Textiles: spinning – twisting – and twining – Apparatus and processes – False twist device
Reexamination Certificate
2001-12-13
2004-01-20
Calvert, John J. (Department: 3765)
Textiles: spinning, twisting, and twining
Apparatus and processes
False twist device
C057S350000, C057S315000, C057S328000
Reexamination Certificate
active
06679044
ABSTRACT:
BACKGROUND
The present invention concerns a pneumatic apparatus for producing a spun yarn or thread from a fibre array using a vortex flow. From DE 41 05 108 (called DE'108 in the following) a pneumatic spinning device is known for producing a yarn or thread from a short fibre sliver. In a nozzle block presenting a hollow room with a conical support member, the fibres are subject to a rotating air stream and thus are caused to rotate in such a manner that they form a yarn or thread. The yarn is taken off via a spindle duct. At the base of the conical support member a fibre guide duct merges into the nozzle room from the exterior. This fibre guide duct serves for feeding the fibres, or the fibre sliver respectively, from the exterior into the hollow room. A needle-shaped guide element protrudes over the free end of the conical support member, the needle point being oriented towards the centre of the spindle duct of the spindle, which is arranged rotating or stationary. This device presents the disadvantage that the quality of the yarn produced cannot readily be influenced. Due to the layout, in particular of the fibre guide duct, the twist imparted to the fibres by the rotating air stream tends to propagate right into the guide duct. Due to abrupt transitions, particularly between the fibre guide duct and the nozzle room, vortices and turbulences are generated, which exert negative influences. This is a substantial disadvantage. The yarn quality in this arrangement thus does not remain constant, but fluctuates.
From DE 40 36 119 (called DE'119 in the following) a further pneumatic spinning device is known serving for producing a yarn or thread from short fibers. This device also comprises a nozzle block. In its inside, however, as different from the arrangement described in DE'108, no conical support member is provided. Instead of the support member this device comprises a guide element substantially consisting of a wire pointed towards an opening of a rotating or stationary spindle. The function of this arrangement otherwise to a large extent is analogous to the one shown in the DE'108 and thus not discussed in more detail here. This device shows the disadvantage, in particular, that yarn quality substantially cannot be controlled. Because of the uncontrolled airflow supplied into the hollow room and to the zone, to which the fibre sliver is supplied, control of yarn quality is very difficult to achieve.
The arrangements known according to the state of the art are laid out in the zone in which the fibre sliver is fed into the nozzle block, and in the zone in which the fibres are exposed to the rotating air flow, which among other points favours uncontrolled air flows. Turbulences and fluctuating airflows negatively affect the yarn quality and limit the processing speed. The rotational movement generated by the air stream acting onto the fibres furthermore can be controlled with difficulties only and acts rights into the fibre guide duct.
SUMMARY
It is thus a principal objective of the present invention laid open here, to develop the arrangements known according to the state of the art in such a manner that an improved and constant yarn quality is achieved. In particular yarn quality is to be rendered settable and controllable specifically. Additional objects and advantages of the invention will be set forth in the following description, or may be obvious from the description, or may be learned through practice of the invention.
The present invention laid open here shows a pneumatic spinning apparatus for producing a yarn spun from staple fibres. A nozzle block internally contains a hollow room with jet nozzles. In this hollow room a guide means is arranged coaxially opposite a substantially cylindrical spindle, which guide means merges into a fibre guide duct, or comes from it respectively. The fibre guide duct merges into the hollow room from the exterior and serves for feeding fibres, or a fibre sliver respectively, e.g. from a supply device. The layout and the arrangement of the fibre guide duct and of the fibre guide means is of considerable importance for the yarn characteristics and the resulting yarn quality. The fibre feed duct advantageously is laid out under consideration of aerodynamic aspects.
The spindle arranged opposite the fibre guide means is stationary or rotatable and comprises a spindle duct extending substantially centric, which serves for taking off the yarn spun. The fibre guide duct advantageously is arranged laterally offset with respect to the spindle. During processing the fibre sliver supplied by a supply device is brought into the hollow room via the fibre guide duct. In close vicinity of the merging point of the spindle duct the fibres are exposed to a spiraling rotating air stream, which is generated by the jet nozzles arranged substantially tangentially with respect to the spindle and the fibre guide means. In this process the fibres around the fibre guide means are exposed directly to the rotating air stream, which exerts a separating force away from the fibre sliver, acting onto fibre ends not guided in the fibre guide duct. The arrangement of the spindle, of the fibre guide means, and of the fibre guide duct are chosen in such a manner that the leading fibre end (fibre end zone entering the opening of the spindle duct first) of the fibres already forms a yarn while the trailing fibre end (fibre end zone entering the opening of the spindle duct not first) of the fibres is lifted off by the force acting towards the outside. This trailing free end of the fibres is arranged spiraling and rotating about the spindle. In the further course of the fibre sliver processing the fibres gradually are taken in into the spindle duct where they wrap around the fibre guide means in such a manner that a spun yarn with real twist results.
Owing to the fibre guide means and the fibre guide duct laid out and arranged according to the present invention, the fibres of the fibre sliver supplied via the fibre guide duct hardly can wrap around each other in uncontrolled manner. The fibre guide means furthermore functions as a so-called false core, which together with the fibre guide duct laid out and arranged to the present invention controls the propagation of the twist during the yarn formation. In this manner false twisting of fibres is prevented, or that a false twist propagating from the fibre guide means back towards the fibre guide duct in the direction towards the delivery device respectively, which would prevent imparting of real twist at least partially, and would affect yarn quality.
The fibre guide duct and the fibre guide means preferentially are formed continuously and aerodynamically shaped, and depending on the effect to be achieved, are laid out symmetrically or asymmetrically, tapered or bulbous. Other shapes and arrangements of the fibre guide means are possible also.
The layout and the arrangement of the fibre guide duct, via which the fibre sliver or the fibres are fed from the delivery device into the hollow room in the nozzle block, exerts considerable influence onto the processing and onto the resulting yarn. In the fibre guide duct the fibres of the fibre sliver are prepared for the spinning process, being oriented and arranged before they enter the hollow room, and before they are exposed to the rotating air stream. The layout and the cross-section profile along the fibre feed duct determine the manner in which the fibre sliver and the fibres are transformed and prepared. The duct is laid out in such a manner that a controlled air stream, directed from the outside into the nozzle block, prevails inside the duct, and influences the orientation and the arrangement of the fibres. Depending on the layout of the cross-section over the duct length it can be achieved that e.g. the fibres are fed into the process in rather crimped form or in rather straightened form in such a manner that yarns of different characteristics can be produced. The form and the arrangement of the duct also influence the twist imparting process, and the
Calvert John J.
Dority & Manning
Hurley Shaun R
Maschinenfabrik Rieter AG
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