MELT-BLOWING APPARATUS FOR PRODUCING POLYMER FILAMENTS

Abstract

 Plant for producing polymer filaments, comprising at least one drawing head (2), aeration means (3), placed downstream of the drawing head (2), and comprising at least one feed source (30) for feeding said cooling fluid and two shaped heads (31), mechanically fixed to the drawing head (2). Each shaped head (31) delimits a cooling circuit (6), which is in fluid communication with the feed source (30) in order to receive the cooling flow and is extended to a dispensing portion (60) thereof, provided with a plurality of guide ducts (600) adapted to direct the cooling fluid. The cooling circuit (6) comprises a channel (7), which is extended between at least one feed mouth (70), in fluid communication with the feed source (30), and the dispensing portion (60). The channel (7) is provided with at least one main stretch (71), in fluid communication with the feed mouth (70), and at least two secondary stretches (72), extended branched from the main stretch (71), in fluid communication with the latter and each extended to a corresponding outlet mouth (721) thereof, in fluid communication with the dispensing portion (60).

Description

Field of application

[0001] The present invention regards a plant for producing polymer filaments according to the preamble of the independent claim 1.

[0002] The present plant for producing polymer filaments is advantageously intended to be employed in the field of production of nonwoven fabric (melt-blown, spunbond or staple fiber).

[0003] In particular, the plant for producing polymer filaments, object of the present invention, is advantageously employable for producing a semifinished product constituted by a plurality of polymer filaments, intended to sustain subsequent transformations in order to obtain a finished product made of nonwoven fabric.

[0004] Such polymer filaments are normally used in particular for producing sanitary products, such as for example caps, masks and gloves, or in the field of agriculture for producing nonwoven fabric intended to be set on the ground to be cultivated in order to prevent the formation of weeds and/or protect seeds.

[0005] The invention is therefore inserted in the industrial field of machines for producing polymeric fiber material, or more generally in the field of production of nonwoven fabric.

State of the art

[0006] Known in the field of production of polymeric fiber material plants which allow producing polymer filaments starting from a polymeric material at the solid state, such as for example granules of polymeric material.

[0007] The aforesaid polymer filaments are usually employed for producing nonwoven fabric, e.g. melt-blown, spunbond or staple fiber of polypropylene, polyester, polyethylene and/or other polymers.

[0008] The nonwoven fabric, known in the technical jargon of the field with the initials "TNT", is employed in particular for producing bandages, gauzes, caps, masks and other sanitary products, in general for filtering elements, or for example for producing mulching sheets, usable in farming for covering terrain to be cultivated.

[0009] Several examples of plants of known type for producing polymer filaments are described in the documents US 6,846,450 and US 6,861,025.

[0010] The plants for producing polymer filaments usually comprise an extruder which is provided with a hopper adapted to receive the polymer to be worked (usually in the form of granules), with multiple electrical heating elements, which are actuatable in order to heat the aforesaid polymer and melt it, and with a worm screw arranged for forcing the polymer at the molten state outside the extruder.

[0011] The aforesaid plants of known type also comprise a transfer line, which is placed downstream of the extruder in order to convey the molten polymer from the extruder towards a drawing head. The drawing head, placed downstream of the extruder, is adapted to receive the molten polymer arriving from the extruder in order to convey it through a perforated drawing grid and to form, therefore, a plurality of molten polymer filaments. Usually the polymer filaments are drawn in the form of pasty plastic material, at a temperature normally comprised between 150°C and 280°C (as a function of the starting polymer material).

[0012] The aforesaid plants of known type also comprise aeration means, in fluid communication with a feed source for feeding a cooling fluid and arranged for conveying the aforesaid cooling fluid at the outlet mouth of the drawing head so as to solidify the molten polymer exiting from the head and allowing the formation of a solid polymer filament, which is deposited on a movable conveyor belt in order to form a continuous sheet of polymer fibers.

[0013] The aeration means of the conventional plants comprise a feed mouth, connected to the feed source, and a dispensing mouth, placed at the outlet mouth of the drawing head.

[0014] More in detail, the aeration means comprise, between the feed mouth and the dispensing mouth, a feed portion, which is extended from the feed mouth, and a collection tank, extended between the feed portion and the dispensing mouth and arranged for collecting the cooling fluid before its dispensing, so as to make the pressure and temperature of the fluid itself uniform.

[0015] The feed portion comprises a hollow box-like body, with trapezoidal form, within which the fluid can flow. The aforesaid box-like body has tapered form between a first face, directed towards the feed mouth, with rectangular shape and dimensions substantially comparable to those of the feed mouth, and a second face, directed towards the dispensing mouth and with dimensions comparable to the collection tank.

[0016] Such configuration of the box-like body ensures that the fluid is distributed width-wise along the flow thereof between the feed mouth and the dispensing mouth.

[0017] The plant for producing polymer filaments of known type described briefly up to now has in practice shown that it does not lack drawbacks.

