US 7716921

I'll search for authoritative information on US 7716921, including any 2026 CAFC docket activity.

Let me verify litigation/docket status with additional targeted searches.

US 7,716,921 B2 — Verification Summary

Search result on dockets: I ran targeted searches for litigation and CAFC 2026 activity on this patent number. I found no evidence of any CAFC 2026 docket, district court litigation, ITC action, or PTAB proceeding involving US 7,716,921. I cannot prove a negative, and I do not have direct access to PACER/CAFC CM-ECF, so treat this as "no activity surfaced in searches," not as an authoritative all-courts clearance. There were no near-number collisions that produced relevant hits.

Bibliographic data (from the patent record)

Note: the patent bears a chain of GM restructuring security interests (US Treasury 2009, Citicorp 2009, UAW Retiree Medical Benefits Trust 2009, Wilmington Trust 2010), all later released or superseded.

Abstract (verbatim)

"A particulate filter for an exhaust system configured to receive an exhaust flow is disclosed. The filter includes a wall-flow filtration element having a first regeneration zone and a second regeneration zone, the first zone being downstream of the second zone, and a heat source disposed at the first regeneration zone. In response to demand for regeneration, the wall-filtration element regenerates according to a staged regeneration such that the first zone initiates regeneration ahead of the second zone, and each zone regenerates in the direction of the exhaust flow."

Plain-language overview of the independent claims

Claim 1 — the apparatus (particulate filter).
A diesel particulate filter whose ceramic wall-flow monolith is divided into two regeneration zones along its length. The "first" regeneration zone sits downstream of the "second" zone (i.e., near the outlet end of the filter), and a heat source is placed at that downstream first zone. Crucially, both zones must be parts of the same wall-flow filter element — the claim is not satisfied by two separate filter bricks. When regeneration is demanded, the element regenerates in a staged manner: the downstream zone lights off first, then the upstream zone, and within each zone the burn front travels in the direction of exhaust flow. The point is to burn the soot at the normally-hottest closed (outlet) end first, so that when the thermal wave arrives there is little fuel left, lowering peak temperature.

Claim 11 — the method.
A method of regenerating such a filter, adding the express limitation that the first-zone element is continuous with the second-zone element without interruption (a single continuous monolith), with the heat source at the downstream first zone. The method step is: on regeneration demand, regenerate in staged fashion — downstream zone first, then upstream zone, each burning in the direction of exhaust flow, with the regeneration front progressing along the continuous element. This claim reads on the same concept as claim 1 but in method form and with the continuity limitation baked in.

Claim 20 — the method, with zone dimension and catalyst specifics.
A method claim that imports the full structural detail of claim 7: a wall-flow element with a first end (inlet side), second end (outlet side), porous internal walls sized to trap carbonaceous particulates; an inlet channel with an inlet port at the first end and a first end-plug at the second end; an outlet channel with a second end-plug at the first end and an outlet port at the second end, the channels in fluid communication through the internal walls. The downstream first zone extends from the second end toward the first end across about 25% to about 50% of the overall length, the upstream second zone covers the remaining about 50% to about 75%, and an oxidation catalyst is disposed on the internal walls of the first zone. The method step is staged regeneration in the same downstream-to-upstream, flow-direction sequence.

Practice notes / uncertainties worth flagging

• Claim 9 recites "the oxidation catalyst comprises Cordierite." Taken literally, this is chemically odd — Cordierite (Mg₂Al₄Si₅O₁₈) is the ceramic substrate/filter material described in the specification, not an oxidation catalyst (the spec discusses Cordierite as the filter body that staged regeneration makes viable, precisely because of its thermal limits). I am reporting the claim as issued rather than correcting it.
• Claim 17 uses a semicolon ("wherein;") instead of a colon — an apparent typographical defect in the printed claim.
• Claim 18 ("the wall-flow filtration element of both the first regeneration zone and the second regeneration zone is a particulate filter") and claim 19 (zone-to-zone "continuous… without interruption") appear to be narrowing limitations added during prosecution, likely to distinguish single-monolith structures from multi-brick or zoned-catalyst prior art. Together with the "same wall-filtration particulate filter element" language in claims 1 and 11, the prosecution history evidently focused on the unity/continuity of the filter body.
• Specification typo: "Cordiertie" appears once in the advantage paragraph; the term is spelled "Cordierite" elsewhere.
• Substantive scope note: the heat source can be an oxidation catalyst (claim 2), a heater such as an electric heater (claims 3–4), or a second heat source on the upstream zone (claim 5), with an optional controller (claim 6). Independent claim 1 requires only that the heat source be "disposed at" the first regeneration zone; claims 16–17 broaden this to "at least partially along a length of" the respective zone.
• Prior art cited of record: 13 US references including US 4,404,795 (Toyota), US 4,519,820 (Nippondenso), US 4,887,427 and US 5,067,320 (Nissan), US 4,934,142 (Toyota), US 5,017,142 (Waschkuttis), US 5,212,948 and US 5,357,755 (Donaldson), WO 2001/096717 (Johnson Matthey), US 6,823,660 (Isuzu), US 7,107,763 (Hitachi Metals), and US 2005/0050870 A1 (Cheng — same inventor). The examiner also cited the PCT search report for PCT/US06/033987. Only one third-party/forward citation family (Ford US 8,844,274) cites it.

Bottom line

US 7,716,921 is a GM (Cheng) patent on staged, downstream-first regeneration of a single continuous wall-flow diesel particulate filter, targeting thermal-runaway/peak-temperature reduction at the filter's closed end and enabling cheaper Cordierite substrates. It expired in 2014 for non-payment of maintenance fees, and my searches surfaced no litigation, PTAB, or CAFC 2026 docket activity for this number.

I'll search several litigation-specific sources for this patent number.

Let me run more targeted searches on litigation databases.

Let me check CourtListener and a couple more litigation-specific sources.

Litigation Search Report — U.S. Patent No. 7,716,921

Bottom Line

No litigation is known involving U.S. Patent No. 7,716,921 ("Exhaust particulate filter"). I searched litigation-oriented sources (including the Unified Patents litigation portal, PTAB/PTACTS filings, CourtListener, and general web/docket queries keyed to the exact number "7716921" / "7,716,921") and found no district court or Federal Circuit case, PTAB proceeding, ITC investigation, or other adversarial proceeding naming this patent.

Case-by-Case Table

There are therefore no case numbers, filing dates, or outcomes to report.

What the Record Does Show (Context, Not Litigation)

• Patent identification: US 7,716,921 B2, "Exhaust particulate filter," inventor Shi‑wai S. Cheng, application 11/335,222, filed 2006‑01‑19, priority 2005‑09‑01, granted 2010‑05‑18.
• Owner: Originally assigned to GM Global Technology Operations, Inc. (later GM Global Technology Operations LLC). It is a captive OEM portfolio asset, not an asset that appears to have been transferred to an assertion entity.
• Legal status (from the patent record): The patent expired for failure to pay maintenance fees. The record shows a maintenance‑fee reminder mailed 2013‑12‑27, lapse for failure to pay 2014‑05‑18, and expiration under 37 CFR 1.362 recorded 2014‑06‑13/16. Google Patents lists it as "Expired – Fee Related," with an "adjusted expiration" of 2026‑01‑23.
• The only "7716921" hits in the searches were unrelated — e.g., a 2022 journal DOI (10.1155/2022/7716921) and patent‑database listing pages — and should not be confused with this patent.
• Related family member US 8,011,177 B2 (the continuation‑in‑part, application 11/833,558) also appears in the family; no litigation was surfaced for that patent either.

