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Patent Searching 102: Using Public PAIR

Written by Gene Quinn
Patent Attorney & Founder of IPWatchdog
Widerman & Malek
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Posted: Aug 21, 2010 @ 3:59 pm
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Doing your own patent search early in the invention process is good for a few reasons. First, if you can find prior art that is too close to what you want to do then you save time, money and energy, provided of course you move on and not try and pound that round peg into a square hole! Patent searches are also critical because they will give you a lot of ideas if you actually read the patents and not just the title and abstract and check out the pictures.  If you read the text a whole host of ideas are likely to come running into your head.  Finally, a patent search will give you a sense of what else is available that might be public domain already and a substitute for your invention in the eyes of the consuming public.

Some time ago I wrote Patent Searching 101, which is a do it yourself guide to conducting a patent search, which I think is a good tutorial as far as it goes, but it is time to take the next step and provide an advanced tip. If you are really serious about doing a high quality patent search on your own I recommend doing whatever you can to find 1 or 2 patents or patent applications that closely relate to your invention, whether that means in terms of structure or concept. I hear all the time that inventors do searches and cannot find anything relevant, which is unbelievable. If you do a search and find nothing then you are doing something wrong. See No Prior Art for my Invention.  Do whatever you have to, and in a pinch to find something quick that is at least somewhat relevant Google Patent Search will do. Then visit Public PAIR and see what you can find out about the prior art found used by the patent examiner against that patent or patent application.

For example, take a look at US Patent No. 7,627,908. I picked this because it is a fairly easy invention to comprehend and is really technology neutral, which makes it a good teaching tool.  Visit Public PAIR and navigate through to the ‘908 patent and then click on “Image File Wrapper.” What you will see is represented in the screenshot below.

Look at all the information that is publicly available through Public PAIR.  Let’s start with my favorite, the Non-Final Rejection (see blue arrow).  In truth, any rejection that you can find is a source of great information.  When you find a rejection issued in a patent or patent application that is closely related in terms of structure or concept you will learn what the prior art is that the patent examiner thought relevant enough to use against the application.  If you iteratively go through this process, looking up the references cited by the patent examiner, you can typically start to see patterns develop, with certain references being used with at least some frequency in similar patent applications.

The next best thing, in my opinion, is stumbling across something characterized as “search information including classification,” (see red arrow).  Definitely open this file.  What you will find is a document titled “search notes.”  This document will list the classifications searched, which is gold!  As I explained in Patent Searching 101, finding the relevant classifications and subclasses is essential to a competent search, and while this listing will likely be over inclusive it still will substantially narrow down your efforts and focus you on where you will most likely find the most highly relevant prior art.  For example, in this case the table below, taken from the the search notes document relating to the ‘908 patent, gives great clues where you should be looking.

You can also typically find a list of references cited by the examiner (see yellow arrow), which will give you a list of patent references that you should take a look at.  You might be able to dismiss them relatively quickly, and these lists are not as helpful sometimes as the prior art actually used, but if you want to get a good feel for what the art is that the patent examiner is likely to find you want to take a look at these lists.

Not shown here, but sometimes helpful, is an Information Disclosure Statement or an IDS.  In fact, there can be many Information Disclosure Statements filed during the life of a patent application.  This is the patent applicant telling the patent examiner of prior art they know about and believe to be material to one extent or another.  Again, not likely as helpful as a Non-Final Rejection or Final Rejection, but worth looking at if you find it in the Image File Wrapper.

The patent process can be an expensive process.  You absolutely want to find whatever prior art you can on your own early in the process.  By finding prior art on your own you save money and might save yourself a good deal of time by not pursuing a path that seems fruitless.  As things progress you should have a professional patent search done with a patent attorney or patent agent giving you at least an opinion on patentability, and hopefully a detailed assessment explaining the likelihood of obtaining a patent and what can realistically be expected to be achieved.  But for starters, as you are doing your do diligence you absolutely should look and find whatever you can.

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Posted in: Educational Information for Inventors, Gene Quinn, Inventors Information, IP News, Articles

About the Author

is a US Patent Attorney, law professor and the founder of He is also a principal lecturer in the top patent bar review course in the nation, which helps aspiring patent attorneys and patent agents prepare themselves to pass the patent bar exam. Gene started the widely popular intellectual property website in 1999, and since that time the site has had many millions of unique visitors. Gene has been quoted in the Wall Street Journal, the New York Times, the LA Times, USA Today, CNN Money, NPR and various other newspapers and magazines worldwide. He represents individuals, small businesses and start-up corporations. As an electrical engineer with a computer engineering focus his specialty is electronic and computer devices, Internet applications, software and business methods.



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  1. Lately I’ve been gaining a greater appreciation for the value of class/subclass searching. This is a great way to search very early patents (e.g. 19th century) which can be quite important for mechanical inventions (e.g. sports equipment, consumer packaging, etc.)