The Claims Interpreted Report

Claim Interpretation and the Enablement Requirement

Providing a reminder about how to interpret elements of a patent claim when analyzing the claim against prior art during patent prosecution, in Technical Consumer Products, Inc. v. Lighting Science Group Corp. (April 8, 2020), the Federal Circuit vacated a PTAB decision that Appellant Technical Consumer Products’ (“TCP”) failed to show that claims of U.S. Patent No. 8,201,968 were invalid based on anticipation and/or obviousness.

The ‘968 patent is owned by Appellee Lighting Science Group Corp. (“LSG”). The ‘968 patent is directed toward an LED assembly this is configured to be retrofitted into an existing light fixture, such as a recessed can lighting fixture. Application of the prior art turned on interpretation of the claim recitation of a “heat sink.” Claim 1 recites:

a heat spreader and a heat sink thermally coupled to the heat spreader, the heat sink being substantially ring-shaped and being disposed around and coupled to an outer periphery of the heat spreader;

wherein the heat spreader, the heat sink and the outer optic, in combination, have an overall height H and an overall outside dimension D such that the ratio of H/D is equal to or less than 0.25.

Figure 12 from the ‘968 patent is reproduced below, illustrating a cross section showing the heat spreader, the heat sink, and the outer optic. Also reproduced is Figure 28 from the ‘968 patent illustrating measurement of the overall height H and the overall outside dimension D for calculating the H/D ratio.

During prosecution of the application for the ‘968 patent, the examiner initially rejected claims based on US Patent 7,670,021. The ‘021 patent discloses a lighting assembly 10 that has a trim 12 for dissipating heat energy, illustrated in Figure 2a of the ‘021 patent, reproduced below. Figure 2a of the ‘021 patent also shows is a heatsink 14 of the lighting assembly 10.

The examiner alleged that the ‘021 patent’s heatsink 14 disclosed the claimed heatsink, and that its trim 12 disclosed the prior claimed heat spreader. In response, the applicant for the ‘968 patent amended claims to clarify that the heat sink must be “substantially ring-shaped” and “disposed around and coupled to an outer periphery of the heat spreader.” The claims of the ‘968 patent were allowed after this amendment.

TCP challenged the validity of the ‘968 patent in an Inter Partes Review (IPR) at the PTAB, alleging that the claims of the ‘968 patent are invalid for anticipation or obviousness based on the ‘021 patent. Specifically, TCP alleged that an outer flange 22 and inner portion of the trim 12 (illustrated in Figure 2B of the ‘021 patent and reproduced below) disclosed the claimed heat sink and heat spreader, respectively. TCP did not rely on the heatsink 14 of the ‘021 patent for disclosing any of the limitations of the claims of ‘968 patent.


In response, LSG argued to the PTAB that the heat sink 14 of the ‘021 patent was a necessary element for enablement and needed to be included as part of the disclosed “heat sink.” According to LSG, removing the heat sink 14 would render the device inoperable. Including the heat sink 14 provided an H/D (height to diameter) ratio greater than the claimed .25 maximum ratio.

The PTAB sided with LSG and determined that the heat sink 14 could not be removed from the device of the ‘021 patent, and therefore must be included in calculating the H/D ratio. Accordingly, without removing the heat sink 14, the PTAB determined the ‘021 patent could not anticipate the H/D ratio claimed in the ‘768 patent.

In vacating the PTAB’s decision, the Federal Circuit found that the PTAB erred in interpreting the claim term “heat sink” such that it was disclosed by “an arrangement of heat sinking elements” that included both the trim 12 and heat sink 14 of the of the ‘021 patent for purposes of calculating the claimed H/D ratio. The Federal Circuit pointed out that the claims required “a heat sink” that was “substantially ring-shaped.” The trim 12 may have disclosed this limitation; however, the trim 12 and heat sink 12 are two individual separate elements – not “a” heat sink. Further, the claims used the term “comprising” signaling that a inventive device may contain additional elements. Accordingly, the Federal Circuit found that a heat sink as claimed (e.g., the trim 12) should be used, and that additional heat sinks (e.g., the heat sink 14) should be excluded, for calculating the H/D ratio as claimed.

The Federal Circuit further pointed out that the PTAB erred in applying the enablement requirement when determining that the heat sink 14 should be included in the H/D ratio. Specifically, the PTAB determined that the device of the ‘021 patent needed the heat sink 14, and therefore did not enable a device without a heat sink that would satisfy the H/D ratio as described by the ‘968 patent. However, the PTAB improperly applied the enablement requirement by comparing the disclosure of the ‘021 patent with that of the ‘968 patent (i.e., no additional heat sink) instead of with the invention as claimed (i.e., indifferent to an additional heat sink). In other words, claim interpretation and whether prior art enables claims are different and separate issues – the claim should be first interpreted, and then compared to the prior art to determine if the prior art is enabling of the interpreted claim.

Lessons for Practice

This case highlights the importance of using proper antecedent basis for identifying newly introduced claim elements and referring back to already introduced elements, and the importance claiming a single element or a groups of items depending on what is to be covered by the claim (e.g., a heat sink vs. an arrangement of heat sinking elements). Additionally, this case highlights the importance of focusing on claims at issue, not the specification supporting the claims, for enablement relating to prior art.