Invalidating a U.S. patent can be a complex and challenging process, and it typically requires a legal proceeding before the U.S. Patent and Trademark Office (USPTO) or a court. Here are some common ways to invalidate a U.S. patent:

     1.    Prior art

Prior art is any document that was available to the public before the filing date of the patent application. Prior art can be used to invalidate a patent if it shows that the invention claimed in the patent was not new or inventive.

     2. Obviousness

 If the claimed invention is deemed to be an obvious variation of an existing invention, it may not meet the criteria for patentability. In this case, the patent could be invalidated.

     3.  Public use or sale

A patent can also be invalidated if it can be shown that the invention was used or sold in public before the filing date of the patent application.

     4.  Fraud

If the patent holder committed fraud during the application process, such as by intentionally misrepresenting the invention or withholding relevant information, the patent could be invalidated.

It is important to note that invalidating a patent is a complex and technical process. It is important to consult with an attorney if you are considering invalidating a patent.