IP Law Daily, PATENT—Fed. Cir.: Canon preserves PTAB obviousness rulings involving heater-chip and thermal-control inkjet printer patents, (Jul 20, 2026)

By Ravindra Kumar Singh, B.L.

The PTAB correctly found two patents directed to inkjet printhead temperature regulation obvious over prior-art combinations and properly construed a disputed claim limitation in holding a third heater-chip patent obvious.

In two nonprecedential dispositions, the U.S. Court of Appeals for the Federal Circuit has affirmed three Patent Trial and Appeal Board (PTAB) final written decisions holding claims of three printer technology patents owned by a licensing entity unpatentable for obviousness. In one opinion, the court upheld the Board's claim construction and obviousness findings involving a heater-chip patent. In the second, it affirmed two related PTAB decisions involving temperature-monitoring technology for inkjet printheads, rejecting arguments that the Board relied on hindsight, improperly combined prior-art references, misconstrued the prior art, or lacked substantial evidence for its findings. Together, the decisions left intact all three PTAB determinations that the challenged claims would have been obvious under 35 U.S.C. § 103 (Slingshot Printing LLC v. Canon U.S.A., Inc., No. 25-1032 (Fed. Cir. Jul. 16, 2026)) and (Slingshot Printing LLC v. Canon U.S.A., Inc., No. 25-1033 (Fed. Cir. Jul. 16, 2026)).

Dispute. Slingshot Printing LLC (Slingshot) owns patents relating to inkjet printing technology. Canon U.S.A., Inc., and Canon Inc. (Canon) instituted three separate inter partes reviews (IPRs) challenging three patents owned by Slingshot. The patents at issue, U.S. Patent Nos. 7,290,864 (the ’864 patent), 7,484,823 (the ’823 patent), and 7,594,708 (the ’708 patent) are directed to different aspects of inkjet printhead technology. The ’864 patent concerns heater chips designed to reduce the number of bondpads needed to distribute electrical power to heater arrays in an inkjet printhead. By contrast, the ’823 and ’708 patents focus on monitoring and regulating temperature on a per-thermal-region basis by placing temperature sensors within defined regions of the heater chip, thereby improving temperature control and print quality.

In each proceeding, the Board concluded that the challenged claims would have been obvious over combinations of prior-art references and issued Final Written Decisions holding the claims unpatentable. Slingshot separately appealed all three decisions. Although the appeals arose from three different IPRs, the Federal Circuit resolved them through two opinions. The first involved only the ’864 patent. The second concerned the ’823 and ’708 patents, which shared substantially similar specifications and raised common questions regarding the placement of temperature sensors and the regulation of heat within inkjet printheads.

Heater-chip patent. In the first appeal, Slingshot principally challenged the Board's construction of the claim limitation requiring power traces to be "physically separated proximal to the bondpad." According to Slingshot, the traces had to separate closer to the bondpad than to the heater arrays. The Federal Circuit disagreed, concluding that the Board correctly interpreted the limitation as referring to separation at a point closer to the bondpad than to the end of the power trace. The court observed that neither the claim language nor the specification required comparing the separation point to the heater arrays and agreed that proximity should instead be measured along the trace itself.

Slingshot also argued that the Board lacked substantial evidence to support its obviousness determination because one of the relied-on prior art figures did not depict a bondpad and was not drawn to scale. The Federal Circuit rejected those arguments, explaining that the Board relied not only on the challenged figure but also on additional prior-art references and expert testimony establishing that a skilled artisan would understand the bondpad to be located at the edge of the heater chip. Citing Nystrom v. TREX Co., 424 F.3d 1136 (Fed. Cir. 2005), the court emphasized that patent drawings may properly be used for general visual comparisons without being treated as precise engineering drawings from which exact measurements are derived.

Temperature-control patents. The companion opinion addressed the ’823 and ’708 patents, which concern regulating temperatures in separate thermal regions of an inkjet printhead through centrally positioned temperature sensors. Slingshot argued that the Board relied on hindsight by reconstructing the claimed inventions using the patents themselves and by improperly combining the prior-art references.

The Federal Circuit found no merit in those contentions. It explained that the Board cited the patents' background sections only as admissions describing what was already known in the prior art rather than as evidence of the claimed inventions. The court further observed that Slingshot improperly attacked each prior-art reference individually, even though the Board's obviousness determination rested on the combined teachings of multiple references. Citing In re Merck & Co., 800 F.2d 1091 (Fed. Cir. 1986), the court reiterated that the obviousness inquiry must evaluate the references collectively rather than in isolation.

Slingshot further argued that another prior-art reference, Yabe, taught away from placing temperature sensors in the central portions of the heater chip. The Federal Circuit concluded that the argument had not been preserved before the Board regarding the relevant prior-art combination. Regardless, the court held that Yabe merely disclosed an alternative sensor placement and did not criticize, discredit, or otherwise discourage the arrangement claimed in the patents. Under Galderma Laboratories, L.P. v. Tolmar, Inc., 737 F.3d 731 (Fed. Cir. 2013), that was insufficient to establish teaching away.

The court likewise rejected Slingshot's contention that a skilled artisan would not have been motivated to incorporate additional temperature-sensing resistors because doing so would increase manufacturing costs. Agreeing with the Board, the Federal Circuit concluded that the improved temperature measurement accuracy and resulting enhancement in print quality would have outweighed any asserted cost concerns. It also upheld the Board's finding that the prior art disclosed temperature sensors positioned "substantially centrally" within the claimed thermal regions, relying in part on expert testimony explaining the relative placement of the sensors and heater arrays.

Outcome. Having rejected each of Slingshot's claim-construction, obviousness, and evidentiary challenges, the Federal Circuit concluded that no reversible error had been shown in any of the three IPR proceedings. It therefore affirmed all three PTAB Final Written Decisions holding the challenged claims of the ’864, ’823, and ’708 patents unpatentable as obvious.

The Case is No. 25-1032.

The Case is No. 25-1033.

Judge: Chen, R.

Attorneys: Rayiner Hashem (MoloLamken LLP) for Slingshot Printing LLC. Julie S. Goldemberg (Morgan, Lewis & Bockius LLP) for Canon U.S.A., Inc.

Companies: Slingshot Printing LLC; Canon U.S.A., Inc.

Cases: Patent FedCirNews TechnologyInternet