Patent GB-519622-A (GB)
Title: Improvements in or relating to variable pitch aerial propellors
IPC: B64C11/30
Filed: 1938-07-29
Abstract: 519,622. Screw propellers. WASEIGE, C. R. July 29, 1938, No. 22571. Convention date, July 29, 1937. [Class 114] Apparatus for varying the pitch of tandem propellers includes at least two sets of planet gears, one of which is located between the propeller and the adjusting mechanism which is driven off the engine driving gear and all the gearing is disposed outside the shafting. Tandem propellers A, B, Fig. 1, are mounted upon concentric shafts 72, 73 respectively and have blades with the circular racks 5 at their roots which engage sliding rack members 7, Fig: 2, carried by a screw 8 upon the shaft of which is a spur wheel 10. The spur wheels 10 of all the blades of the propeller A gear with a pinion 11a mounted between the two propellers. The pinion 11a is connected with a pinion 12a which drives through a pinion 74, shaft 75, pinion 76, and a pinion 77 upon a sleeve 82 which has a pinion 12b coupled to the operating pinion 13. Upon the pinion member 12b there is also a bevel wheel 78 which, through intermediary pinions 79, operates the bevel 82 and thereby a master wheel 11b, which, similarly to the pinion 11a, operates upon all the pinions mounted on the blade roots of propeller B.. For the. purpose of moving the pinion 13, it is mounted upon a shaft 14, Figs. 1 and 5, and carries one member 20 of an electromagnetic clutch. This is adapted to be electrically coupled with members 18 or 19, which in turn carry pinions 22 and 25 gearing with pinions 24, 26 on a sleeve keyed to the outer shaft 73. Current for the clutches is led through rings 28 and leads 29. The gear meshes 22, 24 and 25, 26 are such that when the electromagnetic coupling connects one set or the other, there is a resultant plus or minus motion of the pinion 13 relative to the shaft, whereby the pitch is adjusted up or down. For the purpose of providing a rapid reversal of pitch, a second electromagnetic collar 31 is adapted to bring in, through a coupling 33, another train of gears 34, 35 which gives a higher relative ratio for pitch adjustment. In a modification in which two propellers A', B', Fig. 7, are driven by separate engines, each propeller is provided with its pitch adjusting mechanism of this. kind, but in this case, the various drives 24, 26 are replaced by pinions 24a<1>, 25a<1>, 24b<1> and 25b<1> which are driven by shaft 81a<1>, 81b<1> respectively from the two engines. This drive is effected from 'the propeller shafts 72 and 73 respectively through pinions which gear with free pinions on the shafts and the latter are adapted to be clutched to their shafts by hydraulic clutches, the supply of hydraulic pressure thereto being by way of pipes leading from pumps driven by the respective engines. The terminals 38 are connected in'parallel to one pole of a battery 40 and the terminals 39 of the plates 18, 19 of the slow adjustment gear are connected to terminals 41 of a two-way switch 42 the common terminal 43 being connected to terminal 44a of a two-way switch 45. The common terminal 46 is connected to the second pole of the battery 40 whilst the other terminal 44b is connected in parallel to the terminals 47 of switches 48. The terminals 49 of the latter are connected to the terminals of the plates 33, 32 of the quick adjustment gear. The lever 50 operates both switches 45, 48 and in. the position shown the switch 42 is connected to the battery 40. When the lever is moved the slow control switch is cut out and the switches 48 used to control the quick adjustment. Included 'in the circuits are switches 51 . . . 54 which are automatically operated by the pitch indicator mechanism to limit the maximum and minimum pitch settings at predetermined values. In one form, the shaft 56, Fig. 4, of the pitch indicator carries cams 58 contacting with arms of the switches. The switch 42 may be controlled automatically, the'contacting arm 61 being moved over segments 60. The spindle of the arm has a gear wheel 62, Fig. 6, meshing with a quadrant 63 on a pivoted arm 64 the other end of which is coupled to the governor spindle, which spindle is also used for the revolution carrier. The disc carrying the segments may be connected by gearing 67, 68 with a lever whereby new neutral positions of the switch are set with consequent new mean speed settings. A switch 69 in the slow-adjustment circuit may be cam-controlled from the throttle whereby the automatic pitch adjustment is cut out below a predetermined throttle setting and engine speed. Should the engine fail, the blades are brought to feathering position by stopping or slowing the shaft 14.