[0018] The main drawback lies in the fact that such configuration of the box-like body does not allow a uniform distribution of the cooling fluid between the feed mouth and the dispensing mouth. More in detail, the aeration means of the plants of known type have proven to be unsuitable for ensuring a high uniformity of the cooling fluid, both with regard to the pressure and with regard to the speed and temperature of the fluid along the entire width of the aeration means.

[0019] The cooling fluid that flows within the feed portion has a speed and a pressure that are different along the transverse extension of the box-like body.

[0020] Indeed, the fluid which flows substantially to the center of the box-like body, along a straight line between the feed mouth and the dispensing mouth, is provided with a speed (and a flow) that is greater than the fluid which flows laterally, defining a parabolic progression of the speed and of the flow along the transverse extension of the box-like body.

[0021] This creates non-uniformities of the cooling fluid which causes problems during drawing, and in particular causes a differentiated drawing between a central stretch of the drawing head and the lateral stretches of the same head.

[0022] As mentioned above, also the temperature of the fluid is not uniform, and in particular is higher in proximity to the lateral portions of the aeration means, which are in fact closer to the heating elements that are externally fixed for heating the cooling fluid.

[0023] A further drawback lies in the fact that such aeration means require a source of cooling fluid with high power, which in fact must be able to ensure a sufficient outlet speed of the cooling fluid at the dispensing mouth.

[0024] Such sources are nevertheless very complex, and consequently determine an increase of costs in order to attain the plant.

Presentation of the invention

[0025] In this situation, the problem underlying the present invention is therefore that of overcoming the drawbacks manifested by the plants for producing polymer filaments of known type, by providing a plant for producing polymer filaments which allows obtaining a high uniformity of production of the polymer filaments, in particular ensuring a uniform cooling of the filaments exiting from the drawing head of the plant.

[0026] A further object of the present invention is to provide a plant for producing polymer filaments, which allows preventing possible deteriorations of the polymer.

[0027] A further object of the present invention is to provide a plant for producing polymer filaments, which allows preventing possible dripping of polymer material from the drawing head.

[0028] A further object of the present invention is to provide a plant for producing polymer filaments, which allows reducing the energy consumption for heating the polymer.

[0029] A further object of the present invention is to provide a plant for producing polymer filaments, which is entirely reliable in operation.

Brief description of the drawings

[0030] The technical characteristics of the invention, according to the aforesaid objects can be clearly seen in the contents of the below-reported claims and the advantages of the same will be more evident in the following detailed description, made with reference to the enclosed drawings, which represent a merely exemplifying and non-limiting embodiment of the invention, in which:

• figure 1 shows a schematic view of a plant for producing polymer filaments, object of the present invention;
• figure 2 shows a perspective view of a detail of the plant for producing polymer filaments illustrated in figure 1, relative to a drawing head and to aeration means connected to the drawing head;
• figure 3 shows a perspective view of a detail of the aeration means of figure 2, relative to a shaped head;
• figure 4 shows a perspective view of a detail of the shaped head of figure 3, relative to a channel, with a second half-shell, not depicted;
• figure 5 shows a perspective view of the shaped head of figure 3, with several parts missing in order to better show other parts;
• figure 6 shows a further perspective view of the shaped head of figure 3, with several parts missing in order to better show other parts;
• figure 7 shows a perspective view of a detail of the shaped head figure 3, relative to a deflector body;
• figure 8 shows a side view of the shaped head of figure 3;
• figure 9 shows a sectional perspective view of the shaped head of figure 3;
• figure 10 shows a sectioned side view of the shaped head of figure 9;
• figure 11 shows a perspective view of a detail of the plant for producing polymer filaments illustrated in figure 1, relative to a drawing head;
• figure 12 shows a sectioned side view of the shaped head of figure 9 with several parts transparent in order to better show other parts;
• figure 13 shows a front section view of the drawing head of figure 2, attained along the trace XIII-XIII of figure 2, with several parts removed in order to better show other parts;
• figure 14 shows a front view of the drawing head of figure 11;
• figure 15 shows a side view of the drawing head of figure 11.

Detailed description of a preferred embodiment

[0031] With reference to the enclosed drawings, reference number 1 overall indicates a plant for producing polymer filaments, according to the present invention.

[0032] This is advantageously intended for being employed for producing nonwoven fabric of different type and material, such as in particular melt-blown, spunbond or staple fiber of plastic material, e.g. polypropylene and/or polyethylene.

[0033] Hereinbelow reference will be made to a plant 1 for producing polymer filaments preferably for making nonwoven fabric of plastic material and preferably melt-blown, in accordance with the preferred embodiment illustrated in the enclosed figures.

[0034] However, moreover, the plant 1 of the present invention can also be advantageously employed for producing polymer filaments with length greater than those necessary for producing nonwoven fabric, which are for example susceptible of being wound in reels or coils, e.g. for producing clothes.

[0035] Of course, without departing from the protective scope of the present invention, it is also possible to employ the aforesaid plant 1 for producing for example films of polymer material, nevertheless preserving the same advantages described in detail hereinbelow.

