Spinning head and related apparatus for the production of filaments

Abstract

Apparatus (1) for producing a nonwoven fabric comprising a spinneret (2) and a mechanical drawing device (5) which comprises primary rollers and secondary rollers (21, 22) which are constrained to a frame (50) such that, considering a condition of use, said secondary rollers (21, 22) are movable with respect to said primary rollers (11, 12, 13) between a first position of operational disengagement from said filaments (3), and a second drawing position of said filaments (3).

Claims

1. Apparatus (1) for producing a nonwoven fabric comprising a spinneret (2) for extruding a plurality of filaments (3), a cooling device (4) arranged, in use, below the spinneret (2), a mechanical drawing device (5) arranged below the cooling device, a collecting device (6) to collect the filaments which is arranged below the drawing device (5), the drawing device (5) comprising at least two primary rollers (11, 12, 13) each rotatable about its own axis of rotation (A11, A12, A13), and one or more secondary rollers (21, 22), the secondary rollers (21, 22) each being rotatable about its own axis of rotation (A21, A22), a frame (50), wherein said primary rollers (11, 12, 13) and said secondary rollers (21, 22) are constrained to said frame (50) such that, considering a condition of use, said secondary rollers (21, 22) are movable with respect to said primary rollers (11, 12, 13) between a first position of operational disengagement from said filaments (3), and a second drawing position of said filaments (3), and wherein said primary rollers (11, 12, 13) and said secondary rollers (21, 22) are arranged alternately with each other, so that, in use, the filaments (3) alternately meet a primary roller and a secondary roller, and so that, in the second drawing position, the filaments (3) meet rollers arranged at progressively decreasing distances (D1, D2, D3, D4, D5) from the collecting device (6), the tangential speed of the roller (11) which is placed furthest upstream in the path of the filaments (3) being between 300 and 1500 m/min, the tangential speed of the rollers progressively increasing, wherein said one or more of the secondary rollers is translationally constrained to said frame, by means of a slide, the translation of said slide defining said first and second position.

2. The apparatus (1) according to claim 1 configured so that, considering a sectional plane perpendicular to the axis of rotation (A11, A12, A13) of at least one of the primary rollers (11, 12, 13) and considering, on said sectional plane, a straight line (R) tangent both to the axis of rotation (A11) of the primary roller (11) which, in use, is located furthest upstream in the path of the filaments and to the axis of rotation (A13) of the primary roller (13) which, in use, is located furthest downstream in the path of the filaments (3), the sectional plane being divided into two half-planes by said straight line (R), the frame (50) of said primary and secondary rollers is mainly arranged in one of said half-planes.

3. The apparatus (1) according to claim 2, configured such that, considering a reference plane which is perpendicular to said sectional plane and which comprises said tangent straight line, so as to form two portions of space divided by said reference plane, the frame of said primary and secondary rollers is mainly arranged in one of said portions of space, at least 70% of the volume of said frame being arranged in one of said portions of space.

4. The apparatus (1) according to claim 1, wherein said primary rollers (11, 12, 13) are translationally integral with said frame (50).

5. The apparatus according to claim 1, wherein the tangential speed of each roller is at least 5% higher than the speed of the roller disposed immediately upstream thereof along the direction of movement of said filaments.

6. The apparatus according to claim 5, wherein the tangential speed of each roller is between 105% and 200% of the tangential speed of the roller disposed immediately upstream thereof along the direction of movement of said filaments.

7. The apparatus according to claim 1, configured so that, in use, the tangential speed of the roller furthest upstream in the path of the filaments is between 300 and 2000 m/min.

8. The apparatus according to claim 1, wherein between the mechanical drawing device (5) and the collecting device (6) there is an expansion duct (8) comprising at least two inclined planes and comprising an inlet port (81) and an outlet port (82).

9. The apparatus according to claim 8, wherein the inclination of the inclined planes gives the expansion duct (8) a truncated cone shape having a lower base section facing a collection surface of the collecting device (6) and an upper base section facing the drawing device (5), wherein the lower base section is greater than the upper base section.

10. The apparatus according to claim 1, wherein between the drawing device (5) and the collecting device 6 there is a suctioning duct 9 and a mechanical distributor (10, 10); said mechanical distributor (10, 10) being configured to alter the direction of fall of the filaments (3) exiting the suctioning duct (9) in order to increase the deposition surface of the filaments (3) on the collection surface of the collecting device (6).

