The Broadest Reasonable Interpretation Must Be Consistent with the Specification

Stephen G. Adrian | December 7, 2017

Mexichem Amanco Holding S.A. de C.V., Appellant v. Honeywell International Inc., Appellee

November 17, 2017

Before Prost, Dyk and Chen. Opinion by Prost


This non-precedential opinion provides an important reminder that the broadest reasonable interpretation does not mean the broadest possible interpretation. The decision also highlights (indirectly through the decisions on appeal rendered by the PTAB) that a limitation contained in the preamble can carry weight. In unpredictable arts, an Examiner’s assertion of inherency may not necessarily shift the burden of proof to show otherwise.


Mexichem appeals from three final decisions in inter partes reexaminations:

  1. U.S. Patent No. 8,148,317, Control No. 95/002,188
  2. U.S. Patent No. 7,524,805, Control No. 95/000,574
  3. U.S. Patent No. 7,825,081, Control No. 95/000,630

In each of the appeals at the Patent Trial and Appeal Board (PTAB), the PTAB reversed the Examiner’s rejections based on the construction of the term “azeotrope-like.” The issue on appeal before the CAFC is whether the PTAB’s construction of the term “azeotrope-like” is proper.


According to the opinion of the CAFC, the Examiner had construed the term “azeotrope-like” to mean “a composition containing a mixture of transHFO-1234ze and one or more of HFC-152a, HFC-227ea, HFC-134a or HFC-125.”[1] The Board rejected this construction and instead construed “azeotrope-like” to mean “constant boiling or essentially constant boiling” based on the specification’s definition:

Azeotrope-like compositions are constant boiling or essentially constant boiling. In other words, for azeotrope-like compositions, the composition of the vapor formed during boiling or evaporation is identical, or substantially identical, to the original liquid composition. Thus, with boiling or evaporation, the liquid composition changes, if at all, only to a minimal or negligible extent. This is to be contrasted with non-azeotrope-like compositions in which, during boiling or evaporation, the liquid composition changes to a substantial degree.

The construction proposed by the Examiner would read the term “azeotrope-like” out of the claims entirely, rendering the term meaningless. As such, the CAFC found no error in the PTAB’s construction.

The CAFC’s opinion is very brief, not even reproducing any of the claims from the appeals. As such, a review of the PTAB’s decisions is helpful in understanding some basic patent prosecution fundamentals.

Claim 1 of Control No. 95/002,188

  1. An azeotrope-like composition comprising from greater than zero to about 60 weight percent of trans-1,3,3,3-tetrafluoropropene (transHFO-1234ze) and not less than about 40 weight percent of 1,1,1,2-tetrafluoroethane (HFC-134a).

Claim 1 of Control No. 95/000,574

  1. An azeotrope-like composition consisting essentially of effective amounts of trans-1,3,3,3-tetrafluoroprpene (transHFO-1234ze) and a compound selected from the group consisting of 1,1-difluoroethane (‘HFC-152a”), 1,1,1,2,3,3,3-heptafluoropropane (“HFC-227ea”), 1,1,1,2,-tetrafluoroethane (“HFC-134a”), 1,1,1,2,2-pentafluoroethane (“HFC-125”) and combinations of two or more of these.

Claim 1 of Control No. 95/000,630

  1. A method for cooling an article comprising: condensing a refrigerant composition comprising an azeotrope-like composition comprising effective amounts of … and two or more of these; and thereafter evaporating said refrigerant composition in the vicinity of the article to be cooled.

As can be seen above, the critical term “azeotrope-like” appears in the preamble of two of the patents, whereas it is contained in the body of the claim of the third patent. The construction of the term is very important as the Examiner relied on prior art disclosing the elements recited in the claims. However, the prior art did not state that its compositions formed azeotrope or azeotrope-like compositions. In such situations, patent practitioners would usually be faced with an inherency argument by the Examiner, where the Examiner would reason that the prior art compositions must possess the same properties even though the properties are not stated.

The PTAB recognized that as long as the Examiner has a reasonable basis to believe that the compositions of the prior art would be expected to possess the same or similar properties, the Examiner may shift the burden to the Patent Owner to prove otherwise. Somewhat surprisingly, the PTAB held that there was insufficient evidence to support the Examiner’s belief, and therefore the burden never shifted to the patentee to prove otherwise.

The PTAB reasoned that the formation of azeotropic compositions has been recognized as unpredictable. In addition, the Patent Owner provided declarations to support that azeotrope-like compositions are unpredictable. As such, although the prior art mentioned azeotropes in its background, the prior art never mentioned azeotropes in conjunction with its disclosure of their invention. Therefore, there was not a sufficient basis for the Examiner’s position that the prior art would disclose or render obvious “azeotrope-like” compositions.


  1. Always define the meaning of important terms in the specification, particularly if what you are claiming may not fit the ordinary meaning. In these patents, the compositions were not necessarily azeotropes, so the patentee defined what was meant by “azeotrope-like.”
  2. Whenever an appeal is pursued, ensure your record is complete with expert declarations addressing close issues. Here, the PTAB found the evidence provided in declarations to point in Patentee’s favor.
  3. Never assume that an Examiner’s mere assertion of inherency will shift the burden of proof. Providing evidence in the record to rebut an Examiner’s inherency argument, however, is a must to increase the chances of a successful appeal.
  4. All claim terms have meaning.

[1] As will be seen from the decisions from the PTAB discussed below, the Examiner essentially ignored the term “azeotrope-like.”


Full Opinion

U.S. Application 95/002,188

U.S. Application 95/000,574

U.S. Application 95/000,630

Subscribe | 登録



词典 / 辞書 / 사전
  • dictionary
  • dictionary
  • 英語から日本語

Double click on any word on the page or type a word:

Powered by