Patent GB-474681-A (GB)
Title: Improvements in and relating to aircraft with autorotative sustaining rotors
IPC: B64C27/02
Filed: 1936-05-04
Abstract: 474,681. Aircraft with rotary wing systems. JOSSELYN, J., and BLAKE, R., [Representatives of LA CIERVA, J. DE]. May 4, 1936, No. 12619. [Class 4] In an aircraft having a normally auto-rotative sustaining rotor, the blades of which are articulated for variation of blade pitch angle, the rotor is driven in such a manner that the driving force exercises a positive pitch-decreasing moment about the axis of a pivot on which pitch-angle varying-movements take place. Each rotor blade may be connected to the hub by pivotal mechanism allowing movement about at least two real or virtual axes, the relative disposition of the axes and stops for limiting movement thereabout being such that when the hub is driven, the pitch angle of the blade is substantially less than when the hub is running idle. In one form the aircraft includes a tractor airscrew A driven from an engine from which initiation of rotation of the rotor 32 is effected through shafting S<1>, S<2> and gearing and clutch G. The rotor is mounted for universal movement, on operation of a hand lever C universally mounted on the rotor pylon P and universally connected to the rotor head, on a central mast 31. A member 34 is mounted on trunnions 33b on a member 33 mounted on trunnions 33a. A member 44 is journalled on the member 34 and supports a common flapping pivot 46 for drag links 47 in which the blades 32 are journalled as shown. The swan-necked elements 51 of each blade are provided with arms 56, 66. On the member 44 is mounted a member 57 which carries a pinion wheel 42, relative movement between the wheel 42 and the member 57 being limited by pins 60 which move in slots 61 against the action of centralizing-springs. The pinion wheel 42 has an extension 59 which acts as a brake drum and carries stops 64, 65. The pinion is driven through a pinion 41 from the shaft S<2>. Movement of the blade about the drag pivot 50 is limited by adjustable stops. During speeding up of the rotor, the pinion 42 leads the hub element 44 and the projection 64 engages a lever 55, journalled in the member 48 about an axis parallel to the axis of the drag pivot, to rotate the blade about the drag pivot and hold it in its position of minimum pitch against the leading stop. On cessation of the driving torque the blades rotate on the drag pivots to about their mean radial position. When the brake is applied to the drum 59, the pinion 42 lags relatively to the blades and a stop 65 engages the arm 66. The lever 55 is provided with an adjustable stud. In a modification, the lever 55 is mounted on the member 44. In another form, the shaft S<1> is omitted, the rotor head being mounted in a gimbal ring 70 carried by the pylon structure. The rotor blades are connected by swan-necked elements 51x and inclined drag pivots 50x to drag links 47x mounted as shown on flapping pivots 46x carried by a member 44o integral with the shaft 44x connected with a concentric shaft 73 by a spring 76 and splines allowing about 25‹ of freedom. The shaft 73 carries a pinion 42x and the two concentric shafts are journalled in a member 36x provided with a rotor tilting lever C<3> and carrying a pinion 41x adapted to gear with the pinion 42x to initiate rotation of the rotor. Lugs 77 having spherical contact portions are mounted on the shaft 73 and are adapted to co-operate with lugs 56x on the members 51x such that, during the application of the driving torque, the blades are rotated about the drag pivots with a consequent decrease of pitch angle. On application of a braking torque to the pinion 42x, the blades will lead on the members 36x and will again rotate on the drag pivots into a position of minimum pitch. In a modification, additional pivots are added in order to relieve bending moments on the blades. In a still further form, use is made by selective positioning of the additional pivot to obtain the necessary movements about the pivots, e.g. the axis of the additional pivot 150 is situated parallel to the axis of rotation and intermediate the axis of rotation and the point of intersection of the blade axis and the axis of the drag pivot. When the drag link 47 is driven in the direction of the arrow in Fig. 21, the blade lags on the pivot 150 until the stop 152 is engaged. This lagging gives rise to, as shown, an anti-clockwise couple about the drag pivot which causes a rotation of the drag pivot in an anti-clockwise direction, with a consequent decrease of blade pitch, until the stop 53 is engaged. On cessation of the driving torque, the blade rotates on the pivot 150 and holds itself against the stop 153, Fig. 19. Consequent upon the leading displacement of the blade the arm of the couple is reduced until the line of action of the centrifugal force passes to the leading side of the axis of the drag pivot, when a clockwise couple is produced causing clockwise rotation of the drag pivot with increase in blade pitch until the stop 52 is reached. In order to prevent snatching on the pivots an inward extension of the arm carrying the rotor blade may be adapted to fulcrum on a rearwardly directed projection provided on the leading arm of the drag link 47. In a still further form, the blade arm 51 carries a pivot pin 51x upwardly and outwardly directed and journalled on a link 50x journalled on a downwardly and outwardly directed pivot 50 which is mounted in the member 47 formed with a stop 154 having a surface 155 concentric with the pivot 50 and a surface 156 concentric with the pivot 51x when the link 50x rests against a stop 52. The pivot 51x carries a stop 157 having surfaces 158, 159 adapted to co-operate respectively with the surfaces 156, 155 when the arm 51 rests against a stop 52x or when the link 50x rests against the stop 52. When the hub is driven the link 50x contacts stop 52 and movement about the pivot 50 is prevented. In flight, the arm 51 contacts stop 52x and movement about the pivot 51x is prevented. In this case the minimum blade pitch is preferably zero. In another form, a blade root 51, Fig. 26, is journalled for freedom about the blade axis in a member 160 in turn journalled about a vertical axis in the drag link 47. The drag link 47 is formed with stops 163, 164 and the root 51 with arms 165, 166. Cams 167, 169, 168, 170 are arranged as shown and ensure that, when the blade lags or leads from its mean radial position, its pitch is reduced by movement respectively about the point of contact of stops 163, 165 and stops 164, 166.