What is the significance of the In re Kerkhoven case in 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 In re Kerkhoven case is significant in patent law as it established a key principle regarding the combination of known elements. As cited in MPEP 2144.06, the case states:

“It is prima facie obvious to combine two compositions each of which is taught by the prior art to be useful for the same purpose, in order to form a third composition to be used for the very same purpose…. [T]he idea of combining them flows logically from their having been individually taught in the prior art.”

This case involved claims to a process of preparing a spray-dried detergent by mixing two conventional spray-dried detergents, which were held to be prima facie obvious. The significance of this case lies in its establishment of the principle that combining known elements for their known purpose can be considered obvious, even if the specific combination hasn’t been explicitly taught in the prior art. This principle is widely applied in patent examination to assess the obviousness of combinations of known elements.