Verify the relevancy of CPC classification you found by reviewing the CPC Classification Definition linked to it (if there is one).
Retrieve U.S. patent documents with the CPC classification you selected in the PatFT (Patents Full-Text and Image) database (http://patft.uspto.gov). Review and narrow down the most relevant patent publications by initially focusing on the front page information of abstract and representative drawings.
Using this selected set of most relevant patent publications, review each one in-depth for similarity to your own invention, paying close attention to the additional drawings pages, the specification and especially the claims. References cited by the applicant and/or patent examiner may lead you to additional relevant patents.
Review and References
Retrieve U.S. published patent applications with the CPC classification you selected in Step 3 in the AppFT (Applications Full-Text and Image) database (http://appft.uspto.gov). Use the same search approach used in Step 4 of first narrowing down your results to the most relevant patent applications by studying the abstract and representative drawings of each on its front page. Then examine the selected published patent applications closely, paying close attention to the additional drawings pages, the specifications and especially the claims. Review the claims, specifications and drawings of documents retrieved for relevancy.
Broaden your search to find additional U.S. patent publications using keyword searching in PatFT or AppFT databases, classification searching of non-U.S. patents on the European Patent Office's Worldwide Espacenet patent database (http://worldwide.espacenet.com) and searching non-patent literature disclosures of inventions using the free electronic and print resources of your nearest Patent and Trademark Resource Center (http://www.uspto.gov/ptrc).