Composite friction element
AssigneeAMSTED Industries Incorporated
InventorJohn B. Littlefield
Life of this patent
Estimating the term…
Abstract
A composite friction element suitable for the manufacture of railroad brake shoes of the composition type is prepared from a mixture of a curable rubber binder having distributed therethrough a plurality of fillers and a reinforcing fiber, at least one of the fillers having an oil absorption value of at least 30 and the fiber being formed from an aramid polymer.
Claims16
A brake shoe characterized by a body of a composite friction material having a matrix comprised of a vulcanized rubber binder material having distributed therethrough a plurality of filler particles including hard mineral fillers, friction modifiers and a reinforcing fiber, at least one of the filler particles having an absorptive capacity sufficient to absorb any binder decomposed during braking, the absorptive filler having an oil absorption value of at least 30 and being present in the body at a concentration of about 30 to about 50 percent by weight and the reinforcing fiber being a polymer characterized by recurring units of the formula ##STR6## wherein Ar.sub.1 is selected from the group consisting of p-phenylene, a chloro-substituted p-phenylene, and 4,4'-substituted diphenyl methane and Ar.sub.2 is p-phenylene and the fiber being present in said body at a concentration of about 0.5 to about 10.0 percent by weight.
A brake shoe characterized by a body of a composite friction material having a matrix comprised of a vulcanizable rubber binder material being present in the body at a concentration of about 15 to about 30 percent by weight, the rubber binder material having distributed therethrough a plurality of filler particles including hard mineral fillers, the hard mineral fillers being present in the body at a concentration of about 25 to about 50 percent by weight, and further friction modifiers, the friction modifiers being present in the body at a concentration of about 15 to about 30 percent by weight, at least one of the filler particles having an absorptive capacity sufficient to absorb any binder decomposed during braking, the absorptive filler having an oil absorptive value of at least 30 and being present in the body at a concentration of about 30 to about 50 percent by weight, and a reinforcing fiber formed from a polymer characterized by recurring units of the formula ##STR7## where Ar.sub.1 is selected from the group consisting of p-phenylene, a chloro-substituted p-phenylene, and a 4,4'-substituted diphenyl methane and Ar.sub.2 is p-phenylene and the fiber being present in the body at a concentration of about 0.5 to about 10.0 percent by weight.
In a brake shoe composition including a quantity of friction media, a quantity of a vulcanizable rubber bond material, a quantity of synthetic reinforcing fiber being formed from a polymer characterized by recurring units of the formula ##STR8## where Ar.sub.1 is selected from the group consisting of p-phenylene, a chloro-substituted p-phenylene, and a 4,4'-substituted diphenyl methane and Ar.sub.2 is p-phenylene, a quantity of absorptive media, and a quantity of friction modifiers, the improvement therein comprising,
- said friction media comprising hard mineral fillers,
- said bond material comprising a vulcanizable rubber, synthetic resin and curing agents to react therewith,
- said synthetic reinforcing fiber being of a high strength, chemically inert, and high temperature-resistant and having physical characteristics of a tensile strength proximating 400,000 psi, elongation to break proximating 3 to 4 percent, tensile modulus proximating 8.5.times.10.sup.6 psi, and density proximating 0.052 lb/in.sup.3, and thermal characteristics of decomposition at a temperature proximating 930.degree. F. and a 40 percent decrease in tensile strength of 500.degree. F., said fiber being present in a range by weight of 0.5 to 10.0 percent of the composition and
- said absorptive media comprising at least one filler having an oil absorption value of at least 30 to absorb any of said bond decomposed during braking, said absorptive media being present in a range by weight of 25 to 50 percent of the composition.
Dependencies are inferred from the claim text.