Patent GB-801879-A (GB)
Title: Improved aircraft propeller drive unit
IPC: B64D35/00
Filed: 1957-02-14
Abstract: 801,879. Driving variable pitch aircraft propellers. GENERAL MOTORS CORPORATION. Feb. 14, 1957, No. 5067/57. Classes 4 and 114. An aircraft propeller drive unit comprises a gear unit including a gear journalled on a fixed sleeve and driven by a prime mover, and a propeller unit removably mounted in the gear unit and comprising a shaft releasably secured within the fixed sleeve, a propeller hub rotatably supported on the shaft, and a disengageable splined drive connection between the gear and the hub. Fig. 1 shows the general arrangement, in which the gear unit B is enclosed in two housing portions 11, 12 connected together and to a plate 14 by bolts 13. The unit is driven by two shafts enclosed in corresponding sleeves 10 (one shown) and driven by gas turbines. Two propeller hubs 100, 105 are coupled by a sleeve 103 and driven by the gear unit. Fig. 6 shows a cross-section of part of the gear unit extending from the centre line of the unit to the centre line of one sleeve 10. The fixed sleeve 20 which is tapered, is secured by bolts 21 to the housing portion 11, and contains the shaft 25 which forms part of the propeller unit. The shaft 25 is secured by a nut 22 bearing against one end of sleeve 20 and housing 11, and pulling a shoulder 112 to react through a spacer ring 111, the inner race of a roller bearing 101, and a spacer sleeve 113, against the other end of sleeve 20. A roller bearing 27 on sleeve 20 rotatably supports a gear wheel 30 meshing with a pinion 31 connected through a hydraulically operated clutch 36 to a shaft 33 connected to one of the engine-driven shafts within a sleeve 10. A second pinion 31 (not shown), is similarly connected to the other engine-driven shaft. A clutch element 50 on a shaft 51 is connectable to an electric starting motor (not shown) and can be connected by a slidable member 56 to either of gear wheels 57 or 57<SP>1</SP> each of which meshes, through an idler pinion (not shown) with a gear wheel 61 secured to a shaft 33 (one only shown), so that the starter can engage either engine. Shaft 51 is connected through bevel gears 65, 66 and a one-way clutch 67 with a shaft 68 driving a pump (not shown) supplying pressure fluid for operating the clutches 36, and connected through bevel gears 71, 72 and a one-way clutch 70 to a shaft 74 driving a gear wheel 75 meshing with teeth 76 on gear wheel 30. The teeth 76 also drive a power take-off shaft for driving auxiliaries, Fig. 5 (not shown). Gear 30 is formed with a sleeve 91 internally splined at 92 to engage external splines 93 on a shaft 100 forming part of the rear propeller hub, Fig. 1. The shaft 25 is continued forwardly through both propeller hubs which are secured in place by a nut on the forward end of the shaft similar to the nut 22 in Fig. 6. The hubs 100 and 105 are similar, and only hub 100 will be described, Fig. 3. The hub has three blade sockets 120 each formed with ball races 122, 124 rotatably receiving a blade root 121. The hub contains a triangular block 130 to which is splined a tubular member 143 in each blade socket. In each socket, a cylinder 133 is splined to the blade root at 134 and is mounted by a ball race 132 on the block 130. The cylinder has an end cap 135 resiliently held by a leaf spring 138, and contains a piston 140 splined at 141 and 142 to engage internal and external splines on cylinder 133 and tubular member 143 respectively. These splines are helical, so that as the piston traverses the cylinder, the latter, with the blade root, rotates relatively to the member 143 and block 130. A bevel gear 170 on each cylinder 133 engages a master bevel 171, which is connected by a sleeve 175 to the corresponding master bevel of the forward hub, so that all the blades have equal pitch. A wiper 197, Fig. 2 (not shown), on sleeve 175 engages a potentiometer coil 195 Fig. 2 (not shown), on shaft 103 to give an indication of the angular relation of sleeve 175 and shaft 103. The three blades of one hub are disposed in the radial planes bisecting the angles formed by the three blades of the other hub. The outer chamber 140b of each cylinder is connected by a tube 150 to a groove 154 in a sleeve 155 which groove is connected by bores 156 ,157 and a conduit 158 to the corresponding groove of the forward hub and to a fluid pressure valve in a pitch regulator 228, Fig. 1. The inner chamber 140a of each cylinder is connected by a bore 160 to a second groove 161 in sleeve 155 similarly connected to a second groove in the forward hub sleeve and to the fluid pressure valve. To remove the propeller unit, nut 22, Fig. 6, is removed and shaft 25 withdrawn from the gear unit B, the splines 92, 93 separating. Specification 544,580 is referred to.