All Patents have classification codes, which group similar patents together. Older patents, Plant Patents and Design Patents are classified using the US Classification System. Newer patents are classified using the Cooperative Patent Classification system. All patents have at least one, and some have both kinds of classifications. Searching patents using classification codes is much more efficient and reliable than using simple words and phrases.
You can browse the CPC Classifications starting on this page, and the US Classifications starting on this page. Or you can do a word search of the classification codes on this page.
For example, patent number 11,147,261 has classification number A01M 23/24. This classification breaks down thusly: A10M is the classification group for devices for the "Catching, Trapping or Scaring of Animals". Subsection 23/24 is for devices used for trapping animals using a spring-trap mechanism.
Another example: design patent number D264109 has a classification number of D21/637. D21 is the code for "Games, Toys and Sports Goods" and subsection 637 is for an "astronaut or pilot" toy (or in this case a space bounty hunter)
Plant Patents are more straightforward. This is a patent for a Dwarf Hybrid Blueberry Plant, classification number PLT/157 for Blueberries.
If you apply for a patent, and one of your claims resembles something in a patent that has come before, your application could be rejected. And you'll have wasted a lot of time and money. So searching the existing patents is very important! Existing patents are part of what Patent Law called the "Prior Art". Prior Art basically means any publicly available material that has come out before you apply for your patent.
You can search US Patents going all the way back to 1789 using the USPTO's Public Patent Search. And yes, your application can be rejected if it resembles a patent from 1789. You can also search patent applications, and you should because your application can be rejected even if it resembles something in an application, and that includes failed applications.
The Patent Public Search on the USPTO website has changed greatly in recent years. It's much more accessible, customizable and thorough than it used to be. Information about using Patent Public Search is on the USPTO website. The USPTO website also has a video tutorial on using Patent Public Search.
And here is a step-by-step broad outline of the patent search process from the USPTO.
Remember that you can also ask for help from a Patent & Trademark Resource Center, like ours! PTRC personnel are highly trained in the use of Patent Public Search, and we can show you how to use it.
Even after you do a thorough search on Patent Public Search, you still have work to do! You should check through magazine articles, scholarly journals, books, conference proceedings, YouTube videos, blogs, etc. Because, remember, any publicly available material can be considered part of the Prior Art. And if one of your claims looks like something in the prior art, your patent might get rejected!
If you live here in Maine, you have access to many databases that can help you search both popular and scientific publications. The Digital Maine Library, in their own words "provides every resident of Maine with access to online resources that include a collection of full text articles and abstracts from magazines, newspapers, journals and reference. It also provides students, business people, public library patrons, and higher education students and educators the ability to use online learning tools".
The best source for searching United States Patents is Patent Public Search, on the USPTO website. But there are other free websites for searching patents you can use listed below.