Patent GB-851694-A (GB)
Title: Improvements in or relating to fluid control apparatus for variable pitch propellers
IPC: B63H3/10
Filed: 1959-07-09
Abstract: 851,694. Variable pitch propeller control. WESTINGHOUSE AIR BRAKE CO. July 9, 1959 [July 9, 1958], No. 23610/59. Class 114. A control apparatus for modifying the pitch of a marine propeller comprises a load sensing means operable to provide via fluid under pressure a force proportional to the load on the engine, a means for providing a force corresponding to a desired engine speed, and a means responsive to a preponderance of the first force over the second to cause a reduction in the pitch of the propeller. A valve device 1 openable by a handle 2 to control pressures of fluid in a speed line 3, ahead line 4 and astern line 5 is connected to a supply pipe 19 which is also connected via a load-sensing valve device 9 and pipe 20 to a pitch modifying valve device 12, and is connected via a reducing valve 36 to supply a pipe 35 with fluid at a preselected pressure. The pipe 35 and speed line 3 are connected via a double check valve 34 and pipe 29 to the pitch modifying device 12. The ahead line 4 and astern line 5 control selector valve devices 10, 11 connecting pipes 27, 28 to a doublic-acting power cylinder 13, Fig. 2, for operating a piston 39, movement of which will move a lever 45 to raise or lower a valve element 51 projecting into the propeller shaft 53 which carries the blades 7 and is driven via reduction gear 52 and shaft 54 by the engine 6. The drawings show the handle 2, and hence the members of the apparatus, in neutral position so that the blades 7 are in flat pitch position. When handle 2 is moved upwards to an ahead position, ahead pipe 4 is charged from supply line 19, causing selector device 10 to connect a pipe 26 to pipe 27, the pipe 26 being in connection with the speed line 3. Pipe 28 remains connected to a pipe 25 leading to a pipe 31 which is connected by the valve device 12 to a vent pipe 30. If the handle 2 is then moved from the ahead position into an ahead speed zone for providing in speed line 3 fluid at a selected pressure for providing a desired speed of engine 6, pipe 29 is charged with fluid for biasing device 12 to normal position in which pipe 31 is connected to vent pipe 30, and fluid from speed line 3 flows via pipes 26, 27 to lower piston 39 and hence raise valve element 51 so that the latter allows hydraulic fluid from a source 73 entering passage 71 in said element to flow out of a radial port 74 into a port 80 in a surrounding valve element 56 and thence via a passage 82 in the propeller shaft to a chamber 62 below a piston 63, the chamber 64 above the piston being connected via a passage 83, port 81, chamber 75, and communication 76 in gear box 52 to a sump 77. The piston 63, which is connected to the propeller blades by a rod 66 and to the valve element 56 by a rod 65, is therefore raised, thereby increasing the pitch of the blades 7 and raising valve element 56 relative to the now stationary element 51 until the control valve 61, 56 assumes its closed position. The speed line 3 is connected to a speed-adjusting or actuating device 8 so that when the pressure in the speed line exceeds the force of a spring 15 the piston 14 of said device shifts to increase the bias of a spring 16 to cause a governor 17 to shift a rack 18 downwards and thus cause a fuel injection pump 18a to increase the fuel supply to the engine. Movement of the fuel rack 18 causes a cam 24 and follower 22 to depress the stem 21 of the loadsensing valve device 9 which is thus operated to supply fluid to pipe 20 at a pressure proportional to the engine load condition as denoted by the axial position of the fuel rack cam 24. When the pressure in pipe 20 exceeds that in pipe 29, i.e. exceeds the pre-selected pressure in pipe 35 or speed line pressure in line 3 (whichever is the higher), the pitch modifying valve device 12 will operate to connect pipe 31 to pipe 26 for causing fluid under pressure to flow to pipe 25 and thence via pipe 28 to a chamber under the piston 39. The pressure in this chamber builds up to decrease the pressure differential across the piston 39 until the piston moves slowly upwards, thereby lowering the valve element 51 to effect a reduction in the degree of ahead pitch of the blades. When the handle 2 is moved into an astern position, astern pipe 5 is charged from supply line 19, causing selector device 11 to connect pipe 26 to pipe 28, the pipe 27 being connected to pipe 25 and thus to pipe 31 and thence to vent 30. Movement of the handle into the astern speed zone will result in increase in astern pitch of the blades, the apparatus operating as explained above.