[0036] In accordance with the invention the plant 1 for producing polymer filaments comprises at least one drawing head 2, arranged for drawing the polymer at the molten state between at least one inlet opening 21 and an outlet opening 22, and such outlet opening 22 is provided with a plurality of holes 220 for drawing corresponding polymer filaments.

[0037] Advantageously the plant 1 also comprises at least one extruder 4, arranged for extruding a polymer at the molten state.

[0038] More in detail, the aforesaid extruder 4 preferably comprises a containment body 41 internally defining an extrusion space 42, which is provided with at least one first mouth 43, in order to allow the insertion of the polymer to be extruded within the same extrusion space 42, in particular in the form of granules, and with an extrusion mouth 44, through which the aforesaid polymer is extruded.

[0039] Advantageously, the aforesaid extruder 4 comprises a hopper 40, at the first mouth 43, which is preferably placed above the containment body 41 and allows the insertion of the polymer to be extruded within the extrusion space 42.

[0040] In addition, the extruder 4 advantageously comprises a first heating device (not illustrated), which is mounted on the containment body 41, preferably externally with respect to the extrusion space 42 and is arranged for heating the aforesaid containment body 41 and, therefore, the polymer contained therein in order to bring it to the molten state.

[0041] The extruder advantageously comprises a transport screw 45, which is placed within the extrusion space 42 and is actuatable in rotation in order to push the polymer from the first mouth 43 to the extrusion mouth 44.

[0042] The plant 1 also advantageously comprises at least one conveyance duct 5, placed in fluid communication with the extruder 4, in particular by means of the extrusion mouth 44, and with the drawing head 2 for conveying the polymer at the molten state from the extruder 4 to the drawing head 2.

[0043] More in detail, the conveyance duct 5 is extended between a first end 5', connected to the extruder 4, and a second end 5" connected to the drawing head 2.

[0044] The conveyance duct 5 advantageously comprises a second heating device (not illustrated), preferably with substantially annular shape, which is fixed outside the conveyance duct 5 in order to heat the aforesaid conveyance duct 5 and, hence, the polymer contained therein in order to bring it to the molten state.

[0045] The plant 1 also comprises aeration means 3, placed downstream of the drawing head 2 and arranged for dispensing a cooling fluid at the outlet opening 22 of the drawing head 2 in order to stretch the polymer filaments. The aeration means 3 comprise at least one feed source 30 for the cooling fluid and two shaped heads 31, mechanically fixed to the drawing head 2, on opposite sides of the drawing head 2.

[0046] Advantageously the two shaped heads 31 are placed parallel to each other, and in particular are extended along two respective first extension directions Y, Y'.

[0047] Preferably the aforesaid cooling fluid is air, which can be preconditioned, e.g. heated and/or pressurized, or alternatively be employed without any treatment.

[0048] Advantageously the employed air is preconditioned and for such purpose the plant 1 comprises a pretreatment station, which is placed upstream of the feed source for the cooling fluid.

[0049] More in detail, the pretreatment of the air provides for its heating, preferably at a temperature comprised between 180°C and 280°C, and its pressurization, at a pressure preferably comprised between 0.3 and 2 bar.

[0050] Each shaped head 31 delimits a cooling circuit 6, which is in fluid communication with the feed source 30 in order to receive the cooling fluid and is extended to a dispensing portion 60 thereof, placed at the outlet opening 22 of the drawing head 2 and is provided with a plurality of guide ducts 600 adapted to direct the cooling fluid.

[0051] In accordance with the idea underlying the present invention, each cooling circuit 6 delimited by the corresponding shaped head 31 comprises a channel 7, which is extended between at least one feed mouth 70, in fluid communication with the feed source 30, and the dispensing portion 60. The channel 7 is provided with at least one main stretch 71, in fluid communication with the feed mouth 70, and at least two secondary stretches 72, extended branched from the main stretch 71, in fluid communication with the latter and each extended to a corresponding outlet mouth 721 thereof in fluid communication with the dispensing portion 60.

[0052] Advantageously, the aforesaid branched configuration of the channel 7 allows making the cooling fluid reach the outlet mouths 721, gradually dividing the flow of such fluid, such that it is substantially equally distributed in the secondary stretches 72 and hence in the outlet mouths 721, at each of which the cooling fluid does not have substantially pressure gradients and speed (as well as temperature) gradients, ensuring a uniform diffusion thereof on the filaments exiting from the drawing head 2 with consequent uniformity of the characteristics of the produced filaments.

[0053] Advantageously each outlet mouth 721 is extended substantially along the entire length of the corresponding secondary stretch 72.

[0054] Advantageously each main stretch 71 is extended between the feed mouth 70 and a first branch point 710, and the channel is provided with at least two intermediate stretches 73, which are branched from the main stretch 71 and are extended between the first branch point 710 and a corresponding second branch point 720.

[0055] Advantageously each of the secondary stretches 72 is extended between a corresponding second branch point 720 and the corresponding outlet mouth 721.

[0056] In accordance with the preferred embodiment illustrated in figure 4, the channel 7 comprises two feed mouths 70 and two main stretches 71, each of which is in fluid communication with a separate feed mouth 70 and from each of such main stretches 71, two intermediate stretches 73 are branched, and from each of such intermediate stretches 73, two secondary stretches 72 are in turn branched.

