Drawing method for a sliver

Abstract

A drawing device (4) for webs (8) of textile fibres comprising - a feeder device (12) of a web (8) to be drawn, - a carding machine (28) rotating according to a direction of rotation (S) comprising, on an outer side wall thereof (32), a plurality of teeth (36) arranged with a constant tangential pitch (P), adapted to draw said web (8), - an extraction cylinder (56) placed downstream of the carding machine (28) and of the web (8), wherein - the feeder device (12) comprises a feeder roller (16), facing the carding machine (28), which rotates so as to feed the web to the carding machine (28) at an input speed and according to a direction of advancement (F) concordant with respect to said direction of rotation (S) of the carding machine (28), - wherein the carding machine is driven in rotation so as to have a peripheral speed on the teeth equal to the product of the input speed times the total drawing of the web ± 20%, so that the drawing of the web takes place practically entirely on the carding machine, - the total drawing being the ratio between the thread count of the yarn to be produced and the input web thread count. [Fig. 1]

Description

FIELD OF APPLICATION

[0001] The present invention relates to a drawing method for a sliver with carding roller for air spinning systems thereof.BACKGROUND ART

[0002] As known, slivers with fibre length typically of 38 mm or longer and above all with fibre distribution as homogeneous as possible are required in air spinning systems. These characteristics of the upstream sliver allow obtaining good technical characteristics of the yarn, while the presence of short fibres significantly worsens such characteristics.

[0003] The drawing systems used are normally formed by three or more pairs of drawing and pressure cylinders, each of which performs a partial and progressive drawing of the sliver . The last pair uses belt systems which ensures greater delicacy in fibre parallelization and drawing.

[0004] The output fibre flow continuity is a fundamental requirement.

[0005] The drawing systems used in air spinning devices are derived in toto from those traditionally used in ring spinning and suffer from the same shortcomings, i.e. poor parallelization efficiency at high working speed and limited maximum obtainable drawing.

[0006] Carding roller drawing systems, instead, are used in open-end spinning systems to convey the fibres from the inlet to the rotor using the mechanical action of the teeth to tear the fibres from the sliver and the centrifugal action due to the high rotation speed to remove impurities and short fibres from the flow of fibres which enters into the rotor. In these systems, the continuous flow of fibres is not a fundamental requirement and nor is the presence of short or broken fibres. However, the systems with carding roller are more compact than those with rollers and above all the parallelization function of the fibres, ensured by the action of the teeth of the carding roller, is extremely effective and is not affected in any manner by the working speed or the imparted drawing amount. A drawing device according to prior art is disclosed for example by WO 2017 / 075675 A1.PRESENTATION OF THE INVENTION

[0007] The need is therefore felt to solve the drawbacks and limitations mentioned above with reference to the prior art.

[0008] Such need is met by a drawing method with carding roller for air spinning according to claim 1.DESCRIPTION OF THE DRAWINGS

[0009] Further features and advantages of the present invention will be more comprehensible from the following description of preferred embodiments given by way of nonlimiting examples, in which: figure 1 shows a diagrammatic view of a drawing device with carding roller according to an embodiment of the present invention; figures 2a-2b show enlarged views of detail II in figure 1; figure 3 is an enlarged view of detail III in figure 1.

[0010] Elements or parts in common to the embodiments described below will be indicated using the same reference numerals.DETAILED DESCRIPTION

[0011] With reference to the aforementioned figures, reference numeral 4 indicates a drawing device for slivers 8 of textile fibres as a whole.

[0012] In particular, the drawing device 4 comprises a feeder device 12 of a sliver 8 to be drawn, comprising a feeder roller 16.

[0013] The feeder roller 16 is driven so as to rotate about a rotation pivot thereof.

[0014] According to a possible embodiment, the feeder device 12 further comprises a nozzle or a mouth 20 which conveys the sliver 8 to be drawn towards the successive drawing processes.

[0015] The nozzle or mouth 20 defines a passage channel 24 for the sliver 8 together with the feeder roller 16.

[0016] The nozzle or mouth 20 is preferably pressed towards the feeder roller 16 so as to apply a pressure which is as a function of the input web thread count.

[0017] The feeder roller 16, by virtue of its motorized rotation, sets in motion the sliver web- 8, which is fed at an input speed Vi.

[0018] The drawing device 4 further comprises a carding roller 28 comprising, on its outer side wall 32, a plurality of teeth 36 arranged at a constant tangential pitch P. The teeth 36 are shaped so as to draw the sliver 8.

[0019] The feeder roller 16 rotates and directly faces the carding roller 28 so as to feed the web to the carding roller 28 at said input speed Vi.

