GB832655A - Improved clutch and power transmission units for aircraft engines connected to drive a propeller - Google Patents

Abstract

832,655. Friction clutches; clutch-brake combinations. GENERAL MOTORS CORPORATION. Feb. 5, 1958, No. 3743/58. Class 80 (2). [Also in Group XXXIV] An input shaft and an output shaft can be connected through a clutch having means responsive to input shaft rotation to aid clutch engagement, means actuated by the output shaft opposing such clutch engagement, and means responsive to torque transmitted through the clutch varying the clutching force. As shown, the clutch is arranged between a gas turbine and the propeller of an aeroplane, and disengages immediately on failure of the gas turbine. A driving shaft 14, Fig. 4, is formed with helical splines 74 co-operating with similar splines on a surrounding sleeve 73 forming the inner driving member of a multidisc clutch. Fast with the sleeve 73 is a pressure-plate 80 and secured to the driving shaft 14 is a reaction plate 77. The driven discs of the clutch are splined in a drum 20 fast with an output shaft 50. Belleville springs 93 between a reaction plate 90 and an axially slidable ring 92 bias the clutch sleeve 73 upon the helical splines 74 to give initial light clutching engagement. A space 94 within the Belleville springs 93 receives a gradual flow of oil from an output driven pump (not shown) feeding oil through a pipe 102 to bleed holes 105. The pipe 102 also supplies oil to a cylinder containing a piston 110 abutting slidable pins 115 engaging the edge of the ring 92. On rotation of the driving shaft 14, the light friction engagement of the clutch discs caused by the Belleville springs 93 is sufficient to screw the clutch sleeve 73 along its helical splines 74 for firm clutch engagement. As the speed of rotation of the output shaft 50 increases, the output driven pump supplies oil through the pipe 102 to the space 94 where centrifugal force acts to bias the ring 92 rightwards and assist clutch engagement. Simultaneously, oil pressure acts upon the piston 110 to bias the ring 92 in the clutchdisengaging direction, but the force with which the piston 110 acts is insufficient to overcome the centrifugal force and the bias of the belleville springs 93. The oil supplied through the pipe 102 to the space 94 seeps through passages 106 in the clutch sleeve 73 to lubricate and cool the interleaved clutch discs. In the event of the driving shaft 14 suddenly stopping, due to failure of the gas turbine, the output shaft 50 &c. continues to rotate and the sleeve 73 immediately screws along to the clutch disengaged position. On normal deceleration of the gas turbine, the centrifugal force acting upon the oil in the space 94 decreases to such an extent that the pressure of the oil in the pipe 102 is eventually able to act upon the piston 110 and through the pins 115 to overcome the bias of the Belleville springs 93, so that the clutch completely disengages. When the output shaft 50 finally comes to rest, the output driven pump ceases supplying oil to the pipe 102, and the Bellville springs 93 reengage the clutch lightly ready for normal clutch re-engagement when drive starts again. Two clutches 20, 21, Fig. 1, according to the invention are shown connecting the driving shafts 14, 15 of gas turbines 10, 11 through trains of gearing 16 . . . 18 to a propeller shaft 19 in an aeroplane drive arrangement. Included in the drive arrangement is a disc brake 40 (see Group XXXIV), biased to engage by a spring but disengaged when the propeller shaft rotates by the pressure of oil from the output driven pump acting upon a piston (not shown), thereby moved against the bias of the brakeengaging spring. The drive arrangement also includes a starter motor 32 which drives a shaft 31 connected through a helical spline coupling 39 to the brake 40. The arrangement is such that, on rotation of the starter motor 32 and the shaft 31, the helical spline connection 39 disengages the brake 40. The starter motor 32 drives through trains of gears 33, 34 to two similar starter clutches 37, 38 transmitting drive to the clutches 20, 21. The clutch 37, Fig. 4, comprises a driving drum 121 fast with a gear 35 rotated by the starter motor, and a driven frusto-conical clutch ring 126 having helically splined engagement with the driving shaft 14. A ring spring 128 normally biases the clutch member 126 to engage lightly with the clutch drum 121. On operation of the starter motor, drive is transmitted through the clutch drum 121 to the clutch ring 126 and the clutch screws firmly into engagement to drive the shaft 14. As soon as the associated gas turbine 10 fires, the shaft 14 overruns the driving drum 121 of the starter clutch and screws the clutch member 126 to the disengaged position against the bias of the ring spring 128. Oil from the pipe 102 seeps through holes 129, 130 to cool and lubricate the clutch. Specifications 832,656 and 832,657 are referred to.