Brakes – Elements – Brake wheels
Reexamination Certificate
2000-02-17
2001-09-18
Graham, Matthew C. (Department: 3613)
Brakes
Elements
Brake wheels
C188S25100R
Reexamination Certificate
active
06290032
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a friction-wear aluminum part and an associated method. More particularly, the invention relates to vehicle parts, such as brake rotors, brake drums, flywheels and the like which have at least a portion of their wear surface coated with a friction-wear coating. On a preferred basis, the brake parts and flywheels themselves are also made of aluminum alloys.
“Light-weighting” of vehicles, such as automobiles, is a process of substituting lighter materials, such as aluminum, for heavier materials, such as steel. Some of the obvious advantages of light-weighting are that fuel economy is improved and that less powerful engines are needed to propel such vehicles.
There are several cast iron or steel parts in a vehicle, including brake rotors, brake drums and flywheels. One light-weighting solution, therefore, would be to substitute a light-weight aluminum brake rotor for its heavier cast iron counterpart. However, attempts to make this substitution have not met with success because aluminum brake rotors tend to scuff and score more easily, thus making it less feasible to replace cast iron versions with aluminum equivalents.
Solutions to the latter problem have been proposed. One such proposal in U.S. Pat. No. 3,069,209 discloses a cast iron liner in a light-weight aluminum part, such as a brake drum. Still another proposed solution, in British Patent Application No. 2,268,511 A, sprays a simulated cast iron coating on a substrate before the coating is surface heat treated.
In order to be effective, any friction-wear coating must have good resistance to wear, good high temperature stability and thermal conductivity, good adhesion to aluminum, good machinability and finally solution potentials and coefficients of thermal expansion close to that of the aluminum substrate onto which the coating will be applied. The casting itself should be inexpensive and the coating cost effective to apply. Coatings with good high temperature stability are needed to resist melting and subsequent brake fade. Good thermal conductivity is also necessary to transfer frictional heat from the outer coating to the aluminum drum or rotor substrate. This coating must also have good adhesion to aluminum and a coefficient of thermal expansion so close to that of aluminum as to prevent bond failure during braking due to thermal shock. The coating solution potential must also be close to that of the aluminum substrate in order to prevent galvanic corrosion there between.
Despite the existence of prior art friction-wear parts and coatings, there still remains a need for aluminum brake parts having a ceramic-free, friction-wear coating applied thereto which meets or exceeds all of the above requirements, while at the same time being inexpensive to manufacture and coat.
In U.S. Pat. No. 5,056,630, there was disclosed an aluminum wheel rim for a bicycle. While that reference list several materials for a coating material applied to this rim, among them such metals as Al, Ti, B, Cr, Mo, Ta, Fe, Si, W, Co, Ni, Zn, Y, or an alloy thereof, there is still no express teaching within that reference to a apply a combination of aluminum and stainless steel (or an aluminum alloy-stainless steel alloy “blend”) to their bicycle rims. And while one or more of those metals is combined with a ceramic in an alternative teaching from that patent, the coating of the present invention is ceramic-free. In practice, there should be no need to apply the high temperature resistant coatings of the present invention to the rims of a low speed, 2 wheeled vehicle, such a pedal-powered or motorized bicycle.
SUMMARY OF THE INVENTION
The present invention has met or exceeded the above-described needs as well as others. In one embodiment, the invention includes a friction-wear part, such as a brake rotor, preferably comprising an aluminum substrate, onto which a friction-wear coating has been applied. The coating consists of a blend of aluminum and stainless steel, preferably pure aluminum, such as alloy 1100 (Aluminum Association designation) and 308 stainless steel, though it is to be understood that still other aluminum and/or stainless steel compositions may be combine in accordance with this invention.
The invention further includes a friction-wear aluminum part, such as a brake drum or rotor, comprising an aluminum substrate and a friction-wear coating applied to at least a portion of the outer surface to this aluminum substrate. Said outer surface is preferentially pretreated by being grooved to enhance coating reception thereon and secure bonding thereto.
Finally, a method of producing a friction-wear aluminum part is disclosed which comprises the steps of: (a) providing a metal substrate; (b) heating this substrate to one or more temperatures between about 200° to 1000° F. and; (c) applying a friction-resistant coating to at least a portion of this substrate's outer surface to produce the friction-wear part.
REFERENCES:
patent: 3069209 (1962-12-01), Bauer
patent: 5056630 (1991-10-01), Fujii et al.
patent: 5069937 (1991-12-01), Wall
patent: 5411771 (1995-05-01), Tsai
patent: 5753313 (1998-05-01), Tsai
patent: 2268511 (1994-12-01), None
Kaufold Roger W.
Pajerski A. Victor
Patrick Edward P.
Speer Robert J.
Alcoa Inc.
Graham Matthew C.
Topolosky Gary P.
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