If you are interested in building more complex searches which involve searching for patents where a certain keyword appear a number of times, then you can do this using the $FREQn operator, where n is the minimum number of times that keyword appears within a searched section of a patent.
For example, if you want to search for patents where the keyword "car" appears at least twice within the title, then you can do this using the query TTL:("car" $FREQ2).
As well as this, you are able to view the number of times a set of keywords appear within the different sections of a patent. This can be done by adding "Keyword Count" as a "Displayable Field" in the search results page.