Casting

Details Casting Casting

1996-07-15

1998-01-13

Footland, Lenard A.

Bearings

Rotary bearing

Plain bearing

384286, F16C 1702

Patent

active

057071560

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention pertains to castings and more particularly relate to castings having an opening extending in the axial direction and which is used to hold a shaft or axle.


BACKGROUND OF THE INVENTION

Cast elements of this kind are known. They are produced both from metallic materials and from plastics. In the former case, pressure casting methods are used for their manufacture, and in the second case, injection molding methods are used. In these methods, nondestructive molds are used, which necessitate a relatively simple casting structure. Above all, undercuts must be prevented. In order to preserve the openings in the material for shafts and axles, core pieces are installed. The shape of the core pieces must be simple so that they can be easily removed from the cast element after the casting process.
Cylindrical core pieces cannot be used since the core piece can only be withdrawn from the cast element with difficulty. Between the surface of the cylindrical core piece and the inside wall of the cast element, considerable frictional forces will occur when pulling out the core piece. For this reason it is not possible to create a cast element with an opening for a shaft that is seated in the cast element at two locations from friction bearings with the same diameter.
In these cases a stepped shaft design has been substituted, and in the opening of the cast element, two bearings with different diameters are used. The transition region between the bearings is shaped conically, so that the corresponding conically shaped core piece can be easily detached from the cast element. With a gentle tug in the axial direction, the conical surface of the core loosens from the conically shaped inside surface of the cast element.
But this procedure necessitates the production of a stepped shaft, and this is associated with increased costs. For some applications, even a minor increase in cost is not acceptable.
Therefore the invention solves the problem of designing a cast element of the aforementioned type so that a shaft with uniform cross section can be seated, whereby the core which is needed for casting of the cast element can be easily detached from the east element after the casting process.
In this regard the invention proposes that a cast element of the aforementioned type features friction bearings which are interrupted in the perimeter direction. Preferably each friction bearing consists of several mutually spaced slide elements which each consists of a cylindrical segment, and the cylindrical segments of one bearing are offset to the cylindrical segments of the other bearing. The inside surfaces of the cylindrical segments form the friction bearing for the shaft and/or the axle, whereby the inside surfaces of both friction bearings are located on circles that have the same diameter.
The offset positioning of the cylindrical segments of the two bearings makes it possible for the region between the bearings to be structured so that a correspondingly shaped core piece can easily be detached from the cast element.
In this case it is necessary that the angle regions in which the cylindrical segments are found do not overlap. The inside of the opening in the region between the bearings is now divided into perimeter segments according to the angular organization of the cylindrical segments. In this case each section runs in an axial direction, tapered to the side on which a bearing ring segment is located in the particular sector.
Expressed differently, a sector of the inside of the intermediate region in the opening ends on one side in an opening between two bearing segments and on the other side in a bearing segment. On one side, the distance of the sector to the bearing axis corresponds to the diameter of the opening between two bearing segments, whereas on the other side, the distance of the sector to the bearing axis corresponds to the diameter of the inside surface of a cylindrical segment.
Preferably, on the latter side, the distance of the sector to the bearing axis is somewhat greater than t

REFERENCES:
patent: 3873056 (1975-03-01), Parkinson
patent: 4208075 (1980-06-01), Templeton
patent: 4971459 (1990-11-01), McKenna

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