GB710914A - A device for the regulation of the driving engine for variable pitch propellers - Google Patents

Abstract

710,914. Fluid-pressure servomotor-control systems. LIAAEN. N. J. March 13, 1952, No. 6586/52. Class 135. [Also in Group XXXIII] In a variable-pitch air or marine propeller whose pitch change is effected by a servomotor under manual and automatic control, the automatic control means are additional to the engine governor and are acted upon by the manual control means so as to bring the automatic control means into operation for certain predetermined ranges only of the total turning angle of the blades. The propeller has its pitch varied by a fluid pressure servomotor 3 whose control valve 6 is adjusted manually and automatically to maintain substantially constant load on the driving engine. A rod 12, connected to a manually operated indicator handle on the bridge of a ship, is coupled through links 11, 10, 9 with the control valve 6 to move the latter and control the pitch for ahead or astern motion. A collar 7 connected with the servomotor piston provides the follow-up movement. A stepped piston 14 having a bracket 13 supporting the link 11 opeiates in a cylinder 15 and a space 16 in the latter is supplied with pressure oil through a pipe 20 by a pump 18. A space 17 on the other side of the stepped part of the piston 14 communicates through a duct 21 with the pressure space 16 and also through a pipe 22 with a valve casing 23 containing a pair of lift valves 24, 25 operable by a lever 26. Stops 27, 28, which may be adjustable, are provided on the link or rod 10 for moving the lever 26 to open one or other of the valves 24, 25 and place the pipe 22 into communication through p'pes 29 or 30 respectively with the casing 32 of a slide valve 33. Manual movement of the rod 10 between the stops 27, 28 does not affect the lever 26 and the valves 24, 25, both being then closed, the piston 14 is held in its extreme right hand position by the pressure differential acting thereon. The slide valve 33 has two control edges 33a, 33b, controlling communication between the pipes 29, 30 respectively and an outlet port 31 leading to an oil reservoir 50. The valve 33 is operated by a governor 37 which also regulates the supply of fuel to engine or acts in synchronism with the engine fuel regulator. When either of the valves 24, 25 is opened by the extreme movement of the rod 10 for ahead or astern motion of the ship, the valve 33 controls the pressure in the space 17 and hence the position of the piston 14 which thereby adjusts the pitch according to the load on the engine. The loading of the governor spring 38 and the position of a screwed collar 34 in the linkage between the governor and the valve 33 are adjustable manually from the bridge. In another embodiment the governor 37 is disposed remote from the valve 33 and controls the latter through fluid-pressure relay. A mechanical or electrical servomotor may be used instead of the hydraulic servomotor. The automatic control means may also be operated under the influence of temperature or pressure dependent upon the load on the engine.