US 1558619

US Patent 1,558,619 — Summary

Grounding note: My searches returned no USPTO litigation records and no CAFC 2026 docket entries for this patent number. The only specific hit consistent with the number is the Google Patents record for US1558619A (fetched 2026‑09‑29), whose full text is the source for everything below. I did not find any Federal Circuit activity — which is expected, since this patent expired in 1942 and would be long outside any live 2026 dispute. Treat any "current litigation" question as unanswered rather than answered.

Bibliographic data (per the Google Patents record)

Abstract: The original patent has no formal abstract (abstracts were not standard in 1921–1925 US practice). The closest thing Google Patents displays is a snippet headed "Definitions," taken verbatim from the opening of the specification: heat transfer is performed between a cooling medium and the liquid so that every particle of the liquid is gradually and substantially uniformly reduced in temperature, and so that no portion of the liquid contacts a cooling medium or surface whose temperature differs from it by more than a small fraction of the total temperature range through which the liquid is chilled; the resulting precipitate is separated by centrifugal force.

What the invention is about (plain language)

The patent addresses dewaxing: chilling wax‑bearing petroleum stocks (e.g., cylinder stock) so the wax precipitates and can be spun out centrifugally. The stated discovery is that if oil is chilled rapidly against a much colder fluid or surface — the patent's defined term is "shock chilling" — the wax drops out as a finely divided, colloidal mass that occludes oil that cannot be removed by centrifuging. If instead the oil is cooled uniformly and never has a substantial fraction of its volume pushed below the bulk temperature, the wax comes out coarser, more crystalline, less colloidal, holds less occluded oil, and centrifuges readily.

The disclosed apparatus is a two‑loop brine system: ammonia (pipe 2, expansion valve 3) boils in brine tank 4, whose coils 6 feed a cold‑brine circuit (pipe 7, relief valve 8, tank 9, pipe 10, pump 11, pipe 12). A second, warmer brine loop (pipes 15, 17, pump 16, coils 14) cools the oil in tank 13. A small slip stream of cold brine is bled from pipe 7 through valve 19/pipe 18 into the warm loop, with an equal quantity withdrawn through valve 21/pipe 20 to tank 9. Regulating valve 19 fixes the temperature of the brine entering coils 14 in a set relation to the oil temperature, largely independent of how cold the supply brine is. Worked example from the spec: oil in tank 13 at about 70 °F while coil‑14 brine is about 60 °F, even though brine through valve 19 may be at −20 °F. The coils 14 and pump 16 are sized so the oil‑to‑brine approach is roughly equal on entry and exit and so the mean brine temperature differs from the oil by only a small fraction of the total chilling range — preferably not more than about 10 °F below the oil, with brine temperature lowered as the oil temperature falls. Chilled oil leaves via conduit 22 to centrifugal separator 23 (outlets 23′, 23″). The spec also states contemplated use for other liquids, e.g., separating stearin from vegetable oils.

Independent claims (all six claims are independent — there are no dependent claims)

• Claim 1 (method): Treating a liquid containing a substance precipitable by cooling by forming a discontinuous precipitate, achieved by reducing the liquid's temperature at a substantially constant rate via heat absorption in refrigerant cooled at a rate bearing a substantially constant relation to changes in the liquid's temperature.
• Claim 2 (method): Absorbing heat from the liquid into a refrigerant maintained at a temperature insufficient for shock chilling the liquid and never differing from that liquid by more than a small fraction of the total temperature range through which the liquid is chilled.
• Claim 3 (method, oil/wax): Treating wax‑containing oil by forming a discontinuous waxy precipitate via heat absorption in a refrigerant held at a temperature incapable of shock‑chilling the oil, plus dispersing the precipitate by setting up currents in the oil.
• Claim 4 (method, oil/wax): Absorbing heat from wax‑containing oil in a refrigerant never differing from the oil by more than a small fraction of the total chilling range, and maintaining that refrigerant at a temperature bearing a substantially constant relation to the oil temperature by mixing small quantities of cold refrigerant into the first‑named refrigerant. (This is the claim that reads on the valve‑19 slip‑stream regulation.)
• Claim 5 (apparatus): A liquid reservoir; a refrigerant circulating system to cool liquid in it; a second refrigerant circulating system supplying refrigerant to the first; and connections/controls between the two systems permitting refrigerant from each system to be circulated through the other, to regulate the temperature in the first system.
• Claim 6 (apparatus, wax from oils): An oil reservoir; an agitator; a refrigerant circulating system to cool oil in the reservoir; a second refrigerant circulating system comprising a refrigerant cooler and a tank; means connecting the first system to the second between the cooler and the tank; and means connecting the first system with the tank.

Uncertainty / caveats

• OCR quality is poor. Several numerals in the scanned text are garbled (e.g., "70019." for what is plainly ~70 °F; "60 E." for ~60 °F; "46 F." / "48 hours" and "10 F." readings are ambiguous). I have flagged readings as approximate rather than asserting exact figures.
• The record lists USRE19869E (1936‑02‑25) under "Similar Documents" with a truncated title ("Method and apparatus fob avoiding…"). That strongly suggests a reissue of this patent, but the listing does not state it as such and I could not confirm the relationship — treat it as probable, not established.
• Cited‑by: two later US patents only — US 2,735,457 (urea suspension) and US 2,685,783 (Ohio Commw Eng Co). No assertion of these as pertinent prior art is made here.
• No USPTO PatentCenter, assignment, or CAFC 2026 docket content specific to 1558619 surfaced in my searches; I am not claiming such records do not exist, only that I could not retrieve them.

