Patent GB-670412-A (GB)
Title: Improvements in or relating to propeller systems particularly for aircraft comprising two coaxially mounted, adjustable pitch propellers
IPC: B64C11/30
Filed: 1946-08-01
Abstract: 670,412. Variable-pitch propellers. UNITED AIRCRAFT CORPORATION. Aug. 1, 1946 [Aug. 9, 1945], No. 23004/46. Class 114. [Also in Group XXIX] A contra-rotating propeller arrangement for aircraft comprises two adjustable pitch propellers each with its own pitch changing motor and control means therefor, and means for simnltaneously actuating both control means, each control means having a follow-up device connected to the blades of its respective propeller for determining the pitch of the blades. The motors are of the hydraulic vane type and are simultaneously controlled by piston valves with follow-up sleeves. The valves are actuated by a further servomotor which may be controlled manually or by a constant speed governor. Under the manual control the propellers may be feathered or reversed or set in any predetermined pitch position. Auxiliary power means are provided sufficient to bring the rear propeller out of the feathered position, the front propeller being subsequently unfeathered due to " windmilling " of the rear propeller. The front and rear propeller units are generally similar and each carries its own hydraulic supply system. The front and rear hubs 540, 40, Fig. 1, are mounted on drive shafts 12, 14 respectively, the former 12 being driven directly by the engine 10 and the latter 14 indirectly through gearing 16, 18, 20. Each propeller has four blades with shanks 708, 208 respectively. Each respective shank is rotatably adjustable by a double acting vane motor 528, or 28. The motors 28 are supplied through passages 216, 218 controlled by a valve 26. The motors 528 are similarly controlled by a valve 526. The valves 26, 526 are maintained in operative engagement with each other by an extension 300 of the valve 26 and a flange 302 on a sleeve 304. The valves are simultaneously adjusted by mechanism in a stationary control housing 30 secured to the engine nose by screws 31. Each propeller hub has its own pumps located in housings 524, 24 respectively. The housing 30, Fig. 4, encloses a governor driven from the hub 40 through gears 38, 42. Its flyballs 45 adjust a sleeve valve 46 against the tension of a loading spring 50 adjustable manually or automatically by a spindle 52. The governor may be of the compensating type described in Specifications 560,522 and 573,400, [Group XXIX]. The valve 46 controls supply and exhaust of pressure fluid from a hub driven pump 58 through a normally-open solenoid valve 86 to a servomotor 74 operating a rack 80 against a spring 84. The governor control is cut out on closure of the valve 86. The servomotor 74 may then be connected directly with the pump 58 by opening a normally closed solenoid valve 88 or directly with a sump 60 by opening another normally-closed solenoid valve 96. These valves 86, 88, 96 as well as a solenoidoperated stop 100 and an electric motor 36 which supplies auxiliary power for unfeathering are controlled by manipulation of switches O G, F, R. For unfeathering, the motor 36 drives an auxiliary pump 328 through gearing 126, 124, 122, 324 and an eccentric 326. The position of the rack 80 and therefore the pitch of the blades is indicated by means 106 which may be of the electrical type described in Specification 560,522 and U.S.A. Specification 2,393,189. Movement of the rack 80 is limited in the constant speed range by nuts 102, 104 whilst the " feathered " and " reverse pitch positions are determined by nuts 103, 105 respectively. The gear 124 and therefore the gear 122 are normally held against rotation by ratchet mechanism 125. The rack 80 engages a ring gear 82 on a rotatable sleeve 288, Fig. 5, which by means of rollers 290 in axially directed slots 292 is non- rotatably connected to an internal sleeve 284 having a flange 282 engaging an extension 274 of the valve 26. The sleeve 284 has inclined slots 296 engaging fixed rollers 394. so that rotation of the sleeve 288 causes reciprocation of the sleeve 284 and therefore of the valves 26. 