Learning how to perform a free patent search can be very important, especially if you are trying to get a patent for an invention. It can also be useful if you simply want to know for novelty purposes. There are two ways to search on the United States Patent and Trademark Office website: keyword and patent classification. There are other sites that can perform searches as well and they will have their own ways to locate certain patents.
A free patent search done by keywords is very simple. Enter the main words you think will describe an invention. If you go to the advanced search page of the U.S. Patent and Trademark Office website, you can enter in more specifications to do your search.
For an example, if you want to do a search to find the specifications on dog doors, you would type in spec/dog and spec/door or spec/flap. This will pop up all the patents from 1976 to the present, some of which may appear to be unrelated.
You can narrow the results by searching for just the abstracts or the titles of the patents by typing in abst/dog and abst/flap or abst/door into the query. This usually will show fewer results and they will relate more to what you are looking for.
Your free patent search will show you a lot of information that you'll need to make note of before doing a patent classification search. The results of the keyword search will show you the current United States Classification, listed as a number over another - if you had searched for cat doors instead, the number would be 49/169.
There are also links for "references cited" and "referenced by" that can be a wealth of information. Reading through these links will give you more information about the patent you might be trying to find.
Once you look at all the information provided from your free patent search by keyword you can do a patent classification search. To do this you must first select the years, usually covering the entire database from 1976 to the present. Using the classification number you can perform the search.
There will be a number of references based on that code. You can look through and read the patents. You can look for and find other key words and classification codes to re-search in order to find exactly what you are looking for.
If you want to find a patent from before 1976 you will have to know the exact patent number in order to find it. You can visit your local patent and trademark libraries or office to do a free patent search for all patents ever granted.
If you find it too difficult doing a free patent search, there are many companies out there that will help you perform the search. Be sure to look around while you are here for more information on free patent searches.