US 5910001

I'll search for authoritative information on US 5910001, including any CAFC 2026 docket activity.

Let me try alternative search queries to reach authoritative sources.

No litigation surfaced. Let me confirm with targeted litigation searches.

US Patent 5,910,001 — Summary

Note on search results: My searches for this specific number did not return any USPTO PatentCenter/Patent Public Search page directly, nor any Court of Appeals for the Federal Circuit (CAFC) 2026 docket entry. The one non-patent hit for the string "5910001" (a CTS product notice, "5910001-38M4000") is a component part number, not the patent, and is unrelated. I therefore rely on the authoritative full patent text provided in the task and flag uncertainty where noted.

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Bibliographic data

Abstract

A method of adjusting the engaged clearance between male and female rotors of a screw compressor (rotors kept in rotation at a very small clearance by shrink-fit timing gears), wherein the very small clearance is set to a required value by (1) loosening the shrink fit between one timing gear and its rotor while movement of the other timing gear is restricted, and (2) intermittently applying torques to that rotor with a servo motor. This yields a screw compressor whose rotor clearance can be set to a required value in a short time with high reliability of "symmetrizing" adjustment and high compression performance.

Independent claims — plain language

Claim 1 (method). A method of setting the running clearance between the male and female rotors of a screw compressor whose rotors are kept at a very small clearance by timing gears individually shrink-fit onto them. The method has two steps:

1. Loosen the shrink fit between one of the timing gears and the rotor it sits on, while holding/restricting movement of the other timing gear; and
2. Intermittently apply torque to the rotor carrying that gear using a servo motor to bring the very small rotor-to-rotor clearance to the required value.

Claim 10 (apparatus). An apparatus for the same purpose comprising intermittent torque applying means that (a) loosens the shrink fit between one timing gear and its rotor while movement of the other timing gear is restricted, and (b) intermittently applies command-value-based torques to that rotor via a servo motor.

Claims 2–9 depend on claim 1 (e.g., determining the next torque from the difference between rotor position and target position; applying torque at the rotor end opposite the timing gear; and the forward/backward-torque + median-value refinement of claim 4; helical-gear press-fitting variants of claim 7). Claims 11–12 depend on claim 10, mirroring those features on the apparatus side. So the patent has two independent claims: 1 (method) and 10 (apparatus).

Technical gist (for context)

The disclosed insight is that even after hydraulic loosening of the shrink fit, residual friction elastically deforms the rotor, so the clearance drifts when the servo motor stops. The invention applies a large intermittent torque, then small equal-and-opposite forward/backward torques (each larger than the servo drive's static friction but smaller than the intermittent torque). The median of the resulting rotor positions represents the rotor's un-deformed ("natural shape") position, and the next intermittent torque is computed from the difference between that median and the target clearance. Claim 4 embodies this refinement.

Litigation / CAFC 2026

No CAFC 2026 docket activity for US 5,910,001 was found, and none is reported in the available Google Patents record (no litigation, IPR, or reexamination entries). Given the patent expired under 37 CFR 1.362 in 2011, active 2026 appellate litigation is unlikely, but I cannot authoritatively confirm a negative — I could not reach a live USPTO or CAFC docket source, so treat "no CAFC 2026 activity" as an unverified negative rather than a definitive finding.

I'll search for litigation involving US patent 5910001 across patent litigation sources.

Let me search more targeted litigation databases.

Litigation Search Results — US Patent 5,910,001

No litigation is known involving U.S. Patent No. 5,910,001.

I searched patent litigation sources (including Unified Patents' litigation portal and CourtListener/PACER-oriented results) for the specific number "5910001" and related strings (e.g., "5,910,001"). The only hits returned were for different patents — most notably U.S. Design Patent No. D971,591 ("591 Patent") and U.S. Patent No. 7,020,252, among others. None of these involve the patent at issue here. Per your instruction, I have not extrapolated from those similar/partial number matches.

What the record does show for US 5,910,001

Based on the patent document itself (which is the only authoritative source located):

Key caveats

• No district court, Federal Circuit (CAFC), PTAB, or ITC proceeding referencing this patent was identified in the searches performed.
• This patent appears to be a manufacturing/method patent for internally adjusting rotor clearance during assembly (assignee-controlled), which is consistent with its never having been asserted in litigation.
• Negative findings of this kind are inherently limited by search coverage. If you require a definitive clearance/assertion check, I'd recommend running a portfolio-specific query directly in Unified Patents' litgation caselist (https://portal.unifiedpatents.com/litigation/caselist), PACER, and Lex Machina / Docket Navigator, keyed to patent number 5,910,001 and its assignees (Hitachi Industrial Equipment Systems Co., Ltd.; Hitachi Plant Technologies, Ltd.). I could not complete those site-specific lookups within this session, so I am flagging the result as "no litigation found" rather than "confirmed never litigated."

If you'd like, I can attempt additional targeted searches against specific litigation databases to further confirm the negative result.

Proceedings overview

Zero (0) AIA trial proceedings are on file for US Patent 5,910,001. There is no IPR, no PGR, and no CBM to report — so there is no breakdown by status to give (0 invalidated, 0 sustained, 0 settled, 0 institution-denied). The bottom line for a defendant: this is not a "hardened" patent and it is not a "dead-claims" patent — it is an untested but fully expired patent. It lapsed on 2011-06-08 for failure to pay maintenance fees, its 20-year term ran out on 2017-06-20, and as of 2026-09-28 no PTAB panel has ever construed a single one of its claims. A demand letter citing US 5,910,001 today is worthless for any ongoing or future conduct, and the § 286 six-year damages lookback window closed years ago.

Proceedings

None. No proceeding numbers can be listed because none exist in the structured source data or in any public source located.

The structured "PTAB proceedings on file" block (USPTO Open Data Portal / PatentCenter AIA-trial ingest) returned no AIA trial proceedings for US 5,910,001. Per the operating instruction in that block, the default is "no PTAB activity on file." My independent web searches did not surface anything to the contrary:

• Searches keyed to "5910001" / "5,910,001" plus "IPR," "PTAB," "Patent Trial and Appeal Board," and the assignee names (Hitachi Techno Engineering Co., Ltd.; Hitachi Plant Technologies, Ltd.; Hitachi Industrial Equipment Systems Co., Ltd.) returned zero PTAB documents. Hits were either the patent itself, unrelated patents with similar numbers, or generic PTAB/AIA practice material (e.g., Cuozzo, Wi-Fi One, GAO/CRS background reports).
• The Google Patents record for US 5,910,001 lists only the grant, the EP/DE family members, and ordinary legal events — fee payments, assignments (2007-03-05 name change to Hitachi Plant Technologies; 2007-10-16 assignment to Hitachi Industrial Equipment Systems), a maintenance-fee reminder, lapse, and expiration. No "REEXAM," no "IPR," no "PGR," and no certificate of reexamination appears.
• The "Cited By" and "Families Citing" lists show only later third-party patents on rotor synchronization and screw-compressor clearance (e.g., Carrier's WO 2018093440 A1, "Screw compressor with rotor synchronization"; CN 111396310 A, "Oil-free screw structure and method for adjusting synchronous rotor clearance thereof"), not adversarial PTAB filings against this patent.

Availability caveat on proceeding types (why the menu was narrow): US 5,910,001 issued from an application filed 1997-06-20 with a 1996-07-03 priority date — a pre-AIA, first-to-invent patent. That means PGR was never available (PGR reaches only first-inventor-to-file patents, 35 U.S.C. § 321(b)(1)) and CBM was never available (the patent claims a mechanical rotor-clearance manufacturing method, not a "financial product or service," and CBM sunset on 2020-09-16 anyway). The only AIA-type challenge that ever could have been filed was an IPR, and it never was. That IPR was theoretically available only from 2012-09-16 until the patent's term end (2017-06-20) — a ~4.75-year window that closed with the patent's expiration.

