Background Art In the field of the production of non-woven fabric (NWF), a rapid evolution has long been in progress as regards the design of systems and devices provided with the goal of improving distribution of the web on the forming belt, reducing lateral waste of the web, and increasing the production rate.

Currently, a spinning system of the spunbond type is constituted by a plurality of spinnerets, fed by gear pumps, from which filaments exit which are entrained by the air ejected by ejectors associated with air compression means; said filaments are directed toward a device for distribution on the forming belt of the movable-vane type.

The movable vanes of the distribution device are operated by a single motor, which acts by means of a rod-and-crank system on a linear actuator, to which all the vanes are kinematically connected, moving synchronously.

Operation is as follows: the pumps feed the spinnerets and the air ejectors stretch the filaments that exit from the spinnerets and draw them toward the device for distributing the web onto the forming belt.

Such filaments strike a plurality of fixed vanes (one for each movable vane), which direct them toward the corresponding movable vanes. The movable vanes direct the filaments toward the forming belt with a right-left alternating pattern.

The spunbond spinning systems thus described have several drawbacks.

A first drawback arises from the fact that the web deposited on the forming belt is provided laterally with a smaller quantity of filaments, since it is not possible to superimpose on the outermost filaments the filaments obtained from adjacent spinnerets (see for example Figure 5, which shows a distribution of the filaments according to a current system: the lateral portions of the web are thinner than the center, as shown by the chart that plots the thickness of the web transversely thereto), thus obtaining a product that has a lower unit gram weight in the lateral portions of the web.

In order to solve this drawback, deflectors for redirection toward the center are currently fitted laterally to the outermost vanes.

These deflectors are fixed (adjustable only when the system is not moving) and in any case do not ensure correct distribution at the edges of the forming belt.

These deflectors in fact cause an irregular overlap of the diverted filaments.

Another drawback is that the vane that lies closest to the actuation and the furthest vane have different angular velocities, inevitably leading to an uneven distribution of the filaments.

This phenomenon is due to the plays that occur in the distribution device: in particular, to the plays caused by the elasticity of the linear actuator and to the plays caused by the couplings of the various components, particularly those of the rod-and-crank system.

Another drawback arises from the vibrations generated by the mechanical elements for synchronizing the movable vanes.

These vibrations make the system inaccurate as a whole and make it noisier and prone to breakage.

Another drawback is that it is not possible to adjust the supply flow- rate of the gear pumps, since they have a single actuator.

This flow-rate adjustment can be useful for example if there are changes in flow-rate among the pumps due to wear. These variations lead to

a change in grammage on the forming belt.

Disclosure of the Invention The aim of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that solves the drawbacks noted in known spunbond spinning systems.

Within this aim, an object of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that allows to provide a more uniform distribution of the filaments on the forming belt, particularly at the lateral portions.

Another object of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that allows to reduce the vibrations of the system, reducing noise and extending the average life of said system.

Another object of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that allows to adjust the flow-rate of the gear pumps that supply the spinnerets.

Another object of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that is easy to produce and can be provided by means of components that are already known and commercially available.

Another object of the present invention is to provide an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that ensures safety and durability in operation.

This aim and these and other objects that will become better apparent hereinafter are achieved by an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems, particularly but not exclusively for producing polypropylene and polyester

NWF, comprising actuation means for gear pumps for supplying respective spinnerets from which filaments exit, said filaments being entrained by the air ejected by ejector means and being directed toward an apparatus for distribution on the forming belt of the movable-vane type, characterized in that said actuation means for said gear pumps are independent for each spinneret, said distribution apparatus with movable vanes comprising rotation means for said movable vanes that are independent for each vane, means for adjusting the supply pressure of air ejectors being associated with said ejector means, said automatic device further comprising a programmable electronic management device that is functionally connected to said rotation means for said movable vanes, to said actuation means for said gear pumps, and to said means for adjusting the supply pressure.

