Air-jet spinning device provided with spinning starter system

Abstract

The present application relates to an air-jet type spinning device provided with a spinning starter system, in which the included spinning starter system is arranged to:-pneumatically supply an injector or venturi nozzle (36) at an initial maximum pressure pmax in order to retrieve fibres in a fibre introducer (20),-supply fibres into a spinning chamber (16) and then into a spindle (24) of the spinning chamber (16); the spinning chamber (16) is pneumatically supplied with a main nozzle (40) such that the two compressed air jets overlap each other, and the ejector or venturi nozzle (36) is gradually closed according to an average pressure gradient having an absolute value of less than 6 bar / sec. The utility model has the main advantage of improving and adjusting the starting of the air jet spinning process, which is particularly useful for yarns made of hard fibers and for reducing the fiber passing time in the spinning chamber.

Description

Technical Field

[0001] The utility model relates to an air jet spinning device with an improved spinning starting system and a related air jet spinning starting method. Background Art

[0002] As is known, in air spinning, the fibers constituting the incoming web are appropriately stretched and introduced into the spinning chamber in parallel by an upstream stretching device. Here, due to the specific geometry of the spinning chamber and the air flow conditions inside, the peripheral fibers of the web tend to open and then rewind around the internal fibers with the desired twist.

[0003] In known air-jet spinning systems, one of the most critical phases is the start of the spinning process.

[0004] Usually, to convey the fibers from the spinning chamber to the inside of the spindle, a pneumatic ejector is used, which is supplied with compressed air through a solenoid valve, thus creating a Venturi vacuum effect. This device has the dual purpose of conveying the fibers inside the spindle without dispersing them in the spinning chamber, and of imparting to the fibers, by means of a swirling and rotating flow, a minimum combination of twists opposite to the spinning twist, giving them the continuity they need to be squeezed by the extraction axis and conveyed to the accumulation system and to the reel. Usually, the spinning twist is of the Z type, so the twist that the Venturi ejector tends to impart to the fibers is of the S type.

[0005] Figure 1 The core of the spinning system is shown, namely the fiber introducer, the spinning chamber and the Venturi type system that allows the spinning to start.

[0006] In this regard, a brief overview of the various stages is helpful in order to gain a clearer understanding of the issues associated with managing the start-up cycle of conventional air-jet spinning.

[0007] The cycle initially foresaw the intervention of a venturi ejector and the subsequent feeding of the fiber into the spinning chamber through a drawing unit. Air was then injected into the spinning chamber, producing a yarn with the desired twist (usually Z), but the yarn had properties that did not yet correspond to the desired twist and could not yet be produced in a stable and continuous manner over time.

[0008] This is followed by a time interval during which the two air flows overlap, then the venturi is closed and the spinning process takes place only by the supply from the spinning chamber, and finally a stable output of yarn with the desired properties corresponds to this time interval.

[0009] Figure 2 The typical trend of the Venturi ejector supply pressure is shown, which undergoes a "step" after the ejector is closed.

[0010] In particular, at the initial moment t_0, the ejector opens at maximum pressure and subsequently feeds the fiber through the stretching unit. At moment t_1, the spinning chamber is fed and for a time interval Δt (equal to t_2-t_1), the two air flows overlap. At moment t_2, the Venturi is suddenly closed and its supply pressure gradually decreases to zero. Obviously, Figure 2 The stress levels shown are purely qualitative and illustrative.

[0011] Using the above configuration makes it problematic to start spinning with particularly stiff fibers (e.g. acrylic or PES), high spinning speeds (typically above 420 m / min) and / or too short a fiber transit time in the spinning chamber (a few ms). Under these conditions, spinning start is unsuccessful because the yarn does not have time to be physically fully formed.

[0012] It should be noted that the pneumatic supply of the spinning chamber and the Venturi tube creates a useful conflicting effect on the yarn production. In fact, the Venturi tube usually produces an air flow opposite to the air flow generated by the spinning chamber, and therefore tends to hinder the formation of the yarn (for example, if the spinning machine must produce Z yarn, the Venturi tube produces an air flow that favors the formation of S yarn). For this reason, in order to trigger the spinning process in a stable and effective way, it is necessary to establish an ideal quasi-static equilibrium condition between the air flow in the spinning chamber, which tends to entangle the fibers on itself, and the Venturi air flow, which is responsible for holding the fibers and transporting them to the spindle.

