Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-02-24
2002-01-22
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C057S117000
Reexamination Certificate
active
06340855
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of German patent application DE19910279.1, filed Mar. 9, 1999, herein incorporated by reference.
1. Field of the Invention
The present invention relates to a bearing of a spinning rotor of an open-end spinning apparatus.
2. Background of the Invention
In open-end rotor spinning machines, spinning assemblies are known in which the spinning rotor revolving at high rpm is braced with its rotor shaft in the bearing gap of a support disk bearing arrangement and is fixed via an axial bearing disposed on the end. The support disk bearing arrangement includes two pairs of support disks whose axes are transposed such that an axial thrust is exerted on the rotor shaft that urges the rotor shaft in contact with the mechanical axial bearing.
This type of bearing for open-end spinning rotors is described for instance in published, nonexamined German Patent Application DE-OS 25 14 734, and has been proven itself in practice to allow rotor speeds of 100,000 rpm or more. However, a disadvantage of this type of spinning rotor bearing is that, because of the transposition of the support disks, increased friction occurs between the rotating peripheral surfaces of the support disks and the rotor shaft, which leads to heating of the peripheral surfaces of the support disks. This frictional heat not only causes considerable stress on the peripheral surfaces of the support disks, but also requires additional energy to overcome this friction. Furthermore, the known mechanical axial bearings are subject to not inconsiderable wear, even if they are lubricated as prescribed.
Attempts have therefore already been made in the past to replace these mechanical axial bearings with wear-free axial bearings, such as air bearings or magnetic bearings. However, since even air bearings require an axial thrust of the rotor shaft in the direction of the axial bearing, it has not been possible to overcome most of the above-described fundamental problems with air bearings.
In German Patent Disclosure DE 195 42 079 A1, an axial magnetic bearing assembly is described in which some of the magnetic bearing elements are disposed in stationary fashion in the housing of an axial bearing, while other magnetic bearing elements are disposed detachably on the rotor shaft of the spinning rotor. Various different ways of binding the magnetic bearing elements, which rotate with the spinning rotor, to the rotor shaft have been proposed. Some of these variants pertain to a nonpositive, and others to a positive fastening of the jointly rotating magnetic bearing elements, which can easily be detached as needed.
Although these known magnetic bearing arrangements provide correct axial fixation of the rotor shaft on the support disk arrangement and moreover assure that as needed the spinning rotor can easily be installed and removed, it has nevertheless been found that the positive fastening of the magnetic bearing component to the rotor shaft, which is easily detachable as needed and is advantageous in principle, still needs improvement. In particular, the fastening of the jointly rotating magnetic bearing elements to the rotor shaft is problematic in such magnetic bearing arrangements, because stringent demands are made on the quality of the balance of this connection due to the high rpm of the spinning rotor.
An open-end rotor spinning apparatus with a permanent- magnetic axial bearing is also known from Austrian Patent AT 270 459. In this bearing arrangement, several magnetic ring inserts are disposed on the end of the rotor shaft of a spinning rotor, and opposite thereto are pole pieces of a permanent magnet that is pivotably supported in this region. Such an arrangement achieves a focusing of the magnetic lines of force of the permanent magnet which leads to a relatively rigid fixation of the rotor shaft in the bearing nip of a support disk bearing.
A disadvantage of a magnetic bearing arrangement embodied in this manner, however, is that the ring inserts disposed on the rotor shaft have a markedly greater diameter than the rotor shaft itself. Since the markedly larger-diameter ring inserts make it considerably more difficult or impossible to install and remove the spinning rotor, and especially to mount it on the front, this known magnetic bearing arrangement has not become established in practice.
German Patent Disclosure DE 30 47 606 A1 discloses a bearing for a spindle of a textile machine which revolves at relatively high rpm. This spindle is braced in the radial direction via a three-point bearing arrangement similar to a support disk bearing and is secured in the axial direction by a magnetic bearing. On its end, the spindle has a reduced-diameter bearing region with two ferromagnetic ring inserts. A cuff made of a nonmagnetic material is fixed to the bearing housing, and an annular permanent-magnetic element is fitted into this cuff and is enclosed by lateral pull disks. In the installed state of the spindle, the ferromagnetic ring inserts of the spindle shaft face the pole disks of the permanent-magnetic element that is fixed in the static bearing element.
Although these known embodiments enable relatively easy installation and removal of the spindles in the axial direction, the apparatus has not become established in practice because of its lack of axial bearing rigidity.
A bearing of a spinning rotor of an open-end spinning apparatus is also known from German Patent Disclosure DE 197 29 191 A1, in which the rotor is radially supported in the bearing nip of a support disk bearing and is axially positioned by a magnetic axial bearing. The axial bearing has a static bearing component with at least two permanent-magnetic rings defined on both sides by pole disks. These permanent-magnetic rings are disposed in a bearing body such that in the installed state, identical poles face one another (N/N or S/S). The rotor shaft has at least three ferromagnetic ribs disposed at a distance from the pole disks.
German Patent Disclosure DE 197 29 191 A1 also indicates that the bearing housing is lowered with its center axis relative to the center axis of the rotor shaft defined by the position of the bearing nip of the support disks. As a result, an upward-oriented radial force component is imparted to the rotor shaft in the region of the axial bearing. Thus, when cleaning of the rotor, the rotor is no longer pressed into the bearing nip by the contact pressure roller, which presses the lengthwise-extending tangential belt that drives the rotor shaft, but instead is retained in a horizontal position. However, this radial component has an adverse effect during the drive of the rotor.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved bearing of the basic type described above for use in a spinning rotor.
This object is attained according to the invention by a bearing for a shaft of a spinning rotor of an open-end spinning apparatus which basically comprises a support disk bearing defining a bearing nip for radially supporting the rotor shaft and a magnetic axial bearing for axially positioning the rotor shaft. The axial bearing has a static bearing component with at least two axially polarized permanent-magnetic rings bounded on opposite sides by pole disks, the permanent-magnetic rings being disposed in a bearing body such that corresponding magnetic poles face one another. The rotor shaft has at least three ferromagnetic annuli at respective spacings from the pole disks. The support disk bearing is disposed in relation to the static bearing component of the axial bearing to retain the rotor shaft in the bearing nip with a center axis of the rotor at an offset in the direction of the bearing nip from a center axis of the static bearing component. The static bearing component includes an engagement surface outwardly of the magnetic rings and the pole disks toward the support disk bearing and on the side of the support disk bearing remote from the bearing nip. The engagement surface faces the rotor shaft over an angul
Schlömer Bert
Wassenhoven Heinz-Georg
Dinh Le Dang
Kennedy Covington Lobdell & Hickman LLP
Ramirez Nestor
W. Schlafhorst AG & Co.
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