Caveats on Completeness

• I could not open the Unified Patents litigation caselist page directly at the URL https://portal.unifiedpatents.com/litigation/caselist filtered to this patent; results were derived from indexed searches of that portal's content and other sources. A handful of older, low‑volume district court suits (especially pre‑2010 filings) may not be fully indexed in free databases.
• My statements are based on publicly indexed records as of this search. I make no representation as to the accuracy or completeness of third‑party databases, and the absence of a hit is not a legal conclusion that no case ever existed.

Note on terminology: A "PTAB/IPR" challenge is not "litigation" in the strict sense, but I checked for it as well; none was found for this patent either.

If you need a definitive negative, the authoritative check would be the USPTO Patent Assignment/PatentCenter "Litigation" (formerly PAIR) tab and PACER's nationwide docket search for "7,716,921."

I'll start by verifying the structured data against web sources before drafting.

Confirming absence with additional targeted queries.

One more check for district court assertions and any reexamination, which would matter to a defendant even absent an IPR.

Proceedings overview

Zero (0) AIA trial proceedings on file. The USPTO Open Data Portal returns no IPR, PGR, or CBM petitions for US 7,716,921, and targeted web searches surfaced no PTAB or Federal Circuit activity involving this patent. The breakdown is therefore: 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denied. The defensive posture is not "the patent has survived two IPRs and is hardened" — it is that the patent has never been tested at the PTAB at all, which for a 2005-priority GM diesel-emissions patent means the claims are untested, not validated. Importantly, a defendant's leverage here likely comes from a different direction entirely: the maintenance-fee record (see below), not from any AIA trial.

I want to be explicit about the limits of this report: the absence of PTAB activity is a factual finding, but it is a negative finding. I cannot prove a negative from search alone, and PTAB filings from the 2012–2014 window are less consistently indexed in secondary sources than current ones. What I can say with confidence is that the canonical ODP list is empty and nothing in the public record contradicts it.

No proceedings to report

There are no PROCEEDING_NUMBER entries to populate. I am not going to construct any. No IPR/PGR/CBM number exists in the source data or in any source I could locate, and inventing one — even a plausible-looking IPR2013-00XXX — would be the single most damaging thing this memo could do, because a defendant would build an estoppel strategy around a proceeding that never happened.

For completeness, the neighboring activity that does exist and could easily be mistaken for PTAB work:

• US 8,011,177 B2 ("Exhaust particulate filter") — a continuation-in-part of this patent, filed 2007-08-03 via Ser. No. 11/833,558, same sole inventor (Shi-wai S. Cheng), same assignee, same 2005-09-01 priority claim. This is a sibling patent with its own claim set, not a PTAB proceeding. If a defendant is facing assertion of "the Cheng exhaust particulate filter patent," verify which patent number is in the demand — '921 and '177 have different claims and different expiration math. (Source: Google Patents family data, https://patents.google.com/patent/US7716921/en)
• WO 2007/027864 A2/A3 and DE 11 2006 002 344 T5 — foreign counterparts of '921 under PCT/US2006/033987. Not trials.
• The 12–13 prior-art references cited on the face of '921 (e.g., US 4,404,795 to Toyota; US 4,938,412 to Toyota; US 4,519,820 to Nippondenso; US 5,067,320 to Nissan; US 5,212,948 to Donaldson; WO 2001/096717 to Johnson Matthey; US 2005/0050870 A1 to Cheng) are prior art, not petitioners. They are the raw material a future petitioner would work from — see the estoppel discussion below.
• The only citing document of note is US 2010/0175372 A1 (Christine Kay Lambert), which matured into US 8,844,274 B2 (Ford Global Technologies, 2014-09-30) — again a citing publication, not a challenge.

Strategic summary

Claim status: 1–20 all UNTESTED. There is no PTAB Final Written Decision, no certificate of cancellation, and no reexamination certificate for this patent. Every claim — independent claim 1, independent claim 11 (method), independent claim 20 (method), and dependents 2–10 and 12–19 — stands as issued on 2010-05-18. Do not tell a client that any claim "is dead," because nothing has killed it. If you are looking for claim-level invalidity ammunition, you will have to generate it yourself in district court or in a first-instance petition; there is no prior adjudication to lean on and no estoppel to inherit.

Estoppel landscape: a blank slate, which cuts both ways. Section 315(e)(2) estoppel only attaches to a petitioner that actually reached a final written decision (or settled after institution). With no petitioner on file, no third party is estopped from anything. That means a defendant today could file a clean IPR on any § 102/§ 103 ground without worrying about a previous petitioner's arguments having consumed the art — but it also means the patent owner has never had to defend these claims, has never stipulated to a construction, and has never been forced to disclaim scope. There is no prosecution-history-based narrowing you can borrow from a prior trial, and no IPR-driven claim construction (Phillips-adjacent or otherwise) to leverage. Practically: the whole § 102/§ 103 universe is open, but so is the patent owner's ability to argue for broad claim scope for the first time.

Pattern signals: none of the usual ones. No repeat petitioner (there is no petitioner at all). No patent-owner appeal activity, because there has been nothing to appeal to the Federal Circuit. No defensive aggregator (Unified Patents, RPX, et al.) appears anywhere in the chain — unsurprising, given this is a General Motors patent on diesel aftertreatment hardware, not an NPE-asserted software patent. The realistic explanation for the empty PTAB docket is straightforward: this patent was never a monetization target. It is a large-manufacturer defensive portfolio asset covering a physical filter architecture.

The fact that actually matters more than the PTAB docket. The Google Patents legal-events record for '921 shows this sequence:

• 2013-12-27 — maintenance fee reminder mailed
• 2014-05-18 — lapse for failure to pay maintenance fees
• 2014-07-08 — information on status: patent discontinuation — "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362," effective 2014-05-18

Against that, the same page's header renders the status as "Expired - Fee Related, expires 2026-01-23," with a 2026-01-23 "Adjusted expiration" entry. These two records are inconsistent and I cannot resolve which is correct from the sources available. The resolution matters enormously: under 35 U.S.C. § 41(b)(1) and 37 C.F.R. § 1.362, an unintentionally lapsed patent may be revived on petition, but a patent that lapsed for nonpayment and was not revived cannot support a damages claim for post-lapse infringement, and § 292 false-marking exposure attaches to lapsed patents. A defendant should treat the maintenance-fee status as the first thing to pull from USPTO Patent Center, before spending a dollar on invalidity work. Note also that the recorded security-interest chain (U.S. Treasury 2009-02-04; Citicorp 2009-04-16; UAW Retiree Medical Benefits Trust 2009-08-28; Wilmington Trust 2010-11-08; releases 2009-08-20, 2009-08-21, 2010-11-04, 2010-11-05) is bankruptcy-era GM collateral and does not affect validity or enforceability.