I'll search for litigation records involving US patent 1558619.

Let me search more specifically in litigation databases.

Let me do a few more targeted searches to be thorough.

Litigation Search: US Patent 1,558,619

Bottom line

No litigation involving US Patent 1,558,619 was found. I could not identify any case — historical or modern — in which this patent was asserted, challenged, or otherwise at issue. If you need a negative-clearance assertion for a diligence opinion, this search is consistent with there being none, but it is not a substitute for a docket-level search (see caveats below).

What the record shows about the patent itself

Per the Google Patents record (https://patents.google.com/patent/[US1558619](/patent/US1558619)/en):

Two practical points bearing on the search:

1. The patent expired on October 27, 1942 (standard 17-year term from the 1925 grant). Any infringement action would have had to be brought during the term or within the statutory limitations window thereafter. That places the entire actionable window in the 1920s–1940s — before electronic docketing existed.
2. No litigation-related metadata appears in the record. Google Patents lists only two "Cited By" references (US 2,685,783 and US 2,731,457, both 1950s patents) and a set of "Similar Documents." These are citation relationships, not litigation. Notably, the similar-documents list includes US RE19,869 E, "Method and apparatus for avoiding…" (1936-02-25), which on its face appears to be a reissue in this family worth confirming if your diligence requires it — but a reissue is a prosecution event, not litigation.

Results that searched near the number but are NOT this patent

I want to flag these explicitly because they surfaced in response to the number and are easy to conflate:

• Crye Precision / "the '861 Patent" (Duro Textiles litigation). Search hits referencing "the '861 Patent" and "Substrate with Camouflage Pattern" concern a design patent (US D486,861, Crye Precision), and the case is Crye Precision LLC v. Duro Textiles, LLC (D. Mass., later Fed. Cir.). This is a different patent with a different number and is unrelated to US 1,558,619. I am listing it here only so it is not mistaken for a hit.
• French application FR 1558619 / EP 3350417 (Safran Aircraft Engines, turbine casing cooling). The string "1558619" also appears as a French priority application number in a modern turbomachine family. Unrelated to the US patent.
• Refining, Inc. v. Sharples Specialty Co., 21 F. Supp. 511 (D. Del. 1937), No. 1186. Shares the same assignee (Sharples Specialty Co.) but involves an entirely different subject matter and patent — a process for refining vegetable and animal oils (Clayton/Kerrick/Stadt application Ser. No. 534,533), with an interference involving an application filed in the name of Edward M. James. It does not involve US 1,558,619. Plaintiff: Refining, Inc. Defendant: Sharples Specialty Co. Jurisdiction: D. Del. Outcome: motion to dismiss the bill of complaint (21 F. Supp. 511). I mention it only as a company-level data point, not as '619 litigation.
• Sharples v. Moseley & Stoddard Mfg. Co., 81 F. 179 (2d Cir. 1897). Also a Sharples-family case, but it concerns reissue 11,311 and patent 458,194 (centrifugal milk separators/tester) — decades before and unrelated to '619. Not relevant.

Required table (no qualifying cases)

Caveats and confidence level

• Confidence that no modern litigation exists: high. A 1925 patent that expired in 1942 is not assertable today and would not appear in Unified Patents' litigation caselist, PTAB, or current PACER dockets. Unified's caselist and the Federal Circuit/PTAB sources I reached returned no '619 matches.
• Confidence that no historical (1925–1940s) suit exists: moderate, not high. Pre-1940s federal equity suits are only partially digitized. A case could exist in paper-only records (e.g., a district court file) that would not surface in the web sources I could reach. I was unable to directly query PACER (paywalled) or run a full-text historical docket search, and my search was cut short by a tool-step limit. If a definitive negative is needed, a manual check of the D. Del. and E.D. Pa. historical indices for the 1921–1945 window (the two venues most likely for a Philadelphia-based assignee) would be the appropriate next step.
• Do not rely on the near-miss cases as '619 litigation — none of them involve this patent, and citing them as such would be a misidentification.

If it would help, I can draft the language for a formal "no known litigation" statement suitable for an IDS-style submission or a diligence memo, with the search scope and limitations stated on the record.

Proceedings overview

Total AIA trial proceedings on US 1,558,619: zero. The USPTO Open Data Portal structured block in this prompt returns no IPR, PGR, or CBM petitions — no active proceedings, no claims invalidated, no claims sustained, no settlements, no institution denials. Web search surfaced no PTAB or Federal Circuit activity on this patent number either. That is the canonical answer, and in this instance the silence is not a gap in the data: US 1,558,619 issued 1925-10-27 to Leo D. Jones, assigned to Sharples Specialty Co., and its term expired 1942-10-27 (Google Patents lists status "Expired – Lifetime," anticipated expiration 1942-10-27). There is no defensive-posture question to answer here in the usual sense — nobody can assert these claims, and no AIA tribunal can now issue a certificate canceling them, because the claims lapsed 84 years ago.

Source of record: US1558619A on Google Patents.

Proceedings overview (detail)

No proceeding entries follow, because there are none to describe. I will not populate the per-proceeding template with invented numbers, panels, or dispositions.

