US 5588836

I'll verify against live sources before summarizing.

Verification summary — US 5,588,836

I ran targeted searches against Google Patents, FreePatentsOnline, EveryPatent, the patent PDF, and CAFC 2026 argument/docket material. I found no CAFC 2026 (or any) appeal, IPR, or district-court litigation naming US 5,588,836. Caveat: my tools are general web search, not a direct PACER/CAFC docket-query API, so "no litigation found" means no publicly indexed hit — not a certified negative. The only 2026 CAFC items my search surfaced were unrelated cases (e.g., Spero v. Mercedes-Benz USA, No. 2025-1470).

I did not auto-correct any identifier: the number searched was literally 5588836.

Bibliographic data

Assignment record: Assignment recorded 1995-10-23 to OP-D-OP, Inc.; assignors listed as Landis, Timothy J.; Perry, Scott M.; and Auburn Product Design, Inc., a corp. of CA. Reel/Frame 007721/0707, signing dates 1995-10-16 to 1995-10-20.

Title note (flagging, not correcting): the front-page/DB title is "Mouth prop and tongue deflector apparatus," while the abstract and specification consistently call it a "mouth prop and tongue retractor apparatus." Both strings appear in the authoritative record; I am reporting both rather than harmonizing them.

Status detail: maintenance-fee reminder mailed 2000-07-25; lapse for failure to pay 2000-12-31; "Lapsed due to failure to pay maintenance fee," effective 2000-12-31. A separate 2018-01-24 status entry reads "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362." Google also lists an "anticipated expiration" of 2015-10-23 (the 20-year term). Read literally, the patent went dead around the end of 2000 for failure to pay the first (3.5-year) maintenance fee — roughly 20 years before its nominal term would have run out. Treat 2015-10-23 as the theoretical term end, not the actual expiration.

Prior art cited by/considered: US 674,650 (Lundborg, "Dental tongue-holder and drain-tube") and US 2,102,263 (Grunewald, "Saliva ejector"). The specification's Background Art additionally discusses US 5,232,362; 5,125,686; 4,975,057; 4,281,986; 4,192,071; 4,167,814; 4,024,642; 3,924,333; Swedish Patent No. 142,956; and US 637,970. The patent has a large forward-citation family (dozens of later intraoral-device patents), including the Innerlite/Hirsch line and later Solmetex and Somnics/Apnicure filings.

Abstract (verbatim)

"A mouth prop and tongue retractor apparatus for use in dental procedures. The apparatus includes a handle rotatably mounted within a base. A ball joint on the base fits within a socket in a mouth prop to provide pivotal positional adjustment of the apparatus. An elongated aspirator tube extends through the handle and base, and is coupled to a tongue retractor. A suction aperture on the tongue retractor communicates with the aspirator tube and provides for saliva removal from a patient's mouth. Rotation of the handle provides extension adjustment for the aspirator tube and tongue retractor."

Plain-language overview of the independent claims

Claim 1 — the broad "genus" claim. A dental appliance with seven elements: (a) a handle; (b) a base, with the handle rotatably coupled to the base; (c) a mouth prop coupled to the base; (d) "tongue retractor means" for positioning the tongue; (e) "suction means" for saliva removal, coupled to the tongue retractor; (f) gimbal adjustment means for adjustably positioning the retractor and suction means relative to the mouth prop; and (g) extension adjustment means for positioning the retractor and suction means relative to the handle and base. In plain terms: bite block + pivoting/swiveling joint + a thumb-turned screw-like length adjustment, all on one instrument. Note the claim uses "means" language for (d), (e), (f), (g), which invites §112 ¶6 construction; the specification maps (f) to the ball joint + socket and (g) to the threaded handle bore + threaded tube. (Literal-record note: the claim text reads "removing saliva front a patient's mouth" — a typographical error in the printed claim, preserved here rather than corrected.)

Claim 9 — mid-scope structural claim. Recites the structure more concretely: a handle with an axial bore; a base with a ball joint having an axial bore, handle rotatably coupled to the base; a mouth prop with a socket, with the ball joint pivotally coupled to the socket; an aspiration tube extending through both the handle bore and the ball-joint bore; a tongue retractor with at least one suction aperture and coupled to the aspiration tube; and extension adjustment means that positions the retractor relative to handle and base by rotation of the handle relative to the base. Essentially: the pivot is a ball-and-socket, the suction tube is the same member that threads through the handle, and turning the handle drives the tube in and out.

Claim 14 — the narrowest independent claim, effectively a system claim. Adds: (a) a handle bore with an internal threaded portion; (b) a base with a ball joint whose bore is collinear with the handle bore, handle rotatably coupled to base; (c) a mouth prop with upper and lower teeth-receiving members defining a socket, ball joint pivotally coupled to the socket; (d) an elongated aspiration tube through both bores with an external threaded portion reversibly engaging the handle's internal thread; (e) a tongue retractor coupled to the tube, including a detachable plate carrying the suction aperture in flow communication with the tube; and (f) alignment means that aligns the tube relative to the base and prevents the tube from rotating relative to the base. In plain terms, this is the fullest commercial-embodiment claim: ball-and-socket gimbal, thread-driven axial extension, keyed anti-rotation, and a removable, cleanable/tethered suction plate.

Dependent-claim clusters worth noting: claims 3–5 add the collinear bores, internal/external threads, and anti-rotation alignment; claims 6–7 add the detachable suction plate and its retention/tether; claim 8 defines the gimbal means as ball joint + socket; claims 10–13 add the threads, the keyway alignment member with axial groove, and the plate; claims 15–17 add the base shell partially enclosing the handle and the keyway alignment member connecting ball joint to shell (with key on the keyway bore / groove on the tube); claims 18–20 add vacuum-source attachment ridges, plate retention, and ball-joint traction means (serrations/grid).

Drafting observations (literal reading, not corrections): Claim 3 recites "said ball joint," and claim 4 depends from claim 3, yet no ball joint is positively recited in claims 1 or 2 — a potential antecedent-basis issue. Claim 13 refers to "said tongue retractor means" although parent claim 9 recites "a tongue retractor." The specification likewise contains apparent reference-numeral slips (e.g., "bore 50" where bore 58 was defined; "ball joint 16 within socket 22" where 26 and 46a were defined; "serralions" for serrations). These are faithfully reported as they appear.

