Patent GB-557435-A (GB)
Title: A hydraulically actuated device for adjusting the blades of variable-pitch propellers, especially airscrews
IPC: B64C11/30
Filed: 1942-07-15
Abstract: 557,435. Liquid-forcing apparatus. ESCHER WYSS MASCHINENFABRIKEN AKT.- GES. July 15, 1942, Nos. 9829 and 9830. Convention dates, July 21, 1941 and Oct. 2, 1941. [Class 102 (ii)] [Also in Group XXIX] A hydraulically actuated device for adjusting the blades of variable pitch propellers especially aircraft propellers is controlled by a speed governor within a normal pitch range but adjustment to braking and feathering positions beyond this range is only possible after an increase of hydraulic pressure has been brought about. To do this a storage vessel divided into two chambers by a displaceable member is controlled by a pilot's control in one position of which one chamber is filled with oil during the time the propeller is under automatic control while the other chamber is connected to atmosphere and in another position the first connection is interrupted and the second chamber is connected to an auxiliary pressure reservoir to put the oil under higher pressure for moving the propeller blades quickly beyond their normal range. In the form shown in the Figures the propeller blades 2 are adjusted by a double-acting moving cylinder 6 connected by conduits 7, 8 with pipes 9, 10 leading to ports 24, 26 of a multi-ported change-over valve 13. Ports 23, 27 of this valve are connected by ports 29, 30 to a speed governor actuated control valve 4, a port 28 is connected by a pipe 38 with the oil chamber 37 of the auxiliary reservoir, a port 22 us connected to an oil pump 31 and a port 25 is connected to an oil sump. In the position shown with the change-over valve is held in a mid-position by springs 56, 57 the pipes 33, 38 are connected to refill the auxiliary reservoir and the supply and exhaust of pressure oil to the cylinder 6 is under the control of the governor 4. A compressed air container 49 refilled by a compressor is connected by pipes 48, 51, 60 with three valves 41, 50, 59 selectively operated by a pilot's handle 62, cams 63, 64 and followers 65, 66, 67. the handle is also coupled by linkage 68 with the engine throttle 69 and the loading adjustment of the governor 4. These valves are fitted with shuttle lift valves 43, 44 normally held by springs 45 to close the conduits from the reservoir and connect the outlet conduits to atmosphere. When it is desired to move the blades into a braking position the handle 62 is moved to reverse the valves 41, 50 causing pressure to move a piston to rotate the valve 13. This interrupts the pump connection 33 and at the same time valve 41 admits compressed air to the chamber 36 of the reservoir 34 to put the oil in the other chamber 37 under higher pressure which is transmitted through pipes 38 and 9 to the cylinder 6. To put the blades in the feathered position the handle 62 is moved to reverse the valves 41, 59 which causes the valve 13 to be moved to the reverse extreme position admitting the higher oil pressure to the other end of the cylinder 6. In a modification the control is fitted with a shut-off valve adapted to close when the piston 35 has passed a predetermined position corresponding to the braking position of the blades to prevent wastage of oil by leakage Specification 541,839, [Group XXIX], is referred to. The Specification as open to inspection under Sect. 91 describes the modification shown in Fig. 17 (Cancelled). The Figure shows the device set for automatic adjustment of the pitch within the normal pitch range. In this position the right hand chamber 36 of the reservoir 34 is connected to atmosphere through a pipe 84 and passages 81<SP>1</SP> in a piston 80 and rack 81 while the left hand chamber 37 is connected to the oil pump by pipes 38, 38<SP>1</SP>. To move the propeller blades into the braking position the pilots handle 62 is moved to open the valve 50 and so connect the auxiliary pressure reservoir 49 through pipes 48, 51, 96 to the bottom of the valve chamber 88. This raises the valve member 86 and permits auxiliary pressure fluid to pass through pipe 97 and through the clearance between a differential piston 82 to act on a piston 80 to move it to its extreme left-hand position. This moves the change-over valve to the braking position and auxiliary pressure medium passes through pipe 84 to the chamber 34. As the propeller reaches the braking position the piston 35 uncovers a port 35<SP>1</SP> to admit pressure through a pipe 95 to move a valve to permit pressure to close a valve 71 and interrupt discharge of oil from the chamber 37. Operation of the valve 59 admits auxiliary pressure medium through pipes 48, 60, 89 to depress a valve 85 which allows pressure medium to pass by way of pipes 48, 98, 90 and 93 to the valve 94 which is thereby raised to permit the valve 71 to open. At the same time fluid passes through pipe 90 to act on the piston 80 to move it to its extreme righthand position. When the piston 35 uncovers a second port in the side of the auxiliary reservoir fluid passes through a pipe 92, raises the valve 85 to interrupt communication between pipes 98, 90 and lowers valve 86 to admit pressure through pipe 97 to the main cylinder where it acts differentially to restore the pistons 80, 82 to their mid-position shown on Fig. 17 (Cancelled). This subject-matter does not appear in the Specification as accepted.