Metal fusion bonding – Process – With supplementary mechanical joining
Reexamination Certificate
2000-01-18
2001-07-03
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
With supplementary mechanical joining
C228S134000, C228S165000, C228S139000, C228S154000
Reexamination Certificate
active
06253989
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improved weld retention for press fit joints.
Press fit joints are utilized in many applications. In a typical press fit joint, an outer part has a bore with an inner diameter slightly less than the outer diameter of an inner part. The inner part is forced into the bore, and the larger diameter of the inner part holds the inner part within the outer part.
However, the press fit alone is inadequate for many applications. Thus, press fit joints are often augmented by a secondary locking mechanism. The ability to hold a press fit joint is limited by the size, material and certain manufacturing characteristics of the joint parts. This is particularly true in structural applications where there may be stresses upon the inner and outer parts.
The selection of a particular type of secondary locking mechanism is based in large part on the materials of the inner and outer parts. If both the inner and outer parts are of materials which can provide an adequate weld joint, then a weld may be utilized as the secondary locking mechanism. However, if one or both of the parts is iron, then a dowel pin is often utilized. Iron is often not capable of providing an adequate weld joint. Dowel pins extend through the outer parts and into the inner part to provide the secondary locking mechanism. However, dowel pins require machining after assembly, and thus set high manufacturing costs.
If the inner part is iron and the outer part is steel, then a puddle weld may be utilized. A puddle weld provides a bond weld on the steel part, while the weld integrity on the outer iron member is not as important. Instead, in the iron part, the puddle weld merely provides a stop. In such an application, the puddle weld provides a shear pin which does not typically bond to the outer iron member.
However, a reliable cost effective secondary locking mechanism has not been provided when both of the press fit parts are iron.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a puddle weld is provided wherein the inner part is provided with a dimple to receive the puddle weld. The dimple is formed of a dimension which is greater than a dimension of a hole in the outer part. The puddle weld thus provides a locking member which locks into the dimple, securing the inner and outer parts together. This is true even though the puddle weld material may not provide a weld bond to either part. The greater size of the weld material within the dimple relative to the hole will provide the locking mechanism.
The puddle weld is preferably provided in a generally circular dimple such that it is greater in diameter than the hole through the outer part. It is preferred that the inner part is first forced into the outer part, and the puddle weld material is then moved into the dimple through the hole. The material is then caused to become fluent filling the dimple, and at least partially filling the hole. The puddle weld material then hardens, locking the two together.
While a single puddle weld of this sort may be utilized as the a secondary locking mechanism, plural circumferentially spaced puddle welds may also utilized.
One particular application for this invention is in axle housings wherein relatively large cast iron members are being held together.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
REFERENCES:
patent: 4205219 (1980-05-01), Snell
patent: 4265388 (1981-05-01), Takahashi et al.
patent: 4360961 (1982-11-01), Chlebowski
patent: 5169054 (1992-12-01), Matsui et al.
patent: 5348211 (1994-09-01), White et al.
ASM Handbook: vol. 6 Welding, Brazing, and Soldering. Alia. p. 712-713. (no date available).
Carlson & Gaskey & Olds
Dunn Tom
Johnson Jonathan
Meritor Heavy Vehicle Systems LLC
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