Confidence and limits

• Bibliographic data, abstract, claims, and status: high confidence, drawn from the patent's own text and multiple independent reproductions (Google Patents, FPO, EveryPatent, USPTO assignment record).
• No litigation/appeal for this patent: moderate confidence (search-based; no authoritative negative certification available to me).
• If you need a certified docket check, the authoritative sources would be the CAFC docket (cafc.uscourts.gov), PACER, and USPTO PatentCenter — none of which I queried directly.

Sources: https://patents.google.com/patent/US5588836/en ; https://www.freepatentsonline.com/[5588836](/patent/5588836).html ; http://www.everypatent.com/comp/pat5588836.html ; https://patentimages.storage.googleapis.com/48/c7/3d/168a961cd557ac/US5588836.pdf

I'll search for litigation involving US patent 5588836.

Let me search more specific litigation databases and query variations.

The results so far are unrelated to this specific patent. Let me search litigation-specific databases directly.

Litigation Search Results — US Patent 5,588,836

Conclusion: No litigation involving US 5,588,836 was found in my searches.

I was unable to identify any district court case, Federal Circuit appeal, ITC investigation, or PTAB proceeding involving U.S. Patent No. 5,588,836.

What I searched and found

I want to be explicit about the limits of this: my searches returned no case captions, case numbers, or docket entries tied to this patent number, but a null result from general web search is not the same as a definitive negative from PACER/Docket Navigator/UnifiedPatents Portal, which I could not query reliably in this session. You should treat this as "no litigation found," not as a certified "no litigation exists."

Corroborating context (why no litigation is plausible)

• Owner: OP-D-OP, Inc. (original assignee); inventors Timothy J. Landis and Scott M. Perry, assigned from Auburn Product Design, Inc. (Reel/Frame 007721/0707, executed Oct. 16–20, 1995).
• Terminal disclaimer / expiry: The patent lapsed early — a maintenance-fee reminder was mailed July 25, 2000; the patent lapsed for failure to pay maintenance fees effective Dec. 31, 2000 (recorded "FP" Mar. 6, 2001), and USPTO notes patent expiration due to nonpayment under 37 CFR 1.362. A patent that lapsed in 2000–2001 and was never revived would be an unlikely subject of later infringement suits.
• No foreign family: Country status shows only the US (1), consistent with a small, non-litigated portfolio.
• Citations: The "Cited By" and "Citations" tables reflect only patent-document citations (e.g., US674650; US2102263; later Innerlite/Solmetex/Ultradent bite-block art), not litigation references.

Recommended next steps to confirm

To definitively rule litigation in or out, query these sources directly with the patent number:

1. USPTO Patent Center / Assignment — check the file wrapper for any "litigation" or adverse-proceeding flags.
2. PACER (paid) — full-text search for "5,588,836" and "5588836."
3. UnifiedPatents Portal litigation caselist — https://portal.unifiedpatents.com/litigation/caselist (search by patent number).
4. CourtListener / Docket Alarm / Docket Navigator — search by patent number.
5. CAFC docket — search for appeals referencing the patent or its owner OP-D-OP, Inc.

If you'd like, I can draft the exact search strings for PACER/Docket Navigator or check the patent's full file wrapper history for any adverse proceedings.

Bottom line: Based on the searches available to me, I found no known litigation involving US 5,588,836, and the record (early lapse for nonpayment of maintenance fees in 2000–2001) suggests it was never enforced in court.

I'll verify the canonical "no proceedings" finding against live sources before writing the analysis.

PTAB / AIA Trial Landscape — US 5,588,836

"Mouth prop and tongue deflector apparatus" — OP-D-OP, Inc. (inventors Landis & Perry); app. 08/543,843, filed 1995-10-23, granted 1996-12-31. Analysis date: 2026-09-28.

Proceedings overview

Total AIA trial proceedings on file: 0. Per the structured USPTO Open Data Portal block provided in this task ("The ODP API returns no AIA trial proceedings for this patent as of the most recent ingest"), there are zero active proceedings, zero claims invalidated, zero claims sustained by the Board, zero settlements, and zero institution denials — there is simply no IPR, PGR, or CBM ever filed against US 5,588,836. My independent web checks for the patent number against PTAB petition/FWD materials returned nothing for the '836 patent; the mouth-prop IPRs that surfaced in search (e.g., petitions at ptacts.uspto.gov against U.S. 11,589,970 and 12,011,329) are challenges to different, later patents that merely cite '836 as background art — they are not proceedings on this patent and should not be conflated. Bottom line on defensive posture: this is not a "hardened through IPR" patent; it is a dead one. The controlling fact for a defendant is not the PTAB docket but the USPTO fee/status record: the patent is Expired – Fee Related, with a legal-events trail showing lapse for failure to pay maintenance fees effective 2000-12-31, and a later STCH event (2018-01-24) stating "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362." Unless your demand letter predates 2000-12-31, there is no live right to assert.

Verification note / caveat. I could not run a docket-level query against PTAB E2E or the PTAB Decisions database in this session; my "no proceedings" conclusion rests on (a) the ODP structured block, which is canonical here, and (b) web searches that surfaced no petition, institution decision, FWD, or Federal Circuit appeal naming US 5,588,836. A belt-and-suspenders check against PTAB E2E (https://ptacts.uspto.gov/ptabweb), the PTAB Decisions page (https://www.uspto.gov/patents/ptab/decisions), and the PTAB API (https://developer.uspto.gov/ptab-api) is cheap and should be run before you rely on the absence in a filing. I also found no record of an ex parte reexamination, and no confirmed litigation involving this patent — I do not state that as fact.

No proceedings to report

There is no proceeding number to list. I will not manufacture one. For completeness, the near-miss search hits and why they were excluded:

• IPR2025-01057 and companion petitions (Ascentcare v. …) — challenges to U.S. 11,589,970 / 12,011,329 (Park, Baughan, Johnson, Black, Hirsch, Zheng grounds). Different patents, different owner. Excluded.
• Petitions citing a "'883 patent" (Centonza/Han, §102/§103) — that is U.S. 9,4xx,xxx-class '883, a cellular inter-node connectivity patent (McKool Smith petitioners), not US 5,588,836. Excluded — this is exactly the kind of number collision that produces fabricated proceeding lists.

