Patent GB-599990-A (GB)
Title: Improvements in helicopters
IPC: B64C27/82
Filed: 1945-09-27
Abstract: 599,990. Rotary-wing aircraft; screw propellers. CIERVA AUTOGIRO CO., Ltd., PULLIN, C. G., and SHAPIRO, J. S. Sept. 27, 1945, Nos. 25067 and 25068. [Classes 4 and 114] A helicopter comprises a lifting rotor with means for controllably inclining the lift vector in the pitching plane, and an auxiliary rotor producing a horizontal thrust having means for controllably varying the magnitude and direction of its thrust enabling it to be used for balancing the torque reaction of the lifting rotor and to assist forward propulsion, the control means of the auxiliary rotor and the pitching control means of the lifting rotor being so interconnected that the thrust of the auxiliary rotor, or its propulsive component, is increased progressively as the pitching control member is displaced in the direction for increasing forward speed, at least in respect of a part of the displacement range of the control member lying between a position intermediate the limits of its travel and the limit of its travel in the said direction. In one form, Figs. 1, la; 1b and 2, the main rotor shaft 22 is driven through gearboxes 19, 21 and a shaft 20 from an engine 18 which also drives an auxiliary rotor 38 through a gearbox a clutch 34, shaft 35, gearbox 36, a universally-jointed shaft 37 and bevel gearing 37, 48, Fig. 2. The main rotor blades 24 are mounted for pitch change in sockets con-. nected by flapping and drag hinges to the hub 23, and adjustments of the mean pitch of the blades and cyclical variations of the pitch of individual blades are effected by a swashplate mechanism of the usual type. Vertical movement of the swashplate is controlled by a handwheel 118, and fore and aft and lateral tilting of the plate by fore- and - aft and lateral movements respectively of a control slide 25 transmitted by links and bellcrank levers. The auxiliary rotor is mounted between fairings 56, 57 in a duct 39 rotatable about a vertical axis in the aircraft structure, and comprises blades 38 mounted for pitch change in a dished plate 46 secured to the driven shaft 45. The blade shanks 49 carry bevel pinions 50 meshing with a crown wheel 51 having internally-projecting pins 55 engaging helical slots 54 in an axially-movable shaft 52 splined on the shaft 45. Movement of the shaft to rotate the gears and change the blade pitch is effected by a fork 60 engaging a thrust collar 59 and coupled by a rod 65 to a vertically-movable collar 66, the movement of which is controlled by an arm 68 secured to a pulley 69 engaged by an endless cable 71 which also engages one member of a double pulley 78, Fig. 1. The other member of the pulley is engaged by an endless cable 79, Figs. 1a and 1b, which passes around a pulley 119 operated by the planet carrier of a differential gear (not shown), one side of which is connected to a lever 88 and the other to a pulley 137 engaged by an endless cable 136. The lever 88 is coupled by a link 87 to the third arm 81b of a bell-crank lever 81, 81a, 81b in the linkage transmitting fore-and-aft movement of the control stick 25, and the cable 136 engages a pulley 135 actuated by a lever 134 coupled to a rod 133, the lower end of which carries a pin engaging a slotted bar 131 secured to a lever 130 operated by the rudder pedals 126, 137. The orientation of the duct 39 and auxiliary rotor is controlled by a sprocket 74 engaged by a chain connected. to an endless cable 75, Figs. 1 and 1b, which passes around a pulley 120 operated differentially in a similar manner to the pulley 119 by a pulley 121 and lever 122. The pulley 121 is connected by an endless cable to a pulley 124 rotatable by a hand lever 125, and the lever 122 is coupled to a rod 132 carrying at its lower end a pin engaging the bar 131. The rods 132 and 133 are connected by links 138 and 139 to the lever 125. If the auxiliary rotor axis has been inclined in the fore-and-aft direction and the control stick 25 is in its rear position (hovering flight) with the arm 81b of the bell-crank lever vertical, initial forward movement of the stick produces a substantial movement of the link 82 to incline the main rotor lift vector but little or no movement of the link 87 to increase the auxiliary rotor pitch. As the stick is moved forward, the ratio of swash-plate displacement to control stick displacement decreases progressively and the ratio of auxiliary rotor pitch change to control stick displacement increases progressively so that in the high speed range the increase in forward speed as the result of a forward movement of the stick is mainly due to the increase in auxiliary rotor thrust. With the lever 125 to the rear and the auxiliary rotor axis in a transverse position, control in yaw is effected by operation of the rudder pedals to cause movement of the rod 133 and vary the auxiliary rotor pitch, the rod 132 being unaffected. If the lever 125 is moved forwardly to incline the auxiliary rotor axis forwardly, the rods are moved to the dotted line position and, due to the shape of the slot in the bar 131, the rod 133 is moved upwardly to increase the auxiliary rotor pitch sufficiently to ensure that its thrust is positive when operating in the increased velocity air stream. Control in yaw is now effected by operation of the rudder pedals to cause movement of the rod 132 to vary the orientation of the auxiliary rotor axis, the rod 133 being unaffected. In a modification, the arms 81a, 81b of the bell crank lever are replaced by a slotted cam plate. In a second form, the auxiliary rotor 38 is replaced by a rotor of the paddle wheel type mounted for rotation about a vertical axis and having blades oscillatable once per revolution about spanwise axes to produce a thrust perpendicular to the axis of rotation, the magnitude and direction of the thrust being varied by respectively varying the amplitude and phase of the oscillation. As shown in Figs. 11 and 13, the blades 145 are rotatable in a rim 146 connected by wire spokes 147 to hubs 148, 148a, and are secured to radial rods 151 slidable in ball members 156 pivotally mounted on an inner shell 158. The latter is connected to the hub by an Oldham coupling comprising an intermediate slotted plate 166, and is located by a fixed plate 160 connected to a further fixed plate 155 by an Oldham coupling comprising an intermediate slotted plate 161. The amplitude and phase of the blade oscillations are varied by eccentring the shell 158, and for this purpose the intermediate plate 161 is movable in the fore-and-aft direction by cables 171, 172 coupled to the rudder pedals, and the plate 160 is movable transversely by cables 79a, 79b coupled to a pulley 119 (see Fig. 11a, not shown), which is actuated directly by the lever 88 previously described. According to the first Provisional Specification, the pitch control mechanism of an auxiliary rotor of the screw propeller type enclosed in a duct is connected with the mechanism controlling the mean pitch of the main rotor or a fore-and-aft trimming control, and the inclination of the auxiliary rotor axis is normally controlled by the rudder pedals but may also be controlled by a hand lever, operating through the cable system connecting the rudder pedals and auxiliary rotor. The mounting of the auxiliary rotor may include a horizontal pivot so that the rotor may be inclined to give a vertical thrust component for trimming purposes. According to the second Provisional Specification the control mechanism for varying the fore-and-aft thrust component of an auxiliary rotor of the paddle wheel type is connected with the mechanism for varying the mean pitch of the main rotor or a fore-and-aft trimming control. Specification 572,417 is referred to in the first Provisional Specification.