A spring-type shank for a shoe sole is formed on the bottom of a shoe assembly during manufacture of the shoe. The heel end of the shank is formed so that it is raised slightly from the heel seat region of the insole to provide a "spring shank". The shank is formed directly on the bottom of the shoe...http://www.google.co.uk/patents/US4461101?utm_source=gb-gplus-sharePatent US4461101 - Molded shanks
