[0001] The present invention relates to an electrically-controlled device for programmable
weft cutting in weaving looms.
[0002] It is a fact known to experts that - with improving weaving loom performances both
in terms of speed and in terms of the capability to widen the range of weavable yarns
- the importance of the manner and of the time in which cutting of the wefts inserted
into the loom shed is performed has steadily increased.
[0003] This is particularly true for gripper looms, which are the ones where the range of
woven yarns has widened the most, thanks to the introduction of electronic actuators
capable of controlling the operation of the main members of the weaving machine according
to the weaving parameters.
[0004] Manners and means to increase the versatility of gripper looms acting on the phase
displacement have already been suggested: they act either on a programmed or on a
real-time phase displacement, between main loom motion and weft cutting, after the
weft has been gripped by the carrying gripper.
[0005] As is known, the weft selected by the presenting device is inserted into said looms,
between the holding members of the carrying gripper, until it is locked. Depending
on the features of the weft yarn, the locking may occur also in a position which is
more or less advanced in respect of the holding area of the gripper.
[0006] It is equally known that the cutting device operates in a point of the weft portion
which is tensioned between the line of the false selvedge and the weft-holding member
of the carrying gripper, while said gripper moves towards the inside of the shed.
Now, depending on the weft cutting instant, the weft portion gripped by the holding
member of the carrying gripper slides more or less markedly along the side of the
holding member according to the size (count) and to the nature of the weft yarn. In
other words, the geometric layout taken on by the weft yarn in respect of the gripper
is a function of the size features and of the textile nature of the weft yarn.
[0007] In essence, so far, in each individual case, the instant has been established in
which the weft must be cut, in particular acting on the weft cutting assembly, to
anticipate or delay weft cutting in respect of a nominal reference value, which is
linked to the steady speed of the loom and to the type of weft.
[0008] The choice of said positive or negative phase displacement has hence been linked
(see for example
EP 839,938) to the type of weft selected by the colour selector or by the weft selector, as
well as to the position of the carrying gripper in the weaving cycle and to the rotation
angle of the main shaft of the loom. The result should be particularly effective wherever
the weft gripping system mounted on the carrying gripper consists of a pressure-operated
elastic system, such as the one providing a weft holding lever pushing on the body
of the gripper itself. In said system, as a matter of fact, it is advantageous to
insert the weft for a portion varying according to the weft count and weft type, in
order to avoid both the danger of mistransfers to the drawing gripper, due to too
high a holding force preventing deep insertion, and weft loss in the first portion
of the distance covered by the gripper, due to the insufficient pressure imparted
by the holding member.
[0009] However, the suggestions detailed above have never brought satisfactory results.
As far as the Applicant is aware, up until now controlling the cutting device was
the job of straight-line electric motors acting directly onto the two blades of the
device itself, with the result that the control response was not sufficiently quick
and the controls were excessively stiff. It was also very difficult to monitor the
controls in such an accurate and fine-tuned manner as would be desirable, again due
to the direct operation of the cutting device blades by the straight-line electric
motors.
EP-0 679 744 discloses a weft yarn device comprising a first and second coaxial blade driven by
an electric motor through cam means, wherein the axis of rotation of the first and
second blade is inclined in respect to the feed direction of the fabric and in respect
to the axis of rotation of said motor.
[0010] The present invention instead solves the problem in the most effective and satisfying
way, by resorting to an original and innovative combination of the traditional control
technique of the cutting device with the new concepts described above.
[0011] According to the invention, the weft cutting device of a gripper loom provides that
the two blades thereof are driven by cam means operated by an electric motor which
is programmable according both to the main motion of the loom, and to the textile
features of the weft yarn.
[0012] Preferably, said blades are carried by two oscillating arms and said cam means comprise
two cams arranged side by side and mounted coaxially on the shaft of the programmable
motor and relative cam followers on said arms.
[0013] According to the invention, said blade-mounting arms are mounted parallel and side
by side, oscillating about the same axis, the shaft of the programmable motor and
of the cams being parallel to the oscillating axis of the blade-mounting arms.
