FINAL REJECTION
This is in response to Applicant amendments filed on 10/27/2025 amending Claims 1, 4, 6-13, and 15-17; and adding Claims 18 and 19. Claims 1-19 are examined.
Drawing Objections
The drawings are objected to because in Figures 5-17 illustrate white boxes without description.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
Rejections - 35 USC § 103
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.
Claims 1-6; 9-15; and 19-20 are rejected under 35 U.S.C. 103 as being unpatentable over Burr (US 4,696,156) in view of Glahn (US 2017/0335770) and further in view of Alagappan (US 2011/0100015).
Regarding Claim 1 and 6: Burr discloses a gas turbine engine (10; Fig. 1) for an aircraft (Col 1 L. 13), comprising: a combustor (50; Fig. 1); a primary fuel-oil heat exchanger (28; Fig. 1) arranged to receive fuel (fuel in 38; Fig. 1) and transfer heat from oil to the fuel (Col. 3 L. 25-33) so as to raise the fuel temperature to a desired temperature (the temperature of the fuel is heated and thus reaches a desired temperature) on entry to the combustor; a secondary fuel-oil heat exchanger (20; Fig. 1) arranged to receive the fuel and transfer heat from oil to the fuel (Col. 3 L. 25-33); a fuel recirculation line (52, 54, 56; Fig. 1) arranged to recirculate at least some fuel on a fuel flow path (path through 52, 54, 56; Fig. 1) from a first point (see annotated figure ‘156) on the fuel flow path to a second point (see annotated figure ‘156) on the fuel flow path, the second point being upstream of the first point (see annotated figure ‘156); and a modulator valve (40; Fig. 1) arranged to modulate the flow of fuel along the fuel recirculation line (Col. 5 l. 10-13), wherein the first point is downstream of the primary fuel-oil heat exchanger (see annotated figure ‘156), and the second point is upstream of the primary fuel-oil heat exchanger (see annotated figure ‘156) and upstream of an inlet (see annotated figure ‘156) to the secondary fuel-oil heat exchanger such that the inlet to the secondary fuel-oil heat exchanger is between the second point and the primary fuel-oil heat exchanger along the fuel flow path (see annotated figure ‘156).
Burr is silent regarding the first point being located downstream of an outlet of a line rejoining, from the secondary fuel-oil heat exchanger, the main flow path, i.e. the first point being located downstream of an outlet of a bypass line by passing the primary heat exchanger (see annotated figure ‘156).
However, Glahn teaches a gas turbine engine (20; Fig. 1) comprising: a primary fuel-oil heat exchanger (144; Fig. 2) arranged to receive fuel (fuel in 142; Fig. 2) and transfer heat from oil (see annotated figure ‘770) to the fuel (see annotated figure ‘770); a secondary fuel-oil heat exchanger (19; Fig. 2) arranged to receive the fuel and transfer heat from oil to the fuel (see annotated figure ‘770); a fuel recirculation line (14, or 15; fig. 2) arranged to recirculate at least some fuel on a fuel flow path (see annotated figure ‘770) from a first point (see annotated figure ‘770) on the fuel flow path to a second point (see annotated figure ‘770) on the fuel flow path, the second point being upstream of the first point (see annotated figure ‘770); and a modulator valve (16; Fig. 2) arranged to modulate the flow of fuel along the fuel recirculation line ( [0032]), wherein the first point is downstream of the primary fuel-oil heat exchanger (see annotated figure ‘770), and the second point is upstream of the primary fuel-oil heat exchanger (see annotated figure ‘770) and the first point is located downstream of an outlet (see annotated figure ‘770) of a bypass line (see annotated figure ‘770) bypassing the primary heat exchanger (see annotated figure ‘770), i.e. the first point is located downstream of an outlet of a line rejoining (line from 144 to 16), from the secondary fuel-oil heat exchanger, the main flow path (see annotated figure ‘770).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the invention of Burr, to have the first point being located downstream of an outlet of a bypass line bypassing the primary heat exchanger, i.e. the first point is located downstream of an outlet of a line rejoining, from the secondary fuel-oil heat exchanger, the main flow path, as taught by Glahn. Such a modification would enable to further control the amount of fuel passing through the primary heat exchanger, i.e the temperature of the fuel, as well as to have a supplementary/redundant bypass system in addition to the oil bypass system present in Burr.
