GB1274677A - Improvements in or relating to ram-air turbines - Google Patents

Abstract

1,274,677. Ram-air turbines; oscillating motors. DOWTY ROTOL Ltd. Nov. 5, 1969 [Nov. 15, 1968], No. 54284/68. Headings F1F and F1T. A ram-air turbine comprises a variable pitch bladed rotor 11, a hydraulic actuator 25 for effecting pitch variation of the blades and supplied with operating liquid by a rotor driven pump 103, a flyweight governor 59 to control the supply of liquid to the actuator 25 to maintain the rotor speed constant, and a machine 101 driven by the rotor, the rotor, actuator, pump, governor and driven machine all being coaxially arranged. The turbine has two blades each adjustably mounted at its root 17 in bearings 18, 19 in a hub 20. The roots 17 respectively carry balance weights 41, 42 and bevel gears 39, 40, the latter meshing with forward and rearward bevel gears 38, 44 drivably connected to the hydraulic actuator 25. The latter is of vane type having a casing 26 rotatably mounted in a bore 27 within hub 20, the casing carrying three inwardly extending vanes 28, 29, 30. The actuator 25 also has a hollow rotatable shaft 31 splined at 36 to a tubular member 35 carrying outwardly extending vanes 32, 33, 34 which define with the vanes 28, 29, 30 chambers 87, 88, 89 and 94, 95, 96. The casing 26 and shaft 31 are connected to bevel gears 38, 44 respectively, axial thrust on gear 38 being taken by a bearing 49. The rearward end of shaft 31 carries the governor flyweights 59 which bear at 60 upon an axially slidable hollow valve spool 61 mounted within a ported sleeve 62 itself secured within shaft 31. A speed setting spring 63 bears upon the forward end of spool 61, the compression of spring 63 being pre-set by shims 64. A hollow shaft 24 connected to shaft 31 extends rearwardly and is connected via a quill shaft 98 to the rotatable part 102 of lobe type pump 103 and to a further machine 101 which may be a hydraulic pump or electric generator. Shaft 24 is mounted within bearings 12, 13 supported in a non- rotatable body member 14 formed integrally with a leg (15) by which the turbine is pivotally mounted upon an aircraft. When turbine operation is required the leg is swung about its pivot into the aircraft slipstream. At starting the blades of the rotor 11 are at a relatively coarse pitch angle so that the rotor cannot overspeed should the pitch change mechanism fail. Low-pressure liquid from the aircraft hydraulic system passes through passageways 105, 106, 107 to the inlet of pump 103 and is pumped through passageway 108 into the interiors of shaft 98 and spool 61 and thence through radial port 72 into an annulus 73 in the spool. The liquid then passes through ports 76 in sleeve 62, through axial grooves 66, 69 in the latter, ports 82, 83 in shaft 31, and ports 84, 85, 86 into chambers 87, 88, 89 of the actuator 25. The casing 26 and shaft 31 of the actuator are thus forced to rotate in opposite directions so that their bevel gears 38, 44 move the rotor blades into a finer pitch position. At this time the actuator chambers 94, 95, 96 are in communication with drain. As the rotor speed increases the governor flyweights 59 move spool 61 to the left against the action of setting spring 63 until, at the equilibrium speed, the spool cuts off the flow of liquid to the actuator 25. Any departure from this speed is corrected by the governor and actuator readjusting the pitch angle of the rotor blades. At the equilibrium speed the liquid delivered by pump 103 passes through a relief valve 110 back to the pump inlet. A connection (111), Fig. 3 (not shown) from passageway 105 leads hydraulic fluid to the inlet of pump 101 which forces the liquid through a passageway (114) within the leg (15) to equipment within the aircraft. In a modified hydraulic circuit, Fig. 4 (not shown), the liquid return line (117) from the actuator 25 connects with the input line to the pump 101 so that heat generated in the pitch control system is carried away to the aircraft.