[0020] Preferably, the tangential pitch P between the teeth 36 of the carding roller 28 is comprised between 5 and 15 mm.

[0021] As explained below, this pitch P is particularly wide compared with the pitches of the solutions of the prior art: this reduces the complexity and cost of the carding roller 28.

[0022] Preferably, said teeth 36 have a substantially triangular shape which protrudes from the outer side wall 32 of the carding roller 28, according to a first front portion 40, which directly faces the sliver 8, and a second rear portion 44 which forms a vertex 48 with the first front portion 40.

[0023] Preferably, said vertex 48 has a radial height 52, measured with respect to the outer side wall 32 along a radial direction R passing through a rotation axis C of the carding roller 28, comprised between 0.5 and 2 mm.

[0024] According to an embodiment, the first front portion 40 identifies a first angle β comprised between 5 and 10 degrees with radial direction R, passing through a rotation axis C of the carding roller 28.

[0025] According to an embodiment, the second rear portion 44 identifies a second angle α comprised between 40 and 70 degrees with tangential direction T perpendicular to a radial direction R passing through the rotation axis C of the carding roller 28.

[0026] The sliver 8 is fed by the feeder device 12, at the input speed Vi according to a direction of advancement F agreeing with a direction of rotation S of the carding roller 28.

[0027] In this manner, the teeth of the carding roller 28, during rotation, cling to the sliver web- 8 and draw it according to its direction of advancement F.

[0028] This operating condition is opposite to the known solutions in which the teeth oppose the direction of advancement of the web.

[0029] Advantageously, the carding roller 28 is driven in rotation so as to have a peripheral speed or extraction speed Ve on the teeth 36 equal to the product of the input speed Vi times the total drawing St of the sliver 8, so that the drawing of the sliver web- 8 takes place entirely on the carding roller 28.

[0030] In other words: Ve = Vi x St ± 20%.

[0031] Therefore, the Ve value must remain about 20% of the product of the input speed Vi times the total drawing St.

[0032] Preferably, the Ve value must remain about 10% of the product of the input speed Vi times the total drawing St.

[0033] Even more preferably, the Ve value must remain about 5% of the product of the input speed Vi times the total drawing St.

[0034] Total drawing St means the ratio between the count of the yarn to be produced and the input sliver count.

[0035] The drawing device 4 further comprises an extraction cylinder 56 placed downstream of the carding roller 28 and of the sliver 8.

[0036] In other words, the carding roller 28 receives the sliver 8 from the feeder device 12 and, by rotating in the same direction as the direction of advancement F of the sliver 8, pulls and draws the sliver 8 towards the extraction cylinder 56, arranged downstream of the carding roller 28 and of the sliver 8 with respect to said direction of advancement F of the sliver 8.

[0037] It is worth noting that the carding roller 28 and the extraction cylinder 56 rotate in mutually opposite directions of rotation S,G. In particular, the extraction cylinder 56 rotates in a counter-rotating direction G with respect to the direction of rotation S of the carding roller 28.

[0038] The successive removal of the fibres of the sliver 8 is facilitated and improved by virtue of the counterpoised rotations of the carding roller 28 and of the extraction cylinder 56.

[0039] For this purpose, the extraction cylinder 56 has a specific shape.

[0040] In particular, the extraction cylinder 56 defines an inner cavity 60 and has a perforated side wall 64, provided with a plurality of holes 68 communicating with the inner cavity 60, adapted to create a suction flow in order to facilitate the detachment of the fibres from the carding roller 28. In particular, the inner cavity 60 is connected to a vacuum source so as to create a suction flow through said holes 68 which facilitates the removal of the fibres from the carding roller 28.

[0041] It is apparent that the opposite rotation between carding roller 28 and extraction roller 56 further facilitates such detachment of the fibres of the sliver 8 from the carding roller 28.

[0042] For this purpose, said holes 68 are circular holes having a diameter comprised between 1 and 3 mm.

[0043] According to an embodiment, said holes 68 are arranged according to a matrix diagram along a pair of directions perpendicular to each other, and are spaced apart according to a first and a second pitch L1, L2.

[0044] Preferably, said first and second pitches L1, L2 are comprised between 2 and 4 mm.

[0045] Preferably, said first and second pitches L1, L2 are equal to each other.

[0046] According to a possible embodiment, one of said directions of the matrix diagram is parallel to a rotation axis W of the extraction cylinder 56.

[0047] Obviously, the rotation axes W, C of the extraction cylinder 56 and the carding machine 28 are respectively parallel to each other.