Why there is no PTAB record (and why that is expected)

1. The AIA trial regime postdates the patent by nearly a century. IPR, PGR, and CBM were created by the America Invents Act and became available for petitions on 2012-09-16. US 1,558,619 expired 1942-10-27 — seventy years before the first IPR petition could be filed.
2. Even if a petition were theoretically possible against an expired patent, none of the three vehicles fits. PGR is limited to patents with an effective filing date on or after 2013-03-16 (this patent's priority date is 1921-02-05). CBM required claims directed to a financial product or service — this is a dewaxing/brine-chilling apparatus and method, not a covered business method — and the CBM program sunset for new petitions on 2020-09-16. IPR is not date-limited, but a petitioner would need a live controversy and Article III/§ 315 standing incentive; there is none for a patent that lapsed in 1942.
3. The "Cited By" references are unrelated. US 2,685,783 and US 2,731,457 are 1950s citations to the '619 disclosure, not proceedings against it. Likewise, the litigation hits in search are 1890s Sharples v. Moseley milk-separator appeals — a different century, different patents (Re. 11,311 and 458,194), different technology.

Caveat I could not resolve

USRE19869E, dated 1936-02-25, appears under "Similar Documents" with the truncated title "Method and apparatus fob avoiding…" — which reads like a reissue of this very disclosure. Google Patents' family data for the '619 patent lists only one application (US442691A, Family ID 23757755), which suggests RE19869E is a reissue of a different Sharples/Jones patent in the same art, not of the '619 patent. I could not verify this by search and I am not asserting either conclusion. If you have a live reason to care (e.g., a chain-of-title or defensive-publication question), pull the RE19869E front page directly and confirm the "Original No." field — that will settle it in one line. Note that even if it is a reissue of the '619 disclosure, a reissue expires with the term of the original patent, so it would carry the same 1942-10-27 expiration.

Strategic summary

Claim status. All six claims — method claims 1–4 and apparatus claims 5–6 — are UNTESTED, not because they survived a validity challenge, but because no AIA challenge was ever mounted. For completeness, the claim set as issued is:

• Claim 1 — method: forming a discontinuous precipitate by reducing liquid temperature at a substantially constant rate via heat absorption in refrigerant cooled at a rate bearing a substantially constant relation to changes in liquid temperature.
• Claim 2 — method: heat absorption in a refrigerant maintained at a temperature insufficient for shock chilling and never differing from the liquid by more than a small fraction of the total chilling range.
• Claim 3 — wax-containing oil: discontinuous waxy precipitate by heat absorption in a refrigerant incapable of shock chilling, plus dispersing the precipitate by forming currents in the oil.
• Claim 4 — wax-containing oil: heat absorption in a refrigerant never differing by more than a small fraction of the total range, maintained in constant relation to oil temperature by mixing small quantities of cold refrigerant with the first-named refrigerant.
• Claims 5–6 — apparatus: dual refrigerant circulating systems with interconnections and flow controls (claim 5); oil reservoir + agitator + dual refrigerant systems with a cooler/tank (claim 6).

Estoppel landscape. There is no § 315(e)(2) estoppel to map. No petitioner exists; no final written decision exists; no IPR certificate has issued. No party is barred from anything, because no party has ever petitioned. Conversely, there is no petitioner-side record to mine for admitted prior art or claim constructions — a defendant gets zero free ammunition from the PTAB, but also faces zero risk of inheriting someone else's estoppel.

Pattern signals. None. No serial petitioner, no defensive aggregator (Unified Patents, RPX, etc.) in the chain, no PTAB appeal history, no Patent Owner appeal to the Federal Circuit. The '619 patent does have real historical weight in the art — US 1,881,643 (1932) expressly cites "my Patent No. 1,558,619" and describes its chilling teaching as foundational to centrifugal dewaxing, and the Jones "shock chill" concept recurs across the Sharples-era dewaxing literature (US 2,075,992; US 2,168,141; US 2,435,434; US 2,614,065 and others). But historical significance in the art is not AIA trial activity.

Recommended next steps

1. If you received a demand letter citing US 1,558,619, stop analyzing validity and analyze the demand instead. The patent expired 1942-10-27. There is no subsisting right to license, no infringement to enjoin, and no damages available: 35 U.S.C. § 286 limits recovery to six years before suit, a window that closed decades before any conceivable defendant existed. Any assertion built on these claims is not merely weak — it is facially baseless, which places the sender's counsel at risk under Rule 11 and state UPL/unfair-practices rules. Preserve the letter with its envelope and metadata.
2. Check the number carefully. US 1,558,619 is a 1925 petroleum-dewaxing patent. Demands citing a "1558619" that is not this patent (e.g., the 1990 Soviet certificate SU 1558619 A1 for cylinder-head reclamation, or a modern application number) should be treated as a different right entirely. Do not assume a typo in either direction.
3. Verify no live continuation or reissue. Search the '619 patent's family in PatentCenter and confirm no unexpired reissue sits downstream (see the RE19869E caveat above). If you want a firm answer, order the RE19869E front page or pull it at patents.google.com/patent/USRE19869E and check the "Original No." field.
4. If, contrary to the ODP record, a recently filed petition exists, it would appear in PTAB E2E and on the USPTO PTAB Decisions page before ODP ingest catches up. Search those directly by patent number and by "1,558,619." Also check CourtListener for any CAFC appeal naming this patent. If you find one, the statutory milestones to track are: institution decision within 3 months of the patent owner's preliminary response (or 6 months of petition filing if no POPR), and a final written decision within 12 months of the institution date, extendable up to 6 months for good cause under § 316(a)(11).
5. Bottom line: the absence of PTAB activity here is not the usual "well-asserted patents eventually attract IPRs" signal. It is a term-expiration signal. Treat any assertion of this patent as a documentation problem, not a litigation problem.

I'll start by verifying what's actually in the public assignment record and cross-referencing the corporate history.

Let me check the corporate history and whether any reissue or transfer surfaced, plus confirm the database coverage window.

Let me pin down the corporate successor chain and check that reissue that appears in the "similar documents" list.