11. The apparatus according to claim 10, wherein said mechanical distributor (10, 10) comprises a movable shelf (101) on which the filaments (3) exiting the suctioning duct (9) are laid and which alters the direction of fall of the filaments (3) on the collecting device (6).

12. The apparatus according to claim 10, wherein said mechanical distributor (10, 10) comprises a fixed shelf (102) placed below the suctioning tube (9) and a swinging rod (30) placed to the side of the fixed shelf (10).

13. Process for making a nonwoven fabric by means of an apparatus (1) according to claim 1, comprising the steps of extruding a plurality of the filaments (3) from the spinneret (2), cooling the filaments by means of the cooling device (4), and drawing the filaments by means of the mechanical drawing device (5), wherein the filaments (3) alternately meet a primary roller and a secondary roller, the filaments (3) meeting rollers which are arranged at progressively decreasing distances (D1, D2, D3, D4) from the collecting device (6), wherein the tangential speed of the roller (11) placed furthest upstream in the path of the filaments (3) is between 300 and 2000 m/min, the tangential speed of the rollers progressively increasing.

14. The apparatus (1) according to claim 3, wherein said primary rollers (11, 12, 13) are translationally integral with said frame (50).

15. The apparatus according to claim 1, wherein said one or more of the secondary rollers are mounted on a body which is at least rotatably constrained to said frame, the rotation of said body defining said first and second positions.

16. The apparatus according to claim 15, wherein the tangential speed of each roller is at least 5% higher than the speed of the roller placed immediately upstream thereof, considering the direction of movement of said filaments.

17. The apparatus according to claim 4, wherein between the mechanical drawing device (5) and the collecting device (6) there is an expansion duct (8) comprising at least two inclined planes and comprising an inlet port (81) and an outlet port (82).

18. Apparatus (1) for producing a nonwoven fabric comprising a spinneret (2) for extruding a plurality of filaments (3), a cooling device (4) arranged, in use, below the spinneret (2), a mechanical drawing device (5) arranged below the cooling device, a collecting device (6) to collect the filaments which is arranged below the drawing device (5), the drawing device (5) comprising at least two primary rollers (11, 12, 13) each rotatable about its own axis of rotation (A11, A12, A13), and one or more secondary rollers (21, 22), the secondary rollers (21, 22) each being rotatable about its own axis of rotation (A21, A22), a frame (50), wherein said primary rollers (11, 12, 13) and said secondary rollers (21, 22) are constrained to said frame (50) such that, considering a condition of use, said secondary rollers (21, 22) are movable with respect to said primary rollers (11, 12, 13) between a first position of operational disengagement from said filaments (3), and a second drawing position of said filaments (3), and wherein said primary rollers (11, 12, 13) and said secondary rollers (21, 22) are arranged alternately with each other, so that, in use, the filaments (3) alternately meet a primary roller and a secondary roller, and so that, in the second drawing position, the filaments (3) meet rollers arranged at progressively decreasing distances (D1, D2, D3, D4, D5) from the collecting device (6), the tangential speed of the roller (11) which is placed furthest upstream in the path of the filaments (3) being between 300 and 1500 m/min, the tangential speed of the rollers progressively increasing, wherein said primary rollers (11, 12, 13) are translationally integral with said frame (50) and said one or more of the secondary rollers is translationally constrained to said frame, by means of a slide, the translation of said slide defining said first and second positions.

Description

(1) Hereinafter, referring to the appended figures, exemplary and non-limiting embodiments of the present invention will be described, in which:

(2) FIG. 1 is a schematic side view of a possible embodiment of an apparatus according to the present invention;

(3) FIGS. 2 and 3 are schematic views of the drawing device of the apparatus in FIG. 1, with the secondary rollers in the first and second positions, respectively;

(4) FIGS. 4 and 5 are schematic views of a drawing device of the apparatus according to an embodiment alternative to the one in FIG. 1, with the secondary rollers in the first and second positions, respectively.

(5) FIG. 6 is a schematic view of an expansion channel of an apparatus according to an embodiment.