[0013] In this way, the bonding of the fibers initially imparted by the Venturi tube guarantees the possibility of the yarn being extracted from the spindle with the necessary cohesion, maintaining this cohesion in a reduced manner until the final yarn is completely formed by the pneumatic jet in the spinning chamber. This is made possible by the absence of discontinuities in the quantitative characteristics of the thermofluid dynamics of the outflow, which do not undergo phenomena such as shock waves that would impair the complete development of the flow in the startup transient.

[0014] One possible solution is to reduce the supply pressure of the Venturi ejector; however, during the initial start-up phase, the fiber must be subjected to a technical decompression equal to at least 150 mbar, a value generally only possible at pneumatic pressures above 3 bar, which prevents the feasibility or advantage of this solution. Utility Model Content

[0015] Therefore, there is a need to address the drawbacks and limitations mentioned with reference to the prior art.

[0016] This requirement is met by the jet-type spinning device according to the utility model. Specifically, a jet-type spinning device provided with a spinning starter system is provided, wherein the device comprises: - a stretching unit configured to stretch a fiber web to be supplied to a spinning chamber through a fiber introducer, - a spinning chamber formed to obtain a yarn consisting of a plurality of entangled fibers at an outlet, - the spinning chamber is fluidly connected to a starter nozzle or a venturi nozzle configured to trigger the start of spinning, and is fluidly connected to a main nozzle configured to send a compressed air jet into the spinning chamber, - a pneumatic spinning starter system, fluidly connected to the starter nozzle, - a main pneumatic system, fluidly connected to the main nozzle, - a processing and control unit, operatively connected to the pneumatic spinning starter system, to the main pneumatic system and to the stretching unit; wherein the pneumatic spinning starter system is controlled by at least two separate pneumatic solenoid valves, which are arranged in parallel with each other and connected to at least two separate pressure pipelines.

[0017] Further, the solenoid valves are independently and selectively operated.

[0018] Further, the pneumatic spinning starter system is connected to a pressure regulator, which is placed in series with a flow regulator via a connecting pipe, is controlled by a single solenoid valve, and is provided with a one-way calibrated orifice toward the flow regulator.

[0019] Furthermore, the inner diameter of the connecting pipe is between 2 mm and 2.5 mm.

[0020] Furthermore, the length of the connecting pipe is between 500 mm and 1000 mm.

[0021] Further, the diameter of the calibration orifice is between 0.15 mm and 0.35 mm.

[0022] Furthermore, the length of the connecting pipe is equal to 700 mm.

[0023] Furthermore, the diameter of the calibration orifice is 0.20 mm.

[0024] A major advantage of the invention is the improvement and regulation of the start-up of the air-jet spinning process, which is particularly useful for yarns made of hard fibers and in the case of reduced fiber transit time in the spinning chamber.

[0025] In addition, the increase in the starting efficiency helps to increase the efficiency of the spinning device, thereby increasing the productivity of the machine, helps to significantly reduce unwanted yarn entanglements at the beginning of spinning, helps to improve the cleanliness of the device, and helps to reduce the percentage of waste fibers to be processed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages of the present invention will be more clearly understood from the following description of preferred and non-limiting embodiments of the present invention, in the accompanying drawings:

[0027] Figure 1 A cross-sectional view of a prior art air jet spinning device is shown;

[0028] Figure 2 shows the typical trend of the supply pressure of an ejector or venturi nozzle undergoing a "step" after a shutdown thereof in a prior art air-jet spinning device;

[0029] Figure 3 A perspective side view showing a partial cross section of an air jet spinning device according to the present invention;

[0030] Figure 4 A side view showing a partial cross section of an air jet spinning device according to the present invention;

[0031] Figure 5 A diagram showing a supply pressure pattern for a spinning chamber and a starter nozzle or a venturi nozzle according to one embodiment of the present invention;

[0032] Figure 6 A diagram showing a supply pressure pattern of a spinning chamber and a starter nozzle or a venturi nozzle according to another embodiment of the invention;

[0033] Figure 7 A diagram showing a supply pressure pattern of a spinning chamber and a starter nozzle or a venturi nozzle according to another embodiment of the invention;

[0034] Figure 8 and Fig. 9 Schematic diagrams of pneumatic supply systems of a starter nozzle or a Venturi nozzle of an air jet spinning device according to two embodiment variations of the present invention are respectively shown.

