Format: 

Inventor(s). Title of Patent. Date Issued. U.S. Patent number. Title of Website or Repository, URL. Accessed Day Month Year.

Inventor(s). Title of Patent. Date Issued. U.S. Patent number.

Examples: 

McMillan, William A., et al., inventors. Apparatus for Analysis of a Nucleic Acid Amplification Reaction. 13 Sep. 2005. U.S. Patent 6,942,971. Google Patents, www.google.com/patents/US6942971. Accessed 12 Dec. 2017.

In-text: (McMillan et al.)

Notes: 

Persistent URLs to patents may be difficult to locate; Google Patents is usually the best source for these. As with other electronic sources, omit the http:// or https:// from the citation (MLA 110). Because multiple individuals are involved in the filing of the patent, you should cite the contributor(s) that you wish to emphasize, followed by a descriptive label of their function (typically inventor) (MLA 37). You should also indicate that you are citing a patent by adding Patent after the date issued, or ideally U.S. Patent followed by the patent number (MLA 53; 105).

Source:

This source type is not covered by the MLA Handbook (8th ed.)