Strategic summary

Claim status: 1–12 are all UNTESTED (never construed by the Board), and all 12 are expired. No claim of this patent has ever been canceled, confirmed, or even adjudicated at the PTAB. The record therefore gives you no claim-level invalidity prepackaged for you — but it also gives you no adverse claim-construction precedent binding on any panel. The asserted universe would have been all twelve claims: independent method claim 1; dependent method claims 2–9 (claim 4 adding the forward/backward-torque-plus-median-value limitation, claim 7 adding the helical-gear press-fit sequence); independent apparatus claim 10; and dependent apparatus claims 11–12. Because the patent expired 2017-06-20 and lapsed even earlier (2011-06-08), there is no live claim scope to argue about.

Estoppel landscape: none, in either direction. Because no petition was ever filed, there is no § 315(e)(2) estoppel on any petitioner or privy, and no § 325(e)(2) estoppel either. That cuts both ways: nothing is foreclosed to a defendant on paper — but there is also nothing to leverage. An IPR is now categorically unavailable on this patent (a petitioner must be challenging at least one claim of an unexpired patent; the Board will not institute on expired claims there is no longer any power to amend or cancel in a meaningful way, and the statutory/ Article III-tinged controversy is gone). Any validity theory you would have run at the PTAB is now only useful in the district court — and only if someone is actually still selling against it, which they are not.

Pattern signals: none. No repeat-petitioner pattern (no petitioner at all). No patent-owner PTAB appeal activity to the Federal Circuit on this patent (there is no FWD to appeal under § 319). No defensive aggregator (Unified Patents, RPX, etc.) in the chain — consistent with the overall picture from the litigation screen, where no district court, ITC, or CAFC proceeding involving this patent was identified either. The prior-art landscape that would have been the ammunition sits in the face of the record: JPS 56-083593 (Hitachi, 1981-07-08, "Method of adjusting clearance between two rotors of displacement type compressor"), JPS 58-67987 (Hitachi, 1983-04-22, rotor-clearance adjustment for a screw fluid machine), EP 0135256 A1 (Eaton, 1985-03-27, supercharger rotor phasing fixture), JP 04-232395 (Honda, 1992-08-20), JP 05-71473 (Honda, 1993-03-23), and — most directly — JP 01-155089 (Hitachi, cited in the specification as the very basis of the "measuring work" and "symmetrizing adjustment" the patent builds on). That is a Hitachi self-citation-heavy field, which is characteristic of an internally developed manufacturing process that the assignee controlled and never needed to police.

Recommended next steps

1. If you are a defendant facing a demand on US 5,910,001 — do not file an IPR; do not negotiate as though validity is in play. The patent expired at end of term on 2017-06-20 and lapsed for non-payment of maintenance fees effective 2011-06-08 (Google Patents legal-status field: "Expired – Fee Related"). Twenty-eight years of § 286 damages lookback from today (2026-09-28) reaches back only to about 2020-09-28, all of which post-dates expiration. There is no recoverable period.
2. There is no FWD, no institution decision, no Board opinion, and no CAFC opinion to link. I searched for one and found none, and I will not fabricate a proceeding number, panel, or disposition. For a definitive clearance check, run the number directly in USPTO PTAB E2E (https://developer.uspto.gov/ibd-api / PTAB E2E portal) and in USPTO ODP, keyed to 5910001 and application 08/879,609. CourtListener (https://www.courtlistener.com/?q=%225910001%22) returned nothing relevant in my search.
3. The real defensive posture is expiration, not invalidity. Because there is no PTAB record, a defendant gets neither the "claims canceled, sanction-bait" clean kill of a successful IPR nor the "patent survived two IPRs and is hardened" warning. The correct framing is: untested claims, dead patent, zero estoppel exposure, zero PTAB precedent — resort to the expiration and lapse dates as the primary defense, and treat the cited JP/EP art above only as a fallback if some other member of the family (EP 0816683 B1, DE 69724706 T2 — both expired) were ever asserted.
4. Flag any contradicting evidence. If a search later surfaces a PTAB trial or reexamination on this patent (for example, an ex parte reexamination request that never matured to a certificate, or a terminated IPR that the ODP ingest missed), treat that as a direct contradiction of the "no PTAB activity on file" default and re-run this analysis. I found none, and I am reporting the absence explicitly rather than inferring activity.

Sources consulted: USPTO Open Data Portal structured "PTAB proceedings on file" block (canonical; returned none); Google Patents record for US 5,910,001 (https://patents.google.com/patent/US5910001/en) — citation list, cited-by list, legal events, and status; Google Patents EP 0816683 A1 for the family; USPTO/GAO/CRS AIA-trial background material; and general web searches for "5910001"/"5,910,001" in combination with PTAB and IPR terms (zero relevant hits).

I'll research the assignment record for US 5910001, starting with the records already visible in the patent text and then probing for correspondents and any additional recordings.

Assignment Reconstruction — US 5,910,001

Source note / limitation up front: I could not open the live USPTO Assignment Center (assignmentcenter.uspto.gov) or the legacy Patent Assignment Search (assignment.uspto.gov) in this session — my queries returned only the patent text and unrelated corpora. Consequently the three reel/frame numbers below are taken from the "Legal Events" table of the authoritative patent record supplied in the task, not from a live Assignment Center lookup, and no correspondent of record was retrievable for any of the three recordings. I will not invent correspondents. Run the check at https://assignmentcenter.uspto.gov/ (search the patent number 5910001) and at https://assignment.uspto.gov/patent/index.html to fill that column.

No contradiction was found with the two previously generated sections; this analysis is consistent with them (current assignee Hitachi Industrial Equipment Systems Co., Ltd.; expired fee-related 2011).

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Inventors

Pattern notes: All four inventors assigned to the same employer via a single instrument (Reel 008643/0233), executed 1997-06-04 — i.e., a standard employee invention-assignment, not a mid-career purchase. This is the ordinary "all inventors on the same corporate payroll" signature and is not a fire-sale precursor. I found no evidence of any inventor departing the original assignee within 12 months of filing; that negative is unverified (no employment records were searched). Note the file has two JP priority applications (JP 8-173391 and JP 8-341615) mapping to separate JP patents (JP3301918B2; JP3639396B2) — inventor overlap between those JP filings and this US case is not resolvable from the sources available.

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Original assignee

Hitachi Techno Engineering Co., Ltd. (Japan) — named as assignee and confirmed by Reel 008643/0233 (recorded 1997-06-20, executed 1997-06-04). It is the assignee of record on the issued patent.

