GB497999A - Device for the hydraulic control of the blades of screw propellers, blowers and the like - Google Patents

Abstract

497,999. Fluid-pressure servomotorcontrol systems. ESCHER WYSS MASCHINENFABRIKEN AKT.-GES. June 2, 1938. No. 16569. Convention date, June 2, 1937. Addition to 496,022, [Group XXXIII]. [Class 135] [Also in Group XXXIII] Variable-pitch propellers according to the parent Specification, are modified in that the hydraulic locking device also controls the hydraulic actuating device. The fixed piston 9 and movable cylinder 5 of the hydraulic pitch-actuating apparatus has an exterior serrated surface 12 with which the locking member 21 is adapted to coact. The actuating gear is coupled by the pipes 7, 8, with a valve chest 36 containing a piston valve 33 which is coupled to a centrifugal governor 32. The locking bar 21 is actuated from the spring restrained piston 14, the cylinder of which is coupled by a pipe 25 with a gear wheel pump 27. From a locking cylinder 13 a pipe 26 passes to the valve chest 36 and from the delivery pipe 25 a further pipe 34 passes to this chest. In the pipe 34 is a three-way valve 35, and there is also a relief valve and pipe 37 and a return pipe 41. The valve chest 36 is similarly connected up with a return pipe 40 to the sump 28. In the position of the threeway valve 35 according to Fig. 3, liquid delivered from the pump 27 will, if the propeller is running at the normal number of revolutions, that is to say with the piston valve 33 in its central position, flow back through the pipe 40 into the tank 28. If the revolutions alter, the centrifugal governor 32 moves the piston but liquid cannot pass to the valve chest, so that there results a rise of pressure in the pipe 25 which raises the piston 14 and unlocks the locking gear 21. When the piston 14 has been raised sufficiently to uncover the lead to the pipe 26, liquid then passes through that pipe and, according to the position of the valve 33, to the appropriate pipe 7, or 8 to alter the pitch of the propeller. The alteration having brought the revolutions to normal, the governor returns the valve to its neutral position, and the locking device is brought into operation by the spring 16. If the locking gear 21 is to remain out of action, the threeway cock is brought into position as shown in Fig. 4. In the positions shown in Fig. 5, the adjusting means are cut out, and the locking bar is permanently engaged the propeller then acting as an ordinary fixed pitch propeller.