[0035] Elements or parts of elements common to the embodiments described below will be denoted by the same reference numerals. DETAILED DESCRIPTION

[0036] With reference to the above-mentioned drawings, reference numeral 4 generally designates an air-jet type spinning device.

[0037] The air-jet spinning device 4 is provided with a spinning starter system, which comprises a stretching unit 8 configured to stretch the fiber web 12 to feed it to the spinning chamber 16 via a fiber introducer 20 .

[0038] The fiber introducer 20 in turn faces a spindle 24 having a cavity 28 shaped to receive the fiber partially wound in the spinning chamber 16 at input.

[0039] The spinning chamber 16, the fiber introducer 20, the spindle 24 and the cavity 28 preferably extend along a main extension axis XX.

[0040] The spinning chamber 16 is shaped so as to obtain at the output a yarn 18 comprising a plurality of wound fibers, which yarn is sequentially fed at the outlet of said spinning chamber 16 to a winding unit (not shown) of the produced yarn.

[0041] Additionally, the spinning chamber 16 is fluidly connected to a starter nozzle or venturi nozzle 36 configured to trigger the start of spinning, and to a main nozzle 40 configured to send a jet of compressed air into the spinning chamber 16 .

[0042] The starter nozzle 36 is fluidly connected to a pneumatic spinning starter system 38 , and the main nozzle 40 is fluidly connected to a main pneumatic system 42 .

[0043] The spinning device 4 further comprises a processing and control unit which is operatively connected to the pneumatic spinning starter system 38 , the main pneumatic system 42 and the stretching unit 8 .

[0044] In particular, the processing and control unit is programmed so that during the start-up of spinning:

[0045] At time t_0, it actuates the starter nozzle 36 to send a compressed starting air jet at an initial maximum starting pressure p_max,

[0046] It then actuates the stretching unit 8 to feed the fiber to the fiber introducer 20 of the spinning chamber 16,

[0047] At a time t_1 after t_0, it activates and keeps actuating the main nozzle 40 to supply the spinning chamber 16 under pressure p_f,

[0048] At time t_2 after t_1 , the closing phase of starter nozzle 36 begins, and at time t_3 after t_2 the initial maximum starting pressure is reduced to zero.

[0049] Advantageously, this reduction in starting pressure from an initial maximum value p_max to zero pressure follows a mean pressure gradient of less than 6 bar / s in absolute value.

[0050] In other words, the average reduction per unit of time of the supply pressure of starter nozzle 36 exhibits a maximum value of 6 bar / s in absolute value.

[0051] According to one possible embodiment, said reduction of the supply pressure of starter nozzle 36 follows a plurality of step-wise pressure reductions.

[0052] According to another possible embodiment, said reduction of the supply pressure of starter nozzle 36 follows a linear reduction trend.

[0053] According to a possible further embodiment, said reduction in the supply pressure of starter nozzle 36 follows a decreasing polynomial trend of at least quadratic magnitude.

[0054] According to a possible implementation ( Figure 8 ), the pneumatic spinning starter system 38 is controlled by at least two separate pneumatic solenoid valves 48, 52, which are placed in parallel with each other and connected to at least two separate pressure pipelines.

[0055] Advantageously, the solenoid valves 48, 52 are independently and selectively operated. In this way, in practice, it is possible to divide the total pressure drop into two or more intermediate pressure drops, corresponding to the same number of solenoid valves arranged in parallel, to customize the supply pressure and the on / off times, and thus to make the pressure drop curve more gradual over time.

[0056] According to another possible embodiment ( Fig. 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 equipped with a calibrated one-way orifice 60 towards the flow regulator. This pneumatic configuration is particularly advantageous because it allows a continuous and regular closing of the starter nozzle without steps due to the presence of the calibrated orifice, which dampens and delays the closing of the pressure regulator. In particular, by choosing a suitable combination of the length and diameter of the connecting tube 56 and the diameter of the calibrated orifice 60, the pressure drop time of the starter nozzle from the initial maximum value (p_max) to the zero value can be advantageously set.

[0057] Advantageously, the inner diameter of the connecting tube 56 is between 2 mm and 2.5 mm.

[0058] Advantageously, the length of the connecting pipe 56 is between 500 mm and 1000 mm, preferably 700 mm.

[0059] Advantageously, the diameter of said calibrated orifice 60 is between 0.15 mm and 0.35 mm, preferably 0.20 mm.

[0060] 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.

[0061] The operation of the spinning device and the method of starting spinning according to the present invention will now be described.