• Line of business: A Hitachi Group engineering and plant-construction company. Screw-compressor design/build was an internal engineering activity consistent with this patent, which is a manufacturing/assembly method for setting rotor timing clearance on the factory floor.
• Did it ship a product embodying the claims? Presumed yes, as an assembler: the claims read on the rotor-symmetrizing step of building a screw compressor, and the patent's FIG. 1 apparatus is a production/assembly apparatus (DD motor, encoders, press-fitting jig). I could not obtain an independent product catalogue or serial evidence in this session, so treat "shipped product" as inference from the patent's own manufacturing context, not as a verified commercial fact.
• Current status: Not operating under that name. It was renamed Hitachi Plant Technologies, Ltd., effective 2001-10-01 (recorded as a Change of Name on Reel 019009/0048, 2007-03-05), and its interest was then assigned to Hitachi Industrial Equipment Systems Co., Ltd. (Reel 019984/0810, recorded 2007-10-16, effective 2007-09-28). Hitachi Industrial Equipment Systems is a live operating Hitachi subsidiary (listed address 3 Kanda Neribei-cho, Chiyoda-ku, Tokyo) and appears as assignee on many later, unrelated compressor/motor patents. Distinct from this case, Hitachi Plant Technologies, Ltd. as a separate legal entity was subsequently folded into Hitachi, Ltd.'s infrastructure business — I flag this as general background, not verified from the assignment record, and it does not affect the chain above.
• Bankruptcy: None found (and none consistent with a going-concern Hitachi subsidiary).

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Assignment timeline

Chronological, every recorded conveyance surfaced:

1997-06-04 (executed) / recorded 1997-06-20 — Reel 008643/0233

• Conveyance: Assignment of Assignors' Interest
• Assignor: Kenichi Takahashi; Hiroyuki Matsuno; Hiroyasu Obata; Megumi Kawai (inventors)
• Assignee: Hitachi Techno Engineering Co., Ltd.
• Correspondent: not retrievable this session — the patent-text Legal Events entry omits the correspondent field. No recurrence can be assessed.
• Context: Original employment invention assignment at filing — inventor-to-employer, not an acquisition.

2001-10-01 (effective) / recorded 2007-03-05 — Reel 019009/0048

• Conveyance: Change of Name
• Assignor: Hitachi Techno-Engineering Co., Ltd.
• Assignee: Hitachi Plant Technologies, Ltd.
• Correspondent: not retrievable this session — flag as unable to test the repeat-correspondent signal.
• Context: Internal corporate reorganisation — change of name only; no change in beneficial ownership. (Note the ~5.5-year lag between legal effective date and recording date; that lag is a routine bulk-cleanup artifact and not an NPE tell.)

2007-09-28 (effective) / recorded 2007-10-16 — Reel 019984/0810

• Conveyance: Assignment of Interest
• Assignor: Hitachi Plant Technologies, Ltd.
• Assignee: Hitachi Industrial Equipment Systems Co., Ltd.
• Correspondent: not retrievable this session.
• Context: Intra-Hitachi transfer of the compressor business and its IP to the industrial-equipment operating subsidiary — internal reorg, not a transfer to an asserter.

No further assignment records appear in the patent's legal events. The remaining post-2007 entries are fee-payment/administrative codes (FEPP, FPAY, REMI) and the terminal lapses — not conveyances: 8-year maintenance fee paid 2006-11-29 (this predates the 2007 transfer and reflects pre-transfer ownership), maintenance-fee reminder 2011-01-10, lapse for failure to pay maintenance fees 2011-06-08 (37 CFR 1.362), patent discontinued 2011-07-04, anticipated expiration 2017-06-20.

Note on correspondents (explicit gap): I could not confirm the attorney or firm of record on any of the three reels. One unrelated Hitachi-origin recording surfaced in my searches — Patent Assignment 20043/818 (recorded 2007-10-31), inventors Kikuchi et al. → Hitachi Industrial Equipment Systems and others, correspondent Antonelli, Terry, Stout & Kraus, LLP, 1300 N. 17th St., Ste. 1800, Arlington VA 22209. That is a different reel/frame and a different patent, offered only as a research lead for a Hitachi-Group-2007 correspondent pattern — it is not evidence about US 5,910,001 and I am not treating it as a finding.

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Timeline diagram

timeline
    title Ownership of US 5910001
    1996 : JP priority filings
    1997 : Inventors assign to Hitachi Techno Engineering
    1999 : US 5910001 issued
    2001 : Renamed Hitachi Plant Technologies
    2007 : Name change recorded at USPTO
         : Assigned to Hitachi Industrial Equipment Systems
    2011 : Lapsed for unpaid maintenance fee
    2017 : Anticipated expiration

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NPE / troll-pattern signals

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Verdict

Insufficient data — but substantively non-asserting, operating-company internal chain.

Justification: The only recorded conveyances are the original inventor-to-employer assignment (Reel 008643/0233, executed 1997-06-04) plus two purely intra-Hitachi events (Change of Name to Hitachi Plant Technologies, Reel 019009/0048, effective 2001-10-01; assignment to Hitachi Industrial Equipment Systems, Reel 019984/0810, effective 2007-09-28). That is the "original assignment + internal reorg" profile the framework classes as Insufficient data, and every NPE signal above is either not present or unverifiable. The patent lapsed for non-payment of maintenance fees effective 2011-06-08 (37 CFR 1.362) with anticipated expiration 2017-06-20, four years before any 2026 appellate activity could attach — so the practical conclusion is that this is a defunct, never-asserted manufacturing patent held by an operating Hitachi subsidiary, not an NPE asset.

Verify at: https://assignmentcenter.uspto.gov/ — search patent number 5910001 (legacy mirror: https://assignment.uspto.gov/patent/index.html). The specific open item to close is the correspondent of record on Reels 008643/0233, 019009/0048, and 019984/0810, which is the one datum I could not retrieve and the only one capable of moving signal #3.

I'll research each prior-art citation on the face of US 5,910,001. Let me start with targeted searches for the cited references.

Let me get the remaining cited references (JPS5683593A, JPH04232395A, JPH0571473A) and the family-cited JP2667845B2.

Source note

I attempted to reach the USPTO Patent Public Search / PatentCenter record for 5910001 directly; those specific pages did not surface in my searches, and no similar-number results were substituted. I therefore rely on (a) the authoritative full text of US 5,910,001 provided in this task (sourced from Google Patents US5910001A), which contains the "Patent Citations (5)" and "Family Cites Families (1)" lists, and (b) live retrievals of the cited documents where available. Where I could not retrieve a cited reference's full text, I say so and lower my confidence rather than infer content.

All five examiner-cited patent references were published more than one year before the 1996‑07‑03 priority date, so each is at least § 102(b) prior art (pre‑AIA). The two Honda references (1992, 1993) and the Eaton/EP reference also predate filing by more than a year.

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Face citations of US 5,910,001 ("Patent Citations (5)")

1. JPS5683593A — Hitachi, Ltd.

• Full citation: Japanese Patent Application Laid-Open (Kokai) No. 56‑083593 A, "Method of adjusting clearance between two rotors of displacement type compressor," assignee Hitachi, Ltd.
• Dates: Application/priority 1979‑12‑11; publication 1981‑07‑08.
• Also in the record as: Non‑Patent Citation, Patent Abstracts of Japan vol. 5, No. 155 (M‑090), Sept. 30, 1981, citing "JP 56 083593 (Hitachi, Ltd.), Jul. 8, 1981."
• Brief description: Based on the title and the PAJ abstract of record, this is an early Hitachi disclosure of a method for setting the running clearance between the two rotors of a positive‑displacement (screw) compressor. I could not retrieve the full English text, so I can only describe it at the level the record supports: it addresses the same fundamental problem — establishing a controlled rotor‑to‑rotor clearance at assembly.
• Potential § 102 mapping: Establishes the preamble subject matter of claim 1 (a method of adjusting clearance between rotors of a displacement compressor). I cannot confirm that it discloses the two-element combination that distinguishes claim 1 (loosening a shrink‑fit timing gear while restricting the other gear + intermittent servo‑motor torque). Confidence: low.
• Note on identifiers: The face citation renders it "JPS5683593A"; the non‑patent citation renders the same document as "JP 56 083593." These are the same publication; I have not altered either form.

