Textiles: spinning – twisting – and twining – Apparatus and processes – Open end spinning
Reexamination Certificate
2000-03-08
2001-03-06
Calvert, John J. (Department: 3741)
Textiles: spinning, twisting, and twining
Apparatus and processes
Open end spinning
C057S416000
Reexamination Certificate
active
06195976
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of German patent application DE19910277.5, filed Mar. 9, 1999, herein incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a spinning rotor for open-end spinning machines and, more particularly, to a spinning rotor which basically comprises a rotor cup having an annular wall portion defining a rotor opening, a bottom wall portion merging with the annular wall portion, and a mounting hub extending exteriorly from the bottom wall portion, with a rotor shaft affixed to the mounting hub coaxially with the rotor cup.
The requirement for greater and greater productivity has resulted in the development of current open-end rotor spinning machines operating at rotor speeds of well above 100,000 rpms. At such high speeds, special requirements arise as regards imbalance, bearing and stability (danger of bursting) of the spinning rotors.
European Patent Document EP 0 099 490 B1 describes an open-end spinning rotor shaped in a non-cutting manner and with a fiber collector groove to be used at high rotor speeds. In order to avoid the negative effects of centrifugal forces occurring at high rotor speeds such as, e.g., deformation or bursting of the spinning rotor, a bead is formed on the outer circumference of the edge of the rotor cup opening in order to increase the strength. This reinforcement is intended to increase the bursting speed of the rotor.
German Patent Publication DE 197 34 637 A1 discloses a spinning rotor of an open-end rotor spinning machine having a rotor shaft supported in the bearing slot of a support disk bearing arrangement and in an axial bearing which comprises magnetic bearing components. The spinning rotor is intended for rotor speeds of more than 100,000 rpms. This spinning rotor has a distinctly greater wall thickness in the area of the rotor groove or in the area of the greatest outside diameter of the rotor than in the area between the rotor groove and the opening edge. The stability of a body of rotation is increased with a greater wall thickness and any occurring tensions resulting from high speeds can be better distributed. Such embodiments are customary and are frequently used.
Spinning rotors which are reinforced or designed with a great wall thickness in the area of the greatest diameter have absolutely contributed to a certain increase of the speed. However, further increases in speed without losses of function or of safety can not be achieved with these known spinning rotors or can be achieved only in a very limited manner. In particular, problems of imbalance can be produced in that a slight deviation of measurement occurring in the course of the manufacture of the spinning rotor results in the case of rather large diameters or rather large masses in a greater imbalance.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to improve spinning rotors for use at high speeds.
The invention achieves this objective by providing a spinning rotor for open-end spinning machines which basically comprises a rotor cup having an annular wall portion defining a rotor opening, a bottom wall portion merging with the annular wall portion, and a mounting hub extending exteriorly from the bottom wall portion, and a rotor shaft affixed to the mounting hub coaxially with the rotor cup. The merger of the bottom and annular wall portions of the rotor cup defines thereat a maximum exterior diameter of the rotor cup and defines interiorly thereof a rotor groove. The annular wall portion, the bottom wall portion and the mounting hub are of different cross-sectional thicknesses and the cross-sectional thickness of the bottom wall portion increases from the rotor groove to the mounting hub. In accordance with the present invention, the wall thickness at the maximum exterior diameter of the rotor cup at the merger of the bottom and annular wall portions of the rotor cup is between about 0.3 mm and about 1.2 mm, and the annular wall portion, the bottom wall portion and the mounting hub have an aerodynamic exterior contour free of edges for deterring turbulent boundary layer air flow thereabout while the annular wall portion and the bottom wall portion have an interior contour for promoting fiber spinning into a yarn.
The described design of the present invention providing the rotor cup with a slight wall thickness in the area of its greatest outside diameter improves the distribution of mass and therewith the behavior at high speeds of the rotor cup without inadmissibly weakening the rotor cup in this area. A reduction of weight is thereby possible which has an advantageous effect on the operating qualities of the spinning rotor and on the consumption of energy.
Preferably, the exterior contour of the rotor cup from the rotor opening through the annular wall portion to the transition of the bottom wall portion into the mounting hub is configured to provide only convex curvatures as viewed with respect to the axis of rotation of the rotor cup, which provides for favorable air flow about the rotor. More specifically, the outer contour of annular wall portion is a straight line from the rotor opening to the merger thereof with the bottom wall portion at which a convex curvature in the outer contour merges the annular wall portion with the bottom wall portion. In addition, the ratio of the diameter of the rotor opening to the rotor depth between the rotor opening and the rotor groove has a favorable effect on the surrounding air flow during high speed operation of the rotor.
In order to optimize the compensation of mechanical tension forces acting on the rotor cup and therewith improve the strength of the rotor cup, the wall thickness constantly increases from the rotor opening of the rotor cup to the rotor groove, the rotor groove has a radius in the groove bottom which radius is at least 0.15 mm large, and furthermore, the ratio of the diameter of the rotor opening to the rotor depth is between about 2:1 and 5:1. The danger of a bursting of the rotor cup can be thereby reduced and an increase of the bursting danger countered in spite of an increase in rotor speed.
A marking introduced by the removal of material, preferably by etching or laser, from the exterior surface of the rotor cup simplifies identification during the manufacturing process as well as during operation and is more permanent than an application of colorant, which frequently becomes illegible or disappears entirely after a short period of operation, e.g., due to contact or the action of friction. The removal of material for introducing the marking on the surface of the spinning rotor may serves at the same time to selectively balance out or compensate the mass of the spinning rotor, thereby advantageously making possible an improved rotational behavior of the spinning rotor at high speeds, and also saves expense and time in the manufacturing process of the spinning rotor.
In light of the teachings of the known state of the art that an increase of the rotor wall thickness should be made in order to be able to increase the rotational speeds without loss of function, it is surprising that the spinning rotor of the present invention with a reduced wall thickness in the area of the greatest outside rotor diameter is better suited for high speeds of up to 150,000 rpms and permits an increase in the speed of up to 25,000 rpms as a function of the nominal rotor diameter in comparison to known spinning rotors. Such increases in the rotor speeds by more than 20,000 rpms can be achieved especially with nominal rotor diameters between 33 mm and 40 mm. The increase in speed made possible by this design of the spinning rotor in accordance with the present invention permits a distinct increase in productivity of the open-end spinning positions and of the open-end spinning machines and, therewith, an economical manufacture of yarn.
The reduction of the outside rotor diameter in conjunction with the formation of the exterior contour of the rotor cup to be free of sharp edges, depressions and protru
Grecksch Hans
Klaczynski Elisabeth
Riede Brigitte
Schlomer Bert
Wassenhoven Heinz-Georg
Calvert John J.
Kennedy Covington Lobdell & Hickman LLP
W. Schlafhorst AG & Co.
Welch Gary L.
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