I have never heard of a black activist inventor so the search I typed has discovered this man.this mans name is Elijah McCoy I have found something interesting about this man from this website:http://www.biography.com/people/elijah-mccoy-9391300
Elijah McCoy was a 19th century African-American inventor best known for inventing lubrication devices used to make train travel more efficient.
Elijah McCoy was born on May 2, 1844, in Colchester, Ontario, Canada, to parents who had fled slavery. McCoy trained as an engineer in Scotland as a teenager. Unable to find an engineering position in the United States, he took a job working for a railroad and subsequently invented a lubrication device to make railroad operation more efficient. McCoy died in Detroit, Michigan, on October 10, 1929.The story of this man shows what was achieved in difficult times and what was possible given the tool of education.