Brief description of the Drawings Further characteristics and advantages of the invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment thereof, illustrated by way of nonlimiting example in the accompanying drawings, wherein: Figure 1 is an exploded perspective view of an electric motor associated with movable vanes, usable in an automatic device according to the invention; Figure 2 is another perspective view of the electric motor associated with movable vanes as in Figure 2; Figure 3 is a schematic front view of a portion of the automatic device according to the invention, illustrating a movable vane during operation; Figure 4 is a diagram of the automatic device according to the invention; Figure 5 is a schematic view of the step for distributing the filaments that compose a web on a forming belt, according to a system of a known type, a chart that plots the variation of the thickness of the web transversely to said web being associated with said schematic view;

Figure 6 is a schematic view of a particular step of the distribution of the filaments that compose a web on a forming belt, provided by an automatic device according to the invention, a chart that plots the variation of the thickness of the web transversely to said web being associated with said schematic view; Figure 7 is a schematic view of another particular step of the distribution of the filaments that compose a web on a forming belt, provided by an automatic device according to the invention, a chart that plots the variation of the thickness of the web transversely to said web being associated with said schematic view; Figure 8 is a schematic view of another particular step of the distribution of the filaments that compose a web on a forming belt, performed by an automatic device according to the invention, a chart that plots the variation of the thickness of the web transversely to said web being associated with said schematic view.

Ways of carrying out the Invention With reference to Figure 4, an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems, according to the invention, is generally designated by the reference numeral 100.

The automatic device 100 comprises gear pumps 8 for supplying respective spinnerets 9 (only one of which is shown in Figure 4), from which filaments exit and are entrained by the air ejected by ejector means, said filaments being directed toward an apparatus 36 for distribution on the forming belt of the type with movable vanes.

In the figures, the portions of filament that exit from the spinnerets 9 are designated by the reference numeral 10.

The ejector means comprise ejectors 6, which are associated with a main compensation unit 14, which is functionally connected to a compressor 15.

In the figures, the portions of filaments that exit from the ejectors 6 are designated by the reference numeral 5.

The ejector means are associated with means 35 for adjusting the supply pressure of the ejectors 6.

In particular, with reference to Figure 3, the distribution apparatus 36 comprises, for each movable vane 3, a fixed vane 4, of a per se known type, which is arranged in output from the corresponding ejector 6 (also of a known type), and rotation means 37 for movable vanes 3; in particular, the rotation means 37 are independent for each movable vane 3.

The rotation means 37 are constituted for example (see Figures 1 and 2) by an electric motor 1, of a per se known type and commonly commercially available, for each movable vane 3.

The electric motor 1 is of the type provided with angular control.

The corresponding movable vane 3 is coupled to the output shaft of the electric motor 1 by means of a coupling 2 (also of a known type).

The movable vane 3 has a suitable profile, for example of the aerodynamic type, and is made of a material that withstands the wear caused by the sliding of the filaments 5.

With reference to Figure 3, the electric motor 1 transmits the rotation to the movable vane 3, which can be adjusted to the oscillation angle a by means of a device for varying the oscillation angle 38 that is associated with the electric motor 1.

Moreover, the movable vane 3 can also be adjusted on the inclination of the oscillation angle a by means of a device 39 for varying the inclination of the oscillation angle (Figure 3 shows the rotation of the oscillation axis through an angle P) associated with the electric motor 1.

A device 40 for varying the rotation rate for each movable vane 3 in any point of the oscillation arc of the movable vane 3 is further associated with the electric motor 1.

As mentioned, each movable vane 3 is associated with an electric

motor 1: the fundamental condition is that even if the electric motors 1 are independent for each movable vane 3, the instant"t"of reversal of the motion of the movable vanes 3 remains common to all the vanes.

In accordance with Figure 3, each movable vane spreads the filaments 5, which exit from the corresponding ejector 6 and are diverted by the corresponding fixed vane 4, on the forming belt, here designated by the reference numeral 7.

