GB1566520A - Rotating shafts with lined bearings - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO ROTATING SHAFTS WITH LINED BEARINGS (71) We, CREUSOT-LOIRE, a French Corporate Body of 42, rue d'Anjou, 75008 Paris, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention is concerned with the protection of a rotatable shaft supported in lined bearings.

Rotary machines usually consist of a rotor with impellers and blades which rotates in a stator. The rotor is supported on bearings fitted in bearing housings at either end of the stator.

The supporting bearings are generally supplied with oil under pressure by a mechanical or electrical pump. Safety devices are provided to prevent the oil pressure falling below a predetermined value, such that if the pressure drops to an abnormally low value, the safety devices act and close off the inlet devices, so stopping the machine.

It can happen that the machine must be stopped without any oil being present, in spite of the operation of the safety devices.

The rotor then slows from its maximum speed to zero speed over a period which can be as long as several minutes, during which time the shell bearings are not lubricated.

During this time, the linings of the bearings get hot, and their temperature may rise high enough to soften the lining or even melt it; the rotor then drops until it comes into contact with metal parts of the stator, causing abnormal heating and often severe scoring; there is a risk that the rotor will be seriously damaged.

In accordance with the invention there is provided a rotatable assembly comprising a shaft supported in bearings provided with low friction linings, and a protective device associated with each bearing, each device comprising supplementary support means providing a support surface which faces a portion of the shaft and is offset downwardly relative to said portion of ther shaft by a distance e which is less than the combined thicknesses of the low friction lining and the film of lubricating oil which is established in use.

In one embodiment of the invention, each support means includes at least two rollers mounted on fixed spindles which are spaced from one another and symmetrical relative to the vertical plane which passes through the axis of the shaft, the roller surfaces being at the distance e from the outer surface of the shaft.

In another embodiment, each support means comprises a body having a sliding surface of low friction material and of part.

cylindrical shape, the diameter of the surface being at least equal to that of the shaft and the surface being offset downwardly relative to the surface of the shaft by the distance e.

The invention will be more fully understood from the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through the shaft of the rotor of a rotary machine fitted with an embodiment of a protective device in accordance with the invention; Figure 2 is a transverse cross-section on the line II--II in Figure 1, and Figure 3 is a transverse cross-section through another embodiment of a protective device.

Figure 1 shows one of the bearing housings 1 of the rotor 2 of a rotary machine which has its shaft 20 supported on bearings 10 mounted in the bearing housings. A low friction lining 11 lies between the shaft and the bearing. The bearing housing forms a casing which is closed by seals 12 and inside which oil flows, the oil being delivered through a conduit 13 and exhausted at the bottom through an outlet conduit 14.

A protective device is provided which comprises a semi-circular member 3 inside and concentric with the bearing housing 1, on which are mounted two ball or roller bearings 4 arranged with their axes parallel to that of the rotor. These bearings are preferably situated at 450 on either side of the vertical plane which passes through he axis of the rotor, and are positioned so that there is a clearance between them and the rotor, their bearing faces being at a distance e from the surface of the shaft which is less than the combined thicknesses of the low friction lining and the lubricating oil film.

In normal operation, when the bearings of the shaft are in good condition and properly lubricated, the bearings 4 are idle.

However, following an incident as discussed above where the rotor continues to rotate in the absence of oil, as the low friction lining begins to melt, the rotor 2 drops and the portion 21 comes into contact with and is supported by the two bearings 4, which prevents the rotor shaft rubbing on the metal part of the shell bearing and the active parts of the rotor from coming into contact with the corresponding parts of the stator and thereby becoming damaged.

The clearance between the bearings and the rotor is determined to take account of the thicknesses of the oil film and the low friction lining and the degree of play permitted between the rotor and stator in other parts of the machine.

In another embodiment, the protective device described above is replaced by a supplementary support surface offset downwardly to give the required clearance and on which the shaft can rest without requiring any lubricating oil, to reduce the risk of damage to the rotor.

This support surface might consist, as shown in Figure 3, of the surface of a fixed support block 5 made of a low friction material such as carbon. The support surface 50 may, as shown, have the shape of a cylindrical sector and be located under part of the shaft, with a diameter slightly greater than that of said part of the shaft, with a clearance e equal to that discussed above. The supplementary support surface may instead have the same diameter as the shaft. being merely offset downwardly to give the required clearance e.

There are thus provided protective devices which will protect the shaft if for any reason the machine must be stopped in the absence of lubricating oil.