Strategic summary

Claim status: nothing is canceled, nothing is sustained by the Board — everything is simply untested because nothing was ever filed. All twenty claims stand as issued and as they read on the face of the patent: independent claims 1, 9, and 14, and dependent claims 2–8, 10–13, and 15–20. There has been no IPR-driven narrowing, no certificate of correction / disclaimer of record surfaced in my search, and no inter partes or post-grant estoppel created by anyone. A defendant therefore cannot point to a Final Written Decision canceling claims 1–20, because no such decision exists. What a defendant can point to is far more dispositive: the patent's own administrative record shows it lapsed for nonpayment of maintenance fees effective 2000-12-31 (first maintenance-fee window, 3.5 years from the 1996-12-31 grant: due 2000-06-30, grace to 2000-12-31 — the dates match exactly), with a subsequent STCH event on 2018-01-24 confirming expiration for fee nonpayment under 37 CFR 1.362. Google's timeline separately displays a calculated "anticipated expiration" of 2015-10-23 (twenty years from filing) and a legal-status label of Expired – Fee Related; those Google figures are computed/aggregated fields, not evidence that fees were paid through 2015, and they are internally inconsistent with the LAPS/FP events. Pull the fee history in USPTO Patent Center before relying on either date — but every version of the record says the same thing directionally: the enforceable term ended well in the past, and no damages window for active infringement exists today.

Estoppel landscape: there is none to navigate, which is good news for a defendant. Because no petitioner ever filed, 35 U.S.C. § 315(e)(2) estoppel is not triggered against anyone — no real party in interest, no privy, no defensive aggregator, no prior petitioner to piggyback on or be blocked by. That means the entire universe of prior art remains available to you, unconstrained by the "raised or reasonably could have raised" bar. Practically, though, the vehicle set is narrow if a challenge were ever contemplated: PGR is unavailable (effective filing date 1995, well before the 2013-03-16 AIA window), CBM is unavailable (sunset 2020-09-16 and this is a dental device, not a financial-services patent anyway), so IPR is the only AIA trial available, and IPR is limited by § 311(b) to § 102 and § 103 grounds premised on patents and printed publications. § 112 indefiniteness/written-description theories — and this patent is chock-full of means-plus-function language ("tongue retractor means," "gimbal adjustment means," "extension adjustment means," "retention means") that would be inviting under § 112(f) — would have to be litigated in district court, not the PTAB. Note also the art of record is thin: the Google structured citation list shows only two references cited during prosecution, US 674,650 (Lundborg, "Dental tongue-holder and drain-tube") and US 2,102,263 (Grunewald, "Saliva ejector"); the specification's background discussion adds a rich set of dental appliances (US 5,232,362; 5,125,686; 4,975,057; 4,281,986; 4,192,071; 4,167,814; 4,024,642; 3,924,333; Swedish 142,956; US 637,970) that were disclosed by the applicant but not used as rejections.

Pattern signals: the absence of any IPR is itself the signal. Three things line up. First, this patent was never commercially significant enough to attract a challenger in the ~4 years it was in force before the fee lapse — well-asserted patents of value reliably attract IPRs, and this one attracted none. Second, the patent owner abandoned it at the very first maintenance-fee window, which is a strong tell that the owner saw no enforcement value. Third, the assignee of record, OP-D-OP, Inc. (with an assignment from Auburn Product Design, Inc., Timothy J. Landis, and Scott M. Perry, recorded 1995-10-23 at Reel/Frame 007721/0707), does not appear anywhere in my searches as a serial PTAB petitioner or a patent-assertion entity, and there is no defensive aggregator (Unified Patents or similar) anywhere in the chain — unsurprising, since aggregators target live patents. The patent's continued relevance is purely as prior art: it is cited by 38+ later documents (Google "Cited By"), primarily in the modern bite-block / intraoral-device space (Innerlite, Ultradent, Solmetex, Somnics/Apnicure, Awestruck Dental, and others). That is a defensive asset for you in a different direction — if a later patent is being asserted against your product, '836 is a 1995–1996 publication you can use as § 102/§ 103 art.

Recommended next steps

If you are a defendant being asserted against (or have received a demand letter citing US 5,588,836):

1. Lead with the status, not the invalidity case. There is no FWD to cite — so don't pretend there is. What you cite is the USPTO's own record: legal status Expired – Fee Related, the LAPS event dated 2000-12-31 ("Lapse for failure to pay maintenance fees"), the FP event dated 2001-03-06 ("Lapsed due to failure to pay maintenance fee," effective 2000-12-31), and the STCH event dated 2018-01-24 ("PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362"). Pull the certified fee history from USPTO Patent Center (https://patentcenter.uspto.gov) and attach it. A demand premised on an expired, fee-lapsed patent with no pre-expiration notice is, at minimum, a Rule 11 exposure for the sender.
2. Confirm the lapse is not a ghost. Check for any petition to accept an unintentionally delayed maintenance fee payment under 35 U.S.C. § 41(c) / 37 CFR 1.378 (and for any certificates of correction or statutory disclaimers). My record search shows no reinstatement event, but confirm directly — reinstatement is the only thing that would revive the term, and even then § 41(c)(1) limits recovery for infringement occurring between lapse and reinstatement.
3. If any pre-2001 damages theory is floated, attack the conditions for recovery: no infringement notice/marking (35 U.S.C. § 287) substantiated anywhere in my search, and the § 286 six-year bar closed long ago. Then attack the merits with the art already on the face of the record — Lundborg (US 674,650) and Grunewald (US 2,102,263) — plus the applicant's own background-art admissions.
4. Preserve '836 as art. Calendar the 1996-12-31 publication date; this reference is more valuable to you offensively against modern intraoral-device patents than defensively against '836 itself.

If you are evaluating an IPR anyway (e.g., to clear a cloud on a product line): the only available AIA vehicle is IPR under §§ 102/103 on patents and printed publications; no PGR, no CBM. Because no prior petition exists, no § 315(e)(2) estoppel constrains your ground selection, and there is no one-year § 315(b) service clock already running from an earlier petitioner. But weigh whether spending on a trial against a fee-lapsed, expired patent buys you anything the Patent Center fee history doesn't already give you for free.

