Patent GB-593026-A (GB)
Title: Improvements in or relating to variable speed power transmissions
IPC: F16D67/00
Filed: 1944-05-19
Abstract: 593,026. Hydromechanical variable-speed gear. UNITED AIRCRAFT CORPORATION. May 19, 1944, No. 9763. Convention date, June 26, 1943. [Class 80(ii)] [Also in Groups XXVII and XXIX] Countershaft variable - speed gearing, particularly for driving an aircraft-engine supercharger 23, includes a fluid coupling 40, of which the fluid supply is cut off, to cause disengagement, by an internal valve 180, operated in response to a reversal of the relative speeds of the coupling members. The impeller 23 is driven from an aligned driving shaft 36 through either of two (or three) different ratio countershaftpaths, 44, 46, 48, 50 and 44, 52, 54, 56 introduced by selectively filling and emptying hydrokinetic fluid couplings 40, 42 in the countershafts of the respective ratios. Automatic control, responsive to chargepressure and throttle-control are provided. The fluid couplings have constant peripheral leak-ports 176, Fig. 2, and are variably filled to allow variable slip, through axial-entry pipes 60, 62, supplied with engine lubricating-oil from pump-fed ports 136, 139 controlled by a piston-valve 130, which is moved to the right by differential fluid-pressure to control graduated outlet ports 138, 140, supplying first the lowspeed coupling 40 alone then also the high speed 42. In the high-speed position the valve 130 supplies both high and' low speed couplings at the same time, but the supply to the low-speed coupling 40 is cut off at the coupling itself by the differentially-shifted internal valve 180, Figs. 2 and 6, above referred to, which has a constant frictional connection with the impeller 183 and a lost-motion pin-and-slot connection 186 with the runner 185. When the direction of relative rotation between the runner and impeller of the low-speed coupling 40 changes, due to the overdrive imparted to the runner 185 when drive is established through the high-speed coupling 42, friction-drag turns the valve 180 relatively to the runner 185 so as to move out of registry ports 174, 182 through which the coupling 40 is supplied with oil in the lowspeed position, Fig. 6, so that the coupling then empties through the peripheral ports 176. The impeller has ports 179 behind the valve 180 to release any trapped oil and permit oil-pressure to build up on the front of the valve to increase friction pressure. The selector control-valve 130 is operated by differential oil-pressure on its end faces, applied from a source 118, controlled by a valve 100, which is operated through a floating-lever 82, one end-fulcrum of which is moved, through a link 80, by a bellows 72, responsive to changes in chargepressure at the first stage blower outlet 26 and opposed by a spring-loaded evacuated bellows 74 so as to maintain constant charge-pressure. The other end 86 of the lever 82 is moved by a connection 164 to the engine throttle control-rod 156, which moves the lever-end to the right against spring-pressure 92, when the throttle is moved beyond the full-open position, a spring connection 158 to the throttle-arm 152 permitting this additional movement. An adjustable stop 94 limits the movement of the lever-end 86. A spring 106 urges the valve 100 to the left, and may be such as to cause the valve 130 to cut off the supply to both couplings 40, 42 in part-throttle positions when the arm 164 is inoperative. Either valve 100 or 130 may be operated manually. In the case of the three-speed form (not shown) the couplings of the two lower speeds each have differential-operated internal valves such as 180 in Fig. 2, and the control-valve (Fig. 5, not shown) is similar to the valve 130 but has three lands and three outlets. The impeller 23 shown is a first-stage one and its driving-shaft 36 is the drivenshaft of the second-stage blower 30, which is driven from the engine crankshaft by a fixed-ratio step-up countershaft gear 32. Specification 585,696 is referred to.