Air-jet type spinning device

An air-jet type spinning device (4), comprising a body (8) at least partially hollow which defines a spinning chamber (12), a fibre feed device (16), facing said spinning chamber (12) so as to feed the fibres into the spinning chamber (12), a spinning spindle (20) at least partially inserted in the spinning chamber (12) and fitted with a spinning channel (24) for the suction of yarn obtained from said fibres, the spinning channel (24) defining a spinning direction (X-X), at least one channel (28) for sending a jet of compressed air inside the spinning chamber (12). Advantageously, the spinning chamber (12) is delimited at least partially by an outer side wall (32), opposite the spinning spindle (20), wherein at least one thread (36) is made on said outer side wall (32), wherein said at least one channel (28) is oriented so as to direct the jet of compressed air towards the at least one thread (36) in order to be guided and oriented by the latter.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to Italian Patent Application No. 102016000044012 filed on Apr. 29, 2016.

FIELD OF APPLICATION

The present invention relates to an air-jet type spinning device.

STATE OF THE ART

As is known, air-jet type spinning devices perform yarn production starting from a fibre sliver.

Said sliver is subjected to the action of jets of compressed air (air-jet) which enable the outermost fibres to open up and wrap themselves around the central fibres, forming the yarn.

The solutions of the prior art have a number of drawbacks and limitations.

In fact, there are 4 or more holes for the injection of compressed air which require significant air consumption with an increase of energy consumption and therefore higher production costs of the yarn.

In addition, the known solutions, in order to obtain good quality yarns and limit the consumption of compressed air, require the creation of small spinning chambers. This way however, the chambers are extremely sensitive to the presence of dirt and fibrils which compromise the quality, repeatability and strength of the yarn.

In addition, the prior solutions entail some structural constraints in the realization of the spinning chamber since the jets of compressed air must be directed in an extremely accurate manner in the proximity of the tip of the spinning spindle: in other words the jets must be directed in a tangential direction and tilted downwards to obtain the necessary compressed air whirling motion which must, on the one hand, wind the outermost fibres around the innermost ones and on the other create the necessary vacuum for the suction of the fibres inside the spinning spindle. Despite such geometric constraints the prior solutions do not always guarantee control of the direction of the jets of compressed air inside the spinning chamber since the air, once it has left the nozzles, is not guided in its feed movement but propagates freely inside the spinning chamber. For this reason the air is more prone to deviations both due to the presence of impurities, such as fibrils and dirt, and to the presence of turbulence and vorticity.

This variability in the operating conditions of the spinning, as seen, contributes to scarce repeatability of the yarn quality produced.

In conclusion, the air-jet devices of the prior art entail a significant consumption of compressed air, high production costs and do not always guarantee the constancy and repeatability of obtaining a high quality, strong yarn.

PRESENTATION OF THE INVENTION

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

Such need is satisfied by an air-jet spinning device according to claim1.

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 numeral4globally denotes an air-jet type spinning device comprising an at least partially hollow body8which delimits a spinning chamber12, and a fibre feed device16, facing said spinning chamber12so as to feed the fibre to the spinning chamber12.

The spinning device4further comprises a spinning spindle20at least partially inserted in the spinning chamber12and fitted with a spinning channel24for the passage of yarn obtained from said fibres. The spinning channel24defines a spinning direction X-X.

The spinning device4further comprises at least one channel28for sending a jet of compressed air to the spinning chamber12.

Advantageously, the spinning chamber12is delimited at least partially by an outer side wall32, opposite the spinning spindle20, wherein at least one thread36is made on said outer side wall32, the at least one channel28is oriented so as to direct the jet of compressed air towards the at least one thread36in order to be guided and oriented by the latter. In other words, the nozzle is oriented to direct the jet of compressed air towards the thread36so that the compressed air, thanks to the Coand{hacek over (a)} effect, remains substantially adhered to the thread36and lets itself be guided by the latter, moving along the thread inside the spinning chamber12.

According to one embodiment, the at least one thread36is a spiral thread, coaxial with said spinning channel24and parallel to the spinning direction X-X.

This way the compressed air moves according to a spiral motion inside the spinning chamber12.

According to one embodiment, the outer side wall32of the spinning chamber12comprises two spiral threads36′,36″ coaxial and staggered with each other by 180°, and the spinning device4comprises at least two channels28′,28″, each sending a jet of compressed air to one of said spiral threads36′,36″.

Preferably, the outer side wall32of the spinning chamber12comprises a plurality of spiral threads36, and the spinning device4comprises at least one channel28which sends a jet of compressed air to a corresponding spiral thread36.

