US 10663252

I'll search for authoritative records on this patent number, including any litigation activity.

Let me check for litigation/docket activity and the record's ownership history more specifically.

US 10,663,252 B1 — Summary

Caveat on sources: I retrieved this record from Google Patents, the issued-patent PDF (patentimages), and Justia. I could not directly query USPTO Patent Center, the USPTO assignment database, or PACER/CAFC dockets, so the ownership and litigation statements below carry the uncertainty noted. I also note a literal-reading hazard: the string "10663252" appears in unrelated sources (e.g., the Westlaw citation "2015 WL 10663252"), which are not this patent; I excluded those.

Bibliographic data

Abstract

A recoil attenuator that mounts on the butt of a shoulder-fired firearm to absorb both primary and secondary recoil impulses with distinct spring rates and viscoelastic hysteresis. It has a mount plate attachable to the firearm butt, a shoulder plate spaced apart and parallel to it, and at least one damper between the plates. The damper is a viscoelastic copolymer elastomer with a hollow body elastomer construction, shape-engineered to exhibit time-dependent strain, so the damper shows distinct spring rates for the primary recoil impulse (bullet accelerating through the barrel) and the secondary recoil impulse (propellant gases exiting the barrel).

Independent claim 1 — plain language

The granted independent claim is meaningfully narrower than the abstract and the specification's "one aspect" summary. It requires, in combination:

1. A flat, elongated mount plate attachable to the firearm butt;
2. A flat, elongated shoulder plate spaced apart and parallel to the mount plate;
3. A pair of spaced-apart damper fasteners running through both plates;
4. A pair of spaced-apart dampers mounted on those fasteners, between the plates;
5. A center damper assembly with a center damper, positioned between the two outer dampers and between the plates;
6. Each of the three dampers being made of viscoelastic copolymer elastomer material with a hollow body elastomer construction, shape-engineered to exhibit time-dependent strain, such that all three dampers exhibit distinct spring rates in response to the primary recoil impulse and the secondary recoil impulse.

Note a drafting/prosecution point: the specification's narrative "one aspect" and the abstract describe simply "at least one damper," but the allowed claim 1 adds the two-fastener/two-damper arrangement plus a center damper — i.e., three damper bodies. The claimed scope therefore does not cover a single-damper attenuator.

Dependent claims

• Claim 2 — Details the center damper assembly: a center damper cavity in the shoulder plate, a first damper seat in that cavity and a second damper seat on the mount plate aligned with it; the center damper extends between the two seats.
• Claim 3 — Adds a center damper fastener extending through and between the mount and shoulder plates, with the center damper mounted on it.
• Claim 4 — Adds an attenuator pad on the mount plate made of an elastomeric material, with a concave pad portion (the shoulder-contacting face).

Notable specification content

• The damper is described as compressible more than 50% of its length/volume while retaining structural integrity; the background criticizes conventional urethane/TPE foam pads that "fail if compressed more than approximately 38%." The field-of-invention paragraph cites a minimum 40% compression during recoil.
• One embodiment states the viscoelastic copolymer elastomer has a ratio of plastic strain to elastic strain greater than 1.5:1, and oriented wall sections forming a bend (116) from axial pre-compression.
• The design is presented as shape-engineered — changing the damper's shape and its force-travel curve (FIGS. 7–9) without changing material composition — using a "damper design database" and "damper attribute algorithms." Preload is adjustable (FIG. 9) to avoid a "pulpous" feel that harms sighting.
• FIG. 10 compares the design's behavior to "TEMAX" recoil pad and hydraulic damper curves; the patent asserts elimination of coil springs and hydraulic fluid, fewer failure modes, and durability up to 10× rubber and 20× urethane.
• Alternative embodiments include an outer panel/casing encapsulating the plates and dampers (FIG. 6) and a center damper with buttons and grooves (FIGS. 11–12).
• The specification contains an apparent typo — "the present invention teaches an actuator 100" — where "attenuator" is meant. I reproduce it as written rather than correcting it.

Prior art / forward citations (from the record)

The front page lists 49 cited references, including US 4,198,037 (Miner Enterprises, polyester elastomer compression spring), US 6,305,115 (RA Brands, gel recoil pad), US 7,926,216 (Blackhawk, recoil suppression system for firearm stocks), US 8,286,382 (Vesligaj), and US 10,156,422 (Valin). Later publications citing it include US 12,259,207 and US 2024/0027152 (Robert Duane Hill), FR 3,121,981 and FR 3,140,940 (Silicone Innovation / Sylvain Creton), and US 2023/0173644 (Axxiom Manufacturing).

Litigation / CAFC 2026 docket check — no results found

Searches targeting Court of Appeals for the Federal Circuit 2026 dockets and infringement complaints naming this patent number returned no matching hits. I found no district court complaint, no CAFC appeal, and no PTAB proceeding (IPR/PGR) involving US 10,663,252. This is a negative search result, not affirmative proof of no litigation — I did not have direct PACER, CourtListener docket, or Docket Navigator access here, so a recently filed action might not appear in the sources I could reach. If litigation status matters, it should be confirmed against PACER/CourtListener and the USPTO Patent Center assignment record.

Uncertainty flags

• Assignee: Google Patents shows "Individual" as current assignee, with no recorded corporate transfer shown. I could not verify the USPTO assignment ( reel/frame ) record; the inventors may have assigned rights to a company (e.g., a TEMAX-related entity) that is not reflected in the sources retrieved.
• Litigation: none found; treat as unverified negative.
• Live status: "Active" with a 4th-year fee paid after the reminder (surcharge code M2554) — consistent with the Google Patents legal-events log, but I could not independently confirm the current fee status in Patent Center.

I'll search for litigation involving US Patent 10,663,252.

Initial generic searches returned irrelevant results. Let me search patent-specific litigation sources directly.

Let me check litigation-specific databases directly.

Bottom line

No litigation involving U.S. Patent No. 10,663,252 has been identified. I found no district court action, ITC investigation, CAFC appeal, or PTAB proceeding (IPR/PGR) in which US 10,663,252 is the asserted or challenged patent.

This is a negative finding, and I want to be precise about its strength and its limits.

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What the identifier actually is (confirmed against the authoritative text)

Per the full patent text you provided (source: https://patents.google.com/patent/US10663252/en):

Two structural facts bear directly on litigation likelihood: the patent is held by individuals, not a corporate or PAE/NPE entity, and it remains in force (maintenance fee paid in 2024). An individual owner who is paying maintenance fees could assert the patent, but paying maintenance fees is not evidence of assertion.

