The present invention refers to a controlled system for supplying weft yarn in a loom.

In particular, the present invention refers to a system for unwinding, measuring and accumulating weft yarn suitable for weave wefts whose shape and consistency require attention when weaving, avoiding for example their twisting. Woven wefts such as ribbons and straps falls within these types .

In particular, the present invention refers to a version of weaving looms equipped with a single gripper, which, by moving for the whole width of the fabric, reaches the opposite end, grips the weft and drags it to the other end. These looms are usually defined as mono-grippers .

The means of transport of the gripper can indifferently be flexible belts or rigid rods.

The need of inserting particular wefts, such as straps and ribbons, is more and more felt, for weaving fabrics, whose peculiarity consists in arranging the weft in an orderly way always parallel to the weaving plane.

These types of weft require: a weft unwinding by rotating the reel to prevent further torsions from forming on the weft itself; an accurate measure of the weft section to be inserted in the loom pitch; a weft accumulation during the non- weaving phase.

The prior art related to means for supplying the weft gripping activity, above all in case of particular yarns, is given by several patents.

Patent DE10315347B4 discloses a device for accumulating weft yarn comprising a piston-cylinder assembly and a piston-type deflecting device strongly assembled into the cylinder. A lower pressure is applied both on one side of the deflecting device opposite to the direction of the resultant of the traction force, and on the side along the traction force direction. The position of the deflecting device is detected in certain phases and converted into binary codes through an analogue/digital converter. The binary codes are analysed and then converted into an analogue output signal by a digital/analogue converter to be able to control the drive of the supplying coil. The output signal is passed through a low-pass filter connected to a proportional, integral and differential, PID controller.

Patent application WO2014009063A1 discloses a device for an intermediate storage of two weft yarns shaped as a strap or ribbon for a weaving machine. The device comprises two containers, in each one of which a U-shaped ring of a weft filament can be formed. According to the invention, means are provided for applying weft traction forces, in the internal chamber of the respective container. Deflecting elements are arranged on the containers, so that the respective weft material can be supplied in the internal chamber in a region, which is nearer to the narrow side of the internal chamber.

The above described prior art solves the problem of the controlled unwinding of wide wefts, such as ribbon and strap, through motored means applied to the reel of wound thread controlled in a closed loop. The necessary amount of weft for weaving is measured and accumulated in the same U- shaped device.

A problem present when weaving wide wefts, such as ribbons and straps, is having to comply with parameters such as traction force and accuracy of the weft length to be accumulated before weaving, in addition to having to avoid the torsion of the sliding yarn.

This kind of problems implies the need of increasing the care paid for unwinding, through a greater control of the motive torque applied onto the axle of the reel equipped with wound yarn, for measuring, through a control of the tension acting on the weft section while it is measured and for accumulating a such weft section.

Object of the present invention is solving the above prior art problems, by providing a system for supplying weft yarn wherein the three steps, unwinding, measuring and accumulating, are performed through an increase of the accuracy of the physical quantities in a mutual relationship.

A further object is making the reel unwinding speed constant to avoid the negative influence of various motions.

A further object is using actuators in a mutual relationship having the same resolution accuracy to be able to strongly reduce the degree of discretization and to increase the control accuracy of the section of length of the weft to be woven depending on the traction acting on the yarn itself .

A further object is embedding in a single actuator the measuring and accumulating steps depending on the weft unwinding step.

The above and other objects and advantages of the invention, as will result from the following description, are obtained with a controlled system for supplying weft yarn in a loom as claimed in claim 1. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears form the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

- Figure 1 shows a front view of a first embodiment of the controlled system for supplying weft yarn according to the present invention;

- Figure 2 shows a rear axonometric view of the system of the previous figure;

- Figure 3 shows a front view on the rear of the system of the previous figure, wherein a path of a weft yarn is shown;

- Figure 4 shows a front view of a second embodiment of a device of the controlled system for supplying weft yarn according to the present invention; and

- Figure 5 shows a front axonometric view of the device of the previous figure.