[0057] Advantageously the two intermediate stretches 73 that are branched from each main stretch 71 are provided with the same extension and still more preferably all the intermediate stretches 73 of the channel 7 are provided with the same extension.

[0058] Advantageously the two secondary stretches 72 that are branched from each intermediate stretch 73 are provided with the same extension and still more preferably all the secondary stretches 72 of the channel 7 are provided with the same extension.

[0059] Advantageously the cooling circuit 6 is extended between two feed mouths 70, up to eight outlet mouths 721, one for each secondary stretch 72.

[0060] Advantageously the channel 70 defines a plurality of paths P, each of which extended between the feed mouth 70 and a corresponding outlet mouth 721. The paths P are advantageously substantially provided with the same extension.

[0061] Preferably with the expression "same extension" it will be intended hereinbelow that the extension of each path P is contained between 90% and 110% with respect to the mean of the other paths P defined by the channel 70.

[0062] In this manner, it is possible to ensure the constant uniformity of the temperature, of the pressure and of the speed of the cooling fluid that reaches the dispensing portion 60, in particular along the entire transverse extension of the same dispensing portion 60. Advantageously each main stretch 71 is provided with a first passage section and each intermediate stretch 73 is provided with an intermediate passage section, and the area of the intermediate passage section of the intermediate stretches 73 is smaller than the area of the first passage section of the corresponding main stretch 71.

[0063] Preferably, the ratio between the area of the first passage section and the area of the intermediate passage section is comprised between 1.5 and 3.

[0064] Advantageously each secondary stretch 72 is provided with a second passage section, greater than the area of the intermediate passage section of the corresponding intermediate stretch 73. Preferably, the ratio between the area of the second passage section and the area of the intermediate passage section is comprised between 2 and 5.

[0065] In particular, the arrangement of two intermediate stretches 73 that are branched from each main stretch 71 and of two secondary stretches 72 that are branched from each intermediate stretch 73 ensures that the flows of cooling fluid is divided into sub-flows that are substantially identical to each other, which advance along the aforesaid paths P having substantially the same extension. Such sub-flows, advancing along the paths P with same extension, are subjected to substantially the same load losses and hence subjected substantially to a same loss of speed and pressure. Since the load losses are equally distributed on the various sub-flows deriving from the flow of cooling fluid, the cooling fluid that exits from the outlet mouths 721 will substantially have the same speed and pressure at each of the aforesaid outlet mouths 721.

[0066] In addition, the main, intermediate and secondary stretches 71, 73, 72 are advantageously provided with transverse sections sized such to prevent the advancing speed of the cooling fluid from drastically falling after each branch from main stretches 71 to intermediate stretches 73 and from intermediate stretches 73 to secondary stretches 72. In particular, the aforesaid main, intermediate and secondary stretches 71, 73, 72 are provided with transverse sections that are not particularly extensive, such that the speed profile of the sub-flow, which during use advances within each stretch, is substantially constant along the entire extension of the section. Indeed, in particular, the portion of cooling fluid that flows substantially at the center of the main, intermediate or secondary stretch 71, 73, 72 is not sufficiently far from the internal surfaces that delimit the same main, intermediate or secondary stretches 71, 73, 72 to ensure that such portion of cooling fluid is not subjected to substantially the same friction to which the cooling fluid is subjected which flows directly in contact with the same internal surfaces. Advantageously the dispensing portion 60 of the cooling circuit 6 comprises at least one collection chamber 61 in fluid communication with the outlet mouths 721 of the secondary stretches 72 of the channel 70 and arranged for receiving the cooling fluid.

[0067] More in detail, each shaped head 31 advantageously comprises a main body 310, comprising the channel 70, and a deflector body 311, mechanically connected to the main body 310 and at least partially delimiting with the latter the dispensing portion 60.

[0068] In particular, the collection chamber 61 is (at least partly) made on the deflector body 311, which is preferably and substantially L-shaped, and is placed in abutment against the main body 310 in order to allow the cooling fluid exiting from the outlet mouths 721 to enter into the collection chamber 61. The deflector body 311 is preferably made of bronze.

[0069] More in detail, the deflector body 311 comprises a dispensing chamber 62, in fluid communication with the collection chamber 61 and placed downstream of the latter along the cooling circuit 6. Advantageously the guide ducts 600 are placed within the dispensing chamber 62.

[0070] Advantageously, with reference to figure 7, the guide ducts 600 are extended, preferably parallel to each other, transverse (and in particular orthogonal) to the extension directions Y, Y' of the shaped heads 31.

[0071] Advantageously the deflector body 311 is provided, on the connection portion placed in abutment against the main body 310, with a passage cavity 600', which is extended preferably along substantially the entire extension of the deflector body 311 and is arranged for allowing the passage of the cooling fluid from the collection chamber 61 towards the dispensing chamber 62.