US 1558619 — Ownership Chain Reconstruction

Method note / limitation, stated up front: I could not query assignmentcenter.uspto.gov directly (it is a client-side JavaScript application that is not crawlable by the search tools available to me). My conclusion below is therefore grounded on (a) the authoritative Google Patents legal-events record supplied for this patent, which is the same data mirrored from the USPTO assignment recordation system, and (b) the documented coverage window of the USPTO Patent Assignment Search database. No reel/frame number is reported because I could not verify one; I will not invent one.

Inventors

• Sole named inventor. The patent names only Leo D. Jones; the "In testimony whereof I have hereunto set my name this third day of February, 1921" signature is his alone.
• Employment relationship is well corroborated. The Official Gazette of the U.S. Patent Office (v. 359, 1927) records contemporaneous Jones applications each captioned "LEO D. JONES, Philadelphia, Pa., assignor to The Sharples Specialty Company, Philadelphia, Pa., a Corporation of Delaware" (e.g., Centrifugal Separator, filed Oct. 7, 1921; Centrifugal Machine and Process…, filed May 1, 1924, with co-inventor Arthur U. Ayres). Jones was a staff inventor for Sharples, not an independent.
• No early-departure pattern. The "all inventors leave within 12 months of filing" fire-sale tell is not present: Jones continued filing Sharples-assigned applications at least through 1924–1927, i.e. he stayed with the company well past this 1921 filing.

Original assignee

The Sharples Specialty Company, Philadelphia, Pennsylvania — a corporation of Delaware (as recited on the face of the patent).

• Line of business: high-speed centrifugal separators ("centrifugals") and centrifugal process systems. This patent is a process/apparatus patent for chilling wax-bearing oil so the wax precipitates in coarse, non-colloidal form amenable to centrifugal separation — i.e. it is squarely a Sharples core-business patent (the spec explicitly discharges the chilled oil to "a centrifugal separator 23").
• Did they ship a product embodying the claims? Effectively yes, on the record: Sharples was a commercial manufacturer of centrifuge systems from the 1920s onward (it "has been selling abroad since 1924"; C&EN describes Sharples Corp. as a "Philadelphia manufacturer of centrifuges and centrifuge systems"), and the claimed method is the front-end chilling step feeding its separators.
• Current status: the original corporate entity no longer exists. Reported successor chain (treat as moderate confidence, based on trade-press and historical sources rather than a recorded assignment here): Sharples Corporation became a subsidiary of Pennsalt Chemicals (C&EN, early 1960s); Pennsalt became Pennwalt (1969); Pennwalt was acquired by Elf Atochem (1989), later Atofina/Arkema. Decanter-industry histories record that "Sharples, USA, acquired by Pennsalt/Pennwalt, then sold to Alfa Laval, and the decanter ranges merged." I did not find any recorded patent assignment evidencing any of these steps for US 1558619 — none is expected, because all of it predates the online database.

Assignment timeline

The USPTO Patent Assignment Search database contains NO records for US 1558619.

This is expected and is itself the finding:

• The searchable assignment database "contains all recorded Patent Assignment information back to August 1980" (USPTO, Assignment Database Webinar, 2015-01-20). Pre-August-1980 records are held in a separate historical database not served by the online Assignment Search (MPEP 301.01: "The historical database of assignments is maintained separate and apart from the database of assignments affecting title recorded since 1980"), and records recorded before May 1, 1957 are held by NARA, not USPTO.
• US 1558619 was filed 1921-02-05, issued 1925-10-27, and expired 1942-10-27 — ~38 years before the searchable window opens and ~15 years before the pre-1957 records left USPTO. Any transfer of this patent necessarily occurred in the 1920s–1940s, so it can only appear in the microfilm-era historical record or at NARA.
• Corroborating this, the Google Patents legal-events record for this patent lists only: application filed (1921-02-05), priority to US442691A, application granted (1925-10-27), anticipated expiration (1942-10-27). There are no assignment, security-agreement, merger, change-of-name, or license events.
• The two "Cited By" documents (US 2,685,783 and US 2,731,457, both early 1950s) are later citing art, not assignments of this patent.

Per your instruction, I am stopping the reconstruction here rather than fabricating reel/frame entries for a chain that the online record does not contain. To go further, the only real avenues are (1) a manual search of the pre-1980 historical assignment database / microfilm reel indexes via the USPTO Assignment Recordation Branch, and (2) a NARA request for pre-May-1957 records — both of which require the reel/frame number to be efficient, which is precisely what I could not verify.

On the verdict categories: if you require one of your five labels on the evidence available, the honest answer is Insufficient data — there is no post-issuance assignment in the searchable record, only the original Sharples ownership, and every NPE-pattern signal is untestable for a patent that expired in 1942, four decades before the modern assertion economy existed. I flag this only so the label is on the record; I am not rendering the full signals/verdict sections, consistent with your "stop after this section" rule.

Verification links:

• https://assignmentcenter.uspto.gov/ (search property US1558619)
• https://assignment.uspto.gov/patent/index.html (same underlying records)
• https://patents.google.com/patent/US1558619/en (legal events, cited-by, classifications)

I'll search for the specific patent number and its citation records.

Search outcome (transparency note)

I could not retrieve a live USPTO PatentCenter/PatentsView record for this number through the available search tooling — targeted queries for the number returned no direct hit on a USPTO or Google Patents bibliographic page. The only authoritative full record I have is the one reproduced in your message, sourced from https://patents.google.com/patent/US1558619/en (fetched 2026-09-29). Everything below is grounded in that record, with gaps flagged rather than filled by inference.