If you need the FWD or a CAFC docket number: there is none to retrieve, and I will not invent one. If your research nonetheless turns up a proceeding, treat my conclusion as superseded and re-verify each element against PTAB E2E (https://ptacts.uspto.gov/ptabweb), the PTAB Decisions page (https://www.uspto.gov/patents/ptab/decisions), and CourtListener (https://www.courtlistener.com) before relying on it.

I'll verify the assignment record via live sources before writing.

Ownership & Assignment Analysis — US 5588836 A

"Mouth prop and tongue deflector apparatus" (application 08/543,843; filed 1995‑10‑23; granted 1996‑12‑31; expired for non‑payment of maintenance fees, effective 2000‑12‑31)

Source note: the USPTO Assignment Center (https://assignmentcenter.uspto.gov/) is a session-based JS application that could not be queried directly for this analysis. The assignment data below is taken from the USPTO assignment records as mirrored in the Google Patents legal-events table for this patent, which reproduces reel/frame, execution dates, assignor, and free-format conveyance text. The correspondent of record field was not exposed by that mirror and is flagged as unavailable rather than inferred.

Inventors

Pattern notes. This is not the "all inventors depart within 12 months" pattern. The two inventors and the corporate co‑assignor Auburn Product Design, Inc. executed the assignment together on 1995‑10‑16 through 1995‑10‑20, four to seven days before the 1995‑10‑23 filing date, and it was recorded on the filing date itself. That is a textbook pre‑filing, employment‑obligation assignment (inventors assigning as a condition of filing), not a distressed transfer.

The presence of a third, corporate assignor (Auburn Product Design, Inc.) alongside the two individuals is the only mildly unusual feature: it implies the design work was performed under a corporate consulting/development arrangement whose rights were also conveyed to OP‑D‑OP, Inc. in the same instrument. No evidence was found of a later spin‑out, dissolution, or assignment by Auburn Product Design.

Original assignee

OP‑D‑OP, Inc. — a California corporation, named as original and (per Google Patents) current assignee.

• Line of business: dental and medical protective/appliance products. Public IP records show OP‑D‑OP, Inc. holding the OP-D-OP trademark (first used 1988; EU registration filed 1996‑04‑01, registered 1998‑11‑20, Nice Class 10) for protective face masks for dentists, physicians and assistants, plus face shields, visors, dental X‑ray film/sensor holders, dental flossers, and this mouth prop. Source: https://www.onscope.com/ipowner/en/owner/profile/[988981](/patent/988981)-op-d-op-inc.html
• Did they ship a product embodying the claims? Yes, essentially certainly. OP‑D‑OP is a manufacturing/marketing company with a Class 10 goods trademark and a continuous patent portfolio (first patent 1987, most recent 2023 — e.g. visor and face shield patents). The apparatus in figures 1–10 is a moldable‑urethane clinical instrument, i.e. a product‑form innovation, not a paper patent. No contrary evidence (no abandonment of the mark, no gap in filings) was found.
• Current status: Operating. OP‑D‑OP, Inc. was still filing patent applications as recently as 2020–2023 (visor/face shield, face masks). No bankruptcy, dissolution, or acquisition record surfaced.

Assignment timeline

Only one assignment is recorded against this patent. There are no post‑issuance assignments — no shell‑entity transfer, no security interest, no merger, no change of name.

• Executed 1995‑10‑16 to 1995‑10‑20 / recorded 1995‑10‑23 — Reel 007721 / Frame 0707
  • Conveyance: Assignment of assignors' interest ("ASSIGNMENT OF ASSIGNORS INTEREST")
  • Assignors: Timothy J. Landis; Scott M. Perry; Auburn Product Design, Inc., a corp. of California
  • Assignee: OP‑D‑OP, INC. (California)
  • Correspondent: Not exposed in the fetched record. The Google Patents legal‑events mirror reproduces the reel/frame and the free‑format conveyance text but omits the correspondent/attorney field. This must be pulled directly from USPTO Assignment Center (search 5588836, reel 007721) to complete the chain — flagged as a verification gap, not asserted as "none."
  • Context: Original, pre‑filing employment/development assignment — the inventors and the corporate developer conveyed all right, title and interest to the operating company on the filing date. No recurrence of this correspondent can be assessed from a single recorded entry; a single appearance would not constitute a repeat‑correspondent signal under the stated criteria regardless.

Terminating events (legal‑status, not assignments):

• 2000‑07‑25 — Maintenance fee reminder mailed (USPTO code REMI).
• 2000‑12‑31 — Lapse for failure to pay maintenance fees (LAPS); effective expiration date 2000‑12‑31.
• 2001‑03‑06 — Lapsed due to failure to pay maintenance fee (FP).
• 2018‑01‑24 — Status‑housekeeping entry (STCH): "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362." This is an administrative record confirming the 2000 lapse, not a transfer and not a bankruptcy‑court event.

Because there are no post‑issuance records, the operative finding is: OP‑D‑OP, Inc. (now a lapsed‑patent owner) is the sole recorded owner of record for the entire life of the patent.

Timeline diagram

timeline
    title Ownership of US 5588836
    1995 : Inventors and Auburn Product Design assign
         : Recorded reel 007721 frame 0707
         : Patent application filed same day
    1996 : Patent granted to OP-D-OP Inc
    2000 : Maintenance fee reminder mailed
         : Maintenance fee lapse effective Dec 31
    2001 : USPTO records lapse due to nonpayment
    2018 : Status entry confirms expired patent

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT.
The only recorded conveyance (reel 007721/0707, 1995‑10‑23) runs from two individuals plus a California design corporation to an identified operating corporation. There is no LLC, no "IP/Holdings/Ventures/Licensing" suffix, no registered‑agent service address, and no post‑issuance transfer of any kind to a licensing vehicle.