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What I searched and what came back

1. Google Patents family/legal data (the authoritative record you supplied). The "Family," "Cited By," and "Similar Documents" sections contain only patent literature — French and PCT publications (FR3121981A1, FR3140940A1, WO2023249579A1), U.S. applications, and similar firearm-damper patents. Critically, the page carries no "Family has litigation" flag and no litigation links. By contrast, patent pages that have been litigated carry an explicit metadata field, e.g. US 8,656,250 (Texas A&M) displays "Family has litigation" with a link to https://portal.unifiedpatents.com/litigation/Delaware%20District%20Court/case/1:18-cv-01966. US 10,663,252 shows nothing comparable. That is a meaningful negative signal, though not dispositive (Google's litigation feed is not exhaustive).

2. Unified Patents litigation portal (https://portal.unifiedpatents.com/litigation/caselist). No case list was returned for this patent number.

3. General docket/web searches for "10663252," "10,663,252," and inventor-name combinations ("Sprainis" + lawsuit/infringement). No infringement suit, no declaratory judgment action, no appeal.

4. PTAB. No inter partes review, post-grant review, or covered business method proceeding naming this patent appeared.

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A false positive worth flagging (per your literal-identifier rule)

Searching the bare digit string "10663252" produces a Westlaw-style citation that is unrelated to this patent: Cooper v. Tokyo Electric Power Co., 166 F. Supp. 3d 1103, 2015 WL 10663252 (S.D. Cal.) — surfaced via CourtListener. That is a case-report citation whose numeric tail happens to match the patent number; it has nothing to do with the Sprainis recoil attenuator. Likewise, other hits were unrelated patents with similar numbers (e.g., U.S. 10,621,228; 10,675,325; the "'052 patent" in Pantech v. OnePlus, which is U.S. 8,893,052 — an entirely different patent). I have excluded all of these and report them here only so you can see I did not silently conflate similar numbers.

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No-case result table

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Limits on this conclusion (please read before relying on it)

I want to be explicit rather than overstate confidence:

• I did not obtain a live query result from PACER directly, from CourtListener's RECAP docket search filtered on this patent, from Docket Navigator, or from Lex Machina. My conclusion rests on the authoritative patent record you provided plus web/portal searches that returned no matching case.
• Patent litigation can be sealed or non-public during early filing, and some district court complaints do not name the patent in a text-searchable way in the first days after filing. A newly filed 2026 case could therefore exist and not surface.
• Google Patents' litigation flagging and the Unified Patents portal are aggregations; coverage of small, individual-owner suits (which this would be) can lag.

Recommended definitive verification steps:

1. CourtListener RECAP docket search by patent number: https://www.courtlistener.com/?type=r&q=%2210663252%22
2. USPTO Patent Assignment Search and USPTO PatentCenter for the patent's file wrapper — any assignment away from the individual inventors would precede litigation.
3. Docket Navigator or Lex Machina patent-docket search on 10,663,252.
4. A direct CAFC docket check (no appeal located via search).

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Current status of the patent itself

Active and enforceable, in force through the 4th-year maintenance window (fee paid 2024-02-27, small entity, with a late-payment surcharge recorded). No reissue, reexamination, disclaimer, or adverse PTAB outcome is reflected in the record. If you need this for a freedom-to-operate or clearance opinion, the operative point is that the patent is live — the absence of litigation says nothing about whether your client's product would infringe claims 1–4, which I would address separately.

I'll verify the structured block's default with targeted searches before drafting.

Let me run a few more targeted checks on petitioner/patent-owner names and PTAB dockets.

Proceedings overview

Total AIA trial proceedings on US 10,663,252: 0. The structured "PTAB proceedings on file" block — the canonical USPTO Open Data Portal (ODP) list — returns no IPR, PGR, or CBM proceedings, so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials. The bottom-line defensive posture is the inverse of the usual IPR story: there is no PTAB record to exploit and no estoppel to hide behind — but also no Federal Circuit or Board precedent narrowing the claims. A defendant today faces a live, unamended, 4-claim patent (independent claim 1 plus dependent claims 2–4) that has never been tested at the Board.

Because there are no proceedings, the per-proceeding template below has no entries to populate. I've instead documented the verification trail and what the absence means.

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Verification trail (why I'm reporting zero)

• Canonical source — PTAB proceedings on file (USPTO ODP): empty. Per the prompt's default rule, "no PTAB activity on file."
• Google Patents record for US 10,663,252 (fetched in the authoritative full text): the "Cited By" table lists only patent publications (FR3121981A1, US20230173644A1, WO2023249579A1, US20240027152A1, FR3140940A1) and the family/legal-events tables list only prosecution and maintenance-fee events through the 4th-year fee payment on 2024-02-27. No IPR/PGR/CBM docket lines appear. patents.google.com/patent/US10663252/en
• Citation list (49 references) is drawn entirely from examiner/third-party patent citations (earliest US 247,451 (1881) through US 10,156,422 (2018)) — i.e., prosecution-art citations, not IPR exhibits.
• Web search for "Sprainis" + PTAB/IPR and for the patent number + PTAB returned no petition, institution decision, or FWD referencing this patent. Searches surfaced the Justia and Google Patents mirror pages only.
• False-positive warning: searches for "the '252 patent" in PTAB filings overwhelmingly hit US 11,012,252 (Amphenol/active Ethernet cable, E.D. Tex. + ITC litigation). That is a different patent with a different owner and technology. I found no connection between it and US 10,663,252.
• One anomaly worth flagging, not asserting: a search-result snippet showed the status line STCH — PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 adjacent to a citation of the '252 patent. On inspection that snippet belongs to the Google Patents page of a different patent (US 5,669,168, Perry) that merely cites the '252 patent. The authoritative record for US 10,663,252 shows Active status, an anticipated expiration of 2038-12-05, and payment of the 4th-year maintenance fee on 2024-02-27 (with a small-entity late-payment surcharge). Treat the "expired" line as noise, but re-verify the 7.5-year fee window before relying on enforceability.
• Limits of this check: ODP ingest can lag; Petitions filed but not yet docketed, and pre-institution filings, can be missed. I could not open PTAB E2E / PTAB Decisions or CourtListener dockets directly in this session. The finding is high-confidence for anything through the ingest date, moderate-confidence for the most recent weeks.

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Strategic summary

Claim status: everything is untested. All four claims are intact and unamended — claim 1 (the only independent claim, reciting the flat elongated mount plate, flat elongated shoulder plate, the pair of spaced-apart damper fasteners and dampers, and the center damper assembly with a third damper sharing the viscoelastic copolymer/hollow-body/shape-engineered limitations), claim 2 (center damper cavity + first and second damper seats), claim 3 (center damper fastener), and claim 4 (attenuator pad with concave pad portion). There is no CANCELED set and no SUSTAINED-after-trial set; the entire patent is UNTESTED. The scope a defendant must design around today is the originally granted scope — notably, claim 1 is relatively narrow in that it requires the three-damper architecture (a pair of dampers plus a center damper between them), so a two-damper-only product may fall outside claim 1 on its face without any PTAB help. That is a claim-charting question, not an IPR question.

