A facile answer. How can you tell if I invented the circular ice scraper, or the folks who hold a patent on it invented it? If they invented it, why do I stil

A facile answer. How can you tell if I invented the circular ice scraper, or the folks who hold a patent on it invented it? If they invented it, why do I still scrape frost and ice off my car's windshield with a yellow plastic coffee mug, manufactured by "Tupperware"?