1. What the record actually contains (literal reading)

Important correction to the premise of the request: this record shows no backward citations — there is no "Citations" / "Patent Citations" / "Cited by examiner" list of prior art cited against US1558619. What the record does show is a "Cited By (2)" table, i.e., forward citations — later patents that cite US1558619. Those are categorically incapable of anticipating under 35 U.S.C. § 102, because they post-date the 1921 priority/filing date. I am therefore not going to label them "prior art to 1558619," which would be an error.

2. The two documents in "Cited By (2)" — analyzed as requested, with the correct legal characterization

(a) US 2,685,783 A — "Method of and apparatus for dehydrating by freezing"

• Assignee: Ohio Commw Eng Co (record shows "Ohio Commw Eng Co")
• Priority/filing: 1950-06-09; publication 1950-06-09–1954-08-10 (record lists priority date 1950-06-09, publication 1954-08-10)
• Description: freeze-desalination/dehydration of saline water.
• § 102 relevance to US1558619: None. Filed 29 years after 1558619's 1921-02-05 filing date. No subsection of § 102 (pre-AIA or AIA) permits a later-filed/later-published reference to anticipate an earlier patent. It touches the same general "chilling a liquid to precipitate/separate a phase" subject matter, which is why it cites 1558619 — i.e., it is evidence of the disclosure's influence on later art, not of anticipation.
• Claims potentially affected: none.

(b) US 2,731,457 A — "Production and use of a urea suspension"

• Priority/filing: 1950-05-17; publication 1956-01-17; assignee not shown in the record.
• Description: urea suspension production/use (adduct-type slurry).
• § 102 relevance to US1558619: None, for identical reasons (1950 filing vs. 1921 priority). No claim of 1558619 is implicated.
• Note: the record does not indicate whether either reference was "cited by examiner" (†) or "cited by third party" — the asterisk/† legend is present but the fetched HTML does not resolve which applies to which entry.

3. Closest substantive prior art identified within the four corners of US1558619

Because the citation record is empty, the only prior art I can identify with high confidence is the prior art the inventor admits on the face of the specification — which is usable as prior art under the "applicant's own admission" line of authority (and, for a 1921-filed case, under the pre-1952 statutes, R.S. 4886 et seq., rather than the codified § 102):

1. Direct-expansion chilling — "chilling liquids ... whether by direct action as by boiling liquid ammonia in circulating coils in contact with the liquid to be cooled." Spec. p. 1.
2. Indirect brine chilling with a working temperature differential — "circulating refrigerated calcium or sodium chloride brine through ... coils [in contact with the oil]," where, for a 20 °F target, "brine at a temperature of approximately 10° F." was circulated, and slow chilling was obtained "by limiting the amount of brine flowing thru the chilling coils." Spec. p. 1.
3. The admitted consequence — that practice caused "shock chilling," producing "a finely divided or colloidal state [of wax] with the occlusion of oil which cannot [be separated] centrifugeally."

These admissions are the real § 102 exposure for claims 1–4, because each of claims 1–4 is drafted as a difference over that practice:

• Claim 1 — constant-rate temperature reduction by heat absorption in a refrigerant "cooled at a rate bearing a substantially constant relation to changes in the temperature of the liquid." The admitted prior art cools at non-constant rate and overloads a portion of the liquid to final temperature, so the constant-rate/constant-relation limitation is the distinguishing element.
• Claim 2 — refrigerant "maintained at a temperature insufficient for shock chilling" and "never differing ... by more than a small fraction of the total temperature range." The admitted prior art's ~10 °F-under-target brine, and the "limiting the amount of brine" mode, is the direct target of this negative limitation.
• Claim 3 — adds "dispersing the precipitate by the formation of currents in the oil" (corresponding to the tank 13 convection-current / agitator disclosure).
• Claim 4 — recites the specific control mechanism: mixing "small quantities of cold refrigerant with the first named refrigerant" to hold a substantially constant temperature relation (valve 19 admitting cold brine into the recirculating warm-brine loop).

The specification's stated numbers — oil at about 70 °F with coil-14 brine at about 60 °F, while the makeup brine through valve 19 may be at −20 °F; brine preferably not more than about 10 °F below the oil; chilling over about 48 hours to about 10 °F — are worked examples that a § 112/§ 102 analysis would need to align to the "small fraction" and "substantially constant relation" language, which is decidedly functional and unbounded.

4. "Similar Documents" list — leads only, not citations

The record lists 25 "similar documents" (e.g., US1962580A "Chilling," USRE19869E "Method and apparatus fob avoiding…", US2085521A, US2168141A, US2005988A, US2614065A, US2439434A, US2078992A, US1867580A, US1544734A, US2218511A, GB329193A, etc.). These are classification/topic neighbors generated by the database, not references cited in or against US1558619, and Google's own record labels them "Similar Documents." I therefore cannot assign them § 102 effect without their filing dates, which the fetched record does not supply for most of them.

Two entries warrant flagging as verification leads (I am explicitly not asserting a relationship):

• USRE19869E, published 1936-02-25, title truncated in the record as "Method and apparatus fob avoiding" — the title stem strongly resembles US1558619's title, and an "RE" number is a reissue. I could not verify whether this is a reissue of US1558619 or of a different patent (a 1936 reissue of a 1925 patent would need its own filing-date check under the then-applicable reissue statutes). Treat as an open lead, not a finding.
• US1544734A ("Refining oil," published 1925-07-07) — the only similar document with a publication date near US1558619's; its filing date is unknown from this record and it could conceivably precede 1921-02-05. Also an open lead.

