EP4130360A1

EP4130360A1 - Air-jet type spinning device having an improved spinning starting system and related air-jet type spinning starting method

Info

Publication number: EP4130360A1
Application number: EP22179909.1A
Authority: EP
Inventors: Luca DEOTTO; Fabio D'agnolo; Massimo PUIATTI
Original assignee: Savio Macchine Tessili SpA
Current assignee: Savio Macchine Tessili SpA
Priority date: 2021-08-02
Filing date: 2022-06-20
Publication date: 2023-02-08
Also published as: CN115701457A; IT202100020786A1

Abstract

An air-jet type spinning device wherein the spinning starter system comprises the following steps:
- pneumatic supply of the ejector or Venturi nozzle (36) at an initial maximum pressure p_max so as to recall the fibres within the a fibre introducer (20),
- feeding of the fibres into the spinning chamber (16) and then in the spindle (24) of the spinning chamber (16) ;
- pneumatic supply of the spinning chamber (16) with a main nozzle (40) so that the two jets of compressed air overlap each other,
- gradual switching-off of the ejector or Venturi nozzle (36) according to an average pressure gradient in absolute value of less than 6 bar/s.

Description

FIELD OF APPLICATION

The present invention relates to an air-jet type spinning device having an improved spinning starting system and related air-jet type spinning starting method.

STATE OF THE ART

As is known, in air spinning the fibres constituting the incoming web, suitably drawn and parallelised by the upstream drawing device, are introduced into the spinning chamber. Here, thanks to the particular geometric conformation of the chamber and the pneumatic flow conditions inside, the peripheral fibres of the web tend to open, to then rewind around the inner fibres with the desired twist.
One of the most critical phases in known air-jet spinning systems is the start-up of the spinning process.
Typically, in order to convey the fibres coming from the spinning chamber inside the spindle, a pneumatic ejector is used which, supplied with compressed air by means of a solenoid valve, produces a Venturi vacuum effect. This device has the dual purpose of conveying the fibres inside the spindle, without dispersing them in the spinning chamber, and of imparting, with a whirling and rotating flow, a minimal binding on the fibres with a twist opposite to the spinning twist, giving them the continuity needed to be pinched by the extraction axis and conveyed to the accumulation system and to the reel. Typically, the spinning twist is Z-type, so the twist that the Venturi ejector tends to impart to the fibre is S-type.
Figure 1 shows the heart of the spinning system, i.e. the fibre introducer, the spinning chamber and the Venturi-type system that allows spinning to start.
In this regard, for a clearer understanding of the problems related to managing the conventional air-jet spinning start-up cycle, a brief summary of the various phases is helpful.
The cycle initially foresees the intervention of the Venturi ejector and the subsequent feeding of the fibres into the spinning chamber by the drawing unit. Air is then injected into the spinning chamber thereby generating a yarn with the desired twist (typically Z) but with characteristics that do not yet comply with those desired and not yet in a stable and continuous manner over time.
An interval of time follows in which the two blasts overlap, then the Venturi is switched off and the spinning process proceeds with feeding of the spinning chamber only, to which the stable output of a yarn finally having the desired characteristics corresponds.
Figure 2 shows the typical trend of the Venturi ejector supply pressure, which undergoes a "step" following its shutdown.
In particular, at the initial instant t_0 the ejector is turned on at the maximum pressure, followed by feeding of the fibres by the drawing unit. At instant t_1 the spinning chamber is fed and for a time interval Δt (equal to t_2-t_1) the two air blasts overlap. At instant t_2, the Venturi is abruptly turned off and its supply pressure drops in steps to zero. Obviously, the pressure levels depicted in Figure 2 are purely qualitative and illustrative.
The use of the configuration described above makes it problematic to start spinning in the case of particularly rigid fibres (e.g. acrylic or PES), high spinning speeds (typically higher than 420 m/min) and/or excessively short fibre transit times in the spinning chamber (a few ms). Under these conditions spinning start-ups are not successful, as the yarn does not have the time to be physically fully formed.
It should be pointed out that the pneumatic feed of the spinning chamber and the Venturi generate useful conflicting effects for yarn production. The Venturi, in fact, normally creates a flow of air opposite to that produced by the spinning chamber and therefore tends to oppose the formation of the yarn (if, for example, the spinning machine has to produce Z yarn, the Venturi generates a flow of air that favours the formation of S yarn). For this reason, in order to trigger the spinning process in a stable and effective manner, a condition of ideally quasi-static equilibrium must be established between the flow in the spinning chamber, which tends to wind the fibres onto themselves, and the Venturi flow, which is responsible for retaining the fibres and conveying them into the spindle.
In this way the binding initially imparted to the fibres by the Venturi, which guarantees the yarn the possibility of being extracted from the spindle with the necessary cohesion, remains, in decreasing measure, until the complete development of the final yarn by the pneumatic jet of the spinning chamber. This is made possible by the absence of discontinuities in the thermo-fluid-dynamic quantities characteristic of the outflow, which do not undergo phenomena such as shock waves that would compromise the full development of the flow in the start-up transient.
One possible solution is to reduce the supply pressure of the Venturi ejector; however, in the initial starting phase the fibres must be subjected to a technological depression equal to at least 150 mbar, a value typically made possible only with pneumatic pressures higher than 3 bar, which prevents this solution from being viable or advantageous.

