EP3106555B1

EP3106555B1 - Gripper weaving loom with a pneumatic device for the removal of wrong wefts from the gripper path and method

Info

Publication number: EP3106555B1
Application number: EP16173466.0A
Authority: EP
Inventors: Fabio Rabolini; Diego Poletti; Roberto NAVA; Walter GUERINONI
Original assignee: Itema SpA
Current assignee: Itema SpA
Priority date: 2015-06-16
Filing date: 2016-06-08
Publication date: 2019-08-07
Anticipated expiration: 2036-06-08
Also published as: CN106256937B; JP6856980B2; CN106256937A; JP2017036534A; EP3106555A1

Description

The present invention relates to a gripper weaving loom with a device for the removal of wrong wefts from the gripper path and to a method for the removal of wrong wefts that makes use of such a device.
More particularly, the invention relates to a device as above which temporarily removes wrong wefts, outside the shed, during the stop transient of the loom as a result of the insertion of a wrong weft.

BACKGROUND OF THE INVENTION

During regular operation of the loom, it can happen that the insertion of the weft thread takes place only partially, as the weft regularly inserted from one side of the loom does not reach the other side thereof. This malfunction may be due to a defect of the weft or to an excessive stress imparted to the weft during insertion, causing the mechanical breakage of the weft while being carried into the shed, or to an early release of the weft out of the carrying gripper or of the drawing gripper, or again to a failure of the drawing gripper to pick the weft when exchanging it with the carrying gripper in the middle of the shed. In short, the above three cases of irregular weft insertion are indicated as:

broken weft,
lost weft,
missed exchange between the grippers,

When occurring one of these irregular weft insertions, the loom central control unit detects it immediately, due to the absence of the weft passage through a specific sensor, arranged at the receiving side of the loom, and causes the piloted stop of the loom.
This stop, however - due to the inertia of the loom moving parts and depending on when the stop due to wrong weft occurs, on the speed of the machine and its height - often does not end within the same weft insertion cycle wherein the wrong weft occurred but rather during a subsequent cycle. Thus, once the stop is determined, it is necessary to drive the loom in reverse direction for the needed number of cycles (usually one or two) to bring it back to the same position in which the wrong weft was inserted, to manually or automatically remove that weft, and then restart the loom.
In the above transient period in which loom stopping is performed, it is possible that a drawback arises because the wrong weft - which front end has only reached an intermediate point of the shed - is more or less loose, therefore forming loops partly inside and partly outside the shed.
While the loose weft inside the shed does not cause any inconvenience, since it is immediately caught by the crossing of the warp threads and the beating up of the reed, the loose weft outside the shed, on the contrary, arranges itself along a random path; there is therefore the high risk that it is incidentally hooked by the carrying gripper performing its idle stop transient and misplaced by such a gripper within the shed, possibly causing textile defects. As a matter of fact, since the presentation and weft-cutting devices have been turned off simultaneously with the loom stopping command, the wrong weft has not been cut yet and moreover is still caught by the crossed warp threads. Therefore, depending on the toughness of the weft, such a drawback can turn out as a significative one, in case the wrong weft dragged by the carrying gripper cuts or rips a certain number of warp threads, thus increasing the drawback gravity and extending repair time.

PRIOR STATE OF THE ART

The above described problem has not been satisfactorily addressed so far by the prior art, wherein mechanical gripping devices are proposed, in the form of electrically or pneumatically-driven weft-catching hooks, which complicate the loom structure in an area already crowded with a great number of devices, and whose rate and effectiveness of intervention are unsatisfactory. As a matter of fact, the available time between the loom stop signal and the successive entrance of the carrying gripper into the shed during the loom stop transient is very short; moreover, the wrong weft is loose, thus it is not easy to make a mechanical hook catch it.
EP-1923495 discloses a mechanical device for releasing the weft carrying gripper of a weaving loom from a weft entangled in the same when a wrong weft insertion is detected, and in particular a failed weft exchange in the middle of the loom, and the loom is stopped. The device acts on the carrying gripper at its first return outside the shed, on the weft insertion side of the loom, soon after the weft error has been detected. A mobile finger acts on the gripper to open the thread gripping device while an air jet blows parallel to the weft direction to get the thread out of the gripper. Since, owing to its inertia, the loom still performs some empty strokes before stopping, it is possible to avoid in this way that the weft thread is reinserted into the loom during the subsequent movements of the grippers inside the shed.
DE-2352730 discloses a device for recovering broken wefts from the path using blowing nozzles, both from the weft insertion side and from the weft arrival side of the loom, to withdraw the broken weft from the shed and to move it into a collecting tank, through air jets parallel to the weft direction.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a device having a completely different conception and operation, compared to conventional ones, which can simply and effectively solve the above described drawback, securely preventing the wrong weft from being positioned across the carrying gripper entrance path during the loom stop transient.
This object is achieved by means of a gripper weaving loom with a pneumatic wrong weft removal device and a related method of application having the features defined in the attached claims 1 and 8. Other preferred features of such a device and its related method of application are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the loom with a pneumatic wrong weft removal device according to the present invention and of the related application method will anyhow become more evident thanks to the following detailed description of a preferred embodiment of the same, given as a mere and non-restrictive example and illustrated in the attached drawings, wherein:

Fig. 1 is a perspective view of the wrong weft removal device according to the present invention, detached from the loom;
Fig. 2 is a perspective view, from outside the loom (weft insertion side) of the wrong weft removal device of Fig. 1 mounted in place; and
Fig. 3 is a perspective view, from inside the loom (weft insertion side) of the wrong weft removal device of Fig. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The composition of the device for the removal of wrong wefts according to the present invention, as clearly shown in Fig. 1, is particularly simple and includes an electrovalve 1, controlled by the loom control unit, to which a compressed-air supply 2 and a small tube for air distribution 3 are connected, respectively upstream and downstream, the small tube 3 having a series of holes 4 on its side surface, acting as nozzles for the emission of compressed-air jets.
The electrovalve 1 has a small size and a very small thickness and can therefore be positioned without problems at the side of the sliding guide G of the carrying gripper strap, as shown in Fig. 2, so that the small tube 3 is to be arranged parallel to the same guide G (Fig. 3) in the area comprised between the weft-guiding levers F of the weft presenting machine - through which the wefts to be diverted onto the gripper path for insertion into the shed are selected - and the edge of the forming fabric, i.e. the shed entrance. Obviously, the electrovalve 1 can be replaced with any other remotely operated valve type.
The small tube 3 is fixed along the guide G in such a way that the holes 4 are arranged to direct the compressed-air jet vertically away from the carrying gripper guide G, and preferably upwards. Said holes can be longitudinally aligned along the small tube 3 or also be slightly laterally staggered from each other, e.g. alternately, to provide respectively a plurality of compressed-air jets lying on a same plane parallel to the carrying gripper guide G , or a plurality of jets alternately angled with respect to said plane so that altogether they form an air flow with a desired opening angle.
Alternatively, the small tube 3 can be replaced with a specific channel, formed inside the carrying gripper guide G, wherein holes 4 are opened for the formation of the desired air jets.
The device operation is also particularly simple and effective. The device program, included into the loom central control unit provides that, when the loom central control unit detects the presence of a wrong weft, in addition to starting the usual loom stop procedure - which involves braking and stopping the grippers movement, in one/two cycles, and simultaneously deactivating the weft presenting machine so that said cycles are carried out idly, i.e. without insertion of wefts - the activation of the electrovalve 1 into the open position is also immediately controlled, so that a compressed air flow is ejected from the holes 4 of the small tube 3, causing a lifting action on the loose weft which is positioned in that area.
The wrong weft affected by the aforementioned compressed air flow lifts upwards, spreading itself from the thread guide of the relative weft presenting machine lever F and the fabric being formed to which it is still connected, thus quickly and sharply moving away from the carrying gripper path along its guide G. In subsequent idle cycles of the grippers, any risk of interference between said wrong weft and the carrying gripper is thus eliminated, fully achieving the object of the invention.
Once the loom has been stopped - or even before it effectively stops just as soon as the carrying gripper has finished its entry travels into the shed - the electrovalve 1 is closed and it is therefore possible to start performing usual wrong weft repairing and loom restarting operations.
It is anyhow meant that the invention is not to be considered as limited to the particular embodiment above illustrated, that is just one possible preferred exemplary application, but that different variants are possible, for example concerning the shape and arrangement of the devices which cause said air flow as well as the fact that the air flow is sent directly rather than indirectly towards the area of interest, by means of conveyor or baffle elements. All such modifications are within the reach of a skilled in the art and therefore they fall within the scope of protection of the invention itself, which is solely defined by the following claims.

Claims

Gripper weaving loom with a device for the removal of wrong wefts from the gripper path, the device comprising one or more compressed-air flows controlled in opening and closing by at least one valve (1), said compressed air flows being arranged on said loom in an area comprised between the weft presenting levers (F) and the edge of the fabric being formed characterised in that said compressed-air flows are oriented so as to form an air jet apt to move the wrong weft vertically away from a carrying gripper guide (G).
Gripper weaving loom as in claim 1, wherein said air flows are arranged near the carrying gripper guide (G).
Gripper weaving loom as in claim 2, wherein said air flows are ejected by a plurality of openings (4) provided crosswise on the lateral wall of a small tube (3) axially supplied with compressed air through an electrovalve (1) and associated with the carrying gripper guide (G) so that said openings (4) face upwards.
Gripper weaving loom as in claim 3, wherein said openings (4) are aligned along a line parallel to the small tube (3) axis.
Griper weaving loom as in claim 3, wherein said openings (4) are alternatively staggered on one side and the other with respect to a line parallel to the small tube (3) axis.
Gripper weaving loom as in claims 3, 4 or 5, wherein said openings consist of continuous or discrete holes or slits for air passage.
Gripper weaving loom as in claim 2, wherein said air flows are ejected by a plurality of openings provided in a channel of the carrying gripper guide (G)-.
Method for the removal of wrong wefts from the gripper path in a gripper weaving loom, of the kind in which a loom central control unit starts a loom quick stopping procedure when a wrong weft insertion is detected,
which furthermore comprises - simultaneously or immediately after the start of said loom quick stopping procedure - the activation of one or more compressed-air flows arranged on said loom in an area comprised between the weft-presenting levers (F) and the edge of the fabric being formed, characterised in that said flows are oriented so as to form an air jet apt to move the wrong weft vertically away from a carrying gripper guide (G).
Method for the removal of wrong wefts as in claim 8, wherein the activation of said compressed-air flows lasts at least until the carrying gripper has completed its entry travel into the shed.
Method for the removal of wrong wefts as in claim 9, wherein said compressed-air flows are originated in the proximity of the carrying gripper guide (G) or directly from said guide (G) and are directed upwards.