According to one embodiment, the spinning device4comprises at least two channels28which send compressed air to respective distinct threads36and which are staggered with each other with respect to the spinning direction X-X.

It is also possible to provide a spinning device4comprising at least two channels28which direct compressed air into two distinct emission points40of the same spiral thread36.

According to a possible embodiment, the channels28are directed in a tangential direction T with respect to an emission point40in the respective spiral threads36.

This condition of tangency facilitates the adhesion of the jet of compressed air to the thread36thanks to the Coand{hacek over (a)} effect and thus facilitates the proper targeting of the compressed air inside the spinning chamber12.

According to one embodiment, at least one channel28is directed parallel to a horizontal surface O-O, perpendicular to said spinning direction X-X. Even in the condition of the jet of compressed air in the emission point40being horizontal, thanks to the presence of the spiral thread36, the air can deviate downwards, i.e. towards the spinning spindle20following the geometry of said thread36. There is therefore no need to direct the jets downward as in the solutions of the prior art.

In any case, it is also possible to provide at least one channel28tilted at a sharp angle with respect to a horizontal plane (O-O), perpendicular to said spinning direction X-X, in a direction moving towards the spinning spindle20.

According to one embodiment, the channels28are positioned so as to send the relative jets of compressed air to an emission point40located downstream of a feed hole44of the fibres to the spinning chamber12, relative to the spinning direction X-X. The feed hole44is the opening with which the fibre feed device16opens onto the spinning chamber12.

The threads36may have various geometries; preferably they have a curved or semicircular cross-section geometry with a radius ranging between 0.25 mm and 2 mm.

Preferably, said threads36are tilted at a helix angle of 5° to 15°.

Preferably, the pitch of said36threads is between 1.5 mm and 4 mm.

It is possible to use both fixed pitch threads36and variable pitch threads; in addition it is also possible to use both fixed helix angle threads and variable helix angle threads.

The spinning chamber12has an overall cylindrical cross-section with respect to a cross-section plane perpendicular to said spinning direction X-X. It is also possible to use a spinning chamber with a truncated cone cross-section which tapers towards the fibre feed device16and widening or flaring toward the spinning spindle20.

According to one embodiment, the spinning spindle20has an overall cylindrical cross-section with respect to a cross-section plane perpendicular to said spinning direction X-X.

It is also possible to use a spinning spindle20having a truncated cone cross-section which tapers towards the fibre feed device16.

The fibre feed device16may also comprise a needle56at least partially co-penetrated in said spinning chamber12, so as to create a guide for the fibres being spun. The presence of said needle56is however optional.

As may be appreciated from the description, the air-jet type spinning device according to the invention makes it possible to overcome the drawbacks of the prior art.

In particular, the present invention allows a significant reduction of air consumption compared to the solutions of the prior art, in the configurations where the number of air injection channels (usually 1 per thread) is less than the conventional number (usually 4).

In addition, the present invention allows an increase in the size of the spinning chamber and a consequent greater ability to “digest” dirt and fibrils in the spinning process; this way a better yarn quality and greater consistency and repeatability of the characteristics of the yarn obtained is ensured.

In addition, there is a greater control of the path of the air injected inside the spinning chamber: even in the presence of obstacles (tangled fibres, cotton balls, dirt, etc.) the channel of the outer side wall of the spinning chamber always guides the air the same way. In this case too, a greater regularity of the resulting yarn is ensured.

Moreover, for the same overall size, an additional space is made on the outer side wall of the spinning chamber, thus increasing the overall size of the spinning chamber. This way the fibres are given more space to “open up” during the spinning process; as a result “longer” windings than with the solutions of the prior art can be obtained.

In addition, the solution of the present invention, unlike the solutions of the prior art, allows precise control of the path of the compressed air inside the spinning chamber. In fact, as seen, the outer side wall of the spinning chamber may have two suitably sized spirals (pitch and diameter), out of phase by 180° and inclined at a suitable angle which guide the path of the air injected into them from the nozzles. In fact the air, entering tangentially to the channel of the spiral, using the Coand{hacek over (a)} effect remains adherent to said spiral, thus generating a whirling motion and a given vacuum, in a controlled manner.

Unlike the solutions of the prior art, it is also possible to enter with the compressed air above the point of entry of the fibres in the spinning chamber, since the airflow does not directly “disturb” the incoming fibres. This is a further advantage, since it prevents interference between the fibres and the air, and thus makes the spinning process more controllable, so as to obtain a yarn with features as constant and repeatable as possible.

A person skilled in the art may make numerous modifications and variations to the air-jet type spinning devices described above so as to satisfy contingent and specific requirements while remaining within the sphere of protection of the invention as defined by the following claims.