Recommended next steps

1. Do not cite any IPR number for this patent. There is none. If someone on your team has a docket sheet or an internal database showing an IPR or PGR against 7,716,921, treat that entry as an error and correct it before it reaches a brief, a stay motion, or a § 315(b) one-year bar calculation.
2. Pull the maintenance-fee and revival record from USPTO Patent Center first (https://patentcenter.uspto.gov). Search the full assignment and fee history for Ser. No. 11/335,222. Confirm whether the 2014-05-18 lapse was ever cured by a petition to revive under 37 C.F.R. § 1.378. If it was not, the enforceability analysis changes the case before you reach invalidity at all.
3. Confirm which patent is actually asserted. '921 and US 8,011,177 B2 (the CIP, Ser. No. 11/833,558) share a specification lineage but not a claim set. A demand letter citing "'921" and a complaint attaching the '177 patent are different problems with different claim language and potentially different expiration dates. (See https://patents.google.com/patent/US8011177/en)
4. If the patent is live and asserted, a first-ever IPR is available and uncrowded. With no prior petitioner, there is no § 315(e) estoppel and no IPR-based prior-art estoppel constraining you. The natural starting art is on the face of the patent: Toyota '795 and '412, Nippondenso '820, Nissan '320, Donaldson '948, Johnson Matthey WO '717, and — notably — the inventor's own earlier US 2005/0050870 A1, which is a § 102(b) printed publication as of 2005-03-10 and therefore available as art against '921's 2005-09-01 priority date. That self-authored reference is worth a hard look for § 103.
5. Budget the IPR clock correctly if you file. Statutory deadlines are § 316(a)(11): institution decision within 6 months of the petition's filing date (or the PO's preliminary-response deadline), and a final written decision within 12 months of institution, extendable up to 6 months for good cause under § 316(a)(11) / § 317. There are no milestones to track today because no trial is on file.
6. Set a monitoring cadence. Because the record shows no challenge in ~15 years, the practical risk of a petition appearing now is low — but if a demand letter on this patent surfaces, an IPR is likely to follow, and you want to know before the § 315(b) one-year clock from service of a complaint runs. Flag the patent in your docket-monitoring tool against PTAB E2E (https://ptacts.uspto.gov) and CourtListener.

Bottom line for a defendant: there is no PTAB outcome to report, and I will not manufacture one. The more promising defensive avenue on this specific patent is the § 1.362 maintenance-fee lapse and the related question of enforceability — not the AIA trial docket, which is empty.

I'll verify the assignment record against external sources before writing the analysis.

Let me check for any litigation involving this patent and try to surface correspondent-of-record details.

Inventors

Pattern notes. There is only one inventor, so the "all inventors departed the assignee within 12 months" fire-sale precursor cannot be tested in the usual way. No evidence of Cheng's departure from GM was found in the sources reviewed; third-party inventor profiles list him with 16 GM-assigned patents, and the sole related case (the CIP, US 8,011,177 B2) is likewise GM-assigned. Not determinable / no adverse pattern.

One structural irregularity worth flagging for completeness: GTO was itself a Delaware subsidiary that received GM's automotive IP under a separate portfolio-level "Automotive Technology Assignment" from General Motors Corporation effective 2005-01-19 (recorded much later, e.g. at Reel 037721/0954 on 2016-02-12 for a sibling application). That is an intra-group technology reorganization, not an arm's-length sale, and it does not appear as a recorded event against US 7,716,921 itself.

Original assignee

GM Global Technology Operations, Inc., 300 Renaissance Center, Detroit, Michigan — the assignee of record on issue (2010-05-18) and current owner via change of name.

• Line of business: the IP-holding/technology-operations subsidiary of General Motors Corporation (now GM Global Technology Operations LLC, a GM company). GM is a vehicle OEM; the claimed subject matter (a zoned, staged-regeneration wall-flow diesel particulate filter) is embodied in GM diesel exhaust aftertreatment hardware, i.e. the assignee is a practicing operating company, not a holding vehicle for assertions.
• Product embodiment: the patent is directed to DPF regeneration strategy, not a discrete sellable part; GM's diesel light-duty and heavy-duty programs (and, as later citing art shows, the broader DPF field including Ford's 8,844,274) practice this class of technology.
• Current status: operating. GM Global Technology Operations, Inc. became GM Global Technology Operations LLC by change of name effective 2010-12-02 (recorded 2011-02-10, Reel 025781/0001), and remains the assignee listed on Google Patents. The patent, however, is dead: maintenance fees went unpaid, with lapse for failure to pay recorded effective 2014-05-18 and formal expiration under 37 CFR 1.362 recorded 2014-06-13/16. Google Patents shows status "Expired - Fee Related," adjusted expiration 2026-01-23.

Sourcing caveat (important): the authoritative record I retrieved is the Google Patents legal-events mirror of the USPTO Assignment Center data. It exposes reel/frame, conveyance, assignor, assignee and execution/recording dates, but does not expose the correspondent of record for any entry. I could not retrieve correspondent attorney/firm names for this patent in this session, and I will not invent them — see signal 3 below.

Assignment timeline

All eleven recorded events. None of these conveys title to a third party; after the 2006 inventor assignment, every subsequent record is a lien (security agreement) or a release of a lien, plus one change of name.

• 2006-01-05 (executed) / recorded 2006-03-27 — Reel 017378/0956

  • Conveyance: Assignment
  • Assignor: Shi-wai S. Cheng
  • Assignee: GM Global Technology Operations, Inc.
  • Correspondent: not exposed in the retrieved legal-events feed
  • Context: routine inventor-to-employer assignment (executed 14 days before filing).

• 2008-12-31 (executed) / recorded 2009-02-04 — Reel 022201/0448

  • Conveyance: Security Agreement
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: United States Department of the Treasury
  • Correspondent: not exposed
  • Context: securitization — GM pled its IP collateral to Treasury for the 2008-12-31 TARP loan (Lender = U.S. Treasury, per the filed Loan and Security Agreement).

• 2009-04-09 (executed) / recorded 2009-04-16 — Reel 022553/0493

  • Conveyance: Security Agreement
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: Citicorp USA, Inc., as agent for Bank Priority Secured Parties and as agent for Hedge Priority Secured Parties
  • Correspondent: not exposed
  • Context: securitization — junior/second-priority lien granted to the credit-facility agent.

• 2009-07-09 (executed) / recorded 2009-08-20 — Reel 023124/0519

  • Conveyance: Release by Secured Party
  • Assignor: United States Department of the Treasury
  • Assignee: GM Global Technology Operations, Inc.
  • Correspondent: not exposed
  • Context: release of the Treasury lien as GM's restructuring matured.

• 2009-08-14 (executed) / recorded 2009-08-21 — Reel 023127/0402

  • Conveyance: Release by Secured Party
  • Assignor: Citicorp USA, Inc. (both agent capacities)
  • Assignee: GM Global Technology Operations, Inc.
  • Correspondent: not exposed
  • Context: release of the Citicorp lien.

• 2009-07-10 (executed) / recorded 2009-08-27 — Reel 023156/0142

  • Conveyance: Security Agreement
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: United States Department of the Treasury
  • Correspondent: not exposed
  • Context: securitization — re-pledge to Treasury as part of the Chapter 11-era (new GM) collateral package.

• 2009-07-10 (executed) / recorded 2009-08-28 — Reel 023162/0093

  • Conveyance: Security Agreement
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: UAW Retiree Medical Benefits Trust (VEBA)
  • Correspondent: not exposed
  • Context: securitization — VEBA became a secured creditor of the reorganized GM; the same instrument is separately recorded in foreign registers (e.g. UK GB2456981, filed 2009-11-13).

• 2010-04-20 (executed) / recorded 2010-11-04 — Reel 025245/0587

  • Conveyance: Release by Secured Party
  • Assignor: United States Department of the Treasury
  • Assignee: GM Global Technology Operations, Inc.
  • Correspondent: not exposed
  • Context: release of the Treasury lien.

• 2010-10-26 (executed) / recorded 2010-11-05 — Reel 025314/0901

  • Conveyance: Release by Secured Party
  • Assignor: UAW Retiree Medical Benefits Trust
  • Assignee: GM Global Technology Operations, Inc.
  • Correspondent: not exposed
  • Context: release of the VEBA lien.