PRESENTATION OF THE INVENTION

The need is therefore felt to resolve the drawbacks and limitations mentioned with reference to the prior art.
Such requirement is satisfied by an air-jet type spinning device according to claim 1 and an air-jet type spinning starting method according to claim 12.

DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be more clearly comprehensible from the description given below of its preferred and non-limiting embodiments, wherein:

figure 1 shows a cross-section view of an air-jet type spinning device of the prior art;
figure 2 shows the typical trend of the supply pressure of the ejector or Venturi nozzle that undergoes a "step" following its shutdown in the air-jet type spinning devices of the prior art;
figure 3 shows a perspective side view in partial cross-section of an air-jet type spinning device according to the present invention;
figure 4 shows a side view in partial cross-section of an air-jet type spinning device according to the present invention;
figure 5 shows a diagram of the supply pressure pattern of the spinning chamber and the starter nozzle or Venturi nozzle according to one embodiment of the present invention;
figure 6 shows a diagram of the supply pressure pattern of the spinning chamber and the starter nozzle or Venturi nozzle according to a further embodiment of the present invention;
figure 7 shows a diagram of the supply pressure pattern of the spinning chamber and the starter nozzle or Venturi nozzle according to a further embodiment of the present invention;
figures 8 and 9 show schematic views of the pneumatic supply system of the starter nozzle or Venturi nozzle of an air-jet type spinning device, respectively according to two embodiment variants of the present invention.

The elements or parts of elements common to the embodiments described below will be indicated using the same reference numerals.

DETAILED DESCRIPTION

With reference to the aforementioned figures, reference numeral 4 globally denotes an air-jet type spinning device.
The air-jet type spinning device 4 is provided with a spinning starter system comprising a drawing unit 8 configured to draw a fibre web 12 to be fed to a spinning chamber 16 through a fibre introducer 20.
Said fibre introducer 20 in turn faces a spindle 24, having a cavity 28, shaped so as to receive in input the fibres partially wound in the spinning chamber 16.
The spinning chamber 16, the fibre introducer 20, the spindle 24 and the cavity 28 preferably extend along a prevailing extension axis X-X.
The spinning chamber 16 is shaped so as to obtain in output a yarn 18 comprising a plurality of wound fibres, which is in turn fed to a winding unit (not illustrated) of the yarn produced, at the outlet of said spinning chamber 16.
In addition, the spinning chamber 16 is fluidically connected to a starter nozzle or Venturi nozzle 36, configured to trigger the start-up of spinning, and to a main nozzle 40, configured to send a jet of compressed air into the spinning chamber 16.
The starter nozzle 36 is fluidically connected to a pneumatic spinning starter system 38 and the main nozzle 40 is fluidically connected to a main pneumatic system 42.
The spinning device 4 further comprises a processing and control unit operatively connected to said pneumatic spinning starter system 38, said main pneumatic system 42 and said drawing unit 8.
In particular, the processing and control unit is programmed so that during spinning start-up:

at an instant t_0, it actuates the starter nozzle 36 so as to send the jet of compressed starting air at an initial maximum starting pressure p_max,
then, it actuates the drawing unit 8 to feed the fibre to the fibre introducer 20 of the spinning chamber 16,
at an instant t_1, subsequent to t_0, it actuates and keeps actuated the main nozzle 40 to feed the spinning chamber 16 at a pressure p_f,
at an instant t_2, subsequent to t_1, a shut-down phase of the starter nozzle 36 begins, reducing the initial maximum starting pressure to zero at a time t_3, subsequent to t_2.