Estoppel: § 315(e)(2) is a blank slate, and that cuts both ways. Because no IPR/PGR was ever instituted, no petitioner (or privy) is estopped from raising any § 102/§ 103 ground, and no district court defendant is boxed in by a prior Board record. Conversely, there is no FWD to leverage as a pared-back claim set, no "the Board already found claim 1 obvious" ammunition, and no PTAB-narrowing that a defendant could argue has plain-law preclusive effect. Every prior-art theory a defendant wants to run is available in district court today. If a defendant is currently being accused and was served with a complaint, the ordinary § 315(b) one-year clock applies to any IPR it might file; if no complaint has been served on a given party, it can file a preemptive IPR now.

Pattern signals: none exist. No repeat petitioner (there are no petitioners). The patent owner has never appealed anything to the Federal Circuit, so there is no CAFC docket to consult. No defensive aggregator (Unified Patents, RPX, etc.) appears anywhere in the chain. The patent is held by individuals — inventors John M. Sprainis and Ronald J. Sprainis, per the face of the patent and the Google Patents assignee field ("Individual"). The absence of any IPR is consistent with a patent that has not been asserted broadly: well-asserted, high-damage-exposure patents reliably attract IPRs, and this one hasn't. The practical read is that this is either an unasserted commercial product (the spec discusses a "TEMAX™" recoil pad) or a personal-holder patent without the revenue base to fund serial litigation.

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Recommended next steps

1. Treat the absence of PTAB activity as fact, but re-confirm before you rely on it. Re-run the ODP "PTAB proceedings" query by patent number and by the owner names (John M. Sprainis, Ronald J. Sprainis) at the time of any assertion, and check PTAB E2E at https://ptacts.uspto.gov/ptabweb and the PTAB Decisions library at https://www.uspto.gov/patents/ptab/decisions. There is no FWD to link to or quote — because none was ever issued.
2. Do not build a defense around IPR estoppel or a prior FWD — those levers don't exist here. Your invalidity path is straight district-court § 102/§ 103 using the 49 prosecution citations (Browning US 4,910,904; Benelli US 2004/0144011; Beretta US 2006/0096148; Blackhawk US 7,926,216; Latimer US 2011/0113666; Browning US 2018/0017353, etc.) as a starting prior-art set, refreshed with art post-dating 2018.
3. Claim-chart claim 1's three-damper requirement early. The pair-plus-center-damper architecture is the narrowest point of the only independent claim; a two-damper product may avoid literal infringement regardless of the damper material. That is likely your cheapest non-infringement position.
4. If a demand letter or complaint arrives: check whether § 315(b)'s one-year window is open for the accused party and consider a pre-institution IPR; but weigh it against the fact that no prior Board record exists to validate the claims, so a first IPR is a genuinely open question on the merits. Note the patent's remaining term runs to 2038-12-05, so there is ample runway for a post-grant challenge.
5. Verify maintenance-fee status before assuming enforceability of all claims. The authoritative record shows Active with the 4th-year fee paid 2024-02-27; a § 282/§ 41 maintenance-fee lapse theory is not supported by the data I found, and I would not assert one without a fresh check of the 7.5-year fee window.

Confidence note: I am reporting zero PTAB proceedings with high confidence based on the canonical ODP block plus independent web verification. I did not find, and am not asserting, any proceeding number, judge panel, FWD, settlement, or Federal Circuit appeal for US 10,663,252 — none exists in the sources available to me.

I'll start by probing the USPTO assignment record and the inventors' commercial activity.

Let me dig into the inventors' commercial identity and any recorded assignments.

Strong lead: the earlier Sprainis patents were assigned to Wabtec, and "Copoly Technologies LLC" surfaced. Let me pursue both, plus the assignment record directly.

Analyst note on sources and a limitation up front

I was unable to open the USPTO Assignment Center directly in this session (assignmentcenter.uspto.gov / assignment.uspto.gov are behind interfaces my tools could not render, and my query budget was exhausted mid-verification). Everything below is therefore built from: (a) the Google Patents legal‑events log for US 10,663,252 (which mirrors recordation events), (b) the Justia patent record, and (c) corroborating third‑party records about the inventors' patent history. No reel/frame numbers were retrievable, and I will not invent them.

Flag against the prior section: the earlier summary flagged assignee and litigation as unverified. My searches strengthen the assignee finding (see below) but do not change the litigation result — I still found no suit, IPR, or CAFC appeal naming this patent.

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Inventors

• Employer at the time of filing is not determinable from this record. The decisive negative evidence is that the '252 application names no corporate assignee and no employer — unlike the Sprainises' railcar patents, which were assigned to Wabtec Holding Corp. (Wilmerding, PA). That asymmetry suggests the firearm work was done outside whatever relationship produced the Wabtec filings, but that is an inference, not a record fact.
• Unverified but worth logging: a people‑aggregator page (Radaris) associates a "John Michael Sprainis" with "Copoly Technologies LLC" (Springfield, OR area) and with General Atomics Aeronautical Systems. People‑search aggregators are unreliable; I did not confirm any Copoly Technologies entity, its existence, or its connection to this patent. Treat as a lead only. The word "copoly" is at least on‑theme (the claim recites a "copolymer elastomer" and the cited art includes Miner Enterprises' US 4,198,037 "polyester elastomer compression spring").
• No departure pattern determinable. The "all inventors leaving the original assignee within 12 months" signal requires a named original assignee to leave; here there is none.

Original assignee

• Entity on the issued patent: "Individual" — i.e., the patent issued to the two inventors jointly, with no corporate assignee recorded on the face of the patent (Google Patents shows both "Original Assignee: Individual" and "Current Assignee: Individual").
• Line of business: individual inventors; no corporate business to describe. Their prior commercial/technical line of work was elastomeric energy‑absorption springs for railway draft gear (Wabtec).
• Product embodying the claims: not established. The patent's own FIG. 10 discussion compares its curve against a "TEMAX (trademark) recoil pad," which hints the inventors had a foot in a commercial recoil‑pad product line — but I could not verify who owns the TEMAX mark, or whether any TEMAX product practices these claims. Do not treat this as a product‑in‑commerce finding.
• Current status: no corporate status to report; the individual inventors appear to retain ownership (see next section).

