Patent GB-763585-A (GB)
Title: Improvements in or relating to helicopters
Inventor: VERHAGE GERARD FRANS
IPC: B64C27/30
Filed: 1952-07-28
Abstract: 763,585. Helicopters. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. July 28, 1952 [July 28, 1951], No. 19070/52. Class 4. [Also in Group XXIV] A helicopter having one or more rotors each with two or more blades is characterized in that the blades are connected to the hub by means of two or more skew elements loaded by tensile stress, fastened to the blades and hub by hinged or flexible connections, so that an increase in centrifugal force will produce a moment tending to increase the pitch of the blade, the centre of pressure lying rearwardly of, and the centre of gravity not lying rearwardly of the torsion axis of the connecting mechanism. In Fig. 3, the motor 16 drives shaft 33 by bevel gears 31 and 32, and the blade 22 is connected to the rotor hub 23 by the two rods 25, whose connections to the hub are in a vertical line, and those to the blade in a more nearly horizontal line. Increased rotor speed due to, e.g., a sudden drop in air density, results in increased centrifugal force, tending to straighten out the elements 25, and to twist the blade in a clockwise direction as seen from the hub. The blade flaps 45 are controlled through linkwork by the position of swash plate 37, having a ring 38 rotating on it with the rotor. Bodily movement of the swash plate by lever 29 effects collective pitch control, and a tilting movement, controlled by lever 30 which moves in two directions of right angles, only one set of connecting mechanism being shown, results in cyclic pitch control. Fig. 8 shows a development in which there are many connectors 81, forming substantially the generators of a hyperboloid of one sheet. A biasing spring 84 is provided, and the blades may flap about pivot 86. Fig. 9 shows an embodiment in which the connections of rods 92, 93, 94, 95 to the blades are in vertical line, and those to the hub are effected by joining them to rings 98, 102, and 104, sliding on the cross bar 97. Vertical displacement of rod 100 will shift rings 102 and 104 equally, by means of links 103 and 105, and the pitch of both blades will increase or decrease to the same extent. Tilting of ring 110 by handle 111 is conveyed to ring 112, rotating with the rotor, which in turn tilts ring 114 so that levers 115 and 116 move ring 98 off centre, back to the centre, off centre the other side, and back again in one revolution of the rotor, thus effecting cyclic pitch control. Fig. 10 shows a further embodiment, in which rods 133 and 131 are connected via fork 122 to the hub at one end, and are held apart by separators 145 at the other, where they are joined to a similar pair of rods 132 and 134, fastened to the blade. The separators 145 are prevented from collapsing by a steel wire 155 wound onto a pulley 156 fastened to the rotor blade, and having a weighted lever 159 secured to its axis. A further wire 147 provides a manual control. Increase in centrifugal force tends to move lever 159 so that more wire is wound onto pulley 156, widening the separation caused by links 145, and increasing the effect of the device. Rod 152 affords over-riding manual control.. The mechanism is covered by two cylinders 123 and 124 arranged with collars 125 and 126 so that they can slide and rotate with respect to each other. It is shown in the Specification that greatest efficiency is achieved when, as in Fig. 3, the line joining the connections to the hub and that joining the connections to the blade are at right angles. In Fig. 5 (not shown) is given a rotor blade construction in which the centre of pressure is at one quarter chord, and the leading edge is weighted to bring the centre of gravity to one fifth chord.