Bearings – Rotary bearing – Plain bearing
Patent
1997-04-25
1998-08-18
Hannon, Thomas R.
Bearings
Rotary bearing
Plain bearing
384117, F16C 1703
Patent
active
057950776
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a tilting pad journal bearing for supporting a rotatable shaft.
2. State of the Art
Tilting pad journal bearings are widely used for supporting rotating shafts in high speed rotary machines, in order to minimise effects of shaft vibrations, and uneven shaft loading.
Traditionally such bearings have used hard metallic pivots, pivotal inserts or spring pivots for mounting bearing pads in the bearing housing (for example, U.S. Pat. No. 4,039,228 discloses a tilting pad journal bearing having hard pivotal inserts).
Disadvantages exist with both of the above methods of pad mounting, since a hard pivot tends to amplify shaft vibrations through the bearing housing and into the supporting structure, and spring pivots provide unsatisfactory bearing conformability. Additionally high stresses can occur due to point loading at the pivot point which reduces the life of the bearing, and increases the possibility of bearing failure due to fatigue.
SUMMARY OF THE INVENTION
According to the present invention there is provided a tilting pad journal bearing for supporting a shaft, which bearing comprises an annular housing locatable around said shaft, a plurality of movable bearing members, and a plurality of inwardly projecting pivot members located in said housing, each being disposed contiguous with a respective bearing member. The bearing members each have an arcuate inner bearing surface and an opposed arcuate outer surface, and are disposed around said housing such that in use said inner bearing surfaces make bearing contact with said shaft, or a component attached thereto. Movement restricting means are provided integral with or attached to said housing and arranged to restrict the circumferential movement of said bearing members relative to said housing. The inwardly projecting pivot members are either formed of a polymer material and/or have a concave pivot surface portion arranged to complementarily abut said outer arcuate surface of said bearing member such that each bearing member is pivotable about a respective pivot surface portion.
The provision of concave pivot surface portions and the use of a polymer material for the pivot members alleviates the abovementioned disadvantages of known bearings.
It is preferred that each of said pivot members is in the form of an elongate member, having its longitudinal axis substantially parallel to said shaft. It is further preferred that the pivot members are of substantially circular cross-section. Preferably the pivot members are of an engineering polymer material, such as a polytheretherketone (PEEK) or the like.
It is preferred that the movement restricting means comprises a plurality of stop members (preferably elongate pins) fixable in the housing adjacent the opposed ends of each bearing member, the longitudinal axis of each of the pins preferably being arranged substantially parallel to the shaft.
Preferably the bearing members are of a ceramic material, or at least provided with a ceramics bearing surface.
Preferably bearing contact is made with a component attached to the shaft, which component is preferably an annular sleeve having an interference fit with the shaft. Advantageously the component is of a ceramic material, or at least provided with a bearing contacting surface of a ceramic material.
It is preferred that the bearing members are regularly spaced around the housing. Advantageously at least four, and more preferably six, bearing members are provided around the housing.
In use, the bearing according to the invention may be air or gas lubricated, or hydrodynamically lubricated with a suitable lubricant, which lubricant may be water, oil or the like.
The invention will be further described in a particular embodiment, by way of example only, with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional end view through a shaft supported by a bearing according to the invention; and
FIG. 2 is a sectional view along X--X of the bearing
REFERENCES:
patent: 3318643 (1967-05-01), Pilarczyk et al.
patent: 3370334 (1968-02-01), Pilarczyk et al.
patent: 4039228 (1977-08-01), Repose et al.
patent: 4268094 (1981-05-01), Greene
patent: 4515486 (1985-05-01), Ide
patent: 4927275 (1990-05-01), Lawson
Gordon David P.
Hannon Thomas R.
Jacobson David S.
Welsh Innovations Limited
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