as soon as an original work is published in tangible form it is automatically copyrighted to the original author. registration of a copyright is an official step that would make it easier to prove it, but isn't technically necessary. the key to your claim would be (1) is it truely original and not just derivative; (2) could the other person have been reasonably expected to know they were copying somebody else's work (3) can you prove you published first. if you never show your pattern in a public forum, and somebody else cooks up the same idea and runs with it, you woud not win in court. if you were the first to think of it, did show it publicly, but it isn't truely so unique it's unlikely somebody else would think of it on their own, you still might not win.
read the information at these two links.
this is a great article
http://qnm.com/copyright/index.html
this is an official site with all the gobbledygook you need to read if you decide to register a copyright. includes links to forms
http://www.copyright.gov/circs/circ1.html#cr