Contents
Background of the Case
Case: University of Maryland v. Presens (Federal Circuit, non-precedential).
Issue: Whether claims of U.S. Patent No. 6,673,532 were obvious.
Context: Inter partes reexamination (IPR) affirmed by the PTAB.
The Federal Circuit upheld the rejection of the patent claims as obvious.
The ’532 Patent
Directed to an optical method for monitoring cell culture parameters.
Claim 1 (representative claim) includes:
A cultivation vessel with a single continuous volume.
At least two optical chemical sensors inside the vessel.
Sensors excited by light sources.
Detection and analysis of emissions/absorption to measure parameters.
Prior Art References
Bambot
Described optical methods for measuring:
Glucose
pH
Oxygen
Carbon dioxide
Included similar components:
Sensors
Excitation sources
Detectors
Weigl
Described a triple sensor device for measuring:
pH
Oxygen
Carbon dioxide
Sensors were located outside the cultivation vessel.
Each sensor had a dedicated excitation source and detector.
Examiner’s Obviousness Rejection
Combined Bambot and Weigl.
Concluded that the claimed invention would have been obvious at the time of invention.
Found that together the references disclosed all elements of the claim.
Patent Owner’s Argument
Argued that combining the references:
Would change Weigl’s “fundamental principle of operation.”
Relied on In re Ratti (1959), a case often cited to support this type of argument.
Claimed that moving Weigl’s sensors inside the vessel would fundamentally alter its operation.
Federal Circuit’s Decision
Affirmed the PTAB’s obviousness ruling.
Held that:
The patent owner misapplied Ratti.
Weigl was relied upon for what it measured (parameters), not sensor placement.
Emphasized:
A person of ordinary skill is “not an automaton.”
References need not be physically combined exactly as disclosed.
If the combined teachings disclose all claim elements, obviousness may be found.
Key Lessons for Patent Practice
The “changes the principle of operation” argument is difficult to win.
Courts may:
Focus on what the references teach conceptually.
Not limit analysis to literal structural combinations.
Practitioners must:
Carefully analyze how each reference is being applied.
Ensure the argument aligns precisely with how the examiner relies on the references.
Overuse or misapplication of the “principle of operation” argument can weaken an obviousness defense.
Practical Takeaway
Successfully overcoming obviousness requires:
A precise understanding of the examiner’s rationale.
Careful framing of combination arguments.
Simply asserting that a combination changes a reference’s principle of operation is often insufficient without strong technical support.
