October 2012 Issue

Potential Pitfalls of Broad Claim Language

When drafting patent claims, patentees generally attempt to draft the broadest set of claims possible in order to benefit from the full scope of their inventive contribution.  To pass muster at the U.S. Patent and Trademark Office (USPTO), these broad claims, given their broadest reasonable interpretation, must have sufficient support in the patent specification.  Under section 112, paragraph 1, “[a] patent specification shall contain a written description of the invention . . . in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains . . . to make and use the same.”  35 U.S.C. § 112, ¶ 1.  Enablement law is designed to prevent inadequate disclosure of an invention, and the Federal Circuit has not hesitated to demonstrate that patentees utilizing broad claim language risk losing a claim that cannot be enabled across its full scope of coverage.

For example, in MagSil Corp. v. Hitachi Global, No. 2011-1221 (Fed. Cir. Aug. 14, 2012), the Federal Circuit found MagSil’s patent invalid for lack of enablement, stripping MagSil of any potential patent protection for its invention.  MagSil’s patents are directed to read-write sensors for computer hard disk drive storage systems and the asserted claims relate to a tri-layer tunnel junction device.  One of the keys to novelty in this case related to producing an adequate level of change in the tunneling resistance.  At the district court, MagSil argued for and got a virtually limitless construction of the claim phrase “causing a change in the resistance by at least 10% at room temperature.”  The district court found that the broad construction MagSil argued for resulted in the claim language being open-ended, basically covering any resistance change from 10% to infinity, even though the patent specification only disclosed how to achieve resistance changes of 10% to 11.8%.  MagSil’s own experts and inventors could not explain why it took twelve years after the filing of the patent application to achieve resistive changes between 100% and 120%.  In fact, MagSil’s experts admitted that further experimentation was needed to achieve these results. 

Based on this testimony and MagSil’s broad claim construction, the Federal Circuit upheld the district court’s finding that the claim language was broader than the invention actually disclosed in the patent specification.  The court found that the patent specification had no teachings on how to achieve any changes in resistance greater than 11.8% and, therefore, was not enabled because a person of skill in the art would not have been able to make and use the full scope of the invention.  As this case demonstrates, the Federal Circuit held MagSil accountable to support the full range and scope of its claims that MagSil argued for at the district court.  MagSil was ultimately unable to support the full range and scope of its claims, resulting in a finding of invalidity for lack of enablement. 

The MagSil court relied on In re Fisher, 427 F.2d 833, 839 (CCPA 1970), to support its holding.  In In re Fisher, the patent claimed ACTH potencies of “at least 1 International Unit of ACTH per milligram,” a similarly open-ended claim term to “at least 10%,” providing a lower threshold but not an upper limit.  Id. at 834.  In In re Fisher, the court found that an inventor should only be able to dominate the future patentable inventions of others where those inventions were based in some way on his teachings.  Since the court concluded that the specification in In re Fisher did not enable ACTH potencies much greater than 2.3 International Units of ACTH per milligram, the court found that the open-ended claim language of a potency of “at least 1” renders the claims insufficiently supported by the specification and invalid for lack of enablement.

MagSil attempted to compare its open-ended claim language of “at least 10%” to the “comprising” claim language in Gillette Co. v. Energizer Holdings, Inc., 405 F.3d 1367, 1371 (Fed. Cir. 2005).  The Federal Circuit found that the claim language in Gillette was different than MagSil’s claim language because, even though the patent claims used open-ended claim language by using the term “comprising,” the claims provided important limiting language to preserve their validity.  In analyzing Gillette, the Federal Circuit found that enablement was not at issue in the case because the claims to a safety razor blade unit “comprising . . . a group of first, second, and third blades” were not open-ended because the terms “first, second, and third” did not specify the number of blades, but rather specific characteristics of blades in those categories as defined in the specification and prosecution history.  Thus, the MagSil court found that the claims were limited despite the use of the term “comprising” due to this specific language in the claims.  Conversely, the claims in MagSil did not include any limiting language in the claims, specification, or prosecution history.

As a result of their affirmance of the district court’s finding of invalidity due to lack of enablement, the Federal Circuit dismissed MagSil’s infringement suit in its entirety.  There is an important lesson to be learned from this case.  While patentees can draft broad claims in their patent applications, they must be aware that the Federal Circuit will hold them accountable to support the full range and scope of these broad claims.  To aid in avoiding complete invalidation of a patent when drafting broad claims, patentees should also disclose several nested ranges of values in well-constructed dependent claims that provide specific examples from the embodiments disclosed in the patent specification.  This type of claim drafting may allow at least the narrower, dependent claims to survive an invalidity attack, even if the broadest claims are found invalid.