Burr is silent regarding the desired temperature of the fuel being between 120°C and 180°C (for Claim 1), and between 140°C and 180°C (for Claim 6).
However, Alagappan teaches that fuel in a gas turbine engine (see title) can be heated to a desired temperature between 120°C and 180°C (for Claim 1), and between 140°C and 180°C (for Claim 6) before coking ([0022]).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the invention of Burr, to have the desired temperature of the fuel being between 120°C and 180°C (for Claim 1), and between 140°C and 180°C (for Claim 6). Such a modification would enable to heat the fuel as much as possible to maximize combustion efficiency, i.e. provide thermal energy, while avoiding coking, as recognized by Alagappan ([0022
PNG
media_image1.png
618
718
media_image1.png
Greyscale
PNG
media_image2.png
772
816
media_image2.png
Greyscale
Regarding Claim 2: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 1, as stated above, and Burr further discloses a fuel pump (44; fig. 1) on the fuel flow path, wherein the first point is downstream of the fuel pump and the second point is upstream of the fuel pump (see annotated figure ‘156).
Regarding Claim 3: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 2, as stated above, and Burr further discloses the fuel pump is downstream of the primary fuel-oil heat exchanger on the fuel flow path (see annotated figure ‘156).
Regarding Claim 4: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 1, as stated above, and Burr further discloses the fuel recirculation line is arranged to supply fuel to one or more additional aircraft and/or engine mechanisms (valve 62; Fig. 1).
Regarding Claim 5: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 4, as stated above, and Burr further discloses wherein the one or more additional mechanisms comprise one or more of a nacelle anti-icing system, actuators, bleed valves, heat management modulating valves (valve 62; Fig. 1, manage heat of the fuel).
Regarding Claims 9 and 15: Burr discloses a method (the disclosure of the apparatus discloses its method of operation) of operating a gas turbine engine (10; Fig. 1), the gas turbine engine comprising: a combustor (50; Fig. 1); a primary fuel-oil heat exchanger (28; Fig. 1) arranged to receive fuel (fuel in 38; Fig. 1) and transfer heat from oil to the fuel (Col. 3 L. 25-33) so as to raise the fuel temperature to a desired temperature on entry to the combustor (the temperature of the fuel is heated and thus reaches a desired temperature); a secondary fuel-oil heat exchanger (20; Fig. 1) arranged to receive the fuel and transfer heat from oil to the fuel (Col. 3 L. 25-33); a fuel recirculation line (52, 54, 56; Fig. 1) arranged to recirculate at least some fuel on a fuel flow path (path through 52, 54, 56; Fig. 1) from a first point (see annotated figure ‘156) on the fuel flow path to a second point (see annotated figure ‘156) on the fuel flow path, the second point being upstream of the first point (see annotated figure ‘156); and a modulator valve (40; Fig. 1) arranged to modulate the flow of fuel along the fuel recirculation line (Col. 5 l. 10-13), wherein the method comprises modulating the flow of fuel along the fuel recirculation line using the modulator valve (Col. 5 l. 10-13), and the first point is downstream of the primary fuel-oil heat exchanger, and the second point is upstream of the primary fuel-oil heat exchanger (see annotated figure ‘156) and upstream of an inlet to the secondary fuel-oil heat exchanger (see annotated figure ‘156) such that the inlet to the secondary fuel-oil heat exchanger is between the second point and the primary fuel-oil heat exchanger along the fuel flow path (see annotated figure ‘156).