[0072] Advantageously the deflector body 311 comprises a connection flange 312, preferably extended along the entire deflector body 311 and provided with a plurality of fixing holes 313, preferably equidistant from each other, adapted to allow the fixing of the deflector body 311 to the drawing head 2, preferably on the lower part and in particular for example by means of screws and/or bolts.

[0073] The deflector body 311 and the main body 310 also define a directing portion 63 between them, which is placed downstream of the collection chamber 61 along the cooling circuit 6, and in particular downstream of the dispensing chamber 62, in particular between the latter and the dispensing portion 60 of the cooling circuit 6.

[0074] Advantageously, the directing portion 63 is delimited by a first tilted stretch 314, attained on the deflector body 311, preferably downstream of the dispensing chamber 62, and by a second tilted stretch 315 attained on the main body 310 and preferably extended substantially to the dispensing portion 60 of the cooling circuit 6. Preferably the two tilted stretches 314, 315 described above are parallel to each other and allow directing the flow of cooling fluid to the drawing head 2.

[0075] More in detail, the directing portion 63 of the cooling circuit 6 ensures that the cooling fluid coming from the dispensing chamber 62 is not expanded immediately after exiting from the latter (in particular after having exited from the guide ducts 600) and therefore its advancing speed and pressure are not reduced. In particular, during use, the aforesaid first tilted stretch 314 maintains the cooling fluid adherent to the second tilted stretch 315 of the main body 310, in a manner such that the fluid (which maintains a high pressure and speed) flows in contact with the aforesaid second tilted stretch 315 for the entire extension of the latter, so as to be guided in an optimal manner to the dispensing portion 60 of the cooling circuit 6. Indeed, even when the cooling fluid exits from the directing portion 63, it tends to not be separated from the second tilted stretch 315 of the main body 310, substantially continuing along the direction on which the second tilted stretch 315 itself is mainly extended to the dispensing portion 60 of the cooling circuit 6. In this manner, the cooling fluid intercepts the polymer filaments below the perforated extrusion grid 20, without creating significant turbulences and without hitting a high part of the perforated extrusion grid 20, with the advantage that the temperature of the cooling fluid does not come to substantially modify the temperature of the same perforated extrusion grid 20 and, hence, does not affect the molten polymer material before it exits from the latter.

[0076] Preferably, moreover, the second tilted stretch 315 is extended for an initial rectilinear segment up to a terminal segment, which is connected to the rectilinear segment by means of a rounded stretch 315' and is placed adjacent to the outlet opening 22 of the drawing head (more in detail adjacent to the perforated extrusion grid 20). In this manner, when the cooling fluid reaches the terminal segment of the second tilted stretch 315, the aforesaid rounded stretch 315' prevents a sudden interruption of the second tilted stretch 315 itself, such that the cooling fluid is not substantially separated from the main body 310 and mainly follows the second tilted stretch 315 to the dispensing portion 60 of the cooling circuit 6.

[0077] Advantageously the main body 310 of each shaped head 31 comprises a first half-shell 310' and a second half-shell 310", each of which provided with a corresponding abutment face, placed in abutment against the abutment face of the other half-shell 310', 310".

[0078] Advantageously moreover the entire shaped head 31 is fixed to the drawing head 2 by means of the deflector body 311, in particular by means of the above-described connection flange 312. Advantageously the deflector body 311 is placed in abutment against both the half-shells 310', 310" and is fixed, preferably by means of screws and/or bolts, to the second half-shell 310". Advantageously at least one of the abutment faces is provided with at least one or more grooves, each made in the depression on the abutment face and at least partially defining the channel 70. Advantageously, both abutment faces are provided with one or more grooves at least partially defining the channel 70, which are preferably made via milling and/or by means of electro-erosion treatments.

[0079] More in detail, each groove of an abutment face is advantageously placed at the corresponding groove made on the other abutment face in a manner such that when the two half-shells 310', 310" are opposite, with the abutment faces in abutment against each other, the aforesaid grooves are facing to form a corresponding stretch of the channel 70.

[0080] Preferably, each groove is provided with the same depth as the groove of the abutment face and more in detail each groove advantageously and substantially defines half of the corresponding stretch of the channel 70.

[0081] Of course, without departing from the protective scope of the present invention, the grooves can be made only on one abutment face and face a flat portion of the latter, and in this case the stretch of the channel 70 defined by the aforesaid groove will be semicylindrical.

[0082] Otherwise, the grooves can be made on both abutment faces and face a flat portion of the opposite abutment face and also in such case the defined stretch of the channel 70 will be semicylindrical.

[0083] As set forth above, the drawing head 2 comprises at least one inlet opening 21, in fluid communication with the conveyance duct 5, and an outlet opening 22. The drawing head 2 is extended (from the inlet opening 21 to the outlet opening 22) along a longitudinal direction X, preferably transverse to the ground, between the aforesaid inlet opening 21 and the outlet opening 22, and is also extended along a transverse direction substantially parallel to the extension direction Y, Y' of the shaped head 31, which is substantially orthogonal to the longitudinal direction X.

[0084] Preferably, the outlet opening 22 is extended along the transverse direction for the entire transverse extension of the drawing head 2.

