Patent GB-585696-A (GB)
Title: Improvements in or relating to hydraulic power-transmissions
IPC: F16D67/00
Filed: 1944-05-24
Abstract: 585,696. Variable-speed gearing. UNITED AIRCRAFT CORPORATION. May 24, 1944, No. 10109. Convention date, June 26, 1943. [Class 80 (ii)] [Also in Groups XXVI, XXVII and XXIX] Change-speed gearing, for driving an aircraftengine, supercharger 20, or cooling fan, from the engine crankshaft 24, comprises at least two separate different - ratio countershaft trains such as 26, 28, 32, 34 and 26, 42, 38, 36, each including a hydrokinetic fluid-coupling 30, 40, which are selectively filled and emptied to introduce their respective train, under control of a selector-valve 50, actuated automatically in response to the difference in speed of the driving and driven members 24, 20, whereby the individual 1 fluidcouplings operate, only over a limited range of low slip at which their. efficiency is highest. The effective ratio is determined by the slip in the particular fluid-coupling 30 or 40 which is operating at any time, and this is automatically controlled in response to charge-pressure, atmospheric pressure, and overtravel of the engine throttle-rod 134, acting jointly through fluid-pressure on a valve 56, which controls the supply of oil from a pressuresource 54 through a conduit 52, the couplings having peripheral drain-holes 175 so that the rate of fluid supply determines the degree of filling and thus the slip. Oil from the conduit 52 reaches the couplings 30, 40 through the selector-valve 50, the respective hollow countershafts 156, 157 and central ports 174, 176. The selector-valve 50 has a piston-element 182, Fig. 2, with a groove 188, Fig. 3, for selectively connecting, in its end positions, ports 222, 224, leading to the respective couplings 40, 30, with a central pressure-port 220, connected to the supply conduit 52. The piston-valve 182 is moved to either end-position by internal oilpressure developed on the appropriate end-face of a screw-pump 184, fed with oil through central ports 200, 196 from a reservoir 55, Fig. 2. The direction of movement of the piston-valve 182 is determined by the direction of drive of the screw-pump 184, which receives a differential drive from the runner and impeller of the fluidcoupling 40, in such a way as to rotate in opposite directions above and below a predetermined relative slip in the coupling. For this purpose the screw-pump 184 is driven through a pinion 272 by teeth 270, Fig. 2, on a planet-carrier 268, the planets of which mesh with a sum 254, fixed to the shaft 156 of the coupling-runner 170, and with an annulus 265, integral with a second annulus 267, meshing with wheels 260, on fixed spindles, which mesh with a central wheel 252, fixed to a sleeve carrying the coupling-impeller 172. The annulus 265 has slightly fewer teeth than annulus 267, so that at a predetermined percentage slip, of say 1¢ to 5 per cent., in the coupling 40, equivalent to a predetermined difference in speed between the driving and driven members 24, 20, the planet-carrier 268, and so the screw-pump 184 are stationary. Above this slip-percentage, the screw-pump 184 will be driven in the appropriate direction to develop pressure for moving the piston selector-valve 182 to the left, thereby supplying the high-speed coupling 30, and cutting off the low-speed coupling 40, which then empties. Below the slip-percentage the screwpump direction changes, moving the piston-valve 182 to the right to cut off the high-speed coupling and supply the low. Outlet ports 208, 216 &c. allow escape of oil from within the piston-valve 182 in its end-positions. Since the two impellers and the two runners of the fluid-couplings 30, 40 are always positively-connected together through their gear trains, the degree of slip in the lowspeed coupling 40 will always be effective to determine which coupling is to be filled, irrespective as to which coupling is actually driving at any time. The rate of supply of oil through the conduit 52 to the selector-valve 50, and hence the slip in either coupling, is governed by oil-pressure acting differentially on the end-faces of the valve 56 from a pressure-source 102, controlled by a valve 100, which is operated through a floating- lever 90, one end-fulcrum of which is moved, through a link 93, by a bellows 70, responsive to charge-pressure in the engine inlet-manifold 14, opposed by a spring-loaded bellows 76, connected to a chamber 82, which communicates with the inlet-manifold 14 through an orifice 88 and with atmosphere through another orifice 90, giving altitude control. The other end 96 of the lever 90 is moved to the right, against spring- pressure 142, by an arm 136 on the engine throttle-rod 134 when the throttle 120 is moved beyond the full-open position, a spring connection 130 to the throttle-arm 122 permitting this overtravel. A spring 108 urges the valve 100 to the left, so as to cut off the supply of fluid to both couplings until the throttle overtravel becomes effective on the lever 90. Specification 591,491, [Group XXVII], is referred to.