Burr is silent regarding the first point being located downstream of an outlet of a line rejoining, from the secondary fuel-oil heat exchanger, the main flow path, i.e. the first point being located downstream of an outlet of a bypass line by passing the primary heat exchanger (see annotated figure ‘156).
However, Glahn teaches a gas turbine engine (20; Fig. 1) comprising: a primary fuel-oil heat exchanger (144; Fig. 2) arranged to receive fuel (fuel in 142; Fig. 2) and transfer heat from oil to the fuel (see annotated figure ‘770); a secondary fuel-oil heat exchanger (19; Fig. 2) arranged to receive the fuel and transfer heat from oil to the fuel (see annotated figure ‘770); a fuel recirculation line (14, or 15; fig. 2) arranged to recirculate at least some fuel on a fuel flow path (see annotated figure ‘770) from a first point (see annotated figure ‘770) on the fuel flow path to a second point (see annotated figure ‘770) on the fuel flow path, the second point being upstream of the first point (see annotated figure ‘770); and a modulator valve (16; Fig. 2) arranged to modulate the flow of fuel along the fuel recirculation line ( [0032]), wherein the first point is downstream of the primary fuel-oil heat exchanger (see annotated figure ‘770), and the second point is upstream of the primary fuel-oil heat exchanger (see annotated figure ‘770) and the first point is located downstream of an outlet (see annotated figure ‘770) of a bypass line (see annotated figure ‘770) bypassing the primary heat exchanger (see annotated figure ‘770), i.e. the first point is located downstream of an outlet (see annotated figure ‘770) of a line rejoining (line from 144 to 16),, from the secondary fuel-oil heat exchanger, the main flow path (see annotated figure ‘770).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the invention of Burr, to have the first point being located downstream of an outlet of a bypass line bypassing the primary heat exchanger, i.e. the first point is located downstream of an outlet of a line rejoining, from the secondary fuel-oil heat exchanger, the main flow path, as taught by Glahn. Such a modification would enable to further control the amount of fuel passing through the primary heat exchanger, i.e. the temperature of the fuel, as well as to have a supplementary/redundant bypass system in addition to the oil bypass system present in Burr.
Burr is silent regarding the desired temperature of the fuel being between 120°C and 180°C (for Claim 9), and between 140°C and 180°C (for Claim 15).
However, Alagappan teaches that fuel in a gas turbine engine (see title) can be heated to a desired temperature between 120°C and 180°C (for Claim 9), and between 140°C and 180°C (for Claim 15) before coking ([0022]).
It would have been prima facie obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the invention of Burr, to have the desired temperature of the fuel being between 120°C and 180°C (for Claim 9), and between 140°C and 180°C (for Claim 15). Such a modification would enable to heat the fuel as much as possible to maximize combustion efficiency while avoiding coking.
Regarding Claim 10: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and Burr further discloses modulating the flow of fuel along the fuel recirculation line, using the modulator valve (40 controls the fuel that goes in 52, Fig, 1), from the first point (see annotated figure ‘156).
Regarding Claim 11: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and Burr further discloses a fuel pump (44; Fig. 1) on the fuel flow path, wherein the method comprises modulating the flow of fuel along the fuel recirculation line, using the modulator valve (40 controls the fuel that goes in 52, Fig, 1), from the first point to the second point (see annotated figure ‘156), and the first point is downstream of the fuel pump (see annotated figure ‘156), and the second point is upstream of the fuel pump (see annotated figure ‘156).
Regarding Claim 12: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 11, as stated above, and Burr further discloses the fuel pump is downstream of the primary fuel-oil heat exchanger on the fuel flow path (see annotated figure ‘156).
Regarding Claim 13: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and Burr further discloses supplying fuel to one or more additional aircraft and/or engine mechanisms via the fuel recirculation line (valve 62; Fig. 1).