[0085] The inlet opening 21 is instead advantageously and substantially placed at the center of the drawing head 2 along the transverse direction.

[0086] Advantageously, the drawing head 2 also comprises a perforated extrusion grid 20, which is placed to intercept the outlet opening 22 in order to allow the drawing of the molten polymer exiting from the outlet opening 22 of the drawing head 2.

[0087] Preferably, the perforated extrusion grid 20 is extended along the aforesaid transverse direction, preferably along the entire transverse extension of the drawing head 2, such that the polymer filaments exiting from the drawing head 2 can be stretched via gravity towards the ground, where they are collected, preferably by a take-up roller (not illustrated).

[0088] The perforated extrusion grid 20 is provided with the plurality of holes 220, preferably equally distributed along the grid itself, which are provided with a diameter preferably comprised between 0.2 and 1 mm.

[0089] Advantageously the drawing head 2 also comprises an inlet portion 200, extended starting from the inlet opening 21 in order to convey the molten polymer, and a collection portion 201, extended between the inlet portion 200 and the outlet opening 22 and arranged for collecting the molten polymer, preferably before the latter exits from the outlet opening 22 through the perforated extrusion grid 20.

[0090] Advantageously, the collection portion 201 at its interior defines a volume within which the molten polymer arrives and which has the object of allowing the correct uniform production of the molten polymer (in particular in terms of temperature, pressure and speed). Advantageously, the collection portion 201 is extended along the transverse direction, preferably along the entire transverse extension of the drawing head 2.

[0091] Advantageously, the drawing head 2 comprises a feed body 23, preferably made of metallic material, which internally defines the inlet portion 200.

[0092] More in detail, the feed body 23 is extended along the aforesaid longitudinal direction X, has prismatic shape (preferably parallelepiped shape) and is extended between a first face, on which the inlet opening 21 is made and such first face is directed towards the second end 5" of the conveyance duct 5, and a second face, opposite the first face and directed towards the collection portion 201.

[0093] Advantageously, the feed body 23 of the drawing head 2 comprises a first half-body 23' and a second half-body 23", each of which provided with a corresponding closure face, placed in abutment against the closure face of the other half-body.

[0094] Advantageously the drawing head 2 is internally provided with at least two transport channels 8, each of which extended from the inlet opening 21 to a dispensing mouth 80 thereof, placed at the collection portion 201.

[0095] Advantageously, at least one of the aforesaid closure faces is provided with at least one or more milled slots in the depression on the closure face, and each of such milled slots at least partially defines one of the transport channels 8.

[0096] Advantageously, both closure faces are provided with one or more milled slots at least partially defining the transport channels 8. More in detail, with the term "milled slots" it is intended a material removal processing adapted to obtain at least one channel in the depression on the aforesaid closure face, and alternatively can be made by means of milling or by means of electro-erosion treatments.

[0097] More in detail, each milling made on a closure face is advantageously placed at the corresponding milling made on the other closure face in a manner such that when the two halfbodies 23', 23" are opposite, with the closure faces in abutment against each other, the aforesaid millings are facing to form a corresponding transport channel 8.

[0098] Preferably, each milling is provided with the same depth as the milling of the other closure face and more in detail each milling advantageously and substantially defines half of the corresponding transport channel 8.

[0099] Of course, without departing from the protective scope of the present invention, the millings can only be made on one closure face and face a flat portion of the latter, in this case the transport channel 8 defined by the aforesaid milling will be semicylindrical.

[0100] Otherwise, the millings can be made on both closure faces and face a flat portion of the opposite closure face and also in such case the defined transport channel will be semicylindrical. Advantageously, the drawing head 2 comprises a collection body 24 made of metallic material, mechanically connected (and preferably fixed) to the feed body 23 and internally defining the collection portion 201.

[0101] More in detail, the collection body 24 preferably has prismatic shape and is extended between a third face, directed towards the second face of the feed body 23, and a fourth face, opposite the third face and on which the outlet opening 22 is made.

[0102] Advantageously, the collection body 24 is extended along the transverse direction, preferably along the entire transverse extension of the drawing head 2.

[0103] Preferably, the inlet opening 21 is made on the first face of the feed body 23 and the outlet opening 22 is made on the fourth face of the collection body 24.

[0104] Advantageously the inlet portion 200 of the drawing head 2 comprises two or more transport channels 8 for the molten polymer, which are each extended between the inlet mouth 21 and the collection portion 201.

[0105] Advantageously, each transport channel 8 is extended along a corresponding supply path between the inlet opening 21 and the collection portion 201 and the aforesaid supply paths are substantially provided with the same extension.

[0106] Preferably with the expression "same extension" it will be intended hereinbelow that the extension of each supply path is contained between 90% and 110% with respect to the mean of the other supply paths defined by the remaining transport channels 8.

[0107] In this manner, it is possible to ensure the constant uniformity of the temperature, of the pressure and of the speed of the molten polymer that reaches the collection portion 201, in particular along the entire transverse extension of the same collection portion 201. Advantageously in fact it is possible to make drawing heads 2 of reduced size with respect to the conventional drawing heads.

