If no fields are specified in Quick Search, the search covers all fields. For example, searching for "Monsanto" in Field 1 and "Soybean" in Field 2 results in a list of 1,340 patents. Narrowing the search by searching for "Monsanto" as the Assignee and "Soybean" in All Fields resulted in a list of 622 patents, with the most recently-issued patent at the top of the list. Patent Number 6,653,534 is for a Soybean Cultivar SY 32157, which contains 10 claims. Claim 5 is for "a soybean plant, or parts thereof, having all of the physiological and morphological characteristics of the soybean plant of Claim 2." Claim 2 is for "a soybean plant, or parts thereof, produced by growing the seed of Claim 1." Claim 1 is for "seed of a soybean variety designated SY32157," developed by Monsanto.

Searching by Field: Advanced Search

            A more sophisticated search can be conducted using the Advanced Search. To use this search, field codes must be specified, but the search terms can be nested and more than two fields can be searched. The fields include all of those in the list above, plus two additional fields, Parent Case Information, and Other References.

            For example, searching for: needle ANDNOT ((record AND player) OR sewing) would generate a list of patents containing the word "needle" but not the word "sewing" or the combination of words "record" plus "player." Searching for AN/"General Electric" AND (TTL/television OR TTL/ (cathode AND tube) would produce a list of patents assigned to General Electric where the word "television" appears in the title, or the words "cathode" and "tube" were both present in the title.

Searching the Patent Classification System

            None of the above search methods may apply if an inventor starts with a device he or she wishes to patent and must first do a prior art search to find related patents. The first step in such a case will be to look at the PTO Index to U.S. Patent Classification.

            The PTO maintains a multi-volume Index to the U.S. Patent Classification System, which includes over 400 classes of device, with over 136,000 subclasses. The 400+ major classes in the Classification Index are given in Appendix C. It's much easier to search the Classification Index on-line, but the Index and the Manual of Classification can be purchased from the PTO on CASSIS CD-ROM, available online from the PTO web site or by phone. The Index and Manual of Classifications are also held by Patent and Trademark Depository Libraries (PTDL), located throughout the United States. A complete list of PTDL's is available from the Patent Office.

            The Index to U.S. Patent Classifications is available from the PTO web site:

            http://www.uspto.gov/go/classification/uspcindex/indexa.htm

            An alphabet listed across the top of the page can be used to jump to a particular letter.

            The list is available in either HTML or PDF format.

            The Index is also available from the SunSite from the University of North Carolina:

            http://www.ibiblio.org/patents/index.html

            Suppose you have invented a device for doing balloon angioplasty to open clogged arteries that you think might be patentable. You would start by doing a search by topic of all the classes in the PTO Manual of Classification. The PTO web site:

            http://www.uspto.gov/web/offices/ac/ido/oeip/taf/moc/jobjects/search.htm

presents you with a search box. Searching for "surgical instrument" identifies four classes in the index which might be relevant, D24, Medical and Laboratory Equipment; 206, Special Receptacle or Package; 362, Illumination; and 606, Surgery.

            Now go to the site:

            http://www.uspto.gov/go/classification

and look up each Index class by entering the class number in the box on the left. (The second box is for the subcategory, if known). The class definition distinguishes the class from other classes and gives a list of exclusions, devices which are covered elsewhere in the index. For example, the class D24, Medical and Laboratory Equipment, excludes items such as bandages, bed sheets, ion generator, kiln, light panel, surgical scrub basin, or radio transmitter for transmitting cardiac data.

            Class 206, Receptacle or Package, has a subcategory for "bandage," but refers mainly to general containers (grease gun, tray, container for teeth, container for tobacco). It doesn't seem to be relevant. Class 363, Illumination, has a subcategory for endoscope, but otherwise does not seem to be relevant.

            Classes D24 and 606 seem more relevant. Class 606, Surgery, contains a subclass (606/7) for Angioplasty. Clicking the "P" to the left of the subclass produces a list of patents, in reverse chronological order, which fall into that subclass. Within the subclass for Angioplasty, there are 375 patents listed, most recently from October of 2007. The two most recent patents in the subclass, 7,288,087, Expandable Laser Catheter, and 7,273,478, Endovascular treatment device having a fiber tip spacer, each list dozens of earlier patents constituting prior art for the device.

            Published pre-grant patent applications are available at:

            http://www.uspto.gov/patft/index.html

            A search on this site for "angioplasty" shows an application made in February of 2008 for "Rheological treatment methods and related apheresis systems." Embedded in the description are references to the prior art.

            At this point the inventor would begin reading the patent claims for similar devices, to determine the extent to which they overlap his or her invention, to assess the extent to which at least parts of the invention may qualify for patent protection. Class D24 would also need to be explored, particularly: D24/110.4, Equipment for Treatment, including provision for tube; D24/112, Catheter; D24/137-139, Viewing Instrument; and D24/169, Hematological.

            Of course, searching the non-patent prior art is also required. In this case, a knowledgeable researcher might review recent issues of specialized surgical journals, or do a more general search using Medline or BIOSIS Previews (Ovid; Wolters/ Kluwer). The latter contains, among other things, patent descriptions of medical devices as they are published in the Official Gazette of the PTO.

            Commercial search services are also available, discussed in Appendix B. A web search for "searching patent prior art" will produce dozens of additional sites.