[0048] Generally, the perforated side wall 64 of the extraction cylinder 56 has holes 68 arranged along an extraction band 72 having an axial thickness H, parallel to the rotation axis W of the extraction cylinder 56, comprised between 4 and 11 mm.

[0049] In relation to the relative arrangement of carding roller 28 and extraction cylinder 56, preferably with respect to a direction Q joining the rotation axes C, W of the carding machine 28 and of the extraction cylinder 56, the vertices 48 of the teeth 36 and the side wall 64 of the extraction cylinder 56 are distant by a pitch 76 comprised between 0.1 and 2 mm.

[0050] A conveying device 80 is arranged downstream of the extraction cylinder 56 equipped with an output roller 84 which turns in idle manner and facilitates the extraction of the yarn from the extraction cylinder 56.

[0051] A spinning apparatus for the successive operations to be performed on the yarn may be advantageously arranged downstream of the drawing device 4.

[0052] The operation of the drawing device according to the invention will now be described.

[0053] In particular, as mentioned, the feeder device sends the sliver 8 at an advancement speed Vin through the nozzle or mouth 20. The advancement speed Vin of the sliver web- 8 also corresponds to the tangential rotation speed of the feeder roller 16 at its point of contact with the sliver itself.

[0054] So, the carding roller 28 is driven in rotation, according to a direction of rotation S, in a direction agreeing with the direction of advancement F of the sliver 8.

[0055] The difference in speed between the tangential or extraction speed Ve of the teeth 36 of the carding roller 28 and the advancement speed Vi of the sliver 8 determines the total drawing St of the sliver 8.

[0056] Moreover, the sliver 8 is then passed from the carding roller 28 to the extraction cylinder 56 which, as seen, rotates in direction of rotation G opposite to the direction of rotation S of the carding roller 28.

[0057] The perforated extraction cylinder 56, which delimits the inner cavity 60, has a perforated side wall 64, provided with a plurality of holes 68 communicating with said inner cavity 60 and with a vacuum source.

[0058] The removal of the fibres of the sliver 8 from the carding roller 28 is facilitated by virtue of the vacuum and also by the opposite rotation of the extraction cylinder 56 according to a direction of rotation W opposite to the direction of rotation S of the carding roller 28.

[0059] The rotation speed of the extraction cylinder 56 is such that the tangential speed on the side wall 64 is approximately equal to the tangential speed of the teeth 36 of the carding roller 28.

[0060] The fibres of the sliver 8 is then conveyed from the inner cavity 60 output from the extraction cylinder 56, towards the conveying device 80 and the output roller 84.

[0061] As can be appreciated from the description above, the present invention allows overcoming the drawbacks presented in the prior art.

[0062] The use of the carding roller in the conditions and manner described in the present patent ensures a "soft" manipulation of the fibres, minimizing the possibility of breakage thereof and ensuring the continuity of the fibres at the input of the subsequent spinning units.

[0063] This condition of continuity and the reduced presence of short fibres can be obtained by virtue of the operating condition of the present invention according to which the carding roller works at a linear speed equal to the product of the sliver input speed times the total drawing of the sliver ± 20%.

[0064] As long as the linear speed value is within 20% of such a value, yarn continuity is obtained, with fibres of longer length and with a minimum risk of breakage thereof.

[0065] Advantageously, the present invention allows obtaining a high-quality yarn, according to the desired count because fibre continuity is always ensured. In other words, although the drawing is obtained in a single step on the carding roller, the fibres are drawn rapidly but progressively and above all continuously. The result is a homogeneous and uniform yarn free of broken fibres and / or short length.

[0066] Advantageously, the solution of the present invention envisages that the carding roller rotates according to a direction of rotation agreeing with the direction of rotation of the sliver of fibres: in this manner, it is possible to significantly increase the working speed and drawing amount compared to the solutions of the prior art, without incurring the risk of damaging the fibres.

[0067] Advantageously, the fibres of the sliver are drawn practically entirely on the carding roller, which for this purpose is provided with teeth which are not very dense compared to prior art solutions.

[0068] This reduces the production costs of the carding roller itself. Furthermore, the fibres are less stressed and can be drawn in a more progressive manner than in the solutions of the prior art.

[0069] This therefore strongly limits the risk of obtaining broken and thus "short" fibres due to the excessively abrupt mechanical action of the teeth of the carding roller.

[0070] Moreover, by virtue of the fact that the entire drawing action is performed by the carding roller, it is possible to reduce the overall dimensions and the overall costs of the drawing device.

[0071] A person skilled in the art can make numerous changes and variants to the drawing devices and drawing methods of the present invention, all contained within the scope of protection defined by the following claims in order to satisfy contingent, specific needs.