With reference to Figure 4, the means 35 for adjusting the supply pressure of the ejectors 6 comprise an adjustment valve 13 and a secondary compensation unit 12, which are arranged in series between the main compensation unit 14 and the ejectors 6.

By acting on the characteristic parameters of the adjustment means 35 it is possible to vary appropriately the supply pressure of the ejectors 6.

Advantageously, the automatic device 100 comprises actuation means 41 (such as for example a motor drive, optionally of the electric type) for the gear pumps 8 for supplying respective spinnerets 9.

The actuation means 41 of the gear pumps 8 are independent for each spinneret 9.

The rotation means 37 for the movable vanes 3, the actuation means 41 for the gear pumps 8, and the means 35 for adjusting the supply pressure of the ejectors 6 are functionally connected to a programmable electronic management device 11, such as for example a PLC (Programmable Logic Controller), as shown schematically in Figure 4.

The programmable electronic management device 11 (the PLC) acts on the actuation means 41 of the gear pumps 8, varying the available flow- rate of each individual spinneret 9.

The programmable electronic management device 11, moreover, can change the supply pressure of the ejectors 6 by acting on the adjustment means 35.

Moreover, the programmable electronic management device 11 acts

on each movable vane 3, varying its characteristic parameters by controlling each electric motor 1.

In particular, the programmable electronic management device 11 acts on the device for varying the inclination of the oscillation angle 38 for each movable vane 3, on the device 39 for varying the inclination of the oscillation angle for each movable vane 3, and on the device 40 for varying the rotation rate for each movable vane 3.

In this manner it is possible to vary the rotation rate of the movable vane 3 in critical points, such as for example the top dead center and the bottom dead center, and in any case in any point of the oscillation arc of the movable vane, in practice setting the chosen spot speed diagram (there is in fact a device 40a for setting the spot speed diagram associated with the device 40 for varying the rotation rate).

The motors 1 used allow to obtain oscillation rates between 0 and 2500 full oscillations per minute for each movable vane 3.

It is thus possible to vary the oscillation angle of each movable vane a and to vary the inclination ß of the oscillation angle a for each movable vane 3.

Figure 5 is a partial view of a distribution apparatus with movable vanes of the known type, generally designated by the reference numeral 200, during application; the associated chart that plots the variation of the thickness of the web transversely to said web, generally designated by the reference letter (a) (in practice, the ordinates plot the layers deposited by each movable vane and the abscissas plot the width of the web, with reference to the deposition intervals performed by each movable vane), clearly shows the lateral variation (designated by the reference numeral 16) of grammage that is characteristic of current spunbond spinning systems.

As mentioned, currently an attempt is made to recover part of the lateral variation 16 by fitting rebound deflectors for the outermost filaments.

These deflectors are fixed, with manual adjustment only when the

system is not operating, and do not ensure correct distribution at the edges of the forming belt.

In order to reduce drastically the lateral variation 16, it is necessary to divert inward the outermost filaments, trying to superimpose them uniformly on the adjacent layers.

With reference to Figure 6, the present invention allows to act on the characteristic parameters (oscillation speeds and angles) of the two outermost movable vanes, respectively 3a and 3m (Figure 6 only shows the <BR> <BR> left outermost one, i. e. , the vane 3a), uniformly diverting inward the outermost filaments, which are deposited on the adjacent layers.

The same Figure 6 provides a chart that plots the variation of the thickness of the web transversely to said web, generally designated by the reference letter (b).

Figure 7 is a partial view of the automatic device 100 according to the invention during application if the operation of the chimney 17 fails.

The term"chimney"is understood to reference the portion of automatic device that is comprised between the output of a spinneret 9 and the inlet of the corresponding ejector 6.