5. Bottom line

• No prior-art citations of record exist for US1558619 in the authoritative source available to me. Any answer purporting to list "each patent citation" for it and map them to § 102 would be fabricating a citation list.
• The two items in the "Cited By (2)" table — US2685783A and US2731457A — are forward citations from 1950 filings and cannot anticipate any of claims 1–6 under § 102.
• The only genuine § 102-relevant art I can substantiate is the admitted prior art in the specification's own background (direct ammonia-expansion chilling; brine at ~10 °F below target; rate-limited brine flow), which is the express foil against which claims 1–4 are drafted.
• Claims 5 and 6 are apparatus claims; the record shows no apparatus reference at all, so no § 102 mapping can be made from the available sources.

Recommended next steps to close the gaps: pull the USPTO PatentCenter/Global Dossier file wrapper for application US442691A (1921) to see the examiner's actual cited references, and verify whether USRE19869E corresponds to 1558619. I can run those specific checks if you'd like — I'd need a fresh search allowance, since I exhausted the tool step limit on this pass.

Obviousness Analysis under 35 U.S.C. § 103 — US 1558619 ("Method and apparatus for avoiding shock chill in precipitating substances from liquids")

Note on methodology: per your instruction I have taken the "Prior Art" material displayed on the Google Patents page (https://patents.google.com/patent/US1558619/en) as the universe of prior art for this exercise, and I have dated/literally read each identifier rather than assuming what it "should" be. Where the page does not supply a date needed for a § 102 analysis, I say so rather than filling the gap.

1. The legal frame actually applicable here

Consequence of the 1921 filing date: a reference can only be combined under § 103 if it independently qualifies as prior art under § 102 — i.e., (a) before the invention date (no later than 1921‑02‑05, and Jones himself asserted a 1920 discovery date), (b)/(g) patented or described in a printed publication more than one year before 1921‑02‑05, i.e., before 1920‑02‑05, or (e) a U.S. application/patent filed before Jones's invention date.

2. What the page's "Prior Art" section actually contains — and why it does not support a § 103 rejection

2.1 "Prior art keywords": temperature, oil, brine, tank, pipe. These are algorithmic keyword tags, not references. They carry no probative value for § 103. They do, however, usefully summarize the claimed subject matter (oil/brine/tank/pipe = the two‑circuit brine control loop of claims 5–6).

2.2 "Prior art date 1921‑02‑05" is simply this patent's own filing date used as the search cut‑off — it is not a reference.

2.3 "Cited By (2)" — this is the list of documents that cite US 1558619, not documents cited in it:

Notably, the patent's own front‑page References Cited (the examiner's citation list) is not displayed on the page at all. So the page supplies no § 102(a)/(b)/(e) reference from the 1920‑or‑earlier window.

2.4 "Similar Documents" (≈25 entries): the earliest stated priority dates in the entire list are 1929‑01‑18 (US 1962580 A) and the earliest publication dates cluster in 1931–1939, running forward to 1978 (US 4088565 A). Every one of the substantive, on‑point documents post‑dates the 1921 filing — most by 10–20 years:

• US 1962580 A — priority 1929‑01‑18, granted 1934‑06‑12 ("Chilling"; Max B. Miller & Co.); its own abstract describes "limiting to avoid shock chilling the temperature differential…" (https://patents.google.com/patent/[US1962580A](/patent/US1962580A)/en; abstract also at https://www.osti.gov/biblio/[7215833](/patent/7215833)). This is a later improvement on the '619 principle, i.e., evidence that the art followed Jones, not that Jones followed the art.
• US 1881643 A (1932), US 1930479 A (1935), US 2078992 A (1937), US 2085521 A (1937), US 2168141/2168143 A (1939), US 2218511 A (1940), US 2223939 A, US 2234916 A, US 2439434 A (1948) — the later Sharples/Jones dewaxing family.
• US 1802942 A (1931), US 1867580 A (1932), US 1904900 A (1933), US 1916825 A (1933), US 2005988 A (1935), US 2008570 A (1935), US 20106011 A (1935), US 2168141 A, US 2172320 A, US 2332284 A (1943), US 2356346 A (1944), US 2404677 A (1946), US 2614065 A (1952), US 3009536 A (1961), US 3234122 A (1966), US 4088565 A (1978), GB 329193 A (1930) — all post‑1921.
• Two entries need resolution and are the only conceivable § 102 candidates in the entire list:
  • US RE19869 E (1936‑02‑25), title truncated on the page as "Method and apparatus fob avoiding …" — a reissue, so its effective reference date could be the filing date of its original patent. Because the page's "Family Applications" shows only US 442691 A, the page does not tell us the parent. If RE19869 is the reissue of US 1558619 itself, it is the same invention and can never be art against '619 (and the "limited to the unexpired part of the original term" rule means the 1936 date is merely the print date). If it is the reissue of some other pre‑1921 patent, it is a genuine § 102(e)/102(b) candidate. I could not verify the parent from the material available, and I am not going to guess — this must be checked in USPTO PatentCenter / Espacenet before any rejection is written on it.
  • US 1544734 A ("Refining oil", published 1925‑07‑07) — publication after the 1921 filing, and the page shows no priority/filing date for it. It could only be art under § 102(e) if its underlying application was filed before Jones's invention date. Unresolved on this record.

2.5 Bottom line on this section. As presented, the page yields zero references that qualify as prior art under pre‑AIA § 102 against a 1921‑02‑05 filing (subject only to the two unresolved items in 2.4). Consequently no legally proper § 103 combination can be built from this list alone. Constructing one from the 1929–1978 documents would be textbook ex post facto hindsight of the kind Graham/KSR forbid: using later Sharples/Jones‑family patents that expressly cite US 1558619 to prove that US 1558619 was obvious would invert the direction of the evidence.

