# US 10,501,169 B2 · Propeller blade angle control system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,501,169 B2 - Document ID: US10501169B2 - Status: Granted - Kind: B2 - Application number: 15/185,539 - Filed: 2016-06-17 - Published: 2017-12-21 - Granted: 2019-12-10 - Earliest claimed: 2016-06-17 - Assignees: Pratt & Whitney Canada Corp. - Applicants: Pratt & Whitney Canada Corp. - Inventors: David Waddleton - Web page: https://patentgrep.com/patent/US10501169B2 ## CPC - F15B 21/0423: Cooling - B64C 11/38: fluid, e.g. hydraulic - B64C 11/385: {comprising feathering, braking or stopping systems} - B64C 27/64: using fluid pressure, e.g. having fluid power amplification - F04D 29/063: specially adapted for elastic fluid pumps - F04D 29/325: {for axial flow fans (blade mountings F04D29/34, blades F04D29/38)} - F04D 29/362: {during rotation} - F04D 29/582: {specially adapted for elastic fluid pumps} - F15B 2211/50536: using unloading valves controlling the supply pressure by diverting fluid to the return line - F15B 2211/611: Diverting circuits, e.g. for cooling or filtering - F15B 2211/62: Cooling or heating means - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - B64C: AEROPLANES; HELICOPTERS - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A control circuit for changing the angle of propeller blades includes a propeller control unit controlling a supply of oil to modify an angle of propeller blades, and a fixed-displacement pump providing the supply of oil from an engine oil return system to the propeller control unit. An oil cooling line extends between an outlet of the pump and the engine oil return system. The oil cooling line defines an oil leakage path leading to the engine oil return system for cooling the oil. A flow regulator between the pump and the propeller control unit is operable between an open position where oil is directed through the oil cooling line to the engine oil return system for cooling the oil, and a closed position blocking the oil cooling line and directing oil toward the propeller control unit to modify the angle of the propeller blades. ## Claims ### Claim 1 An oil system for a turboprop gas turbine engine adapted to drive a propeller of an aircraft, the propeller having a plurality of variable pitch propeller blades, the oil system comprising: an engine oil return system; and a propeller blade angle control circuit, comprising: a propeller control unit having a servo valve controlling a supply of oil output therefrom adapted to be used to modify a pitch angle of the propeller blades; a fixed-displacement pump located upstream of the propeller control unit and providing the supply of oil from the engine oil return system to the propeller control unit; an oil cooling line extending between an outlet of the pump and the engine oil return system to define an oil leakage path leading to the engine oil return system for cooling the oil; and a flow regulator between the pump and the servo valve, the flow regulator being fluidly connected to the oil cooling line and operable between an open position and a closed position, wherein in the open position the flow regulator directs oil through the oil cooling line along the oil leakage path to the engine oil return system for cooling the oil and in the closed position the flow regulator blocks the oil cooling line and directs oil toward the propeller control unit, in use, to modify the pitch angle of the propeller blades. ### Claim 2 (depends on 1) The oil system as defined in claim 1, wherein the flow regulator operates in the closed position during transient operation of the propeller control unit. ### Claim 3 (depends on 1) The oil system as defined in claim 1, wherein the flow regulator operates in the open position during steady-state operation of the propeller control unit. ### Claim 4 (depends on 1) The oil system as defined in claim 1, wherein the flow regulator includes a pressure regulator valve having a housing with an inlet aperture in fluid communication with the outlet of the pump and an outlet aperture in fluid communication with the oil leakage path leading to the engine oil return system, the pressure regulator valve having a spool disposed within the housing and displaceable relative to the housing to block and expose the inlet aperture. ### Claim 5 (depends on 4) The oil system as defined in claim 4, wherein the spool exposes the inlet aperture in the open position to direct oil through the outlet aperture along the oil leakage path leading to the engine oil return system. ### Claim 6 (depends on 4) The oil system as defined in claim 4, wherein the spool blocks the inlet aperture in the closed position to restrict access to the oil leakage path. ### Claim 7 (depends on 4) The oil system as defined in claim 4, wherein the housing includes a second outlet aperture in fluid communication with an inlet of the pump, the spool being displaceable to expose and block the second outlet aperture. ### Claim 8 (depends on 4) The oil system as defined in claim 4, wherein the