256. The valve 20, Fig. 5, is of the type shown in Specification 752/44 (as open to inspection under Sect. 91) and comprises a fixed sleeve 220 secured in the hub 40. a ported follow-up sleeve 22 held against rotation by a boss 256, Fig 13, in a slot 258, a double-landed piston valve 228, Fig. 5, urged towards low pitch position by a spring 270. The follow-up sleeve 222 is moved axially to lap the valve 228 after a control movement by a sleeve 244 with a cam slot 250 engaging a follower 252 supported on the sleeve 222. The cam sleeve 244 which is axially fixed is rotated by the blade shank and the movable outer part of the vane motor 28 through bevel gearing 230, 232 and gears 236, 240, 242. The valve 526 is similar to the valve 26 except that the slot 760 in its cam sleeve 744 is oppositely inclined since the front propeller is of opposite pitch. The slot 760 may. however, be shaped to position the front propeller in a predetermined position with respect to the rear propeller. Thus the front propellers may have some selected proportion of the pitch of the rear propeller to compensate for the effect of the slip stream of the front propeller on the rear propeller. The valve 26 is supplied with pressure fluid through a passage 164 from a manifold 148 secured by hollow studs 146, Fig. 8, around the inner periphery of the hollow pump housing 24. The latter contains a sump 138 and is shaped at 154, Fig. 7, to embrace the blade sockets of the hub 40. A number of pump cylinders 134 are secured in the housing 24 by screws 152. Fig. 3. Each pump cylinder 134 contains a two diameter piston 110. 112, the larger diameter piston 110 pumping fluid from the hub space into the sump 138, and the smaller diameter piston 112 pumping fluid from the sump past the check valve 142 into the stud 146 and thence to the manifold 148. The pump pistons 110 each carry a roller 128 engaging a normally fixed cam 114. The rollers are embraced by a ring 130 to ensure their inward movement. The cam 114 is carried on one end of a sleeve 120 mounted in bearings 116 and carrying the gear 122 normally held stationary by the ratchet mechanism 125. The housing 24 is secured to a hub web 160 by four pairs of hollow screw interconnected studs 156, 158, Fig. 1; 166, 168, Fig. 7; 178, 180; and 346, 352. The pressure supply from the manifold 148 to the passage 164 passes through the first pair 156, 158. The second pair 166, 168 contain a spring-loaded relief valve 172 adapted to connect the manifold 148 with the sump 138. The third pair 178, 180 provides a connection via a passage 182 to return fluid in the hub space to the sump 138; and a further connection through passages 188, 190 and a relief valve 186 to relieve pressure in the sump. The fourth pair 346, 352 may be utilised to convey de-icing fluid to the front propeller. The de-icing system comprises slinger rings 332, 832 bolted to the respective pump housings 24, 524 and troughs 340, 840 on the blade shanks, supplied from the slinger rings through passages in hollow bolts 336, 836 respectively. Fluid is distributed to the leading edges of the propellers from the troughs 340, 840. The ring 332 is supplied by a stationary pipe. The ring 332 is connected with the ring 832 through passages 342, 344, Fig. 16, a cork or rubber lined passage 348 in the fourth pair of interconnected hollow studs 346, 352 and a pipe 354, Fig. 16, supported by a frame 355 on an oil guard 308 between the hubs. The hubs 40, 540 are similar except that the front hub is of smaller diameter and the cam 614 operating the pumps in the housing 524 is driven through a projection 314 from the rear hub. To render the pumping capacity of the two hubs equal, the bore or stroke of the front hub pumps is reduced, or half of them are rendered inoperative. Sealing means 196, 696 are provided between the hub 40 and the control unit 30 and between the hub 540 and the oil guard 308 respectively. The pump housings have recesses such as 204, Fig. 3, some of which have balance weights 206, Fig. 1. Fig. 4 shows the switches O, G, F, R set for constant speed regulation. The servomotor 74 and hence the pitch may be locked by turning the switch O to the " ON position and the switch G to the " OFF " position i.e. the position in which the contacts are closed and the governor is cut off by the valve 86. To feather the propeller, the switch O is turned to the " ON " position and the switch F to the " feathered " position i.e. to the right in Fig. 4. It is immaterial whether switch G is then " ON" or " OFF." To unfeather the propeller, the switches O and G are turned to the " ON " position and the switch F is turned to the " unfeathered " position i.e. to the left in Fig. 4. To place the propeller in reverse pitch, the switches O and G are again turned to the " ON " position and the switch R is moved to the left in Fig. 4 to the "reverse" position. The propeller is moved out of the reverse pitch simply by moving the switch R to the right in Fig. 4, switches O and G being still in the " ON " position. Specifications 505,077, 605,045 and 670,484 also are referred to.