Regarding Claim 14: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 13, as stated above, and Burr further discloses wherein the one or more additional mechanisms comprise one or more of a nacelle anti-icing system, actuators, bleed valves, heat management modulating valves (valve 62; Fig. 1, manage heat of the fuel).
Regarding Claim 18: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 1, as stated above, and Burr further discloses wherein the fuel passing from the primary fuel-oil heat exchanger to the combustor does not pass through the secondary fuel-oil heat exchanger before entering the combustor (see Col. 4 L. 55-65 wherein some fuel, i.e. fuel corresponding to engine demand, from 28, i.e. primary heat exchanger, is not recycled via 52, and is directly sent to the combustor without passing through 20, i.e. the primary heat exchanger ), and Burr in view of Glahn further teaches the fuel passing from the secondary fuel-oil heat exchanger to the combustor does not pass through the primary fuel-oil heat exchanger before entering the combustor (see annotated figure ‘156 wherein the fuel in the by-pass of Glahn that passed through 28, i.e. secondary heat exchanger, does not passed through 20, i.e. primary heat exchanger).
Regarding Claim 19: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and Burr further discloses wherein the fuel passing from the primary fuel-oil heat exchanger to the combustor does not pass through the secondary fuel-oil heat exchanger before entering the combustor (see Col. 4 L. 55-65 wherein some fuel, i.e. fuel corresponding to engine demand, from 28, i.e. primary heat exchanger, is not recycled via 52, and is directly sent to the combustor without passing through 20, i.e. the primary heat exchanger ), and Burr in view of Glahn further teaches the fuel passing from the secondary fuel-oil heat exchanger to the combustor does not pass through the primary fuel-oil heat exchanger before entering the combustor (see annotated figure ‘156 wherein the fuel in the by-pass of Glahn that passed through 28, i.e. secondary heat exchanger, does not passed through 20, i.e. primary heat exchanger).
Claims 7-8, 16-17 are rejected under 35 U.S.C. 103 as being unpatentable over Burr (US 4,696,156) in view of Glahn (US 2017/0335770), Alagappan (US 2011/0100015), and further in view of Martin (US 5,118, 258).
Regarding Claim 7: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 1, as stated above, and Burr further discloses wherein the modulator valve is arranged to modulate the flow of fuel along the fuel recirculation line such that a ratio of fuel mass recirculated to fuel mass delivered to the combustor has certain value at cruise conditions (see valve 40, and Col. 6 L.18-27), but does not explicitly recite the value being between 0 and 9.
However, Martin teaches that typically in a gas turbine engine for aircraft a ratio of fuel mass recirculated to fuel mass delivered to the combustor is between 0 and 9 at cruise conditions (see Col. 1 L. 53-63)
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 valve of Burr to provide a ratio value between 0 and 9, as taught by Martin. Such modification would allow to have a constant speed pump that provide sufficient fuel flow during high power demand phases, e.g. take-off, and wherein excess of fuel flow during low power demand phases, e.g. taxiing, is sufficiently recycle to provide low power output, as recognized by Martin (Col. 1 L. 24).
Regarding Claim 8: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 1, as stated above, and further discloses wherein the modulator valve is arranged to modulate the flow of fuel along the fuel recirculation line such that a ratio of fuel mass recirculated to fuel mass delivered to the combustor has certain value at cruise conditions (see Col. 1 L. 53-63),
However, Martin teaches that typically in a gas turbine engine for aircraft a ratio of fuel mass recirculated to fuel mass delivered to the combustor is between 2.2 and 9 at cruise conditions (see Col. 1 L. 53-63).
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 valve of Burr to provide a ratio value between 2.2 and 9, as taught by Martin. Such modification would allow to have a constant speed pump that provide sufficient fuel flow during high power demand phases, e.g. take-off, and wherein excess of fuel flow during low power demand phases, e.g. taxiing, is sufficiently recycle to provide low power output, as recognized by Martin (Col. 1 L. 24).