3. The prior art that does exist on this record: applicant's own admissions

The specification itself is the only § 102‑quality art available, and it is substantial. Statements in the specification describing the prior art are treated as admitted prior art (MPEP § 2129; Constant v. Advanced Micro‑Devices, Inc., 848 F.2d 1560 (Fed. Cir. 1988)). US 1558619 admits:

1. Direct chilling: "boiling liquid ammonia in circulating coils in contact with the liquid to be cooled."
2. Indirect chilling: "circulating refrigerated calcium or sodium chloride brine through such coils," i.e., the exact two‑circuit ammonia→brine→coil architecture recited in claims 5–6.
3. The deliberate large temperature differential: "it has been customary to control the temperature of the chilling media so that this temperature was always appreciably lower than the lowest temperature to which the liquid to be chilled was carried. Thus, if the process required the chilling of an oil to 20° F., it was customary to circulate … brine at a temperature of approximately 10° F."
4. "Slow chilling" by throttling, with local shock chilling: "If slow chillings were required, this was accomplished by limiting the amount of brine flowing thru the chilling coils. Small portions of the liquid to be chilled were chilled rapidly to the lowest required temperature."
5. Dilution, cold settling and centrifugation of wax‑bearing oil as the known separation context (also documented in Jones's own 1924 AIME paper, Centrifugal Removal of Wax from Petroleum Lubricating Oils, https://www.onemine.org/documents/tulsa-paper-centrifugal-removal-of-wax-from-petroleum-lubricating-oils).

Independent secondary corroboration of the pre‑1921 commercial state of the art appears in The Science of Petroleum, Vol. III (Oxford Univ. Press, 1938), dewaxing chapter ("Non‑Shock Chilling"): chilling was done "by circulation of brine through pipe coils in batch chilling tanks … chilled by ammonia expansion," chilling over "about 48 hours," with a 10–15 °F medium‑to‑oil differential — i.e., the commercial practice that '619 formalized. (Located via web search; the host URL is an archive path and I would not cite it as a stable link.)

This is the baseline against which claims 1–6 must be assessed.

4. Claim‑by‑claim obviousness assessment

Because § 2 yields no usable secondary reference, the analysis below is necessarily conditional: for each claim I identify the type of reference that would have to be combined, the motivation that would be articulated, and how the claim would likely fare. This is where an examiner's rejection would come from — not from the 1930s–1950s documents on the page.

Claim 1 — constant chilling rate; refrigerant cooled at a rate bearing a substantially constant relation to the liquid's temperature change

• Would be obvious over: admitted art (1)–(4) in view of routine process control (flow‑throttling of brine was already admitted) — motivation: the prior "slow chill" method produced objectionable rapid local chilling of "small portions," so one of ordinary skill, seeking to make slow chilling actually uniform, would reduce and then continuously trim the medium‑to‑oil differential as the oil cools (a plain control‑loop design choice; predictable result). In re Aller, 220 F.2d 454 (CCPA 1955).
• Best counter: the claim's limitation is not merely "chill slowly" but a substantially constant relation between refrigerant temperature and the changing oil temperature — a specific process control that the admitted art (constant 10 °F brine regardless of oil temperature) does not disclose, and that the admitted art's own critique ("portions … chilled rapidly") shows was not the practice.
• Assessment: vulnerable but not clearly anticipated; would turn on whether the asserted secondary reference discloses closed‑loop tracking of refrigerant temperature to batch temperature (a pre‑1921 refrigeration‑control patent or handbook would suffice).

Claim 2 — refrigerant never more than a small fraction of the total chilling range below the liquid; incapable of shock chilling

• Would be obvious over: admitted art (2)–(4) only if combined with a reference teaching a small, maintained‑throughout differential. On the face of the admission, the difference is real: the admitted practice (brine at 10 °F vs. oil endpoint 20 °F) is a 10 °F differential at the end of the batch, but at the start (oil at, e.g., 70 °F) the differential is roughly 60 °F — precisely the shock‑chilling event the claim excludes.
• Motivation a rejection would assert: avoid incrustation/local subcooling on coil surfaces and improve crystal form; use automatic brine‑temperature regulation (tempering) to hold the differential within a narrow band — a "known technique to improve a similar device" (KSR).
• Assessment: the most defensible claim on this record. Absent a pre‑1921 reference disclosing close‑tracking temperature control in a batch chiller, the claim would survive; with such a reference, it falls because the claim recites a result‑effective variable (temperature differential) rather than a new mechanism — recognizing a new consequence of a known variable is not enough (In re Kao, 639 F.3d 1057 (Fed. Cir. 2011)).

Claim 3 — waxy oil; discontinuous waxy precipitate; precipitate dispersed by currents in the oil

• Would be obvious over: admitted art + the known use of agitators/forced convection in chilling tanks (the patent's own specification states that the convection established by the coil circulation serves "for preventing subsidence of the precipitate and assist agitation"). Motivation: agitation is the standard remedy for stratification and poor heat‑transfer film coefficients in batch tanks; the reference to "convection currents" in the specification is an admission that the expedient was known.
• Assessment: highly vulnerable — the "dispersing … by formation of currents" limitation reads on the admitted natural/induced convection.

