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A propeller control system provides for actuation through supply pressure only. A transfer bearing thereby requires only a single land. The supply pressure is metered at a pitch change valve within the rotating propeller shaft downstream of the transfer bearing to provide hydraulic pressure for actu

A propeller control system provides for actuation through supply pressure only. A transfer bearing thereby requires only a single land. The supply pressure is metered at a pitch change valve within the rotating propeller shaft downstream of the transfer bearing to provide hydraulic pressure for actuation and control. A feather override mode is provided by energizing a feathering solenoid. The increased supply pressure changes the hydraulic force balance of the pitch change valve to allow the increased supply pressure into a Coarse Pitch chamber and simultaneously allow fluid within the Fine Pitch chamber to flow to drain pressure. The flow to drain changes the hydraulic balance on the Pitch Change Actuator Piston to drive a pitch link attached to each propeller blade and thereby change the pitch thereof towards coarse pitch.

대표청구항 ▼

1. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in r

1. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;a pitch change motor which rotates a pitch lock screw to axially adjust said pitch change valve; anda transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance. 2. The propeller control system as recited in claim 1, further comprising a feathering solenoid in communication with a main pump and said transfer bearing. 3. The propeller control system as recited in claim 2, further comprising a controller in communication with said feathering solenoid, said controller operable to actuate and deactivate said feathering solenoid. 4. The propeller control system as recited in claim 3, wherein actuation of said feathering solenoid increases said supply pressure. 5. The propeller control system as recited in claim 4, wherein said pitch change valve comprises a feathering valve movable relative to a pitch change valve spool, said feathering valve movable relative to said pitch change valve spool in response to said increase in said supply pressure. 6. The propeller control system as recited in claim 5, wherein actuation of said feathering valve upsets said hydraulic balance of said pitch change valve and change the pitch of said plurality of propeller blades toward coarse pitch. 7. The propeller control system as recited in claim 1, wherein said supply pressure is metered into a first metered pressure within a pitch change signal chamber formed between a pitch change signal valve and a pitch change valve spool and into a second metered pressure within a feather override chamber formed between a feather actuating valve and said pitch change valve spool. 8. The propeller control system as recited in claim 1, further comprising a controller mounted within said rotational field. 9. The propeller control system as recited in claim 8, further comprising a linear variable differential transformer in communication with said controller. 10. The propeller control system as recited in claim 9, wherein said linear variable differential transformer identifies the pitch of the plurality of propeller blades through a mechanical linkage. 11. The propeller control system as recited in claim 10, wherein said mechanical linkage is attached to a pitch change actuating piston, said pitch change actuating piston movably mounted between a coarse pitch actuator chamber and a fine pitch actuator chamber. 12. The propeller control system as recited in claim 1, wherein said pitch change valve comprises a pitch change signal valve movable relative to a pitch change valve spool, said pitch lock screw operable to upset said hydraulic balance between said pitch change signal valve and said pitch change valve spool. 13. The propeller control system as recited in claim 1, wherein said pitch lock screw rotates within a threaded pitch nut mounted to a pitch change actuator piston such that said pitch lock screw and said threaded pitch nut axially slide in response to movement of the pitch change actuator piston. 14. The propeller control system as recited in claim 13, wherein said pitch change lock screw moves without rotation. 15. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change actuating piston between a coarse pitch actuator chamber and a fine pitch actuator chamber, said pitch change actuating piston movable along said first axis in r esponse to a differential pressure between said coarse pitch actuator chamber and a fine pitch actuator chamber, said pitch change actuating piston linked to said plurality of propeller blades to change the pitch thereof;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, movement of said pitch change valve operable to selectively communicate each of said coarse pitch actuator chamber and said fine pitch actuator chamber with either a supply pressure or a drain pressure;a transfer bearing comprising a single land for supplying said supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance; anda feathering solenoid in communication with said transfer bearing, actuation of said feathering solenoid operable to increase said supply pressure and upset said hydraulic balance such that said coarse pitch actuator chamber communicates with said supply pressure and said fine pitch actuator chamber communicates with said drain pressure to change the pitch of said plurality of propeller blades toward coarse pitch. 