The same statute that specifies the enablement requirement (35 U.S.C. 112(a)) also spells out the best mode requirement:
"The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention."
This above statutory language requires that if the the inventor knew of a best mode of practicing the invention at the time the application was filed, that inventor then must disclose that best mode within his or her patent application. A couple of points need to be highlighted here. First, the "best mode" of an invention is not measured objectively, but subjectively from the viewpoint of the inventor. For example, if the inventor truly believed the best mode of practicing his patented airplane was using a propeller engine, rather than a jet engine, that inventor would need to sufficiently describe the propeller engine embodiment within his patent application. Notice also that only the inventor's conception of best mode matters -- it doesn't matter if other engineers or mechanics who happened to work for the inventor believed the jet engine was the best mode of practicing the invention. Also, it is the "best mode" contemplated by the inventor at the time the application was filed. If the inventor, one day later, realizes that an airplane with a jet engine was a better mode of practicing the invention than one with a propeller engine, he will not need to update the patent application disclosing this--it was sufficient that he believed the propeller engine was the best mode of practicing the invention at the time the application was filed.
Note that it is very difficult to prove an inventor knew of a "best mode" of practicing the invention, but that he did not disclose it at the time the application was filed. There is a line of cases where litigants attempt to argue that the best mode was "concealed" by the inventor's disclosure. In some of these cases, the claim is that the best mode was so poorly described in the specification that it appears the patentee tried to purposefully withhold it from the public (See Gypsum Co. v. National Gypsum Co., 74 F.3d 1209, 1215 (Fed. Cir. 1996). In some cases, the best mode was provided, but it was disclosed between so many inferior modes that it was claimed to be inadequately differentiated, and therefore concealed (See Randomex, Inc. v. Scopus Corp., 849 F.2d 585, 592 (Fed. Cir. 1988)). However, even when such evidence of concealment is presented, many courts allow the patentee to present evidence that the concealment was merely "accidental." See Spectra-Physics Inc. v. Coherent Inc., 827 F.2d 1524, 1535 (Fed. Cir. 1987).
"The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention."
This above statutory language requires that if the the inventor knew of a best mode of practicing the invention at the time the application was filed, that inventor then must disclose that best mode within his or her patent application. A couple of points need to be highlighted here. First, the "best mode" of an invention is not measured objectively, but subjectively from the viewpoint of the inventor. For example, if the inventor truly believed the best mode of practicing his patented airplane was using a propeller engine, rather than a jet engine, that inventor would need to sufficiently describe the propeller engine embodiment within his patent application. Notice also that only the inventor's conception of best mode matters -- it doesn't matter if other engineers or mechanics who happened to work for the inventor believed the jet engine was the best mode of practicing the invention. Also, it is the "best mode" contemplated by the inventor at the time the application was filed. If the inventor, one day later, realizes that an airplane with a jet engine was a better mode of practicing the invention than one with a propeller engine, he will not need to update the patent application disclosing this--it was sufficient that he believed the propeller engine was the best mode of practicing the invention at the time the application was filed.
Note that it is very difficult to prove an inventor knew of a "best mode" of practicing the invention, but that he did not disclose it at the time the application was filed. There is a line of cases where litigants attempt to argue that the best mode was "concealed" by the inventor's disclosure. In some of these cases, the claim is that the best mode was so poorly described in the specification that it appears the patentee tried to purposefully withhold it from the public (See Gypsum Co. v. National Gypsum Co., 74 F.3d 1209, 1215 (Fed. Cir. 1996). In some cases, the best mode was provided, but it was disclosed between so many inferior modes that it was claimed to be inadequately differentiated, and therefore concealed (See Randomex, Inc. v. Scopus Corp., 849 F.2d 585, 592 (Fed. Cir. 1988)). However, even when such evidence of concealment is presented, many courts allow the patentee to present evidence that the concealment was merely "accidental." See Spectra-Physics Inc. v. Coherent Inc., 827 F.2d 1524, 1535 (Fed. Cir. 1987).