## Facts

- Stratoflex and Aeroquip manufactured electrically conductive polytetrafluoroethylene (PTFE) tubing used in aircraft and missile applications to convey pressurized fluids.
- The asserted patent, U.S. Patent No. 3,473,087, claimed composite PTFE tubing with a conductive inner PTFE layer (e.g., containing carbon black) and an outer layer of essentially pure, relatively nonconductive PTFE.
- Stratoflex filed an action in the Eastern District of Michigan seeking a declaratory judgment that claims 1, 3, 4, 6, and 7 were invalid and not infringed.
- Aeroquip, the patent assignee, counterclaimed for infringement.
- After a bench trial, the district court held the asserted claims invalid for obviousness under 35 U.S.C. § 103 and not infringed.
- Aeroquip appealed to the Federal Circuit.

## Issues

1. Whether the district court erred in holding claims 1, 3, 4, 6, and 7 invalid as obvious under 35 U.S.C. § 103.
2. Whether the district court erred in finding no infringement.

## Decision

- The Federal Circuit affirmed the judgment that the asserted claims were invalid as obvious under § 103.
- The court affirmed the district court’s noninfringement finding.
- The court treated obviousness as a legal conclusion based on underlying factual findings and reviewed the factual findings for clear error.
- The court held that “analogous art” properly included rubber hose references because they were reasonably pertinent to the problem addressed by the claimed invention.
- The court rejected arguments that the statutory presumption of validity under 35 U.S.C. § 282 is “weakened” by the introduction of prior art not considered during examination.

## Legal Principles

- The presumption of validity in 35 U.S.C. § 282 is a procedural rule allocating the burden of persuasion to the challenger; it does not fluctuate based on whether particular prior art was before the Patent Office.
- Obviousness must be analyzed under the Graham v. John Deere framework: (1) scope and content of the prior art, (2) differences between the prior art and the claims, (3) level of ordinary skill, and (4) objective indicia (secondary considerations).
- A reference is within the scope of analogous art if it is reasonably pertinent to the problem the inventor sought to solve; art from a different material or field may qualify when directed to the same problem.
- Secondary considerations (e.g., commercial success, long-felt need) require a nexus to the claimed invention and cannot overcome a strong prima facie showing of obviousness absent that connection.
- Applying known composite hose concepts (conductive inner layer with nonconductive outer layer) to PTFE tubing, in view of the pertinent prior art and the level of ordinary skill, can support a conclusion of obviousness.

## Conclusion

The Federal Circuit affirmed that the claimed composite PTFE hose structure was obvious in view of pertinent prior art, including analogous rubber hose references, and it reiterated that the patent validity presumption is a constant procedural allocation of the burden of persuasion; the court also affirmed the district court’s determination of noninfringement.


Stratoflex, Inc. v. Aeroquip Corp., 713 F.2d 1530 (Fed. Cir. 1983)