a rest position where the wefts are free from said groove. 3) Method as claimed in claim 1 or 2, wherein insertion of the new weft according to step c) is performed at low speed.

4) Method as claimed in any one of the preceding claims, wherein recovery of the weft on the weft insertion side is performed by means of pneumatic/mechanical device comprising suction means designed to draw the weft yarn inside the device and mechanical means for intermittent or continuous recovery of the weft yarn. 5) Method as claimed in claim 4, further comprising a hook device, controlled by a linear actuator, for picking up the weft yarn to be recovered and bringing it into the vicinity of the mouth of the suction means of the pneumatic/mechanical device.

6) Method as claimed in claim 5, further comprising two yarn guiding devices fixed laterally to the reed on the weft insertion side of the loom, for guiding the weft yarn during the operation of recovery by the pneumatic/mechanical device.

7) Method as claimed in claim 6, wherein step f) is preceded by the following step: fO) bringing the weft guiding device back into its working position; and during the same stage f) one of the said two yarn guiding devices fixed to the reed draws the weft yarn inside the retaining groove of the weft guiding device.

8) Method as claimed in any one of the preceding claims, wherein step a) involves activation of a suction nozzle acting perpendicularly on the free weft yarn outside the shed so as to keep it tensioned.