Assignment timeline

The USPTO/Google Patents legal‑events log for US 10,663,252 contains no assignment (recordation) events at all. The complete event set is:

There is no "AS" (assignment) event, no reel/frame, no assignor, no assignee, and no correspondent of record to report. The filing event itself reads "Application filed by Individual."

Finding: on the record available to me, this patent has never been assigned. Ownership remains with the two named inventors, John M. Sprainis and Ronald J. Sprainis. Two pieces of circumstantial corroboration: (i) small‑entity status was claimed and the 4th‑year fee was paid late, with a surcharge — behavior typical of an individual/small holder without a corporate docketing or licensing operation; (ii) Google Patents still resolves both the original and current assignee to "Individual."

Explicit caveat: an assignment could exist that is unrecorded (unrecorded assignments are valid between the parties but vulnerable against subsequent purchasers under 35 U.S.C. § 261). Confirming the absence of any recorded instrument requires a live Assignment Center query by patent number (16/211,102 or 10,663,252), which I could not run.

Timeline diagram

timeline
    title Ownership of US 10663252
    2017 : Provisional filed by Sprainis inventors
    2018 : Nonprovisional filed by Individual
         : Small entity status claimed
    2020 : Patent issued to the two inventors
    2024 : Fourth year fee paid late with surcharge
         : No assignment ever recorded

NPE / troll-pattern signals

Verdict

Insufficient data — more precisely: no NPE chain exists on the available record. The sole ownership entry is the original one (two individual inventors, Springfield OR), and the Google Patents legal‑events log — the only recordation-adjacent source I could reach — shows no assignment events whatsoever, only entity‑status, grant, and maintenance‑fee entries, including a late 4th‑year fee with surcharge on 2024‑02‑27. There are accordingly zero of the eight troll‑pattern signals present, and the "individual owner paying fees late without a corporate docket" profile is the opposite of an NPE licensing operation. The verdict is "insufficient data" rather than "defensive/non‑asserting" only because the correct label for a null assignment chain is a null chain — and because I could not query Assignment Center directly to prove the negative.

Verify at: USPTO Assignment Center (search patent 10,663,252 / application 16/211,102) and assignment.uspto.gov patent index; bibliographic cross‑check at Google Patents US10663252B1 and Justia 10663252.

Residual uncertainties I am not able to close: (1) any unrecorded assignment (e.g., to a Copoly Technologies or TEMAX‑related entity) would not appear in any of my sources; (2) the prosecution attorney of record on the patent face was not retrieved, so signal #3 cannot be scored; (3) the TEMAX mark ownership is unverified, so the "product embodying the claims" question is open.

I'll research this patent and its cited prior art. Let me start with targeted searches.

Let me gather detail on the most relevant firearm-recoil references.

A. Target confirmation

Searches for the literal string 10663252 resolved to a single U.S. grant, US 10,663,252 B1, titled "Shoulder-fired firearm primary and secondary recoil attenuator," inventors John M. Sprainis and Ronald J. Sprainis, application 16/211,102, filed Dec. 5, 2018, priority to provisional 62/599,257 (Dec. 15, 2017), granted May 26, 2020. I did not fold in results for numerically similar patents (e.g., US 10,663,250/10,663,251 or the unrelated Westlaw cite "2015 WL 10663252"), per the literal-reading rule.

Sources used: Google Patents (https://patents.google.com/patent/US10663252/en), Justia (https://patents.justia.com/patent/10663252), and the issued-PDF (http://patentimages.storage.googleapis.com/04/6d/81/4e5e4f5a83a346/US10663252.pdf).

B. Method, and an important structural conclusion up front

The examiner cited 49 references on the face of US 10,663,252 (the "Patent Citations" list — note these carry the asterisk as cited by examiner). I applied the §102 anticipation test element-by-element against granted claim 1, whose full combination is:

1. flat, elongated mount plate attachable to the butt;
2. flat, elongated shoulder plate spaced-apart/parallel;
3. a pair of spaced-apart damper fasteners through both plates;
4. a pair of spaced-apart dampers on those fasteners, between the plates;
5. a center damper assembly with a center damper between the pair and between the plates;
6. each of the pair and the center damper being viscoelastic copolymer elastomer with a hollow-body elastomer construction, shape-engineered to exhibit time-dependent strain;
7. whereby the dampers exhibit distinct spring rates for the primary recoil impulse (bullet accelerating through the barrel) and the secondary recoil impulse (propellant gases exiting the barrel).

Bottom-line §102 finding: no single examiner-cited reference discloses all seven elements, and in particular none discloses the three-damper (outer pair + center) architecture of element 5 combined with element 6 applied to all three. Because claims 2, 3, and 4 all depend from claim 1, they cannot be anticipated by a reference that fails to anticipate claim 1. On the record available to me, the cited art is therefore §103 (obviousness) art, not §102 art. I flag this explicitly rather than forcing anticipation onto references that do not support it.

C. The 49 examiner-cited references (as recorded on the patent)

(Dates are from the Google Patents citation table for this record; the earliest pre‑1900 entries show only a publication date. Descriptions are the record's own short titles.)

D. Tier 1 — most relevant cited references

US 4,198,037 A — Miner Enterprises (Anderson), Dec. 28, 1976 / Apr. 15, 1980.
Method of making polyester elastomer compression spring and resulting product. Verified via uspto.report (https://uspto.report/patent/grant/[4198037](/patent/4198037)). Teaches casting a copolyester polymer elastomer (e.g., HYTREL) block, annealing, then precompressing it in excess of 30% (optimum ~50%) of axial length between plates so it will not take a permanent set, and bonding the block to multi-apertured metal plates. It explicitly notes the copolyester is "velocity sensitive."
§102 mapping: This is the closest cited art for the material + precompression/"shape‑engineering" concepts (elements 6, partially), and it explicitly recites >30%/>50% compression of a copolymer elastomer (echoing the patent's "compresses more than 50%"). But it is a railroad draft‑gear/cushion teaching — no firearm, no mount/shoulder plate pair, no outer‑pair‑plus‑center damper arrangement, and no distinct primary/secondary recoil spring rates. It does not anticipate claim 1 (or dependent claims 2–4). It is strong §103 art against the material/precompression limitations.

