GB457808A - Improvements in or relating to control mechanism for propellers or the like - Google Patents

Abstract

457,808. Screw propellers. UNITED AIRCRAFT CORPORATION, 400, South Main Street, East Hartford, Connecticut, U.S.A.-(Assignees of Caldwell, F. W., and Martin, E.) June 6, 1935, No. 16464. Convention date, June 6, 1934. [Class 114] [See also Groups XXVI and XXIX] Mechanism for controlling the speed of a rotating body or engine comprises a control mechanism actuated bv difference of speed of a device driven at constant speed and a device actuated by the rotating body is utilised for changing the pitch of a screw propeller driven by the engine or rotating body. The blades of the screw propeller are connected to one element of a hydraulic mechanism which is supplied with oil under pressure and is controlled by a valve. This control is applied automatically by means of a constant speed electric motor 60 driving a cam disc 58 disposed opposite a cam disc 56 on one end of the control valve 38 whilst at the other end is a cam disc 48 beside a cam disc 52 on a shaft 54 driven from the engine. The two discs 58 and 52 are inwardly urged by springs 66. When the electric motor 60 and the shaft 54 are running at equal speeds the control valve 38 rotates with them but remains centrally disposed with regard to its inlet and outlet ports. When the speeds differ one of the cam members attempts to over-ride the other and so force the valve to right or left and establishes communication between the ports whereby oil is passed to the hydraulic mechanism and the blade is adjusted. In an alternative arrangement two shafts 70, 72, running at speeds represented by a constant-speed reference motor and the driven engine, carry bevel wheels 74, 75 meshing with a free bevel 76 carried by a casing 78 under restraint of a brake 80, the brake 80 being linked directly with the control valve 36. When there is a difference of speed between the two shafts 70, 72 there is a resultant motion of the brake 80 and piston valve 36 which affects the change of pitch as above. In a modification the brake casing carries a projection 84 adapted to contact with a disc 86 on an extension of the valve spindle which is normally retained in the neutral position by springs 90, 92. Specification 416,255 is referred to.