Federal Circuit Finds Prosecution History Narrowed Literal Scope of Claims

In Erbe Elektromedizin GmbH v. Canady Tech. LLC, 97 USPQ2d 1048 (Fed. Cir. 2010), ERBE Elektromedizin GmbH and ERBE USA, Inc. (collectively, “ERBE”) is the owner of U.S. Patent No. 5,720,745 (“’745 patent”), which is directed generally to argon gas-enhanced electrosurgical products for electrosurgery.  The ‘745 patent includes a “low flow” limitation in the independent claims as follows:

  1. Claim 1 recites that the “gas flows from the source, through the tube and exits through the opening at the distal end of the tube at a low flow rate of less than about 1 liter/minute”; and
  2. Claim 35 recites that “supplying the inert gas from the source of said gas through the tube to the distal end opening of said tube with such a low flow rate, that gas exiting through said distal end opening is a not directed, non laminar stream but forms an inert gas atmosphere” and has a depending claim 38 which defines that “the stream of gas exits through said distal end opening with a flow rate of less than about one liter per minute.”

The “low flow” feature was added during prosecution in response to the Examiner’s construction of the prior art as containing “argon flow rates ranging from 1 to 12 liters per minute, but did not disclose argon flow rates of “less than 1 liter per minute.”  In response, ERBE indicated that the low flow rate distinguished from the 1 to 12 liters per minute since a “flow rate of 1 litre per minute leads to a flow velocity of 19 m/h” and “12 litres per minute gives an outlet gas speed of 229 km/h”, which “would certainly be classified as laminar jets and would likely lead to” problems including being toxic to the patient.  In response to the amendment and argument, the Examiner allowed the application.

ERBE sued Canady Tech. LLC in the United States District Court for the Western District of Pennsylvania for, among other claims, infringing claims 1 and 35.  During the Markman Hearing, the District Court relied upon the ERBE’s statements to the Examiner to construe the low flow rate feature of claims 1 and 35 as requiring a rate of less than about 1 liter/minute producing a flow velocity of 19 km/h.  Since it was undisputed that Canady Tech. LLC. did not sell probes which produced flow velocities below 19 km/hr, the District Court granted summary judgment for non-infringement of the ‘745 patent.  ERBE appealed this construction since the flow velocities and flow rates were not expressly recited in the claims.

On appeal, the Federal Circuit, cited Phillips v. AWH Corp., 415 F.3d 1303, 1312 (Fed. Cir. 2005) (en banc) for proposition that claim terms are generally construed in accordance with the specification and the prosecution history.  The Federal Circuit found that, while claim 1 recites a low flow rate as being less than about 1 liter/minute, claim 35 alternately defines a low flow rate as being when “gas exiting through said distal end opening is a not directed, non laminar stream but forms an inert gas atmosphere” without reciting specific speeds.  In reviewing the specification, the Federal Circuit found the only example of what is a low flow rate, and found that the example was at less than 1 liter per minute.  The specification also indicates that this low flow rate forms the not directed, non-laminar stream that distinguished the invention from the prior art.  Thus, the specification did not discuss other flow rates and velocities.

Additionally, the Federal Circuit found that, in distinguishing the recited low flow rate from the prior art during prosecution, the applicant made specific admissions that the term “low flow rate” means less than 1 liter per minute, and specifically noted that the low flow rate of less than 1 liter per minute produces a flow velocity of 19 m/h which avoids the problems in the prior art which have higher flow rates which produce laminar jets.  Thus, the Federal Circuit agreed with the District Court that the applicants “clearly and unambiguously disclaimed such flow rates that produced laminar jets and limited the claims to flow velocities less than 19 km/hr to overcome unpatentability.”

In response, ERBE countered that the District Court’s claim interpretation as to claim 35 in requiring the specific low flow rate renders claim 38 superfluous.  Specifically, ERBE noted that claim 38, which depends from claim 35, recites a “flow rate of less than about one liter per minute.”  As such, ERBE asserted that claim 35 must be broader than claim 38 under the doctrine of claim differentiation.  In rejecting this argument, the Federal Circuit quoted Renishaw PLC v. Marposs Societa’ Per Azioni, 158 F.3d 1243, 1248 (Fed. Cir. 1998) for proposition that “no canon of [claim] construction is absolute in its application” and therefore claim differentiation is only “one of many tools used by courts”.  As such, since the disclaimer and definition was sufficiently unambiguous, the doctrine of claim differentiation does not override the definition arrived at by the District Court.

Significance for Patent Applicants

Erbe Elektromedizin GmbH serves as a reminder that any argument as to the patentability of a claim feature should be limited to that specific claim feature.  Thus, statements as to the significance of a claim feature can be used to narrow the scope of the literal language by adding details as being essential which might otherwise be considered optional.  Moreover, while adding depending claims to attempt to broaden the claims can be helpful to overcome a narrow interpretation, claim differentiation will itself not overcome clear arguments which define the features of the depending claim as being inherent in the independent claims.  Thus, to the extent possible, arguments for patentability should be limited to the literal claim language as opposed to relying upon generalizations applicable to a diverse set of claims.

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