# US 8,784,057 B2 · Disc rotor retraction system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,784,057 B2 - Document ID: US8784057B2 - Status: Granted - Kind: B2 - Application number: 13/037,205 - Filed: 2011-02-28 - Published: 2012-08-30 - Granted: 2014-07-22 - Earliest claimed: 2011-02-28 - Assignees: The Boeing Company - Applicants: Daniel M. Podgurski - Inventors: Daniel M. Podgurski - Web page: https://patentgrep.com/patent/US8784057B2 ## CPC - B64C 27/32: Rotors - B64C 11/003: {Variable-diameter propellers; Mechanisms therefor} - B64C 27/00: Rotorcraft; Rotors peculiar thereto - B64C 27/30: with provision for reducing drag of inoperative rotor - B64C 27/46: Blades - B64C 27/467: Aerodynamic features - B64C 27/473: Constructional features - B64C: AEROPLANES; HELICOPTERS ## Abstract A disc rotor blade retraction system includes a main blade spar incorporating a hydraulic cylinder and having a screw thread. A ball screw is concentrically carried within the main blade spar and is operably connected to a ball nut which has an outboard end connected to an intermediate spar with a hydraulic piston received for reciprocation in the hydraulic cylinder. A first geared actuator engages the ball screw and a second geared actuator engages the main blade spar screw thread. A hydraulic fluid accumulator providing pressurized hydraulic fluid is connected to an outboard end of the hydraulic cylinder and a controller actuates the first and second geared actuators. ## Claims ### Claim 1 A disc rotor blade retraction system comprising: a main blade spar incorporating a hydraulic cylinder and having a screw thread; a ball screw concentrically carried within the main blade spar and operably carrying a ball nut having an outboard end connected to an intermediate spar and a hydraulic piston received for reciprocation in the hydraulic cylinder; a first geared actuator operably engaging the ball screw; a second geared actuator operably engaging the main blade spar screw thread; a hydraulic fluid accumulator connected to an outboard end of the hydraulic cylinder; and, a controller for actuation of the first and second geared actuators. ### Claim 2 (depends on 1) The disc rotor blade retraction system as defined in claim 1 further comprising a pitch control assembly concentrically engaging the main blade spar. ### Claim 3 (depends on 2) The disc rotor blade retraction system as defined in claim 2 wherein the pitch control assembly includes a ball sleeve engaging grooves in a ball spline on the main blade spar. ### Claim 4 (depends on 2) The disc rotor blade retraction system as defined in claim 2 wherein the pitch control assembly is mounted for rotation in a collar carried by a rotor hub. ### Claim 5 (depends on 1) The disc rotor blade retraction system as defined in claim 1 wherein the intermediate spar supports at least one outer aero panel. ### Claim 6 (depends on 5) The disc rotor blade retraction system as defined in claim 5 wherein the intermediate spar is connected at an outboard end to a tip aero panel telescopically receivable in a mid aero panel upon retraction. ### Claim 7 (depends on 6) The disc rotor blade retraction system as defined in claim 6 wherein said mid aero panel is retractable into a root aero panel supported by the main blade spar, said root aero panel retractable into a disc fairing. ### Claim 8 (depends on 1) The disc rotor blade retraction system as defined in claim 1 further comprising a fluid manifold incorporating a check valve intermediate the accumulator and hydraulic cylinder; a pressure relief valve intermediate the accumulator and hydraulic cylinder; and a solenoid valve selectively connecting the pressure relief valve to the hydraulic cylinder, said solenoid valve responsive to the controller. ### Claim 9 A disc rotor system comprising a plurality of rotor blades, each blade having a tip aero panel, a mid aero panel and a root aero panel, each blade having a retraction system supported by a rotor hub and incorporating a main blade spar carrying the root aero panel and incorporating a hydraulic cylinder, said main blade spar having a screw thread; a ball screw concentrically carried within the main blade spar operably carrying a ball nut having an outboard end connected to an intermediate spar carrying the mid aero panel and further connected to a hydraulic piston received for reciprocation in the