Patent GB-506722-A (GB)
Title: Improvements in swivelling screw propellers
IPC: B64C27/41
Filed: 1937-08-30
Abstract: 506,722. Screw propellers ; stabilizing aircraft; universal joints. LOTH, W. A., and GUYOT, S. M. H. Aug. 30, 1937, No. 21213. [A Specification was laid open to inspection under Sect. 91 of the Acts, Jan. 2, 1939.] [Classes 4 and 114] [Also in Group XXIV] The mounting of a swivelling screw propeller for all uses, the axis of rotation of which can be freely displaced into any angular position relatively to the driving shaft within an imaginary cone whose apex coincides with the centre of the joint, is such that the ratio of the instantaneous speeds of the propeller and the driving shaft is maintained constant both in and during movements to all angular positions. Means for stabilizing aircraft are alsodescribed wherein, when the inclination of the propeller axis reaches the surface of the imaginary cone, a precession impulse is imparted to it compelling it to move round a portion of the conic surface to a position in which the propeller exerts a stabilizing torque. In Fig. 1, the rotor blades P secured to the outer element E1 of the universal joint are rotated about an initial axis Am by a pinion I on the driving shaft V. through gearing J, K, the inner element E2, and three caged balls B each lying in a pair of oppositely inclined grooves T1, T2 (e.g. loxodromics) in the surfaces of the elements. The balls thus remain in a plane bisecting the angle between the driving and driven shafts, and the instantaneous speed ratio remains constant when the outer element moves over the inner. The stabilizing mechanism comprises an annulus C1 driven by the inner element E2 through ring and planet gears U1, S, U2. A second annulus C2 is mounted within the outer element E on a bearing R3 and is friction-faced for engagement with annulus C1 on tilting of the rotor axis, the faces eventually locking together. Fig. 5 is a plan diagram of the rotor movements of a helicopter. The propeller axis at the point Am normally coincides with the driving axis V. Under the action of a squall the propeller is inclined and a point along its axis, after starting in the direction Am Ao, is by gyroscopic effect carried along the line A. If this line meets the cone surface as at A1, a precession impulse is imparted owing to the locking of the annuli C1, C2, whereby the rotor axis is carried from the position Am A1 to the position Am A2, at which point the propeller itself exerts a torque counterbalancing the squall, thus restoring the axis to the position Am and disengaging the annuli C1, C2. ro, r1, r2 indicate the positions of a blade of a non- driven rotor during these movements, showing that acceleration and deceleration forces are not produced. In a modification, Fig. 3 (not shown.), the clutch surface of the annulus C1 is movable thereon, being driven therefrom by balls in grooves, whereby the rotor axis may be set at an initial inclination to the driving shaft, this initial inclination now forming the axis of the imaginary cone. Specification 878/03, [Class 4], is referred to. In the Specification as open to inspection under Sect. 91, the problem is examined mathematically, and a variable pitch mechanism, which is not fully described, is shown. This subject-matter does not appear in the Specification as accepted.