[0014] The invention will now be described more in detail - merely by way of example - with
reference to a currently preferred embodiment thereof, illustrated in the accompanying
drawings, wherein:
[0015] fig. 1 is a diagrammatic representation of the weft cutting device according to the
invention, and of the application thereof to a gripper loom; and
[0016] fig. 2 shows more in detail, in a perspective view, the weft cutting device according
to the invention and the motor for the operation thereof.
[0017] With reference to the enclosed drawings, the electrically-controlled device for the
programmable cutting of the weft in gripper weaving looms according to the invention
comprises in a known manner two blades 1 and 2 to be operated at the time of insertion
of the weft T - fed by one of the rods A of a presenting device - into the carrying
gripper P of a weaving loom.
[0018] As is apparent from fig. 2, the two blades 1 and 2 of the device are carried by two
corresponding arms 3 and 4, which are mounted parallel and side by side, oscillating
about the same axis O. On the arms 3 and 4, cam followers 5 and 6 are provided, onto
which two cams 7 and 8 act, mounted coaxially on the shaft 9A of a programmable electric
motor 9.
[0019] This motor is electronically controlled according to the general motion of the loom
and to the textile features of the weft yarn (weft count and yarn nature, among others),
as is diagrammatically shown in fig. 1. In this drawing the block 10 represents the
hardware of the presenting device and comprises sensors of the position of the rods
A presenting the weft T. The block 11 manages the data concerning the general motion
of the loom; furthermore, data relating to size (count) and nature of the yarn used
as weft for the weaving are set therein. The data originating from the block 10 and
from the block 11 are transmitted to the block 12, which processes them to control
the functioning of the motor 9 and to programme the instant in which the cutting blades
1 and 2 are operated to perform the cutting of the weft T.
[0020] The good functioning of the device (which could not be obtained with the electrically-controlled
solutions of the prior art mentioned at the beginning of the present description)
is due to the fact that the motor 9 does not operate directly onto the blades 1 and
2 - with low inertias, high pickup requirements in order to adapt to the laws of motion
of the loom and the resulting high powers of the motor which are difficult to reconcile
with those of the miniaturisation of the device on the whole and of the electric motor
in particular -, but acts through the cam means 5 to 8, which create an excellent
flywheel effect, increasing the inertias at play in the control of the levers 3 and
4. This allows, on the one hand, to make the controls of the blades 1 and 2 smooth
and gradual, as well as extremely accurate in the timing, and on the other hand to
reduce the power of the motor 9 and consequently its size and its manufacturing and
running costs. Furthermore, the importance of the cutting speed being apparent in
order to prevent - especially for wefts with a significant weft count - the weft from
being torn in its final fibres after an initial cut, using cams to control the motion
of the two blades can have the result that, during the usable cutting period, the
speeds of the two blades (with the same direction but opposite sense) add to each
other to form the total cutting speed. This allows not to concentrate the stress onto
one blade only and onto its corresponding cam-roller assembly, i.e. to obtain a high
cutting speed, without stress increase and with a single motor of limited power. For
all these reasons, the electrically-controlled device for programmable weft cutting
in gripper weaving looms according to the invention is at the same time more effective,
more compact and less expensive than those already devised, despite the more elaborate
and consequently less foreseeable combination which distinguishes it therefrom.
[0021] It is understood that the invention may be carried out also according to different
embodiments from that described in detail, without departing from the scope of the
present claims.
1. Electrically-controlled device for programmable weft cutting in gripper weaving looms,
of the type comprising two blades to be operated at the time of insertion of the weft
into the carrying gripper, said blades (1, 2) being controlled by cam means (5-8)
operated by an electric motor (9) programmable according both to the main motion of
the loom and to the textile features of the weft yarn and carried by two oscillating
arms (3, 4) mounted parallel to each other, side by side, and oscillating about the
same axis (O), characterised in that the shaft (9A) of the motor (9) and of the cams (7, 8) are parallel to the oscillation
axis (O) of said blade-mounting arms (3, 4).