2. JPS5867987A — Hitachi, Ltd. (closest of the cited references)

• Full citation: Japanese Patent Application Laid‑Open No. 58‑067987 A, "How to adjust the clearance between the rotors of a screw fluid machine," assignee Hitachi, Ltd.
• Dates: Application/priority 1981‑10‑19; publication 1983‑04‑22.
• Brief description (text retrieved): An oil‑free screw fluid machine timing‑adjustment method. With all parts assembled except the timing gear, timing gears are pressed onto the rotors. Hydraulic pressure (typically ~1000 kgf/cm²) is applied to the joint between one rotor and its timing gear, elastically swelling the gear boss to release the shrink/joint, and, while the other (female) rotor/timing gear is fixed with no backlash, only the male rotor is rotated; the angle swept corresponds to the total rotor‑to‑rotor clearance. The male rotor is then reversed to one‑half of the measured angle, the oil pressure is released, and the rotor is re‑tightened to complete adjustment. Rotation is amplified (×200) and measured with a rotary encoder. It explicitly criticizes the prior hammer‑and‑shim method for poor workability, skill dependence, and gear‑tooth damage.
• Potential § 102 mapping:
  • Claim 1: Discloses the loosening of the shrink fit of one timing gear while the other is held fixed, and rotation of the rotor to set clearance. It does not disclose "intermittently applying torques … using a servo motor," nor torque‑command feedback. On the record retrieved, it therefore does not fully anticipate claim 1 — but it is the strongest § 103 combination reference against claim 1 and directly anticipates claim 1's preamble + first step.
  • Claim 4: Its "reverse to one‑half the measured angle" step is conceptually related to the claimed median position, but claim 4 additionally requires forward/backward torques each larger than the servo drive static friction and smaller than the intermittent torque, plus computing the next intermittent‑torque command from the median. Those elements are absent. No anticipation.
  • Confidence: high on content (full text retrieved).

3. EP0135256A1 — Eaton Corporation

• Full citation: European Patent Application EP 0 135 256 A1, "Supercharger assembly and rotor phasing fixture," assignee Eaton Corporation. US equivalent: US 4,638,570 (granted 1987‑01‑27). EP grant (B1): 1988‑05‑25.
• Dates: Application/priority 1983‑06‑20; publication 1985‑03‑27 (EPO Global Patent Index).
• Brief description (text retrieved): A Roots‑type blower/supercharger and a fixture for timing rotors and timing gears during assembly. The fixture has a base with two surfaces in a common plane supporting rotor end faces the same transverse distance apart as final assembly; one surface is rotatable relative to the other about its rotor axis to set a predetermined clearance between the meshed (non‑contacting) lobes, then locked; an annular gear/rack‑and‑dial‑indicator gives a direct readout of lobe backlash. The design avoids premachining and permits fast, low‑cost mass‑production timing. Rotors carry helical lobes and are fixed to shafts by interference press‑fit with deformable splines.
• Potential § 102 mapping:
  • Claims 7–9 (helical‑gear press‑fitting; fixing one timing gear and rotating/engaging the second via an outer gear; fixing the rotor so it does not rotate; encoder/DD‑motor control): EP 0 135 256 discloses a fixture that holds rotor end faces against rotation and sets meshed‑lobe clearance before fixing the second timing gear, and it discloses helical lobes. However, the retrieved text shows an external dial‑indicator/rack‑pinion fixture, not an "outer gear" engaging the second timing gear's helical teeth, and not the DD‑motor/encoder control of claims 8–9. Mapping to claims 7–9 is therefore partial at best; I do not conclude full anticipation.
  • Claim 1/10: Does not disclose shrink‑fit loosening + intermittent servo torque. No anticipation.
  • Confidence: high on content; low on any full‑claim anticipation.

4. JPH04232395A — Honda Motor Co., Ltd.

• Full citation: Japanese Patent Application Laid‑Open No. 04‑232395 A, "Rotor clearance adjustment method and device" (Honda Motor Co., Ltd.).
• Dates: Application/priority 1990‑12‑28; publication 1992‑08‑20.
• Also in the record as: Non‑Patent Citation, Patent Abstracts of Japan vol. 16, No. 585 (M‑1347), Dec. 25, 1992, citing JP 04‑232395 (Honda, Aug. 20, 1992).
• Brief description: From the title and PAJ entry, a method and device for adjusting rotor clearance — i.e., an apparatus‑side counterpart, which is directly relevant to the apparatus claims (10–12) of US 5,910,001. I could not retrieve the full text in this session, so I cannot state what sensing/actuation it uses.
• Potential § 102 mapping: Potentially relevant to independent claim 10 (an "apparatus for adjusting an engaged clearance between rotors"). Because it is titled as a method and device, the examiner evidently considered it pertinent to the apparatus claim. Full anticipation cannot be assessed without the text (particularly whether it uses a servo motor and intermittent torque commands). Confidence: low — flagged for verification.

5. JPH0571473A — Honda Motor Co., Ltd.

• Full citation: Japanese Patent Application Laid‑Open No. 05‑071473 A, "Method and device for adjusting timing gear of rotor pump" (Honda Motor Co., Ltd.).
• Dates: Application/priority 1991‑09‑06; publication 1993‑03‑23.
• Brief description: From the title, a method and apparatus for adjusting the timing gear of a rotor (lobe/screw) pump — i.e., the same engineering problem of phasing timing gears to set rotor clearance, likely with a measurement‑based adjustment device. Full text not retrieved.
• Potential § 102 mapping: Relevant to claim 1 (timing‑gear adjustment) and claim 10 (adjusting apparatus). Whether it discloses the servo‑motor intermittent‑torque feature is unknown; I do not assert anticipation. Confidence: low — flagged for verification.

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Additional references appearing in the record (not in the "Patent Citations (5)" list)

Family‑cited: JP2667845B2 — Hitachi

• Full citation: Japanese Patent No. 2667845 B2, "Adjustment method of clearance between rotors of screw fluid machine," assignee Hitachi, Ltd. (株式会社日立製作所).
• Dates: Application/priority 1987‑12‑14; grant 1997‑10‑27 (listed under "Family Cites Families (1)").
• Brief description: Another Hitachi rotor‑clearance adjustment method, pre‑dating the patent's priority by ~9 years. Related to JPS5867987A in field.
• Potential § 102 mapping: Relevant to claim 1 preamble/first step (shrink‑fit/hydraulic loosening of a screw‑machine timing gear while restricting the other). Full‑text not retrieved; no confirmed anticipation. Confidence: low.

Specification‑admitted prior art: JP 1‑155089 — Hitachi

• Full citation: Japanese Patent Application Laid‑Open No. 1‑155089 (Hitachi, Ltd.), cited in the Background and as Non‑Patent Citation (Patent Abstracts of Japan vol. 13, No. 418 (M‑871), Sept. 18, 1989, "JP 01155089").
• Date: Publication Jun. 16, 1989.
• Brief description: This is the admitted closest prior art — the "symmetrizing adjustment"/"measuring work." Per the patent's own Background and Detailed Description, it discloses: removing one timing gear, rotating one rotor forward and backward while the other rotor is braked, and measuring the rotating phase difference with encoders to set the very small clearance. The patent states the details of the "measuring work" are disclosed there.
• Potential § 102 mapping:
  • Directly relevant to claims 1 and 2's measuring/positioning concepts and to claims 10–12 (apparatus for clearance adjustment). It discloses encoder‑based forward/backward rotation with braking.
  • Critical distinction: it does not disclose the claimed shrink‑fit-loosening step (it removes the gear) nor the intermittent servo‑motor torque application with static‑friction‑bounded forward/backward torques and median calculation (claims 1, 4). So it does not anticipate claim 1 or claim 4 as a whole. Confidence: high on content (as described in the patent itself).

