FIELD OF APPLICATION
[0001] The present invention relates to a drawing device for a web with carding machine
for air spinning systems, an air spinning apparatus comprising said drawing device
of a web with carding machine and a drawing method for a web with carding machine
for air spinning systems thereof.
BACKGROUND ART
[0002] As known, webs 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 web 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
web. 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 machine 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 web 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
machine 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 machine,
is extremely effective and is not affected in any manner by the working speed or the
imparted drawing amount.
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 device with carding machine according to claim 1, by
an air spinning apparatus according to claim 20 and by a drawing method with carding
machine for air spinning according to claim 21.
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 machine 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 webs 8 of textile fibres as a whole.
[0012] In particular, the drawing device 4 comprises a feeder device 12 of a web 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 web 8 to be drawn towards the successive drawing processes.
[0015] The nozzle or mouth 20 defines a passage channel 24 for the web 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 web
8, which is fed at an input speed Vi.
[0018] The drawing device 4 further comprises a carding machine 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 web 8.
[0019] The feeder roller 16 rotates and directly faces the carding machine 28 so as to feed
the web to the carding machine 28 at said input speed Vi.
[0020] Preferably, the tangential pitch P between the teeth 36 of the carding machine 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
machine 28.
[0022] Preferably, said teeth 36 have a substantially triangular shape which protrudes from
the outer side wall 32 of the carding machine 28, according to a first front portion
40, which directly faces the web 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
machine 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 machine 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 machine 28.
[0026] The web 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 machine 28.
[0027] In this manner, the teeth of the carding machine 28, during rotation, cling to the
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 machine 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 web 8, so that the drawing of the web 8 takes
place entirely on the carding machine 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 thread count of the yarn to be produced
and the input web thread count.
[0035] The drawing device 4 further comprises an extraction cylinder 56 placed downstream
of the carding machine 28 and of the web 8.
[0036] In other words, the carding machine 28 receives the web 8 from the feeder device
12 and, by rotating in the same direction as the direction of advancement F of the
web 8, pulls and draws the web 8 towards the extraction cylinder 56, arranged downstream
of the carding machine 28 and of the web 8 with respect to said direction of advancement
F of the web 8.
[0037] It is worth noting that the carding machine 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 machine 28.
[0038] The successive removal of the fibres of the web 8 is facilitated and improved by
virtue of the counterpoised rotations of the carding machine 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 machine 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 machine 28.
[0041] It is apparent that the opposite rotation between carding machine 28 and extraction
roller 56 further facilitates such detachment of the fibres of the web 8 from the
carding machine 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 machine 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 web 8 at an advancement
speed Vin through the nozzle or mouth 20. The advancement speed Vin of the web 8 also
corresponds to the tangential rotation speed of the feeder roller 16 at its point
of contact with the web itself.
[0054] So, the carding machine 28 is driven in rotation, according to a direction of rotation
S, in a direction agreeing with the direction of advancement F of the web 8.
[0055] The difference in speed between the tangential or extraction speed Ve of the teeth
36 of the carding machine 28 and the advancement speed Vi of the web 8 determines
the total drawing St of the web 8.
[0056] Moreover, the web 8 is then passed from the carding machine 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 machine 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 web 8 from the carding machine 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 machine 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 machine 28.
[0060] The fibres of the web 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 machine 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 machine works at a linear speed equal to the product of the web input speed
times the total drawing of the web ± 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 thread count because fibre continuity is always ensured. In other words,
although the drawing is obtained in a single step on the carding machine, 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
machine rotates according to a direction of rotation agreeing with the direction of
rotation of the web 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 web are drawn practically entirely on the carding
machine, 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 machine 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 machine.
[0070] Moreover, by virtue of the fact that the entire drawing action is performed by the
carding machine, 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.
1. 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), suitable 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 (28) is driven in rotation so as to have a peripheral
speed on the teeth equal to the product of the input speed for the total drawing of
the web ± 20%, so that all the drawing of the web takes place substantially between
the carding machine (28) and the feed roller (16),
- the total drawing being the ratio between the thread count of the yarn to be produced
and the thread count of the web in input.
2. Drawing device (4) according to claim 1, wherein the carding machine (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 web ± 10%.
3. Drawing device (4) according to claim 1 or 2, wherein the carding machine (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 web ± 5%.
4. Drawing device (4) according to any of the preceding claims, wherein said tangential
pitch (P) between the teeth (36) of the carding machine (28) is between 5 and 15 mm.
5. Drawing device (4) 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 machine (28), in a first front portion (40), which directly faces
the web (8), and a second back portion (44) which forms a vertex (48) with the first
front portion (40).
6. Drawing device (4) 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 machine (28), between 0.5 and 2
mm.
7. Drawing device (4) 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 machine (28), a first angle (B) between 5 and 10 degrees.
8. Drawing device (4) 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 machine (28), a second
angle (A) between 40 and 70 degrees.
9. Drawing device (4) 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 machine (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. Drawing device (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 machine.
11. Drawing device (4) according to claim 10, wherein said holes (68) are circular holes
having a diameter between 1 and 3 mm.
12. Drawing device (4) 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. Drawing device (4) according to claim 12, wherein said first and second pitches (L1,
L2) are comprised between 2 and 4 mm.
14. Drawing device (4) according to claim 12 or 13, wherein said first and second pitches
(L1, L2) are the same as each other.
15. Drawing device (4) according to any one of the claims from 1 to 14, wherein the carding
machine (28) and the extraction cylinder (56) rotate in directions of rotation (S,
W) opposite to each other.
16. Drawing device (4) 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. Drawing device (4) 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 web is pinched between the extraction cylinder and the carding
machine, to an extraction end point, in which the web is pinched between the extraction
cylinder and the output roller.
18. Drawing device (4) 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 machine.
19. Drawing device (4) 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 web extracted from the carding machine.
20. Air spinning apparatus comprising at least one drawing device (4) according to any
one of the claims from 1 to 19 and at least one air spinning device.
21. Method of drawing a textile fibre web comprising the steps of:
- providing a feeder device (12) of a web (8) to be drawn,
- providing a carding machine (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 web (8),
- preparing an extraction cylinder (56) placed downstream of the carding machine (28)
and of the web (8),
- providing the feeder device (12) with a feed 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
rotation direction (S) of the carding machine (28),
- driving the carding machine (28) 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 web ± 20%, so that all the drawing of the web takes place on the carding
machine,
- the total drawing being the ratio between the thread count of the yarn to be produced
and the thread count of the web in input.
22. Drawing method according to claim 21, comprising the step of providing a drawing device
(4) according to any of the claims from 1 to 19.