A patent gives you legal protection against infringement on your ideas and inventions. Before you can claim your own, however, you'll need to determine what's already been patented.

Don Farrall/Photodisc/Getty Images

Have you ever had an idea for some gadget to make life easier and wondered if it had been invented yet? Ever thought about selling your invention and needed to know if someone already beat you to it? One way to find these answers is to look for patents on similar gadgets and determine whether your invention is unique.

A patent is a legal document describing the unique details of an invention and granting one or more persons the right to prevent others from making or selling that invention [source: FreePatentsOnline, "Legal Definition"]. Others may still try to take credit for and profit from the invention, but the patent gives the grantee the option to take legal action against those who do. In the U.S., patents are approved and managed by the Patent and Trademark Office (USPTO), part of the Department of Commerce. For more on patents themselves, see our article How Patents Work.

To find out if someone has a patent on a particular idea or object, you'll need to do a patent search. However, this isn't as easy as entering a few keywords into a Web search engine. The USPTO patent database alone is massive, and an international search could be overwhelming. So, start by narrowing down what you're searching for and why.

First, identify the type of patent you're trying to find from the three types managed by the USPTO:

  • Utility patents are the most common type, covering objects that either function in some new way or produce some completely new result that similar objects hadn't been able to before.
  • Design patents encompass enhancements to an existing object that don't change its functionality.
  • Plant patents deal with new types of plants that are grown using grafts, cuttings or some other asexual method. However, genetically engineered plants fall under the umbrella of utility patents.

Next, choose your search approach based on the reason you're searching. If you're just checking for information, novelty or state-of-the-art searches are the best approaches. If you're looking to take legal action or defend yourself against it, an infringement or validity search is more appropriate.

This article will focus mainly on how the online patent searching process works in the United States, with nods to international systems and offline searches. First, let's find out how patents are classified in the U.S. so we know where to start looking.