16. The propeller control system as recited in claim 15, wherein said pitch change valve comprises a pitch change valve sleeve, a pitch change valve spool, a pitch change signal valve, and a feather actuating valve, said pitch change valve spool movable relative said pitch change valve sleeve and said pitch change signal valve and said feather actuating valve movable relative said pitch change valve spool. 17. The propeller control system as recited in claim 16, wherein said supply pressure is metered into a first metered pressure within a pitch change signal chamber formed between said pitch change signal valve and said pitch change valve spool and into a second metered pressure within a feather override chamber formed between said feather actuating valve and said pitch change valve spool. 18. The propeller control system as recited in claim 16, further comprising a pitch lock screw adjacent said pitch change signal valve, rotation of said pitch lock screw operable to upset a metered pressure within a pitch change signal chamber formed between said pitch change signal valve and said pitch change valve spool and hydraulically drive said pitch change valve spool relative said pitch change valve sleeve. 19. The propeller control system as recited in claim 15, wherein said transfer bearing is mounted about said propeller shaft. 20. A method of controlling a propeller blade pitch comprising the steps of:(1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;(2) mechanically upsetting the hydraulic balance of the pitch change valve through rotation of a pitch lock screw and a pitch change motor to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator; and(3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof. 21. A method as recited in claim 20, further comprising the step of:supplying the fluid at a second supply pressure greater than the first supply pressure to upset the hydraulic balance of the pitch change valve to increase the first pressure and decrease the second pressure such that the pitch of the plurality of propeller blades move toward coarse pitch. 22. A method as recited in claim 20, further comprising the step of:self-nulling axial movement of the pitch change valve. 23. A method as recited in claim 20, further comprising the step of:selectively communicating each of the first pressure and the second pressure with the first supply pressure or a drain pressure in response to axially movement of the pitch change valve. 24. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;a transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance;a feathering solenoid in communication with a main pump and said transfer bearing; anda controller in communication with said feathering solenoid, said controller operable to actuate and deactivate said feathering solenoid to selectively increases said supply pressure. 25. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades; anda transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance, said supply pressure is metered into a first metered pressure within a pitch change signal chamber formed between a pitch change signal valve and a pitch change valve spool and into a second metered pressure within a feather override chamber formed between a feather actuating valve and said pitch change valve spool. 26. A propeller control system comprising:a propeller shaft which rotates about a first axis to drive a propeller hub and a plurality of propeller blades extending therefrom;a pitch change valve mounted along said first axis in a hydraulic balance, said pitch change valve movable along said axis in response to upset of said hydraulic balance, axial movement of said pitch change valve operable to change a pitch of said plurality of propeller blades;a transfer bearing comprising a single land for supplying a supply pressure from a stationary field to said pitch change valve within a rotational field, said supply pressure operable to maintain said hydraulic balance; anda controller mounted within said rotational field. 27. A method of controlling a propeller blade pitch comprising the steps of:(1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;(2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;(3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof; and(4) supplying the fluid at a second supply pressure greater than the first supply pressure to upset the hydraulic balance of the pitch change valve to increase the first pressure and decrease the second pressure such that the pitch of the plurality of propeller blades move toward coarse pitch. 28. A method of controlling a propeller blade pitch comprising the steps of:(1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;(2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pr essure within fine pitch actuator;(3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof; and(4) self-nulling axial movement of the pitch change valve. 29. A method of controlling a propeller blade pitch comprising the steps of:(1) supplying a fluid at a first supply pressure to a pitch change valve to maintain the pitch change valve in a hydraulic balance;(2) mechanically upsetting the hydraulic balance of the pitch change valve to axially move the pitch change valve and change a first pressure within a coarse pitch actuator chamber and a second pressure within fine pitch actuator;(3) axially moving a pitch change actuating piston in response to said step (2), said pitch change actuating piston linked to a plurality of propeller blades to change the pitch thereof; and(4) selectively communicating each of the first pressure and the second pressure with the first supply pressure or a drain pressure in response to axially movement of the pitch change valve.