CTFR 19/323,341 CTFR 93213 DETAILED ACTION Notice of Pre-AIA or AIA Status 07-03-aia AIA 15-10-aia The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA. Response to Amendment The amendment filed on 13 May 2026 has been entered. Claim(s) 1-2, 4, 6-9 and 11-12 remain pending in this application. Claim(s) 3, 5 and 10 have been cancelled. The amendments to the claims have overcome the §112(b) rejections set forth in the office action mailed 13 February 2026. Claim Rejections - 35 USC § 103 07-20-aia AIA The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. 07-21-aia AIA Claim (s) 3-4 are rejected under 35 U.S.C. 103 as being unpatentable over Rambo (U.S. Patent No. 11,946,415), hereinafter Rambo, in view of Vandermolen (U.S. Patent No. 7,334,411), hereinafter Vandermolen, Taylor (U.S. Patent No. 11,536,164), hereinafter Taylor, and Lear (WIPO Publication WO 2024/172924), hereinafter Lear . Regarding Independent Claim 1 , Rambo discloses a gas turbine engine (Figures 3 and 8) comprising an engine core, 16, having first and second engine core exhaust paths (Figure 8 – the path through which the flow, 322, flows is the first core exhaust path and the path through which the flow, 320, flows is the second core exhaust path) arranged to pass first, 322, and second portions, 320, respectively of the mass flow of the engine core exhaust of the engine during operation thereof (the first path provides the first mass flow, 322, and the second path provides the second mass flow, 320), and a heat-exchange system, 86, 94, 96 and 98, comprising: (i) a recuperator system, 94, disposed within the first engine core exhaust path (Figure 8 – the recuperator, 94, is provided in the first engine core exhaust path) and arranged to transfer heat from the first portion of the mass flow of the engine core exhaust to a buffer fluid (Column 8, Lines 4-20 – the recuperator, 94, transfers heat from the first portion of the mass flow of the exhaust to a thermal transfer/buffer fluid); and (ii) a heat exchanger, 96, arranged to transfer heat from the buffer fluid to fuel (Column 10, Lines 61-67 – the heat exchanger, 96, transfers heat from the buffer fluid to the fuel in the fuel system) within a fuel path, 64, arranged to convey fuel to a combustor, 92, of the gas turbine engine, wherein: the recuperator system within a loop path, 86/98, which includes a pump, 100, and which is arranged to circulate the buffer fluid through the recuperator (Column 9 Lines 2-11 – the pump circulates the buffer fluid through the recuperator). Rambo does not disclose the recuperator system comprises a plurality of heat-exchangers arranged in series or in parallel, the buffer fluid circulating through the heat-exchangers, the heat-exchangers being distributed azimuthally with respect to a central longitudinal axis of the gas turbine engine, the loop path includes a heater arranged to heat buffer fluid within the loop path, and the gas turbine engine is a hydrogen-burning gas turbine engine and the fuel path is arranged convey hydrogen fuel to the combustor. However, Vandermolen teaches a gas turbine engine (Figures 3 and 4) with a recuperator system, 60, that comprises a plurality of heat-exchangers arranged in parallel (Figure 4 – Column 4, Lines 2-13 – the recuperator comprises a plurality of heat-exchangers, 80, 84 and 94, the heat-exchangers being distributed azimuthally with respect to a central longitudinal axis of the gas turbine engine (Figures 3 and 4 – Column 4, Lines 3-13 – the heat exchangers are distributed circumferentially/azimuthally about the central longitudinal axis of the engine, as shown in Figure 3). Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the invention of Rambo by making he recuperator system comprise a plurality of heat-exchangers arranged in parallel, the heat-exchangers being distributed azimuthally with respect to the central longitudinal axis of the gas turbine engine, as taught by Vandermolen, resulting in the buffer fluid circulating through the heat-exchangers in order to provide a smaller heat exchanger/recuperator and thus reduce the weight of the system (Vandermolen – Column 1, Lines 39-43 and Column 5, Lines 31-32). Rambo in view of Vandermolen doe not disclose the loop path includes a heater arranged to heat buffer fluid within the loop path, and the gas turbine engine is a hydrogen-burning gas turbine engine and the fuel path is arranged convey hydrogen fuel to the combustor. However, Taylor teaches a recuperator system (Figure 2) with a loop path (the recuperator system has a loop path as shown) with a heater, 24, to heat a working fluid (Column 6, Lines 46-51 – the heater, 24, heats the working fluid). Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the invention of Rambo in view of Vandermolen by making the loop path include a heater arranged to heat buffer fluid within the loop path, as taught by Taylor, in order to allow the temperature of the working/buffer fluid to be provided at the desired temperature (Taylor – Abstract, Lines 11-13). Rambo in view of Vandermolen and Taylor do not disclose the gas turbine engine is a hydrogen-burning gas turbine engine and the fuel path is arranged convey hydrogen fuel to the combustor. However, Lear teaches that hydrogen utilization in gas turbine engines is an intense focus in the industry, with efforts under way by essentially every original equipment manufacturer of gas turbines in the world. The motivation is aimed at meeting government mandates driven by decarbonization goals (Paragraph 0013). Hydrogen can be produced from non-carbon primary energy sources such as solar or wind energy, and it does not produce carbon products when combusted (Paragraph 0013). Further, Lear teaches that existing gas turbine engines can be retrofitted to operate on hydrogen fuel without significant or costly modifications to existing systems (Paragraphs 0002, 0003 and 0019) . Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have retrofitted Rambo in view of Vandermolen and Taylor existing gas turbine engine to use hydrogen fuel, as taught by Lear, resulting in the gas turbine engine is a hydrogen-burning gas turbine engine and the fuel path is arranged convey hydrogen fuel to the combustor in order to meet stringent government emissions standards driven by decarbonization goals (Lear - Paragraphs 0002, 0003, 0013, 0019) . Regarding Claim 2 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses the engine core comprises an engine core nacelle, 180, 330, 350 and 355, having first, 180, 330 and 355, and second engine core nacelle portions, 350, the first engine core nacelle portion extending axially from the upstream end of the engine core nacelle (Figure 3 – the first portion extends to from a upstream end that is upstream/left of the low pressure compressor, 22) to a first axial position downstream of a turbine section of the gas turbine engine (Figure 8 – the first portion, which is the outer casing/nacelle extends to the downstream end at the section, 330, that is to the right/downstream of the turbine section, 210 – See annotated figure below for clarification) and the second engine core nacelle portion being disposed radially inwardly of the first engine core nacelle portion (Figure 8 – the second nacelle portion, 350, is radially within the first nacelle portion) and extending axially from a second axial position downstream of the turbine section (Figure – the second nacelle portion extends from an upstream/left end that is to the right/downstream of the turbine section, 210 – See annotated figure below for clarification) to a downstream end of the engine core nacelle (the second nacelle portion extends to the downstream/right end of the core nacelle), the second axial position being upstream of the first axial position (the second axial position, which is the upstream end of the second nacelle portion, 350, is to the left/upstream of the right end of the first nacelle portion, which is the first axial position, thus the second axial position is upstream of the first axial position), and wherein the first engine core exhaust path is located radially within an annulus defined by the first and second engine core nacelle portions (Figure 8 – Column 16, Lines 22-29 – the first core path, which has the recuperator, 94, is a ring/annulus that is defined by first and second nacelle portions) and the second engine core exhaust path is located radially inwardly of the second engine core nacelle portion (the second exhaust path for the flow, 320, is located radially within the second nacelle portion, 350). PNG media_image1.png 520 974 media_image1.png Greyscale Regarding Claim 4 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Vandermolen further discloses the individual heat-exchangers are distributed axially with respect to the central longitudinal axis of the gas turbine engine (Figure 3 – the heat exchangers are shown to be at an axial location and therefore distributed axially along the central axis). Thus the combination of Rambo in view of Vandermolen, Taylor and Lear would result in the limitations of Claim 4. Regarding Claim 6, Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses the cross-sectional area of the annulus defined by the first and second engine nacelle portions increases downstream of the second axial position (the annulus of the first flow path increases in cross-sectional area to the right/downstream of the second axial position). Regarding Claim 7, Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses the engine core has an exhaust cone section defined by the engine core nacelle at positions downstream of the second axial position (Figure 8 – the engine core has an exhaust cone section, 340, defined by the engine core nacelle, 350, to the right/downstream of the second axial position). Regarding Claim 9 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses the first engine core exhaust path is arranged to pass between 10% and 15% of the engine core exhaust mass flow output by the turbine section of the gas turbine engine (Column 16, Line 55 – Column 17, Line 15 – the first engine exhaust path that provides flow to the recuperator, 94, provides a flow in a range that includes between 10% and 15% of the flow from the turbine section, 210). Regarding Claim 12 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses an aircraft (Column 5, Lines 50-52 – the system is on an aircraft) comprising a gas turbine engine according to claim 1 (See rejection for Claim 1 above) . 