US 6,305,115 B1 — RA Brands, L.L.C. (T. D. Cook), Jul. 29, 1998 / Oct. 23, 2001.
Gel recoil pad. (https://patents.google.com/patent/[US6305115B1](/patent/US6305115B1)/en). Claims a solid viscoelastic (polyurethane gel) core of Shore 00 60–90 with a covering and a fastener/backer mounting it to the firearm stock; explicitly "deforms and rapidly returns to its original shape in response to a recoil event." Discusses viscoelastic energy dissipation and compares to vented rubber/fluid pads.
§102 mapping: Discloses a viscoelastic recoil‑attenuating body attached at the butt (elements 1, 6‑material concept). It does not disclose two plates, fasteners with dampers mounted thereon, a three‑damper arrangement, or copolymer‑elastomer hollow‑body construction, or distinct primary/secondary spring rates. Does not anticipate claim 1; highly relevant §103 art (and directly on point for the "viscoelastic recoil body" concept).

US 5,669,168 A — Perry, G. R., Aug. 6, 1996 / Sep. 23, 1997.
Firearm recoil pad. (https://patents.google.com/patent/US5669168). A resilient closed‑cell foam boot (base wall + retaining sleeve with an integral stretchable strap) universally mountable to varied stocks; recoil forces temporarily compress the pad, which then returns to shape.
§102 mapping: Relevant to the "pad on the butt"/cushioning concept and to claim 4's attenuator pad (elastomeric material) as a structural analog — but it is a single foam boot, no plate pair, no dampers, no viscoelastic copolymer hollow‑body shape engineering. Does not anticipate claim 1. §103/§102‑type art only for the pad sub‑feature, and even then claim 4 is narrower (concave pad portion).

US 5,353,681 A — Sugg, R. E., Mar. 16, 1993 / Oct. 11, 1994.
Recoil dampening device for large caliber weapons. (https://www.freepatentsonline.com/[5353681](/patent/5353681).html). A coaxial tube‑frame dynamic‑braking recoil damper using a spring, expansion/compression rings, and a one‑way pneumatic valve to spread the recoil impulse over time.
§102 mapping: Addresses the same problem (spreading/attenuating recoil), but the structure is entirely different (barrel‑mounted coaxial brake/spring/pneumatic, no buttstock elastomer pad). Not anticipatory of any claim. Background/§103 only.

E. Tier 2 — secondary relevance

• US 7,926,216 B2 (Blackhawk, 2008‑11‑03/2011‑04‑19) and US 8,286,382 B2 (Vesligaj, 2008‑09‑22/2012‑10‑16) and US 10,156,422 B1 (Valin, 2015‑03‑10/2018‑12‑18) — each is a stock-mounted recoil‑reduction assembly (mechanical spring/hydraulic/insert systems). They show that multi‑component, plate‑and‑damper buttstock recoil devices were known, supporting a §103 combination argument, but none discloses a viscoelastic copolymer‑elastomer hollow‑body damper or distinct primary/secondary spring rates. Not anticipatory.
• US 2017/0356717 A1 (Outdoor Sport Innovations LLC, 2016‑06‑08/2017‑12‑14) and US 2018/0017353 A1 (Browning, 2016‑07‑15/2018‑01‑18) — a "firearm recoil absorber" and a "composite recoil absorber insert for a firearm stock," respectively. These are the closest in time to the priority date and are the met. I could not retrieve their full texts within the search budget, so I flag them as candidates warranting a full‑text element‑by‑element check for the "damper between two members at the butt" concept. On the record available, neither is confirmed to disclose the three‑damper copolymer‑elastomer architecture, so neither is a confirmed §102 reference.
• US 2013/0174461 A1 (Ballard, butt pad) and US 2011/0113666 A1 (Latimer, shock absorbing pad for rifle) — butt‑pad cushioning art; analogous to claim 4's pad but not the damper architecture.
• US 3,371,442 A (Miner, "damped spring means") and US 3,707,797 A (Ruth, "recoil absorber") — generic damped‑spring/recoil‑absorber teachings; §103 background.

F. Tier 3 — background / remote art

The pre‑1900 and early‑20th‑century grants (US 247451, 311755, 480587, 524458, 935163, 1042132, 1213951, 1255566, 1307529, 1334467, 1785977, 1964649) are recoil‑pad/butt‑plate and shock‑absorber antecedents. They establish that mounting a cushioning body at the butt of a shoulder‑fired arm is old, but they disclose no viscoelastic copolymer‑elastomer hollow‑body damper and no primary/secondary‑recoil spring‑rate differentiation. They are §102/§103 background only and do not anticipate any of claims 1–4. US 2012/0067432 A1 (Volvo Construction Equipment, hydraulic system) is non‑analogous art and appears to be an examiner search artifact with no bearing on the recoil claims.

I could not retrieve full texts for many of the mid‑century and pre‑1900 references; their descriptions above rest on the titles recorded on the patent face plus retrieved sources where available. Treat the Tier 3 characterizations as lower‑confidence title‑based reads.

G. §102 conclusion (per claim)

• Claim 1 — not anticipated by any cited reference. No single reference discloses the (i) flat mount plate + (ii) parallel shoulder plate + (iii) two damper fasteners + (iv) two outer dampers + (v) a center damper, with (vi) each being a viscoelastic copolymer elastomer, hollow‑body construction, shape‑engineered to exhibit time‑dependent strain, producing (vii) distinct primary/secondary recoil spring rates. The cited art individually supplies only fragments (Miner '037 → copolymer‑elastomer precompression; RA Brands '115 → viscoelastic recoil body at the butt).
• Claims 2–4 — not anticipated, as each depends from claim 1 and adds further structure (center damper cavity/seats; center damper fastener; concave elastomeric attenuator pad). A reference lacking claim 1's elements cannot anticipate a dependent claim.

Practical takeaway: The examiner appears to have used these 49 references as §103 combination art (recoil‑pad background + copolymer‑elastomer compression‑spring art) rather than as §102 anticipatory art, which is consistent with the narrow, architecture‑specific wording of the granted claim 1. The single strongest §102 candidates that a challenger would attempt to combine are US 4,198,037 (material/precompression) and US 6,305,115 (viscoelastic recoil body at the butt) — but even combined, these two still do not teach elements (iii)–(v) or the primary/secondary distinct‑spring‑rate feature, so an anticipation theory is not sustainable on the cited set.

H. Caveats and uncertainty flags

• Source coverage: I verified full/partial text for US 4,198,037; US 6,305,115; US 5,669,168; and US 5,353,681. The remaining descriptions rely on the citation titles/dates recorded on the US 10,663,252 face and are title‑level characterizations.
• US 2017/0356717 A1 and US 2018/0017353 A1 (the temporally closest references) were not retrieved in full; they are flagged as requiring a complete element‑by‑element §102/§103 review before any anticipation conclusion could be drawn.
• Status of the list: all 49 are marked on the record as cited by examiner; the patent's forward citations (US 2024/0027152, US 12,259,207, FR 3,121,981, FR 3,140,940, US 2023/0173644) and the "Similar Documents" set (e.g., US 10,578,394, US 6,684,547) are not prior art against this patent and were excluded from the anticipation analysis.
• No litigation/PTAB statements are made here; this task is limited to prior‑art analysis of the cited references.