hydraulic cylinder, said intermediate spar connected at an outboard end to the tip aero panel; a first geared actuator operably engaging the ball screw; a second geared actuator operably engaging the main blade spar screw thread; a hydraulic fluid accumulator connected to an outboard end of the hydraulic cylinder; a controller fir simultaneous actuation of the first and second geared actuators associated with each blade; and, a disc fairing supported by the rotor hub. ### Claim 10 (depends on 9) The disc rotor system as defined in claim 9 further comprising a pitch control assembly concentrically engaging the main blade spar. ### Claim 11 (depends on 10) The disc rotor system as defined in claim 10 wherein the pitch control assembly includes a ball sleeve engaging grooves in a ball spline on the main blade spar. ### Claim 12 (depends on 10) The disc rotor system as defined in claim 10 wherein the pitch control assembly is mounted for rotation in a collar carried by the rotor hub. ### Claim 13 (depends on 9) The disc rotor system as defined in claim 9 wherein the tip aero panel is telescopically receivable in the mid aero panel upon retraction. ### Claim 14 (depends on 13) The disc rotor system as defined in claim 13 wherein said mid aero panel is retractable into the root aero panel, said root aero panel retractable into the disc fairing. ### Claim 15 (depends on 9) The disc rotor system as defined in claim 9 wherein the retraction system for each blade further comprises a fluid manifold incorporating a check valve intermediate the accumulator and hydraulic cylinder; a pressure relief valve intermediate the accumulator and hydraulic cylinder; and a solenoid valve for selectively connecting the pressure relief valve to the hydraulic cylinder, said solenoid valve responsive to the controller. ### Claim 16 (depends on 15) The disc rotor system as defined in claim 15 wherein the accumulator and fluid manifold for each blade retraction system is mounted on a structural tray mounted to the hub within the disc fairing. ### Claim 17 A method for operation of a disc rotor blade comprising: commanding retraction of a plurality of blades; for each blade, setting a solenoid valve for flow through a check valve for hydraulic fluid to flow from an accumulator; providing power to a first geared actuator; rotating a ball screw responsive to the geared actuator and with the assistance of pressurized hydraulic fluid from the accumulator acting on a piston head, telescopically withdrawing a tip aero panel connected to a ball nut into a mid aero panel; withdrawing the nested tip and mid aero panels into a root aero panel; upon reaching a retraction limit of the ball nut on the ball screw, removing power from the geared actuator; providing power to a second geared actuator for each blade; and, rotating a nut with the second geared actuator, said nut acting on a thread on a main blade spar carrying the root aero panel to withdraw the main blade spar into a disc fairing. ### Claim 18 (depends on 17) The method of claim 17 wherein the main blade spar includes a grooved spline and the step of rotating a nut further comprises: withdrawing the main blade spar through a ball sleeve assembly; controlling pitch on each blade by input through pitch arms connected to each ball sleeve assembly to rotate the ball sleeve assembly and, through engagement of the ball sleeve assembly by the ball spline, rotate the main blade spar and blade. ### Claim 19 (depends on 17) The method of claim 17 further comprising: commanding extension of the blades; for each blade, providing power to the second geared actuator for counter rotation of the nut; extending the main blade spar by the thread to extend the root aero panel from the disc fairing; upon full extension of the root aero panel, positioning the solenoid valve for flow of hydraulic fluid through the regulator; providing power to the first gear actuator for counter rotation of the ball screw; extending the nested tip and mid panels from the root aero panel; by centrifugal force and power from the cleared actuator, pressurizing the hydraulic fluid for flow into the accumulator; upon reaching the extension limit of the ball nut, removing power from the first geared actuator. ### Claim 20 (depends on 17) The method of claim 17 further comprising applying a motor brake upon removing power front the geared actuator.