From the US Patent and Trademark website
A patent for an invention is the grant of a property right to the inventor, issued by the United States Patent and Trademark Office. Generally, the term of a new patent is 20 years from the date on which the application for the patent was filed in the United States or, in special cases, from the date an earlier related application was filed, subject to the payment of maintenance fees. U.S. patent grants are effective only within the United States, U.S. territories, and U.S. possessions. Under certain circumstances, patent term extensions or adjustments may be available.
The right conferred by the patent grant is, in the language of the statute and of the grant itself, “the right to exclude others from making, using, offering for sale, or selling” the invention in the United States or “importing” the invention into the United States. What is granted is not the right to make, use, offer for sale, sell or import, but the right to exclude others from making, using, offering for sale, selling or importing the invention. Once a patent is issued, the patentee must enforce the patent without aid of the USPTO.
Note: it takes 1½ to 2½ years for a patent to be approved. There is now a searchable application file that covers patents still in process after 18 months. However, an inventor can elect to ask that the patent be confidential until granted which means it won’t be in the application file database.
How to search for patents
The most complete method of searching by subject for patents is to determine the class/subclass (there may be more than one) that apply to that subject.
There are three USPTO resources or tools that help in this undertaking. The online versions are available at http://www.uspto.gov/go/classification/index.htm.
The recommended procedure is to look in the 1) Index by an appropriate term that will identify the class/subclass for that term. Then further examine the class/subclass by looking in the 2) Class Schedule which provides a hierarchy of the relationships between the subclasses within a class and 3) Class Definitions which provides descriptions of the class/ subclass functions as well as references to other class/ subclass areas that are closely related.
Alternatively, you could look in the online patent database by keyword, and after identifying patents with similar subject areas to your interests, identify the primary class/ subclass for that patent (listed in the online full-text patent in bold). It is still recommended that you check the Manual and the Definitions to fully understand the class/ subclass description.
Why not just search by keyword?
Although keyword searching is quick and will identify some potential patents of interest, it will be an incomplete and haphazard search. Patents are notorious for variations in words used to describe a particular application. For example, the patent titles of “Frisbee” type applications have keywords including flying saucer, flying disc or disk, airfoil projectile, aerial disc, throwing disc, aerodynamic toy, disk for throwing, throwing toy, flying toy, flexible toss device, and flying object. Unless you can think of every possible wording for such an entity, your search will be incomplete. Keyword searching also brings in “false drops” or patents that include your words but are peripheral to your interest. For example, searching for flying saucer brings patents of the Frisbee variety, but also games that have flying saucers in their visual imagery. Class/ subclass searching is the only effective method for a complete topical search.
Can I search by a company name?
You can search the patent file “assignee name” field for a company and retrieve patents that have been assigned to that company. Please note: patents are granted to inventors, not companies. The inventor may then assign the patent to a company.
If the patent is assigned to a company after the patent is issued or the patent assignment changes after the patent is issued, search the Patent Assignment Database. A link is provided on the Patents Search opening page, the direct link is: http://assignments.uspto.gov/assignments/?db=pat
Other categories that may be useful…
Many products have the patent number inscribed on them. You can search by “patent number” to find the patent for that product. Some products have a “patent pending” notice; search both the granted patents, and the application file. Remember, however, that if the inventor has requested confidentiality until the patent is granted, that patent will not be found in the application file.
You can limit by “application date” or “issue date”. Limiting by a pre-defined date range is also available. In fact, the default search is for 1976-present.
For some topics, patents may provide some useful information. Although the most likely reason to search the patent literature is to identify specific technological advances and inventions, other reasons include noting trends in an area, and identifying areas of interest of particular companies.
More about searching
University of Texas at Austin Patent Tutorials
Other US Patent Search Tools:
Need a patent in pdf format?
US Patent & Trademark Office Fee Schedules