With reference to the Figures, it is possible to note that a controlled system for supplying weft yarn in a loom comprises supply control means of the weft yarn to allow inserting means to insert the weft in the pitch, unwinding means 1 of the weft yarn wound on a reel, measuring and accumulating means 2 of an unwound section of length of the weft yarn. The measuring and accumulating means 2 comprise first sliding means 21 adapted to deviate the weft yarn with respect to second sliding means 22.

Advantageously, the system comprises further measuring and accumulating means 3, 4 of an unwound section of length of the weft yarn adapted to allow that the motion of the unwinding means 1 is approximately constant.

With reference to Figure 2, the unwinding means 1 of the weft yarn wound on a reel, the measuring and accumulating means 2 of an unwound section of length of the weft yarn and the further measuring and accumulating means 3, 4 of an unwound section of length of the weft yarn are connected to a drive 100, 200, 300 controlled by the supply control means of the weft yarn to allow the inserting means to insert the weft in the pitch.

The further measuring and accumulating means 3, 4 comprise oscillating means 30, 40 adapted to allow accumulating the weft yarn, in strict relationship with the motion of the unwinding means 1 and in strict relationship with the motion of the inserting means of the weft in the pitch.

The oscillating means 30, 40 comprise at least one oscillating arm 31, 41 with respect to a rotation axis. The oscillating arm 31, 41 comprises third sliding means 32, 42 adapted to allow deviating the weft yarn with respect to fourth sliding means 33, 43. Moreover, the oscillating arm 31, 41 is connected to a motor, which moves approximately with a constant torque.

In particular, the oscillating arm 31, 41 moves with a first motion law adapted to allow deviating the weft yarn to be able to follow the speed of the unwinding means 1 and with a second motion law adapted to allow deviating the weft yarn to be able to follow the speed of the inserting means of the weft in the pitch.

The control means of the system allow actuating a self-learning cycle, without knowing the weaving height, through suitable sensors for detecting the sliding of the weft.

According to a variation of the system, not shown, the measuring and accumulating means 2 comprise at least one oscillating arm with respect to a rotation axis. Such oscillating arm comprises the first sliding means 21 adapted to allow deviating the weft yarn with respect to the second sliding means 22.

The controlled system for supplying weft yarn of the present invention allows obtaining its preset objects.

The system is particularly useful for unwinding and accumulating weft yarn in a controlled way, in the application of unwinding a weft with a rotating reel. The unwinding device unwinds, at a substantially constant speed, the weft from the reel, allowing to accumulate a predefined length of weft available for an insertion in a weaving machine, to inserting members of the machine in a controlled way.

The system is composed of a motor actuating a reel adapted to unwind the weft yarn, means for measuring the unwound and consumed length adapted to measure the weft yarn, means for accumulating the weft yarn, in the period in which this latter one is not inserted in the pitch by the inserting means adapted to accumulate the weft yarn, electronic means for managing motors and sensors.

The accumulating means allow making the weft available according to defined modes, starting from a certain instant in which the inserting members are ready to insert the weft.

Unwinding of the weft yarn from the reel occurs at an optimum speed, depending on the required number of colors and the design.

For example, in case of a single color, the system comprises an unwinding machine equipped with motor operating for unwinding the weft, a measuring device equipped with a sensor and a pressurized or depressurized tunnel adapted to house the weft according to a U-shaped arrangement, thanks to a light-weight mass. The weft, upon exiting the tunnel, is inserted in an accumulator composed by an oscillating lever and actuated by a servomotor. At the end of such lever, shunts are placed, operating with respect to shunts hinged onto the fixed structure to be able to engage the weft so that this latter one is arranged according to an obliged path during its oscillation. A weft- blocking brake is provided at the accumulator outlet, which prevents the weft from being re- accumulated, once having ended the insertion of the weft in the pitch.