I'll ground this analysis in the actual prior-art references of record. Let me pull details on the key cited references.

Significant lead: "Ronald J. Sprainis" appears as inventor on Miner Enterprises elastomeric-spring patents. Let me verify that connection and pull the other key references.

§ 103 Obviousness Analysis — US 10,663,252 B1

"Shoulder-fired firearm primary and secondary recoil attenuator"
Sprainis & Sprainis · App. 16/211,102 · filed 2018-12-05 · priority 2017-12-15 · granted 2020-05-26

Scope note. This is an examiner-style/validity-style obviousness assessment built from the prior-art references of record on the patent page you supplied (49 cited references plus the cited-by art), supplemented by targeted web verification of the references I could retrieve. It is not a legal opinion and not an infringement or validity conclusion. Where I could not verify a reference's actual text, I say so explicitly rather than inferring its contents. All patent numbers are read literally as given; I flag (rather than silently fix) mangled identifiers I encountered in search results.

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1. A threshold finding that reshapes the whole analysis

The named inventor Ronald J. Sprainis, Springfield, Oregon 97477 — the same name and city as the co-inventor of the '252 patent as reported in the previously generated summary — appears as the named inventor on an extensive family of Miner Enterprises / Wabtec "compressible elastomeric spring" patents:

• US 8,465,009 B2 / US 2008/0272080 A1 — Elastomeric pad for a compressible elastomeric spring
• US 8,783,670 B2, US 8,701,290 B2, US 8,336,209 B2, US 8,096,432 B2 — Compressible elastomeric spring / methods
• US 2008/0272081 A1, US 2009/0308829 A1 — draft gear assemblies
• Confirmed inventor address "SPRAINIS, RONALD, Springfield, Oregon 97477, US" (WIPO Gazette listings via zis.gov.rs, mijnoctrooi.rvo.nl)

And US 8,465,009 claims, verbatim, the concept the '252 patent calls its own:

"said pad manufactured from a predetermined material being modified to orient a molecular structure during a forming process and having a predetermined shape factor achieved during said forming process to enable repetitive absorption and dissipation of the energy in excess of about one hundred thirty percent (130%) of an ultimate tensile strength of said predetermined material."
(US 2008/0272080 A1)

Its specification also recites: "The pad 110 also has its molecular structure oriented above 70% during the forming process and a predetermined shape factor achieved after the forming process... The shape factor of the pad 110 is defined and limited by... the travel..."

That is, in all material respects, the '252 patent's "shape engineering" that "orient[s] the molecular structure" to achieve "specific performance in the force vs travel performance and hysteresis." Caution / contradiction flag: the earlier summary describes the material process as "proprietary" with no identification of a source. The search results indicate the process is the publicly patented Miner/Wabtec copolyester pad process, and its seminal reference — US 4,198,037 (Anderson, Miner Enterprises) — is itself already on the face of the '252 patent. I could not confirm identity of person beyond name-plus-city match; that inference is strong but not certain, and it should be verified against the USPTO assignment record before being relied on.

Consequence for § 103: the "shape-engineered / time-dependent strain / molecularly-oriented viscoelastic elastomer" limitations of claim 1 are not merely suggested by analogous art — they are the same concept the inventor's own earlier patents claim, and one of them (US 4,198,037) is cited as prior art in the '252 record. The only genuinely open question for claim 1 is the mechanical arrangement (two fastener-mounted dampers plus a center damper) and its application to a firearm butt.

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2. Framework and level of ordinary skill

Governing law. Graham v. John Deere, 383 U.S. 1 (1966) (scope/content, differences, PHOSITA level, objective indicia); KSR Int'l v. Teleflex, 550 U.S. 398 (2007) (predictable combinations of known elements; "obvious to try" where the prior art gives a finite number of identified, predictable solutions); In re Keller, 642 F.2d 413 (CCPA 1981) (art must be considered in combination, not piecemeal); In re Best, 562 F.2d 1252 (CCPA 1977) and In re Kubin, 561 F.3d 1351 (Fed. Cir. 2009) (inherent property of a prior-art composition cannot confer patentability).

PHOSITA. A mechanical or ordnance design engineer with a bachelor's degree in mechanical engineering (or equivalent) and roughly 2–4 years of experience in firearm accessories, recoil management, or elastomeric energy-absorption devices; familiar with viscoelastic materials, hysteretic dampers, recoil pads, and the standard practice of pre-loading a butt-plate assembly. This is the level that matters because essentially every claim limitation is a matter of routine mechanical design choice plus a known materials property.

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3. Claim 1, decomposed

Load-bearing conclusion: limitations 1.1–1.4, 1.6–1.8 are each individually and collectively taught or suggested; the case turns on 1.5.

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4. The reference set

4.1 Verified

US 10,156,422 B1 — Valin, "Firearm stock assembly, recoil reduction device and related methods" (cited by Examiner; priority 2015-03-10). Verified claim text (patents-review):

• cl. 1: butt plate + a first collapsible element connected between the butt end and the butt plate, comprising a cylinder, piston, and releasable engagement mechanism, releasing above a recoil threshold;
• cl. 2: "a second collapsible element... substantially identical to the first";
• cl. 3: "a mounting plate connected to the firearm stock, the first and second collapsible elements being connected in parallel between the mounting plate and the butt plate";
• cl. 9: "a recoil pad that covers the firearm stock and the recoil reduction device";
• cl. 10: "a mounting recess is defined in the butt end... and the first collapsible element extends thereinto."

That is a drop-in structural map to claim 1.1–1.4 and 1.5's framing: two parallel, spaced-apart damping elements between a stock-mounted plate and a butt (shoulder) plate, with a pad over the assembly.

US 8,516,730 B2 / US 2013/0145668 A1 — Valin (cited by Examiner; priority 2011-12-07). Verified (FreePatentsOnline, Patsnap): "two parallel spaced-apart spring operated piston assemblies mounted between two spaced-apart plates, wherein one of the plates is configured to be attached to an outside surface of a butt end of a rifle stock," with pre-load "of about 250 kg (550 pounds), and can be changed to increase or decrease the pre-load" and a recoil pad on the distal plate. The pre-load adjustability here maps directly onto the '252 patent's FIG. 9 "preload adjustability profile" and its stated purpose of preventing a "pulpous" damper that harms sighting.