[0062] As shown in the figure, the solution according to the invention provides that the Venturi ejector or starter nozzle 36 used to start spinning is deactivated in a gradual manner, thereby slowly reducing the pressure and therefore the air speed, so as to ensure the continuity of the balance between the air pressure in the spinning chamber 16 obtained by the main nozzle 40 and the low pressure generated by the Venturi nozzle or starter nozzle 36.

[0063] In fact, the aim is to ensure the necessary time interval in order to allow the instantaneous adaptation effect between the pressure in the spinning chamber 16 and the pressure in the Venturi nozzle 36 to fully develop, avoiding any form of discontinuity in the evolution of the effluent which would therefore trigger the undesirable phenomenon of the start of a poor or failed spinning process.

[0064] Generally, the most important aspect is that the transition from the maximum starting pressure p_max to the zero pressure does not occur abruptly in a single step, but rather in a plurality of steps or more generally according to a continuously decreasing curve.

[0065] In summary, the innovation startup cycle consists of the following stages:

[0066] pneumatic supply of ejector or venturi nozzle 36 at maximum pressure p_max;

[0067] Supplying fibers into the spinning chamber 16;

[0068] Pneumatic supply of the spinning chamber 16: at time t_1, the spinning chamber 16 is also supplied with pressure and the two streams or jets of compressed air overlap for, for example, 250 ms, producing a yarn 18, even if it does not yet meet the desired properties;

[0069] gradually closing the ejector or venturi nozzle 36 according to an average pressure gradient with an absolute value of less than 6 bar / s;

[0070] Spinning starts and the yarn 18 is drawn off in its final form.

[0071] As can be understood from the description, the present invention makes it possible to overcome the disadvantages of the prior art.

[0072] A major advantage of the invention is the improvement and regulation of the start-up of the air-jet spinning process, which is particularly useful for yarns made of hard fibers and in the case of reduced fiber transit time in the spinning chamber.

[0073] In addition, the increase in the starting efficiency helps to increase the efficiency of the spinning device, thereby increasing the productivity of the machine, helps to significantly reduce unwanted yarn entanglements at the beginning of spinning, helps to improve the cleanliness of the device, and helps to reduce the percentage of waste fibers to be processed.

[0074] A person skilled in the art may make numerous modifications and variations to the above solutions in order to meet possible and specific requirements.

[0075] The protection scope of the present utility model is defined by the appended claims.

Claims

1. An air jet spinning device (4) provided with a spinning starter system, characterized in that: include: a stretching unit (8) configured to stretch the fiber web (12) to be supplied to the spinning chamber (16) via a fiber introducer (20), - a spinning chamber (16) shaped so as to obtain at the outlet a yarn (18) consisting of a plurality of entangled fibers, - the spinning chamber (16) is fluidly connected to a starter nozzle (36) or a venturi nozzle configured to trigger the start 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), fluidly connected to said starter nozzle (36), - a main pneumatic system (42), fluidly connected to said main nozzle (40), - a processing and control unit, operatively connected to the pneumatic spinning starter system (38), to the main pneumatic system (42) and to the stretching unit (8), wherein the pneumatic spinning starter system (38) is controlled by at least two separate pneumatic solenoid valves (48, 52), which are arranged in parallel with each other and connected to at least two separate pressure pipelines.

2. The air jet spinning device (4) according to claim 1, characterized in that: The solenoid valves (48, 52) are independently and selectively operable.

3. The air jet spinning device (4) according to claim 1 or 2, characterized in that: The pneumatic spinning starter system (38) is connected to a pressure regulator (54) which is placed in series with a flow regulator (58) via a connecting tube (56), controlled by a single solenoid valve (62) and provided with a unidirectional calibrated orifice (60) towards the flow regulator.

4. The air-jet spinning device (4) according to claim 3, characterized in that: The inner diameter of the connecting tube (56) is between 2 mm and 2.5 mm.

5. The air-jet spinning device (4) according to claim 3, characterized in that: The length of the connecting pipe (56) is between 500 mm and 1000 mm.

6. The air-jet spinning device (4) according to claim 3, characterized in that: The diameter of the calibrated orifice (60) is between 0.15 mm and 0.35 mm.

7. The air-jet spinning device (4) according to claim 5, characterized in that: The length of the connecting pipe (56) is equal to 700 mm.

8. The air-jet spinning device (4) according to claim 6, characterized in that: The diameter of the calibrated orifice (60) is 0.20 mm.

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