Claim Differentiation

Andersen Corp. v. Fiber Composites (Fed. Cir. 2007).

Claim differentiation is based on a “common sense” presumption that different words used in the various claims indicate that the claims differ in focus and scope. Andersen holds a number of patents related to fiber materials and sued Fiber Composites for infringement.  Fiber Composites used the material for deck railing. Several of the claims included terms such as pellets, linear extrudates, or composites. 

Overcoming the Presumption of Claim Differentiation: Based on the concept of claim differentiation, Andersen argued that the composite limitation must not be limited to pellets and linear extrudates.  In its decision, the CAFC agreed that – in the abstract – Andersen’s argument was sound.  However, the appellate body found “powerful evidence” in both the specification and prosecution history that overcome the presumption of claim differentiation. In particular, the applicant lumped the three elements together when making arguments and discussed the pellet form as an ‘essential’ part of the invention.

Differentiation of Elements vs. Claims: It is also important to remember that the doctrine is that of claim differentiation rather than element differentiation.  Claim differentiation is not necessary unless the claims as a whole are redundant.

“A further reason for not applying the doctrine of claim differentiation in this case is that the … claims are not otherwise identical but for the references to pellets, linear extrudates, and composite compositions, and thus the district court’s construction does not make the composite composition claims redundant. Instead, there are numerous other differences varying the scope of the claimed subject matter….

Even though the “composite composition” claims, as construed by the district court, cover substantially the same subject matter that is covered by the “pellet” and “linear extrudate” claims, overlapping patent claims are not unusual, and the overlap does not require us to construe the “composite composition” claims to cover subject matter that differs from the subject matter covered by the other two sets of claims. Under these circumstances, the doctrine of claim differentiation does not require rejection of the district court’s construction of the claims.

Consequently, the CAFC ruled that the composite elements were no broader than the claimed pellets or extrudates.


  • This is a case from January 2007.  I missed it because the Seagate en banc order was released the same day.

One thought on “Claim Differentiation

  1. 1

    I question the extent to which claim differentiation reflects “common sense.” While statute drafters may be trying to avoid redundancy, the same is often not true of patent claim drafters. Sometimes patent lawyers use different words intending to cover precisely the same thing, either to hedge their bets or to game the system by taking advantage of claim differentiation.

    I’ve got a draft paper called “The Limits of Claim Differentiation,” arguing for guidelines on the use of the doctrine. Andersen is consistent with those guidelines. If you’d like a copy, let me know off-list.

Comments are closed.