Advantageously, this reduction in starting pressure from the initial maximum value p_max to zero pressure follows an average pressure gradient in absolute value of less than 6 bar/s.
In other words, the average reduction in the time unit of the supply pressure of the starter nozzle 36 presents a maximum value, in absolute value, of 6 bar/s.
According to a possible embodiment, said reduction in the supply pressure of the starter nozzle 36 follows a plurality of stepped pressure reductions.
According to a further possible embodiment, said reduction in the supply pressure of the starter nozzle 36 follows a linear decreasing trend.
According to a possible further embodiment, said reduction in the supply pressure of the starter nozzle 36 follows a decreasing polynomial trend of at least two degrees.
According to a possible embodiment, (Figure 8), the pneumatic spinning starter system 38 is controlled by at least two separate pneumatic solenoid valves 48,52 placed in parallel with each other and connected to at least two separate pressure lines.
Advantageously, said solenoid valves 48, 52 are operated independently and selectively. In this way, in fact, it is possible to divide the overall pressure drop into two or more intermediate drops, corresponding to the same number of solenoid valves placed in parallel, customizing the supply pressure and the on/off time and thus making the pressure decrease profile more gradual over time.
According to a possible further embodiment (Figure 9), the pneumatic spinning starter system 38 is connected to a pressure regulator 54, placed in series via a connector tube 56 to a flow regulator 58, controlled by a single solenoid valve 62 and fitted with a calibrated one-way orifice 60 towards the flow regulator. This pneumatic configuration is particularly advantageous because it allows a continuous and regular shutdown of the starter nozzle without steps thanks to the presence of the calibrated orifice, which dampens and delays the closing of the pressure regulator. In particular, the pressure decrease time of the starter nozzle from the initial maximum value (p_max) to the zero value can be advantageously set by choosing a suitable combination of length and diameter of the connection tube 56 and diameter of the calibrated orifice 60.
Advantageously, the inner diameter of said connection tube 56 is between 2 mm and 2.5 mm.
Advantageously, the length of said connection tube 56 is between 500 mm and 1000 mm, preferably 700 mm.
Advantageously, the diameter of said calibrated orifice 60 is between 0.15 mm and 0.35 mm, preferably 0.20 mm.
Preferably, the processing and control unit is programmed such that the difference between the instant t_2 and the instant t_1 is between 0 ms and 500 ms, preferably 250 ms.
The operation of the spinning device and the method of starting spinning according to the present invention will now be described.
As illustrated, the solution according to the invention provides that the Venturi ejector or starter nozzle 36 for starting the spinning is deactivated in a gradual manner, slowly reducing the pressure and thus the air speed so as to ensure a continuity of equilibrium between the air pressure in the spinning chamber 16, obtained by means of the main nozzle 40, and the depression created by the Venturi nozzle or starter nozzle 36.
The objective is in fact to guarantee the necessary time interval to allow the transient adaptation effect between the pressure of the spinning chamber 16 and the pressure of the Venturi nozzle 36 to develop completely, avoiding any form of discontinuity in the evolution of the outflow, which would consequently trigger undesired phenomena of bad or failed starting of the spinning process.
In general, the most important aspect is that the transition from the maximum starting pressure p_max to zero pressure does not occur suddenly with a single step, but with a plurality of steps or more generally according to a continuous decreasing profile.
To summarize, the innovative starting cycle consists of the following phases:

pneumatic supply of the ejector or Venturi nozzle 36 at maximum pressure p_max;
feeding of the fibres into the spinning chamber 16;
pneumatic supply of the spinning chamber 16: at the instant t_1 the spinning chamber 16 is also supplied with pressure and the two blasts or jets of compressed air overlap, for example for 250 ms, producing a yarn 18, even though not yet meeting the desired characteristics;
gradual switching-off of the ejector or Venturi nozzle 36 according to an average pressure gradient in absolute value of less than 6 bar/s;
spinning start-up and extraction of the yarn 18 in the final format.

As may be appreciated from the description, the present invention makes it possible to overcome the drawbacks of the prior art.
One of the main advantages of the present invention is the improvement and regularization of the starting of the air-jet spinning process, which is particularly useful for yarns made of stiff fibres and in case of reduced fibre transit times in the spinning chamber.
In addition, the increase in starting efficiency contributes to increasing the efficiency of the spinning device and thus the productivity of the machine, to significantly reducing unwanted windings of yarn at the start of spinning, to improving the cleanliness of the device and to reducing the percentage of waste fibre to be disposed of.
A person skilled in the art may make numerous modifications and variations to the solutions described above so as to satisfy contingent and specific requirements.
The scope of protection of the present invention is defined by the following claims.

Claims

An air-jet type spinning device (4) provided with a spinning starter system comprising:
- a drawing unit (8) configured to draw a fibre web (12) to be fed to a spinning chamber (16) by means of a fibre introducer (20),

- a spinning chamber (16) shaped to obtain at the outlet a yarn (18) composed of a plurality of wound fibres,

- the spinning chamber (16) being fluidically connected to a starter nozzle or Venturi nozzle (36), configured to trigger the start-up of spinning, and to a main nozzle (40), configured to send a jet of compressed air into the spinning chamber (16),

- a pneumatic spinning starter system (38), fluidically connected to said starter nozzle (36),