pressure regulator valve includes a spill return line extending from the housing and in fluid communication with an inlet of the pump, the spool being displaceable to expose and block the spill return line, the spool exposing the spill return line in the open position to direct oil along the oil leakage path leading to the engine oil return system or toward the inlet of the pump. ### Claim 9 (depends on 8) The oil system as defined in claim 8, further comprising a check valve between the inlet of the pump and the spill return line, the check valve preventing oil from flowing from the inlet of the pump to the oil leakage path. ### Claim 10 (depends on 4) The oil system as defined in claim 4, wherein the spool includes a main spool and a pilot spool being displaceable relative to the main spool, the displacement of the pilot spool relative to the main spool providing access to the outlet aperture to direct oil through the outlet aperture along the oil leakage path leading to the engine oil return system. ### Claim 11 A method of supplying oil to a propeller blade angle control unit, comprising: pumping the oil at a constant flow rate to the propeller blade angle control unit; and controlling access of the pumped oil to an oil cooling leakage path extending from downstream of pumping the oil to an engine oil return system and upstream of a servo valve, including directing the oil along the oil cooling leakage path to the engine oil return system to cool the oil, and blocking access to the oil cooling leakage path to direct the oil toward the propeller blade angle control unit to modify an angle of propeller blades. ### Claim 12 (depends on 11) The method as defined in claim 11, wherein blocking access to the oil cooling leakage path includes blocking access to the oil cooling leakage path during transient operation of the propeller blade angle control unit. ### Claim 13 (depends on 11) The method as defined in claim 11, wherein directing the oil along the oil cooling leakage path includes directing the oil along the oil cooling leakage path during steady-state operation of the propeller blade angle control unit. ### Claim 14 (depends on 11) The method as defined in claim 11, wherein directing the oil along the oil cooling leakage path includes directing some of the oil upstream of pumping the oil. ### Claim 15 (depends on 11) The method as defined in claim 11, further comprising preventing oil upstream of pumping the oil from flowing along the oil cooling leakage path. ### Claim 16 A propeller blade angle control circuit, comprising: a propeller control unit having a servo valve controlling a supply of oil to modify an angle of propeller blades; a fixed-displacement pump located upstream of the propeller control unit and providing the supply of oil from an engine oil return system to the propeller control unit; an oil cooling line extending between an outlet of the pump and the engine oil return system to define an oil leakage path leading to the engine oil return system for cooling the oil; and a flow regulator between the pump and the servo valve, the flow regulator engaging the oil cooling line and operable between an open position directing oil through the oil cooling line along the oil leakage path to the engine oil return system for cooling the oil, and a closed position blocking the oil cooling line and directing oil toward the propeller control unit to modify the angle of the propeller blades. ### Claim 17 (depends on 16) The circuit as defined in claim 16, wherein the flow regulator operates in the closed position during transient operation of the propeller control unit, and wherein the flow regulator operates in the open position during steady-state operation of the propeller control unit. ### Claim 18 (depends on 16) The circuit as defined in claim 16, wherein the flow regulator includes a pressure regulator valve having a housing with an inlet aperture in fluid communication with the outlet of the pump and an outlet aperture in fluid communication with the oil leakage path leading to the engine oil return system, the pressure regulator valve having a spool disposed within the housing and displaceable relative to the housing to block and expose the inlet aperture. ### Claim 19 (depends on 18) The circuit as defined in claim 18, wherein the spool exposes the inlet aperture in the open position to direct oil through the outlet aperture along the oil leakage path leading to the engine oil return system, and wherein the spool blocks the inlet aperture in the closed position to restrict access to the oil leakage path. ### Claim 20 (depends on 18) The circuit as defined in claim 18, wherein the pressure regulator valve includes a spill return line extending from the housing and in fluid communication with an inlet of the pump, the spool being displaceable to expose and block the spill return line, the spool exposing the spill return line in the open position to direct oil along the oil leakage path leading to the engine oil return system or toward the inlet of the pump.