2. Electrically-controlled device as in Claim 1, comprising sensors (10) of the position
of the rods (A) presenting the weft (T) , means (11) for managing both the data concerning
the general motion of the loom and the textile features of the weft yarn being woven,
and a processing unit (12) apt to process the data provided by said sensors (10) and
said means (11) and to control said programmable election motor (9) to perform the
cutting of the weft yarn (T).
3. Electrically-controlled device as in Claim 2), wherein said textile features of the
weft yarn are the size (count) and nature of the weft yarn being woven.
1. Elektrisch gesteuerte Vorrichtung zum programmierbaren Abschneiden von Schussfäden
in Greiferwebstühlen, der Bauart, die zwei Klingen umfasst, die zu dem Zeitpunkt des
Einfügens des Schussfadens in den tragenden Greifer zu betätigen sind, wobei die Klingen
(1, 2) durch Nockenmittel (5-8) gesteuert sind, die durch einen Elektromotor (9),
der sowohl entsprechend der Hauptbewegung des Webstuhls als auch der Textilmerkmale
des Schussfadens programmierbar ist, betätigt sind und von zwei Schwingarmen (3, 4)
gehalten sind, die parallel zueinander und nebeneinander angebracht sind und um die
gleiche Achse (O) schwingen, dadurch gekennzeichnet, dass die Welle (9A) des Motors (9) und der Nocken (7, 8) parallel zu der Schwingachse
(O) der genannten die Klingen haltenden Arme (3, 4) sind.
2. Elektrisch gesteuerte Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, dass sie Sensoren (10) für die Position der Stangen (A) aufweist, die den Schussfaden
(T) vorlegen, Mittel (11) zum Verwalten sowohl der Daten, die die allgemeine Bewegung
des Webstuhls betreffen als auch die Textilmerkmale des Schussfadens, der verwoben
wird, und eine Verarbeitungseinheit (12), die sich dafür eignet, die Daten zu verarbeiten,
die von den genannten Sensoren (10) und den genannten Mitteln (11) bereitgestellt
werden, und um den genannten programmierbaren Auswahlmotor (9) zu steuern, um das
Abschneiden des Schussfadens (T) durchzuführen.
3. Elektrisch gesteuerte Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, dass die Textilmerkmale des Schussfadens die Größe (Zählung) und die Art des Schussfadens,
der verwoben wird, sind.
1. Dispositif à commande électrique pour une coupe programmable du fil de trame dans
des métiers à tisser à pinces, du type comportant deux lames destinées à être actionnées
au moment de l'insertion du fil de trame dans la pince de transport, lesdites lames
(1, 2) étant commandées par des moyens à cames (5-8) actionnés par un moteur électrique
(9) programmable en fonction à la fois du mouvement principal du métier et des caractéristiques
textiles du fil de trame, et portées par deux bras oscillants (3, 4) montés parallèlement
l'un à l'autre, côte à côte, et oscillant autour du même axe (O), caractérisé en ce que l'arbre (9A) du moteur (9) et celui des cames (7, 8) sont parallèles à l'axe d'oscillation
(O) desdits bras (3, 4) de montage des lames.
2. Dispositif à commande électrique selon la revendication 1, comportant des capteurs
(10) de la position des tiges (A) présentant la trame (T), des moyens (11) destinés
à gérer à la fois les données concernant le mouvement général du métier et les caractéristiques
textiles du fil de trame en cours de tissage, et une unité de traitement (12) apte
à traiter les données fournies par lesdits capteurs (10) et lesdits moyens (11) et
à commander ledit moteur électrique programmable (9) pour exécuter la coupe de fil
du trame (T).
3. Dispositif à commande électrique selon la revendication 2, dans lequel lesdites caractéristiques
textiles du fil de trame sont la taille (le comptage) et la nature du fil de trame
en cours de tissage.