Are Patents Foolproof? Our Invention Protection Expert shows you how to keep other companies from stealing your idea.

Q: I understand a patent must clearly describe how to make and use an invention. If I invent a product, manufacture and sell it, get a patent on it, and then can't anyone look up my patent and learn how to make my product? If this is the case, then why should I get a patent? Also, is it true that if a competing company were to duplicate my product but modify one feature of it or one step in the manufacturing process, would the company be able to escape prosecution for "stealing" my invention?

A: It's true that a patent application, which eventually is printed verbatim as a patent, must clearly show how to make and use the invention. And it also follows from this that anyone can read any patent and learn how to make the patented invention. However, if anyone did create, use, import or sell a patented invention, then they would infringe the patent. An infringer is liable for monetary damages for past activity (manufacture, use, sale or importation of the invention). Monetary damages can be quite high and can even be trebled and include attorney fees in exceptional cases, so a patent provides a strong financial deterrent against infringement. Also, the court will issue an injunction prohibiting the infringer from any further infringement of the patent. If an infringer violates an injunction, they can be held in contempt of court. For example, their infringing equipment can be seized, and they can be imprisoned. Thus the right of a patent holder to obtain an injunction provides another powerful deterrent against infringing the patent.

Also note that even if there's no patent on a product, an interested party can usually learn how to make it by "reverse engineering" the product. Without patent coverage, anyone is free to reverse engineer and manufacture any product, provided they don't copy any trademark (brand name) or any copyrighted material (artwork or writing) associated with the product.

As to whether a company can escape liability for infringement by copying a patented product but changing one or more features, this depends on the scope of the coverage or monopoly afforded by the patent. The coverage of a patent can range from broad to narrow. When a patent is broad, it will be difficult for an infringer to provide a product with the same function, yet avoid infringing the patent. For example, modifying the patented product won't avoid infringing a broad patent. With a narrow patent, some other party can usually avoid infringement by making minor modifications.

The scope or breadth of a patent is determined by its claims. Claims are sentence fragments at the end of a patent that are written in legalese and describe the invention in precise terms. If the invention is a broad one, which is very different from the "prior art," then the Patent and Trademark Office (PTO) will allow broad claims, which will be difficult to avoid infringing. However, if the invention is only a minor improvement, then the PTO will force the patent applicant to narrow the claims to avoid the prior art, so the patent will be relatively easy to avoid infringing. See chapters nine and 15 of Patent It Yourself (Nolo Press) to learn more about claims.

David Pressman, a practicing intellectual property attorney, is author of the bestselling book Patent It Yourself and the interactive software program Patent It Yourself, both published by Nolo Press. Formerly an electronic engineer, David has more than 30 years' experience in the patent profession-as a patent examiner, a columnist for EDN Magazine and a patent law instructor at San Francisco State University. Patent It Yourself can be obtained in bookstores (brick-and-mortar and online), from the publisher (www.nolo.com) and through David's Web site (www.PatentItYourself.com).

The opinions expressed in this column are those of the author, not of Entrepreneur.com. All answers are intended to be general in nature, without regard to specific geographical areas or circumstances, and should only be relied upon after consulting an appropriate expert, such as an attorney or accountant.