Textiles: spinning – twisting – and twining – Apparatus and processes – Open end spinning
Reexamination Certificate
1999-04-27
2001-04-24
Calvert, John J. (Department: 3741)
Textiles: spinning, twisting, and twining
Apparatus and processes
Open end spinning
C057S100000, C057S263000, C057S404000, C188S290000, C188S306000, C310S06700R, C310S090000, C310S156030
Reexamination Certificate
active
06220009
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a damping device for a contactless, passive, radial support of a rotor rotating at a high rotary frequency, especially of a textile open-end rotor spinning device.
A rotor with passive radial support which is supported in a contactless manner, e.g., magnetically or aerostatically, has the problem that undesired radial oscillations can occur. There is the danger that the oscillations can assume a magnitude at which the radial deflection of the rotor becomes so great that the rotor makes contact with its cushioning bearing or some other close component and therefore a further increasing of the rotary frequency out of the range of the natural resonance is only possible with very great accelerations of speed of rotation or not at all. For this reason support systems are used in such instances which comprise a radial damping of oscillations.
A rotor supported in a contactless manner can be actively damped, e.g., as regards the radial excitation of oscillations. A relatively great expense for the sensory mechanism, actuator mechanism and control is necessary for this purpose.
Another possibility for radial damping of oscillations is in the form of a passive damping of oscillations in which the attempt is also made to reduce the radial deflection. Such a device is known, e.g., from German Patent Publication DE 195 437 45 A1. In this publication, the stator magnet of a magnetic bearing is elastically suspended on spring legs. The magnetic bearing, located on the stator side, is additionally held by a frictional connection which begins to start with friction upon an appropriately large oscillatory amplitude of the rotor and thus effects a damping.
It is disadvantageous, for example, in the case of a bearing arrangement in accordance with German Patent Publication DE 195 437 45 A1, that the compensation of oscillations does not become effective until the oscillatory amplitude has assumed a magnitude at which the friction begins. Before this value at which the friction device begins to operate has been achieved, there is an undamped operation . The damping act ion, which does not begin until later, is opposed by a lastingly oscillation-poor running of the rotor.
A further disadvantage is the fact that the manufacturing of the spring-leg arrangement is very difficult and expensive. Inaccuracies in it result in a radial offset and/or in an error as regards the maintaining of the desired air gap and or in an error as regards the planar parallelism of the bearing magnets, which jeopardizes the operation of the bearing arrangement.
Another disadvantage is the fact that the rigidity of the magnetic bearing is reduced by the rigidity of the spring-leg arrangement. As a result of the fact that the stator magnet fixing the rotor is not completely stationary since it was attached so that it could oscillate, the position of the rotor is inconstant in analogy with the oscillatory movements of the stator magnet. The damping oscillation of the stator magnet can result in an additional impairment of the smooth running of the rotor. An unfavorable superpositioning of the two oscillatory frequencies can not be excluded.
The above-mentioned disadvantages can occur either alone or in combination and an unobjectionable operation of the damping device is present in neither instance.
SUMMARY OF THE INVENTION
Therefore, the invention has an object, based upon the devices of the initially described type, of improving such devices. In particular, it is an object to provide a damping device which avoids the previously cited disadvantages and brings about an improved and smoother running of the spinning rotor.
The present invention achieves these and other objectives in an open-end spinning device of the type having a spinning rotor mounted to a rotor shaft and supported for rotation at a high rotary frequency by a contactless, passive, radial support. According to the present invention, a device is provided for damping the contactless, passive, radial support of the spinning rotor which comprises a friction device having friction components which include mechanically loaded friction surfaces. One of the friction components is arranged in a manner which is stationary at least radially and the other friction component is disposed for shifting its position radially, the shiftable friction component comprising a bearing component which surrounds the rotor shaft of the rotor.
This design of the present invention has the particular advantage that the occurrence of large oscillatory amplitudes at which the rotor can strike the stator is reliably avoided by the bearing component surrounding the rotor shaft. That is, it is assured in a simple manner that when the contactless, passively supported spinning rotor is highly accelerated, no problems due to oscillations which build up can occur, even when the rotor passes through the frequency ranges of its natural oscillations.
In particular, the design of the damping device in accordance with the invention has the advantage that the damping begins immediately at the first appreciable oscillations and thus rather large oscillatory amplitudes in the deflection do not occur.
In addition thereto, the non-critical manufacture of the components of the damping device is advantageous since hardly any disadvantageous influences are exerted on the rotor support itself due to manufacturing tolerances or dimension errors.
The use of a special roller bearing for high rotary frequencies is advantageous since in this manner an almost play-free “reaction” of the damping device to the oscillations produced takes place.
It is also contemplated to be possible to use an aerostatic bearing as the bearing component. This has the advantage that the damping begins immediately upon the first oscillation, just as when a roller bearing is used and in addition the bearing friction is distinctly minimized by the use of the aerostatic bearing. If an aerostatic support of the rotor itself is used an integration of the aerostatic bearing of the damping device into the radial support of the rotor would be conceivable.
As a further alternative, a plain bearing bush may be used as the bearing component, which offers an economical support. The constructive design of the plain bearing bush and of the rotor shaft with a certain bearing play provides that during the normal oscillation-free spinning operation no contact occurs between the rotor and the bearing component so that no wear occurs during normal operation. Essentially only a radial limitation of oscillation takes place when the areas of natural oscillation are passed through.
It is to be noted in all such embodiments that the particular bearing component used during normal, oscillation-free running of the rotor does not participate in the radial support of the rotor shaft.
According to one feature of the invention, friction occurs immediately after the occurrence of the first oscillation. The low-play immediate coupling between radial deflection and damping results in a direct radial damping of the rotor.
Moreover, it is preferred that the bearing component surrounds the rotor shaft with a bearing play of only a few &mgr;m which has the advantage that as a result of the minimal air gap which is present the maximum opening of the bearing location is limited and thus a protection against contamination is created at the same time.
Another aspect of the invention provides that the stationary friction component comprises a limiting bearing and the bearing component surrounds the rotor shaft with a bearing play in the area of a plain bearing bush which is less than a bearing play of the limiting bearing, which has the advantage that the difference of the two bearing plays results in an acceptable damping path. After overcoming the bearing play, initiated by an oscillation, the damping starts until either the limiting bearing play has been bridged or a friction component which can be varied in its position, e.g., a moveable friction plate, strikes against a stop.
It is preferred to provide an adjustm
Calvert John J.
Hurley Shaun R
Kennedy Covington Lobdell & Hickman LLP
W. Schlafhorst AG & Co.
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