PTAB challenges

As a senior PTAB practitioner, I've reviewed the history of US Patent 5,359,647. Based on the USPTO's Open Data Portal and a comprehensive web search conducted on 2026-05-11, there have been no inter partes review (IPR), post-grant review (PGR), or covered business method (CBM) proceedings filed against this patent.

The absence of any AIA trial proceedings is the most critical fact for a defendant.

Proceedings overview

There have been zero AIA trial proceedings filed against US patent 5,359,647. This means the patent has never been challenged at the PTAB, and all of its original claims remain untested in this venue. For a defendant, this indicates that any invalidity defense would have to be developed from scratch, without the benefit of prior arguments or PTAB decisions.

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(No proceedings to list)

Strategic summary

The claims of US patent 5,359,647 are entirely UNTESTED at the PTAB. No claims have been canceled or sustained through an AIA trial.

The estoppel landscape is completely open. Since no IPRs have been filed, the limitations under 35 U.S.C. § 315(e)(2) do not apply to any potential petitioner. A defendant is free to file an IPR on any grounds based on prior art patents or printed publications that they can identify.

There are no pattern signals to analyze. The patent owner, Plantronics (now an HP company), has not had to defend this patent at the PTAB. There is no history of aggressive appeals or involvement from defensive aggregators concerning this specific patent. The lack of PTAB challenges is itself a signal: despite the patent being owned by a major industry player and relating to common technology, it has not been asserted in a manner that provoked an AIA challenge, or potential licensees have chosen to settle rather than challenge its validity at the board.

Recommended next steps

For a defendant facing an assertion of US patent 5,359,647, the path is clear but requires foundational work.

1. Acknowledge the Clean Slate: The primary takeaway is that no prior art has been successfully used to invalidate these claims at the PTAB. This means there is no pre-existing roadmap for an invalidity case, but also no negative precedent.

2. Conduct a Thorough Prior Art Search: The patent expired on May 28, 2013, so any current assertion would be for past damages only. A defendant's primary non-infringement or invalidity arguments would need to be developed in district court. A fresh, comprehensive prior art search focused on the limitations of the asserted claims would be the immediate first step. The prior art and obviousness analyses provided in earlier sections of this report serve as a strong starting point for such an invalidity contention.

3. Evaluate Business Resolution: Given that the patent is expired and owned by a large operating company (HP Inc.), any dispute is likely a licensing matter for past sales. The cost of litigation versus a potential settlement for historical damages should be carefully weighed, especially since there is no PTAB history to leverage for a quick invalidity resolution.

In summary, US patent 5,359,647 has no PTAB trial history. A defendant must proceed as if they are the first to formally challenge the patent's validity.