The present invention allows to act on the movable vanes 3, by extending the inclination angle by one step in the compensation direction, by increasing the rotation rate of the movable vanes 3, and by increasing the flow-rate of the corresponding gear pump 8 by a preset quantity, with the result of compensating the lack of filaments 5 on the forming belt 7.

In the example of Figure 7, the chimney 17 leads to non-use of the movable vane 3d and to correction by moving the movable vanes 3e, 3f, 3g and 3h.

The same Figure 7 illustrates a chart that plots the variation of the thickness of the web transversely to said web, generally designated by the reference letter (c).

Figure 8 is a partial view of the automatic device 100 according to the

invention during application, in the case in which an entire spinneret 9 (shown in dashed lines and corresponding to the movable vanes 3e and 3f) fails to operate.

The automatic device 100 allows to act on the movable vanes 3a, 3b, 3c, 3d, 3g, 3h, 3i and 3m by extending the inclination angle by one step, by increasing the rotation rate of the movable vanes, and by increasing the flow-rates of the gear pumps by a preset quantity, with the result of compensating for the lack of filaments 5 on the forming belt.

Figure 8 also shows a chart that plots the variation of the thickness of the web transversely to the web, generally designated by the reference letter (d).

Advantageously, it is possible to introduce a unit 43 for measuring the grammage of the web deposited on the forming belt, as shown schematically in Figure 3.

The grammage measurement unit 43 is connected electronically to the programmable electronic management device 11 (PLC). By way of software, the PLC can thus perform automatically any corrections to be made to the parameters of the automatic device in order to correct the grammage variations beyond a chosen average value that are indicated by the grammage measurement unit. These corrections occur by acting on the flow-rate of the gear pumps 8 of the spinnerets 9, on the oscillation angle a of the movable vanes 3, on their angular velocity, on the inclination P of the oscillation angle a of the movable vanes 3, and on the supply pressure of the ejectors 6.

In this manner it is possible to have automatically an extremely uniform and regular distribution of filaments on the forming belt.

In practice it has been found that the invention thus described solves the problems noted in known types of spunbond spinning system; in particular, the present invention provides an automatic device for optimizing the distribution of the web on the forming belt in spunbond

spinning systems that allows to provide a more uniform distribution of the filaments on the forming belt, particularly at the lateral portions.

The introduction of independent motors for each movable vane and the introduction of independent actuation systems for the gear pumps in fact allows, together with the association of a PLC, to correct the reduced presence of filaments on the lateral portions of the forming belt, in practice reducing drastically the lateral waste.

Further, the automatic device 100 allows to optimize the distribution of the web on the forming belt and allows to compensate for the lack of filaments if chimneys or spinnerets fail.

It is evident that such automatic device can be used with single- and/or double-beam spinning heads having any geometric shape.

In the case of double-beam spinning heads, the spinneret adjustments are performed for 50% on the first beam and for 50% on the second beam.

In view of what has been stated and described, the present invention provides in practice an automatic device for optimizing the distribution of the web on the forming belt in spunbond spinning systems that allows to adjust the oscillation angle and to adjust the inclination of the oscillation angle of each movable vane while the system is in motion.

Moreover, with the device according to the invention the movable vanes can reach an oscillation rate of over 2000 complete oscillations per minute.

The device according to the present invention ensures constancy of grammage on the produced NWF by adjustment of the involved gear pumps.

Further, the device allows to reduce lateral waste drastically, by diverting inward the outermost filaments and by acting on the rotation rate of the involved pumps, on the pressure of the ejectors and on the variation of the symmetry of the outermost movable vanes.

Thanks to what has been described above, in case of failure of a spinneret and/or stretching unit (ejectors) and/or distribution device with

movable vanes, the invention can compensate for the lack of filaments on the forming belt by acting both on the supply pumps and on the supply pressure of the ejectors as well as on the angle and speed of the distribution vanes.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements.

In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. VI2003A000124 from which this application claims priority are incorporated herein by reference.