# US 10,767,568 B2 · Dual spool power extraction with superposition gearbox > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,767,568 B2 - Document ID: US10767568B2 - Status: Granted - Kind: B2 - Application number: 16/127,305 - Filed: 2018-09-11 - Published: 2020-03-12 - Granted: 2020-09-08 - Earliest claimed: 2018-09-11 - Assignees: Raytheon Technologies Corporation - Applicants: United Technologies Corporation - Inventors: Nicholas D. Leque; Joseph H. Polly - Web page: https://patentgrep.com/patent/US10767568B2 ## CPC - F02C 7/36: Power transmission arrangements between the different shafts of the gas turbine plant, or between the gas-turbine plant and the power user ({F02C3/107 - F02C3/13 and} F02C7/32 take precedence; couplings for transmitting rotation F16D; gearing in general F16H) - F01D 25/18: Lubricating arrangements (of machines or engines in general F01M) - F02C 7/268: Starting drives for the rotor {, acting directly on the rotor of the gas turbine to be started} - F02C 7/32: Arrangement, mounting, or driving, of auxiliaries - F05D 2260/4023: through a friction clutch - F05D 2260/4031: as in toothed gearing - F05D 2260/40311: of the epicyclical, planetary or differential type - H02K 7/108: with friction clutches - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract A turbofan engine according to an exemplary embodiment of this disclosure includes, among other possible things, a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine; a first tower shaft engaged to the first spool; a second tower shaft engaged to the second spool; a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears, wherein the second tower shaft is engaged to drive the sun gear; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the sun gear to the carrier; and an accessory gearbox driven by an output of the superposition gearbox. ## Claims ### Claim 1 A turbofan engine comprising: a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine; a first tower shaft engaged to the first spool; a second tower shaft engaged to the second spool; a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears, wherein the second tower shaft is engaged to drive the sun gear; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the sun gear to the carrier; and an accessory gearbox driven by an output of the superposition gearbox. ### Claim 2 (depends on 1) The turbofan engine as recited in claim 1, wherein the output of the superposition gearbox comprises a lay shaft coupled to the carrier. ### Claim 3 (depends on 1) The turbofan engine as recited in claim 1, wherein the first turbine comprises a low pressure turbine and the second turbine comprises a high pressure turbine. ### Claim 4 (depends on 1) The turbofan engine as recited in claim 1, wherein the first tower shaft and the second tower shaft are concentric about a common axis. ### Claim 5 (depends on 1) The turbofan engine as recited in claim 1, wherein the first tower shaft and the second tower shaft are disposed about different axes. ### Claim 6 (depends on 1) The turbofan engine as recited in claim 1, wherein the first clutch and the second clutch comprise one-way mechanical clutches. ### Claim 7 (depends on 1) The turbofan engine as recited in claim 1, wherein the first clutch couples the first tower shaft to the ring gear and the second tower shaft drives the sun gear in a first operating condition such that both the first tower shaft and the second tower shaft combine to drive the output. ### Claim 8 (depends on 2) The turbofan engine as recited in claim 2, wherein the second clutch couples the sun gear to the carrier and the lay shaft drives the carrier and thereby the second tower shaft and the second spool in a starting operating condition. ### Claim 9 (depends on 1) The turbofan engine as recited in claim 1, wherein the first clutch couples the first tower shaft to the ring gear and the ring gear drives the carrier to drive the output in a forward wind milling operating conditions. ### Claim 10 (depends on 1) The turbofan as recited in claim 1, wherein both the first clutch and the second clutch are disengaged in a rear wind milling operating condition such that rotation of either the first spool and the second spool is not communicated to the output. ### Claim 11 (depends on 1) The turbofan as recited in claim 1, wherein the superposition gearbox is not fixed to a static structure of the engine. ### Claim 12 An auxiliary gearbox drive system for a turbofan engine, the auxiliary gearbox comprising: a sun gear, wherein the sun gear is configured to be coupled to a second tower shaft of the turbofan engine; a plurality of intermediate gears engaged to the sun gear and supported in a carrier; a ring gear circumscribing the intermediate gears; a first means for selectively coupling the ring gear to a first tower shaft of the turbofan engine; a second means for selectively coupling the sun gear to the carrier; and an output to an auxiliary gearbox. ### Claim 13 (depends on 12) The auxiliary gearbox as recited in claim 12, wherein the output comprises a lay shaft coupled to the carrier. ### Claim 14 (depends on 12) The auxiliary gearbox as recited in claim 12, wherein both the first means for selectively coupling the ring gear to the first tower shaft and the second means for selectively coupling the sun gear to the carrier comprise a one-way mechanical clutch. ### Claim 15 (depends on 12) The auxiliary gearbox as recited in claim 12, wherein the first means couples the first tower shaft to the ring gear and the second tower shaft drives the sun gear in a first operating condition such that both the first tower shaft and the second tower shaft combine to drive the output. ### Claim 16 (depends on 13) The auxiliary gearbox as recited in claim 13, wherein the second means couples the sun gear to the carrier and the lay shaft drives the carrier and thereby the second tower shaft and a high speed spool in a starting operating condition. ### Claim 17 A method of operating an auxiliary gearbox for a turbofan engine comprising: coupling a first tower shaft to engage a first spool; coupling a second tower shaft to engage a second spool; coupling a sun gear of a superposition gearbox to the second tower shaft, wherein the superposition gearbox includes the sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears; and selectively coupling the first tower shaft to the ring gear and/or the sun gear to the carrier to generate a driving output to an accessory gearbox or a driving input to the second tower shaft. ### Claim 18 (depends on 17) The method as recited in claim 17, including coupling the first tower shaft to the ring gear such that the first tower shaft drives the ring gear and the second tower shaft drives the sun gear in a first operating condition such that both the first tower shaft and the second tower shaft combine to drive the output. ### Claim 19 (depends on 17) The method as recited in claim 17, including coupling the sun gear to the carrier and driving the carrier and thereby the second tower shaft and the second spool in a starting operating condition. ### Claim 20 (depends on 17) The method as recited in claim 17, including coupling the first tower shaft to the ring gear such that the ring gear drives the carrier to drive the output in a forward wind milling operating conditions. ### Claim 21 (depends on 17) The method as recited in claim 17, including decoupling both the first tower shaft from the ring gear and the sun gear from the carrier in a rear wind milling operating condition such that rotation of either the first spool and the second spool is not communicated to the output.