Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2000-03-31
2001-11-06
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S585000
Reexamination Certificate
active
06312161
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
This invention relates in general to a bearing assembly for axle journals and, more particularly, to a bearing assembly having an improved end cap and to the end cap itself.
One type of bearing (
FIG. 1
) which finds widespread use on the journals of rail car axles, has an outer race known as a double cup, an inner race composed of two cones arranged end to end, and tapered rollers arranged in two rows between the cup and cones, there being a separate row around each cone. The bearing actually forms part of a package or assembly which further includes a backing ring that seats against a fillet or shoulder at one end of a journal and an end cap that fits over the opposite end of the journal where it is secured with three cap screws that thread into the journal. The two cones fit around the journal between the backing ring and the end cap, and the cap screws clamp the cones firmly in place, with the clamping force being transferred through the end cap. Seals fit into the ends of the cup and establish fluid barriers along the cones in some assemblies and along seal wear rings in others, with those wear rings likewise being clamped up by the cap screws—there being one wear ring between the backing ring and inboard cone and the other between the end cap and the outboard cone. The two cones should be fitted to the journal with an interference fit and relatively heavy torque should be applied to the cap screws, all to minimize fretting along the journal.
More particularly, loose cones will themselves rotate around the journal, that is to say, the cylindrical surface of the journal will roll along the surfaces of the cone bores. This in itself produces fretting and hence, the need for the interference fit between the cones and the journal. But additional flexure develops as a consequence of the journal supporting the rail car and its load in the manner of a cantilever. This flexure produces minute movement axially between the journal and the cone bores, primarily at the bore of the inboard cone. A large clamping force exerted by the cap screws and transferred through the end cap minimizes this type of fretting, but does not eliminate it.
Indeed, the flexure produces wear along the faces where the end cap abuts a mating surface, whether that face be on the outboard cone or on a wear ring, and that wear leads to greater movement and more fretting. Cap screws can tolerate only a limited amount of torque, and furthermore, when turned down with excessive torque can distort the end cap. This may produce gaps which allow water to seep onto the surface of the journal and exacerbate the fretting that occurs. In this regard, this typical end cap has an axial wall which extends along the journal and a cross wall which is formed integral with the axial wall and extends over the end face of the journal. The cap screws pass through the cross wall, and when turned down urge that wall toward the end of the journal and the surrounding axial wall toward the cones of the bearing. The cross wall generally has uniform thickness (
FIG. 1
) and tends to deflect more in the region of the cap screws than elsewhere. This distortion transfers to the axial wall.
SUMMARY OF THE INVENTION
An end cap for retaining an antifriction bearing on the journal of an axle has an abutment face and a cross wall around which the abutment faces extends. The end cap is secured to the journal with cap screws which pass through bolt holes in its cross wall and thread into the journal. The cross wall of the end cap is thicker between the bolt holes than it is in the regions of the bolt holes. This produces a more uniform force along the abutment face when the cap screws are tightened. The invention also resides in a bearing assembly including the end cap.
REFERENCES:
patent: 2901299 (1959-08-01), Cramer et al.
patent: 3603655 (1971-09-01), Keller et al.
patent: 3790238 (1974-02-01), Otto
patent: 3833277 (1974-09-01), Jones
patent: 4819949 (1989-04-01), Otto
patent: 5462367 (1995-10-01), Davidson et al.
patent: 54135948-A (1979-10-01), None
Hannon Thomas R.
Polster Lieder Woodruff & Lucchesi L.C.
The Timken Company
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