How has the view on negative limitations in patent claims evolved over time?
The view on negative limitations in patent claims has evolved significantly over time, becoming more accepting. The MPEP 2173.05(i) provides insight into this evolution:
“The current view of the courts is that there is nothing inherently ambiguous or uncertain about a negative limitation. […] Some older cases were critical of negative limitations because they tended to define the invention in terms of what it was not, rather than pointing out the invention.”
This statement reflects a shift from earlier skepticism to the current acceptance of negative limitations. For example, in the older case of In re Schechter, a negative limitation was considered indefinite because it attempted to claim the invention by excluding what wasn’t invented. However, more recent cases like In re Wakefield and In re Barr have found negative limitations to be definite when they clearly set forth the boundaries of patent protection.
Today, the focus is on whether the negative limitation complies with the definiteness requirement of 35 U.S.C. 112(b) and has support in the original disclosure, rather than dismissing them outright.
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