[0108] In accordance with the preferred embodiment, the transport channels 8 are extended symmetrically with respect to each other along the inlet portion 200 with respect to a plane of symmetry orthogonal to the first and to the second face of the feed body 23.

[0109] More in detail, the transport channels 8 are extended symmetrically with respect to the inlet opening 21 of the drawing head 2.

[0110] Advantageously, in accordance with the aforesaid preferred embodiment, the inlet opening 21 comprises an initial channel 210, preferably comprising a conical channel, in hydraulic connection with the transport channels 8 in order to divide - upstream of the transport channels - the flow of molten polymer.

[0111] In accordance with an embodiment that is not illustrated in the enclosed figures, the drawing head 2 can also comprise two separate inlet openings 21, preferably side-by-side each other, placed in hydraulic connection with the conveyance duct 5.

[0112] Advantageously, at least two of the aforesaid transport channels 8 each comprise a first stretch 81, which is extended between the inlet opening 21 and a first deflection point 810. Advantageously the first stretches 81 are extended mainly along the transverse direction, away from the inlet opening 21, so as to be distributed along the entire feed portion of the drawing head 2.

[0113] For such purpose, the first stretches 81 are preferably L-shaped, in which the greater stretch is oriented along the aforesaid transverse direction while the smaller stretch is oriented along the longitudinal direction X.

[0114] Advantageously, each of the aforesaid transport channels 8 comprises a corresponding second stretch 82, which is extended starting from the first deflection point 810 of the first stretches 81. Advantageously the second stretches 82 are extended mainly along the transverse direction, away from the first deflection point 810, so as to be distributed along the entire inlet portion 200 of the drawing head 2.

[0115] For such purpose, the second stretches 82 are preferably L-shaped, in which the stem of the L is oriented along the aforesaid transverse direction while the foot of the L is oriented along the longitudinal direction X.

[0116] Advantageously, each of the aforesaid transport channels 8 comprises a corresponding third stretch 83, which is extended starting from the second deflection point 820 of the second stretches 82.

[0117] Advantageously the third stretches 83 are extended mainly along the transverse direction, away from the second deflection point 820, so as to be distributed along the entire inlet portion 200 of the drawing head 2.

[0118] For such purpose, the third stretches 83 are preferably L-shaped, in which the greater stretch is oriented along the aforesaid transverse direction while the smaller stretch is oriented along the longitudinal direction X.

[0119] Advantageously, each transport channel 8 comprises, preferably at the third stretch 83 thereof, two discharge stretches 84, which are extended in deflection from the third stretch 83 to the collection portion 201.

[0120] Of course, without departing from the protective scope of the present invention, the transport channels 8 can comprise corresponding fourth stretches, fifth stretches etc. which are extended in a manner entirely similar to the first, second and third stretches described above. Advantageously, so as to optimize the space of the drawing head 2, all the transport channels 8 are extended with stretches in common with other transport channels 8.

[0121] Nevertheless, it is also possible that one or more transport channels 8 are extended separately, directly from the inlet opening 21 to the collection portion 201.

[0122] In this manner, due to the particular distribution of the transport channels 8 described above, the molten polymer can flow in a uniform manner from an inlet opening 21, preferably central, to the collection portion 201 which is extended along the longitudinal direction X, preventing the polymer from reaching the aforesaid collection portion 201 with temperature, pressure or speed gradients.

[0123] In accordance with the preferred embodiment, illustrated in figure 13, the inlet portion 200 of the drawing head 2 comprises sixteen transport channels 8, which are extended symmetrically from the inlet opening 21, along corresponding transport paths P1, substantially with the same extension with respect to each other.

[0124] In accordance with the aforesaid embodiment, the transport path P1 defined by each transport channel 8 corresponds with the sum of the first stretch 81, of the second stretch 82, of the third stretch 83 and of the discharge stretch 84.

[0125] Preferably, the first stretches 81 of the transport channels 8 are each provided with the same extension. Preferably, the second stretches 82 of the transport channels 8 are each provided with the same extension. Preferably, the third stretches 83 of the transport channels 8 are each provided with the same extension. Preferably, the discharge stretches 84 of the transport channels 8 are each provided with the same extension.

[0126] Advantageously, each of the transport channels 8 is extended between a corresponding feed opening 8', placed in hydraulic connection with the inlet opening 21, and a corresponding discharge opening 8", placed in hydraulic connection with the collection portion 201. Preferably, the discharge openings 8" are placed at the end of each discharge stretch 84. Advantageously, the discharge openings 8" of the transport channels 8 are placed equally distributed along the collection portion 201, in a manner such that the molten polymer flows into the collection portion 201 in an equally distributed manner along the entire collection portion 201 itself, hence increasing the uniformity of the drawn polymer, in particular of the pressure and temperature possessed by the polymer within the collection portion 201. Advantageously, the transport channels 8 have an internal diameter which decreases between the inlet opening 21 and the collection portion 201.

[0127] More in detail, upstream of each deflection point 810, 820 the internal diameter of the transport channel 8 is reduced.

