Obviously, it is not reasonable or even desirable to examine every patent for relevance to a new invention. While the long-term goal of the U.S. Patent and Trademark Office is to automate the patent search, attempts at automation have met with limited success and thus far involve only a small percentage of U.S. patents. As a result, patent searching has remained largely unchanged over the years. To aid in conducting a search, the Patent and Trademark Office employs a patent classification system, the primary characteristic of which classifies patents according to the utility of the invention. For example, arts and instruments having like functions, producing like products or achieving like results are classified together.
Subject matter is divided into major classes, each with a hierarchy of subclasses.
Overall, there are over t00,000 classifications. Conveniently, most patents are classified in more than one subclass, so the public search file ultimately includes many more than the five million original patents. Performing a good patent search is an art. Economics dictate that only limited time can be spent on the search and analysis of the selected patents. The patent examiners are, for the most part, helpful in suggesting likely classifications to search in their areas of expertise if a dead end is reached.