GB359517A - Apparatus for reducing torsional oscillations in shafts - Google Patents

Abstract

359,517. Reducing torsional oscillations in shafts. KJ ãR, V. A., 16, Hoyensgade, Copenhagen. June 25, 1930, No. 19324. [Class 80 (ii).] Torsional oscillations in shafts, particularly in crank shafts of internal-combustion engines, are reduced by cyclic variation of the natural frequency of oscillation of the shaft, the means comprising inertia masses coupled to the shaft in such a way that the stiffness of the coupling varies cyclicly during rotation of the shaft. The natural frequency may be caused to vary according to a sine law or to a curve composed of a series of straight lines. In Fig. 8 there is an intermittent hydraulic coupling in combination with springs 59, the coupling comprising cylinders 2 attached to a sleeve 54 keyed to the rotating shaft, and co-operating with pistons connected to cross-pins 58 mounted between circular side plates 1 which form a flywheel freely mounted on the sleeve 54. The hydraulic coupling is controlled by a fixed plunger 60 which has axial grooves in its periphery so that as the shaft together with the sleeve 54 rotates, the cylinders 56 are intermittently put into communication through ports 62. The flywheel is thereby alternately rigid with the shaft or connected with it only by the springs 59. The corners 64 of the plunger grooves are rounded to give a gradual change of the coupling. In the form shown in Fig. 11, the flywheel 1 is driven from the shaft 80 through a flat blade spring 69 which is caused to rotate about its longitudinal axis so that the flywheel is successively resiliently connected to the shaft, such as when the plane of the spring is perpendicular to that of the flywheel as shown, or is rigidly connected thereto such as when the spring has rotated through a right-angle and its plane is parallel to that of the flywheel. The ends of the spring are carried in bearings 72 in the flywheel 1 and it is clamped at its centre 68 between cylinders 65 screwed together and caused to rotate in bearings 67 by the rotation of the shaft through bevel gearing 74, 75. In another form the effective length of a radial blade spring between the flywheel and the shaft is continuously varied, the spring being fixed to the flywheel and projecting radially inwards into blocks sliding in radial guides fixed to the shaft. The radial position of the blocks is continuously varied to vary the effective length of the spring, by means of a connecting rod pivoted to a fixed crank. In a further form, an arm on the shaft carries a bell-crank lever one end of which has a roller engaging a star-shaped fixed cam wheel, the other end carrying a block slidable in a grooved arm pivoted on the flywheel. The outer end of the grooved arm engages between the ends of two tangential helical springs attached at their opposite ends to the flywheel. The cam continuously varies the radial position of the block and so varies the pressure of the springs on the grooved arm. In a further form the flywheel is coupled to the shaft by a helical spring arranged between a point on the flywheel rim and a crank mounted on an arm fixed to the shaft, the crank being caused to rotate so that the spring is alternately radial or tangential to the flywheel, by means of a planet wheel on the arm and a fixed sun wheel coaxial with the flywheel and shaft. In a further form the flywheel is driven from a parallel shaft by means of a crank and coupling rod which comprises a telescopic spring link. The parallel shaft is driven by chain gearing from the main shaft which is coaxial with the flywheel.