A closure for a container with a neck portion and an external helical thread formed on the neck portion includes an upper wall and a skirt formed integrally with and extending generally downwardly from the upper wall. An internal helical thread is formed on the skirt for engaging the external helical...http://www.google.es/patents/US6491175?utm_source=gb-gplus-sharePatente US6491175 - Single piece closure for a pressurized container
