Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
2000-02-24
2001-05-29
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
C228S114500, C029S514000, C029S525130
Reexamination Certificate
active
06237834
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to vehicle brake shoe assemblies where the web members and the brake shoe table are joined by a linear friction welding process.
Modern vehicles require precisely made brake shoe assemblies. Typically, brake shoes are made with a multiple step, relatively complex and expensive process. For example, the brake shoe table is roll formed to a prescribed curvature. Two webs are then aligned and projection welded to the table. After the webs are joined to the table, appropriate slots are cut or formed in the webs to make the brake shoe workable with the remainder of a brake assembly. The slots in the webs must be heat treated to achieve a high hardness. Heat treating the webs is more difficult after they have been joined to the table. Previously, however, it was not possible to perform the hardening process before joining the webs to the table because of the requirements of providing a precisely aligned set of slots in the webs, which would be distorted during the typical process of joining the webs to the table.
There are several disadvantages and drawbacks to the usual method of assembling a brake shoe. Performing the heat treatment step after assembling the webs to the shoe as discussed above is less controlled than is desirable and adds an expensive step to the assembly process. Projection welding the webs to the table also is undesirably expensive because it requires complex, energy intensive and high maintenance machinery. It is therefore desirable to replace current brake shoe assembly process technology with a more reliable, flexible procedure.
This invention addresses the needs and shortcomings presented by conventional processes. This invention provides a more precise, less expensive and less labor intensive method of assembling brake shoes compared to the prior art. The method of this invention includes using a linear friction welding process to join the webs to the brake shoe table.
SUMMARY OF THE INVENTION
In general terms, the method associated with this invention for making a vehicle brake shoe that has two web members and a brake shoe table member is performed in four basic steps. First, two web members are aligned in a preselected alignment relative to each other. Second, the brake shoe table member is aligned with the two web members such that a portion of the brake shoe table contacts a portion of each web. The brake shoe table is held in contact with the web members and the web members are maintained in their preselected alignment while the table and the webs are moved relative to each other. This movement, while the webs are held in contact with the table, causes an increase in temperature in the contacting portions of the table and the web members. Once a sufficient temperature increase occurs, and the table member is still pressed against the web members, the web members and the table member become fixedly joined together.
In a preferred embodiment each web member has a number of projections that contact the table member at the start of the assembly process. The relative movement between the table and the web members causes the temperature of the projections to increase, but that temperature is not raised to the melting point of the metal of the web members. After a sufficient temperature increase has occurred, the table member is pressed against the web members using a force greater than the force to maintain them in alignment during the relative movement. This greater force causes the projections to be deformed in a manner that the table becomes welded to the webs at the location of each of the projections.
In the preferred embodiment, the table and the web members are generally arcuate. Each web member has a generally arcuate edge from which the projections extend outwardly. When the assembly process is complete, the brake shoe table rests against the entirety of the arcuate surface on the web members.
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Mahoney Murray
Naerheim Yngve
Carlson & Gaskey & Olds
Cooke Colleen
Meritor Heavy Vehicle Systems LLC
Ryan Patrick
LandOfFree
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