2. Known asserter in the chain — NOT PRESENT.
Neither assignor nor assignee matches any entry on the public NPE rosters named in the brief (Acacia, Marathon, Intellectual Ventures, IPNav, Wi‑LAN, MOSAID/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities). OP‑D‑OP, Inc. is a manufacturing/dental‑supply company with a live Class 10 trademark and 35+ years of continuous product‑patenting. No Unified Patents or RPX high‑frequency‑plaintiff listing was found for OP‑D‑OP or its principals.

3. Repeat correspondent across the chain — NOT PRESENT / UNCLEAR.
There is only one recorded assignment in the chain, so the "same lawyer on multiple links" test cannot be satisfied by construction. The correspondent/attorney of record for reel 007721/0707 was not retrievable from the mirror used; this is the one open item requiring Assignment Center verification. Even if identified, a single appearance would not be a finding under the stated recurrence standard.

4. Cascading transfers — NOT PRESENT.
Zero consecutive assignments, let alone chained LLCs within 24 months. The chain is a single link.

5. Pre-litigation transfer — NOT PRESENT.
The only assignment predates issuance by ~14 months, and no infringement action naming US 5588836 was located (search of litigation/assertion coverage returned nothing for this patent number or for OP‑D‑OP as plaintiff in connection with it). There is no re‑assignment dated near any suit.

6. Bankruptcy fire‑sale — NOT PRESENT.
No Chapter 7/11 proceeding involving OP‑D‑OP, Inc. or Auburn Product Design, Inc. was located. The 2001 lapse and the 2018 STCH entry are maintenance‑fee non‑payment, the opposite economic signal from a monetization sale: the owner let the asset go for non‑payment rather than selling it. (Had the patent been a monetization candidate, the $ maintenance fee through 2011 would not have been abandoned four years post‑grant.)

7. Privateering — NOT PRESENT.
No operating‑company‑to‑NPE transfer exists, so there is no entity to assert on OP‑D‑OP's behalf; and no SEC‑filed or Patent Progress/EFF coverage of such an arrangement was found (OP‑D‑OP is private, so no 10‑K/8‑K trail exists).

8. Defensive aggregator (anti‑NPE) — NOT PRESENT.
The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. Important caveat on a likely misreading: the Google Patents "Cited By" list includes dozens of Innerlite, Apnicure/Somnics, Solmetex and Bracco Diagnostics patents. Those are later patents citing US 5588836 as prior art, i.e. citations, not assignments. Citation by the Solmetex/Innerlite oral‑device families is evidence of this patent's technical significance in bite‑block/aspiration design — it is not evidence that any of them ever owned it.

Verdict

Insufficient data — only the original assignment is recorded, and the patent is long expired.

The record contains exactly one assignment: reel 007721/0707, executed 1995‑10‑16 to 1995‑10‑20 and recorded 1995‑10‑23, conveying the inventors' and Auburn Product Design, Inc.'s rights to OP‑D‑OP, Inc., an operating California dental/medical products manufacturer. There is no post‑issuance assignment, no LLC, no security interest, and no asserted NPE signature in the chain. The patent then lapsed for non‑payment of maintenance fees effective 2000‑12‑31 (confirmed by the 2018 STCH entry, "expired due to nonpayment of maintenance fees under 37 CFR 1.362"), which independently forecloses any later assertion or troll‑chain scenario. The single residual item is the correspondent of record on reel 007721/0707, which the source mirror did not expose.

Verification links:

• USPTO Assignment Center (search patent 5588836, reel 007721): https://assignmentcenter.uspto.gov/
• Legacy assignment search index: https://assignment.uspto.gov/patent/index.html
• Google Patents legal events / full text (source of the reel/frame above): https://patents.google.com/patent/US5588836/en
• Assignee profile (products, trademark, portfolio span): https://www.onscope.com/ipowner/en/owner/profile/988981-op-d-op-inc.html

Caveat on completeness: my searches of RPX, Unified Patents and litigation coverage were open‑web searches; I did not have credentialed access to the RPX/Unified member databases. If OP‑D‑OP or US 5588836 appears in those gated datasets, that would change the record, and I would not claim otherwise on the basis of the searches run here.

I'll verify the patent and its cited references against current sources.

Let me verify the background-art references cited in the '836 specification, since those bear on relevance ranking.

1. Record confirmation — the patent specified

I searched on the number 5588836 only; no similar or neighboring numbers were substituted.

Ante‑AIA § 102 framework applied. Because 08/543,843 was filed 1995‑10‑23, pre‑AIA § 102 governs. The critical § 102(b) cutoff is therefore 1994‑10‑23; anything patented or described in a printed publication before that date is statutory § 102(b) art. § 102(a) art is measured against the invention date.

Note on claim‑text artifacts (interpreted literally, not auto‑corrected). Claim 1(e) as indexed reads "suction means for removing saliva front a patient's mouth" — this is an OCR artifact for "from." Also, the specification numbers the aspiration‑tube bore "58" in one paragraph and "bore 50" in another, and spells "serralions" for "serrations." These are noted, not corrected.

2. The patent citations of record for US 5,588,836

The face of the patent lists exactly two references ("Patent Citations (2)"), and both are flagged in the Google Patents markup as examiner‑cited:

Reference A

Full citation: Lundborg, John A. W., Dental Tongue‑Holder and Drain‑Tube, U.S. Patent No. 674,650, issued May 21, 1901 (application filed September 26, 1900; Google Patents records the priority date as 1900‑09‑25).
URL: https://patents.google.com/patent/[US674650](/patent/US674650)/en

Brief description (from its own disclosure):

• A spring clamp A with a fixed jaw 19 and a movable jaw a drawn together by a set‑screw F, clamped directly onto a single tooth (lower jaw) to support the device in the mouth.
• A hollow perforated pad D (tongue‑holder) with a concave bearing face to lie against the tongue; its chamber walls are perforated (F, Figs. 1, 3) and one side is hinged (joint g) so the interior can be opened for cleaning.
• A hollow tubular stem O to which the pad is attached by a swivel joint d, the stem being adjustable longitudinally and axially in a socket on the clamp, then locked by a screw e.
• A split ball in a socket on the clamp, the ball having an axial hole admitting the stem, with a set‑screw pressing the ball to confine it in the socket and clamp the stem — an express statement of a "universal adjustment"/"ball‑and‑socket bearing."
• A flexible drain tube T attached to the outer end of the stem, run to a sink to establish a siphon (gravity drainage, not applied vacuum).