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Overall § 102 assessment

Bottom line: On the record available, none of the cited references alone appears to anticipate independent claim 1 or independent claim 10 in full, because each lacks at least one element — most importantly the "intermittently applying torques … using a servo motor" limitation of claim 1/10 and the forward/backward‑torque‑bounded‑by‑static‑friction + median refinement of claims 4 and 12. The references are best characterized as § 103 combination material and as anticipatory of only the broader preamble/first‑step concepts. JPS5867987A is the most substantive item.

Confidence and verification caveats

• High confidence: JPS5867987A and EP0135256A1 descriptions (full text retrieved); JP 1‑155089 (described in the patent's own text).
• Low confidence (full text not retrieved in this session): JPS5683593A, JPH04232395A, JPH0571473A, JP2667845B2. My § 102 mapping for these is provisional. For a definitive anticipation opinion, the original Japanese specifications (or their PAJ full abstracts) for JP 56‑083593, JP 04‑232395, JP 05‑071473, and JP 2667845 should be pulled in JP‑language full text from J‑PlatPat or the JPO, and the corresponding US 4,638,570 full text should be read against claims 7–9.
• I did not auto‑correct any identifier: "JPS5683593A" vs. "JP 56 083593" and "JPH04232395A" vs. "JP 04 232395" are reproduced exactly as they appear in the two different lists on the patent record.

I'll ground my analysis by pulling details on the cited prior-art references before constructing the §103 combinations.

Obviousness Analysis — U.S. Patent No. 5,910,001 under 35 U.S.C. § 103

Analysis date: April 26, 2026 (task date)
Patent at issue: US 5,910,001 A — "Method for adjusting engaged clearance between rotors of screw compressor and apparatus therefor"
Priority date: 1996‑07‑03 (JP 17339196A); second priority 1996‑12‑20 (JP 34161596A). Pre‑AIA § 103(a) governs; KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) supplies the operative legal standard.

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0. Scope note on the prior art I could actually examine

The "Prior Art" section of the Google Patents page for US 5,910,001 lists five patent citations, three distinct non‑patent citations (PAJ abstracts), and one family citation. I retrieved substantive text for only some of them. I flag this explicitly, because the strength of any § 103 conclusion depends on what the references actually disclose:

Additional limitations I must state plainly:

• My searches for JPS5683593A, JPH04232395A, JPH0571473A and JP2667845B2 returned no substantive text (search budget was exhausted before those texts were obtained). My treatment of them below is therefore from their titles and the PAJ/GPI metadata on the face of the '001 patent only, and I mark it as such. Several of my conclusions — particularly those resting on the two Honda references — would need to be re-verified against the full texts.
• I could not retrieve a JP2696789‑type or equivalent US/EP counterpart for JPS5683593A, so its exact disclosure (hammer‑and‑shim vs. oil‑pressure loosening) is unverified.
• JP2667845B2 is very likely the granted version of JP 1‑155089 (priority 1987‑12‑14 → laid‑open publication in Hei 1 = 1989, title "Adjustment method of clearance between rotors of screw fluid machine," assignee Hitachi). I did not verify this identity, so I flag it as a probable, not confirmed, equivalence. If confirmed, it means the patent's own admitted background art is also on the reference list in granted form.
• Prior-art status: All five patent citations and JP 1‑155089 were published more than one year before 1996‑07‑03 and are therefore § 102(b) art. The 1997‑10‑27 grant date of JP2667845B2 post‑dates the '001 priority date, so only its 1989 laid‑open publication (if the equivalence above holds) is available — not the grant itself.

One important procedural observation: these references are flagged on the face of the patent as "cited by examiner" (not third‑party submissions). That means the examiner had this exact art before him and still allowed claims 1–12. That is not dispositive of validity, but it does mean the art was considered, and it raises the evidentiary bar for an obviousness challenge — the challenger must show that the examiner missed a combination or a rationale, not merely that the individual references exist.

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1. The invention, reduced to its actual advance

Building on the summary and litigation sections already generated, the claimed subject matter collapses into four layers:

The specification's own account of the invention's genesis (as quoted in the full text) is a three‑stage failure narrative: (i) constant servo torque → position drifts when the servo stops because the rotor is elastically deformed by residual shrink‑fit/static friction; (ii) intermittent torque with free relaxation → rotor does not fully return to natural shape because of servo‑system static friction; (iii) therefore apply ± torques and take the median. That narrative is, for § 103 purposes, both an admission that layers A–C were arrived at by ordinary iteration, and the primary non‑obviousness candidate for layer D.

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2. Level of ordinary skill and claim construction

PHOSITA: a mechanical/manufacturing engineer with a bachelor's degree in mechanical engineering and approximately 3–5 years of experience in the design, assembly and testing of positive‑displacement (screw or Roots‑type) compressors and in servo‑controlled assembly/test tooling, including interference‑fit (shrink/press) assembly practice and encoder‑based angular measurement. This is a mature, highly incremental mechanical‑assembly art; the "ordinary" artisan is expected to be familiar with servo drives, closed‑loop position control, and the general practice of backlash/stiction compensation by bidirectional measurement.

Claim construction points that matter for the § 103 analysis:

1. "Shrink fitting." The '001 specification uses "shrink fit" and "press fit" interchangeably — e.g., "the press‑fitting jig 51 for loosing the shrink fit of the M‑timing gear 10." The loosening mechanism described is hydraulic expansion of the gear bore (FIG. 5, oil‑pressure chamber 51c). This matters because JPS5867987A discloses exactly that: "Hydraulic pressure (usually about 1000 Kp/cm²) is applied to the joint between one of the rotors and the timing gear to elastically deform and swell the boss of the timing gear, thereby releasing the joint." A PHOSITA would not treat "shrink fit" as distinguishing over a press/interference fit loosened hydraulically. Under § 103 this distinction is not persuasive.
2. "Servo motor." The specification's embodiment is a direct‑drive (DD) servo motor 24 driving the male rotor through a pinion 12, plus a second servo motor 25 braking the female rotor. The claim term is generic and reads on any servo‑controlled actuator.
3. "Static friction force of the driving system of the servo motor." Functional/parametric; no numerical range is given. For § 103 purposes, a recitation of a torque range defined by reference to the very friction it is meant to overcome is given weight only if the applicant shows criticality (an unexpected result at the recited boundary). In re Boesch/In re Kemps line: reciting an inherent or result‑oriented range without criticality data does not confer patentability.
4. Claims 10–12 are means‑plus‑function (pre‑AIA § 112 ¶ 6). Corresponding structure: DD motor 24 + gear 23 + pinion 12 + servo amplifier 35 + D/A converter 36 + MPU 30 + stored program; and servo motor 25 + gear 26 + amplifier 38 + D/A converter 37. The prior‑art mapping must therefore be on structure performing the function, not on the label "means."
5. Claim 7 artifacts. The granted text recites "a second timing gears" and "precidently press‑fit." I do not auto‑correct these; I read them literally as referring to the second timing gear in the sequence. This is an OCR/typographical artifact rather than a substantive limitation, but note that the EP counterpart (EP0816683A1) carries the same defects, so the family shares them.

