Textiles: spinning – twisting – and twining – Apparatus and processes – Open end spinning
Reexamination Certificate
2002-06-21
2004-04-20
Calvert, John J. (Department: 3765)
Textiles: spinning, twisting, and twining
Apparatus and processes
Open end spinning
C057S404000
Reexamination Certificate
active
06722118
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for open-end rotor spinning, wherein the fibers to be spun are conveyed via a fiber guide channel into the rotor, are collected in its rotor groove of the largest interior diameter, are tied while being twisted into the yarn end in the area of a so-called tie-in zone by means of the rotor rotation and are drawn off as finished yarn through a draw-off nozzle, which is arranged centered and substantially on one level with the rotor groove.
The development of rotor spinning goes back a very long time, wherein the industrial use of this method only started on a larger scale in the sixties. A multitude of inventions was created not only in peripheral areas, i.e. from the sliver feed, the opening up into individual fibers and feeding of the individual fibers to the spinning rotor, as well as the drawing-off and winding-up of the yarn, but also in the core area of yarn formation, i.e. inside the rotor, only a small portion of which has entered into the present-day, very efficient automatic rotor spinning machines, which produce a yarn of high quality.
All methods have essentially in common that fibers from a sliver, which have been opened into individual fibers by means of an opening cylinder, are conducted together by means of a vacuum air flow to the rotor and are conveyed against a circumferential wall by means of the air flow and/or centrifugal force. As a rule, the shape of the inner rotor wall permits the collection of these fibers by forming an almost closed fiber ring. These collected fibers are continuously tied-up into a yarn end, wherein the yarn performs a true twist with every revolution of the rotor. The yarn rotation wanders opposite the yarn draw-off direction from the draw-off nozzle in the direction toward the yarn collection and, by the twisting of the doubled yarn, makes its continuous spinning on the open yarn end possible. The area where this piecing of the fibers to the yarn end takes place, is located between the detachment point of the yarn being created from the rotor wall, and the transition from the twisted yarn into the untwisted small sliver. It is called the tie-in zone.
Normally a yarn end for a piecing, which is fed into the rotor by the draw-off nozzle, is taken along in the direction of the rotor rotation by the air flow formed by the rotor rotation, at the latest when reaching the rotor groove. This curvature of the yarn end in the direction of rotor rotation is then maintained during the entire spinning process.
As can be seen from JP-OS 49-54 639, a malfunction can be caused by intensive soiling in the rotor, large bundlings of fibers, or the loss of the vacuum supply. The flipping of the curvature of the yarn end caused by this is quite undesirable, as stated in this Japanese laid-open document, since the yarn created in the course of this is said to show considerable disadvantages in respect to strength and evenness in comparison with a yarn, whose yarn end is curved in the direction of the rotor rotation. To prevent this flipping of the curvature opposite the rotor rotation direction, it is proposed in JP-OS 49-54 639 to arrange appropriate yarn contact elements on the draw-off nozzle and the rotor bottom, which are intended to stabilize the desired direction of curvature.
Within the scope of the further developments of the open-end spinning methods it was possible to definitely improve the processes, so that it is normally possible to avoid large collections of fibers, soiling or the failure of a vacuum. Accordingly, modern open-end spinning machine in principle are operated without additional aids for maintaining the curvature of the yarn end in the direction of rotation of the rotor.
A rotor spinning arrangement is described in “Breakspinning”, report of the Shirley Institute, Manchester, England, 1968, pages 76 to 79, wherein a funnel-shaped false twist element is arranged inside of the actual spinning rotor, which itself has the shape of a pan. This false twist element extends directly up to the fiber collection surface of the rotor. The rotor and the false twist element are separately seated and can also be separately driven. This means that the false twist element can be arranged in a stationary manner, as well as being driven in the direction of the rotor rotation, or opposite the direction of rotor rotation. Openings are arranged in the area of the collecting surface, by means of which a suction flow is created because of the centrifugal force of the rotor rotation. The fibers are fed in the radial direction on the collecting surface, which has the approximate shape of a cylinder surface. The yarn is drawn off through the rotor shaft, i.e. at the location opposite the fiber feed-in.
As described there, the relative direction of rotation of the yarn leg can be changed in relation to the rotor rotation as a function of the direction of rotation of the false twist arrangement. It is stated in conclusion that this relative rotation direction of the yarn leg clearly affects the yarn quality. Thus, in the positive direction, i.e. with the yarn leg running faster than the rotor, the yarn quality is said to be better by approximately 18% than with the oppositely directed relative speed of the yarn leg in relation to the rotor rotation.
A problem, which reduces the employment options of the rotor yarn produced on modern open-end rotor spinning machines, which otherwise has very even and good physical textile properties, resides in the formation of cover yarn, the so-called “belly bands”, which are wound in alternating directions of rotation either loosely, but partially very tightly, around the yarn periphery. The yarn structure, or the fiber orientation and fiber stretching, suffers because of this, with the result that the range of application of open-end rotor yarns becomes limited.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to propose a method which limits the creation of cover yarn at least noticeably.
In accordance with the invention, this object is attained by providing a method for open-end rotor spinning, wherein the fibers to be spun are conveyed via a fiber guide channel into the rotor, are collected in its rotor groove of the largest interior diameter, are tied while being twisted into the yarn end in the area of a so-called tie-in zone by means of the rotor rotation and are drawn off as finished yarn through a draw-off nozzle which is arranged centered and substantially on one level with the rotor groove. The fiber flow exiting from a fiber guide channel has a directional component in the direction of rotation of the rotor, and the yarn leg extending from the draw-off nozzle to the rotor groove is curved, at least in the vicinity of the rotor groove, opposite the direction of rotation of the rotor during the spinning process.
The invention is advantageously further developed in a preferred embodiment of the method wherein the fiber flow is essentially fed to a fiber slide surface located between the rotor opening and the rotor groove. The direction of curvature of the yarn leg is created during the piecing process. In a first phase of the piecing process, a rotary flow directed tangentially opposite the direction of rotation of the rotor during its operation is caused to act on the yarn end introduced into the rotor for piecing, which flow is sufficient for creating the intended direction of curvature of the yarn leg. In such first phase of the piecing process, the rotor is initially driven opposite the direction of rotation of the rotor during its operation in such a way that the intended direction of curvature of the yarn leg occurs, and that the direction of rotation of the rotor during its operation does not exceed an angular acceleration which could lead to the flipping of the direction of curvature.
The method in accordance with the invention is based on the knowledge that, with a curvature direction of the yarn end in the direction of rotation of the rotor, fibers which, coming from the fiber slide face, directly reach the tie-in zone o
Lassmann Manfred
Meyer Jürgen
Calvert John J.
Hurley Shaun R
Kennedy Covington Lobdell & Hickman LLP
W. Schlafhorst AG & Co.
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