- a main pneumatic system (42), fluidically connected to said main nozzle (40),

- a processing and control unit, operatively connected to said pneumatic spinning starter system (38), to said main pneumatic system (42) and to said drawing unit (8), programmed so that during spinning start-up:
- at an instant t_0, it actuates the starter nozzle (36) so as to send the jet of compressed starting air at an initial maximum starting pressure p_max,

- it actuates the drawing unit (8) to feed the fibre to the fibre introducer (20) of the spinning chamber (16),

- at an instant t_1, subsequent to t_0, it actuates and keeps actuated the main nozzle (40) to feed the spinning chamber (16) at a pressure p_f,

at an instant t_2, subsequent to t_1, it begins the shutdown phase of the starter nozzle (36), reducing the initial maximum starting pressure (p_max) to zero at a time t_3, subsequent to t_2,
- wherein said reduction in pressure of the starter nozzle from the initial maximum value (p_max) follows an average pressure gradient in absolute value of less than 6 bar/s.
The air-jet type spinning device (4) according to claim 1, wherein said reduction of the supply pressure of the starter nozzle (36) comprises a plurality of step reductions.
The air-jet type spinning device (4) according to claim 1, wherein said reduction of the supply pressure of the starter nozzle (36) follows a linear decreasing trend.
The air-jet type spinning device (4) according to claim 1, wherein said reduction of the supply pressure of the starter nozzle (36) follows a polynomial decreasing trend of at least two degrees.
The air-jet type spinning device (4) according to claim 1, 2, 3 or 4, wherein said pneumatic spinning starter system (38) is controlled by at least two separate pneumatic solenoid valves (48,52) placed in parallel with each other and connected to at least two separate pressure lines.
The air-jet type spinning device (4) according to claim 5, wherein said solenoid valves (48,52) are operated independently and selectively.
The air-jet type spinning device (4) according to claim 1, 2, 3 or 4, wherein said pneumatic spinning starter system (38) is connected to a pressure regulator (54), placed in series via a connection tube (56) to a flow regulator (58), controlled by a single solenoid valve (62) and provided with a calibrated, one-way orifice (60) towards the flow regulator.
The air-jet type spinning device (4) according to claim 7, wherein the inner diameter of said connection tubes (56) is between 2 mm and 2.5 mm.
The air-jet type spinning device (4) according to claim 7 or 8, wherein the length of said connection tube (56) is between 500 mm and 1000 mm, preferably equal to 700 mm.
The air-jet type spinning device (4) according to claims 7, 8 or 9, wherein the diameter of said calibrated orifice (60) is between 0.15 mm and 0.35 mm, preferably 0.20 mm.
The air-jet type spinning device (4) according to any of the claims from 1 to 10, wherein the processing and control unit is programmed so that the difference between the instant t_2 and the instant t_1 is between 0 ms and 500 ms, preferably 250 ms.
Starting method of an air-jet type spinning device comprising the steps of:
- providing a drawing unit (8) configured to draw a fibre web (12) to be fed to a spinning chamber (16) by means of a fibre introducer (20),

- providing a spinning chamber (16) shaped to obtain at the outlet a yarn (18) composed of a plurality of wound fibres,

- the spinning chamber (16) being connected to a starter nozzle or Venturi nozzle (36) configured to trigger the start-up of spinning, and to a main nozzle (40) configured to send a jet of compressed air into the spinning chamber (16),
the method also comprising, at the start of spinning, the steps of:
- at an instant t_0, actuating the starter nozzle (36) at a maximum initial starting pressure (p_max),

- actuating the drawing unit (8) to feed the fibre to the fibre introducer (8) of the spinning chamber (16),

- at an instant t_1, subsequent to t_0, actuating and keeping actuated the main nozzle (40) to feed the spinning chamber (16) at a pressure p_f,

- at a time t_2, subsequent to t_1, beginning the shutdown phase of the starter nozzle (36), reducing the supply pressure from the initial maximum value (p_max) to zero pressure at an instant t_3, subsequent to t_2,

- wherein said reduction in pressure of the starter nozzle (36) from the initial maximum value (p_max) to zero pressure follows an average pressure gradient in absolute value of less than 6 bar/s.
A starting method of air-jet type spinning according to claim 12, wherein said reduction of the supply pressure of the starter nozzle (36) comprises a plurality of step reductions.
A starting method of air-jet type spinning according to claim 12, wherein said reduction of the supply pressure of the starter nozzle (36) follows a linear decreasing trend.
A starting method of air-jet type spinning according to claim 12, wherein said reduction of the supply pressure of the starter nozzle (36) follows a polynomial decreasing trend of at least two degrees.
A starting method of air-jet type spinning according to any one of the claims from 12 to 15, wherein the difference between the instant t_2 and the instant t_1is between 0 ms and 500 ms, preferably is equal to 250 ms.