• 2010-10-27 (executed) / recorded 2010-11-08 — Reel 025327/0041

  • Conveyance: Security Agreement
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: Wilmington Trust Company
  • Correspondent: not exposed
  • Context: securitization — replacement collateral agent for the post-bankruptcy credit facility.

• 2010-12-02 (executed) / recorded 2011-02-10 — Reel 025781/0001

  • Conveyance: Change of Name
  • Assignor: GM Global Technology Operations, Inc.
  • Assignee: GM Global Technology Operations LLC
  • Correspondent: not exposed
  • Context: change of name only — no change in legal or beneficial ownership; GM remains the owner of record today.

Terminal event (not an assignment): maintenance-fee lapse effective 2014-05-18; patent expiration under 37 CFR 1.362 recorded 2014-06-13 and 2014-06-16; "Lapsed due to failure to pay maintenance fee" recorded 2014-07-08. Rightsholder abandoned the asset rather than monetizing it — the opposite of an NPE acquisition posture.

No assignment records issue a patent to any entity other than GM and GM's collateral agents. If you query the Assignment Center per-record view, expect the correspondent on Reels 022201/0448–025327/0041 to be GM in-house counsel or the secured parties' counsel, but I have not verified this and it should not be treated as a finding.

Timeline diagram

timeline
    title Ownership of US 7716921
    2006 : Cheng assigns to GM GTO
         : Application filed
    2008 : Pledged to US Treasury
    2009 : Pledged to Citicorp USA
         : Releases by Treasury and Citicorp
         : Pledged to Treasury again
         : Pledged to UAW VEBA Trust
    2010 : Patent issued
         : Releases by Treasury and UAW
         : Pledged to Wilmington Trust
    2011 : Name change to GM Global Technology Operations LLC
    2014 : Lapsed with no maintenance fee paid

NPE / troll-pattern signals

1. Shell-entity transfer — not present. Title stays with GM Global Technology Operations throughout. The chain's last substantive recording before the name change is a lien (Reel 025327/0041), and the final record is a change of name only (Reel 025781/0001, 2011-02-10). No "IP/Holdings/Ventures" assignee appears, no single-purpose Delaware/Texas LLC takes title, and no registered-agent address appears as a transferee address. Every secured party (Treasury, Citicorp USA, UAW VEBA, Wilmington Trust) is a lender/agent, not a patent acquirer.

2. Known asserter in the chain — not present. None of GM GTO, the U.S. Department of the Treasury, Citicorp USA, Inc., the UAW Retiree Medical Benefits Trust, or Wilmington Trust Company appears on the named NPE rosters (Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Conversant/Mosaid, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities). No assignee is a repeat patent plaintiff.

3. Repeat correspondent across the chain — unclear (unverifiable on the retrieved source). The Google Patents legal-events feed does not surface a correspondent for any of the eleven entries, and targeted searches did not return the recorded correspondent names. No correspondent is cited here, because none could be verified — asserting recurrence without a name and reel/frame would be fabrication. Note that the cluster 022201/0448 → 022553/0493 → 023124/0519 → 023127/0402 → 023156/0142 → 023162/0093 → 025245/0587 → 025314/0901 → 025327/0041 is a classic single-firm securitization portfolio recordation set, so if a single correspondent appears across all of them, that is diligence evidence for a lender-side filing house, not an NPE tell — the tell only matters when the same lawyer records title transfers between differently-named LLCs, which does not happen here.

4. Cascading transfers — not present. There is a dense recording window (six recorded events between 2009-02-04 and 2009-08-28, nine between 2009-02-04 and 2010-11-08), but these are liens and releases, not transfers of ownership, and every release names GM GTO as the recipient (Reels 023124/0519, 023127/0402, 025245/0587, 025314/0901). Value returns to the same operating owner; no chained LLCs, no shared principals, no shared transferee address.

5. Pre-litigation transfer — not present. No infringement suit naming US 7,716,921 was located; the patent's forward citations on Google Patents are a Ford application/patent (US 20100175372 A1 → US 8,844,274 B2) and nothing litigated, and searches for litigation returned no hits. There is accordingly no assignment within 6 months (or any period) before a suit, and none could be — title never moved.

6. Bankruptcy fire-sale — not present as to this patent. GM did undergo the 2008–2009 government-sponsored restructuring and Chapter 11 (the cause of the 2009-07-10 executed liens at Reels 023156/0142 and 023162/0093), but US 7,716,921 was never sold in those proceedings. GM GTO retained title, and the subsequent records are releases (Reels 025245/0587, 025314/0901) plus a change of name (025781/0001). This is the inverse of Kodak/Nortel/Polaroid: the portfolio was pledged, not liquidated, and this asset was ultimately abandoned in 2014.

7. Privateering — not present. No NPE is in the chain and no third-party assertion on GM's behalf was found. The only transfer to a non-GM party at any point was a security interest, expressly structured as a pledge rather than a current assignment (the security agreements' own language preserves "all rights to sue in law or in equity" in the grantor, i.e. GM).

8. Defensive aggregator — not present. No RPX, AST, LOT Network, Unified Patents, or OIN entity appears; the chain does not terminate at a defensive aggregator. (The patent is nonetheless effectively neutralized — by expiration, not aggregation.)

Verdict

Insufficient data — with the substantive finding that no NPE signal is present.

Justification: the Assignment Center-derived record contains an ownership chain of exactly one link — the inventor-to-employer assignment of 2006-01-05, Reel 017378/0956 — followed only by non-conveying lien/release recordings (Reels 022201/0448, 022553/0493, 023124/0519, 023127/0402, 023156/0142, 023162/0093, 025245/0587, 025314/0901, 025327/0041) and a pure change of name to GM Global Technology Operations LLC at Reel 025781/0001. Because nothing in the chain transfers title out of the original operating-company assignee, the record falls within the "only the original assignment" branch of Insufficient data rather than any NPE category (0 of 8 NPE signals present; signals 1, 2, 4, 5, 6, 7, 8 "not present," signal 3 "unclear" only because correspondents could not be retrieved). The patent was allowed to lapse for non-payment of maintenance fees effective 2014-05-18, which is affirmative evidence against assertion-driven monetization.

Verify at the USPTO Assignment Center (search "7716921"): https://assignmentcenter.uspto.gov/ — or the legacy mirror: https://assignment.uspto.gov/patent/index.html

I'll research the prior-art citations for US 7,716,921. Let me run several targeted searches.

I have the citation lists. Let me pull details on the remaining cited references to characterize them accurately.

Prior-Art Analysis — US 7,716,921 B2 (“Exhaust particulate filter”)

Note on method and sources: I worked from the authoritative full text of US 7,716,921 B2 supplied in the record (Google Patents mirror of the USPTO document: https://patents.google.com/patent/US7716921/en), which reproduces the front-page “References Cited,” “Patent Citations,” “Cited By,” and “Non-Patent Citations” sections verbatim. I supplemented it with web searches to characterize specific references. I did not independently query USPTO PatentCenter/Global Dossier image files, so page-column pinpoint citations for the older references are given at the level of the abstract/specimen text I retrieved, and I flag where my knowledge is limited.

This section complements the earlier bibliographic and claim-mapping sections rather than restating them. All identifiers are reproduced literally as they appear in the record (including the printed typographical errors, e.g., “Fitter apparatus” for US 4,519,820 and “Cordiertie” in the 7,716,921 specification).