Burr modified by Martin does not explicitly recites a ratio between 2.3 and 9.
However, it has been held that “where the claimed ranges or amounts do not overlap with the prior art but are merely close” a prima facie case of obviousness exists. Titanium Metals Corp. of America v. Banner, 778 F.2d 775, 783, 227 USPQ 773, 779 (Fed. Cir. 1985) MPEP 2144.05 I.
It would have been obvious to one skill in the art before the effective filing date of the claimed invention to have a ratio between 2.3 and 9, as the claimed the claimed ranges or amounts do not overlap with the prior art but are merely close.
Regarding Claim 16: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and further discloses modulating the flow of fuel along the fuel recirculation line such that a ratio of fuel mass recirculated to fuel mass delivered to the combustor has certain value at cruise conditions (see valve 40, and Col. 6 L.18-27), but does not explicitly recite the value being between 0 and 9.
However, Martin teaches that typically in a gas turbine engine for aircraft a ratio of fuel mass recirculated to fuel mass delivered to the combustor is between 0 and 9 at cruise conditions (see Col. 1 L. 53-63).
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 valve of Burr to provide a ratio value between 0 and 9, as taught by Martin. Such modification would allow to have a constant speed pump that provide sufficient fuel flow during high power demand phases, e.g. take-off, and wherein excess of fuel flow during low power demand phases, e.g. taxiing, is sufficiently recycle to provide low power output, as recognized by Martin (Col. 1 L. 24).
Regarding Claim 17: Burr in view of Glahn and Alagappan teaches all the limitations of Claim 9, as stated above, and further discloses modulating the flow of fuel along the fuel recirculation line such that a ratio of fuel mass recirculated to fuel mass delivered to the combustor has certain value at cruise conditions (see valve 40, and Col. 6 L.18-27), but does not explicitly recite the value being between 2.3 and 9.
However, Martin teaches that typically in a gas turbine engine for aircraft a ratio of fuel mass recirculated to fuel mass delivered to the combustor is between 2.2 and 9 at cruise conditions (see Col. 1 L. 53-63).
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 valve of Burr to provide a ratio value between 2.2 and 9, as taught by Martin. Such modification would allow to have a constant speed pump that provide sufficient fuel flow during high power demand phases, e.g. take-off, and wherein excess of fuel flow during low power demand phases, e.g. taxiing, is sufficiently recycle to provide low power output, as recognized by Martin (Col. 1 L. 24).
Burr modified by Martin does not explicitly recites a ratio between 2.3 and 9
However, it has been held that “where the claimed ranges or amounts do not overlap with the prior art but are merely close” a prima facie case of obviousness exists. Titanium Metals Corp. of America v. Banner, 778 F.2d 775, 783, 227 USPQ 773, 779 (Fed. Cir. 1985) MPEP 2144.05 I.
It would have been obvious to one skill in the art before the effective filing date of the claimed invention to have a ratio between 2.3 and 9, as the claimed the claimed ranges or amounts do not overlap with the prior art but are merely close.
Response to Arguments
Applicant’s arguments filed on 10/27/2025 have been considered but are moot because they do not apply to the current prior arts:
Pertinent Prior Art
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. Please see notice of references cited.
Conclusion
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 extension fee 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 date of this final action.
Contact Information
Any inquiry concerning this communication or earlier communications from the examiner should be directed to RODOLPHE ANDRE CHABREYRIE whose telephone number is (571)272-3482. The examiner can normally be reached on 8:30-18:30.
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 on (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 an application may be obtained from the Patent Application Information Retrieval (PAIR) system.
Status information for published applications may be obtained from either Private PAIR or Public PAIR.
Status information for unpublished applications is available through Private PAIR only. For more information about the PAIR system, see http://pair-direct.uspto.gov. Should you have questions on access to the Private PAIR system, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative or access to the automated information system, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/RODOLPHE ANDRE CHABREYRIE/Examiner, Art Unit 3741