GB507460A - Improvements in and relating to automatic gear-changing devices for two-speed gears - Google Patents

Abstract

507,460. Fluid-pressure servomotor-control systems. JUNKERS FLUGZEUG-UNDMOTORENWERKE AKT.-GES. Aug. 24, 1938, No. 24919. Convention date, Sept. 11, 1937. [Class 136] [Also in Group XXIV] An automatic gear-changing device for two-speed gears, for use more particularly with superchargers on aircraft engines and operating in accordance with changes in an atmospheric condition, e.g. changes in pressure or temperature, comprises a quick-change device which is adapted to move from one end position to the other under the action of an auxiliary force controlled by the atmospheric condition and, in so doing, effects the changing of the gear either directly or indirectly. The invention is described as applied to gearing comprising driven pinions on the supercharger shaft in engagement with idle pinions on a driving shaft, a slidable clutch non-rotatably mounted on the driving shaft being interposed between said idle pinions. The slidable clutch (not shown) is actuated by an oscillating vane 61 which is mounted in a housing 60 and is coupled to the clutch by a lever 62 and rod 63, movement of the vane being effected by pressure fluid under the control of a piston valve 69 located in a chamber 85 which is provided with a pressure fluid inlet 70, outlets 71, 72 and pipes 65, 66 leading to opposite sides of the vane. The piston valve is provided with a mechanical quickchange device constituted by spring- pressed balls 104 in engagement with projections 102 in the valve chamber, and the latter is formed with an extension 96 housing a bellows diaphragm 94 which contains atmospheric air and carries a check valve 91 to coact with an orifice 86 which leads from the main valve chamber 85 to a chamber 88 having an outlet 89 leading to a continuously-operating pump 75 supplying the valve inlets 71, 72. With the valve 69 and vane 61 in the positions shown, the low gear is set for low-altitude working, pressure fluid being supplied from the pipe 70 to the pipe 66, and excess fluid being returned to the pump 75 through a bore 78 in the valve 69, the orifice 86 and the pipe 89. Simultaneously the pipe 65 is in communication with the outlet pipe 71. When a higher altitude is reached, however, the diaphragm 94 expands and causes the valve 91 to close the orifice 86, whereupon a pressure builds up in the chamber 85 and effects movement of the valve 69 against the pressure of a spring 106, putting the pressure pipe 70 into communication with the pipe 65, the pipe 66 into communication with the outlet 72, and operating the vane 61 to move the clutch into high-gear position. Means controlled by a governor 115, mounted on the engine shaft, are also provided for effecting a change into low gear at any time within the range of low airpressure in the event of excessive engine speed, said means comprising a valve 110 which is coupled to the governor and, when actuated, effects a reduction in pressure in the chamber 85. This change may also be effected by opening a hand-controlled valve 117.