The step of inserting the weaving machines does not take the whole cycle, but ranges from 100° to 270°.

It is clear that, in case it is needed to unwind with reel rotation, it is not suitable to try and accelerate and brake the reel, since this latter one cannot have high inertias, for example bobbins of metallic threads can have a mass of 40 kg, in addition to high structural stresses with risk of structural collapse.

A solution to the problem of reel inertia is keeping the reel rotating accumulating the weft when this is not inserted in the pitch. It is moreover important to store the weft in an orderly position and without rotations with respect to its own axis, supplying the inserting members in the softest possible way.

The device allows satisfying the following objectives: optimizing the winding speed of the reel by not being constrained by the insertion step; orderly accumulating the weft; making the weft available in an orderly way, compelling it to follow a well defined path.

After having set the insertion length for every cycle, the controlled system can operate in a self-learning mode, according to a motion law adapted to comply with certain space-time coordinates depending on known values of: angular position of the machine and of the inserting members, sensor position, insertion starting and ending positions. The motion law of the accumulator is a function of:

- passive weaving phase (interval in which the weft is not inserted) : the accumulator follows the reel speed;

- active phase: the accumulator follows the movement of the inserting members, being them pliers, mono-gripper, projectile, air, water, taking into account that in the meantime the reel is unwound.

During the active and passive phases, the reel goes on unwinding the weft to make available a further amount of weft. The accumulator allows uncoupling the unwinding device from the inserting members of the weft in the pitch. In fact, while the weft entering the accumulator has a nominally constant speed, the reel unwinding speed, the outlet speed is instead similar, theoretically identical, to the speed of the inserting member. It is important to know that the weft, while it is accumulated and made available, is anyway orderly configured between the moving means of the accumulator and the fixed means of the structure, in order not to assume warped arrangements. This is fundamental to guarantee an always plane insertion with the weft.

From a theoretical point of view, such speed following can be very rigorous, with almost null errors: this depending on inertias and on the types of motors and sensors, which actuated the accumulator. The more rigorous and exact is the following, the higher can be the performances. The accumulator to follow the gripper can acquire information through:

an initial processing making the device recognize the motion law of the inserting members in the configuration set for such fabric (the weaving width will be entered) ; an algorithm linked to the insertion length will define the motor movement, related to the angular position of the machine;

- a self-learning cycle, which, without even keying-in the weaving height, will detect its amount due to the sensors and the sliding weft sensor normally present on all machines.

The common criteria of the two methods is:

the oscillation amplitude determines the accumulation length, which is determined by the unwound length of weft from the reel during the passive phase. In practice, the length of weft inserted in every cycle;

- the accumulator will go on accumulating till the speed of the inserting members does not exceed the reel speed, which then makes its reference. It will reach the zero position, meant as standby zero, when the inserting members cease their interaction with the weft: this movement is function of the unwound amount from the reel and of the amount required by the inserting means. The difference between the two amounts is the amount that the accumulator must provide due to its oscillation, driven by the motor. The oscillating arm, according to different types of weft, can have a double or simple configuration.

A variation of the device is given by the replacement of the measuring device with a pneumatic tunnel with a further motored arm, which engages the weft operating as dynamometric meter. The motor-arm assembly has a driving position defined, detected by the encoder of the servomotor and a driving torque. If the weft tension increases or decreases, the motor will react to keep the maintenance torque constant, performing a weft recovering or unwinding action. These actions are composed of rotations of the motor detected by its encoder, so that the necessary length variation amount will be known. Such information is the one which the electronic means will manage to change the unwinding speed. In some cases, the dynamometric measuring device can replace the accumulator itself when the sum of system inertias, insertion speed, weft resistance, efficiency of the inserting means allow that wide oscillations of this latter one can be managed by all these elements. At the end of the insertion, the system will be defined as balanced if the zero accumulation position is reached when the interaction ceases between the inserting members and the weft: different more or less values will activate corrections to the reel unwinding speed .