07-22-aia AIA C laim (s) 8 is rejected under 35 U.S.C. 103 as being unpatentable over Rambo in view of Vandermolen, Taylor and Lear as applied to claim 2 above, and further in view of Stretton (U.S. Patent No. 11,339,713), hereinafter Stretton , Regarding Claim 8 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo further discloses an engine nacelle, 50. Rambo in view of Vandermolen, Taylor and Lear do not disclose the engine nacelle which terminates at an axial position intermediate the first and second axial positions. However Stretton teaches the engine nacelle of a gas turbine engine may be designed to terminate at multiple locations (Figures 4B, 7C, 8C and 11B) including a position where the core nacelle terminates at between the end of the core nacelle and the turbine (Figure 11b – the right end of the nacelle, 21, is an axial position that the engine nacelle terminates between the end of the core nacelle and the turbine). Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the invention of Rambo in view of Vandermolen, Taylor and Lear by making the engine nacelle which terminates at an axial position intermediate the first and second axial positions of Rambo in view of Vandermolen, Taylor and Lear as a matter of design choice having no effect on the operation of Rambo in view of Vandermolen, Taylor and Lear . 07-22-aia AIA Claim (s) 11 is rejected under 35 U.S.C. 103 as being unpatentable over Rambo in view of Vandermolen, Taylor and Lear as applied to claim 1 above, and further in view of Yan (U.S. Patent No. 5,544,479), hereinafter Yan . Regarding Claim 11 , Rambo in view of Vandermolen, Taylor and Lear disclose the invention as claimed and discussed above. Rambo in view of Vandermolen, Taylor and Lear do not disclose the buffer fluid is nitrogen. However, Yan teaches a gas turbine system (Figure 1) with a recuperator system, 17, and buffer fluid (Column 3, Lines 12-19 -the fluid that flows through the closed loop through the recuperator, 17, is a buffer fluid) that is nitrogen (Column 3, Lines 12-19 – the buffer fluid is nitrogen). Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the invention of Rambo in view of Vandermolen, Taylor and Lear by making the buffer fluid nitrogen, as taught by Yan, since it has been held that the selection of a known material (in the present case nitrogen) based on its suitability for its intended use (providing thermal transfer/buffer fluid) would have been an obvious extension of prior art teachings. Sinclair & Carroll Co. v. Interchemical Corp. , 325 U.S. 327, 65 USPQ 297 (1945), See also In re Leshin , 277 F.2d 197, 125 USPQ 416 (CCPA 1960), MPEP 2144.07 . Response to Arguments 07-37 AIA Applicant's arguments filed 13 May 2026 have been fully considered but they are not persuasive. In response to Applicant’s argument that one of ordinary skill in the art would not have incorporated the heater of Taylor into the loop of Rambo because the loop of Taylor is a closed loop Brayton cycle it is respectfully pointed out that the loop of Rambo that uses the buffer fluid is a type of closed loop buffer cycle. The loop of Rambo includes a compressor/compression, a turbine/expansion as well as heat addition and heat rejection thereby meeting the definition of a Brayton cycle. Thus one of ordinary skill in the art would reasonably look to the teachings of Taylor and apply them to a similar loop/cycle in Rambo. Further while the claims do not claim the heater being used to prevent the buffer fluid from freezing, Taylor teaches the use of the heater to keep the working fluid/buffer fluid at a desired temperature which would further be applicable to address freezing of the buffer fluid. Therefore the combination of Rambo, Vandermolen, Taylor and Lear disclose the limitations of Claim 1. Conclusion 07-40 AIA Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL . See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a). A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action. Any inquiry concerning this communication or earlier communications from the examiner should be directed to KYLE ROBERT THOMAS whose telephone number is (571)272-4813. The examiner can normally be reached Monday-Friday 8:00am-4pm EST. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Devon Kramer can be reached at (571)272-7118. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /KYLE ROBERT THOMAS/Examiner, Art Unit 3741 Application/Control Number: 19/323,341 Page 2 Art Unit: 3741 Application/Control Number: 19/323,341 Page 3 Art Unit: 3741 Application/Control Number: 19/323,341 Page 4 Art Unit: 3741 Application/Control Number: 19/323,341 Page 5 Art Unit: 3741 Application/Control Number: 19/323,341 Page 6 Art Unit: 3741 Application/Control Number: 19/323,341 Page 7 Art Unit: 3741 Application/Control Number: 19/323,341 Page 8 Art Unit: 3741 Application/Control Number: 19/323,341 Page 9 Art Unit: 3741 Application/Control Number: 19/323,341 Page 10 Art Unit: 3741 Application/Control Number: 19/323,341 Page 11 Art Unit: 3741
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