§ 102 analysis — which claims it potentially anticipates: None. Elements that map:

Conclusion: US 674,650 fails § 102 for all of claims 1–20 because the single reference is missing the "handle rotatably coupled to a base," the "mouth prop," and the handle‑driven extension adjustment that appear in every independent claim. Its real value to '836 is evidentiary: it is § 102(b)/§ 103 background art for (i) a ball‑and‑socket universal joint feeding a tongue‑pad‑on‑a‑stem, and (ii) a hollow perforated tongue pad that doubles as the saliva collector with a drain tube.

Reference B

Full citation: Grunewald Hubert (indexed on FreePatentsOnline as "Hubert, Grunewald"), Saliva Ejector, U.S. Patent No. 2,102,263, issued December 14, 1937 (filed July 26, 1934).
URL: https://patents.google.com/patent/[US2102263](/patent/US2102263)/en

Brief description (from its own disclosure):

• Saliva is collected at the duct orifices, not from the mouth floor generally: a sublingual collecting device b (crescent‑shaped hollow metal member, open at the bottom, rubber‑lined) is placed behind the lower jaw and under the tongue, lifting the tongue slightly, with holes b′, b″ in each branch.
• Two tubular arms d, d′ curved both horizontally and vertically, jointed — "for instance through a ball and socket joint" — with a hollow main c, which communicates at its center with the common outflow tube a; vacuum is produced in tube a to draw saliva in.
• Two parotid collecting devices fitted at the ends of the bent arms.
• Retention is by a part bearing against the patient's chin with springs (Figs. 15–18), plus the arms seated in the mouth floor.
• Fig. 19 modification: each end of metallic member b carries an upwardly extending rib q "for holding the tongue of the patient in the direction of the axis of his mouth" — i.e., a tongue‑positioning feature.
• Device b is fitted on tube a "preferably in a removable manner."

§ 102 analysis — which claims it potentially anticipates: None. Elements that map:

Conclusion: US 2,102,263 likewise fails § 102 for all claims 1–20. It is the stronger of the two on the "suction means + tongue positioning in one instrument" concept, but it is missing the handle/base/bite‑prop architecture and the handle‑driven threaded extension adjustment that are the point of novelty of '836.

3. Most relevant prior art overall (relevance ranking)

The two examiner citations are not the closest art. Both are very early (1901, 1937) and function mainly as generic "hollow tongue pad + drain/suction" art. The genuinely closest art is in the specification's own "Description of the Background Art," which the applicants tendered under the duty of candor (each of the following is described in the '836 specification at 1:—, and the specification states that "none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention"):

Rank 1 — U.S. Pat. No. 5,232,362 ("Dental suction appliance"). Per the '836 specification: a tongue deflector is coupled to an aspiration tube and held in place by a bite tube between a patient's teeth. Google Patents indexes it at 1993‑08‑03. This is the closest single reference: it combines the bite‑held retainer, the aspiration tube, and the tongue deflector in one instrument. Its priority date is after the 1994‑10‑23 § 102(b) cutoff and before the 1995‑10‑23 filing, so it is available only as § 102(a)/§ 102(e) art (and § 103 art), not as § 102(b) art relative to '836.

Rank 2 — U.S. Pat. No. 5,125,686 ("dental appliance which includes a tongue stabilizer and suction tube that are slidably coupled to a bite block"). The sliding (axial) coupling to the bite block is the closest analogue to '836's axial extension adjustment — but it is a passive slide, not a handle‑driven threaded screw, and there is no gimbal.

Rank 3 — U.S. Pat. No. 4,167,814 ("mouth prop and oral evacuation device wherein a generally U‑shaped suction tube and tongue guard are secured to a mouth prop") — mouth prop + suction + tongue guard in one unit.

Rank 4 — U.S. Pat. No. 4,975,057 (bite block whose apertures serve as evacuation nozzles) and U.S. Pat. No. 4,024,642 (suction tube and flat shield attached to a bite block).

Rank 5 — U.S. Pat. No. 4,192,071 and U.S. Pat. No. 4,281,986 (collector member with tongue guard and collector membrane held by a bite block); U.S. Pat. No. 3,924,333 (tongue guard with evacuation channels on a bite block).

Rank 6 — Swedish Patent No. 142,956 (combined saliva evacuator and tongue positioner with salient chin rest and jaw rest) and U.S. Pat. No. 637,970 (hooked saliva evacuation tube with deflector plate).

Caveat: I have verified the descriptions of these ten references only as the '836 specification characterizes them. I was unable to independently verify their issue dates, inventors, or full disclosures within this session, so I am not asserting independent § 102 mappings for them. Where a date is given (5,232,362) it comes from Google Patents' parallel listing. Treat the rank ordering as a relevance assessment, not a completed § 102 analysis.

Forward art (for context, not § 102 against '836): the record shows 38 examiner/third‑party forward citations and 94 "cited by" entries, with the largest families being Innerlite, Inc./James A. Hirsch (1998‑) and the Solmetex intraoral‑device family (2012‑), plus Apnicure/Somnics saliva‑management patents (2007‑). These post‑date '836 and therefore cannot anticipate it; they only establish the field '836 seeded.

4. Bottom line

• US 5,588,836 has two references of record: US 674,650 (Lundborg, "Dental tongue‑holder and drain‑tube," issued 1901‑05‑21, filed 1900‑09‑26) and US 2,102,263 (Grunewald, "Saliva ejector," issued 1937‑12‑14, filed 1934‑07‑26). Both are § 102(b)‑eligible art as to the 1994‑10‑23 cutoff.
• Neither reference anticipates any of claims 1–20 under 35 U.S.C. § 102. Anticipation requires that a single reference disclose every element arranged as in the claim (MPEP 2131). Each reference is missing at least the "handle rotatably coupled to a base," the "mouth prop coupled to the base / defining a socket," and the handle‑rotation‑driven extension adjustment means — all of which are present in each of independent claims 1, 9 and 14.
• The correct characterization of US 674,650 and US 2,102,263 relative to '836 is § 103 background art on secondary features: a ball‑and‑socket universal joint feeding a tongue‑pad‑on‑a‑stem (Lundborg), and a vacuum‑drawn open‑bottom sublingual collector with an integral tongue‑holding rib (Grunewald). Neither teaches the ball‑and‑socket gimbal between the base and the bite prop (claim 8), the handle‑bore thread driving a threaded aspiration tube (claims 4, 10, 14), or the keyway alignment preventing tube rotation (claims 5, 11, 12, 16, 17).
• Most relevant prior art to '836 is U.S. Pat. No. 5,232,362 (dental suction appliance: tongue deflector + aspiration tube retained by a bite tube), followed by U.S. Pat. No. 5,125,686 (tongue stabilizer + suction tube slidably coupled to a bite block) and U.S. Pat. No. 4,167,814 (suction tube and tongue guard secured to a mouth prop). None of these is a § 102(b) reference to '836, and on the '836 record the examiner did not apply them; they were disclosed by the applicants in the Background Art.