US 6,305,115 B1 — RA Brands, "Gel recoil pad" (cited by Examiner; filed 1998). Verified text (Google Patents, uspto.report). Material disclosures:

• "A recoil pad... compris[ing] a solid viscoelastic core" — polyurethane gel, Shore 00 60–90, i.e., a viscoelastic elastomer damper mounted on the firearm butt;
• mounting: "threaded member 32 is inserted through the core 16... and fastened through the semi-rigid backer 12 into the stock 20. The viscoelastic core 'self heals' behind the threaded member" — a fastener passing through the damper body (maps to claim 3's architecture);
• express teaching toward viscoelasticity: "If this fluid could be viscoelastic with an appropriate amount of elasticity, the felt recoil could be reduced... and keep the felt recoil low through the entire recoil event" — a direct motivation to substitute viscoelastic elastomer for mechanical dampers;
• express teaching of hollow/voided elastomer constructions in recoil pads: "Vented rubber recoil pads were intended to overcome the problems with solid rubber pads by providing energy absorbing voids in the pad structure. The open, relatively thin-walled structures were designed to compress under the firearm's recoil force in a controlled manner" — i.e., "hollow body elastomer construction" for recoil attenuation is squarely old in the recoil-pad art.

US 4,198,037 — Anderson / Miner Enterprises (cited by Examiner; filed 1976-12-28). Verified via uspto.report, Casemine (Rodgard Corp. v. Miner Enterprises, W.D.N.Y.), and Chinese family member discussing it: copolyester (Hytrel) elastomer compression spring made by (i) forming a preform, optionally with a central opening/hollow, (ii) annealing ≥50 h, (iii) axially compressing the preform by at least 30%, preferably at least 50%, of its axial dimension, then releasing — producing a shape-engineered spring that recovers and does not permanently deform when subsequently compressed far beyond 10%, with documented energy-absorption/hysteresis behavior. The district court found the commercial part was a "holeless doughnut" or "hockey puck" mechanically bonded between metal plates, and separately discussed voids (hollow spots) in the Hytrel. This reference alone supplies 1.6, 1.7 and the compression/recovery and hysteresis behavior underlying 1.8.

US 8,465,009 B2 / US 2008/0272080 A1 — Sprainis et al. (Wabtec/Miner): "molecular structure oriented above 70% during the forming process," shape factor ~3.30, energy dissipation >130% of UTS. Supplies the same limitations in modern form, and is § 102(a)(1) art (issued 2013-06-18, more than one year before the 2017-12-15 priority date).

4.2 Cited references I could not verify in this session

I obtained no confirming text for US 7,926,216 (Blackhawk, Recoil suppression system for the stock of a firearm), US 8,286,382 (Vesligaj, Stock assembly with recoil suppression), US 2014/0075801 (Benelli, Recoil damping device for portable firearms), US 2006/0096148 (Beretta, Recoil damper system), US 2017/0356717 (Outdoor Sport Innovations, Firearm recoil absorber), US 2018/0017353 (Browning, Composite recoil absorber insert for firearm stock), US 5,353,681 (Sugg), US 4,662,062/US 4,661,877 (Bragg), US 2010/0281727 (Browning, Shoulder fire arm), or US 2005/0246931 (Poff, Recoil dampening assembly). All are of record as Examiner-cited art, and on their titles and classifications they are the most likely sources for the center damper, damper seat/cavity, and concave pad limitations. I flag them as unverified leads, not as established disclosures. I also note an identifier hazard: the patenthub.cn listing renders Miner/Wabtec records with mangled numbers (e.g. "US12150809," "US08783670B2"); those are application serials (12/150,809) and patent 8,783,670 mis-rendered, and I am not treating them as distinct patent numbers.

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5. Obviousness combinations

Combination A — Valin (US 10,156,422) + RA Brands (US 6,305,115) + Miner/Anderson (US 4,198,037)

Anticipates/suggests 1.1–1.4, 1.6–1.8; renders 1.5 obvious as a third parallel element.

• Motivation (structural substitution): Valin's two parallel collapsible elements between a stock-mounted plate and a butt plate sit exactly where the '252 dampers sit. Swapping Valin's cylinder/piston/ball-bearing collapsible elements for RA Brands' solid viscoelastic gel damper is the substitution of a known damper for a known damper to obtain the known benefit — KSR, 550 U.S. at 416–17 ("a known technique... to a known device... to improve it in the same way"), and a "predictable variation" of a known method. The '252 specification itself articulates the advantage (no steel coil springs, no hydraulic fluid, fewer failure modes, lower maintenance) — those are precisely the benefits that motivate replacing Valin's mechanical elements.
• Motivation (materials/field bridge): RA Brands expressly states the desirability of a viscoelastic material for recoil dissipation and describes voided/vented recoil-pad structures — supplying 1.6 directly in the same field.
• Motivation (enabling the >50% compression): RA Brands' background is candid that conventional urethane/TPE foam pads fail above ~38% compression. The '252 patent's claim to compressibility "more than 50%" is met by the Miner/Anderson process — anneal plus axial pre-compression with molecular orientation — which is expressly described as producing a copolyester elastomer spring that recovers after being compressed well beyond 30–50% without permanent deformation. This supplies the missing element and the reasonable expectation of success. See also the express cross-reference in the Wabtec/Sprainis family: "the absorbing capacity of such compressible elastomeric springs is affected by... material selection, by the forming process and by mechanical attachment" — i.e. the art teaches that this performance is designable.
• Motivation (claim 1.5, center damper): Valin's rationale for two elements is stated — "separated in part to work simultaneously together to provide an equal amount of pressure" and to provide a "controlled clamping system." Adding a third, centrally-located element between them to further equalize load distribution and add damping capacity is the paradigm of a "mere duplication of parts" / addition of a known element to a known structure for its known function — an established obviousness rationale (In re Harza; KSR). It yields no change in principle and no unexpected result.

Combination B — Valin (US 8,516,730 / US 2013/0145668) + RA Brands + Anderson

Adds express pre-load teaching (250 kg ± 50 kg) matching the '252 FIG. 9 preload adjustability, and the damper-covering recoil pad matching claim 4's attenuator pad. Together with Combination A, the entire two-plate/two-damper/pre-loaded viscoelastic/padded architecture is accounted for.

Combination C — Browning US 2018/0017353 + RA Brands + Anderson (unverified lead)

The Browning reference — "Composite recoil absorber insert for firearm stock" — is on its face an elastomeric composite absorber insert for a firearm stock, which is the '252 architecture's closest analogue in the stock-insert genre. If its disclosure of a composite/elastomeric insert seated in a stock recess is as its title suggests, it supplies the "seat/cavity" concept of claim 2 as well. I could not verify its text; treat as a research lead, not a finding.

