Patent GB-563008-A (GB)
Title: Controllable pitch propeller
IPC: B64C11/30
Filed: 1941-12-12
Abstract: 563,008. Fluid-pressure servomotors. HOOVER, W. S. Dec. 12, 1941, No. 16069. [Class 135] [Also in Group XXXIII] In a variable pitch propeller in which an hydraulic motor for adjusting the pitch of the blades, is supplied with low pressure fluid for normal pitch adjustments and high pressure fluid for feathering and reversing, both fluids being controlled by a governor-actuated valve having a manually adjustable spring, the manual control is adapted, in certain positions, to start an electric motor to drive a pump for supplying the high pressure fluid. Fig. 8 shows diagrammatically, the arrangement adjusted for feathering the blades in which high pressure fluid from the electrically driven pump 55, Figs. 8 and 10, passes from a source 57, e.g. the engine lubricating system, through the control valve 26 and passage 58 to a vane motor 49 comprising fixed vanes 51 and movable vanes 50, the motor exhausting through passage 59. The valve is moved to the position shown by manual control of a hand lever 38, the governor weights 8b, 8c which normally control the valve being inactive. For unfeathering, the valve is moved to its opposite extreme position by the hand lever, the pressure fluid passing to the motor through the passage 59 and exhausting through the passage 58. For ordinary pitch control, the hand lever is set to a middle position in which the governor 8b, 8c controls the movements of the valve, the pump 55 being inactive and low pressure fluid being supplied by an enginedriven pump 12, 13 from the lubricating system. The valve 26 is shown in Fig. 1. A pump casing 2, valve casing, and governor casing 3 are secured together and mounted on the engine housing so that a central shaft 6 carrying the governor weights 8b, 8c is driven by a spline 7 from the engine. The shaft 6 carries one member 12 of the low pressure gear pump, the other member 13 being supported in the parts 1, 2. From an arcuate passage 42a in communication with the engine lubricating oil system, two passages lead to opposite sides of the gear 12 and to a pump delivery chamber 40. According to the direction in which the shaft 6 is driven, the outer end of one passage and the inner end of the other passage are closed by plugs. The valve 26 is mounted within the shaft 6 and is moved axially in one direction by the weights 8b, 8c and in the opposite direction by a spring 29, the pressure of which is adjusted by a sleeve 30 actuated by a rack 34 and a pinion 35 connected by suitable linkage to the hand control lever 38, The upper part of Fig. 1 shows the spring 29 expanded and the lower part shows it compressed. A non-return valve 43 controls the pressure in the chamber 40 which communicates with the annular passage 41 round the valve 26. Upon movement of the valve in either direction, fluid passes from the passage 41 to either of two passages 47, 48 leading to the passages 59, 58. The exhaust takes place through the shaft 6. The motor driving the high pressure pump 55 is started automatically by a contact 64 or 65 closed by the hand lever 38 at either extreme position and may be stopped by the opening of a switch 55b by the hydraulic pressure generated in the system.