Format: 

Inventor, A. A. (Year issued). Patent Identifier Number. Location: Source Name.

Examples: 

Borkholder, D.A. (2005). U. S. Patent No. 6,942,971. Washington, DC: U.S. Patent and Trademark Office.

In-text: (U.S. Patent No. 6,942,971, 2005)

Source:
APA - A7.07