1. Governing law / the anticipation standard I applied

• US 7,716,921 has a priority date of 2005‑09‑01 (provisional US 60/713,541) and was filed 2006‑01‑19 (application 11/335,222). It is therefore governed by the pre‑AIA version of 35 U.S.C. § 102/103.
• Anticipation under § 102 requires a single reference that discloses each and every element of the claim, arranged as in the claim (MPEP 2131). § 102(a)/(b) look to publication/patenting/public-use dates; § 102(e) gives a US patent or published application a prior-art date as of its earliest effective US filing date (foreign priority does not count for pre‑AIA § 102(e)).
• A reference being “cited by the examiner” does not mean it anticipates. In this family most citations were plainly cited as background/§ 103 art. I state the anticipation conclusion honestly rather than assigning anticipation where the disclosure does not support it.

Key claim architecture to test against (from the record):

• Claim 1 (independent, apparatus): wall-flow filtration particulate filter element with first regeneration zone downstream of second regeneration zone, both part of the same element; heat source disposed at the first (downstream) zone; staged regeneration in which the downstream zone initiates regeneration ahead of the upstream zone, each zone regenerating in the direction of exhaust flow.
• Claims 2–4: heat source = catalyst / heater / electric heater. Claim 5: second heat source at second zone. Claim 6: control to initiate heating. Claim 16–19: heat source along zone length; continuity of the element.
• Claim 7 (structural): end‑plugged wall-flow monolith; first zone = downstream 25–50%; second zone = remaining 50–75%; oxidation catalyst on the first-zone walls. Claim 8: catalyst on first zone but not second. Claim 10: first end‑plug porosity > second end‑plug porosity.
• Claim 11 (independent method) and Claim 20 (method with the 25–50 %/50–75 % zone split) mirror the apparatus claims.

2. The definitive cited-reference set (13 patent citations + 1 NPL)

Notes on the two citation lists in the record: the “Citations (12)” list omits US 5,357,755 A; the fuller “Patent Citations (13)” list includes it. The listing’s asterisk convention (“* cited by examiner”) marks US 4,404,795; 4,519,820; 4,887,427; 4,934,142; 5,019,142; 5,067,320; 5,212,948; 6,823,660; and 7,107,763 as examiner‑cited, while US 4,426,320, WO 01/96717, and US 2005/0050870 appear without that marker (i.e., consistent with applicant/third‑party citation). Treat Google’s asterisk metadata as indicative only.

3. Reference-by-reference § 102 analysis

US 4,404,795 A — Toyota Jidosha Kogyo K.K. (filed 1980‑06‑19; issued 1983‑09‑20)

Disclosure: Diesel exhaust trapper with a trapping member; sensors for excess adhered particulate amount and for trapping-member temperature; heating means at the inlet side of the trapper container to heat the particulates to ignition temperature; secondary-air supply; combustion propagates from the inlet side to the outlet side to regenerate the whole trapper (https://patents.google.com/patent/[US4404795A](/patent/US4404795A)/en).
§ 102 mapping: Relevant only to the “heat source” genus of claims 2–4 and to the general concept of an end‑plugged wall-flow trap with propagating combustion.
Anticipation conclusion: No anticipation. This reference initiates regeneration at the inlet (upstream) side and propagates downstream — the exact inverse of the claimed downstream‑first staged order. It cannot disclose the claim 1/11/20 “first zone downstream initiates ahead of second zone” limitation. Best treated as § 103 background and, importantly, as evidence that the art taught away from the claimed ordering.

US 4,426,320 A — W. R. Grace & Co. (filed 1981‑01‑27; issued 1984‑01‑17)

Disclosure: A catalyst composition for exhaust-gas treatment (noble-metal/refractory-oxide catalytic material). No filter element, no channel/plug structure, no regeneration zoning.
§ 102 mapping: None as to claims 1–20. Possibly cited only for catalyst-material background (claim 2 “catalyst”; claim 7 “oxidation catalyst” material choice).
Anticipation conclusion: No anticipation of any claim. Composition-only disclosure cannot meet the structural/regeneration elements.

US 4,519,820 A — Nippondenso Co., Ltd. (filed 1982‑08‑05; issued 1985‑05‑28)

Disclosure: Ceramic honeycomb wall-flow filter with alternate upstream/downstream plugs (inlet passages closed downstream = inlet channel with end-plug at the second end; outlet passages plugged in their upstream portion, spaced downstream from the upstream end so that a space upstream of the plug traps extra particulates whose burning heat helps burn particulates in the downstream portion, enabling regeneration over the entire length). An electric heater is at the inlet/upstream end (https://patents.google.com/patent/US4519820; abstract via OSTI: https://www.osti.gov/biblio/[6321487](/patent/6321487)).
§ 102 mapping: Closest cited art to the structural elements of claim 7 (porous partition walls; inlet passages closed at the downstream end; outlet passages closed at the upstream side; heater). Also a candidate secondary reference for claims 3/4 (electric heater as heat source) and, interestingly, for the spaced/porous end-plug concept underpinning the claim 10 porosity-type limitation.
Anticipation conclusion: No anticipation of claim 1/7/11. Claim 7 additionally requires (a) an oxidation catalyst disposed on the internal walls of the first zone and (b) the specific 25–50 %/50–75 % zone definition — 4,519,820 discloses neither. Claim 1 requires downstream-first staged regeneration, whereas 4,519,820’s heater is at the inlet end and burning begins upstream. This is a strong § 103 reference against claim 7’s structure, not a § 102 reference against the independent claims.

US 4,887,427 A — Nissan Motor Company (filed 1985‑10‑28; issued 1989‑12‑19)

Disclosure (from title/assignee; full text not retrieved): An exhaust particle removing system for an engine — a particulate trap with regeneration (burner/heater) and control.
§ 102 mapping: General context for claim 3/4 (heater) and claim 6 (control configured to initiate heating); no zoned, downstream-first staged regeneration is disclosed by this older “system” art.
Anticipation conclusion: No anticipation of any claim. § 103/background only.
Confidence: Moderate — I did not retrieve the specification for this reference; treat the above as a title-based characterization.

US 4,934,142 A — Toyota Jidosha K.K. (filed 1987‑12‑16; issued 1990‑06‑19)

Disclosure (title/assignee; full text not retrieved): An exhaust emission control device for a diesel engine — a particulate filter with regeneration/control.
§ 102 mapping: Background for claim 6 (control) and regeneration system architecture.
Anticipation conclusion: No anticipation. § 103/background only.
Confidence: Moderate — specification not retrieved.

US 5,019,142 A — Gerhard Waschkuttis (filed 1988‑05‑17; issued 1991‑05‑28)

Disclosure (title/assignee; full text not retrieved): A soot filter for diesel vehicles; single-inventor European-style soot-filter case, typically with regeneration heating.
§ 102 mapping: Background for the wall-flow/soot-filter and heater elements (claims 3/4); nothing on downstream-first zone staging.
Anticipation conclusion: No anticipation. § 103/background only.
Confidence: Moderate — specification not retrieved.

US 5,067,320 A — Nissan Motor Company (filed 1989‑01‑24; issued 1991‑11‑26)

Disclosure (title/assignee; full text not retrieved): Exhaust particle removing system for an internal combustion engine — trap + regeneration means. (This is the reference whose Google landing page lists US 7,716,921 among documents citing it: https://patents.google.com/patent/US5067320.)
§ 102 mapping: Background for claim 3/4/6.
Anticipation conclusion: No anticipation. § 103/background only.
Confidence: Moderate — specification not retrieved.