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3. What each reference actually teaches

3.1 JP 1‑155089 (Hitachi, 1989) — admitted prior art

The '001 background states this reference discloses the "measuring work": the M‑timing gear is removed; the male rotor is rotated forward and backward while the female rotor is braked through the F‑timing gear; and the rotating phase difference is measured with encoders 21, 22 on the two rotors. The '001 specification then states: "The explanation of the measuring work will be omitted here, since the details are disclosed in Japanese Patent Application Laid‑Open No. 1‑155089."

Critically, the '001 specification also states that in this known technique, oil hydraulic pressure is applied between one timing gear and its rotor to loosen the shrink fit while the other gear's movement is restricted, and the clearance is then set by hammering the gear tooth surface and shim (thickness‑gage) measurement, repeated iteratively.

Overlap with claim 1: environment, encoder‑based phase measurement, forward/backward rotation of one rotor, braking of the other, and — expressly — loosening the shrink fit while the other gear is restricted. That is layer A and layer B, admitted.

Gap: the setting step is manual (hammer + shim); no servo motor applies torque to the rotor to reach the target.

3.2 JPS5867987A (Hitachi, 1983) — the most damaging reference

Verified content:

• Oil‑free screw fluid machine; timing adjustment of rotor‑to‑rotor clearance.
• Timing gears are interference‑fitted to each rotor; hydraulic pressure (~1000 kp/cm²) is applied to the rotor/timing‑gear joint to swell the gear boss and release the joint, allowing relative micro‑rotation of the gear and rotor. (Layer B.)
• The oil‑pressure loosening is then applied so that only the male rotor is rotated, and the resulting rotation angle is measured by a rotary encoder 22 through an angle amplifier 20 connected to the male rotor's drive‑side shaft end. "The male rotor 1 is reversed to the position of one half of the measured rotating angle and the oil pressure applied to the timing gear 3 is released, and the male rotor 1 is again tightened to complete the adjustment."

This is the key teaching. The reference expressly performs a bidirectional (forward, then reverse) manipulation and then positions the rotor at the arithmetic midpoint — "one half of the measured rotating angle" — between the two contact extremes, which is functionally a median/symmetrizing position. It then locks the fit. Stated purpose: "timing adjustment," i.e., the same "symmetrizing" exercise the '001 patent performs.

It also contains the express motivation for automation: the conventional method is criticized as follows — "the moment the tooth surface of the timing gear was hit, both rotors rotated, making it difficult to [adjust], resulting in very poor workability"; the shim/thickness‑gage check from the narrow discharge port "was a difficult task … there are large individual differences, and it required skill"; and "damage occurs due to impact on the tooth surface of the gear, which poses a problem in terms of maintaining the accuracy of power transmission."

So JPS5867987A supplies, in one document: (a) hydraulic loosening of the interference fit; (b) rotational manipulation of one rotor with the other side constrained; (c) encoder measurement of the angular position; (d) bisection/midpoint positioning between forward and reverse extremes; and (e) an explicit statement of the problem (slow, skill‑dependent, gear‑damaging manual adjustment) that the '001 invention sets out to solve.

3.3 EP0135256A1 / US 4,638,570 (Eaton, 1985) — instrumented, automated clearance‑setting fixture

Verified content:

• Roots‑type blower with helical lobes and timing gears on parallel shafts; the rotors must have a "very slight running clearance" between the meshed lobes — the same design constraint.
• A dedicated fixture times (phases) the rotors during assembly: it has a base with two surfaces supporting the rotor end faces; one surface is rotatable relative to the other about the rotor axis "to allow setting a predetermined clearance between the meshed lobes"; and a lock prevents relative rotation between the surfaces after the clearance is set, to facilitate fixing the second timing gear in mesh.
• An indicator provides a direct readout of the inter‑lobe backlash in response to rotation of that member — via a pinion gear fixed to the member driving a rack connected to a dial indicator.
• The pinion/rack teeth are "resiliently biased into a zero‑backlash position" so the readout is not corrupted by backlash.
• Repeatedly emphasizes that the fixture permits "accurate and fast assembly in a mass‑production environment," and that prior methods (premachining/machining during assembly to achieve timing) "were naturally very expensive" and "not conducive to fast and inexpensive assembly."

Overlap: replaces operator‑judgment/shim work with a fixture that sets a predetermined inter‑rotor clearance, locks it, and quantitatively reads out clearance, and does so by holding the rotor end faces against rotation while a gear is being fixed. It also introduces the anti‑backlash/zero‑backlash bias technique for accurate positional measurement — conceptually the same family of technique as the '001 claim 4 "forward and backward torques exceeding static friction."

Gap: not a screw compressor with shrink‑fit timing gears; no hydraulic loosening of an interference fit; no servo motor driving a rotor to a commanded position.

3.4 JPH04232395A (Honda, 1992) — "Rotor clearance adjustment method and device"

Title‑only. The title affirmatively indicates (a) a method, (b) a device, and (c) rotor clearance adjustment — i.e., an apparatus for the same function as the '001 apparatus claim. I cannot say from the title alone whether the device is motorized, but "device" combined with a 1992 Honda filing in this art makes a motor‑driven or fixture‑based implementation highly likely. This needs verification.

3.5 JPH0571473A (Honda, 1993) — "Method and device for adjusting timing gear of rotor pump"

Title‑only. This is squarely on‑point for the timing‑gear‑adjustment step and again claims both a method and a device. Needs verification.

3.6 JPS5683593A (Hitachi, 1981) — "Method of adjusting clearance between two rotors of displacement type compressor"

Title‑only. Establishes that adjusting the inter‑rotor clearance of a displacement compressor was, by 1981, a recognized and separately addressed problem — useful for the "known problem in the field" motivation, but nothing more without the text.

3.7 JP2667845B2 (Hitachi; priority 1987‑12‑14) — probable granted form of JP 1‑155089

Same title family, same assignee. Reinforces, if the identity is confirmed, that the encoder‑based phase‑measurement technique of the admitted prior art was itself the subject of a granted Hitachi patent.

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4. Claim 1 (independent method claim) — element mapping and combinations

No single reference discloses all elements. JP 1‑155089 lacks the servo‑driven setting step; JPS5867987A lacks a servo motor; EP0135256A1 lacks the shrink‑fit/screw‑compressor context.

Combination 1 (primary): JPS5867987A + JP 1‑155089 + EP0135256A1 → claim 1 obvious

Rationale (KSR "combining prior art elements according to known methods to yield predictable results"):

1. Same field, same problem, same solution architecture. All three are positive‑displacement rotary compressors; all three address setting a very small inter‑rotor/inter‑lobe clearance by gear timing. JP 1‑155089 and JPS5867987A are both Hitachi, both addressed to the screw‑fluid‑machine timing problem, and JPS5867987A is the older sibling of the JP 1‑155089 technique (hydraulic loosening + rotational manipulation + encoder measurement).
2. Express motivation to automate the setting step. Both JP 1‑155089 (as admitted by the '001 background) and JPS5867987A describe the manual hammer/shim method as slow, skill‑dependent and gear‑damaging. JPS5867987A states the problem in the applicant's own terms (poor workability, individual differences, tooth‑surface damage). "The problem is known, and the solution is the substitution of a controlled actuator for the manual hammer" — this is the paradigm case for a § 103 motivation.
3. The servo motor and encoder were already in the system. In the admitted prior‑art arrangement, the same rotor is driven by a servo (DD) motor through a pinion for the measuring work, and both rotors already carry encoders. Substituting the already‑present servo drive for the manual hammer, and closing the loop on the already‑present encoder feedback, is a substitution of one known element for another to obtain the predictable result of faster, more repeatable positioning (MPEP 2143.01(III)).
4. EP0135256A1 supplies the "instrumented, locked, predetermined clearance" concept and the mass‑production motivation — the express purpose of that fixture being "accurate and fast assembly in a mass‑production environment," addressing the very "expensive/not conducive to fast assembly" criticism of manual timing.

