Patent GB-572909-A (GB)
Title: Improvements in and relating to helicopters
IPC: B64C27/54
Filed: 1943-09-15
Abstract: 572,909. Helicopters. PULLIN, C. G., and CIERVA AUTOGIRO CO., Ltd. Sept. 15, 1943, No. 15120. [Class 4] A helicopter of the kind which is controlled in flight by tilting the plane of the path swept by the tips of the rotor blades to obtain horizontal components of the lift, has means for varying the relationship between the blade tip path and the pilot's control member to enable a steady setting of said path to be maintained without a corresponding displacement of the pilot's control member which remains free to effect balancing movements of the rotor. The tilting of the blade tip path may be effected indirectly by a tiltable swashplate which causes cyclical variations of blade pitch, or by the direct tilting of an axle member upon which the rotor hub rotates. Such an axle member has a projection 106, Figs. 8 and 9, having a spherical bearing for a block 103 engaged by a spigot 101b on a block 101 secured to a sleeve 101a slidable and rotatable in bearings 95a in a casing 95. The sleeve is movable axially by a spindle 100 having a quick pitch thread 99 engaging a nut 200 which has an external thread 202 of coarser pitch engaging a nut having a sprocket wheel 207. The thread 99 is interrupted to engage splines 98 in a sleeve 97 on which a sprocket wheel 92 is mounted, and the thread 202 is interrupted to engage splines 204 in an end cap 203 of the casing 95. Consequently, rotation of either sprocket wheel causes axial movement of the spindle 100, the sprocket 92 causing the spindle to rotate and screw through the nut 200 which is held against rotation by the splines 204, and the sprocket 207, by screwing on the thread 202 causing axial movement of the nut 200. The sprocket 92 is connected by a chain 91 to gearing operated by fore-and-aft movements of the usual control lever and the sprocket 207 is connected by a chain 226 to an independent control lever near the pilot's seat. The sleeve 101a is rotated, to effect lateral movements of the projection 106, by a forked member 111 pivoted to the block 101 by a spindle 108, the lower end of the fork having a spherical bearing 112, Fig. 9, engaging a block 114 on a slidable rod 115 connected through a double thrustbearing 210 to a spindle 209 pinned to an extension 211. An interrupted thread on the extension 211 engages a nut 214 and splines on a sleeve 212, the latter being keyed to a sprocket wheel 213 operable by lateral movements of the pilot's control lever. The nut 212 has an external interrupted thread engaging splines 215 on a casing cap and an internal thread in the hub of a sprocket 217 movable by a hand wheel near the pilot's seat. The device is shown and described as applied to a tiltable rotor with articulated blades having means for changing their incidence as they move about their flapping axes as described in Specifications 567,989, 569,724 and 570,004. The screw devices described are irreversible, but as applied to a control column of the hanging type, the fulcrum on which the column is suspended may be slidably mounted to move in the fore-and-aft direction by a screw jack operated by a hand wheel to effect a steady setting, and to counteract the reaction on the control column it may be spring loaded, the tension of the spring being, adjusted simultaneously with the setting control. An adjustable spring loading may be provided in the irreversible type to relieve the load on the control connections.