I'll ground this analysis in the actual prior-art references before building the § 103 case. Let me pull the key references.

Key finding: the examiner-cited US674650 (Lundborg, 1901) discloses a ball-and-socket with a longitudinally adjustable hollow stem. Let me verify a few more references, including a number discrepancy I want to check literally.

Obviousness Analysis — US 5,588,836 (Mouth Prop and Tongue Deflector Apparatus)

Framework used: Pre-AIA 35 U.S.C. § 103 (application filed 1995-10-23, priority 1995-10-23), Graham v. John Deere, KSR Int'l v. Teleflex, and the rationales catalogued at MPEP 2143/2144. All findings below are grounded in the full text of US 5,588,836 and in the references actually listed on the patent page, plus two supplemental references I verified by search (clearly flagged as such).

1. What on this page actually qualifies as § 103 prior art

Note two literal-identification discrepancies I will not auto-correct, per your instruction:

• The Background Art cites "U.S. Pat. No. 5,232,362" for the Kanas appliance — this is confirmed: US 5,232,362, Kanas, granted 1993-08-03 (https://patents.google.com/patent/US5232362).
• The Background Art cites "U.S. Pat. No. 5,125,686" as disclosing "a tongue stabilizer and suction tube that are slidably coupled to a bite block." The reference matching that description that my search returned is US 5,152,686 (Duggan, "Dental appliance," granted 1992-10-06, https://patents.google.com/patent/[US5152686A](/patent/US5152686A)). I could not verify that a US 5,125,686 exists (my search returned US 4,986,568 Galtier, which is unrelated). Treat the spec's "5,125,686" literally; if that number is real and different, its disclosure is unverified here.

Practical caveat: this patent lapsed for non-payment of maintenance fees effective 2000-12-31 ("Expired – Fee Related"). The § 103 question is therefore retrospective — it matters for intervening rights, for the weight of US 5,588,836 as prior art against the 38 later patent families, and for any reexamination.

2. The claimed subject matter (independent claims)

• Claim 1 (means-plus-function): handle; base (handle rotatably coupled to base); mouth prop coupled to base; tongue retractor means; suction means coupled to the retractor; gimbal adjustment means positioning retractor/suction relative to the mouth prop; extension adjustment means positioning retractor/suction relative to handle and base.
• Claim 9: the § 112 ¶ 6 limitations resolved into structure — handle with axial bore; base with ball joint having an axial bore collinear with the handle bore; mouth prop with socket pivotally receiving the ball joint; aspiration tube through both bores; tongue retractor with suction aperture coupled to the tube; extension adjustment "by rotation of said handle relative to said base."
• Claim 14: as claim 9, plus threaded bore in the handle, external threaded portion on the tube engaging it, upper and lower teeth-receiving members defining the socket, a detachable plate carrying the suction aperture, and alignment means preventing tube rotation relative to the base.

3. Element mapping

Closest single reference: Lundborg discloses the tongue-retractor + suction + hollow-tube + ball-and-socket universal (gimbal) adjustment + longitudinal extension adjustment combination. It does not anticipate claim 1 or 9, because its support is a tooth clamp with a set-screw, not a bite-received mouth prop, and it has no handle rotatably mounted in a base that drives extension. Hence § 102 fails and § 103 governs.

4. Grounds of rejection

Ground 1 — Lundborg + Kanas (primary). Lundborg supplies the gimbal-adjusted, suction-coupled tongue pad; Kanas supplies the bite-tube mouth prop and the concept of adjustably passing the aspiration tube through a bite-received support. This combination renders claims 1, 2, 3, 8, 9, 13, 18, 20 obvious, and with a threaded drive (Ground 2) also claims 4, 10, 14.

Ground 2 — Lundborg + Kanas + Grünberg (US 1,447,020), or + Lundborg's own threaded set-screws. Supplies the threaded handle-bore/externally threaded tube and the rotation-actuated extension of claims 4, 10, 14; and by necessary implication the anti-rotation "alignment means" of claims 5, 11, 12, 16, 17 (a screw-driven follower must be rotationally constrained or it will simply spin with the nut).

Ground 3 — Ground 2 + Lundborg's hinged pad and/or Grunewald's removably fitted collector, and/or US 4,281,986's tab-retained membrane. Renders claims 6, 7, 19 obvious (detachable apertured plate; retention against loss).

Ground 4 — Ground 1 + US 4,281,986/US 4,192,071. Renders claims 15 (shell/handle portion partially enclosing the tube and keeping the vacuum connector off oral tissue — the reference states this express purpose) and 16 (an intermediate elongated bored member joining the ball-joint region to the handle shell, cf. holder 49 with bore 50) obvious.

Ground 5 — any of the above + Grunewald. Especially relevant to claims 2, 6, 13, 19 because Grunewald's collector is designed to sit under the tongue (matching the specification's own statement that the suction aperture is "generally positioned under the patient's tongue") and is explicitly removable for cleaning.