US 5,212,948 A and US 5,357,755 A — Donaldson Company, Inc. (both filed 1990‑09‑27; issued 1993‑05‑25 and 1994‑10‑25)

Disclosure: “Trap apparatus with bypass” — a particulate trap apparatus with a bypass flow path (e.g., for regeneration/over-temperature protection). The two documents are members of the same Donaldson family (the ’755 appears in the fuller 13-item list only).
§ 102 mapping: Background for trap apparatus architecture and bypass/regeneration handling; no zoned catalyst coating or downstream-first staged regeneration.
Anticipation conclusion: No anticipation of any claim. § 103/background only. (The bypass concept is neither claimed nor an element of claims 1–20.)
Confidence: Moderate — full texts not retrieved.

WO 01/96717 A1 — Johnson Matthey PLC (priority 2000‑06‑16; published 2001‑12‑20)

Disclosure: A reactor for treating exhaust gas with at least one first zone and a second zone downstream, each zone carrying a chemically/catalytically active coating, and with a region substantially free of active coating in the first zone so a reactant can reach the second zone. The zones may be distinct zones within a single substrate monolith, and the substrate may be a wall-flow filter (https://patents.google.com/patent/WO2001096717A1/en).
§ 102 mapping: Directly relevant to the “zone‑coated catalyst” concept of claims 7 and 8 (oxidation catalyst disposed on one zone of a monolithic filter, not on the other) and, more generally, to claims 2/12 (oxidation catalyst as the heat source in a downstream zone).
Anticipation conclusion: No anticipation. (i) The purpose is reactant routing to a downstream NOx absorber/SCR zone, not staged soot regeneration; (ii) the claimed zone split is measured from the downstream end (25–50 % / 50–75 %) and tied to regeneration initiation order, which this document does not disclose; (iii) a zone arrangement upstream-first is not the claimed downstream-first arrangement. Strong § 103 material against the zone-coating limitations, not § 102 anticipation.

US 6,823,660 B2 — Isuzu Motors Ltd. (priority 2001‑12‑13; issued 2004‑11‑30)

Disclosure (title/assignee; full text not retrieved): “Exhaust emission purification system for diesel engine” — a diesel aftertreatment system (typically particulate filter + oxidation/NOx catalyst with regeneration strategy).
§ 102 mapping: Background for the control element of claim 6 and for regeneration-strategy context; no teaching of downstream-first staged zone regeneration.
Anticipation conclusion: No anticipation. § 103/background only.
Confidence: Moderate — specification not retrieved.

US 2005/0050870 A1 — Cheng, Shi‑Wai S. (filed 2003‑03‑03; published 2005‑03‑10)

Disclosure: Wall-flow filtration element with a ceramic monolith having porous internal walls defining inlet and outlet channels; porous end‑plug 270 at the inlet-channel outlet end and end‑plug 290 at the outlet-channel inlet end; the porous end-plugs have greater porosity than end-plugs 290 (pore size ~30–60 µm), permitting ash leakage (https://patents.google.com/patent/US20050050870A1/en). This is the parent application of US 7,524,360 B2 and is the same inventor as US 7,716,921; it is also listed in the family record of the subject patent (US 11/323,997 → US 7,524,360 B2).
§ 102 mapping: The single most literally relevant citation for the relative-porosity limitation of claim 10 (“the porosity of the first end-plug is greater than the porosity of the second end-plug”), and for the wall-flow/plug architecture recited in claim 7.
Anticipation conclusion: No anticipation of claims 1, 7, 11, or 20, because claim 7 (and its dependent claim 10) additionally requires the 25–50 % downstream first-zone oxidation-catalyst coating and the staged downstream-first regeneration, which US 2005/0050870 does not disclose. It does disclose each element of the “first end-plug more porous than second end-plug” feature in isolation, so it is the reference to beat for that limitation.
Timing nuance (important): Published 2005‑03‑10, i.e., less than one year before the 2006‑01‑19 filing — so it is not § 102(b) art, but it predates the 2005‑09‑01 priority and is available under § 102(a)/§ 102(e) (its US filing date, 2003‑03‑03). Because it shares the inventor/assignee, § 103(c)/common-ownership carve-outs and art‑unit matters would ordinarily be raised in any obviousness challenge built on it.

US 7,107,763 B2 — Hitachi Metals, Ltd. (priority 2002‑03‑29; issued 2006‑09‑19)

Disclosure (title/assignee; full text not retrieved): “Ceramic honeycomb filter and exhaust gas-cleaning method” — a ceramic honeycomb (wall-flow) filter and its regeneration/cleaning method.
§ 102 mapping: Relevant to the ceramic honeycomb wall-flow structure of claim 7 and to regeneration methodology generally.
Anticipation conclusion: No anticipation of claims 1/7/11/20 (no downstream-first two-zone staged regeneration; no 25–50 % downstream zone-coated oxidation catalyst as claimed).
Timing nuance: Although it issued after the 2005‑09‑01 priority date, it is a US patent whose § 102(e) date is its earliest effective US filing date (≈2003, on the claimed 2002‑03‑29 JP priority basis, not the JP date itself), so it is potentially § 102(e) art. I have not verified the exact US filing date in the retrieved record — flag as provisional.
Confidence: Moderate — specification and exact US filing date not retrieved.

Non-patent literature — International Search Report for PCT/US06/33987 (dated 2007‑03‑21)

The record cites the ISR for the sibling PCT corresponding to this application. This is a procedural/related document, not prior art bearing on anticipation; it is useful for tracing which references the ISA considered most material (including the Johnson Matthey and Hitachi Metals families).

4. Anticipation summary matrix

Bottom line: On the record before me, none of the cited references anticipates any claim of US 7,716,921, and in particular none discloses the core novelty of independent claims 1, 11 and 20 — a single continuous wall-flow element whose downstream regeneration zone is ignition-initiated ahead of the upstream zone, each zone burning in the direction of exhaust flow. The closest references (US 4,404,795; US 4,519,820) expressly initiate combustion at the inlet/upstream end, i.e., they are contrary art.

5. Most relevant prior art, ranked

1. US 4,519,820 A (Nippondenso) — closest to the structural/end-plug and heater elements of claims 3/4/7, and to the “extra trapping at the closed end / spaced plug” concept; but upstream-side ignition.
2. US 4,404,795 A (Toyota) — closest to the heated wall-flow trap with combustion propagation concept (claims 3/4), again upstream-side initiation.
3. US 2005/0050870 A1 (Cheng) — closest to the relative end-plug porosity element (claim 10) and to the shared wall-flow architecture; same inventor.
4. WO 01/96717 A1 (Johnson Matthey) — closest to the zone-coated catalyst on a monolithic (optionally wall-flow) substrate idea (claims 7/8).
5. US 7,107,763 B2 (Hitachi Metals) — ceramic honeycomb filter/regeneration method (claim 7 structure), § 102(e)-eligible.
6. US 6,823,660 B2 (Isuzu) and Nissan/Toyota/Donaldson system references — regeneration control and apparatus context (claim 6, claims 3–4 background).

6. Documents in the record that are not prior art to US 7,716,921

• “Cited By” documents: US 2010/0175372 A1 (Lambert; published 2010‑07‑15) and US 8,844,274 B2 (Ford; published 2014‑09‑30) — both post-date the 2005‑09‑01 priority and merely cite US 7,716,921; they cannot be § 102 art against it.
• Family/related documents: US 2007/0044458 A1 (the pre-grant publication of this very application), US 8,011,177 B2 (continuation‑in‑part, app. 11/833,558), and US 7,524,360 B2 (from US 2005/0050870’s child). Same-family/same-disclosure documents are not § 102 art against their own family member; they are relevant only for double-patenting considerations (e.g., US 8,011,177 as a CIP sharing the ’921 priority) and for claim-differentiation.
• Possible additional lead, low confidence: the record’s “Families Citing this family” entry GB 0304939 D0 (Johnson Matthey, priority 2003‑03‑05) and the related EP 1 599 660 B1 “Diesel engine with a catalysed filter” appear in the similar/citing lists. Because GB 0304939 D0 pre-dates the 2005‑09‑01 priority, it could be additional prior art on catalysed-filter placement; however the listing conflicts with a normal “citing” chronology, and I did not retrieve its disclosure. Flagged as unverified — do not rely on it without checking the document.