(6) FIG. 7 is a schematic view of a suction channel and a mechanical distributor according to an embodiment.

(7) FIG. 8 is a schematic view of a suction channel and a mechanical distributor according to an embodiment alternative to the one of FIG. 7.

(8) An apparatus 1 for the production of a nonwoven fabric comprises a spinneret 2 for extruding a plurality of filaments 3, a cooling device 4 arranged, in use, below the spinneret 2, a mechanical drawing device 5 (hereinafter also drawing device 5) arranged below the cooling device, and a collecting device 6 to collect the filaments which is arranged below the drawing device 5.

(9) The spinneret 2, the cooling device 4 can be made according to what known to the field technician and are not discussed in detail herein.

(10) In short, the spinneret 2 is typically able to receive molten material and to extrude a plurality of filaments 3 through extrusion holes not shown in detail in the figures.

(11) It should be noted that, for the sake of simplicity, the figures only show one bundle of filaments, which is directed substantially vertically from the spinneret 2 towards the drawing device 5. Actually, the filaments 3 may initially be distributed more widely and converge from the spinneret 2 at the drawing device. The spinneret is preferably a linear spinneret.

(12) The cooling device 4 is typically configured to direct one or more flows of gas, typically air, towards the filaments 3 extruded from the spinneret 2, in order to cause them to cool. Typically, when the filaments come into contact with the drawing device 5, they are substantially at room temperature or at least substantially solid.

(13) Additional suctioning devices, not shown in detail, can be provided below the spinneret for suctioning harmful gases such as oligomers and the like formed by the extrusion process of the filaments 3.

(14) The collecting device 6 typically has a collection surface, such as a belt, which is typically movable in a horizontal direction and is adapted to collect the falling filaments and form a nonwoven fabric. Thanks to the collection surface, the nonwoven fabric can be directed towards further processing (e.g., suitable for consolidating the nonwoven fabric, such as one or more needle-felting devices, one or more calenders, etc.).

(15) The collecting device 6 may comprise a suction element 7 below the collection surface of the collecting device 6. This suction element 7 allows gas to be suctioned below the collection surface.

(16) The suction element 7 is connected to an aspirator adapted to suction gas at a speed between 8 m/s and 15 m/s, preferably between 12 m/s and 15 m/s.

(17) The width of the suction element 7 and, accordingly, the width of the suction area on the collection surface of the collecting device is between 100 mm and 500 mm, preferably it is 250 mm.

(18) It should be noted that the collecting device 6 is not necessarily the first device downstream of the drawing device 5, since additional processing, known in the art, can be provided on the falling filaments as better described below.

(19) The drawing device 5 comprises a plurality of rollers 11, 12, 13, 21, 22, specifically primary rollers 11, 12, 13, and one or more secondary rollers 21, 22, mounted on a frame 50.

(20) Each roller 11, 12, 13, 22, 23 is rotatable with respect to the frame 50 about an axis of rotation A11, A12, A13, A21, A22.

(21) The primary rollers and the secondary rollers 11-13, 21, 22 are constrained so as to allow mutual movement between secondary rollers and primary rollers.

(22) The primary rollers 11-13 are typically fixedly constrained to the frame 50, i.e., with no possibility of translation, the only degree of freedom being given by the rotation about their own axis A11, A12, A13.

(23) In contrast, the secondary rollers 21, 22 are preferably movably constrained with respect to the frame 50. This can be achieved in various ways, according to known mechanical principles. Preferred embodiments provide secondary rollers constrained by means of the slides 51 translationally mounted to the frame 50, and/or by means of bodies 52 hinged to the frame 50. In the second case, the secondary rollers 21, 22 are constrained to the body 52 apart from the hinge which constrains the body 52 to the frame 50, so that the rotation of the body 52 with respect to the frame 50 causes the roller to move with respect to the frame 50, typically along a circular trajectory.

(24) In general, the secondary rollers 21, 22 are movable with respect to the primary rollers 11-13 between a first position of operational disengagement from the filaments 3 and a second position of drawing the filaments 3. Thus, the second position is the one taken by the rollers during the operating condition of the apparatus 1, which allows the filaments 3 to be drawn. The first position is the rest position, in which the apparatus 1 is not operating or, in any case, in which the rollers do not draw the filaments 3. Typically, in this first position, the secondary rollers 21, 22 are not in contact with the filaments 3.