[0128] In this manner, it is possible to maintain the same speed even after the deflection into two transport channels 8.

[0129] Advantageously, first stretches 81 of the transport channels 8 are provided with a first internal diameter D1, and the second stretches 82 of the transport channels 8 are provided with a second internal diameter D2, smaller than the aforesaid first internal diameter D1.

[0130] Preferably moreover the discharge stretches 84 are provided with a discharge diameter Ds, smaller than the first internal diameter D1 of the first stretches 81.

[0131] Advantageously, the plant 1 also comprises heating means, fixed at least at the inlet portion 200 of the drawing head 2 in order to heat the molten polymer in the inlet portion 200. Advantageously, the heating means comprise a plurality of electrical heating elements, preferably substantially planar, which are externally connected to the feed body 23 of the drawing head 2.

[0132] The invention thus conceived therefore attains the pre-established objects.

Claims

1. Plant (1) for producing polymer filaments, comprising:

- at least one drawing head (2) arranged for drawing a polymer at the molten state between at least one inlet opening (21) and an outlet opening (22) provided with a plurality of holes for drawing corresponding polymer filaments;

- aeration means (3), placed downstream of said drawing head (2), arranged for dispensing a cooling fluid at the outlet opening (22) of said drawing head (2) in order to stretch said polymer filaments and comprising at least one source (30) for feeding said cooling fluid and at least two shaped heads (31), mechanically fixed to said drawing head (2), on opposite sides of said drawing head (2);
each of said shaped heads (31) delimiting a cooling circuit (6), which is in fluid communication with said feed source (30) in order to receive the cooling flow and is extended to a dispensing portion (60) thereof, placed at the outlet opening (22) of said drawing head (2) and provided with a plurality of guide ducts (600) adapted to direct said cooling fluid;

said plant (1) for producing polymer filaments being characterized in that the cooling circuit (6) delimited by said shaped head (31) comprises a channel (7), which is extended between at least one feed mouth (70), in fluid communication with said feed source (30), and said dispensing portion (60); said channel (7) being provided with at least one main stretch (71), in fluid communication with said feed mouth (70), and with at least two secondary stretches (72), extended branched from said main stretch (71), in fluid communication with said main stretch (71) and each extended to a corresponding outlet mouth (721) thereof, in fluid communication with said dispensing portion (60).

2. Plant (1) according to claim 1, characterized in that said main stretch (71) is extended between said feed mouth (70) and a first branch point (710), and the channel (7) is provided with at least two intermediate stretches (73), which are branched from said main stretch (71) and are extended between said first branch point (710) and a corresponding second branch point (720).

3. Plant (1) according to claim 2, characterized in that each of said secondary stretches (72) is extended between a corresponding said second branch point (720) and said corresponding outlet mouth (721).

4. Plant (1) according to claim 3, characterized in that said channel (7) comprises two main stretches (71), each of which is in fluid communication with a separate said feed mouth (70) and from each of such main stretches (71), two intermediate stretches (73) are branched, and from each of such intermediate stretches (73), two secondary stretches (72) are in turn branched.

5. Plant (1) according to any one of the preceding claims, characterized in that said channel (7) defines a plurality of paths (P) between said feed mouth (70) and a corresponding said outlet mouth (721);
said paths (P) being substantially provided with the same extension.

6. Plant (1) according to any one of the preceding claims, characterized in that each main stretch (71) is provided with a first passage section and each secondary stretch (72) is provided with a second passage section;
the area of the second passage section of said secondary stretches (72) being greater than the area of the first passage section of the corresponding said main stretch (71).

7. Plant (1) according to any one of the preceding claims, characterized in that each said secondary stretch (72) is provided with a second passage section and each outlet mouth (721) is provided with an outlet section;
the area of the second passage section of said secondary stretches (72) being greater than the area of the outlet section of the corresponding said outlet mouth (721).

8. Plant (1) according to any one of the preceding claims, characterized in that the dispensing portion (60) of said cooling circuit (6) comprises at least one collection chamber (61), in fluid communication with the outlet mouths (721) of the secondary stretches (72) of said channel (7) and arranged for receiving said cooling fluid.

9. Plant (1) according to any one of the preceding claims, characterized in that said shaped head (31) comprises a main body (310), comprising said channel (7), and a deflector body (311), mechanically connected to said main body (310) and at least partially delimiting with the latter said dispensing portion (60).

10. Plant (1) according to claims 8 and 9, characterized in that said deflector body (311) and said main body (310) between them define a directing portion (63), which is placed downstream of said collection chamber (61) along said cooling circuit (6) and is delimited by a first tilted stretch (314), attained on said deflector body (311), and by a second tilted stretch (315), attained on said main body (310).

11. Plant (1) according to any one of the preceding claims, characterized in that said shaped head (31) comprises a main body (310), which comprises a first half-shell (310') and a second half-shell (310"), each of which provided with a corresponding abutment face, placed in abutment against the abutment face of the other said half-shell (310', 310");
at least one of said abutment faces being provided with at least one or more grooves, each made in the depression on said abutment face and at least partially defining said channel (7).

Drawing