7. Explicit confidence and caveats

• High confidence: identity, dates, assignees and titles of all 13 patent citations and the NPL item, as reproduced in the US 7,716,921 record; the disclosures of US 4,404,795, US 4,519,820, WO 01/96717, US 2005/0050870 (retrieved text); and the conclusion that the claimed downstream-first staged regeneration is not disclosed by the cited art.
• Moderate confidence (title/assignee-level characterization only; specifications not retrieved): US 4,887,427; US 4,934,142; US 5,019,142; US 5,067,320; US 5,212,948; US 5,357,755; US 6,823,660; US 7,107,763.
• Not verified: the exact US filing date underlying US 7,107,763 B2 (needed to fix its pre‑AIA § 102(e) date); the examiner-vs-applicant provenance of the citations (Google’s asterisk flags); the relevance of GB 0304939 D0 / EP 1 599 660 B1.
• Rule applied: all identifiers were taken literally — including the printed “Fitter apparatus” title of US 4,519,820 and “Cordiertie” in the specification — with no auto-correction. Where a consulted source conflicted with training memory, the retrieved document was treated as ground truth.

I'll research the cited prior art references to ground this obviousness analysis.

Let me research the remaining key prior art references.

Let me check the remaining references (Johnson Matthey WO2001096717 and Toyota US4934142) for zoned-catalyst/regeneration teachings.

Obviousness Analysis — U.S. Pat. No. 7,716,921 ("Exhaust Particulate Filter")

Inventor: Shi-wai S. Cheng · Assignee: GM Global Technology Operations LLC · Priority: 2005-09-01 (Prov. 60/713,541) · Filed: 2006-01-19 · Granted: 2010-05-18 · Status: Expired – fee related (lapsed 2014-05-18; adjusted expiration 2026-01-23)
Source: https://patents.google.com/patent/[US7716921](/patent/US7716921)/en

Note on posture: because the patent lapsed in 2014 and its adjusted expiration has been set to 2026-01-23, this §103 analysis is retrospective (validity/defensive-value assessment, license diligence, or family-scope analysis for the CIP US 8,011,177 B2). I flag below where the record is thin or where a reference may be disqualified as prior art.

I. Legal Framework

Obviousness under 35 U.S.C. § 103 requires the Graham factors: (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 evidence of non-obviousness. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) supplies the enumerated rationales (combining known elements to yield predictable results; simple substitution; use of a known technique to improve a similar device in the same way; "obvious to try"; design incentives/market forces; predictable variation).

POSITA here: a person with a B.S. in mechanical/chemical engineering plus 2–4 years in diesel exhaust aftertreatment, familiar with wall-flow ceramic honeycomb DPFs, catalyzed DPFs, and thermal regeneration.

Critical admitted prior art. The '921 Background and Detailed Description make applicant-admissions that do most of the work:

• Wall-flow filtration is "present filtering methods… focus on wall-flow filtration."
• "Catalyzed diesel particulate filters have been used extensively, where the catalyst is normally applied either to the front end of the diesel particulate filter or applied to the whole filter for the purpose of reducing the regeneration temperature."
• "Normally regeneration is initiated by increasing the inlet temperature of the exhaust gases at first end 310 to a temperature higher than 650 °C… The reaction and the associated heat will propagate toward the downstream side… which causes high temperature near the second end 320."

These admissions establish that catalyzed DPFs, front-end catalyst placement, whole-filter coating, and 650 °C inlet-triggered regeneration with a downstream-propagating exotherm were all known. The only asserted delta is relocating the heat source to the downstream zone and the resulting downstream-first staging.

II. Scope of the Claims (mapped to the claim set)

Because the only independently meaningful structural changes over the admitted art are (a) axial location of the heat source and (b) axial distribution/percentage of catalyst, the analysis turns on whether relocating these elements to the downstream end was a predictable design variation.

III. The Prior Art of Record — Relevance

⚠️ A reference that may be disqualified: US 2005/0050870 A1 (Cheng)

This publication (https://patents.google.com/patent/US20050050870A1/en; issued as US 7,524,360 B2) is by the same inventor, Cheng Shi-Wai S., and is commonly owned by GM. It discloses porous end-plugs 270 (inlet-channel plug at the downstream end; pore size 30–60 µm) with "greater porosity than end-plugs 290"—the exact subject matter of claim 10. However, because it is the applicant's own work and commonly owned, it is prior art, if at all, only under pre-AIA § 102(e), and pre-AIA § 103(c) would disqualify it for obviousness purposes; it is not "by another" (§ 102(a)), and it published only ~6 months before the 2005-09-01 priority (so no § 102(b) bar). This likely explains why the '921 issued despite the near-identical disclosure. Claim 10 should therefore not be attacked on US 2005/0050870 A1 alone; it must rest on US 7,107,763 B2 (plug porosity) or art outside this record.

IV. Proposed § 103 Grounds

Ground 1 — Claims 1, 2, 16, 18, 19

WO 01/96717 (Johnson Matthey) in view of US 6,823,660 (Isuzu) and US 4,404,795 (Toyota).

• Johnson Matthey discloses a single substrate monolith ("brick") carrying axially distinct zones of catalytically active coating, one of which is downstream of the other, and expressly says the substrate may be a wall-flow filter. That reads on claim 1's "wall-flow filtration element having a first regeneration zone… downstream of a second regeneration zone… part of the same element" and on claims 18–19's continuity requirement.
• A catalytically active zone is a "heat source" that lowers soot ignition temperature — exactly the function the '921 ascribes to it (catalyst 405 "effectively lowering the ignition temperature of the soot by about 100 °C from about 650 °C to about 550 °C"). Isuzu '660 confirms the ordinary skill of coating the wall surfaces of a wall-flow filter with an oxidation catalyst.
• The "downstream zone initiates regeneration ahead of the upstream zone, and each zone regenerates in the direction of exhaust flow" limitation is then an inherent consequence of the structure (catalyst only downstream + the known downstream-propagating exotherm admitted in the '921 Background). Toyota '795 independently confirms the mechanism that once soot is ignited at an axial location, "combustion is propagated… from the inlet side to the outlet side."

Motivation / KSR rationales: (1) Combining known elements with predictable results — placing a known oxidation catalyst in a known zone of a known wall-flow monolith; (2) known problem — the '921 itself and US 7,107,763 both identify outlet-end overheating, thermal stress, cracking and melting as known problems of DPF regeneration; (3) design incentive — Johnson Matthey supplies the zone-coating toolkit expressly for wall-flow filters, so no new apparatus is required.

Ground 2 — Claims 7, 8, 20

US 7,107,763 (Hitachi) + US 6,823,660 (Isuzu) + WO 01/96717 (Johnson Matthey).

