Stratoflex, Inc. v. Aeroquip Corporation

United States Court of Appeals, Federal Circuit
713 F.2d 1530 (1983)

ELI5:

Rule of Law:

Evidence of secondary considerations, such as commercial success, long-felt but unsolved needs, and failure of others, must always be considered as part of the legal analysis for determining patent obviousness under 35 U.S.C. § 103, and it is legal error to only consider such evidence in close cases.

Facts:

Both Stratoflex and Aeroquip manufactured polytetrafluoroethylene (PTFE) tubing for the aircraft and missile industry.
In 1959, it was discovered that hydrocarbon jet fuels flowing through pure PTFE tubing created electrostatic charges that could arc through the tubing wall, creating 'pin holes' and causing fuel leaks.
Aeroquip engineers Abbey and Upham investigated the problem and concluded that adding carbon black to PTFE tubing increased its conductivity, which helped dissipate the static charge.
In 1960, Aeroquip enlisted Raybestos-Manhattan, a PTFE hose manufacturer, to develop a solution.
Winton Slade, an inventor at Raybestos, conceived of a composite tube formed of an inner layer of conductive PTFE (containing carbon black) and an outer layer of non-conductive, pure PTFE to prevent leaks.
Slade filed a patent application for his composite tube in 1962, which eventually issued as the '087 patent and was assigned to Aeroquip.
Stratoflex later began manufacturing and selling its own composite PTFE tubing that had a conductive inner layer and a non-conductive outer layer.
In 1978, Aeroquip accused Stratoflex of infringing the '087 patent.

Procedural Posture:

Stratoflex, Inc. filed a lawsuit in the U.S. District Court for the Eastern District of Michigan against Aeroquip Corp., seeking a declaratory judgment that U.S. Patent No. 3,473,087 was invalid and not infringed.
Aeroquip filed a counterclaim alleging patent infringement.
Following a non-jury trial, the district court entered a judgment declaring the asserted patent claims invalid for obviousness under 35 U.S.C. § 103 and not infringed.
Aeroquip, as the appellant, appealed the district court's judgment to the U.S. Court of Appeals for the Federal Circuit, with Stratoflex as the appellee.

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Issue:

Is a patent for composite polytetrafluoroethylene (PTFE) tubing with a conductive inner layer and a non-conductive outer layer invalid for obviousness under 35 U.S.C. § 103 when the prior art taught using conductive fillers to solve static electricity problems in other types of tubing and the advantages of layered composite tubes?

Opinions:

Majority - Markey, Chief Judge

Yes, the patent is invalid for obviousness. An invention is obvious if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art. The court found that the prior art, including that related to rubber hoses, was reasonably pertinent because it addressed the same problem of electrostatic buildup. Prior art taught the use of conductive fillers like carbon black to dissipate static charges and the use of composite layers to combine the benefits of different materials. The court concluded that substituting PTFE for other materials and creating a composite tube to solve a known problem was obvious to a person of ordinary skill in the art. Although the district court erred by refusing to consider secondary evidence because it deemed the case 'not close,' this error was harmless because Aeroquip's evidence of commercial success lacked a sufficient nexus to the merits of the claimed invention to overcome the strong evidence of obviousness.

Analysis:

This case is significant for its definitive statement on the role of secondary considerations in the patent obviousness analysis. The Federal Circuit established that such evidence is not merely a tie-breaker for close cases but must always be considered as part of the whole picture under the Graham framework. This ruling strengthens the objective nature of the obviousness inquiry by requiring courts to weigh real-world evidence of an invention's impact and value. The decision also discourages the use of non-statutory, amorphous concepts like 'synergism' or special rules for 'combination patents,' directing the analysis back to the statutory language of 35 U.S.C. § 103 and the factual inquiries mandated by Graham v. John Deere Co.

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