What was the Lincoln Engineering case and its impact on patent law?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The Lincoln Engineering case (Lincoln Engineering Co. v. Stewart-Warner Corp., 303 U.S. 545, 37 USPQ 1 (1938)) was a significant ruling that established the Old Combination principle. According to MPEP 2173.05(j):

“The principle was that an inventor who made an improvement or contribution to but one element of a generally old combination, should not be able to obtain a patent on the entire combination including the new and improved element.”

However, this principle has been effectively overturned by subsequent legislation and court decisions. The 1952 Patent Act and later court interpretations have invalidated the reasoning behind the Lincoln Engineering decision, making it no longer applicable in modern patent examination.