Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1999-06-29
2001-01-09
Marmor, Charles A (Department: 3681)
Bearings
Rotary bearing
Antifriction bearing
Reexamination Certificate
active
06170994
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a cylindrical roller bearing which allows the components to be reassembled more efficiently after they have been separately mounted in a machine. The invention is an improvement to existing roller bearings.
BACKGROUND OF THE INVENTION
There are four basic types of radial rolling element bearings. There is the ball, spherical roller, tapered roller, and cylindrical roller. They are characterized by the shape of their rolling elements. The first two types are non-separable which means that they do not come apart in normal handling and machine assembly or disassembly. The latter two types are easily separable into an inner component and an outer component. For the user, being able to handle separate components makes it easier to tightly fit an inner race to a shaft and an outer race into a housing. The bearing components are then mated when the whole machine is assembled. For tapered roller bearings the open nature of a cup or outer race makes it very easy to assemble the machine and its bearings. Cylindrical roller bearings are somewhat more difficult to mate, especially when the bearings are large and the shaft and housing assemblies are heavy and cannot be lifted or manipulated by hand. In the design of a cylindrical roller bearing the internal clearance between a separable race and a sub-assembly consisting of the other race and rollers is only a few thousandths of an inch. A cage of the bearing functions to hold all of the rollers in the sub-assembly. Necessary clearances allow the rollers to drop as much as {fraction (1/16)}th to {fraction (3/32)}'s of an inch. For a typical and most commonly used style of roller bearings (designations “AD” and/or “NU”) the “hole” which is the circumscribed diameter under the roller, must permit the inner race outside diameter to pass through it. The “hole” formed by the assembly is significantly smaller than the outside diameter of the inner race due to the previously described roller drop. It has been a common practice for decades to point the ends of inner races so that they will enter this “hole” and spread the rollers outward to allow completion of the assembly. The traditional method of pointing the inner race outside diameter over the years has been to machine a shallow angle or a chamfer on one or both ends of the inner race. This is done in the first step of manufacturing the part when the raw material is turned in a lathe to its approximate finished size and shape. The part is then heat treated to become very hard. Lathe turning would be difficult, so the part must be ground to its final dimensions. If the chamfer is properly designed for the bearing and stock removal, then its original machine surface can be left intact and will not require finished grinding, which is an additional expense. Chamfers are by definition a truncated conical surface of a specified single angle. Their simplicity makes them easy to lathe turn, or machine, particularly with older manual or mechanical automatic lathes, which has been performed by the prior art. In some special instances, prior art has changed from a single, constant angle chamfer to a two angle chamfer, approximately 20° and 30°. The prior art also has incorporated a small blend radius where the chamfer intersects a bearing end face. The major deficiency of the prior art design is that it has sharp corners where the two chamfers intersect and where the 20° chamfer intersects the outside diameter surface. The roller ends tend to catch on these breaks or sharp corners and halt the assembly of the roller bearing with the race and scratch the rollers and the race in the process. Various manufacturers have been putting radii and other corner shapes on boundary comers of the bearings and other components for many years. These outside comers have a different function from the lead-in chamfers and are not applicable to the solution addressed by the existing invention.
SUMMARY OF THE INVENTION
The invention has significant advantages over the existing structures. The present invention improves a method of configuring a lead-in bevel on bearing races. The lead-in configuration or bevel has a shape which allows more drop below the inner race outside diameter surface. This provides a smaller entrance diameter or point to enable easier entry into the inside “hole” which is defined by a diameter circumscribed by the rollers. The design of the invention reduces chances of scoring and scratching the precision surfaces. The shape of the inner race can be generated by a design so that it can economically be applied with existing manufacturing equipment.
One aspect of the design of the invention is the intrinsic consideration of stock removal and tolerances between the lathe turn dimensions and finished ground dimensions. This consideration incorporates anticipated distortions which occur in heat-treating. Specifically, the parts go out of round and out of flat between machining and grinding, which means that some portions of the end faces and the outside diameter will have more material removed than others. This affects the final dimensions of the bevel and which will vary somewhat around the part's axis. The design of the bevel seeks to minimize this variation and controls the minimum and maximum limits of its final dimensions.
The improved design bevel blends a rudimentary chamfer to the inner race outside diameter with a curved surface. The design provides a new combination of a straight line with tangential radii.
I provide a cylindrical roller bearing having an inner race and an outer race and a plurality of rollers between the races in which the improvement comprises a bevel on the inner race and formed by a curved surface connecting an end face of the inner race to an outside diameter surface which serves as a rollerpath of the inner race. The curved surface is a non-linear shape, having a slope that constantly changes as one advances along the contour of the curved surface. The curved surface can be an arc. The curved surface excludes approximations by flat surfaces of less than four individual or separate flat surfaces.
I also provide a cylindrical roller bearing having an inner race and an outer race and a plurality of rollers between the races in which the improvement comprises a bevel on the outer race and formed by a curved surface connecting an end face of the outer race to the inside diameter surface which serves as a rollerpath of the outer race. The curved surface also follows all of the contours as described above for the inner race.
REFERENCES:
patent: 1865796 (1932-07-01), Seifarth
patent: 4336996 (1982-06-01), Grandel
patent: 5669719 (1997-09-01), Kinno et al.
patent: 1102201 (1955-10-01), None
American Roller Bearing Company
Marmor Charles A
Parekh Ankur
Paul A. Beck & Associates
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