Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-07-14
2001-11-13
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S215000
Reexamination Certificate
active
06315453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid lubricated radial sliding bearing comprising a bearing sleeve of wear-resistant bearing material which is elastically fastened in an outer part and which together with a shaft part forms an elastic journalling which can follow thermal heat expansions and inclined positions of the shaft to a limited extent.
2. Description of the Prior Art
In EP-B-0 204 235 a bearing with a bearing sleeve of silicon carbide is shown in which a further shaft sleeve runs, which rotates with the shaft. The bearing sleeve is outwardly covered over by an elastic rubber hose, which additionally engages into grooves on its jacket surface and is fastened at the outside with an adhesive bonding in a housing bore in the housing. The elasticity of the intermediate layer of rubber is intended to prevent over-stressing due to bending deflections of the shaft, thrusts or inclined positions. Due to the use of rubber and an adhesive bonding, an application for all kinds of water is envisaged. The use of rubber restricts the range of application of a bearing of this kind. Solvents and aging can strongly modify the elastic properties of rubber; softening, hardening or becoming brittle can take place.
A further construction is shown by the CERATEC company (Technical Ceramics BV, P. O. Box 57, 4190 CB Geldermalsen, The Netherlands) in its brochure of May 1997 for compact sliding bearings. Shown are ceramic sliding pairings in which ceramic bearing sleeves and shaft sleeves are in each case embedded in a support ring. In the jacket surface of the support rings, U-shaped slits are provided and U-shaped lobes are cut free at which the ceramic bearing sleeves and shaft sleeves lie in contact in order to compensate different thermal expansions. The cutting free of the U-shaped lobes must be done with spark-erosive wire cutting or spark-erosively with electrodes of thin U-shaped cross-section, which in both cases is a time consuming and expensive treatment. The length of the slits to be produced by spark erosion is substantially greater than the bearing circumference. Methods other than spark erosion do not make the manufacture of these slits less expensive. Furthermore, direct pressure peaks are present at the ceramic bearing sleeves and shaft sleeves which alternate with pressure-less zones, and at positions of greater inclination diagonally displaced pressure points arise at the ceramic sleeves.
SUMMARY OF THE INVENTION
The object of the invention is to achieve an elastic bearing suspension in which the stiffness of the suspension can be predetermined and remains unchanged. The bearing material is fastened in a bearing ring; wherein the outer part is formed in a single part to a resilient ring and a support ring, with the resilient ring being braced at the support ring by bridges which are distributed over its periphery and have resilient support surfaces which are directed inwardly and at which the bearing ring lies in contact under a bias force.
This arrangement has the advantage that a sufficiently elastic bearing suspension is achieved with metallic materials and brittle bearing materials such as ceramics, hard materials and, for example, silicon carbide can be used. Bearings of this kind are advantageous in multiply journalled shafts such as, for example, in vertical pumps and in single or multiple stage centrifugal pumps. With this construction, an elastic bearing suspension can be achieved both at high temperatures and at low temperatures.
In a resilient ring which is closed uninterruptedly, drawing tensions can be produced for the clamping in position of the bearing ring.
The radial forces which are produced via these drawing tensions cancel out over the periphery of the bearing ring so that a controlled radial stiffness of the bearing arises in spite of a large force transmission between the resilient ring and the bearing ring. The arrangement and length of the bridges between the resilient ring and the support ring has an influence on the manufacture and the space requirement. The separating slits between the resilient ring and the support ring should be narrow in order not to require too much space. Narrow slits also increase the passive safety in the event of an accident when the resilient ring strikes against the support ring in the presence of excessive forces. Since the length of all the slits still always turns out to be less than the bearing circumference, these slits can still be produced fairly economically by means of spark erosion.
With an axial displacement in the support ring axially arranged bridges can be produced; and the slits can be manufactured economically by normal turning and milling operations which interpenetrate in the region of the slits. The bearing ring, which accommodates the bearing material, can be executed in different manners. The bearing material, for example a hard material, ceramic or silicon carbide, can be shrunk in. The bearing material can, however, also be applied as a wear resistant layer, for example, in the plasma spraying process. The bearing ring is anchored in the resilient ring with a predetermined bias force. For safety, a rotational securing and an axial securing can be provided between the bearing ring and the outer part. For the simplification of the assembly, the jacket of the bearing ring can be formed as a conical surface and the support surfaces can be formed at the resilient ring as corresponding counter-surfaces in order to produce the bias force of the connection through axial pressing in along the conical surfaces. With a separate flange, the securing against rotation of the bearing ring can also be used as an axial securing of the conical seat. If the outer part is designed as a built in flange which has standard dimensions to the housing, then constructionally similar bearings with different stiffnesses for the suspension of the bearing shell can be manufactured and installed. Metals and metal alloys are provided as a material for the outer part. Other materials are conceivable in so far as they have sufficient strength and elasticity.
REFERENCES:
patent: 153952 (1903-10-01), None
patent: 1266570 (1968-04-01), None
patent: 3613776A1 (1987-10-01), None
patent: 3728039A1 (1989-03-01), None
patent: 0204235B1 (1986-12-01), None
patent: WO 93/22575 (1993-11-01), None
Footland Lenard A.
Sulzer Pumpen AG
Townsend and Townsend / and Crew LLP
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