Patent GB-781356-A (GB)
Title: Improvements in or relating to helicopters
IPC: B64C27/50
Filed: 1955-09-28
Abstract: 781,356. Folding helicopter rotor blades. UNITED AIRCRAFT CORPORATION. Sept. 28, 1955 [Oct. 1, 1954], No. 27616/55. Class 4. Each blade of a helicopter rotor is provided with hinge means about which the blade can be folded, means for locking said hinge means with the blade in flight position, and means responsive to the unlocking operation of said locking means to fold the blade. The hub comprises two spaced parallel plates 36, 38, Fig. 2, supporting each of five blades through a drag hinge 42 and flapping hinge 40, Fig. 5, mounting a link 44 having a spindle 95 on which the root of the blade is journalled for pitch change. The root 88 of each blade 27 is attached to a member 94 by bolts through co-operating flanges 90, 92. The member 94 is pivoted about a folding hinge 100 to a member 96, a flange 98 on which is bolted to a rotatable collar 46 having a horn 56 attached by vertical link 58 to an arm 60 on shaft 62 for pitch change. A further arm 68, Fig. 2, rigid with shift 62 is pivoted to a link 72 pivoted at its lower end to the rotating element 76 of a swashplate having a non- rotating element 78. Four lugs 84 are formed on the element 78, one being used for the attachment of a scissors linkage 80, and the other three for attachment to hydraulic servos for cyclic and collective pitch change in the normal manner, By using a large number of bolt holes in the flanges 90 and 92, and flange 98 and collar 46, the members 94 and 96 can be secured in any one of a number of angular positions, thus altering the inclination of hinge 100 to the vertical. The preferred arrangement is that blade 1, Fig. 3, is brought to rest in an aft-extending position, blades 2 and 5 are folded back through 72 degrees, their hinge pins being inclined by 3 degrees to raise them slightly, and blades 3 and 4 are folded back through 131 degrees, their hinge pins being inclined by 12 degrees to lower them. A member 77, Fig. 2, on the arm 64 engages an abutment 77<SP>1</SP> on the member 96 to take up the torque which results when the blade is folded. The pitch change collar 46 can be locked to a lug 48 on the arm 64 by a pin 52 operated by a hydraulic servo 54. In the locked position, the pin operates a sequence valve 150. A pin 106 operated by a hydraulic servo 114 is adapted to lock the members 94 and 96 together, and also operates a sequence valve 152 in the unlocked position. A toothed sector 136 is secured to member-94, and meshes with a rack operated by a hydraulic servo 145 on the member 94. Retraction of the piston rod folds the blade, and extension returns it to the flight position. In the flight position, the member 94 operates a sequence valve 154, Fig. 6. A drag movement damper 118 combined with a hydraulic servo 126 extends between the hub and a sleeve 116, Fig. 5, rotatably mounted on the flapping axes 40. The hydraulic operating system is shown in Fig. 6, and comprises a reservoir 158, a pump 156, a change-over valve 170, and rotating joints 163, 163a connecting conduits 165, 200 with distributors 160, 162 in the rotor hub. With the valve 170 in the position shown, and the blades folded back, fluid under pressure is supplied through conduit 200 and joint 163a to the distributor 162 and conduit 182. Piston 146 is moved to the right, fluid exhausting through valves 152, 150 and 148. The blade and member 94 are thus moved to the flight position, and member 94 opens the square valve 154, admitting fluid through conduits 202, 180 to the servo 115, moving piston 112 to the left, and locking the blades in the flight position by pins 108. Fluid exhaust through valves 150, 148. When the blade is fully locked, valve 138 is opened by piston 112, which admits fluid by conduits 178 and 176 to cylinder 54, moving piston 127 to the right and freeing the pitch change locking pin. The drag dashpot piston 121 functions normally, the left hand side of piston 130 being connected to fluid exhaust and the right hand to atmosphere. To fold the blades, the valve 170 is changed over, and fluid under pressure passes through conduit 165 and joint 163 to the distributor 160. Piston 130 moves to the right, extending the blade fully about its drag axis. This operates a valve 148, admitting fluid to the right hand side of cylinder 54, locking the pitch change mechanism and operating valve 150. This admits fluid to the left hand side of servo 115, withdrawing the fold locking pins 108, and operating valve 152. This finally admits fluid to servo 145, folding back the blades. The apparatus of Fig. 8 ensures that blade 1 is aft extending for folding. To fold the blades, the pilot closes switch 204, and makes contact 232. A relay 214 is energized, causing a hydraulic motor 220 to drive the rotor until a contact is made between elements 222 and 224. This operates relay 212 stopping the motor, and energizes relay 230, which energizes relay 234. This puts valve 170 in the blade folding position. For resuming the flight position the pilot closes switch 204, and makes contact 238, energizing relay 242 to put valve 170 in the blade extending position.