Conducting a Search
lead to subclasses that may be closer to the invention than those
identified in the index. Lastly, the definitions further identify the
subject matter assigned to each subclass and possible cross-refer-
ences to related classes. After identifying the classes and subclasses,
the patent bundles relating to the subclasses are obtained and the
patents in the bundles reviewed for relevance.
When a relevant patent reference has been found, the informa-
tion on the front of the patent may lead to more references. Figure
5.1 shows the front page of a patent. Note that some of the sections
have field identifiers (the small numbers in brackets) and some of
them do not. These field identifiers are used by the U.S.P.T.O. for
data entry. Table 5.2 provides a brief explanation for each field iden-
From a search perspective, the most important sections on the
front of the patent are those relating to the references cited, U.S.
classification, and field of search. Once a patent is identified that is
close to the invention, the next step is to look at the references cited
in the patent. These references were cited by the Examiner because
they were considered to be material to the patentability of the inven-
tion described in the patent. It is likely that they may be relevant to
the invention for which the search is being conducted and should be
If a patent is identified that is close to the subject
matter of the searched invention, look up the refer-
ences cited on the front of the patent.
The references cited will also identify the classes and subclass-
es for the patents listed. The U.S. classification and field of search
sections identify other classes and subclasses for the patented tech-
nology. As with the references cited, these other classes and subclass-
es should also be searched.