The Claims Interpreted Report

Words of Approximation: The Fine Line between being Definite or Indefinite in Prosecution

By Chris Francis

Categories: The Claims Interpreted Report

A search of PTAB ex partes appeals over the past three months shows that relatively few decisions have dealt with words of approximation.  The two recent ex partes decisions discussed below both determine whether the claim term “about” is definite.  One decision held that “about” was definite, while the other decision held that “about” was indefinite.

In Ex parte Karl M. Nelson, Appeal No. 2017-000766 (decided Sept. 29, 2017), the PTAB considered the following claim:

22. A method for curing a part, the method comprising:

connecting a tool to a temperature control system including a phase change material;

placing a part on the tool;

selecting the phase change material with a phase change temperature that is about a cure temperature for the part, the phase change temperature also configured to control heat generated by the part during curing of the part;

curing the part; and

transferring heat, while curing, from the part to the phase change material while maintaining a third temperature of the part within a desired temperature range near the cure temperature.

In this case, the Board essentially found support in the specification to determine that “about” was definite.  In the Appeal Brief, the Appellant argued that “about” is used to modify properties that are quantifiably measurable, and that “about” is used in the claims of over a million issued U.S patents.  In the Reply Brief, the Appellant further argued that the Examiner had ignored the context of the claim and the skill of the ordinary artisan by requiring that the assessment of the term “about” can only be made by the specification, which is contrary to the case law cited by the Appellant.  The Appellant goes on to provide examples of how a skilled artisan could determine the meaning of “about” without entirely relying on the specification. 

Ultimately, it appears that the Board relied on the specification itself by referring to a paragraph of the specification that states, “The passive temperature control system may have a phase change material selected as having a phase change temperature that may be capable of controlling heat generated by the part during curing of the part held by the tool.”  This, taken in combination with the context of claim 22 itself, persuaded the Board that “about” is definite and means that “the phase change temperature must be close enough to the cure temperature to be able to absorb heat (via phase change) during the curing process.” 

In contrast, the PTAB held that “about” was indefinite in the claim below in Ex parte Trevor Howard Wood et al., Appeal No. 2016-007468 (decided Sept. 1, 2017):

29. The surface cooler of claim 1, wherein the outer layer comprises an aluminum foam having a thermal conductivity of about 189 W/m*K.

In this case, the PTAB stated that, “although Appellants have provided a generic definition for the claim term ‘about,’ Appellants have not provided a standard for approximating a thermal conductivity.”  In making this statement, the PTAB even referenced a paragraph of the specification that discloses the “thermal conductivity of about 189 W/m*K” and states, “It may be noted, that the thermal conductivity of metal foam may vary greatly, depending not only on the porosity, but also on finer details of the integrity of the webs that interconnect various cells in a foam.”

The distinction, if any, between these two cases appears to be fine.  The use of words of approximation can be unavoidable in order to obtain meaningful patent protection, but also arguably create competing considerations when drafting a patent application.  To increase the odds of avoiding/overcoming an indefiniteness rejection, one might err on the side of being over-descriptive when discussing the word of approximation in the specification and also providing explicit description about quantification, while also being mindful that this description could be used in a limiting way in future claim construction during enforcement.  Stay tuned for a future blog post to compare the CAFC’s handling of words of approximation. 

Click here for a previous post on examples of the PTAB’s interpretation of “substantially,” which is another word of approximation.