Claims

1. Method of drawing a textile fibre sliver web- comprising the steps of: - providing a feeder device (12) of a sliver (8) to be drawn, - providing a carding roller (28) comprising, on an outer side wall thereof (32), a plurality of teeth (36) arranged at a constant tangential pitch (P), suitable for drawing said sliver (8), - preparing an extraction cylinder (56) placed downstream of the carding roller (28) and of the sliver (8), - providing the feeder device (12) with a feed roller (16), facing the carding roller (28), which rotates so as to feed the sliver to the carding roller (28) at an input speed and according to a direction of advancement (F) concordant with respect to said rotation direction (S) of the carding roller (28), the method being characterized by: - driving the carding roller (28) in rotation so as tc have a peripheral speed on the teeth or extraction speed equal to the product of the input speed for the total drawing of the sliver ± 20%, so that all the drawing of the sliver takes place on the carding roller, - the total drawing being the ratio between the count of the yarn to be produced and the count of the sliver in input.

2. Method according to claim 1, wherein the carding roller (28) is driven in rotation so as to have a peripheral speed on the teeth or extraction speed equal to the product of the input speed for the total drawing of the sliver ± 10%.

3. Method according to claim 1 or 2, wherein the carding roller (28) is driven in rotation so as to have a peripheral speed on the teeth or extraction speed equal to the product of the input speed for the total drawing of the sliver ± 5%.

4. Method according to any of the preceding claims, wherein said tangential pitch (P) between the teeth (36) of the carding roller (28) is between 5 and 15 mm.

5. Method according to any of the claims from 1 to 4, wherein said teeth (36) have a substantially triangular shape which protrudes from the outer side wall (32) of the carding roller (28), in a first front portion (40), which directly faces the sliver (8), and a second back portion (44) which forms a vertex (48) with the first front portion (40).

6. Method according to claim 5, wherein said vertex (48) has a radial height (52), measured with respect to the outer side wall (32) along a radial direction (R) passing through a rotation axis (C) of the carding roller (28), between 0.5 and 2 mm.

7. Method according to claim 5 or 6, wherein the first front portion (40) identifies with a radial direction (R), passing through a rotation axis (C) of the carding roller (28), a first angle (B) between 5 and 10 degrees.

8. Method according to any of the claims from 5 to 7, wherein the second rear portion (44) identifies with a tangential direction (T), perpendicular to a radial direction (R) passing through a rotation axis (C) of the carding roller (28), a second angle (A) between 40 and 70 degrees.

9. Method according to any of the claims from 5 to 8, wherein with respect to a direction (Q) joining the rotation axes (C, W) of the carding roller (28) and of the extraction cylinder (56), the vertices (48) of the teeth (36) and a side wall (64) of the extraction cylinder (56) are distant by a pitch (76) of between 0.1 and 2 mm.

10. Method (4) according to any of the preceding claims, wherein the extraction cylinder (56) delimits an inner cavity (60) fluidically connected to a vacuum source and has a perforated side wall (64), provided with a plurality of holes (68) communicating with the inner cavity (60), suitable for detaching the fibres from the carding roller.

11. Method according to claim 10, wherein said holes (68) are circular holes having a diameter between 1 and 3 mm.

12. Method according to claim 10 or 11, wherein said holes (68) are arranged according to a matrix diagram along a pair of directions perpendicular to each other, and are spaced apart according to a first and a second pitch (L1, L2).

13. Method according to claim 12, wherein said first and second pitches (L1, L2) are comprised between 2 and 4 mm.

14. Method according to claim 12 or 13, wherein said first and second pitches (L1, L2) are the same as each other.

15. Method according to any one of the claims from 1 to 14, wherein the carding roller (28) and the extraction cylinder (56) rotate in directions of rotation (S, W) opposite to each other.

16. Method according to any one of the preceding claims, wherein downstream of the extraction cylinder (56) a conveying device is arranged (80) equipped with an output roller (84) which idles and facilitates the extraction of the yarn from the extraction cylinder (56).

17. Method according to claim 16, wherein the extraction cylinder identifies, on its own outer side wall, an extraction arc extending from an extraction starting point, in which the sliver is pinched between the extraction cylinder and the carding roller, to an extraction end point, in which the sliver is pinched between the extraction cylinder and the output roller.

18. Method according to claim 17, wherein said extraction arc is in fluidic connection with an internal cavity (60) of the extraction cylinder fluidically connected to a vacuum source to facilitate detachment of the fibres from the carding roller.

19. Method according to claim 17 or 18, wherein said extraction arc has an extension comprised between 0.7 and 1.5 times the average length of the fibres of the sliver extracted from the carding roller.

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