Combination D — Benelli US 2014/0075801 or Beretta US 2006/0096148 (unverified lead) + RA Brands

The "recoil damper / damping device for portable firearms" references are the most likely sources for the claim 2 center damper cavity / first damper seat / second damper seat arrangement, since that genre conventionally uses a guide-rod or bushing damper captured in a socket in the butt plate. Unverified.

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6. Dependent claims

Claim 2 (center damper cavity in shoulder plate; first damper seat in the cavity; second, aligned damper seat on the mount plate; center damper extending between seats). A seat/socket-and-abutment arrangement for capturing a damper between two plates. Valin's cl. 10 (mounting recess receiving the collapsible element) is a direct analogue; RA Brands' structural core plus backer plate provides the second seat; and the Miner references teach mechanical interlock of an elastomeric pad to plates via projections/grooves/prongs — i.e. elastomer-to-plate seating is an established, designable feature. The remaining detail (a cavity in the shoulder rather than mount plate) is an arbitrary orientation choice with no stated functional consequence beyond packaging — obvious under KSR.

Claim 3 (center damper fastener through and between the plates; center damper mounted on it). This is the strongest of the dependent claims for obviousness: RA Brands expressly mounts its viscoelastic core by driving a threaded member through the core and into the stock, and Valin expressly mounts its damping elements to the end plates by fasteners. Mounting the third (center) damper on a third fastener is the same fastener-plus-damper arrangement already present in claim 1 for the outer pair — a duplication of parts. Additionally, a fastener through the damper is structurally necessary or at least strongly suggested once claim 1 requires two dampers mounted on through-fasteners: the POSITA would use the identical fastening scheme for the third body.

Claim 4 (attenuator pad on the mount plate, elastomeric, with a concave pad portion). Valin US 10,156,422 cl. 9 (recoil pad covering the device) and Valin US 8,516,730 (recoil pad on the distal plate) supply an elastomeric pad on the plate. The concave pad portion is the one limitation for which I have no verified reference and which is not squarely supplied by the combinations above; however, a shoulder-contacting face contoured to the shoulder is the definitional shape of a recoil pad, and the '252 patent offers no asserted function or advantage for concavity beyond comfort. I would expect this to fall to art not on the '252 face (e.g., the Browning, Poff, or Latimer references) or to routine design. Flag: claim 4 is the limitation I am least able to support from verified sources.

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7. Objective indicia (§ 103 rebuttal analysis)

No objective evidence of nonobviousness appears in the record supplied:

Teaching-away check: US 4,198,037 is drawn to railway draft gears, and US 6,305,115 to recoil pads. Valin and the stock/damper references are in the firearm field itself. Because the draft-gear art is directed to the identical problem — absorbing large, high-rate dynamic compressive impact with a recoverable elastomer body — it is reasonably pertinent to the problem the inventor faced and therefore available as analogous art even though the field of use differs (In re Clay; In re Bigio). That the same named inventor carried this technology from draft gears to firearms strengthens, not weakens, the pertinence argument.

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8. The strongest nonobviousness arguments the patent owner could make

Presented so they can be met rather than ignored:

1. No reference teaches a center damper between two fastener-mounted dampers. The patent owner will point out that Valin's cl. 3 has two parallel elements, not three, and that nothing of record expressly places a third damper centrally. The counter is KSR: adding a known element (a viscoelastic damper) to a known structure (Valin's two-element, two-plate assembly) in a known way (in parallel, to distribute load) to obtain a predictable result (more damping, better load sharing) is obvious, and the "equal amount of pressure" rationale in Valin supplies the express motivation.
2. The "shape-engineered to exhibit time-dependent strain" limitation is not disclosed as applied to a firearm damper. The counter is that the limitation is a functional/process-by-result recitation of an inherent property of a hysteretic viscoelastic body, and the prior art teaches that the property is engineerable (molecular orientation, shape factor) in the very material class claimed.
3. "Whereby the dampers have distinct spring rates in response to primary and secondary recoil." A whereby clause defining no structure gets no patentable weight (Minton v. NSC, 674 F.3d 1339 (Fed. Cir. 2012); Hoffer v. Microsoft, 405 F. App'x 502 (Fed. Cir. 2010)). Even if given weight, distinct response to high-rate vs. low-rate loading is inherent in a viscoelastic/hysteretic device and is expressly relied on by RA Brands ("keep the felt recoil low through the entire recoil event").
4. The "proprietary molecular orientation process" is not fully disclosed. This is a § 112 concern, not a § 103 defense — and to the extent it is disclosed, it is disclosed in the cited Miner/Wabtec art, which is worse for the patent owner on § 103.

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9. Verification gaps I could not close (please treat as open)

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10. Bottom line

1. Claim 1 is, in my assessment, vulnerable under § 103 on the combination of Valin US 10,156,422 (or Valin US 8,516,730/US 2013/0145668) as the two-plate / two-parallel-damper / padded butt-plate architecture, RA Brands US 6,305,115 for the viscoelastic elastomer recoil-pad damper, voided ("hollow body") construction, and through-damper fastening, and Miner/Anderson US 4,198,037 — an Examiner-cited reference — for the shape-engineered, molecularly-oriented copolyester elastomer that survives compression well beyond the ~38% failure threshold of conventional pads. The only structurally distinctive limitation, the center damper, is supplied by a predictable duplication of the known valved element for its known load-sharing function, on a stated motivation.

2. The limitation that is hardest to defeat from the face of the record is claim 4's concave pad portion, and the second-hardest is claim 2's specific cavity/seat geometry. Both are of the character that generally falls to art that does not appear on the '252 front page (composite stock inserts, dedicated recoil-damper devices), and both should be researched against the unverified references in § 9 before an opinion is formed.

3. The most important single finding is the Ronald J. Sprainis / Miner–Wabtec connection. If confirmed, it means the patent's central technical contribution — "shape engineering" that orients the molecular structure of a copolyester elastomer — is the inventor's own already-patented rail-draft-gear technology, one of whose seminal references (US 4,198,037) is cited on the face of the '252 patent. That substantially collapses the obviousness inquiry on limitations 1.6–1.8 and shifts the entire § 103 dispute onto the mechanical arrangement of claim 1 and the dependent-claim details.

Recommended next steps: (i) confirm the Sprainis identity via USPTO Assignment Search and Patent Center; (ii) retrieve the full texts of the nine unverified cited references, in that order of priority — US 2014/0075801 and US 2006/0096148 (center damper/seats), US 2018/0017353 (stock insert), US 2010/0281727, US 2005/0246931 (pads/concavity), US 7,926,216 and US 8,286,382; (iii) retrieve the 16/211,102 file wrapper to see exactly what was traversed and why.