Patent Update: Uncloaking Stealth Prior Art

Can you guess what a press release, a contract manufacturer’s quote, an offer to sell a new product, a trade show display, a grant application, and a regulatory submission may all have in common when it comes to patenting an invention? They can all be forms of stealth prior art that could prevent patent protection. Stealth prior art is prior art that does not attract attention.

Consider the story of Wayne Pfaff, who filed an application for a patent on a computer chip socket on April 19, 1982. The U.S. Patent and Trademark Office duly examined the application and issued Pfaff a patent on his application in January 1985. Pfaff later filed a patent infringement lawsuit against Wells Electronics, a manufacturer of a competing socket. Wells Electronics defended itself on the basis that Pfaff’s patent was invalid, and succeeded in invalidating Pfaff’s patent based on stealth prior art. In Pfaff’s case, it was his own engineering drawings and his sale of sockets to Texas Instruments (TI) that were used to invalidate his patent.

Pfaff began working on his socket design in November 1980 after TI asked him to develop a new device for mounting and removing semiconductor chip carriers. Pfaff prepared detailed engineering drawings that described the design, dimensions, and materials to make the socket. Pfaff then sent those drawings to a contract manufacturer in February or March 1981. Pfaff next showed a sketch of his concept to TI and, on April 8, 1981, TI ordered 30,100 of the new sockets from Pfaff for a total price of $91,155. The sockets were then delivered to TI in July 1981.

The problem for Pfaff...