Prior art can include patent documents and other disclosures relevant under patent law. A search limited to current products or exact keywords can miss useful material.
Describe the Function
Write down what the mechanism does and several ways to describe its parts. Search those variations. Technical vocabulary changes, and an older patent may use a different name for a familiar component.
Follow Classifications and Citations
The USPTO’s Patent Public Search provides access to U.S. patent documents. Once you find a useful result, inspect its classifications and cited references. Classification searching can reveal related documents that a keyword query misses.
Search non-patent sources too, such as technical publications. Keep a record of the document, relevant date, and passage or figure that made it useful.
Separate the Questions
Finding similar material does not by itself determine patentability, validity, or freedom to operate. Those questions involve different legal analyses. Even a careful search has limits, including material that has not yet become public.
Use how to read a patent to examine a promising result and find a practitioner for help with a particular application.