The invention relates to a centering and safety device for rotors supported without contact, especially in magnetic bearings.
In known bearings systems of this type, uncontrollable radial motions of the rotor are unavoidable in vertically arranged rotors and if flexure-critical frequencies are traversed, due to the air gap present between the rotor shaft and the bearing. These motions cause vibrations of the rotor and can lead to considerable damage to the rotor bearings.
This is essentially the case in "emergency or damping safety bearings for high-speed or overcritically running rotors" according to the publications:
1. German Published, Prosecuted Patent Application No. DE-AS 2 658 925, PA0 2. German Published, Non-Prosecuted Patent Application No. DE-OS 2 711 065, and PA0 3. German Published, Non-Prosecuted Patent Application No. DE-OS 2 821 177.
The emergency bearing according to Publication No. 1, which is suitable only for the vertical, but not horizontal support of the rotor body, becomes effective only if a given shaft vibration amplitude is exceeded and thereby the required centrifugal force is generated, where only the latter reduces on its part the bearing play or the annular air gap (28) successively to zero. If, however, any damage or damage which does not result in the generation of a centrifugal force, occurs in a bearing still prior to this instant of becoming effective due to centrifugal force, then its above-mentioned adverse effects can at least not be precluded.
The safety and damping bearings according to Publications Nos. 2 and 3 are damping bearings which become effective only if radial rotor vibrations occur, the amplitudes of which are larger than the bearing gap itself which exists between the roof shaft and the bearing. The same applies here as said above, namely that shaft vibrations can cause uncontrollable and damaging stresses of all bearings due to centrifugal forces and vibration still before the extent of the gap is reached, i.e. still before the damping effect effect of the bearing is reached.
It is an object of the invention to provide by simple means a device of the type defined above, by means of which in horizontally as well as in vertically supported electrically energized magnetic bearings, a mechanical rotor support is provided which simultaneously provides centering in the event of trouble in one or all electrically energized magnetic rotor bearings, for instance, through loss of their carrying capacity, due to loss of electric power to the bearing magnets.
According to the invention, this problem of bearing damage, due to loss of carrying capacity is solved by providing a centering and supporting device in parallel to the electromagnetic rotor bearings and so that it forms a rotatable bearing sleeve which has at least one centering and bearing surface at an end face, so that the bearing bushing is brought into frictional support and centering contact with a corresponding annular area of a collar attached to the rotor in case the rotor should move axially in relation to the rotor shaft and the bearing sleeve.
In an advantageous further embodiment of the subject of the invention, there may be provided matching surfaces on both the bearing sleeve and on the rotor collar and that these surfaces are of annular and conical shape and that the bearing sleeve can be quickly moved and forced by fast-releasing elements with its bearing and centering surface axially against the bearing and centering surface of the collar of the rotor and wherein these elements include at least one electrically powered electromagnet ring acting against a flange of a sliding sleeve and therethrough against the force of springs acting on the sliding sleeve, the electro magnetic rotor bearings and the electromagnet ring of the centering and supporting device being electrically connected together, and that, finally, so that the bearing sleeve is supported in antifriction or sliding bearings which are fastened in a bearing housing, the latter being connected to a sliding sleeve.
The device according to the invention therefore has the substantial advantage that it goes into action simultaneously with failure, for instance, failure of the electric current supply for the bearing electro magnets, and takes over the support and centering of the rotor until the failure is corrected, without having to interrupt the running of the rotor or even to disassemble the bearings, so that unbalance vibrations and rotor vibrations cannot occur, whereby trouble-free uninterrupted operation is always ensured.