Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-08-11
2001-02-06
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S202000, C384S206000
Reexamination Certificate
active
06183136
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to sleeve bearing assemblies for fractional or sub-fractional horsepower electric motors and more particularly to self-aligning, floating bearings for use in such motors.
It is known to use sleeve bearings to support the rotating shaft of fractional and sub-fractional horsepower motors. The sleeve bearings typically include a tubular bore for accepting and supporting the shaft. To compensate for variations in shaft angle during rotation, self-aligning floating sleeve bearings are used so that the tubular bore can constantly align itself with the shaft, minimizing wear on the shaft, bearing, and motor.
While the floating sleeve bearing must be free to align itself with the shaft, the bearing must be restricted from rotating with the shaft. One common design incorporates a bearing with a spherical exterior that is seated in a spherical bearing pocket. To prevent rotation of the bearing, a spring force is applied to the exterior of the bearing, causing friction between the bearing and the pocket. The spring force applied creates enough friction to prevent rotation of the bearing in the pocket, while still allowing the bearing to align itself with the shaft.
Another common design involves cutting grooves into the exterior of the spherical bearing and aligning those grooves with ribs in the bearing seat. The bearing is thus free to align itself with the shaft, while the ribs and grooves prevent rotation.
Yet another design involves machining flat portions on the exterior of an otherwise round or spherical bearing and placing the bearing in a seat designed to engage the flat portions and prevent rotation. Alternatively, the bearing could be press-fit into the seat such that during the press-fitting, the interference between the bearing and the seat deforms the bearing, creating flat portions that engage the seat and anti-rotate the bearing. An example of this design is disclosed in U.S. Pat. No. 4,368,931 issued Jan. 18, 1983.
SUMMARY OF THE INVENTION
The above-mentioned designs are costly to manufacture due to the intricate machining of grooves, ribs, and flats. Assembly is also costly as it involves difficult calculations and installments for delicate spring settings, difficult groove/rib alignments, or difficult press-fit operations that often require special machinery. Furthermore, some of the known methods of anti-rotation unduly restrict the optimal self-alignment of the bearing.
The present invention alleviates the problems commonly associated with the current designs by providing an improved floating bearing that freely aligns with the rotating shaft, but does not rotate with the shaft. The design of the present invention makes it more cost effective to manufacture and assemble. Furthermore, the present invention provides improved bearing performance which, in turn, improves the performance of the motor.
Specifically, the invention provides a floating sleeve bearing assembly including a bearing having a plurality of cylindrical outer surface portions that are centered on respective axes which are substantially perpendicular to the axis of rotation and which all lie in the same plane substantially perpendicular to the axis of rotation. Preferably, the bearing has six such surfaces, with three sets of diametrically opposed surfaces, the two surfaces in each set being centered on the same axis. The surfaces are evenly spaced around the bearing, so that each has an angular extent of sixty degrees (about the rotational axis).
The sleeve bearing assembly also includes a bearing support bracket having a bearing socket defined by a plurality of circuitously spaced resilient projections extending generally parallel to the rotational axis (the projections ideally are exactly parallel to the rotational axis if the bracket is properly mounted, but in practice are likely to be slightly misaligned). Preferably, the number of projections corresponds to the number of cylindrical outer surface portions on the bearing, with each projection engaging a respective bearing surface.
Each of the projections preferably has an inwardly facing surface which is convex at the intersection of the surface with a plane substantially perpendicular to the axis. The inwardly facing surface is also preferably concave at the intersection of the surface with a plane including the bracket axis. Even more particularly, each inwardly facing surface preferably intersects the plane including the bracket axis along a circle centered on the axis of the mating bearing cylindrical surface portion. Thus, the inwardly facing surface of the bracket and the mating cylindrical surface portion of the bearing engage along a portion of the circle. The bracket projections engage the cylindrical outer surface portions so as to allow angular movement of the bearing within the socket to compensate for axial misalignment between the axis of rotation and the bracket, while at the same time substantially preventing rotation of the bearing about the axis of rotation.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.
REFERENCES:
patent: 2767034 (1956-10-01), McCloskey
patent: 2996308 (1961-08-01), Cislo
patent: 3273948 (1966-09-01), Hoddy et al.
patent: 3325849 (1967-06-01), Waters
patent: 3539234 (1970-11-01), Rapata
patent: 3820861 (1974-06-01), Strang
patent: 4227826 (1980-10-01), Conrad
patent: 4318573 (1982-03-01), Hamman
patent: 4368931 (1983-01-01), Casler et al.
patent: 4986675 (1991-01-01), Dye et al.
patent: 5405199 (1995-04-01), Mabuchi et al.
patent: 5484211 (1996-01-01), Uthoff
A. O. Smith Corporation
Hannon Thomas R.
Michael & Best & Friedrich LLP
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