The Software IP Report

Not All Patent Prosecution Disclaimers Are Broadly Construed

Not all patent prosecution disclaimers are broadly construed; rather, in construing patent claim terms disclaimers must be closely aligned to actual arguments made during prosecution.  On March 3, 2017 the Federal Circuit in Technology Properties Limited, et al v. Huawei, again gave guidance on the issue of prosecution history disclaimer.

The patent at issue in Technology Properties related to a microprocessor with different clocks and improving performance by decoupling a variable frequency CPU and I/O clocks with the CPU clock fabricated on the same silicon as the rest of the microprocessor.  The claim term at issue in Technology Properties was “an entire oscillator disposed upon said integrated circuit substrate”.  The district court found two disclaimers based on two different prior art references – Magar and Sheets.

The disclaimer based on the Magar reference limited “an entire oscillator” to one “whose frequency is not fixed by any external crystal.”  Technology Properties argued how the Magar reference was different from the claimed invention in ways unrelated to the disclaimer.  The Federal Circuit acknowledged that the claimed invention may be different from the prior art in the manner in which Technology Properties argued, but nonetheless upheld the disclaimer.  Specifically, the Federal Circuit stated “The argument Technology Properties raises on appeal may have been sufficient to traverse the Magar rejection and avoid a narrow construction, but this is not the same argument the patentee presented during prosecution.”  The Federal Circuit held that since the district court’s disclaimer aligned precisely with the arguments to distinguish Magar the disclaimer was proper and it did not matter that the patentee surrendered more than was necessary.

The disclaimer based on the Sheets reference further limited “an entire oscillator” to one” that does not require a control signal” Here the Federal Circuit found that the patentee distinguished a particular use of a command signal, namely to control the clock frequency” not all use of a control signal.  The Federal noted that the elimination of a control signal for clock frequency aligned with the patentee’s characterizations of the benefits of the invention – namely the elimination of a command input to change clock frequency.


The takeaway from the Technology Properties case is that disclaimers will continue to be closely aligned with the argument actually made during prosecution.  When discussing the specifics of a prior art rejection a narrower discussion of the prior art will be less likely to lead to a broad disclaimer.  Further, when arguments can be tied to the stated benefits of an invention that too will mitigate against a broad disclaimer.