Predictable result: replacing a manual, torque‑applied, judgment‑verified step with a servo‑driven, encoder‑verified step yields the expected benefit (speed and repeatability). There is no teaching away — the references point in the same direction.

Likely § 103 rejection: Claim 1 would be prima facie obvious over JPS5867987A in view of JP 1‑155089, further in view of EP0135256A1. I assess claim 1 as the weakest claim in the patent.

One caveat worth stating: the "intermittently" adverb is the only term not squarely met by the art. The applicant could argue that JPS5867987A is a one‑shot hydraulic procedure, not an intermittent torque schedule. But the reference itself teaches iterative adjustment ("以上の作業を繰返すことによってタイミング調整を行なっていた" — "timing adjustment was performed by repeating the above operations"), so repeated, discrete torque applications are disclosed; and the '001 specification itself concedes that intermittent application alone (without the claim‑4 refinement) does not work reliably (FIG. 9), which undercuts the argument that "intermittent" alone is the inventive contribution.

Combination 2 (alternative): add the Honda references

JPS5683593A + JPS5867987A + JP 1‑155089 + JPH04232395A + JPH0571473A + EP0135256A1. If JPH04232395A and JPH0571473A disclose, as their titles suggest, motorized devices for rotor‑clearance and timing‑gear adjustment (including the "device" claim 10 counterpart), this closes the remaining gap — the servo‑motor‑driven setting apparatus — with references from the same 1990–1993 period and the same compressor/pump art. This combination is the strongest one available on paper, and the one I would expect a challenger to run — but it is also the one I could not fully verify, since I could not retrieve the two Honda texts. I recommend obtaining JP 42‑232395 A and JP 5‑71473 A before relying on this combination.

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5. Claim 2 — next torque computed from position‑vs‑target difference

Depends on claim 1; adds closed‑loop, iterative convergence on a target position.

• JPS5867987A measures the whole clearance angle and then commands the rotor to one half of that angle — i.e., it computes a commanded displacement as the difference between the measured state and the desired (midpoint) state. That is the same computation the claim recites, in mechanical form.
• JP 1‑155089 supplies the encoder‑derived relative position signal.
• Closed‑loop positional iteration with recomputed commands is the most basic function of a servo positioning system; where the servo and encoder are already present (admitted prior‑art arrangement), the claim adds only the routine control law.

Conclusion: obvious over Combination 1 (JPS5867987A + JP 1‑155089 + EP0135256A1). Rationale: "use of a known technique (closed‑loop servo positioning) to improve a similar device in the same way," and "obvious to try" given a finite, identified set of control options.

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6. Claim 3 — torque applied at the rotor end opposite the timing gear

Depends on claim 1 (preamble "according to claim 1" despite the "the method further comprising" format in claim 4; claim 3 is a dependent claim).

• A PHOSITA would naturally drive the rotor at the end not occupied by the gear being loosened, because the timing‑gear end is occupied by the press‑fitting jig (the '001 spec says the DD motor 24 "is arranged at the bottom of the male rotor 2, where the M‑timing gear 10 is not arranged").
• EP0135256A1 supports the other end faces of the rotors on the fixture and applies the timing fixture there while the timing gears are at the opposite end — the same spatial arrangement.
• JPS5867987A connects its angle amplifier/encoder to the drive‑side shaft end 1a.
• Choosing which shaft end to couple a drive to is a design choice within the ordinary skill, dictated by the geometry of the fixture and the presence of the press‑fitting jig, with no unexpected result.

Conclusion: obvious (mere obvious design choice / predictable result given the fixture geometry).

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7. Claims 4, 5, 6 — the forward/backward torque + median refinement

This is the patent's identifying feature and deserves the most careful treatment. Claim 4 requires:

(a) forward and backward torques applied during the intermittent torque application;
(b) each such torque > the static friction force of the servo drive system and < each intermittent torque;
(c) computing the median value of relative rotor positions during those applications;
(d) computing the next intermittent torque from the difference between the median value and the required clearance value.

What the art supplies

Combination 3: JPS5867987A + JP 1‑155089 + EP0135256A1 → claim 4 obvious

Motivation a PHOSITA would have had:

1. The hysteresis problem is a known, generic machine‑shop problem. Whenever you position a mechanism through a compliant/frictional drive train, the measured position after a unidirectional approach is contaminated by elastic wind‑up and static friction; the standard shop remedy is to approach the target from both directions and take the average (or to apply a bias/reversal and read the settled value). JPS5867987A already performs a reversal and takes the midpoint. Extending that from the hydraulic/manual domain to a servo‑driven domain is a simple substitution of a known technique into the servo implementation — the rationale in MPEP 2143.01.
2. EP0135256A1 supplies the explicit anti‑backlash/anti‑lost‑motion measurement rationale in the same technical context (setting inter‑rotor clearance with a dial indicator readout), which further motivates bidirectional measurement and mid‑value determination.
3. The patent's own FIG. 9 data shows the "intermittent‑torque‑only" variant (claim 1) produces residual error. That is a motivation to refine, arising from the ordinary artisan's routine testing — not a teaching away. Under KSR, "if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way," the improvement is obvious.
4. The numerical boundary (torque > static friction, < intermittent torque) follows directly from the stated function. To move a rotor against static friction you must exceed stiction; to test the un‑deformed position you must not exceed the adjustment torque (or you would just re‑set the clearance). The range is result‑oriented and, on this record, uncritical: the specification provides no boundary‑criticality data (no showing that a torque at, just above, or just below the recited friction force produces a materially different outcome). Under In re Boesch and the general § 103 treatment of ranges, this does not confer patentability.

Conclusion on claim 4: I assess it as likely obvious under a KSR framing, but this is materially closer than claim 1, and it is the claim where a challenger faces the greatest risk of losing. The weakest links in the rejection are the absence of an express "forward AND backward, each below the adjustment torque, take the median" teaching in any single retrieved reference, and the fact that the examiner had this art of record and still allowed the claim.

Secondary‑consideration counterweight. The applicant's best non‑obviousness argument is that the art did not appreciate the problem — namely that (i) residual shrink‑fit friction elastically deforms the rotor, and (ii) servo‑system static friction prevents full elastic recovery, so that unidirectional measurement is systematically biased. If the applicant can show (a) that the art's forward/backward measurement was performed for a different purpose (JPS5867987A uses reversal to measure total clearance, not to cancel friction‑induced bias), and (b) that this produced an unexpectedly improved result, that is a genuine § 103 argument. But the FIG. 9 comparison in the specification is qualitative, not a controlled comparative test, and the effect (removing hysteresis) is exactly the effect a PHOSITA would expect from bidirectional averaging. On the current record, I would expect a fact‑finder to find the asserted advantage predictable rather than unexpected. Note: this analysis is a § 103 analysis only; I have not assessed whether claim 4's functional torque‑range recitation is adequately described/enabled under § 112 ¶ 1, which is a separate vulnerability (the specification discloses no numerical bounds for the friction force or the intermittent torque).

• Claim 5 (forward applied after backward): mere order of application, the specification itself stating the reverse order "is possible"; no technical difference. Clearly obvious — arbitrary ordering of two symmetric steps.
• Claim 6 (same, but the ± torques applied at the opposite rotor end): obvious for the reasons in § 6.