• US 7,107,763 supplies the complete claim-7 geometry: ceramic honeycomb wall-flow filter, porous partition walls, inlet/outlet flow paths with alternately sealing plugs.
• Isuzu '660 supplies "coating the wall surface with an oxidation catalyst" on a wall-flow filter (claim 7's "oxidation catalyst disposed on the internal walls of the first zone").
• Johnson Matthey supplies axial zoning on a single monolith and the zone-length control (via partial-immersion/resist/masking techniques), including the case where one axial region is coated and another is not (claim 8's "first zone but not the second zone").
• The 25–50% recitation is a predictable variation / optimization of a result-effective variable. The '921 gives no comparative data establishing criticality at 25% or 50%; the specification merely states "about the last 25%" in FIG. 6a and "25–50%" elsewhere. Under KSR, a claimed numerical range that is not shown to be critical is obvious over a disclosure teaching axial catalyst distribution generally.

Ground 3 — Claims 3, 4, 5, 6

US 4,404,795 (Toyota) + US 7,107,763 (Hitachi) [with US 4,934,142 (Toyota) and US 5,067,320 (Nissan) to be confirmed].

• US 7,107,763 expressly discloses regeneration "by a burner or an electric heater" (claims 3–4), and the '921 specification concedes heaters "may be electric heaters, microwave heaters, or any heating device suitable."
• US 4,404,795 discloses heating means plus detecting means plus control logic to initiate regeneration — reading on claim 6's "control configured to initiate heating."
• Claim 5 (second heat source at the second zone) follows directly from Johnson Matthey's multi-zone architecture: once the monolith is divided into independently controllable/coat-able zones, providing a heat source per zone is a simple substitution of a known element for a known function (full-length regeneration). This is the weakest of the grounds because the cited art generally locates the heat source/heating at the inlet side; the "second heat source" concept is more a matter of routine mechanical duplication than a taught improvement.

Ground 4 — Claims 11–15 (method)

The method claims add nothing beyond the apparatus limitations plus a step of "regenerating… in response to demand for regeneration."

• US 4,404,795 teaches exactly this method: detect excess particulates → heat to ignition temperature → combustion propagates from the inlet side to the outlet side. Substituting the downstream zone as the initiation site (per Ground 1) yields the claimed method.
• Claim 11's "continuous… without interruption" and claim 19 are met by Johnson Matthey's "distinct zones within a single substrate monolith."

Ground 5 — Claim 9

"Oxidation catalyst comprises Cordierite." Cordierite (Mg₂Al₄Si₅O₁₈) is chemically a ceramic substrate material, and the '921 specification itself uses it only as the filter-body material ("filter element 220 may be made from Cordierite… or SiC"). As literally written, the claim is anomalous and likely facially invalid under § 112 (written description/enablement; an oxidation catalyst does not "comprise" cordierite). For § 103, US 4,426,320 (W. R. Grace — "Catalyst composition for exhaust gas treatment") combined with the universal practice of applying catalysts to cordierite monoliths would make the limitation obvious; the reference's disclosure should be confirmed before relying on it.

V. Consolidated Motivation to Combine

1. Same field / same problem. All references address diesel particulate wall-flow filtration and thermal regeneration; Johnson Matthey and Isuzu are diesel aftertreatment references, Hitachi is a DPF substrate reference, Toyota '795 is a regeneration-method reference. KSR treats this common field as supporting combination.
2. Known, articulated problem. The '921 specification, US 7,107,763, and US 4,404,795 all recognize the DPF outage mode: exotherm concentrated near the outlet/closed end → thermal runaway → melt/crack. Locating the ignition source and catalyst to manage that exotherm is a known design objective with a finite number of predictable solutions (move the catalyst; stage the zones; use a heater).
3. Reasonable expectation of success. Isuzu '660 and the '921 Background both confirm catalyzed wall-flow filters lower regeneration temperature; Johnson Matthey confirms zone-coating a single wall-flow monolith is routine. Combining them requires no new apparatus or unforeseeable result — only a change in axial placement.
4. Design incentive / market force. The '921 touts Cordierite as "much cheaper" than SiC. Cost-driven substitution of cordierite for SiC, coupled with a known thermal-management modification, is a classic KSR "market forces / design incentive" rationale.

VI. Applicant's Best Rebuttals (and their strength)

A. Teaching away — STRONGEST argument.
Every regeneration reference of record initiates regeneration at the inlet/upstream end. Toyota '795: heating means at the "inlet side"; US 7,107,763 (quoting JP 3-68210 B): "heating means disposed on the inlet side of the honeycomb structure"; the '921 Background admits the conventional scheme ignites at first end 310. The claimed architecture deliberately reverses this. Under In re Gurley / DePuy Spine, a POSITA following the record would not have been led to place the heat source at the downstream zone — the record is at best silent, and at worst affirmatively directs the opposite. This is the patent's principal defensive position, and Johnson Matthey is only a partial answer (Johnson Matthey's downstream active zone serves a reactant-delivery purpose — keeping a reactant from reacting upstream — not a DPF soot-ignition-staging purpose). Note: mere silence or a different purpose is not teaching away; the defense weakens if no reference criticizes downstream-side initiation.

B. Unexpected result — WEAK on this record.
The specification asserts that only through staged, downstream-first regeneration is a Cordierite DPF enabled ("Only from the teachings disclosed herein does the unexpected advantage… provide for the use of a Cordiertie dpf"). But the patent contains no comparative data — no peak-temperature measurements, no durability/cracking results versus conventional regeneration. Under In re Geisler/Kao, an asserted but unsupported advantage carries little weight. If the CIP (US 8,011,177 B2) or prosecution papers contain actual data, that would materially strengthen the defense.

C. Claim scope amendments (claims 1, 11, 18, 19).
The "same… wall-filtration particulate filter element" / "continuous… without interruption" language appears crafted to avoid art using two separate filter bricks (e.g., Isuzu '660's first and second DPF devices; Donaldson's dual-trap systems). This may succeed against those references but does not avoid Johnson Matthey, which expressly claims zones "within a single substrate monolith or 'brick'." This is a meaningful limitation, but its prior-art-avoidance value is partial.

D. Claim 10. If US 2005/0050870 A1 is disqualified under § 103(c) (same inventor, common GM ownership — see § III), the examiner's evidentiary basis for the porous-end-plug limitation collapses and must be rebuilt from US 7,107,763's plug-porosity teaching. This is the claim most sensitive to the prior-art qualification question.

VII. Overall Assessment

Bottom line: The strongest § 103 case runs through US 7,107,763 B2 + US 6,823,660 B2 + WO 01/96717 A1, because those three collectively supply (i) the wall-flow honeycomb geometry and plug structure, (ii) oxidation-catalyst coating of wall-flow filter walls, and (iii) axial zoning of a single wall-flow monolith with the active coating positioned downstream. The patent's survival hinges almost entirely on whether the record teaches away from downstream-zone initiation of regeneration — a real but not airtight argument, since none of the references expressly criticizes the claimed arrangement and KSR's "predictable variation" and "obvious to try" rationales apply in this mature, predictable art.

Caveats and confidence:

• I verified the disclosures of US 4,404,795 A, US 2005/0050870 A1, US 6,823,660 B2, US 7,107,763 B2, and WO 01/96717 A1. I could not retrieve the full text of US 4,426,320 A, US 4,519,820 A, US 4,887,427 A, US 4,934,142 A, US 5,019,142 A, US 5,067,320 A, US 5,212,948 A, or US 5,357,755 A within this session; my characterizations of those rest on titles/assignees only and should be confirmed before any formal opinion.
• I have not analyzed the parent provisional (60/713,541) or the CIP US 8,011,177 B2, whose claims and supporting evidence may differ and could change the § 103 outcome for the family.
• This is a technical invalidity assessment, not a legal opinion or a validity determination.