WHAT WE CLAIM IS: 1. An assembly comprising a shaft rotatably supported in bearings provided with low friction linings, and a protective device associated with each bearing, each device comprising supplementary support means providing a surface which faces a portion of the shaft and is offset downwardly relative to said portion of the shaft by a distance e which is less than the combined thicknesses of the low friction lining and the film of lubricating oil which is established in use.

2. A rotatable assembly according to claim 1, wherein each support means includes at least two rollers mounted on fixed spindles which are spaced from one another and symmetrical relative to the vertical plane which passes through the axis of the shaft, the roller surfaces being at the distance e from the outer surface of the shaft.

3. A rotatable assembly according to claim 1, wherein each support means comprises a body having a sliding surface of low friction material and of part-cylindrical shape, the diameter of the surface being at least equal to that of the shaft and the surface being offset downwardly relative to the surface of the shaft by the distance e.

4. A rotatable assembly according to claim 1, wherein each support means comprises, beneath the shaft, a body having a sliding surface of low friction material and having the shape of a cylindrical sector coaxial with the shaft and of a diameter greater than that of the shaft.

5. A rotatable assembly according to claim 2, wherein the spindles of the rollers are mounted on a member attached to the bearing housing of the respective shell bearing.

6. A rotatable assembly according to either claim 3 or claim 4, wherein the sliding surface is of graphite.

7. A rotatable assembly substantially as herein described with refernece to Figures 1 and 2 or Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. and concentric with the bearing housing 1, on which are mounted two ball or roller bearings 4 arranged with their axes parallel to that of the rotor. These bearings are preferably situated at 450 on either side of the vertical plane which passes through he axis of the rotor, and are positioned so that there is a clearance between them and the rotor, their bearing faces being at a distance e from the surface of the shaft which is less than the combined thicknesses of the low friction lining and the lubricating oil film. In normal operation, when the bearings of the shaft are in good condition and properly lubricated, the bearings 4 are idle. However, following an incident as discussed above where the rotor continues to rotate in the absence of oil, as the low friction lining begins to melt, the rotor 2 drops and the portion 21 comes into contact with and is supported by the two bearings 4, which prevents the rotor shaft rubbing on the metal part of the shell bearing and the active parts of the rotor from coming into contact with the corresponding parts of the stator and thereby becoming damaged. The clearance between the bearings and the rotor is determined to take account of the thicknesses of the oil film and the low friction lining and the degree of play permitted between the rotor and stator in other parts of the machine. In another embodiment, the protective device described above is replaced by a supplementary support surface offset downwardly to give the required clearance and on which the shaft can rest without requiring any lubricating oil, to reduce the risk of damage to the rotor. This support surface might consist, as shown in Figure 3, of the surface of a fixed support block 5 made of a low friction material such as carbon. The support surface 50 may, as shown, have the shape of a cylindrical sector and be located under part of the shaft, with a diameter slightly greater than that of said part of the shaft, with a clearance e equal to that discussed above. The supplementary support surface may instead have the same diameter as the shaft. being merely offset downwardly to give the required clearance e. There are thus provided protective devices which will protect the shaft if for any reason the machine must be stopped in the absence of lubricating oil. WHAT WE CLAIM IS:

1. An assembly comprising a shaft rotatably supported in bearings provided with low friction linings, and a protective device associated with each bearing, each device comprising supplementary support means providing a surface which faces a portion of the shaft and is offset downwardly relative to said portion of the shaft by a distance e which is less than the combined thicknesses of the low friction lining and the film of lubricating oil which is established in use.

2. A rotatable assembly according to claim 1, wherein each support means includes at least two rollers mounted on fixed spindles which are spaced from one another and symmetrical relative to the vertical plane which passes through the axis of the shaft, the roller surfaces being at the distance e from the outer surface of the shaft.

3. A rotatable assembly according to claim 1, wherein each support means comprises a body having a sliding surface of low friction material and of part-cylindrical shape, the diameter of the surface being at least equal to that of the shaft and the surface being offset downwardly relative to the surface of the shaft by the distance e.

4. A rotatable assembly according to claim 1, wherein each support means comprises, beneath the shaft, a body having a sliding surface of low friction material and having the shape of a cylindrical sector coaxial with the shaft and of a diameter greater than that of the shaft.

5. A rotatable assembly according to claim 2, wherein the spindles of the rollers are mounted on a member attached to the bearing housing of the respective shell bearing.

6. A rotatable assembly according to either claim 3 or claim 4, wherein the sliding surface is of graphite.

7. A rotatable assembly substantially as herein described with refernece to Figures 1 and 2 or Figure 3 of the accompanying drawings.