(25) In the second position, the first and secondary rollers are in contact with the filaments 3. Preferably, in use, the filaments 3 do not wrap around the rollers 11, 12, 13, 21, 22 but are in contact only with a part of the outer surface of the rollers 11, 12, 13, 21, 22.

(26) In other words, considering one of the rollers and a sectional plane perpendicular to the axis of rotation of that roller, the outer surface of the roller has a substantially circular shape. The filaments are in contact with only part of the circumference defined by the outer portion of the roller, that is, they are in contact only along an arc of the circle formed by the outer surface of the roller. The angle defined by this arc of a circle is therefore less than 360.

(27) For example, with reference to FIG. 3, at the primary roller 11 and the primary roller 13, the filaments 3 are in contact with these rollers along an arc extending through an angle of about 90, while at the other rollers the filaments are in contact therewith along an arc of a circle extending through an angle of about 180.

(28) The primary rollers and the secondary rollers 11, 12, 13, 21, 22 are arranged alternately with each other so that, in use, the filaments alternately meet a primary roller and a secondary roller. Typically, the roller placed furthest upstream and the roller placed furthest downstream in the path of the filaments 3 are primary rollers, for example, the primary roller 11 and the primary roller 13 in the embodiment shown in the figures.

(29) The rollers 11, 12, 13, 21, 22 are arranged so as to be progressively closer to the collecting device 6, that is, the filaments in their path meet rollers arranged at distances D1, D2, D3, D4, D5 progressively decreasing with respect to the collecting device.

(30) As explained, the distance D1, D2, D3, D4, D5 between each roller (i.e., between its outer surface) and the collecting device is measured in the direction perpendicular to the collecting device, i.e., perpendicular to the surface of the collecting device 6 on which the filaments 3 are deposited. The roller furthest upstream in the path of the filaments 3 has the maximum value of this distance, while the roller furthest downstream has the minimum value of this distance.

(31) Considering the condition of use, the rollers are arranged one below the other.

(32) Preferably, in section, the axes of rotation A11, A12, A13 of the primary rollers are arranged on a straight line typically, in use, perpendicular to the collecting device (i.e., the surface on which the filaments are deposited) and/or substantially vertical.

(33) In case of two or more secondary rollers 21, 22, also the axes of rotation A21, A22 of the secondary rollers are arranged on a straight line typically perpendicular to the collecting device (i.e., the surface on which the filaments are deposited) and/or substantially vertical in use.

(34) The frame 50 is preferably configured to comply with the following property. Consider a sectional plane perpendicular to the axis of rotation A11, A12, A13 of at least one of the primary rollers 11, 12, 13 and a straight line R on this plane tangent to the axis of rotation A11 of the primary roller 11 which is placed, in use, furthest upstream in the path of the filaments and tangent to the axis of rotation A13 of the primary roller 13 which is placed furthest downstream in the path of the filament 3. The frame 50 is arranged mainly to the right or left of this straight line R, preferably at least 70% of the frame is arranged to the right or left of the straight line R.

(35) The same can be said for the filaments 3. Consider the (typically curved) line formed by the path of the filaments 3 from the furthest upstream roller to the furthest downstream roller. Consider the portions of section of the frame 50 to the right and left of this line. One of the two portions is larger (i.e., has larger area) than the other, typically at least 70% larger than the other.

(36) The property discussed above applies to at least one possible sectional plane. Since the frame is a three-dimensional object, an additional preferred property of the frame 50 can be defined. Given a reference plane passing through the straight line R (and perpendicular to the sectional plane), the frame 50 is divided into two portions by that reference plane. One of the two portions has greater volume than the other, preferably at least 70% greater, more preferably at least 80% greater.

(37) In preferred embodiments, therefore, the frame is predominantly arranged on one side of such a reference plane and, generally, as a result on one side of the filaments 3.

(38) Thus, the frame 50 is compact and is a single element arranged predominantly on one side of the filaments, while the rollers mounted on this frame are located, in the operating condition, alternately on the left and on the right of the filaments, considering a viewpoint aligned with the axis of rotation of at least one of the rollers, such as the view shown in the exemplary embodiments in the figures.

