Is “Substantially” Particular Enough?
© 2003, Dawsey Co., LPA
May 2003
Those familiar with the patent application process recognize that patent attorneys use phrases such as “substantially” and “approximately” all too often. In fact, some patent applications could be reduced in length by several pages simply by removing such phrases. However, such expressions are used to avoid strict numerical boundaries that may result in narrow patent protection. The question often presented is whether phrases such as “substantially” and “approximately” satisfy the requirement of 35 USC §112 that the applicant “particularly point out and distinctly claim” the invention.
The Court of Appeals for the Federal Circuit (CAFC) recently held, in Verve, LLC v. Crane Cams, Inc., that such language is permissible when warranted by the nature of the invention. The CAFC found that the lower court erred in requiring that the intrinsic evidence of the specification and prosecution history is the sole source of meaning of words that are used in a technologic context. The CAFC stated that determination of the meaning of such words is that as would be understood by persons in the field of the invention. In other words, an applicant need not explicitly state in the body of the patent application that the terms “substantially” or “about” mean plus, or minus, so many units.
The controversy in Verve centered on a claim for an internal combustion engine push rod that is hollow and defined as having a “substantially constant wall thickness.” The lower court recognized that the usage of “substantially” may be adequately definite in some cases, but ruled that it was indefinite in this case because it was not further defined in the application. The CAFC vacated the lower court finding of indefiniteness based upon the “understanding of persons in the field” logic expressed above. The CAFC reasoned that since patent documents are written for persons familiar with the relevant field, the patentee is not required to include information in the specification that is readily understood by such persons.
Therefore, patent attorneys may continue in their exaggerated use of “substantially” and “approximately” in patent applications, provided it is warranted by the nature of the invention, with reduced fears of later having a finding of indefiniteness used against their client.