Patent Searching Tip: Go for Class

“Money can't buy friends but it can get you a better class of enemy” -- Spike Milligan (Indian Humorist and Actor, 1918-2002)

The Web has made it so easy to keyword search for patents that it is easy to forget to use a very powerful advanced tool … patent classification numbers.

Each patent submitted to the Patent Office is assigned to an examiner knowledgeable in the area addressed by the patent. He or she then assigns one or more classification numbers to the patent.

A major advantage of searching by classification numbers is that it can produce results containing patents of interest even if some of those patents have none of the keywords you would have used to look for them.

So how do you figure out which classification number or numbers to use?

That is the subject of today’s search tip. Using Google® Patents …

Step one: Keyword search, using keywords that fit your topic
Step two: Browse the results for useful hits.
Step three: Select a patent and view it
Step four: Note the classification number(s) assigned to the patent
Step five: Click on each classification number to see how it is defined
Step six: Select and copy one or more classification numbers that seem to address your topic
Step seven: In the Google Patent Advanced Search form, paste your selected number(s) into the search box labeled Current U.S. Classification
Step eight: Click Google Search and browse the results
Here is an example. I found the following patent …

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Ultrasound-Assisted Oxidative Desulfurization Of Diesel Fuel Using Quaternary Ammonium Fluoride And Portable Unit For Ultrasound-Assisted Oxidative Desulfurization Abstract
The desulfurization of fossil fuels is effected by the combination of fossil fuels with an aqueous mixture of hydroperoxide and quaternary ammonium fluoride phase transfer catalyst, the mixture then subjected to ultrasound to oxidize sulfur compounds present in the fuels. The polar oxidized species are removed via extraction. Another aspect is a portable, continuous ultrasound assisted desulfurization device having a sonoreactor for subjecting mixtures of fossil fuels to sonication to effect removal of sulfur containing compounds.
Inventors: Teh-Fu Yen, Meng-Wei Wan
Application number: 11/854,927
Publication number: US 2008/0173571 A1
Filing date: Sep 13, 2007
Assignee: University of Southern California
Current U.S. Classification: 208/213; 422/127///////

Clicking on the Current U.S. Classification numbers, I found the following definitions …

CLASS 208, MINERAL OILS: PROCESSES AND PRODUCTS
SUBCLASS 213 With solid catalyst or absorbent: This subclass is indented under subclass 209. Processes wherein the hydrodesulfurization takes place in the presence of a solid catalyst or adsorbent.
CLASS 422, CHEMICAL APPARATUS AND PROCESS DISINFECTING, DEODORIZING, PRESERVING, OR STERILIZING
SUBCLASS 127 SHOCK OR SOUND WAVE: This subclass is indented under the class definition. Apparatus having means for creating sonic energy which is used to initiate or perfect a process. Included herein is apparatus for destroying organisms by the sudden release of high pressure.
Subclass 127 looked interesting, so I created a Google Patents Advanced Search using that class number.

Google Patents Advanced Search: oil uspclass:"422/127"

Note that I added the keyword oil to focus the results a bit.

One of the hits was …

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Method and apparatus for separating petroleumPatent number: 7399405
Filing date: Aug 5, 2005
Issue date: Jul 15, 2008
Application number: 11/197,333
Abstract
In the present invention, petroleum is separated into hydrocarbon mixtures having different components at an atomizing step and a collecting step. At the atomizing step, the petroleum is ultrasonically vibrated and is discharged and atomized in a state of an atomized fine particle floating in a carrier gas. At this step, the petroleum is separated into a mixed fluid containing the atomized fine particle and the carrier gas and residual petroleum which is not atomized. At the collecting step, the hydrocarbon mixture is separated and collected from the mixed fluid obtained at the collecting step. In the separating method, the petroleum is separated into the residual petroleum and the mixed fluid at the atomizing step, and the mixed fluid is collected at the collecting step so that the petroleum is separated into hydrocarbon mixtures having different components.
Inventor: Kazuo Matsuura
Original Assignee: Ultrasound Brewery
source: http://www.google.com/patents/US7399405?dq=oil+uspclass:%22422/127%22&ei=Lk_rT66dLufu0gHCuJW2BQ
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Using Current U.S. Classification numbers requires more work, but the results are worth the extra effort.