(39) The roller furthest upstream in the path of the filaments 3, which in the embodiments is the primary roller 11, has tangential speeds between 300 and 2000 m/min. For example, this speed can be calculated by multiplying the angular speed of rotation of the roller, multiplied by the radius of the roller itself.

(40) Both the primary rollers and the secondary rollers, which are downstream of the primary roller 11, preferably have progressively increasing speeds, typically each roller having a roller immediately upstream thereof has tangential speed at least 10% higher than the tangential speed of the roller immediately upstream thereof.

(41) Preferably, the speed difference between two rollers arranged sequentially in the path of the filaments 3 does not exceed a predetermined threshold, whereby the tangential speed of a roller is between 110% and 200% of the speed of the roller placed immediately upstream thereof.

(42) The rollers 11, 12, 13, 21, 22 are preferably heated to temperatures different from each other.

(43) In use, a plurality of filaments 3 is extruded from the spinneret 2. The filaments 3 are then cooled by the cooling device 4.

(44) Below the cooling device 4 the mechanical drawing device 5 is arranged.

(45) The drawing device 5 is operated so that the secondary rollers 21, 22 are arranged in the second drawing position, so that the filaments are in contact with the various rollers 11, 12, 13, 21, 22 of the drawing device 5.

(46) As explained, the filaments do not wrap completely around the rollers but are in contact with only part of the outer surface thereof. Typically, the filaments 3 have a basically S pattern between the various rollers 11, 12, 13, 21, 22 of the drawing device 5.

(47) The filaments meet the primary and the secondary rollers alternately, so that following a primary roller 11, 12, 13 meet a secondary roller 21, 22 and vice versa.

(48) The rollers 11, 12, 13, 21, 22 are rotationally operated so as to draw the filaments 3. As discussed, the rollers 11, 12, 13, 21, 22 typically have progressively increasing speeds, so that the speed of a roller is preferably between 110% and 200% of the speed value of the roller immediately upstream thereof.

(49) The primary rollers 11, 12, 13 are typically rotated in the opposite direction with respect to the secondary rollers 21, 22.

(50) After the drawing step, the filaments 3 are deposited on the collecting device 6 to form a nonwoven fabric.

(51) As explained, additional devices can be provided between the mechanical drawing device 5 and the collecting device 6 so that additional processing can be made to the filaments 3 before they are deposited on the collecting device 6.

(52) According to a possible aspect, between the mechanical drawing device 5 and the collecting device 6 there is an expansion duct 8 comprising at least two inclined planes and comprising an inlet port 81 and an outlet port 82.

(53) The inclination of the inclined planes gives the expansion duct 8 a truncated cone shape whose lower base section (facing the collection surface of the collecting device 6) is greater than the upper base section (facing the drawing device 5).

(54) The width of the inlet port 81 is between 25 mm and 120 mm, preferably it is 60 mm.

(55) The width of the outlet port 82 is between 130 mm and 350 mm, preferably it is 250 mm.

(56) The height H of the expansion duct 8 is between 500 mm and 2000 mm, preferably it is 1000 mm.

(57) The distance K between the outlet port 82 of the expansion duct 8 and the collection surface of the collecting device 6 is between 20 mm and 180 mm, preferably it is 50 mm.

(58) According to an alternative embodiment, between the drawing device 5 and the collecting device 6 there are a suctioning duct 9 and a mechanical distributor 10, 10.

(59) The mechanical distributor 10, 10 alters the direction of fall of the filaments 3 exiting the suctioning duct 9, in order to increase the deposition surface of the filaments 3 on the collection surface of the collecting device 6.

(60) Preferably, the mechanical distributor 10, 10 may comprise a movable shelf 101 on which the filaments 3 exiting the suctioning duct 9 are laid and which alters the direction of fall of the filaments 3 on the collecting device 6.

(61) According to an alternative embodiment the mechanical distributor 10, 10 may comprise a fixed shelf 102 placed below the suctioning tube 9 and a swinging rod 30 placed to the side of the fixed shelf 10.

(62) In this case, the filaments 3 exiting the suctioning duct 9 come into contact with the fixed plane 10 which alters the direction of fall of the filaments 3 which are then subject to swinging as a result of contact with the swinging rod 30 before being deposited on the collection surface of the collecting device 6.