Claim 4 — mixing small quantities of cold refrigerant with the main refrigerant to hold a substantially constant temperature relation

• Would be obvious over: admitted art (2) + a standard blending/bleed temperature‑control loop (three‑way tempering/mixing valve with a bypass and an equal‑volume bleed, as actually shown in the patent: pipe 18/valve 19 in, pipe 20/valve 21 out). Motivation: to modulate brine supply temperature without cycling the refrigeration compressor and to trim the differential — a routine engineering solution, predictable result.
• Assessment: vulnerable; the "mixing small quantities of cold refrigerant with the first named refrigerant" step is the classic injection‑blending control known in refrigeration practice long before 1921. A refrigerator/ice‑plant handbook or a brine‑temperature‑regulator patent from before 1920 would very likely dispose of it.

Claims 5–6 (apparatus) — two refrigerant circulating systems with interconnecting connections and controls; agitator

• Would be obvious over: admitted art (2) (ammonia→brine indirect system with coils in a tank — exactly elements 1, 4, 6, 9, 11) + any known brine temperature‑regulating valve arrangement, connected as: first system = tank/coil/pump (14, 15, 16, 17); second system = cooler + tank (9) + pump (11); connections = the bypass/bleed pair. Motivation: temperature regulation of a secondary coolant is a recognized need; providing a bypass leg and a bleed leg between two circuits is a mechanical arrangement one of ordinary skill would adopt as a matter of design choice (KSR; Lincoln Eng'g aggregation principles cut the other way here because the elements coact in a single temperature‑control function).
• Assessment: vulnerable on the face of it, since the only structural addition over the admitted brine system is the two cross‑pipes and valves. The specification's own functional recital (the apparatus is described entirely in terms of attaining the desired temperature relation) invites a "printed matter/function" argument that the structure is merely the admitted art arranged for a known control purpose.

5. Secondary considerations that must be weighed (and their limits)

Arguably strong Graham factor‑two/three material exists, but note that the corroborating sources are post‑1921 and thus usable only as non‑prior‑art background, not as § 103 art:

1. Long‑felt need: cold settling of steam‑refined cylinder stock gave bright stock of ~50 °F cold test with 70% yields and unpredictable settling (Jones, AIME Tulsa paper, 1924 — including the anecdote of men holding pneumatic hammers against tanks to force the wax down). This is exactly the kind of "need in the art" that supplies motivation to combine — which cuts against the patentee on § 103.
2. Failure of others / teaching away: The Science of Petroleum (1938) records that "[m]any efforts have been made to avoid the limitation of 'Non‑Shock Chilling'. None of them appeared to be economically justifiable," and that departing from non‑shock chilling sacrifices pour test and increases oil entrainment. This is pro‑patentee evidence of unexpected results and of a technical prejudice against large differentials — but it post‑dates the filing by 17 years, so it is useful for a later validity challenge or for historical context, not for the 1921 obviousness date.
3. Nexus: any commercial‑success argument must be tied to the claimed temperature‑differential control, not to Sharples centrifuges generally.

6. Answer to the question as posed

On the prior art shown on this page, US 1558619 is not obvious under § 103 — because the page supplies no prior art at all. The two "Cited By" documents (US 2685783 A, 1950; US 2731457 A, 1950) and essentially all ~25 "Similar Documents" (1929–1978, including US 1962580 A, US 1881643 A, US 1930479 A, US 2085521 A, US 2168141 A, US 2223939 A, US 2234916 A, US 2439434 A, US 4088565 A) post‑date the 1921‑02‑05 filing and therefore cannot be combined; several of them are the applicant's/assignee's own later improvements that cite US 1558619 as the originating disclosure.

If the exercise requires hypothetical combinations, the only legally coherent ones are built on the applicant's admitted prior art in the specification (ammonia‑expansion brine chilling, brine‑to‑oil differentials of ~10 °F against a 20 °F endpoint, "slow chilling" by throttling brine flow, agitation, centrifugation):

• Claims 1, 2, 4 (and by extension 5–6's control function): admitted art + a pre‑1920 temperature‑regulating/blending brine control (mixing‑valve/bypass temperature control of a secondary refrigerant). Motivation: eliminate the admitted local "rapid chilling of small portions," improve heat‑transfer stability, standard control‑loop engineering. Claims 1 and 4 would likely fall; claim 2 would fall only if that reference teaches a differential maintained within a narrow band throughout the batch, not just at the endpoint.
• Claim 3: admitted art + known tank agitation. Motivation: prevent stratification/subsidence and improve film coefficients; the specification itself concedes the convection expedient. Likely obvious.
• Claim 5–6: admitted brine‑coil tank system + known bypass/bleed mixing loop (the very pipes 18/19 and 20/21). Likely obvious as an arrangement of known elements performing their known coacting functions.
• The strongest nonobviousness position rests on claim 2 (and the "substantially constant relation" language of claims 1 and 4) because the admitted art affirmatively teaches away from narrow differentials by using a fixed ~10 °F brine against a 20 °F target with rapid chilling of portions.

7. Explicit gaps / items I could not verify (flagged rather than assumed)

• US RE19869 E (1936‑02‑25) — parent patent and its filing date are not shown on this page. It is either (i) the reissue of US 1558619 itself (in which case it is not art and its presence in "Similar Documents" is an artifact), or (ii) a reissue of a different, possibly pre‑1921 patent (in which case it becomes the single most important § 102/§ 103 candidate here). Verify in USPTO PatentCenter/Espacenet before relying on it.
• US 1544734 A — shown only with a 1925‑07‑07 grant; the underlying filing date (needed for a § 102(e) analysis) is not on the page.
• The patent's own References Cited list did not render on the fetched page; the examiner's actual citations (if any) may exist in the USPTO file wrapper / Google Patents "Citations" tab and would be the correct starting point for any § 103 rejection.