[header] How to look up patent numbers [title] Go to the us patent full-text and image database (patft). [step] The patft holds full-text patents issued from 1976 to the present. [substeps] Older patents exist in the database as pdf images only. 
However, you can only search for pre-1976 patents if you have the patent number or know the official classification scheme. [title] Gather the information you have about the patent you want to research.