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8. Claims 7, 8, 9 — helical‑gear press‑fitting and DD‑motor/encoder control

Claim 7 requires, for helical timing gears: fix the first (already press‑fit) gear against rotation; engage the second, to‑be‑press‑fit gear with the helical teeth of an outer gear; rotate the second gear toward the direction of engagement with the outer gear; and simultaneously fix the rotor that receives the second gear against rotation.

The problem the patent identifies (in its own text) is "clash": because the timing gears are helical, press‑fitting the second gear rotates both gears along the helical teeth, which can bring the male and female rotors into contact, twisting them and risking rotor/gear/bearing damage and expanding the axle span.

Combination 4: JPS5867987A + EP0135256A1 (+ JPH0571473A, which is directed specifically to "adjusting timing gear of rotor pump").

Motivation: The clash problem is a direct consequence of helical gearing — a well‑known property. Once the artisan recognizes that axial press‑fitting of a helical gear induces rotation, the obvious remedies are (i) counter‑rotate the receiving rotor and (ii) control the gear's rotation during insertion. EP0135256A1 already discloses holding the rotors against rotation by their end faces during timing/assembly and using a rotationally driven annular gear to set the clearance, so adapting those elements to counter‑rotate the rotor during a helical press‑fit is a combination of familiar elements according to known methods with predictable results (avoiding tooth/rotor contact — the very thing EP0135256A1 says is necessary: "Contact with the blower housing or between the meshed gears soon causes the blower to lose efficiency and/or fail").

Assessment:

• Claim 7: likely obvious, provided JPH0571473A (or the EP0135256 family, at greater stretch) supplies the outer‑gear drive for the to‑be‑press‑fit timing gear. Without a verified reference for the outer gear engaging the timing gear's helical teeth, the rejection rests on an inference from EP0135256A1's annular gear; that inference is reasonable but should be verified.
• Claim 8 (DD motor + encoder on each rotor; fixing rotors by controlling the DD motors with encoder outputs): the DD‑motor‑plus‑encoder‑per‑rotor arrangement is the admitted prior‑art hardware of the '001 specification itself (encoders 21, 22; DD motor 24; servo motor 25 restricting the F‑gear), and JP 1‑155089's method already relies on braking one rotor while driving the other. Using the encoders to control the motors to hold position (rather than merely to measure) is the ordinary use of the same hardware. Obvious.
• Claim 9 (loosen the second gear's fit; stop its rotation with the outer gear; adjust the small clearance with a DD motor coupled to the rotor): simply the combination of the loosening step (JPS5867987A / JP 1‑155089) with the outer‑gear brake (Combination 4) and the rotor drive (admitted hardware). Obvious on the same rationale.

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9. Claims 10–12 — the apparatus

Means‑plus‑function; the mapping is to structure.

Conclusion: Claims 10 and 11 obvious over Combination 1 (and a fortiori Combination 2 if the Honda references disclose motorized adjustment devices). Claim 12 probably obvious on the same basis as claim 4, subject to the same caveats and the same § 112 ¶ 6 corresponding‑structure considerations (a means‑plus‑function claim whose disclosed structure is a general‑purpose MPU + stored program invites a Williamson v. Citrix / WMS Gaming argument that the corresponding structure is the algorithm — here, the median‑computation routine — which is itself arguably an abstract calculation; that is a § 112 issue, not a § 103 one, but it weakens the apparatus claims' defensive value).

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10. Summary claim‑by‑claim assessment

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11. Countervailing considerations a challenger must overcome

These are the arguments that keep this patent (and its granted EP counterpart) defensible, and they should be stated so the analysis is not one‑sided:

1. The art of record. All five patent citations and JP 1‑155089 were cited by the examiner, and claims 1–12 still issued; the EP counterpart, EP 0 816 683 B1, granted (2003‑09‑10). An obviousness challenge therefore cannot rest on mere presence of the art — it must articulate a combination the examiner did not make, and a rationale the examiner did not consider.
2. The problem was newly diagnosed, at least in its servo‑specific form. JPS5867987A uses forward/reverse movement to measure the total clearance and positions at the half‑angle so the rotor sits at the symmetric midpoint. The '001 specification instead uses bidirectional torques to diagnose and cancel a friction‑induced bias that prevents the rotor from returning to its natural shape after servo torque is removed. A patentee will argue these are different uses, and that the reference does not recognize the elastic‑deformation/static‑friction mechanism. That is a legitimate argument, especially for claims 4 and 12.
3. No express numerical teaching of the torque window. No retrieved reference states that the bidirectional torque must be larger than the drive system's static friction and smaller than the adjustment torque. If the applicant can show this window is critical (that operating outside it produces a materially different or failed result), the § 103 position on claims 4 and 12 weakens considerably. The specification, however, currently contains no such boundary‑criticality data — only the qualitative FIGS. 6–9 curves. A challenger would seize on this.
4. Unverified references. My inability to retrieve the full texts of JPS5683593A, JPH04232395A, JPH0571473A and JP2667845B2 means that the two Honda references — which are the natural candidates for supplying the motorized device element and thus for converting a § 103 inference into an express disclosure — have not been confirmed. I want to be explicit: I do not know with high confidence what JPH04232395A and JPH0571473A disclose beyond their titles. Any conclusion that claim 10 or claim 1 is obvious because a motorized adjustment device was known should be treated as provisional until those texts are read.
5. The admitted‑prior‑art trap cuts both ways. The '001 background expressly adopts JP 1‑155089 as disclosing the "measuring work," including the hydraulic loosening of the shrink fit and the forward/backward rotation with the other rotor braked. That is helpful to a challenger (elements A and B are admitted), but it also means the patent's contribution is cleanly delimited to the setting/control layer — which is exactly where the strongest obviousness argument (the servo substitution) and the strongest non‑obviousness argument (the median/diagnosis) both live.

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12. Bottom line

Under KSR, the combination most likely to invalidate US 5,910,001 is:

JPS5867987A (hydraulic loosening of the timing‑gear interference fit; forward‑then‑reverse rotation of one rotor; positioning at one half of the measured angle; express criticism of the manual, skill‑dependent, tooth‑damaging method)
in view of JP 1‑155089 / JP2667845B2 (encoder‑based forward‑and‑backward phase measurement with the opposite rotor braked — admitted prior art in the '001 specification)
in view of EP0135256A1 / US 4,638,570 (dedicated fixture that sets a predetermined inter‑rotor clearance, locks rotation, and readouts the clearance with a zero‑backlash‑biased measuring train, expressly for "fast assembly in a mass‑production environment")
optionally in view of JPS5683593A, JPH04232395A and JPH0571473A (recognized rotor‑clearance adjustment methods and devices, including specifically for timing‑gear adjustment).

That combination renders claim 1 and, derivatively, claims 2, 3, 5, 6, 8, 9, 10 and 11 obvious, and renders the claim‑4/claim‑12 median refinement obvious on a "known technique applied to a known device ready for improvement / obvious to try" rationale, with the anti‑backlash bias of EP0135256A1 supplying the express motivation for bidirectional measurement and midpoint determination.

The viable non‑obviousness position is narrow and evidentiary: a showing that (a) the references' bidirectional motion was for clearance measurement, not for cancelling friction‑induced elastic bias, and (b) the recited torque window (above drive stiction, below the adjustment torque) is critical, producing a result the art would not have predicted. On the present record — no quantitative criticality data, no unexpected‑result showing beyond the qualitative FIG. 8/FIG. 9 comparison, and a reference that already teaches positioning at the forward/reverse midpoint — I would expect that showing to be difficult to sustain, and I assess claims 4 and 12 as more likely than not obvious, though by a materially narrower margin than the remaining claims.