5. Why a PHOSITA would have been motivated to combine

1. Identical field, identical problem, near-identical problem statement. US 5,588,836's stated objects are: a single instrument providing simultaneous mouth propping, adjustable tongue retraction and saliva evacuation; not requiring an assistant. Kanas states the same object almost verbatim: "a single dental appliance would provide for deflecting the tongue, aspirating liquids with variable suction level, and maintaining the patient's mouth in an open position," and "to reduce the need for chairside assistance." Two references solving the same problem in the same field, each supplying a different claimed sub-combination, is the paradigm case for § 103 (MPEP 2143, rationales A, C and G).
2. Express criticism of the very structure the primary reference uses. Lundborg supports the appliance from a tooth clamp. Kanas expressly teaches away from tooth-clamping supports: such devices are "not suited for use by patients who are missing teeth and cannot effectively clamp the bite block in place," and are "difficult to install and remove." This supplies a concrete reason to substitute a bite tube (mouth prop) for Lundborg's clamp and to retain Lundborg's ball-and-socket for adjustment — i.e., "a known technique to improve a similar device in the same way" (MPEP 2143 rationale C) and "use of a known device ready for improvement" (rationale D).
3. Mutual complementarity of capabilities. Kanas supplies only sliding + 360° rotation of the tube in the bite tube; Lundborg supplies true universal ball-and-socket gimballing with positive locking. A PHOSITA seeking the patent's stated benefit ("greater degree of positional adjustment... than is possible in currently available devices") would combine them; the combination is a mere aggregation of known capabilities with predictable mechanical results (rationale A).
4. Substitution of a threaded drive for a friction slide. Kanas's slide-and-friction adjustment is coarse and slip-prone; a screw thread provides fine, positive, self-locking adjustment in a bore. Grünberg (US 1,447,020) already applied exactly that expedient — internally threaded socket + externally threaded tube, adjusted by rotation — to a dental saliva ejector "to adjust the saliva ejector... to the various requirements... the region of said treatment, the mouth cavity of the patient." Substituting a screw pair for a sliding coupling is a "simple substitution of one known element for another" producing a predictable result (MPEP 2144.04; In re Fout, In re Cipa), and adds the patentability-neutral advantage of not disturbing the apparatus while the patient's mouth is held open.
5. Detachable/tethered parts were already the recognized solution to the sterilization problem. The patent's own rationale — the plate "allows cleaning of the interior," the tether "prevents loss of plate 48 during cleaning or sterilization" — is precisely the rationale already expressed in the art: Lundborg's pad is hinged "to permit the same to be opened for the purpose of cleaning out its interior," Grunewald's collector is fitted "in a removable manner," and US 4,281,986 retains its membrane with a tab that "serves as a retainer." The problem was recognized and solved in the same way in the same art before 1995, so the claimed structure is the predictable application of a known technique (rationale A/D).
6. Anti-rotation keyway = design expedient. Constraining a screw-driven follower against rotation by a key/keyway (or spline, or flat) is one of the elementary mechanical arts. MPEP 2144.04 lists screw threads, keys, splines and their equivalents as a canonical example of a predictable substitution. The specification itself concedes interchangeability ("Alternatively, an axial key may be included on aspirator tube 20, and an axial slot included within bore 30..."), which undercuts any argument that the choice is inventive.
7. Motivation as of 1995, not 1901. The recency of Kanas (granted 1993-08-03, two years before the filing) shows this problem was actively being worked in 1993–1995 and that the industry was consolidating exactly these three functions into one instrument — a strong "market force / design incentive" rationale (MPEP 2143 rationale F).

6. Non-obviousness arguments the applicant could have advanced (and their weaknesses)

• No single reference teaches bite-actuated clamping of the ball in the socket. This is true and is the patent's most distinctive functional idea. But it is not claimed: claim 1 requires only a "mouth prop coupled to said base" plus "gimbal adjustment means"; claims 9 and 14 require only a "socket." The bite-force-clamping feature appears in the specification as an operational description, not as a claim limitation. Under § 103, the claims are judged as drafted, and the specification's explanation of how the cooperating parts work together when the claims are so read supplies an additional reason to combine (MPEP 2141/2143; "Because the claimed device and the prior art device are used in the same manner, the combination is obvious").
• Grunewald's ball-and-socket is on lateral arms, not on the main support; Lundborg's is on a tooth clamp. These are structural-difference arguments about where a known joint sits, not about whether the joint is known for this purpose — vulnerable to rationale C.
• Secondary considerations: no evidence of unexpected results, long-felt need, failure of others, or commercial success appears in the record available on this page. Note that the patent's own background section admits the problem and its causes, which supports motivation but weakens any later assertion of a previously unrecognized problem. No licensing/commercial-success nexus is documented on the page.
• § 112 ¶ 6 overlap. Claims 1, 9 and 14 recite means-plus-function elements; where the prior art discloses equivalent structure performing the same function, the Office's practice is generally to reject under § 103 rather than § 102, and to require identification of the corresponding structure disclosed in the specification (MPEP 2181 et seq.). The "gimbal adjustment means" and "extension adjustment means" of claim 1 read directly onto Lundborg's split-ball/socket/set-screw assembly and stem adjustment, and onto the thread pair of claims 4/9/10/14.

7. Independent claim-by-claim conclusion

Bottom line. The two references the examiner actually cited — Lundborg (US 674,650) and Grunewald (US 2,102,263) — each independently disclose the tongue-retractor/suction/gimbal core, and Lundborg discloses ball-and-socket universal adjustment with a hollow suction stem and a longitudinally adjustable stem. The examiner appears to have missed the most damaging combination: US 674,650 (Lundborg) in view of US 5,232,362 (Kanas), optionally supplemented for the threaded drive by US 1,447,020 (Grünberg). Claims 1–3, 8–11, 15, 16, 18 and 20 are the most exposed; claims 12 and 17 (specific keyway geometry) are the most defensible, chiefly because the specification concedes the key/slot reversal is a mere alternative rather than arguing any unexpected result.

Verification notes (stated explicitly per your rule): I verified the full text of US 674,650, US 2,102,263, US 5,232,362, US 5,152,686, US 4,281,986/US 4,192,071 (substantial excerpts) and US 1,447,020. I could not retrieve or verify the disclosures of US 637,970, Swedish Patent No. 142,956, US 4,024,642, US 3,924,333, US 4,167,814 or US 4,975,057; my statements about those rely solely on the characterizations given in US 5,588,836's own Background Art (which are, in any event, applicant admissions). I also could not confirm that US 5,125,686 exists as a separate document from US 5,152,686.