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Balancing Definiteness Against Ambiguity

Posted Thursday, August 30, 2012 by Mike Cicero

In both non-provisional patent applications and issued patents, the claims serve the primary purpose of defining the novel and nonobvious invention that the inventor seeks to protect. For this and other reasons, the claims are the most important (and difficult) task in drafting a patent application. Under 35 U.S.C. §112, claims can be rejected for being indefinite if they fail to “particularly point out and distinctly claim” the invention. Essentially, a claim is indefinite when the line between what is and is not covered by the claim is unclear or the claim is ambiguous. However, a claim is not indefinite if, when read in the light of the specification, the claim is unambiguous and reasonably apprises potential infringers of the scope of the invention. Jones Knitting Corp. v. Morgan, 361 F.2d 451, 149 U.S.P.Q. 659 (3d Cir. 1966). Because the claims are to be read in light of the specification, any terms used in the claims which might be considered indefinite or ambiguous may be, and probably should be, explicitly defined in the specification.

The degree of precision required for a claim to withstand the definiteness requirement of 35 U.S.C. §112 is flexible and depends on just how precisely the claims are capable of being written. Patent claims have been held invalid when at the time the patent was drafted the terms used in the claims could have been precisely defined in the specification but were not. E.g., In Re Burke, 786 F. Supp. 1537, 22 U.S.P.Q. 2d 1368 (C.D. Cal. 1992). In the case of In Re Burke, a broad claim used the term “removably” to define a connection between two components of a personal mobility vehicle. The court was not persuaded by the patentee’s contention that a connection is “removable” if it can be severed without the use of tools because such a definition was supported by neither the dictionary nor the specification itself. Ultimately the court invalidated the claim for being indefinite. Id. Had the patentee taken the opportunity to define the term “removably” in the specification the claim would not have been invalidated based on this term.

Patent statutes do not, however, aim to bar patent protection for inventions which were incapable of being precisely defined at the time the application was filed. For example, imprecise claims have been held valid when an element of the claim is ill-suited to be defined with precision because it requires appropriate design optimizations based on the environment of its intended use. E.g., Gen. Elec. Co. v. Nitro Tungsten Lamp Co., 266 F. 994, 1000 (2d Cir. 1920). In this case, the court upheld as valid an imprecise claim directed to a light bulb comprising a tungsten filament “of large effective diameter” because the dimensions of the filament are variable and must be designed appropriately based upon the intended wattage of the light bulb. Id.

While it is of course desired that patent claims be sufficiently definite and nonambiguous to survive an indefinite challenge under 35 U.S.C. §112, it is also desirable that at least some claims in the patent possess ambiguity. A full discussion on the reasons for including ambiguous claims in a patent application is beyond the scope of this blog post. One such reason is to deter potential infringers from competing with the invention by making it very difficult to accurately and confidently discern the bounds of the patent’s monopoly. Thus, effective claim drafting requires a practitioner to balance the competing interests of being as clear as the Patent Office and §112 demand while also being sufficiently unclear to deter potential patent infringers from offering products and services just beyond the patents monopoly.

This blog post highlights only a few of many issues that a skilled practitioner is likely to take into consideration when drafting claims for a patent application. It is at least in part due to the multitude of considerations that must be balanced in claim drafting that the Patent Office recommends that inventors seek assistance from a skilled practitioner rather than preparing and filing an application on their own.

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