Machine element or mechanism – Elements – Gear casings
Reexamination Certificate
1999-07-12
2001-02-20
Wright, Dirk (Department: 3681)
Machine element or mechanism
Elements
Gear casings
Reexamination Certificate
active
06189413
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to cast fabrications and more particularly to a cast fabrication having a cast portion and an insert of a material dissimilar to that of the cast portion.
2. Discussion
The design criteria for many types of housings typically includes considerations for the strength as well as the overall weight of the housing. This is particularly true for housings designed for use in highway vehicles, such as automobiles and trucks. One such component employed by such vehicles is a differential housing which supports the axles and drive shaft of a vehicle. Conventionally, differential housings have been formed out of lightweight materials, such as aluminum, to reconcile the competing design criteria of strength and weight.
While this strategy has provided satisfactory results with the engine and drive train combinations known in the art, the modern trend of vehicle manufacturers is toward vehicles having more power and torque. In some instances, conventional differential housings have not been satisfactorily integrated into such new vehicles with sufficient durability and failures have been noted in high-stress areas, primarily in the area where the drive shaft is supported for rotation within the differential housing. Attempts to improve the durability of the prior art differential housings have included various measures ranging from the fabrication of the differential housing from different materials having improved load carrying characteristics to the complete redesign of the axle system. Neither solution, however, has proven to be entirely satisfactory.
The use of a different material, such as cast iron, for example, entails not only a substantial weight penalty, but also substantial increases in the fabrication piece costs due to increased variability in the casting processes where the aluminum differential housing had been die cast. Additionally, conversion to a different material may necessitate the purchase of new equipment designed specifically to machine the new material. Examples of such equipment could range from new spindles, feed screws and tool resharpening equipment, to new machine tools designed to accommodate the specific characteristics of the material to be machined. In addition to being extremely costly, this approach may not be implementable in a given facility due to floor space limitations where production of conventional differential housings is still required.
The second alternative, redesigning the complete axle system, is also extremely costly, typically requiring vast resources to design, model and test the new axle system. Furthermore, the final design of many components is based on criteria established by “concurrent engineering” groups which utilize input from several disciplines, such as those associated with the casting, machining, assembly and servicing of the axle system. This additional criteria permits the component to be fabricated and serviced in a reliable and cost-effective manner. While such “concurrent engineering” efforts generally produce high quality, robust components, it is frequently difficult and costly to accommodate even the key fabrication and servicing concerns where the component is subjected to loads generating high stresses.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide an improved housing fabricated from two dissimilar materials.
It is a more specific object of the present invention to provide an improved housing which selectively employs an insert member of a material dissimilar to the primary material from which the housing is formed to provide the housing with one or more enhanced properties in a predetermined area.
An improved housing, particularly one for an automotive differential assembly, is provided. The housing of the present invention includes a cast portion formed from a first material and a preformed insert member formed from a second material which is cast into the cast portion. The insert member is strategically placed in an area of the housing to selectively enhance or alter the properties of the housing at that point. The insert member may be encased in a wall of the cast portion or may extend partially through a wall of cast portion depending upon the characteristics which are being enhanced or altered. The properties which may be enhanced or altered include, for example the strength, electric or thermal conductivity, magnetic potential, chemical compatibility or the coefficient of friction.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3726154 (1973-04-01), Diessner
patent: 3745854 (1973-07-01), Haag et al.
patent: 4008747 (1977-02-01), Devers et al.
patent: 5495885 (1996-03-01), Fowlkes et al.
patent: 5660156 (1997-08-01), Whitacre et al.
patent: 5678298 (1997-10-01), Colvin et al.
patent: 5713247 (1998-02-01), Skelton et al.
patent: 5730199 (1998-03-01), Shimmell
Kumashi Rajendra G.
Morse David M.
American Axle & Manufacturing Inc.
Harness & Dickey & Pierce P.L.C.
Wright Dirk
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