GB685340A - Improvements relating to propeller drive mechanisms - Google Patents

Abstract

685,340. Gas turbine plant. GENERAL MOTORS CORPORATION. Nov. 8, 1950 [Nov. 19, 1949], No. 27249/50. Class 110(iii) [Also in Groups XXXIII and XXXIV] A pair of contra-rotating aircraft propellers 48, 56 are driven by gas turbines 10, 12 through shafts 22, 28, clutches 24, 30 and pinions 26, 32 meshing with a common pinion 34 coupled to the propellers by sun and planet gearing 38, 40 ... a propeller brake 64 being geared to the pinion 34 and so arranged as to be inoperative when the propellers are engine-driven, and operative when non powerdriven a " self-energising " action being obtained when the propellers rotate in reverse direction under such conditions to prevent windmilling due to over-feathering, but not when rotating in the forward direction. The brake is of the cone type and comprises two friction elements 84, 86, of which the former is driven by a pinion 68 meshing with the gear pinion 34, the pinion 68 being integral with a sleeve 74, 107, of which the portion 107 forms a cylinder for a piston 112. When the propellers are power-driven a gear-wheel pump 132, driven by the engine, supplies pressure liquid to the face of the piston 112 to overcome a compression spring 110 and thus disengage the brake friction elements, 84, 86. In the event of momentary oil failure at high engine speed the centrifugal head generated by the liquid rotating in the cylinder sets up sufficient pressure to maintain the brake elements disengaged until the speed falls sufficiently to allow safe brake application. If the propellers rotate in the forward direction when non power-driven the brake element 84 forces its co-operating element 86 into engagement with the fixed housing 37, but if in the reverse direction the members 84, 86 are drawn together by the action of a screw thread 90, by which the element 86 is mounted on a fixed sleeve 78, to give the self-energising action. Upon subsequent rotation in the normal direction the element 86 is moved back to its normal position against the housing 37, being assisted by a return spring 94. The brake elements 84, 86 are cooled, when engaged, by oil from the pump 132 which is delivered to the interior of a hollow sleeve 98 integral with the piston 112, from which it passes to the brake through aligned radial openings 75, 99 in sleeves 74, 98, respectively; when the brake elements are disengaged the openings 75, 99 move out of alignment and the oil supply is cut off.